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Sample records for pseudo first-order kinetic

  1. THERMOKINETIC STUDY OF THE ZERO, FIRST AND SECOND ORDER REACTIONS IN A PSEUDO-ADIABATIC CALORIMETER: Numerical approach and experimental dat

    Directory of Open Access Journals (Sweden)

    Johanna Mendoza

    2012-11-01

    Full Text Available The signal produced by a pseudo-adiabaticcalorimeter is simulated by numericalsolution of the differential equations thatmodel the chemical kinetics [1], the thermalproperties of the calorimetric cell[2], and the response of the thermistorused as a thermometric sensor [3]. These equations show that the calorimetricsignal is related with concentrationin a complex way. Therefore, a comparisonbetween the signals of the threebasic kinetics reactions (zero, first andsecond order was made, as a first stepto obtain a standard procedure to followchemical kinetics using a calorimeter. Inorder to help understanding this relationship,the initial rate method was applied to the simulated data to assess the relationshipbetween the order and the kineticconstants calculated with those usedfor the simulations. As it was expected,the initial rate method for the calorimetricdata, do not give a slope directly relatedwith the order of the reaction, as itwould be produced, for example, in datafrom a spectrophotometer. However, alinear relationship was found betweenwhat we call the “calorimetric order”and the kinetic order. Finally, the developedprocedure was applied to the studyof the H2O2 decomposition catalyzedwith Fe3+ in homogeneous phase andwith activated carbon in heterogeneousphase, finding the order and the kineticsconstants of the global processes, whichwere in close agreement with those inthe literature.

  2. Ammonia removal in electrochemical oxidation: Mechanism and pseudo-kinetics

    International Nuclear Information System (INIS)

    Li Liang; Liu Yan

    2009-01-01

    This paper investigated the mechanism and pseudo-kinetics for removal of ammonia by electrochemical oxidation with RuO 2 /Ti anode using batch tests. The results show that the ammonia oxidation rates resulted from direct oxidation at electrode-liquid interfaces of the anode by stepwise dehydrogenation, and from indirect oxidation by hydroxyl radicals were so slow that their contribution to ammonia removal was negligible under the condition with Cl - . The oxidation rates of ammonia ranged from 1.0 to 12.3 mg N L -1 h -1 and efficiency reached nearly 100%, primarily due to the indirect oxidation of HOCl, and followed pseudo zero-order kinetics in electrochemical oxidation with Cl - . About 88% ammonia was removed from the solution. The removed one was subsequently found in the form of N 2 in the produced gas. The rate at which Cl - lost electrons at the anode was a major factor in the overall ammonia oxidation. Current density and Cl - concentration affected the constant of the pseudo zero-order kinetics, expressed by k = 0.0024[Cl - ] x j. The ammonia was reduced to less than 0.5 mg N L -1 after 2 h of electrochemical oxidation for the effluent from aerobic or anaerobic reactors which treated municipal wastewater. This result was in line with the strict discharge requirements

  3. 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.

  4. Effect of electrolyte nature on kinetics of remazol yellow G removal by electrocoagulation

    Science.gov (United States)

    Rajabi, M.; Bagheri-Roochi, M.; Asghari, A.

    2011-10-01

    The present study describes an electrocoagulation process for the removal of remazol yellow G from dye solutions using Iron as the anode and Steel as the cathode. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations in different conditions. The adsorption kinetics was well described by the pseudo-second-order kinetic model.

  5. Kinetic Study of Curcumin on Modal Fabric

    Directory of Open Access Journals (Sweden)

    Abu Naser Md. Ahsanul Haque

    2018-03-01

    Full Text Available A kinetic study of curcumin on modal fabric was carried out using an initial dye concentration of 1 g/L at three different temperatures, 70 °C, 85 °C and 100 °C, at pH 7 and an material to liquor ratio of 1:20. Pseudo first-order and pseudo second-order kinetics were applied, and it was found that the adsorption kinetics of curcumin on modal fabric matched the pseudo second-order kinetic model. The activation energy was found to be equal to 71.14 kJ/mol, while the enthalpy and entropy of activation were 68.16 kJ/mol and –66.02 J/molK respectively.

  6. A critical look at the kinetic models of thermoluminescence-II. Non-first order kinetics

    International Nuclear Information System (INIS)

    Sunta, C M; Ayta, W E F; Chubaci, J F D; Watanabe, S

    2005-01-01

    Non-first order (FO) kinetics models are of three types; second order (SO), general order (GO) and mixed order (MO). It is shown that all three of these have constraints in their energy level schemes and their applicable parameter values. In nature such restrictions are not expected to exist. The thermoluminescence (TL) glow peaks produced by these models shift their position and change their shape as the trap occupancies change. Such characteristics are very unlike those found in samples of real materials. In these models, in general, retrapping predominates over recombination. It is shown that the quasi-equilibrium (QE) assumption implied in the derivation of the TL equation of these models is quite valid, thus disproving earlier workers' conclusion that QE cannot be held under retrapping dominant conditions. However notwithstanding their validity, they suffer from the shortcomings as stated above and have certain lacunae. For example, the kinetic order (KO) parameter and the pre-exponential factor which are assumed to be the constant parameters of the GO kinetics expression turn out to be variables when this expression is applied to plausible physical models. Further, in glow peak characterization using the GO expression, the quality of fit is found to deteriorate when the best fitted value of KO parameter is different from 1 and 2. This means that the found value of the basic parameter, namely the activation energy, becomes subject to error. In the MO kinetics model, the value of the KO parameter α would change with dose, and thus in this model also, as in the GO model, no single value of KO can be assigned to a given glow peak. The paper discusses TL of real materials having characteristics typically like those of FO kinetics. Theoretically too, a plausible physical model of TL emission produces glow peaks which have characteristics of FO kinetics under a wide variety of parametric combinations. In the background of the above findings, it is suggested that

  7. An improved solution of first order kinetics for biochemical oxygen ...

    African Journals Online (AJOL)

    This paper evaluated selected Biochemical Oxygen Demand first order kinetics methods. Domesticinstitutional wastewaters were collected twice in a month for three months from the Obafemi Awolowo University, Ile-Ife waste stabilization ponds. Biochemical Oxygen Demand concentrations at different days were determined ...

  8. Higher-order Jordan Osserman pseudo-Riemannian manifolds

    International Nuclear Information System (INIS)

    Gilkey, Peter B; Ivanova, Raina; Zhang Tan

    2002-01-01

    We study the higher-order Jacobi operator in pseudo-Riemannian geometry. We exhibit a family of manifolds so that this operator has constant Jordan normal form on the Grassmannian of subspaces of signature (r, s) for certain values of (r, s). These pseudo-Riemannian manifolds are new and non-trivial examples of higher-order Osserman manifolds

  9. Higher-order Jordan Osserman pseudo-Riemannian manifolds

    Energy Technology Data Exchange (ETDEWEB)

    Gilkey, Peter B [Mathematics Department, University of Oregon, Eugene, OR 97403 (United States); Ivanova, Raina [Mathematics Department, University of Hawaii - Hilo, 200 W Kawili St, Hilo, HI 96720 (United States); Zhang Tan [Department of Mathematics and Statistics, Murray State University, Murray, KY 42071 (United States)

    2002-09-07

    We study the higher-order Jacobi operator in pseudo-Riemannian geometry. We exhibit a family of manifolds so that this operator has constant Jordan normal form on the Grassmannian of subspaces of signature (r, s) for certain values of (r, s). These pseudo-Riemannian manifolds are new and non-trivial examples of higher-order Osserman manifolds.

  10. Stiffness Confinement Method with Pseudo Absorption for Spatial Kinetics

    International Nuclear Information System (INIS)

    Park, Beom Woo; Joo, Han Gyu; Chao, Yungan

    2013-01-01

    The primary advantage of the SCM is that it is possible to use larger time step sizes. This advantage comes from the fact because the SCM involves the solution of an eigenvalue problem instead of the ordinary form of a fixed source problem. Since using a large time step size is strongly desired in the direct whole core transport calculation for transient problems, we investigate here the SCM for spatial kinetics first with a simple one-dimensional, one-group diffusion equation and propose an improved formulation. The performance of the improved SCM for spatial kinetics is assessed by comparing the SCM solutions with the standard method solutions employing the Crank-Nicholson method with exponential transform. The stiffness confinement method for spatial kinetics was refined with the pseudo absorption term representing the dynamic frequencies. It was verified that the proposed SCM works much better than the Crank-Nicholson method with exponential transform in that time step sizes larger than 20 msec can be using in a super prompt-critical transient involving 1.5$ reactivity insertion

  11. Stiffness Confinement Method with Pseudo Absorption for Spatial Kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Park, Beom Woo; Joo, Han Gyu [Seoul National Univ., Seoul (Korea, Republic of); Chao, Yungan [Retired in China, Beijing (China)

    2013-05-15

    The primary advantage of the SCM is that it is possible to use larger time step sizes. This advantage comes from the fact because the SCM involves the solution of an eigenvalue problem instead of the ordinary form of a fixed source problem. Since using a large time step size is strongly desired in the direct whole core transport calculation for transient problems, we investigate here the SCM for spatial kinetics first with a simple one-dimensional, one-group diffusion equation and propose an improved formulation. The performance of the improved SCM for spatial kinetics is assessed by comparing the SCM solutions with the standard method solutions employing the Crank-Nicholson method with exponential transform. The stiffness confinement method for spatial kinetics was refined with the pseudo absorption term representing the dynamic frequencies. It was verified that the proposed SCM works much better than the Crank-Nicholson method with exponential transform in that time step sizes larger than 20 msec can be using in a super prompt-critical transient involving 1.5$ reactivity insertion.

  12. Comparative evaluation of adsorption kinetics of diclofenac and isoproturon by activated carbon.

    Science.gov (United States)

    Torrellas, Silvia A; Rodriguez, Araceli R; Escudero, Gabriel O; Martín, José María G; Rodriguez, Juan G

    2015-01-01

    Adsorption mechanism of diclofenac and isoproturon onto activated carbon has been proposed using Langmuir and Freundlich isotherms. Adsorption capacity and optimum adsorption isotherms were predicted by nonlinear regression method. Different kinetic equations, pseudo-first-order, pseudo-second-order, intraparticle diffusion model and Bangham kinetic model, were applied to study the adsorption kinetics of emerging contaminants on activated carbon in two aqueous matrices.

  13. Rate kernel theory for pseudo-first-order kinetics of diffusion-influenced reactions and application to fluorescence quenching kinetics.

    Science.gov (United States)

    Yang, Mino

    2007-06-07

    Theoretical foundation of rate kernel equation approaches for diffusion-influenced chemical reactions is presented and applied to explain the kinetics of fluorescence quenching reactions. A many-body master equation is constructed by introducing stochastic terms, which characterize the rates of chemical reactions, into the many-body Smoluchowski equation. A Langevin-type of memory equation for the density fields of reactants evolving under the influence of time-independent perturbation is derived. This equation should be useful in predicting the time evolution of reactant concentrations approaching the steady state attained by the perturbation as well as the steady-state concentrations. The dynamics of fluctuation occurring in equilibrium state can be predicted by the memory equation by turning the perturbation off and consequently may be useful in obtaining the linear response to a time-dependent perturbation. It is found that unimolecular decay processes including the time-independent perturbation can be incorporated into bimolecular reaction kinetics as a Laplace transform variable. As a result, a theory for bimolecular reactions along with the unimolecular process turned off is sufficient to predict overall reaction kinetics including the effects of unimolecular reactions and perturbation. As the present formulation is applied to steady-state kinetics of fluorescence quenching reactions, the exact relation between fluorophore concentrations and the intensity of excitation light is derived.

  14. Cardiorespiratory Kinetics Determined by Pseudo-Random Binary Sequences - Comparisons between Walking and Cycling.

    Science.gov (United States)

    Koschate, J; Drescher, U; Thieschäfer, L; Heine, O; Baum, K; Hoffmann, U

    2016-12-01

    This study aims to compare cardiorespiratory kinetics as a response to a standardised work rate protocol with pseudo-random binary sequences between cycling and walking in young healthy subjects. Muscular and pulmonary oxygen uptake (V̇O 2 ) kinetics as well as heart rate kinetics were expected to be similar for walking and cycling. Cardiac data and V̇O 2 of 23 healthy young subjects were measured in response to pseudo-random binary sequences. Kinetics were assessed applying time series analysis. Higher maxima of cross-correlation functions between work rate and the respective parameter indicate faster kinetics responses. Muscular V̇O 2 kinetics were estimated from heart rate and pulmonary V̇O 2 using a circulatory model. Muscular (walking vs. cycling [mean±SD in arbitrary units]: 0.40±0.08 vs. 0.41±0.08) and pulmonary V̇O 2 kinetics (0.35±0.06 vs. 0.35±0.06) were not different, although the time courses of the cross-correlation functions of pulmonary V̇O 2 showed unexpected biphasic responses. Heart rate kinetics (0.50±0.14 vs. 0.40±0.14; P=0.017) was faster for walking. Regarding the biphasic cross-correlation functions of pulmonary V̇O 2 during walking, the assessment of muscular V̇O 2 kinetics via pseudo-random binary sequences requires a circulatory model to account for cardio-dynamic distortions. Faster heart rate kinetics for walking should be considered by comparing results from cycle and treadmill ergometry. © Georg Thieme Verlag KG Stuttgart · New York.

  15. Biosorption kinetics of Cd (II), Cr (III) and Pb (II) in aqueous solutions by olive stone

    OpenAIRE

    M. Calero; F. Hernáinz; G. Blázquez; M. A. Martín-Lara; G. Tenorio

    2009-01-01

    A by-product from olive oil production, olive stone, was investigated for the removal of Cd (II), Cr (III) and Pb (II) from aqueous solutions. The kinetics of biosorption are studied, analyzing the effect of the initial concentration of metal and temperature. Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models have been used to represent the kinetics of the process and obtain the main kinetic parameters. The results show that the pseudo-second order model is th...

  16. Laboratory studies on the adsorption kinetics of 137Cs in sediment

    International Nuclear Information System (INIS)

    Jaison, T.J.; Patra, A.K.; Ravi, P.M.; Sarkar, P.K.

    2012-01-01

    During the operation of a nuclear reactor, extreme care is taken to minimize the release of radionuclides to the environment. Low level radioactive liquid waste generated is treated and released to the nearest water body after monitoring to ensure that the activity levels are well within the regulatory limits. Environmental Survey Laboratories (ESL) attached to power plants carry out a systematic environmental monitoring and impact assessment to ensure that the dose to the member of public is well within the limits. This paper presents the results of a systematic laboratory study carried out at ESL, Kakrapar Atomic Power Station (KAPS) on the adsorption kinetics of 137 Cs in sediment. The study is to evaluate the sorption kinetics of 137 Cs + onto site specific sediment. Sets of adsorption experiments were conducted at specific time intervals for two different 137 Cs + concentrations, keeping other experimental conditions same. The kinetics of 137 Cs + adsorption on sediment is analyzed using pseudo first order, pseudo second order, and intra-particle diffusion kinetic models. The pseudo-second order kinetic model is better correlated with the kinetics data compared with the pseudo first-order model. This indicates 137 Cs + ions can be involved in chemical bonding during the adsorption process to the analysed sediment. This chemi-sorption processes show a good compliance with the pseudo-second order kinetic model. It is also evident that lower concentration exhibits greater adsorption rate (k 2 value is 1.85 x 10 -5 Bq g -1 min -1 for 1245 Bq sets and 1.05 x 10 -5 Bq g -1 min -1 for 2456 Bq sets) from the pseudo second order model. Intra-particle diffusion rate constants (K id ) were also obtained by two different models for both the concentrations and found to be higher for higher concentration. (author)

  17. MODELLING OF KINETICS OF FLUORINE ADSORPTION ONTO MODIFIED DIATOMITE

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    VEACESLAV ZELENTSOV

    2017-03-01

    Full Text Available The paper presents kinetics modelling of adsorption of fluorine onto modified diatomite, its fundamental characteristics and mathematical derivations. Three models of defluoridation kinetics were used to fit the experimental results on adsorption fluorine onto diatomite: the pseudo-first order model Lagergren, the pseudo-second order model G. McKay and H.S. Ho and intraparticle diffusion model of W.J. Weber and J.C. Morris. Kinetics studies revealed that the adsorption of fluorine followed second-order rate model, complimented by intraparticle diffusion kinetics. The adsorption mechanism of fluorine involved three stages – external surface adsorption, intraparticle diffusion and the stage of equilibrium.

