WorldWideScience

Sample records for linear sorption model

  1. Sorption of malachite green from aqueous solution by potato peel: Kinetics and equilibrium modeling using non-linear analysis method

    Directory of Open Access Journals (Sweden)

    El-Khamsa Guechi

    2016-09-01

    Full Text Available Potato peel (PP was used as a biosorbent to remove malachite green (MG from aqueous solution under various operating conditions. The effect of the experimental parameters such as initial dye concentration, biosorbent dose, initial pH, stirring speed, temperature, ionic strength and biosorbent particle size was investigated through a number of batch sorption experiments. The sorption kinetic uptake for MG by PP at various initial dye concentrations was analyzed by non-linear method using pseudo-first, pseudo-second and pseudo-nth order models. It was found that the pseudo-nth order kinetic model was the best applicable model to describe the sorption kinetic data and the order n of sorption reaction was calculated in the range from 0.71 to 2.71. Three sorption isotherms namely the Langmuir, Freundlich and Redlich–Peterson isotherms in their non-linear forms were applied to the biosorption equilibrium data. Both the Langmuir and Redlich–Peterson models were found to fit the sorption isotherm data well, but the Redlich–Peterson model was better. Thermodynamic parameters show that the sorption process of MG is endothermic and more effective process at high temperatures. The results revealed that PP is very effective for the biosorption of MG from aqueous solutions.

  2. Second-order kinetic model for the sorption of cadmium onto tree fern: a comparison of linear and non-linear methods.

    Science.gov (United States)

    Ho, Yuh-Shan

    2006-01-01

    A comparison was made of the linear least-squares method and a trial-and-error non-linear method of the widely used pseudo-second-order kinetic model for the sorption of cadmium onto ground-up tree fern. Four pseudo-second-order kinetic linear equations are discussed. Kinetic parameters obtained from the four kinetic linear equations using the linear method differed but they were the same when using the non-linear method. A type 1 pseudo-second-order linear kinetic model has the highest coefficient of determination. Results show that the non-linear method may be a better way to obtain the desired parameters.

  3. Modelling of a diffusion-sorption experiment on sandstone

    International Nuclear Information System (INIS)

    Smith, P.A.

    1989-11-01

    The results of a diffusion-sorption experiment on a sample of Darley Dale sandstone, using simulated groundwater spiked with a mixture of 125 I, 85 Sr and 137 Cs, are modelled by a one-dimensional porous medium approach in which sorption is described by Freundlich isotherms. The governing equations are solved analytically for the special case of a linear isotherm, and numerically using the computer code RANCHDIFF for non-linear isotherms. A set of time-dependent, ordinary differential equations is obtained using the Lagrange interpolation technique and integrated by Gear's variable order predictor-corrector method. It is shown that the sorption behaviour of 85 Sr can be modelled successfully by a linear isotherm, using a sorption parameter consistent with batch-sorption tests. The behaviour of 137 Cs may be modelled by a non-linear isotherm, but the amount of 137 Cs sorbed is less than that anticipated from batch-sorption tests. 125 I is assumed to be non-sorbing and is used to determine the porosity of the sandstone. (author) 10 figs., 4 tabs., 6 refs

  4. Interim report on modeling sorption with EQ3/6

    International Nuclear Information System (INIS)

    Viani, B.

    1988-01-01

    Reversible, equilibrium models of sorption to be incorporated into the EQ3/6 geochemical modeling package are summarized. Empirical sorption models as formulated in linear, Langmuir, and Freundlich isotherms will be developed as options to EQ3/6. This work will be done at LLNL. Options for modeling sorption using surface- complexation constructs (diffuse, constant capacitance, and triple-layer models) will also be developed. Development of the surface-complexation options will require part of the work be done under contract. 27 refs., 1 fig

  5. Sorption mechanisms and sorption models

    International Nuclear Information System (INIS)

    Fedoroff, M.; Lefevre, G.; Duc, M.; Neskovic, C.; Milonjic, S.

    2004-01-01

    Sorption at the solid-liquid interfaces play a major role in many phenomena and technologies: chemical separations, catalysis, biological processes, transport of toxic and radioactive species in surface and underground waters. The long term safety of radioactive waste repositories is based on artificial and natural barriers, intended to sorb radionuclides after the moment when the storage matrixes and containers will be corroded. Predictions on the efficiency of sorption for more than 10 6 years have to be done in order to demonstrate the safety of such depositories, what is a goal never encountered in the history of sciences and technology. For all these purposes, and, especially for the long term prediction, acquiring of sorption data constitutes only a first step of studies. Modeling based on a very good knowledge of sorption mechanisms is needed. In this review, we shall examine the main approaches and models used to quantify sorption processes, including results taken from the literature and from our own studies. We shall compare sorption models and examine their adequacy with sorption mechanisms. The cited references are only a few examples of the numerous articles published in that field. (orig.)

  6. Review of sorption models, and their suitability for use in performance assessments

    International Nuclear Information System (INIS)

    Harvey, K.B.

    1997-02-01

    The sorption of radionuclides on mineral surfaces is an important mechanism for retarding the movement of radionuclides from a geological nuclear fuel disposal vault, through the geosphere, to the biosphere. Sorption processes are known to increase the travel times for some radionuclides by 103 to 106 times relative to the groundwater flow, and this delay can provide the opportunity for radioactive decay before the radionuclide enters the biosphere. Sorption models are, or can be, used as a means of including the effects of sorption in the transport equations which describe the movement of radionuclides through the geosphere. Sorption models are, or could be, based on sorption isotherms, such as the Langmuir and Freundlich isotherms, ion-exchange models, surface-complexation models, or parametric models that are, essentially, interpolated databases. All national nuclear fuel waste disposal programs currently assume the linear adsorption isotherm, which states that the degree of sorption on a surface is a linear function of the concentration of sorbing ion in solution. The sorption models that are, or could be, applied to the movement of radionuclides in the geosphere are reviewed. It is concluded that, at the present state of knowledge, no single model has been demonstrated to provide an adequate description of radionuclide sorption. Reasons for this inadequacy vary, ranging from lack of data, through restricted ability to describe sorption under a variety of conditions, to current levels of development of the models. It is concluded that a parametric model, associated with a linear sorption isotherm, is currently the most practical choice that can be made. Following the completion of an earlier draft of this report, a new approach to surface complexation modelling, the 'discrete-log-K-spectrum' model, was published. This model appears to have the potential to achieve a synthesis of many of the concepts used in sorption modelling. For this reason, a description of

  7. Applicability of the Linear Sorption Isotherm Model to Represent Contaminant Transport Processes in Site Wide Performance Assessments

    International Nuclear Information System (INIS)

    FOGWELL, T.W.; LAST, G.V.

    2003-01-01

    The estimation of flux of contaminants through the vadose zone to the groundwater under varying geologic, hydrologic, and chemical conditions is key to making technically credible and sound decisions regarding soil site characterization and remediation, single-shell tank retrieval, and waste site closures (DOE 2000). One of the principal needs identified in the science and technology roadmap (DOE 2000) is the need to improve the conceptual and numerical models that describe the location of contaminants today, and to provide the basis for forecasting future movement of contaminants on both site-specific and site-wide scales. The State of Knowledge (DOE 1999) and Preliminary Concepts documents describe the importance of geochemical processes on the transport of contaminants through the Vadose Zone. These processes have been identified in the international list of Features, Events, and Processes (FEPs) (NEA 2000) and included in the list of FEPS currently being developed for Hanford Site assessments (Soler et al. 2001). The current vision for Hanford site-wide cumulative risk assessments as performed using the System Assessment Capability (SAC) is to represent contaminant adsorption using the linear isotherm (empirical distribution coefficient, K d ) sorption model. Integration Project Expert Panel (PEP) comments indicate that work is required to adequately justify the applicability of the linear sorption model, and to identify and defend the range of K d values that are adopted for assessments. The work plans developed for the Science and Technology (S and T) efforts, SAC, and the Core Projects must answer directly the question of ''Is there a scientific basis for the application of the linear sorption isotherm model to the complex wastes of the Hanford Site?'' This paper is intended to address these issues. The reason that well documented justification is required for using the linear sorption (K d ) model is that this approach is strictly empirical and is often

  8. Experimental study and modelling of selenite sorption onto illite and smectite clays.

    Science.gov (United States)

    Missana, T; Alonso, U; García-Gutiérrez, M

    2009-06-15

    This study provides a large set of experimental selenite sorption data for pure smectite and illite. Similar sorption behavior existed in both clays: linear within a large range of the Se concentrations investigated (from 1x10(-10) to 1x10(-3) M); and independent of ionic strength. Selenite sorption was also analysed in the illite/smectite system with the clays mixed in two different proportions, as follows: (a) 30% illite-70% smectite and (b) 43% illite-57% smectite. The objective of the study was to provide the simplest model possible to fit the experimental data, a model also capable of describing selenite sorption in binary illite/smectite clay systems. Selenite sorption data, separately obtained in the single mineral systems, were modeled using both a one- and a two-site non-electrostatic model that took into account the formation of two complexes at the edge sites of the clay. Although the use of a two-site model slightly improved the fit of data at a pH below 4, the simpler one-site model reproduced satisfactorily all the sorption data from pH 3 to 8. The complexation constants obtained by fitting sorption data of the individual minerals were incorporated into a model to predict the adsorption of selenium in the illite/smectite mixtures; the model's predictions were consistent with the experimental adsorption data.

  9. Isotherm, kinetic, and thermodynamic study of ciprofloxacin sorption on sediments.

    Science.gov (United States)

    Mutavdžić Pavlović, Dragana; Ćurković, Lidija; Grčić, Ivana; Šimić, Iva; Župan, Josip

    2017-04-01

    In this study, equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin concentration, temperature and ionic strength on the sorption process were studied. The K d parameter from linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin-Radushkevich (D-R) sorption models were applied to describe the equilibrium isotherms by linear and nonlinear methods. The estimated K d values varied from 171 to 37,347 mL/g. The obtained values of E (free energy estimated from D-R isotherm model) were between 3.51 and 8.64 kJ/mol, which indicated a physical nature of ciprofloxacin sorption on studied sediments. According to obtained n values as measure of intensity of sorption estimate from Freundlich isotherm model (from 0.69 to 1.442), ciprofloxacin sorption on sediments can be categorized from poor to moderately difficult sorption characteristics. Kinetics data were best fitted by the pseudo-second-order model (R 2  > 0.999). Thermodynamic parameters including the Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to estimate the nature of ciprofloxacin sorption. Results suggested that sorption on sediments was a spontaneous exothermic process.

  10. Diffusion and sorption on hardened cement pastes - experiments and modelling results

    Energy Technology Data Exchange (ETDEWEB)

    Jakob, A.; Sarott, F.-A.; Spieler, P.

    1999-08-01

    Large parts of repositories for low and intermediate level radioactive waste consist of cementitious materials. Radionuclides are transported by diffusion in the cement matrix or, in case of fractured or highly permeable cement, by advection and dispersion. In this work we aim at a mechanistic understanding of diffusion processes of some reactive tracers. On the laboratory scale, ten through-diffusion experiments were performed to study these processes for Cl{sup -}, I{sup -}, Cs{sup +} and Ni{sup 2+} ions in a Sulphate Resisting Portland Cement (SRPC) equilibrated with an artificial pore water. Some of the experiments continued up to nearly three years with daily measurements. In all the experiments, a cement disk initially saturated with an artificial pore water was exposed on one side to a highly diluted solution containing the species of interest. On the second side, a near-zero concentration boundary was maintained to drive through-diffusion of the tracer. The changes of concentrations on both sides of the samples were monitored, allowing careful mass balances. From these data, values of the diffusive flux and the mass of tracer taken up by the cementitious material were determined as a function of time. In the subsequent modelling, the time histories of these tracer breakthroughs were fitted using five different models. The simplest model neglects all retarding mechanisms except pure diffusion. More complex models either account for instantaneous equilibrium sorption in form of linear or non-linear (Freundlich) sorption or for first-order sorption kinetics where the forward reaction may be linear or non-linear according to the Freundlich isotherm, while the back-reaction is linear. Hence, the analysis allows the extraction of the diffusion coefficient and parameter values for the sorption isotherm or rate-constants for sorption and desorption. The fits to the experimental data were carried out by an automated Marquardt-Levenberg procedure yielding error

  11. Column Chromatography To Obtain Organic Cation Sorption Isotherms.

    Science.gov (United States)

    Jolin, William C; Sullivan, James; Vasudevan, Dharni; MacKay, Allison A

    2016-08-02

    Column chromatography was evaluated as a method to obtain organic cation sorption isotherms for environmental solids while using the peak skewness to identify the linear range of the sorption isotherm. Custom packed HPLC columns and standard batch sorption techniques were used to intercompare sorption isotherms and solid-water sorption coefficients (Kd) for four organic cations (benzylamine, 2,4-dichlorobenzylamine, phenyltrimethylammonium, oxytetracycline) with two aluminosilicate clay minerals and one soil. A comparison of Freundlich isotherm parameters revealed isotherm linearity or nonlinearity was not significantly different between column chromatography and traditional batch experiments. Importantly, skewness (a metric of eluting peak symmetry) analysis of eluting peaks can establish isotherm linearity, thereby enabling a less labor intensive means to generate the extensive data sets of linear Kd values required for the development of predictive sorption models. Our findings clearly show that column chromatography can reproduce sorption measures from conventional batch experiments with the benefit of lower labor-intensity, faster analysis times, and allow for consistent sorption measures across laboratories with distinct chromatography instrumentation.

  12. Experimental Study and modelling of the Sorption of Selenite and Europium Onto Smectite and Illite Clays

    Energy Technology Data Exchange (ETDEWEB)

    Missana, T.; Alonso, U.; Garcia-Gutierrez, M.

    2009-10-12

    This study provides a large set of experimental selenite sorption data for pure smectite and illite. Similar sorption behavior existed in both clays: linear within a large range of the Se concentrations investigated and independent of ionic strength. Selenite sorption was also analysed in the illite/smectite system with the clays mixed in two different proportions. The objective of the study was to provide the simplest model possible to fit the experimental data, a model also capable of describing selenite sorption in binary illite/smectite clay systems. Selenite sorption data were modeled using both a one-and a two-site non-electrostatic model that took into account the formation of two complexes at the edge sites of the clay. The complexation constants obtained by fitting sorption data of the individual minerals were incorporated into a model to predict the adsorption of selenium in the illite/ smectite mixtures; the models predictions were consistent with the experimental adsorption data. (Author) 42 refs.

  13. Experimental Study and modelling of the Sorption of Selenite and Europium Onto Smectite and Illite Clays

    International Nuclear Information System (INIS)

    Missana, T.; Alonso, U.; Garcia-Gutierrez, M.

    2009-01-01

    This study provides a large set of experimental selenite sorption data for pure smectite and illite. Similar sorption behavior existed in both clays: linear within a large range of the Se concentrations investigated and independent of ionic strength. Selenite sorption was also analysed in the illite/smectite system with the clays mixed in two different proportions. The objective of the study was to provide the simplest model possible to fit the experimental data, a model also capable of describing selenite sorption in binary illite/smectite clay systems. Selenite sorption data were modeled using both a one-and a two-site non-electrostatic model that took into account the formation of two complexes at the edge sites of the clay. The complexation constants obtained by fitting sorption data of the individual minerals were incorporated into a model to predict the adsorption of selenium in the illite/ smectite mixtures; the models predictions were consistent with the experimental adsorption data. (Author) 42 refs

  14. Integrated sorption and diffusion model for bentonite. Part 1. Clay-water interaction and sorption modeling in dispersed systems

    International Nuclear Information System (INIS)

    Tachi, Yukio; Suyama, Tadahiro; Ochs, Michael

    2014-01-01

    To predict the long-term migration of radionuclides (RNs) under variable conditions within the framework of safety analyses for geological disposal, thermodynamic sorption models are very powerful tools. The integrated sorption and diffusion (ISD) model for compacted bentonite was developed to achieve a consistent combination of clay–water interaction, sorption, and diffusion models. The basic premise considered in the ISD model was to consistently use the same simple surface model design and parameters for describing RNs sorption/diffusion as well as clay surface and porewater chemistry. A simple 1-site non-electrostatic surface complexation model in combination with a 1-site ion exchange model was selected to keep sorption model characteristics relatively robust for compacted systems. Fundamental parameters for the proposed model were evaluated from surface titration data for purified montmorillonite. The resulting basic model was then parameterized on the basis of selected published sorption data-sets for Np(V), Am(III), and U(VI) in dispersed systems, which cover a range of key geochemical conditions such as pH, ionic strength, and carbonate concentration. The sorption trends for these RNs can be quantitatively described by the model considering a full suite of surface species including hydrolytic and carbonate species. The application of these models to the description of diffusive-sorptive transport in compacted bentonites is presented in Part 2. (author)

  15. Effects of sorption behaviour on contaminant migration

    International Nuclear Information System (INIS)

    Melnyk, T.W.

    1985-11-01

    The effects of sorption behaviour on contaminant migration in groundwater systems are varied. Retardation of migration and dispersive effects can vary widely and contaminant concentration profiles can take a number of different shapes. This report examines the nature of some of these effects, especially those due to sorption behaviours that are dependent on the concentration of the contaminant in the groundwater. The effects are calculated using, in most cases, analytical solutions to the chemical equations imbedded in a simple reaction-cell or box-model transport algorithm. The hydrogeological parameters are held constant, and radioactive decay and hydrodynamic dispersion are excluded. A general discussion of the role of sorption equations in transport modelling is followed by presentation of migration results for a number of models of sorption behaviour varying from linear isotherms, Langmuir, Freundlich and ion-exchange isotherms, to precipitation reactions and multiple-site sorption reactions. The results are compared and general conclusions are drawn about the various migration behaviours calculated. The conclusions are that equilibrium sorption of trace contaminants can be modelled with linear isotherms (constant distribution coefficients or constant retardation factors) but the evaluation and extrapolation of the distribution coefficient are not easy. Nonlinear isotherms lead to unsymmetrical migration fronts. A comparison of Freundlich and linear isotherms is made. Sorption/desorption kinetic factors can be significant on the time scale of laboratory experiments and can cause large dispersive effects. Slow but important reactions can be missed altogether. Precipitation or mineralization behaviour cannot be modelled with constant distribution coefficients. Also, mineralization reactions can be kinetically slow even on the geological time scale. 89 refs

  16. Gallium sorption on montmorillonite and illite colloids: Experimental study and modelling by ionic exchange and surface complexation

    International Nuclear Information System (INIS)

    Benedicto, Ana; Degueldre, Claude; Missana, Tiziana

    2014-01-01

    Highlights: • Ga sorption onto illite and montmorillonite was studied and modelled for the first time. • The developed sorption model was able to well explain Ga sorption in both clays. • Number of free parameters was reduced applying the linear free energy relationship. • Cationic exchange dominate sorption at pH < 4.5; surface complexation at higher pH. - Abstract: The migration of metals as gallium (Ga) in the environment is highly influenced by their sorption on clay minerals, as montmorillonite and illite. Given the increased usage of gallium in the industry and the medicine, the Ga-associated waste may result in environmental problems. Ga sorption experiments were carried out on montmorillonite and illite colloids in a wide range of pH, ionic strength and Ga concentration. A Ga sorption model was developed combining ionic exchange and surface complexation on the edge sites (silanol and aluminol-like) of the clay sheets. The complexation constants were estimated as far as possible from the Ga hydrolysis constants applying the linear free energy relationship (LFER), which allowed to reduce the number of free parameters in the model. The Ga sorption behaviour was very similar on illite and montmorillonite: decreasing tendency with pH and dependency on ionic strength at very acidic conditions. The experimental data modelling suggests that the Ga sorption reactions avoid the Ga precipitation, which is predicted in absence of clay colloids between pH 3.5 and 5.5. Assuming this hypothesis, clay colloids would affect Ga aqueous speciation, preventing precipitation in favour of sorption. Ga sorption on montmorillonite and illite can be explained on the basis of three main reactions: Ga 3+ exchange at very acidic conditions (pH < ∼3.8); Ga(OH) 4 - complexation on protonated weak sites in acidic-neutral conditions (between pH ∼5.2 and pH ∼7.9); and Ga(OH) 3 complexation on strong sites at basic conditions (pH > ∼7.9)

  17. Surface complexation modeling of zinc sorption onto ferrihydrite.

    Science.gov (United States)

    Dyer, James A; Trivedi, Paras; Scrivner, Noel C; Sparks, Donald L

    2004-02-01

    A previous study involving lead(II) [Pb(II)] sorption onto ferrihydrite over a wide range of conditions highlighted the advantages of combining molecular- and macroscopic-scale investigations with surface complexation modeling to predict Pb(II) speciation and partitioning in aqueous systems. In this work, an extensive collection of new macroscopic and spectroscopic data was used to assess the ability of the modified triple-layer model (TLM) to predict single-solute zinc(II) [Zn(II)] sorption onto 2-line ferrihydrite in NaNO(3) solutions as a function of pH, ionic strength, and concentration. Regression of constant-pH isotherm data, together with potentiometric titration and pH edge data, was a much more rigorous test of the modified TLM than fitting pH edge data alone. When coupled with valuable input from spectroscopic analyses, good fits of the isotherm data were obtained with a one-species, one-Zn-sorption-site model using the bidentate-mononuclear surface complex, (triple bond FeO)(2)Zn; however, surprisingly, both the density of Zn(II) sorption sites and the value of the best-fit equilibrium "constant" for the bidentate-mononuclear complex had to be adjusted with pH to adequately fit the isotherm data. Although spectroscopy provided some evidence for multinuclear surface complex formation at surface loadings approaching site saturation at pH >/=6.5, the assumption of a bidentate-mononuclear surface complex provided acceptable fits of the sorption data over the entire range of conditions studied. Regressing edge data in the absence of isotherm and spectroscopic data resulted in a fair number of surface-species/site-type combinations that provided acceptable fits of the edge data, but unacceptable fits of the isotherm data. A linear relationship between logK((triple bond FeO)2Zn) and pH was found, given by logK((triple bond FeO)2Znat1g/l)=2.058 (pH)-6.131. In addition, a surface activity coefficient term was introduced to the model to reduce the ionic strength

  18. Sorption of cesium and uranium to Feldspar

    International Nuclear Information System (INIS)

    Wijland, G.C.; Pennders, R.M.J.

    1990-07-01

    Within safety assessment studies, for nuclear waste disposal in deep geologic formations, calculation for the migration of radionuclides through the geosphere are often carried out with models taking sorption into account. In the past 8 years the insight grew that other physico-chemical processes, besides sorption, could affect migration behaviour. While the currently used transport models were being improved taking either linear or non-linear sorption into account, the coupling of geochemical and transport models came into scope. In spite of these developments models which are still based on the sorption theory are frequently applied in studying migration behaviour of radionuclides. This is caused by the necessity of making preliminary pronouncements, while coupled models are still in stage of development and thermodynamic data are very limited available. Therefore one has to obtain insight in the reliability of the models based on the sorption theory. within the sorption database there is a lack of knowledge about mineralogy, composition of the fluid and the experimental conditions underlying the data. Therefore the Expert Group on geochemical Modelling supported by the Finnish proposal in order to obtain insight in the possible deviation of the sorption coefficients that can be estimated from experiments performed with standard samples, fluid composition and experimental conditions. Nine laboratories from OECD membership countries took part in this intercalibration study. In the framework of the Dutch safety assessment studies the Dutch National Institute of Public health and Environmental protection (RIVM) has decided to participate in this exercise. In this report the results are presented of sorption experiments for cesium and natural Uranium to Feldspar. (H.W.). 4 refs.; 1 fig.; 7 tabs

  19. Geochemical modelling of the sorption of tetravalent radioelements

    International Nuclear Information System (INIS)

    Bond, K.A.; Tweed, C.J.

    1991-05-01

    The results of an experimental study of the sorption of a range of tetravalent radioelements, plutonium (IV), tin (IV), thorium(IV) and uranium(IV), onto clay at pH8 and pH11 have been successfully simulated using a triple layer sorption model. The model has been incorporated into HARPHRQ, a geochemical program based on PHREEQE. The model has been parameterised using data for sorption onto ferric oxyhydroxide and goethite. The effects of hydroxycarboxylic acids on the sorption process have also been investigated experimentally. It was generally observed that in the presence of 2x10 -3 M gluconate, sorption was reduced by up two orders of magnitude. The model has satisfactorily simulated these lower sorptivities, through assuming competing sorption and complexation reactions. This work, therefore, further confirms the need to take account of such organic materials in safety assessment modelling. (author)

  20. Modeling volatile organic compounds sorption on dry building materials using double-exponential model

    International Nuclear Information System (INIS)

    Deng, Baoqing; Ge, Di; Li, Jiajia; Guo, Yuan; Kim, Chang Nyung

    2013-01-01

    A double-exponential surface sink model for VOCs sorption on building materials is presented. Here, the diffusion of VOCs in the material is neglected and the material is viewed as a surface sink. The VOCs concentration in the air adjacent to the material surface is introduced and assumed to always maintain equilibrium with the material-phase concentration. It is assumed that the sorption can be described by mass transfer between the room air and the air adjacent to the material surface. The mass transfer coefficient is evaluated from the empirical correlation, and the equilibrium constant can be obtained by linear fitting to the experimental data. The present model is validated through experiments in small and large test chambers. The predicted results accord well with the experimental data in both the adsorption stage and desorption stage. The model avoids the ambiguity of model constants found in other surface sink models and is easy to scale up

  1. Recent progress in sorption mechanisms and models

    International Nuclear Information System (INIS)

    Fedoroff, M.; Lefevre, G.

    2005-01-01

    Full text of publication follows: Sorption-desorption phenomena play an important role in the migration of radioactive species in surface and underground waters. In order to predict the transport of these species, we need a good knowledge of sorption processes and data, together with reliable models able to be included in transport calculation. Traditional approaches based on experimentally determined distribution coefficients (Kd) and sorption isotherms have a limited predictive capability, since they are very sensitive to the numerous parameters characterizing the solution and the solid. Models based on thermodynamic equilibria were developed to account for the influence these parameters: the ion exchange model and the surface complexation models (2-pK mono-site, 1-pK multi-site, with several different electrostatic models: CCM, DLM, BSM, TLM,...). Although these models are very useful, studies performed in recent years showed that they have important theoretical and experimental limitations, which result in the fact that we must be very careful when we use them for extrapolating sorption data to long term and to large natural systems. Among all problems which can be found are: the possibility to fit a set of experimental data with different models, sometimes bad adequacy with the real sorption processes, some theoretical limitations such as a rigorous definition of reference and standard states in surface equilibria, slow kinetics which prevent from equilibrium achievement, irreversibility, solubility and evolution of solid phases... Through the increase of the number of sensitive spectroscopic methods, we are now able to know more about sorption processes at the atomic scale. Models such as the 1-pK CD-MUSIC model can account for the influence of orientation of the faces of the solid. More and more examples of the influence of this orientation on the sorption properties are known. Calculations performed by 'ab initio' modeling is also useful to predict the

  2. Development of mechanistic sorption model and treatment of uncertainties for Ni sorption on montmorillonite/bentonite

    International Nuclear Information System (INIS)

    Ochs, Michael; Ganter, Charlotte; Tachi, Yukio; Suyama, Tadahiro; Yui, Mikazu

    2011-02-01

    Sorption and diffusion of radionuclides in buffer materials (bentonite) are the key processes in the safe geological disposal of radioactive waste, because migration of radionuclides in this barrier is expected to be diffusion-controlled and retarded by sorption processes. It is therefore necessary to understand the detailed/coupled processes of sorption and diffusion in compacted bentonite and develop mechanistic /predictive models, so that reliable parameters can be set under a variety of geochemical conditions relevant to performance assessment (PA). For this purpose, JAEA has developed the integrated sorption and diffusion (ISD) model/database in montmorillonite/bentonite systems. The main goal of the mechanistic model/database development is to provide a tool for a consistent explanation, prediction, and uncertainty assessment of K d as well as diffusion parameters needed for the quantification of radionuclide transport. The present report focuses on developing the thermodynamic sorption model (TSM) and on the quantification and handling of model uncertainties in applications, based on illustrating by example of Ni sorption on montmorillonite/bentonite. This includes 1) a summary of the present state of the art of thermodynamic sorption modeling, 2) a discussion of the selection of surface species and model design appropriate for the present purpose, 3) possible sources and representations of TSM uncertainties, and 4) details of modeling, testing and uncertainty evaluation for Ni sorption. Two fundamentally different approaches are presented and compared for representing TSM uncertainties: 1) TSM parameter uncertainties calculated by FITEQL optimization routines and some statistical procedure, 2) overall error estimated by direct comparison of modeled and experimental K d values. The overall error in K d is viewed as the best representation of model uncertainty in ISD model/database development. (author)

  3. Evaluation of sorption distribution coefficient of Cs onto granite using sorption data collected in sorption database and sorption model

    International Nuclear Information System (INIS)

    Nagasaki, S.

    2013-01-01

    Based on the sorption distribution coefficients (K d ) of Cs onto granite collected from the JAERI Sorption Database (SDB), the parameters for a two-site model without the triple-layer structure were optimized. Comparing the experimentally measured K d values of Cs onto Mizunami granite carried out by JAEA with the K d values predicted by the model, the effect of the ionic strength on the K d values of Cs onto granite was evaluated. It was found that K d values could be determined using the content of biotite in granite at a sodium concentration ([Na]) of 1 x 10 -2 to 5 x 10 -1 mol/dm 3 . It was suggested that in high ionic strength solutions, the sorption of Cs onto other minerals such as microcline should also be taken into account. (author)

  4. Evaluation of sorption distribution coefficient of Cs onto granite using sorption data collected in sorption database and sorption model

    Energy Technology Data Exchange (ETDEWEB)

    Nagasaki, S., E-mail: nagasas@mcmaster.ca [McMaster Univ., Hamilton, Ontario (Canada)

    2013-07-01

    Based on the sorption distribution coefficients (K{sub d}) of Cs onto granite collected from the JAERI Sorption Database (SDB), the parameters for a two-site model without the triple-layer structure were optimized. Comparing the experimentally measured K{sub d} values of Cs onto Mizunami granite carried out by JAEA with the K{sub d} values predicted by the model, the effect of the ionic strength on the K{sub d} values of Cs onto granite was evaluated. It was found that K{sub d} values could be determined using the content of biotite in granite at a sodium concentration ([Na]) of 1 x 10{sup -2} to 5 x 10{sup -1} mol/dm{sup 3} . It was suggested that in high ionic strength solutions, the sorption of Cs onto other minerals such as microcline should also be taken into account. (author)

  5. Effect of humic acid on sorption of technetium by alumina

    International Nuclear Information System (INIS)

    Kumar, S.; Rawat, N.; Kar, A.S.; Tomar, B.S.; Manchanda, V.K.

    2011-01-01

    Highlights: → Tc sorption on alumina has been studied under aerobic as well anaerobic condition over pH 3-10. → Effect of humic acid on sorption of Tc by alumina has been investigated. → Linear additive modeling and surface complexation modeling were carried out to delineate the role of humic acid in Tc(IV) sorption in ternary system of Tc(IV)-humic acid-alumina. → Sorption of humic acid onto alumina and strong complexation of Tc(IV) with humic acid were found to govern the sorption of Tc(IV) in the ternary system. - Abstract: Sorption of technetium by alumina has been studied in absence as well as in presence of humic acid using 95 Tc m as a tracer. Measurements were carried out at fixed ionic strength (0.1 M NaClO 4 ) under varying pH (3-10) as well as redox (aerobic and reducing anaerobic) conditions. Under aerobic conditions, negligible sorption of technetium was observed onto alumina both in absence and in presence of humic acid. However, under reducing conditions (simulated with [Sn(II)] = 10 -6 M), presence of humic acid enhanced the sorption of technetium in the low pH region significantly and decreased at higher pH with respect to that in absence of humic acid. Linear additive as well as surface complexation modeling of Tc(IV) sorption in presence of humic acid indicated the predominant role of sorbed humic acid in deciding technetium sorption onto alumina.

  6. Thermodynamic sorption modelling in support of radioactive waste disposal safety cases - NEA sorption project phase III

    International Nuclear Information System (INIS)

    2012-01-01

    A central safety function of radioactive waste disposal repositories is the prevention or sufficient retardation of radionuclide migration to the biosphere. Performance assessment exercises in various countries, and for a range of disposal scenarios, have demonstrated that one of the most important processes providing this safety function is the sorption of radionuclides along potential migration paths beyond the engineered barriers. Thermodynamic sorption models (TSMs) are key for improving confidence in assumptions made about such radionuclide sorption when preparing a repository's safety case. This report presents guidelines for TSM development as well as their application in repository performance assessments. They will be of particular interest to the sorption modelling community and radionuclide migration modellers in developing safety cases for radioactive waste disposal Contents: 1 - Thermodynamic sorption models and radionuclide migration: Sorption and radionuclide migration; Applications of TSMs in radioactive waste disposal studies; Requirements for a scientifically defensible, calibrated TSM applicable to radioactive waste disposal; Current status of TSMs in radioactive waste management; 2 - Theoretical basis of TSMs and options in model development: Conceptual building blocks of TSMs and integration with aqueous chemistry; The TSM representation of sorption and relationship with Kd values; Theoretical basis of TSMs; Example of TSM for uranyl sorption; Options in TSM development; Illustration of TSM development and effects of modelling choices; Summary: TSMs for constraining Kd values - impact of modelling choices; 3 - Determination of parameters for TSMs: Overview of experimental determination of TSM parameters; Theoretical estimation methods of selected model parameters; Case study: sorption modelling of trivalent lanthanides/actinides on illite; Indicative values for certain TSM parameters; Parameter uncertainty; Illustration of parameter sensitivity

  7. Moisture sorption of Thai red curry powder

    Directory of Open Access Journals (Sweden)

    Sudathip Inchuen

    2009-12-01

    Full Text Available Moisture sorption study was conducted on Thai red curry powder prepared by two different drying methods, viz. microwave and hot-air drying. Moisture sorption isotherms of the red curry powder at 30 C and water activity in the range of 0.113-0.970 were determined by a static gravimetric method. The isotherms exhibited Type III behaviour. The moisture sorption data were fitted to several sorption models and a non-linear regression analysis method was used to evaluate the constants of the sorption equations. The fit was evaluated using the coefficient of determination (R2, the reduced chi-square (2 and the root mean square error (RMSE. The GAB model followed by the Lewiski-3 model gave the best fit to the experimental data. The monolayer moisture content, taken as the safe minimum moisture level in the red curry powder, was determined using the BET equation and was found to range between 0.080 - 0.085 gram water per gram dry matter.

  8. Experimental measurements and integrated modelling studies of actinide sorption onto cement

    International Nuclear Information System (INIS)

    Sugiyama, Daisuke; Fujita, Tomonari; Baston, G.M.N.

    2003-01-01

    An Integrated Cement Sorption Model (ICSM) for actinides onto Ordinary Portland Cement (OPC) is developed. The experimental measurements using the batch sorption technique for actinides onto cement and constituent minerals, which were considered in the modelling calculations, are also described. The actinide elements studied (thorium, uranium, neptunium, plutonium and americium) were strongly sorbed onto OPC. An initial comparison of the experimental data relating the sorption values of actinides onto cement-component phases with those onto OPC is carried out. The results suggest that the Calcium Silicate Hydrate (C-S-H) phases were found to be the most likely candidates to be the dominant-sorbing phases in order to describe the sorption of a actinides onto OPC. An approach to develop the integrated cement sorption model, based on a thermodynamic surface complexation model, is described with discussions on the possible mineralogy and phase distribution of OPC. Another approach than sorption, assuming that co-precipitation on the surface of the cement phase dominates 'sorption', is proposed and discussed. A scoring system is introduced to assess the applicability of the proposed ICSMs. It is suggested that the thermodynamic sorption model is recommended for the sorption of ionic species and the surface co-precipitation model is recommended for the sorption of neutral species though the sorption model is still recommended to be used to model OPC-based systems. (author)

  9. Modelling Ni diffusion in bentonite using different sorption models

    International Nuclear Information System (INIS)

    Pfingsten, W.; Baeyens, B.; Bradbury, M.

    2010-01-01

    different modelling approaches a) an analytical solution with constant Kd using a constant Ni(II) concentration level at x = 0 (e.g. at the canister surface) and zero Ni(II) initial background concentration in the bentonite, b) a numerical 'constant K d approach' taking into account the initial Ni(II) background concentration in the bentonite pore water, and c) a reactive transport approach using the code MCOTAC in one-dimensional spatial geometry with an incorporated mechanistic sorption model which includes surface proto-lysis, surface complexation and cation exchange reactions. Charge balance is explicitly formulated for the surface complexation reactions. Selectivity coefficients and surface complexation data for Ni(II) were taken from Bradbury and Baeyens (2005); the related Fe(II) data were obtained from the Linear Free Energy Relationship (LFER) contained in the same publication. The Ni(II) breakthrough in the bentonite was calculated for different Ni(II) concentration levels with and without considering competition with Fe(II) on exchange and surface complexation sites for different Fe(II) concentrations in the bentonite pore water. The comparison allows the following observations to be made: for trace Ni(II) concentrations, the numerical 'constant K d approach' yield similar results to the reactive transport approach. For higher Ni(II) concentrations, the calculated Ni(II) breakthroughs differ from each other: the reactive transport approach yields an earlier breakthrough than the numerical 'constant K d approach' for a Ni concentration level of 10 -5 M. However, for a Ni(II) concentration level of 10 -4 M, the reactive transport approach yield a later but steeper breakthrough, reaching the maximum Ni(II) concentration level earlier than the numerical 'constant K d approach'. Fe(II) competition reactions could only be taken into account using the reactive transport approach. The results yield a general dependency of the Ni

  10. Computer codes for three dimensional mass transport with non-linear sorption

    International Nuclear Information System (INIS)

    Noy, D.J.

    1985-03-01

    The report describes the mathematical background and data input to finite element programs for three dimensional mass transport in a porous medium. The transport equations are developed and sorption processes are included in a general way so that non-linear equilibrium relations can be introduced. The programs are described and a guide given to the construction of the required input data sets. Concluding remarks indicate that the calculations require substantial computer resources and suggest that comprehensive preliminary analysis with lower dimensional codes would be important in the assessment of field data. (author)

  11. Mathematical modelling of the sorption isotherms of quince

    Directory of Open Access Journals (Sweden)

    Mitrevski Vangelce

    2017-01-01

    Full Text Available The moisture adsorption isotherms of quince were determined at four temperatures 15, 30, 45, and 60°C over a range of water activity from 0.110 to 0.920 using the standard static gravimetric method. The experimental data were fitted with generated three parameter sorption isotherm models on Mitrevski et al., and the referent Anderson model known in the scientific and engineering literature as Guggenheim- Anderson-de Boer model. In order to find which models give the best results, large number of numerical experiments was performed. After that, several statistical criteria for estimation and selection of the best sorption isotherm model was used. The performed statistical analysis shows that the generated three parameter model M11 gave the best fit to the sorption data of quince than the referent three parameter Anderson model.

  12. Nonlinear chemical sorption isotherms in the assessment of nuclear fuel waste disposal

    International Nuclear Information System (INIS)

    Walker, J.R.; LeNeveu, D.M.

    1987-01-01

    Radionuclides emplaced in an underground disposal vault can possibly migrate from the vault, and through the geosphere, to enter Man's environment. Chemical sorption is a primary mechanism for retarding this migration. The effects of nonlinear chemical sorption isotherms on radionuclide transport are discussed. A method is given by which nonlinear isotherms can be approximated by the linear sorption isotherm used in the vault submodel. The relevance of nonlinear isotherms to transport in the geosphere is discussed, and it is shown that the linear isotherm model is conservative for deep geologic disposal. 22 refs

  13. Sorption of biodegradation end products of nonylphenol polyethoxylates onto activated sludge.

    Science.gov (United States)

    Hung, Nguyen Viet; Tateda, Masafumi; Ike, Michihiko; Fujita, Masanori; Tsunoi, Shinji; Tanaka, Minoru

    2004-01-01

    Nonylphenol(NP), nonylphenoxy acetic acid (NP1EC), nonylphenol monoethoxy acetic acid (NP2EC), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) are biodegradation end products (BEPs) of nonionic surfactant nonylphenolpolyethoxylates (NPnEO). In this research, sorption of these compounds onto model activated sludge was characterized. Sorption equilibrium experiments showed that NP, NP1EO and NP2EO reached equilibrium in about 12 h, while equilibrium of NP1EC and NP2EC were reached earlier, in about 4 h. In sorption isotherm experiments, obtained equilibrium data at 28 degrees C fitted well to Freundlich sorption model for all investigated compounds. For NP1EC, in addition to Freundlich, equilibrium data also fitted well to Langmuir model. Linear sorption model was also tried, and equilibrium data of all NP, NP1EO, NP2EO and NP2EC except NP1EC fitted well to this model. Calculated Freundlich coefficient (K(F)) and linear sorption coefficient (K(D)) showed that sorption capacity of the investigated compounds were in order NP > NP2EO > NP1EO > NP1EC approximately NP2EC. For NP, NP1EO and NP2EO, high values of calculated K(F) and K(D) indicated an easy uptake of these compounds from aqueous phase onto activated sludge. Whereas, NP1EC and NP2EC with low values of K(F) and K(D) absorbed weakly to activated sludge and tended to preferably remain in aqueous phase.

  14. Predicting sediment sorption coefficients for linear alkylbenzenesulfonate congeners from polyacrylate-water partition coefficients at different salinities.

    NARCIS (Netherlands)

    Rico Rico, A.; Droge, S.T.J.|info:eu-repo/dai/nl/304834017; Hermens, J.L.M.|info:eu-repo/dai/nl/069681384

    2010-01-01

    The effect of the molecular structure and the salinity on the sorption of the anionic surfactant linear alkylbenzenesulfonate (LAS) to marine sediment has been studied. The analysis of several individual LAS congeners in seawater and of one specific LAS congener at different dilutions of seawater

  15. Modeling Fission Product Sorption in Graphite Structures

    International Nuclear Information System (INIS)

    Szlufarska, Izabela; Morgan, Dane; Allen, Todd

    2013-01-01

    The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high-temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products

  16. Modeling and Prediction of Soil Water Vapor Sorption Isotherms

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Tuller, Markus; Moldrup, Per

    2015-01-01

    Soil water vapor sorption isotherms describe the relationship between water activity (aw) and moisture content along adsorption and desorption paths. The isotherms are important for modeling numerous soil processes and are also used to estimate several soil (specific surface area, clay content.......93) for a wide range of soils; and (ii) develop and test regression models for estimating the isotherms from clay content. Preliminary results show reasonable fits of the majority of the investigated empirical and theoretical models to the measured data although some models were not capable to fit both sorption...... directions accurately. Evaluation of the developed prediction equations showed good estimation of the sorption/desorption isotherms for tested soils....

  17. Radionuclide sorption database for Swiss safety assessment

    International Nuclear Information System (INIS)

    McKinley, I.G.; Hadermann, J.

    1984-10-01

    Recommended sorption data for use in transport models for a Swiss High-Level Waste repository are presented. The models used in 'Project Gewaehr 1985' assume linear sorption isotherms and require elemental partition coefficient (Kd) data. On the basis of a literature search 'realistic' Kd data for 22 elements have been selected for weathered crystalline rock and sediments in contact with a reducing groundwater and also sediments with a less reducing groundwater. In an appendix sorption data for 28 elements on bentonite backfill are given. These data are supplemented with 'conservative' estimates taken to represent minimum reasonable values. Available data are discussed for each element clearly exhibiting (i) the large gaps in knowledge, (ii) their unbalanced distribution between different elements and, hence, (iii) the need for further experiments in the laboratory, the field and analogue studies. An overview of the theoretical concepts of sorption, experimental methodology and data interpretation is given in order to put the values into context. General problem areas are identified. (Auth.)

  18. A Sorption Hysteresis Model For Cellulosic Materials

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Damkilde, Lars

    2006-01-01

    The equilibrium concentration of adsorbed water in cellulosic materials is dependent on the history of the variations of vapor pressure in the ambient air, i.e. sorption hysteresis. Existing models to describe this phenomenon such as the independent domain theory have numerical drawbacks and....../or imply accounting for the entire history variations of every material point. This paper presents a sorption hysteresis model based on a state formulation and expressed in closed-form solutions, which makes it suitable for implementation into a numerical method....

  19. Kinetic and equilibrium study for the sorption of cadmium(II) ions from aqueous phase by eucalyptus bark

    International Nuclear Information System (INIS)

    Ghodbane, Ilhem; Nouri, Loubna; Hamdaoui, Oualid; Chiha, Mahdi

    2008-01-01

    The efficiency of eucalyptus bark as a low cost sorbent for removing cadmium ions from aqueous solution has been investigated in batch mode. The equilibrium data could be well described by the Langmuir isotherm but a worse fit was obtained by the Freundlich model. The five linearized forms of the Langmuir equation as well as the non-linear curve fitting analysis method were discussed. Results show that the non-linear method may be a better way to obtain the Langmuir parameters. Maximum cadmium uptake obtained at a temperature of 20 deg. C was 14.53 mg g -1 . The influence of temperature on the sorption isotherms of cadmium has been also studied. The monolayer sorption capacity increased from 14.53 to 16.47 when the temperature was raised from 20 to 50 deg. C. The ΔG o values were negative, which indicates that the sorption was spontaneous in nature. The effect of experimental parameters such as contact time, cadmium initial concentration, sorbent dose, temperature, solution initial pH, agitation speed, and ionic strength on the sorption kinetics of cadmium was investigated. Pseudo-second-order model was evaluated using the six linear forms as well as the non-linear curve fitting analysis method. Modeling of kinetic results shows that sorption process is best described by the pseudo-second-order model using the non-linear method. The pseudo-second-order model parameters were function of the initial concentration, the sorbent dose, the solution pH, the agitation speed, the temperature, and the ionic strength

  20. Sorption of fission nuclides on model milk components. II. Sorption of radiostrontium on hydroxyapatite in milk and whey

    International Nuclear Information System (INIS)

    Rosskopfova, O.; Kopunec, R.; Matel, L.; Macasek, F.

    1999-01-01

    In this work the whey was chosen as a model solution of liquid phase for sorption study of strontium on hydroxyapatite. The whey was obtained using two methods - ultracentrifugation and precipitation of casein. The sorption was studied at a different pH and at a different concentration of calcium. The sorption of strontium on hydroxyapatite from milk was studied, too. (authors)

  1. Development of a Self-Consistent Model of Plutonium Sorption: Quantification of Sorption Enthalpy and Ligand-Promoted Dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Brian [Clemson Univ., SC (United States); Kaplan, Daniel I [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Arai, Yuji [Univ. of Illinois, Urbana-Champaign, IL (United States); Becker, Udo [Univ. of Michigan, Ann Arbor, MI (United States); Ewing, Rod [Stanford Univ., CA (United States)

    2016-12-29

    This university lead SBR project is a collaboration lead by Dr. Brian Powell (Clemson University) with co-principal investigators Dan Kaplan (Savannah River National Laboratory), Yuji Arai (presently at the University of Illinois), Udo Becker (U of Michigan) and Rod Ewing (presently at Stanford University). Hypothesis: The underlying hypothesis of this work is that strong interactions of plutonium with mineral surfaces are due to formation of inner sphere complexes with a limited number of high-energy surface sites, which results in sorption hysteresis where Pu(IV) is the predominant sorbed oxidation state. The energetic favorability of the Pu(IV) surface complex is strongly influenced by positive sorption entropies, which are mechanistically driven by displacement of solvating water molecules from the actinide and mineral surface during sorption. Objectives: The overarching objective of this work is to examine Pu(IV) and Pu(V) sorption to pure metal (oxyhydr)oxide minerals and sediments using variable temperature batch sorption, X-ray absorption spectroscopy, electron microscopy, and quantum-mechanical and empirical-potential calculations. The data will be compiled into a self-consistent surface complexation model. The novelty of this effort lies largely in the manner the information from these measurements and calculations will be combined into a model that will be used to evaluate the thermodynamics of plutonium sorption reactions as well as predict sorption of plutonium to sediments from DOE sites using a component additivity approach.

  2. Mathematical Modeling of Moisture Sorption Isotherms and Determination of Isosteric Heats of Sorption of Ziziphus Leaves

    Directory of Open Access Journals (Sweden)

    Amel Saad

    2014-01-01

    Full Text Available Desorption and adsorption equilibrium moisture isotherms of Ziziphus spina-christi leaves were determined using the gravimetric-static method at 30, 40, and 50°C for water activity (aw ranging from 0.057 to 0.898. At a given aw, the results show that the moisture content decreases with increasing temperature. A hysteresis effect was observed. The experimental data of sorption were fitted by eight models (GAB, BET, Henderson-Thompson, modified-Chung Pfost, Halsey, Oswin, Peleg, and Adam and Shove. After evaluating the models according to several criteria, the Peleg and Oswin models were found to be the most suitable for describing the sorption curves. The net isosteric heats of desorption and adsorption of Ziziphus spina-christi leaves were calculated by applying the Clausius-Clapeyron equation to the sorption isotherms and an expression for predicting these thermodynamic properties was given.

  3. Prediction of metal sorption in soils

    International Nuclear Information System (INIS)

    Westrich, Henry R.; Anderson, Harold L. Jr.; Arthur, Sara E.; Brady, Patrick V.; Cygan, Randall T.; Liang, Jianjie; Zhang, Pengchu; Yee, N.

    2000-01-01

    Radionuclide transport in soils and groundwaters is routinely calculated in performance assessment (PA) codes using simplified conceptual models for radionuclide sorption, such as the K D approach for linear and reversible sorption. Model inaccuracies are typically addressed by adding layers of conservativeness (e.g., very low K D 's), and often result in failed transport predictions or substantial increases in site cleanup costs. Realistic assessments of radionuclide transport over a wide range of environmental conditions can proceed only from accurate, mechanistic models of the sorption process. They have focused on the sorption mechanisms and partition coefficients for Cs + , Sr 2+ and Ba 2+ (analogue for Ra 2+ ) onto iron oxides and clay minerals using an integrated approach that includes computer simulations, sorption/desorption measurements, and synchrotron analyses of metal sorbed substrates under geochemically realistic conditions. Sorption of Ba 2+ and Sr 2+ onto smectite is strong, pH-independent, and fully reversible, suggesting that cation exchange at the interlayer basal sites controls the sorption process. Sr 2+ sorbs weakly onto geothite and quartz, and is pH-dependent. Sr 2+ sorption onto a mixture of smectite and goethite, however, is pH- and concentration dependent. The adsorption capacity of montmorillonite is higher than that of goethite, which may be attributed to the high specific surface area and reaction site density of clays. The presence of goethite also appears to control the extent of metal desorption. In-situ, extended X-ray absorption fine structure (EXAFS) spectroscopic measurements for montmorillonite and goethite show that the first shell of adsorbed Ba 2+ is coordinated by 6 oxygens. The second adsorption shell, however, varies with the mineral surface coverage of adsorbed Ba 2+ and the mineral substrate. This suggests that Ba 2+ adsorption on mineral surfaces involves more than one mechanism and that the stability of sorbed

  4. Characterization of U(VI) Sorption-Desorption Processes and Model Upscaling

    International Nuclear Information System (INIS)

    Bai, Jing; Dong, Wenming; Ball, William P.

    2006-01-01

    The objectives of the overall collaborative EMSP effort (with which this project is associated) were to characterize sorption and desorption processes of U(VI) on pristine and contaminated Hanford sediments over a range of sediment facies and materials properties and to relate such characterization both to fundamental molecular-scale understanding and field-scale models of geochemistry and mass transfer. The research was intended to provide new insights on the mechanisms of U(VI) retardation at Hanford, and to allow the development of approaches by which laboratory-developed geochemical models could be upscaled for defensible field-scale predictions of uranium transport in the environment. Within this broader context, objectives of the JHU-based project were to test hypotheses regarding the coupled roles of adsorption and impermeable-zone diffusion in controlling the fate and transport of U(VI) species under conditions of comparatively short-term exposure. In particular, this work tested the following hypotheses: (1) the primary adsorption processes in the Hanford sediment over the pH range of 7 to 10 are surface complexation reactions of aqueous U(VI) hydroxycarbonate and carbonate complexes with amphoteric edge sites on detrital phyllosilicates in the silt/clay size fraction; (2) macroscopic adsorption intensity (at given aqueous conditions) is a function of mineral composition and aquatic chemistry; and (3) equilibrium sorption and desorption to apply in short-term, laboratory-spiked pristine sediments; and (4) interparticle diffusion can be fully understood in terms of a model that couples molecular diffusion of uranium species in the porewater with equilibrium sorption under the relevant aqueous conditions. The primary focus of the work was on developing and applying both models and experiments to test the applicability of ''local equilibrium'' assumptions in the modeling interpretation of sorption retarded interparticle diffusion, as relevant to processes of

  5. SITE-94. Adaptation of mechanistic sorption models for performance assessment calculations

    International Nuclear Information System (INIS)

    Arthur, R.C.

    1996-10-01

    Sorption is considered in most predictive models of radionuclide transport in geologic systems. Most models simulate the effects of sorption in terms of empirical parameters, which however can be criticized because the data are only strictly valid under the experimental conditions at which they were measured. An alternative is to adopt a more mechanistic modeling framework based on recent advances in understanding the electrical properties of oxide mineral-water interfaces. It has recently been proposed that these 'surface-complexation' models may be directly applicable to natural systems. A possible approach for adapting mechanistic sorption models for use in performance assessments, using this 'surface-film' concept, is described in this report. Surface-acidity parameters in the Generalized Two-Layer surface complexation model are combined with surface-complexation constants for Np(V) sorption ob hydrous ferric oxide to derive an analytical model enabling direct calculation of corresponding intrinsic distribution coefficients as a function of pH, and Ca 2+ , Cl - , and HCO 3 - concentrations. The surface film concept is then used to calculate whole-rock distribution coefficients for Np(V) sorption by altered granitic rocks coexisting with a hypothetical, oxidized Aespoe groundwater. The calculated results suggest that the distribution coefficients for Np adsorption on these rocks could range from 10 to 100 ml/g. Independent estimates of K d for Np sorption in similar systems, based on an extensive review of experimental data, are consistent, though slightly conservative, with respect to the calculated values. 31 refs

  6. GEOQUIMICO : an interactive tool for comparing sorption conceptual models (surface complexation modeling versus K[D])

    International Nuclear Information System (INIS)

    Hammond, Glenn E.; Cygan, Randall Timothy

    2007-01-01

    Within reactive geochemical transport, several conceptual models exist for simulating sorption processes in the subsurface. Historically, the K D approach has been the method of choice due to ease of implementation within a reactive transport model and straightforward comparison with experimental data. However, for modeling complex sorption phenomenon (e.g. sorption of radionuclides onto mineral surfaces), this approach does not systematically account for variations in location, time, or chemical conditions, and more sophisticated methods such as a surface complexation model (SCM) must be utilized. It is critical to determine which conceptual model to use; that is, when the material variation becomes important to regulatory decisions. The geochemical transport tool GEOQUIMICO has been developed to assist in this decision-making process. GEOQUIMICO provides a user-friendly framework for comparing the accuracy and performance of sorption conceptual models. The model currently supports the K D and SCM conceptual models. The code is written in the object-oriented Java programming language to facilitate model development and improve code portability. The basic theory underlying geochemical transport and the sorption conceptual models noted above is presented in this report. Explanations are provided of how these physicochemical processes are instrumented in GEOQUIMICO and a brief verification study comparing GEOQUIMICO results to data found in the literature is given

  7. New approach in modeling Cr(VI) sorption onto biomass from metal binary mixtures solutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang [College of Environmental Science and Engineering, Anhui Normal University, South Jiuhua Road, 189, 241002 Wuhu (China); Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Fiol, Núria [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Villaescusa, Isabel, E-mail: Isabel.Villaescusa@udg.edu [Chemical Engineering Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain); Poch, Jordi [Applied Mathematics Department, Escola Politècnica Superior, Universitat de Girona, Ma Aurèlia Capmany, 61, 17071 Girona (Spain)

    2016-01-15

    In the last decades Cr(VI) sorption equilibrium and kinetic studies have been carried out using several types of biomasses. However there are few researchers that consider all the simultaneous processes that take place during Cr(VI) sorption (i.e., sorption/reduction of Cr(VI) and simultaneous formation and binding of reduced Cr(III)) when formulating a model that describes the overall sorption process. On the other hand Cr(VI) scarcely exists alone in wastewaters, it is usually found in mixtures with divalent metals. Therefore, the simultaneous removal of Cr(VI) and divalent metals in binary mixtures and the interactive mechanism governing Cr(VI) elimination have gained more and more attention. In the present work, kinetics of Cr(VI) sorption onto exhausted coffee from Cr(VI)–Cu(II) binary mixtures has been studied in a stirred batch reactor. A model including Cr(VI) sorption and reduction, Cr(III) sorption and the effect of the presence of Cu(II) in these processes has been developed and validated. This study constitutes an important advance in modeling Cr(VI) sorption kinetics especially when chromium sorption is in part based on the sorbent capacity of reducing hexavalent chromium and a metal cation is present in the binary mixture. - Highlights: • A kinetic model including Cr(VI) reduction, Cr(VI) and Cr(III) sorption/desorption • Synergistic effect of Cu(II) on Cr(VI) elimination included in the modelModel validation by checking it against independent sets of data.

  8. New approach in modeling Cr(VI) sorption onto biomass from metal binary mixtures solutions

    International Nuclear Information System (INIS)

    Liu, Chang; Fiol, Núria; Villaescusa, Isabel; Poch, Jordi

    2016-01-01

    In the last decades Cr(VI) sorption equilibrium and kinetic studies have been carried out using several types of biomasses. However there are few researchers that consider all the simultaneous processes that take place during Cr(VI) sorption (i.e., sorption/reduction of Cr(VI) and simultaneous formation and binding of reduced Cr(III)) when formulating a model that describes the overall sorption process. On the other hand Cr(VI) scarcely exists alone in wastewaters, it is usually found in mixtures with divalent metals. Therefore, the simultaneous removal of Cr(VI) and divalent metals in binary mixtures and the interactive mechanism governing Cr(VI) elimination have gained more and more attention. In the present work, kinetics of Cr(VI) sorption onto exhausted coffee from Cr(VI)–Cu(II) binary mixtures has been studied in a stirred batch reactor. A model including Cr(VI) sorption and reduction, Cr(III) sorption and the effect of the presence of Cu(II) in these processes has been developed and validated. This study constitutes an important advance in modeling Cr(VI) sorption kinetics especially when chromium sorption is in part based on the sorbent capacity of reducing hexavalent chromium and a metal cation is present in the binary mixture. - Highlights: • A kinetic model including Cr(VI) reduction, Cr(VI) and Cr(III) sorption/desorption • Synergistic effect of Cu(II) on Cr(VI) elimination included in the modelModel validation by checking it against independent sets of data

  9. Validation of water sorption-based clay prediction models for calcareous soils

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Razzaghi, Fatemeh; Moosavi, Ali

    2017-01-01

    on prediction accuracy. The soils had clay content ranging from 9 to 61% and CaCO3 from 24 to 97%. The three water sorption models considered showed a reasonably fair prediction of the clay content from water sorption at 28% relative humidity (RMSE and ME values ranging from 10.6 to 12.1 and −8.1 to −4......Soil particle size distribution (PSD), particularly the active clay fraction, mediates soil engineering, agronomic and environmental functions. The tedious and costly nature of traditional methods of determining PSD prompted the development of water sorption-based models for determining the clay...... fraction. The applicability of such models to semi-arid soils with significant amounts of calcium carbonate and/or gypsum is unknown. The objective of this study was to validate three water sorption-based clay prediction models for 30 calcareous soils from Iran and identify the effect of CaCO3...

  10. Surface complexation modelling: Experiments on the sorption of nickel on quartz

    International Nuclear Information System (INIS)

    Puukko, E.; Hakanen, M.

    1995-10-01

    Assessing the safety of a final repository for nuclear wastes requires knowledge concerning the way in which the radionuclides released are retarded in the geosphere. The aim of the work is to aquire knowledge of empirical methods repeating the experiments on the sorption of nickel on quartz described in the reports published by the British Geological Survey (BGS). The experimental results were modelled with computer models at the Technical Research Centre of Finland (VTT Chemical Technology). The results showed that the experimental knowledge of the sorption of Ni on quartz have been acheved by repeating the experiments of BGS. Experiments made with the two quartz types, Min-U-Sil 5 (MUS) and Nilsiae, showed the difference in sorption of Ni in the low ionic strength solution (0.001 M NaNO 3 ). The sorption of Ni on MUS was higher than predicted by the Surface Complexation Model (SCM). The phenomenon was also observed by the BGS, and may be due to the different amounts of inpurities in the MUS and in the NLS. In other respects, the results of the sorption experiments fitted quite well with those predicted by the SCM model. (8 refs., 8 figs., 11 tabs.)

  11. Use of thermodynamic sorption models to derive radionuclide Kd values for performance assessment: Selected results and recommendations of the NEA sorption project

    Science.gov (United States)

    Ochs, M.; Davis, J.A.; Olin, M.; Payne, T.E.; Tweed, C.J.; Askarieh, M.M.; Altmann, S.

    2006-01-01

    For the safe final disposal and/or long-term storage of radioactive wastes, deep or near-surface underground repositories are being considered world-wide. A central safety feature is the prevention, or sufficient retardation, of radionuclide (RN) migration to the biosphere. To this end, radionuclide sorption is one of the most important processes. Decreasing the uncertainty in radionuclide sorption may contribute significantly to reducing the overall uncertainty of a performance assessment (PA). For PA, sorption is typically characterised by distribution coefficients (Kd values). The conditional nature of Kd requires different estimates of this parameter for each set of geochemical conditions of potential relevance in a RN's migration pathway. As it is not feasible to measure sorption for every set of conditions, the derivation of Kd for PA must rely on data derived from representative model systems. As a result, uncertainty in Kd is largely caused by the need to derive values for conditions not explicitly addressed in experiments. The recently concluded NEA Sorption Project [1] showed that thermodynamic sorption models (TSMs) are uniquely suited to derive K d as a function of conditions, because they allow a direct coupling of sorption with variable solution chemistry and mineralogy in a thermodynamic framework. The results of the project enable assessment of the suitability of various TSM approaches for PA-relevant applications as well as of the potential and limitations of TSMs to model RN sorption in complex systems. ?? by Oldenbourg Wissenschaftsverlag.

  12. Experimental studies of Cs, Sr, Ni, and Eu sorption on Na-illite and the modelling of Cs sorption

    International Nuclear Information System (INIS)

    Poinssot, C.; Baeyens, B.; Bradbury, M.H.

    1999-08-01

    A natural illite (illite du Puy) was purified and converted to the homo-ionic Na-form. The conditioned Na-illite was characterised in terms of its mineralogy, chemical inventory and physico-chemical properties. The structural formula was determined from energy dispersive spectroscopic analyses (SEM/TEM-EDS) and bulk chemistry measurements. A cation exchange capacity of 127 meq kg -1 was determined by the 22 Na isotope dilution method at neutral pH. The Na-CEC was also measured as a function of pH. The stability of Na-illite as a function of pH in the range between 3 and 6 was investigated. At low pH values partial dissolution of the illite occurs releasing the structural elements Al, Si, Mg, and K into solution. The presence of Ca and Sr in solution was interpreted as being due to desorption from cation exchange sites. All of these elements are also present at neutral pH but at considerably lower levels. Such effects cannot be avoided and must be considered in the interpretation of the sorption measurements. The main focus of the experimental work presented here is on the sorption behaviour of Cs, Sr, Ni and Eu on conditioned Na-illite as a function of NaClO 4 background electrolyte concentration (0.1 and 0.01 M), nuclide concentration and pH in the range between 3 and 11. Sorption edge data (R d versus pH) and sorption isotherms (quantity of nuclide sorbed versus equilibrium nuclide concentration) are presented for these four elements. Prior to beginning these experiments, sorption kinetics were measured. The broad based pool of sorption measurements generated from this work will provide the source data sets for subsequent modelling. So far only the Cs sorption measurements have been modelled. A two site cation exchange model was developed to describe the sorption of Cs over the whole range of experimental conditions. The two site types were termed 'frayed edge sites' (FES, high affinity/low capacity) and 'type II sites' (low affinity/high capacity). Selectivity

  13. Equilibrium sorption of cobalt, cesium, and strontium on Bandelier Tuff: analysis of alternative mathematical modeling

    International Nuclear Information System (INIS)

    Polzer, W.L.; Fuentes, H.R.; Essington, E.H.; Roensch, F.R.

    1985-01-01

    Sorption isotherms are derived from batch equilibrium data for cobalt, cesium and strontium on Bandelier Tuff. Experiments were conducted at an average temperature of 23 0 C and equilibrium was defined at 48 hours. The solute concentrations ranged from 0 to 500 mg/L. The radioactive isotopes 60 Co, 137 Cs, and 85 Sr were used to trace the sorption of the stable solutes. The Linear, Langmuir, Freundlich and a Modified Freundlich isotherm equations are evaluated. The Modified Freundlich isotherm equation is validated as a preferred general mathematical tool for representing the sorption of the three solutes. The empirical constants derived from the Modified Freundlich isotherm equation indicate that under dynamic flow conditions strontium will move most rapidly and cobalt least rapidly. On the other hand, chemical dispersion will be greatest for cesium and least for strontium. Hill Plots of the sorption data suggest that in the region of low saturation sorption of all three solutes is impeded by interactions among sorption sites; cobalt exhibits the greatest effect of interactions and strontium shows only a minimal effect. In the saturation region of 50% or more, sorption of cobalt is enhanced slightly by interactions among sorption sites whereas sorption of cesium and strontium appears to be independent of site interactions. 9 references, 4 figures, 2 tables

  14. Sorption of organic compounds to activated carbons. Evaluation of isotherm models

    NARCIS (Netherlands)

    Pikaar, I.; Koelmans, A.A.; Noort, van P.C.M.

    2006-01-01

    Sorption to 'hard carbon' (black carbon, coal, kerogen) in soils and sediments is of major importance for risk assessment of organic pollutants. We argue that activated carbon (AC) may be considered a model sorbent for hard carbon. Here, we evaluate six sorption models on a literature dataset for

  15. Performance of chromatographic systems to model soil-water sorption.

    Science.gov (United States)

    Hidalgo-Rodríguez, Marta; Fuguet, Elisabet; Ràfols, Clara; Rosés, Martí

    2012-08-24

    A systematic approach for evaluating the goodness of chromatographic systems to model the sorption of neutral organic compounds by soil from water is presented in this work. It is based on the examination of the three sources of error that determine the overall variance obtained when soil-water partition coefficients are correlated against chromatographic retention factors: the variance of the soil-water sorption data, the variance of the chromatographic data, and the variance attributed to the dissimilarity between the two systems. These contributions of variance are easily predicted through the characterization of the systems by the solvation parameter model. According to this method, several chromatographic systems besides the reference octanol-water partition system have been selected to test their performance in the emulation of soil-water sorption. The results from the experimental correlations agree with the predicted variances. The high-performance liquid chromatography system based on an immobilized artificial membrane and the micellar electrokinetic chromatography systems of sodium dodecylsulfate and sodium taurocholate provide the most precise correlation models. They have shown to predict well soil-water sorption coefficients of several tested herbicides. Octanol-water partitions and high-performance liquid chromatography measurements using C18 columns are less suited for the estimation of soil-water partition coefficients. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. A study of sorption mechanism onto cement hydrates by isotherm measurements

    International Nuclear Information System (INIS)

    Sugiyama, Daisuke; Fujita, Tomonari

    2003-01-01

    In the concept for TRU waste disposal in Japan, cement is a potential waste packaging and backfilling material and is expected to provide chemical containment. In particular, the sorption of radionuclides onto cement material, which controls the aqueous concentrations of elements in the porewater, is a very important parameter when considering the release of radionuclides from the near field of a repository. Many safety assessment calculations currently assume radionuclide retardation as linear sorption equilibrium and describe it with a distribution ratio (R d value). In this study, the sorption mechanism is discussed by measuring the sorption isotherm of caesium, strontium and thorium onto Ordinary Portland Cement (OPC) and Calcium Silicate Hydrate (C-S-H gel), to justify and support this assumption. In addition, the effect of competitive sorption between thorium and uranium and other groundwater ions is studied by examining sorption using a range of sodium chloride concentrations to simulate different groundwater ionic strengths. Based on the experimental results, we have showed that: Caesium and strontium sorb by substitution for Ca in C-S-H phases and the presence of some calcium sites with different ion-exchange log K values is suggested; Thorium would be fixed in a surface co-precipitation to form a solubility-limiting phase. The results of sorption experiments are reasonably well modelled by the ion-exchange model for caesium and strontium and the surface co-precipitation model for thorium, respectively. (author)

  17. Modeling coupled sorption and transformation of 17β-estradiol–17-sulfate in soil–water systems

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Xuelian; Shrestha, Suman L.; Casey, Francis X. M.; Hakk, Heldur; Fan, Zhaosheng

    2014-11-01

    Animal manure is the primary source of exogenous free estrogens in the environment, which are known endocrine-disrupting chemicals to disorder the reproduction system of organisms. Conjugated estrogens can act as precursors to free estrogens, which may increase the total estrogenicity in the environment. In this study, a comprehensive model was used to simultaneously simulate the coupled sorption and transformation of a sulfate estrogen conjugate, 17 beta-estradiol-17-sulfate (E2-17S), in various soil-water systems (non-sterile/sterile; topsoil/subsoil). The simulated processes included multiple transformation pathways (i.e. hydroxylation, hydrolysis, and oxidation) and mass transfer between the aqueous, reversibly sorbed, and irreversibly sorbed phases of all soils for E2-17S and its metabolites. The conceptual model was conceived based on a series of linear sorption and first-order transformation expressions. The model was inversely solved Using finite difference to estimate process parameters. A global optimization method was applied for the inverse analysis along with variable model restrictions to estimate 36 parameters. The model provided a satisfactory simultaneous fit (R-adj(2) = 0.93 and d = 0.87) of all the experimental data and reliable parameter estimates. This modeling study improved the understanding on fate and transport of estrogen conjugates under various soil-water conditions.

  18. Pedotransfer functions for isoproturon sorption on soils and vadose zone materials.

    Science.gov (United States)

    Moeys, Julien; Bergheaud, Valérie; Coquet, Yves

    2011-10-01

    Sorption coefficients (the linear K(D) or the non-linear K(F) and N(F)) are critical parameters in models of pesticide transport to groundwater or surface water. In this work, a dataset of isoproturon sorption coefficients and corresponding soil properties (264 K(D) and 55 K(F)) was compiled, and pedotransfer functions were built for predicting isoproturon sorption in soils and vadose zone materials. These were benchmarked against various other prediction methods. The results show that the organic carbon content (OC) and pH are the two main soil properties influencing isoproturon K(D) . The pedotransfer function is K(D) = 1.7822 + 0.0162 OC(1.5) - 0.1958 pH (K(D) in L kg(-1) and OC in g kg(-1)). For low-OC soils (OC isoproturon sorption in soils in unsampled locations should rely, whenever possible, and by order of preference, on (a) site- or soil-specific pedotransfer functions, (b) pedotransfer functions calibrated on a large dataset, (c) K(OC) values calculated on a large dataset or (d) K(OC) values taken from existing pesticide properties databases. Copyright © 2011 Society of Chemical Industry.

  19. Kinetic modeling of antimony(III) oxidation and sorption in soils.

    Science.gov (United States)

    Cai, Yongbing; Mi, Yuting; Zhang, Hua

    2016-10-05

    Kinetic batch and saturated column experiments were performed to study the oxidation, adsorption and transport of Sb(III) in two soils with contrasting properties. Kinetic and column experiment results clearly demonstrated the extensive oxidation of Sb(III) in soils, and this can in return influence the adsorption and transport of Sb. Both sorption capacity and kinetic oxidation rate were much higher in calcareous Huanjiang soil than in acid red Yingtan soil. The results indicate that soil serve as a catalyst in promoting oxidation of Sb(III) even under anaerobic conditions. A PHREEQC model with kinetic formulations was developed to simulate the oxidation, sorption and transport of Sb(III) in soils. The model successfully described Sb(III) oxidation and sorption data in kinetic batch experiment. It was less successful in simulating the reactive transport of Sb(III) in soil columns. Additional processes such as colloid facilitated transport need to be quantified and considered in the model. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Modelling Zn(II) sorption onto clayey sediments using a multi-site ion-exchange model

    International Nuclear Information System (INIS)

    Tertre, E.; Beaucaire, C.; Coreau, N.; Juery, A.

    2009-01-01

    In environmental studies, it is necessary to be able to predict the behaviour of contaminants in more or less complex physico-chemical contexts. The improvement of this prediction partly depends on establishing thermodynamic models that can describe the behaviour of these contaminants and, in particular, the sorption reactions on mineral surfaces. In this way, based on the mass action law, it is possible to use surface complexation models and ion exchange models. Therefore, the aim of this study is (i) to develop an ion-exchange model able to describe the sorption of transition metal onto pure clay minerals and (ii) to test the ability of this approach to predict the sorption of these elements onto natural materials containing clay minerals (i.e. soils/sediments) under various chemical conditions. This study is focused on the behaviour of Zn(II) in the presence of clayey sediments. Considering that clay minerals are cation exchangers containing multiple sorption sites, it is possible to interpret the sorption of Zn(II), as well as competitor cations, by ion-exchange equilibria with the clay minerals. This approach is applied with success to interpret the experimental data obtained previously in the Zn(II)-H + -Na + -montmorillonite system. The authors' research team has already studied the behaviour of Na + , K + , Ca 2+ and Mg 2+ versus pH in terms of ion exchange onto pure montmorillonite, leading to the development of a thermodynamic database including the exchange site concentrations associated with montmorillonite and the selectivity coefficients of Na + , K + , Ca 2+ , Mg 2+ , and Zn 2+ versus H + . In the present study, experimental isotherms of Zn(II) on two different sediments in batch reactors at different pH and ionic strengths, using NaCl and CaSO 4 as electrolytes are reported. Assuming clay minerals are the main ion-exchanging phases, it is possible to predict Zn(II) sorption onto sediments under different experimental conditions, using the previously

  1. Model Based Control of Moisture Sorption in a Historical Interior

    Directory of Open Access Journals (Sweden)

    P. Zítek

    2005-01-01

    Full Text Available This paper deals with a novel scheme for microclimate control in historical exhibition rooms, inhibiting moisture sorption phenomena that are inadmissible from the preventive conservation point of view. The impact of air humidity is the most significant harmful exposure for a great deal of the cultural heritage deposited in remote historical buildings. Leaving the interior temperature to run almost its spontaneous yearly cycle, the proposed non-linear model-based control protects exhibits from harmful variations in moisture content by compensating the temperature drifts with an adequate adjustment of the air humidity. Already implemented in a medieval interior since 1999, the proposed microclimate control has proved capable of permanently maintaining constant a desirable moisture content in organic or porous materials in the interior of a building. 

  2. Surface complexation modelling applied to the sorption of nickel on silica

    International Nuclear Information System (INIS)

    Olin, M.

    1995-10-01

    The modelling based on a mechanistic approach, of a sorption experiment is presented in the report. The system chosen for experiments (nickel + silica) is modelled by using literature values for some parameters, the remainder being fitted by existing experimental results. All calculations are performed by HYDRAQL, a model planned especially for surface complexation modelling. Allmost all the calculations are made by using the Triple-Layer Model (TLM) approach, which appeared to be sufficiently flexible for the silica system. The report includes a short description of mechanistic sorption models, input data, experimental results and modelling results (mostly graphical presentations). (13 refs., 40 figs., 4 tabs.)

  3. Kinetics and equilibrium modeling of uranium(VI) sorption by bituminous shale from aqueous solution

    International Nuclear Information System (INIS)

    Ortaboy, Sinem; Atun, Gülten

    2014-01-01

    Highlights: • Oil shales are sedimentary rocks containing a polymeric matter in a mineral matrix. • Sorption potential of bituminous shale (BS) for uranium recovery was investigated. • U(VI) sorption increased with decreasing pH and increasing temperature. • Kinetic data were analyzed based on single and two resistance diffusion models. • The results fit well to the McKay equation assuming film and intraparticle diffusion. - Abstract: Sorption of U(VI) onto a bituminous shale (BS) from a nuclear power plant project site in Black Sea region was investigated for potential risk assessment when it releases into the environment with contaminated ground and surface water. The sorption characteristics of the BS for U(VI) recovery were evaluated as a function of contact time, adsorbent dosage, initial concentration, pH and temperature. Kinetic results fit better with pseudo-second-order model rather than pseudo-first-order. The possibility of diffusion process was analyzed based on Weber–Morris intra-particle diffusion model. The McKay equation assuming film- and intraparticle diffusion better predicted the data than the Vermeulen approximation presuming surface diffusion. Equilibrium sorption data were modeled according to the Langmuir, Dubinin–Radushkevich (D–R) and Freundlich isotherm equations. Sorption capacity increased from 0.10 to 0.15 mmol g −1 in 298–318 K temperature range. FT-IR analysis and pH dependent sorption studies conducted in hydroxide and carbonate media revealed that U(VI) species were sorbed in uranyl and its hydroxo forms on the BS. Desorption studies showed that U(VI) leaching with Black Sea water was negligible from the loaded BS. The activation parameters (E a , ΔH ∗ and ΔG ∗ ) estimated from diffusion coefficients indicated the presence of an energy barrier in the sorption system. However, thermodynamic functions derived from sorption equilibrium constants showed that overall sorption process was spontaneous in nature

  4. Sorption of curium by silica colloids: Effect of humic acid

    International Nuclear Information System (INIS)

    Kar, Aishwarya Soumitra; Kumar, Sumit; Tomar, B.S.; Manchanda, V.K.