  18. First-order hydrothermal oxidation kinetics of digested sludge compared with raw sludge.

    Science.gov (United States)

    Shanableh, A; Imteaz, M

    2008-09-01

    This article presents an assessment of the first-order hydrothermal oxidation kinetics of a selected digested sludge at subcritical ( 374 degrees C) temperatures in the range of 250-460 degrees C. Furthermore, the results were compared with reported oxidation kinetics of raw sludge treated under identical experimental conditions. In the assessment, oxidation was considered to proceed in two steps: (1) decomposition of the particulate, or non-filterable, chemical oxygen demand (PCOD); followed by (2) ultimate oxidation and removal of the total, particulate and soluble, COD. The accumulation and removal of soluble COD (SCOD) was determined from the difference between the rates of sludge decomposition and ultimate oxidation. Using results from batch and continuous-flow hydrothermal treatment experiments, the reacting organic ingredients were separated into groups according to the ease or difficulty at which they were decomposed or removed, with Arrhenius-type activation energy levels assigned to the different groups. The analysis confirmed that within the treatment range of 75% to more than 97% COD removal, the oxidation kinetics of the digested and raw sludges were nearly identical despite differences in the proportions of their original organic ingredients. The original organic ingredients were mostly removed above 75% COD removal, and the oxidation kinetics appeared to be dominated by the removal of acetic acid, an intermediate by-product which constituted 50% to more than 80% of the remaining COD. Furthermore, the oxidation kinetics of both sludge types were consistent with reported first-order oxidation kinetics of pure acetic acid solutions. The resulting kinetic models adequately represented hydrothermal oxidation of digested sludge, in terms of COD and PCOD removals, as well as accumulation and removal of the soluble SCOD.

  19. Kinetics and thermodynamics of first-order Markov chain copolymerization

    Energy Technology Data Exchange (ETDEWEB)

    Gaspard, P.; Andrieux, D. [Center for Nonlinear Phenomena and Complex Systems, Université Libre de Bruxelles, Code Postal 231, Campus Plaine, B-1050 Brussels (Belgium)

    2014-07-28

    We report a theoretical study of stochastic processes modeling the growth of first-order Markov copolymers, as well as the reversed reaction of depolymerization. These processes are ruled by kinetic equations describing both the attachment and detachment of monomers. Exact solutions are obtained for these kinetic equations in the steady regimes of multicomponent copolymerization and depolymerization. Thermodynamic equilibrium is identified as the state at which the growth velocity is vanishing on average and where detailed balance is satisfied. Away from equilibrium, the analytical expression of the thermodynamic entropy production is deduced in terms of the Shannon disorder per monomer in the copolymer sequence. The Mayo-Lewis equation is recovered in the fully irreversible growth regime. The theory also applies to Bernoullian chains in the case where the attachment and detachment rates only depend on the reacting monomer.

  20. Kinetics of Oxidation of Aliphatic Alcohols by Potassium Dichromate ...

    African Journals Online (AJOL)

    The kinetics of oxidation of four aliphatic alcohols in acidic aqueous and micellar media were investigated. The reaction was found to be first-order with respect to both alcohol and oxidant. Pseudo-first-order kinetics were found to be perfectly applicable with ethanol, 1-propanol and 2-propanol while deviation was observed ...

  1. Kinetic Approach for the Adsorption of Organophosphorous Pesticides from Aqueous Solution Using “Waste” Jute Fiber Carbon

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    S. Senthilkumaar

    2010-01-01

    Full Text Available Chemically activated “Waste” Jute Fiber carbon has been effectively used for the removal of five organophosphorous pesticides (malathion, monocrotophos, methylparathion, phosphamidon and dimethoate from aqueous solutions. The prepared activated jute fiber carbon was characterized by using Elemental analyzer and proximate analysis methods. The adsorption equilibrium was examined at 28 ºC. Three different kinetic models, the pseudo first order, pseudo second order and Elovich kinetic models were selected to analyses the adsorption process. To compare the fitness of pseudo first order and pseudo second order, sum of the squares of the errors and correlation coefficient, r2 values were calculated. The Elovich model was used to confirm the chemisorptions.

  2. Adsorption kinetics of Rhodamine-B on used black tea leaves

    Directory of Open Access Journals (Sweden)

    Hossain Mohammad

    2012-08-01

    Full Text Available Abstract Rhodamine B (Rh-B is one of the most common pollutants in the effluents of textile industries effluents in developing countries. This study was carried out to evaluate the applicability of used black tea leaves (UBTL for the adsorptive removal of Rh-B from aqueous system by investigating the adsorption kinetics in batch process. The effects of concentration and temperature on adsorption kinetics were examined. First-, second- and pseudo-second order kinetic equations were used to investigate the adsorption mechanism. The adsorption of Rh-B on UBTL followed pseudo-second order kinetics. The equilibrium amount adsorbed and the equilibrium concentration were calculated from pseudo-second-order kinetic plots for different initial concentrations of Rh-B to construct the adsorption isotherm. The adsorption isotherm was well expressed by Langmuir equation. The maximum adsorption capacity of UBTL to Rh-B was found to be 53.2 mg/g at pH = 2.0. The equilibrium amount adsorbed, calculated from pseudo-second-order kinetic plots, increased with temperature increase. The positive value of enthalpy of adsorption, ΔHads = 31.22 kJ/mol, suggested that the adsorption of Rh-B on UBTL at pH = 2.0 is an endothermic process.

  3. Equilibrium and Kinetic Sorption of Some Heavy Metals from Aqueous Waste Solutions Using p (AAc-HEMA)

    International Nuclear Information System (INIS)

    El-Sayed, A.H.; Khalil, F.H.; Elnesr, E.; Mansour, T.; El-Gammal, B.; El -Sabbah, M.M.B.

    2013-01-01

    Removal of heavy metals from aqueous waste solution using poly acrylic acid / 2-hydroxy ethyle methacrylate ( p-AAc/ HEMA) was investigated. Experiments were carried out as function of contact time, initial concentration, ph, particle size and temperature. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. The results indicated that poly acrylic acid / 2-hydroxy ethyle methacrylate (p-AAc/ HEMA) is suitable as adsorbent material for adsorption of Sr 2+ , Co 2+ , Cd 2+ , Zn 2+ , Nd 3+ and Eu 3+ radio active nuclei from aqueous solutions.

  4. Distributions of Autocorrelated First-Order Kinetic Outcomes: Illness Severity.

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    James D Englehardt

    Full Text Available Many complex systems produce outcomes having recurring, power law-like distributions over wide ranges. However, the form necessarily breaks down at extremes, whereas the Weibull distribution has been demonstrated over the full observed range. Here the Weibull distribution is derived as the asymptotic distribution of generalized first-order kinetic processes, with convergence driven by autocorrelation, and entropy maximization subject to finite positive mean, of the incremental compounding rates. Process increments represent multiplicative causes. In particular, illness severities are modeled as such, occurring in proportion to products of, e.g., chronic toxicant fractions passed by organs along a pathway, or rates of interacting oncogenic mutations. The Weibull form is also argued theoretically and by simulation to be robust to the onset of saturation kinetics. The Weibull exponential parameter is shown to indicate the number and widths of the first-order compounding increments, the extent of rate autocorrelation, and the degree to which process increments are distributed exponential. In contrast with the Gaussian result in linear independent systems, the form is driven not by independence and multiplicity of process increments, but by increment autocorrelation and entropy. In some physical systems the form may be attracting, due to multiplicative evolution of outcome magnitudes towards extreme values potentially much larger and smaller than control mechanisms can contain. The Weibull distribution is demonstrated in preference to the lognormal and Pareto I for illness severities versus (a toxicokinetic models, (b biologically-based network models, (c scholastic and psychological test score data for children with prenatal mercury exposure, and (d time-to-tumor data of the ED01 study.

  5. Kinetics of the Adsorption of Bovine Serum Albumin of White Wine ...

    African Journals Online (AJOL)

    This study investigates the kinetics of adsorption of bovine serum albumin, BSA, in white wine model solutions onto activated carbon, AC, and alumina, AL. Pseudo-first order and pseudo-second order models were applied to determine the rate and mechanism of adsorption of the white wine protein during the haze removal ...

  6. A comparison of zero-order, first-order, and Monod biotransformation models

    International Nuclear Information System (INIS)

    Bekins, B.A.; Warren, E.; Godsy, E.M.

    1998-01-01

    Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K S , this assumption is often made without verification of this condition. The authors present a formal error analysis showing that the relative error in the first-order approximation is S/K S and in the zero-order approximation the error is K S /S. They then examine the problems that arise when the first-order approximation is used outside the range for which it is valid. A series of numerical simulations comparing results of first- and zero-order rate approximations to Monod kinetics for a real data set illustrates that if concentrations observed in the field are higher than K S , it may be better to model degradation using a zero-order rate expression. Compared with Monod kinetics, extrapolation of a first-order rate to lower concentrations under-predicts the biotransformation potential, while extrapolation to higher concentrations may grossly over-predict the transformation rate. A summary of solubilities and Monod parameters for aerobic benzene, toluene, and xylene (BTX) degradation shows that the a priori assumption of first-order degradation kinetics at sites contaminated with these compounds is not valid. In particular, out of six published values of K S for toluene, only one is greater than 2 mg/L, indicating that when toluene is present in concentrations greater than about a part per million, the assumption of first-order kinetics may be invalid. Finally, the authors apply an existing analytical solution for steady-state one-dimensional advective transport with Monod degradation kinetics to a field data set

  7. Kinetics and Isotherm of Sunset Yellow Dye Adsorption on Cadmium Sulfide Nanoparticle Loaded on Activated Carbon

    Directory of Open Access Journals (Sweden)

    N. Mosallanejad, A. Arami

    2012-03-01

    Full Text Available The objective of this study was to assess the potential of cadmium sulfide nanoparticles loaded onto activated carbon (CdSN-AC for the removal of sunset yellow (SY dye from aqueous solution. Adsorption studies were conducted in a batch mode varying solution pH, contact time, initial dye concentration, CdSN-AC dose. In order to investigate the efficiency of SY adsorption on CdSN-AC, pseudo-first-order, pseudo-second-order kinetic models were studied. It was observed that the pseudo-second-order kinetic model fits better than other kinetic models with good correlation coefficient. Equilibrium data were fitted to the Langmuir model. It was found that the sorption of SY onto CdSN-AC is followed by these results. 

  8. Kinetics of heat-induced color change of a tuna-vegetable mixture

    OpenAIRE

    Scherer, Erika; Sandoval, Aleida J; Barreiro, José A

    2009-01-01

    Heat induced color change kinetics in a tuna-vegetable mixture was evaluated by measuring color parameter "L" (Hunter-Lab) and 5-hydroxi-methyl-furfural (5-HMF) accumulation. For this purpose small reusable stainless steel TDT cans were used and the kinetic studies performed in a temperature range characteristic of thermal processing of low acid canned foods (110-125°C). The color parameter L was better described by a pseudo zero order while a pseudo first order reaction was found for 5-HMF a...

  9. Equilibrium, kinetics and thermodynamics studies of textile dyes adsorption on modified Tunisian clay

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    naghmouchi nahed

    2016-04-01

    Full Text Available The adsorption capacity of two anionic textile dyes (RR120 and BB150 on DMSO intercalated Tunisian raw clay was investigated with respect to contact time, initial dye concentration, pH and Temperature. The equilibrium data were fitted into Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. The kinetic parameters were calculated using pseudo-first order, pseudo second-order, intra-particle diffusion and Elovich kinetic models. The thermodynamic parameters (DH°, DS° and DG° of the adsorption process were also evaluated.

  10. Sorption Kinetics for the Removal of Cadmium and Zinc onto Palm Kernel Shell Based Activated Carbon

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    Muhammad Muhammad

    2010-12-01

    Full Text Available The kinetics and mechanism of cadmium and zinc adsorption on palm kernel shell based activated carbons (PKSAC have been studied. A series of batch laboratory studies were conducted in order to investigate the suitability of palm kernel shell based activated carbon (PKSAC for the removal of cadmium (cadmium ions and zinc (zinc ions from their aqueous solutions. All batch experiments were carried out at pH 7.0 and a constant temperature of 30+-1°C using an incubator shaker that operated at 150 rpm. The kinetics investigated includes the pseudo first order, the pseudo-second order and the intraparticle diffusion models. The pseudo-second order model correlate excellently the experimental data, suggesting that chemisorption processes could be the rate-limiting step. Keywords: adsorption, cadmium, kinetics, palm kernel shell, zinc

  11. Evaluation of the kinetic oxidation of aqueous volatile organic compounds by permanganate.

    Science.gov (United States)

    Mahmoodlu, Mojtaba G; Hassanizadeh, S Majid; Hartog, Niels

    2014-07-01

    The use of permanganate solutions for in-situ chemical oxidation (ISCO) is a well-established groundwater remediation technology, particularly for targeting chlorinated ethenes. The kinetics of oxidation reactions is an important ISCO remediation design aspect that affects the efficiency and oxidant persistence. The overall rate of the ISCO reaction between oxidant and contaminant is typically described using a second-order kinetic model while the second-order rate constant is determined experimentally by means of a pseudo first order approach. However, earlier studies of chlorinated hydrocarbons have yielded a wide range of values for the second-order rate constants. Also, there is limited insight in the kinetics of permanganate reactions with fuel-derived groundwater contaminants such as toluene and ethanol. In this study, batch experiments were carried out to investigate and compare the oxidation kinetics of aqueous trichloroethylene (TCE), ethanol, and toluene in an aqueous potassium permanganate solution. The overall second-order rate constants were determined directly by fitting a second-order model to the data, instead of typically using the pseudo-first-order approach. The second-order reaction rate constants (M(-1) s(-1)) for TCE, toluene, and ethanol were 8.0×10(-1), 2.5×10(-4), and 6.5×10(-4), respectively. Results showed that the inappropriate use of the pseudo-first-order approach in several previous studies produced biased estimates of the second-order rate constants. In our study, this error was expressed as a function of the extent (P/N) in which the reactant concentrations deviated from the stoichiometric ratio of each oxidation reaction. The error associated with the inappropriate use of the pseudo-first-order approach is negatively correlated with the P/N ratio and reached up to 25% of the estimated second-order rate constant in some previous studies of TCE oxidation. Based on our results, a similar relation is valid for the other volatile

  12. Time discretization of the point kinetic equations using matrix exponential method and First-Order Hold

    International Nuclear Information System (INIS)

    Park, Yujin; Kazantzis, Nikolaos; Parlos, Alexander G.; Chong, Kil To

    2013-01-01

    Highlights: • Numerical solution for stiff differential equations using matrix exponential method. • The approximation is based on First Order Hold assumption. • Various input examples applied to the point kinetics equations. • The method shows superior useful and effective activity. - Abstract: A system of nonlinear differential equations is derived to model the dynamics of neutron density and the delayed neutron precursors within a point kinetics equation modeling framework for a nuclear reactor. The point kinetic equations are mathematically characterized as stiff, occasionally nonlinear, ordinary differential equations, posing significant challenges when numerical solutions are sought and traditionally resulting in the need for smaller time step intervals within various computational schemes. In light of the above realization, the present paper proposes a new discretization method inspired by system-theoretic notions and technically based on a combination of the matrix exponential method (MEM) and the First-Order Hold (FOH) assumption. Under the proposed time discretization structure, the sampled-data representation of the nonlinear point kinetic system of equations is derived. The performance of the proposed time discretization procedure is evaluated using several case studies with sinusoidal reactivity profiles and multiple input examples (reactivity and neutron source function). It is shown, that by applying the proposed method under a First-Order Hold for the neutron density and the precursor concentrations at each time step interval, the stiffness problem associated with the point kinetic equations can be adequately addressed and resolved. Finally, as evidenced by the aforementioned detailed simulation studies, the proposed method retains its validity and accuracy for a wide range of reactor operating conditions, including large sampling periods dictated by physical and/or technical limitations associated with the current state of sensor and

  13. 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.

  14. Oxidation kinetics of polycyclic aromatic hydrocarbons by permanganate.

    Science.gov (United States)

    Forsey, Steven P; Thomson, Neil R; Barker, James F

    2010-04-01

    The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalenepermanganate. 2010 Elsevier Ltd. All rights reserved.

  15. Modeling and Elucidation of the Kinetics of Multiple Consecutive Photoreactions AB4(4Φ) With Φ-order Kinetics. Application to the Photodegradation of Riboflavin.

    Science.gov (United States)

    Maafi, Mounir; Maafi, Wassila

    2016-12-01

    New semi-empirical rate-law system of equations is proposed for the first time for consecutive photoreactions that involve up to 4 photoreaction steps, AB 4 (4Φ). The equation system was developed, tested, and validated against synthetic kinetic traces generated by fifth-order Runge-Kutta calculations. The model accurately fitted the kinetic traces of Riboflavin photodegradation in ethanol which decomposes via the AB 2 (2Φ) mechanism involving 2 consecutive photoreaction steps. A kinetic elucidation methodology useful for consecutive photoreactions was also proposed to determine all the kinetic parameters and reaction attributes defining AB 2 (2Φ) reactions. The quantum yields of photodegradation, determined for wavelengths in the visible region 400-480 nm, ranged from 0.005 to 0.00756 and 0.0012 to 8 10 -5 for the first and second photoreaction steps, respectively. They were found to increase with wavelength in defined sigmoid functions. For this monochromatic irradiation range, riboflavin proved to be a useful actinometer. Finally, a photodegradation scale based on pseudo-rate-constant values was also proposed for drugs. This scale (including 4 groups) is thought to contribute to rationalizing photodegradation testing and might prove useful in categorizing drugs' photodegradation reactivity. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  16. Kinetics of 2-chlorobiphenyl Reductive Dechlorination by Pd-fe0 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jiang Junrong

    2016-01-01

    Full Text Available Kinetics of 2-chlorobiphenyl (2-Cl BP catalytic reductive dechlorination by Pd-Fe0 nanoparticles were investigated. Experimental results showed that ultrafine bimetallic Pd-Fe0e nanoparticles were synthesized in the presence of 40 kHz ultrasound in order to enhance disparity and avoid agglomeration. The application of ultrasonic irradiation during the synthesis of Pd-Fe0 nanoparticles further accelerated the dechlorinated removal ratio of 2-Cl BP. Up to 95.0% of 2-Cl BP was removed after 300 min reaction with the following experimental conditions: initial 2-Cl BP concentration 10 mg L-1, Pd content 0.8 wt. %, bimetallic Pd-Fe0 nanoparticles prepared in the presence of ultrasound available dosage 7g L-1, initial pH value in aqueous solution 3.0, and reaction temperature 25°C. The catalytic reductive dechlorination of 2-Cl BP followed pseudo-first-order kinetics and the apparent pseudo-first-order kinetics constant was 0.0143 min-1.

  17. Removal of ibuprofen, naproxen and carbamazepine in aqueous solution onto natural clay: equilibrium, kinetics, and thermodynamic study

    Science.gov (United States)

    Khazri, Hassen; Ghorbel-Abid, Ibtissem; Kalfat, Rafik; Trabelsi-Ayadi, Malika

    2017-10-01

    This study aimed to describe the adsorption of three pharmaceuticals compounds (ibuprofen, naproxen and carbamazepine) onto natural clay on the basis of equilibrium parameters such as a function of time, effect of pH, varying of the concentration and the temperature. Adsorption kinetic data were modeled using the Lagergren's first-order and the pseudo-second-order kinetic equations. The kinetic results of adsorption are described better using the pseudo-second order model. The isotherm results were tested in the Langmuir, Freundlich and Dubinin-Radushkevich models. The thermodynamic parameters obtained indicate that the adsorption of pharmaceuticals on the clay is a spontaneous and endothermic process.

  18. Discrete Weighted Pseudo Asymptotic Periodicity of Second Order Difference Equations

    Directory of Open Access Journals (Sweden)

    Zhinan Xia

    2014-01-01

    Full Text Available We define the concept of discrete weighted pseudo-S-asymptotically periodic function and prove some basic results including composition theorem. We investigate the existence, and uniqueness of discrete weighted pseudo-S-asymptotically periodic solution to nonautonomous semilinear difference equations. Furthermore, an application to scalar second order difference equations is given. The working tools are based on the exponential dichotomy theory and fixed point theorem.

  19. Adsorption of saturated fatty acid in urea complexation: Kinetics and equilibrium studies

    Science.gov (United States)

    Setyawardhani, Dwi Ardiana; Sulistyo, Hary; Sediawan, Wahyudi Budi; Fahrurrozi, Mohammad

    2018-02-01

    Urea complexation is fractionation process for concentrating poly-unsaturated fatty acids (PUFAs) from vegetable oil or animal fats. For process design and optimization in commercial industries, it is necessary to provide kinetics and equilibrium data. Urea inclusion compounds (UICs) as the product is a unique complex form which one molecule (guest) is enclosed within another molecule (host). In urea complexation, the guest-host bonding exists between saturated fatty acids (SFAs) and crystalline urea. This research studied the complexation is analogous to an adsorption process. The Batch adsorption process was developed to obtain the experimental data. The ethanolic urea solution was mixed with SFA in certain compositions and adsorption times. The mixture was heated until it formed homogenous and clear solution, then it cooled very slowly until the first numerous crystal appeared. Adsorption times for the kinetic data were determined since the crystal formed. The temperature was maintained constant at room temperature. Experimental sets of data were observed with adsorption kinetics and equilibrium models. High concentration of saturated fatty acid (SFA) was used to represent adsorption kinetics and equilibrium parameters. Kinetic data were examined with pseudo first-order, pseudo second-order and intra particle diffusion models. Linier, Freundlich and Langmuir isotherm were used to study the equilibrium model of this adsorption. The experimental data showed that SFA adsorption in urea crystal followed pseudo second-order model. The compatibility of the data with Langmuir isotherm showed that urea complexation was a monolayer adsorption.

  20. Adsorption of Acid Red 18 (AR18 by Activated Carbon from Poplar Wood- A Kinetic and Equilibrium Study

    Directory of Open Access Journals (Sweden)

    Reza Shokoohi

    2010-01-01

    Full Text Available Adsorption process by activated carbon is widely used for removal of dyes. Because of economical limits, activated carbon derived from low cost materials seem to be economical. The aim of this work is preparation of activated carbon from poplar wood and investigation of its ability to removal of (AR18 dye. In this work, we prepared the activated carbon by chemical activation method in electric furnace. In addition we have investigated effect of various parameters such as pH, contact time, dye concentration and adsorbent dosage on dye removal. Langmuir and Freundlich isotherm models have been investigated. Pseudo-first order, pseudo-second order and modified pseudo-first order kinetic models have been used for experimental data. The results showed that removal efficiency was increased with increasing of adsorbent dosage, contact time and decreasing of pH, but with increasing of dye concentration, the removal efficiency was decreased. Adsorption isotherm models showed that Langmuir isotherm model was best fitted onto collected data (r2>0.978. In addition, kinetic models showed that sorption of AR18 onto activated carbon prepared from poplar wood follows the pseudo-first order model (r2>0.9758.

  1. Kinetics and Mechanism of the Oxidation of Coomassie Brilliant Blue ...

    African Journals Online (AJOL)

    , in aqueous solution by hypochlorite as a function of pH was investigated. While the degradation of dye obeyed pseudo-first-order kinetics, the oxidation of the dye occurred through two competitive reactions facilitated by [OCl–] and [HOCl].

  2. Biotransformation kinetics and sorption of cocaine and its metabolites and the factors influencing their estimation in wastewater

    DEFF Research Database (Denmark)

    Plósz, Benedek G.; Reid, Malcolm J.; Borup, Morten

    2013-01-01

    and ecgonine methyl ester. The activated sludge modelling framework for xenobiotic organic micro-pollutants (ASM-X) is used for model structure identification and calibration. Biotransformation was observed to follow pseudo first-order kinetics. The biodegradation kinetics of cocaine, benzoylecgonine...

  3. Generalized first-order kinetic model for biosolids decomposition and oxidation during hydrothermal treatment.

    Science.gov (United States)

    Shanableh, A

    2005-01-01

    The main objective of this study was to develop generalized first-order kinetic models to represent hydrothermal decomposition and oxidation of biosolids within a wide range of temperatures (200-450 degrees C). A lumping approach was used in which oxidation of the various organic ingredients was characterized by the chemical oxygen demand (COD), and decomposition was characterized by the particulate (i.e., nonfilterable) chemical oxygen demand (PCOD). Using the Arrhenius equation (k = k(o)e(-Ea/RT)), activation energy (Ea) levels were derived from 42 continuous-flow hydrothermal treatment experiments conducted at temperatures in the range of 200-450 degrees C. Using predetermined values for k(o) in the Arrhenius equation, the activation energies of the various organic ingredients were separated into 42 values for oxidation and a similar number for decomposition. The activation energy values were then classified into levels representing the relative ease at which the organic ingredients of the biosolids were oxidized or decomposed. The resulting simple first-order kinetic models adequately represented, within the experimental data range, hydrothermal decomposition of the organic particles as measured by PCOD and oxidation of the organic content as measured by COD. The modeling approach presented in the paper provide a simple and general framework suitable for assessing the relative reaction rates of the various organic ingredients of biosolids.

  4. Removal of Congo Red from Aqueous Solution by Anion Exchange Membrane (EBTAC): Adsorption Kinetics and Themodynamics

    Science.gov (United States)

    Khan, Muhammad Imran; Akhtar, Shahbaz; Zafar, Shagufta; Shaheen, Aqeela; Khan, Muhammad Ali; Luque, Rafael; ur Rehman, Aziz

    2015-01-01

    The adsorption behavior of anionic dye congo red (CR) from aqueous solutions using an anion exchange membrane (EBTAC) has been investigated at room temperature. The effect of several factors including contact time, membrane dosage, ionic strength and temperature were studied. Kinetic models, namely pseudo-first-order and pseudo-second-order, liquid film diffusion and Elovich models as well as Bangham and modified freundlich Equations, were employed to evaluate the experimental results. Parameters such as adsorption capacities, rate constant and related correlation coefficients for every model were calculated and discussed. The adsorption of CR on anion exchange membranes followed pseudo-second-order Kinetics. Thermodynamic parameters, namely changes in Gibbs free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) were calculated for the adsorption of congo red, indicating an exothermic process. PMID:28793430

  5. Carrageenan-based semi-IPN nanocomposite hydrogels: Swelling kinetic and slow release of sequestrene Fe 138 fertilizer

    Directory of Open Access Journals (Sweden)

    Mohammad Kazem Bahrami

    2016-09-01

    Full Text Available Nanocomposite hydrogels based on kappa-carrageenan were synthesized by incorporating natural sodium montmorillonite (Cloisite nanoclay. Acrylamide (AAm and methylenebisacrylamide (MBA were used as a monomer and a crosslinker, respectively. Effects of reaction variables on the swelling kinetics were studied. The results revealed that the rate of swelling for nanocomposites with high content of MBA was higher than those of nanocomposites consisting of low content of MBA. Similar to the effect of MBA, the rate of swelling enhanced as the carrageenan content was decreased. The influence of clay content on swelling rate was not remarkable. The experimental swelling data were evaluated by pseudo-first-order and pseudo-second-order kinetic models. The swelling data described well by pseudo-second-order kinetic model. Sequestrene Fe 138 (Sq as an agrochemical was loaded into nanocomposites and releasing of this active agent from nanocomposites was studied. The clay-free hydrogel released the whole loaded Sq; whereas the presence of clay restricted the release of Sq.

  6. Equilibrium, kinetic and thermodynamic studies of the biosorption of textile dye (Reactive Red 195) onto Pinus sylvestris L

    International Nuclear Information System (INIS)

    Aksakal, Ozkan; Ucun, Handan

    2010-01-01

    This study investigated the biosorption of Reactive Red 195 (RR 195), an azo dye, from aqueous solution by using cone biomass of Pinus sylvestris Linneo. To this end, pH, initial dye concentration, biomass dosage and contact time were studied in a batch biosorption system. Maximum pH for efficient RR 195 biosorption was found to be 1.0 and the initial RR 195 concentration increased with decreasing percentage removal. Biosorption capacity increased from 6.69 mg/g at 20 deg. C to 7.38 mg/g at 50 deg. C for 200 mg/L dye concentration. Kinetics of the interactions was tested by pseudo-first-order and pseudo-second-order kinetics, the Elovich equation and intraparticle diffusion mechanism. Pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order kinetic model and intraparticle diffusion mechanism. Moreover, the Elovich equation also showed a good fit to the experimental data. Freundlich and Langmuir adsorption isotherms were used for the mathematical description of the biosorption equilibrium data. The activation energy of biosorption (Ea) was found to be 8.904 kJ/mol by using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the study also evaluated the thermodynamic constants of biosorption (ΔG o , ΔH o and ΔS). The results indicate that cone biomass can be used as an effective and low-cost biosorbent to remove reactive dyes from aqueous solution.

  7. Adsorption Kinetics of Cd(ll and Pb(ll Ions from Aqueous Solutions by Bamboo-Based Activated Charcoal and Bamboo Dust

    Directory of Open Access Journals (Sweden)

    Stevens Azubuike Odoemelam

    2015-01-01

    Full Text Available The use of bamboo dust (BD and bamboo-based activated charcoal for adsorption of Pb(ll and Cd(ll ions from aqueous solutions were assessed in this work. The effect of contact time on the uptake of these metal ions was studied in batch process. The adsorption data were correlated with pseudo first-order, pseudo second-order and diffusivity kinetic models. Results show that pseudo second-order kinetic model gave the best description for the adsorption process. Kinetic studies further showed that the adsorption transport mechanism was particle-diffusion controlled for the adsorption process. Results obtained generally showed that lead(ll ions were better adsorbed onto both adsorbents as compared to cadmium(ll. Comparison of sorption capacity for the two adsorbents shows that bamboo-based activated charcoal exhibited better removal for the metal ions than the bamboo dust.

  8. Kinetic modelling for zinc (II) ions biosorption onto Luffa cylindrica

    International Nuclear Information System (INIS)

    Oboh, I.; Aluyor, E.; Audu, T.

    2015-01-01

    The biosorption of Zinc (II) ions onto a biomaterial - Luffa cylindrica has been studied. This biomaterial was characterized by elemental analysis, surface area, pore size distribution, scanning electron microscopy, and the biomaterial before and after sorption, was characterized by Fourier Transform Infra Red (FTIR) spectrometer. The kinetic nonlinear models fitted were Pseudo-first order, Pseudo-second order and Intra-particle diffusion. A comparison of non-linear regression method in selecting the kinetic model was made. Four error functions, namely coefficient of determination (R 2 ), hybrid fractional error function (HYBRID), average relative error (ARE), and sum of the errors squared (ERRSQ), were used to predict the parameters of the kinetic models. The strength of this study is that a biomaterial with wide distribution particularly in the tropical world and which occurs as waste material could be put into effective utilization as a biosorbent to address a crucial environmental problem

  9. Removal of mercury(II) from aqueous media using eucalyptus bark: Kinetic and equilibrium studies

    International Nuclear Information System (INIS)

    Ghodbane, Ilhem; Hamdaoui, Oualid

    2008-01-01

    In this study, eucalyptus camaldulensis bark, a forest solid waste, is proposed as a novel material for the removal of mercury(II) from aqueous phase. The operating variables studied were sorbent dosage, ionic strength, stirring speed, temperature, solution pH, contact time, and initial metal concentration. Sorption experiments indicated that the sorption capacity was dependent on operating variables and the process was strongly pH-dependent. Kinetic measurements showed that the process was uniform and rapid. In order to investigate the mechanism of sorption, kinetic data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations, and intraparticle diffusion model. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analyzed using the Langmuir and the Freundlich isotherms. The Langmuir model yields a much better fit than the Freundlich model. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy, and entropy of sorption. The maximum sorption capacity was 33.11 mg g -1 at 20 deg. C and the negative value of free energy change indicated the spontaneous nature of sorption. These results demonstrate that eucalyptus bark is very effective in the removal of Hg(II) from aqueous solutions

  10. Kinetics of diuron and amitrole adsorption from aqueous solution on activated carbons.

    Science.gov (United States)

    Fontecha-Cámara, M A; López-Ramón, M V; Pastrana-Martínez, L M; Moreno-Castilla, C

    2008-08-15

    A study was conducted on the adsorption kinetics of diuron and amitrole from aqueous solutions on activated carbons of different particle sizes and on an activated carbon fiber. Different kinetic models were applied to the experimental results obtained. A pseudo-second-order rate equation fitted the adsorption kinetics data better than a pseudo-first-order rate equation. Amitrole showed faster adsorption kinetics compared with diuron because of the smaller size of the former herbicide, despite its lower driving force for adsorption. Both reaction rate constants increased when the particle size decreased. The activated carbon fiber and the activated carbon of smallest particle size (0.03 mm) showed similar adsorption kinetics. The intraparticle diffusion rate constant increased with higher initial concentration of herbicides in solution and with lower particle size of the adsorbent. This is because the rise in initial concentration increased the amount adsorbed at equilibrium, and the reduction in particle size increased the number of collisions between adsorbate and adsorbent particles. Demineralization of the activated carbon with particle size of 0.5mm had practically no effect on the adsorption kinetics.

  11. Modular Transformations, Order-Chaos Transitions and Pseudo-Random Number Generation

    Science.gov (United States)

    Bonelli, Antonio; Ruffo, Stefano

    Successive pairs of pseudo-random numbers generated by standard linear congruential transformations display ordered patterns of parallel lines. We study the "ordered" and "chaotic" distribution of such pairs by solving the eigenvalue problem for two-dimensional modular transformations over integers. We conjecture that the optimal uniformity for pair distribution is obtained when the slope of linear modular eigenspaces takes the value n opt =maxint (p/√ {p-1}), where p is a prime number. We then propose a new generator of pairs of independent pseudo-random numbers, which realizes an optimal uniform distribution (in the "statistical" sense) of points on the unit square (0, 1] × (0, 1]. The method can be easily generalized to the generation of k-tuples of random numbers (with k>2).

  12. Adsorption of basic dye on high-surface-area activated carbon prepared from coconut husk: Equilibrium, kinetic and thermodynamic studies

    Energy Technology Data Exchange (ETDEWEB)

    Tan, I.A.W.; Ahmad, A.L. [School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia); Hameed, B.H. [School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia)], E-mail: chbassim@eng.usm.my

    2008-06-15

    Adsorption isotherm and kinetics of methylene blue on activated carbon prepared from coconut husk were determined from batch tests. The effects of contact time (1-30 h), initial dye concentration (50-500 mg/l) and solution temperature (30-50 {sup o}C) were investigated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The equilibrium data were best represented by Langmuir isotherm model, showing maximum monolayer adsorption capacity of 434.78 mg/g. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and was found to follow closely the pseudo-second-order kinetic model. Thermodynamic parameters such as standard enthalpy ({delta}H{sup o}), standard entropy ({delta}S{sup o}) and standard free energy ({delta}G{sup o}) were evaluated. The adsorption interaction was found to be exothermic in nature. Coconut husk-based activated carbon was shown to be a promising adsorbent for removal of methylene blue from aqueous solutions.