    2011-01-01

    Sorption of curium by silica colloids has been studied as a function of pH and ionic strength using 244 Cm as a tracer. The sorption was found to increase with increasing pH and reach a saturation value of ∼95% at pH beyond 5.3. The effect of humic acid on the sorption of 244 Cm onto silica was studied by changing the order of addition of the metal ion and humic acid. In general, in the presence of humic acid (2 mg/L), the sorption increased at lower pH (<5) while it decreased in the pH range 6.5-8 and above pH 8, the sorption was found to increase again. As curium forms strong complex with humic acid, its presence results in the enhancement of curium sorption at lower pH. At higher pH the humic acid present in the solution competes with the surface sites for curium thus decreasing the sorption. The decrease in the Cm sorption in presence of humic acid was found to be less when humic acid was added after the addition of curium. Linear additive model qualitatively reproduced the profile of the Cm(III) sorption by silica in presence of humic acid at least in the lower pH region, however it failed to yield quantitative agreement with the experimental results. The results of the present study evidenced the incorporation of Cm into the silica matrix.

  5. Thermodynamic Properties, Sorption Isotherms and Glass Transition Temperature of Cape Gooseberry (Physalis peruviana L.

    Directory of Open Access Journals (Sweden)

    Jessica López

    2014-01-01

    Full Text Available Adsorption and desorption isotherms of fresh and dried Cape gooseberry (Physalis peruviana L. were determined at three temperatures (20, 40 and 60 °C using a gravimetric technique. The data obtained were fitted to several models including Guggenheim-Anderson- De Boer (GAB, Brunauer-Emmett-Teller (BET, Henderson, Caurie, Smith, Oswin, Halsey and Iglesias-Chirife. A non-linear least square regression analysis was used to evaluate the models. The Iglesias-Chirife model fitted best the experimental data. Isosteric heat of sorption was also determined from the equilibrium sorption data using the Clausius-Clapeyron equation and was found to decrease exponentially with increasing moisture content. The enthalpy-entropy compensation theory was applied to the sorption isotherms and indicated an enthalpy-controlled sorption process. Glass transition temperature (Tg of Cape gooseberry was also determined by differential scanning calorimetry and modelled as a function of moisture content with the Gordon-Taylor, the Roos and the Khalloufi models, which proved to be excellent tools for predicting glass transition of Cape gooseberry.

  6. A new safety assessment model for shallow land burial of LLW based on multicomponent sorption theory

    International Nuclear Information System (INIS)

    Katoh, N.; Asano, T.; Tasaka, H.

    1984-01-01

    A new model on the radionuclide migration in underground environment is developed based on ''multicomponent sorption theory''. The model is capable of predicting the behaviors of the coexisting materials in soil-ground water system as ''multicomponent sorption phenomena'' and also predicting the radinuclide migration affected by the changes of concentrations of coexisting materials. The model is not a ''statistical model'' but a ''chemical model'' based on the ''ion exchange theory'' and ''adsorption theory''. Additionally, the model is a ''kinetic model'' capable of estimating the effect of ''rate of sorption'' on the radionuclide migration. The validity of the model was checked by the results of column experiments for sorption. Finally, sample calculations on the radionuclide migration in reference shallow land burial site were carried out for demonstration

  7. Retention/sorption and geochemical modelling

    Energy Technology Data Exchange (ETDEWEB)

    Arcos, D.; Grandia, F.; Domenech, C. [Enviros Spain, S.L., Barcelona (Spain); SCK-CEN, Mol (Belgium); Sellin, P. [SKB - Swedish Nuclear Fuel and Waste Management, SE, Stockholm (Sweden); Hunter, F.M.I.; Bate, F.; Heath, T.G.; Hoch, A. [Serco Assurance, Oxfordshire (United Kingdom); Werme, L.O. [SKB - Svensk Karnbranslehantering AB, Stockholm (Sweden); Bruggeman, C.; Maes, I.A.; Breynaert, E.; Vancluysen, J. [Leuven Katholieke Univ., Lab. for Colloid Chemistry (Belgium); Montavon, G.; Guo, Z. [Ecole des Mines, 44 - Nantes (France); Riebe, B.; Bunnenberg, C.; Meleshyn, A. [Leibniz Univ. Hannover, Zentrum fur Strahlenschutz und Radiookologie, Hannover (Germany); Dultz, S. [Leibniz Univ. Hannover, Institut fur Bodenkunde, Hannover (Germany)

    2007-07-01

    This session gathers 4 articles dealing with: the long-term geochemical evolution of the near field of a KBS-3 HLNW repository: insights from reactive transport modelling (D. Arcos, F. Grandia, C. Domenech, P. Sellin); the investigation of iron transport into bentonite from anaerobically corroding steel: a geochemical modelling study (F.M.I. Hunter, F. Bate, T.G. Heath, A. Hoch, L.O. Werme); SeO{sub 3}{sup 2-} adsorption on conditioned Na-illite: XAS spectroscopy, kinetics, surface complexation model and influence of compaction (C. Bruggeman, A. Maes, G. Montavon, E. Breynaert, Z. Guo, J. Vancluysen); the influence of temperature and gamma-irradiation on the anion sorption capacity of modified bentonites (B. Riebe, C. Bunnenberg, A. Meleshyn, S. Dultz)

  8. Sorption of agrochemical model compounds by sorbent materials containing beta-cyclodextrin.

    Science.gov (United States)

    Wilson, Lee D; Mohamed, Mohamed H; Guo, Rui; Pratt, Dawn Y; Kwon, Jae Hyuck; Mahmud, Sarker T

    2010-04-01

    Polymeric sorbent materials that incorporate beta-cyclodextrin (CD) have been prepared and their sorption behavior toward two model agrochemical contaminant compounds, p-nitrophenol (PNP) and methyl chloride examined. The sorption of PNP was studied in aqueous solution using ultraviolet-visible (UV-Vis) spectroscopy, whereas the sorption of methyl chloride from the gas phase was studied using a Langmuir adsorption method. The sorption results for PNP in solution were compared between granular activated carbon (GAC), modified GAC, CD copolymers, and CD-based mesoporous silica hybrid materials. Nitrogen porosimetry at 77 K was used to estimate the surface area and pore structure properties of the sorbent materials. The sorbents displayed variable surface areas as follows: copolymers (36.2-157 m(2)/g), CD-silica materials (307-906 m(2)/g), surface modified GAC (657 m(2)/g), and granular activated carbon (approximately 10(3) m(2)/g). The sorption capacities for PNP and methyl chloride with the different sorbents are listed in descending order as follows: GAC > copolymers > surface modified GAC > CD-silica hybrid materials. In general, the differences in the sorption properties of the sorbents were related to the following: (i) surface area of the sorbent, (ii) CD content and accessibility, (iii) and the chemical nature of the sorbent material.

  9. Surface complexation modelling: Experiments on sorption of nickel on quartz, goethite and kaolinite and preliminary tests on sorption of thorium on quartz

    Energy Technology Data Exchange (ETDEWEB)

    Puukko, E.; Hakanen, M. [Univ. of Helsinki (Finland). Dept. of Chemistry. Lab. of Radiochemistry

    1997-09-01

    The aim of the work was to study the sorption behaviour of Ni on quartz, goethite and kaolinite at different pH levels and in different electrolyte solutions of different strength. In addition preliminary experiments were made to study the sorption of thorium on quartz. The MUS quartz and Nilsiae quartz were analysed for MnO{sub 2} by neutron activation analysis (NAA) and the experimental results were modelled with the HYDRAQL computer model. 9 refs.

  10. Europium sorption on zirconia at elevated temperatures: experimental study and modeling

    International Nuclear Information System (INIS)

    Eglizaud, N.; Catalette, H.

    2005-01-01

    Full text of publication follows: Direct disposal of spent nuclear fuel in deep underground repository is being considered by several countries. The waste package maintains an elevated temperature for thousands of years. As sorption is one of the main phenomenon limiting the dispersion of radionuclides in the environment, it has to be studied at elevated temperatures. Zirconia is an oxide produced by cladding oxidation which is suspected in the near field of a nuclear repository. It then could possibly be in contact with waste elements as Europium (III), the sorption of which is therefore studied on zirconia. Experiments were performed by the batch method at a solid/liquid ratio of 10 g.L-1. The sorption edges were recorded in the pH-range from 2 to 10 at 2.10 -5 mol.L -1 Eu(NO 3 ) 3 (I = 0.1 mol.L -1 KNO 3 ). An over-pressure device in an autoclave with an incorporated filtering system allowed the experiments, carbonate free, at 25 deg. C, 50 deg. C, 80 deg. C, 120 deg. C and 150 deg. C and in situ pH measurements. Filtrates were analyzed by the ICP-AES method. Sorption isotherms show an increase in the sorption phenomenon when the temperature raises. The half sorption pH decreases from 7 at 25 deg. C to 3,6 at 150 deg. C. The distribution coefficients that were obtained at elevated temperatures enriched the databases of integrated performance assessment codes. Raw data were modeled with the surface complexation theory using the double layer model (DLM). Several possible surface complexes were examined and discussed, taking into account aqueous hydrolyzed and precipitated species of Europium. A good agreement between experimental values and modeled isotherms was found at all studied temperatures. Results were consistent with a bidentate complex formed by Europium (III) on the zirconia surface. Associated formation constants were then determined with the geochemical computer code CHESS. (authors)

  11. Soil Cd, Cr, Cu, Ni, Pb and Zn sorption and retention models using SVM: Variable selection and competitive model.

    Science.gov (United States)

    González Costa, J J; Reigosa, M J; Matías, J M; Covelo, E F

    2017-09-01

    The aim of this study was to model the sorption and retention of Cd, Cu, Ni, Pb and Zn in soils. To that extent, the sorption and retention of these metals were studied and the soil characterization was performed separately. Multiple stepwise regression was used to produce multivariate models with linear techniques and with support vector machines, all of which included 15 explanatory variables characterizing soils. When the R-squared values are represented, two different groups are noticed. Cr, Cu and Pb sorption and retention show a higher R-squared; the most explanatory variables being humified organic matter, Al oxides and, in some cases, cation-exchange capacity (CEC). The other group of metals (Cd, Ni and Zn) shows a lower R-squared, and clays are the most explanatory variables, including a percentage of vermiculite and slime. In some cases, quartz, plagioclase or hematite percentages also show some explanatory capacity. Support Vector Machine (SVM) regression shows that the different models are not as regular as in multiple regression in terms of number of variables, the regression for nickel adsorption being the one with the highest number of variables in its optimal model. On the other hand, there are cases where the most explanatory variables are the same for two metals, as it happens with Cd and Cr adsorption. A similar adsorption mechanism is thus postulated. These patterns of the introduction of variables in the model allow us to create explainability sequences. Those which are the most similar to the selectivity sequences obtained by Covelo (2005) are Mn oxides in multiple regression and change capacity in SVM. Among all the variables, the only one that is explanatory for all the metals after applying the maximum parsimony principle is the percentage of sand in the retention process. In the competitive model arising from the aforementioned sequences, the most intense competitiveness for the adsorption and retention of different metals appears between

  12. A sorption model for alkalis in cement-based materials - Correlations with solubility and electrokinetic properties

    Science.gov (United States)

    Henocq, Pierre

    2017-06-01

    In cement-based materials, radionuclide uptake is mainly controlled by calcium silicate hydrates (C-S-H). This work presents an approach for defining a unique set of parameters of a surface complexation model describing the sorption behavior of alkali ions on the C-S-H surface. Alkali sorption processes are modeled using the CD-MUSIC function integrated in the Phreeqc V.3.0.6 geochemical code. Parameterization of the model was performed based on (1) retention, (2) zeta potential, and (3) solubility experimental data from the literature. This paper shows an application of this model to sodium ions. It was shown that retention, i.e. surface interactions, and solubility are closely related, and a consistent sorption model for radionuclides in cement-based materials requires a coupled surface interaction/chemical equilibrium model. In case of C-S-H with low calcium-to-silicon ratios, sorption of sodium ions on the C-S-H surface strongly influences the chemical equilibrium of the C-S-H + NaCl system by significantly increasing the aqueous calcium concentration. The close relationship between sorption and chemical equilibrium was successfully illustrated by modeling the effect of the solid-to-liquid ratio on the calcium content in solution in the case of C-S-H + NaCl systems.

  13. Sorption by cation exchange

    International Nuclear Information System (INIS)

    Bradbury, M.H.; Baeyens, B.

    1994-04-01

    A procedure for introducing exchange into geochemical/surface complexation codes is described. Beginning with selectivity coefficients, K c , defined in terms of equivalent fractional ion occupancies, a general expression for the molar based exchange code input parameters, K ex , is derived. In natural systems the uptake of nuclides onto complex sorbents often occurs by more than one mechanism. The incorporation of cation exchange and surface complexation into a geochemical code therefore enables sorption by both mechanisms to be calculated simultaneously. The code and model concepts are tested against sets of experimental data from widely different sorption studies. A proposal is made to set up a data base of selectivity coefficients. Such a data base would form part of a more general one consisting of sorption mechanism specific parameters to be used in conjunction with geochemical/sorption codes to model and predict sorption. (author) 6 figs., 6 tabs., 26 refs

  14. Influence of soil properties on vapor-phase sorption of trichloroethylene

    International Nuclear Information System (INIS)

    Bekele, Dawit N.; Naidu, Ravi; Chadalavada, Sreenivasulu

    2016-01-01

    Highlights: • Vapor intrusion is a major exposure pathway for volatile hydrocarbons. • Certainty in transport processes enhances vapor intrusion model precision. • Detailed understanding of vadose zone vapor transport processes save resources. • Vapor sorption near-steady-state conditions at sites may take months or years. • Type of clay fractions equitably affects sorption of trichloroethylene vapor. - Abstract: Current practices in health risk assessment from vapor intrusion (VI) using mathematical models are based on assumptions that the subsurface sorption equilibrium is attained. The time required for sorption to reach near-steady-state conditions at sites may take months or years to achieve. This study investigated the vapor phase attenuation of trichloroethylene (TCE) in five soils varying widely in clay and organic matter content using repacked columns. The primary indicators of TCE sorption were vapor retardation rate (R_t), the time required for the TCE vapor to pass through the soil column, and specific volume of retention (V_R), and total volume of TCE retained in soil. Results show TCE vapor retardation is mainly due to the rapid partitioning of the compound to SOM. However, the specific volume of retention of clayey soils with secondary mineral particles was higher. Linear regression analyses of the SOM and clay fraction with V_R show that a unit increase in clay fraction results in higher sorption of TCE (V_R) than the SOM. However, partitioning of TCE vapor was not consistent with the samples' surface areas but was mainly a function of the type of secondary minerals present in soils.

  15. Influence of soil properties on vapor-phase sorption of trichloroethylene

    Energy Technology Data Exchange (ETDEWEB)

    Bekele, Dawit N. [Global Center for Environmental Remediation, University of Newcastle, Callaghan, NSW 2308 (Australia); CRC for Contamination Assessment & Remediation of the Environment, Building X (Environmental Sciences Building), University of South Australia, Mawson Lakes, SA 5095 (Australia); Naidu, Ravi, E-mail: Ravi.Naidu@newcastle.edu.au [Global Center for Environmental Remediation, University of Newcastle, Callaghan, NSW 2308 (Australia); CRC for Contamination Assessment & Remediation of the Environment, Building X (Environmental Sciences Building), University of South Australia, Mawson Lakes, SA 5095 (Australia); Chadalavada, Sreenivasulu [Global Center for Environmental Remediation, University of Newcastle, Callaghan, NSW 2308 (Australia); CRC for Contamination Assessment & Remediation of the Environment, Building X (Environmental Sciences Building), University of South Australia, Mawson Lakes, SA 5095 (Australia)

    2016-04-05

    Highlights: • Vapor intrusion is a major exposure pathway for volatile hydrocarbons. • Certainty in transport processes enhances vapor intrusion model precision. • Detailed understanding of vadose zone vapor transport processes save resources. • Vapor sorption near-steady-state conditions at sites may take months or years. • Type of clay fractions equitably affects sorption of trichloroethylene vapor. - Abstract: Current practices in health risk assessment from vapor intrusion (VI) using mathematical models are based on assumptions that the subsurface sorption equilibrium is attained. The time required for sorption to reach near-steady-state conditions at sites may take months or years to achieve. This study investigated the vapor phase attenuation of trichloroethylene (TCE) in five soils varying widely in clay and organic matter content using repacked columns. The primary indicators of TCE sorption were vapor retardation rate (R{sub t}), the time required for the TCE vapor to pass through the soil column, and specific volume of retention (V{sub R}), and total volume of TCE retained in soil. Results show TCE vapor retardation is mainly due to the rapid partitioning of the compound to SOM. However, the specific volume of retention of clayey soils with secondary mineral particles was higher. Linear regression analyses of the SOM and clay fraction with V{sub R} show that a unit increase in clay fraction results in higher sorption of TCE (V{sub R}) than the SOM. However, partitioning of TCE vapor was not consistent with the samples' surface areas but was mainly a function of the type of secondary minerals present in soils.

  16. Sorption behavior of nonylphenol (NP) on sewage-irrigated soil: Kinetic and thermodynamic studies

    International Nuclear Information System (INIS)

    Liao, Xiaoping; Zhang, Caixiang; Yao, Linlin; Li, Jiale; Liu, Min; Xu, Liang; Evalde, Mulindankaka

    2014-01-01

    The reuse of wastewater for irrigation of agricultural land is a well established resources management practice but has the disadvantage of inputting various forms of contaminants into the terrestrial environment including nonylphenol (NP), a well known endocrine disrupting substance. To elucidate the environmental fate and transport of NP, the sorption behavior on sewage-irrigated soil was studied by batch experiment. It was found that sorption processes of NP on different sorbents (soil, humic acid (HA) and silica) could be expressed well using two compartment pseudo first-order model, where both surface and intra-particle diffusion were probable rate-controlling processes. Linear model could better express the sorption of NP on soil, black carbon (BC) and mineral (e.g., SiO 2 ) except HA than Freundlich model. The large value of distribution coefficients of normalized organic carbon (K oc ) on soils indicated that NP was limited to migrate to deep soil. The higher desorption partition coefficient of NP on soil showed enhanced hysteresis. According to the experimental data, the calculated thermodynamic parameters implied that the sorption reaction on sewage-irrigation was spontaneous, exothermic and entropy decreasing process. The amount of soil organic matter (SOM) dominated the sorption capacity, whereas the sorption behavior of NP on soil showed no significant correlation with ionic strength. - Highlights: • Both surface and intra-particle diffusion were rate-controlling processes. • Soil composition influences the partition activity of NP. • Soil organic matter has dominated the sorption capacity of NP on soil. • NP molecule was limited to migrate to deep soil in sewage-irrigated area

  17. A FIXED BED SORPTION SYSTEM FOR DEFLUORIDATION OF GROUND WATER

    Directory of Open Access Journals (Sweden)

    Ayoob Sulaiman

    2009-06-01

    Full Text Available The presence of excess fluoride in ground water has become a global threat with as many as 200 million people affected in more than 35 countries in all the continents. Of late, there have been significant advances in the knowledge base regarding the effects of excess fluoride on human health. As a result, defluoridation of ground water is regarded as one of the key areas of attention among the universal water community triggering global research. This study describes the sorptive responses of a newly developed adsorbent, alumina cement granules (ALC, in its real-life application in fixed beds, for removing fluoride from the ground waters of a rural Indian village. ALC exhibited almost consistent scavenging capacity at various bed depths in column studies with an enhanced adsorption potential of 0.818 mg/g at a flow rate of 4 ml/min. The Thomas model was examined to describe the sorption process. The process design parameters of the column were obtained by linear regression of the model. In all the conditions examined, the Thomas model could consistently predict its characteristic parameters and describe the breakthrough sorption profiles in the whole range of sorption process.

  18. Evaluation of theoretical and empirical water vapor sorption isotherm models for soils

    Science.gov (United States)

    Arthur, Emmanuel; Tuller, Markus; Moldrup, Per; de Jonge, Lis W.

    2016-01-01

    The mathematical characterization of water vapor sorption isotherms of soils is crucial for modeling processes such as volatilization of pesticides and diffusive and convective water vapor transport. Although numerous physically based and empirical models were previously proposed to describe sorption isotherms of building materials, food, and other industrial products, knowledge about the applicability of these functions for soils is noticeably lacking. We present an evaluation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0.93 based on measured data of 207 soils with widely varying textures, organic carbon contents, and clay mineralogy. In addition, the potential applicability of the models for prediction of sorption isotherms from known clay content was investigated. While in general, all investigated models described measured adsorption and desorption isotherms reasonably well, distinct differences were observed between physical and empirical models and due to the different degrees of freedom of the model equations. There were also considerable differences in model performance for adsorption and desorption data. While regression analysis relating model parameters and clay content and subsequent model application for prediction of measured isotherms showed promise for the majority of investigated soils, for soils with distinct kaolinitic and smectitic clay mineralogy predicted isotherms did not closely match the measurements.

  19. Sorption behaviour of perfluoroalkyl substances in soils.

    Science.gov (United States)

    Milinovic, Jelena; Lacorte, Silvia; Vidal, Miquel; Rigol, Anna

    2015-04-01

    The sorption behaviour of three perfluoroalkyl substances (PFASs), perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutane sulfonic acid (PFBS), was studied in six soils with contrasting characteristics, especially in the organic carbon content. Sorption isotherms were obtained by equilibrating the soil samples with 0.01 mol L(-1) CaCl2 solutions spiked with increasing concentrations of the target PFAS. The sorption reversibility of PFASs was also tested for some of the samples. Liquid chromatography coupled to tandem mass spectrometry was used to quantify the target PFASs in the solutions. Both the Freundlich and linear models were appropriate to describe the sorption behaviour of PFASs in soils, and enabled us to derive solid-liquid distribution coefficients (Kd) for each compound in each soil. Kd values increased from 19 to 295 mL g(-1) for PFOS, from 2.2 to 38 mL g(-1) for PFOA and from 0.4 to 6.8 mL g(-1) for PFBS, and were positively correlated with the organic carbon content of the soil. KOC values obtained from the correlations were 710, 96 and 17 mL g(-1) for PFOS, PFOA and PFBS, respectively. Whereas Kd values decreased in the sequence PFOS>PFOA>PFBS, desorption yields were lower than 13% for PFOS, from 24 to 58% for PFOA, and from 32 to 60% for PFBS. This shows that the physicochemical characteristics of PFASs, basically their hydrophobicity, controlled their sorption behaviour in soils, with PFOS being the most irreversibly sorbed PFAS. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Detailed sorption characteristics of the anti-diabetic drug metformin and its transformation product guanylurea in agricultural soils.

    Science.gov (United States)

    Briones, Rowena M; Sarmah, Ajit K

    2018-07-15

    Detection of metformin, an antidiabetic drug and its transformation product guanylurea in various environmental matrices such as surface water and groundwater, coupled with their effects on aquatic organisms warrant an understanding of the compounds fate and behaviour in the environment. Batch studies were conducted with the aim of evaluating the sorption of these two emerging contaminants in six New Zealand agricultural soils of contrasting physico-chemical properties. Kinetic studies revealed that metformin and guanylurea sorption in Te Kowhai soil was very rapid initially achieving 90% sorption within the first 4 and 13h, respectively. Fit of several isotherm models to the measured batch sorption data showed that the hybrid models Langmuir-Freundlich and Redlich-Peterson best described the isotherms. Freundlich isotherm showed higher linearity for guanylurea (n F =0.58-0.93) in all soils compared to metformin (n F =0.25-0.71). A linear isotherm was fitted at environmentally relevant low concentrations (< 3mg/L) of target compounds and calculated values of sorption distribution coefficient (K d ) were in the range of 8.97 to 53.49L/kg for metformin and between 10.6 and 37.51L/kg for guanylurea. Sorption of both metformin and guanylurea was dependent on the soil characteristics, however, no generalisation could be made as to which had higher affinity to soils studied. Pearson's correlation and multiple regression analyses indicate that Si/Al (p=0.042) and clay (p=0.015) significantly influenced metformin K d values, whereas the soil's cation exchange capacity (p=0.024) is the single most significant factor determining guanylurea sorption in soils. It is likely that the type of minerals present in soils and its ion-exchange capacity could play an important role in metformin and guanylurea sorption, respectively. Copyright © 2018. Published by Elsevier B.V.

  1. Uranium(VI) sorption on iron oxides in Hanford Site sediment: Application of a surface complexation model

    International Nuclear Information System (INIS)

    Um, Wooyong; Serne, R. Jeffrey; Brown, Christopher F.; Rod, Kenton A.

    2008-01-01

    Sorption of U(VI) on Hanford fine sand (HFS) with varying Fe-oxide (especially ferrihydrite) contents showed that U(VI) sorption increased with the incremental addition of synthetic ferrihydrite into HFS, consistent with ferrihydrite being one of the most reactive U(VI) sorbents present in natural sediments. Surface complexation model (SCM) calculations for U(VI) sorption, using only U(VI) surface-reaction constants obtained from U(VI) sorption data on freshly synthesized ferrihydrite at different pHs, were similar to the measured U(VI) sorption results on pure synthetic ferrihydrite and on HFS with high contents of ferrihydrite (5 wt%) added. However, the SCM prediction using only U(VI) sorption reactions and constants for synthetic ferrihydrite overestimated U(VI) sorption on the natural HFS or HFS with addition of low amounts of added ferrihydrite (1 wt% added). Over-predicted U(VI) sorption was attributed to reduced reactivity of natural ferrihydrite present in Hanford Site sediments, compared to freshly prepared synthetic ferrihydrite. Even though the SCM general composite (GC) approach is considered to be a semi-quantitative estimation technique for contaminant sorption, which requires systematic experimental data on the sorbent-sorbate system being studied to obtain credible SCM parameters, the general composite SCM model was still found to be a useful technique for describing U(VI) sorption on natural sediments. Based on U(VI) batch sorption results, two simple U(VI) monodentate surface species, SO U O 2 HCO 3 and SO U O 2 OH on ferrihydrite and phyllosillicate in HFS, respectively, can be successfully used to describe U(VI) sorption onto Hanford Site sediment contacting varying geochemical solutions

  2. Behaviour of selenate in soils: experimental approach and modeling of hysteresis of sorption/desorption

    International Nuclear Information System (INIS)

    Loffredo, N.

    2010-01-01

    In the context of future storage of nuclear material in deep geological layers, the transfer of selenium-79 from groundwater to biosphere through irrigation is one of the scenarios considered by the ANDRA (National Agency for Radioactive Waste Management). So, the soil would act as an interface between the geosphere and biosphere. Actually the model adopted to evaluate the element mobility in soil is based on a simple representation of its distribution between the quantity adsorbed on the soil and the amount remaining in the solution (KD model). Such distribution is considered as instantaneous, reversible and linear with the concentration of contamination. This model has some inadequacies with respect to selenium because this latter can be present in different redox states that control its mobility and whose transformation kinetics among states are poorly known (Se(-II), Se(0), Se(IV) and Se(VI)). In order to improve predictions on the mobility of selenium in soil, selenate (Se(VI)) - which is the most mobile form - has been used to study its interactions with respect to two different soils (soil B and soil R). A kinetic model, alternative to the K d model, has been developed to describe the evolution of stocks of Se(VI) in solution. This model considers that a fraction of selenium is associated with soil in a reversibly way (potentially mobile) and a portion of it is stabilized in soil (pseudo-irreversibly fixed). This model integrates on one hand, in the soil, kinetics of biotic and abiotic stabilization and on the other hand, in solution, a reduction kinetic. With the goal of acquiring the parameters of the models, various experiments using dialysis bags have been effectuated, both in batch and with open-flow reactors. The parameter acquisition has allowed kinetic and K d models to be compared in different realistic scenarios of contamination (chronic or sequential) of a surface soil with 79 Se(VI). In addition, the sorption mechanisms of Se(VI) have been

  3. Three-parameter modeling of the soil sorption of acetanilide and triazine herbicide derivatives.

    Science.gov (United States)

    Freitas, Mirlaine R; Matias, Stella V B G; Macedo, Renato L G; Freitas, Matheus P; Venturin, Nelson

    2014-02-01

    Herbicides have widely variable toxicity and many of them are persistent soil contaminants. Acetanilide and triazine family of herbicides have widespread use, but increasing interest for the development of new herbicides has been rising to increase their effectiveness and to diminish environmental hazard. The environmental risk of new herbicides can be accessed by estimating their soil sorption (logKoc), which is usually correlated to the octanol/water partition coefficient (logKow). However, earlier findings have shown that this correlation is not valid for some acetanilide and triazine herbicides. Thus, easily accessible quantitative structure-property relationship models are required to predict logKoc of analogues of the these compounds. Octanol/water partition coefficient, molecular weight and volume were calculated and then regressed against logKoc for two series of acetanilide and triazine herbicides using multiple linear regression, resulting in predictive and validated models.

  4. A kinetic approach to model sorption dynamics of radionuclides in soils: from desire to operational application?

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Garin, A.; Garcia-Sanchez, L.; Coppin, F. [Institut de Radioprotection et de Surete Nucleaire (France); Krimissa, M. [Electricite de France (France)

    2014-07-01

    The understanding of radionuclides (RN) behaviour and subsequent fluxes in the soil/solution/plant system is still a challenging question for realistic short, medium or long term risk assessments. Several years of researches have been devoted to improve the modeling of radionuclides migration in soils and their transfer to other compartments of the biosphere (eg. plants), as well as to constitute databases of model parameters (eg. distribution coefficient (K{sub d})). These works contributed to define, and then to extend, the domain of applicability of radioecological models, but they also helped to identify gaps and ways to improve them. However, these improvements have not been fully taken into account. Within this framework, the evolution of RN chemical speciation in time (often described as aging) was specifically addressed, as it control RN retention properties and bioavailability. Regarding soluble and RN solid speciation in soils, such processes generally lead to a shift from low to high K{sub d} values. Common explanations consist in the transfer of sorbed RN to non-(or less) exchangeable solid species, or in the lixiviation of the most available radionuclide fraction, both decreasing the reversibly sorbed RN fraction. Kinetics studies have examined such changes in K{sub d} value with time and various models have been proposed to fit the different evolutions. Among them, an empirical three-box model is often used to describe the kinetics of RN sorption when RN mostly occurs in the soil solution as a free ion (eg. Cs and Sr). This model assumes that the radionuclide may be sorbed either as a labile fraction, defining an exchangeable K{sub d}-like liquid/solid distribution, or sorbed as a less or non-exchangeable fraction. The last is estimated through its corresponding sorption and desorption rate constants, which describes a pseudo-first order reaction. Modeling of sorption dynamic is a way to link K{sub d} values derived from field-contaminated soils to

  5. Sorption of Atrazine in Tropical Soil by Biochar Prepared from Cassava Waste

    Directory of Open Access Journals (Sweden)

    Hui Deng

    2014-09-01

    Full Text Available Biochar (BC is a carbonaceous and porous product generated from the incomplete combustion of biomass and has been recognized as an efficient adsorbent. This study evaluated the ability of BC to sorb atrazine pesticide in tropical soil, and explored potential environmental values of BC on mitigating organic micro-pollutants. BC was produced from cassava waste via pyrolyzation under oxygen-limiting conditions at 350, 550, and 750 °C (MS350, MS550, and MS750, respectively. Three biochars were characterized and investigated as sorbents for the removal atrazine from tropical soil. BC pyrolyzed at higher temperatures more quickly reached equilibrium. The pseudo-second-order model perfectly simulated the sorption kinetics for atrazine with the coefficients R2 above 0.996, and the sorption amount at equilibrium (qe was 0.016 mg/g for MS350, 0.025 mg/g for MS550 and 0.050 mg/g for MS750. The isotherms of MS350 displayed relatively linear behavior, whereas the sorption of atrazine on MS550 and MS750 followed a nonlinear isotherm. The sorption data were well described by the Freundlich model with logKF of 0.476 for MS350, 0.771 for MS550, 1.865 for MS750. A thermodynamic study indicated that the sorption of atrazine in BC-added soil was a spontaneous and endothermic process and was primarily controlled by physisorption. In addition, lower pH was conducive to the sorption of atrazine in BC-added soil.

  6. The influence of Fe(II) competition on the sorption and migration of Ni(II) in MX-80 bentonite

    International Nuclear Information System (INIS)

    Pfingsten, Wilfried; Bradbury, Mike; Baeyens, Bart

    2011-01-01

    Highlights: → We model the diffusion of Ni(II) through bentonite using different sorption models. → We examine sorption competition of Fe(II) and Ni(II) at different concentrations. → Ni(II) breakthrough is 15 times earlier with Fe(II) sorption competition. → Ni(II) sorption is non-linear and depends on the Fe(II) concentration levels. → Sorption competition is important and has to be modelled by reactive transport codes. - Abstract: The results from batch sorption experiments on montmorillonite systems have demonstrated that bivalent transition metals compete with one another for sorption sites. For safety analysis studies of high level radioactive waste repositories with compacted bentonite near fields, the importance of competitive sorption on the migration of radionuclides needs to be evaluated. Under reducing conditions, the bentonite porewater chosen has a Fe(II) concentration of ∼5.3 x 10 -5 M through saturation with siderite. The purpose of this paper is to assess the influence of such high Fe(II) concentrations on the transport of Ni(II) through compacted bentonite, Ni(II) was chosen as an example of a bivalent transition metal. The one-dimensional calculations were carried out at different Ni(II) equilibrium concentrations at the boundary (Ni(II) EQBM ) with the reactive transport code MCOTAC incorporating the two site protolysis non electrostatic surface complexation/cation exchange sorption model, MCOTAC-sorb. At a Ni(II) EQBM level of 10 -7 M without Fe(II) competition, the reactive transport calculations using a constant K d approach and the MCOTAC-sorb calculation yielded the same breakthrough curves. At higher Ni(II) EQBM (10 -5 M), the model calculations with MCOTAC-sorb indicated a breakthrough which was shifted to later times by a factor of ∼5 compared with the use of the constant K d approach. When sorption competition was included in the calculations, the magnitude of the influence depended on the sorption characteristics of the

  7. Sorption isotherms: A review on physical bases, modeling and measurement

    Energy Technology Data Exchange (ETDEWEB)

    Limousin, G. [Atomic Energy Commission, Tracers Technology Laboratory, 38054 Grenoble Cedex (France) and Laboratoire d' etude des Transferts en Hydrologie et Environnement (CNRS-INPG-IRD-UJF), BP 53, 38041 Grenoble Cedex (France)]. E-mail: guillaumelimousin@yahoo.fr; Gaudet, J.-P. [Laboratoire d' etude des Transferts en Hydrologie et Environnement (CNRS-INPG-IRD-UJF), BP 53, 38041 Grenoble Cedex (France); Charlet, L. [Laboratoire de Geophysique Interne et Techtonophysique - CNRS-IRD-LCPC-UJF-Universite de Savoie, BP 53, 38041 Grenoble Cedex (France); Szenknect, S. [Atomic Energy Commission, Tracers Technology Laboratory, 38054 Grenoble Cedex (France); Barthes, V. [Atomic Energy Commission, Tracers Technology Laboratory, 38054 Grenoble Cedex (France); Krimissa, M. [Electricite de France, Division Recherche et Developpement, Laboratoire National d' Hydraulique et d' Environnement - P78, 6 quai Watier, 78401 Chatou (France)

    2007-02-15

    The retention (or release) of a liquid compound on a solid controls the mobility of many substances in the environment and has been quantified in terms of the 'sorption isotherm'. This paper does not review the different sorption mechanisms. It presents the physical bases underlying the definition of a sorption isotherm, different empirical or mechanistic models, and details several experimental methods to acquire a sorption isotherm. For appropriate measurements and interpretations of isotherm data, this review emphasizes 4 main points: (i) the adsorption (or desorption) isotherm does not provide automatically any information about the reactions involved in the sorption phenomenon. So, mechanistic interpretations must be carefully verified. (ii) Among studies, the range of reaction times is extremely wide and this can lead to misinterpretations regarding the irreversibility of the reaction: a pseudo-hysteresis of the release compared with the retention is often observed. The comparison between the mean characteristic time of the reaction and the mean residence time of the mobile phase in the natural system allows knowing if the studied retention/release phenomenon should be considered as an instantaneous reversible, almost irreversible phenomenon, or if reaction kinetics must be taken into account. (iii) When the concentration of the retained substance is low enough, the composition of the bulk solution remains constant and a single-species isotherm is often sufficient, although it remains strongly dependent on the background medium. At higher concentrations, sorption may be driven by the competition between several species that affect the composition of the bulk solution. (iv) The measurement method has a great influence. Particularly, the background ionic medium, the solid/solution ratio and the use of flow-through or closed reactor are of major importance. The chosen method should balance easy-to-use features and representativity of the studied

  8. Phosphorus sorption on marine carbonate sediment: phosphonate as model organic compounds.

    Science.gov (United States)

    Huang, Xiao-Lan; Zhang, Jia-Zhong

    2011-11-01

    Organophosphonate, characterized by the presence of a stable, covalent, carbon to phosphorus (C-P) bond, is a group of synthetic or biogenic organophosphorus compounds. The fate of these organic phosphorus compounds in the environment is not well studied. This study presents the first investigation on the sorption of phosphorus (P) in the presence of two model phosphonate compounds, 2-aminothylphosphonoic acid (2-AEP) and phosphonoformic acid (PFA), on marine carbonate sediments. In contrast to other organic P compounds, no significant inorganic phosphate exchange was observed in seawater. P was found to adsorb on the sediment only in the presence of PFA, not 2-AEP. This indicated that sorption of P from phosphonate on marine sediment was compound specific. Compared with inorganic phosphate sorption on the same sediments, P sorption from organic phosphorus is much less in the marine environment. Further study is needed to understand the potential role of the organophosphonate compounds in biogeochemical cycle of phosphorus in the environment. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Effects of oil dispersant on solubilization, sorption and desorption of polycyclic aromatic hydrocarbons in sediment–seawater systems

    International Nuclear Information System (INIS)

    Zhao, Xiao; Gong, Yanyan; O’Reilly, S.E.; Zhao, Dongye

    2015-01-01

    Highlights: • Oil dispersant enhances solubilization of PAHs more effectively than surfactants. • Dispersant and dispersed oil enhance sediment sorption of PAHs and induce hysteresis. • Partitioning to sediment-sorbed dispersant is the mechanism for enhanced PAH uptake. • Dual-mode models well simulate dispersant-facilitated sorption of PAHs on sediment. • Deepwater conditions reduce solubilization of PAHs and lessen dispersant effects. - Abstract: This work investigated effects of a prototype oil dispersant on solubilization, sorption and desorption of three model PAHs in sediment–seawater systems. Increasing dispersant dosage linearly enhanced solubility for all PAHs. Conversely, the dispersant enhanced the sediment uptake of the PAHs, and induced significant desorption hysteresis. Such contrasting effects (adsolubilization vs. solubilization) of dispersant were found dependent of the dispersant concentration and PAH hydrophobicity. The dual-mode models adequately simulated the sorption kinetics and isotherms, and quantified dispersant-enhanced PAH uptake. Sorption of naphthalene and 1-methylnaphthalene by sediment positively correlated with uptake of the dispersant, while sorption of pyrene dropped sharply when the dispersant exceeded its critical micelle concentration (CMC). The deepwater conditions diminished the dispersant effects on solubilization, but enhanced uptake of the PAHs, albeit sorption of the dispersant was lowered. The information may aid in understanding roles of dispersants on distribution, fate and transport of petroleum PAHs in marine systems

  10. Sorption of neptunium(V) on opalinus clay under aerobic/anaerobic conditions

    International Nuclear Information System (INIS)

    Froehlich, D.R.; Amayri, S.; Drebert, J.; Reich, T.

    2011-01-01

    The interaction between neptunium(V) and a natural argillaceous rock (Opalinus Clay (OPA), Mont Terri, Switzerland) has been investigated in batch sorption experiments by varying pH (6-10), Np(V) concentration (10 -12 -10 -4 M), solid-to-liquid ratio (2-20 g/L), and partial pressure of CO 2 (10 -3.5 and 10 -2.3 atm) under aerobic/anaerobic conditions in saturated calcite solution. All batch experiments were carried out using well characterized aerobic and anaerobic dry powders of OPA. The results show a great influence of pH on Np(V) sorption. Under aerobic conditions sorption increases with increasing pH until maximum sorption is reached between pH 8-9. At pH > 9 sorption decreases due to the formation of negatively charged Np(V)-carbonate complexes. By increasing p CO 2 from 10 -3.5 to 10 -2.3 atm, the sorption edge is shifted ∼ 0.5 units to lower pH values. Under anaerobic conditions stronger sorption of 8 x 10 -6 M Np(V) was found, possibly due to partial reduction of Np(V) to Np(IV). The sorption of 8 x 10 -6 M Np(V) under aerobic conditions at pH 8.2 in saturated calcite solution increases continuously with increasing solid-to-liquid ratio of OPA in the range of 2-20 g/L with a constant K d value of 126 ± 13 L/kg. The sorption isotherm was measured over seven orders of magnitude in Np(V) concentration using 239 Np as tracer. The sorption isotherm could be divided in a part of linear sorption behaviour between 10 -13 -10 -9 M Np(V) and non-linear behaviour in the range of 10 -9 -10 -4 M Np(V). (orig.)

  11. Predicting the uptake of Cs, Co, Ni, Eu, Th and U on argillaceous rocks using sorption models for illite

    International Nuclear Information System (INIS)

    Marques Fernandes, Maria; Vér, Nóra; Baeyens, Bart

    2015-01-01

    Highlights: • Contaminant retention in argillaceous rocks controlled by sorption on clay minerals. • Cs, Ni, Co, Eu, Th and UO 2 sorption isotherm measurements on Boda and Opalinus Clay. • Boda and Opalinus Clay exhibit different mineralogies and porewater compositions. • Blind predictions using quasi-mechanistic sorption models developed for illite. • Good agreement between measurements and blind predictions. - Abstract: Reliable predictions of radiocontaminant migration are a requirement for the establishment of radioactive waste repositories. Parametrization of the necessary sorption models seems to be, however, extremely challenging given the multi-mineralic composition of the lithosphere. In this study it is shown for two argillaceous rocks – Boda and Opalinus Clay relevant for the Hungarian and Swiss repository concepts, respectively – that this task can be substantially simplified by taking into account only the most sorptive mineral fraction, namely the 2:1 clay minerals illite and illite/smectite mixed layers. Two different models were required to blind predict the sorption isotherms of Cs, Co, Ni, Eu, Th and UO 2 measured on the two clay rock samples in a synthetic porewater. Cs sorption was modelled with the generalised Cs (GCs) sorption model and the sorption of the other cations with the 2site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) model. The 2SPNE SC/CE model for illite was extended with surface complexation reactions on weak sites for Co, Ni, Eu, UO 2 and on strong sites for Eu-carbonato complexes. Complementary to the sorption measurements and modelling, extended X-ray absorption fine structure (EXAFS) spectroscopy was used to probe the retention mechanism of Ni on illite, Boda and Opalinus Clay at higher loadings. The reliable blind predictions of the selected metal cations, which are representative for monovalent alkaline metals, divalent transition metals, lanthanides, and trivalent

  12. Influence of sorption competition on sorption data for MX-80 bentonite used in performance assessment

    International Nuclear Information System (INIS)

    Bradbury, M.H.; Baeyens, B.; Marques Fernandes, M.

    2012-01-01

    Document available in extended abstract form only. In order to obtain a (quasi) mechanistic understanding of radionuclide uptake on clay minerals and argillaceous rocks, the majority of sorption experiments have been carried out on purified clay minerals such as montmorillonite and illite at trace concentrations (sorption edges), or as a function of concentration (sorption isotherms), with a single radionuclide under well-defined conditions in simple background electrolytes. As a result of such studies the 2 site proto-lysis non electrostatic surface complexation cation exchange (2SPNE SC/CE) sorption model, was developed and has been successfully applied to quantitatively describe the uptake of numerous radionuclides of differing valences as a function of pH and concentration on montmorillonite. In a deep geological repository for high level waste, stable impurities arise from many sources: they are present in the pore waters, in the tunnel back fill materials and host rock formations, they arise from the corrosion of the carbon steel canister and finally they are dissolved from the spent fuel and vitrified high level waste simultaneously with the radionuclides. These impurities, which are an integral part of a realistic repository system, can potentially compete with radionuclides for the sorption sites on the backfill materials and host rock and thus reduce their uptake on them. The influence of competitive sorption is not intrinsically included (or only partly so) in the sorption model. It is clearly an inherently important issue to quantify the influence of sorption competition on the transport of released radionuclides through the multi-barrier system in a deep repository. In this study an extreme case of a competitive sorption scenario in the near field of a HLW repository is presented. Two factors are considered: one associated with the high concentrations and the other with competitive sorption effects. The tendency in both cases is to cause a reduction in

  13. Uranium(VI) sorption onto magnetite. Increasing confidence in surface complexation models using chemically evident surface chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Bok, Frank [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    Surface complexation models have made great efforts in describing the sorption of various radionuclides on naturally occurring mineral phases. Unfortunately, many of the published sorption parameter sets are built upon unrealistic or even wrong surface chemistry. This work describes the benefit of combining spectroscopic and batch sorption experimental data to create a reliable and consistent surface complexation parameter set.

  14. Modeling approaches of competitive sorption and transport of trace metals and metalloids in soils: a review.

    Science.gov (United States)

    Selim, H M; Zhang, Hua

    2013-01-01

    Competition among various heavy metal species for available adsorption sites on soil matrix surfaces can enhance the mobility of contaminants in the soil environment. Accurate predictions of the fate and behavior of heavy metals in soils and geologic media requires the understanding of the underlying competitive-sorption and transport processes. In this review, we present equilibrium and kinetic models for competitive heavy metal sorption and transport in soils. Several examples are summarized to illustrate the impact of competing ions on the reactivities and mobility of heavy metals in the soil-water environment. We demonstrate that equilibrium Freundlich approaches can be extended to account for competitive sorption of cations and anions with the incorporation of competition coefficients associated with each reaction. Furthermore, retention models of the multiple-reaction type including the two-site nonlinear equilibrium-kinetic models and the concurrent- and consecutive-multireaction models were modified to describe commonly observed time-dependent behaviors of heavy metals in soils. We also show that equilibrium Langmuir and kinetic second-order models can be extended to simulate the competitive sorption and transport in soils, although the use of such models is limited due to their simplifying assumptions. A major drawback of the empirically based Freundlich and Langmuir approaches is that their associated parameters are specific for each soil. Alternatively, geochemical models that are based on ion-exchange and surface-complexation concepts are capable of quantifying the competitive behavior of several chemical species under a wide range of environmental conditions. Such geochemical models, however, are incapable of describing the time-dependent sorption behavior of heavy metal ions in competitive systems. Further research is needed to develop a general-purpose model based on physical and chemical mechanisms governing competitive sorption in soils. Copyright

  15. The ternary sorption system U(VI)-phosphate-silica explained by spectroscopy and thermodynamic modelling

    Energy Technology Data Exchange (ETDEWEB)

    Foerstendorf, Harald; Stockmann, Madlen; Heim, Karsten; Mueller, Katharina; Brendler, Vinzenz [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Comarmond, M.J.; Payne, T.E. [Australian Nuclear Science and Technology Organisation, Lucas Heights (Australia); Steudtner, Robin [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology

    2017-06-01

    Spectroscopic data of sorption processes potentially provide direct impact on Surface Complexation Modelling (SCM) approaches. Based on spectroscopic data of the ternary sorption system U(VI)/phosphate/silica strongly suggesting the formation of a precipitate as the predominant surface process, SCM calculations accurately reproduced results from classical batch experiments.

  16. The ternary sorption system U(VI)-phosphate-silica explained by spectroscopy and thermodynamic modelling

    International Nuclear Information System (INIS)

    Foerstendorf, Harald; Stockmann, Madlen; Heim, Karsten; Mueller, Katharina; Brendler, Vinzenz; Steudtner, Robin

    2017-01-01

    Spectroscopic data of sorption processes potentially provide direct impact on Surface Complexation Modelling (SCM) approaches. Based on spectroscopic data of the ternary sorption system U(VI)/phosphate/silica strongly suggesting the formation of a precipitate as the predominant surface process, SCM calculations accurately reproduced results from classical batch experiments.

  17. Sorption of caesium and strontium onto calcium silicate hydrate in saline groundwater

    International Nuclear Information System (INIS)

    Sugiyama, D.; Fujita, T.

    2005-01-01

    Full text of publication follows: In the concept for radioactive waste disposal in Japan, cement is a potential waste packaging and backfilling material and is expected to provide chemical containment. The sorption of radionuclides onto cement materials, which controls the aqueous concentrations of elements in the pore-water, is a very important parameter when considering the release of radionuclides from the near field of a cementitious radioactive waste repository. Many safety assessment calculations currently assume radionuclide retardation as linear sorption equilibrium and describe it with a distribution ratio (R d value). In this study, the sorption mechanism is discussed by measuring the sorption isotherm of caesium, strontium (10 -5 ∼ 10 -2 mol dm -3 ) and sodium (10 -4 ∼ 10 -1 mol dm -3 ) onto Calcium Silicate Hydrate (C-S-H gel, Ca/Si 0.65 ∼ 1.2) at a liquid:solid ratio of 100:1, to support the assumption. In addition, the competitive sorption between caesium or strontium, and sodium is studied by sorption measurements using a range of sodium chloride concentration to simulate different ionic strengths in saline groundwater. The initial and equilibrated aqueous compositions were measured in the sorption experiments and it was found that caesium, strontium and sodium were sorbed by substitution for Ca in C-S-H phases by examining the mass balance. Based on the experimental results, we propose a modelling approach in which the ion-exchange model is employed and the presence of some calcium sites with different ion-exchange log K values in C-S-H is assumed by considering the composition and the structure of C-S-H. The modelling calculation results predict the measured Rd values well and also describe the competition of sorption of caesium or strontium, and sodium in the experiments. The log K values for sorption of each cation element decreased as Ca/Si ratio of C-S-H gel increased. This agrees with the trend that C-S-H gel is negatively charged at low

  18. Re-evaluation of the sorption behaviour of Bromide and Sulfamethazine under field conditions using leaching data and modelling methods

    Science.gov (United States)

    Gassmann, Matthias; Olsson, Oliver; Höper, Heinrich; Hamscher, Gerd; Kümmerer, Klaus

    2016-04-01

    The simulation of reactive transport in the aquatic environment is hampered by the ambiguity of environmental fate process conceptualizations for a specific substance in the literature. Concepts are usually identified by experimental studies and inverse modelling under controlled lab conditions in order to reduce environmental uncertainties such as uncertain boundary conditions and input data. However, since environmental conditions affect substance behaviour, a re-evaluation might be necessary under environmental conditions which might, in turn, be affected by uncertainties. Using a combination of experimental data and simulations of the leaching behaviour of the veterinary antibiotic Sulfamethazine (SMZ; synonym: sulfadimidine) and the hydrological tracer Bromide (Br) in a field lysimeter, we re-evaluated the sorption concepts of both substances under uncertain field conditions. Sampling data of a field lysimeter experiment in which both substances were applied twice a year with manure and sampled at the bottom of two lysimeters during three subsequent years was used for model set-up and evaluation. The total amount of leached SMZ and Br were 22 μg and 129 mg, respectively. A reactive transport model was parameterized to the conditions of the two lysimeters filled with monoliths (depth 2 m, area 1 m²) of a sandy soil showing a low pH value under which Bromide is sorptive. We used different sorption concepts such as constant and organic-carbon dependent sorption coefficients and instantaneous and kinetic sorption equilibrium. Combining the sorption concepts resulted in four scenarios per substance with different equations for sorption equilibrium and sorption kinetics. The GLUE (Generalized Likelihood Uncertainty Estimation) method was applied to each scenario using parameter ranges found in experimental and modelling studies. The parameter spaces for each scenario were sampled using a Latin Hypercube method which was refined around local model efficiency maxima

  19. Binary Component Sorption of Cadmium, and Copper Ions onto Yangtze River Sediments with Different Particle Sizes

    Directory of Open Access Journals (Sweden)

    Jianxin Fan

    2017-11-01

    Full Text Available Sorption is a crucial process that influences immobilization and migration of heavy metals in an aqueous environment. Sediments represent one of the ultimate sinks for heavy metals discharged into water body. Moreover, the particle size of sediments plays an extremely important role in the immobilization of heavy metals. In this study, the sorption and desorption of cadmium (Cd and copper (Cu onto sediments with different particle sizes were investigated to predict the rate and capacity of sorption, to understand their environmental behaviors in an aqueous environment. Batch sorption and kinetic experiments were conducted to obtain the retained amount and rate of Cd and Cu in a binary system. Experimental data were simulated using sorption models to ascertain the sorption capacity and the kinetic rate. Results of European Communities Bureau of Reference (BCR sequential extraction showed the highest concentration of Cd (0.344 mg kg−1, and its distribution varied with sediment particle size and site. Furthermore, most of Cu (approximately 57% to 84% existed as a residual fraction. The sorption of Cu onto six sediments followed a pseudo-first order reaction, whereas that of Cd followed a pseudo-second order reaction. Additionally, the competitive Langmuir model fitted the batch sorption experimental data extremely well. The highest sorption capacities of Cd and Cu reach 0.641 mmol kg−1 and 62.3 mmol kg−1, respectively, on the smallest submerged sediment particles. The amounts of Cu and Cd desorbed (mmol kg−1 increased linearly with the initial concentration increasing. Thus, sediment texture is an important factor that influences the sorption of heavy metal onto sediments.

  20. Modelling of niobium sorption on clay minerals in sodium and calcium perchlorate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Ervanne, Heini; Hakanen, Martti; Lehto, Jukka [Helsinki Univ. (Finland). Laboratory of Radiochemistry

    2014-11-01

    The sorption behaviour of niobium on kaolinite and illite minerals in sodium and calcium perchlorate solutions was evaluated with use of the mass distribution coefficient, Rd, obtained in batch sorption experiments. Very high distribution coefficient values, about 100 m{sup 3}/kg, were obtained for both minerals in the neutral pH range between 6 and 8. Values were somewhat lower at pH 5. In NaClO{sub 4} solution, the sorption of niobium starts to decrease at pH higher than 8. This is in agreement with the increase, with pH, in the proportion of anionic niobate species, which are presumed to be low or non-sorbing. A similar decrease was not observed in Ca(ClO{sub 4}){sub 2} solution, probably owing to the influence of Ca on niobium solution speciation and surface species. The surface complexation model was applied to model the Rd values. The model fitted well for the NaClO{sub 4} solution but only at pH below 9 for the Ca(ClO{sub 4}){sub 2} solution. The discrepancy between the strong sorption of niobium in calcium-bearing solution at high pH and the calculated speciation is due in part to the non-inclusion of calcium niobate solution species and Ca-Nb compounds in the present NEA and other similar thermodynamic databases.

  1. A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-montmorillonite. Part III: modelling

    International Nuclear Information System (INIS)

    Baeyens, B.; Bradbury, M.H.

    1995-07-01

    Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this work. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. A basic data set comprising of site capacities and protonation/deprotonation constants was defined, which was valid for all surface complexation sorption reactions. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the =SOH type sites included in the model. The sorption of Mg, Ca and Mn is also considered, though in less detail, and estimated surface complexation constants for these nuclides are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na, Zn-Na and Ca-Na exchange reactions are given. The model, with the derived parameters, allowed all the data from titration measurements through sorption edges to sorption isotherms to be calculated. (author) 31 figs., 9 tabs., refs

  2. A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-Montmorillonite. Part III: Modelling

    International Nuclear Information System (INIS)

    Baeyens, B.; Bradbury, M.H.

    1995-07-01

    Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this work. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. A basic data set comprising of site capacities and protonation/deprotonation constants was defined, which was valid for all surface complexation sorption reactions. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the ≡SOH type sites included in the model. The sorption of Mg, Ca and Mn is also considered, though in less detail, and estimated surface complexation constants for these nuclides are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na, Zn-Na and Ca-Na exchange reactions are given. The model, with the derived parameters, allowed all the data from titration measurements through sorption edges to sorption isotherms to be calculated. (author) 31 figs., 9 tabs., refs

  3. Modelling decreased food chain accumulation of HOCs due to strong sorption to carbonaceous materials and metabolic transformation

    NARCIS (Netherlands)

    Moermond, C.T.A.; Traas, T.P.; Roessink, I.; Veltman, K.; Hendriks, A.J.; Koelmans, A.A.

    2007-01-01

    The predictive power of bioaccumulation models may be limited when they do not account for strong sorption of organic contaminants to carbonaceous materials (CM) such as black carbon, and when they do not include metabolic transformation. We tested a food web accumulation model, including sorption

  4. Effects of Citrate and Arginine on Sorption of Nickel to Yazd Sepiolite and Calcite

    Directory of Open Access Journals (Sweden)

    Ahmadreza Sheikhhosseini

    2017-03-01

    , and W was the mass (g of the sorbent. The Langmuir, Freundlich and linear isotherm models were fitted to sorption data using Graphpad prism 5.0. For kinetic study,30 mL of 0.01 M CaCl2 solution, with or without 0.1 mM citrate or arginine, containing Ni at a concentration corresponding to the maximum sorption capacity of each mineral (estimated from sorption isotherms were transferred into 50-ml polyethylene centrifuge tubes containing 0.3 g of sepiolite or calcite. The suspensions were shaken (180±2 rpm, 25 °C continuously and after 0.5, 1.5, 3, 6, 12, 18 and 24 hours, corresponding tubes were centrifuged (4000×g for 10 min and supernatants were analyzed for Ni concentration by atomic absorption spectrophotometer. Using Graphpad prism 5.0, kinetic data were fitted to Pseudo-first order, pseudo-second order and power function kinetic models. Results: With or without ligands, the Langmuir model was the best description of Ni sorption to sepiolite while the linear model was the best fit of calcite data showing the physical nature of Ni sorption by this mineral. Kinetics of Ni sorption to sepiolite and calcite were best described by power function model. In the presence of citrate, both capacity and rate of sorption of Ni to sepiolite decreased. There was no considerable change in sorption of Ni to calcite. In the presence of arginine, however, sorption capacity of minerals for Ni increased. Arginine enhanced the rate of Ni sorption on all three minerals. Citrate showed opposing effects on Ni sorption kinetics depending on the studied minerals. Totally, citrate and arginine had opposite effects on sorption of Ni to sepiolite and calcite. Conclusion: Organic ligands can change sorption characteristics of the minerals. It seems that citrate decreases sorption of Ni to sepiolite but its effect on Ni sorption to calcite is negligible, while arginine increases Ni sorption to both minerals. Our results suggested that presence of citrate and arginine in soil influence Ni

  5. Metal sorption on kaolinite

    International Nuclear Information System (INIS)

    Westrich, H.R.; Brady, P.V.; Cygan, R.T.; Nagy, K.L.; Anderson, H.L.

    1997-01-01

    A key issue in performance assessment of low-level radioactive waste sites is predicting the transport and retardation of radionuclides through local soils under a variety of hydrologic and geochemical conditions. Improved transport codes should include a mechanistic model of radionuclide retardation. The authors have been investigating metal sorption (Cs + , Sr 2+ , and Ba 2+ ) on a simple clay mineral (kaolinite) to better understand the geochemical interactions of common soil minerals with contaminated groundwaters. These studies include detailed characterizations of kaolinite surfaces, experimental adsorption measurements, surface complexation modeling, and theoretical simulations of cation sorption. The aluminol edge (010) site has been identified as the most likely site for metal sorption on kaolinite in natural solutions. Relative metal binding strengths decrease from Ba 2+ to Sr 2+ to Cs + , with some portion sorbed on both kaolinite edges and basal surfaces. Some Cs + also appears to be irreversibly sorbed on both sites. Molecular dynamics simulations suggest that Cs + is sorbed at aluminol (010) edge sites as an inner-sphere complex and weakly sorbed as an outer-sphere complex on (001) basal surfaces. These results provide the basis to understand and predict metal sorption onto kaolinite, and a framework to characterize sorption processes on more complex clay minerals

  6. Sorption of uranyl ions on hydrous oxides

    International Nuclear Information System (INIS)

    Gupta, A.R.; Venkataramani, B.

    1988-01-01

    Sorption of uranyl ions on hydrous titanium oxide (HTiO), magnetite (MAG), and hydrous thorium oxide (HThO) has been studied as a function of pH. Hydrous oxides have been characterized by their pH-titration curves, intrinsic dissociation constants (pK ai * ) and point of zero charge (pH pzc ). The fraction of protonated surface hydroxyl groups as well as the surface pH (pH surf ) as a function of solution pH have been computed. The distribution of various hydrolyzed species of uranyl ions with solution pH have been compared with uranyl sorption isotherm on these oxides. Sorption edge in all the cases occurs when free hydroxyl groups are available on the surface and pH surf is sufficiently high to favor the formation of dimer-like species on the surface. A new model for the sorption process, called surface hydrolysis model, which explains these and other features of uranyl sorption on hydrous oxides has been proposed. The model visualizes the sorption process as linking of uranyl ions with two adjacent free surface hydroxyl groups without deprotonation (provided the surface pH is high for the hydrolysis of uranyl ions) and formation of dimer-like structures on the surface. The new model has been successfully applied to the present and other available data on uranyl ion sorption on hydrous oxides. (author)

  7. Effects of chemical oxidation on sorption and desorption of PAHs in typical Chinese soils

    International Nuclear Information System (INIS)

    Chen Wei; Hou Lei; Luo Xiaoli; Zhu Lingyan

    2009-01-01

    In situ chemical oxidation is a commonly applied soil and groundwater remediation technology, but can have significant effects on soil properties, which in turn might affect fate and transport of organic contaminants. In this study, it was found that oxidation treatment resulted mainly in breakdown of soil organic matter (SOM) components. Sorption of naphthalene and phenanthrene to the original soils and the KMnO 4 -treated soils was linear, indicating that hydrophobic partitioning to SOM was the predominant mechanism for sorption. Desorption from the original and treated soils was highly resistant, and was well modeled with a biphasic desorption model. Desorption of residual naphthalene after treating naphthalene-contaminated soils with different doses of KMnO 4 also followed the biphasic desorption model very well. It appears that neither changes of soil properties caused by chemical oxidation nor direct chemical oxidation of contaminated soils had a noticeable effect on the nature of PAH-SOM interactions. - Chemical oxidation of soils had little effect on the mechanisms controlling sorption and desorption of PAHs.

  8. INTRAVAL test case 1b - modelling results

    International Nuclear Information System (INIS)

    Jakob, A.; Hadermann, J.

    1991-07-01

    This report presents results obtained within Phase I of the INTRAVAL study. Six different models are fitted to the results of four infiltration experiments with 233 U tracer on small samples of crystalline bore cores originating from deep drillings in Northern Switzerland. Four of these are dual porosity media models taking into account advection and dispersion in water conducting zones (either tubelike veins or planar fractures), matrix diffusion out of these into pores of the solid phase, and either non-linear or linear sorption of the tracer onto inner surfaces. The remaining two are equivalent porous media models (excluding matrix diffusion) including either non-linear sorption onto surfaces of a single fissure family or linear sorption onto surfaces of several different fissure families. The fits to the experimental data have been carried out by Marquardt-Levenberg procedure yielding error estimates of the parameters, correlation coefficients and also, as a measure for the goodness of the fits, the minimum values of the χ 2 merit function. The effects of different upstream boundary conditions are demonstrated and the penetration depth for matrix diffusion is discussed briefly for both alternative flow path scenarios. The calculations show that the dual porosity media models are significantly more appropriate to the experimental data than the single porosity media concepts. Moreover, it is matrix diffusion rather than the non-linearity of the sorption isotherm which is responsible for the tailing part of the break-through curves. The extracted parameter values for some models for both the linear and non-linear (Freundlich) sorption isotherms are consistent with the results of independent static batch sorption experiments. From the fits, it is generally not possible to discriminate between the two alternative flow path geometries. On the basis of the modelling results, some proposals for further experiments are presented. (author) 15 refs., 23 figs., 7 tabs

  9. Sorption of polycyclic aromatic hydrocarbons on particulate organic matters

    International Nuclear Information System (INIS)

    Guo Xueyan; Luo Lei; Ma Yibing; Zhang Shuzhen

    2010-01-01

    Particulate organic matter (POM) is a key organic matter fraction which can influence soil fertility. Its interactions with hydrophobic organic pollutants (HOCs) have not been characterized and the mechanisms of retention of HOCs by POM remain unclear. In the present study, sorption behaviors of polycyclic aromatic hydrocarbons (PAHs) naphthalene (NAP), phenanthrene (PHE), and pyrene (PYR) by POMs separated from different soils were examined and the POMs were characterized by elemental analysis, solid state 13 C NMR, and Fourier transform infrared spectroscopy (FT-IR). The results indicated that POMs were mainly composed of aliphatic components with high polarity. The different original POMs showed similar chemical composition and configuration. Sorption behaviors of PAHs indicated that there was no significant difference in sorption capacity among the POMs. Sorption of NAP and PHE by POMs displayed a nonlinear isotherm, while sorption of PYR yielded a linear isotherm. No significant hysteresis and ionic strength effect were observed for PAH desorption from the POMs.

  10. The effect of particle size on sorption of estrogens, androgens and progestagens in aquatic sediment

    Energy Technology Data Exchange (ETDEWEB)

    Sangster, Jodi L.; Oke, Hugues; Zhang, Yun; Bartelt-Hunt, Shannon L., E-mail: sbartelt2@unl.edu

    2015-12-15

    Highlights: • Two sediments were used to evaluate the effects of particle size on steroid sorption. • Sorption capacity did not increase with decreasing particle size for all steroids. • Particle interactions affect the distribution of steroids within the whole sediments. • Preferential sorption to fine particles was observed. - Abstract: There is growing concern about the biologic effects of steroid hormones in impacted waterways. There is increasing evidence of enhanced transport and biological effects stemming from steroid hormones associated with soils or sediments; however, there are limited studies evaluating how steroid hormone distribution between various particle sizes within whole sediments affects steroid fate. In this study, sorption of 17β-estradiol, estrone, progesterone, and testosterone was evaluated to different size fractions of two natural sediments, a silty loam and a sandy sediment, to determine the steroid sorption capacity to each fraction and distribution within the whole sediment. Sorption isotherms for all steroid hormones fit linear sorption models. Sorption capacity was influenced more by organic carbon content than particle size. Interactions between size fractions were found to affect the distribution of steroids within the whole sediments. All four steroids preferentially sorbed to the clay and colloids in the silty loam sediment at the lowest aqueous concentration (1 ng/L) and as aqueous concentration increased, the distribution of sorbed steroid was similar to the distribution by weight of each size fraction within the whole sediment. In the sandy sediment, preferential sorption to fine particles was observed.

  11. The effect of particle size on sorption of estrogens, androgens and progestagens in aquatic sediment

    International Nuclear Information System (INIS)

    Sangster, Jodi L.; Oke, Hugues; Zhang, Yun; Bartelt-Hunt, Shannon L.

    2015-01-01

    Highlights: • Two sediments were used to evaluate the effects of particle size on steroid sorption. • Sorption capacity did not increase with decreasing particle size for all steroids. • Particle interactions affect the distribution of steroids within the whole sediments. • Preferential sorption to fine particles was observed. - Abstract: There is growing concern about the biologic effects of steroid hormones in impacted waterways. There is increasing evidence of enhanced transport and biological effects stemming from steroid hormones associated with soils or sediments; however, there are limited studies evaluating how steroid hormone distribution between various particle sizes within whole sediments affects steroid fate. In this study, sorption of 17β-estradiol, estrone, progesterone, and testosterone was evaluated to different size fractions of two natural sediments, a silty loam and a sandy sediment, to determine the steroid sorption capacity to each fraction and distribution within the whole sediment. Sorption isotherms for all steroid hormones fit linear sorption models. Sorption capacity was influenced more by organic carbon content than particle size. Interactions between size fractions were found to affect the distribution of steroids within the whole sediments. All four steroids preferentially sorbed to the clay and colloids in the silty loam sediment at the lowest aqueous concentration (1 ng/L) and as aqueous concentration increased, the distribution of sorbed steroid was similar to the distribution by weight of each size fraction within the whole sediment. In the sandy sediment, preferential sorption to fine particles was observed.

  12. Sorption Behavior of CO2 and CH4 of Glassy Polymeric Membranes and Analytical Discussion of Partial Immobilization Model

    Directory of Open Access Journals (Sweden)

    M. Mahdavian

    2007-06-01

    Full Text Available Among various reported membrane-based gas separation processes, the best explanation is generally achieved by the solution-diffusion model. The main factors in this model are the solubility and diffusivity of permeationcomponents through the membrane. The prediction of permeability and diffusivity in multicomponent gas permeation as well as the separation evaluation equilibrium and kinetic interactions requires a proper explanation of sorption and diffusion phenomena in the polymer matrix. Investigation made by various researchers in this area shows that the equilibrium interaction (sorption step plays the key role in determining diffusion and permeation in multicomponent system. Therefore, the proper description of sorption behaviour of gas mixture in the polymer is an essential task. The dual-mode sorption (Langmuir-Henry is usually used for the description of equilibrium isotherm of gases in glassy polymers based on this model; the diffusive behaviour of the system is subsequently analyzed by the partial immobilization model. In this study, the equilibrium sorption of CO2/CH4 mixture in various polymers was modelled using the experimental data available in the literature. The differences in the mechanism of adsorption for CO2 and CH4 were analyzed by considering variations in mode of sorption for each adsorbed component at different pressures. By introducing a new adsorption parameter, P50/50, (the pressure at which the portion of two modes in sorption are equal the contribution of each adsorbed component in occupying Langmuir sites was evaluated. The results indicate that the relative significance of sorption mode for each component is a function of pressure and it is different for various polymers.

  13. Sorption isotherms, GAB parameters and isosteric heat of sorption

    NARCIS (Netherlands)

    Quirijns, E.J.; Boxtel, van A.J.B.; Loon, van W.K.P.; Straten, van G.

    2005-01-01

    The diffusion-sorption drying model has been developed as a physics-based way to model the decreasing drying rate at low moisture contents. This new model is founded on the existence of different classes of water: free and bound water. The transition between these classes and the corresponding

  14. A surface complexation model of YREE sorption on Ulva lactuca in 0.05-5.0 M NaCl solutions

    Science.gov (United States)

    Zoll, Alison M.; Schijf, Johan

    2012-11-01

    We present distribution coefficients, log iKS, for the sorption of yttrium and the rare earth elements (YREEs) on BCR-279, a dehydrated tissue homogenate of a marine macroalga, Ulva lactuca, resembling materials featured in chemical engineering studies aimed at designing renewable biosorbents. Sorption experiments were conducted in NaCl solutions of different ionic strength (0.05, 0.5, and 5.0 M) at T = 25 °C over the pH range 2.7-8.5. Distribution coefficients based on separation of the dissolved and particulate phase by conventional filtration (3 kDa) using an existing pH-dependent model. Colloid-corrected values were renormalized to free-cation concentrations by accounting for YREE hydrolysis and chloride complexation. At each ionic strength, the pH dependence of the renormalized values is accurately described with a non-electrostatic surface complexation model (SCM) that incorporates YREE binding to three monoprotic functional groups, previously characterized by alkalimetric titration, as well as binding of YREE-hydroxide complexes (MOH2+) to the least acidic one (pKa ∼ 9.5). In non-linear regressions of the distribution coefficients as a function of pH, each pKa was fixed at its reported value, while stability constants of the four YREE surface complexes were used as adjustable parameters. Data for a single fresh U. lactuca specimen in 0.5 M NaCl show generally the same pH-dependent behavior but a lower degree of sorption and were excluded from the regressions. Good linear free-energy relations (LFERs) between stability constants of the YREE-acetate and YREE-hydroxide solution complex and surface complexes with the first and third functional group, respectively, support their prior tentative identifications as carboxyl and phenol. A similar confirmation for the second group is precluded by insufficient knowledge of the stability of YREE-phosphate complexes and a perceived lack of YREE binding in 0.05 M NaCl; this issue awaits further study. The results

  15. How the sorption of benzene in soils contaminated with aromatic hydrocarbons is affected by the presence of biofuels

    Directory of Open Access Journals (Sweden)

    Maria Manuela Carvalho

    2015-04-01

    Full Text Available The increasing use of biofuels as additives to gasoline may have potential indirect effects on the efficiency of soil remediation technologies used to remediate fuel spills. This problem has not yet been studied. Sorption is one of the controlling processes in soil remediation. The effect of biofuels on sorption and phase distribution of contaminants by different natural soils has not been reported on the literature. The present work examines how two different biofuels, n-butanol and soybean biodiesel, affect benzene sorption in two naturally occurring subsoils (granite and limestone. Sorption isotherms were made with soils deliberately contaminated with benzene, benzene and n-butanol and benzene plus biodiesel, using lab-scale reactors operated at constant temperature, each one loaded with 700 grams of wet sterilized soil. For each type of soil, five isotherms were determined corresponding to different contamination profiles. It was concluded that sorption was strongly affected by the nature of the soil. The partition of benzene into the different phases of the soil was significantly affected by the presence of biofuels. The experimental data was fitted to conventional sorption models, Freundlich, Langmuir and a second order polynomial. Model parameters were determined using a non-linear least squares (NLLS optimization algorithm and showed a good agreement between experimental and fitted data.

  16. Sorption behaviour of cobalt-60 on Suez Canal bottom sediments

    International Nuclear Information System (INIS)

    Abdel Gawad, S.A.; El-Shinawy, R.M.K.; Abdel Malik, W.E.Y.

    1981-01-01

    Mineralogical, elemental analysis and sorption behaviour of the Suez Canal bottom sediments in the Port Said area were investigated. It was found that the bottom sediment consist mainly of quartz, feldspars and traces of calcite mineral. The cation-exchange capacity was found to increase as the particle size of the sediment decreased. Sorption of 60 Co by the bottom sediment increased with contact time up to 6 h. Variation of the solution pH from 4 to 9 showed limited increase in the sorption of 60 Co. As carrier concentrations increase from 10 -7 N to 10 -3 N, sorption of Co was found to increase linearly following Freundlich isotherm. The presence of Mg 2+ and Fe 3+ in solution depressed the sorption of 60 Co by the sediments. The desorption of 60 Co from bottom sediment with distilled and Suez Canal water was found to increase with contact time. (author)

  17. Nitrate Sorption in an Agricultural Soil Profile

    Directory of Open Access Journals (Sweden)

    Wissem Hamdi

    2013-01-01

    Full Text Available Increasing concentrations of in surface water and groundwater can cause ecological and public health effects and has come under increased scrutiny by both environmental scientists and regulatory agencies. For many regions though, including the Sahel of Tunisia, little is known about the sorption capacity of soils. In this project we measured sorption by a profile of an iso-humic soil from Chott Meriem, Tunisia. Soil samples were collected from four soil depths (0–25, 25–60, 60–90, and 90–120 cm on 1 June 2011, and their sorption capacity was determined using batch experiments under laboratory conditions. The effects of contact time, the initial concentration, and the soil-solution ratio on sorption were investigated. In general, the results suggested that was weakly retained by the Chott Meriem soil profile. The quantity of sorption increased with depth, contact time, initial concentration, and soil-solution ratios. To evaluate the sorption capacities of the soil samples at concentrations ranging between 25 and 150 mg L−1 experimental data were fitted to both Freundlich and Langmuir isotherm sorption models. The results indicated that Freundlich model was better for describing sorption in this soil profile.

  18. Summary report on the evaluation of a 1977--1985 edited sorption data base for isotherm modeling

    International Nuclear Information System (INIS)

    Polzer, W.L.; Beckman, R.J.; Fuentes, H.R.; Yong, C.; Chan, P.; Rao, M.G.

    1993-01-01

    Sorption data bases collected by Los Alamos National Laboratory (LANL) from 1977 to 1985 for the Yucca Mountain Project.(YMP) have been inventoried and fitted with isotherm expressions. Effects of variables (e.g., particle size) on the isotherm were also evaluated. The sorption data are from laboratory batch measurements which were not designed specifically for isotherm modeling. However a limited number of data sets permitted such modeling. The analysis of those isotherm data can aid in the design of future sorption experiments and can provide expressions to be used in radionuclide transport modeling. Over 1200 experimental observations were inventoried for their adequacy to be modeled b isotherms and to evaluate the effects of variables on isotherms. About 15% of the observations provided suitable data sets for modeling. The data sets were obtained under conditions that include ambient temperature and two atmospheres, air and CO 2

  19. Modeling bioaccumulation in humans using poly-parameter linear free energy relationships (PPLFERS)

    Energy Technology Data Exchange (ETDEWEB)

    Undeman, Emma, E-mail: emma.undeman@itm.su.se; Czub, Gertje; McLachlan, Michael S.

    2011-04-01

    Chemical partition coefficients between environmental media and biological tissues are a key component of bioaccumulation models. The single-parameter linear free energy relationships (spLFERs) commonly used for predicting partitioning are often derived using apolar chemicals and may not accurately capture polar chemicals. In this study, a poly-parameter LFER (ppLFER) based model of organic chemical bioaccumulation in humans is presented. Chemical partitioning was described by an air-body partition coefficient that was a volume weighted average of ppLFER based partition coefficients for the major organs and tissues constituting the human body. This model was compared to a spLFER model treating the body as a mixture of lipid ({approx} octanol) and water. Although model agreement was good for hydrophobic chemicals (average difference 15% for log K{sub OW} > 4 and log K{sub OA} > 8), the ppLFER model predicted {approx} 90% lower body burdens for hydrophilic chemicals (log K{sub OW} < 0). This was mainly due to lower predictions of muscle and adipose tissue sorption capacity for these chemicals. A comparison of the predicted muscle and adipose tissue sorption capacities of hydrophilic chemicals with measurements indicated that the ppLFER and spLFER models' uncertainties were similar. Consequently, little benefit from the implementation of ppLFERs in this model was identified. - Research Highlights: {yields}Implementation of ppLFERs resulted in on average 90% lower predicted body burdens. {yields}Uncertainties in spLFER and ppLFER predictions were similar. {yields}The benefit from implementation of ppLFERs in bioaccumulation models was limited.