  13. [Influence of pH on Kinetics of Anilines Oxidation by Permanganate].

    Science.gov (United States)

    Wang, Hui; Sun, Bo; Guan, Xiao-hong

    2016-02-15

    To investigate the effect of pH on the oxidation of anilines by potassium permanganate, aniline and p-Chloroaniline were taken as the target contaminants, and the experiments were conducted under the condition with potassium permanganate in excess over a wide pH range. The reaction displayed remarkable autocatalysis, which was presumably ascribed to the formation of complexes by the in situ generated MnOx and the target contaminants on its surface, and thereby improved the oxidation rate of the target contaminants by permanganate. The reaction kinetics was fitted with the pseudo-first-order kinetics at different pH to obtain the pseudo-first-order reaction constants (k(obs)). The second-order rate constants calculated from permanganate concentration and k,b, increased with the increase of pH and reached the maximum near their respective pKa, after which they decreased gradually. This tendency is called parabola-like shaped pH-rate profile. The second-order rate constants between permanganate and anilines were well fitted by the proton transfer model proposed by us in previous work.

  14. 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

  15. A kinetic study of the enhancement of solution chemiluminescence of glyoxylic acid oxidation by manganese species.

    Science.gov (United States)

    Otamonga, Jean-Paul; Abdel-Mageed, Amal; Agater, Irena B; Jewsbury, Roger A

    2015-08-01

    In order to study the mechanism of the enhancement of solution chemiluminescence, the kinetics of the decay of the oxidant and the chemiluminescence emission were followed for oxidations by permanganate, manganese dioxide sol and Mn(3+) (aq) of glyoxylic acid, using stopped-flow spectrophotometry. Results are reported for the glyoxylic acid oxidized under pseudo first-order conditions and in an acidic medium at 25 °C. For permanganate under these conditions, the decay is sigmoidal, consistent with autocatalysis, and for manganese dioxide sol and Mn(3+) it is pseudo first order. The effects of the presence of aqueous formaldehyde and Mn(2+) were observed and a fit to a simple mechanism is discussed. It is concluded that chemiluminescent enhancement in these systems is best explained by reaction kinetics. Copyright © 2014 John Wiley & Sons, Ltd.

  16. Kinetics, isothermal and thermodynamics studies of electrocoagulation removal of basic dye rhodamine B from aqueous solution using steel electrodes

    Science.gov (United States)

    Adeogun, Abideen Idowu; Balakrishnan, Ramesh Babu

    2017-07-01

    Electrocoagulation was used for the removal of basic dye rhodamine B from aqueous solution, and the process was carried out in a batch electrochemical cell with steel electrodes in monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process, were investigated. Equilibrium was attained after 10 min at 30 °C. Pseudo-first-order, pseudo-second-order, Elovich and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process; pseudo-first-order and Avrami models best fitted the data. Experimental data were analysed using six model equations: Langmuir, Freudlinch, Redlich-Peterson, Temkin, Dubinin-Radushkevich and Sips isotherms and it was found that the data fitted well with Sips isotherm model. The study showed that the process depends on current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (Δ G°, Δ H° and Δ S°) indicated that the process is spontaneous and endothermic in nature.

  17. Removal Rate of Organic Matter Using Natural Cellulose via Adsorption Isotherm and Kinetic Studies.

    Science.gov (United States)

    Din, Mohd Fadhil Md; Ponraj, Mohanadoss; Low, Wen-Pei; Fulazzaky, Mohamad Ali; Iwao, Kenzo; Songip, Ahmad Rahman; Chelliapan, Shreeshivadasan; Ismail, Zulhilmi; Jamal, Mohamad Hidayat

    2016-02-01

    In this study, the removal of natural organic matter (NOM) using coconut fiber (CF) and palm oil fiber (POF) was investigated. Preliminary analysis was performed using a jar test for the selection of optimal medium before the fabricated column model experiment. The equilibrium studies on isotherms and kinetic models for NOM adsorption were analyzed using linearized correlation coefficient. Results showed that the equilibrium data were fitted to Langmuir isotherm model for both CF and POF. The most suitable adsorption model was the pseudo-first-order kinetic model for POF and pseudo-second-order kinetic model for CF. The adsorption capacities achieved by the CF and POF were 15.67 and 30.8 mg/g respectively. Based on this investigation, it can be concluded that the POF is the most suitable material for the removal of NOM in semi polluted river water.

  18. Adsorption equilibrium and kinetic studies of crystal violet and naphthol green on torreya-grandis-skin-based activated carbon

    International Nuclear Information System (INIS)

    Dai, Wei; Yu, Huijing; Ma, Na; Yan, Xiaoyang

    2015-01-01

    A new type of activated carbon, torreya-grandis-skin-based activated carbon (TAC), has been used to remove the harmful dyes (cationic dye crystal violet (CV) and anionic dye naphthol green (NG)) from contaminated water via batch adsorption. The effects of solution pH, adsorption time and temperature were studied. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and isotherm constant calculation. It was found that the maximum equilibrium adsorption capacities were 292mg/g and 545mg/g for CV and NG, respectively. Adsorption kinetics was verified by pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. Results indicated that the rate of dye adsorption followed pseudo-second-order kinetic model for the initial dye concentration range studied. Temperature-dependent adsorption behavior of CV and NG shows that the adsorption is spontaneous and endothermic, accompanying an entropy increase. This work indicates that TAC could be employed as a low-cost alternative for the removal of the textile dyes from effluents

  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. Focus on adsorptive equilibrium, kinetics and thermodynamic components of petroleum produced water biocoagulation using novel Tympanotonos Fuscatus extract

    Directory of Open Access Journals (Sweden)

    Matthew Menkiti

    2018-03-01

    Full Text Available Adsorptive component of produced water (PW coagulation using Tympanotonos Fuscatus coagulant (TFC was studied. Influence of the following parameters: pH, coagulant dose, settling time, and temperature were investigated. The functional group, crystalline nature, morphological observation and thermal characteristics of the sample were evaluated. Equilibrium data were analyzed using Langmuir, Freundlich, Temkin, Frumkin, and Dubinin-Radushkevich (D-R adsorption isotherms. The kinetics data were fitted to reversible first order, pseudo-first-order, pseudo-second-order, elovich, intra-particle diffusion and Boyd kinetic models. Adsorption Gibbs energy, enthalpy and entropy were evaluated. Equilibrium data best fitted the Langmuir isotherm (R2 > 0.99; X2 < 1.6; SSE < 1.6. Reversible first order model correlated best to the kinetics data. The values of process average Gibb's free energy, enthalpy and entropy were 30.35, 27.88 and 0.1891 kJ/mol, respectively. The process was spontaneous, feasible and endothermic in nature. The maximum efficiency of 83.1% was favored at pH 2.0. This study indicated significant adsorptive component, while using Tympanotonos Fuscatus extract as readily available, renewable, ecofriendly bio – coagulant for efficient treatments of PW.

  1. Biosorption kinetics of Cd (II, Cr (III and Pb (II in aqueous solutions by olive stone

    Directory of Open Access Journals (Sweden)

    M. Calero

    2009-06-01

    Full Text Available A by-product from olive oil production, olive stone, was investigated for the removal of Cd (II, Cr (III and Pb (II from aqueous solutions. The kinetics of biosorption are studied, analyzing the effect of the initial concentration of metal and temperature. Pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models have been used to represent the kinetics of the process and obtain the main kinetic parameters. The results show that the pseudo-second order model is the one that best describes the biosorption of the three metal ions for all the range of experimental conditions investigated. For the three metal ions, the maximum biosoption capacity and the initial biosorption rate increase when the initial metal concentration rises. However, the kinetic constant decreases when the initial metal concentration increases. The temperature effect on biosorption capacity for Cd (II and Cr (III is less significant; however, for Pb (II the effect of temperature is more important, especially when temperature rises from 25 to 40ºC. The biosorption capacity at mmol/g of olive stone changes in the following order: Cr>Cd>Pb. Thus, for an initial concentration of 220 mg/ℓ, a maximum sorption capacity of 0.079 mmol/g for Cr (III, 0.065 mmol/g for Cd (II and 0.028 mmol/g for Pb (II has been obtained.

  2. Exploring the interaction of silver nanoparticles with pepsin and its adsorption isotherms and kinetics.

    Science.gov (United States)

    Li, Xiangrong; Wang, Kaiwei; Peng, Yanru

    2018-04-25

    The interaction of nanoparticles (NPs) with proteins is a topic of high relevance for the medical application of nanomaterials. In the study, a comprehensive investigation was performed for the binding properties of silver nanoparticles (AgNPs) to pepsin. The results indicate that the binding of AgNPs to pepsin may be a static quenching mechanism. Thermodynamic analysis reveals that AgNPs binds to pepsin is synergistically driven by enthalpy and entropy, and the major driving forces are hydrophobic and electrostatic interactions. Synchronous fluorescence spectroscopy shows that AgNPs may induce microenvironmental changes of pepsin. The hydrophobicity of Trp is increased while the hydrophility of Tyr is increased. The adsorption of pepsin on AgNPs was analyzed by Langmuir and Freundlich models, suggesting that the equilibrium adsorption data fit well with Freundlich model. The equilibrium adsorption data were modeled using the pseudo-first-order and pseudo-second-order kinetic equations. The results indicate that pseudo-second-order kinetic equation better describes the adsorption kinetics. The study provides an accurate and full basic data for clarifying the binding mechanism, adsorption isotherms and kinetic behaviors of AgNPs with pepsin. These fundamental works will provide some new insights into the safe and effective application of AgNPs in biological and medical areas. Copyright © 2018 Elsevier B.V. All rights reserved.

  3. An Analogy Using Pennies and Dimes to Explain Chemical Kinetics Concepts

    Science.gov (United States)

    Cortes-Figueroa, Jose E.; Perez, Wanda I.; Lopez, Jose R.; Moore-Russo, Deborah A.

    2011-01-01

    In this article, the authors present an analogy that uses coins and graphical analysis to teach kinetics concepts and resolve pseudo-first-order rate constants related to transition-metal complexes ligand-solvent exchange reactions. They describe an activity that is directed to upper-division undergraduate and graduate students. The activity…

  4. Assessment of Ex-Vitro Anaerobic Digestion Kinetics of Crop Residues Through First Order Exponential Models: Effect of LAG Phase Period and Curve Factor

    Directory of Open Access Journals (Sweden)

    Abdul Razaque Sahito

    2013-04-01

    Full Text Available Kinetic studies of AD (Anaerobic Digestion process are useful to predict the performance of digesters and design appropriate digesters and also helpful in understanding inhibitory mechanisms of biodegradation. The aim of this study was to assess the anaerobic kinetics of crop residues digestion with buffalo dung. Seven crop residues namely, bagasse, banana plant waste, canola straw, cotton stalks, rice straw, sugarcane trash and wheat straw were selected from the field and were analyzed on MC (Moisture Contents, TS (Total Solids and VS (Volatile Solids with standard methods. In present study, three first order exponential models namely exponential model, exponential lag phase model and exponential curve factor model were used to assess the kinetics of the AD process of crop residues and the effect of lag phase and curve factor was analyzed based on statistical hypothesis testing and on information theory. Assessment of kinetics of the AD of crop residues and buffalo dung follows the first order kinetics. Out of the three models, the simple exponential model was the poorest model, while the first order exponential curve factor model is the best fit model. In addition to statistical hypothesis testing, the exponential curve factor model has least value of AIC (Akaike's Information Criterion and can generate methane production data more accurately. Furthermore, there is an inverse linear relationship between the lag phase period and the curve factor.

  5. Assessment of ex-vitro anaerobic digestion kinetics of crop residues through first order exponential models: effect of lag phase period and curve factor

    International Nuclear Information System (INIS)

    Sahito, A.R.; Brohi, K.M.

    2013-01-01

    Kinetic studies of AD (Anaerobic Digestion) process are useful to predict the performance of digesters and design appropriate digesters and also helpful in understanding inhibitory mechanisms of biodegradation. The aim of this study was to assess the anaerobic kinetics of crop residues digestion with buffalo dung. Seven crop residues namely, bagasse, banana plant waste, canola straw, cotton stalks, rice straw, sugarcane trash and wheat straw were selected from the field and were analyzed on MC (Moisture Contents), TS (Total Solids) and VS (Volatile Solids) with standard methods. In present study, three first order exponential models namely exponential model, exponential lag phase model and exponential curve factor model were used to assess the kinetics of the AD process of crop residues and the effect of lag phase and curve factor was analyzed based on statistical hypothesis testing and on information theory. Assessment of kinetics of the AD of crop residues and buffalo dung follows the first order kinetics. Out of the three models, the simple exponential model was the poorest model, while the first order exponential curve factor model is the best fit model. In addition to statistical hypothesis testing, the exponential curve factor model has least value of AIC (Akaike's Information Criterion) and can generate methane production data more accurately. Furthermore, there is an inverse linear relationship between the lag phase period and the curve factor. (author)

  6. 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.

  7. Kinetics of biosorption of hazardous metals by green soil supplement

    Science.gov (United States)

    Bagla, Hemlata; Khilnani, Roshan

    2016-04-01

    of the biosorption in terms of the order of the rate constant were studied applying different kinetic models such as First order, Second order, Pseudo-first order, Pseudo-second order and the intra particle diffusion model. But among these models best fitting model was Lagergren pseudo second order model. The correlation coefficients of all the elements have R2 values close to 1 indicating the applicability of pseudo second order model to the present system. The applicability of this model suggested that biosorption of elements under study, on DCP was based on chemical interactions between metals and active sites of biosorbent. References 1. E. Tipping, Cation Binding by Humic Substances. Cambridge University Press, 2002. 2. S. Lagergren, Zur theorie der sogenannten adsorption geloster stoffe. Kungliga Svenska Vetenskapsakademiens, Handlingar vol. 24, no.4, pp. 1-39, 1898. 3. Y. S. Ho and G. McKay, "Pseudo-second order model for sorption processes," Process Biochem., vol. 34, no. 5, pp. 451-465, Jul. 1999. 4. N. S. Barot and H. K. Bagla, "Extraction of humic acid from biological matrix - dry cow dung powder," Green Chem. Lett. Rev., vol. 2, no. 4, pp. 217-221, 2009.

  8. Electro-oxidation of the dye azure B: kinetics, mechanism, and by-products.

    Science.gov (United States)

    Olvera-Vargas, Hugo; Oturan, Nihal; Aravindakumar, C T; Paul, M M Sunil; Sharma, Virender K; Oturan, Mehmet A

    2014-01-01

    In this work, the electrochemical degradation of the dye azure B in aqueous solutions was studied by electrochemical advanced oxidation processes (EAOPs), electro-Fenton, and anodic oxidation processes, using Pt/carbon-felt and boron-doped diamond (BDD)/carbon-felt cells with H₂O₂ electrogeneration. The higher oxidation power of the electro-Fenton (EF) process using BDD anode was demonstrated. The oxidative degradation of azure B by the electrochemically generated hydroxyl radicals ((•)OH) follows a pseudo-first-order kinetics. The apparent rate constants of the oxidation of azure B by (•)OH were measured according to pseudo-first-order kinetic model. The absolute rate constant of azure B hydroxylation reaction was determined by competition kinetics method and found to be 1.19 × 10(9) M(-1) s(-1). It was found that the electrochemical degradation of the dye leads to the formation of aromatic by-products which are then oxidized to aliphatic carboxylic acids before their almost mineralization to CO₂ and inorganic ions (sulfate, nitrate, and ammonium). The evolution of the TOC removal and time course of short-chain carboxylic acids during treatment were also investigated.

  9. Kinetics and Mechanisms of Phosphorus Adsorption in Soils from Diverse Ecological Zones in the Source Area of a Drinking-Water Reservoir.

    Science.gov (United States)

    Zhang, Liang; Loáiciga, Hugo A; Xu, Meng; Du, Chao; Du, Yun

    2015-11-10

    On-site soils are increasingly used in the treatment and restoration of ecosystems to harmonize with the local landscape and minimize costs. Eight natural soils from diverse ecological zones in the source area of a drinking-water reservoir in central China are used as adsorbents for the uptake of phosphorus from aqueous solutions. The X-ray fluorescence (XRF) spectrometric and BET (Brunauer-Emmett-Teller) tests and the Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectral analyses are carried out to investigate the soils' chemical properties and their potential changes with adsorbed phosphorous from aqueous solutions. The intra-particle diffusion, pseudo-first-order, and pseudo-second-order kinetic models describe the adsorption kinetic processes. Our results indicate that the adsorption processes of phosphorus in soils occurred in three stages and that the rate-controlling steps are not solely dependent on intra-particle diffusion. A quantitative comparison of two kinetics models based on their linear and non-linear representations, and using the chi-square (χ2) test and the coefficient of determination (r2), indicates that the adsorptive properties of the soils are best described by the non-linear pseudo-second-order kinetic model. The adsorption characteristics of aqueous phosphorous are determined along with the essential kinetic parameters.