  20. Sorption of fission nuclides on model milk components. I. Sorption of radiostrontium on hydroxyapatite in aqueous solutions

    International Nuclear Information System (INIS)

    Rosskopfova, O.; Kopunec, R.; Matel, L.; Macasek, F.; Kristin, J.

    1999-01-01

    Hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 is a mineral widely spread in nature as a main constituent of phosphate rocks, and also as the major inorganic component of bones and teeth. It was found that sorption process occurs by an ion exchange reaction mechanism between strontium ions in solution and calcium ions in apatite. Ca 2+ → Sr 2+ substitution in hydroxyapatite is important since it explains the mechanism of incorporation of beta-active Sr-90 of atomic debris into the human skeletal system. The strontium uptake at 100 grad C is done by adsorption and diffusion while at 25 grad C it is done by the process of adsorption only. The hydroxyapatite was prepared from aqueous solutions and characterized by standard analytical methods. Some samples of hydroxyapatite were modified by heating after its precipitation from aqueous solution. The sample obtained had characteristics of well crystallized stoichiometric hydroxyapatite. Also, commercial hydroxy-apatites were used. Sorption of strontium ions on synthetic hydroxyapatite was examined using batch method and sorption depends on the method of preparation of hydroxyapatite. In generally, sorption of strontium decreases with the increase in the particle size of hydroxyapatite and decreases with the increase in the pH ( hydroxyapatite surface is amphoteric and acts as a buffer in a wide pH range). The sorption of strontium increases with the increase in [Sr 2+ ] or [Ca 2+ ] in solution to ∼ 10 -5 mol · dm -3 for the hydroxyapatite prepared by heating. The experimental data for sorption of strontium has been fitted with Langmuir-adsorption isotherm. (authors)

  1. Isotherms and thermodynamics by linear and non-linear regression analysis for the sorption of methylene blue onto activated carbon: Comparison of various error functions

    International Nuclear Information System (INIS)

    Kumar, K. Vasanth; Porkodi, K.; Rocha, F.

    2008-01-01

    A comparison of linear and non-linear regression method in selecting the optimum isotherm was made to the experimental equilibrium data of methylene blue sorption by activated carbon. The r 2 was used to select the best fit linear theoretical isotherm. In the case of non-linear regression method, six error functions, namely coefficient of determination (r 2 ), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), average relative error (ARE), sum of the errors squared (ERRSQ) and sum of the absolute errors (EABS) were used to predict the parameters involved in the two and three parameter isotherms and also to predict the optimum isotherm. For two parameter isotherm, MPSD was found to be the best error function in minimizing the error distribution between the experimental equilibrium data and predicted isotherms. In the case of three parameter isotherm, r 2 was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. The present study showed that the size of the error function alone is not a deciding factor to choose the optimum isotherm. In addition to the size of error function, the theory behind the predicted isotherm should be verified with the help of experimental data while selecting the optimum isotherm. A coefficient of non-determination, K 2 was explained and was found to be very useful in identifying the best error function while selecting the optimum isotherm

  2. Sorption studies of radioiodine on soils with special references to soil microbial biomass

    International Nuclear Information System (INIS)

    Bors, J.; Erten, H.; Martens, R.

    1991-01-01

    In batch experiments with two types of soils, chernozem and podzol, radioiodine ( 125 I) showed an initial rapid sorption, followed by a long and slow further increase. Very little sorption (R d d -values were observed for the chernozem soil, characterized by a higher amount of organic substance and of soil biomass. The sorption process was predominantly irreversible, the isotherms were linear at low ion concentrations and deviated from linearity starting at 10 -5 mmol.ml -1 . Sorption ratio was found to increase with increasing volume to mass ratio. The composition of liquid phases (bidistilled water, synthetic soil water, rain water) highly affected iodine sorption. In experiments with KBr solution, the sorption of I - was found to be strongly preferred to Br - . Incubation of soil samples under varied conditions (decreased or increased soil biomass, O 2 -concentration, incubation temperature, soil water content and storage conditions) delivered indications for the participation of soil microflora in iodine immobilization. Test with isolated soil bacteria and fungi showed that radioiodine can be incorporated by soil microorganisms under certain conditions only: Considerable uptake of radioiodine was found in washed (NaCl, CaCl 2 ) cells with both bacteria and fungi, but no incorporation was detected into cells incubated with radioiodine in the culture medium. (orig.)

  3. Sorption of a nonionic surfactant Tween 80 by minerals and soils

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Soyoung, E-mail: soyoung@pusan.ac.kr; Jeong, Hoon Young, E-mail: hjeong@pusan.ac.kr

    2015-03-02

    Highlights: • Tween 80 sorption varies significantly among soil minerals. • Sorption mechanisms and atomic compositions explain to mineral-specific sorption. • Clay minerals and SOM in soils are the key contributors to Tween 80 sorption. • Hysteresis suggests the potential difficulty in removing residual surfactants. - Abstract: Batch experiments were conducted to evaluate Tween 80 sorption by oxides, aluminosilicates, and soils. For oxides, the sorption by silica and alumina follow linear isotherms, and that by hematite follows a Langmuir isotherm. Considering isotherm type and surface coverage, Tween 80 may partition into the silica/alumina–water interface, whereas it may bind to hematite surface sites. Among aluminosilicates, montmorillonite shows the greatest sorption due to the absorption of Tween 80 into interlayers. For other aluminosilicates, it sorbs to surfaces, with the sorption increasing as plagioclase < vermiculite < kaolinite. This results from the relative reactivity among surface sites: ≡NaOH, ≡CaOH << ≡SiOH < ≡AlOH. Experiments using dry- and wet-sieved soils reveal that fine-grained clay minerals, difficult to separate by dry-sieving, contribute significantly to Tween 80 sorption. The greater sorption by untreated soils than H{sub 2}O{sub 2}-treated soils indicates that soil organic matter is a vital sorbent. The sorption hysteresis, contributed to by clay minerals and soil organic matter, is characterized by the greater sorption during the desorption than the sorption stages. This suggests the potential difficulty in removing surfactants from soils. Also, sorption of surfactants can adversely affect surfactant-enhanced remediation by decreasing the aquifer permeability and the availability of surfactants for micellar solubilization.

  4. Modeling of kinetics of Cr(VI) sorption onto grape stalk waste in a stirred batch reactor

    International Nuclear Information System (INIS)

    Escudero, Carlos; Fiol, Nuria; Poch, Jordi; Villaescusa, Isabel

    2009-01-01

    Recently, Cr(VI) removal by grape stalks has been postulated to follow two mechanisms, adsorption and reduction to trivalent chromium. Nevertheless, the rate at which both processes take place and the possible simultaneity of both processes has not been investigated. In this work, kinetics of Cr(VI) sorption onto grape stalk waste has been studied. Experiments were carried out at different temperatures but at a constant pH (3 ± 0.1) in a stirred batch reactor. Results showed that three steps take place in the process of Cr(VI) sorption onto grape stalk waste: Cr(VI) sorption, Cr(VI) reduction to Cr(III) and the adsorption of the formed Cr(III). Taking into account the evidences above mentioned, a model has been developed to predict Cr(VI) sorption on grape stalks on the basis of (i) irreversible reduction of Cr(VI) to Cr(III) reaction, whose reaction rate is assumed to be proportional to the Cr(VI) concentration in solution and (ii) adsorption and desorption of Cr(VI) and formed Cr(III) assuming that all the processes follow Langmuir type kinetics. The proposed model fits successfully the kinetic data obtained at different temperatures and describes the kinetics profile of total, hexavalent and trivalent chromium. The proposed model would be helpful for researchers in the field of Cr(VI) biosorption to design and predict the performance of sorption processes.

  5. Imidacloprid sorption and transport in cropland, grass buffer and riparian buffer soils

    Science.gov (United States)

    Satkowski, Laura E.; Goyne, Keith W.; Anderson, Stephen H.; Lerch, Robert N.; Allen, Craig R.; Snow, Daniel D.

    2018-01-01

    An understanding of neonicotinoid sorption and transport in soil is critical for determining and mitigating environmental risk associated with the most widely used class of insecticides. The objective of this study was to evaluate mobility and transport of the neonicotinoid imidacloprid (ICD) in soils collected from cropland, grass vegetative buffer strip (VBS), and riparian VBS soils. Soils were collected at six randomly chosen sites within grids that encompassed all three land uses. Single-point equilibrium batch sorption experiments were conducted using radio-labeled (14C) ICD to determine solid–solution partition coefficients (Kd). Column experiments were conducted using soils collected from the three vegetation treatments at one site by packing soil into glass columns. Water flow was characterized by applying Br− as a nonreactive tracer. A single pulse of 14C-ICD was then applied, and ICD leaching was monitored for up to 45 d. Bromide and ICD breakthrough curves for each column were simulated using CXTFIT and HYDRUS-1D models. Sorption results indicated that ICD sorbs more strongly to riparian VBS (Kd = 22.6 L kg−1) than crop (Kd = 11.3 L kg−1) soils. Soil organic C was the strongest predictor of ICD sorption (p < 0.0001). The column transport study found mean peak concentrations of ICD at 5.83, 10.84, and 23.8 pore volumes for crop, grass VBS, and riparian VBS soils, respectively. HYDRUS-1D results indicated that the two-site, one-rate linear reversible model best described results of the breakthrough curves, indicating the complexity of ICD sorption and demonstrating its mobility in soil. Greater sorption and longer retention by the grass and riparian VBS soils than the cropland soil suggests that VBS may be a viable means to mitigate ICD loss from agroecosystems, thereby preventing ICD transport into surface water, groundwater, or drinking water resources.

  6. Extended sorption partitioning models for pesticide leaching risk assessments: Can we improve upon the k{sub oc} concept?

    Energy Technology Data Exchange (ETDEWEB)

    Jarvis, Nicholas, E-mail: nicholas.jarvis@slu.se

    2016-01-01

    Models used to assess leaching of pesticides to groundwater still rely on the sorption k{sub oc} value, even though its limitations have been known for several decades, especially for soils of low organic carbon content (i.e. subsoils). This is mainly because the general applicability of any improved model approach that is also simple enough to use for regulatory purposes has not been demonstrated. The objective of this study was to test and compare alternative models of sorption that could be useful in pesticide risk assessment and management. To this end, a database containing the results of batch sorption experiments for pesticides was compiled from published studies in the literature, which placed at least as much emphasis on measurements in subsoil horizons as in topsoil. The database includes 785 data entries from 34 different published studies and for 21 different active substances. Overall, the apparent k{sub oc} value, k{sub oc(app)}, roughly doubled as the soil organic carbon content decreased by a factor of ten. Nevertheless, in nearly half of the individual datasets, a constant k{sub oc} value proved to be an adequate model. Further analysis showed that significant increases in k{sub oc(app)} in subsoil were found primarily for the more weakly adsorbing compounds (k{sub oc} values < ca. 100–200 L kg{sup −1}) and that sorption to clay in loamy and clayey-textured subsoil horizons was the main cause. Tests with the MACRO model demonstrated that sorption to clay minerals may significantly affect the outcome of regulatory exposure and risk assessments for leaching to groundwater. The k{sub oc} concept currently used in leaching models should therefore be replaced by an alternative approach that gives a more realistic representation of pesticide sorption in subsoil. The two alternative models tested in this study appear to have widespread applicability and are also simple enough to parameterize for this purpose. - Highlights: • A database was collated

  7. Sorption-desorption of imidacloprid onto a lacustrine Egyptian soil and its clay and humic acid fractions.

    Science.gov (United States)

    Kandil, Mahrous M; El-Aswad, Ahmed F; Koskinen, William C

    2015-01-01

    Sorption-desorption of the insecticide imidacloprid 1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine onto a lacustrine sandy clay loam Egyptian soil and its clay and humic acid (HA) fractions was investigated in 24-h batch equilibrium experiments. Imidacloprid (IMDA) sorption-desorption isotherms onto the three sorbents were found to belong to a non-linear L-type and were best described by the Freundlich model. The value of the IMDA adsorption distribution coefficient, Kd(ads), varied according to its initial concentration and was ranged 40-84 for HA, 14-58 for clay and 1.85-4.15 for bulk soil. Freundlich sorption coefficient, Kf(ads), values were 63.0, 39.7 and 4.0 for HA, clay and bulk soil, respectively. The normalized soil Koc value for imidacloprid sorption was ∼800 indicating its slight mobility in soils. Nonlinear sorption isotherms were indicated by 1/n(ads) values imidacloprid sorption process with all tested sorbents. Gibbs free energy (ΔG) values indicated a spontaneous and physicosorption process for IMDA and a more favorable sorption to HA than clay and soil. In conclusion, although the humic acid fraction showed the highest capacity and affinity for imidacloprid sorption, the clay fraction contributed to approximately 95% of soil-sorbed insecticide. Clay and humic acid fractions were found to be the major two factors controlling IMDA sorption in soils. The slight mobility of IMDA in soils and the hysteresis phenomenon associated with the irreversibility of its sorption onto, mainly, clay and organic matter of soils make its leachability unlikely to occur.

  8. PCB congener sorption to carbonaceous sediment components: Macroscopic comparison and characterization of sorption kinetics and mechanism

    International Nuclear Information System (INIS)

    Choi, Hyeok; Al-Abed, Souhail R.

    2009-01-01

    Sorption of polychlorinated biphenyls (PCBs) to sediment is a key process in determining their mobility, bioavailability, and chemical decomposition in aquatic environments. In order to examine the validity of currently used interpretation approaches for PCBs sorption, comparative results on 2-chlorobiphenyl sorption to carbonaceous components in sediments (activated carbon, carbon black, coal, soot, graphite, flyash, wood) were macroscopically correlated with the structural, morphological, crystallographic, and compositional properties of the carbonaceous components. Since the Freundlich sorption constant, K F (L kg -1 ) spanned several orders of magnitude, ranging from log K F of 6.13-5.27 for activated carbon, 5.04 for carbon black, 3.83 for coal to 3.08 for wood, organic carbon partitioning approach should be more specifically categorized, considering the various forms, nature and origins of organic carbon in sediment. Sorption rate constants and fraction parameters, which were numerically defined from empirical kinetic model with fast and slow sorption fractions, were closely related to the physicochemical properties of the carbonaceous components. Sorption interpretation approaches with a specific property and viewpoint, such as organic carbon partitioning, soot carbon distribution, or surface area correlation, did not properly explain the overall results on sorption capacity, fast and slow sorption kinetics, and partitioning coefficient. It is also important to emphasize the heterogeneous nature of sediment and the difficulties of encompassing the partitioning among its carbonaceous components.

  9. PCB congener sorption to carbonaceous sediment components: Macroscopic comparison and characterization of sorption kinetics and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hyeok [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States); Al-Abed, Souhail R., E-mail: al-abed.souhail@epa.gov [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States)

    2009-06-15

    Sorption of polychlorinated biphenyls (PCBs) to sediment is a key process in determining their mobility, bioavailability, and chemical decomposition in aquatic environments. In order to examine the validity of currently used interpretation approaches for PCBs sorption, comparative results on 2-chlorobiphenyl sorption to carbonaceous components in sediments (activated carbon, carbon black, coal, soot, graphite, flyash, wood) were macroscopically correlated with the structural, morphological, crystallographic, and compositional properties of the carbonaceous components. Since the Freundlich sorption constant, K{sub F} (L kg{sup -1}) spanned several orders of magnitude, ranging from log K{sub F} of 6.13-5.27 for activated carbon, 5.04 for carbon black, 3.83 for coal to 3.08 for wood, organic carbon partitioning approach should be more specifically categorized, considering the various forms, nature and origins of organic carbon in sediment. Sorption rate constants and fraction parameters, which were numerically defined from empirical kinetic model with fast and slow sorption fractions, were closely related to the physicochemical properties of the carbonaceous components. Sorption interpretation approaches with a specific property and viewpoint, such as organic carbon partitioning, soot carbon distribution, or surface area correlation, did not properly explain the overall results on sorption capacity, fast and slow sorption kinetics, and partitioning coefficient. It is also important to emphasize the heterogeneous nature of sediment and the difficulties of encompassing the partitioning among its carbonaceous components.

  10. Sorption of metaldehyde using granular activated carbon

    Directory of Open Access Journals (Sweden)

    S. Salvestrini

    2017-09-01

    Full Text Available In this work, the ability of granular activated carbon (GAC to sorb metaldehyde was evaluated. The kinetic data could be described by an intra-particle diffusion model, which indicated that the porosity of the sorbent strongly influenced the rate of sorption. The analysis of the equilibrium sorption data revealed that ionic strength and temperature did not play any significant role in the metaldehyde uptake. The sorption isotherms were successfully predicted by the Freundlich model. The GAC used in this paper exhibited a higher affinity and sorption capacity for metaldehyde with respect to other GACs studied in previous works, probably as a result of its higher specific surface area and high point of zero charge.

  11. Kinetic Modelling of the Removal of Multiple Heavy Metallic Ions from Mine Waste by Natural Zeolite Sorption

    Directory of Open Access Journals (Sweden)

    Amanda L. Ciosek

    2017-07-01

    Full Text Available This study investigates the sorption of heavy metallic ions (HMIs, specifically lead (Pb2+, copper (Cu2+, iron (Fe3+, nickel (Ni2+ and zinc (Zn2+, by natural zeolite (clinoptilolite. These HMIs are combined in single-, dual-, triple-, and multi-component systems. The batch mode experiments consist of a total initial concentration of 10 meq/L normality for all systems, acidified to a pH of 2 by concentrated nitric (HNO3 acid. A zeolite dosage of 4 g per 100 mL of synthetic nitrate salt aqueous solution is applied, for a contact period of 5 to 180 min. Existing kinetic models on HMIs sorption are limited for multi-component system combinations. Therefore, this study conducts kinetic analysis by both reaction and diffusion models, to quantify the sorption process. The study concludes that the process correlates best with the pseudo-second-order (PSO kinetic model. In the multi-component system combining all five HMIs, the initial sorption rate and theoretical equilibrium capacity are determined as 0.0033 meq/g·min and 0.1159 meq/g, respectively. This provides significant insight into the mechanisms associated with the sorption process, as well as contributing to the assessment of natural zeolite as a sorbent material in its application in industrial wastewater treatment.

  12. Differences in sorption behavior of the herbicide 4-chloro-2-methylphenoxyacetic acid on artificial soils as a function of soil pre-aging.

    Science.gov (United States)

    Waldner, Georg; Friesl-Hanl, Wolfgang; Haberhauer, Georg; Gerzabek, Martin H

    The sorption behavior of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) to three different artificial soil mixtures was investigated. Artificial soils serve as model systems for improving understanding of sorption phenomena. The soils consisted of quartz, ferrihydrite, illite, montmorillonite, and charcoal. In a previous study, several selected mixtures had been inoculated with organic matter, and microbial aging (incubation) had been performed for different periods of time (3, 12, and 18 months) before conducting the sorption experiments. The effect of this pre-incubation time on the sorption behavior was determined. Interaction of MCPA with soil surfaces was monitored by aqueous phase sorption experiments, using high-performance liquid chromatography/ultraviolet and in selected cases Fourier-transformed infrared spectroscopy. The sorption behavior showed large differences between differently aged soils; Freundlich and linear sorption model fits (with sorption constants K f , 1/ n exponents, and K d values, respectively) were given for pH = 3 and the unbuffered pH of ∼7. The largest extent of sorption from diluted solutions was found on the surfaces with a pre-incubation time of 3 months. Sorption increased at acidic pH values. Regarding the influence of aging of artificial soils, the following conclusions were drawn: young artificial soils exhibit stronger sorption at lower concentrations, with a larger K f value than aged soils. A correlation with organic carbon content was not confirmed. Thus, the sorption characteristics of the soils are more influenced by the aging of the organic carbon than by the organic carbon content itself.

  13. Effect of humic substances on P sorption capacity of three different soils

    Science.gov (United States)

    Delgado, Antonio

    2010-05-01

    Organic matter decreases P sorption by soils. It has been demonstrated the effect of low molecular weight compounds decreasing P adsorption on active surfaces and the effect of humic and fulvic acids inhibiting the precipitation of hydroxyapatite and favouring the formation of more soluble phosphates. This contributes to increase the recovery of applied P fertilizer. The objective of this work was to study the effect of 4 different humic substances (commercially available and provided by Tradecorp Internacional S.A.) on the sorption capacity of three soils differing widely in chemical properties (two calcareous from south Spain, pH 8 and 8.5, and other acidic from Brazil, pH 5.9 and 50 % of exchangeable basic cations). To this end, sorption isotherms were performed at a soil:0.01 M CaCl2 ratio of 1:10 at 6, 30 and 90 days. 2.5 mg of humic substances per g of soil were added to the solution. Data were fitted to the best model and linearized sorption curves for each humic substance were compared with the linearized sorption curve for the control without humic substances application (intersection point and slopes). Soil from Brazil showed a much higher sorption capacity (400 mg P kg-1 soil sorbed at 1 mg L-1 of P in the solution at 1 day) than the other two soils (50 and 100 mg P kg-1). Slow reactions significantly contributed to P sorption in the three soils, amounts sorbed at 90 days being twice than those sorbed at 1 day. Two of the products increased P sorption in the soil from Brazil at 1 day. At 90 days all the products increased P sorption significantly. This increased P sorption can be only explained by metal complexation by the substances applied, which may result in organo-metallic compounds with a high P sorption capacity. This effect was independent of the proportion of humic and fulvic acids in the applied products because the amounts of metal complexed by these compouds depend on the amount of functional groups to coordinate with metals. In the Spanish

  14. Experimental determination of sorption in fractured flow systems

    Science.gov (United States)

    Zimmerman, Mitchell D.; Bennett, Philip C.; Sharp, John M.; Choi, Wan-Joo

    2002-09-01

    Fracture "skins" are alteration zones on fracture surfaces created by a variety of biological, chemical, and physical processes. Skins increase surface area, where sorption occurs, compared to the unaltered rock matrix. This study examines the sorption of organic solutes on altered fracture surfaces in an experimental fracture-flow apparatus. Fracture skins containing abundant metal oxides, clays, and organic material from the Breathitt Formation (Kentucky, USA) were collected in a manner such that skin surface integrity was maintained. The samples were reassembled in the lab in a flow-through apparatus that simulated ˜2.7 m of a linear fracture "conduit." A dual-tracer injection scheme was utilized with the sorbing or reactive tracer compared to a non-reactive tracer (chloride) injected simultaneously. Sorption was assessed from the ratio of the first temporal moments of the breakthrough curves and from the loss of reactive tracer mass and evaluated as a function of flow velocity and solute type. The breakthrough curves suggest dual-flow regimes in the fracture with both sorbing and non-sorbing flow fields. Significant sorption occurs for the reactive components, and sorption increased with decreasing flow rate and decreasing compound solubility. Based on moment analysis, however, there was little retardation of the center of solute mass. These data suggest that non-equilibrium sorption processes dominate and that slow desorption and boundary layer diffusion cause extensive tailing in the breakthrough curves.

  15. Colloid chemistry: available sorption models and the question of colloid adhesion

    International Nuclear Information System (INIS)

    Grauer, R.

    1990-05-01

    A safety analysis of a radioactive waste repository should consider the possibility of nuclide transport by colloids. This would involve describing the sorption properties of the colloids and their transport in porous and fissured media. This report deals with a few selected aspects of the chemistry of this complex subject. Because the mechanisms of ion adsorption onto surfaces are material-specific, increased attention should be paid to identifying the material constitution of aquatic colloids. Suitable models already exist for describing reversible adsorption; these models describe sorption using mass action equations. The surface coordination model, developed for hydrous oxide surfaces, allows a uniform approach to be adopted for different classes of materials. This model is also predictive and has been applied successfully to natural systems. From the point of view of nuclide transport by colloids, irreversible sorption represents the most unfavourable situation. There is virtually no information available on the extent of reversibility and on the desorption kinetics of important nuclide/colloid combinations. Experimental investigations are therefore necessary in this respect. The only question considered in connection with colloid transport and its modelling is that of colloid sticking. Natural colloids, and the surfaces of the rock on which they may be collected, generally have negative surface charges so that colloid sticking will be difficult. The DLVO theory contains an approach for calculating the sticking factor from the surface potentials of the solid phases and the ionic strength of the water. However, it has been shown that this theory is inapplicable because of inherent shortcomings which lead to completely unrealistic predictions. The sticking probability of colloids should therefore be determined experimentally for systems which correspond as closely as possible to reality. (author) 66 figs., 12 tabs., 204 refs

  16. Reversible Second Order Kinetics of Sorption-Desorption of Cr(VI Ion on Activated Carbon from Palm Empty Fruit Bunches

    Directory of Open Access Journals (Sweden)

    Iip Izul Falah

    2015-11-01

    Full Text Available Activated carbon (AC from palm empty fruit bunches has been prepared, and this material was then used to adsorb Cr(VI from a solution. Characterization of the AC was conducted by detection of its functional groups, determination of total volatile compounds (VC content and its iodine number. Study on sorption-desorption kinetics was conducted by comparing results of evaluations of several models with proposed reversible second order model using the data produced in this work. Results of the works showed that the AC had similar characters compared with the AC produced by previous researchers. Application of the kinetics models on sorption Cr(VI onto the AC showed that nearly all of the models gave a good linearity. However, only the proposed model had a good relation with Langmuir isotherm, with respectively sorption (ks and desorption (kd constants were 5.75 x 10-4 L.mg‑1.min-1 and 2.20 x 10-3 min-1; maximum sorption capacity, qm = 20.00 mg.g-1; and equilibrium constant, K from kinetics experiment (0.261 L.mg-1 was comparable with the result from the isotherm experiment (0.269 L.mg-1. Hence, using this model, kinetics and Langmuir parameters can probably be determined from a single kinetics data experiment.

  17. Kinetics, equilibrium data and modeling studies for the sorption of chromium by Prosopis juliflora bark carbon

    Directory of Open Access Journals (Sweden)

    M. Kumar

    2017-05-01

    Full Text Available In this study, the activated carbon was prepared from Prosopis juliflora bark as a novel adsorbent. Removal of chromium (Cr was assessed by varying the parameters like metal concentration, temperature, pH, adsorbent dose and contact time. The feasibility of the sorption was studied using Freundlich and Langmuir isotherms including linear and non-linear regression methods. In Langmuir, various forms of linearized equations were evaluated. The isotherm parameter of dimensionless separation factor (RL was also studied. The kinetics of adsorption was studied by using Lagergren’s pseudo-first order and pseudo-second order equations and the results have shown that the adsorption process follows pseudo-second order kinetics and the adsorption process depends on both time and concentration. The mechanistic pathway of the adsorption process was evaluated with intraparticle diffusion model. The effect of heat of adsorption of the adsorbate onto the adsorbent material was determined using the thermodynamic parameters and the reusability of the adsorbent materials was ascertained with desorption studies. The adsorbent material characterization was done by using Fourier Transform Infrared Spectroscopy (FTIR, X-ray Diffraction (XRD method and morphology of the surface of adsorbent was identified with Scanning Electron Microscope (SEM.

  18. Development of JAEA sorption database (JAEA-SDB). Update of sorption/QA data in FY2015

    International Nuclear Information System (INIS)

    Tachi, Yukio; Suyama, Tadahiro

    2016-03-01

    Sorption and diffusion of radionuclides in buffer materials (bentonite) and rocks are the key processes in the safe geological disposal of radioactive waste, because migration of radionuclides in these barrier materials is expected to be diffusion-controlled and retarded by sorption processes. It is therefore necessary to understand the sorption and diffusion processes and develop databases compiling reliable data and mechanistic/predictive models, so that reliable parameters can be set under a variety of geochemical conditions relevant to performance assessment (PA). For this purpose, Japan Atomic Energy Agency (JAEA) has developed databases of sorption and diffusion parameters in bentonites and rocks. These sorption and diffusion databases (SDB/DDB) were firstly developed as an important basis for the H12 PA of high-level radioactive waste disposal, and have been provided through the Web. JAEA has been continuing to improve and update the SDB/DDB in view of potential future data needs, focusing on assuring the desired quality level and testing the usefulness of the databases for possible applications to PA-related parameter setting. The present report focuses on improving and updating of the sorption database (JAEA-SDB) as basis of integrated approach for PA-related K d setting and mechanistic sorption model development. This includes an overview of database structure, contents and functions including additional data evaluation function focusing on statistical data evaluation and grouping of data related to potential perturbations. K d data and their QA results are updated by focusing our recent activities on the K d setting and mechanistic model development. As a result, 11,206 K d data from 83 references were added, total number of K d values in the JAEA-SDB reached about 58,000. The QA/classified K d data reached about 60% for all K d data in JAEA-SDB. The updated JAEA-SDB is expected to make it possible to obtain quick overview of the available data, and to

  19. Physico-chemical characterisation and sorption measurements of Cs, Sr, Ni, Eu, Th, Sn and Se on Opalinus clay from Mont Terri

    International Nuclear Information System (INIS)

    Lauber, Matthias; Baeyens, Bart; Bradbury, Michael H.

    2000-12-01

    Opalinus Clay is currently under investigation as a potential host rock for the disposal of high level and long-lived intermediate radioactive waste. A throughout physico-chemical characterisation was carried out on a bore core sample from the underground rock laboratory Mont Terri (Canton Jura). The results of these investigations indicate that the major characteristics (mineralogy, cation exchange capacity, cation occupancies, selectivity coefficients, chloride and sulphate inventories) were very similar to a different core sample, previously used for pore water modelling studies. It was concluded that the pore water compositions derived in the earlier studies were reliable and could be used in this work. The organic matter which dissolved from the Opalinus Clay rock was not humic or fulvic acids and the concentration remaining in the liquid phase in the sorption experiments was < 0.5 ppm C. The organic matter is therefore considered to have little or no influence on the sorption behaviour of the studied radionuclides. Redox potential measurements of the Opalinus Clay/synthetic pore water system inside the glove boxes indicated anoxic conditions. The main focus of the experimental work presented here is on the sorption behaviour of Cs (I), Sr (II), Ni (II), Eu (III), Th (IV), Sn (IV) and Se (IV) on Opalinus Clay equilibrated with synthetic pore waters at pH 6.3 and 8. Sorption isotherms were measured for Cs, Ni, Eu, Th and Se. Single point data were measured for Sr and Sn. For all radionuclides studied the sorption kinetics were measured first. The times required to complete the sorption on the Opalinus Clay varied between one day for Th and one month for Ni and Se. Within the concentration ranges under study the uptake of Cs, Ni, Eu and Se on Opalinus Clay was non-linear, whereas for Th a linear sorption behaviour was observed. For Ni, Eu and Th the sorption increased with increasing pH. For Cs a pH independent sorption behaviour was observed. The concentration

  20. Sorption and migration of neptunium in porous sedimentary materials

    International Nuclear Information System (INIS)

    Tanaka, Tadao; Mukai, Masayuki; Nakayama, Shinichi

    2005-01-01

    Column migration experiments of neptunium were conducted for porous sedimentary materials: coastal sand, tuffaceous sand, ando soil, reddish soil, yellowish soil and loess, and migration behavior, sorption mechanisms and chemical formation of Np were investigated. The migration behavior of Np in each material was much different each other, due to chemical formation in solution and/or sorption mechanism of Np. Mathematical models of different concepts were applied to the experimental results to interpret the sorption mechanism and the migration behavior. It can be concluded that both of instantaneous equilibrium sorption and sorption-desorption kinetics have to be considered to model the Np migration in sedimentary materials. (author)

  1. Sorption isotherms modeling approach of rice-based instant soup mix stored under controlled temperature and humidity

    Directory of Open Access Journals (Sweden)

    Yogender Singh

    2015-12-01

    Full Text Available Moisture sorption isotherms of rice-based instant soup mix at temperature range 15–45°C and relative humidity from 0.11 to 0.86 were determined using the standard gravimetric static method. The experimental sorption curves were fitted by five equations: Chung-Pfost, GAB, Henderson, Kuhn, and Oswin. The sorption isotherms of soup mix decreased with increasing temperature, exhibited type II behavior according to BET classification. The GAB, Henderson, Kuhn, and Oswin models were found to be the most suitable for describing the sorption curves. The isosteric heat of sorption of water was determined from the equilibrium data at different temperatures. It decreased as moisture content increased and was found to be a polynomial function of moisture content. The study has provided information and data useful in large-scale commercial production of soup and have great importance to combat the problem of protein-energy malnutrition in underdeveloped and developing countries.

  2. Sorption studies of radioiodine on soils with special references to soil microbial biomass

    Energy Technology Data Exchange (ETDEWEB)

    Bors, J. (Niedersaechsisches Inst. fuer Radiooekologie, Hannover (Germany, F.R.)); Erten, H. (Bilkent Univ., Ankara (Turkey). Dept. of Chemistry); Martens, R. (Bundesforschungsanstalt fuer Landwirtschaft, Braunschweig (Germany, F.R.). Inst. fuer Bodenbiologie)

    1991-01-01

    In batch experiments with two types of soils, chernozem and podzol, radioiodine ({sup 125}I) showed an initial rapid sorption, followed by a long and slow further increase. Very little sorption (R{sub d} < 1) was detected in clay minerals. Generally, higher R{sub d}-values were observed for the chernozem soil, characterized by a higher amount of organic substance and of soil biomass. The sorption process was predominantly irreversible, the isotherms were linear at low ion concentrations and deviated from linearity starting at 10{sup -5} mmol.ml{sup -1}. Sorption ratio was found to increase with increasing volume to mass ratio. The composition of liquid phases (bidistilled water, synthetic soil water, rain water) highly affected iodine sorption. In experiments with KBr solution, the sorption of I{sup -} was found to be strongly preferred to Br{sup -}. Incubation of soil samples under varied conditions (decreased or increased soil biomass, O{sub 2}-concentration, incubation temperature, soil water content and storage conditions) delivered indications for the participation of soil microflora in iodine immobilization. Test with isolated soil bacteria and fungi showed that radioiodine can be incorporated by soil microorganisms under certain conditions only: Considerable uptake of radioiodine was found in washed (NaCl, CaCl{sub 2}) cells with both bacteria and fungi, but no incorporation was detected into cells incubated with radioiodine in the culture medium. (orig.).

  3. Sorption data bases for generic Swiss argillaceous rock systems

    International Nuclear Information System (INIS)

    Bradbury, M. H.; Baeyens, B.; Thoenen, T.

    2010-09-01

    implies, these factors were used to convert the (predominantly) illite sorption values into sorption values valid for the defined generic conditions with regard to mineralogy and porewater composition. Conversion factors were used to adapt sorption values to mineralogy (CF min ), to pH value (CF pH ) and to radionuclide speciation (CF spec ). Finally, a Lab→Field conversion factor (CF Lab→Field ) was applied to adapt sorption data measured in dispersed systems (batch experiments) to intact rock under in-situ conditions. Calcareous rock is used in safety analyses as being representative of a clay rock which has lost most of its favorable sorption properties due to near-field effects such as alteration by an alkaline plume and subsequent processes. It is assumed that calcareous rocks do not contain any significant quantities of phyllosilicates and that only uptake data on calcite are relevant. Sorption data on calcite are extremely sparse and the uptake mechanisms are not fully understood. However, when the existing sorption data (log R d values) are plotted against the ionic radii of the respective metals, an acceptable linear correlation between these two quantities is found. This so-called linear free energy relationship is used to complement the sparse experimental data in the SDB for calcareous systems. (authors)

  4. Sorption and Transport of Pharmaceutical chemicals in Organic- and Mineral-rich Soils

    Science.gov (United States)

    Vulava, V. M.; Schwindaman, J.; Murphey, V.; Kuzma, S.; Cory, W.

    2011-12-01

    Pharmaceutical, active ingredients in personal care products (PhACs), and their derivative compounds are increasingly ubiquitous in surface waters across the world. Sorption and transport of four relatively common PhACs (naproxen, ibuprofen, cetirizine, and triclosan) in different natural soils was measured. All of these compounds are relatively hydrophobic (log KOW>2) and have acid/base functional groups, including one compound that is zwitterionic (cetirizine.) The main goal of this study was to correlate organic matter (OM) and clay content in natural soils and sediment with sorption and degradation of PhACs and ultimately their potential for transport within the subsurface environment. A- and B-horizon soils were collected from four sub-regions within a pristine managed forested watershed near Charleston, SC, with no apparent sources of anthropogenic contamination. These four soil series had varying OM content (fOC) between 0.4-9%, clay mineral content between 6-20%, and soil pH between 4.5-6. The A-horizon soils had higher fOC and lower clay content than the B-horizon soils. Sorption isotherms measured from batch sorption experimental data indicated a non-linear sorption relationship in all A- and B-horizon soils - stronger sorption was observed at lower PhAC concentrations and lower sorption at higher concentrations. Three PhACs (naproxen, ibuprofen, and triclosan) sorbed more strongly with higher fOC A-horizon soils compared with the B-horizon soils. These results show that soil OM had a significant role in strongly binding these three PhACs, which had the highest KOW values. In contrast, cetirizine, which is predominantly positively charged at pH below 8, strongly sorbed to soils with higher clay mineral content and least strongly to higher fOC soils. All sorption isotherms fitted well to the Freundlich model. For naproxen, ibuprofen, and triclosan, there was a strong and positive linear correlation between the Freundlich adsorption constant, Kf, and f

  5. Effect of natural organic materials on cadmium and neptunium sorption

    International Nuclear Information System (INIS)

    Kung, K.S.; Triay, I.R.

    1994-01-01

    In a batch sorption study of the effect of naturally occurring organic materials on the sorption of cadmium and neptunium on oxides and tuff surfaces, the model sorbents were synthetic goethite, boehmite, amorphous silicon oxides, and a crushed tuff material from Yucca Mountain, Nevada. An amino acid, 3-(3,4-dihydroxypheny)-DL-alanine (DOPA), and an aquatic-originated fulvic material, Nordic aquatic fulvic acid (NAFA), were used as model organic chemicals. Sorption isotherm results showed that DOPA sorption followed the order aluminum oxide > iron oxide > silicon oxide and that the amount of DOAP sorption for a given sorbent increased as the solution pH was raised. The sorption of cadmium and neptunium on the iron oxide was about ten times higher than that on the aluminum oxide. The sorption of cadmium and neptunium on natural tuff material was much lower than that on aluminum and iron oxides. The sorption of cadmium on iron and aluminum oxides was found to be influenced by the presence of DOPA, and increasing the amount of DOPA coating resulted in higher cadmium sorption on aluminum oxide. However, for iron oxide, cadmium sorption decreased with increasing DOPA concentration. The presence of the model organic materials DOPA and NAFA did not affect the sorption of neptunium on tuff material or on the iron and aluminum oxides. Spectroscopic results indicate that cadmium complexes strongly with DOPA. Therefore, the effect of the organic material, DOPA, on the cadmium sorption is readily observed. However, neptunium is possibly complexed weakly with organic material. Thus, DOPA and NAFA have little effect on neptunium sorption on all sorbents selected for study

  6. Incorporating classic adsorption isotherms into modern surface complexation models: implications for sorption of radionuclides

    International Nuclear Information System (INIS)

    Kulik, D.A.

    2005-01-01

    Full text of publication follows: Computer-aided surface complexation models (SCM) tend to replace the classic adsorption isotherm (AI) analysis in describing mineral-water interface reactions such as radionuclide sorption onto (hydr) oxides and clays. Any site-binding SCM based on the mole balance of surface sites, in fact, reproduces the (competitive) Langmuir isotherm, optionally amended with electrostatic Coulomb's non-ideal term. In most SCM implementations, it is difficult to incorporate real-surface phenomena (site heterogeneity, lateral interactions, surface condensation) described in classic AI approaches other than Langmuir's. Thermodynamic relations between SCMs and AIs that remained obscure in the past have been recently clarified using new definitions of standard and reference states of surface species [1,2]. On this basis, a method for separating the Langmuir AI into ideal (linear) and non-ideal parts [2] was applied to multi-dentate Langmuir, Frumkin, and BET isotherms. The aim of this work was to obtain the surface activity coefficient terms that make the SCM site mole balance constraints obsolete and, in this way, extend thermodynamic SCMs to cover sorption phenomena described by the respective AIs. The multi-dentate Langmuir term accounts for the site saturation with n-dentate surface species, as illustrated on modeling bi-dentate U VI complexes on goethite or SiO 2 surfaces. The Frumkin term corrects for the lateral interactions of the mono-dentate surface species; in particular, it has the same form as the Coulombic term of the constant-capacitance EDL combined with the Langmuir term. The BET term (three parameters) accounts for more than a monolayer adsorption up to the surface condensation; it can potentially describe the surface precipitation of nickel and other cations on hydroxides and clay minerals. All three non-ideal terms (in GEM SCMs implementation [1,2]) by now are used for non-competing surface species only. Upon 'surface dilution

  7. Modeling of Cd(II) sorption on mixed oxide

    International Nuclear Information System (INIS)

    Waseem, M.; Mustafa, S.; Naeem, A.; Shah, K.H.; Hussain, S.Y.; Safdar, M.

    2011-01-01

    Mixed oxide of iron and silicon (0.75 M Fe(OH)3:0.25 M SiO/sub 2/) was synthesized and characterized by various techniques like surface area analysis, point of zero charge (PZC), energy dispersive X-rays (EDX) spectroscopy, Thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR) and X-rays diffraction (XRD) analysis. The uptake of Cd/sup 2+/ ions on mixed oxide increased with pH, temperature and metal ion concentration. Sorption data have been interpreted in terms of both Langmuir and Freundlich models. The Xm values at pH 7 are found to be almost twice as compared to pH 5. The values of both DH and DS were found to be positive indicating that the sorption process was endothermic and accompanied by the dehydration of Cd/sup 2+/. Further, the negative value of DG confirms the spontaneity of the reaction. The ion exchange mechanism was suggested to take place for each Cd/sup 2+/ ions at pH 5, whereas ion exchange was found coupled with non specific adsorption of metal cations at pH 7. (author)

  8. Foundations of linear and generalized linear models

    CERN Document Server

    Agresti, Alan

    2015-01-01

    A valuable overview of the most important ideas and results in statistical analysis Written by a highly-experienced author, Foundations of Linear and Generalized Linear Models is a clear and comprehensive guide to the key concepts and results of linear statistical models. The book presents a broad, in-depth overview of the most commonly used statistical models by discussing the theory underlying the models, R software applications, and examples with crafted models to elucidate key ideas and promote practical model building. The book begins by illustrating the fundamentals of linear models,

  9. Kinetic Study of Zn2+ and Cd2+ Ions Sorption by Ceric Oxide Powder

    International Nuclear Information System (INIS)

    Hassan, H.S.; Abd El-Rahman, K.M.; El Sayed, A.A.

    2008-01-01

    Ceric Oxide powder was chemically synthesized and characterized using infrared spectra and x-ray diffraction. The sorptive removal of Zinc and Cadmium ions from aqueous waste solution using synthetic ceric oxide powder was investigated using batch technique. Experiments were carried out as a function of ph, particle size, solute concentration and temperature. The uptake of zinc was found to be greater than that of cadmium. A comparison of kinetic models applied to the sorption process of each ion was evaluated for the pseudo first order, the pseudo second order, and homogeneous particle diffusion kinetic models, respectively. The results showed that both the pseudo second order and the homogeneous particle diffusion model (HPDM) were found to best correlate the experimental rate data. The numerical values of the rate constants and particle diffusion coefficients were determined from the graphical representation of the proposed models. Activation energy (Ε a ) and entropy (δ S * ) of activation for each sorption process were also calculated from the linearized form of Arrhenius equation

  10. Sorption of phosphate onto calcite; results from batch experiments and surface complexation modeling

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus

    2011-01-01

    The adsorption of phosphate onto calcite was studied in a series of batch experiments. To avoid the precipitation of phosphate-containing minerals the experiments were conducted using a short reaction time (3h) and low concentrations of phosphate (⩽50μM). Sorption of phosphate on calcite was stud......The adsorption of phosphate onto calcite was studied in a series of batch experiments. To avoid the precipitation of phosphate-containing minerals the experiments were conducted using a short reaction time (3h) and low concentrations of phosphate (⩽50μM). Sorption of phosphate on calcite...... of a high degree of super-saturation with respect to hydroxyapatite (SIHAP⩽7.83). The amount of phosphate adsorbed varied with the solution composition, in particular, adsorption increases as the CO32- activity decreases (at constant pH) and as pH increases (at constant CO32- activity). The primary effect...... of ionic strength on phosphate sorption onto calcite is its influence on the activity of the different aqueous phosphate species. The experimental results were modeled satisfactorily using the constant capacitance model with >CaPO4Ca0 and either >CaHPO4Ca+ or >CaHPO4- as the adsorbed surface species...

  11. [Study on moisture sorption process model and application traditional Chinese medicine extract powder].

    Science.gov (United States)

    Lin, Tingting; He, Yan; Xiao, Xiong; Yuan, Liang; Rao, Xiaoyong; Luo, Xiaojian

    2010-04-01

    Study on the moisture sorption process characteristics of traditional Chinese medicine extract powder, to establish a mathematical model, provide a new method for in-depth study for moisture sorption behavior of traditional Chinese medicine extract powder and a reference for determine the production cycle, and predict product stability. Analyzed moisture absorption process of traditional Chinese medicine extract powder by utilized the law of conservation of mass and Fick's first law to establish the double exponential absorption model, fitted the moisture absorption data and compared with other commonly used five kinds of model to estimate the double-exponential absorption model. The statistical analysis showed that the coefficient of determination (R2) of double exponential model, Weibull distribution model and first order kinetics model were large, but the residues sum of squares (RSS) and AIC values were small. Synthesized the practical application meaning, we consided that the double exponential model was more suitable for simulating the process of Chinese medicine extract powder moisture absorption. The double exponential is suitable for characterization the process of traditional Chinese medicine extract moisture absorption.

  12. p-Nitrophenol, phenol and aniline sorption by organo-clays

    International Nuclear Information System (INIS)

    Ko, C.H.; Fan Chihhao; Chiang, P.N.; Wang, M.K.; Lin, K.C.

    2007-01-01

    The aims of this study were to make use of organo-clays (i.e., Cloisite-10A, Cloisite-15A, Cloisite-30B and Cloisite-93A), to remove p-nitrophenol, phenol and aniline of organic pollutants. The organo-clays were characterized by X-ray diffraction (XRD). Sorption isotherm, kinetic and pH effect of p-nitrophenol, phenol and aniline sorbed by four organo-clays were evaluated. The d-spacings (0 0 1) of the XRD peak of Cloisite-10A, Cloisite-15A, Cloisite-30B and Cloisite-93A are 1.98, 2.76, 1.93 and 2.64 nm, respectively. The d(0 0 1)-spacings of XRD indicated that these p-nitropheno, phenol and aniline could penetrate into the interlayer of clays and expand the d(0 0 1)-spacings. The linear sorption isotherm of constant partition was employed to describe the sorption isotherms of phenols sorbed by organo-clays through hydrophobic-hydrophobic chemical reactions. The parabolic diffusion and power-function of kinetic models were employed to describe properly the kinetic experiments. The rate limiting step of the p-nitrophenol sorption reactions on organo-clays were diffusion-controlled processes (i.e., 15A, 30B, 93A) and chemical-controlled process for 10A organo-clays. The pre-exponential factor of the p-nitrophenol sorbed by four organo-clays showed the trend as follows: 10A > 30B > 93A > 15A. The efficiency of these organo-clays in removing phenol compounds in water treatments merit further study

  13. INFLUENCES OF SOIL PROPERTIES ON CHROMIUM (III SORPTION

    Directory of Open Access Journals (Sweden)

    R. Salmasi, F. Salmasi

    2007-07-01

    Full Text Available Soil adsorbing properties reduce sorption ability of the metal, which in turn may influence decision for remediation at contaminated sites. The objective of this study is presentation of a model based on soil properties to estimate the sorption of Cr(III in chromium contaminated soils. Twenty uncontaminated soil samples, with properties similar to the contaminated soils were selected from around of city of Tabriz and treated with Cr as CrCl3. A multiple regression analysis with statgraph software was used to drive an expression that related Cr sorption to common soil properties. The results showed that four soil properties were important in determining the amount of Cr adsorbed by the soils including pH, cation exchange capacity, total inorganic carbon and clay content with nearly 80% variability in Cr sorption and a reasonable level of confidence by this model. The obtained model suggested that Cr(III sorption was enhanced by higher soil pH, more total inorganic carbon, more clay, and higher cation exchange capacity.

  14. Radionuclide sorption from the safety evaluation perspective

    International Nuclear Information System (INIS)

    1992-01-01

    Research and development directed towards the assessment of the long-term performance of radioactive waste disposal systems has been recognised as a priority area with a strong need for international co-operation and co-ordination. The ultimate aims is to promote the quality and credibility of safety assessment techniques for radioactive waste disposal. Sorption in the geosphere is one of the key processes for retarding the transport of radionuclide from the underground disposal facility to the biosphere. In many cases, sorption in the near field and in the biosphere is also important. A workshop, organised to favor discussion around a small number of invited papers, was held in October 1991: - to evaluate critically the way sorption processes are incorporated in performance assessment models; - to identify open issues of high priority, and; - to propose future activities to resolve these issues. These proceedings reproduce the invited papers and the conclusions and recommendations adopted by the workshop. Eight papers are in the INIS SCOPE. The main subjects studied are: sorption database comparison, sorption database development and three case studies, experimental techniques, adsorption models

  15. Migration and sorption phenomena in packaged foods.

    Science.gov (United States)

    Gnanasekharan, V; Floros, J D

    1997-10-01

    Rapidly developing analytical capabilities and continuously evolving stringent regulations have made food/package interactions a subject of intense research. This article focuses on: (1) the migration of package components such as oligomers and monomers, processing aids, additives, and residual reactants in to packaged foods, and (2) sorption of food components such as flavors, lipids, and moisture into packages. Principles of diffusion and thermodynamics are utilized to describe the mathematics of migration and sorption. Mathematical models are developed from first principles, and their applicability is illustrated using numerical simulations and published data. Simulations indicate that available models are system (polymer-penetrant) specific. Furthermore, some models best describe the early stages of migration/sorption, whereas others should be used for the late stages of these phenomena. Migration- and/or sorption-related problems with respect to glass, metal, paper-based and polymeric packaging materials are discussed, and their importance is illustrated using published examples. The effects of migrating and absorbed components on food safety, quality, and the environment are presented for various foods and packaging materials. The impact of currently popular packaging techniques such as microwavable, ovenable, and retortable packaging on migration and sorption are discussed with examples. Analytical techniques for investigating migration and sorption phenomena in food packaging are critically reviewed, with special emphasis on the use and characteristics of food-simulating liquids (FSLs). Finally, domestic and international regulations concerning migration in packaged foods, and their impact on food packaging is briefly presented.

  16. Identification of TCE and PCE sorption and biodegradation parameters in a sandy aquifer for fate and transport modelling: batch and column studies.

    Science.gov (United States)

    Kret, E; Kiecak, A; Malina, G; Nijenhuis, I; Postawa, A

    2015-07-01

    The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, K d = 0.0016; PCE, soil 1, K d = 0.0051; PCE, soil 2, K d = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, K f = 0.6493 and S max = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ(13)C values within the range of -23.6 ÷ -24.3‰ and -26.3 ÷-27.7‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer.

  17. Removal of cobalt and strontium from groundwater by sorption onto fishbone

    International Nuclear Information System (INIS)

    Younjin Park; Won Sik Shin; Sang-June Choi

    2013-01-01

    Fishbone as a main backfill material of permeable reactive barrier to remediate groundwater contaminated with Co and Sr was investigated through single- and bi-solute competitive sorptions. The single-solute sorption data were fitted by Freundlich, Langmuir and Dubinin-Radushkevich models. The coefficients of determination (R 2 > 0.91) indicated that all models fitted well. Maximum sorption capacities (q mL ) of Co and Sr predicted by the Langmuir model were 0.55 mmol/g and 0.50 mmol/g, respectively. The bi-solute competitive sorption of the metals was analyzed by the Langmuir, competitive Langmuir, Sheindorf-Rebhun-Sheintuch (SRS) and P-factor models. The sorbed amount of one solute in bi-solute system decreased due to competition with the other solute. Langmuir model parameters for single- (q mL and b L ) and bi-solute (q mL * and b L * ) competitive sorptions were compared to analyze the effect of competition between the metals. The competitive Langmuir, SRS and P-factor models predicted the bi-solute competitive sorption data well (R 2 > 0.93). (author)

  18. Radionuclide sorption on crushed and intact granitic rock

    International Nuclear Information System (INIS)

    Eriksen, Tryggve E.; Locklund, Birgitta

    1989-05-01

    The specific surface areas and distribution ratios for sorption of 85 Sr, 137 Cs and 152 Eu were measured for crushed and intact granite rock. The experimental data can be accommodated by a sorption model encompassing sorption on outer and inner surface. It is clearly demonstrated that the time required to obtain reliable Kd-values for the sorption of strongly sorbing radionuclides like 152 Eu is very long due to solution depletion and slow diffusion into the rock. A combination of surface area measurements and batch sorption with small particles may therefore be preferable when studying strongly sorbing nuclides. (authors) (17 figs., 6 tabs.)

  19. Kinetic study of Cs+ and Eu3+ ions sorption by zirconium oxide powder

    International Nuclear Information System (INIS)

    Hanafi, H.A.; Hassan, H.S.; Hamed, M.M.

    2009-01-01

    Full text: Zirconium oxide powder was chemically synthesized by sol-gel method and characterized using infrared spectra and x-ray diffraction. The sorptive removal of cesium and europium ions from aqueous waste solution using synthetic zirconium oxide powder was investigated using batch technique. Experiments were carried out as a function of pH, time and temperature. The uptake of europium was found to be greater than that of cesium. A comparison of kinetic models applied to the sorption process of each ion was evaluated for the pseudo first order, the pseudo second order, and homogeneous particle diffusion kinetic models, respectively. The results showed that both the pseudo second order and the homogeneous particle diffusion models (HPDM) were found to best correlate the experimental rate data. The numerical values of the rate constants and particle diffusion coefficients were determined from the graphical representation of the proposed models. Activation energy (Ea) and entropy (Δ S*) of activation for each sorption process were also calculated from the linearized form of Arrhenius equation. (author)

  20. β-Zeolite modified by ethylenediamine for sorption of Th(IV)

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Peng; Wu, Hanyu; Yuan, Ni; Yin, Zhuoxin; Pan, Duoqiang; Wu, Wangsuo [Lanzhou Univ. (China). Radiochemistry Lab.; Ministry of Education, Lanzhou (China). Key Lab. of Special Function Materials and Structure Design

    2017-08-01

    β-Zeolite-EDA was modified with ethylenediamine (EDA) after synthesized. The synthesized material was characterized and used for removal of Th(IV) from aqueous solutions. The influences of pH, ionic strength, contact time, temperature and humic acid (HA) on Th(IV) sorption onto synthesized β-zeolite-EDA was studied by batch technique. The dynamic process showed that the sorption of Th(IV) onto β-zeolite-EDA matched the pseudo-second-order kinetics model. The sorption of Th(IV) on β-zeolite-EDA was significantly dependent on pH values, the sorption percentage increased markedly at pH 3.5-4.5, and then maintained a steady state as pH values increased. Through simulating the sorption isotherms by Langmuir, Freundlich and Dubini-Radushkevich (D-R) models, it could be seen respectively that the sorption pattern of Th(IV) on β-zeolite-EDA was mainly controlled by surface complexation, and that the sorption processes was endothermic and spontaneous. The presence of HA increased Th(IV) sorption on β-zeolite-EDA.

  1. Sorption Energy Maps of Clay Mineral Surfaces

    International Nuclear Information System (INIS)

    Cygan, Randall T.; Kirkpatrick, R. James

    1999-01-01

    A molecular-level understanding of mineral-water interactions is critical for the evaluation and prediction of the sorption properties of clay minerals that may be used in various chemical and radioactive waste disposal methods. Molecular models of metal sorption incorporate empirical energy force fields, based on molecular orbital calculations and spectroscopic data, that account for Coulombic, van der Waals attractive, and short-range repulsive energies. The summation of the non-bonded energy terms at equally-spaced grid points surrounding a mineral substrate provides a three dimensional potential energy grid. The energy map can be used to determine the optimal sorption sites of metal ions on the exposed surfaces of the mineral. By using this approach, we have evaluated the crystallographic and compositional control of metal sorption on the surfaces of kaolinite and illite. Estimates of the relative sorption energy and most stable sorption sites are derived based on a rigid ion approximation

  2. Behavior of Cs in Grimsel granodiorite. Sorption on main minerals and crushed rock

    Energy Technology Data Exchange (ETDEWEB)

    Muuri, Eveliina; Ikonen, Jussi; Matara-aho, Minja; Voutilainen, Mikko; Siitari-Kauppi, Marja [Helsinki Univ. (Finland). Dept. of Chemistry; Lindberg, Antero [Geological Survey of Finland, Espoo (Finland); Holgersson, Stellan [Chalmers University of Technology, Goeteborg (Sweden). Dept. of Chemical and Biological Engineering, Nuclear Chemistry; Martin, Andrew [Nagra (National Cooperative for the Disposal of Radioactive Waste), Wettingen (Switzerland)

    2016-11-01

    In this study the sorption of cesium was investigated on four different minerals; quartz, plagioclase, potassium feldspar and biotite as well as granodiorite obtained from the Grimsel test site in Switzerland. The experiments were conducted in the presence of the weakly saline Grimsel groundwater simulant by determining the distribution coefficients using batch sorption experiments and PHREEQC-modelling across a large concentration range. In addition, the purity of the minerals was measured by XRD and the specific surface areas by BET method using krypton. The distribution coefficients of cesium were largest on biotite (0.304±0.005 m{sup 3}/kg in 10{sup -8} M). Furthermore, the sorption of cesium on quartz was found to be negligibly small in all investigated concentrations and the sorption of cesium on potassium feldspar and plagioclase showed similar behavior against a concentration isotherm with distribution coefficients of 0.0368±0.0004 m{sup 3}/kg and 0.18±0.04 m{sup 3}/kg in 10{sup -8} M. Finally, cesium sorption behavior on crushed granodiorite followed the trend of one of its most abundant mineral, plagioclase with distribution coefficient values of 0.107±0.003 m{sup 3}/kg in 10{sup -8} M. At low concentrations (<1.0.10{sup -6} M) cesium was sorbed on the frayed edge sites of biotite and once these sites are fully occupied cesium sorbs additionally to the Type II and Planar sites. As a consequence, the sorption of cesium on biotite is decreased at concentrations >1.0.10{sup -6} M. Secondly cesium sorption on potassium feldspar and plagioclase showed similar non-linear behavior with varying concentration. The results were used to assist the interpretation of cesium diffusion process in the 2.5 year in-situ experiment carried out in the underground laboratory at Grimsel test site in Switzerland (2007-2009).

  3. Evaluation of theoretical and empirical water vapor sorption isotherm models for soils

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Tuller, Markus; Moldrup, Per

    2016-01-01

    sorption isotherms of building materials, food, and other industrial products, knowledge about the 24 applicability of these functions for soils is noticeably lacking. We present validation of nine models for characterizing adsorption/desorption isotherms for a water activity range from 0.03 to 0...

  4. The sorption of polonium, actinium and protactinium onto geological materials

    International Nuclear Information System (INIS)

    Baston, G.M.N.; Berry, J.A.; Brownsword, M.; Heath, T.G.; Ilett, D.J.; McCrohon, R.; Tweed, C.J.; Yui, M.

    1999-01-01

    This paper describes a combined experimental and modeling program of generic sorption studies to increase confidence in the performance assessment for a potential high-level radioactive waste repository in Japan. The sorption of polonium, actinium and protactinium onto geological materials has been investigated. Sorption of these radioelements onto bentonite, tuff and granodiorite from equilibrated de-ionized water was studied under reducing conditions at room temperature. In addition, the sorption of actinium and protactinium was investigated at 60 C. Thermodynamic chemical modeling was carried out to aid interpretation of the results

  5. The sorption of polonium, actinium and protactinium onto geological materials

    Energy Technology Data Exchange (ETDEWEB)

    Baston, G.M.N.; Berry, J.A.; Brownsword, M.; Heath, T.G.; Ilett, D.J.; McCrohon, R.; Tweed, C.J.; Yui, M.

    1999-07-01

    This paper describes a combined experimental and modeling program of generic sorption studies to increase confidence in the performance assessment for a potential high-level radioactive waste repository in Japan. The sorption of polonium, actinium and protactinium onto geological materials has been investigated. Sorption of these radioelements onto bentonite, tuff and granodiorite from equilibrated de-ionized water was studied under reducing conditions at room temperature. In addition, the sorption of actinium and protactinium was investigated at 60 C. Thermodynamic chemical modeling was carried out to aid interpretation of the results.

  6. Sensitivity of Deep Soil Organic Carbon Age to Sorption, Transport and Microbial Interactions - Insights from a Calibrated Process Model

    Science.gov (United States)

    Ahrens, B.; Schrumpf, M.; Reichstein, M.

    2013-12-01

    Subsoil soil organic carbon (SOC) is characterized by conventional radiocarbon ages on the order of centuries to millennia. Most vertically explicit SOC turnover models represent this persistence of deep SOC by one pool that has millennial turnover times. This approach lumps different stabilizing mechanisms such as chemical recalcitrance, sorptive stabilization and energy limitation into a single rate constant. As an alternative, we present a continuous, vertically explicit SOC decomposition model that allows for stabilization via sorption and microbial interactions (COMISSION model). We compare the COMISSION model with the SOC profile of a Haplic Podzol under a Norway spruce forest. In the COMISSION model two pools receive aboveground litter input and vertically distributed root litter input. The readily leachable and soluble fraction of litter input enters a dissolved organic carbon pool (DOC), while the rest enters the residue pool which represents polymeric, non-soluble SOC. The residue pool is depolymerized with extracellular enzymes produced by a microbial pool to enter the DOC pool which represents SOC potentially available for assimilation by microbes. The adsorption/desorption of DOC from/to mineral surfaces controls the availability of carbon in the DOC pool for assimilatory uptake by microbes. The sorption of DOC is modeled with dynamic Langmuir equations. The desorbed part of the DOC pool not only constitutes the substrate for the microbial pool, but is also transported via advection. Interactions of microbes with the residue and DOC pool are modeled with Michaelis-Menten kinetics - this not only allows representing ';priming', but also the retardation of decomposition via energy limitation in the deep soil where substrate is scarce. Further, soil organic matter is recycled within the soil profile through microbial processing - dead microbes either enter the DOC or the residue pool, and thereby also contribute to longer residence times with soil depth

  7. Sorption of cesium in intact rock

    International Nuclear Information System (INIS)

    Puukko, E.

    2014-04-01

    The mass distribution coefficient K d is used in performance assessment (PA) to describe sorption of a radionuclide on rock. The R d is determined using crushed rock which causes uncertainty in converting the R d values to K d values for intact rock. This work describes a method to determine the equilibrium of sorption on intact rock. The rock types of the planned Olkiluoto waste disposal site were T-series mica gneiss (T-MGN), T-series tonalite granodiorite granite gneiss (T-TGG), P-series tonalite granodiorite granite gneiss (P-TGG) and pegmatitic granite (PGR). These rocks contain different amount of biotite which is the main sorbing mineral. The sorption of cesium on intact rock slices was studied by applying an electrical field to speed up migration of cesium into the rock. Cesium is in the solution as a noncomplex cation Cs + and it is sorbed by ion exchange. The tracer used in the experiments was 134 Cs. The experimental sorption on the intact rock is compared with values calculated using the in house cation exchange sorption model (HYRL model) in PHREEQC program. The observed sorption on T-MGN and T-TGG rocks was close to the calculated values. Two PGR samples were from a depth of 70 m and three samples were from a depth of 150 m. Cesium sorbed more than predicted on the two 70 m PGR samples. The sorption of Cs on the three 150 m PGR samples was small which was consistent with the calculations. The pegmatitic granite PGR has the smallest content of biotite of the four rock types. In the case of P-TGG rock the observed values of sorption were only half of the calculated values. Two kind of slices were cut from P-TGG drill core. The slices were against and to the direction of the foliation of the biotite rims. The sorption of cesium on P-TGG rock was same in both cases. The results indicated that there was no effect of the directions of the electric field and the foliation of biotite in the P-TGG rock. (orig.)

  8. Surface complexation modeling of U(VI) sorption on GMZ bentonite in the presence of fulvic acid

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jie [Lanzhou Univ. (China). Radiochemistry Laboratory; Ministry of Industry and Information Technology, Guangzhou (China). The 5th Electronics Research Inst.; Luo, Daojun [Ministry of Industry and Information Technology, Guangzhou (China). The 5th Electronics Research Inst.; Qiao, Yahua; Wang, Liang; Zhang, Chunming [Ministry of Environmental Protection, Beijing (China). Nuclear and Radiation Safety Center; Wu, Wangsuo [Lanzhou Univ. (China). Radiochemistry Laboratory; Ye, Yuanlv [Ministry of Environmental Protection, Beijing (China). Nuclear and Radiation Safety Center; Lanzhou Univ. (China). Radiochemistry Laboratory

    2017-03-01

    In this work, experiments and modeling for the interactions between uranyl ion and GMZ bentonite in the presence of fulvic acid are presented. The results demonstrated that FA is strongly bound to GMZ bentonite, and these molecules have a very large effect on the U(VI) sorption. The results also demonstrated that U(VI) sorption to GMZ bentonite in the presence and absence of sorbed FA can be well predicted by combining SHM and DLM. According to the model calculations, the nature of the interactions between FA with U(VI) at GMZ bentonite surface is mainly surface complex. The first attempt to simulate clay interaction with humus by the SHM model.

  9. Sorption of strontium by magnetically modified yeast cells

    International Nuclear Information System (INIS)

    Hu Yantao; Ji Yanqin; Tian Qing; Shao Xianzhang; Shi Jianhe; Ivo Safarik; Zhang Shengdong; Li Jinying

    2008-01-01

    Magnetically modified fodder's yeast (Kluyveromyces fragilis) cells using water based magnetic fluid, were characterized by scanning electron microscopy (SEM) and Vibrating Sample Magnetometer (VSM). The sorption-desorption properties of Sr 2+ by these yeast cells from nitrate salt of Sr 2+ were studied. The results demonstrated that the Sr 2+ sorption volume by these cells enhanced with increasing pH and reached a plateau between pH 4.0 and 7.0. A minor effect by temperature was observed. The sorption volumes are 19.5 mg/g and 53.5 mg/g from 10 ppm and 40 ppm Sr 2+ solution respectively within 20 min. The sorption of Sr 2+ in these cells can be desorbed under 0.1 mol/L HNO 3 solution. The maximum Sr 2+ sorption volume is 96.7 mg/g at 20℃. The sorption characteristic fits Langmuir model well with 140.8 mg/g calculated maximum sorption volume by these yeast cells. (authors)

  10. Application of iron-rich natural clays in Camlica, Turkey for boron sorption from water and its determination by fluorimetric-azomethine-H method

    International Nuclear Information System (INIS)

    Seyhan, Serap; Seki, Yoldas; Yurdakoc, Mueruevvet; Merdivan, Melek

    2007-01-01

    In this study, iron-rich natural Camlica Bentonites, CB1 and CB2, were used for the sorption of boron in water samples. Boron was determined by newly progressed fluorimetric azomethine-H method. The optimum conditions found using factorial designs are pH 10, 45 deg. C, 0.250 g of clay and 20 mL of sample volume. It was found that 180 min is enough time for the equilibrium state to be reached in boron adsorption. At these conditions, boron sorption percentage was 80% for CB1 and 30% for CB2. The adsorption isotherms are well described by linear Freundlich model. Various geothermal waters in our country were also studied for boron sorption

  11. Effect of competing cations on strontium sorption to surficial sediments

    International Nuclear Information System (INIS)

    Bunde, R.L.; Rosentreter, J.J.

    1995-01-01

    The following study was conducted to determine strontium distribution coefficients (K d 'S) of a surficial sediment at the Idaho National Engineering Laboratory (INEL), Idaho. Batch experimental techniques were used to determine K d 's which describe the partitioning of a solute between the solution and solid phase. A surficial sediment was mixed with synthesized aqueous solutions designed to chemically simulate wastewater disposed to infiltrations ponds near the Idaho Chemical Processing Plant at the INEL with respect to major ionic character and pH. The effects of variable concentrations of competing cations (sodium, potassium, calcium and magnesium) on strontium sorption were investigated at a fixed pH of 8.00. The pH of the natural system shows no appreciable variation, whereas a marked variability in cation concentration has been noted. Strontium sorption was impacted to a greater degree by the concentration of calcium and magnesium in solution than by the presence of sodium or potassium. However, extreme sodium solution concentrations of 1.0 to 5.0 g/L dramatically reduced strontium sorption. In all cases, strontium K d 's decreased as the concentration of calcium and magnesium in solution increased. Linear isotherm model K d 's ranged from 12.0 to 84.7 mL/g. Analysis of data from these experiments indicated that moderate concentrations of calcium and magnesium (less than 40 mg/L) and high concentrations of sodium (1.0 to 5.0 g/L) in wastewater increase strontium mobility by decreasing the sorption of strontium on surficial sediments beneath infiltration ponds at the INEL

  12. Sorption of Heterocyclic Organic Compounds to Multiwalled Carbon Nanotubes.

    Science.gov (United States)

    Metzelder, Florian; Funck, Matin; Schmidt, Torsten C

    2018-01-16

    Sorption is an important natural and technical process. Sorption coefficients are typically determined in batch experiments, but this may be challenging for weakly sorbing compounds. An alternative method enabling analysis of those compounds is column chromatography. A column packed with the sorbent is used and sorption data are determined by relating sorbate retention to that of a nonretarded tracer. In this study, column chromatography was applied for the first time to study sorption of previously hardly investigated heterocyclic organic compounds to multiwalled carbon nanotubes (MWCNTs). Sorption data for these compounds are very limited in literature, and weak sorption is expected from predictions. Deuterium oxide was used as nonretarded tracer. Sorption isotherms were well described by the Freundlich model and data showed reasonable agreement with predicted values. Sorption was exothermic and physisorption was observed. H-bonding may contribute to overall sorption, which is supported by reduced sorption with increasing ionic strength due to blocking of functional groups. Lowering pH reduced sorption of ionizable compounds, due to electrostatic repulsion at pH 3 where sorbent as well as sorbates were positively charged. Overall, column chromatography was successfully used to study sorption of heterocyclic compounds to MWCNTs and could be applied for other carbon-based sorbents.

  13. Sorption of cesium and strontium from concentrated brines by backfill barrier materials

    International Nuclear Information System (INIS)

    Winslow, C.D.

    1981-03-01

    The sorption of radionuclides from potentially intruding groundwater at a nuclear waste repository is a major chemical function of backfill barriers. In this study, various materials (including clays, zeolites and an inorganic ion exchanger) were screened for the sorption of the fission products cesium and strontium in concentrated brines. Representative brines A and B for the Waste Isolation Pilot Plant (WIPP), a proposed radioactive waste repository and test facility in bedded salt were used. Sorption properties were quantified using empirical distribution coefficients, k/sub d/. Of the materials examined, sodium titanate had the highest k/sub d/ for the sorption of Sr(II) in both brine A (k/sub d/ = 125 ml/g) and brine B(k/sub d/ = 500 to 600 ml/g). A mordenite-type zeolite was the most effective getter for Cs(I) in brine A (k/sub d = 27 ml/g), while illite yielded the highest k/sub d/ for Cs(I) in brine B (k/sub d/ = 115 ml/g). The relative merit of these k/sub d/ values is evaluated in terms of calculated estimates of breakthrough times for a backfill barrier containing the getter. Results show that a backfill mixture containing these getters is potentially an effective barrier to the migration of Sr(II) and Cs(I), although further study (especially for the sorption of cesium from brine A) is recommended. Initial mechanistic studies revealed competing ion effects which would support an ion exchange mechanism. K/sub d/'s were constant over a Sr(II) concentration range of 10 -11 to 10 -5 M and a Cs(I) concentration range of 10 -8 to 10 -5 M, supporting the choice of a linear sorption isotherm as a model for the results. Constant batch composition was shown to be attained within one week

  14. Kinetic characteristic of phenanthrene sorption in aged soil amended with biochar

    Science.gov (United States)

    Kim, Chanyang; Kim, Yong-Seong; Hyun, Seunghun

    2015-04-01

    Biochar has been recently highlighted as an amendment that affects yield of the crops by increasing pH, cation exchange capacity and water retention, and reduces the lability of contaminants by increasing sorption capacity in the soil system. Biochar's physico-chemical properties, high CEC, surfaces containing abundant micropores and macropores, and various types of functional groups, play important roles in enhancing sorption capacity of contaminants. Aging through a natural weathering process might change physico-chemical properties of biochar amended in soils, which can affect the sorption behavior of contaminants. Thus, in this study, the sorption characteristics of phenanthrene (PHE) on biochar-amended soils were studied with various types of chars depending on aging time. To do this, 1) soil was amended with sludge waste char (SWC), wood char (WC), and municipal waste char (MWC) during 0, 6, and 12 month. Chars were applied to soil at 1% and 2.5% (w/w) ratio. 2) Several batch kinetic and equilibrium studies were conducted. One-compartment first order and two-compartment first order model apportioning the fraction of fast and slow sorbing were selected for kinetic models. Where, qt is PHE concentration in biochar-amended soils at each time t, qeis PHE concentration in biochar-amended soils at equilibrium. ff is fastly sorbing fraction and (1-ff) is slowly sorbing fraction. k is sorption rate constant from one-compartment first order model, k1 and k2 are sorption rate constant from two-compartment first order model, t is time (hr). The equilibrium sorption data were fitted with Fruendlich and Langmuir equation. 3) Change in physico-chemical properties of biochar-amended soils was investigated with aging time. Batch equilibrium sorption results suggested that sorbed amount of PHE on WC was greater than SWC and MWC. The more char contents added to soil, the greater sorption capacity of PHE. Sorption equilibrium was reached after 4 hours and equilibrium pH ranged

  15. Carbon dioxide sorption on EDTA modified halloysite

    Directory of Open Access Journals (Sweden)

    Waszczuk Patrycja

    2016-01-01

    Full Text Available In this paper the sorption study of CO2 on EDTA surface modified halloysite was conducted. In the paper chemical modification of halloysite from the Dunino deposit (Poland and its influence on sorption of CO2 are presented. A halloysite samples were washed with water-EDTA 1% solution, centrifuged to separate liquid and impurities and dried. The samples were tested for the sorption capacity using a manometric method with pressure up to 3 MPa. A Langmuir adsorption model was fitted to the data. The results showed that EDTA had a limited effect on the increase of sorption potential at low pressure and the samples exhibited similar results to that ones treated solely with the water solution.

  16. Effect of sediment properties on the sorption of C12-2-LAS in marine and estuarine sediments

    NARCIS (Netherlands)

    Rico Rico, A.; Temara, A.; Behrends, T.; Hermens, J.L.M.

    2009-01-01

    Linear alkylbenzene sulfonates (LAS) are anionic high production volume surfactants used in the manufacture of cleaning products. Here, we have studied the effect of the characteristics of marine and estuarine sediments on the sorption of LAS. Sorption experiments were performed with single sediment

  17. Sorption of uranium (VI) on homoionic sodium smectite experimental study and surface complexation modeling.

    Science.gov (United States)

    Korichi, Smain; Bensmaili, Aicha

    2009-09-30

    This paper is an extension of a previous paper where the natural and purified clay in the homoionic Na form were physico-chemically characterized (doi:10.1016/j.clay.2008.04.014). In this study, the adsorption behavior of U (VI) on a purified Na-smectite suspension is studied using batch adsorption experiments and surface complexation modeling (double layer model). The sorption of uranium was investigated as a function of pH, uranium concentration, solid to liquid ratio, effect of natural organic matter (NOM) and NaNO(3) background electrolyte concentration. Using the MINTEQA2 program, the speciation of uranium was calculated as a function of pH and uranium concentration. Model predicted U (VI) aqueous speciation suggests that important aqueous species in the [U (VI)]=1mg/L and pH range 3-7 including UO(2)(2+), UO(2)OH(+), and (UO(2))(3)(OH)(5)(+). The concentration of UO(2)(2+) decreased and that of (UO(2))(3)(OH)(5)(+) increased with increasing pH. The potentiometric titration values and uptake of uranium in the sodium smectite suspension were simulated by FITEQL 4.0 program using a two sites model, which is composed of silicate and aluminum reaction sites. We compare the acidity constants values obtained by potentiometric titration from the purified sodium smectite with those obtained from single oxides (quartz and alpha-alumina), taking into account the surface heterogeneity and the complex nature of natural colloids. We investigate the uranium sorption onto purified Na-smectite assuming low, intermediate and high edge site surfaces which are estimated from specific surface area percentage. The sorption data is interpreted and modeled as a function of edge site surfaces. A relationship between uranium sorption and total site concentration was confirmed and explained through variation in estimated edge site surface value. The modeling study shows that, the convergence during DLM modeling is related to the best estimation of the edge site surface from the N(2

  18. Modeling Np and Pu transport with a surface complexation model and spatially variant sorption capacities: Implications for reactive transport modeling and performance assessments of nuclear waste disposal sites

    Science.gov (United States)

    Glynn, P.D.

    2003-01-01

    One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) seminal findings on the spatial and temporal variability of partitioning (of 90Sr) are reexamined and found partially caused by his assumption of a kinetically limited reaction. In the present work, sorption is assumed the predominant retardation process controlling Pu and Np transport, and is simulated using a diffuse-double-layer-surface-complexation (DDLSC) model. Transport simulations consider the infiltration of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, but with different variances and spatial correlation structures). Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant K d advection-dispersion transport model and compared. Functional differences often are great enough that they prevent a meaningful fit of the simulation results with a constant K d (or even a Langmuir or Freundlich) model, even in the case of Np, a weakly sorbed radionuclide under the

  19. A mechanistic approach to the generation of sorption databases

    International Nuclear Information System (INIS)

    Bradbury, M.H.; Baeyens, B.

    1992-01-01

    Sorption of radionuclides in the near and far fields of an underground nuclear waste repository is one of the most important processes retarding their release to the environment. In the vast majority of cases sorption data have been presented in terms of empirical parameters such as distribution coefficients and isotherm equations. A consequence of this empirical methodology is that the sorption data are only strictly valid under the experimental conditions at which they were measured. Implicit in this approach is the need to generate large amounts of data and fitting parameters necessary for an empirical description of sorption under all realistically conceivable conditions which may arise in space and time along the migration pathway to Man. An alternative approach to the problem is to try to understand, and develop model descriptions of, underlying retention mechanisms and to identify those systems parameters which essentially determine the extent of sorption. The aim of this work is to see to what extent currently existing mechanistic models, together with their associated data, can be applied to predict sorption data from laboratory experiments on natural systems. This paper describes the current status of this work which is very much in an early stage of development. An example is given whereby model predictions are compared with laboratory results for the sorption of Np at trace concentrations under oxidizing conditions on a series of minerals relevant to granite formations. 31 refs., 11 figs., 5 tabs

  20. Water sorption and water permeability properties of edible film made from potato peel waste

    Directory of Open Access Journals (Sweden)

    Siti Hajar OTHMAN

    Full Text Available Abstract The water sorption and permeability properties of edible film produced from potato peel waste was investigated under different levels of relative humidity (23, 33, 43, 57, 75% RH and temperatures (5, 30, 50 °C. The water sorption behaviour and isotherms of the film were investigated by fitting water sorption data to the Peleg model and the Guggenheim, Anderson de Boer model (GAB model. The amount of moisture content, time required for the moisture content of the film to reach equilibrium, water sorption rate, and water sorption capacity increased when the relative humidity increased. The effect of temperature on moisture content, water sorption rate, water sorption capacity, and monolayer moisture content is complex and related to the water activity as well as the moisture content. Based on R2 and RMSE values, the Peleg and GAB models were respectively determined as excellent models to predict the water sorption properties of the films, thus supporting the reliability of water sorption behaviour prediction. The water vapour transmission rate and water vapour permeability increased with an increase in relative humidity and temperature. The sorption and permeability properties of the film are worth investigation since the final application of the film as food packaging is ultimately dependent on these behaviours.

  1. Sorption mechanism of U(VI) on to natural soil system: a study using intra-particle diffusion model

    International Nuclear Information System (INIS)

    Rout, S.; Kumar, A.; Ravi, P.M.; Tripathi, R.M.

    2015-01-01

    The rate of U(VI) adsorption onto natural soils from different parent materials has been studied experimentally using the batch adsorption method at five different initial U(VI) concentrations. The utility of Weber and Morris Interparticle diffusion model for describing the mechanism and kinetics of sorption is discussed. The study reveals that the mechanism of U(VI) sorption involves three steps such as: external surface adsorption, gradual adsorption stage which is the rate determining step and the last portion refers to the final equilibrium stage. The steps involved in sorption of U(VI) on to soil is same irrespective of soil types and initial U(VI) concentration. (author)

  2. Implementation of sorption hysteresis in multi-Fickian moisture transport

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Svensson, Staffan

    2007-01-01

    In the cellular structure of wood, bound-water diffusion and water-vapor diffusion interact via sorption in a complex moisture-transportation system. At low relative humidities, moisture transport may be modeled by a Fickian diffusion equation with a good approximation. At higher relative......-35% in moisture content. Hence, for a precise moisture content computation, sorption hysteresis must be taken into account. The present paper explains the relation between sorption hysteresis and multi-Fickian moisture transport, and clarifies how models for the two phenomena are coupled. To illustrate...

  3. Transport and sorption of volatile organic compounds and water vapor in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Tsair-Fuh [Univ. of California, Berkeley, CA (United States)

    1995-07-01

    To gain insight on the controlling mechanisms for VOC transport in porous media, the relations among sorbent properties, sorption equilibrium and intraparticle diffusion processes were studied at the level of individual sorbent particles and laboratory columns for soil and activated carbon systems. Transport and sorption of VOCs and water vapor were first elucidated within individual dry soil mineral grains. Soil properties, sorption capacity, and sorption rates were measured for 3 test soils; results suggest that the soil grains are porous, while the sorption isotherms are nonlinear and adsorption-desorption rates are slow and asymmetric. An intragranular pore diffusion model coupled with the nonlinear Freundlich isotherm was developed to describe the sorption kinetic curves. Transport of benzene and water vapor within peat was studied; partitioning and sorption kinetics were determined with an electrobalance. A dual diffusion model was developed. Transport of benzene in dry and moist soil columns was studied, followed by gaseous transport and sorption in activated carbon. The pore diffusion model provides good fits to sorption kinetics for VOCs to soil and VOC to granular activated carbon and activated carbon fibers. Results of this research indicate that: Intraparticle diffusion along with a nonlinea sorption isotherm are responsible for the slow, asymmetric sorption-desorption. Diffusion models are able to describe results for soil and activated carbon systems; when combined with mass transfer equations, they predict column breakthrough curves for several systems. Although the conditions are simplified, the mechanisms should provide insight on complex systems involving transport and sorption of vapors in porous media.

  4. Equilibrium modeling of mono and binary sorption of Cu(II and Zn(II onto chitosan gel beads

    Directory of Open Access Journals (Sweden)

    Nastaj Józef

    2016-12-01

    Full Text Available The objective of the work are in-depth experimental studies of Cu(II and Zn(II ion removal on chitosan gel beads from both one- and two-component water solutions at the temperature of 303 K. The optimal process conditions such as: pH value, dose of sorbent and contact time were determined. Based on the optimal process conditions, equilibrium and kinetic studies were carried out. The maximum sorption capacities equaled: 191.25 mg/g and 142.88 mg/g for Cu(II and Zn(II ions respectively, when the sorbent dose was 10 g/L and the pH of a solution was 5.0 for both heavy metal ions. One-component sorption equilibrium data were successfully presented for six of the most useful three-parameter equilibrium models: Langmuir-Freundlich, Redlich-Peterson, Sips, Koble-Corrigan, Hill and Toth. Extended forms of Langmuir-Freundlich, Koble-Corrigan and Sips models were also well fitted to the two-component equilibrium data obtained for different ratios of concentrations of Cu(II and Zn(II ions (1:1, 1:2, 2:1. Experimental sorption data were described by two kinetic models of the pseudo-first and pseudo-second order. Furthermore, an attempt to explain the mechanisms of the divalent metal ion sorption process on chitosan gel beads was undertaken.

  5. Factors influencing sorption of ciprofloxacin onto activated sludge: Experimental assessment and modelling implications

    DEFF Research Database (Denmark)

    Polesel, Fabio; Lehnberg, Kai; Dott, Wolfgang

    2015-01-01

    was registered under anaerobic conditions. The activated sludge model for xenobiotics (ASM-X) was extended with Freundlich-based sorption kinetics and used to predict the fate of ciprofloxacin in a wastewater treatment plant (WWTP). Scenario simulations, using experimental Freundlich parameters, were used...

  6. Sorption study of U+6 in Brazilian soils

    International Nuclear Information System (INIS)

    Junior, Antonio P.; Wasserman, Maria A.V.; Mantovano, Jose L.; Carvalho, Leonel M.; Perez, Daniel V.

    2015-01-01

    The uranium mining is one of the main activities of the nuclear fuel cycle that can contribute to the increased exposure to radioactive materials and is one of the main routes of contamination of soil by natural radionuclides. This study investigated the sorption of uranium in brazilian soils, through sorption isotherms performed in batch. In this study, two types of soils were selected: Ferralsols Red and Nitosol. The adjustment of the experimental data to the kinetic models were evaluated by two approaches: the traditional, based on the coefficient of determination (R 2 ); and the theoretical and informative, based on Corrected Akaike Information Criteria (AIC C ). The coefficient of determination (R 2 ), revealed that, although empirical, both the kinetic model, Freundlich and Langmuir, describes satisfactorily the experimental data, showing R 2 values higher than 0.9, while the partition constant model was not suitable for describe these sorption data. The AICC model analysis showed that the Langmuir model fit the U sorption curve well for Ferralsols Red, while the Freundlich model fits better to Nitosol. This study has highlighted the role of organic matter on the sorption of uranium in highly weathered soils, rich in oxyhydroxides and low activity clays. The Kd values reported in this study differ from those recommended by the United States Environmental Protection Agency, therefore must be considered as reference values for highly weathered soils, since it refers to Brazilian pedoenvironmental conditions. The low Kd values obtained in this study allowed to evaluate the high vulnerability of highly weathered soils to uranium contamination. (author)

  7. Radionuclide sorption on granitic drill core material

    International Nuclear Information System (INIS)

    Eriksen, T.E.; Locklund, B.

    1987-11-01

    Distribution ratios were determined for Sr-85, Cs-134 and Eu-152 on crushed granite and fissure coating/filling material from Stripa mines. Measurements were also carried out on intact fissure surfaces. The experimental data for Sr-85, Cs-134 on crushed material can be accomodated by a sorption model based on the assumption that the crushed material consists of porous spheres with outer and inner surfaces available for sorption. In the case of Eu-152 only sorption on the outer surfaces of the crushed material was observed. The absence of sorption on inner surfaces is most probably due to high depletion of the more strongly sorbed Eu-152 in the water phase and very low diffusivity of Eu-152 in the sorbed state. (orig./HP)

  8. Comparative evaluation for the sorption capacity of four carbonaceous sorbents to phenol

    Directory of Open Access Journals (Sweden)

    Ding Feng Jin

    2016-10-01

    Full Text Available Sorption kinetics and isotherms of phenol by four carbonaceous sorbents (activated carbon (AC, mesoporous carbon (MPC, bamboo biochar (BBC and oak wood biochar (OBC were compared in this study. MPC has the fastest sorption rate and initial sorption potential, which were indicated by sorption rate constants and initial sorption rate “h” in a pseudo-second-order kinetic model. The ordered and straight pore structure of MPC facilitated the accessibility of phenol. The AC showed the greatest sorption capacity towards phenol with maximum sorption of 123 mg/g as calculated by the Langmuir model. High surface area, complexity of pore structure, and the strong binding force of the π–π electron-donor-acceptor interaction between phenol molecules and AC were the main mechanisms. The BBC and OBC had much slower sorption and lower sorption capacity (33.04 and 29.86 mg/g, respectively, compared to MPC (73.00 mg/g and AC, indicating an ineffective potential for phenol removal from water.

  9. Modelling female fertility traits in beef cattle using linear and non-linear models.

    Science.gov (United States)

    Naya, H; Peñagaricano, F; Urioste, J I

    2017-06-01

    Female fertility traits are key components of the profitability of beef cattle production. However, these traits are difficult and expensive to measure, particularly under extensive pastoral conditions, and consequently, fertility records are in general scarce and somehow incomplete. Moreover, fertility traits are usually dominated by the effects of herd-year environment, and it is generally assumed that relatively small margins are kept for genetic improvement. New ways of modelling genetic variation in these traits are needed. Inspired in the methodological developments made by Prof. Daniel Gianola and co-workers, we assayed linear (Gaussian), Poisson, probit (threshold), censored Poisson and censored Gaussian models to three different kinds of endpoints, namely calving success (CS), number of days from first calving (CD) and number of failed oestrus (FE). For models involving FE and CS, non-linear models overperformed their linear counterparts. For models derived from CD, linear versions displayed better adjustment than the non-linear counterparts. Non-linear models showed consistently higher estimates of heritability and repeatability in all cases (h 2  linear models; h 2  > 0.23 and r > 0.24, for non-linear models). While additive and permanent environment effects showed highly favourable correlations between all models (>0.789), consistency in selecting the 10% best sires showed important differences, mainly amongst the considered endpoints (FE, CS and CD). In consequence, endpoints should be considered as modelling different underlying genetic effects, with linear models more appropriate to describe CD and non-linear models better for FE and CS. © 2017 Blackwell Verlag GmbH.

  10. Sorption behaviour of caesium on a bentonite sample

    International Nuclear Information System (INIS)

    Hurel, C.; Marmier, N.; Fromage, F.; Seby, F.; Bourg, A.C.M.; Giffaut, E.

    2002-01-01

    Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models. (orig.)

  11. Sorption kinetics of diuron on volcanic ash derived soils.

    Science.gov (United States)

    Cáceres-Jensen, Lizethly; Rodríguez-Becerra, Jorge; Parra-Rivero, Joselyn; Escudey, Mauricio; Barrientos, Lorena; Castro-Castillo, Vicente

    2013-10-15

    Diuron sorption kinetic was studied in Andisols, Inceptisol and Ultisols soils in view of their distinctive physical and chemical properties: acidic pH and variable surface charge. Two types of kinetic models were used to fit the experimental dates: those that allow to establish principal kinetic parameters and modeling of sorption process (pseudo-first-order, pseudo-second-order), and some ones frequently used to describe solute transport mechanisms of organic compounds on different sorbents intended for remediation purposes (Elovich equation, intraparticle diffusion, Boyd, and two-site nonequilibrium models). The best fit was obtained with the pseudo-second-order model. The rate constant and the initial rate constant values obtained through this model demonstrated the behavior of Diuron in each soil, in Andisols were observed the highest values for both parameters. The application of the models to describe solute transport mechanisms allowed establishing that in all soils the mass transfer controls the sorption kinetic across the boundary layer and intraparticle diffusion into macropores and micropores. The slowest sorption rate was observed on Ultisols, behavior which must be taken into account when the leaching potential of Diuron is considered. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Sorption and diffusion of FE(II) in bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Tournassat, C.; Hadi, J.; Greneche, J.-M.

    2014-02-01

    . Qualitatively, the sorption of the radioactive 55 Fe on all the clays shows the same type of behaviour, i.e. sorption increases with increasing pH. In the measurements with the bentonite purified at VTT, the sorption occurs at a higher pH than in the measurements carried out with bentonite purified at BRGM. The sorption experiments in the acetate buffer of pH 5 show decreasing sorption of 55 Fe as a function of the increasing concentration of the added Fe(II). A general model for the investigated clays is proposed where Fe sorption is due to adsorption on exchange sites, strong and weak complexation sites and electron transfer with the structural Fe. All mechanisms identified apply to all clay samples but with variations in CEC values, structural Fe redox potential and strong and weak sites' surface density. The measured diffusivities show rather low values (10 -15 - 10 -16 m 2 /s) at pH 8 and 5. At pH 8, the diffusion curve calculated with a reactive transport model on the basis of the sorption matches fairly well the experimental results. At pH 5, the model predicts a much longer diffusion distance than found in the experiment. The reason for this discrepancy is not yet understood. A possible explanation could be a slow redox/sorption process which does not appear in the short batch sorption measurements. (orig.)

  13. Sorption and diffusion of FE(II) in bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Muurinen, A. [VTT Technical Research Centre of Finland, Espoo (Finland); Tournassat, C.; Hadi, J. [BRGM, Orleans (France); Greneche, J.-M. [LPCE, Le Mans (France)

    2014-02-15

    . Qualitatively, the sorption of the radioactive {sup 55}Fe on all the clays shows the same type of behaviour, i.e. sorption increases with increasing pH. In the measurements with the bentonite purified at VTT, the sorption occurs at a higher pH than in the measurements carried out with bentonite purified at BRGM. The sorption experiments in the acetate buffer of pH 5 show decreasing sorption of {sup 55}Fe as a function of the increasing concentration of the added Fe(II). A general model for the investigated clays is proposed where Fe sorption is due to adsorption on exchange sites, strong and weak complexation sites and electron transfer with the structural Fe. All mechanisms identified apply to all clay samples but with variations in CEC values, structural Fe redox potential and strong and weak sites' surface density. The measured diffusivities show rather low values (10{sup -15} - 10{sup -16} m{sup 2}/s) at pH 8 and 5. At pH 8, the diffusion curve calculated with a reactive transport model on the basis of the sorption matches fairly well the experimental results. At pH 5, the model predicts a much longer diffusion distance than found in the experiment. The reason for this discrepancy is not yet understood. A possible explanation could be a slow redox/sorption process which does not appear in the short batch sorption measurements. (orig.)

  14. Sorption data bases and mechanistic sorption studies

    International Nuclear Information System (INIS)

    Bradbury, M.H.

    2000-01-01

    In common with many other countries with a nuclear programme, the Swiss concept for the disposal of radioactive waste is focused on deep burial in specially constructed repositories in geologically stable host rocks. Under such conditions, the most likely means whereby radionuclides might return to the biosphere involves their transport in slowly moving groundwater. The sorption of radionuclides by solid phases in the engineered barriers within the repository, and in the surrounding geological media, limits their release and retards their movement. Performance assessment studies for disposal concepts are carried out by Nagra, the National Cooperative for the Disposal of Radioactive Waste, in which various release scenarios are examined, and 'doses to man' calculated. The uptake of radionuclides by immobile phases is one of the pillars upon which the safety case rests. Hence, sorption databases are very important data sets for performance assessments. The methodology lying behind the construction of sorption databases, and some aspects of the supporting experimental work, are briefly described in this report. Flexible, long-term, focused research programmes are required to properly understand the radionuclide/rock/groundwater system, and this is an essential pre-requisite for producing robust state-of-the-art sorption databases. (author)

  15. A compilation and evaluation of sorption coefficients used in the geosphere model of SYVAC for the 1990 assessment of the Whiteshell Research Area

    Energy Technology Data Exchange (ETDEWEB)

    Vandergraaf, T T; Ticknor, K V

    1994-09-01

    We describe the development of a parametric model that expresses sorption of trace amounts of radioactive and chemically toxic elements from groundwater on geological material as a function of two independent variables: the concentration of the trace element, and the total dissolved solids used to provide sorption coefficients for a contaminant transport model used in performance assessment calculations for a case study of a hypothetical nuclear fuel waste disposal concept in an extensively characterized intrusive rock formation, the Lac du Bonnet batholith. The sorption database in this report is based on laboratory results, literature surveys, and chemical homologs. The arguments used to apply sorption data obtained on unconsolidated material to contaminant transport through intact rock are described. Data are presented for the sorption of 39 elements on three rock types and on 13 primary and secondary minerals, under oxic and anoxic conditions. 166 refs., 12 figs., 4 tabs.

  16. Experimental study of strontium sorption on fissure filling material

    Energy Technology Data Exchange (ETDEWEB)

    Eriksen, T E; Cui, Daqing [Royal Institute of Technology, Stockholm (Sweden). Dept. of Chemistry

    1994-12-01

    We have carried out a comparative study of sorption and desorption of strontium in groundwater on separated magnetic and size fractions of fissure filling material taken from natural fissures in granitic rock. Complete reversibility of the sorption process was demonstrated by identical Freundlich isotherms, isotopic exchangeability and pH dependence of the distribution coefficients Rd. The sorption was found to be strongly pH dependent in the range 3-11. The pH effect can be accommodated in the sorption model by considering the surface areas and surface charges of the minerals in the fissure filling material. 20 refs, 9 figs, 3 tabs.

  17. Experimental study of strontium sorption on fissure filling material

    International Nuclear Information System (INIS)

    Eriksen, T.E.; Cui, Daqing

    1994-12-01

    We have carried out a comparative study of sorption and desorption of strontium in groundwater on separated magnetic and size fractions of fissure filling material taken from natural fissures in granitic rock. Complete reversibility of the sorption process was demonstrated by identical Freundlich isotherms, isotopic exchangeability and pH dependence of the distribution coefficients Rd. The sorption was found to be strongly pH dependent in the range 3-11. The pH effect can be accommodated in the sorption model by considering the surface areas and surface charges of the minerals in the fissure filling material. 20 refs, 9 figs, 3 tabs

  18. Effects of sorption hysteresis on radionuclide releases from waste packages

    International Nuclear Information System (INIS)

    Barney, G.S.; Reed, D.T.

    1985-01-01

    A one-dimensional, numerical transport model was used to calculate radionuclide releases from waste packages emplaced in a nuclear waste repository in basalt. The model incorporates both sorption and desorption isotherm parameters measured previously for sorption of key radionuclides on the packing material component of the waste package. Sorption hysteresis as described by these isotherms lowered releases of some radionuclides by as much as two orders of magnitude. Radionuclides that have low molar inventories (relative to uranium), high solubility, and strongly sorbed, are most affected by sorption hysteresis. In these cases, almost the entire radionuclide inventory is sorbed on the packing material. The model can be used to help optimize the thickness of the packing material layer by comparing release rate versus packing material thickness curves with Nuclear Regulatory Commission (NRC) and Environmental Protection Agency (EPA) release limits

  19. Performance of Cationic Surfactant Modified Sepiolite and Bentonite in Lead Sorption from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    H.R. Rafiei

    2014-12-01

    Full Text Available The remediation of soils and water contaminated with heavy metals generate a great need to develop efficient adsorbents for these pollutants. This study reports the sorption of lead (Pb by bentonite (Bent, and sepiolite (Sep, that were modified with cetyltrimethyl ammonium (CTMA+ organic cations. The natural and surfactant modified clays (organo-clays were characterized with some instrumental techniques including XRF, XRD, FTIR and SEM. Sorption studies were performed in a batch system, and the effects of various experimental parameters including contact time and initial Pb concentration were evaluated upon the Pb sorption onto sorbents. Maximum sorption of Pb was found to be, 83.26, 71.36, 56.25 and 37 mg g-1 for Sep, CTMA-Sep, Bent and CTMA-Bent adsorbents, respectively. The Pb sorption data were fitted to both the Langmuir and Freundlich models. The Freundlich model represented the sorption process better than the Langmuir model. Lead sorption rate was found to be considerably slower for organo-clays than that for unmodified clays. Sorption kinetics was evaluated by pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models. The sorption processes of organo-clays followed intraparticle diffusion kinetics. The results showed that the cationic surfactant modified bentonite and sepiolite sorbed less Pb than the unmodified clays.

  20. The sorption of uranium and technetium on bentonite, tuff and granodiorite

    International Nuclear Information System (INIS)

    Baston, G.M.N.; Berry, J.A.; Brownsword, M.; Cowper, M.M.; Heath, T.G.; Tweed, C.J.

    1995-01-01

    A combined experimental and modeling study of the sorption of uranium and technetium on geological materials has been carried out as part of the PNC program to increase confidence in the performance assessment for a high-level radioactive waste (HLW) repository in Japan. Batch sorption experiments have been performed in order to study the sorption of uranium and technetium onto bentonite, tuff and granodiorite from both equilibrated seawater and de-ionized water under strongly-reducing and non-reducing conditions. A preliminary study of the sorption of uranium on mineral surfaces in granodiorite has also been undertaken using a nuclear microprobe. Mathematical modeling using the geochemical speciation program HARPHRQ in conjunction with the HATCHES database has been carried out in order to interpret the results of the sorption experiments

  1. Phosphorus sorption-desorption and effects of temperature, pH and salinity on phosphorus sorption in marsh soils from coastal wetlands with different flooding conditions.

    Science.gov (United States)

    Bai, Junhong; Ye, Xiaofei; Jia, Jia; Zhang, Guangliang; Zhao, Qingqing; Cui, Baoshan; Liu, Xinhui

    2017-12-01

    Wetland soils act as a sink or source of phosphorus (P) to the overlaying water due to phosphorus sorption-desorption processes. Litter information is available on sorption and desorption behaviors of phosphorus in coastal wetlands with different flooding conditions. Laboratory experiments were conducted to investigate phosphorus sorption-desorption processes, fractions of adsorbed phosphorus, and the effects of salinity, pH and temperature on phosphorus sorption on soils in tidal-flooding wetlands (TW), freshwater-flooding wetlands (FW) and seasonal-flooding wetlands (SW) in the Yellow River Delta. Our results showed that the freshly adsorbed phosphorus dominantly exists in Occluded-P and Fe/AlP and their percentages increased with increasing phosphorus adsorbed. Phosphorus sorption isotherms could be better described by the modified Langmuir model than by the modified Freundlich model. A binomial equation could be properly used to describe the effects of salinity, pH, and temperature on phosphorus sorption. Phosphorus sorption generally increased with increasing salinity, pH, and temperature at lower ranges, while decreased in excess of some threshold values. The maximum phosphorus sorption capacity (Q max ) was larger for FW soils (256 mg/kg) compared with TW (218 mg/kg) and SW soils (235 mg/kg) (p < 0.05). The percentage of phosphorus desorption (P des ) in the FW soils (7.5-63.5%) was much lower than those in TW (27.7-124.9%) and SW soils (19.2-108.5%). The initial soil organic matter, pH and the exchangeable Al, Fe and Cd contents were important factors influencing P sorption and desorption. The findings of this study indicate that freshwater restoration can contribute to controlling the eutrophication status of water bodies through increasing P sorption. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Sorption of humic acid to functionalized multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Wang, Fei; Yao, Jun; Chen, Huilun; Yi, Zhengji; Xing, Baoshan

    2013-01-01

    The environmental behavior of carbon nanotubes (CNTs) and humic acid (HA) is a prominent concern, but effect of functionalities on their sorption is not clear yet. Functionalized multi-walled CNTs (MCNT15) and HA were used to study their sorption behavior. Sorption rate of HA to MCNTs was dominantly controlled by its diffusion from liquid-MCNT boundary to MCNT surfaces. The sorption is in the sequence of MCNT15 > MCNT15-NH 2 > MCNT15-OH > MCNT15-COOH > MCNT15-Ni, which was dependent on their surface area and meso- and macro-pore volume. The functionalities of MCNTs regulated the sorption by affecting their interaction mechanisms (i.e., H-bonding, π–π, and hydrophobic interaction). Additionally, the amount of these functionalities on the MCNT surface reduced indirectly the sorption sites due to the steric hindrance. Electrostatic repulsion deceased the sorption of HA by MCNTs with increasing pH. This study demonstrated the importance of functionalities on the MCNTs for the sorption of HA. -- Highlights: •HA sorption kinetics was well fitted using Lagergren pseudo second-order model. •Sorption rate of HA was controlled by diffusion from liquid-MCNT boundary to MCNT surfaces. •Sorption was dependent on their surface area and meso- and macro-pore volume. •Functionalities of MCNTs regulated the sorption by affecting interaction mechanisms. -- The functionalities of MCNTs regulated the sorption behavior between MCNTs and HA

  3. Sorption of Sr, Co and Zn on illite: Batch experiments and modelling including Co in-diffusion measurements on compacted samples

    Science.gov (United States)

    Montoya, V.; Baeyens, B.; Glaus, M. A.; Kupcik, T.; Marques Fernandes, M.; Van Laer, L.; Bruggeman, C.; Maes, N.; Schäfer, T.

    2018-02-01

    Experimental investigations on the uptake of divalent cations (Sr, Co and Zn) onto illite (Illite du Puy, Le-Puy-en-Velay, France) were carried out by three different international research groups (Institute for Nuclear Waste Disposal, KIT (Germany), Group Waste & Disposal, SCK-CEN, (Belgium) and Laboratory for Waste Management, PSI (Switzerland)) in the framework of the European FP7 CatClay project. The dependence of solid-liquid distribution ratios (Rd values) on pH at trace metal conditions (sorption edges) and on the metal ion concentration (sorption isotherms) was determined in dilute suspensions of homo-ionic Na-illite (Na-IdP) under controlled N2 atmosphere. The experimental results were modelled using the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) sorption model. The sorption of Sr depends strongly on ionic strength, while a rather weak pH dependence is observed in a pH range between 3 and 11. The data were modelled with cation exchange reactions, taking into account competition with H, K, Ca, Mg and Al, and surface complexation on weak amphotheric edge sites at higher pH values. The sorption of Co on Na-IdP, however, is strongly pH dependent. Cation exchange on the planar sites and surface complexation on strong and weak amphoteric edge sites were used to describe the Co sorption data. Rd values for Co derived from in-diffusion measurements on compacted Na-IdP samples (bulk-dry density of 1700 kg m-3) between pH 5.0 and 9.0 are in good agreement with the batch sorption data. The equivalence of both approaches to measure sorption was thus confirmed for the present test system. In addition, the results highlight the importance of both major and minor surface species for the diffusive transport behaviour of strongly sorbing metal cations. While surface complexes at the edge sites determine largely the Rd value, the diffusive flux may be governed by those species bound to the planar sites, even at low fractional

  4. Competitive sorption of persistent organic pollutants onto microplastics in the marine environment

    International Nuclear Information System (INIS)

    Bakir, Adil; Rowland, Steven J.; Thompson, Richard C.

    2012-01-01

    Highlights: ► Organic pollutants are present as complex mixtures in the marine environment. ► The competitive sorption of phenanthrene and DDT in a bi-solute system was investigated onto PVC and PE. ► DDT outcompeted phenanthrene for sorption onto plastic. ► DDT also appeared to have a negative effect on the sorption of phenanthrene onto plastic when added at high concentration. - Abstract: Plastics are known to sorb persistent organic pollutants from seawater. However, studies to quantify sorption rates have only considered the affinity of chemicals in isolation, unlike the conditions in the environment where contaminants are present as complex mixtures. Here we examine whether phenanthrene and 4,4′-DDT, in a mixture, compete for sorption sites onto PVC with no added additives (unplasticised PVC or uPVC) and Ultra-High Molecular Weight polyethylene. Interactions were investigated by exposing particles of uPVC and UHMW PE to mixtures of 3H and 14C radiolabelled Phe and DDT. Changes in sorption capacity were modelled by applying a Freundlich binding sorption isotherms. An Extended Langmuir Model and an Interaction Factor Model were also applied to predict equilibrium concentrations of pollutants onto plastic. This study showed that in a bi-solute system, DDT exhibited no significantly different sorption behaviour than in single solute systems. However, DDT did appear to interfere with the sorption of Phe onto plastic, indicating an antagonistic effect.

  5. Development of JAEA sorption database (JAEA-SDB). Update of data evaluation functions and sorption/QA data

    International Nuclear Information System (INIS)

    Tachi, Yukio; Suyama, Tadahiro; Ochs, Michael; Ganter, Charlotte

    2011-03-01

    Sorption and diffusion of radionuclides in buffer materials (bentonite) and rocks are the key processes in the safe geological disposal of radioactive waste, because migration of radionuclides in this barrier is expected to be diffusion-controlled and retarded by sorption processes. It is therefore necessary to understand the sorption and diffusion processes and develop database compiling reliable data and mechanistic/predictive models, so that reliable parameters can be set under a variety of geochemical conditions relevant to performance assessment (PA). For this purpose, Japan Atomic Energy Agency (JAEA) has developed databases of sorption and diffusion parameters in buffer materials (bentonite) and rocks. These sorption and diffusion databases (SDB/DDB) were firstly developed as an important basis for the H12 PA of high-level radioactive waste disposal, and have been provided through the Web. JAEA has been continuing to improve and update the SDB/DDB in view of potential future data needs, focusing on assuring the desired quality level and testing the usefulness of the databases for possible applications to PA-related parameter setting. The present report focuses on developing and updating of the sorption database (JAEA-SDB) as basis of integrated approach for PA-related K d setting. This includes an overview of database structure, contents and functions including additional data evaluation function focusing on multi-parameter dependence, operating method, PA-related applications of the web-based JAEA-SDB. K d data and their QA results are updated by focusing our recent activities on the K d setting and mechanistic model development. As a result, 4,250 K d data from 32 references are added, total K d values in the JAEA-SDB are about 28,540. The QA/classified K d data are about 39% for all K d data in JAEA-SDB. The updated JAEA-SDB is expected to make it possible to obtain quick overview of the available data, and to have suitable access to the respective data

  6. Sorption kinetics of Cs and Sr in sediments of a Savannah River Site reservoir

    International Nuclear Information System (INIS)

    Stephens, J.A.

    1997-07-01

    Laboratory measurements of the sorption and desorption of 134 Cs and 85 Sr to sediments were conducted. These sediments were sampled from the profundal zone of Par Pond at the Savannah River Site, Aiken, South Carolina. The isotopes 134 Cs and 85 Sr were used to trace the sorption properties of the main contaminants found in the reservoir which are 137 Cs and 90 Sr respectively. The sorption behavior of these two elements was studied using spiked sediment/water slurries of a known mass to volume ratio. The results reveal that Sr undergoes significant reversible sorption while a fraction of Cs irreversibly sorbs to the sediment. The calculated distribution coefficient Kd at equilibrium was (3 ± 0.6) x 10 3 for 134 Cs after 60 d and (1 ± 0.2) x 10 3 for 85 Sr after 7 d at pH ∼ 6 and slurry ratio of 1:1000 g/ml. The K d for 134 Cs ranged from 2 x 10 2 to 3 x 10 4 depending on pH and conductivity. The 85 Sr reached equilibrium in a few days, while 134 Cs reached an apparent equilibrium in 1--2 months. The K d for 134 Cs was a function of the slurry ratio, pH, conductivity, and contact time. These factors were interrelated since the sediments released ions to the slurry mixture which decreased the pH and increased the conductivity. A sorption isotherm measured for 134 Cs was linear at water concentrations from 60 mBq/ml to 20 Bq/ml. A kinetic model was proposed to describe the basic sorption of 134 Cs to Par Pond sediments under homogeneous laboratory conditions

  7. Sorption of organic gases in a furnished room

    Energy Technology Data Exchange (ETDEWEB)

    Singer, Brett C.; Revzan, Kenneth L.; Hotchi, Toshifumi; Hodgson, Alfred T.; Brown, Nancy J.

    2003-11-30

    We present experimental data and semi-empirical models describing the sorption of organic gases in a simulated indoor residential environment. Two replicate experiments were conducted with 20 volatile organic compounds (VOCs) in a 50-m{sup 3} room finished with painted wallboard, carpet and cushion, draperies and furnishings. The VOCs span a wide volatility range and include ten Hazardous Air Pollutants. VOCs were introduced to the static chamber as a pulse and their gas-phase concentrations were measured during a net adsorption period and a subsequent net desorption period. Three sorption models were fit to the measured concentrations for each compound to determine the simplest formulation needed to adequately describe the observed behavior. Sorption parameter values were determined by fitting the models to adsorption period data then checked by comparing measured and predicted behavior during desorption. The adequacy of each model was evaluated using a goodness of fit parameter calculated for each period. Results indicate that sorption usually does not greatly affect indoor concentrations of methyl-tert-butyl ether, 2-butanone, isoprene and benzene. In contrast, sorption appears to be a relevant indoor process for many of the VOCs studied, including C{sub 8}-C{sub 10} aromatic hydrocarbons (HC), terpenes, and pyridine. These compounds sorbed at rates close to typical residential air change rates and exhibited substantial sorptive partitioning at equilibrium. Polycyclic aromatic HCs, aromatic alcohols, ethenylpyridine and nicotine initially adsorbed to surfaces at rates of 1.5 to >6 h{sup -1} and partitioned 95 to >99% in the sorbed phase at equilibrium.

  8. Considerations about the correct evaluation of sorption thermodynamic parameters from equilibrium isotherms

    International Nuclear Information System (INIS)

    Salvestrini, Stefano; Leone, Vincenzo; Iovino, Pasquale; Canzano, Silvana; Capasso, Sante

    2014-01-01

    Highlights: • Different methods to derive sorption thermodynamic parameters have been discussed. • ΔG° and, ΔS° values depend on the selected standard states. • Isosteric heat values help in evaluating the applicability of the sorption models. -- Abstract: This is a comparative analysis of popular methods currently in use to derive sorption thermodynamic parameters from temperature dependence of sorption isotherms. It is emphasized that the standard and isosteric thermodynamic parameters have sharply different meanings. Moreover, it is shown with examples how the sorption model adopted conditions the standard state and consequently the value of ΔG° and ΔS°. These trivial but often neglected aspects should carefully be considered when comparing thermodynamic parameters from different literature sources. An effort by the scientific community is needed to define criteria for the choice of the standard state in sorption processes

  9. The measurement and estimation method of the sorption of lead onto cementitious materials

    International Nuclear Information System (INIS)

    Nakanishi, Kiyoshi; Tsukamoto, Masaki; Fujita, Tomonari; Sugiyama, Daisuke

    2002-01-01

    Cementitious material is a potential waste packaging material for radioactive waste disposal, and is expected to provide chemical containment. In particular, the sorption of radionuclides onto cementitious material is a very important parameter when considering the release of radionuclides from radioactive waste. In this study, sorption of lead, onto hydrated Ordinary Portland Cement (OPC), OPC/Blast Furnace Slag blended cement (BFS), Highly containing Flyash and Silica Fume Cement (HFSC) and cement constituent minerals (portlandite, ettringite, hydrotalcite and C-S-H gels (Ca/Si = 0.9 and 1.65)) was measured using the batch sorption technique. Lead is one of the important nuclides for safety assessment. The obtained distribution ratios, Rd values, for sorption of lead onto hydrated (freshly cured) OPC and HFSC are very high:>1000 cm3g-1. The distribution ratio for sorption of lead onto OPC/BFS could not be determined quantitatively due to the precipitation of PbS. Comparing the Rd values onto cements and minerals, it was suggested the sorption onto C-S-H gel phases dominate the sorption for lead onto hydrated cements. Once a cementitious material is altered in the disposal environment, its sorption ability may be affected. The sorption of lead onto degraded OPC and degraded HFSC, which were altered in the presence of distilled water, was also measured. It was observed that the alteration did not cause changes that decreased the sorption of lead onto OPC and HFSC. An approach, in which it is assumed that each of the component phases contributes to the composite material, is proposed and discussed to describe the sorption of lead onto cement using a knowledge of the phase components in a linear additive manner. The results showed reasonably good agreement between the predicted and measured Rd values for lead onto freshly cured and altered cements. (author)

  10. Status report on SIRS: sorption information retrieval system

    International Nuclear Information System (INIS)

    Hostetler, D.D.; Serne, R.J.; Baldwin, A.J.; Petrie, G.M.

    1980-11-01

    Two major uses were identified for the Sorption Information Retrieval System: (1) to aid geochemists in the elucidation of sorption mechanisms; and (2) to aid safety assessment modelers in selection of Kds for any given scenerio. Other benefits such as providing an auditable vehicle for the Kd selection were also discussed

  11. Sorption study of U{sup +6} in Brazilian soils

    Energy Technology Data Exchange (ETDEWEB)

    Junior, Antonio P.; Wasserman, Maria A.V.; Mantovano, Jose L.; Carvalho, Leonel M., E-mail: apjunior@ien.gov.br, E-mail: mwasserman@ien.gov.br, E-mail: mantovan@ien.gov.br, E-mail: leonel@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Perez, Daniel V., E-mail: daniel@cnps.embrapa.br [Empresa Brasileira de Pesquisas Agropecuarias (Embrapa Solos-CNPS), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    The uranium mining is one of the main activities of the nuclear fuel cycle that can contribute to the increased exposure to radioactive materials and is one of the main routes of contamination of soil by natural radionuclides. This study investigated the sorption of uranium in brazilian soils, through sorption isotherms performed in batch. In this study, two types of soils were selected: Ferralsols Red and Nitosol. The adjustment of the experimental data to the kinetic models were evaluated by two approaches: the traditional, based on the coefficient of determination (R{sup 2}); and the theoretical and informative, based on Corrected Akaike Information Criteria (AIC{sub C}). The coefficient of determination (R{sup 2}), revealed that, although empirical, both the kinetic model, Freundlich and Langmuir, describes satisfactorily the experimental data, showing R{sup 2} values higher than 0.9, while the partition constant model was not suitable for describe these sorption data. The AICC model analysis showed that the Langmuir model fit the U sorption curve well for Ferralsols Red, while the Freundlich model fits better to Nitosol. This study has highlighted the role of organic matter on the sorption of uranium in highly weathered soils, rich in oxyhydroxides and low activity clays. The Kd values reported in this study differ from those recommended by the United States Environmental Protection Agency, therefore must be considered as reference values for highly weathered soils, since it refers to Brazilian pedoenvironmental conditions. The low Kd values obtained in this study allowed to evaluate the high vulnerability of highly weathered soils to uranium contamination. (author)

  12. Experimental And Modelling Investigations on Na-Illite: Acid-Base Behaviour And the Sorption Of Strontium, Nickel, Europium And Uranyl

    International Nuclear Information System (INIS)

    Bradbury, M.H.; Baeyens, B.

    2005-06-01

    In an extensive study the physico-chemical, protolysis and sorption characteristics of Sr(II), Ni(II), Eu(III) and U(VI) have been measured on illite and modeled over a wide range of pH, sorbate and NaCI0 4 concentrations. SampIes of Illite du Puy, collected in the region of Le Puy-en- Velay, France, were carefully conditioned to the Na-form and physico-chemically characterised. Potentiometric titrations on suspensions of the Na-illite were carried out using a batch back titration technique in 0.01, 0.1 and 0.5 M NaCI0 4 background electrolytes from pH 2 to 12 in an inert atmosphere glove box. The supernatant solutions from each titration experiment in each series were analysed for K, Mg, Ca, Sr, Si, Al, Fe and Mn. The titration data were modeled in terms of the protolysis of two amphoteric edge sites (=S W1 0H and =S W2 0H) without an electrostatic term. The protonation/deprotonation constants and site capacities obtained from the titration measurements were then fixed. The sorption edge and isotherm data were modeled with strong (=S S OH) and weak (=S W1 0H) surface complexation sites, assumed to have the same protolysis constants, again without electrostatic terms. Uptake by cation exchange was included in all of the calculations. This sorption model, the 2 site protolysis non electrostatic surface complexation and cation exchange model, had been developed previously for montmorillonite and was successful in describing the sorption characteristics of Sr, Ni, Eu and U on Na-illite over a wide range of conditions. Cation exchange capacity, strong and weak site capacities and protolysis constants for Na-illite are given, together with surface complexation constants and selectivity coefficients for Sr, Ni, Eu and U. At 0.01 M NaCI0 4 and pH below 8 the sorption of Sr, Ni, Eu and U was dominated by a cation exchange mechanism. The strong dependency of sorption on pH observed under these conditions arose from the competitive effects of Ca and Al on the uptake of the

  13. Isotermas de sorção de tâmaras: determinação experimental e avaliação de modelos matemáticos Dates sorption isotherms: experimental determination and mathematics models evaluation

    Directory of Open Access Journals (Sweden)

    Mônica E.T. PRADO

    1999-01-01

    Full Text Available As isotermas de sorção de tâmaras (Phoenix dactylifera L., da variedade Zahidi, foram determinadas para três temperaturas, 60, 70 e 80° C pelo método estático gravimétrico. As curvas experimentais foram ajustadas pelas equações de BET, BET linearizada, GAB, HALSEY, OSWIN e PELEG. O desvio relativo entre os valores experimentais e os valores estimados foi calculado para cada curva, a fim de se avaliar qual equação melhor se ajustou aos dados experimentais.Dates sorption isotherms were determined by gravimetric at three differents temperatures (60, 70 and 80° C. Experimental data was adjusted to six sorption models de BET, linear BET, GAB, HALSEY, OSWIN and PELEG. The average relative deviations between calculated and experimental data were calculated do select best fit model.

  14. Linear models with R

    CERN Document Server

    Faraway, Julian J

    2014-01-01

    A Hands-On Way to Learning Data AnalysisPart of the core of statistics, linear models are used to make predictions and explain the relationship between the response and the predictors. Understanding linear models is crucial to a broader competence in the practice of statistics. Linear Models with R, Second Edition explains how to use linear models in physical science, engineering, social science, and business applications. The book incorporates several improvements that reflect how the world of R has greatly expanded since the publication of the first edition.New to the Second EditionReorganiz

  15. Two-Dimensional Model for Reactive-Sorption Columns of Cylindrical Geometry: Analytical Solutions and Moment Analysis.

    Science.gov (United States)

    Khan, Farman U; Qamar, Shamsul

    2017-05-01

    A set of analytical solutions are presented for a model describing the transport of a solute in a fixed-bed reactor of cylindrical geometry subjected to the first (Dirichlet) and third (Danckwerts) type inlet boundary conditions. Linear sorption kinetic process and first-order decay are considered. Cylindrical geometry allows the use of large columns to investigate dispersion, adsorption/desorption and reaction kinetic mechanisms. The finite Hankel and Laplace transform techniques are adopted to solve the model equations. For further analysis, statistical temporal moments are derived from the Laplace-transformed solutions. The developed analytical solutions are compared with the numerical solutions of high-resolution finite volume scheme. Different case studies are presented and discussed for a series of numerical values corresponding to a wide range of mass transfer and reaction kinetics. A good agreement was observed in the analytical and numerical concentration profiles and moments. The developed solutions are efficient tools for analyzing numerical algorithms, sensitivity analysis and simultaneous determination of the longitudinal and transverse dispersion coefficients from a laboratory-scale radial column experiment. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. Sorption data bases and mechanistic sorption studies

    Energy Technology Data Exchange (ETDEWEB)

    Bradbury, M.H

    2000-07-01

    In common with many other countries with a nuclear programme, the Swiss concept for the disposal of radioactive waste is focused on deep burial in specially constructed repositories in geologically stable host rocks. Under such conditions, the most likely means whereby radionuclides might return to the biosphere involves their transport in slowly moving groundwater. The sorption of radionuclides by solid phases in the engineered barriers within the repository, and in the surrounding geological media, limits their release and retards their movement. Performance assessment studies for disposal concepts are carried out by Nagra, the National Cooperative for the Disposal of Radioactive Waste, in which various release scenarios are examined, and 'doses to man' calculated. The uptake of radionuclides by immobile phases is one of the pillars upon which the safety case rests. Hence, sorption databases are very important data sets for performance assessments. The methodology lying behind the construction of sorption databases, and some aspects of the supporting experimental work, are briefly described in this report. Flexible, long-term, focused research programmes are required to properly understand the radionuclide/rock/groundwater system, and this is an essential pre-requisite for producing robust state-of-the-art sorption databases. (author)

  17. Sorption characteristics and mechanisms of organic contaminant to carbonaceous biosorbents in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A series of carbonaceous biosorbents was prepared by pyrolyzing pine needles,a model biomass,at various temperatures (100-700℃) under an oxygen-limited condition for 6h. The elemental composi-tions and the specific surface areas (BET-N2) of the biosorbents were analyzed. Sorption properties of 4-nitrotoluene to the biosorbents and their mechanisms were investigated,and then correlated with the structures of the biosorbents. The result shows that with the increase of the pyrolytic temperature,the aromaticity of the carbonaceous biosorbents increases dramatically and the polarity (the (N+O)/C atomic ratio) decreases sharply. Correspondingly,conformations of the organic matter in the biosor-bents transform gradually from a "soft-state" to a "hard-state" and the specific surface areas of the resultant biosorbents extend rapidly. The sorption isotherms fit well with the Freundlich equation. The regression parameters (i.e.,N and lgKf) are linearly related to the aromaticity indices (the H/C atomic ratio). Contributions of adsorption and partition to total sorption of the carbonaceous biosorbents are quantified. The adsorption of the carbonaceous biosorbents increases quickly with the increase of the pyrolytic temperature. The saturated adsorption amounts (Qmax) increase linearly with the increase of the specific surface areas (SA) of the biosorbents. For the carbonaceous biosorbents with hard-state carbon,the calculated normalized-Qmax values by SA are comparable to the theoretical estimation (2.45 μmol/m2). In comparison,for the carbonaceous sorbents with soft-state carbon,the calculated nor-malized-Qmax values by SA are much higher than the theoretical estimation. The partition coefficients (Kom) increase with the decrease of the polarity of the biosorbents,reaching a maximum,and then de-crease sharply with further decreasing the polarity,suggesting that partition mechanism be dominated by the compatibility and accessibility of the sorbent medium with organic

  18. Sorption characteristics and mechanisms of organic contaminant to carbonaceous biosorbents in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    CHEN BaoLiang; ZHOU DanDan; ZHU LiZhong; SHEN XueYou

    2008-01-01

    A series of carbonaceous biosorbents was prepared by pyrolyzing pine needles, a model biomass, at various temperatures (100-700℃) under an oxygen-limited condition for 6 h. The elemental composi-tions and the specific surface areas (BET-N2) of the biosorbents were analyzed. Sorption properties of 4-nitrotoluene to the biosorbents and their mechanisms were investigated, and then correlated with the structures of the biosorbents. The result shows that with the increase of the pyrolytic temperature, the sromaticity of the carbonaceous biosorbents increases dramatically and the polarity (the (N+O)/C atomic ratio) decreases sharply. Correspondingly, conformations of the organic matter in the biosor-bents transform gradually from a "soft-state" to a "hard-state" and the specific surface areas of the resultant biosorbents extend rapidly. The sorption isotherms fit well with the Freundlich equation. The regression parameters (I.e., N and IgKf) are linearly related to the aromaticity indices (the H/C atomic ratio). Contributions of adsorption and partition to total sorption of the carbonaceous biosorbents are quantified. The adsorption of the carbonaceous biosorbents increases quickly with the increase of the pyrolytic temperature. The saturated adsorption amounts (Qmax) increase linearly with the increase of the specific surface areas (SA) of the biosorbents. For the carbonaceous biosorbents with hard-state carbon, the calculated normalized-Qmax values by SA are comparable to the theoretical estimation (2.45 μmol/m2). In comparison, for the carbonaceous sorbents with soft-state carbon, the calculated nor-malized-Qmax values by SA are much higher than the theoretical estimation. The partition coefficients (Kom) increase with the decrease of the polarity of the biosorbents, reaching a maximum, and then de-crease sharply with further decreasing the polarity, suggesting that partition mechanism be dominated by the compatibility and accessibility of the sorbent medium with

  19. Sorption of organophosphate esters by carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei; Yan, Li [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China); Duan, Jinming [School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an 710055 (China); Jing, Chuanyong, E-mail: cyjing@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085 (China)

    2014-05-01

    Graphical abstract: The interfacial interactions between the OPE molecules and CNTs. - Highlights: • Oxygen-containing groups on CNTs change the sorption property for OPEs. • Molecular configuration of OPEs has insignificant impact on their sorption. • Hydrophobic, π–π EDA and Brønsted acid–base interaction occurred between the CNTs and OPEs. - Abstract: Insights from the molecular-level mechanism of sorption of organophosphate esters (OPEs) on carbon nanotubes (CNTs) can further our understanding of the fate and transport of OPEs in the environment. The motivation for our study was to explore the sorption process of OPEs on multi-walled CNTs (MWCNTs), single-walled CNTs (SWCNTs) and their oxidized counterparts (O-MWCNTs and O-SWCNTs), and its molecular mechanism over a wide concentration range. The sorption isotherm results revealed that the hydrophobicity of OPEs dominated their affinities on a given CNT and the π–π electron donor–acceptor (EDA) interaction also played an important role in the sorption of aromatic OPEs. This π–π EDA interaction, verified with Raman and FT-IR spectroscopy, could restrict the radial vibration of SWCNTs and affect the deformation vibration γ(CH) bands of OPE molecules. The OPE surface coverage on CNTs, estimated using the nonlinear Dubinin–Ashtakhov model, indicated that the oxygen-containing functional groups on CNTs could interact with water molecules by H-bonding, resulting in a decrease in effective sorption sites. In addition, FTIR analysis also confirmed the occurrence of Brønsted acid–base interactions between OPEs and surface OH groups of SWCNTs. Our results should provide mechanistic insights into the sorption mechanism of OPE contaminants on CNTs.

  20. Sorption of simazine to corn straw biochars prepared at different pyrolytic temperatures

    International Nuclear Information System (INIS)

    Zhang Guixiang; Zhang Qing; Sun Ke; Liu Xitao; Zheng Wenjuan; Zhao Ye

    2011-01-01

    Simazine sorption to corn straw biochars prepared at various temperatures (100-600 deg. C) was examined to understand its sorption behavior as influenced by characteristics of biochars. Biochars were characterized via elemental analysis, BET-N 2 surface area (SA), FTIR and 13 C NMR. Freundlich and dual-mode models described sorption isotherms well. Positive correlation between log K oc values and aromatic C contents and negative correlation between log K oc values and (O + N)/C ratios indicate aromatic-rich biochars have high binding affinity to simazine (charge transfer (π-π*) interactions) and hydrophobic binding may overwhelm H-bonding, respectively. Dual-mode model results suggest adsorption contribution to total sorption increases with carbonization degree. Positive correlation between amounts of adsorption (Q ad ) and SA indicates pore-filling mechanism. Comparison between our results and those obtained with other sorbents indicates corn straw biochars produced at higher temperature can effectively retain simazine. These observations will be helpful for designing biochars as engineered sorbents to remove triazine herbicides. - Highlights: → Biochars were characterized via elemental analysis, BET-N 2 , FTIR and 13 C NMR. → Freundlich and dual-mode models described sorption isotherms well. → Biochar produced at higher temperature had larger sorption capacity for simazine. → Aromatic-rich biochars have high binding affinity to simazine. → Dual-mode model results suggest adsorption contribution to total sorption. - The corn straw biochar prepared at higher temperature with stronger hydrophobicity, more aromatic C and larger surface area had higher sorption capacity for simazine.

  1. Preliminary report on the statistical evaluation of sorption data: Sorption as a function of mineralogy, temperature, time, and particle size

    International Nuclear Information System (INIS)

    Beckman, R.; Thomas, K.; Crowe, B.

    1988-05-01

    This report studies the transport of radionuclides from a repository to the environment by dissolution of the stored solid-waste form and subsequent transport in water. The sorption process may retard this movement of radionuclides from the repository to the accessible environment. A measure of this retardation process is the sorption ratio, R/sub D/, where R/sub D/ = (activity in solid phase per unit mass of solid)(activity in solution per unit volume of solution). In this study, predictions of the R/sub D/ values for the elements barium, cerium, cesium, europium, and strontium are developed from linear regression techniques. An R/sub D/ value was obtained for numerous drill core samples. Additional data include the particle size of the rock, temperature condition during the experiment, concentration of the sorbing element, and length of the sorption experiment. Preliminary regression results based on these data show that the temperature and length of the experiment are the most significant factors influencing the R/sub D/ values. Particle size has a slight effect, and based on a small amount of data, it appears that concentration had no effect. The x-ray diffraction data are used to classify the samples by mineralogy, and regression techniques are used to develop estimates of the R/sub D/ values. Zeolite abundance of 10% or more with some addition of clay increases the sorption values significantly. 12 refs., 3 figs., 6 tabs

  2. Capacity and mechanisms of ammonium and cadmium sorption on different wetland-plant derived biochars

    International Nuclear Information System (INIS)

    Cui, Xiaoqiang; Hao, Hulin; Zhang, Changkuan; He, Zhenli; Yang, Xiaoe

    2016-01-01

    The objective of this study was to investigate the relationship between Cd 2+ /NH 4 + sorption and physicochemical properties of biochars produced from different wetland plants. Biochars from six species of wetland plants (i.e., Canna indica, Pennisetum purpureum Schum, Thalia dealbata, Zizania caduciflora, Phragmites australis and Vetiveria zizanioides) were obtained at 500 °C and characterized, and their sorption for ammonium and cadmium was determined. There were significant differences in elemental composition, functional groups and specific surface area among the biochars derived from different wetland plant species. Sorption of ammonium and cadmium on the biochars could be described by a pseudo second order kinetic model, and the simple Langmuir model fits the isotherm data better than the Freundlich or Temkin model. The C. indica derived biochar had the largest sorption capacity for NH 4 + and Cd 2+ , with a maximum sorption of 13.35 and 125.8 mg g −1 , respectively. P. purpureum Schum derived biochar had a similar maximum sorption (119.3 mg g −1 ) for Cd 2+ . Ammonium sorption was mainly controlled by cation exchange, surface complexation with oxygen-containing functional groups and the formation of magnesium ammonium phosphate compounds, whereas for Cd 2+ sorption, the formation of cadmium phosphate precipitates, cation exchange and binding to oxygen-containing groups were the major possible mechanisms. In addition, the sorption of ammonium and cadmium was not affected by surface area and microporosity of the biochars. - Highlights: • Biochars varied in physicochemical properties and adsorption capacity. • Canna indica derived biochar has a high sorption capacity for Cd 2+ . • NH 4 + and Cd 2+ sorption on biochars fits a pseudo second order and Langmuir model. • Sorption mechanism is related to complexation, cation exchange and precipitation.

  3. Capacity and mechanisms of ammonium and cadmium sorption on different wetland-plant derived biochars

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Xiaoqiang [Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Hao, Hulin [Ningbo Raw Water Resource Research Academy, Ningbo (China); Zhang, Changkuan [Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); He, Zhenli [Indian River Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Fort Pierce, FL 34945 (United States); Yang, Xiaoe, E-mail: xyang571@yahoo.com [Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China)

    2016-01-01

    The objective of this study was to investigate the relationship between Cd{sup 2+}/NH{sub 4}{sup +} sorption and physicochemical properties of biochars produced from different wetland plants. Biochars from six species of wetland plants (i.e., Canna indica, Pennisetum purpureum Schum, Thalia dealbata, Zizania caduciflora, Phragmites australis and Vetiveria zizanioides) were obtained at 500 °C and characterized, and their sorption for ammonium and cadmium was determined. There were significant differences in elemental composition, functional groups and specific surface area among the biochars derived from different wetland plant species. Sorption of ammonium and cadmium on the biochars could be described by a pseudo second order kinetic model, and the simple Langmuir model fits the isotherm data better than the Freundlich or Temkin model. The C. indica derived biochar had the largest sorption capacity for NH{sub 4}{sup +} and Cd{sup 2+}, with a maximum sorption of 13.35 and 125.8 mg g{sup −1}, respectively. P. purpureum Schum derived biochar had a similar maximum sorption (119.3 mg g{sup −1}) for Cd{sup 2+}. Ammonium sorption was mainly controlled by cation exchange, surface complexation with oxygen-containing functional groups and the formation of magnesium ammonium phosphate compounds, whereas for Cd{sup 2+} sorption, the formation of cadmium phosphate precipitates, cation exchange and binding to oxygen-containing groups were the major possible mechanisms. In addition, the sorption of ammonium and cadmium was not affected by surface area and microporosity of the biochars. - Highlights: • Biochars varied in physicochemical properties and adsorption capacity. • Canna indica derived biochar has a high sorption capacity for Cd{sup 2+}. • NH{sub 4}{sup +} and Cd{sup 2+} sorption on biochars fits a pseudo second order and Langmuir model. • Sorption mechanism is related to complexation, cation exchange and precipitation.

  4. Investigation of metal ions sorption of brown peat moss powder

    Science.gov (United States)

    Kelus, Nadezhda; Blokhina, Elena; Novikov, Dmitry; Novikova, Yaroslavna; Chuchalin, Vladimir

    2017-11-01

    For regularities research of sorptive extraction of heavy metal ions by cellulose and its derivates from aquatic solution of electrolytes it is necessary to find possible mechanism of sorption process and to choice a model describing this process. The present article investigates the regularities of aliovalent metals sorption on brown peat moss powder. The results show that sorption isotherm of Al3+ ions is described by Freundlich isotherm and sorption isotherms of Na+ i Ni2+ are described by Langmuir isotherm. To identify the mechanisms of brown peat moss powder sorption the IR-spectra of the initial brown peat moss powder samples and brown peat moss powder samples after Ni (II) sorption were studied. Metal ion binding mechanisms by brown peat moss powder points to ion exchange, physical adsorption, and complex formation with hydroxyl and carboxyl groups.

  5. Soft computing modelling of moisture sorption isotherms of milk-foxtail millet powder and determination of thermodynamic properties.

    Science.gov (United States)

    Simha, H V Vikram; Pushpadass, Heartwin A; Franklin, Magdaline Eljeeva Emerald; Kumar, P Arun; Manimala, K

    2016-06-01

    Moisture sorption isotherms of spray-dried milk-foxtail millet powder were determined at 10, 25 and 40 °C. Sorption data was fitted using classical and soft-computing approaches. The isotherms were of type II, and equilibrium moisture content (EMC) was temperature dependent. The BET monolayer moisture content decreased from 3.30 to 2.67 % as temperature increased from 10 to 40 °C. Amongst the classical models, Ferro-Fontan gave the best fit of EMC-aw data. However, the Sugeno-type adaptive neuro-fuzzy inference system (ANFIS) with generalized bell-shaped membership function performed better than artificial neural network and classical models with RMSE as low as 0.0099. The isosteric heat of sorption decreased from 150.32 kJ mol(-1) at 1 % moisture content to 44.11 kJ mol(-1) at 15 % moisture. The enthalpy-entropy compensation theory was validated, and the isokinetic and harmonic mean temperatures were determined as 333.1 and 297.5 K, respectively.

  6. Linear and Generalized Linear Mixed Models and Their Applications

    CERN Document Server

    Jiang, Jiming

    2007-01-01

    This book covers two major classes of mixed effects models, linear mixed models and generalized linear mixed models, and it presents an up-to-date account of theory and methods in analysis of these models as well as their applications in various fields. The book offers a systematic approach to inference about non-Gaussian linear mixed models. Furthermore, it has included recently developed methods, such as mixed model diagnostics, mixed model selection, and jackknife method in the context of mixed models. The book is aimed at students, researchers and other practitioners who are interested

  7. Influence of selected factors on strontium sorption on bentonites

    International Nuclear Information System (INIS)

    Galambos, M.; Kufcakova, J.; Rajec, P.

    2007-01-01

    Sorption on bentonite will play an important role in retarding the migration of radionuclides from a waste repository. Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level nuclear waste. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by sorption. Bentonite is characterized by low permeability, water swelling capability and excellent sorption potential for cationic radionuclides. To correctly assess the sorption potential of radionuclides on bentonite is essential for the development of predictive migration models. The sorption of strontium on bentonite from different Slovak deposits - Jelsovy potok, Kopernica and Lieskovec has been investigated under various experimental conditions, such as contact time, sorbate concentrations, presence of complementary cation. Sorption was studied using the batch technique. The uptake of Sr was rapid and equilibrium was reached almost instantaneously. The instantaneous uptake may be due to adsorption and/or exchange of the metal with some ions on the surface of the adsorbent. The best sorption characteristics distinguish bentonite Kopernica, sorption capacity for Sr of the fraction under 45 mm is 0,48 mmol·g -1 for Sr. The highest values of distribution coefficient were reached for the bentonite Jelsovy potok. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites, which can be explained by the increase of specific surface of the bentonite samples. The presence of complementary cations depresses the sorption of Sr on bentonite. Cations Ca 2+ exhibit higher effect on cesium sorption than the Na 2+ ions. Results indicate that the sorption of Sr 2+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water

  8. Thermodynamic parameters and sorption of U(VI) on ACSD

    International Nuclear Information System (INIS)

    Donat, R.; Cilgi, G.K.; Cetisli, H.; Aytas, S.

    2009-01-01

    This paper discusses the sorption properties for U(VI) by alginate coated CaSO 4 x 2H 2 O sepiolite and calcined diatomite earth (Kieselguhr) (ACSD). The removal of U(VI) from aqueous solution by sorption onto ACSF in a single component system with various contact times, pH, temperatures, and initial concentrations of U(VI) was investigated. The sorption patterns of uranium on the composite adsorbent followed the Langmuir, Freundlich and Dubinin-Radushkhevic (D-R) isotherms. The Freundlich, Langmuir, and D-R models have been applied and the data correlated well with Freundlich model and that the sorption was physical in nature (sorption energy, E a = 17.05 kJ/mol). The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated from the slope and intercept of lnK 0 vs. 1/T plots. Thermodynamic parameters (ΔH ads = 31.83 kJ/mol, ΔS ads = 167 J/mol x K, ΔGdeg ads (293.15 K) = -17.94 kJ/mol) showed the endothermic heat of sorption and the feasibility of the process. The thermodynamics of U(VI) ion/ACSD system indicates the spontaneous and endothermic nature of the process. It was noted that an increase in temperature resulted in a higher uranium loading per unit weight of the adsorbent. (author)

  9. Sorption behavior of neptunium on bentonite -- Effect of calcium ion on the sorption

    International Nuclear Information System (INIS)

    Kozai, Naofumi; Ohnuki, Toshihiko; Muraoka, Susumu

    1995-01-01

    The sorption behavior of neptunium on bentonite was studied with batch type sorption and desorption experiments over a pH range of 2 to 8. A series of parallel studies using Na-smectite, Ca-smectite and admixtures of Na-smectite and calcite quantified the capacity of Ca 2+ (which occurs in bentonite as an exchangeable cation of smectite and as a component of calcite) to inhibit the sorption of neptunium. The distribution coefficient (K d ) of neptunium for bentonite was constant from pH 2 to 7, while for pure Na-smectite K d increased below pH 5 due to specific sorption of neptunium on Na-smectite. Specific sorption was defined as occurring when neptunium could be desorbed by a strong acid (1 M HCl) but was stable in the presence of 1 M KCl. It was found that the quantity of neptunium sorbed on Na-smectite was inversely proportional to the concentration of Ca 2+ in solution, an effect most pronounced at pH 2+ limits the specific sorption capacity of Na-smectite for neptunium. Similarly, in the mixture of Na-smectite and calcite, sufficient Ca 2+ was solubilized to depress neptunium sorption. This investigation demonstrates that Ca 2+ contained in bentonite as exchangeable cation and released from calcite reduces the specific sorption of neptunium

  10. Numerical simulation of advective-dispersive multisolute transport with sorption, ion exchange and equilibrium chemistry

    Science.gov (United States)

    Lewis, F.M.; Voss, C.I.; Rubin, Jacob

    1986-01-01

    A model was developed that can simulate the effect of certain chemical and sorption reactions simultaneously among solutes involved in advective-dispersive transport through porous media. The model is based on a methodology that utilizes physical-chemical relationships in the development of the basic solute mass-balance equations; however, the form of these equations allows their solution to be obtained by methods that do not depend on the chemical processes. The chemical environment is governed by the condition of local chemical equilibrium, and may be defined either by the linear sorption of a single species and two soluble complexation reactions which also involve that species, or binary ion exchange and one complexation reaction involving a common ion. Partial differential equations that describe solute mass balance entirely in the liquid phase are developed for each tenad (a chemical entity whose total mass is independent of the reaction process) in terms of their total dissolved concentration. These equations are solved numerically in two dimensions through the modification of an existing groundwater flow/transport computer code. (Author 's abstract)

  11. Improved understanding of tributyltin sorption on natural and biochar-amended sediments.

    Science.gov (United States)

    Xiao, Xiaoyu; Sheng, G Daniel; Qiu, Yuping

    2011-12-01

    A poor understanding of tributyltin (TBT) sorption on sediments has hindered an accurate evaluation of its environmental fate. The present study determined TBT sorption by a freshwater sediment (BH) and a coastal marine sediment (TZ) as influenced by pH, salinity, and biochar (BC) amendment into TZ. The isotherms were essentially linear, with K(OC) values in the range of 10(4) to 10(5) L/kg. Tributyltin sorption at pH 3.56 and 8.00 occurred mainly via partitioning. It reached maxima at pH equal to its pK(a) (=6.25) because of added ion exchange. A salinity increase from 5 to 35 practical salinity units enhanced TBT sorption at pH 3.56 and 8.00 on TZ by approximately 30% and on BH by approximately 80%, ascribed to the salting-out effect that reduced the solubilities of tributyltin hydroxide (TBTOH) and tributyltin chloride (TBTCl). At pH 6.25, the same salinity increase reduced TBT sorption on TZ by approximately 20% but enhanced TBT sorption on BH by approximately 35%. This was attributed to the enhancing role of salting out and the reducing role of metal competition for ion exchange. Tributyltin was two orders of magnitude more effectively sorbed by BC than by total organic carbon of TZ, mainly because of the high level of surface area of the BC. Although BC affinity for TBT may be significantly diminished when present in TZ, it was considered to be the primary contributor to TBT sorption from water. Biochar may thus be used to immobilize TBT in sediment for potential remediation. Copyright © 2011 SETAC.

  12. Sorption behavior of thorium onto montmorillonite and illite

    International Nuclear Information System (INIS)

    Iida, Yoshihisa; Barr, Logan; Yamaguchi, Tetsuji; Hemmi, Ko

    2016-01-01

    Thorium (Th)-229 is one of the important radionuclides for the performance assessment calculations for high-level radioactive waste repositories. The sorption behavior of Th onto montmorillonite and illite were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. The sorbability of montmorillonite was higher than that of illite. Distribution coefficients, K d (m 3 kg -1 ), decreased with increased carbonate concentrations and showed the minimal value at around pH 10. The sorption behaviors of Th were analyzed by the non-electrostatic surface complex model with PHREEQC computer program. The model calculations were able to explain the experimental results reasonably well. The decreases of K d was likely due to the stabilization of aqueous species by hydroxo-carbonate complexations in the solutions. (author) [ja

  13. Properties of diclofenac sodium sorption onto natural zeolite modified with cetylpyridinium chloride.

    Science.gov (United States)

    Krajišnik, Danina; Daković, Aleksandra; Milojević, Maja; Malenović, Anđelija; Kragović, Milan; Bogdanović, Danica Bajuk; Dondur, Vera; Milić, Jela

    2011-03-01

    In this study an investigation of a model drug sorption onto cationic surfactant-modified natural zeolites as a drug formulation excipient was performed. Natural zeolite was modified with cetylpyridinium chloride in amounts equivalent to 100, 200 and 300% of its external cation-exchange capacity. The starting material and obtained organozeolites were characterized by Fourier transform infrared spectroscopy, zeta potential measurements and thermal analysis. In vitro sorption of diclofenac sodium as a model drug was studied for all surfactant/zeolite composites by means of sorption isotherm measurements in aqueous solutions (pH 7.4). The modified zeolites with three levels of surfactant coverage within the short activation time were prepared. Zeta potential measurements and thermal analysis showed that when the surfactant loading level was equal to external cation-exchange value, almost monolayer of organic phase were present at the zeolitic surface while higher amounts of surfactant produced less extended bilayers, ordered bilayers or admicelles at the zeolitic surface. Modified zeolites, obtained in this manner, were effective in diclofenac sodium sorption and the organic phase derived from adsorbed cetylpyridinium chloride was the primary sorption phase for the model drug. The Langmuir isotherm was found to describe the equilibrium sorption data well over the entire concentration range. The separate contributions of the adsorption and partition to the total sorption of DS were analyzed mathematically. Results revealed that that adsorption and partitioning of the model drug take place simultaneously. 2010 Elsevier B.V. All rights reserved.

  14. Applicability of sorption data determined by laboratory experiments for evaluation of strontium-85 mobility in subsurface field

    International Nuclear Information System (INIS)

    Tanaka, Tadao; Mukai, Masayuki

    2003-01-01

    Applicability of laboratory measurements to radionuclide transport in a natural environment was studied using the data from the field tests. The K d values obtained in the laboratory experiments were input into the instantaneous equilibrium sorption model, which simulates the migration of 85 Sr in the unsaturated loess. This simulation managed to reproduce results of the aforementioned field tests. To evaluate more accurately migration behavior of 85 Sr, based on the sorption data obtained by the laboratory experiments, the hybrid sorption model consisting of the equilibrium sorption process and the kinetic sorption process was proposed. When compared with predictions using the K d -based equilibrium sorption model, the results of the field migration tests of 85 Sr were more successfully reproduced by introducing the hybrid sorption model. (author)

  15. Sorption-desorption of antimony species onto calcined hydrotalcite: Surface structure and control of competitive anions.

    Science.gov (United States)

    Constantino, Leonel Vinicius; Quirino, Juliana Nunes; Abrão, Taufik; Parreira, Paulo Sérgio; Urbano, Alexandre; Santos, Maria Josefa

    2018-02-15

    Calcined hydrotalcite can be applied to remove anionic contaminants from aqueous systems such as antimony species due to its great anion exchange capacity and high surface area. Hence, this study evaluated antimonite and antimonate sorption-desorption processes onto calcined hydrotalcite in the presence of nitrate, sulfate and phosphate. Sorption and desorption experiments of antimonite and antimonate were carried out in batch equilibrium and the post-sorption solids were analyzed by X-ray fluorescence (EDXRF). Sorption data were better fitted by dual-mode Langmuir-Freundlich model (R 2 >0.99) and desorption data by Langmuir model. High maximum sorption capacities were found for the calcined hydrotalcite, ranging from 617 to 790meqkg -1 . The competing anions strongly affected the antimony sorption. EDXRF analysis and mathematical modelling showed that sulfate and phosphate presented higher effect on antimonite and antimonate sorption, respectively. High values for sorption efficiency (SE=99%) and sorption capacity were attributed to the sorbent small particles and the large surface area. Positive hysteresis indexes and low mobilization factors (MF>3%) suggest very low desorption capacity to antimony species from LDH. These calcined hydrotalcite characteristics are desirable for sorption of antimony species from aqueous solutions. Copyright © 2017. Published by Elsevier B.V.

  16. Moisture sorption isotherms of dehydrated whey proteins

    Directory of Open Access Journals (Sweden)

    Suzana Rimac Brnčić

    2010-03-01

    Full Text Available Moisture sorption isotherms describe the relation between the moisture content of the dry material (food and relative humidity of the surrounding environment. The data obtained are important in modelling of drying process conditions, packaging and shelf-life stability of food that will provide maximum retaining of aroma, colour and texture as well as nutritive and biological value. The objective of this research was to establish the equilibrium moisture content and water activity, as well as monolayer value of two commercial powdered whey protein isolates before and after tribomechanical micronisation and enzymatic hydrolysis, respectively. At the same time it was necessary to evaluate the best moisture sorption isotherm equation to fit the experimental data. The equilibrium moisture contents in investigated samples were determined using standard gravimetric method at 20 °C. The range of water activities was 0.11 to 0.75. The monolayer moisture content was estimated from sorption data using Brunauer-Emmett-Teller (BET and Guggenheim-Anderson-de Boer (GAB models. The results have shown that tribomechanically treated whey protein isolates as well as protein hydrolizates had lower monolayer moisture content values as well as higher corresponding water activity. Therefore, in spite of the fact that they have lower moisture content, they can be storage at higher relative humidity compared to untreated samples. BET model gave better fit to experimental sorption data for a water activity range from 0.11-0.54, while GAB model gave the closest fit for a water activity to 0.75.

  17. Mathematical model of the sorption phenomenon of methanol in activated coal

    Energy Technology Data Exchange (ETDEWEB)

    Cortes, Farid B.; Chejne, Farid; Mejia, Juan M.; Londono, Carlos A. [Grupo de Termodinamica Aplicada y Energias Alternativas - Instituto de Energia, Facultad de Minas, Universidad Nacional de Colombia, sede Medellin (Colombia)

    2009-05-15

    A transient model of a sorption refrigerator using activated carbon/methanol pair is presented. It is a non-uniform pressure model conformed by the mass, energy and momentum balance equations in cylindrical coordinates, for the activated coal bed contained in the adsorber. The results obtained from the simulation were suitably validated by the experimental information obtained from field test data and from data reported in the literature, presenting errors below 1.6% for each cycle step. The model allows to get data of temperature, pressure, density and gas velocity profiles in radial direction, as well as the solid temperature and the quantity of adsorbed methanol in the activated carbon bed in adsorption/evaporation and desorption/condensation steps. (author)

  18. Mathematical model of the sorption phenomenon of methanol in activated coal

    International Nuclear Information System (INIS)

    Cortes, Farid B.; Chejne, Farid; Mejia, Juan M.; Londono, Carlos A.

    2009-01-01

    A transient model of a sorption refrigerator using activated carbon/methanol pair is presented. It is a non-uniform pressure model conformed by the mass, energy and momentum balance equations in cylindrical coordinates, for the activated coal bed contained in the adsorber. The results obtained from the simulation were suitably validated by the experimental information obtained from field test data and from data reported in the literature, presenting errors below 1.6% for each cycle step. The model allows to get data of temperature, pressure, density and gas velocity profiles in radial direction, as well as the solid temperature and the quantity of adsorbed methanol in the activated carbon bed in adsorption/evaporation and desorption/condensation steps.

  19. Radionuclide sorption kinetics and column sorption studies with Columbia River basalts

    International Nuclear Information System (INIS)

    Barney, G.S.

    1983-09-01

    The kinetics of radionuclide sorption and desorption reactions in basalt-groundwater systems were evaluated at 60 degrees C using a batch equilibration method. It was found that many sorption reactions on surfaces of fresh (unaltered) basalt from the Umtanum and Cohassett flows are slow. Some reactions require more than 50 days to reach a steady state. Sorption of neptunium and uranium in oxidizing (air saturated) groundwater appears to be controlled by slow reduction of these elements by the basalt surfaces. The resulting lower oxidation states are more strongly sorbed. Technetium and selenium, which are anionic under oxidizing conditions, are not measurably sorbed on fresh basalt surfaces, but are slightly sorbed on the altered surfaces of flow top basalt. Under reducing conditions, where the groundwater contains dilute hydrazine, sorption is faster for neptunium, uranium, technetium, selenium, and lead. Plutonium sorption rates were not affected by the groundwater Eh. It was shown that radium was precipitated rather than sorbed under the conditions of these experiments. Umtanum flow top material sorbed radionuclides much faster than fresh basalt surfaces due to its greater surface area and cation exchange capacity. Desorption rates for plutonium, uranium, neptunium, technetium, and selenium were generally much less than sorption rates (especially for reducing conditions). These radionuclides are irreversibly sorbed on the basalts. 25 refs., 20 figs., 19 tabs

  20. Understanding the sorption behavior of Pu{sup 4+} on poly(amidoamine) dendrimer functionalized carbon nanotube. Sorption equilibrium, mechanism, kinetics, radiolytic stability, and back-extraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Parveen [Indian Institute of Technology, Himachal Pradesh (India); Sengupta, Arijit [Bahbha Atomic Research Centre, Mumbai (India). Radiochemistry Div.; Deb, Ashish Kumar Singha; Ali, S. Musharaf [Bahbha Atomic Research Centre, Mumbai (India). Chemical Engineering Div.; Homi Bhabha National Institute, Mumbai (India); Dasgupta, Kinshuk [Bhabha National Institute, Mumbai (India). Mechanical Metallurgy Div.