  10. Kinetic and isotherm modeling of Cd (II) adsorption by L-cysteine functionalized multi-walled carbon nanotubes as adsorbent.

    Science.gov (United States)

    Taghavi, Mahmoud; Zazouli, Mohammad Ali; Yousefi, Zabihollah; Akbari-adergani, Behrouz

    2015-11-01

    In this study, multi-walled carbon nanotubes were functionalized by L-cysteine to show the kinetic and isotherm modeling of Cd (II) ions onto L-cysteine functionalized multi-walled carbon nanotubes. The adsorption behavior of Cd (II) ion was studied by varying parameters including dose of L-MWCNTs, contact time, and cadmium concentration. Equilibrium adsorption isotherms and kinetics were also investigated based on Cd (II) adsorption tests. The results showed that an increase in contact time and adsorbent dosage resulted in increase of the adsorption rate. The optimum condition of the Cd (II) removal process was found at pH=7.0, 15 mg/L L-MWCNTs dosage, 6 mg/L cadmium concentration, and contact time of 60 min. The removal percent was equal to 89.56 at optimum condition. Langmuir and Freundlich models were employed to analyze the experimental data. The data showed well fitting with the Langmuir model (R2=0.994) with q max of 43.47 mg/g. Analyzing the kinetic data by the pseudo-first-order and pseudo-second-order equations revealed that the adsorption of cadmium using L-MWSNTs following the pseudo-second-order kinetic model with correlation coefficients (R2) equals to 0.998, 0.992, and 0.998 for 3, 6, and 9 mg/L Cd (II) concentrations, respectively. The experimental data fitted very well with the pseudo-second-order. Overall, treatment of polluted solution to Cd (II) by adsorption process using L-MWCNT can be considered as an effective technology.

  11. Adsorption capacity of Curcuma longa for the removal of basic green 1 dye--equilibrium, kinetics and thermodynamic study.

    Science.gov (United States)

    Roopavathi, K V; Shanthakumar, S

    2016-09-01

    In the present study, Curcuma longa (turmeric plant) was used as an adsorbent to remove Basic Green 1 (BG) dye. Batch study was carried out to evaluate the adsorption potential of C. longa and influencing factors such as pH (4-10), adsorbent dose (0.2-5 g l-1), initial dye concentration (50-250 mg l-1) and temperature (30-50°C) on dye removal were analysed. The characterisation of adsorbent was carried out using fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) method. Isotherm models that included Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich, and kinetic models such as pseudo first order, pseudo second-order, Elovich and intraparticle diffusion models were studied. A maximum removal percentage (82.76%) of BG dye from aqueous solution was obtained with optimum conditions of pH 7, 1g l-1 adsorbent dose and 30°C temperature, for 100 mg l-1 initial dye concentration. The equilibrium and kinetic study revealed that the experimental data fitted suitably the Freundlich isotherm and Pseudo second order kinetic model. Thermodynamic analysis proved that adsorption system in this study was spontaneous, feasible and endothermic in nature.

  12. Adsorption of cationic dye from aqueous solution by clay as an adsorbent: thermodynamic and kinetic studies

    International Nuclear Information System (INIS)

    Fil, B.A.; Ozmetn, C.

    2012-01-01

    In the study, montmorillonite was used as an adsorbent for the removal of methylene blue (MB) from aqueous solutions. Batch studies were performed to address various experimental parameters like contact time, pH, temperature, stirring speed, ionic strength, adsorbent dosage and initial concentration for the removal of this dye. Adsorption rate increased with the increase in initial dye concentration, ionic strength, stirring speed, pH and temperature. Kinetic study showed that the adsorption of dye on montmorillonite was a gradual process. Quasi-equilibrium reached in 3 h. Pseudo-first-order, pseudo-second-order, Elovich, Bangham, mass transfer and intra-particle particle diffusion models were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. Intra-particle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. The diffusion coefficient, D, was found to increase when the stirring speed, ionic strength and temperature were raised. Thermodynamic activation parameters such as delt G, delt S and del H were also calculated. (author)

  13. Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: a kinetic and equilibrium study.

    Science.gov (United States)

    Caliskan, Necla; Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan

    2011-10-15

    The removal of Zn(II) ions from aqueous solution was studied using natural and MnO(2) modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol(-1), indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH(0)), Gibbs' free energy (ΔG(0)) and entropy (ΔS(0)) were calculated for natural and MnO(2) modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Adsorption kinetics of surfactants on activated carbon

    Science.gov (United States)

    Arnelli; Aditama, WP; Fikriani, Z.; Astuti, Y.

    2018-04-01

    A study on the adsorption of both cationic and anionic surfactants using activated carbon as well as the investigation of the adsorption isotherms and adsorption kinetics has been conducted. The results showed that the adsorption of sodium lauryl sulfate (SLS) by activated carbon was Langmuir’s adsorption isotherm while its adsorption kinetics showed pseudo-second order with an adsorption rate constant of 2.23 x 103 g mg-1 hour-1. Meanwhile, the adsorption of HDTMA-Br by activated carbon showed that the isotherm adsorption tended to follow Freundlich’s isotherm and was pseudo-second order with an adsorption rate constant of 89.39 g mg-1 hour-1.

  15. Kinetic and isotherm studies of Cu(II) biosorption onto valonia tannin resin

    Energy Technology Data Exchange (ETDEWEB)

    Sengil, I. Ayhan [Department of Environmental Engineering, Engineering Faculty, Sakarya University, 54100 Sakarya (Turkey)], E-mail: asengil@sakarya.edu.tr; Ozacar, Mahmut [Department of Chemistry, Science and Arts Faculty, Sakarya University, 54100 Sakarya (Turkey); Tuerkmenler, Harun [Institute of Sciences and Technology, Sakarya University, 54040 Sakarya (Turkey)

    2009-03-15

    The biosorption of Cu(II) from aqueous solutions by valonia tannin resin was investigated as a function of particle size, initial pH, contact time and initial metal ion concentration. The aim of this study was to understand the mechanisms that govern copper removal and find a suitable equilibrium isotherm and kinetic model for the copper removal in a batch reactor. The experimental isotherm data were analysed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analysed using four sorption kinetic models - the pseudo-first- and second-order equations, the Elovich and the intraparticle diffusion model equation - to determine the best fit equation for the biosorption of copper ions onto valonia tannin resin. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process, whereas the Elovich equation also fits the experimental data well.

  16. Kinetic studies on carbon dioxide capture using lignocellulosic based activated carbon

    International Nuclear Information System (INIS)

    Rashidi, Nor Adilla; Yusup, Suzana; Hameed, Bassim H.

    2013-01-01

    CO 2 (Carbon dioxide) emissions are one of the greenhouse gases that cause global warming. The power generation industry is one of the main emitters of CO 2 , and the emissions are expected to increase in the coming years as there seems to be no abatement in the consumption of fossil fuels for the production of electricity. Thus, there is a need for CO 2 adsorption technologies to mitigate the emissions. However, there are several disadvantages associated with the current adsorption technologies. One of the issues is corrosion and the need for specialized equipment. Therefore, alternative and more sustainable materials are sought after to improve the viability of the adsorption technology. In this study, several types of agricultural wastes were used as activated carbon precursors for CO 2 adsorption process in a TGA (thermogravimetric analyser). The adsorption was also modelled through a pseudo-first order and second order model, Elovich's kinetic model, and an intra-particle diffusion model. From the correlation coefficient, it was found that pseudo-second order model was well-fitted with the kinetic data. In addition, activation energy below than 42 kJ/mol confirmed that the physisorption process occurred. - Highlights: • Utilization of lignocellulosic wastes for production of activated carbon. • Single CO 2 activation that yields good adsorptive capacity of adsorbent. • Activation temperature has the most prominent effect on adsorptive properties. • CO 2 adsorption capacity reduces with increasing of adsorption temperature. • Pseudo-second order kinetic model shows best fits to the experimental data

  17. Oxidation kinetics of polycyclic aromatic hydrocarbons by permanganate

    Energy Technology Data Exchange (ETDEWEB)

    Forsey, S.P.; Thomson, N.R.; Barker, J.F. [University of Waterloo, Waterloo, ON (Canada). Dept. of Civil & Environmental Engineering

    2010-04-15

    The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalene < phenanthrene < pyrene. The rate of side chain reactivity is controlled by the C-H bond strength. For the alkyl substituted benzenes an excellent correlation was observed between the reaction rate coefficients and bond dissociation energies, but for the substituted PAHs the relationship was poor. A trend was found between the reaction rate coefficients and the calculated heats of complexation indicating that significant ring oxidation occurred in addition to side chain oxidation. Clar's aromatic sextet theory was used to predict the relative stability of arenes towards ring oxidation by permanganate.

  18. Kinetics of adsorption of dyes from aqueous solution using activated carbon prepared from waste apricot

    International Nuclear Information System (INIS)

    Onal, Yunus

    2006-01-01

    Adsorbent (WA11Zn5) has been prepared from waste apricot by chemical activation with ZnCl 2 . Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by N 2 adsorption and DFT plus software. Adsorption of three dyes, namely, Methylene Blue (MB), Malachite Green (MG), Crystal Violet (CV), onto activated carbon in aqueous solution was studied in a batch system with respect to contact time, temperature. The kinetics of adsorption of MB, MG and CV have been discussed using six kinetic models, i.e., the pseudo-first-order model, the pseudo-second-order model, the Elovich equation, the intraparticle diffusion model, the Bangham equation, the modified Freundlich equation. Kinetic parameters and correlation coefficients were determined. It was shown that the second-order kinetic equation could describe the adsorption kinetics for three dyes. The dyes uptake process was found to be controlled by external mass transfer at earlier stages (before 5 min) and by intraparticle diffusion at later stages (after 5 min). Thermodynamic parameters, such as ΔG, ΔH and ΔS, have been calculated by using the thermodynamic equilibrium coefficient obtained at different temperatures and concentrations. The thermodynamics of dyes-WA11Zn5 system indicates endothermic process

  19. Adsorption isotherm, kinetic and mechanism of expanded graphite for sulfadiazine antibiotics removal from aqueous solutions.

    Science.gov (United States)

    Zhang, Ling; Wang, Yong; Jin, SuWan; Lu, QunZan; Ji, Jiang

    2017-10-01

    The adsorption of sulfadiazine from water by expanded graphite (EG), a low cost and environmental-friendly adsorbent, was investigated. Several adsorption parameters (including the initial sulfadiazine concentration, contact time, pH of solution, ionic strength and temperature) were studied. Results of equilibrium experiments indicated that adsorption of sulfadiazine onto EG were better described by the Langmuir and Tempkin models than by the Freundlich model. The maximum adsorption capacity is calculated to be 16.586 mg/g at 298 K. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and intraparticle models. The results indicated that the adsorption process followed pseudo-second-order kinetics and may be controlled by two steps. Moreover, the pH significantly influenced the adsorption process, with the relatively high adsorption capacity at pH 2-10. The electrostatic and hydrophobic interactions are manifested to be two main mechanisms for sulfadiazine adsorption of EG. Meanwhile, the ionic concentration of Cl - slightly impacted the removal of sulfadiazine. Results of thermodynamics analysis showed spontaneous and exothermic nature of sulfadiazine adsorption on EG. In addition, regeneration experiments imply that the saturated EG could be reused for sulfadiazine removal by immersing sodium hydroxide.

  20. Analysis for the Sorption Kinetics of Ag Nanoparticles on Natural Clinoptilolite

    Directory of Open Access Journals (Sweden)

    Alvaro Ruíz-Baltazar

    2015-01-01

    Full Text Available The kinetic adsorption behavior of silver nanoparticles deposited on a natural zeolite from Oaxaca is presented. Theoretical models as Lagergren first-order, pseudo-second-order, Elovich, and intraparticle diffusion were employed and compared with experimental data obtained by atomic absorption spectrophotometry technique. Correlation factors R2 of the order of 0.99 were observed. Analysis by transmission electron microscopy revealed that the silver nanoparticles were homogeneously distributed on the zeolite. Additionally, chemical characterization of the material was carried out through a dilution process with lithium metaborate. An average value of 9.3 in the Si/Al ratio was observed and related to the kinetic adsorption behavior of the zeolite.

  1. Kinetic study on UV-absorber photodegradation under different conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bubev, Emil, E-mail: ebubev@my.uctm.edu [University of Chemical Technology and Metallurgy, Department of Physical Chemistry (Bulgaria); Georgiev, Anton [University of Chemical Technology and Metallurgy, Department of Organic Chemistry (Bulgaria); Machkova, Maria [University of Chemical Technology and Metallurgy, Department of Physical Chemistry (Bulgaria)

    2016-09-12

    The photodegradation kinetics of two benzophenone derivative UV-absorbers (UVAs)-BP-4 (benzophenone-4) and 4-HBP (4-hydroxybenzophenone), as additives in polyvinyl acetate (PVAc) films, were studied. Solution-processed PVAc films were irradiated in different environments in order to study oxygen and atmospheric humidity influence on UVA photodegradation. Photodegradation was traced by absorption intensity loss via UV–vis spectroscopy. Both UVAs exhibited excellent photostability in an inert atmosphere. Rate constants showed that BP-4 has better permanence in absence of oxygen. Both film types experienced rapid absorption loss, when irradiated in an oxygen containing atmosphere. UVA degradation was treated as a two-stage process. The photodegradation kinetics in the first stage agreed with the adopted complex rate law, but the second stage was best described by pseudo-first order kinetics. BP-4 exhibited better stability. Oxygen was established as the main accelerating factor for photodegradation of benzophenone derivatives UV-absorbers in thin PVAc films.

  2. Integration of differential equations by the pseudo-linear (PL) approximation

    International Nuclear Information System (INIS)

    Bonalumi, Riccardo A.

    1998-01-01

    A new method of integrating differential equations was originated with the technique of approximately calculating the integrals called the pseudo-linear (PL) procedure: this method is A-stable. This article contains the following examples: 1st order ordinary differential equations (ODEs), 2nd order linear ODEs, stiff system of ODEs (neutron kinetics), one-dimensional parabolic (diffusion) partial differential equations. In this latter case, this PL method coincides with the Crank-Nicholson method

  3. 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.

  4. The kinetics of reductive dehalogenation of a set of halogenated aliphatic hydrocarbons in anaerobic sediment slurries.

    Science.gov (United States)

    Peijnenburg, W; Eriksson, L; de Groot, A; Sjöström, M; Verboom, H

    1998-01-01

    Disappearance rate constants are reported for the reductive transformation of 17 halogenated aliphatic hydrocarbons in anaerobic sediment-water samples. Statistical experimental design in combination with multivariate chemical characterization of their chemical properties was used to select the compounds. Degradation followed pseudo first-order kinetics through at least two half-lives for 15 of the 17 compounds. Of all the compounds investigated, 1,2,3-trichloropropane and dichloromethane were unique in that they were dehalogenated according to zero-order kinetics. Reductive dehalogenation was the sole transformation reaction taking place.

  5. The kinetics and thermodynamics of adsorption of heavy metal ions ...

    African Journals Online (AJOL)

    Titanium-Pillared and Un-Pillared bentonite clays were studied in order to evaluate the thermodynamics and kinetics of heavy metal ion removal from aqueous solutions. The results showed that the maximum sorption of Cu, Cd, Hg and Pb ions occurred within 30 minutes. A pseudo-second order kinetic model was used to ...

  6. Adsorptive removal of congo red dye from aqueous solution using bael shell carbon

    International Nuclear Information System (INIS)

    Ahmad, Rais; Kumar, Rajeev

    2010-01-01

    This study investigates the potential use of bael shell carbon (BSC) as an adsorbent for the removal of congo red (CR) dye from aqueous solution. The effect of various operational parameters such as contact time, temperature, pH, and dye concentration were studied. The adsorption kinetics was modeled by first-order reversible kinetics, pseudo-first-order kinetics, and pseudo-second-order kinetics. The dye uptake process obeyed the pseudo-second-order kinetic expression at pH 5.7, 7 and 8 whereas the pseudo-first-order kinetic model was fitted well at pH 9. Langmuir, Freundlich and Temkin adsorption models were applied to fit adsorption equilibrium data. The best-fitted data was obtained with the Freundlich model. Thermodynamic study showed that adsorption of CR onto BSC was endothermic in nature and favorable with the positive ΔH o value of 13.613 kJ/mol.