    2017-07-01

    Poly(amidoamine) dendrimer functionalized carbon nanotube was demonstrated as highly efficient sorbent of the Pu{sup 4+} from radioactive waste solution. The second generation dendrimer was found to have more efficiency as compared to the 1{sup st} generation might be due to the availability of more functionality for coordinating to the Pu{sup 4+} ion. Analysis of different isotherm models revealed that, Langmuir isotherm was predominantly operating through chemi-sorption (with the sorption energy 10.07 and 16.95 kJ mol{sup -1} for 1{sup st} and 2{sup nd} generation dendrimer) with the sorption capacity 89.22 mg g{sup -1} and 92.48 mg g{sup -1} for 1{sup st} and 2{sup nd} generation dendrimer, respectively. Analysis of different sorption kinetics model revealed that the sorption proceeded via pseudo 2{sup nd} order reaction. The 2{sup nd} generation dendrimer was found to be radiolytically more stable while oxalic acid was found to be suitable for quantitative back extraction of Pu{sup 4+}.

  1. Experimental And Modelling Investigations on Na-Illite: Acid-Base Behaviour And the Sorption Of Strontium, Nickel, Europium And Uranyl

    Energy Technology Data Exchange (ETDEWEB)

    Bradbury, M.H.; Baeyens, B

    2005-06-01

    In an extensive study the physico-chemical, protolysis and sorption characteristics of Sr(II), Ni(II), Eu(III) and U(VI) have been measured on illite and modeled over a wide range of pH, sorbate and NaCI0{sub 4} concentrations. SampIes of Illite du Puy, collected in the region of Le Puy-en- Velay, France, were carefully conditioned to the Na-form and physico-chemically characterised. Potentiometric titrations on suspensions of the Na-illite were carried out using a batch back titration technique in 0.01, 0.1 and 0.5 M NaCI0{sub 4} background electrolytes from pH 2 to 12 in an inert atmosphere glove box. The supernatant solutions from each titration experiment in each series were analysed for K, Mg, Ca, Sr, Si, Al, Fe and Mn. The titration data were modeled in terms of the protolysis of two amphoteric edge sites (=S{sup W1}0H and =S{sup W2}0H) without an electrostatic term. The protonation/deprotonation constants and site capacities obtained from the titration measurements were then fixed. The sorption edge and isotherm data were modeled with strong (=S{sup S}OH) and weak (=S{sup W1}0H) surface complexation sites, assumed to have the same protolysis constants, again without electrostatic terms. Uptake by cation exchange was included in all of the calculations. This sorption model, the 2 site protolysis non electrostatic surface complexation and cation exchange model, had been developed previously for montmorillonite and was successful in describing the sorption characteristics of Sr, Ni, Eu and U on Na-illite over a wide range of conditions. Cation exchange capacity, strong and weak site capacities and protolysis constants for Na-illite are given, together with surface complexation constants and selectivity coefficients for Sr, Ni, Eu and U. At 0.01 M NaCI0{sub 4} and pH below 8 the sorption of Sr, Ni, Eu and U was dominated by a cation exchange mechanism. The strong dependency of sorption on pH observed under these conditions arose from the competitive effects of

  2. Sorption of phenanthrene on agricultural soils

    DEFF Research Database (Denmark)

    Soares, Antonio; Møldrup, Per; Minh, Luong Nhat

    2013-01-01

    Polyaromatic hydrocarbon (PAH) sorption to soil is a key process deciding the transport and fate of PAH, and potential toxic impacts in the soil and groundwater ecosystems, for example in connection with atmospheric PAH deposition on soils. There are numerous studies on PAH sorption in relatively......, 0.25–1-m depth) by the single-point adsorption method. The organic carbon partition coefficient, KOC (liter per kilogram) for topsoils was found generally to fall between the KOC values estimated by the two most frequently used models for PAH partitioning, the Abdul et al. (Hazardous Waste...... & Hazardous Materials 4(3):211–222, 1987) model and Karickhoff et al. (Water Research 13:241–248, 1979) model. A less-recognized model by Karickhoff (Chemosphere 10:833–846, 1981), yielding a KOC of 14,918 L kg−1, closely corresponded to the average measured KOC value for the topsoils, and this model...

  3. Hydro-mechanical coupling and permeability of an unsaturated swelling clay under hydrous and thermal stress: sorption curve and water permeability; Couplage hydromecanique et permeabilite d'une argile gonflante non saturee sous sollicitations hydriques et thermiques: courbe de sorption et permeabilite a l'eau

    Energy Technology Data Exchange (ETDEWEB)

    Olchitzky, E

    2002-02-15

    The use of swelling clay for engineered safety barriers of radioactive waste disposal require the understanding of its thermal-hydro-mechanical behaviour. This work concerns particularly the characterization and the modelling of the behaviour of one of these clays: the FoCa7 clay. The characteristics of the studied material are: the sorption (desorption) curve and the water permeability. For each of them, new experiments have allowed to acquire data in fields still few explored: in temperature (between 20 and 80 C) for the sorption curve and in the unsaturated field for the water permeability. The analysis of these results and of bibliographic data has allowed in one hand to estimate the importance of the hysteresis phenomenon and the temperature influence on the sorption curve and in another hand, to establish the requirement to introduce in the modelling of the sorption curve, a plastic parameter due to the irreversible deformations occurring during the compaction. Moreover, the tests carried out for data acquirement have been used too to give validation elements to the non linear behaviour laws proposed by O. Coussy and P. Dangla for the non saturated porous media. The particularity of these laws is to suppose the existence of an effective constraint in the non saturated field, this shows the importance of the validation elements presented here. (O.M.)

  4. Introduction to generalized linear models

    CERN Document Server

    Dobson, Annette J

    2008-01-01

    Introduction Background Scope Notation Distributions Related to the Normal Distribution Quadratic Forms Estimation Model Fitting Introduction Examples Some Principles of Statistical Modeling Notation and Coding for Explanatory Variables Exponential Family and Generalized Linear Models Introduction Exponential Family of Distributions Properties of Distributions in the Exponential Family Generalized Linear Models Examples Estimation Introduction Example: Failure Times for Pressure Vessels Maximum Likelihood Estimation Poisson Regression Example Inference Introduction Sampling Distribution for Score Statistics Taylor Series Approximations Sampling Distribution for MLEs Log-Likelihood Ratio Statistic Sampling Distribution for the Deviance Hypothesis Testing Normal Linear Models Introduction Basic Results Multiple Linear Regression Analysis of Variance Analysis of Covariance General Linear Models Binary Variables and Logistic Regression Probability Distributions ...

  5. Dimension of linear models

    DEFF Research Database (Denmark)

    Høskuldsson, Agnar

    1996-01-01

    Determination of the proper dimension of a given linear model is one of the most important tasks in the applied modeling work. We consider here eight criteria that can be used to determine the dimension of the model, or equivalently, the number of components to use in the model. Four of these cri......Determination of the proper dimension of a given linear model is one of the most important tasks in the applied modeling work. We consider here eight criteria that can be used to determine the dimension of the model, or equivalently, the number of components to use in the model. Four...... the basic problems in determining the dimension of linear models. Then each of the eight measures are treated. The results are illustrated by examples....

  6. Extending the linear model with R generalized linear, mixed effects and nonparametric regression models

    CERN Document Server

    Faraway, Julian J

    2005-01-01

    Linear models are central to the practice of statistics and form the foundation of a vast range of statistical methodologies. Julian J. Faraway''s critically acclaimed Linear Models with R examined regression and analysis of variance, demonstrated the different methods available, and showed in which situations each one applies. Following in those footsteps, Extending the Linear Model with R surveys the techniques that grow from the regression model, presenting three extensions to that framework: generalized linear models (GLMs), mixed effect models, and nonparametric regression models. The author''s treatment is thoroughly modern and covers topics that include GLM diagnostics, generalized linear mixed models, trees, and even the use of neural networks in statistics. To demonstrate the interplay of theory and practice, throughout the book the author weaves the use of the R software environment to analyze the data of real examples, providing all of the R commands necessary to reproduce the analyses. All of the ...

  7. Hydro-mechanical coupling and permeability of an unsaturated swelling clay under hydrous and thermal stress: sorption curve and water permeability

    International Nuclear Information System (INIS)

    Olchitzky, E.

    2002-02-01

    The use of swelling clay for engineered safety barriers of radioactive waste disposal require the understanding of its thermal-hydro-mechanical behaviour. This work concerns particularly the characterization and the modelling of the behaviour of one of these clays: the FoCa7 clay. The characteristics of the studied material are: the sorption (desorption) curve and the water permeability. For each of them, new experiments have allowed to acquire data in fields still few explored: in temperature (between 20 and 80 C) for the sorption curve and in the unsaturated field for the water permeability. The analysis of these results and of bibliographic data has allowed in one hand to estimate the importance of the hysteresis phenomenon and the temperature influence on the sorption curve and in another hand, to establish the requirement to introduce in the modelling of the sorption curve, a plastic parameter due to the irreversible deformations occurring during the compaction. Moreover, the tests carried out for data acquirement have been used too to give validation elements to the non linear behaviour laws proposed by O. Coussy and P. Dangla for the non saturated porous media. The particularity of these laws is to suppose the existence of an effective constraint in the non saturated field, this shows the importance of the validation elements presented here. (O.M.)

  8. Evaluation of sorption capacity of modified wood biomass for arsenic five-valent oxyanions

    International Nuclear Information System (INIS)

    Littera, P.; Antoska, R.; Cernansky, S.; Sevc, J.; Kolencik, M.; Budzakova, M.

    2009-01-01

    In the present work is assessed bio-sorption of arsenic oxyanions, which represent one of two most common special arsenic occurring in contaminated waters. A wood biomass was used as sorbent, which was modified by amorphous oxohydroxides of iron to increase sorption capacity, to whom arsenic has high affinity. The work estimated sorption capacity of wood biomass adjusted by oxohydroxides of iron. The Langmuir model as well as the Freundlich model were suitable for evaluation of experimental results. Maximal sorption capacity of investigated sorbent was 9.259 mg/g, what is comparable with values published by other authors.

  9. Nitrate sorption on activated carbon modified with CaCl2: Equilibrium, isotherms and kinetics

    Directory of Open Access Journals (Sweden)

    Zanella Odivan

    2015-01-01

    Full Text Available In this study, nitrate (NO3- removal from aqueous solutions was investigated using granular activated carbon (GAC modified with CaCl2. Batch sorption studies were performed as a function of sorbent dose, initial nitrate concentration and pH. Sorption was maximized between pH 3 and 9. Studies on the effect of pH showed that the ion exchange mechanism might be involved in the sorption process. The percentage of nitrate removed increased with increasing sorbent concentration, and the ideal sorbent dose was found to be 20 g•L-1. Four isotherm models-Langmuir, Freundlich, Redlich-Peterson and Sips-were used to fit the experimental data. The Redlich-Peterson isotherm model explained the sorption process well and showed the best coefficient of determination (0.9979 and Chi-square test statistic (0.0079. Using the Sips isotherm model, the sorption capacity (qe was found to be 1.93 mg nitrate per g of sorbent. Kinetic experiments indicated that sorption was a fast process, reaching equilibrium within 120 min. The nitrate sorption kinetic data were successfully fitted to a pseudo-second-order kinetic model. The overall results demonstrated potential applications of modified GAC for nitrate removal from aqueous solutions.

  10. A primer on linear models

    CERN Document Server

    Monahan, John F

    2008-01-01

    Preface Examples of the General Linear Model Introduction One-Sample Problem Simple Linear Regression Multiple Regression One-Way ANOVA First Discussion The Two-Way Nested Model Two-Way Crossed Model Analysis of Covariance Autoregression Discussion The Linear Least Squares Problem The Normal Equations The Geometry of Least Squares Reparameterization Gram-Schmidt Orthonormalization Estimability and Least Squares Estimators Assumptions for the Linear Mean Model Confounding, Identifiability, and Estimability Estimability and Least Squares Estimators F

  11. Co-contaminants and factors affecting the sorption behaviour of two sulfonamides in pasture soils

    International Nuclear Information System (INIS)

    Srinivasan, Prakash; Sarmah, Ajit K.; Manley-Harris, Merilyn

    2013-01-01

    We investigated the effect of soil pH, organic carbon, ionic strength and steroid hormones on the sorption of sulfamethoxazole (SMO) and sulfachloropyridazine (SCP) in three pastoral soils of New Zealand. A model linking sorbate speciation with species-specific sorption coefficients describing the pH dependence of the apparent sorption coefficients was used to derive the fraction of each species of SMO. All soils displayed a decrease in sorption when pH was increased, with SMO exhibiting the highest sorption at pH 2. The cationic form of SMO appeared to sorb more close to pH ≥ pK a1 and, when pH ≥ pK a2 (6.5, 7.5 and 8.5) the anionic species seems to dominate, however, its sorption affinity to all soils was low. SMO sorption was affected by ionic strengths and organic carbon content, while the presence of hormones showed only a subtle decrease in SCP sorption in a selected model pasture soil. -- Highlights: •The effect of OC content on sulfamethoxazole sorption is nullified by the pH effect. •Steroid hormone has a subtle influence on the sulfachloropyridazine sorption in pastoral soil. •Increased hormone concentrations decrease sulfachloropyridazine sorption in soils. -- Sorption affinity of SMO and SCP are strongly governed by multitude of factors, and variations in these factors can be significant when manure and fertilisers are added to soil

  12. Sorption of perfluoroalkyl substances to two types of minerals.

    Science.gov (United States)

    Hellsing, Maja S; Josefsson, Sarah; Hughes, Arwel V; Ahrens, Lutz

    2016-09-01

    The sorption of perfluoroalkyl substances (PFASs) was investigated for two model soil mineral surfaces, alumina (Al2O3) and silica (SiO2), on molecular level using neutron scattering. The PFASs were selected (i.e. perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonic acid (PFOS)) to examine the role of hydrophobic chain length and hydrophilic functional group on their sorption behaviour. All four PFASs were found to sorb to alumina surface (positively charged) forming a hydrated layer consisting of 50% PFASs. The PFAS solubility limit, which decrease with chain length, was found to strongly influence the sorption behaviour. The sorbed PFAS layer could easily be removed by gentle rinsing with water, indicating release upon rainfall in the environment. No sorption was observed for PFOA and PFOS at silica surface (negatively charged), showing electrostatic interaction being the driving force in the sorption process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Quantification of Cation Sorption to Engineered Barrier Materials Under Extreme Conditions

    International Nuclear Information System (INIS)

    Powell, Brian; Schlautman, Mark; Rao, Linfeng; Nitsche, Heino; Gregorich, Kenneth

    2016-01-01

    The objective of this research is to examine mechanisms and thermodynamics of actinide sorption to engineered barrier materials (iron (oxyhydr)oxides and bentonite clay) for nuclear waste repositories under high temperature and high ionic strength conditions using a suite of macroscopic and microscopic techniques which will be coupled with interfacial reaction models. Gaining a mechanistic understanding of interfacial processes governing the sorption/sequestration of actinides at mineral-water interfaces is fundamental for the accurate prediction of actinide behavior in waste repositories. Although macroscale sorption data and various spectroscopic techniques have provided valuable information regarding speciation of actinides at solid-water interfaces, significant knowledge gaps still exist with respect to sorption mechanisms and the ability to quantify sorption, particularly at high temperatures and ionic strengths. This objective is addressed through three major tasks: (1) influence of oxidation state on actinide sorption to iron oxides and clay minerals at elevated temperatures and ionic strengths; (2) calorimetric titrations of actinide-mineral suspensions; (3) evaluation of bentonite performance under repository conditions. The results of the work will include a qualitative conceptual model and a quantitative thermodynamic speciation model describing actinide partitioning to minerals and sediments, which is based upon a mechanistic understanding of specific sorption processes as determined from both micro-scale and macroscale experimental techniques. The speciation model will be a thermodynamic aqueous and surface complexation model of actinide interactions with mineral surfaces that is self-consistent with macroscopic batch sorption data, calorimetric and potentiometric titrations, X-ray absorption Spectroscopy (XAS, mainly Extended X-ray Absorption Fine Structure (EXAFS)), and electron microscopy analyses. The novelty of the proposed work lies largely in

  14. Quantification of Cation Sorption to Engineered Barrier Materials Under Extreme Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Powell, Brian [Clemson Univ., SC (United States); Schlautman, Mark [Clemson Univ., SC (United States); Rao, Linfeng [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nitsche, Heino [Univ. of California, Berkeley, CA (United States); Gregorich, Kenneth [Univ. of California, Berkeley, CA (United States)

    2016-02-02

    The objective of this research is to examine mechanisms and thermodynamics of actinide sorption to engineered barrier materials (iron (oxyhydr)oxides and bentonite clay) for nuclear waste repositories under high temperature and high ionic strength conditions using a suite of macroscopic and microscopic techniques which will be coupled with interfacial reaction models. Gaining a mechanistic understanding of interfacial processes governing the sorption/sequestration of actinides at mineral-water interfaces is fundamental for the accurate prediction of actinide behavior in waste repositories. Although macroscale sorption data and various spectroscopic techniques have provided valuable information regarding speciation of actinides at solid-water interfaces, significant knowledge gaps still exist with respect to sorption mechanisms and the ability to quantify sorption, particularly at high temperatures and ionic strengths. This objective is addressed through three major tasks: (1) influence of oxidation state on actinide sorption to iron oxides and clay minerals at elevated temperatures and ionic strengths; (2) calorimetric titrations of actinide-mineral suspensions; (3) evaluation of bentonite performance under repository conditions. The results of the work will include a qualitative conceptual model and a quantitative thermodynamic speciation model describing actinide partitioning to minerals and sediments, which is based upon a mechanistic understanding of specific sorption processes as determined from both micro-scale and macroscale experimental techniques. The speciation model will be a thermodynamic aqueous and surface complexation model of actinide interactions with mineral surfaces that is self-consistent with macroscopic batch sorption data, calorimetric and potentiometric titrations, X-ray absorption Spectroscopy (XAS, mainly Extended X-ray Absorption Fine Structure (EXAFS)), and electron microscopy analyses. The novelty of the proposed work lies largely in

  15. Sorption of radionickel to goethite: Effect of water quality parameters and temperature

    International Nuclear Information System (INIS)

    Baowei Hu; ShaoXing University, ShaoXing; Wen Cheng; Hui Zhang; Guodong Sheng; Chinese Academy of Sciences, Hefei

    2010-01-01

    In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found at pH 8.0. The Langmuir, Freundlich, and D-R models were applied to simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters (ΔH 0 , ΔS 0 and ΔG 0 ) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na + /H + on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. (author)

  16. New sorption-reagent materials for decontamination of liquid radioactive waste

    International Nuclear Information System (INIS)

    Avramenko, V.A.; Golikov, A.P.; Zheleznov, V.V.; Kaplun, E.V.; Marinin, D.V.; Sokolnitskaya, T.A.

    2001-01-01

    -reagent materials and it was shown that a dramatic increase of the sorption selectivity results from radionuclide co-precipitation on micro- particles of insoluble precipitates inside the pores of inorganic matrices and from selective ion exchange on the matrix. The most interesting features of the sorption-reagent method of LRW decontamination are observed in the process dynamics. We have studied the sorption dynamics in sulfate, sulfide and permanganate sorption-reagent systems and it has been shown that the radionuclide sorption dynamics in such systems is substantially different from sorption and ion-exchange dynamics. We have developed a mathematical model of simultaneous reagent front motions, ion exchange and radionuclide co-precipitation. The radionuclide sorption dynamics was simulated and the model was found to explain main features of the sorption- reagent radionuclide decontamination. The efficiency of decontamination of LRW of complex chemical composition from cesium, strontium and cobalt radionuclides by the sorption- reagent method was shown. While conventional selective sorbents (zeolites, titanates, silicotitanates, different forms of manganese dioxide) are not capable to remove selectively strontium and cobalt radionuclides from solutions with high complexing agent content, the sorption-reagent materials enable to achieve the extent of LRW decontamination meeting the radiation safety normative documents. The pilot-plant scale sorption-reagent installation for LRW management has been tested at different nuclear industry objects and waste decontamination facilities of the A.A. Bochvar Research Center VNIINM (Moscow, Russia). (author)

  17. An Exact Solution for the Assessment of Nonequilibrium Sorption of Radionuclides in the Vadose Zone

    International Nuclear Information System (INIS)

    Drake, R. L.; Chen, J-S.

    2002-01-01

    In a report on model evaluation, the authors ran the HYDRUS Code, among other transport codes, to evaluate the impacts of nonequilibrium sorption sites on the time-evolution of 99Tc and 90Sr through the vadose zone. Since our evaluation was based on a rather low, annual recharge rate, many of the numerical results derived from HYDRUS indicated that the nonequilibrium sorption sites, in essence, acted as equilibrium sorption sites. To help explain these results, we considered a ''stripped-down'' version of the HYDRUS system. This ''stripped-down'' version possesses two dependent variables, one for the radionuclides in solution and the other for the radionuclides adsorbed to the nonequilibrium sites; and it possesses constant physical parameters. The resultant governing equation for the radionuclides in solution is a linear, advection-dispersion-reaction (i.e., radioactive decay) partial differential equation containing a history integral term accounting for the nonequilibrium sorption sites. It is this ''stripped-down'' version, which is the subject of this paper. We found an exact solution to this new version of the model. The exact solution is given in terms of a single definite integral of terms involving elementary functions of the independent variables and the system parameters. This integral possesses adequate convergence properties and is easy to evaluate, both in a quantitative matter and in a qualitative manner. The parameters that are considered in the system are as follows: the radionuclide's equilibrium partition coefficient between water and soil, the bulk density of the soil, the fractions of equilibrium/nonequilibrium sorption sites, the volumetric water content, the first order equilibrium adsorption rate constant, the first order radioactive decay rate constant, the liquid water soil tortuosity factor, the molecular diffusion coefficient in water, the longitudinal dispersivity factor, and the Darcian fluid flux density. In addition, the system

  18. Acceptability of inversely-modelled parameters for non-equilibrium sorption of pesticides in soil

    NARCIS (Netherlands)

    Horst, ter M.M.S.; Boesten, J.J.T.I.; Beinum, van W.; Beulke, S.

    2013-01-01

    Simulation of the increase of sorption in time is one of the options in higher tiers of pesticide regulatory leaching assessments to obtain more realistic leaching estimates. Therefore, accurate estimates of non-equilibrium sorption parameters are required as input for the pesticide leaching

  19. MEASUREMENT AND MODELLING OF SORPTION EQUILIBRIUM CURVE OF WATER ON PA6, PP, HDPE AND PVC BY USING FLORY-HUGGINS MODEL

    Directory of Open Access Journals (Sweden)

    Suherman Suherman

    2012-02-01

    Full Text Available The sorption of water on granular polyamide-6 (PA6, granular polypropylene (PP, and powdery high density polyethylene (HDPE and powdery polyvinyl chloride (PVC were measured using a gravimetric method in a magnetic suspension balance (MSB. The Flory-Huggins model was successfully applied on the sorption equilibrium curve of all investigated polymers. The influence of temperature is low. The value of Flory-Huggins parameters(c of PA6, PVC, PP and HDPE were 1.8, 5.8, 6.3, and 8.1, respectively. The water in PA6 is mainly bound moisture, while in PP, HDPE and PVC it is mainly surface moisture.

  20. Sepiolite functionalized with N-[3-(trimethoxysilylpropyl]-ethylenediamine triacetic acid trisodium salt. Part II: Sorption of Ni2+ from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Lazarević Slavica S.

    2016-01-01

    Full Text Available sorption of Ni2+ on the sepiolite functionalized by covalent grafting of N-[3-(trimethoxysilylpropyl]ethylenediamine triacetic acid trisodium salt, MSEAS, was studied in batch experiments as a function of the initial metal concentration, the equilibration time, pH value, and temperature. The modification of sepiolite resulted in an enhanced Ni2+ retention with a capacity of 0.261 mmol/g at 298 K. The retention of Ni2+ ions occurred dominantly by specific sorption and exchange of Mg2+ ions from the sepiolite structure. The sorption process followed pseudo-second-order kinetics. The sorption equilibrium results were best described by the non-linear form of the Langmuir Sorption Equation. The values of the thermodynamic parameters (enthalpy, free energy and entropy were calculated from temperature dependent sorption isotherms and these values showed that the sorption of Ni2+ onto modified sepiolite was endothermic. [Projekat Ministarstva nauke Republike Srbije, br. III 45019 i FP7 NANOTECH FTM No. 245916

  1. P-EXAFS investigations of Zn uptake by montmorillonite. The strong and weak sites concept in the 2SPNE SC/CE sorption model

    International Nuclear Information System (INIS)

    Daehn, R.; Baeyens, B.; Bradbury, M.H.

    2012-01-01

    Document available in extended abstract form only. The sorption of radioactive elements on the immobile components in the near- and far-fields of a deep geological radioactive waste repository is a significant process in retarding their aqueous phase transport and an important component in safety assessment studies. The development of robust and well-founded mechanistic sorption models to predict the uptake of radionuclides under different geochemical conditions would enhance the justification and defensibility of the sorption values used in safety studies and thereby represent a considerable contribution to the scientific basis for radioactive waste disposal. The 2 site proto-lysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model has been used over the past decade or so to quantitatively describe the uptake of metals with oxidation states from II to VI on 2:1 clay minerals; montmorillonite and illite (Bradbury and Baeyens, 1997). One of the main features in this model is that there are two broad categories of amphoteric edge sorption sites; the so called strong (≡SSOH) and weak (≡SW1OH) sites. Because of their different sorption characteristics, it was expected that the coordination environments of the surface complexes on the two site types would be different. Although the 2SPNE SC/CE model uses different mechanistic uptake processes to describe sorption, it can only be described as a 'quasi mechanistic' model because the exact nature of the surface binding sites and surface complexes is not known. In order to check the 'strong site / weak site' sorption sites hypothesis in the 2SPNE SC/CE sorption model, it was essential to perform polarised extended X-ray absorption fine structure (P-EXAFS) measurements on an uptake system, in which it was possible to obtain good spectra particularly at the low metal loadings (∼2 mmol kg-1 or less) corresponding to occupancies dominated by strong sites. The Zn-montmorillonite system

  2. Sorption and mobility of 14C-fenamiphos in Brazilian soils.

    Science.gov (United States)

    Cáceres, Tanya; Venkateswarlu, Kadiyala

    2018-02-02

    Although fenamiphos is widely used as an insecticide and nematicide in bowling greens and agriculture, information on its sorption in tropical soils is limited. In this study, mobility, sorption, and desorption dynamics of 14 C-fenamiphos in three contrasting Brazilian soils were examined both in batch and column experiments. Fenamiphos sorption coefficients (K d ) were 2.33, 3.86, and 3.9 L kg -1 for the three soils tested. The insecticide exhibited linear adsorption isotherms in all the three soils, and desorption was in a range of 30-40% during a 72-h period. With its low mobility, fenamiphos did not percolate through the soil profile even after 48 h. However, there is a risk of leaching to water bodies due to runoff because of its high solubility in water. In view of the fact that fenamiphos and its oxidation products are highly toxic to aquatic invertebrates and could affect the soil microbial activities even at low concentrations, the present information is of great importance in risk assessment of fenamiphos in the environment.

  3. Application of Hierarchical Linear Models/Linear Mixed-Effects Models in School Effectiveness Research

    Science.gov (United States)

    Ker, H. W.

    2014-01-01

    Multilevel data are very common in educational research. Hierarchical linear models/linear mixed-effects models (HLMs/LMEs) are often utilized to analyze multilevel data nowadays. This paper discusses the problems of utilizing ordinary regressions for modeling multilevel educational data, compare the data analytic results from three regression…

  4. Dynamic Simulation of a Periodic 10 K Sorption Cryocooler

    Science.gov (United States)

    Bhandari, P.; Rodriguez, J.; Bard, S.; Wade, L.

    1994-01-01

    A transient thermal simulation model has been developed to simulate the dynamic performance of a multiple-stage 10 K sorption cryocooler for spacecraft sensor cooling applications that require periodic quick-cooldown (under 2 minutes) , negligible vibration, low power consumption, and long life (5 to 10 years). The model was specifically designed to represent the Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE), but it can be adapted to represent other sorption cryocooler systems as well. The model simulates the heat transfer, mass transfer, and thermodynamic processes in the cryostat and the sorbent beds for the entire refrigeration cycle, and includes the transient effects of variable hydrogen supply pressures due to expansion and overflow of hydrogen during the cooldown operation. The paper describes model limitations and simplifying assumptions, with estimates of errors induced by them, and presents comparisons of performance predictions with ground experiments. An important benefit of the model is its ability to predict performance sensitivities to variations of key design and operational parameters. The insights thus obtained are expected to lead to higher efficiencies and lower weights for future designs.

  5. Sorption of natural uranium by algerian bentonite

    International Nuclear Information System (INIS)

    Megouda, N.; Kadi, H.; Hamla, M.S.; Brahimi, H.

    2004-01-01

    Full text.Batch sorption experiments have been used to assess the sorption behaviour of uranium onto natural and drilling bentonites. The operating parameters (pH, aolis-liquid ratio, particle size, time and initial uranium concentration) influenced the rate of adsorption. The distribution coefficient (Kd) range values at equilibrium time are 45.95-1079.26 ml/g and 32.81-463053 ml/g for the drilling and natural bentonites respectively. The equilibrium isotherms show that the data correlate with both Freundlich and Langmuir models

  6. Applicability of surface complexation modelling in TVO's studies on sorption of radionuclides

    International Nuclear Information System (INIS)

    Carlsson, T.

    1994-03-01

    The report focuses on the possibility of applying surface complexation theories to the conditions at a potential repository site in Finland and of doing proper experimental work in order to determine necessary constants for the models. The report provides background information on: (1) what type experiments should be carried out in order to produce data for surface complexation modelling of sorption phenomena under potential Finnish repository conditions, and (2) how to design and perform properly such experiments, in order to gather data, develop models or both. The report does not describe in detail how proper surface complexation experiments or modelling should be carried out. The work contains several examples of information that may be valuable in both modelling and experimental work. (51 refs., 6 figs., 4 tabs.)

  7. Sorption of cobalt in zeolites and natural clays of the clinoptilolite and kaolinite type

    International Nuclear Information System (INIS)

    Davila R, J.I.; Solache R, M.

    2006-01-01

    In this work the sorption of cobalt of aqueous solutions in two natural zeolites (clinoptilolite) and a clay (kaolinite) of origin in the center-north region of Mexico is evaluated. The effect of the pH and the time of contact in the process of sorption were evaluated. The cobalt retained in the aluminosilicates was determined by neutron activation analysis. The cobalt sorption in the materials in a range of pH from 4 to 7 does not present significant variations. The studies of reaction kinetics show a very fast sorption in the first 5 hours of contact, reaching the equilibrium in approximately 24 hours. The kinetics of sorption of the cobalt ions was represented better by the Ritchie reaction model modified of second order. The experimental data for the zeolites obtained at ambient temperature and varying the concentration were adjusted to the models of Freundlich, Langmuir and Freundlich-Langmuir isotherms and it was observed that the cobalt sorption it behaves according to the Freundlich isotherm model. (Author)

  8. Sorption Modeling and Verification for Off-Gas Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Tavlarides, Lawrence [Syracuse Univ., NY (United States); Yiacoumi, Sotira [Georgia Inst. of Technology, Atlanta, GA (United States); Tsouris, Costas [Georgia Inst. of Technology, Atlanta, GA (United States); Gabitto, Jorge [Prairie View Texas A& M; DePaoli, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-12-20

    processes. These models were built on a numerical framework for solving conservation law problems in one-dimensional geometries such as spheres, cylinders, and lines. Coupled with the framework are specific models for adsorption in commercial adsorbents, such as zeolites and mordenites. Utilizing this modeling approach, the authors were able to accurately describe and predict adsorption kinetic data obtained from experiments at a variety of different temperatures and gas phase concentrations. A demonstration of how these models, and framework, can be used to simulate adsorption in fixed- bed columns is provided. The CO2 absorption work involved modeling with supportive experimental information. A dynamic model was developed to simulate CO2 absorption using high alkaline content water solutions. The model is based upon transient mass and energy balances for chemical species commonly present in CO2 absorption. A computer code was developed to implement CO2 absorption with a chemical reaction model. Experiments were conducted in a laboratory scale column to determine the model parameters. The influence of geometric parameters and operating variables on CO2 absorption was studied over a wide range of conditions. Continuing work could employ the model to control column operation and predict the absorption behavior under various input conditions and other prescribed experimental perturbations. The value of the validated models and numerical frameworks developed in this project is that they can be used to predict the sorption behavior of off-gas evolved during the reprocessing of nuclear waste and thus reduce the cost of the experiments. They can also be used to design sorption processes based on concentration limits and flow-rates determined at the plant level.

  9. Preparation, characterization of electrospun meso-hydroxylapatite nanofibers and their sorptions on Co(II)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hualin, E-mail: hlwang@hfut.edu.cn [School of Chemical Technology, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang, Peng; Ma, Xingkong; Jiang, Suwei; Huang, Yan; Zhai, Linfeng [School of Chemical Technology, Hefei University of Technology, Hefei, Anhui 230009 (China); Jiang, Shaotong [School of Biotechnology and Food Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China)

    2014-01-30

    Highlights: • PVA/HA nanofibers could change into meso-HA nanofibers by calcination process. • Sorption of Co(II) on meso-HA was strongly dependent on pH and ionic strength. • Sorption kinetic data were well fitted by the pseudo-second-order rate equation. • Sorption isotherms could be well described by the Langmuir model. • Sorption process of Co(II) on meso-HA nanofibers was spontaneous and endothermic. -- Abstract: In this work, mesoporous hydroxylapatite (meso-HA) nanofibers were prepared via calcination process with polyvinyl alcohol/HA (PVA/HA) hybrid nanofibers fabricated by electrospinning technique as precursors, and the removal efficiency of meso-HA nanofibers toward Co(II) was evaluated via sorption kinetics and sorption isotherms. Furthermore, the sorption behaviors of Co(II) on meso-HA nanofibers were explored as a function of pH, ionic strength, and thermodynamic parameters. There existed hydrogen bonds between HA and PVA matrix in precursor nanofibers which could change into meso-HA nanofibers with main pore diameter at 27 nm and specific surface area at 114.26 m{sup 2}/g by calcination process. The sorption of Co(II) on meso-HA was strongly dependent on pH and ionic strength. Outer-sphere surface complexation or ion exchange was the main mechanisms of Co(II) adsorption on meso-HA at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The sorption kinetic data were well fitted by the pseudo-second-order rate equation. The sorption isotherms could be well described by the Langmuir model. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature-dependent sorption isotherms suggested that the sorption process of Co(II) on meso-HA nanofibers was spontaneous and endothermic.

  10. Determination of Sorption Coefficient of Phosphorus Applied for Sugarcane Production in Southwestern Florida.

    Science.gov (United States)

    Muwamba, A; Nkedi-Kizza, P; Morgan, K T

    2016-09-01

    Phosphorus is among the essential nutrients applied to sugarcane ( L.) fields in the form of a fertilizer mixture (N, P, and K) in southwestern Florida. Sorption coefficient is used for modeling P movement, and in this study, we hypothesized that the sorption coefficient determined using fertilizer mixture (N, P, and K) will be significantly different from values determined using KCl and CaCl, the electrolytes most commonly used for conducting sorption experiments. Supporting electrolytes, 0.01 mol L KCl, 0.005 mol L CaCl, deionized (DI) water, simulated Florida rain, and fertilizer mixture prepared in Florida rain were used to characterize P sorption. Immokalee (Sandy, siliceous, hyperthermic Arenic Alaquods) and Margate (Sandy, siliceous hyperthermic Mollic Psammaquents) are the dominant mineral soils used for sugarcane production in southwestern Florida; we used the A and B horizons of Margate soil and the A and B horizons of the Immokalee soil for sorption experiments in this study. Freundlich sorption isotherms described P sorption data. The Freundlich sorption isotherm coefficients followed the trend 0.005 mol L CaCl > 0.01 mol L KCl ≈ fertilizer mixture > simulated Florida rain ≈ DI water. Sorption coefficients were used for modeling P movement with HYDRUS 1D; similar P results were obtained with the 0.01 mol L KCl and fertilizer mixture electrolyte treatments. The sorption coefficient for DI water and simulated Florida rain overpredicted P movement. The P sorption data showed the importance of choosing the appropriate electrolyte for conducting experiments based on the composition of fertilizer. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  11. Sorption of perfluorooctanoic acid, perfluorooctane sulfonate and perfluoroheptanoic acid on granular activated carbon.

    Science.gov (United States)

    Zhang, Di; Luo, Qi; Gao, Bin; Chiang, Sheau-Yun Dora; Woodward, David; Huang, Qingguo

    2016-02-01

    The sorption of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluoroheptanoic acid (PFHpA) on granular activated carbon (GAC) was characterized and compared to explore the underlying mechanisms. Sorption of the three perfluoroalkyl acids (PFAAs) on GAC appeared to be a rapid intra-particle diffusion process, which were well represented by the pseudo-second-order rate model with the sorption rate following the order PFOS > PFOA > PFHpA. Sorption isotherm data were well fitted by the Freundlich model with the sorption capacity (Kf) of PFOS, PFOA and PFHpA being 4.45, 2.42 and 1.66 respectively. This suggests that the hydrophilic head group on PFAAs, i.e. sulfonate vs carboxylic, has a strong influence on their sorption. Comparison between PFOA and PFHpA revealed that hydrophobicity could also play a role in the sorption of PFAAs on GAC when the fluorocarbon chain length is different. Analyses using Attenuated Total Reflection (ATR)-Fourier Transform Infrared (FTIR) spectroscopy suggested possible formation of a negative charge-assisted H-bond between PFAAs and the functionalities on GAC surfaces, including non-aromatic ketones, sulfides, and halogenated hydrocarbons. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. A Numerical Approach for Non-Linear Moisture Flow in Porous Materials with Account to Sorption Hysteresis

    DEFF Research Database (Denmark)

    Johannesson, Björn; Nyman, U.

    2010-01-01

    . History-dependent sorption behaviour is introduced by considering scanning curves between the bounding desorption and absorption curves. The method, therefore, makes it possible to calculate equilibrium water contents for arbitrary relative humidity variations at every material point considered...

  13. Radionuclide sorption in Yucca Mountain tuffs with J-13 well water: Neptunium, uranium, and plutonium. Yucca Mountain site characterization program milestone 3338

    International Nuclear Information System (INIS)

    Triay, I.R.; Cotter, C.R.; Kraus, S.M.; Huddleston, M.H.

    1996-08-01

    We studied the retardation of actinides (neptunium, uranium, and plutonium) by sorption as a function of radionuclide concentration in water from Well J-13 and of tuffs from Yucca Mountain. Three major tuff types were examined: devitrified, vitric, and zeolitic. To identify the sorbing minerals in the tuffs, we conducted batch sorption experiments with pure mineral separates. These experiments were performed with water from Well J-13 (a sodium bicarbonate groundwater) under oxidizing conditions in the pH range from 7 to 8.5. The results indicate that all actinides studied sorb strongly to synthetic hematite and also that Np(V) and U(VI) do not sorb appreciably to devitrified or vitric tuffs, albite, or quartz. The sorption of neptunium onto clinoptilolite-rich tuffs and pure clinoptilolite can be fitted with a sorption distribution coefficient in the concentration range from 1 X 10 -7 to 3 X 10 -5 M. The sorption of uranium onto clinoptilolite-rich tuffs and pure clinoptilolite is not linear in the concentration range from 8 X 10 -8 to 1 X 10 -4 M, and it can be fitted with nonlinear isotherm models (such as the Langmuir or the Freundlich Isotherms). The sorption of neptunium and uranium onto clinoptilolite in J-13 well water increases with decreasing pH in the range from 7 to 8.5. The sorption of plutonium (initially in the Pu(V) oxidation state) onto tuffs and pure mineral separates in J-13 well water at pH 7 is significant. Plutonium sorption decreases as a function of tuff type in the order: zeolitic > vitric > devitrified; and as a function of mineralogy in the order: hematite > clinoptilolite > albite > quartz

  14. Water sorption kinetics of damaged beans: GAB model

    Directory of Open Access Journals (Sweden)

    Fernanda M. Baptestini

    Full Text Available ABSTRACT The objective of this study was to model the water sorption kinetics of damaged beans. Grains with initial moisture content of 53.85%, dry basis (d.b., were used. One portion of the grains was used to obtain desorption isotherms, while the other was subjected to drying until the moisture content of 5.26% (d.b., so that it was subjected to the adsorption. For the induction of damage, a Stein Breakage Tester was used. To obtain the equilibrium moisture content, grains were placed in a climatic chamber at 20, 30, 40 and 50 ± 1 °C combined with relative humidity of 30, 40, 50, 70 and 90 ± 3%. The GAB model fitted well to the equilibrium moisture experimental data of damaged grains and control. With increasing temperature, the monolayer moisture contents decreased in adsorption and desorption processes, ranging from 9.84 to 5.10% d.b. The lower moisture content in the monolayer in damaged grains indicates that lower moisture content is necessary to ensure their conservation.

  15. Sorption of actinides onto nanodiamonds

    Energy Technology Data Exchange (ETDEWEB)

    Buchatskaya, Yulia; Romanchuk, Anna; Yakovlev, Ruslan; Kulakova, Inna [Lomonosov Moscow State Univ., Moscow (Russian Federation). Dept. of Chemistry; Shiryaev, Andrei [Russian Academy of Sciences, Moscow (Russian Federation). Frumkin Institute of Physical Chemistry and Electrochemistry; Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry; Kalmykov, Stepan [Lomonosov Moscow State Univ., Moscow (Russian Federation). Dept. of Chemistry; Russian Academy of Sciences, Moscow (Russian Federation). Frumkin Institute of Physical Chemistry and Electrochemistry; Russian Academy of Sciences, Moscow (Russian Federation). Vernadsky Institute of Geochemistry and Analytical Chemistry

    2015-06-01

    Detonation nanodiamonds (ND) present a significant part of nanocarbons group, which could be produced on commercial scale by detonation of explosives in a closed chamber. Their unique properties of high surface area, low weight and radiation resistance make ND a prospective candidate for applications in sorption processes in radiochemistry. To study the influence of surface chemistry on sorption properties, apristine sample of ND was treated with acids and hydrogen. The surface chemistry of the samples was characterised by infrared spectroscopy, X-ray photoelectron spectroscopy and Boehm titration. The sorption properties of ND were tested fordifferent radionuclides. The sorption capacity of ND was shown to be higher than those of commonly used radionuclide sorbents like activated carbon and compariable to other members of nanocarbon group like graphene oxide and carbon nanotubes. The sorption properties were shown to be influenced by the presence of oxygen-containing groups on the surface of ND. This represents an opportunity to increase the sorption capacity of ND.

  16. Sorption of actinides onto nanodiamonds

    International Nuclear Information System (INIS)

    Buchatskaya, Yulia; Romanchuk, Anna; Yakovlev, Ruslan; Kulakova, Inna; Shiryaev, Andrei; Russian Academy of Sciences, Moscow; Kalmykov, Stepan; Russian Academy of Sciences, Moscow; Russian Academy of Sciences, Moscow

    2015-01-01

    Detonation nanodiamonds (ND) present a significant part of nanocarbons group, which could be produced on commercial scale by detonation of explosives in a closed chamber. Their unique properties of high surface area, low weight and radiation resistance make ND a prospective candidate for applications in sorption processes in radiochemistry. To study the influence of surface chemistry on sorption properties, apristine sample of ND was treated with acids and hydrogen. The surface chemistry of the samples was characterised by infrared spectroscopy, X-ray photoelectron spectroscopy and Boehm titration. The sorption properties of ND were tested fordifferent radionuclides. The sorption capacity of ND was shown to be higher than those of commonly used radionuclide sorbents like activated carbon and compariable to other members of nanocarbon group like graphene oxide and carbon nanotubes. The sorption properties were shown to be influenced by the presence of oxygen-containing groups on the surface of ND. This represents an opportunity to increase the sorption capacity of ND.

  17. A suggested approach toward measuring sorption and applying sorption data to repository performance assessment

    International Nuclear Information System (INIS)

    Rundberg, R.S.

    1992-01-01

    The prediction of radionuclide migration for the purpose of assessing the safety of a nuclear waste repository will be based on a collective knowledge of hydrologic and geochemical properties of the surrounding rock and groundwater. This knowledge along with assumption about the interactions of radionuclides with groundwater and minerals form the scientific basis for a model capable of accurately predicting the repository's performance. Because the interaction of radionuclides in geochemical systems is known to be complicated, several fundamental and empirical approaches to measuring the interaction between radionuclides and the geologic barrier have been developed. The approaches applied to the measurement of sorption involve the use of pure minerals, intact, or crushed rock in dynamic and static experiments. Each approach has its advantages and disadvantages. There is no single best method for providing sorption data for performance assessment models which can be applied without invoking information derived from multiple experiments. 53 refs., 12 figs

  18. Influence of light-weight organic matters on strontium sorption to bentonite

    International Nuclear Information System (INIS)

    Wang, Tsing-Hai; Wu, Ding-Chiang; Teng, Shi-Ping

    2010-01-01

    Document available in extended abstract form only. Light-weight organic matters were frequently observed in groundwater. Their existence had significant influence on the transport of radionuclides. In this study, light-weight organic acid species including oxalic (MW 90), succinic (MW 118), adipic (MW 146), azelaic (MW 188), eicosanedioic (MW 306), benzoic (MW 122), salicylic (MW 138), and gallic (MW 170) were selected as the surrogate of natural organic matters. Their effects on strontium sorption to bentonite were evaluated by using a surface complexation model MINEQL+. Under this framework, three sorption mechanisms were considered: 1. structure sorption sites, 2. edge sorption sites, 3. further hydration of adsorbed Sr 2+ . The presence of organic species had no influence on Sr cation sorption to structure sorption sites. However, Sr cation sorption to edge sorption was affected by the organics to certain extent. For example, sorption capability of edge sites toward Sr was increased by the gallic species. Furthermore, hydration of adsorbed Sr was significantly affected by the presence of organic species. This might relate to that adsorbed Sr would become the bridge associating organic species on bentonite surfaces, but this argument required more solid spectral evidences to support. Some preliminary observations on Sr sorption to bentonite were obtained in this work; however, further experiments are still required by conducting experiments with more variety of organic species. By doing a comprehensive study, it would be much beneficial to make a more accurate evaluation of the influence of organic matters on Sr sorption

  19. Sorption of strontium and fractal scaling of the heterogeneous media in a candidate VLLW disposal site

    International Nuclear Information System (INIS)

    Jinsheng Wang; Rui Zuo; Yanguo Teng; Zongjian Sun; Qinhong Hu

    2010-01-01

    Because of the deposit and accumulation from the debris flow, the heterogeneous geological characteristics is obvious for a candidate very low level waste (VLLW) disposal site, with the grain size ranging from tens of microns to 75 cm. Therefore, it is challenging to directly measure the sorption capacity of the media and the distribution coefficient of some radionuclides, such as strontium. We have studies the correlation of the particle mass content with different grade size and the sorption capacity, which is important in the modeling of radionuclide migration in the heterogeneous disposal site. A total of three deep pits and five shallow trenches were excavated, and 21 solid samples were collected for laboratory experiments. The grade and percentage of the different-sized particles were obtained, and the fractal dimension (D) of the media was calculated from the results of sieved experiments. Steady state sorption time and sorption isotherm of strontium was determined in the heterogeneous media, and sorption and distribution of strontium in the heterogeneous media were evaluated by the relationship between the mass percentage and distribution coefficient (K d ) of the fine-particle media, which was comprised of selected particles with a diameter less than 1 mm, and the correlation on the K d and D was regressed fit. The results indicated that fractal dimension bounded from 2.39 to 2.62 in the media, and K d values of strontium ranged between 119 and 126 in the fine-particle media, and corresponding value was 11 and 43 in the original media. The correlation between K d and D was approximately linear. (author)

  20. Sorption Isotherm of Southern Yellow Pine—High Density Polyethylene Composites

    Directory of Open Access Journals (Sweden)

    Feihong Liu

    2015-01-01

    Full Text Available Temperature and relative humidity (RH are two major external factors, which affect equilibrium moisture content (EMC of wood-plastic composites (WPCs. In this study, the effect of different durability treatments on sorption and desorption isotherms of southern yellow pine (SYP-high density polyethylene (HDPE composites was investigated. All samples were equilibriumed at 20 °C and various RHs including 16%, 33%, 45%, 66%, 75%, 85%, 93%, and100%. EMCs obtained from desorption and absorption for different WPC samples were compared with Nelson’s sorption isotherm model predictions using the same temperature and humidity conditions. The results indicated that the amount of moisture absorbed increased with the increases in RH at 20 °C. All samples showed sorption hysteresis at a fixed RH. Small difference between EMC data of WPC samples containing different amount of ultraviolet (UV stabilizers were observed. Similar results were observed among the samples containing different amount of zinc borate (ZB. The experimental data of EMCs at various RHs fit to the Nelson’s sorption isotherm model well. The Nelson’s model can be used to predicate EMCs of WPCs under different RH environmental conditions.

  1. Acetone-butanol-ethanol competitive sorption simulation from single, binary, and ternary systems in a fixed-bed of KA-I resin.

    Science.gov (United States)

    Wu, Jinglan; Zhuang, Wei; Ying, Hanjie; Jiao, Pengfei; Li, Renjie; Wen, Qingshi; Wang, Lili; Zhou, Jingwei; Yang, Pengpeng

    2015-01-01

    Separation of butanol based on sorption methodology from acetone-butanol-ethanol (ABE) fermentation broth has advantages in terms of biocompatibility and stability, as well as economy, and therefore gains much attention. In this work a chromatographic column model based on the solid film linear driving force approach and the competitive Langmuir isotherm equations was used to predict the competitive sorption behaviors of ABE single, binary, and ternary mixture. It was observed that the outlet concentration of weaker retained components exceeded the inlet concentration, which is an evidence of competitive adsorption. Butanol, the strongest retained component, could replace ethanol almost completely and also most of acetone. In the end of this work, the proposed model was validated by comparison of the experimental and predicted ABE ternary breakthrough curves using the real ABE fermentation broth as a feed solution. © 2014 American Institute of Chemical Engineers.

  2. Sorption of niobium on boreal forest soil

    Energy Technology Data Exchange (ETDEWEB)

    Soederlund, Mervi; Hakanen, Martti; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry

    2015-07-01

    The sorption of niobium (Nb) was investigated on humus and mineral soil samples taken from various depths of a four-metre deep forest soil pit on Olkiluoto Island, southwestern Finland. Mass distribution coefficients, K{sub d}, were determined in batch sorption tests. The steady state of Nb sorption was observed in the mineral soil samples already after one week of equilibration, and sorption decreased with depth from a very high value of 185000 mL/g at 0.7 m to 54000 mL/g at 3.4 m. The reason behind this decrease is probably the tenfold reduction in the specific surface area of the soil at the same depth range. Distribution coefficients were clearly lower in the humus layer (1000 mL/g). The K{sub d} values determined in pure water at a pH range of 4.7-6.5 were at a high level (above 55000 mL/g), but decreased dramatically above pH 6.5, corresponding to the change in the major Nb species from the neutral Nb(OH){sub 5} to the low-sorbing anionic Nb(OH){sub 6}{sup -} and Nb(OH){sub 7}{sup 2-}. However, the K{sub d} values in the model soil solution were in the slightly alkaline range an order of magnitude higher than in pure water, which is probably caused by the formation of calcium niobate surface precipitate or electrostatic interaction between surface-sorbed calcium and solute Nb. Among nine soil constituent minerals kaolinite performed best in retaining Nb in both pure water and model soil solution at pH 8, whereas potassium feldspar showed the poorest sorption. The K{sub d} value for kaolinite was above 500000 mL/g in both solutions, while the respective potassium feldspar values were in the range of 120-220 mL/g.

  3. Pollution and pollution tolerance as regards the sorption of organic chemicals in urban soils; Sorption organischer Chemikalien

    Energy Technology Data Exchange (ETDEWEB)

    Blume, H.P.; Wu Qinglan; Strehl, M. [Kiel Univ. (Germany). Inst. fuer Pflanzenernaehrung und Bodenkunde; Abend, S. [Kiel Univ. (Germany). Inst. fuer Anorganische Chemie; Rexilius, L. [Pflanzenschutzamt des Landes Schleswig-Holstein, Kiel (Germany); Schleuss, U. [Kiel Univ. (Germany). Oekologie-Zentrum]|[Zentrum fuer Agrarlandschafts- und Landnutzungsforschung Muencheberg (Germany)

    1997-12-31

    The behaviour of pollutants in soils concerning, for example, their immobilisation, transport, biodegradation, or uptake by useful plants is to large degree determined by the sorption properties of the soil in question. The degree of sorption is an all-important parameter in any model description of the behaviour of pollutants in soils. The aim of the present part-project was to estimate by means of simple field methods the binding capacity of anthropogenic urban soils for environmentally consequential organic chemicals and to assess the results with regard to soil and water protection. [Deutsch] Das Verhalten von Schadstoffen in Boeden, wie z.B. Immobilisierung, Transport, biologischer Abbau, Aufnahme durch Kulturpflanzen, wird von den Sorptionseigenschaften im Boden wesentlich beeinflusst. Bei allen Modellbeschreibungen ueber das Verhalten von Schadstoffen in Boeden ist die Staerke der Sorption ein unersetzbarer Parameter. Ziel dieses Teilprojektes war es, das Bindungsvermoegen der anthropogenen Stadtboeden fuer umweltrelevante organische Chemikalien mittels einfacher Feldmethoden abzuschaetzen und im Hinblick auf Boden- und Gewaesserschutz zu bewerten. (orig./SR)

  4. Moisture sorption isotherms and thermodynamic properties of bovine leather

    Science.gov (United States)

    Fakhfakh, Rihab; Mihoubi, Daoued; Kechaou, Nabil

    2018-04-01

    This study was aimed at the determination of bovine leather moisture sorption characteristics using a static gravimetric method at 30, 40, 50, 60 and 70 °C. The curves exhibit type II behaviour according to the BET classification. The sorption isotherms fitting by seven equations shows that GAB model is able to reproduce the equilibrium moisture content evolution with water activity for moisture range varying from 0.02 to 0.83 kg/kg d.b (0.9898 thermodynamic properties such as isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy. Net isosteric heat of sorption and differential entropy were evaluated through direct use of moisture isotherms by applying the Clausius-Clapeyron equation and used to investigate the enthalpy-entropy compensation theory. Both sorption enthalpy and entropy for desorption increase to a maximum with increasing moisture content, and then decrease sharply with rising moisture content. Adsorption enthalpy decreases with increasing moisture content. Whereas, adsorption entropy increases smoothly with increasing moisture content to a maximum of 6.29 J/K.mol. Spreading pressure increases with rising water activity. The net integral enthalpy seemed to decrease and then increase to become asymptotic. The net integral entropy decreased with moisture content increase.

  5. From spiking neuron models to linear-nonlinear models.

    Science.gov (United States)

    Ostojic, Srdjan; Brunel, Nicolas

    2011-01-20

    Neurons transform time-varying inputs into action potentials emitted stochastically at a time dependent rate. The mapping from current input to output firing rate is often represented with the help of phenomenological models such as the linear-nonlinear (LN) cascade, in which the output firing rate is estimated by applying to the input successively a linear temporal filter and a static non-linear transformation. These simplified models leave out the biophysical details of action potential generation. It is not a priori clear to which extent the input-output mapping of biophysically more realistic, spiking neuron models can be reduced to a simple linear-nonlinear cascade. Here we investigate this question for the leaky integrate-and-fire (LIF), exponential integrate-and-fire (EIF) and conductance-based Wang-Buzsáki models in presence of background synaptic activity. We exploit available analytic results for these models to determine the corresponding linear filter and static non-linearity in a parameter-free form. We show that the obtained functions are identical to the linear filter and static non-linearity determined using standard reverse correlation analysis. We then quantitatively compare the output of the corresponding linear-nonlinear cascade with numerical simulations of spiking neurons, systematically varying the parameters of input signal and background noise. We find that the LN cascade provides accurate estimates of the firing rates of spiking neurons in most of parameter space. For the EIF and Wang-Buzsáki models, we show that the LN cascade can be reduced to a firing rate model, the timescale of which we determine analytically. Finally we introduce an adaptive timescale rate model in which the timescale of the linear filter depends on the instantaneous firing rate. This model leads to highly accurate estimates of instantaneous firing rates.

  6. Numerical analysis of coupled water transport in wood with a focus on the coupling parameter sorption

    DEFF Research Database (Denmark)

    Hozjan, T.; Turk, G.; Rodman, U.

    2011-01-01

    This paper presents a study of sorption rate function in a so-called multi-Fickian or multi-phase model. This model describes the complex moisture transport system in wood, which consists of separate water-vapour and bound-water diffusion interacting through sorption. In the numerical example inf...... influence of the sorption rate function on water transport is presented. It can be seen that the sorption rate function has a noticeable influence on coupled water transport in wood....

  7. Sorption of 4-ethylphenol and 4-ethylguaiacol by suberin from cork.

    Science.gov (United States)

    Gallardo-Chacón, Joan-Josep; Karbowiak, Thomas

    2015-08-15

    Cork shows an active role in the sorption of volatile phenols from wine. The sorption properties of 4-ethylphenol and 4-ethylguaiacol phenols in hydro-alcoholic medium placed in contact with suberin extracted from cork were especially investigated. To that purpose, suberin was immersed in model wine solutions containing several concentrations of each phenol and the amount of the compound remaining in the liquid phase was determined by SPME-GC-MS. Sorption isotherms of 4-ethylguaiacol and 4-ethylphenol by suberin followed the Henry's model. The solid/liquid partition coefficients (KSL) between the suberin and the model wine were also determined for several other volatile phenols. Suberin displayed rather high sorption capacity, which was positively correlated to the hydrophobicity of the volatile. Finally, the capacity of suberin to decrease the concentration of 4-ethylphenol and 4-ethylguaiacol was also tested in real wines affected by a Brettanomyces character. It also lead to a significant reduction of their concentration in wine. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Sorption of short-lived radionuclides in a layer of sorbent with spherical granules

    International Nuclear Information System (INIS)

    Karlin, Yu.V.

    1993-01-01

    Sorption methods have found wide application in the purification of liquid radioactive wastes. The working element in sorption methods for this purpose is usually a sorption column with a fixed layer of sorbent. Continuous-action equipment with a moving layer of sorbent is very seldom used. When a fixed layer of sorbent is used its wear and prolonged mixing in the sorption column are reduced to a minimum, and maximum purification is achieved due to the advantages of the dynamic method of sorption over the static method. The time of protective action of the sorbent layer is determined by the time taken for the radionuclide to pass through the sorption column, and for the majority of radionuclides is determined by numerous parameters, including the type of sorbent and radionuclide, the rate of flow through the sorbent, the size of the sorbent granules, etc. The physical and chemical aspects of this process have been investigated in detail, and numerous methods for modeling it mathematically have been developed and have been used to develop methods of designing sorption column apparatus. The specific nature of the radionuclides as unstable materials enables the hypothetical case of a open-quotes perpetualclose quotes sorption filter to be represented. In fact, to achieve this it is only necessary to assume that the half-life of the radionuclide is so small that the rate of decay of the radionuclide in the sorption column (both in the sorbed state and in the aqueous phase of the sorption layer) is equal to the rate that it is fed into the column in the flow of liquid radioactive waste. In this case the sorption front of the radionuclide in the column wall remains fixed after a certain initial period. In this paper, a mathematical model of such a hypothetical filter for the case of spherical sorbent granules is considered

  9. On the derivation of a sorption database

    International Nuclear Information System (INIS)

    Ewart, F.T.; Haworth, A.; Wisbey, S.J.

    1992-01-01

    The safety arguments in support of many radioactive waste repository concepts are heavily dependent on the existence of a sorption reaction. Such a reaction will, in the near field, reduce the magnitude of the release of a number of hazardous radionuclides so that their release to the geosphere is dispersed in time. In the geosphere, the sorption reactions provide a mechanism whereby the migration of the elements released from the repository is retarded and the radioisotopes then subsequently decay. The processes involved in sorption cannot in many cases be satisfactorily represented in thermodynamic terms such as are employed in the description of dissolution and precipitation. Experiments that investigate these reactions are not easy to perform. The sorption parameters that are obtained experimentally for the near field relate, in the UK case, to sorption on to a cementitious surface. These surfaces, since they consist substantially of calcium hydroxide or calcium silicate hydrates, control the aqueous chemistry, do not permit pH changes to be made and limit the range of concentrations of sorbate that may be used. In the far field, on the other hand, the surfaces are not in general so active with respect to the solution chemistry and data can be obtained across a wide spectrum of aqueous chemistries. These data, although they may be useful in testing and parameterizing models, may not have validity under field conditions since the minerals will, inevitably, react to the changes in water chemistry, over geological timescales. The uncertainties in the experimental data are, for many elements and solids, balanced by a reasonable agreement between workers in the values of the parameters used to describe sorption. 22 refs., 1 fig., 1 tab

  10. Web-based sorption database (KAERI-SDB)

    International Nuclear Information System (INIS)

    Lee, Jae Kwang; Baik, Min Hoon

    2010-10-01

    Radionuclide sorption data is necessary for the safety assessment of radioactive waste disposal. However the accessibility to the nuclide sorption database is limited. The web-based sorption database (KAERI-SDB) was developed to provide sorption data in a convenient way. The development of the KAERI-SDB was achieved by improving the performance of pre-existing sorption DB programme (SDB-21C) and incorporating the user requirement. The KAERI-SDB was designed that users can access it by using a web browser. Main functions of the KAERI-SDB include (1) log-in/join, (2) search and store of sorption data and (3) scatter plot chart and index chart. It is expected that the KAERI-SDB is widely applied to the safety assessment of radioactive waste disposal by enhancing the accessibility to experts and practitioner related the nuclear industry and governmental administration. It is also expected that reliabilities for the radioactive waste disposal increased by opening the web-based sorption DB to public

  11. Kinetic study in the sorption of cesium on some egyptian soils

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, A S; Hegazi, W S [University College for Girls, Ain Shams University, Cairo (Egypt); Abdel-Malik, W E.W.; Kamel, N H.M. [Radiation protection Department, Nuclear Research Center, Atomic Energy, Authority, Cairo (Egypt)

    1997-12-31

    Soil samples were Collected from different locations of the egyptian desert and were subjected to physical, chemical, mineralogical and sorption studies. Kinetic analysis were made on the sorption of radiocesium by these soil samples. Two models of analysis were treated namely; the one step first order model (the integer model), and the sum of the exponential components (the compartmental model). Statistical treatment of the results obtained showed that. For the one step first order model, samples having the lowest rate constant showed the longest reaction half life t{sup 1} /2 (771 to 121 minutes), while the samples having higher rate constant the reaction half life decreased markedly ranging from 56 to 14 minutes. The compartmental model of analysis showed that the sorption of cesium of the soil samples involved two or three steps represented by two or three exponential equations. The equation of each step was calculated. 4 figs., 3 tabs.

  12. Thermodynamics of the sorption of 1,3,4-oxadiazole and 1,2,4,5-tetrazine derivatives from solutions on hypercrosslinked polystyrene

    Science.gov (United States)

    Saifutdinov, B. R.; Davankov, V. A.; Il'in, M. M.

    2014-03-01

    The sorption of a series of aromatic heterocycles on neutral hypercrosslinked polystyrene from maximally dilute acetonitrile and water.acetonitrile solutions of them is investigated by high-performance liquid chromatography in a range of column temperatures from 308 to 348 K at 5 K intervals. It is found that for all heterocycles, the logarithm of the retention factor versus the reciprocal of the temperature dependences can be approximated by linear functions with r 2 ≥ 0.999. It is established that the true compensation effect (which does not result from the correlation between enthalpy and entropy determination errors) occurs during the sorption of heterocycles on hypercrosslinked polystyrene from both acetonitrile and water-acetonitrile solutions. It is shown that in the compensation diagram, the points corresponding to sorbates are grouped together according to the type of sorbate-sorbent interactions. It is found that changes in the Gibbs energy, enthalpy, and entropy of sorption from acetonitrile solutions and for sorption from water-acetonitrile solutions are related to one another by linear dependences.

  13. Further developments of the RES3T sorption database

    International Nuclear Information System (INIS)

    Brendler, V.

    2002-01-01

    RES 3 T - the Rossendorf expert system for surface and sorption thermodynamics currently under development has been expanded towards the provision of comprehensive sorption data sets suitable for complex natural systems of rocks and soils. Also a statistical evaluation of the available SCM (surface complexation model) data is now implemented. Finally, a normalization of SCM parameters to a standard site density has been incorporated. (orig.)

  14. Sorption of Arsenic from Desalination Concentrate onto Drinking Water Treatment Solids: Operating Conditions and Kinetics

    Directory of Open Access Journals (Sweden)

    Xuesong Xu

    2018-01-01

    Full Text Available Selective removal of arsenic from aqueous solutions with high salinity is required for safe disposal of the concentrate and protection of the environment. The use of drinking water treatment solids (DWTS to remove arsenic from reverse osmosis (RO concentrate was studied by batch sorption experiments. The impacts of solution chemistry, contact time, sorbent dosage, and arsenic concentration on sorption were investigated, and arsenic sorption kinetics and isotherms were modeled. The results indicated that DWTS were effective in removing arsenic from RO concentrate. The arsenic sorption process followed a pseudo-second-order kinetic model. Multilayer adsorption was simulated by Freundlich equation. The maximum sorption capacities were calculated to be 170 mg arsenic per gram of DWTS. Arsenic sorption was enhanced by surface precipitation onto the DWTS due to the high amount of calcium in the RO concentrate and the formation of ternary complexes between arsenic and natural organic matter (NOM bound by the polyvalent cations in DWTS. The interactions between arsenic and NOM in the solid phase and aqueous phase exhibited two-sided effects on arsenic sorption onto DWTS. NOM in aqueous solution hindered the arsenic sorption onto DWTS, while the high organic matter content in solid DWTS phase enhanced arsenic sorption.

  15. U(VI) sorption on kaolinite. Effects of pH, U(VI) concentration and oxyanions

    International Nuclear Information System (INIS)

    Liang Gao; Ziqian Yang; Keliang Shi; Xuefeng Wang; Zhijun Guo; Wangsuo Wu

    2010-01-01

    U(VI) sorption on kaolinite was studied as functions of contact time, pH, U(VI) concentration, solid-to-liquid ratio (m/V) by using a batch experimental method. The effects of sulfate and phosphate on U(VI) sorption were also investigated. It was found that the sorption kinetics of U(VI) can be described by a pseudo-second-order model. Potentiometric titrations at variable ionic strengths indicated that the titration curves of kaolinite were not sensitive to ionic strength, and that the pH of the zero net proton charge (pH PZNPC ) was at 6.9. The sorption of U(VI) on kaolinite increased with pH up to 6.5 and reached a plateau at pH >6.5. The presence of phosphate strongly increased U(VI) sorption especially at pH <5.5, which may be due to formation of ternary surface complexes involving phosphate. In contrast, the presence of sulfate did not cause any apparent effect on U(VI) sorption. A double layer model was used to interpret both results of potentiometric titrations and U(VI) sorption on kaolinite. (author)

  16. Linear Models

    CERN Document Server

    Searle, Shayle R

    2012-01-01

    This 1971 classic on linear models is once again available--as a Wiley Classics Library Edition. It features material that can be understood by any statistician who understands matrix algebra and basic statistical methods.

  17. Sorption Behavior of Dye Compounds onto Natural Sediment of Qinghe River.

    Science.gov (United States)

    Liu, Ruixia; Liu, Xingmin; Tang, Hongxiao; Su, Yongbo

    2001-07-15

    The objective of this study is to assess the adsorption behavior of C.I. Basic Yellow X-5GL, C.I. Basic Red 13, C.I. Direct Blue 86, C.I. Vat Yellow 2, and C.I. Mordant Black 11 on natural sediment and to identify sediment characteristics that play a predominant role in the adsorption of the dyes. The potentiometric titration experiment is used to investigate acid-base properties of the sediment surface with a constant capacitance surface complexation model. The parameters controlling the sorption such as solution pH and ion strength, as well as the influence of organic carbon and Ca(2+) ion on the adsorption, are evaluated. It is shown that the titration data can be successfully described by the surface protonation and deprotonation model with the least-squares FITEQL program 2.0. The sorption isotherm data are fitted to the Freundlich equation in a nonlinear form (1/n=0.3-0.9) for all tested dyes. With increasing pH value, the sorption of C.I. Mordant Black 11 and C.I. Direct Blue 86 on the sediment decreases, while for C.I. Basic Yellow X-5GL and C.I. Basic Red 13, the extent of sorption slightly increases. In addition, ion strength also exhibits a considerably different effect on the sorption behavior of these dye compounds. The addition of Ca(2+) can greatly reduce the sorption of C.I. Basic Red 13 on the sediment surface, while it enhances the sorption of C.I. Direct Blue 6. The removal of organic carbon decreases the sorption of C.I. Mordant Black 11 and C.I. Direct Blue 86. In contrast, the sorption of C.I. Basic Red 13 and C.I. Basic Yellow X-5GL is obviously enhanced after the removal of organic carbon. The differences in adsorption behavior are mainly attributed to the physicochemical properties of these dye compounds. Copyright 2001 Academic Press.

  18. Sorption mechanism of solvent vapors to coals; Sekitan eno yobai joki no shuchaku kiko no kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, K.; Takanohashi, T.; Iino, M. [Tohoku University, Sendai (Japan). Institute for Chemical Reaction Science

    1996-10-28

    With an objective to clarify the interactions between micropore structure of coal and solvent reagents, a sorption experiment was carried out under solvent saturated vapor pressure. Low-volatile bituminous coal, Pocahontas No. 3 coal, has the aromatic ring structure developed, and makes solvent more difficult to diffuse into coal, hence sorption amount is small. Methanol has permeated since its polarity is high. High-volatile bituminous coal, Illinois No. 6 coal, makes solvent penetrate easily, and the sorption amount was large with both of aromatic and polar solvents. Since brown coal, Beulah Zap coal, contains a large amount of oxygen, and hydrogen bonding is predominant, sorption amount of cyclohexane and benzene having no polarity is small. Methanol diffuses while releasing hydrogen bond due to its polarity, and its sorption amount is large. A double sorption model is available, which expresses the whole sorption amount as a sum of physical sorption amount and amount of permeation into coal. This model was applied when it explained successfully the sorption behavior of the solvents relative to coals, excepting some of the systems. However, also observed were such abnormal behavior as sorption impediment due to interactions between coal surface and solvents, and permeation impediment due to hydroxyl groups inside the coals. 1 ref., 10 figs., 2 tabs.

  19. Environmental Conditions Influencing Sorption of Inorganic Anions to Multiwalled Carbon Nanotubes Studied by Column Chromatography.

    Science.gov (United States)

    Metzelder, Florian; Schmidt, Torsten C

    2017-05-02

    Sorption to carbon-based nanomaterials is typically studied in batch experiments. An alternative method offering advantages to study sorption is column chromatography. Sorbent packed columns are used and sorption data are determined by relating sorbate retention to that of a nonretarded tracer. We have now for the first time applied this technique to study the influence of environmental conditions on sorption of inorganic anions (bromide, nitrite, nitrate, and iodide) to multiwalled carbon nanotubes. Deuterium oxide was used as nonretarded tracer. Sorption isotherms were best described by the Freundlich model. Sorption increased in the order bromide 4.5 the surface charge was negative, but sorption was still detectable at pH 6 and 9. Consequently, other forces than electrostatic attraction contributed to sorption. These forces may include H-bonding as indicated by sorption enthalpy determined by variation of column temperature. Overall, column chromatography represents a promising alternative in sorption studies to reveal sorbent properties.

  20. Sorption of heavy metals by the soil fungi 'Aspergillus niger' and Mucor rouxii

    Energy Technology Data Exchange (ETDEWEB)

    Mullen, M.D.; Wolf, D.C.; Beveridge, T.J.; Bailey, G.W.

    1992-01-01

    Sorption of the nitrate salts of cadmium(II), copper(II), lanthanum(III) and silver(I) by two fungi, Aspergillus niger and Mucor rouxii, was evaluated using Freundlich adsorption isotherms and energy dispersive X-ray electron microscopy. The linearized Freundlich isotherm described the metal sorption data well for metal concentrations of 5 microM-1 mM metal. Differences in metal binding were observed among metals, as well as between fungal species. Calculated Freundlich K values indicated that metal binding decreased in the order La(3+) > or = Ag(+) > Cu(2+) > Cd(2+). However, sorption of Ag(+) was greater than that of La(3+) from solutions of 0.1 and 1 mM metal and likely due to precipitation at the cell wall surface. At the 1 mM initial concentration, there were no significant differences between the two fungi in metal sorption, except for Ag(+) binding. At the 5 microM concentration, there was no difference between the fungi in their sorption capacities for the four metals. Electron microscopy-energy dispersive X-ray analysis indicated that silver precipitated onto cells as colloidal silver. The results indicate that Freundlich isotherms may be useful for describing short-term metal sorption by fungal biomass and for comparison with other soil constituents in standardized systems. (Copyright (c) 1992 Pergamon Press plc.)

  1. Sorption of uranyl ions on hydrous silicon dioxide

    International Nuclear Information System (INIS)

    Lieser, K.H.; Quandt-Klenk, S.; Thybusch, B.

    1992-01-01

    Sorption of uranyl ions on SiO 2 .χH 2 O (silica gel) is investigated in absence and in presence of carbonate as function of pH. The curves obtained are very similar to those observed for sorption of uranyl ion on TiO 2 .χH 2 O, indicating the dominating influence of the uranium species in solution. Between pH 2 and 5 the sorption ratio R s increases with hydrolysis of uranyl ions (formation of UO 2 OH + ), around pH 7 it is nearly independent of pH, and at higher pH it decreases again. The equilibrium constants are calculated for these ranges. In presence of carbonate R s decreases drastically above pH 6, due to the formation of carbonato complexes in solution. Sorption of uranyl ions on SiO 2 .χH 2 O, on TiO 2 .χH 2 O, and on cryst. SiO 2 and Al 2 O 3 is compared. The problems of 'surface complexation' modelling are discussed. (orig.)

  2. Dynamic Linear Models with R

    CERN Document Server

    Campagnoli, Patrizia; Petris, Giovanni

    2009-01-01

    State space models have gained tremendous popularity in as disparate fields as engineering, economics, genetics and ecology. Introducing general state space models, this book focuses on dynamic linear models, emphasizing their Bayesian analysis. It illustrates the fundamental steps needed to use dynamic linear models in practice, using R package.

  3. Modelling and Predicting Backstroke Start Performance Using Non-Linear and Linear Models.

    Science.gov (United States)

    de Jesus, Karla; Ayala, Helon V H; de Jesus, Kelly; Coelho, Leandro Dos S; Medeiros, Alexandre I A; Abraldes, José A; Vaz, Mário A P; Fernandes, Ricardo J; Vilas-Boas, João Paulo

    2018-03-01

    Our aim was to compare non-linear and linear mathematical model responses for backstroke start performance prediction. Ten swimmers randomly completed eight 15 m backstroke starts with feet over the wedge, four with hands on the highest horizontal and four on the vertical handgrip. Swimmers were videotaped using a dual media camera set-up, with the starts being performed over an instrumented block with four force plates. Artificial neural networks were applied to predict 5 m start time using kinematic and kinetic variables and to determine the accuracy of the mean absolute percentage error. Artificial neural networks predicted start time more robustly than the linear model with respect to changing training to the validation dataset for the vertical handgrip (3.95 ± 1.67 vs. 5.92 ± 3.27%). Artificial neural networks obtained a smaller mean absolute percentage error than the linear model in the horizontal (0.43 ± 0.19 vs. 0.98 ± 0.19%) and vertical handgrip (0.45 ± 0.19 vs. 1.38 ± 0.30%) using all input data. The best artificial neural network validation revealed a smaller mean absolute error than the linear model for the horizontal (0.007 vs. 0.04 s) and vertical handgrip (0.01 vs. 0.03 s). Artificial neural networks should be used for backstroke 5 m start time prediction due to the quite small differences among the elite level performances.

  4. Ammonia-nitrogen and phosphates sorption from simulated reclaimed waters by modified clinoptilolite

    International Nuclear Information System (INIS)

    Huo, Hanxin; Lin, Hai; Dong, Yingbo; Cheng, Huang; Wang, Han; Cao, Lixia

    2012-01-01

    Highlights: ► The salt and thermally modified clinoptilolite can effectively sorb NH 3 -N and phosphates. ► The phosphorus and nitrogen removal was consistent with Langmuir isotherm model. ► The modified clinoptilolite possesses rapid adsorption and slow balance characteristics. ► The adsorption is more in line with the Elovich adsorption dynamics equation. ► The entropy effect plays the role of the main driving force in the adsorption. - Abstract: This paper presents the investigation of the ammonia-nitrogen and phosphates sorption from simulated reclaimed wastewater by modified clinoptilolite. The results showed that the modified clinoptilolite has a high sorption efficiency and removal performance. The ammonia-nitrogen and phosphates removal rate of the modified clinoptilolite reached to 98.46% and 99.80%, respectively. The surface of modified clinoptilolite became loose and some pores appeared, which enlarged the specific surface area; the contents of Na and Fe increased, and the contents of Ca and Mg decreased. The modified clinoptilolite possesses rapid sorption and slow balance characteristics and ammonia-nitrogen and phosphates sorption is more consistent with the Langmuir isotherm model. The adsorption kinetics of ammonia-nitrogen and phosphates follows the Elovich adsorption dynamics equation, which describes the sorption of ammonia-nitrogen and phosphates in aqueous solution as mainly a chemical sorption. Results from the thermodynamics experiment involving ammonia-nitrogen and phosphates sorption reveal that the process is a spontaneous and endothermic process, and is mainly driven by entropy effect.

  5. Highly sensitive sorption-luminescence determination of trace europium with preconcentration on silica chemically modified with iminodiacetic acid

    International Nuclear Information System (INIS)

    Voronina, R.D.; Zorov, N.B.

    2007-01-01

    Features of a sorption-luminescence method for the determination of trace europium were studied. The method includes the preliminary sorption of europium at pH 7.1 from solutions with silica chemically modified with iminodiacetic acid, the subsequent treatment of the sorbent with 2-thenoyltrifluoroacetone at pH 8.0, and the measurement of the intensity of luminescence of the surface three-component europium complex at 613 nm. The effect of moisture as the quencher of luminescence of the surface europium complex was studied, and techniques for its removal were proposed. Sorption in the static mode provides the detection limit of europium of 7 x 10 -5 g/ml. The calibration plot is linear in the range of two orders of magnitude of europium concentration in solutions. The relative standard deviation in the determination of 1.5 x 10 -2 μg/ml europium is 5%. In the dynamic mode of sorption from 1000 ml of an analyzed solution with the use of sorption-desorption, the detection limit of europium of 8 x 10 -7 μg/ml was attained [ru

  6. Sorption-desorption behavior of polybrominated diphenyl ethers in soils

    International Nuclear Information System (INIS)

    Olshansky, Yaniv; Polubesova, Tamara; Vetter, Walter; Chefetz, Benny

    2011-01-01

    Polybrominated diphenyl ethers (PBDEs) are flame retardants that are commonly found in commercial and household products. These compounds are considered persistent organic pollutants. In this study, we used 4,4'-dibromodiphenyl ether (BDE-15) as a model compound to elucidate the sorption and desorption behavior of PBDEs in soils. The organic carbon-normalized sorption coefficient (K OC ) of BDE-15 was more than three times higher for humin than for bulk soils. However, pronounced desorption hysteresis was obtained mainly for bulk soils. For humin, increasing concentration of sorbed BDE-15 resulted in decreased desorption. Our data illustrate that BDE-15 and probably other PBDEs exhibit high sorption affinity to soils. Moreover, sorption is irreversible and thus PBDEs can potentially accumulate in the topsoil layer. We also suggest that although humin is probably a major sorbent for PBDEs in soils, other humic materials are also responsible for their sequestration. - Highlights: → BDE-15 exhibited pronounced desorption hysteresis. → BDE-15 sowed higher sorption affinity to humin as compared to the bulk soils. → Sequestration of PBDEs depends on soil organic matter constitutes other than humin. - Pronounced desorption hysteresis was observed for BDE-15 in natural soils.

  7. Piecewise Linear-Linear Latent Growth Mixture Models with Unknown Knots

    Science.gov (United States)

    Kohli, Nidhi; Harring, Jeffrey R.; Hancock, Gregory R.

    2013-01-01

    Latent growth curve models with piecewise functions are flexible and useful analytic models for investigating individual behaviors that exhibit distinct phases of development in observed variables. As an extension of this framework, this study considers a piecewise linear-linear latent growth mixture model (LGMM) for describing segmented change of…

  8. Impacts of environmental conditions on the sorption of volatile organic compounds onto tire powder

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Dong I. [Division of R and D Planning and Management, Korea Institute of Environmental Science and Technology, Seoul (Korea, Republic of); Nam, Kyongphile [School of Civil, Urban and Geosystem Engineering, College of Engineering, Seoul National University, Gwanak-Ku, 151-742 Seoul (Korea, Republic of); Park, Jae W. [Department of Civil Engineering, Hanyang University, Seoul (Korea, Republic of); Khim, Jee H. [Department of Civil and Environmental Engineering, Korea University, Seoul (Korea, Republic of); Kim, Yong K. [School of Civil, Urban and Geosystem Engineering, College of Engineering, Seoul National University, Gwanak-Ku, 151-742 Seoul (Korea, Republic of); Kim, Jae Y. [School of Civil, Urban and Geosystem Engineering, College of Engineering, Seoul National University, Gwanak-Ku, 151-742 Seoul (Korea, Republic of)], E-mail: jaeykim@snu.ac.kr

    2008-05-01

    A series of batch tests were performed and the impacts of environmental conditions and phase change on the sorption of volatile organic compounds (VOCs) were investigated. Benzene, trichloroethylene, tetrachloroethylene, and ethylbenzene were selected as target VOCs. Sorption of VOCs onto tire powder was well demonstrated by a linear-partitioning model. Water-tire partition coefficients of VOCs (not tested in this study) could be estimated using a logarithmic relationship between observed water-tire partition coefficients and octanol-water partition coefficients of the VOCs tested. The target VOCs did not seem to compete with other VOCs significantly when sorbed onto the tire powder for the range of concentrations tested. The influence of environmental conditions, such as pH and ionic strength also did not seem to be significant. Water-tire partition coefficients of benzene, trichloroethylene, tetrachloroethylene, and ethylbenzene decreased as the sorbent dosage increased. However, they showed stable values when the sorbent dosage was greater than 10 g/L. Air-tire partition coefficient could be extrapolated from Henry's law constants and water-tire partition coefficient of VOCs.

  9. Impacts of environmental conditions on the sorption of volatile organic compounds onto tire powder

    International Nuclear Information System (INIS)

    Oh, Dong I.; Nam, Kyongphile; Park, Jae W.; Khim, Jee H.; Kim, Yong K.; Kim, Jae Y.

    2008-01-01

    A series of batch tests were performed and the impacts of environmental conditions and phase change on the sorption of volatile organic compounds (VOCs) were investigated. Benzene, trichloroethylene, tetrachloroethylene, and ethylbenzene were selected as target VOCs. Sorption of VOCs onto tire powder was well demonstrated by a linear-partitioning model. Water-tire partition coefficients of VOCs (not tested in this study) could be estimated using a logarithmic relationship between observed water-tire partition coefficients and octanol-water partition coefficients of the VOCs tested. The target VOCs did not seem to compete with other VOCs significantly when sorbed onto the tire powder for the range of concentrations tested. The influence of environmental conditions, such as pH and ionic strength also did not seem to be significant. Water-tire partition coefficients of benzene, trichloroethylene, tetrachloroethylene, and ethylbenzene decreased as the sorbent dosage increased. However, they showed stable values when the sorbent dosage was greater than 10 g/L. Air-tire partition coefficient could be extrapolated from Henry's law constants and water-tire partition coefficient of VOCs

  10. Effect of grain size on the sorption and desorption of SeO42- and SeO32- in columns of crushed granite and fracture infill from granitic water under dynamic conditions

    International Nuclear Information System (INIS)

    Videnska, K.; Institute of Chemical Technology, Prague; Palagyi, S.; Czech Technical University, Prague; Stamberg, K.; Vodickova, H.; Havlova, V.

    2013-01-01

    The sorption of 2 x 10 -5 mol/dm 3 Na 2 SeO 4 and Na 2 SeO 3 dissolved in synthetic granitic water (SGW) were investigated in columns of crushed granite and fracture infill (clay minerals) of various grain sizes. Desorption was studied using pure SGW. The goal of study was the quantification of the effect of grain size on the retardation and distribution coefficients of SeO 4 2- and SeO 3 2- , as well as on the other transport parameters (Peclet number and hydrodynamic dispersion coefficient). A model based on the erfc-function, assuming a non-linear reversible equilibrium sorption/desorption isotherm, was used for evaluation of sorption/desorption and transport parameters. The determination of selenium was performed using an ICP-MS technique. The experimental breakthrough curves were fitted using non-linear regression procedure, in the course of which the parameters mentioned were sought. Summing up, no sorption was recorded in the case of SeO 4 2- under these conditions. The values of retardation coefficients were practically one for all studied grain sizes. On the other hand, significant sorption was found for SeO 3 2- : depending on the grain size, the retardation coefficients varied between 1.6-8.7 in pure granite and 1.8-37.2 in infill materials. These values correspond to distribution coefficients of 0.2-2.5 and 0.2-12.7 cm 3 /g, respectively. The both parameters have similar values in a case of desorption which reflects the reversible character of sorption process. It was found that retardation and distribution coefficients and sorption capacity for SeO 3 2- also increase with decreasing grain size. (author)

  11. Influence of organic matter type and medium composition on the sorption affinity of C12-benzalkonium cation

    International Nuclear Information System (INIS)

    Chen, Yi; Hermens, Joop L.M.; Droge, Steven T.J.

    2013-01-01

    We used the 7-μm polyacrylate ion-exchange SPME fibers to investigate C12-benzalkonium sorption to 10 mg/L natural organic matter at concentrations well below the cation-exchange capacity. C12-BAC sorption at constant medium conditions differed within 0.4 log units for two humic acids (Aldrich, Leonardite) and peat (Sphagnum, Pahokee), with similar nonlinear sorption isotherms (K F ∼ 0.8). Sorption to the SPME fibers and Aldrich humic acid (AHA) was reduced at both low pH and high electrolyte concentration, and reduced more strongly by Ca 2+ compared with Na + at similar concentrations. Sorption isotherms for AHA (5–50–500 mM Na + , pH 6) was modeled successfully by the NICA-Donnan approach, resulting in an intrinsic sorption coefficient of 5.35 (C aq = 1 nM). The NICA-Donnan model further explained the stronger specific binding of Ca 2+ compared to Na + by differences in Boltzmann factors. This study provides relevant information to interpret bioavailability of quaternary ammonium compounds, and possibly for other organic cations. -- Highlights: •The ion-exchange SPME was used to investigate C12-benzalkonium sorption behavior. •Sorption to different organic matter differed within 0.4 log units (5 mM Ca 2+ , pH6). •Sorption to AHA was reduced at both low pH and high electrolyte concentration. •The NICA-Donnan approach lead to an intrinsic log D OC,IE of 5.35 (C aq = 1 nM). •The Boltzmann factors in NICA-Donnan model explained the specific binding of Ca 2+ . -- C12-BAC sorption to the four organic matter samples were investigated by the ion-exchange SPME and the NICA-Donnan model explained the different sorption affinities caused by Na + and Ca 2+

  12. Estimation of biotransformation and sorption of emerging organic compounds (EOCs) during artificial recharge through a reactive barrier.

    Science.gov (United States)

    Valhondo, C.; Martinez-Landa, L.; Carrera, J.; Hidalgo, J. J.; Ayora, C.

    2016-12-01

    The reuse of lesser quality water such as effluents from wastewater treatment plants or effluent-receiving water bodies has been promoted due to the water shortages affecting many regions of the world. Artificial recharge through infiltration basins is known to improve several water quality parameters including the attenuation of emerging organic compounds (EOCs). Many of these contaminants exhibit redox dependent biotransformation because the redox state is one of the factors controlling microbial community development. Together with biotransformation, sorption also affects the behavior of EOCs in their passage through the soil. We studied EOCs attenuation in an infiltration system is located in Sant Vicenç dells Horts on the Llobregat delta (Barcelona, Spain), where the local water agency has an artificial recharge pilot project . The Llobregat river water used for the artificial recharge is affected by treatment plant effluents which contain EOCs. A reactive barrier consisting of vegetable compost, clay, and iron oxide was installed in the bottom of the infiltration basin to enhance biotransformation and sorption of EOCs. The barrier releases dissolved organic carbon, which favors the development of a broad range of redox environments, and supplies neutral, cationic, and anionic surfaces to favor sorption of different types of contaminants. Results were excellent, but quantitative evaluation of the EOCs attenuation requires knowledge of the residence time distribution of infiltrated water. A tracer test was performed by adding tracers to the infiltration water and interpreting the breakthrough curves at diverse monitoring points with a 2D multilayer numerical model. The calibrated model quantify degradation, as a first order law, and sorption through a linear distribution coefficient for ten selected EOCs. Results indicate higher degradation rates and sorption coefficients in the reactive barrier than in the rest of the aquifer for nine and eight of the ten

  13. Sorption equilibrium of mercury onto ground-up tree fern.

    Science.gov (United States)

    Ho, Yuh-Shan; Wang, Chung-Chi

    2008-08-15

    The sorption behavior of mercury at different temperatures onto ground-up tree fern was investigated. The experimental results were fitted to two two-parameter isotherms, the Freundlich and Langmuir isotherms, as well as to two three-parameter isotherms, the Redlich-Peterson and Sips isotherms to obtain the characteristic parameters of each model. A comparison of best-fitting was performed using the coefficient of determination and Chi-square test. Both the Langmuir and Redlich-Peterson isotherms were found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of mercury ions onto ground-up tree fern was 26.5 mg/g at 298 K. It was noted that an increase in temperature resulted in a higher mercury ion loading per unit weight of the tree fern. In addition, various thermodynamic parameters, such as DeltaG degrees, DeltaH degrees, and DeltaS degrees, were calculated and compared with the sorption of mercury by other sorbents.

  14. Sorption equilibrium of mercury onto ground-up tree fern

    International Nuclear Information System (INIS)

    Ho, Y.-S.; Wang, C.-C.

    2008-01-01

    The sorption behavior of mercury at different temperatures onto ground-up tree fern was investigated. The experimental results were fitted to two two-parameter isotherms, the Freundlich and Langmuir isotherms, as well as to two three-parameter isotherms, the Redlich-Peterson and Sips isotherms to obtain the characteristic parameters of each model. A comparison of best-fitting was performed using the coefficient of determination and Chi-square test. Both the Langmuir and Redlich-Peterson isotherms were found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of mercury ions onto ground-up tree fern was 26.5 mg/g at 298 K. It was noted that an increase in temperature resulted in a higher mercury ion loading per unit weight of the tree fern. In addition, various thermodynamic parameters, such as ΔG o , ΔH o , and ΔS o , were calculated and compared with the sorption of mercury by other sorbents

  15. Sorption equilibrium of mercury onto ground-up tree fern

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Y.-S. [Department of Chemical Engineering, I-Shou University, No. 1, Section 1, Hsueh-Cheng Road, Ta-Hsu Hsiang, Kaohsiung County 840, Taiwan (China)], E-mail: ysho@isu.edu.tw; Wang, C.-C. [Department of Chemical Engineering, I-Shou University, No. 1, Section 1, Hsueh-Cheng Road, Ta-Hsu Hsiang, Kaohsiung County 840, Taiwan (China)

    2008-08-15

    The sorption behavior of mercury at different temperatures onto ground-up tree fern was investigated. The experimental results were fitted to two two-parameter isotherms, the Freundlich and Langmuir isotherms, as well as to two three-parameter isotherms, the Redlich-Peterson and Sips isotherms to obtain the characteristic parameters of each model. A comparison of best-fitting was performed using the coefficient of determination and Chi-square test. Both the Langmuir and Redlich-Peterson isotherms were found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of mercury ions onto ground-up tree fern was 26.5 mg/g at 298 K. It was noted that an increase in temperature resulted in a higher mercury ion loading per unit weight of the tree fern. In addition, various thermodynamic parameters, such as {delta}G{sup o}, {delta}H{sup o}, and {delta}S{sup o}, were calculated and compared with the sorption of mercury by other sorbents.

  16. Competitive sorption between glyphosphate and inorganic phosphate on clay minerals and low organic matter soils

    International Nuclear Information System (INIS)

    Dion, H.M.; Hill, H.H.Jr.; Washington State Univ., Pullmann, WA; Harsh, J.B.; Washington State Univ., Pullmann, WA

    2001-01-01

    Inorganic phosphate may influence the adsorption of glyphosate to soil surface sites. It has been postulated that glyphosphate sorption is dominated by the phosphoric acid moiety, therefore, inorganic phosphate could compete with glyphosate for surface sorption sites. Sorption of glyphosate is examined in low organic carbon systems where clay minerals dominate the available adsorption sites using 32 P-labeled phosphate and 14 C-labeled glyphosate to track sorption. Glyphosate sorption was found to be strongly dependent on phosphate additions. Isotherms were generally of the L type, which is consistent with a limited number of surface sites. Most sorption on whole soils could be accounted for by sorption observed on model clays of the same mineral type as found in the soils. (author)

  17. Studies of Dye Sensitisation Kinetics and Sorption Isotherms of Direct Red 23 on Titania

    Directory of Open Access Journals (Sweden)

    Peter J. Holliman

    2008-01-01

    Full Text Available Sorption kinetics and isotherms have been measured for a commercial dye (Direct Red 23 on different samples of powdered Titania, and the data were analysed to better understand the dye sensitization process for dye sensitised solar cells (DSSCs. For the sorption kinetics, the data show rapid initial sorption (<1 hour followed by slower rate of increasing uptake between 1 and 24 hours. While higher initial concentrations of dye correspond to higher sorption overall, less dye is absorbed from higher initial dye concentrations when considered as percentage uptake. The correlation between the sorption data and model isotherms has been considered with time. The Langmuir model shows better correlations compared to the Freundlich isotherm. The dye uptake data has also been correlated with Titania characterization data (X-ray diffraction, scanning electron microscopy, BET and zero point charge analysis. Kinetic data show significantly better fits to second-order models compared to first order. This suggests that chemisorption is taking place and that the interaction between the dye sorbate and the Titania sorbent involves electron sharing to form an ester bond.

  18. Alligator Rivers Analogue project. Uranium sorption. Final Report - Volume 13

    International Nuclear Information System (INIS)

    Waite, T.D.; Payne, T.E.; Davis, J.A.; Sekine, K.

    1992-01-01

    In this volume, the results of studies of uranium sorption (adsorption and desorption) to both single, well-defined mineral phases, and to selected natural (Koongarra) substrates are reported. The single phases included the amorphous iron oxide ferrihydrite, crystalline silica and two naturally occurring kaolinites, KGa-1 and Nichika. The surface properties of these materials were rigorously defined, and adsorption studies were conducted over a range of solution pH, ionic strength, carbonate content, adsorbent and adsorbate concentrations, and in the presence of uranium complexants and (potentially) competing adsorbates (such as phosphate and fluoride). The results of these studies were modelled using the 'surface complexation' approach, with a diffuse layer description of the electrical double layer. The impacts of mineral phase transformations (specifically the aging of amorphous ferrihydrite to more crystalline forms) on the uptake and desorption of uranium are also reported. The amount of data obtained in this study, with a number of experimental parameters being varied over a wide range, has enabled more confidence to be placed in the modelling results. The derived model for ferrihydrite adequately accounts for the effect on U sorption of a number of parameters, most notably pH, pCO 2 and total U present. Few (if any) of the models previously proposed are adequate in this respect. While the modelling of the data for the natural substrates is not as advanced, the U sorption data on the natural substrates show similar features to the U sorption on the model substrates. This suggests that the insights obtained in the modelling of the data for ferrihydrite will be valuable in deriving a model for the more complex natural substrates

  19. Sorption of Ochratoxin A from aqueous solutions using beta-cyclodextrin-polyurethane polymer

    Science.gov (United States)

    The ability of a cyclodextrin-polyurethane polymer to remove ochratoxin A from aqueous solutions, including wine, was examined by batch rebinding assays and equilibrium sorption isotherms. The results were fit to two parameter models. Freundlich analysis of the sorption isotherm indicates the polyme...

  20. Sorption mechanisms of perfluorinated compounds on carbon nanotubes

    International Nuclear Information System (INIS)

    Deng Shubo; Zhang Qiaoying; Nie Yao; Wei Haoran; Wang Bin; Huang Jun; Yu Gang; Xing Baoshan

    2012-01-01

    Sorption of perfluorinated compounds (PFCs) on carbon nanotubes (CNTs) is critical for understanding their subsequent transport and fate in aqueous environments, but the sorption mechanisms remain largely unknown. In this study, the sorption of six PFCs on CNTs increased with increasing C-F chain length when they had a same functional group, and the CNTs with hydroxyl and carboxyl groups had much lower adsorbed amount than the pristine CNTs, indicating that hydrophobic interaction dominated the sorption of PFCs on the CNTs. Electrostatic repulsion suppressed the sorption of PFCs on the CNTs, resulting in the lower sorption with increasing pH. Hydrogen bonding interaction was negligible. The hydrophobic C-F chains can be closely adsorbed on the CNTs surface in parallel to the axis or along the curvature, making it impossible to form micelles on the CNT surface, leading to the lower sorption than other adsorbents. Highlights: ► Sorption capacities of PFOA on different CNTs are less than that on activated carbon and resins. ► Hydrophobic interaction is principally involved in the sorption of PFCs on CNTs. ► Electrostatic repulsion suppresses the sorption of PFCs on CNTs. - Hydrophobic interaction dominated the sorption of perfluorinated compounds on carbon nanotubes, while electrostatic repulsion suppressed their sorption.

  1. Cs sorption to potential host rock of low-level radioactive waste repository in Taiwan: experiments and numerical fitting study.

    Science.gov (United States)

    Wang, Tsing-Hai; Chen, Chin-Lung; Ou, Lu-Yen; Wei, Yuan-Yaw; Chang, Fu-Lin; Teng, Shi-Ping

    2011-09-15

    A reliable performance assessment of radioactive waste repository depends on better knowledge of interactions between nuclides and geological substances. Numerical fitting of acquired experimental results by the surface complexation model enables us to interpret sorption behavior at molecular scale and thus to build a solid basis for simulation study. A lack of consensus on a standard set of assessment criteria (such as determination of sorption site concentration, reaction formula) during numerical fitting, on the other hand, makes lower case comparison between various studies difficult. In this study we explored the sorption of cesium to argillite by conducting experiments under different pH and solid/liquid ratio (s/l) with two specific initial Cs concentrations (100mg/L, 7.5 × 10(-4)mol/L and 0.01 mg/L, 7.5 × 10(-8)mol/L). After this, numerical fitting was performed, focusing on assessment criteria and their consequences. It was found that both ion exchange and electrostatic interactions governed Cs sorption on argillite. At higher initial Cs concentration the Cs sorption showed an increasing dependence on pH as the solid/liquid ratio was lowered. In contrast at trace Cs levels, the Cs sorption was neither s/l dependent nor pH sensitive. It is therefore proposed that ion exchange mechanism dominates Cs sorption when the concentration of surface sorption site exceeds that of Cs, whereas surface complexation is attributed to Cs uptake under alkaline environments. Numerical fitting was conducted using two different strategies to determine concentration of surface sorption sites: the clay model (based on the cation exchange capacity plus surface titration results) and the iron oxide model (where the concentration of sorption sites is proportional to the surface area of argillite). It was found that the clay model led to better fitting than the iron oxide model, which is attributed to more amenable sorption sites (two specific sorption sites along with larger site

  2. The selection and use of a sorption database for the geosphere model in the Canadian nuclear fuel waste management program

    International Nuclear Information System (INIS)

    Vandergraaf, T.T.; Ticknor, K.V.; Melnyk, T.W.

    1992-01-01

    An extensively characterized intrusive granitic formation, the Lac du Bonnet batholith, is being used as a test case for environmental and safety assessment calculations of the impact of a hypothetical disposal vault. The conceptual vault has dimensions of 2 x 2 km and is located at a depth of 500 m, near the Whiteshell Nuclear Research Establishment (WNRE) (CANADA). Hydraulic investigations of the batholith have shown that the bulk of the groundwater flow will be limited to the existing network of water-bearing fractures. Groundwater flow and contaminant transport modelling is based on a porous-medium concept for both the fracture systems and the rock matrix. Geochemical investigations have identified a number of alteration minerals in these fracture systems. The geochemistry encountered along the flow field is too complex to allow the interaction of radionuclides with the geological material to be represented by a single sorption coefficient for each radionuclide on a single rock type. However, the level of understanding of radionuclide interaction with geological materials is not sufficiently well developed to calculate radionuclide transport using models based on chemical thermodynamics or on advanced sorption models based on surface complexation or mass action. Instead, a parametric model has been developed using the total dissolved solids and radionuclide concentrations as independent variables. The mineralogical complexity of the flow field is addressed by selecting sorption data on the nine most commonly occurring fracture infilling minerals in this batholith, four common rock-forming minerals, and on altered and unaltered granite. This approach produces two polynomial equations for each radionuclide/mineral combination, one under oxic and one under anoxic conditions. Where insufficient information is available, these polynomial expressions are reduced to an equation with one variable or to a single sorption coefficient. 48 refs., 6 figs., 4 tabs

  3. Sorption equilibria of ethanol on cork.

    Science.gov (United States)

    Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Bellat, Jean-Pierre

    2013-06-05

    We report here for the first time a thermodynamic study of gaseous ethanol sorption on raw cork powder and plate. Our study aims at a better understanding of the reactivity of this material when used as a stopper under enological conditions, thus in close contact with a hydroethanolic solution, wine. Sorption−desorption isotherms were accurately measured by thermogravimetry at 298 K in a large range of relative pressures. Sorption enthalpies were determined by calorimetry as a function of loading. Sorption−desorption isotherms exhibit a hysteresis loop probably due to the swelling of the material and the absorption of ethanol. Surprisingly, the sorption enthalpy of ethanol becomes lower than the liquefaction enthalpy as the filling increases. This result could be attributed to the swelling of the material, which would generate endothermic effects. Sorption of SO₂ on cork containing ethanol was also studied. When the ethanol content in cork is 2 wt %, the amount of SO₂ sorbed is divided by 2. Thus, ethanol does not enhance the sorption rate for SO₂ but, on the contrary, decreases the SO₂ sorption activity onto cork, probably because of competitive sorption mechanisms.

  4. Quantifying the effect of sorption and bioavailability of hydrophobic organic contaminants

    International Nuclear Information System (INIS)

    Zhang, W.; Bouwer, E.; Cunningham, A.

    1994-01-01

    In-situ bioremediation has been applied successfully at a few sites. Several restrictions presently exist which could greatly limit the effectiveness of this promising technology. Hydrophobic organic contaminants tend to sorb onto soil. However, microorganisms are most effective in utilizing substrates from the aqueous phase. Sorption tends to separate the direct contact between microorganisms and contaminants necessary for biodegradation to occur. A series of experiments, which represented scenarios with fast sorption/desorption, slow sorption/desorption, mass transfer across boundary layer and mass transfer within attached microorganisms (biofilm), was conducted to demonstrate the concentration effect and the mass transfer effect. A method has been developed to quantify bioavailability of organic contaminants in aquatic environments. Bioavailability Factor (B f ), a dimensionless parameter derived from mathematical models and verified by experimental results, has been formulated to describe the impact of equilibrium sorption, nonequilibrium sorption, and mass transfer processes on the rate and extent of biodegradation of petroleum hydrocarbons

  5. Application of surface complexation modelling: Nickel sorption on quartz, manganese oxide, kaolinite and goethite, and thorium on silica

    International Nuclear Information System (INIS)

    Olin, M.; Lehikoinen, J.

    1997-12-01

    The study is a follow-up to a previous modelling task on mechanistic sorption. The experimental work has been carried out at the Laboratory of Radiochemistry, University of Helsinki (HYRL), and the sorption modelling was performed using the HYDRAQL code. Parameters taken from the open literature were employed in the modelling phase. The thermodynamic data for aqueous solutions were extracted from the EQ3/6 database and subsequently modified for HYDRAQL where necessary. The experimental data were obtained from five different experiments, four of which concerned the adsorption of nickel. The first experimental system was a mixture of Nilsiae quartz and manganese dioxide. In the second experiment, quartz was equilibrated with a fresh and saline groundwater simulant instead of an electrolyte solution. The third and fourth experiments dealt with nickel adsorption from an electrolyte solution onto goethite and kaolinite surfaces respectively. In the fifth experiment, adsorption of thorium onto a quartz surface was investigated

  6. Neptunium(V) sorption on kaolinite

    Energy Technology Data Exchange (ETDEWEB)

    Amayri, S.; Jermolajev, A.; Reich, T. [Mainz Univ. (Germany). Inst. of Nuclear Chemistry

    2011-07-01

    The sorption behavior of neptunium(V) onto the clay mineral kaolinite was studied in batch experiments under different experimental conditions: [Np(V)] = 7 x 10{sup -12}-8 x 10{sup -6} M, solid-to-liquid ratio 2-20 g L{sup -1}, I = 0.1 and 0.01 M NaClO{sub 4}, pH = 6-10, ambient air and Ar atmosphere. The short-lived isotope {sup 239}Np (T{sub 1/2} = 2.36 d) was used instead of {sup 237}Np (T{sub 1/2} = 2.14 x 10{sup 6} a) to study the sorption behavior of Np(V) at environmentally-relevant concentrations, i.e., 7 x 10{sup -12} M Np. In addition, {sup 239}Np(V) served as tracer to measure sorption isotherms over six orders of magnitude in Np concentration (4.8 x 10{sup -12}-1.0 x 10{sup -4} M). The results show that Np(V) sorption on kaolinite is strongly influenced by pH, CO{sub 2}, and ionic strength. The sorption of 8 x 10{sup -6} M Np(V) at pH 9.0, and ionic strength of 0.1 M NaClO{sub 4} was proportional to the solid-to-liquid ratio of kaolinite in the range of 2-10 g L{sup -1}. In the absence of CO{sub 2}, the Np(V) uptake increased continuously with increasing pH value up to 97% at pH 10. Under ambient CO{sub 2}, the sorption of Np decreased above pH 8 up to zero at pH 10. An increase of Np(V) concentration from 7 x 10{sup -12} to 8 x 10{sup -6} M resulted in a shift of the sorption pH edge by up to one pH unit to higher pH values. The ionic strength influenced the Np(V) sorption onto kaolinite only in the presence of ambient CO{sub 2}. Under Ar atmosphere the sorption of Np(V) was independent from ionic strength, indicating the formation of inner-sphere complexes of Np(V) with kaolinite. Time-dependent batch experiments at pH 9.0 under ambient CO{sub 2} showed that the sorption of Np(V) on kaolinite is fast and fully reversible over six orders in Np(V) concentration. (orig.)

  7. Sorption properties of wool

    Directory of Open Access Journals (Sweden)

    Radetić Maja M.

    2004-01-01

    Full Text Available Strict ecological legislation, especially in highly developed countries, imposed requirements for the purification of industrial effluents and the need for efficient oil clean up after sea and inland water spills. Although numerous processes have been developed, the application of sorbents is still one of the most efficient methods to remove heavy metal ions, dyes and crude oil from water. Recently, special attention was paid to sorbents based on natural fibres. A review of studies concerning the sorption properties of wool is presented in this paper. The presence of various functional groups on the wool fibre surface contributes to the efficient sorption of heavy metal ions and dyes. A hydrophobic, scaly surface and fibre crimp strongly influence the high sorption capacity of wool for oil. Wool has great sorption potential even as a recycled material. Accordingly, it can be used as a viable substitute to commercially available synthetic sorbents that show poor biodegradab ility.

  8. Acquisition of sorption isotherms for modified woods by the use of dynamic vapour sorption instrumentation. Principles and Practice

    DEFF Research Database (Denmark)

    Engelund, Emil Tang; Klamer, Morten; Venås, Thomas Mark

    2010-01-01

    The complex wood-water relationship has been the topic of numerous studies. Sorption isotherms – in particular – have been derived for hundreds of wood species, their sap- and heartwood sections as well as for decayed, engineered and modified wood materials. However, the traditional methods...... for obtaining sorption isotherms are very time consuming. With new dynamic vapour sorption (DVS) instrumentation, the acquisition of data for constructing sorption isotherms is suddenly dramatically lowered. Where the traditional methods often required months, data can now be obtained in a matter of days...... depending on the number of data points required. The fast data acquisition makes DVS a useful tool in studying the sorption properties of wood, and especially in studying the effect of different modification treatments on these properties. This study includes an investigation of the sorption properties...

  9. Comparing uranyl sorption complexes on soil and reference clays

    International Nuclear Information System (INIS)

    Chisholm-Brause, C.J.; Berg, J.M.; Conradson, S.D.; Morris, D.E.; McKinley, J.P.; Zachara, J.M.

    1993-01-01

    Clay minerals and other components in natural soils may play a key role in limiting the mobility of uranium in the environment through the formation of sorption complexes. Reference clays are frequently used as models to study sorption processes because they have well-known chemical and physical properties, but they may differ chemically and morphologically from clays derived from natural soils. Therefore, inferences based on reference clay data have been questioned. The authors have used luminescence and x-ray absorption spectroscopies to characterize the sorption complexes of aqueous uranyl (UO 2 2+ ) species on two soil smectites from the Kenoma and Ringold formations, and compared these results to those obtained on reference smectite clays. The pH dependence of uptake suggests that the ratio of sorption on amphoteric edge sites is greater for the soil smectites than for reference clays such as Wyoming montmorillonite (SWy-1). The luminescence spectra for uranyl sorbed to the soil clays are very similar to those for uranyl sorbed principally to the edge sites of SWy-1. This observation supports the solution data suggesting that adsorption to amphoteric sites is a more important mechanism for soil clays. However, the spectral data indicate that the sorption complexes on natural and reference clays are quite similar. Furthermore, as with the reference clays, the authors have found that the chemistry of the solution plays a greater role in defining the sorption complex than does the clay matrix. Thus, if differences in surface properties are adequately taken into account, the reference clays may serve as useful analogs for soil clays in investigations of metal-ion sorption

  10. Sorption Energies for Atrazine onto Devolatalized Vitellaria paradoxa

    International Nuclear Information System (INIS)

    Itodo, A. U.; Abdulrahman, F. W.; Hassan, L. G.; Happiness, U. I.

    2012-01-01

    We utilize isotherm models in contributing to scholarly knowledge in simple terms, to measure the forces or energy defining certain adsorption phenomenon. Gas Chromatography coupled with Mass Spectrophotometer detector was utilized to measure equilibrium phase atrazine after adsorption onto Shea nut Shells acid derived activated carbon. Data were fitted into the D-R and Temkin isotherm relationships for energy data estimation of Sorption energy value (B D ), mean free energy (E D ) and heat of sorption (B). They were estimated as 0.7600mol 2 KJ -2 , 0.8111 kjmor -1 and 0.790Jmol -1 respectively. The parameter predicting the type of adsorption was evaluated B D , B D 2 = 0.979 proves a better choice in explaining sorption energies. Generally, shea nut shells can be used as alternative precursors for activated carbon production via the two steps and acid treatment method.

  11. Sorption Isotherm Modelling Of Fermented Cassava Flour by Red Yeast Rice

    Science.gov (United States)

    Cahyanti, M. N.; Alfiah, M. N.; Hartini, S.

    2018-04-01

    The objective of the study is to determine the characteristic of moisture sorption isotherm from fermented cassava flour by red yeast rice using various modeling. This research used seven salt solutions and storage temperature of 298K, 303K, and 308K. The models used were Brunauer-Emmet-Teller (BET), Guggenheim-Anderson-de Boer (GAB) and Caurie model. The monolayer moisture content was around 4.51 – 5.99% db. Constant related to absorption heat in the multilayer area of [GAB model was around 0.86-0,91. Constant related to absorption heat in the monolayer area of GAB model was around 4.67-5.97. Constant related to absorption heat in the monolayer area of BET model was around 4.83-7.04. Caurie constant was around 1.25-1.59. The equilibrium and monolayer moisture content on fermented cassava flour by red yeast rice was decreasing as increasing temperature. GAB constant value indicated that the process of moisture absorption on the fermented cassava flour by red yeast rice categorized in type II.

  12. Modelling the fate of ciprofloxacin in activated sludge systems - The relevance of the sorption process

    DEFF Research Database (Denmark)

    Polesel, Fabio; Lehnberg, Kai; Dott, Wolfgang

    The sorption process can impact the removal of specific pharmaceuticals in municipal wastewater treatment plants (WWTPs). Ionic interactions (e.g., pH-driven equilibria and complexation), rather than hydrophobic interactions, are known to affect the sorption of zwitterionic pharmaceuticals...

  13. Experimental Results and Model Calculations of a Hybrid Adsorption-Compression Heat Pump Based on a Roots Compressor and Silica Gel-Water Sorption

    Energy Technology Data Exchange (ETDEWEB)

    Van der Pal, M.; De Boer, R.; Wemmers, A.K.; Smeding, S.F.; Veldhuis, J.B.J.; Lycklama a Nijeholt, J.A.

    2013-10-15

    Thermally driven sorption systems can provide significant energy savings, especially in industrial applications. The driving temperature for operation of such systems limits the operating window and can be a barrier for market-introduction. By adding a compressor, the sorption cycle can be run using lower waste heat temperatures. ECN has recently started the development of such a hybrid heat pump. The final goal is to develop a hybrid heat pump for upgrading lower (<100C) temperature industrial waste heat to above pinch temperatures. The paper presents the first measurements and model calculations of a hybrid heat pump system using a water-silica gel system combined with a Roots type compressor. From the measurements can be seen that the effect of the compressor is dependent on where in the cycle it is placed. When placed between the evaporator and the sorption reactor, it has a considerable larger effect compared to the compressor placed between the sorption reactor and the condenser. The latter hardly improves the performance compared to purely heat-driven operation. This shows the importance of studying the interaction between all components of the system. The model, which shows reasonable correlation with the measurements, could proof to be a valuable tool to determine the optimal hybrid heat pump configuration.

  14. Time-dependent sorption of two novel fungicides in soils within a regulatory framework.

    Science.gov (United States)

    Gulkowska, Anna; Buerge, Ignaz J; Poiger, Thomas; Kasteel, Roy

    2016-12-01

    Convincing experimental evidence suggests increased sorption of pesticides on soil over time, which, so far, has not been considered in the regulatory assessment of leaching to groundwater. Recently, Beulke and van Beinum (2012) proposed a guidance on how to conduct, analyse and use time-dependent sorption studies in pesticide registration. The applicability of the recommended experimental set-up and fitting procedure was examined for two fungicides, penflufen and fluxapyroxad, in four soils during a 170 day incubation experiment. The apparent distribution coefficient increased by a factor of 2.5-4.5 for penflufen and by a factor of 2.5-2.8 for fluxapyroxad. The recommended two-site, one-rate sorption model adequately described measurements of total mass and liquid phase concentration in the calcium chloride suspension and the calculated apparent distribution coefficient, passing all prescribed quality criteria for model fit and parameter reliability. The guidance is technically mature regarding the experimental set-up and parameterisation of the sorption model for the two moderately mobile and relatively persistent fungicides under investigation. These parameters can be used for transport modelling in soil, thereby recognising the existence of the experimentally observed, but in the regulatory leaching assessment of pesticides not yet routinely considered phenomenon of time-dependent sorption. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  15. Thermodynamics of imidacloprid sorption in Croatian soils

    Science.gov (United States)

    Milin, Čedomila; Broznic, Dalibor

    2015-04-01

    Neonicotinoids are increasingly replacing the organophosphate and methylcarbamate acetylcholinesterase inhibitors which are losing their effectiveness because of selection for resistant pest populations. Imidacloprid is the most important neonicotinoid with low soil persistence, high insecticidal potency and relatively low mammalian toxicity. In Croatia, imidacloprid is most commonly used in olive growing areas, including Istria and Kvarner islands, as an effective means of olive fruit fly infestation control. Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equation, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were of non-linear and may be classified as L-type suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the KFsor values decreased for all the tested soils as the temperature increases, indicating that the temperature strongly influence the sorption. Values of ΔG° were negative (-4.65 to -2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous process. The negative and small ΔH° values (-19.79 to -8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and par¬titioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of -57.12 to -14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature

  16. Removal of organic compounds from natural underground water in sorption and sono-sorption processes on selected activated carbons

    Directory of Open Access Journals (Sweden)

    Pietrzyk Andżelika

    2017-01-01

    Full Text Available The article rated removal efficiency of organic matter in the processes of sorption and sono-sorption of underground water grasped for municipal purposes. The studies were conducted in laboratory scale and verified in pilot scale at the Water Treatment Plant Tarnobrzeg-Jeziórko. In the research used granular activated carbons, ie. WD-Extra, WG-12, Norit Row 0.8 and Filtrasorb 300. The processes efficiency was evaluated on the basis of changes in the following parameters, ie.: total organic carbon (TOC, permanganate index, UV absorbance, turbidity and colour. The ultrasounds were generated by means of disintegrator Sonics&Materials VCX 130, using the sonication time of 1 and 5 minutes. The results obtained for the batch tests allowed to observe a beneficial effect of ultrasound on the efficiency of the removal of organic material in the sorption process. The combination of sonication and sorption on activated carbon increased the efficiency of the removal of organic matter by 6–37% for TOC, and 18.6–27.9% for permanganate index, depending on the sorbent used. The positive laboratory results were not confirmed in a pilot scale. In the flow conditions the sonication process did not affect the efficiency of removal of organic matter on the filter model with a bed of activated carbon.

  17. Study of thermodynamic water properties and moisture sorption hysteresis of mango skin

    Directory of Open Access Journals (Sweden)

    Silvio José Ferreira de Souza

    2015-03-01

    Full Text Available The equilibrium moisture content for adsorption and desorption isotherms of mango skin was determined using the static gravimetric method at temperatures of 20, 26, 33, 38 and 44 oC in the 0.056 to 0.873 water activity range. Both sorption curves show a decrease in equilibrium moisture content as the temperature increasing. The hysteresis effect was observed at constant water activity. The Guggenheim, Anderson, and de Boer (GAB model presented the best fitting accuracy among a group of models and was used to determine the thermodynamic properties of water sorption. Integral enthalpy and integral entropy areas showed inverted values for the adsorption and desorption isotherms over the wide range of water activity studied. These values confirm, in energetic terms, the difference between adsorption and desorption isotherms observed in the hysteresis phenomenon. Finally, the Gibbs free energy revealed that the sorption process was spontaneous for both sorption isotherms.

  18. Equilibrium and kinetic studies for the sorption of 3-methoxybenzaldehyde on activated kaolinites

    Energy Technology Data Exchange (ETDEWEB)

    Koyuncu, Huelya [Forensic Medicine Foundation, Nasuhpasa Bath Street, No. 12, 16010 Heykel, Bursa (Turkey)]. E-mail: hkoyuncu@yyu.edu.tr; Kul, Ali Riza [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey)]. E-mail: alirizakul@yyu.edu.tr; Yildiz, Nuray [Ankara University, Faculty of Engineering, Department of Chemical Engineering, 06100 Tandogan, Ankara (Turkey)]. E-mail: nyildiz@eng.ankara.edu.tr; Calimli, Ayla [Ankara University, Faculty of Engineering, Department of Chemical Engineering, 06100 Tandogan, Ankara (Turkey)]. E-mail: calimli@eng.ankara.edu.tr; Ceylan, Hasan [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey)]. E-mail: hceylan@yyu.edu.tr

    2007-03-06

    The sorption of 3-methoxybenzaldehyde on activated kaolinites has been investigated at different temperatures. Two types of activation tests were performed. The sorption equilibrium was studied by sorption isotherms in the temperature range 303-333 K for natural (untreated), thermally and acid activated kaolinites. It was shown that the isotherm shapes were not affected by temperature and activation types of kaolinite. The absorbance data at 312 nm were fitted reasonably well with the Langmuir and Freundlich isotherm models and the model parameters were determined for different temperatures. Thermodynamic quantities such as Gibbs free energy ({delta}G), the enthalpy ({delta}H) and the entropy change of sorption ({delta}S) were determined for natural, thermally and acid activated kaolinites. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. Adsorption capacity of acid activated kaolinite for 3-methoxybenzaldehyde was higher compared to that of natural and thermally activated kaolinites at various temperatures. The adsorption and desorption rate constants (k {sub a} and k {sub d}) were obtained separately by applying a geometric approach to the first order Langmuir model. This method provided good conformity between the K from Langmuir parameters and K {sub geo} (k {sub a}/k {sub d}) from geometric approach.

  19. Equilibrium and kinetic studies for the sorption of 3-methoxybenzaldehyde on activated kaolinites

    International Nuclear Information System (INIS)

    Koyuncu, Huelya; Kul, Ali Riza; Yildiz, Nuray; Calimli, Ayla; Ceylan, Hasan

    2007-01-01

    The sorption of 3-methoxybenzaldehyde on activated kaolinites has been investigated at different temperatures. Two types of activation tests were performed. The sorption equilibrium was studied by sorption isotherms in the temperature range 303-333 K for natural (untreated), thermally and acid activated kaolinites. It was shown that the isotherm shapes were not affected by temperature and activation types of kaolinite. The absorbance data at 312 nm were fitted reasonably well with the Langmuir and Freundlich isotherm models and the model parameters were determined for different temperatures. Thermodynamic quantities such as Gibbs free energy (ΔG), the enthalpy (ΔH) and the entropy change of sorption (ΔS) were determined for natural, thermally and acid activated kaolinites. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. Adsorption capacity of acid activated kaolinite for 3-methoxybenzaldehyde was higher compared to that of natural and thermally activated kaolinites at various temperatures. The adsorption and desorption rate constants (k a and k d ) were obtained separately by applying a geometric approach to the first order Langmuir model. This method provided good conformity between the K from Langmuir parameters and K geo (k a /k d ) from geometric approach

  20. Evaluation of Lagergren Kinetics Equation by Using Novel Kinetics Expression of Sorption of Zn2+ onto Horse Dung Humic Acid (HD-HA

    Directory of Open Access Journals (Sweden)

    Bambang Rusdiarso

    2016-12-01

    Full Text Available Extraction and purification of humic acid from dry horse dung powder (HD-HA was performed successfully and the purified HD-HA was then applied as sorbent to adsorb Zn2+. Extraction and purification were performed based on procedure of Stevenson (1994 under atmospheric air. Parameters investigated in this work consist of effect of medium sorption acidity, sorption rate (ka and desorption rate constant (kd, Langmuir (monolayer and Freundlich (multilayer sorption capacities, and energy (E of sorption. The ka and kd were determined according to the kinetic model of second order sorption reaching equilibrium, monolayer sorption capacity (b and energy (E were determined according to Langmuir isotherm model, and multilayer sorption capacity (B was determined based on Freundlich isotherm model. Sorption of Zn2+ on purified HD-HA was maximum at pH 5.0. The novel kinetic expression resulted from proposed kinetic model has been shown to be more applicable than the commonly known Lagergren equation obtained from the pseudo-first order sorption model. The application of the equation revealed that the intercept of Lagergren equation, ln qe was more complex function of initial concentration of Zn2+ (a, Langmuir sorption capacity (b, and sorbed Zn2+ at equilibrium (xe.

  1. Alligator Rivers Analogue project. Uranium sorption. Final Report - Volume 13

    Energy Technology Data Exchange (ETDEWEB)

    Waite, T D; Payne, T E [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia); Davis, J A [United States Geological Survey, Water Resources Division, Menlo Park, CA (United States); Sekine, K [Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki (Japan)

    1993-12-31

    In this volume, the results of studies of uranium sorption (adsorption and desorption) to both single, well-defined mineral phases, and to selected natural (Koongarra) substrates are reported. The single phases included the amorphous iron oxide ferrihydrite, crystalline silica and two naturally occurring kaolinites, KGa-1 and Nichika. The surface properties of these materials were rigorously defined, and adsorption studies were conducted over a range of solution pH, ionic strength, carbonate content, adsorbent and adsorbate concentrations, and in the presence of uranium complexants and (potentially) competing adsorbates (such as phosphate and fluoride). The results of these studies were modelled using the `surface complexation` approach, with a diffuse layer description of the electrical double layer. The impacts of mineral phase transformations (specifically the aging of amorphous ferrihydrite to more crystalline forms) on the uptake and desorption of uranium are also reported. The amount of data obtained in this study, with a number of experimental parameters being varied over a wide range, has enabled more confidence to be placed in the modelling results. The derived model for ferrihydrite adequately accounts for the effect on U sorption of a number of parameters, most notably pH, pCO{sub 2} and total U present. Few (if any) of the models previously proposed are adequate in this respect. While the modelling of the data for the natural substrates is not as advanced, the U sorption data on the natural substrates show similar features to the U sorption on the model substrates. This suggests that the insights obtained in the modelling of the data for ferrihydrite will be valuable in deriving a model for the more complex natural substrates 87 refs., 27 tabs., 56 figs.

  2. Sorption performance and mechanism of a sludge-derived char as porous carbon-based hybrid adsorbent for benzene derivatives in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lingjun [School of Environmental Science and Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China); Xiong, Ya, E-mail: cesxya@mail.sysu.edu.cn [School of Environmental Science and Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275 (China); Sun, Lianpeng; Tian, Shuanghong [School of Environmental Science and Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275 (China); Xu, Xianyan; Zhao, Cunyuan [School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China); Luo, Rongshu [School of Environmental Science and Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China); Yang, Xin [School of Environmental Science and Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275 (China); Shih, Kaimin [Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR (China); Liu, Haiyang [Department of Chemistry, South China University of Technology, Guangzhou, 510641 (China)

    2014-06-01

    Highlights: • Hierarchical porous sludge char were fabricated by pyrolysis at 500 °C. • A stronger Si–O bond (1.83 Å and 1.87 Å) between the carboxyl and SiO{sub 2} was found. • Quantum chemistry calculation confirmed the interaction of Si–O and H–O bonds. • Multiple model (Q{sub T} = Q{sub A} + K{sub P}Ce) was presented in the sludge char sorption process. - Abstract: A porous sludge-derived char was prepared by a new one-step pyrolytic process with citric acid–ZnCl{sub 2} mixed fabricating-pore agents. The sludge-derived char was confirmed to be a hierarchically porous hybrid adsorbent containing-elemental carbon, -highly carbonized organic species and -inorganic ash with a great surface area of 792.4 m{sup 2} g{sup −1}. It was used as a carbon-based hybrid adsorbent for four benzene derivatives including 4-chlorophenol, phenol, benzoic acid and 4-hydroxylbenzoic acid in aqueous solution. Results showed that their sorption isotherms were nonlinear at low concentrations and linear at high concentrations. The sorption performance could be described by a multiple sorption model (Q{sub T} = Q{sub A} + K{sub P}C{sub e}). The order of these partition sorption coefficients (K{sub P}) of these benzene derivatives was consistent with their octanol–water partition coefficients (log K{sub ow}), but those saturated amounts (Q{sub A}) were inconsistent with their log K{sub ow}. The inconstancy was found to be considerably dependent on the preferential interaction of benzoic acid with SiO{sub 2} in the sludge-derived char. Quantum theoretical calculation confirmed that the preferential interaction was attributed to the formation of hydrogen bonds (1.61 and 1.69 Å) and new Si–O bonds (1.83 and 1.87 Å) between the carboxyl of benzoic acid and the SiO{sub 2} surface in the sorption process.

  3. Phenanthrene sorption on biochar-amended soils

    DEFF Research Database (Denmark)

    Kahawaththa Gamage, Inoka Damayanthi Kumari; Moldrup, Per; Paradelo Pérez, Marcos

    2014-01-01

    on their influences on the sorption of environmental contaminants. In a field-based study at two experimental sites in Denmark, we investigated the effect of birch wood-derived biochar (Skogans kol) on the sorption of phenanthrene in soils with different properties. The soil sorption coefficient, Kd (L kg-1......), of phenanthrene was measured on sandy loam and loamy sand soils which have received from zero up to 100 t ha-1 of biochar. Results show that birch wood biochar had a higher Kd compared to soils. Furthermore, the application of birch wood biochar enhanced the sorption of phenanthrene in agricultural soils...... carbon, while it negatively correlated with clay content. The results also revealed that biochar-mineral interactions play an important role in the sorption of phenanthrene in biochar-amended soil....

  4. Sorption of benzothiazoles onto sandy aquifer material under equilibrium and nonequlibrium conditions

    Directory of Open Access Journals (Sweden)

    Kragulj Marijana M.

    2014-01-01

    Full Text Available In this study, the sorption behaviour of 1,3-benzothiazole (BT and 2-(methylthiobenzothiazole (MTBT was investigated on Danube geosorbent under equilibrium and nonequilibrium conditions. All sorption isotherms fitted well with the Freundlich model (R2=0.932-0.993. The results showed that organic matter of the Danube geosorbent has a higher sorption affinity for the more hydrophobic MTBT compared to BT. However, sorption-desorption experiments showed that MTBT was more easily desorbed than BT molecules, which indicates the importance of absorption relative to adsorption in the overall sorption mechanism of MTBT. In general, molecules of BT and MTBT were more easily desorbed in the lower concentration range, which resulted in an increase in the hysteresis indices with increasing concentrations. Column experiments revealed that retention of the investigated compounds on the aquifer material followed the compound’s hydrophobicity. BT showed a lower retention, in accordance with its lower sorption affinity obtained in the static experiments, while MTBT showed a greater sorption affinity, and thus had a longer retention time on the column. Thus during transport BT represent greater risk for groundwaters than MTBT. These results have increased our understanding of benzothiazoles sorption and desorption process which represent one of the most important factors which influence the behaviour of organic compounds in the environment.

  5. Kinetics and thermodynamic for sorption of arsenate by Lanthanum-exchanged zeolite

    International Nuclear Information System (INIS)

    Mohd Jelas Haron; Saiful Adli Masdan; Mohd Zobir Hussein; Zulkarnain Zainal; Anuar Kassim

    2007-01-01

    Zeolites are crystalline, hydrated aluminosilicate containing exchangeable alkaline and alkaline earth cations in their structural frameworks. Since zeolites have permanent negative charges on their surfaces, they have no affinity for anions. However recent studies have shown that modification of zeolites with certain surfactants or metal cations yield sorbents with a strong affinity for many anions. In this paper, modification of zeolites (zeolite A, X and ZSM5) were performed by exchange of naturally occurring cations with lanthanum ion that forms low solubility arsenate salt. The exchanged zeolites were used to sorb arsenate from aqueous solution. Among parameters investigated were effect of pH, arsenate initial concentrations, contact time and temperature. The maximum exchanged capacity of La (III) ion was obtained when using solution with initial pH of 4. Zeolite X gives the highest La (III) exchanged capacity compared to other zeolites. The results showed that As (V) sorption by La-zeolites occurred at about pH 6.5 and increased as pH increased and reaching maximum at equilibrium pH about 7.8. On the other hand, almost no arsenate sorption occurred on un exchanged zeolites. This indicates that La (III) ion on the exchanged zeolites is taking part on the As(V) sorption via surface precipitation. The results also showed that the sorption capacities increased with increasing initial As (V) concentrations. The sorption followed Langmuir model with maximum sorption capacities of 0.41, 0.21 and 0.19 mmol/g at 25 degree Celsius for La exchanged zeolite X (La-ZX), La exchanged zeolite ZSM5 (La-ZSM) and La exchanged zeolite A (La-ZA), respectively. The amounts of sorption of As (V) by La exchanged zeolite increased as temperature increased from 25 to 70 degree Celsius indicating that the process is endothermic. The free energy changes ( ΔG degree) for the sorption at 25 degree Celsius were -10.25, -9.65 and -8.49 kJ/ mol for La-ZX, La-ZSM and La-ZA, respectively. The

  6. Dimension of linear models

    DEFF Research Database (Denmark)

    Høskuldsson, Agnar

    1996-01-01

    Determination of the proper dimension of a given linear model is one of the most important tasks in the applied modeling work. We consider here eight criteria that can be used to determine the dimension of the model, or equivalently, the number of components to use in the model. Four...... the basic problems in determining the dimension of linear models. Then each of the eight measures are treated. The results are illustrated by examples....... of these criteria are widely used ones, while the remaining four are ones derived from the H-principle of mathematical modeling. Many examples from practice show that the criteria derived from the H-principle function better than the known and popular criteria for the number of components. We shall briefly review...

  7. Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

    Science.gov (United States)

    Rodionova, D. O.; Voronyuk, I. V.; Eliseeva, T. V.

    2016-07-01

    Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.

  8. Sorption Coefficients for Iodine, Silver, and Cesium on Dust Particles

    International Nuclear Information System (INIS)

    Stempniewicz, M.M.; Goede, P.

    2014-01-01

    This paper describes the work performed to find relevant experimental data and find the sorption coefficients that represent well the available data for cesium, iodine, and silver on dust particles. The purpose of this work is to generate a set of coefficients that may be recommended for the computer code users. The work was performed using the computer code SPECTRA. Calculations were performed for the following data: • I-131 on AVR dust; • Ag-110m on AVR dust; • Cs-13 and Cs-137 on AVR dust. Available data was matched using the SPECTRA Sorption Model. S = A(T) · C_V-B(T) · C_d. The results are summarized as follows: • The available data can be correlated. The data scatter is about 4 orders of magnitude. Therefore the coefficients of the Langmuir isotherms vary by 4 orders of magnitude. • Sorption rates are higher at low temperatures and lower at high temperatures. This tendency has been observed in the data compiled at Oak Ridge. It is therefore surmised that the highest value of the sorption coefficients are appropriate for the low temperatures and the lowest value of the sorption coefficients are appropriate for the high temperatures. The recommended sorption coefficients are presented in this paper. • The present set of coefficients is very rough and should be a subject for future verification against experimental data. (author)

  9. A three-compartment model for micropollutants sorption in sludge: methodological approach and insights.

    Science.gov (United States)

    Barret, Maialen; Patureau, Dominique; Latrille, Eric; Carrère, Hélène

    2010-01-01

    In sludge resulting from wastewater treatment, organic micropollutants sorb to particles and to dissolved/colloidal matter (DCM). Both interactions may influence their physical and biological fate throughout the wastewater treatment processes. To our knowledge, sludge has never been considered as a three-compartment matrix, in which micropollutants coexist in three states: freely dissolved, sorbed-to-particles and sorbed-to-DCM. A methodology is proposed to concomitantly determine equilibrium constants of sorption to particles (K(part)) and to DCM (K(DCM)). Polycyclic Aromatic Hydrocarbons (PAHs) were chosen as model compounds for the experiments. The logarithm of estimated equilibrium constants ranged from 3.1 to 4.3 and their usual correlation to PAH hydrophobicity was verified. Moreover, PAH affinities for particles and for DCM could be compared. Affinity for particles was found to be stronger, probably due to their physical and chemical characteristics. This work provided a useful tool to assess the freely dissolved, sorbed-to-particles and sorbed-to-DCM concentrations of contaminants, which are necessary to accurately predict their fate. Besides, guidelines to investigate the link between sorption and the fundamental concept of bioavailability were proposed. (c) 2009 Elsevier Ltd. All rights reserved.

  10. Sorption properties of carbon nanostructures

    International Nuclear Information System (INIS)

    Eletskii, Aleksandr V

    2004-01-01

    The current status of research in sorption properties of carbon nanotubes (CNTs) is reviewed. The structural peculiarities of CNTs, determining their sorption characteristics, are considered. The mechanisms of sorption of gaseous and condensed substances by such structures are analyzed. Special attention is paid to the problem of using CNTs for storing hydrogen and other gaseous substances. Methods for filling CNTs with liquid materials, based on capillary phenomena and wetting the graphite surface of the CNT with liquids of various nature, are considered. Properties of 'peapods' formed as a result of filling single-walled CNTs with fullerene molecules are reviewed. Also considered are perspectives on the applied usage of the sorption properties of CNTs in electrochemical and fuel cells, and material storage devices, as well as for producing superminiature metallic conductors. (reviews of topical problems)

  11. Ordinal Log-Linear Models for Contingency Tables

    Directory of Open Access Journals (Sweden)

    Brzezińska Justyna

    2016-12-01

    Full Text Available A log-linear analysis is a method providing a comprehensive scheme to describe the association for categorical variables in a contingency table. The log-linear model specifies how the expected counts depend on the levels of the categorical variables for these cells and provide detailed information on the associations. The aim of this paper is to present theoretical, as well as empirical, aspects of ordinal log-linear models used for contingency tables with ordinal variables. We introduce log-linear models for ordinal variables: linear-by-linear association, row effect model, column effect model and RC Goodman’s model. Algorithm, advantages and disadvantages will be discussed in the paper. An empirical analysis will be conducted with the use of R.

  12. Application of simplified desorption method to sorption study. (2) Sorption of neptunium (V) on montmorillonite-based mixtures

    International Nuclear Information System (INIS)

    Kozai, Naofumi; Ohnuki, Toshihiko

    2013-01-01

    To elucidate the sorption behaviors of radionuclides in multi-mineral systems and the mutual effects of minerals on the sorption, this paper carried out the sorption and desorption experiments of neptunium(V) on montmorillonite-based two-mineral mixtures. The Np sorbed on montmorillonite at pH from 4 to 8 was desorbed with 1M KCl solutions, indicating that the sorption was cation exchange. The Np sorbed on apatite and calcite was nondesorbable with 1M KCl solutions, which is in harmony with the knowledge that Np forms strong complexes with the phosphate groups of apatite and the carbonate groups of calcite. This study utilized these clear distinguishes of the desorption behaviors for examining the two-mineral systems. In montmorillonite-apatite mixtures, the sorption on the montmorillonite was decreased and Np was accumulated on the apatite. In montmorillonite-calcite mixtures, the sorption on the montmorillonite was decreased due to the interference by the calcium and carbonate ions dissolved from calcite while no accumulation of Np to calcite was observed. (author)

  13. Sorption and desorption of glyphosate in Mollisols and Ultisols soils of Argentina.

    Science.gov (United States)

    Gómez Ortiz, Ana Maria; Okada, Elena; Bedmar, Francisco; Costa, José Luis

    2017-10-01

    In Argentina, glyphosate use has increased exponentially in recent years as a result of the widespread adoption of no-till management combined with genetically modified glyphosate-resistant crops. This massive use of glyphosate has created concern about its potential environmental impact. Sorption-desorption of glyphosate was studied in 3 Argentinean soils with contrasting characteristics. Glyphosate sorption isotherms were modeled using the Freundlich equation to estimate the sorption coefficient (K f ). Glyphosate sorption was high, and the K f varied from 115.6 to 1612 mg 1-1/n L 1/n /kg. Cerro Azul soil had the highest glyphosate sorption capacity as a result of a combination of factors such as higher clay content, cation exchange capacity, total iron, and aluminum oxides, and lower available phosphorus and pH. Desorption isotherms were also modeled using the Freundlich equation. In general, desorption was very low (glyphosate strongly sorbs to the soils and that it is almost an irreversible process. Anguil soil had a significantly higher desorption coefficient (K fd ) than the other soils, associated with its lower clay content and higher pH and phosphorus. Glyphosate high sorption and low desorption to the studied soils may prevent groundwater contamination. However, it may also affect its bioavailability, increasing its persistence and favoring its accumulation in the environment. The results of the present study contribute to the knowledge and characterization of glyphosate retention in different soils. Environ Toxicol Chem 2017;36:2587-2592. © 2017 SETAC. © 2017 SETAC.

  14. Investigating the gas sorption mechanism in an rht -metal-organic framework through computational studies

    KAUST Repository

    Pham, Tony T.

    2014-01-09

    Grand canonical Monte Carlo (GCMC) simulations were performed to investigate CO2 and H2 sorption in an rht-metal-organic framework (MOF) that was synthesized with a ligand having a nitrogen-rich trigonal core through trisubstituted triazine groups and amine functional groups. This MOF was synthesized by two different groups, each reporting their own distinct gas sorption measurements and crystal structure. Electronic structure calculations demonstrated that the small differences in the atomic positions between each group\\'s crystal structure resulted in different electrostatic parameters about the Cu2+ ions for the respective unit cells. Simulations of CO2 sorption were performed with and without many-body polarization effects and using our recently developed CO2 potentials, in addition to a well-known bulk CO2 model, in both crystallographic unit cells. Simulated CO2 sorption isotherms and calculated isosteric heats of adsorption, Qst, values were in excellent agreement with the results reported previously by Eddaoudi et al. for both structures using the polarizable CO2 potential. For both crystal structures, the initial site for CO2 sorption were the Cu 2+ ions that had the higher positive charge in the unit cell, although the identity of this electropositive Cu2+ ion was different in each case. Simulations of H2 sorption were performed with three different hydrogen potentials of increasing anisotropy in both crystal structures and the results, especially with the highest fidelity model, agreed well with Eddaoudi et al.\\'s experimental data. The preferred site of H 2 sorption at low loading was between two Cu2+ ions of neighboring paddlewheels. The calculation of the normalized hydrogen dipole distribution for the polarizable model in both crystal structures aided in the identification of four distinct sorption sites in the MOF, which is consistent to what was observed in the experimental inelastic neutron scattering (INS) spectra. Lastly, while the

  15. Parameterized Linear Longitudinal Airship Model

    Science.gov (United States)

    Kulczycki, Eric; Elfes, Alberto; Bayard, David; Quadrelli, Marco; Johnson, Joseph

    2010-01-01

    A parameterized linear mathematical model of the longitudinal dynamics of an airship is undergoing development. This model is intended to be used in designing control systems for future airships that would operate in the atmospheres of Earth and remote planets. Heretofore, the development of linearized models of the longitudinal dynamics of airships has been costly in that it has been necessary to perform extensive flight testing and to use system-identification techniques to construct models that fit the flight-test data. The present model is a generic one that can be relatively easily specialized to approximate the dynamics of specific airships at specific operating points, without need for further system identification, and with significantly less flight testing. The approach taken in the present development is to merge the linearized dynamical equations of an airship with techniques for estimation of aircraft stability derivatives, and to thereby make it possible to construct a linearized dynamical model of the longitudinal dynamics of a specific airship from geometric and aerodynamic data pertaining to that airship. (It is also planned to develop a model of the lateral dynamics by use of the same methods.) All of the aerodynamic data needed to construct the model of a specific airship can be obtained from wind-tunnel testing and computational fluid dynamics

  16. Predictive models of circulating fluidized bed combustors: SO[sub 2] sorption in the CFB loop

    Energy Technology Data Exchange (ETDEWEB)

    Gidaspow, D.; Therdthianwong, A. (Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering)

    1993-02-01

    The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. Sorption of S0[sub 2] with calcined limestone was studied in a PYROFLOW type CFB loop at conditions approximating those found in a CFB combustor. Initially the CFB loop contained 150 micron CaO particles of a density of 3.3 g/cm[sup 3] and air at 1143[degrees]K and 3.25 atm. Atzero time, air containing 600 ppm SO[sub 2], was introduced into the riser bottom at 1143[degrees]K. The effect of gas velocity, sorbent inventory and inlet pressure on the sorption of SO[sub 2], were studied isothermally by running our hydrodynamic code with the S0[sub 2] sorption conservation of species equation. At a velocity of 5m/sec., reported to be a typical velocity by PYROPOWER, there is reasonably good S0[sub 2] removal. At 10 m/sec the S0[sub 2] removal is poor. The best SO[sub 2], removal is for a velocity of 5 m/s and a high bed inventory, initial bed height, H = 9m. Most of the S0[sub 2] is removed in the first two meters of the reactor. However, the S0[sub 2] removal is not complete at the bed outlet. This is due to mixing. At the left wall of the reactor (wall opposite the solids inlet) the S0[sub 2] removal was poor due to gas bypassing caused by the asymmetrical solids inlet. Simulation of the PYROPOWER loop with a symmetrical inlet gave us an order of magnitude improvement over the conventional PYROPOWER system. These results demonstrate the practical utility of the predictive model that we have developed over the last three years.

  17. Linear and non-linear autoregressive models for short-term wind speed forecasting

    International Nuclear Information System (INIS)

    Lydia, M.; Suresh Kumar, S.; Immanuel Selvakumar, A.; Edwin Prem Kumar, G.

    2016-01-01

    Highlights: • Models for wind speed prediction at 10-min intervals up to 1 h built on time-series wind speed data. • Four different multivariate models for wind speed built based on exogenous variables. • Non-linear models built using three data mining algorithms outperform the linear models. • Autoregressive models based on wind direction perform better than other models. - Abstract: Wind speed forecasting aids in estimating the energy produced from wind farms. The soaring energy demands of the world and minimal availability of conventional energy sources have significantly increased the role of non-conventional sources of energy like solar, wind, etc. Development of models for wind speed forecasting with higher reliability and greater accuracy is the need of the hour. In this paper, models for predicting wind speed at 10-min intervals up to 1 h have been built based on linear and non-linear autoregressive moving average models with and without external variables. The autoregressive moving average models based on wind direction and annual trends have been built using data obtained from Sotavento Galicia Plc. and autoregressive moving average models based on wind direction, wind shear and temperature have been built on data obtained from Centre for Wind Energy Technology, Chennai, India. While the parameters of the linear models are obtained using the Gauss–Newton algorithm, the non-linear autoregressive models are developed using three different data mining algorithms. The accuracy of the models has been measured using three performance metrics namely, the Mean Absolute Error, Root Mean Squared Error and Mean Absolute Percentage Error.

  18. Amide mediated enhancement of sorption efficiency of trivalent f-elements on functionalized carbon nanotube: evidence of physiosorption

    International Nuclear Information System (INIS)

    Gupta, Nishesh K.; Sengupta, Arijit; Rane, Vinayak G.; Kadam, R.M.

    2017-01-01

    Amide Functionalized multi-walled carbon nanotube (CNT-DHA) was found to enhance the sorption efficiency of trivalent lanthanides and actinides from aqueous acidic solution. Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models were employed to understand the sorption mechanism revealing the predominance of Fruendlich isotherm. The sorption energy evaluated from D-R isotherm revealed the sorption process is physisorption, which was confirmed by the no shift in the IR frequency of amide functionality of carbon nanotube on sorption. The EPR spectra of the Gd"3"+ sorbed on carbon nanotube also showed no perturbation on the local environment of Gd"3"+ on sorption again revealing the physisorption. Analysis of the sorption kinetics through Lagergren's first order kinetics, intra particle diffusion model and pseudo second order kinetics revealed that the sorption kinetics followed pseudo second order kinetics for Am"3"+ and Eu"3"+ with rate constants 4.04E-05mg g"-"1 min"-"1 and 8.27E-05 mg g"-"1 min"-"1 respectively. The radiolytic stability of CNT-DHA was evaluated and found to be satisfactory. EDTA was found to strip the trivalent lanthanides and actinides almost quantitatively. (author)

  19. Sorption of streptococcus faecium to glass

    International Nuclear Information System (INIS)

    Oerstavik, D.

    1977-01-01

    A method has been developed by which to study the sorption of Streptococcus faecium to soda-lime cover glasses. Conditions were chosen to minimize the influence on sorption of bacterial polymer production, passive sorption being studied rather than attachment mediated by metabolic activities. Sorption of S. faecium increased with increasing temperature (to 50degC), time, and cell concentration, but equilibrium apparently was not reached even after incubation for 8 hours or at a cell concentration of 3 x 10 10 per ml. Sorption increased with solute molarity up to 0.1 M concentration of NaCl and KCl, indicating an effect of the electrical double layers on the apposition of cells to the glass surface. Desorption of bacteria could be obtained after multiple washings of the glasses in buffer or by the action of Tween 80, but not if sorbed bacteria were left in distilled water, various salt solutions, urea, or in suspensions of unlabelled bacteria. It was concluded that sorption occurred as a result of chemical interactions between the glass and the cell surface. Tween 80 at a concentration of 1 per cent inhibited sorption to 26 per cent of buffer controls, 2 M urea was less effective, and 1 M NaCl was without effect. It is suggested that hydrophobic interactions may be of importance in the binding of S. faecium to glass. (author)

  20. The sorption of metal ions on nanoscale zero-valent iron

    Directory of Open Access Journals (Sweden)

    Suponik Tomasz

    2017-01-01

    Full Text Available The injection of the colloidal suspensions of nano-iron (nZVI into an aquifer is a novel method of removing metal ions from acidic water. In the batch tests, the equilibrium study of the sorption of metal ions, Cu(II and Zn(II, on Green Tea nanoscale Zero-Valent Ion (GT-nZVI was carried out. The sorption of metal ions on this reactive material was described using the Langmuir, Freundlich and Sips models. This last model described in a better way the sorption equilibrium in the tested range of concentrations and temperature. The value of determination coefficient (R2 for the Sips model, for copper and zinc, was 0.9735 to 0.9995, respectively. GT-nZVI has very good properties in removing Cu(II and Zn(II from acidic water. The high values of qmaxS, the maximum adsorption capacity in the Sips model, amounting to 348.0 and 267.3 mg/g for Cu(II and Zn(II, indicate the high adsorption capacity of GT-nZVI. The analyzed metals have good or very good affinity with GT-nZVI.

  1. Sorption of U(VI) species on hydroxyapatite

    International Nuclear Information System (INIS)

    Thakur, P.; Moore, R.C.; Choppin, G.R.

    2005-01-01

    The sorption of uranyl (UO 2 2+ ) cations to hydroxyapatite was studied as a function of the amount of sorbent, ionic strength, U(VI) concentration, pH and temperature. The rate of uranyl sorption on hydroxyapatite decreased with increased uranyl concentrations. The amount sorbed decreased with increased ionic strength and increased with pH to a maximum at 7-8. The sorption data for UO 2 2+ were fitted well by the Freundlich and Dubinin-Radushkevich (D-R) isotherms. The anions Cl - , NO 3 - , SO 4 2- and CH 3 COO - decreased the sorption of uranium on hydroxyapatite while S 2 O 3 2- slightly increased it. The sorbed uranium was desorbed by 0.10 M and 1.00 M solutions of HCl and HNO 3 . The thermodynamic parameters for the sorption of UO 2 2+ were measured at temperatures of 298, 313, 323 and 333 K. The temperature dependence confirmed an endothermic heat of sorption. The activation energy for the sorption process was calculated to be +2.75±0.02 kJ/mol. (orig.)

  2. Modeling of radionuclide and heavy metal sorption around low and high pH waste disposal sites at Oak Ridge, Tennessee: Classification review package

    International Nuclear Information System (INIS)

    Saunders, J.A.

    1994-10-01

    Modeling of mineral precipitation and metal sorption reactions using MINTEQA2 and the iron oxyhydroxide diffuse-layer model has provided insights into geochemical processes governing contaminant migration from low-level radioactive waste disposal sites at the US Department of Energy's Oak Ridge National Laboratory and Y-12 Plant at Oak Ridge, Tennessee. Both acidic and basic nuclear-fuel reprocessing wastes, locally mixed with decontamination solvents, were disposed of in unlined trenches and lagoons. Model results show that as wastes move toward neutral pH due to reactions with surrounding soils and saprolite, mineral precipitation and sorption can limit the solubility of heavy metals and radionuclides. However, observed contaminant levels in monitoring wells indicate that at least locally, wastes are moving in faults and fractures and are not retarded by sorption reactions along such flow paths. Model results also support previous studies that have indicated organic complexing agents used in decontamination procedures can enhance radionuclide and heavy metal solubility when mixed with nuclear fuel reprocessing wastes. However, complex interactions between metal-organic complexes and mineral surfaces and natural organic matter, biodegradation, and fracture flow complicate the interpretation of contaminant mobility

  3. Isothermal, kinetic and thermodynamic studies on basic dye sorption ...

    African Journals Online (AJOL)

    PRECIOUS

    2009-12-15

    Dec 15, 2009 ... The isothermal data correlated with the Langmuir model better than the. Freundlich model. ... there were two intra-particle diffusion steps in the dye sorption processes. .... rated monolayer of sorbate molecule on the sorbent.

  4. The removal of heavy metals in urban runoff by sorption on mulch

    International Nuclear Information System (INIS)

    Jang, Am; Seo, Youngwoo; Bishop, Paul L.

    2005-01-01

    A series of adsorption experiments was conducted in order to assess the ability of three mulches to remove several of the heavy metal ions typically encountered in urban runoff. Three types of mulch, cypress bark (C), hardwood bark (H), and pine bark nugget (P), were selected as potential sorbents to capture heavy metals in urban runoff. The hardwood bark (H) mulch had the best physicochemical properties for adsorption of heavy metal ions. In addition, because of its fast removal rate and acceptably high capacity for all the heavy metal ions, it was concluded that the H mulch is the best of the three adsorbents for treatment of urban runoff containing trace amounts of heavy metals. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The sorption of these metals on H mulch conformed to the linear form of the Langmuir adsorption equation. At pH 5 and 6, the Langmuir constants (S m ) for each metal were found to be 0.324 and 0.359 mmol/g (Cu); 0.306 and 0.350 mmol/g (Pb); and 0.185 and 0.187 mmol/g (Zn) at 25 deg. C. - Capsule: Hardwood bark had the best physicochemical properties for adsorption of metal ions

  5. SORPTION OF Au(III BY Saccharomyces cerevisiae BIOMASS

    Directory of Open Access Journals (Sweden)

    Amaria Amaria

    2010-07-01

    Full Text Available Au(III sorption by S. cerevisiae biomass extracted from beer waste industry was investigated. Experimentally, the sorption was conducted in batch method. This research involved five steps: 1 identification the functional groups present in the S. cerevisiae biomass by infrared spectroscopic technique, 2 determination of optimum pH, 3 determination of the sorption capacity and energy, 4 determination of the sorption type by conducting desorption of sorbed Au(III using specific eluents having different desorption capacity such as H2O (van der Waals, KNO3 (ion exchange, HNO3 (hydrogen bond, and tiourea (coordination bond, 5 determination of effective eluents in Au(III desorption by partial desorption of sorbed Au(III using thiourea, NaCN and KI. The remaining Au(III concentrations in filtrate were analyzed using Atomic Absorption Spectrophotometer. The results showed that: 1 Functional groups of S. cerevisiae biomass that involved in the sorption processes were hydroxyl (-OH, carboxylate (-COO- and amine (-NH2, 2 maximum sorption was occurred at pH 4, equal to 98.19% of total sorption, 3 The sorption capacity of biomass was 133.33 mg/g (6.7682E-04 mol/g and was involved sorption energy 23.03 kJ mol-1, 4 Sorption type was dominated by coordination bond, 5 NaCN was effective eluent to strip Au(III close to 100%.   Keywords: sorption, desorption, S. cerevisiae biomass, Au(III

  6. Correlations and Non-Linear Probability Models

    DEFF Research Database (Denmark)

    Breen, Richard; Holm, Anders; Karlson, Kristian Bernt

    2014-01-01

    the dependent variable of the latent variable model and its predictor variables. We show how this correlation can be derived from the parameters of non-linear probability models, develop tests for the statistical significance of the derived correlation, and illustrate its usefulness in two applications. Under......Although the parameters of logit and probit and other non-linear probability models are often explained and interpreted in relation to the regression coefficients of an underlying linear latent variable model, we argue that they may also be usefully interpreted in terms of the correlations between...... certain circumstances, which we explain, the derived correlation provides a way of overcoming the problems inherent in cross-sample comparisons of the parameters of non-linear probability models....