  7. Equilibrium and kinetic studies of Remazol Black B dye sorption by cocoa pod husk waste

    International Nuclear Information System (INIS)

    Tan Ton Siang; Mohd Azmier Ahmad

    2010-01-01

    Preparation of the activated carbons from cocoa pod husk (CPH) waste by physical activation was carried out for the removal of Remazol Black B (RBB) reactive dye from aqueous solutions. The effects of various process parameters i.e., temperature, initial RBB concentration and contact time on the adsorption capacity of activated carbon were investigated in batch system. Langmuir isotherm showed better fit than Freundlich and Temkin isotherms. The kinetic model for RBB adsorption follows pseudo-first-order kinetics. (author)

  8. Isotherm, Kinetic and Thermodynamic Characteristics for Adsorption of Congo Red by Activated Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Jib [Kongju National University, Cheonan (Korea, Republic of)

    2015-02-15

    Batch experiment studies were carried out for adsorption of congo red using granular activated carbon with various parameters such as activated carbon dose, pH, initial dye concentration, temperature and contact time. Equilibrium experimental data are fitted to the Langmuir, Freundlich, Temkin and Dubin-Radushkevich isotherm equations. From Freundlich's separation factor (1/n) estimated, adsorption could be employed as effective treatment method for adsorption of congo red from aqueous solution. Base on Temkin constant (B) and Dubinin-Radushkevich constant (E), this adsorption process is physical adsorption. Adsorption kinetics has been tested using pseudo-first order and pseudo second order models. The results followed pseudo second order model with good correlation. Adsorption process of congo red on granular activated carbon was endothermic (ΔH=42.036 kJ/mol) and was accompanied by decrease in Gibbs free energy (ΔG=-2.414 to -4.596 kJ/mol) with increasing adsorption temperature.

  9. Isotherm, Kinetic and Thermodynamic Characteristics for Adsorption of Congo Red by Activated Carbon

    International Nuclear Information System (INIS)

    Lee, Jong Jib

    2015-01-01

    Batch experiment studies were carried out for adsorption of congo red using granular activated carbon with various parameters such as activated carbon dose, pH, initial dye concentration, temperature and contact time. Equilibrium experimental data are fitted to the Langmuir, Freundlich, Temkin and Dubin-Radushkevich isotherm equations. From Freundlich's separation factor (1/n) estimated, adsorption could be employed as effective treatment method for adsorption of congo red from aqueous solution. Base on Temkin constant (B) and Dubinin-Radushkevich constant (E), this adsorption process is physical adsorption. Adsorption kinetics has been tested using pseudo-first order and pseudo second order models. The results followed pseudo second order model with good correlation. Adsorption process of congo red on granular activated carbon was endothermic (ΔH=42.036 kJ/mol) and was accompanied by decrease in Gibbs free energy (ΔG=-2.414 to -4.596 kJ/mol) with increasing adsorption temperature

  10. Third-order optical intensity correlation measurements of pseudo-thermal light

    International Nuclear Information System (INIS)

    Chen Xi-Hao; Wu Wei; Meng Shao-Ying; Li Ming-Fei

    2014-01-01

    Third-order Hanbrury Brown—Twiss and double-slit interference experiments with a pseudo-thermal light are performed by recording intensities in single, double and triple optical paths, respectively. The experimental results verifies the theoretical prediction that the indispensable condition for achieving a interference pattern or ghost image in Nth-order intensity correlation measurements is the synchronous detection of the same light field by each reference detector, no matter the intensities recorded in one, or two, or N optical paths. It is shown that, when the reference detectors are scanned in the opposite directions, the visibility and resolution of the third-order spatial correlation function of thermal light is much better than that scanned in the same direction, but it is no use for obtaining the Nth-order interference pattern or ghost image in the thermal Nth-order interference or ghost imaging. (general)

  11. Adsorption of Pb(II) ions from aqueous solution by native and activated bentonite: Kinetic, equilibrium and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Kul, Ali Riza [Yuzuncu Yil University, Faculty of Art and Science, Department of Chemistry, 65080 Van (Turkey); Koyuncu, Huelya, E-mail: hkoyuncu@yyu.edu.tr [Forensic Medicine Foundation, Felek Street No. 45, 06300 Kecioren, Ankara (Turkey)

    2010-07-15

    In this study, the adsorption kinetics, equilibrium and thermodynamics of Pb(II) ions on native (NB) and acid activated (AAB) bentonites were examined. The specific surface areas, pore size and pore-size distributions of the samples were fully characterized. The adsorption efficiency of Pb(II) onto the NB and AAB was increased with increasing temperature. The kinetics of adsorption of Pb(II) ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 16.51 and 13.66 kJ mol{sup -1} for NB and AAB, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations at different temperatures. R{sub L} separation factor for Langmuir and the n value for Freundlich isotherm show that Pb(II) ions are favorably adsorbed by NB and AAB. Thermodynamic quantities such as Gibbs free energy ({Delta}G), the enthalpy ({Delta}H) and the entropy change of sorption ({Delta}S) were determined as about -5.06, 10.29 and 0.017 kJ mol{sup -1} K{sup -1}, respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously.

  12. Adsorption of Nile Blue A from Wastewater Using Magnetic Multi-Walled Carbon Nanotubes: Kinetics and Equilibrium Studies

    Directory of Open Access Journals (Sweden)

    Mehrnaz Ghoochian

    2016-04-01

    Full Text Available Background: Synthetic dyes are serious pollutants and wide ranges of methods have been employed for their removal from aquatic systems. We studied the adsorption of "Nile blue A" (NBA, an anionic dye, from aqueous solution by oxidized multi-walled carbon nanotubes (MWCNTs. Methods: Scanning electron microscope and Fourier transform infrared spectroscopy were used to characterize function groups produced at MWCNTs surface. Kinetics and adsorption isotherms of NBA, the effect of temperature, pH, contact time and initial dosage of nanotubes on the adsorption capacity were also assessed. The experimental data were analyzed by Langmuir and Freundlich models. Results: Most of the dye was removed in the first 5 min and best adsorption percentage was at pH 7.0. The equilibrium reached at 45 min. The experimental data were analyzed by Langmuir and Freundlich models and the results fitted well with the Freundlich model. The adsorption kinetic data were analyzed using first-order and the pseudo-second order model and the adsorption kinetic data of NBA dye onto MWCNTs fitted the pseudo-second order model. The maximum adsorption capacity was obtained as 169.49 mg g-1. Conclusion: Freundlich model suggested that the adsorption process followed heterogeneous distribution onto MWCNTs and pseudo-second model of adsorption implied that chemical processes controlled the rate-controlling step. Oxidized MWCNTs could be used as an effective adsorbent for the removal of "Nile Blue A" dye. Oxidization of MWCNTs by nitric acid, improves the efficiency of NBA removal due to increases in functional groups and total number of adsorption sites.

  13. Removal of reactive blue 19 dyes from textile wastewater by pomegranate seed powder: Isotherm and kinetic studies

    Directory of Open Access Journals (Sweden)

    Mahboobeh Dehvari

    2016-01-01

    Full Text Available Aims: The aim of this study was the evaluation of adsorption kinetics and equilibrium of reactive blue 19 dyes from textile synthetic wastewater by pomegranate seed powder. Materials and Methods: This study is an experimental research, which was performed in laboratory scale. In this study, the parameters such as adsorbent dose, pH and retention time, initial concentration of dye and agitation rate have been investigated. After washing and boiling of pomegranate seeds for 2 h, they dried, milled and finally pulverized by standard ASTM sieves (40-100 mesh. Maximum adsorption wave length (λmax by spectrophotometer ultra violet/visible (model SP-3000 Plus 592 nm was determined. The Langmuir, Freundlich and Temkin isotherm models and the pseudo-first-order and pseudo-second-order kinetic models were analyzed. Results: According to results, the removal efficiency with adsorbent dose, retention time and agitation rate has a direct relation. Maximum adsorption occurred in the first 60 min. The removal efficiency with initial concentration of dye and pH of solution has indirect relation. The Freundlich isotherm fits the experimental data better than the other isotherms. It was recognized that the adsorption followed by pseudo-second-order model (R2 > 0.99. Conclusion: Based on the results, pomegranate seeds as a new natural sorbent can be used in removal of dye and other environmental pollutants with desirable absorption capacity.

  14. Comparison of three combined sequencing batch reactor followed by enhanced Fenton process for an azo dye degradation: Bio-decolorization kinetics study

    Energy Technology Data Exchange (ETDEWEB)

    Azizi, A., E-mail: armina_84@yahoo.com [Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413 (Iran, Islamic Republic of); Alavi Moghaddam, M.R., E-mail: alavim@yahoo.com [Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413 (Iran, Islamic Republic of); Maknoon, R., E-mail: rmaknoon@yahoo.com [Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413 (Iran, Islamic Republic of); Kowsari, E., E-mail: kowsarie@aut.ac.ir [Department of Chemistry, Amirkabir University of Technology, Hafez Ave., Tehran 15875-4413 (Iran, Islamic Republic of)

    2015-12-15

    Highlights: • Three combined advanced SBR and enhanced Fenton process as post treatment was compared. • Higher biomass concentration, dye, COD and metabolites removal was presented together. • Pseudo zero and pseudo first-order bio-decolorization kinetics were observed in all SBRs. • High reduction of AR18 to intermediate metabolites was monitored by HPLC. - Abstract: The purpose of this research was to compare three combined sequencing batch reactor (SBR) – Fenton processes as post-treatment for the treatment of azo dye Acid Red 18 (AR18). Three combined treatment systems (CTS1, CTS2 and CTS3) were operated to investigate the biomass concentration, COD removal, AR18 dye decolorization and kinetics study. The MLSS concentration of CTS2 reached 7200 mg/L due to the use of external feeding in the SBR reactor of CTS2. The COD concentration remained 273 mg/L and 95 mg/L (initial COD = 3270 mg/L) at the end of alternating anaerobic–aerobic SBR with external feeding (An-A MSBR) and CTS2, respectively, resulting in almost 65% of Fenton process efficiency. The dye concentration of 500 mg/L was finally reduced to less than 10 mg/L in all systems indicating almost complete AR18 decolorization, which was also confirmed by UV–vis analysis. The dye was removed following two successive parts as parts 1 and 2 with pseudo zero-order and pseudo first-order kinetics, respectively, in all CTSs. Higher intermediate metabolites degradation was obtained using HPLC analysis in CTS2. Accordingly, a combined treatment system can be proposed as an appropriate and environmentally-friendly system for the treatment of the azo dye AR18 in wastewater.

  15. Kinetics of microwave assisted extraction of pectin from Balinese orange peel using Pseudo-homogeneous model

    Science.gov (United States)

    Megawati, Wulansarie, Ria; Faiz, Merisa Bestari; Adi, Susatyo; Sammadikun, Waliyuddin

    2018-03-01

    The objective of this work was to study the homogeneous kinetics of pectin extraction of Balinese orange peel conducted using Microwave Assisted Extraction (MAE). The experimental data showed that the power increases (180 to 600 W), so that the extraction yield of pectin also increases (12.2 to 30.6 % w/w). Moreover, the extraction time is longer (10, 15, and 20 min) the yield of pectin increases (8.8, 20.2, and 40.5). At time after of 20 min (25 and 30 min), the yield starts to decrease (36.6 and 22.9). This phenomena shows pectin degradation. Therefore, pectin extraction is a series reaction, i.e. extraction and degradation. The calculation result showed that pseudo series homogeneous model can quantitatively describe the extraction kinetics. The kinetic constants can be expressed by Arrhenius equation with the frequency factors of 1.58 × 105 and 2.29 × 105 1/min, while the activation energies are 64,350 and 56,571 J/mole for extraction and degradation, respectively.

  16. Kinetic and Thermodynamic Studies for the Removal of Europium Ions from Waste Solution Using Some Local Clay Minerals

    International Nuclear Information System (INIS)

    El-Kamash, A.M.; El-Masry, E.H.; El-Dessouky, M.I.

    2008-01-01

    Thermodynamic and kinetic investigations on the removal of Eu 3+ ions from aqueous waste solution using bentonite and sandstone, as local clay minerals, has been done using batch technique. The influences of ph, contact time between liquid and solid phases, initial metal ion concentration, and temperature have been evaluated. Pseudo first-order and pseudo second-order kinetic models were used to analyze the sorption rate data and the results showed that the pseudo second-order model is best correlate the kinetic data. Equilibrium isotherms were determined to assess the maximum sorption capacity of bentonite and sandstone and the equilibrium sorption data were analyzed using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm models. All tested models fit the data reasonably well in terms of regression coefficients. The maximum sorption capacity of bentonite was found to be greater than that of sandstone and the mean free energy is in all cases in the range corresponding to the ion exchange type of sorption. Sorption studies were also performed at different temperatures to obtain the thermodynamic parameters of the process. The numerical value of δG degree decreases with an increase in temperature, indicating that the sorption reaction is more favorable at higher temperature. The positive values of δH degree correspond to the endothermic nature of the sorption process

  17. Pre-exponential factor in general order kinetics of thermoluminescence and its influence on glow curves

    International Nuclear Information System (INIS)

    Sunta, C.M.; Ayta, W.E.F.; Chen, R.; Watanabe, S.

    1997-01-01

    A model of thermoluminescence kinetics based on a physically meaningful approach shows that the glow curve shapes undergo systematic changes with the change of trap occupancy (dose). In terms of the general order kinetics model it means that the kinetic order changes with sample dose. In parallel to the kinetic order, the pre-exponential factor also changes. In contrast to these results the glow curves calculated from the general order kinetics model show that the peak shape remains nearly constant when the trap occupancy is changed. When appropriately defined, the pre-exponential factor also has a fixed value independent of trap occupancy. In these respects the general order kinetics model, though empirical, seems to describe the glow peak behaviour quite successfully. However, regarding the peak temperature the theoretical results both from the physical as well as the empirical model seem to diverge from the experimental observations when the experimentally determined kinetics is non-first order. (author)

  18. Kinetics, isotherms, and thermodynamic studies of lead, chromium, and cadmium bio-adsorption from aqueous solution onto Picea smithiana sawdust.

    Science.gov (United States)

    Mahmood-Ul-Hassan, Muhammad; Yasin, Muhammad; Yousra, Munazza; Ahmad, Rizwan; Sarwar, Sair

    2018-05-01

    Lead (Pb), chromium (Cr), and cadmium (Cd) removal capacity of sawdust (Picea smithiana) from aqueous solution was investigated by conducting batch experiments. Thermodynamic parameters, like change in standard free energy (ΔG Θ ), enthalpy (ΔH Θ ) and entropy (ΔS Θ ) during bio-adsorption process were estimated using the Van't Hoff equation. The maximum metals adsorption was observed at pH 8, 20 g L -1 bio-adsorbent and at 60 min of contact time. The metal adsorption kinetics was examined by fitting the pseudo-first-order as well as four forms of pseudo-second-order kinetic models. Type 1 pseudo-second-order equation described adsorption kinetics better than others. Langmuir model and Freundlich equations were used for calculation of sorption parameters. The Langmuir maximum adsorption capacity of Pb, Cr, and Cd was 6.35, 3.37, and 2.87 mg g -1 at room temperature, respectively. The values of the separation factor (RL) were in between 0 and 1, indicating that bio-adsorption was favorable. Thermodynamics study revealed that the Pb, Cr, and Cd uptake reactions were endothermic and spontaneous. Results of the study asserted that the removal of heavy metal ions from aqueous solution is viable and the sawdust could be used in the treatment of effluents from industries, thereby reducing the level of water pollution.

  19. Removal of Dye (Blue 56 From Aqueous Solution via Adsorption onto Pistachio Shell: kinetic and isotherm study of removal process

    Directory of Open Access Journals (Sweden)

    A. Ravanpaykar

    2012-03-01

    Full Text Available In the present investigation, shells of pistachio are used as adsorbents and they have been successfully used for the removal of Blue 56, from water samples. The effect of various parameters such as: pH, amounts of adsorbents, size of adsorbent particles and contact time on removal processing were investigated. Inthisstudy Freundlichabsorptionisotherms and Langmuir were investigated. The experimental data were correlated reasonably well by the Freundlich adsorption isotherm and isotherm parameters were calculated. In order to investigate the efficiency of Blue 56 adsorption on the pistachio shell, pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion kinetic models were studied. Themodel that hadgoodcorrelationtoattractFreundlichwas chosenasthemodel. Its kineticsfollowsthepseudosecond order reaction.

  20. Adsorption of an anionic dye on a novel low-cost mesoporous adsorbent: kinetic, thermodynamic and isotherm studies

    Science.gov (United States)

    Msaad, Asmaa; Belbahloul, Mounir; Zouhri, Abdeljalil

    2018-05-01

    Our activated carbon was prepared successfully using phosphoric acid as an activated agent. The activated carbon was characterized by Scanning Electron Micrograph (SEM), Brunauer-Emmett- Teller (BET), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The aim of our study is to evaluate the adsorption capacity of Methyl Orange (MO) on Ziziphus lotus activated carbon. Adsorption isotherms were studied according to Langmuir and Freundlich Model, and adsorption kinetics according to pseudo-first and second-order. Results show that the maximum adsorption was reached in the first 10min at ambient temperature with a yield of 96.31%. The Langmuir isotherm shows a correlation coefficient of 99.4 % higher than Freundlich model and the adsorption kinetic model follow a pseudo-second-order with a maximum adsorption capacity of 769.23 mg/g. FTIR and X-Ray spectroscopy indicate that our activated carbon has an amorphous structure with the presence of functional groups, where BET analysis revealed a high surface area of 553 mg/g, which facilitate the adsorption process

  1. A Kinetic Study of the Diels-Alder Reaction. An Experiment Illustrating Simple Second-Order Reaction Kinetics.

    Science.gov (United States)

    Silvestri, Michael G.; Dills, Charles E.