  7. Prediction of uranium and technetium sorption during titration of contaminated acidic groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Fan, E-mail: zhangfan@itpcas.ac.cn [Institute of Tibetan Plateau Research, Chinese Academy of Sciences, 18 Shuangqing Road, P.O. Box 2871, Beijing 100085 (China); Parker, Jack C. [Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Brooks, Scott C.; Watson, David B. [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 (United States); Jardine, Philip M. [Biosystems Engineering and Soil Science Department, University of Tennessee, Knoxville, TN 37996 (United States); Gu, Baohua [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6038 (United States)

    2010-06-15

    This study investigates uranium and technetium sorption onto aluminum and iron hydroxides during titration of acidic groundwater. The contaminated groundwater exhibits oxic conditions with high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U, Tc, and various metal cations. More than 90% of U and Tc was removed from the aqueous phase as Al and Fe precipitated above pH 5.5, but was partially resolublized at higher pH values. An equilibrium hydrolysis and precipitation reaction model adequately described variations in aqueous concentrations of metal cations. An anion exchange reaction model was incorporated to simulate sulfate, U and Tc sorption onto variably charged (pH-dependent) Al and Fe hydroxides. Modeling results indicate that competitive sorption/desorption on mixed mineral phases needs to be considered to adequately predict U and Tc mobility. The model could be useful for future studies of the speciation of U, Tc and co-existing ions during pre- and post-groundwater treatment practices.

  8. Sorption of diclofenac and naproxen onto MWCNT in model wastewater treated by H2O2 and/or UV.

    Science.gov (United States)

    Czech, Bożena; Oleszczuk, Patryk

    2016-04-01

    The application of oxidation processes such as UV and/or H2O2 will change the physicochemical properties of carbon nanotubes (CNT). It may affect the sorption affinity of CNT to different contaminants and then affect their fate in the environment. In the present study the adsorption of two very common used pharmaceuticals (diclofenac and naproxen) onto CNT treated by UV, H2O2 or UV/H2O2 was investigated. Four different adsorption models (Freundlich, Langmuir, Temkin, Dubinin-Radushkevich) were tested. The best fitting of experimental data was observed for Freundlich or Langmuir model. The significant relationships between Q calculated from Langmuir model with O% and dispersity were observed. Kinetics of diclofenac and naproxen followed mainly pseudo-second order indicating for chemisorption limiting step of adsorption. The data showed that the mechanism of sorption was physical or chemical depending on the type of CNT modification. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Experimental study of Pb (II) solution sorption behavior onto Coffee Husk Bioactivated Carbon

    Science.gov (United States)

    Fona, Z.; Habibah, U.

    2018-04-01

    Coffee husk which is abundantly produced in the coffee plantations is potential to be a challenging adsorbent. The fate of Pb (II) solution in the sorption mechanism onto the adsorbent has been investigated. This paper aimed to study the efficiency of Pb (II) aqueous solution removal using activated carbon from coffee husk (CAC). The sorption characteristics were using two isotherm models, Langmuir and Freundlich, were also reported. The coffee husk from local plantations in Middle Aceh was carbonized and sieved to 120/140 mesh. The charcoal was activated using hydrochloric acid before contacted with the different initial concentrations of Pb (II) solution. The remaining concentrations of the metal in the specified contact times were determined using Atomic Adsorption Spectrophotometer at 283.3 wavelength. The result showed that the equilibrium concentrations were obtained in about 30 minutes which depended on the initial concentration. The sorption mechanism followed Freundlich isotherm model where the adsorption constant and capacity were accordingly 1.353 and 1.195 mgg‑1. The iodine sorption was up to 1,053 mgg‑1. Based on the ash and moisture content, as well as iodine sorption, the activated carbon met the national standard.

  10. Generalized, Linear, and Mixed Models

    CERN Document Server

    McCulloch, Charles E; Neuhaus, John M

    2011-01-01

    An accessible and self-contained introduction to statistical models-now in a modernized new editionGeneralized, Linear, and Mixed Models, Second Edition provides an up-to-date treatment of the essential techniques for developing and applying a wide variety of statistical models. The book presents thorough and unified coverage of the theory behind generalized, linear, and mixed models and highlights their similarities and differences in various construction, application, and computational aspects.A clear introduction to the basic ideas of fixed effects models, random effects models, and mixed m

  11. Characterization of aqueous interactions of copper-doped phosphate-based glasses by vapour sorption.

    Science.gov (United States)

    Stähli, Christoph; Shah Mohammadi, Maziar; Waters, Kristian E; Nazhat, Showan N

    2014-07-01

    Owing to their adjustable dissolution properties, phosphate-based glasses (PGs) are promising materials for the controlled release of bioinorganics, such as copper ions. This study describes a vapour sorption method that allowed for the investigation of the kinetics and mechanisms of aqueous interactions of PGs of the formulation 50P2O5-30CaO-(20-x)Na2O-xCuO (x=0, 1, 5 and 10mol.%). Initial characterization was performed using (31)P magic angle spinning nuclear magnetic resonance and attenuated total reflectance-Fourier transform infrared spectroscopy. Increasing CuO content resulted in chemical shifts of the predominant Q(2) NMR peak and of the (POP)as and (PO(-)) Fourier transform infrared absorptions, owing to the higher strength of the POCu bond compared to PONa. Vapour sorption and desorption were gravimetrically measured in PG powders exposed to variable relative humidity (RH). Sorption was negligible below 70% RH and increased exponentially with RH from 70 to 90%, where it exhibited a negative correlation with CuO content. Vapour sorption in 0% and 1% CuO glasses resulted in phosphate chain hydration and hydrolysis, as evidenced by protonated Q(0)(1H) and Q(1)(1H) species. Dissolution rates in deionized water showed a linear correlation (R(2)>0.99) with vapour sorption. Furthermore, cation release rates could be predicted based on dissolution rates and PG composition. The release of orthophosphate and short polyphosphate species corroborates the action of hydrolysis and was correlated with pH changes. In conclusion, the agreement between vapour sorption and routine characterization techniques in water demonstrates the potential of this method for the study of PG aqueous reactions. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. Sorption of radon-222 to natural sediments

    International Nuclear Information System (INIS)

    Wong, C.S.; Chin, Y.P.; Gschwend, P.M.

    1992-01-01

    The sorption of radon to sediments was investigated, since this may affect the use of porewater radon profiles for estimating bed irrigation rates. Batch experiments showed that radon has an organic-carbon-normalized sediment-water partition coefficient (K oc , L kg oc -1 ) of 21.1 ± 2.9 for a Boston Harbor sediment, 25.3 ± 2.1 for a Charles River sediment, and 22.4 ± 2.6 for a Buzzards Bay sediment. These values are in close agreement with predictions using radon's octanol-water partition coefficient (K ow ), which was measured to be 32.4 ± 1.5. Temperature and ionic strength effects on K oc were estimated to be small. Given rapid sorption kinetics, the authors suggest that slurry stripping techniques used by many investigators to measure 222 Rn in sediment samples collect both sorbed and dissolved radon. Sorption effects were included in a transport model to obtain revised estimates of irrigation rates from existing literature profiles. Irrigation rates had to be increased over previously reported values in proportion to the sediment organic matter content

  13. Multivariate generalized linear mixed models using R

    CERN Document Server

    Berridge, Damon Mark

    2011-01-01

    Multivariate Generalized Linear Mixed Models Using R presents robust and methodologically sound models for analyzing large and complex data sets, enabling readers to answer increasingly complex research questions. The book applies the principles of modeling to longitudinal data from panel and related studies via the Sabre software package in R. A Unified Framework for a Broad Class of Models The authors first discuss members of the family of generalized linear models, gradually adding complexity to the modeling framework by incorporating random effects. After reviewing the generalized linear model notation, they illustrate a range of random effects models, including three-level, multivariate, endpoint, event history, and state dependence models. They estimate the multivariate generalized linear mixed models (MGLMMs) using either standard or adaptive Gaussian quadrature. The authors also compare two-level fixed and random effects linear models. The appendices contain additional information on quadrature, model...

  14. Investigation of strontium and uranium sorption onto zirconium-antimony oxide/polyacrylonitrile (Zr-Sb oxide/PAN) composite using experimental design

    Energy Technology Data Exchange (ETDEWEB)

    Cakir, Pelin; Inan, Suleyman, E-mail: suleyman.inan@ege.edu.tr; Altas, Yuksel

    2014-04-01

    Highlights: • We model Sr{sup 2+} and UO{sub 2}{sup 2+} sorption onto Zr-Sb oxide/PAN composite. • Central composite design was separately employed for Sr{sup 2+} and UO{sub 2}{sup 2+} sorption. • The model F values indicate that both models are statistically significant. • All of the single factors were determined as significant for the sorption of Sr{sup 2+} and UO{sub 2}{sup 2+}. • Zr-Sb oxide/PAN can be used effectively for Sr{sup 2+} and UO{sub 2}{sup 2+} removal from acidic solutions. - Abstract: A study on the sorption of strontium (Sr{sup 2+}) and uranium (UO{sub 2}{sup 2+}) onto zirconium-antimony oxide/PAN (Zr-Sb oxide/PAN) composite was conducted. The zirconium-antimony oxide was synthesized and was then turned into composite spheres by mixing it with polyacrylonitrile (PAN). The single and combined effects of independent variables such as initial pH, temperature, initial ion concentration and contact time on the sorption of Sr{sup 2+} and UO{sub 2}{sup 2+} were separately analyzed using response surface methodology (RSM). Central composite design (CCD) was separately employed for Sr{sup 2+} and UO{sub 2}{sup 2+} sorption. Analysis of variance (ANOVA) revealed that all of the single effects found statistically significant on the sorption of Sr{sup 2+} and UO{sub 2}{sup 2+}. Probability F-values (F = 2.45 × 10{sup −08} and F = 9.63 × 10{sup −12} for Sr{sup 2+} and UO{sub 2}{sup 2+}, respectively) and correlation coefficients (R{sup 2} = 0.96 for Sr{sup 2+} and R{sup 2} = 0.98 for UO{sub 2}{sup 2+}) indicate that both models fit the experimental data well. At optimum sorption conditions Sr{sup 2+} and UO{sub 2}{sup 2+} sorption capacities of the composite were found as 39.78 and 60.66 mg/g, respectively. Sorption isotherm data pointed out that Langmuir model is more suitable for the Sr{sup 2+} sorption, whereas the sorption of UO{sub 2}{sup 2+} was correlated well with the Langmuir and Freundlich models. Thermodynamic parameters such as

  15. Modeling patterns in data using linear and related models

    International Nuclear Information System (INIS)

    Engelhardt, M.E.

    1996-06-01

    This report considers the use of linear models for analyzing data related to reliability and safety issues of the type usually associated with nuclear power plants. The report discusses some of the general results of linear regression analysis, such as the model assumptions and properties of the estimators of the parameters. The results are motivated with examples of operational data. Results about the important case of a linear regression model with one covariate are covered in detail. This case includes analysis of time trends. The analysis is applied with two different sets of time trend data. Diagnostic procedures and tests for the adequacy of the model are discussed. Some related methods such as weighted regression and nonlinear models are also considered. A discussion of the general linear model is also included. Appendix A gives some basic SAS programs and outputs for some of the analyses discussed in the body of the report. Appendix B is a review of some of the matrix theoretic results which are useful in the development of linear models

  16. Sorption of chlorophenols from aqueous solution by granular activated carbon, filter coal, pine and hardwood.

    Science.gov (United States)

    Hossain, G S M; McLaughlan, R G

    2012-09-01

    Wood and coal, as low-cost sorbents, have been evaluated as an alternative to commercial granular activated carbon (GAC) for chlorophenol removal. Kinetic experiments indicated that filter coal had a significantly lower rate of uptake (approximately 10% of final uptake was achieved after three hours) than the other sorbents, owing to intra-particle diffusion limitations. The data fitted a pseudo-second-order model. Sorption capacity data showed that GAC had a high sorption capacity (294-467 mg g(-1)) compared with other sorbents (3.2-7.5 mg(g-1)). However, wood and coal had a greater sorption capacity per unit surface area than GAC. Sorption equilibrium data was best predicted using a Freundlich adsorption model. The sorption capacity for all sorbents was 2-chlorophenol coal than the other sorbents. The results showed that pine, hardwood and filter coal can be used as sorbent materials for the removal of chlorophenol from water; however, kinetic considerations may limit the application of filter coal.

  17. INTRAVAL Finnsjoen Test - modelling results for some tracer experiments

    International Nuclear Information System (INIS)

    Jakob, A.; Hadermann, J.

    1994-09-01

    This report presents the results within Phase II of the INTRAVAL study. Migration experiments performed at the Finnsjoen test site were investigated. The study was done to gain an improved understanding of not only the mechanisms of tracer transport, but also the accuracy and limitations of the model used. The model is based on the concept of a dual porosity medium, taking into account one dimensional advection, longitudinal dispersion, sorption onto the fracture surfaces, diffusion into connected pores of the matrix rock, and sorption onto matrix surfaces. The number of independent water carrying zones, represented either as planar fractures or tubelike veins, may be greater than one, and the sorption processes are described either by linear or non-linear Freundlich isotherms assuming instantaneous sorption equilibrium. The diffusion of the tracer out of the water-carrying zones into connected pore space of the adjacent rock is calculated perpendicular to the direction of the advective/dispersive flow. In the analysis, the fluid flow parameters are calibrated by the measured breakthrough curves for the conservative tracer (iodide). Subsequent fits to the experimental data for the two sorbing tracers strontium and cesium then involve element dependent parameters providing information on the sorption processes and on its representation in the model. The methodology of fixing all parameters except those for sorption with breakthrough curves for non-sorbing tracers generally worked well. The investigation clearly demonstrates the necessity of taking into account pump flow rate variations at both boundaries. If this is not done, reliable conclusions on transport mechanisms or geometrical factors can not be achieved. A two flow path model reproduces the measured data much better than a single flow path concept. (author) figs., tabs., 26 refs

  18. Sorption of nitrate onto amine-crosslinked wheat straw: characteristics, column sorption and desorption properties.

    Science.gov (United States)

    Xing, Xu; Gao, Bao-Yu; Zhong, Qian-Qian; Yue, Qin-Yan; Li, Qian

    2011-02-15

    The nitrate removal process was evaluated using a fixed-bed column packed with amine-crosslinked wheat straw (AC-WS). Column sorption and desorption characteristics of nitrate were studied extensively. Solid-state (13)C NMR and zeta potential analysis validated the existence of crosslinked amine groups in AC-WS. Raman shift of the nitrate peaks suggested the electrostatic attraction between the adsorbed ions and positively charged amine sites. The column sorption capacity (q(ed)) of the AC-WS for nitrate was 87.27 mg g(-1) in comparison with the raw WS of 0.57 mg g(-1). Nitrate sorption in column was affected by bed height, influent nitrate concentration, flow rate and pH, and of all these, influent pH demonstrated an essential effect on the performance of the column. In addition, desorption and dynamic elution tests were repeated for several cycles, with high desorption rate and slight losses in its initial column sorption capacity. Copyright © 2010 Elsevier B.V. All rights reserved.

  19. Limitations of sorption isotherms on modeling groundwater contaminant transport

    International Nuclear Information System (INIS)

    Silva, Eduardo Figueira da

    2007-01-01

    Design and safety assessment of radioactive waste repositories, as well as remediation of radionuclide contaminated groundwater require the development of models capable of accurately predicting trace element fate and transport. Adsorption of trace radionuclides onto soils and groundwater is an important mechanism controlling near- and far- field transport. Although surface complexation models (SCMs) can better describe the adsorption mechanisms of most radionuclides onto mineral surfaces by directly accounting for variability of system properties and mineral surface properties, isotherms are still used to model contaminant transport in groundwater, despite the much higher system dependence. The present work investigates differences between transport model results based on these two approaches for adsorption modeling. A finite element transport model is used for the isotherm model, whereas the computer program PHREEQC is used for the SCM approach. Both models are calibrated for a batch experiment, and one-dimensional transport is simulated using the calibrated parameters. At the lower injected concentrations there are large discrepancies between SCM and isotherm transport predictions, with the SCM presenting much longer tails on the breakthrough curves. Isotherms may also provide non-conservative results for time to breakthrough and for maximum concentration in a contamination plume. Isotherm models are shown not to be robust enough to predict transport behavior of some trace elements, thus discouraging their use. The results also illustrate the promise of the SCM modeling approach in safety assessment and environmental remediation applications, also suggesting that independent batch sorption measurements can be used, within the framework of the SCM, to produce a more versatile and realistic groundwater transport model for radionuclides which is capable of accounting more accurately for temporal and spatial variations in geochemical conditions. (author)

  20. Effect of glutamic acid on copper sorption onto kaolinite. Batch experiments and surface complexation modeling

    Energy Technology Data Exchange (ETDEWEB)

    Karimzadeh, Lotfallah; Barthen, Robert; Gruendig, Marion; Franke, Karsten; Lippmann-Pipke, Johanna [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Reactive Transport; Stockmann, Madlen [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

    2017-06-01

    In this work, we study the mobility behavior of Cu(II) under conditions related to an alternative, neutrophile biohydrometallurgical Cu(II) leaching approach. Sorption of copper onto kaolinite influenced by glutamic acid (Glu) was investigated in the presence of 0.01 M NaClO{sub 4} by means of binary and ternary batch adsorption measurements over a pH range of 4 to 9 and surface complexation modeling.

  1. Effect of glutamic acid on copper sorption onto kaolinite. Batch experiments and surface complexation modeling

    International Nuclear Information System (INIS)

    Karimzadeh, Lotfallah; Barthen, Robert; Gruendig, Marion; Franke, Karsten; Lippmann-Pipke, Johanna; Stockmann, Madlen

    2017-01-01

    In this work, we study the mobility behavior of Cu(II) under conditions related to an alternative, neutrophile biohydrometallurgical Cu(II) leaching approach. Sorption of copper onto kaolinite influenced by glutamic acid (Glu) was investigated in the presence of 0.01 M NaClO_4 by means of binary and ternary batch adsorption measurements over a pH range of 4 to 9 and surface complexation modeling.

  2. Parametric study of the sorption of Cs(I) and Sr(II) on mixture of bentonite and magnetite using SCM + IEXM

    International Nuclear Information System (INIS)

    Filipska, H.; Stamberg, K.

    2005-01-01

    Full text of publication follows: The behaviour and subsequent fate of released radionuclides in bentonite barrier surrounding the degraded canister is influenced mainly by sorption. We studied sorption processes in such system experimentally and we modelled and simulated them using surface-complexation (SCM) and ion exchange (IExM) models. Our experimental system consisted of: (1) synthetic granitic water with a given ionic strength (0.1 or 0.01 NaNO 3 ), (2) radionuclides studied (10 -6 mol/l CsCl or SrCl 2 .6H 2 O spiked with 137 Cs or 85 Sr), (3) bentonite pre-treated with the aim to remove carbonates, and magnetite as a representative of corrosion products of steel canister. The alkali-metric and acidimetric titrations under exclusion of CO 2 and the percentage of sorption as a function of pH under oxic conditions at room temperature for bentonite, magnetite and their mixtures under different conditions were determined. The resulting data were modelled and appropriate mathematical description was found: SCM non-electrostatic so called Chemical Model (CEM) for the description of sorption on edge sites and ion exchange model (IExM) for sorption on layer sites. Component Additivity Approach (CA) composed of weighted combination of models describing sorption on bentonite and magnetite was verified. In the course of evaluation procedures, the protonation constants, total concentrations of edge sites and layer sites, cation exchange constants and sorption constants for present Cs and Sr forms were obtained by fitting corresponding experimental data. Consequently, CEM+IExM models and the calculated model parameters were used for predictive (simulation) calculations and parametric study of the sorption of Cs(I) and Sr(II) on bentonite, magnetite and their mixtures. The parametric study covered the influence of pH, solid to liquid ratio, bentonite to magnetite ratio, initial concentrations of Cs and Sr, pCO 2 and ionic strength on the values of selectivity coefficients

  3. Isotherms and isosteric heat of sorption of two varieties of Peruvian quinoa

    OpenAIRE

    Pumacahua-Ramos, Augusto; Gomez Vieira, José Antonio; Telis- Romero, Javier; Villa-Vélez, Harvey Alexander; Lopes Filho, Jose Francisco

    2016-01-01

    The isosteric heats of sorption of two varieties of quinoa (Chenopodium quinoa Willd.) grain were determined by the static gravimetric method at four temperatures (40, 50, 60 and 70 °C) and in relative humidity environments provided by six saturated salt solutions. Six mathematical equations were used to model the experimental data:  GAB, Oswin, Henderson, Peleg, Smith and Halsey. The isosteric heat of sorption was determined using the parameters of the GAB model. All the equations were shown...

  4. Comparison of linear and non-linear models for predicting energy expenditure from raw accelerometer data.

    Science.gov (United States)

    Montoye, Alexander H K; Begum, Munni; Henning, Zachary; Pfeiffer, Karin A

    2017-02-01

    This study had three purposes, all related to evaluating energy expenditure (EE) prediction accuracy from body-worn accelerometers: (1) compare linear regression to linear mixed models, (2) compare linear models to artificial neural network models, and (3) compare accuracy of accelerometers placed on the hip, thigh, and wrists. Forty individuals performed 13 activities in a 90 min semi-structured, laboratory-based protocol. Participants wore accelerometers on the right hip, right thigh, and both wrists and a portable metabolic analyzer (EE criterion). Four EE prediction models were developed for each accelerometer: linear regression, linear mixed, and two ANN models. EE prediction accuracy was assessed using correlations, root mean square error (RMSE), and bias and was compared across models and accelerometers using repeated-measures analysis of variance. For all accelerometer placements, there were no significant differences for correlations or RMSE between linear regression and linear mixed models (correlations: r  =  0.71-0.88, RMSE: 1.11-1.61 METs; p  >  0.05). For the thigh-worn accelerometer, there were no differences in correlations or RMSE between linear and ANN models (ANN-correlations: r  =  0.89, RMSE: 1.07-1.08 METs. Linear models-correlations: r  =  0.88, RMSE: 1.10-1.11 METs; p  >  0.05). Conversely, one ANN had higher correlations and lower RMSE than both linear models for the hip (ANN-correlation: r  =  0.88, RMSE: 1.12 METs. Linear models-correlations: r  =  0.86, RMSE: 1.18-1.19 METs; p  linear models for the wrist-worn accelerometers (ANN-correlations: r  =  0.82-0.84, RMSE: 1.26-1.32 METs. Linear models-correlations: r  =  0.71-0.73, RMSE: 1.55-1.61 METs; p  models offer a significant improvement in EE prediction accuracy over linear models. Conversely, linear models showed similar EE prediction accuracy to machine learning models for hip- and thigh

  5. Kinetics and reversibility of micropollutant sorption in sludge.

    Science.gov (United States)

    Barret, Maialen; Carrère, Hélène; Patau, Mathieu; Patureau, Dominique

    2011-10-01

    The fate of micropollutants throughout wastewater treatment systems is highly dependent on their sorption interactions with sludge matter. In this study, both the sorption and desorption kinetics of polycyclic aromatic hydrocarbons (PAHs) in activated sludge were shown to be very rapid in comparison to biodegradation kinetics. It was concluded that PAH transfer does not limit their biodegradation and that their fate is governed by the sorption/desorption equilibrium state. The effect of contact time between sludge and PAHs was also investigated. It was shown that aging did not influence the sorption/desorption equilibrium although PAH losses during aging suggest that sequestration phenomena had occurred. This implies that for PAH sorption assessment within treatment processes there is no need to include a contact time dimension. As a consequence, thanks to an innovative approach taking into account sorption equilibria and sequestration, this work has demonstrated that studies in the literature which, in main, deal with micropollutant sorption in sewage sludge with only a short contact time can be extrapolated to real systems in which sorption, desorption and aging occur.

  6. Predicting Organic Cation Sorption Coefficients: Accounting for Competition from Sorbed Inorganic Cations Using a Simple Probe Molecule.

    Science.gov (United States)

    Jolin, William C; Goyetche, Reaha; Carter, Katherine; Medina, John; Vasudevan, Dharni; MacKay, Allison A

    2017-06-06

    With the increasing number of emerging contaminants that are cationic at environmentally relevant pH values, there is a need for robust predictive models of organic cation sorption coefficients (K d ). Current predictive models fail to account for the differences in the identity, abundance, and affinity of surface-associated inorganic exchange ions naturally present at negatively charged receptor sites on environmental solids. To better understand how organic cation sorption is influenced by surface-associated inorganic exchange ions, sorption coefficients of 10 organic cations (including eight pharmaceuticals and two simple probe organic amines) were determined for six homoionic forms of the aluminosilicate mineral, montmorillonite. Organic cation sorption coefficients exhibited consistent trends for all compounds across the various homoionic clays with sorption coefficients (K d ) decreasing as follows: K d Na + > K d NH 4 + ≥ K d K + > K d Ca 2+ ≥ K d Mg 2+ > K d Al 3+ . This trend for competition between organic cations and exchangeable inorganic cations is consistent with the inorganic cation selectivity sequence, determined for exchange between inorganic ions. Such consistent trends in competition between organic and inorganic cations suggested that a simple probe cation, such as phenyltrimethylammonium or benzylamine, could capture soil-to-soil variations in native inorganic cation identity and abundance for the prediction of organic cation sorption to soils and soil minerals. Indeed, sorption of two pharmaceutical compounds to 30 soils was better described by phenyltrimethylammonium sorption than by measures of benzylamine sorption, effective cation exchange capacity alone, or a model from the literature (Droge, S., and Goss, K. Environ. Sci. Technol. 2013, 47, 14224). A hybrid approach integrating structural scaling factors derived from this literature model of organic cation sorption, along with phenyltrimethylammonium K d values, allowed for

  7. Ammonium, Nitrate, and Phosphate Sorption to and Solute Leaching from Biochars Prepared from Corn Stover ( L.) and Oak Wood ( spp.).

    Science.gov (United States)

    Hollister, C Colin; Bisogni, James J; Lehmann, Johannes

    2013-01-01

    Biochar (BC) was evaluated for nitrogen (N) and phosphorus (P) removal from aqueous solution to quantify its nutrient pollution mitigation potential in agroecosystems. Sorption isotherms were prepared for solutions of ammonium (NH), nitrate (NO), and phosphate (PO-P) using BC of corn ( L.) and oak ( spp.) feedstock, each pyrolyzed at 350 and 550°C highest treatment temperature (HTT). Sorption experiments were performed on original BC as well as on BC that went through a water extraction pretreatment (denoted WX-BC). Ammonium sorption was observed for WX-Oak-BC and WX-Corn-BC, and Freundlich model linearization showed that a 200°C increase in HTT resulted in a 55% decrease in * values for WX-Oak-BC and a 69% decrease in * for WX-Corn-BC. Nitrate sorption was not observed for any BC. Removing metals by water extraction from WX-Oak-350 and WX-Oak-550 resulted in a 25 to 100% decrease in phosphate removal efficiency relative to original Oak-350 and Oak-550, respectively. No PO-P sorption was observed using any Corn-BC. Calcium (Ca) leached from BC produced at 550°C was 63 and 104% higher than from BC produced at 350°C for corn and oak, respectively. Leaching of P was two orders of magnitude lower in WX-Oak-BC than in WX-Corn-BC, concurrent with similar difference in magnesium (Mg). Nitrate and NH leaching from consecutive water extractions of all tested BCs was mostly below detection limits. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  8. Anaerobic degradation of linear alkylbenzene sulfonate

    DEFF Research Database (Denmark)

    Mogensen, Anders Skibsted; Haagensen, Frank; Ahring, Birgitte Kiær

    2003-01-01

    Linear alkylbenzene sulfonate (LAS) found in wastewater is removed in the wastewater treatment facilities by sorption and aerobic biodegradation. The anaerobic digestion of sewage sludge has not been shown to contribute to the removal. The concentration of LAS based on dry matter typically...... increases during anaerobic stabilization due to transformation of easily degradable organic matter. Hence, LAS is regarded as resistant to biodegradation under anaerobic conditions. We present data from a lab-scale semi-continuously stirred tank reactor (CSTR) spiked with linear dodecylbenzene sulfonate (C...

  9. Effect of Cosolutes on the Sorption of Phenanthrene onto Mineral Surface of River Sediments and Kaolinite

    Directory of Open Access Journals (Sweden)

    Yinghong Wu

    2014-01-01

    Full Text Available Sorption of phenanthrene onto the natural sediment with low organic carbon content (OC%, organic-free sediment, and kaolinite was investigated through isotherm experiments. Effects of cosolutes (pyrene, 4-n-nonyphenol (NP, and humic acid (HA on phenanthrene sorption were also studied by comparing apparent solid-water distribution coefficients (Kdapp of phenanthrene. Two addition sequences, including “cosolute added prior to phenanthrene” and “cosolute and phenanthrene added simultaneously,” were adopted. The Freundlich model fits phenanthrene sorption on all 3 sorbents well. The sorption coefficients on these sorbents were similar, suggesting that mineral surface plays an important role in the sorption of hydrophobic organic contaminants on low OC% sediments. Cosolutes could affect phenanthrene sorption on the sorbents, which depended on their properties, concentrations, and addition sequences. Pyrene inhibited phenanthrene sorption. Sorbed NP inhibited phenanthrene sorption at low levels and promoted sorption at high levels. Similar to NP, effect of HA on phenanthrene sorption onto the natural sediment depended on its concentrations, whereas, for the organic-free sediment and kaolinite, preloading of HA at high levels led to an enhancement in phenanthrene Kdapp while no obvious effect was observed at low HA levels; dissolved HA could inhibit phenanthrene sorption on the two sorbents.

  10. Determination of Chlorinated Solvent Sorption by Porous Material-Application to Trichloroethene Vapor on Cement Mortar.

    Science.gov (United States)

    Musielak, Marion; Brusseau, Mark L; Marcoux, Manuel; Morrison, Candice; Quintard, Michel

    2014-08-01

    Experiments have been performed to investigate the sorption of trichloroethene (TCE) vapor by concrete material or, more specifically, the cement mortar component. Gas-flow experiments were conducted using columns packed with small pieces of cement mortar obtained from the grinding of typical concrete material. Transport and retardation of TCE at high vapor concentrations (500 mg L -1 ) was compared to that of a non-reactive gas tracer (Sulfur Hexafluoride, SF6). The results show a large magnitude of retardation (retardation factor = 23) and sorption (sorption coefficient = 10.6 cm 3 g -1 ) for TCE, compared to negligible sorption for SF6. This magnitude of sorption obtained with pollutant vapor is much bigger than the one obtained for aqueous-flow experiments conducted for water-saturated systems. The considerable sorption exhibited for TCE under vapor-flow conditions is attributed to some combination of accumulation at the air-water interface and vapor-phase adsorption, both of which are anticipated to be significant for this system given the large surface area associated with the cement mortar. Transport of both SF6 and TCE was simulated successfully with a two-region physical non-equilibrium model, consistent with the dual-medium structure of the crushed cement mortar. This work emphasizes the importance of taking into account sorption phenomena when modeling transport of volatile organic compounds through concrete material, especially in regard to assessing vapor intrusion.

  11. Core seismic behaviour: linear and non-linear models

    International Nuclear Information System (INIS)

    Bernard, M.; Van Dorsselaere, M.; Gauvain, M.; Jenapierre-Gantenbein, M.

    1981-08-01

    The usual methodology for the core seismic behaviour analysis leads to a double complementary approach: to define a core model to be included in the reactor-block seismic response analysis, simple enough but representative of basic movements (diagrid or slab), to define a finer core model, with basic data issued from the first model. This paper presents the history of the different models of both kinds. The inert mass model (IMM) yielded a first rough diagrid movement. The direct linear model (DLM), without shocks and with sodium as an added mass, let to two different ones: DLM 1 with independent movements of the fuel and radial blanket subassemblies, and DLM 2 with a core combined movement. The non-linear (NLM) ''CORALIE'' uses the same basic modelization (Finite Element Beams) but accounts for shocks. It studies the response of a diameter on flats and takes into account the fluid coupling and the wrapper tube flexibility at the pad level. Damping consists of one modal part of 2% and one part due to shocks. Finally, ''CORALIE'' yields the time-history of the displacements and efforts on the supports, but damping (probably greater than 2%) and fluid-structures interaction are still to be precised. The validation experiments were performed on a RAPSODIE core mock-up on scale 1, in similitude of 1/3 as to SPX 1. The equivalent linear model (ELM) was developed for the SPX 1 reactor-block response analysis and a specified seismic level (SB or SM). It is composed of several oscillators fixed to the diagrid and yields the same maximum displacements and efforts than the NLM. The SPX 1 core seismic analysis with a diagrid input spectrum which corresponds to a 0,1 g group acceleration, has been carried out with these models: some aspects of these calculations are presented here

  12. Sorption of a branched nonylphenol isomer and perfluorooctanoic acid on geosorbents and carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengliang

    2011-10-13

    As metabolites of organic surfactants, both nonylphenol (NP) and perfluorooctanoic acid (PFOA) are toxic and ubiquitous in the environment. Their sorption on soils and sediments is of importance for their fate and transport in the environment. Especially in China, there is still a lack of consolidated knowledge on the sorption behavior of NP and PFOA on geosorbents such as Yangtze River sediments. Thus, the present thesis investigates the sorption of a branched NP isomer [4-(1-ethyl-1, 3-dimethylpentyl) phenol] (NP111) and PFOA on Yangtze River sediments and their model components, i.e. a clay mineral (illite), metal oxides (goethite and {delta}-Al{sub 2}O{sub 3}) and organic matter (isolated from Yangtze River sediments and commercial organic matter) by both batch and dialysis techniques. NP111 is the most environmentally relevant NP isomer and its fate in the environment is unknown. Because PFOA is weakly adsorbed on geosorbents, multi-walled carbon nanotubes (MWCNTs) were studied as promising adsorbents. One of the MWCNTs studied contained traces of metal catalyst on the outer surface. Sorption isotherms of NP111 and PFOA on the sediments and their model components were fitted well by the Freundlich model. Sorption of NP111 on the sediments depended largely on their organic carbon content, resulting in organic carbon-normalized sorption coefficient (K{sub OC}) values between 6.3 x 10{sup 3} and 1.1 x 10{sup 4} L kg{sup -1}. The sorption of NP111 on {delta}-Al{sub 2}O{sub 3} and illite was comparable to that on sediments, but significantly lower than that on goethite. In contrast, the sorption of PFOA on the sediments was significantly lower. The affinity of PFOA to goethite and {delta}-Al{sub 2}O{sub 3} was slightly higher than to the sediments, but it was negligible to natural organic matter and illite. The results suggest that the organic carbon content of the sediments plays a dominant role in the sorption of NP111, whereas goethite acts as a potential sink

  13. Reactive solute transport in streams: A surface complexation approach for trace metal sorption

    Science.gov (United States)

    Runkel, Robert L.; Kimball, Briant A.; McKnight, Diane M.; Bencala, Kenneth E.

    1999-01-01

    A model for trace metals that considers in-stream transport, metal oxide precipitation-dissolution, and pH-dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron- oxide-coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH-modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation-dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.

  14. Linear Logistic Test Modeling with R

    Science.gov (United States)

    Baghaei, Purya; Kubinger, Klaus D.

    2015-01-01

    The present paper gives a general introduction to the linear logistic test model (Fischer, 1973), an extension of the Rasch model with linear constraints on item parameters, along with eRm (an R package to estimate different types of Rasch models; Mair, Hatzinger, & Mair, 2014) functions to estimate the model and interpret its parameters. The…

  15. Sorption of Lead (Pb from Aqueous Solutions by Sepiolite and Bentonite Modified with Chitosan Biopolymers: Isotherms and Kinetics

    Directory of Open Access Journals (Sweden)

    Hamid Reza Rafiei

    2016-07-01

    Full Text Available In this study, sepiolite and bentonite clay minerals were modified with a natural chitosan biopolymer and the modified-clays were characterized using XRF, XRD, FTIR, SEM, and TOC analyses. The isothermal and kinetic parameters of lead (Pb sorption by both the minerals and the modified-minerals were determined in a batch mode under various conditions such as different contact times and initial concentrations of Pb. It was found that the Freundlich model described well the isotherm experimental data of Pb sorption by the sorbents. Modification with chitosan, however, decreased the Pb adsorption capacity of sepiolite from 83 to 27 mg g-1 and that of bentonite from 56 to 29 mg g-1. Kinetic results showed that more than 24 hours was required for Pb sorption by the natural clays to reach equilibrium, while the equilibrium time reduced to 16 and 4 hours for Pb sorption on chitosan-sepiolite and chitosan–bentonite, respectively. The pseudo-second-order model well described the time-dependent Pb sorption data by sepiolite, chitosan-sepiolite, and chitosan-bentonite, suggesting that chemical sorption is the rate-limiting step of Pb adsorption mechanism. The Pb sorption data by bentonite showed the best fit with Elovich model.

  16. Simultaneous sorption and catalytic oxidation of trivalent antimony by Canna indica derived biochars.

    Science.gov (United States)

    Cui, Xiaoqiang; Ni, Qijun; Lin, Qiang; Khan, Kiran Yasmin; Li, Tingqiang; Khan, Muhammad Bilal; He, Zhenli; Yang, Xiaoe

    2017-10-01

    The simultaneous sorption and oxidation of Sb(III) on biochars were investigated using batch experiments. The biochars were derived from Canna indica at different pyrolysis temperatures (300-600 °C, referred as CIB300-CIB600), and characterized by FTIR, BET, XRD, SEM-EDS, EPR and Boehm titration. The Sb(III) sorption data could be well fitted by both the Langmuir and Freundlich models, and the pseudo-second order model is best for describing the kinetic data. The maximum Sb(III) sorption capacity of CIB300 was 16.1 mg g -1 , which was greater than that of other biochars. Inner-sphere complexation with oxygen-containing functional groups and coordination with π electrons are the possible sorption mechanisms. It is worthwhile to note that 4.7-32.3% of Sb(III) was oxidized to Sb(V) after sorption equilibration, demonstrating the occurrence of Sb(III) oxidation during the sorption process. Further study of oxidation under anoxic condition confirmed the catalytic role of biochar for Sb(III) oxidation, and free radicals in biochars were crucial for electron transfer. CIB400 exhibited the highest catalytic oxidative ability for Sb(III), which could be ascribe to its reserve of more electroactive polyphenolic macromolecule and less electroinactive cellulose. These results imply that biochars have good potential as a green effective sorbent for remediation of Sb(III) contaminated water, and simultaneously reduce the toxicity of Sb(III) by catalytic oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Sorption of copper, zinc and cobalt by oat and oat products.

    Science.gov (United States)

    Górecka, Danuta; Stachowiak, Jadwiga

    2002-04-01

    We determined copper, zinc and cobalt sorption by oat and its products under variable pH conditions as well as the content of neutral dietary fiber (NDF) and its fractional composition. Adsorbents in a model sorption system were: oat, dehulled oat, oats bran and oats flakes. Three various buffers (pH 1.8, 6.6 and 8.7) were used as dispersing solutions. Results collected during this study indicate that copper, zinc and cobalt sorption is significantly affected by the type of cereal raw material. Zinc and copper ions are subjected to higher sorption than cobalt ions. Examined metal ions were subjected to high sorption under conditions corresponding to the duodenum environment (pH 8.7), regardless of the kind of adsorbent. A little lower sorption capacity is observed under conditions close to the neutral environment, while the lowest one is found in environment reflecting conditions of stomach juice (pH 1.8). Zinc ions are bound intensively by dehulled oat, while oats flakes bound mostly copper and cobalt, independently on environmental conditions. Contents of dietary fiber in oat, dehulled oat, oat bran and oat flakes were: 40.1, 19.3, 20.3 and 14.3%, respectively. The dominating fraction in all oat products was the fraction of hemicelluloses. The content of remaining fractions varies in dependence on the product.

  18. Explorative methods in linear models

    DEFF Research Database (Denmark)

    Høskuldsson, Agnar

    2004-01-01

    The author has developed the H-method of mathematical modeling that builds up the model by parts, where each part is optimized with respect to prediction. Besides providing with better predictions than traditional methods, these methods provide with graphic procedures for analyzing different feat...... features in data. These graphic methods extend the well-known methods and results of Principal Component Analysis to any linear model. Here the graphic procedures are applied to linear regression and Ridge Regression....

  19. Sparse Linear Identifiable Multivariate Modeling

    DEFF Research Database (Denmark)

    Henao, Ricardo; Winther, Ole

    2011-01-01

    and bench-marked on artificial and real biological data sets. SLIM is closest in spirit to LiNGAM (Shimizu et al., 2006), but differs substantially in inference, Bayesian network structure learning and model comparison. Experimentally, SLIM performs equally well or better than LiNGAM with comparable......In this paper we consider sparse and identifiable linear latent variable (factor) and linear Bayesian network models for parsimonious analysis of multivariate data. We propose a computationally efficient method for joint parameter and model inference, and model comparison. It consists of a fully...

  20. Sorption behavior of cesium onto bentonite colloid

    International Nuclear Information System (INIS)

    Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

    2004-01-01

    It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

  1. Investigation of solution chemistry effects on sorption behavior of radionuclide 64Cu(II) on illite

    International Nuclear Information System (INIS)

    Shitong Yang; Guodong Sheng; Zhiqiang Guo; Yubing Sun; Donglin Zhao

    2011-01-01

    In this work, a series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, coexisting electrolyte ions, humic substances and temperature on the sorption behavior of illite towards 64 Cu(II). The results indicated that 64 Cu(II) sorption on illite achieved equilibrium quickly. The pH- and ionic strength-dependent sorption suggested that 64 Cu(II) sorption on illite was dominated by ion exchange or outer-sphere surface complexation at pH 7. A positive effect of humic substances on 64 Cu(II) sorption was found at pH 6.5. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 64 Cu(II) at three different temperatures of 293, 313, and 333 K. The thermodynamic parameters (ΔH 0 , ΔS 0 , and ΔG 0 ) of 64 Cu(II) sorption on illite were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption of 64 Cu(II) on illite was endothermic and spontaneous. From the experimental results, it is possible to conclude that illite has good potentialities for cost-effective treatments of 64 Cu(II)-contaminated wastewaters. (author)

  2. Models of sorption and migration of radionuclides in geologic media

    International Nuclear Information System (INIS)

    Fukui, Masami

    1987-01-01

    Full understanding of the transportation of nuclides by groundwater is essential in designing an underground radioactive waste disposal site. What is the most important is to clarify in detail the process of sorption of nuclides by rock and soil. This report outlines various theories and experimental data that are currently available. In addition, studies made in various countries are reviewed and some problems are pointed out. First, a review is made of studies that deal with adsorption and behaviors of contaminants in natural barriers (rock, soil). Next, migration models that have been developed in studying migration processes in the field of chemical engineering or behaviors of agricultural chemicals in the field of soil physics are examined to see if they can be applied to investigations of the migration of radioactive contaminants in a porous medium. Finally, a review is made of basic underground migration models that are used in various countries in studying deep underground disposal of long-life radionuclides. Some laboratory experiments on TRU nuclides in rock are also outlined. (Nogami, K.)

  3. Sorption of Cs, Eu and U(VI) onto rock samples from Nizhnekansky massive

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, V.; Vlasova, I.; Kalmykov, S. [Lomonosov Moscow State University (Russian Federation); Kuzmenkova, N. [Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Science (Russian Federation); Petrov, V.; Poluektov, V. [Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences - IGEM RAS (Russian Federation)

    2014-07-01

    The accepted in Russia concept for high level wastes (HLW) and spent nuclear fuel (SNF) disposal is based on their isolation into the deep underground crystalline rock formations. The 'Eniseysky' area (Nizhnekansky massive) is supposed as the most perspective location for the future HLW and SNF repository. Core materials from different areas of Nizhnekasnsky massive have been studied in terms of petrographic and mineralogical characterization; definition of filtration, elastic, petro-physical and strength properties; estimation of hydrothermal-metasomatic transformation of rocks. We used both undisturbed sliced cores and crushed material for the sorption experiments. Preliminary results of uranium sorption show some significant differences between used rock samples from different depth in sorption rate and pH-dependence. In all cases maximum sorption (more than 90%) is reached in 2-3 weeks. The pH-dependence of sorbed uranium fraction has typical hump-shape: increase of sorption percentage with increasing pH values to 6, plateau (90-98 % of uranium sorbed), decrease of sorption percentage with increasing pH values from 8 due to U(VI) hydrolysis. In the case of cesium the sorption maximum is reached within 10-12 days and in the case of europium - about 5 days. All radionuclides sorbed preferentially onto dark minerals. Local distribution and preferential sorption of cesium, europium and uranium (VI) onto different minerals within the sample were studied by radiography, SEM-EDX, etc. These data accompanying with rock sample composition will allow the development of quantitative model for Cs, Eu and U(VI) sorption onto investigated rocks. Document available in abstract form only. (authors)

  4. Sorption of Emerging Organic Wastewater Contaminants to Four Soils

    Directory of Open Access Journals (Sweden)

    Sarah Roberts

    2014-04-01

    Full Text Available Conventional onsite wastewater treatment system design relies on a septic tank and soil treatment unit (STU for treatment of wastewater and integration of the final effluent into the environment. Organic water contaminants (OWCs, chemicals found in pharmaceutical drugs, detergents, surfactants, and other personal care and cleaning products, have been observed in septic tank effluent and the environment. Sorption of OWC mass to soil is a key mechanism in the removal and retardation of many of these chemicals in effluent as it travels through an STU. The primary purpose of this study was to investigate the relationship between the fraction of organic carbon of soil and the equilibrium sorption partitioning coefficient of a selected group of relevant and diverse OWCs. A secondary goal is to evaluate current methods of modeling the sorption of selected OWCs in soil. Five point Freundlich isotherms were constructed from equilibrium sorption batch tests for target OWCs with four different soils. For soils with organic carbon fraction between 0.021 and 0.054, Kd values were calculated between 60 and 185 for 4-nonylphenol, 75 to 260 for triclosan, 115 to 270 for bisphenol-A, 3 to 255 for 17β-estradiol, 40 to 55 for 17α-ethynylestradiol, and 28 to 70 for estrone. An empirically derived, direct relationship between foc and Kd may be a useful approach to estimating sorption for a soil based on organic carbon content.

  5. Equilibrium and kinetic studies of Pb(II, Cd(II and Zn(II sorption by Lagenaria vulgaris shell

    Directory of Open Access Journals (Sweden)

    Mitić-Stojanović Dragana-Linda

    2012-01-01

    Full Text Available The sorption of lead, cadmium and zinc ions from aqueous solution by Lagenaria vulgaris shell biosorbent (LVB in batch system was investigated. The effect of relevant parameters such as contact time, biosorbent dosage and initial metal ions concentration was evaluated. The Pb(II, Cd(II and Zn(II sorption equilibrium (when 98% of initial metal ions were sorbed was attained within 15, 20 and 25 min, respectively. The pseudo first, pseudo-second order, Chrastil’s and intra-particle diffusion models were used to describe the kinetic data. The experimental data fitted the pseudo-second order kinetic model and intra-particle diffusion model. Removal efficiency of lead(II, cadmium(II and zinc(II ions rapidly increased with increasing biosorbent dose from 0.5 to 8.0 g dm-3. Optimal biosorbent dose was set to 4.0 g dm-3. An increase in the initial metal concentration increases the sorption capacity. The sorption data of investigated metal ions are fitted to Langmuir, Freundlich and Temkin isotherm models. Langmuir model best fitted the equilibrium data (r2 > 0.99. Maximal sorption capacities of LVB for Pb(II, Cd(II and Zn(II at 25.0±0.5°C were 0.130, 0.103 and 0.098 mM g-1, respectively. The desorption experiments showed that the LVB could be reused for six cycles with a minimum loss of the initial sorption capacity.

  6. The one-dimensional transport code CHET2, taking into account nonlinear, element-specific equilibrium sorption

    International Nuclear Information System (INIS)

    Luehrmann, L.; Noseck, U.

    1996-03-01

    While the verification report on CHET1 primarily focused on aspects such as the correctness of algorithms with respect to the modeling of advection, dispersion and diffusion, the report in hand is intended to primarily deal with nonlinear sorption and numerical sorption modeling. Another aspect discussed is the correct treatment of decay within established radioactive decay chains. First, the physical fundamentals are explained of the processes determining the radionuclide transport in the cap rock, and hence are the basis of the program discussed. The numeric algorithms the CHET2 code is based are explained, showing the details of realisation and the function of the various defaults and corrections. The iterative coupling of transport and sorption computation is illustrated by means of a program flowchart. Furthermore, the actvities for verification of the program are explained, as well as qualitative effects of computations assuming concentration-dependent sorption. The computation of the decay within decay chains is verified, and application programming using nonlinear sorption isotherms as well as the entire process of transport calculations with CHET2 are shown. (orig./DG) [de

  7. Sorption of organic gases in residential bedrooms andbathrooms

    Energy Technology Data Exchange (ETDEWEB)

    Singer, B.C.; Hodgson, A.T.; Hotchi, T.; Ming, K.Y.; Sextro,R.G.; Wood, E.E.; Brown, N.J.

    2005-01-05

    Experiments were conducted to characterize organic gas sorption in residential bedrooms (n=4), bathrooms (n=2), and a furnished test chamber. Rooms were studied ''as-is'' with material surfaces and furnishings unaltered. Surface materials were characterized and areas quantified. Experiments included rapid volatilization of a volatile organic compound (VOC) mixture with the room closed and sealed for a 5-h Adsorb phase, followed by 30-min Flush and 2-h closed-room Desorb phases. The mixture included n-alkanes, aromatics, glycol ethers, 2-ethyl-1-hexanol, dichlorobenzene, and organophosphorus compounds. Measured gas-phase concentrations were fit to three variations of a mathematical model that considers sorption occurring at one surface sink and one potential embedded sink. The 2-parameter sink model tracked measurements for most compounds, but improved fits were obtained for some VOCs with a 3-parameter sink-diffusion or a 4-parameter two-sink model. Sorptive partitioning and initial adsorption rates increased with decreasing vapor pressure within each chemical class.

  8. Pressure impact of autoclave treatment on water sorption and pectin composition of flax cellulosic-fibres.

    Science.gov (United States)

    Alix, S; Colasse, L; Morvan, C; Lebrun, L; Marais, S

    2014-02-15

    The tensile properties of flax fibres might permit them to be used in composites as reinforcement in organic resin, as long as their mechanical properties are reproducible and their water sorption are reduced. In this study, to minimise the variability of mechanical properties, several samples of flax fibres were blended as a non-woven fabric. In order to reduce the water absorption of this non-woven technical fibres, an autoclave treatment was performed which was expected to remove the pectins and then to reduce the water sorption on their negative charges. The impact of autoclave pressure (0.5, 1 and 2 bars) on water sorption was investigated by using a gravimetric static equilibrium method. The Park model based on the three sorption modes: Langmuir, Henry's law and clustering, was successfully used to simulate the experimental sorption data. The lowest pressure treatments impacted only the Langmuir contribution while the 2 bar autoclave-treatment positively impacted the water resistance in the core of fibres by reducing Henry's absorption rate. This was shown to be related to the chemical modifications at the surface and in the core of fibres. A schematic model is presented relating the water sorption and the pectic composition of the fabric. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Latent log-linear models for handwritten digit classification.

    Science.gov (United States)

    Deselaers, Thomas; Gass, Tobias; Heigold, Georg; Ney, Hermann

    2012-06-01

    We present latent log-linear models, an extension of log-linear models incorporating latent variables, and we propose two applications thereof: log-linear mixture models and image deformation-aware log-linear models. The resulting models are fully discriminative, can be trained efficiently, and the model complexity can be controlled. Log-linear mixture models offer additional flexibility within the log-linear modeling framework. Unlike previous approaches, the image deformation-aware model directly considers image deformations and allows for a discriminative training of the deformation parameters. Both are trained using alternating optimization. For certain variants, convergence to a stationary point is guaranteed and, in practice, even variants without this guarantee converge and find models that perform well. We tune the methods on the USPS data set and evaluate on the MNIST data set, demonstrating the generalization capabilities of our proposed models. Our models, although using significantly fewer parameters, are able to obtain competitive results with models proposed in the literature.

  10. Sorption of uranyl species on zircon and zirconia

    International Nuclear Information System (INIS)

    Lomenech, C.; Drot, R.; Simoni, E.; Ehrhardt, J.J.; Mielczarski, J.

    2002-01-01

    The safety of a long-term storage of radioactive waste in deep geological repositories would be strongly affected by the migration properties of radionuclides through the different barriers to the surface of the earth. Since the main process involved in the retention of radioactive ions is their sorption at the water/ mineral interface, a quantitative description of the sorption reactions is needed. Macroscopic data have for a long time been the only source of information used to propose a modelling of sorption equilibria, although they bring no direct information on the nature of the sorbed species; a microscopic structural investigation of the surface complexes is difficult indeed, because of the small amount of matter sorbed. Thus, in this study, parallel to the macroscopic measurements, different complementary spectroscopic techniques have been used in order to determine the nature of the surface species. As the final purpose of such a study is the simulation of the experimental retention data, the precise structural identification of the sorption equilibria will then be very useful to constrain the data simulation code. In this work, we present the results of both macroscopic and microscopic studies of the sorption of uranyl species on zircon and zirconia. The first part of our macroscopic approach was the surface characterisation of the non-sorbed materials by the determination of the specific areas, of the pH of the isoelectric points, and of the sorption site numbers, while the second part aimed at obtaining the sorption isotherms (percentage of sorption versus pH), which was performed using alpha spectrometry, for different uranyl concentrations, media (NaClO 4 or KNO 3 ) and ionic strengths. The spectroscopic identification of the different surface complexes and sorption sites has been carried out using four different spectroscopies. Whereas tune-resolved laser spectro-fluorimetry gave a direct answer concerning the number of surface species (only for a

  11. Iodine sorption by microwave irradiated hydrotalcites

    Energy Technology Data Exchange (ETDEWEB)

    Paredes, S.P. [Universidad Autonoma de Puebla, Facultad de Ciencias Quimicas, C.P. 72570, Puebla, Pue (Mexico); Instituto Politecnico Nacional, ESIQIE, C.P. 07738, Mexico, D.F. (Mexico); Fetter, G. [Universidad Autonoma de Puebla, Facultad de Ciencias Quimicas, C.P. 72570, Puebla, Pue (Mexico)]. E-mail: geolarfetter@yahoo.com.mx; Bosch, P. [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, C.P. 04510, Mexico, D.F. (Mexico); Bulbulian, S. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, C.P. 11801, Mexico, D.F. (Mexico)

    2006-12-15

    Mg-Al hydrotalcite-like compounds (HT) were prepared by the microwave method on the one hand with ethoxide-acetylacetonate and on the other with acetylacetonate as precursors. They presented a maximum sorption capacity of 2.179 and 1.517 meq of {sup 131}I{sup -}/g of hydrotalcite respectively. When the hydrotalcites were calcined and rehydrated in a {sup 131}I{sup -} solution, iodine sorption decreased in both samples to 1.515 and 1.446, respectively. The corresponding value for nitrated hydrotalcite which was prepared by the conventional method for comparison purposes, was 0.570. The radionuclide content in hydrotalcites was determined by {gamma}-spectrometry. {sup 131}I{sup -} sorption is dependent on two main parameters: one is the type of the interlayer organic material and the second the surface area. It was found that hydrotalcites prepared with ethoxide-acetylacetonate were better sorbents for {sup 131}I{sup -} than those with acetylacetonate. Still, if the specific surface area increased, {sup 131}I{sup -}sorption increased as well; nitrated HT resulted in low specific surface area and a low sorption capacity. It is, therefore, concluded that organic residues present in the samples prepared by the microwave method favor the sorption of radioactive anions, in particular {sup 131}I{sup -} if compared with nitrated and/or carbonate interlayered hydrotalcites.

  12. Equivalent linear damping characterization in linear and nonlinear force-stiffness muscle models.

    Science.gov (United States)

    Ovesy, Marzieh; Nazari, Mohammad Ali; Mahdavian, Mohammad

    2016-02-01

    In the current research, the muscle equivalent linear damping coefficient which is introduced as the force-velocity relation in a muscle model and the corresponding time constant are investigated. In order to reach this goal, a 1D skeletal muscle model was used. Two characterizations of this model using a linear force-stiffness relationship (Hill-type model) and a nonlinear one have been implemented. The OpenSim platform was used for verification of the model. The isometric activation has been used for the simulation. The equivalent linear damping and the time constant of each model were extracted by using the results obtained from the simulation. The results provide a better insight into the characteristics of each model. It is found that the nonlinear models had a response rate closer to the reality compared to the Hill-type models.

  13. Dynamic design of gas sorption J-T refrigerator

    International Nuclear Information System (INIS)

    Chan, C.K.

    1986-01-01

    A long-life Joule-Thomson refrigerator which is heat powered, involves no sealing, and has few mechanical parts and is desirable for longterm sensor cooling in space. In the gas-sorption J-T refrigerator, cooling is achieved by gas sorption (either adsorption or absorption) processes. Currently, a modular, single-stage refrigerator is being designed and built to be operated at 20 K. The design was analyzed using a dynamic model, which is described here. The model includes the kinetics of the compressors and the heat switches, the heat transfer of the pre-coolers and the heat exchangers, the on/off ratio of the check valves, and the impedance of the J-T valve. The cooling power, the cycle time, and the operating conditions were obtained in terms of the power input, the heat sink temperature, and the J-T impedance

  14. Dynamic design of gas sorption J-T refrigerator

    Science.gov (United States)

    Chan, C. K.

    1986-01-01

    A long-life Joule-Thomson refrigerator which is heat powered, involves no sealing, and has few mechanical parts is desirable for long-term sensor cooling in space. In the gas-sorption J-T refrigerator, cooling is achieved by gas sorption (either adsorption or absorption) processes. Currently, a modular, single-stage refrigerator is being designed and built to be operated at 20 K. The design was analyzed using a dynamic model, which is described here. The model includes the kinetics of the compressors and the heat switches, the heat transfer of the pre-coolers and the heat exchangers, the on/off ratio of the check valves, and the impedance of the J-T valve. The cooling power, the cycle time, and the operating conditions were obtained in terms of the power input, the heat sink temperature, and the J-T impedance.

  15. Applicability of microautoradiography to sorption studies

    International Nuclear Information System (INIS)

    Thompson, J.L.; Wolfsberg, K.

    1979-01-01

    The technique of microautoradiography was applied to the study of the sorption of uranium and americium on five rock types which exist at the Nevada Test Site. It was found that autoradiograms could be prepared in a few days which would allow the specific minerals responsible for sorption to be identified. Furthermore, the state of aggregation of the sorbed species was clearly indicated. It was concluded that microautoradiography was a useful adjunct to currently used methods for studying sorption of certain radionuclides

  16. Development of Web-based Software for Sorption Database

    International Nuclear Information System (INIS)

    Han, Byoung Sub; Lee, Jae Min; Seo, Min Seok; Kim, Dong Keon

    2009-08-01

    Sorption studies of radionuclides are important parts of research on radioactive waste disposal which is commonly faced in most countries where nuclear programs (power production, a variety of peaceful applications, and research) are implemented. The Sorption Database (DB) plays a very important role in the safety assessment of the radioactive waste disposal. The Sorption DB which is opened externally can be used as reference material of establishing a national policy by improving and changing the pre-developed Sorption program to be web-based. From the industrial point of view, if the Sorption DB is opened to the outside, the safety-related confidence can be achieved for nuclear industry. As the information of Sorption DB is opened, not only credibility can be provided to the administration, local governments and nearby residents, but also input of the collected information can be achieved by online. In addition, the reference material and external awareness/reliability about the domestic level of the Sorption DB management system and the current state can be achieved internationally. In order to provide the information of Sorption DB to users in more efficient way, the analysis and complement of management and search capability for the existing Sorption DB program have been performed and web-based management system has been built to provide services to users. In addition, by applying statistical techniques, it has been designed and implemented to display the accuracy and error of the information

  17. Cobalt sorption onto Savannah River Plant soils

    International Nuclear Information System (INIS)

    Hoeffner, S.L.

    1985-06-01

    A laboratory study of cobalt-60 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that cobalt sorption is most strongly a function of pH. Over a pH range of 2 to 9, the distribution coefficient ranged from 2 to more than 10,000 mL/g. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence cobalt sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect on cobalt sorption. Ferrous ion, added to groundwater to simulate the condition of water at the bottom of the waste trenches, accounts for part of the decrease in cobalt sorption observed with trench waters. 17 refs., 3 figs., 4 tabs

  18. Artificial Weathering of Biotite and Uranium Sorption Characteristics

    International Nuclear Information System (INIS)

    Lee, Seung Yeop; Baik, Min Hoon; Lee, Jae Kwang

    2009-01-01

    An experiment for uranium sorption onto fresh and weathered biotites was performed. After centrifugation, concentrations of uranium in the supernatants were analyzed using ICP-MS, and biotite samples were investigated using XRD and SEM. With powdered biotites (<3 mm in size), we have conducted uranium sorption experiments about fresh and weathered biotites to obtain uranium sorption amounts in various pH conditions. The uranium sorption was not high at a low pH (e.g., pH 3), but increased with increasing pH. There were lower uranium sorption by the weathered biotites than by the fresh ones, and the difference was much larger at higher pH (e.g., pH 11). The lower sorption values of uranium by the weathered biotites may be caused by a change of mineral surfaces and a chemical behavior of surrounding dissolved elements. It seems that the uranium-mineral interaction has been diminished, especially, in the weathered biotite by a destruction and dissolution of preferential sorption sites on the mineral surfaces and by the colloidal formation from dissolved elements.

  19. Field-scale predictions of soil contaminant sorption using visible–near infrared spectroscopy

    DEFF Research Database (Denmark)

    Paradelo Pérez, Marcos; Hermansen, Cecilie; Knadel, Maria

    2016-01-01

    . By means of the vis–NIR spectra we were able to predict phenanthrene (R2 = 0.95, RMSECV = 31 L kg−1) and glyphosate (R2 = 0.79, RMSECV = 45 L kg−1) sorption capacities. A model using vis–NIR spectra plus pH values improved the prediction of glyphosate sorption capacity (R2 = 0.88, RMSECV = 34 L kg−1......) and glyphosate (sorbed on mineral fractions). Forty-five bulk soil samples were collected from an agricultural field in Estrup, Denmark, in a 15 m × 15 m grid. Samples were air-dried, sieved to 2 mm and analysed for selected soil properties. Sorption coefficients were obtained from a batch equilibration...

  20. Effect of the cationic composition of sorption solution on the quantification of sorption-desorption parameters of heavy metals in soils

    International Nuclear Information System (INIS)

    Sastre, J.; Rauret, G.; Vidal, M.

    2006-01-01

    We obtained the sorption isotherms of Cd, Cu, Pb and Zn in clay, clay saline and organic soils. The distribution coefficients (K d ) were determined in 0.02 eq l -1 CaCl 2 and in a solution that simulated the soil solution cationic composition. The K d values greatly varied with the composition of the sorption solution and the initial metal concentration. The sorption experiments were complemented with the quantification of the extractable metal, to estimate the reversibility of metal sorption. The extraction yields depended on the metal-soil combination, and the initial metal concentration, showing no correlation with previous K d values. The effect of the solution composition in mobility predictions was estimated through a Retention Factor, defined as the ratio of the K d versus the extraction yield. Results showed that risk was over- or underestimated using the CaCl 2 medium in soils with a markedly different soil solution composition. - Sorption solution composition modifies metal sorption-desorption pattern in soils

  1. Sorption of trivalent lanthanides and actinides onto montmorillonite: Macroscopic, thermodynamic and structural evidence for ternary hydroxo and carbonato surface complexes on multiple sorption sites.

    Science.gov (United States)

    Fernandes, M Marques; Scheinost, A C; Baeyens, B

    2016-08-01

    The credibility of long-term safety assessments of radioactive waste repositories may be greatly enhanced by a molecular level understanding of the sorption processes onto individual minerals present in the near- and far-fields. In this study we couple macroscopic sorption experiments to surface complexation modelling and spectroscopic investigations, including extended X-ray absorption fine structure (EXAFS) and time-resolved laser fluorescence spectroscopies (TRLFS), to elucidate the uptake mechanism of trivalent lanthanides and actinides (Ln/An(III)) by montmorillonite in the absence and presence of dissolved carbonate. Based on the experimental sorption isotherms for the carbonate-free system, the previously developed 2 site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) model needed to be complemented with an additional surface complexation reaction onto weak sites. The fitting of sorption isotherms in the presence of carbonate required refinement of the previously published model by reducing the strong site capacity and by adding the formation of Ln/An(III)-carbonato complexes both on strong and weak sites. EXAFS spectra of selected Am samples and TRLFS spectra of selected Cm samples corroborate the model assumptions by showing the existence of different surface complexation sites and evidencing the formation of Ln/An(III) carbonate surface complexes. In the absence of carbonate and at low loadings, Ln/An(III) form strong inner-sphere complexes through binding to three Al(O,OH)6 octahedra, most likely by occupying vacant sites in the octahedral layers of montmorillonite, which are exposed on {010} and {110} edge faces. At higher loadings, Ln/An(III) binds to only one Al octahedron, forming a weaker, edge-sharing surface complex. In the presence of carbonate, we identified a ternary mono- or dicarbonato Ln/An(III) complex binding directly to one Al(O,OH)6 octahedron, revealing that type-A ternary complexes form with the one

  2. Sorption and release of organics by primary, anaerobic, and aerobic activated sludge mixed with raw municipal wastewater.

    Directory of Open Access Journals (Sweden)

    Oskar Modin

    Full Text Available New activated sludge processes that utilize sorption as a major mechanism for organics removal are being developed to maximize energy recovery from wastewater organics, or as enhanced primary treatment technologies. To model and optimize sorption-based activated sludge processes, further knowledge about sorption of organics onto sludge is needed. This study compared primary-, anaerobic-, and aerobic activated sludge as sorbents, determined sorption capacity and kinetics, and investigated some characteristics of the organics being sorbed. Batch sorption assays were carried out without aeration at a mixing velocity of 200 rpm. Only aerobic activated sludge showed net sorption of organics. Sorption of dissolved organics occurred by a near-instantaneous sorption event followed by a slower process that obeyed 1st order kinetics. Sorption of particulates also followed 1st order kinetics but there was no instantaneous sorption event; instead there was a release of particles upon mixing. The 5-min sorption capacity of activated sludge was 6.5±10.8 mg total organic carbon (TOC per g volatile suspend solids (VSS for particulate organics and 5.0±4.7 mgTOC/gVSS for dissolved organics. The observed instantaneous sorption appeared to be mainly due to organics larger than 20 kDa in size being sorbed, although molecules with a size of about 200 Da with strong UV absorbance at 215-230 nm were also rapidly removed.

  3. Fate of sulfonamide antibiotics in contact with activated sludge--sorption and biodegradation.

    Science.gov (United States)

    Yang, Sheng-Fu; Lin, Cheng-Fang; Wu, Chien-Ju; Ng, Kok-Kwang; Lin, Angela Yu-Chen; Hong, Pui-Kwan Andy

    2012-03-15

    The sorption and biodegradation of three sulfonamide antibiotics, namely sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfamonomethoxine (SMM), in an activated sludge system were investigated. Experiments were carried out by contacting 100 μg/L of each sulfonamide compound individually with 2.56 g/L of MLSS at 25±0.5 °C, pH 7.0, and dissolved oxygen of 3.0±0.1 mg/L in a batch reactor over different periods of 2 d and 14 d. All sulfonamides were removed completely over 11-13 d. Sorptive equilibrium was established well within the first few hours, followed by a lag period of 1-3 days before biodegradation was to deplete the antibiotic compounds linearly in the ensuing 10 days. Apparent zeroth-order rate constants were obtained by regression analysis of measured aqueous concentration vs. time profiles to a kinetic model accounting for sorption and biodegradation; they were 8.1, 7.9, and 7.7 μg/L/d for SDM, SMX, and SMM, respectively, at activated sludge concentration of 2.56 g/L. The measured kinetics implied that with typical hydraulic retention time (e.g. 6 h) provided by WWTP the removal of sulfonamide compounds from the wastewater during the activated sludge process would approximate 2 μg/L. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. Sorption of fluoride using chemically modified Moringa oleifera leaves

    Science.gov (United States)

    Dan, Shabnam; Chattree, Amit

    2018-05-01

    Contamination of drinking water due to fluoride is a severe health hazard problem. Excess of fluoride (> 1.5 mg/L) in drinking water is harmful to human health. Various treatment technologies for removing fluoride from groundwater have been investigated. The present study showed that the leaves of Moringa oleifera, a herbal plant is an effective adsorbent for the removal of fluoride from aqueous solution. Acid treated Moringa oleifera leaves powder showed good adsorption capacity than alkali treated Moringa oleifera leaves powder. Batch sorptive defluoridation was conducted under the variable experimental condition such as pH, contact time, adsorbent dose and initial fluoride ion concentration. Maximum defluoridation was achieved at pH 1. The percentage of fluoride removal increases with adsorbent dose. The equilibrium sorption data were fitted into Langmuir, Freundlich and Temkin isotherms. Of the three adsorption isotherms, the R 2 value of Langmuir isotherm model was the highest. The maximum monolayer coverage ( Q max) from Langmuir isotherm model was determined to be 1.1441 mg/g, the separation factor indicating a favorable sorption experiment is 0.035. It was also discovered that the adsorption did not conform to the Freundlich adsorption isotherm. The heat of sorption process was estimated from Temkin Isotherm model to be - 0.042 J/mol which vividly proved that the adsorption experiment followed a physical process.

  5. Analysis of three sets of SWIW tracer test data using a two-population complex fracture model for matrix diffusion and sorption

    International Nuclear Information System (INIS)

    Doughty, Christine; Chin-Fu Tsang

    2009-03-01

    This study has been undertaken to obtain a better understanding of the processes underlying retention of radionuclides in fractured rock by using different model conceptualisations when interpreting SWIW tests. In particular the aim is to infer the diffusion and sorption parameters from the SWIW test data by matching tracer breakthrough curves (BTC) with a complex fracture model. The model employs two populations for diffusion and sorption. One population represents the semi-infinite rock matrix and the other represents finite blocks that can become saturated, thereafter accepting no further diffusion or sorption. For the non-sorbing tracer uranine, both the finite and the semi-infinite populations play a distinct role in controlling BTC. For the sorbing tracers Cs and Rb the finite population does not saturate, but acts essentially semi-infinite, thus the BTC behaviour is comparable to that obtained for a model containing only a semi-infinite rock matrix. The ability to match BTC for both sorbing and non-sorbing tracers for these three different SWIW data sets demonstrates that the two-population complex fracture model may be useful to analyze SWIW tracer test data in general. One of the two populations should be the semi-infinite rock matrix and the other finite blocks that can saturate. The latter can represent either rock blocks within the fracture, a fracture skin zone or stagnation zones. Three representative SWIW tracer tests recently conducted by SKB have been analyzed with a complex fracture model employing two populations for diffusion and sorption, one population being the semi-infinite rock matrix and the other, finite blocks. The results show that by adjusting diffusion and sorption parameters of the model, a good match with field data is obtained for BTC of both conservative and non-conservative tracers simultaneously. For non-sorbing tracer uranine, both the finite and the semi-infinite populations play a distinct role in controlling BTC. At early

  6. Characterization of the sorption of uranium(VI) on different complexing resins

    Energy Technology Data Exchange (ETDEWEB)

    Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela [Dipartimento di Chimica Generale dell' Universita degli Studi di Pavia, Via Taramelli 12, 27100, Pavia (Italy)

    2003-08-01

    The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log{beta}{sub 110i}=-1.16, in more acidic solution, and ML{sub 2}with log {beta}{sub 120i}=-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML {sub 2}, in more acidic solution, with log {beta}{sub 120i}=-3.16. In the presence of the ligand EDTA, the complex ML {sub 2}(OH) {sub 2}was characterized with log {beta}{sub 12-2i}=-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

  7. Characterization of the sorption of uranium(VI) on different complexing resins

    International Nuclear Information System (INIS)

    Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela

    2003-01-01

    The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with logβ 110i =-1.16, in more acidic solution, and ML 2 with log β 120i =-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML 2 , in more acidic solution, with log β 120i =-3.16. In the presence of the ligand EDTA, the complex ML 2 (OH) 2 was characterized with log β 12-2i =-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

  8. From linear to generalized linear mixed models: A case study in repeated measures

    Science.gov (United States)

    Compared to traditional linear mixed models, generalized linear mixed models (GLMMs) can offer better correspondence between response variables and explanatory models, yielding more efficient estimates and tests in the analysis of data from designed experiments. Using proportion data from a designed...

  9. Sorption on inactive repository components

    International Nuclear Information System (INIS)

    Gardiner, M.P.; Smith, A.J.; Williams, S.J.

    1990-11-01

    The near-field of an intermediate level/low level radioactive waste repository will contain significant quantities of iron and steel, Magnox and Zircaloy. Their corrosion products may possess significant sorption capacity for radioelements. The sorption of americium and plutonium onto magnesium hydroxide, zirconium hydroxide, colloidal magnetite and colloidal haematite has been studied under conditions typical of the porewater of a cementitious near-field. R D values ≥ 10 5 m g -1 were measured for both actinides on the oxides and hydroxides. These values are at least as great as those measured on crushed 3:1 Blast Furnace Slag/Ordinary Portland cement. Competitive sorption experiments have shown that sorption onto the corrosion products does not take place in preference to that on the cement or the converse. Magnetite and haematite colloids are positively charged in cement-equilibrated water whilst zirconium hydroxide is negatively charged. Crushed cement was found to be positively charged. Simple experiments show that only a small proportion of haematite colloids is potentially mobile through a column of crushed cement. (author)

  10. Sorption on inactive repository components

    International Nuclear Information System (INIS)

    Gardiner, M.P.; Smith, A.J.; Williams, S.J.

    1990-07-01

    The near-field of an intermediate level/low level radioactive waste repository will contain significant quantities of iron and steel, Magnox and Zircaloy. Their corrosion products may possess significant sorption capacity for radioelements. The sorption of americium and plutonium onto magnesium hydroxide, zirconium hydroxide, colloidal magnetite and colloidal haematite has been studied under conditions typical of the porewater of a cementitious near-field. R D values ≥ 10 5 ml g -1 were measured for both actinides on the oxides and hydroxides. These values are at least as great at those measured on crushed 3:1 Blast Furnace Slag/Ordinary Portland Cement. Competitive sorption experiments have shown that sorption onto the corrosion products does not take place in preference to that on the cement or the converse. Magnetite and haematite colloids are positively charged in cement-equilibrated water whilst zirconium hydroxide is negatively charged. Crushed cement was found to be positively charged. Simple experiments show that only a small proportion of haematite colloids is potentially mobile through a column of crushed cement. (author)

  11. Extended Linear Models with Gaussian Priors

    DEFF Research Database (Denmark)

    Quinonero, Joaquin

    2002-01-01

    In extended linear models the input space is projected onto a feature space by means of an arbitrary non-linear transformation. A linear model is then applied to the feature space to construct the model output. The dimension of the feature space can be very large, or even infinite, giving the model...... a very big flexibility. Support Vector Machines (SVM's) and Gaussian processes are two examples of such models. In this technical report I present a model in which the dimension of the feature space remains finite, and where a Bayesian approach is used to train the model with Gaussian priors...... on the parameters. The Relevance Vector Machine, introduced by Tipping, is a particular case of such a model. I give the detailed derivations of the expectation-maximisation (EM) algorithm used in the training. These derivations are not found in the literature, and might be helpful for newcomers....

  12. Linear mixed models for longitudinal data

    CERN Document Server

    Molenberghs, Geert

    2000-01-01

    This paperback edition is a reprint of the 2000 edition. This book provides a comprehensive treatment of linear mixed models for continuous longitudinal data. Next to model formulation, this edition puts major emphasis on exploratory data analysis for all aspects of the model, such as the marginal model, subject-specific profiles, and residual covariance structure. Further, model diagnostics and missing data receive extensive treatment. Sensitivity analysis for incomplete data is given a prominent place. Several variations to the conventional linear mixed model are discussed (a heterogeity model, conditional linear mixed models). This book will be of interest to applied statisticians and biomedical researchers in industry, public health organizations, contract research organizations, and academia. The book is explanatory rather than mathematically rigorous. Most analyses were done with the MIXED procedure of the SAS software package, and many of its features are clearly elucidated. However, some other commerc...

  13. Strontium sorption on Savannah River Plant soils

    International Nuclear Information System (INIS)

    Hoeffner, S.L.

    1984-12-01

    A laboratory study of strontium-85 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that strontium sorption is most strongly a function of pH. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence strontium sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect. Ferrous ion, added to groundwater to simulate the conditions of water at the bottom of waste trenches, did not account for low strontium sorption observed with some trench waters

  14. Study of the radium sorption/desorption on goethite

    International Nuclear Information System (INIS)

    Bassot, S.; Stammose, D.; Mallet, C.; Lefebvre, C.; Ferreux, J.-M.