    1989-01-01

    Describes an organic chemistry experiment for teaching the basic concepts of chemical kinetics. Provides background information about first- and second-order reactions, experimental procedures of the Diels-Alder reaction between cyclopentadiene and dimethyl fumarate, and the experimental results. (YP)

  2. Kinetic Studies of Catalytic Oxidation of Cyclohexene Using ...

    African Journals Online (AJOL)

    acer

    Kinetic Studies of Catalytic Oxidation of Cyclohexene Using Chromium VI Oxide in. Acetic Acid ... respect to the oxidant using pseudo-order approximation method. .... making the concentration of the cyclohexene in ..... on Titanium Silicate.

  3. Kinetic study of ozonation of molasses fermentation wastewater

    International Nuclear Information System (INIS)

    Coca, M.; Pena, M.; Gonzalez, G.

    2007-01-01

    A kinetic study of molasses wastewater ozonation was carried out in a stirred tank reactor to obtain the rate constants for the decolorization reaction and the regime through which ozone is absorbed. First, fundamental mass transfer parameters such as ozone solubility, volumetric mass transfer coefficients and ozone decomposition kinetics were determined from semi-batch experiments in organic-free solutions with an ionic composition similar that of industrial wastewater. The influence of operating variables such as the stirring rate and gas flow rate on the kinetic and mass transfer parameters was also studied. The application of film theory allows to establish that the reactions between ozone and colored compounds in wastewater take place in the fast and pseudo-first-order regime, within the liquid film. The decolorization rate constants were evaluated at pH 8.7 and 25 deg. C, varying from 0.6 x 10 7 to 3.8 x 10 7 L mol -1 s -1 , depending on the stirring rate and the inlet gas flow

  4. Investigation of kinetics and absorption isotherm models for hydroponic phytoremediation of waters contaminated with sulfate.

    Science.gov (United States)

    Saber, Ali; Tafazzoli, Milad; Mortazavian, Soroosh; James, David E

    2018-02-01

    Two common wetland plants, Pampas Grass (Cortaderia selloana) and Lucky Bamboo (Dracaena sanderiana), were used in hydroponic cultivation systems for the treatment of simulated high-sulfate wastewaters. Plants in initial experiments at pH 7.0 removed sulfate more efficiently compared to the same experimental conditions at pH 6.0. Results at sulfate concentrations of 50, 200, 300, 600, 900, 1200, 1500 and 3000 mg/L during three consecutive 7-day treatment periods with 1-day rest intervals, showed decreasing trends of both removal efficiencies and uptake rates with increasing sulfate concentrations from the first to the second to the third 7-day treatment periods. Removed sulfate masses per unit dry plant mass, calculated after 23 days, showed highest removal capacity at 600 mg/L sulfate for both plants. A Langmuir-type isotherm best described sulfate uptake capacity of both plants. Kinetic studies showed that compared to pseudo first-order kinetics, pseudo-second order kinetic models slightly better described sulfate uptake rates by both plants. The Elovich kinetic model showed faster rates of attaining equilibrium at low sulfate concentrations for both plants. The dimensionless Elovich model showed that about 80% of sulfate uptake occurred during the first four days' contact time. Application of three 4-day contact times with 2-day rest intervals at high sulfate concentrations resulted in slightly higher uptakes compared to three 7-day contact times with 1-day rest intervals, indicating that pilot-plant scale treatment systems could be sized with shorter contact times and longer rest-intervals. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Adsorption of Zinc(II) on diatomite and manganese-oxide-modified diatomite: A kinetic and equilibrium study

    Energy Technology Data Exchange (ETDEWEB)

    Caliskan, Necla, E-mail: ncaliskan7@hotmail.com [Department of Physical Chemistry, Faculty of Science, Yuezuencue Yil University, Van 65080 (Turkey); Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan [Department of Physical Chemistry, Faculty of Science, Yuezuencue Yil University, Van 65080 (Turkey)

    2011-10-15

    Highlights: {center_dot}The removal of Zn(II) ions from aqueous solution was studied using natural and MnO{sub 2} modified diatomite samples at different temperatures. {center_dot} The sorption of Zn(II) on the natural and modified diatomite was an endothermic processes, controlled by physical mechanisms and spontaneously. {center_dot} Adsorption of zinc metal ion on diatomite samples is more or less a two step process. {center_dot} Adsorption of Zn(II) on natural and modified diatomite could be explained by the mechanism of pseudo-second-order. - Abstract: The removal of Zn(II) ions from aqueous solution was studied using natural and MnO{sub 2} modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol{sup -1}, indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy ({Delta}H{sup 0}), Gibbs' free energy ({Delta}G{sup 0}) and entropy ({Delta}S{sup 0}) were calculated for natural and MnO{sub 2} modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously.

  6. Kinetic and equilibrium study of adsorption of di-azo dyes on commercial activated carbon

    International Nuclear Information System (INIS)

    Hyali, E.A.S.A.; Abady, T.G.A.

    2013-01-01

    This research work is concerned with studying the adsorption of a number of di-azo dyes on commercial activated carbon (CAC). The synthesized dyes vary in their structures by the central parts. which are either ortho, meta or para phenvlene diamine. This variation affects the linearity of molecules, their spatial arrangement and electron movement throughout the molecule by resonance. Factors a fleeting adsorption process, such as the efiect of contact time, initial concentration, p1-I of the adsorption medium, adsorbent dose, effect of solvent and temperature were studied. The results indicated that, the adsorption process is fast in the first 10 mm, then gradually decreased with time and approaches maximum within 70-80 min for all the studied dyes. The increase of initial concentration and temperature decreased the adsorption efficiency. The results also shows that, the adsorption is found to be more efficient at low Ph value. The increase of the adsorbent dose increases the adsorption efficiency and decreases its capacity. The variation of solvent (ethanol-water ratio) indicates that the decrease of dielectric constant lowers the adsorption efficiency. The study included application of three adsorption isotherms, Freundlich, Langmuir and Tempkin on the experimental data of the studied systems. The results indicated that, Freundlich isotherm fits better the adsorption data. Kinetic analysis of the adsorption data was also conducted by employing 4 kinetic models; pseudo first order and pseudo second order, Elovich and intra particle diffusion equations. The results obtained conclude that, the studied systems follow the Pseudo second order model. (author)

  7. Pseudo-Haptic Feedback in Teleoperation.

    Science.gov (United States)

    Neupert, Carsten; Matich, Sebastian; Scherping, Nick; Kupnik, Mario; Werthschutzky, Roland; Hatzfeld, Christian

    2016-01-01

    In this paper, we develop possible realizations of pseudo-haptic feedback in teleoperation systems based on existing works for pseudo-haptic feedback in virtual reality and the intended applications. We derive four potential factors affecting the performance of haptic feedback (calculation operator, maximum displacement, offset force, and scaling factor), which are analyzed in three compliance identification experiments. First, we analyze the principle usability of pseudo-haptic feedback by comparing information transfer measures for teleoperation and direct interaction. Pseudo-haptic interaction yields well above-chance performance, while direct interaction performs almost perfectly. In order to optimize pseudo-haptic feedback, in the second study we perform a full-factorial experimental design with 36 subjects performing 6,480 trials with 36 different treatments. Information transfer ranges from 0.68 bit to 1.72 bit in a task with a theoretical maximum of 2.6 bit, with a predominant effect of the calculation operator and a minor effect of the maximum displacement. In a third study, short- and long-term learning effects are analyzed. Learning effects regarding the performance of pseudo-haptic feedback cannot be observed for single-day experiments. Tests over 10 days show a maximum increase in information transfer of 0.8 bit. The results show the feasibility of pseudo-haptic feedback for teleoperation and can be used as design basis for task-specific systems.

  8. Kinetics, equilibrium and thermodynamic studies on biosorption of Ag(I) from aqueous solution by macrofungus Pleurotus platypus.

    Science.gov (United States)

    Das, Devlina; Das, Nilanjana; Mathew, Lazar

    2010-12-15

    Reports are available on silver binding capacity of some microorganisms. However, reports on the equilibrium studies on biosorption of silver by macrofungi are seldom known. The present study was carried out in a batch system using dead biomass of macrofungus Pleurotus platypus for the sorption of Ag(I). P. platypus exhibited the highest silver uptake of 46.7 mg g(-1) of biomass at pH 6.0 in the presence of 200 mg L(-1) Ag(I) at 20°C. Kinetic studies based on fractional power, zero order, first order, pseudo-first order, Elovich, second order and pseudo-second order rate expressions have been carried out. The results showed a very good compliance with the pseudo-first order model. The experimental data were analyzed using two parameter isotherms (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Halsey), three parameter isotherms (Redlich-Peterson, Sips, Khan, Koble-Corrigan, Hill, Toth, Radke-Prausmitz, Jossens, Langmuir-Freundlich), four parameter isotherms (Weber-van Vliet, Fritz-Schlunder, Baudu) and five parameter isotherm (Fritz-Schlunder). Thermodynamic parameters of the biosorption (ΔG, ΔH and ΔS) were also determined. The present study confirmed that macrofungus P. platypus may be used as a cost effective efficient biosorbent for the removal of Ag(I) ions from aqueous solution. Copyright © 2010 Elsevier B.V. All rights reserved.

  9. The Fermi pseudo-potential in one dimension

    International Nuclear Information System (INIS)

    Coutinho, F A B; Nogami, Y; Tomio, Lauro; Toyama, F M

    2004-01-01

    Wu and Yu recently examined point interactions in one dimension in the form of the Fermi pseudo-potential. On the other hand there are point interactions in the form of self-adjoint extensions (SAEs) of the kinetic energy operator. We examine the relationship between the point interactions in these two forms in the one-channel and two-channel cases. In the one-channel case the pseudo-potential leads to the standard three-parameter family of SAEs. In the two-channel case the pseudo-potential furnishes a ten-parameter family of SAEs

  10. P1-17: Pseudo-Haptics Using Motion-in-Depth Stimulus and Second-Order Motion Stimulus

    Directory of Open Access Journals (Sweden)

    Shuichi Sato

    2012-10-01

    Full Text Available Modification of motion of the computer cursor during the manipulation by the observer evokes illusory haptic sensation (Lecuyer et al., 2004 ACM SIGCHI '04 239–246. This study investigates the pseudo-haptics using motion-in-depth and second-order motion. A stereoscopic display and a PHANTOM were used in the first experiment. A subject was asked to move a visual target at a constant speed in horizontal, vertical, or front-back direction. During the manipulation, the speed was reduced to 50% for 500 msec. The haptic sensation was measured using the magnitude estimation method. The result indicates that perceived haptic sensation from motion-in-depth was about 30% of that from horizontal or vertical motion. A 2D display and the PHANTOM were used in the second experiment. The motion cue was second order—in each frame, dots in a square patch reverses in contrast (i.e., all black dots become white and all white dots become black. The patch was moved in a horizontal direction. The result indicates that perceived haptic sensation from second-order motion was about 90% of that from first-order motion.

  11. An eco-friendly dyeing of woolen yarn by Terminalia chebula extract with evaluations of kinetic and adsorption characteristics.

    Science.gov (United States)

    Shabbir, Mohd; Rather, Luqman Jameel; Shahid-Ul-Islam; Bukhari, Mohd Nadeem; Shahid, Mohd; Ali Khan, Mohd; Mohammad, Faqeer

    2016-05-01

    In the present study Terminalia chebula was used as an eco-friendly natural colorant for sustainable textile coloration of woolen yarn with primary emphasis on thermodynamic and kinetic adsorption aspects of dyeing processes. Polyphenols and ellagitannins are the main coloring components of the dye extract. Assessment of the effect of pH on dye adsorption showed an increase in adsorption capacity with decreasing pH. Effect of temperature on dye adsorption showed 80 °C as optimum temperature for wool dyeing with T. chebula dye extract. Two kinetic equations, namely pseudo first-order and pseudo second-order equations, were employed to investigate the adsorption rates. Pseudo second-order model provided the best fit (R (2) = 0.9908) to the experimental data. The equilibrium adsorption data were fitted by Freundlich and Langmuir isotherm models. The adsorption behavior accorded well (R (2) = 0.9937) with Langmuir isotherm model. Variety of eco-friendly and sustainable shades were developed in combination with small amount of metallic mordants and assessed in terms of colorimetric (CIEL(∗) a (∗) b (∗) and K/S) properties measured using spectrophotometer under D65 illuminant (10° standard observer). The fastness properties of dyed woolen yarn against light, washing, dry and wet rubbing were also evaluated.

  12. An eco-friendly dyeing of woolen yarn by Terminalia chebula extract with evaluations of kinetic and adsorption characteristics

    Science.gov (United States)

    Shabbir, Mohd; Rather, Luqman Jameel; Shahid-ul-Islam; Bukhari, Mohd Nadeem; Shahid, Mohd; Ali Khan, Mohd; Mohammad, Faqeer

    2016-01-01

    In the present study Terminalia chebula was used as an eco-friendly natural colorant for sustainable textile coloration of woolen yarn with primary emphasis on thermodynamic and kinetic adsorption aspects of dyeing processes. Polyphenols and ellagitannins are the main coloring components of the dye extract. Assessment of the effect of pH on dye adsorption showed an increase in adsorption capacity with decreasing pH. Effect of temperature on dye adsorption showed 80 °C as optimum temperature for wool dyeing with T. chebula dye extract. Two kinetic equations, namely pseudo first-order and pseudo second-order equations, were employed to investigate the adsorption rates. Pseudo second-order model provided the best fit (R2 = 0.9908) to the experimental data. The equilibrium adsorption data were fitted by Freundlich and Langmuir isotherm models. The adsorption behavior accorded well (R2 = 0.9937) with Langmuir isotherm model. Variety of eco-friendly and sustainable shades were developed in combination with small amount of metallic mordants and assessed in terms of colorimetric (CIEL∗a∗b∗ and K/S) properties measured using spectrophotometer under D65 illuminant (10° standard observer). The fastness properties of dyed woolen yarn against light, washing, dry and wet rubbing were also evaluated. PMID:27222752

  13. Removal of Chromium by Using of Adsorption onto Strong Base Anion Resin: Study of Equilibrium and Kinetic

    Directory of Open Access Journals (Sweden)

    Mehdi Shirzad Siboni

    2011-10-01

    Full Text Available Chromium is one of the heavy metals that is found in industrial effluents and is very toxic for human and environment. In this work the removal of hexavalent chromium by using of adsorption onto strongly basic anion was investigated. Various parameters such as pH, initial hexavalent chromium concentration, contact time and resin dosage were studied. Experimental data were expressed by Langmiur and Freundlich isotherm Pseudo-first order, Pseudo-second order and modified Pseudo-first order kinetic models. The results showed chromium removal was increased by increase of contact time and resin dosage, while decreased by increase of pH and initial hexavalent chromium concentration. At contact time equal 120 min, resin dosage 0.2 g/100 ml and initial hexavalent chromium concentration of 30 mg/l, by increasing pH from 3 to 11, removal efficiency was decreased from 93.56 % to 69.12 %. In addition, by increasing contact time from 5 min to 120 min, removal efficiency was increased from 39.51 % to 94.41 %. The results also showed hexavalent chromium sorption follows Langmiur isotherm model. Pseudo second order models best describe chromium removal by using of adsorption onto strongly basic anion resin. The results revealed that removal of hexavalent chromium from aqueous solution by using of adsorption onto stringly basic onion resins can be done quick and effective.

  14. Equilibrium, kinetic and thermodynamic studies of adsorption of Pb(II) from aqueous solution onto Turkish kaolinite clay

    International Nuclear Information System (INIS)

    Sari, Ahmet; Tuzen, Mustafa; Citak, Demirhan; Soylak, Mustafa

    2007-01-01

    The adsorption of Pb(II) onto Turkish (Bandirma region) kaolinite clay was examined in aqueous solution with respect to the pH, adsorbent dosage, contact time, and temperature. The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms and both models fitted well. The monolayer adsorption capacity was found as 31.75 mg/g at pH 5 and 20 deg. C. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data. The mean free energy of adsorption (13.78 kJ/mol) indicated that the adsorption of Pb(II) onto kaolinite clay may be carried out via chemical ion-exchange mechanism. Thermodynamic parameters, free energy (ΔG o ), enthalpy (ΔH o ) and entropy (ΔS o ) of adsorption were also calculated. These parameters showed that the adsorption of Pb(II) onto kaolinite clay was feasible, spontaneous and exothermic process in nature. Furthermore, the Lagergren-first-order, pseudo-second-order and the intraparticle diffusion models were used to describe the kinetic data. The experimental data fitted well the pseudo-second-order kinetics

  15. Kinetics and mechanism of permanganate oxidation of iota- and lambda-carrageenan polysaccharides as sulfated carbohydrates in acid perchlorate solutions.