    2000-01-01

    The oxi-hydroxides, present at trace level in uranium mill tailings, are responsible of about 70% of the 226 radium sorption, half being fixed on crystallized forms. This radionuclide (half time=1622y), present at high level (50 to 100kBq.kg -1 ), can be released in groundwater, involving a possible contamination of the food chain (actual concentration limit=0.37Bq.1 -1 ). So, it is very important to point out the mechanisms of the radium sorption/desorption on crystallized oxi-hydroxides as a function of chemical conditions of the system. The radium sorption on synthetic goethite α-FeOOH has been studied as a function of contact time, initial radium activity, pH, sodium and calcium concentrations. The results show that, after one hour of contact time (necessary to reach equilibrium), the radium sorption increases widely in a pH range 6-7. The increase of Na + concentration is without influence on the radium sorption, indicating the low interactions between sodium and surface sites. At the opposite, the presence of calcium in solution decreases widely the radium sorption, that indicates a competition between calcium and radium for the same kind of sorption sites of the oxi-hydroxide surface. The percentage of radium desorbed increases widely with time, from 1 to 120h and becomes constant at a time higher than 120h. This long equilibrium time for desorption in comparison with sorption one can be explain by a local evolution of the sorption sites of the solid, which become less accessible for the solution in contact. (author)

  15. Non-linear finite element modeling

    DEFF Research Database (Denmark)

    Mikkelsen, Lars Pilgaard

    The note is written for courses in "Non-linear finite element method". The note has been used by the author teaching non-linear finite element modeling at Civil Engineering at Aalborg University, Computational Mechanics at Aalborg University Esbjerg, Structural Engineering at the University...

  16. Sorption of citalopram, irbesartan and fexofenadine in soils: Estimation of sorption coefficients from soil properties.

    Science.gov (United States)

    Klement, Aleš; Kodešová, Radka; Bauerová, Martina; Golovko, Oksana; Kočárek, Martin; Fér, Miroslav; Koba, Olga; Nikodem, Antonín; Grabic, Roman

    2018-03-01

    The sorption of 3 pharmaceuticals, which may exist in 4 different forms depending on the solution pH (irbesartan in cationic, neutral and anionic, fexofenadine in cationic, zwitter-ionic and anionic, and citalopram cationic and neutral), in seven different soils was studied. The measured sorption isotherms were described by Freundlich equations, and the sorption coefficients, K F (for the fixed n exponent for each compound), were related to the soil properties to derive relationships for estimating the sorption coefficients from the soil properties (i.e., pedotransfer rules). The largest sorption was obtained for citalopram (average K F value for n = 1 was 1838 cm 3  g -1 ) followed by fexofenadine (K F  = 35.1 cm 3/n μg 1-1/n g -1 , n = 1.19) and irbesartan (K F  = 3.96 cm 3/n μg 1-1/n g -1 , n = 1.10). The behavior of citalopram (CIT) in soils was different than the behaviors of irbesartan (IRB) and fexofenadine (FEX). Different trends were documented according to the correlation coefficients between the K F values for different compounds (R IRB,FEX  = 0.895, p-valuesoil properties in the pedotransfer functions. While the K F value for citalopram was positively related to base cation saturation (BCS) or sorption complex saturation (SCS) and negatively correlated to the organic carbon content (Cox), the K F values of irbesartan and fexofenadine were negatively related to BCS, SCS or the clay content and positively related to Cox. The best estimates were obtained by combining BCS and Cox for citalopram (R 2  = 93.4), SCS and Cox for irbesartan (R 2  = 96.3), and clay content and Cox for fexofenadine (R 2  = 82.9). Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Sorption of methylxanthines by different sorbents

    Science.gov (United States)

    Dmitrienko, S. G.; Andreeva, E. Yu.; Tolmacheva, V. V.; Terent'eva, E. A.

    2013-05-01

    Sorption of caffeine, theophylline, theobromine, diprophylline, and pentoxyphylline on different sorbents (supercross-linked polystyrene, surface-modified copolymer of styrene and divinylbenzene Strata-X, and carbon nanomaterials Taunit and Diasorb-100-C16T) was studied in a static mode in an effort to find new sorbents suitable for sorption isolation and concentration of methylxanthines. The peculiarities of sorption of methylxanthines were explained in relation to the solution acidity, the nature of the sorbates and their concentration, the nature of the solvent, and the structural characteristics of the sorbents.

  18. Sorption isolation of strontium from seawater

    International Nuclear Information System (INIS)

    Avramenko, V.A.; Zheleznov, V.V.; Kaplun, E.V.; Sokol'nitskaya, T.A.; Yukhkam, A.A.

    2001-01-01

    Sorption isolation of strontium from seawater is considered and prospects of use of selective adsorbents for purification of seawater or liquid radioactive wastes mixed with seawater from 90 Sr are discussed. Comparative analysis of sorptive properties of adsorbents of different nature is done. It is shown that sorption-reagent materials developed by authors can to afford effective separation of 90 Sr from seawater. Possible mechanism of strontium sorption by these adsorbents is considered. The prospect of their use for purification of liquid radioactive wastes from strontium is shown [ru

  19. Effects of nitrate, fulvate, phosphate, phthalate, salicylate and catechol on the sorption of uranyl onto SiO2. A comparative study

    International Nuclear Information System (INIS)

    Zhang Hongxia; Wen Chuanxi; Tao Zuyi; Wu Wangsuo

    2011-01-01

    We have performed a large number of batch sorption experiments of uranyl onto SiO 2 and examined the effects of nitrate or ionic strength, phosphate, fulvic acid(FA), phthalic acid (PH), salicylic acid (SA), and catechol (CA) on the uranyl sorption onto SiO 2 . Three sorption edges and three sorption isotherms at ionic strengths 0.05, 0.1, and 0.5 mol/L KNO 3 were used to investigate the effect of ionic strength or nitrate on the sorption and the Langmuir, Freundlich, and Dubinin-Radushkevich models are used to simulate the sorption isotherms, respectively. Five sorption edges in the presence of phosphate, FA, PH, SA, and CA were compared with that in the absence of complexing ligand. The results suggest that the effect of complexation of uranyl with nitrate on the uranyl sorption can be negligible and the sorption can be described Freundlich and D-R model very well. The positive effect of phosphate on the uranyl sorption was found, though the extent of effect was decreased with increasing pH. The positive effect and the negative effect of FA on the uranyl sorption were found at low pH and high pH ranges, respectively. The sorption edge of uranyl sorption remained unaffected in the presence of PH in the pH 2-10. In the presence of SA, the no effect and the negative effect on the uranyl sorption were, respectively, found at low pH and high pH ranges. The negative effect of CA on the uranyl sorption was found in the pH 2-10. (author)

  20. Sorption of Uranium(VI and Thorium(IV by Jordanian Bentonite

    Directory of Open Access Journals (Sweden)

    Fawwaz I. Khalili

    2013-01-01

    Full Text Available Purification of raw bentonite was done to remove quartz. This includes mixing the raw bentonite with water and then centrifuge it at 750 rpm; this process is repeated until white purified bentonite is obtained. XRD, XRF, FTIR, and SEM techniques will be used for the characterization of purified bentonite. The sorption behavior of purified Jordanian bentonite towards and Th4+ metal ions in aqueous solutions was studied by batch experiment as a function of pH, contact time, temperature, and column techniques at 25.0∘C and . The highest rate of metal ions uptake was observed after 18 h of shaking, and the uptake has increased with increasing pH and reached a maximum at . Bentonite has shown high metal ion uptake capacity toward uranium(VI than thorium(IV. Sorption data were evaluated according to the pseudo- second-order reaction kinetic. Sorption isotherms were studied at temperatures 25.0∘C, 35.0∘C, and 45.0∘C. The Langmuir, Freundlich, and Dubinin-Radushkevich (D-R sorption models equations were applied and the proper constants were derived. It was found that the sorption process is enthalpy driven for uranium(VI and thorium(IV. Recovery of uranium(VI and thorium(IV ions after sorption was carried out by treatment of the loaded bentonite with different concentrations of HNO3 1.0 M, 0.5 M, 0.1 M, and 0.01 M. The best percent recovery for uranium(VI and thorium(IV was obtained when 1.0 M HNO3 was used.

  1. Sorption studies of radioelements on geological materials

    International Nuclear Information System (INIS)

    Berry, John A.; Yui, Mikazu; Kitamura, Akira

    2007-11-01

    Batch sorption experiments have been carried out to study the sorption of uranium, technetium, curium, neptunium, actinium, protactinium, polonium, americium and plutonium onto bentonite, granodiorite and tuff. Mathematical modelling using the HARPHRQ program and the HATCHES database was carried out to predict the speciation of uranium and technetium in the equilibrated seawater, and neptunium, americium and plutonium in the rock equilibrated water. Review of the literature for thermodynamic data for curium, actinium, protactinium and polonium was carried out. Where sufficient data were available, predictions of the speciation and solubility were made. This report is a summary report of the experimental work conducted by AEA Technology during April 1991-March 1998, and the main results have been presented at Material Research Society Symposium Proceedings and published as proceedings of them. (author)

  2. Testosterone sorption and desorption: Effects of soil particle size

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yong, E-mail: yqi01@unomaha.edu [Civil Engineering Dept., University of Nebraska-Lincoln at Omaha Campus, Omaha, NE 68182 (United States); Zhang, Tian C. [Civil Engineering Dept., University of Nebraska-Lincoln at Omaha Campus, Omaha, NE 68182 (United States); Ren, Yongzheng [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-08-30

    Graphical abstract: - Highlights: • Smaller soil particles have higher sorption and lower desorption rates. • The sorption capacity ranks as clay > silt > sand. • Small particles like clays have less potential for desorption. • Colloids (clays) have high potential to facilitate the transport of hormones in soil–water environments. - Abstract: Soils contain a wide range of particles of different diameters with different mobility during rainfall events. Effects of soil particles on sorption and desorption behaviors of steroid hormones have not been investigated. In this study, wet sieve washing and repeated sedimentation methods were used to fractionate the soils into five ranges. The sorption and desorption properties and related mechanisms of testosterone in batch reactors filled with fractionated soil particles were evaluated. Results of sorption and desorption kinetics indicate that small soil particles have higher sorption and lower desorption rates than that of big ones. Thermodynamic results show the sorption processes are spontaneous and exothermal. The sorption capacity ranks as clay > silt > sand, depending mainly on specific surface area and surface functional groups. The urea control test shows that hydrogen bonding contributes to testosterone sorption onto clay and silt but not on sand. Desorption tests indicate sorption is 36–65% irreversible from clay to sand. Clays have highest desorption hysteresis among these five soil fractions, indicating small particles like clays have less potential for desorption. The results provide indirect evidence on the colloid (clay)-facilitated transport of hormones (micro-pollutants) in soil environments.

  3. Adsorption-desorption isotherms and heat of sorption of prickly pear fruit (Opuntia ficus indica)

    International Nuclear Information System (INIS)

    Lahsasni, S.; Kouhila, M.; Mahrouz, M.

    2004-01-01

    The equilibrium moisture contents were determined for prickly pear fruit using the gravimetric static method at t=30, 40 and 50 deg. C over a range of relative humidities from 0.05 to 0.9. The sorption curves of prickly pear fruit decreased with increase in temperature at constant relative humidity. The hysteresis effect was observed. The GAB, modified Halsey, modified Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures are calculated using a modified BET equation. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures

  4. Adsorption-desorption isotherms and heat of sorption of prickly pear fruit (Opuntia ficus indica)

    Energy Technology Data Exchange (ETDEWEB)

    Lahsasni, S.; Kouhila, M. E-mail: kouhila@hotmail.com; Mahrouz, M

    2004-01-01

    The equilibrium moisture contents were determined for prickly pear fruit using the gravimetric static method at t=30, 40 and 50 deg. C over a range of relative humidities from 0.05 to 0.9. The sorption curves of prickly pear fruit decreased with increase in temperature at constant relative humidity. The hysteresis effect was observed. The GAB, modified Halsey, modified Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures are calculated using a modified BET equation. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures.

  5. Sorption studies of uranium in sediment-groundwater systems from the natural analogue sites of Needle's Eye and Broubster

    International Nuclear Information System (INIS)

    Higgo, J.J.; Falck, W.E.; Hooker, P.J.

    1990-01-01

    This report describes the results of sorption experiments designed to provide essential data for migration modelling. Sorption of 233 U from natural ground-water onto peat from Broubster and silt from Needle's Eye was studied under atmospheric conditions and different pH regimes. The temperature was maintained at 10 0 C and, in the case of Needle's Eye silt, the kinetics of sorption were followed. The results were analyzed in conjunction with speciation modelling in an attempt to understand the sorption mechanisms and to extrapolate the findings to cover the range of conditions likely to be met in the field. This work is part of the CEC project Mirage - Second phase, research area 'Natural analogues'

  6. Sorption of strontium on bentonites from Slovak deposits

    International Nuclear Information System (INIS)

    Kufcakova, J.; Galambos, M.; Rajc, P.

    2005-01-01

    Sorption on bentonite from different Slovak deposits / Jelsovy potok, Kopernica and Lieskove has been investigated under various experimental conditions, such as contact time, pH, sorbate concentrations, presence of complementary cation. The sorption of strontium from aqueous solutions was investigated using a radiometric determination of distribution coefficient, Kd. The individual solutions were labelled with radiotracer. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites /tab.l/ , which can be explained by the increase of specific surface and change of solubility of the irradiated samples of bentonite. The presence of complementary cations, Na + , K + , NH 4 + , Ca 2+ , Mg 2+ and Ba 2+ depresses the sorption of Sr on bentonite. In the case of bentonite Kopernica the effectiveness in reducing the sorption of strontium by cations followed the order K + 4 + + 2+ 2+ 2+ . Results indicate that the sorption of Sr + on bentonite will be affected by the presence of high concentrations of various salts in the waste water effluents. (author)

  7. Isotherms and isosteric heat of sorption of two varieties of Peruvian quinoa

    OpenAIRE

    Augusto Pumacahua-Ramos; José Antonio Gomez Vieira; Javier Telis-Romero; Harvey Alexander Villa-Vélez; Jose Francisco Lopes Filho

    2016-01-01

    The isosteric heats of sorption of two varieties of quinoa (Chenopodium quinoaWilld.) grain were determined by the static gravimetric method at four temperatures (40, 50, 60 and 70 °C) andin relative humidity environments provided by six saturated salt solutions. Six mathematical equations were used to model the experimental data: GAB, Oswin, Henderson, Peleg, Smith and Halsey. The isosteric heat of sorption was determined using the parameters ...

  8. Microplastics play a minor role in tetracycline sorption in the presence of dissolved organic matter.

    Science.gov (United States)

    Xu, Baile; Liu, Fei; Brookes, Philip C; Xu, Jianming

    2018-05-02

    Microplastics have a great potential to sorb organic pollutants from the adjacent environment. In this study, the sorption of tetracycline, a polar and ionizable antibiotic, on three types of microplastics (polyethylene (PE), polypropylene (PP) and polystyrene (PS)) were investigated in batch sorption experiments. The sorption isotherms were well fitted by the Langmuir model, indicating that not only hydrophobic interactions but also other interactions (e.g. electrostatic interactions) played important roles in the sorption process. PS had the maximum sorption capacity, following the order PS > PP > PE, which can be attributed to polar interactions and π-π interactions. The sorption of tetracycline on microplastics was significantly influenced by pH, with sorption capacity increasing gradually, peaking at pH 6.0 and then decreasing, likely due to the influence of tetracycline speciation with the change of pH. Fulvic acid was selected as representative dissolved organic matter (DOM) to examine the effect on sorption. The increasing concentration of fulvic acid inhibited the sorption of tetracycline on three microplastics, decreasing them by more than 90% at the fulvic acid concentration of 20 mg/L, which implied a greater affinity of tetracycline to fulvic acid than to microplastics. Increasing salinity from 0.05 to 3.5% had negligible effects on the sorption of tetracycline on the three microplastics. Our results highlight the importance of pH and DOM on the sorption of tetracycline on microplastics, and suggest the relatively minor role of microplastics in the fate and transport of tetracycline in the aquatic environment in the presence of DOM. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Sorption of mercury on chemically synthesized polyaniline

    International Nuclear Information System (INIS)

    Remya Devi, P.S.; Verma, R.; Sudersanan, M.

    2006-01-01

    Sorption of inorganic mercury (Hg 2+ ) and methyl mercury, on chemically synthesized polyaniline, in 0.1-10N HCl solutions has been studied. Hg 2+ is strongly sorbed at low acidities and the extent of sorption decreases with increase in acidity. The sorption of methyl mercury is very low in the HCl concentration range studied. Sorption of Hg 2+ on polyaniline in 0.1-10N LiCl and H 2 SO 4 solutions has also been studied. The analysis of the data indicates that the sorption of Hg 2+ depends on the degree of protonation of polyaniline and the nature of mercury(II) chloride complexes in solution. X-ray photoelectron spectroscopy analysis (XPS) of polyaniline sorbed with mercury show that mercury is bound as Hg 2+ . Sorbed mercury is quantitatively eluted from polyaniline with 0.5N HNO 3 . Polyaniline can be used for separation and pre-concentration of inorganic mercury from aqueous samples. (author)

  10. Sorption of organic water pollutants on dead vegetable biomass; Sorption organischer Wasserschadstoffe an abgestorbene pflanzliche Biomasse

    Energy Technology Data Exchange (ETDEWEB)

    Kraeuter, A.

    2001-03-01

    Hemp-derived biological sorption agents were produced, and their physical, chemical and sorptive characteristics were tested in batch and filter tests. The experiments were accompanied by model calculations. In the natural state, the sorption agents had a kation exchange capacity of 0.1-0.3 mmol/g, modified sorption agents had about 2 mmol/g. Kationized hemp had values of 0.34 mmol/g and thermally modified hemp absorption agents absorbed more than 1.2 mmol/g of dichlorophenol. In the case of a liquid effluent from a textile dyeing plant, only a discoloration effect was achieved. The absorption agents can be regenerated, combusted or composted after use. [German] Im Rahmen dieser Arbeit wurden naturbelassene und modifizierte Billig-Biosorbentien aus Hanfschaeben zur Entfernung organischer Schadstoffe aus Waessern hergestellt und ihre physikalischen, chemischen und sorptiven Eigenschaften in Batch- und Filterversuchen untersucht. Wegen der Komplexheit des Systems ''Biosorption organischer Wasserschadstoffe'' wurden die ermittelten Sorptionsisothermen mit den Ansaetzen nach Langmuir und Freundlich beschrieben. Die Sorptionskinetik und das Durchbruchsverhalten wurde ebenfalls mit einfachen Ansaetzen modelliert. Naturbelassene Hanfschaeben erreichten Kationenaustauschkapazitaeten von 0,1-0,3 mmol/g, entsprechend modifizierte Hanfschaeben ca. 2 mmol/g. Kationisierte Hanfschaeben dagegen erreichten Anionenaustauschkapazitaeten von 0,34 mmol/g und thermisch modifizierte Hanfschaeben sorbierten bis ueber 1,2 mmol/g Dichlorphenol. Bei der Behandlung eines Abwassers aus einer Textilfaerberei beschraenkte sich die Reinigungsleistung der hergestellten Biosorbentien auf eine Entfaerbung. Nach Schadstoffbeladung koennen die Hanfschaeben regeneriert, thermisch verwertet oder kompostiert werden. (orig.)

  11. Sorption interactions of heavy metals with biochar in soil remediation studies

    Science.gov (United States)

    Fristak, Vladimir; Friesl-Hanl, Wolfgang; Wawra, Anna; Soja, Gerhard

    2015-04-01

    The search for new materials in soil remediation applications has led to new conversion technologies such as carbonization and pyrolysis. Biochar represents the pyrolytic product of different biomass input materials processed at 350-1000°C and anoxic conditions. The pyrolysis temperature and feedstock have a considerable influence on the quality of the charred product and also its main physico-chemical properties. Biochar as porous material with large specific surface and C-stability is utilized in various environmental and agricultural technologies. Carbon sequestration, increase of soil water-holding capacity and pH as well as sorption of different xenobiotics present only a fraction of the multitude of biochar application possibilities. Heavy metals as potential sources of ecotoxicological risks are characterized by their non-degradability and the potential transfer into the food chain. Carbonaceous materials have been used for a long time as sorbents for heavy metals and organic contaminants in soil and water technologies. The similarity of biochar with activated carbon predetermines this material as remediation tool which plays an important role in heavy metal immobilization and retention with a parallel reduction in the risk of ground water and food crop contamination. In all this processes the element-specific sorption behaviour of biochar creates new conditions for pollutant binding. Sorption interaction and separation of contaminants from soil solution or waste effluent can be affected by wide-ranging parameters. In detail, our study was based on batch-sorption comparisons of two biochars produced from wood chips and green waste residues. We observed that sorption efficiency of biochar for model bivalent heavy metals (Cd, Zn, Cu) can be influenced by equilibrium parameters such as pH, contact time, initial concentration of metal in reaction solutions, presence of surfactants and chemical modification by acid hydrolysis, esterification and methylation. The

  12. Evidence of micropore filling for sorption of nonpolar organic contaminants by condensed organic matter.

    Science.gov (United States)

    Ran, Yong; Yang, Yu; Xing, Baoshan; Pignatello, Joseph J; Kwon, Seokjoo; Su, Wei; Zhou, Li

    2013-01-01

    Although microporosity and surface area of natural organic matter (NOM) are crucial for mechanistic evaluation of the sorption process for nonpolar organic contaminants (NOCs), they have been underestimated by the N adsorption technique. We investigated the CO-derived internal hydrophobic microporosity () and specific surface area (SSA) obtained on dry samples and related them to sorption behaviors of NOCs in water for a wide range of condensed NOM samples. The is obtained from the total CO-derived microporosity by subtracting out the contribution of the outer surfaces of minerals and NOM using N adsorption-derived parameters. The correlation between or CO-SSA and fractional organic carbon content () is very significant, demonstrating that much of the microporosity is associated with internal NOM matrices. The average and CO-SSA are, respectively, 75.1 μL g organic carbon (OC) and 185 m g OC from the correlation analysis. The rigid aliphatic carbon significantly contributes to the microporosity of the Pahokee peat. A strong linear correlation is demonstrated between / and the OC-normalized sorption capacity at the liquid or subcooled liquid-state water solubility calculated via the Freundlich equation for each of four NOCs (phenanthrene, naphthalene, 1,3,5-trichlorobenzene, and 1,2-dichlorobenzene). We concluded that micropore filling ("adsorption") contributes to NOC sorption by condensed NOM, but the exact contribution requires knowing the relationship between the dry-state, CO-determined microporosity and the wet-state, NOC-available microporosity of the organic matter. The findings offer new clues for explaining the nonideal sorption behaviors of NOCs. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  13. The sorption behavior of DDT onto sediment in the presence of surfactant cetyltrimethylammonium bromide

    International Nuclear Information System (INIS)

    Cao Xiaoyan; Han Huayu; Yang Guipeng; Gong Xiaofei; Jing Jianning

    2011-01-01

    Highlights: → The sorption behavior of a complex system consists of DDT and CTAB onto marine sediment was studied. → Batch experiments were carried out to investigate the kinetics and thermodynamics. → The presence of CTAB could remarkably accelerate and enhance the sorption of DDT. → The sorption of DDT had relatively more negative ΔG 0 and ΔH 0 in the presence of CTAB. - Abstract: The sorption behavior of p,p'- and o,p'-dichlorodiphenyltrichloroethane (DDT) in the presence of a cationic surfactant cetyltrimethylammonium bromide (CTAB) on sediment was studied. Batch experiments were carried out to investigate the kinetics and thermodynamics of the process. The kinetic behavior of these three chemicals on sediment was described by pseudo-second-order kinetic equations, and the isotherms followed the Freundlich model well. The presence of CTAB was able to remarkably accelerate and enhance the sorption of DDT, whereas DDT showed no effect on the sorption of CTAB in our considered concentration ranges. The thermodynamic parameters, such as standard enthalpy change (ΔH 0 ), standard entropy change (ΔS 0 ) and standard Gibbs free energy change (ΔG 0 ) showed that the sorption process of p,p'- and o,p'-DDT was physical, spontaneous and exothermic, and the randomness at the solid-liquid interface increased during the process. In the presence of CTAB, the sorption of DDT showed significantly negative ΔG 0 and ΔH 0 values.

  14. Sorption of Np(V) by synthetic hydroxyapatite

    International Nuclear Information System (INIS)

    Moore, R.C.; Holt, K.; Zhao, H.; Hasan, A.; Awwad, N.; Gasser, M.; Sanchez, C.

    2003-01-01

    The sorption of Np(V) to synthetic hydroxyapatite was determined in batch experiments in a 0.1 M NaClO 4 solution. The hydroxyapatite used was of high purity as determined by SEM, EDS, XRD, FT-IR and ICP-MS analysis. Results from kinetic experiments with an initial Np(V) concentration of 1 x 10 -7 to 1 x 10 -6 M indicate the sorption process is relatively fast with more than 90% of the Np(V) being sorbed in approximately 3 hours. Equilibrium experiments performed over the pH range of 6 to 11 indicated sorption is strongly pH dependent with distribution coefficients, K d values (mL/g), increasing from 123 L/mole at pH 6 to 69 200 L/mole at pH 8.5. K d values are observed to decrease as pH further increases. Data points over a range of Np(V) concentrations were collected at pH 8 and fitted to the Langmuir isotherm model for simple adsorption. The Langmuir equation gave an excellent representation of the data. Langmuir parameters were determined to be C a = 0.032 mole/mole and K = 1.22 x 10 6 L/mole, indicating the high affinity of hydroxyapatite for Np(V) adsorption. (orig.)

  15. Predicting sorption of organic acids to a wide range of carbonized sorbents

    Science.gov (United States)

    Sigmund, Gabriel; Kah, Melanie; Sun, Huichao; Hofmann, Thilo

    2016-04-01

    Many contaminants and infochemicals are organic acids that undergo dissociation under environmental conditions. The sorption of dissociated anions to biochar and other carbonized sorbents is typically lower than that of neutral species. It is driven by complex processes that are not yet fully understood. It is known that predictive approaches developed for neutral compounds are unlikely to be suitable for organic acids, due to the effects of dissociation on sorption. Previous studies on the sorption of organic acids to soils have demonstrated that log Dow, which describes the decrease in hydrophobicity of acids upon dissociation, is a useful alternative to log Kow. The aim of the present study was to adapt a log Dow based approach to describe the sorption of organic acids to carbonized sorbents. Batch experiments were performed with a series of 9 sorbents (i.e., carbonized wood shavings, pig manure, and sewage sludge, carbon nanotubes and activated carbon), and four acids commonly used for pesticidal and biocidal purposes (i.e., 2,4-D, MCPA, 2,4-DB, and triclosan). Sorbents were comprehensively characterized, including by N2 and CO2 physisorption, Fourier transform infrared spectroscopy, and elemental analysis. The wide range of sorbents considered allows (i) discussing the mechanisms driving the sorption of neutral and anionic species to biochar, and (ii) their dependency on sorbate and sorbent properties. Results showed that the sorption of the four acids was influenced by factors that are usually not considered for neutral compounds (i.e., pH, ionic strength). Dissociation affected the sorption of the four compounds, and sorption of the anions ranged over five orders of magnitude, thus substantially contributing to sorption in some cases. For prediction purposes, most of the variation in sorption to carbonized sorbents (89%) could be well described with a two-parameter regression equation including log Dow and sorbent specific surface area. The proposed model

  16. Technetium sorption by stibnite from natural water

    International Nuclear Information System (INIS)

    Peretroukhine, V.; Sergeant, C.; Deves, G.; Poulain, S.; Vesvres, M.H.; Thomas, B.; Simonoff, M.

    2006-01-01

    The sorption of technetium by powdered and polished mineral stibnite Sb 2 S 3 has been investigated in simulated and natural underground waters from the Meuse/Haute-Marne region (France). The sorption by powdered stibnite has been found to be complete under both aerobic and anaerobic conditions in batch experiments. The sorption rate is higher in the absence of oxygen than under aerobic condition. Increasing the temperature from 30 C to 60 C results in a rise of the sorption rate by 9.1 and 27 times under anaerobic and aerobic conditions, respectively. The observed differences in sorption kinetics in the presence and in absence of oxygen are explained by the interaction of oxygen with sulfide ion in aerobic conditions and by the reduction of technetium(VII) by iron(II) and by other impurities present in natural water and in the mineral, and by the subsequent sorption of Tc(IV) on stibnite under anaerobic conditions. The sorption on a polished mineral surface resulted in the formation of a technetium film, probably Tc 2 S 7 , with a thickness of 1-3 μg Tc/cm 2 pH 3-6 and 4-12 μg Tc/cm 2 at 9-12. The simultaneous formation of stibnite colloids with adsorbed technetium occurs at pH 9-12. The study of the technetium film on the mineral by proton induced X-ray emission analysis showed it to be at least one order of magnitude thinner on the SiO 2 impurities than on the main Sb 2 S 3 component and the iron impurities. (orig.)

  17. Sorption of radionuclides by tertiary clays

    International Nuclear Information System (INIS)

    Wagner, J.F.; Czurda, K.A.

    1990-01-01

    The sorption capacity of different clay types for some metals (Co, Cs, Sr and Zn), occurring as common radionuclides in radioactive waste deposits, had been analysed by a static (batch technique) and a dynamic method (percolation tests, in which the driving force is a hydraulic gradient). Sorption capacity generally increased with an increasing pH of solution. A decrease of sorption capacity had been observed in the order Zn > Cs ≥ Co > Sr for the batch and Cs > Zn > Sr > Co for the percolation tests. Clay marls showed a distinctly higher sorption respectively retention capacity as pure clays. Sorption capacity depends on solution parameters like type and concentration of radionuclide, pH, salt concentration, etc., and on rock parameters like mineral content (e.g. swelling clay minerals and carbonates), organic material, rock pH, micro fabric, etc. A third parameter of great influence is the contact time between clay and solution. The adsorption isotherms reflect two different adsorption mechanisms: a very rapid adsorption (a few minutes) on the external surfaces of clay minerals and a slow adsorption process (weeks and longer), due to the diffusion of metal ions into the interlayer space of clay minerals. 12 refs., 9 figs., 1 tab

  18. Diffusion and sorption of neptunium(V) in compacted montmorillonite: effects of carbonate and salinity

    International Nuclear Information System (INIS)

    Tachi, Y.; Yotsuji, K.; Suyama, T.; Seida, Y.; Yui, M.; Nakazawa, T.; Yamada, N.; Ochs, M.

    2010-01-01

    Diffusion and sorption of radionuclides in compacted bentonite/montmorillonite are key processes in the safe geological disposal of radioactive waste. In this study, the effects of carbonate and salinity on neptunium(V) diffusion and sorption in compacted sodium montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients (D e ) and distribution coefficients (K d ) of 237 Np(V) in sodium montmorillonite compacted to a dry density of 800 kg m -3 were measured under four chemical conditions with different salinities (0.05/0.5 M NaCl) and carbonate concentrations (0.0.01 M NaHCO 3 ). D e values for carbonate-free conditions were of the order of 10 -10 -10 -11 m 2 s -1 and decreased as salinity increased, and those for carbonate conditions were of the order of 10 -11 -10 -12 m 2 s -1 and showed the opposite dependence. Diffusion-derived K d values for carbonate-free conditions were higher by one order of magnitude than those for carbonate conditions. Diffusion and sorption behaviors were interpreted based on mechanistic models by coupling thermodynamic aqueous speciation, thermodynamic sorption model (TSM) based on ion exchange, and surface complexation reactions, and a diffusion model based on electrical double layer (EDL) theory in homogeneous narrow pores. The model predicted the experimentally observed tendency of D e and K d qualitatively, as a result of the following mechanisms; 1) the dominant aqueous species are NpO 2 + and NpO 2 CO 3 - for carbonate-free and carbonate conditions, respectively, 2) the effects of cation excess and anion exclusion result in opposite tendencies of D e for salinity, 3) higher carbonate in solution inhibits sorption due to the formation of carbonate complexes. (orig.)

  19. linear-quadratic-linear model

    Directory of Open Access Journals (Sweden)

    Tanwiwat Jaikuna

    2017-02-01

    Full Text Available Purpose: To develop an in-house software program that is able to calculate and generate the biological dose distribution and biological dose volume histogram by physical dose conversion using the linear-quadratic-linear (LQL model. Material and methods : The Isobio software was developed using MATLAB version 2014b to calculate and generate the biological dose distribution and biological dose volume histograms. The physical dose from each voxel in treatment planning was extracted through Computational Environment for Radiotherapy Research (CERR, and the accuracy was verified by the differentiation between the dose volume histogram from CERR and the treatment planning system. An equivalent dose in 2 Gy fraction (EQD2 was calculated using biological effective dose (BED based on the LQL model. The software calculation and the manual calculation were compared for EQD2 verification with pair t-test statistical analysis using IBM SPSS Statistics version 22 (64-bit. Results: Two and three-dimensional biological dose distribution and biological dose volume histogram were displayed correctly by the Isobio software. Different physical doses were found between CERR and treatment planning system (TPS in Oncentra, with 3.33% in high-risk clinical target volume (HR-CTV determined by D90%, 0.56% in the bladder, 1.74% in the rectum when determined by D2cc, and less than 1% in Pinnacle. The difference in the EQD2 between the software calculation and the manual calculation was not significantly different with 0.00% at p-values 0.820, 0.095, and 0.593 for external beam radiation therapy (EBRT and 0.240, 0.320, and 0.849 for brachytherapy (BT in HR-CTV, bladder, and rectum, respectively. Conclusions : The Isobio software is a feasible tool to generate the biological dose distribution and biological dose volume histogram for treatment plan evaluation in both EBRT and BT.

  20. Statistical Tests for Mixed Linear Models

    CERN Document Server

    Khuri, André I; Sinha, Bimal K

    2011-01-01

    An advanced discussion of linear models with mixed or random effects. In recent years a breakthrough has occurred in our ability to draw inferences from exact and optimum tests of variance component models, generating much research activity that relies on linear models with mixed and random effects. This volume covers the most important research of the past decade as well as the latest developments in hypothesis testing. It compiles all currently available results in the area of exact and optimum tests for variance component models and offers the only comprehensive treatment for these models a

  1. Sorption and Transport of Sildenafil in Natural Soils

    Science.gov (United States)

    Boudinot, F. G.; Vulava, V. M.

    2013-12-01

    Pharmaceutical Chemicals (PCs) mainly enter our ecosystems from discharges of treated wastewater and have direct effects on the ecological health of that area. Sildenafil citrate (Viagra) is one such PC, whose presence has been reported in stream waters. Although one study has shown that sildenafil is not harmful in bacterial and fungal environments, there remains much unknown about its fate elsewhere in ecosystems. Sildenafil is a complex organic molecule with two amino functional groups that result in pKa's of 7.27 and 5.97. It also has a high solubility of 3.5 g/L. Given that sildenafil consumption (and concurrently disposal) is on the rise, it is essential that its behavior in the natural environment be better understood. The goal of this study was to quantify the sorption and transport behavior of sildenafil in differing natural soils with varying compositions. Pristine A- and B- horizon soil samples from several soil series were collected in a managed forest near Charleston, SC and used for these studies. The soils were characterized for physical and chemical properties: soil organic matter content ranged between 0.6-7.6%, clay content between 6-20%, and soil pH between 4-5. These soils were then used to perform kinetic reaction, sorption, and column transport experiments. Batch kinetic experiments showed a fast reaction rate in both clay-rich and organic-rich soils and an equilibration time of less than 24 hours. Batch reactor sorption experiments provided data for sorption isotherms (plot of sildenafil in solution, C vs. sildenafil sorbed in soil, q) which were nonlinear. The isotherms were fit using Freundlich model (q=KfCn, where Kf and n are fitting parameters). Sildenafil sorbed more strongly to clay-rich soils compared with organic-rich soils with less clay. It is hypothesized that permanent negative charge on clay mineral surfaces form ionic bonds with positively charged amines in sildenafil in acidic pHs. Transport experiments were conducted using

  2. Matrix Tricks for Linear Statistical Models

    CERN Document Server

    Puntanen, Simo; Styan, George PH

    2011-01-01

    In teaching linear statistical models to first-year graduate students or to final-year undergraduate students there is no way to proceed smoothly without matrices and related concepts of linear algebra; their use is really essential. Our experience is that making some particular matrix tricks very familiar to students can substantially increase their insight into linear statistical models (and also multivariate statistical analysis). In matrix algebra, there are handy, sometimes even very simple "tricks" which simplify and clarify the treatment of a problem - both for the student and

  3. An online re-linearization scheme suited for Model Predictive and Linear Quadratic Control

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian; Poulsen, Niels Kjølstad

    This technical note documents the equations for primal-dual interior-point quadratic programming problem solver used for MPC. The algorithm exploits the special structure of the MPC problem and is able to reduce the computational burden such that the computational burden scales with prediction...... horizon length in a linear way rather than cubic, which would be the case if the structure was not exploited. It is also shown how models used for design of model-based controllers, e.g. linear quadratic and model predictive, can be linearized both at equilibrium and non-equilibrium points, making...

  4. 3.3. Sorption activity of cross-linked polymers of ethynyl-piperidol

    International Nuclear Information System (INIS)

    Khalikov, D.Kh.

    2012-01-01

    The sorption activity of cross-linked polymers of ethynyl-piperidol was studied. The bilirubin sorption was studied as well. The kinetic of bilirubin sorption and human serum albumin at their joint presence in hydrogel solutions was defined. Bilirubin sorption and change of albumin composition was considered. The sorption of middle molecular peptides was considered as well. The sorption of endogenous toxin by means of ethynyl-piperidol polymers was done.

  5. Study of sorption of technetium on pyrrhotine

    International Nuclear Information System (INIS)

    Shen Dong; Fan Xianhua; Su Xiguang; Zeng Jishu

    2001-01-01

    The sorption behaviors of technetium on pyrrhotine are studied with batch experiment and dilute sulfuric acid is used to dissolve the technetium adsorbed on pyrrhotine. Sorption and desorption experiment are performed under aerobic and anaerobic conditions (inert gas box). The results show that a significant sorption of technetium on pyrrhotine is found under aerobic and anaerobic conditions, and the sorption on the mineral is supposed to be due to the reduction of TcO 4 - to insoluble TcO 2 ·nH 2 O. Desorption process of the sorbed technetium into dilute sulfuric acid is found to be different under aerobic and anaerobic conditions. On addition of H 2 O 2 to the leach solution a sudden increase of the technetium concentration is observed

  6. Characteristics of and sorption to biochars derived from waste material

    Science.gov (United States)

    Sun, Huichao; Kah, Melanie; Sigmund, Gabriel; Hofmann, Thilo

    2015-04-01

    Biochars can exhibit a high sorption potential towards heavy metals and organic contaminants in various environmental matrices (e.g., water, soil). They have therefore been proposed for environmental remediation purposes to sequester contaminants. To date, most studies have focused on the physicochemical and sorption properties of mineral phases poor biochars, which are typically produced from plant residues. Only little knowledge is available for biochars derived from human and animal waste material, which are typically characterized by high mineral contents (e.g., sewage sludge, manure). Using human and animal waste as source material to produce biochars would support the development of attractive combined strategies for waste management and remediation. The potential impact of mineral phases on the physicochemical and sorption properties of biochars requires further studies so that the potential as sorbent material can be evaluated. With this purpose, different source material biochars were produced at 200°C, 350°C and 500°C, to yield a series of biochars representing a range of mineral content. The derived biochars from wood shavings (sludge (50-70% ash) and pig manure (30-60% ash), as well as a commercial biochar derived from grain husks (40% ash), were extensively characterized (e.g., element composition, surface area, porosity, Fourier transform infrared spectroscopy). The contents of potentially toxic elements (i.e., heavy metals and polycyclic aromatic hydrocarbons) of all materials were within the guidelines values proposed by the International Biochar Initiative, indicating their suitability for environmental application. Single point sorption coefficients for the model sorbate pyrene were measured to investigate the effect of mineral content, feedstock, pyrolysis temperature, particle size fractions and acid demineralization on sorption behavior. Overall, sorption of pyrene was strong for all materials (4 waste material and exhibiting high mineral

  7. Modeling of Volatility with Non-linear Time Series Model

    OpenAIRE

    Kim Song Yon; Kim Mun Chol

    2013-01-01

    In this paper, non-linear time series models are used to describe volatility in financial time series data. To describe volatility, two of the non-linear time series are combined into form TAR (Threshold Auto-Regressive Model) with AARCH (Asymmetric Auto-Regressive Conditional Heteroskedasticity) error term and its parameter estimation is studied.

  8. Competitive sorption and desorption of heavy metals by individual soil components

    International Nuclear Information System (INIS)

    Covelo, E.F.; Vega, F.A.; Andrade, M.L.

    2007-01-01

    Knowledge of sorption and desorption of heavy metals by individual soil components should be useful for modelling the behaviour of soils of arbitrary composition when contaminated by heavy metals, and for designing amendments increasing the fixation of heavy metals by soils polluted by these species. In this study the competitive sorption and desorption of Cd, Cr, Cu, Ni, Pb and Zn by humified organic matter, Fe and Mn oxides, kaolinite, vermiculite and mica were investigated. Due to the homogeneity of the sorbents, between-metal competition for binding sites led to their preferences for one or another metal being much more manifest than in the case of whole soils. On the basis of k d100 values (distribution coefficients calculated in sorption-desorption experiments in which the initial sorption solution contained 100 mg L -1 of each metal), kaolinite and mica preferentially sorbed and retained chromium; vermiculite, copper and zinc; HOM, Fe oxide and Mn oxide, lead (HOM and Mn oxide also sorbed and retained considerable amounts of copper). Mica only retained sorbed chromium, Fe oxide sorbed cadmium and lead, and kaolinite did not retain sorbed copper. The sorbents retaining the greatest proportions of sorbed metals were vermiculite and Mn oxide, but the ratios of k d100 values for retention and sorption suggest that cations were least reversibly bound by Mn oxide, and most reversibly by vermiculite

  9. Applicability of linear and non-linear potential flow models on a Wavestar float

    DEFF Research Database (Denmark)

    Bozonnet, Pauline; Dupin, Victor; Tona, Paolino

    2017-01-01

    as a model based on non-linear potential flow theory and weakscatterer hypothesis are successively considered. Simple tests, such as dip tests, decay tests and captive tests enable to highlight the improvements obtained with the introduction of nonlinearities. Float motion under wave actions and without...... control action, limited to small amplitude motion with a single float, is well predicted by the numerical models, including the linear one. Still, float velocity is better predicted by accounting for non-linear hydrostatic and Froude-Krylov forces.......Numerical models based on potential flow theory, including different types of nonlinearities are compared and validated against experimental data for the Wavestar wave energy converter technology. Exact resolution of the rotational motion, non-linear hydrostatic and Froude-Krylov forces as well...

  10. Forecasting Volatility of Dhaka Stock Exchange: Linear Vs Non-linear models

    Directory of Open Access Journals (Sweden)

    Masudul Islam

    2012-10-01

    Full Text Available Prior information about a financial market is very essential for investor to invest money on parches share from the stock market which can strengthen the economy. The study examines the relative ability of various models to forecast daily stock indexes future volatility. The forecasting models that employed from simple to relatively complex ARCH-class models. It is found that among linear models of stock indexes volatility, the moving average model ranks first using root mean square error, mean absolute percent error, Theil-U and Linex loss function  criteria. We also examine five nonlinear models. These models are ARCH, GARCH, EGARCH, TGARCH and restricted GARCH models. We find that nonlinear models failed to dominate linear models utilizing different error measurement criteria and moving average model appears to be the best. Then we forecast the next two months future stock index price volatility by the best (moving average model.

  11. Sorption and diffusion of Cs and I in concrete

    International Nuclear Information System (INIS)

    Andersson, K.; Torstenfelt, B.; Allard, B.

    1983-01-01

    Concrete has been suggested as a possible encapsulation material for long-term storage of low and medium level radioactive waste. At an underground storage of concrete encapsulated waste, a slow release of radioactive elements into the groundwater by diffusion through the concrete must be considered in the safety analysis. The diffusion may be delayed by sorption reactions on the solid. A wide range of long-lived radionuclides may be present in the low and medium level radioactive waste. Here, the sorption and diffusion of iodide and cesium on slag cement paste and concrete has been studied. The influence of four different water phases (pore water, groundwater, Baltic Sea water and sea water) as well as the influence of some added species (carbonate, sulphate and magnesium) has been investigated. A significant sorption of iodide on cement paste in contact with pore water was observed, indicating that the diffusion may be expected to be retarded in this medium. For cesium the highest sorption was found for concrete and groundwater. This means that the sorption increases as the concrete is weathered. Low or insignificant sorption was found for the cement paste, indicating that the ballast is responsible for the Cs-sorption. Carbonatization enhances the Cs-sorption by about a factor of 3. The diffusivity of Cs in concrete and cement paste was determined to between 2x10 - 14 and 8x10 - 14 m 2 /s in pore water (where an insignificant sorption was observed). The choice of ballast as well as addition of suitable getters with high sorption of the long-lived radionuclides might decrease the mass transfer rate through the cement. (Authors)

  12. Study of sorption processes of copper on synthetic hydroxyapatite

    International Nuclear Information System (INIS)

    Rosskopfova, O.; Galambos, M.; Ometakova, J.; Rajec, P.; Caplovicova, M.

    2012-01-01

    The sorption of copper on synthetic hydroxyapatite was investigated using a batch method and radiotracer technique. The hydroxyapatite sample prepared by a wet precipitation process was of high crystallinity with Ca/P ratio of 1.688. The sorption of copper on hydroxyapatite was pH independent ranging from 4 to 6 as a result of buffering properties of hydroxyapatite. The adsorption of copper was rapid and the percentage of Cu sorption was >98% during the first 15-30 min of the contact time. The experimental data for sorption of copper have been interpreted in the term of Langmuir isotherm. The sorption of Cu 2+ ions was performed by ion-exchange with Ca 2+ cations on the crystal surface of hydroxyapatite under experimental conditions. The competition effect of Zn 2+ , Fe 2+ and Pb 2+ towards Cu 2+ sorption was stronger than that of Co 2+ , Ni 2+ and Ca 2+ ions. The ability of the bivalent cations to depress the sorption of copper on hydroxyapatite was in the following order Pb 2+ > Fe 2+ > Zn 2+ > Co 2+ ∼ Ni 2+ . (author)

  13. Water vapor sorption thermodynamics of the Nafion ionomer membrane.

    Science.gov (United States)

    Wadsö, Lars; Jannasch, Patric

    2013-07-18

    The water interactions of polymer electrolyte membranes are of significant interest when these materials are used in, for example, fuel cells. We have therefore studied the sorption thermodynamics of Nafion with a sorption calorimeter that simultaneously measures the sorption isotherm and the mixing (sorption) enthalpy. This unique method is suitable for investigating the sorption thermodynamics of ionic polymers. The measurements were made at 25 °C on a series of samples dried at different temperatures from 25 to 120 °C. The sorption isotherms indicate that the samples dried at 120 °C lost about 0.8 more water molecules per sulfonic group during the drying than did the samples dried at 25 °C, and this result was verified gravimetrically. The mixing enthalpies showed several peaks or plateaus for the samples dried at 60-120 °C. This behavior was seen up to about 2 water molecules per sulfonic group. As these peaks were not directly related to any feature in the sorption isotherm, they probably have their origin in a secondary process, such as a reorganization of the polymer.

  14. Sorption/desorption reversibility of polycyclic aromatic hydrocarbons (PAHs) in soils and carbonaceous materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guohui

    2008-07-01

    the determination of the sorption/desorption enthalpies which gives insight into the sorbent-sorbate interactions. In order to attain sorption/desorption equilibrium, all the samples were pulverized to shorten the laboratory experimental time. The sorbate losses were carefully monitored and considered in the isotherm calculation. Additionally, release of native phenanthrene was also investigated at different temperatures and compared with the freshly spiked samples to investigate the aging effect. The batch results show that for all individual temperature steps sorption and desorption isotherms coincide. Furthermore, the solubility-normalized sorption/desorption isotherms at different temperatures collapse to unique overall isotherms. Leaching of native phenanthrene occurred at much lower concentrations but was well predicted by extrapolation of the spiked equilibrium sorption isotherms. The absolute values of sorption/desorption isosteric heats ({delta}H) determined are in a range of 19 - 35 kJ mol{sup -1}, which is higher than the heat of aqueous solution of subcooled phenanthrene but much less than the heat of condensation of solid phenanthrene from water. No significant difference of the enthalpies between sorption and desorption was observed. Furthermore, the desorption enthalpy of the native phenanthrene was not significantly higher than expected from the sorption experiments with spiked samples. Sorption and desorption kinetics were monitored in on-line column experiments with stepwise increases of temperature. An intraparticle diffusion model was used to simulate the desorption profile in order to get the apparent diffusion coefficients of phenanthrene from the carbonaceous materials. Desorption activation energies were calculated by Arrhenius relationship based on the high-resolution measurement of concentration increases at each temperature step. The activation energies determined range from 58 - 71 kJ mol{sup -1}. No significant trend of increasing

  15. Sorption/desorption reversibility of polycyclic aromatic hydrocarbons (PAHs) in soils and carbonaceous materials

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guohui

    2008-07-01

    determination of the sorption/desorption enthalpies which gives insight into the sorbent-sorbate interactions. In order to attain sorption/desorption equilibrium, all the samples were pulverized to shorten the laboratory experimental time. The sorbate losses were carefully monitored and considered in the isotherm calculation. Additionally, release of native phenanthrene was also investigated at different temperatures and compared with the freshly spiked samples to investigate the aging effect. The batch results show that for all individual temperature steps sorption and desorption isotherms coincide. Furthermore, the solubility-normalized sorption/desorption isotherms at different temperatures collapse to unique overall isotherms. Leaching of native phenanthrene occurred at much lower concentrations but was well predicted by extrapolation of the spiked equilibrium sorption isotherms. The absolute values of sorption/desorption isosteric heats ({delta}H) determined are in a range of 19 - 35 kJ mol{sup -1}, which is higher than the heat of aqueous solution of subcooled phenanthrene but much less than the heat of condensation of solid phenanthrene from water. No significant difference of the enthalpies between sorption and desorption was observed. Furthermore, the desorption enthalpy of the native phenanthrene was not significantly higher than expected from the sorption experiments with spiked samples. Sorption and desorption kinetics were monitored in on-line column experiments with stepwise increases of temperature. An intraparticle diffusion model was used to simulate the desorption profile in order to get the apparent diffusion coefficients of phenanthrene from the carbonaceous materials. Desorption activation energies were calculated by Arrhenius relationship based on the high-resolution measurement of concentration increases at each temperature step. The activation energies determined range from 58 - 71 kJ mol{sup -1}. No significant trend of increasing desorption activation

  16. Comparing linear probability model coefficients across groups

    DEFF Research Database (Denmark)

    Holm, Anders; Ejrnæs, Mette; Karlson, Kristian Bernt

    2015-01-01

    of the following three components: outcome truncation, scale parameters and distributional shape of the predictor variable. These results point to limitations in using linear probability model coefficients for group comparisons. We also provide Monte Carlo simulations and real examples to illustrate......This article offers a formal identification analysis of the problem in comparing coefficients from linear probability models between groups. We show that differences in coefficients from these models can result not only from genuine differences in effects, but also from differences in one or more...... these limitations, and we suggest a restricted approach to using linear probability model coefficients in group comparisons....

  17. Study on sorption capacity of synthetic zeolite for simulated nuclide Cs+

    International Nuclear Information System (INIS)

    Wang Jinming; Yi Facheng

    2006-01-01

    For the sake of understanding the functionary order of simulated nuclide Cs + and Synthetic Zeolite (ZF), the sorption equilibrium time and sorption capacity of simulated nuclide Cs + on ZF are studied with the intermittence method. The difference of temperature, pH value, Cs + concentration and medium on sorption capacity and sorption ratio are investigated. The results show that the sorption complexion of simulated nuclide Cs + on ZF in the same concentration solution are sorption equilibrium quantity in range of 155-190 mg/g in different temperatures and that in range of 165-190 mg/g in different pH values and that in range of 120-210 mg/g in different media; and changing order of equilibrium adsorption ratio is the same to that of sorption equilibrium quantity, but their changing range are wider than that of sorption equilibrium quantity; equilibrium adsorption quantity in range of 180-380 mg/g in different concentration solutions, and changing order of equilibrium adsorption ratio is opposite to that of sorption equilibrium quantity, and more-over, their changing range are wider than that of the sorption equilibrium quantity. Sorption equilibrium time of simulated nuclide Cs + on ZF is about ten to fifteen days. So the changing range of sorption capacity of simulated nuclide Cs + on ZF with conditions effects is smaller and the sorption equilibrium time is also less and ZF preferably absorbs Cs in radiation wastes and thus consumedly reduces the effect of radwaste on the environment. (authors)

  18. Sorption and direct speciation of neptunium(V) on aluminium oxide and montmorillonite

    International Nuclear Information System (INIS)

    Wendt, Sonja

    2009-01-01

    This study comprised batch experiments, direct speciation studies via EXAFS, and modelling with the 2SPNE SC/CE model to elucidate the mechanisms of Np(V) sorption on montmorillonite and, for reference, on γ-Al 2 O 3 . The sorption of pM 239 Np(V) and μM 237 Np(V) on montmorillonite (STx-1, 4 g/L) and γ-Al 2 O 3 (0.5 g/L) was studied at room temperature in the presence and absence of ambient CO 2 covering a pH-range from 2.5 (STx-1) or 5 (γ-Al 2 O 3 ) to 10.5 with 0.01 or 0.1M NaClO 4 as background electrolyte. The Np(V) uptake was determined by γ spectroscopy of the supernatants and calculated as percentage as well as distribution coefficient K d . Sorption starts from pH ∼6 and, under exclusion of CO 2 , increases continuously, while, in the presence of ambient air, it reaches a maximum at pH ∝8.5 (γ-Al 2 O 3 : logK d max ∼ 4 mL/g; STx-1: logK d max ∼ 2.7 mL/g). Beyond that it decreases again due to the formation of aqueous neptunium carbonate complexes. Furthermore, neptunium sorption on montmorillonite is influenced by ionic strength at pH <6 through ion exchange processes pointing towards the formation of outer-sphere surface complexes there. Isotherms measured at the sorption maximum showed the precipitation of presumably neptunium carbonate complexes above 3.10 -5 M under ambient air conditions. Additionally, they indicated progressive saturation of the sorption sites of γ-Al 2 O 3 . At selected pH (STx-1: 5.0, 7.0, 8.0, 8.5, 9.0, 9.5; γ-Al 2 O 3 : 8.5, 9.5) EXAFS samples were prepared as wet pastes with μM 237 Np and measured at room temperature in fluorescence mode at ANKA and ESRF. Several spectra were averaged and analysed with EXAFSPAK and FEFF 8.20 employing models of NaNpO 2 (CO 3 ) or soddyite, (UO 2 ) 2 SiO 4 .2(H 2 O). The shorter atomic distances of the neptunyl ion at pH 5 compared to the others hinted at the retention of the hydration shell and, thus, at outer-sphere sorption. On average the bond lengths for Np(V) sorbed on STx

  19. Yucca Mountain Project far-field sorption studies and data needs

    International Nuclear Information System (INIS)

    Meijer, A.

    1990-09-01

    Batch sorption experiments in which radionuclides dissolved in groundwaters from Yucca Mountain were sorbed onto samples of crushed tuff have resulted in a substantial database of sorption coefficients for radionuclides of interest to the repository program. Although this database has been useful in preliminary evaluations of Yucca Mountain as a potential site for a nuclear waste repository, the database has limitations that must be addressed before it can be used for performance assessment calculations in support of a license application for a waste repository. The purpose of this paper is to: review the applicability of simple (constant) sorption coefficients in transport calculations; review and evaluate alternative methods for the derivation of sorption coefficients; summarize and evaluate the present YMP sorption database to identify areas of data sufficiency and significant data gaps; summarize our current understanding of pertinent sorption mechanisms and associated kinetic parameters; evaluate the significance to the YMP of potential problems in the experimental determination and field application of sorption coefficients as enumerated by the NRC (Nuclear Regulatory Commission, 1987) in its technical position paper on sorption; formulate and evaluate strategies for the resolution of NRC concerns regarding experimental problems; and formulate a position on the sorption coefficient database and the level of understanding of sorption mechanisms likely to be required in the licensing application. 75 refs., 1 fig., 2 tabs

  20. Boron removal from aqueous solutions by ion-exchange resin: Column sorption-elution studies

    International Nuclear Information System (INIS)

    Koese, T. Ennil; Oztuerk, Nese

    2008-01-01

    A column sorption-elution study was carried out by using a strong base anion-exchange resin (Dowex 2 x 8) for the removal of boron from aqueous solutions. The breakthrough curve was obtained as a function of feed flow rate and the total and breakthrough capacity values of the resin were calculated. The boron on the resin was quantitatively eluted with 0.5 M HCl solution at different flow rates. Three consecutive sorption-elution-washing-regeneration-washing cycles were applied to the resin in order to investigate the reusability of the ion-exchange resin. Total capacity values remained almost the same after three sorption-elution-regeneration cycles. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic column parameters required for process design. The results proved that the models would describe the breakthrough curves well

  1. Testing Parametric versus Semiparametric Modelling in Generalized Linear Models

    NARCIS (Netherlands)

    Härdle, W.K.; Mammen, E.; Müller, M.D.

    1996-01-01

    We consider a generalized partially linear model E(Y|X,T) = G{X'b + m(T)} where G is a known function, b is an unknown parameter vector, and m is an unknown function.The paper introduces a test statistic which allows to decide between a parametric and a semiparametric model: (i) m is linear, i.e.

  2. Sorption of radionuclides on inorganic sorbents

    International Nuclear Information System (INIS)

    Rajec, P.; Matel, L.

    1995-01-01

    The sorption of cesium, strontium, plutonium and americium from water solution on natural zeolite, clay minerals, synthetic zeolites and ferrocyanides in silica gel matrix was studied. The same experiments but with synthetic zeolites irradiated by the dose 100 kGy proved no change in sorption properties. 1 tab., 4 refs

  3. Improved hydrogen sorption kinetics in wet ball milled Mg hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Li

    2011-05-04

    H{sub 2} with Nb{sub 2}O{sub 5} is much larger than the standard wet ball milled MgH{sub 2} with Nb{sub 2}O{sub 5} and the corresponding sorption behavior is also much improved. Furthermore, a simple model is built up in which the key parameter is main specific surface area and it follows the experimental desorption results quite well. (orig.)

  4. A study of sorption of cadmium by goethite in aqueous solution

    Directory of Open Access Journals (Sweden)

    N. Salami

    2002-06-01

    Full Text Available Investigation has been carried out on the potential of a locally sourced goethite for the removal of cadmium ion from aqueous solutions using batch equilibration technique. The maximum uptake of cadmium is 6.4  10-2 mg/g-goethite. The sorption kinetics appears to be rapid as equilibrium was attained within a period of 1 hour. The highest sorption capacity was obtained for particle size with diameter (Φ 0.09 mm. Both infrared spectrophotometric and X-ray diffraction (XRD techniques have also provided evidence for cadmium fixation on to the surface of the goethite. The sorption mechanism appears to follow Langmuir adsorption isotherm model. The Langmuir constants K and Xm (mass of Cd2+ required to form monolayer on the entire surface of the goethite were 0.096 mg/g-goethite and 0.075 mg/g-goethite, respectively.

  5. The NEA sorption data base (SDB)

    International Nuclear Information System (INIS)

    Ruegger, B.; Ticknor, K.

    1992-01-01

    The current NEA Sorption Data Base is developed to replace the former International Sorption Information Retrieval System (ISIRS) initiated at Pacific Northwest Laboratory and contains about 11,000 distribution coefficients with corresponding experimental condition parameters describing sorption of key nuclides for a large variety of solid and liquid phases. The SDB is designed to run on a micro-computer using the commercially available database software dBASE III Plus. For each recorded sorption experiment, the SDB provides a bibliographical reference, the most complete characterization of the solid and liquid phases available, a description of the experimental conditions and the distribution coefficient or retardation factor for each element studied. When available, parameters such as temperature, initial radionuclide concentration, pH, Eh, contact time, solid to solution ratio, sample origin, oxidation state and type of solution are included. The SDB provides information for a wide variety of rocks or geological materials, buffer backfill candidates, concretes/cements, elements (Am, Cs, Co, I, Np, Pu, Ra, Sr, Se, Tc, U and, to a lesser extent, Ag, Ba, C, Ce, Eu, Fe, Mn, Mo, Na, Nb, Ni, Pd, Pm, Ru, Sb, Sn, Y, Zn, and Zr), or radioisotopes. A compilation of sorption data like SDB provide a readily available source of data for radioactive waste repository performance assessments when site specific data are not available or essential, for example, during a site selection phase. 2 appendices

  6. Sorption of uranium and cesium by Hanford basalts and associated secondary smectite

    International Nuclear Information System (INIS)

    Ames, L.L.; McGarrah, J.E.; Walker, B.A.; Salter, P.F.

    1982-01-01

    Three characterized basalts and an associated secondary smectite were used in comparative uranium and cesium sorption studies. Experiments utilizing two synthetic characteristic basalt groundwaters at 23 and 60 0 C allowed comparison of increased temperature and carbonate concentration effects on Cs and U sorption. The sorption data were fitted to the Dubinin-Radushkevich (D-R) isotherm, and loading maxima and energetics derived. An increase in temperature caused a decrease in Cs sorption maxima on all solids from all groundwaters studied and an increase in U sorption maxima, especially from the higher-carbonate-content groundwater. Sorption energies were characteristic of ion exchange for both Cs and U sorption processes. Basalt U sorption maxima were relatively insignificant, but smectite U sorption maxima surpassed Cs sorption maxima in both groundwaters at 60 0 C. The uranyl carbonate complexes thus may be relatively temperature-sensitive. Upon removal of excess Fe-oxides from the secondary smectite, U sorption decreased and the D-R isotherm reverted to a normal Freundlich sorption isotherm. Removal of excess Fe-oxides from the basalts and secondary smectite would probably result in Freundlich sorption isotherms for both Cs and U. (Auth.)

  7. Dynamic moisture sorption characteristics of enzyme-resistant recrystallized cassava starch.

    Science.gov (United States)

    Mutungi, Christopher; Schuldt, Stefan; Onyango, Calvin; Schneider, Yvonne; Jaros, Doris; Rohm, Harald

    2011-03-14

    The interaction of moisture with enzyme-resistant recrystallized starch, prepared by heat-moisture treatment of debranched acid-modified or debranched non-acid-modified cassava starch, was investigated in comparison with the native granules. Crystallinities of the powdered products were estimated by X-ray diffraction. Moisture sorption was determined using dynamic vapor sorption analyzer and data fitted to various models. Percent crystallinities of native starch (NS), non-acid-modified recrystallized starch (NAMRS), and acid-modified recrystallized starch (AMRS) were 39.7, 51.9, and 56.1%, respectively. In a(w) below 0.8, sorption decreased in the order NS > NAMRS > AMRS in line with increasing sample crystallinities but did not follow this crystallinity dependence at higher a(w) because of condensation and polymer dissolution effects. Adsorbed moisture became internally absorbed in NS but not in NAMRS and AMRS, which might explain the high resistance of the recrystallized starches to digestion because enzyme and starch cannot approach each other over fairly sufficient surface at the molecular level.

  8. The sorption behaviour of 99Tc on activated carbon

    International Nuclear Information System (INIS)

    Xia Deying; Zeng Jishu

    2004-01-01

    The sorption behaviour of 99 Tc on apricot-pit activated carbon with batch experiment is studied. The influence of such factors as sorbent particle size, temperature, pH value on sorption ratio, and the Freundlich sorption isotherms are reported in this paper. (author)

  9. Benzene and MTBE Sorption in Fine Grain Sediments

    Science.gov (United States)

    Leal-Bautista, R. M.; Lenczewski, M. E.

    2003-12-01

    The practice of adding methyl tert-butyl ether (MTBE) to gasoline started in the late 1970s and increased dramatically in the 1990s. MTBE first was added as a substitute for tetra-ethyl lead then later as a fuel oxygenate. Although the use of MTBE has resulted in significant reduction in air pollution, it has become a significant groundwater contaminant due to its high solubility in water, high environmental mobility, and low potential for biodegradation. A recent report (1999-2001) by the Metropolitan Water District of Southern California in collaboration with United State Geological Survey and the Oregon Health and Science University found that MTBE was the second most frequent detected volatile organic compound in groundwater. In Illinois, MTBE has been found in 26 of the 1,800 public water supplies. MTBE has also been blended in Mexico into two types of gasoline sold in the country by the state oil company (PEMEX) but is not monitored in groundwater at this time. Early research on MTBE considered it unable to adsorb to soils and sediments, however, by increasing the organic matter and decreasing the size of the grains (silts or clays) this may increase sorption. The objective of this study is to determine if fine grained materials have the potential for sorption of MTBE due to its high specific surface area (10-700 m 2/g) and potentially high organic matter (0.5-3.8%). The experiment consisted of sorption isotherms to glacial tills from DeKalb, Illinois and lacustrine clays from Chalco, Mexico. Experiments were performed with various concentrations of MTBE and benzene (10, 50, 100, 500 and 1000 ug/L) at 10° C and 25° C. Results showed a range of values for the distribution coefficient (Kd, linear model). At 10° C the Kd value for MTBE was 0.187 mL/g for lacustrine clay while the glacial loess had a value of 0.009 mL/g. The highest Kd values with MTBE were 0.2859 mL/g for organic rich lacustrine clays and 0.014 mL/g for glacial loess at 25° C. The highest

  10. Properties comparison of biochars from corn straw with different pretreatment and sorption behaviour of atrazine.

    Science.gov (United States)

    Zhao, Xuchen; Ouyang, Wei; Hao, Fanghua; Lin, Chunye; Wang, Fangli; Han, Sheng; Geng, Xiaojun

    2013-11-01

    Biochar has been recognised as an efficient pollution control material. In this study, biochars (CS450 and ADPCS450) were produced using corn straw with different pretreatment techniques (without and with ammonium dihydrogen phosphate (ADP)). The character of the two biochars was compared using elemental analysis, specific surface area (SSA) and Fourier transform infrared spectra (FTIR). ADPCS450 had a higher residue yield and a much larger specific surface area than CS450. The Freundlich, Langmuir and Redlich-Peterson models were used to interpret the sorption behaviour of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), and the results fit the Redlich-Peterson equation best. The isothermal sorption parameters indicated that the sorption capacity of atrazine on ADPCS450 was much larger than the sorption capacity of atrazine on CS450. Atrazine sorption was also favoured in acidic solution and under higher temperature conditions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Model Predictive Control for Linear Complementarity and Extended Linear Complementarity Systems

    Directory of Open Access Journals (Sweden)

    Bambang Riyanto

    2005-11-01

    Full Text Available In this paper, we propose model predictive control method for linear complementarity and extended linear complementarity systems by formulating optimization along prediction horizon as mixed integer quadratic program. Such systems contain interaction between continuous dynamics and discrete event systems, and therefore, can be categorized as hybrid systems. As linear complementarity and extended linear complementarity systems finds applications in different research areas, such as impact mechanical systems, traffic control and process control, this work will contribute to the development of control design method for those areas as well, as shown by three given examples.

  12. Compilation of radionuclide sorption coefficients for performance assessment

    International Nuclear Information System (INIS)

    Carbol, P.; Engkvist, I.

    1997-09-01

    The report presents four possible site-specific conditions in Sweden. The different sorption mechanisms applicable to the studied elements together with the K d concept are shortly summarised. The influence of organic substances present in the groundwater on the element's sorption and mobility is also discussed. Criteria for selection of K d values are presented together with sensitivity of the values to pH, E h and salinity. Sorption coefficients are recommended for elements in the repository with half-life above 5.3 years. The elements reviewed are: Cs, Sr, Ra, Ln, Ac, Th, Pa, U, Np, Pu, Am, Cm, Co, Ni, Cd, Zr, Nb, Tc, Pd, Ag, Sn, C, I, Cl, Se and Kr. For every element there is a recommendation of a realistic K d value with an uncertainty limit. The selection is based on experimental investigations or chemical analogues. In some cases few or no K d data were found, and it is recommended that sorption studies be performed on elements such as Cd, Pa, Cm, Zr, Nb, Pd, Ag and Sn. The recommended K d values for the different element's sorption on granitic rock, serve as a guidance of the sorption performance

  13. Sorption behaviour of Np(IV) on illite, shale and MX-80 in high ionic strength solutions

    International Nuclear Information System (INIS)

    Shinya Nagasaki; Riddoch, Justin; Goguen, Jared; Walker, Andrew; Tammy Tianxiao Yang

    2017-01-01

    The dependence of sorption distribution coefficient (K_d) of Np(IV) for illite, shale and MX-80 was investigated as a function of pH_c and ionic strength (I) under high ionic strength, reducing conditions. The overall trends of K_d on three solids were independent of pH_c at 5 ≤ pH_c ≤ 10 and I at 0.5 M ≤ I ≤ 6 M. The surface complexation constants of Np(IV) sorption on illite and MX-80 were estimated by the 2 SPNE SC/CE model. The sorption model well predicted the pH_c dependence of K_d, but could not completely describe the ionic strength dependence. (author)

  14. Competitive sorption of heavy metals by water hyacinth roots.

    Science.gov (United States)

    Zheng, Jia-Chuan; Liu, Hou-Qi; Feng, Hui-Min; Li, Wen-Wei; Lam, Michael Hon-Wah; Lam, Paul Kwan-Sing; Yu, Han-Qing

    2016-12-01

    Heavy metal pollution is a global issue severely constraining aquaculture practices, not only deteriorating the aquatic environment but also threatening the aquaculture production. One promising solution is adopting aquaponics systems where a synergy can be established between aquaculture and aquatic plants for metal sorption, but the interactions of multiple metals in such aquatic plants are poorly understood. In this study, we investigated the absorption behaviors of Cu(II) and Cd(II) in water by water hyacinth roots in both single- and binary-metal systems. Cu(II) and Cd(II) were individually removed by water hyacinth roots at high efficiency, accompanied with release of protons and cations such as Ca 2+ and Mg 2+ . However, in a binary-metal arrangement, the Cd(II) sorption was significantly inhibited by Cu(II), and the higher sorption affinity of Cu(II) accounted for its competitive sorption advantage. Ionic exchange was identified as a predominant mechanism of the metal sorption by water hyacinth roots, and the amine and oxygen-containing groups are the main binding sites accounting for metal sorption via chelation or coordination. This study highlights the interactive impacts of different metals during their sorption by water hyacinth roots and elucidates the underlying mechanism of metal competitive sorption, which may provide useful implications for optimization of phytoremediation system and development of more sustainable aquaculture industry. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Non-linear degradation model of cement barriers in a borehole repository for disused radioactive sources

    International Nuclear Information System (INIS)

    Gharbieh, Heidar K.; Cota, Stela

    2015-01-01

    Narrow diameter borehole facilities (a few tens of centimeters), like the BOSS concept developed by the IAEA, provide a safe and cost effective disposal option for radioactive waste and particularly disused sources. The BOSS concept (borehole disposal of sealed radioactive sources) comprises a multi-barrier system of cement grout and stainless steel components. In order to predict the long-time performance of the cement barriers as an input of a future safety assessment under the specific hydrochemical and hydrological conditions, a non-linear degradation model was developed in this work. With the assistance of the program 'PHREEQC' it describes the change of the porosity and the hydraulic conductivity with time, which also let to conclusions concerning the change of the sorption capacity of the cement grout. This work includes the theoretical approach and illustrates the non-liner degradation by means of an exemplary water composition found in the saturated zone and the dimensions of the backfill made of cement grout representing a barrier of the BOSS borehole facility. (author)

  16. Sorption data base for performance assessment of radwaste repository

    International Nuclear Information System (INIS)

    Cho, Y.H.; Jung, J.; Lee, J.K.; Hahn, P.S.

    2001-01-01

    Sorption data base (SDB) provides readily available data for the performance assessment of radwaste repository when site-specific data are not available and/or more reference data are needed. The software developed in the Korea Atomic Energy Research Institute (KAERI), SDB-21C, is a graphic user interface (GUI) program that provides efficient and user friendly tools for evaluating the large amount of sorption data. The data base of distribution coefficients compiled in the program contains about 11,000 Nuclear Energy Agency (NEA) data and 2,000 KAERI data up to now while the addition of new data is under progress. Furthermore, the parametric model and its compiled data sets are also included in SDB-21C. (author)

  17. Radionuclide sorption on low-exchange capacity Hanford site soils

    International Nuclear Information System (INIS)

    Routson, R.C.; Barney, G.S.; Smith, R.M.

    1984-01-01

    Trace Distribution Coefficients (Kd values) for 134 Cs, 85 Sr, and 60 Co sorption were found to be a function of sediment type (soil type) and of the solution concentration of macroions including NA + , K + , and Ca +2 over wide macroion concentration ranges. These Kd value functions are required as input sorption parameters to a mass transport model. Four methods were evaluated for measuring the Kd value macroion functional relationships for each sediment type. Precision, bias, and cost effectiveness were compared for choosing a preferred method. The prefered method, an empirical-statistical method (Box-Behnken method), was found to be as precise and unbiased as the other methods and the most cost effective. 12 references, 7 figures, 10 tables

  18. Kinetic, equilibrium and thermodynamic studies on sorption of uranium and thorium from aqueous solutions by a selective impregnated resin containing carminic acid

    International Nuclear Information System (INIS)

    Rahmani-Sani, Abolfazl; Hosseini-Bandegharaei, Ahmad; Hosseini, Seyyed-Hossein; Kharghani, Keivan; Zarei, Hossein; Rastegar, Ayoob

    2015-01-01

    Highlights: • The objective of the study is to investigate the potential application of a selective EIR for sorption of U(VI) and Th(IV) ions. • The effects of several physiochemical parameters were investigated. • The sorption kinetics and sorption isotherms were used to explain the sorption mechanism. • The thermodynamic studies showed the feasibility of sorption process. • The EIR beads showed a great potential for effective removal of U(VI) and Th(IV) ions. - Abstract: In this work, the removal of uranium and thorium ions from aqueous solutions was studied by solid–liquid extraction using an advantageous extractant-impregnated resin (EIR) prepared by loading carminic acid (CA) onto Amberlite XAD-16 resin beads. Batch sorption experiments using CA/XAD-16 beads for the removal of U(VI) and Th(IV) ions were carried out as a function of several parameters, like equilibration time, metal ion concentration, etc. The equilibrium data obtained from the sorption experiments were adjusted to the Langmuir isotherm model and the calculated maximum sorption capacities in terms of monolayer sorption were in agreement with those obtained from the experiments. The experimental data on the sorption behavior of both metal ions onto the EIR beads fitted well in both Bangham and intra-particle diffusion kinetic models, indicating that the intra-particle diffusion is the rate-controlling step. The thermodynamic studies at different temperatures revealed the feasibility and the spontaneous nature of the sorption process for both uranium and thorium ions

  19. U(VI) sorption on granite: prediction and experiments

    International Nuclear Information System (INIS)

    Nebelung, C.; Brendler, V.

    2010-01-01

    One widely accepted approach - component additivity (CA) - to describe the sorption of contaminants onto complex materials such as rocks or soils is based on the assumption that the surface of a complex mineral assemblage is composed of a mixture of mineral constituents whose surface properties are known from independent studies. An internally consistent SCM (surface complexation model) database can be developed that describes the adsorption reactions of solutes to each phase. Here, the capability of such a methodology was tested, using the code MINTEQA2 including thermodynamic data of the NEA-TDB, and literature data for SCM, namely the DDL model. The sorption characteristics of U(VI) on granite (from Eibenstock, Saxony, Germany, with the main components quartz, albite, orthoclase, and muscovite) was predicted and then compared to batch experiments. Granite plays an important role in the remediation of former uranium ore mining and milling sites, but is also one of the host rocks considered for final disposal of nuclear materials. Safety assessment requires a detailed understanding of this system and its retention potential with regard to hazardous components. Namely the sorption of uranium in this complex rock is not fully understood yet. The experiments thus also provided a better understanding of the far-field behaviour in granitic geological nuclear repositories. The robustness of the prediction was tested by variation of the granite composition and the variation of the specific surface area (SSA) - first all components were predicted with a uniform granite SSA, second with a distinct SSA for each granite component (determined on pure minerals for the same grain size fractions). Changes in compositions yielded only marginal differences in the prediction. Different approaches to SSA showed somewhat larger deviations. In conclusion, the CA methodology is a valid and robust approach to U(VI) sorption onto complex substrates such as granite, provided sufficient

  20. Computer simulation of molecular sorption in zeolites

    International Nuclear Information System (INIS)

    Calmiano, Mark Daniel

    2001-01-01

    The work presented in this thesis encompasses the computer simulation of molecular sorption. In Chapter 1 we outline the aims and objectives of this work. Chapter 2 follows in which an introduction to sorption in zeolites is presented, with discussion of structure and properties of the main zeolites studied. Chapter 2 concludes with a description of the principles and theories of adsorption. In Chapter 3 we describe the methodology behind the work carried out in this thesis. In Chapter 4 we present our first computational study, that of the sorption of krypton in silicalite. We describe work carried out to investigate low energy sorption sites of krypton in silicalite where we observe krypton to preferentially sorb into straight and sinusoidal channels over channel intersections. We simulate single step type I adsorption isotherms and use molecular dynamics to study the diffusion of krypton and obtain division coefficients and the activation energy. We compare our results to previous experimental and computational studies where we show our work to be in good agreement. In Chapter 5 we present a systematic study of the sorption of oxygen and nitrogen in five lithium substituted zeolites using a transferable interatomic potential that we have developed from ab initio calculations. We show increased loading of nitrogen compared to oxygen in all five zeolites studied as expected and simulate adsorption isotherms, which we compare to experimental and simulated data in the literature. In Chapter 6 we present work on the sorption of ferrocene in the zeolite NaY. We show that a simulated, low energy sorption site for ferrocene is correctly located by comparing to X-ray powder diffraction results for this same system. The thesis concludes with some overall conclusions and discussion of opportunities for future work. (author)