    Science.gov (United States)

    Hassan, Refat M; Fawzy, Ahmed; Ahmed, Gamal A; Zaafarany, Ishaq A; Asghar, Basim H; Takagi, Hideo D; Ikeda, Yasuhisa

    2011-10-18

    The kinetics of oxidation of iota- and lambda-carrageenan as sulfated carbohydrates by permanganate ion in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm(-3) have been investigated spectrophotometrically. The pseudo-first-order plots were found to be of inverted S-shape throughout the entire courses of reactions. The initial rates were found to be relatively slow in the early stages, followed by an increase in the oxidation rates over longer time periods. The experimental observations showed first-order dependences in permanganate and fractional first-order kinetics with respect to both carrageenans concentration for both the induction and autoacceleration periods. The results obtained at various hydrogen ion concentrations showed that the oxidation processes in these redox systems are acid-catalyzed throughout the two stages of oxidation reactions. The added salts lead to the prediction that Mn(III) is the reactive species throughout the autoacceleration periods. Kinetic evidence for the formation of 1:1 intermediate complexes was revealed. The kinetic parameters have been evaluated and tentative reaction mechanisms in good agreement with the kinetic results are discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. Effect of cations in the background electrolyte on the adsorption kinetics of copper and cadmium and the isoelectric point of imogolite

    International Nuclear Information System (INIS)

    Arancibia-Miranda, Nicolás; Silva-Yumi, Jorge; Escudey, Mauricio

    2015-01-01

    Highlights: • Effect of various cations on the IEP of imogolite was studied. • Studied adsorption kinetics of Cd and Cu on imogolite in the presence of cations. • K"+ acted as an indifferent electrolyte and did not affect the IEP of imogolite. • Adsorption in the presence of K"+ is described well by three of the four models. • These include pseudo-second order, Elovich equation, and Weber–Morris model. - Abstract: Modification of surface charge and changes in the isoelectric point (IEP) of synthetic imogolite were studied for various cations in the background electrolyte (K"+, NH_4"+, Mg"2"+, and Ca"2"+). From the electrophoretic mobility data, it was established that the K"+ (KCl) concentration does not affect the IEP of imogolite; therefore, KCl is a suitable background electrolyte. In terms of the magnitude of changes in the IEP and surface charge, the cations may be ranked in the following order: Mg"2"+ ≈ Ca"2"+ >> NH_4"+ >> K"+. Four different kinetic models were used to evaluate the influence of Mg"2"+, Ca"2"+, NH_4"+, and K"+ on the adsorption of Cd and Cu on synthetic imogolite. When adsorption occurs in the presence of cations with the exception of K"+, the kinetics of the process is well described by the pseudo-first order model. On the other hand, when adsorption is conducted in the presence of K"+, the adsorption kinetics is well described by the pseudo-second order, Elovich, and Weber–Morris models. From the surface charge measurements, the affinity between imogolite and the cations and their effect on the adsorption of trace elements, namely Cu and Cd, were established.

  17. Adsorption kinetic parameters of Fe3+ and Ni2+ ions by gyrolite

    Directory of Open Access Journals (Sweden)

    Kestutis Baltakys

    2015-03-01

    Full Text Available In this work the adsorption kinetic parameters for Fe3+ and Ni2+ ions by gyrolite are presented. Additionally, the adsoption mechanism was described by using pseudo first order and pseudo second order  equations. It was determined that the adsorption capacity of gyrolite and intrusion of heavy metals ions in its structure depends on reaction time and the pH value of adsorptive. It was observed that the incorporation of Fe3+ ions occurs more intensive than Ni2+ ions. It was found that in the acidic solution the intrusion of Fe3+ ions into gyrolite structure proceeds by two types of chemical reaction mechanisms: substitution and addition. Meanwhile, nickel ions were participated only in substitution reaction: gyrolite-Ca0 + Mex+ ↔ gyrolite-Me0 + Ca2+. It was observed that the pseudo second order model fit well for iron and nickel ions adsorption mechanism. It was estimated that the adsorption reactions are not reversible process and the crystal structure of gyrolite is stable. Moreover, synthetic adsorbent and the products of sorption were characterized by XRD, STA and FT-IR methods.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5735

  18. Kinetic Study of Water Contaminants Adsorption by Bamboo Granular Activated and Non-Activated Carbon

    Directory of Open Access Journals (Sweden)

    Opololaoluwa Oladimarun Ijaola

    2013-10-01

    Full Text Available The adsorptive capacity of metal ions from surface water with activated and non-activated carbon derived from bamboo was investigated. The validation of adsorption kinetics of Cl, PO4 and Pb was done by pseudo-first and second order model while adsorption isotherms was proved by Langmuir and Freundlich isotherm model for activated and non- activated bamboo granular carbon. Generally, the amount of metal ions uptake increases with time and activation levels and the pH of bamboo granular carbon increase with activation. Similarly, the pore space of the activated carbon also increases with activation levels. The correlation coefficients (R2 show that the pseudo-second order model gave a better fit to the adsorption process with 0.9918 as the least value and 1.00 as the highest value as compared with the pseudo-first order with 0.813 as the highest value and 0 as the least. The Freundlich isotherm was more favorable when compared with the Langmuir isotherm in determining the adsorptive capacity of bamboo granular activated carbon. The study has shown that chemical activation increases the pore space, surface area and the pH of bamboo granular carbon which ultimately increases the adsorption rate of metal ions in the contaminated surface water.

  19. Genetic characterization, nickel tolerance, biosorption, kinetics, and uptake mechanism of a bacterium isolated from electroplating industrial effluent.

    Science.gov (United States)

    Nagarajan, N; Gunasekaran, P; Rajendran, P

    2015-04-01

    Electroplating industries in Madurai city produce approximately 49,000 L of wastewater and 1200 L of sludge every day revealing 687-5569 ppm of nickel (Ni) with other contaminants. Seventeen Ni-tolerant bacterial strains were isolated from nutrient-enriched effluents. Among them one hyper Ni accumulating strain was scored and identified as Bacillus cereus VP17 on the basis of morphology, biochemical tests, 16S rDNA gene sequencing, and phylogenetic analysis. Equilibrium data of Ni(II) ions using the bacterium as sorbent at isothermal conditions (37 °C) and pH 6 were best adjusted by Langmuir (R(2) = 0.6268) and Freundlich models (R(2) = 0.9505). Experimental validation reveals Ni sorption takes place on a heterogeneous surface of the biosorbent, and predicted metal sorption capacity is 434 ppm. The pseudo-second-order kinetic model fitted the biosorption kinetic data better than the pseudo-first-order kinetic model (R(2) = 0.9963 and 0.3625). Scanning electron microscopy, energy dispersive X-ray, and Fourier transform infrared spectroscopy studies of the bacterial strain with and without Ni(II) ion reveals the biosorption mechanism. The results conclude possibilities of using B. cereus VP17 for Ni bioremediation.

  20. Heavy and toxic metal uptake by mesoporous hypercrosslinked SMA beads: Isotherms and kinetics

    Directory of Open Access Journals (Sweden)

    Renuka Gonte

    2016-09-01

    Full Text Available Hypercrosslinked styrene-maleic acid copolymer beads were used for the removal of metal ions from mimicked industrial effluents. The polymer was characterized by SEM which revealed the presence of a porous network. Carboxyl acid groups of the polymer were identified as active sites for metal uptake. Highly porous surface enhanced metal ion uptake was achieved through a physicochemical process. Equilibrium sorption of metal ions was best described by the Freundlich and Temkin model with R2 > 0.99. Adsorption followed pseudo first and pseudo second order reaction kinetics. Intraparticle diffusion model suggested a three step equilibrium. Desorption was a fast process with ∼90% in 60 min.

  1. The Efficient Removal of Heavy Metal Ions from Industry Effluents Using Waste Biomass as Low-Cost Adsorbent: Thermodynamic and Kinetic Models

    Science.gov (United States)

    Indhumathi, Ponnuswamy; Sathiyaraj, Subbaiyan; Koelmel, Jeremy P.; Shoba, Srinivasan U.; Jayabalakrishnan, Chinnasamy; Saravanabhavan, Munusamy

    2018-05-01

    The ability of green micro algae Chlorella vulgaris for biosorption of Cu(II) ions from an aqueous solution was studied. The biosorption process was affected by the solution pH, contact time, temperature and initial Cu(II) concentration. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order and intra particle diffusion models. Results showed that the sorption process of Cu(II) ions followed pseudo-second order kinetics. The sorption data of Cu(II) ions are fitted to Langmuir, Freundlich, and Redlich-Peterson isotherms, and the Temkin isotherm. The thermodynamic study shows the Cu(II) biosorption was exothermic in nature. The Cu(II) ions were recovered effectively from Chlorella vulgaris biomass using 0.1 M H2SO4 with up to 90.3% recovery, allowing for recycling of the Cu. Green algae from freshwater bodies showed significant potential for Cu(II) removal and recovery from industrial wastewater.

  2. Low rank approach to computing first and higher order derivatives using automatic differentiation

    International Nuclear Information System (INIS)

    Reed, J. A.; Abdel-Khalik, H. S.; Utke, J.

    2012-01-01

    This manuscript outlines a new approach for increasing the efficiency of applying automatic differentiation (AD) to large scale computational models. By using the principles of the Efficient Subspace Method (ESM), low rank approximations of the derivatives for first and higher orders can be calculated using minimized computational resources. The output obtained from nuclear reactor calculations typically has a much smaller numerical rank compared to the number of inputs and outputs. This rank deficiency can be exploited to reduce the number of derivatives that need to be calculated using AD. The effective rank can be determined according to ESM by computing derivatives with AD at random inputs. Reduced or pseudo variables are then defined and new derivatives are calculated with respect to the pseudo variables. Two different AD packages are used: OpenAD and Rapsodia. OpenAD is used to determine the effective rank and the subspace that contains the derivatives. Rapsodia is then used to calculate derivatives with respect to the pseudo variables for the desired order. The overall approach is applied to two simple problems and to MATWS, a safety code for sodium cooled reactors. (authors)

  3. Quasi-phases and pseudo-transitions in one-dimensional models with nearest neighbor interactions

    Science.gov (United States)

    de Souza, S. M.; Rojas, Onofre

    2018-01-01

    There are some particular one-dimensional models, such as the Ising-Heisenberg spin models with a variety of chain structures, which exhibit unexpected behaviors quite similar to the first and second order phase transition, which could be confused naively with an authentic phase transition. Through the analysis of the first derivative of free energy, such as entropy, magnetization, and internal energy, a "sudden" jump that closely resembles a first-order phase transition at finite temperature occurs. However, by analyzing the second derivative of free energy, such as specific heat and magnetic susceptibility at finite temperature, it behaves quite similarly to a second-order phase transition exhibiting an astonishingly sharp and fine peak. The correlation length also confirms the evidence of this pseudo-transition temperature, where a sharp peak occurs at the pseudo-critical temperature. We also present the necessary conditions for the emergence of these quasi-phases and pseudo-transitions.

  4. Low cost biosorbent "banana peel" for the removal of phenolic compounds from olive mill wastewater: kinetic and equilibrium studies.

    Science.gov (United States)

    Achak, M; Hafidi, A; Ouazzani, N; Sayadi, S; Mandi, L

    2009-07-15

    The aim of this work is to determine the potential of application of banana peel as a biosorbent for removing phenolic compounds from olive mill wastewaters. The effect of adsorbent dosage, pH and contact time were investigated. The results showed that the increase in the banana peel dosage from 10 to 30 g/L significantly increased the phenolic compounds adsorption rates from 60 to 88%. Increase in the pH to above neutrality resulted in the increase in the phenolic compounds adsorption capacity. The adsorption process was fast, and it reached equilibrium in 3-h contact time. The Freundlich and Langmuir adsorption models were used for mathematical description of the adsorption equilibrium and it was found that experimental data fitted very well to both Freundlich and Langmuir models. Batch adsorption models, based on the assumption of the pseudo-first-order, pseudo-second-order and intraparticle diffusion mechanism, showed that kinetic data follow closely the pseudo-second-order than the pseudo-first-order and intraparticle diffusion. Desorption studies showed that low pH value was efficient for desorption of phenolic compounds. These results indicate clearly the efficiency of banana peel as a low-cost solution for olive mill wastewaters treatment and give some preliminary elements for the comprehension of the interactions between banana peel as a bioadsorbent and the very polluting compounds from the olive oil industry.

  5. Kinetic and Thermodynamics of Methylene Blue Adsorption onto Zero Valent Iron Supported on Mesoporous Silica

    Directory of Open Access Journals (Sweden)

    Atyaf Khalid Hameed

    2016-08-01

    Full Text Available Zero valent iron supported on mesoporous silicanano particles (NZVI/MSNs was prepared by the aqueous phase borohydride reduction methods. Prior to the reduction, mesoporous silica nanoparticles (MSNs were prepared through the activation of fumed silica with concentrated HCl by refluxing at 90 °C. FTIR, XRD, FESEM, EDX and BET were used to characterize theadsorbents prepared. BET surface areas of MSNs, NZVI, and NZVI/MSNs were 126, 41, and 72 m2/g for, respectively. The performance of NZVI/MSNs as adsorbent was examined by adsorption of methylene blue (MB, performed in series of batch experiments. In the kinetic studies, pseudo first order and pseudo second order kinetic models were examined. The pseudo second order equation provided the best fit with the experimental data. Thermodynamic studies indicated that the adsorption process is endothermic with ΔH° was 90.53 kJ/mol. Positive ΔS° (300 J/mol and negative ΔG° (-6.42 kJ/mol was recorded, indicating the spontaneous of the adsorption process and naturally favorable. Copyright © 2016 BCREC GROUP. All rights reserved Received: 5th March 2016; Revised: 18th March 2016; Accepted: 18th March 2016 How to Cite: Hameed, A.K., Dewayanto, N., Dongyun, D., Nordin, M.R., Mohd Hasbi Ab. Rahim, M.H.A. (2016. Kinetic and Thermodynamics of Methylene Blue Adsorption onto Zero Valent Iron Supported on Mesoporous Silica. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (2: 250-261 (doi:10.9767/bcrec.11.2.443.250-261 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.2.443.250-261

  6. Pseudo-Newtonian planar circular restricted 3-body problem

    International Nuclear Information System (INIS)

    Dubeibe, F.L.; Lora-Clavijo, F.D.; González, Guillermo A.

    2017-01-01

    We study the dynamics of the planar circular restricted three-body problem in the context of a pseudo-Newtonian approximation. By using the Fodor–Hoenselaers–Perjés procedure, we perform an expansion in the mass potential of a static massive spherical source up to the first non-Newtonian term, giving place to a gravitational potential that includes first-order general relativistic effects. With this result, we model a system composed by two pseudo-Newtonian primaries describing circular orbits around their common center of mass, and a test particle orbiting the system in the equatorial plane. The dynamics of the new system of equations is studied in terms of the Poincaré section method and the Lyapunov exponents, where the introduction of a new parameter ϵ, allows us to observe the transition from the Newtonian to the pseudo-Newtonian regime. We show that when the Jacobian constant is fixed, a chaotic orbit in the Newtonian regime can be either chaotic or regular in the pseudo-Newtonian approach. As a general result, we find that most of the pseudo-Newtonian configurations are less stable than their Newtonian equivalent.

  7. Pseudo-Newtonian planar circular restricted 3-body problem

    Energy Technology Data Exchange (ETDEWEB)

    Dubeibe, F.L., E-mail: fldubeibem@unal.edu.co [Facultad de Ciencias Humanas y de la Educación, Universidad de los Llanos, Villavicencio (Colombia); Grupo de Investigación en Relatividad y Gravitación, Escuela de Física, Universidad Industrial de Santander, A.A. 678, Bucaramanga (Colombia); Lora-Clavijo, F.D., E-mail: fadulora@uis.edu.co [Grupo de Investigación en Relatividad y Gravitación, Escuela de Física, Universidad Industrial de Santander, A.A. 678, Bucaramanga (Colombia); González, Guillermo A., E-mail: guillermo.gonzalez@saber.uis.edu.co [Grupo de Investigación en Relatividad y Gravitación, Escuela de Física, Universidad Industrial de Santander, A.A. 678, Bucaramanga (Colombia)

    2017-02-12

    We study the dynamics of the planar circular restricted three-body problem in the context of a pseudo-Newtonian approximation. By using the Fodor–Hoenselaers–Perjés procedure, we perform an expansion in the mass potential of a static massive spherical source up to the first non-Newtonian term, giving place to a gravitational potential that includes first-order general relativistic effects. With this result, we model a system composed by two pseudo-Newtonian primaries describing circular orbits around their common center of mass, and a test particle orbiting the system in the equatorial plane. The dynamics of the new system of equations is studied in terms of the Poincaré section method and the Lyapunov exponents, where the introduction of a new parameter ϵ, allows us to observe the transition from the Newtonian to the pseudo-Newtonian regime. We show that when the Jacobian constant is fixed, a chaotic orbit in the Newtonian regime can be either chaotic or regular in the pseudo-Newtonian approach. As a general result, we find that most of the pseudo-Newtonian configurations are less stable than their Newtonian equivalent.

  8. Linearized pseudo-Einstein equations on the Heisenberg group

    Science.gov (United States)

    Barletta, Elisabetta; Dragomir, Sorin; Jacobowitz, Howard

    2017-02-01

    We study the pseudo-Einstein equation R11bar = 0 on the Heisenberg group H1 = C × R. We consider first order perturbations θɛ =θ0 + ɛ θ and linearize the pseudo-Einstein equation about θ0 (the canonical Tanaka-Webster flat contact form on H1 thought of as a strictly pseudoconvex CR manifold). If θ =e2uθ0 the linearized pseudo-Einstein equation is Δb u - 4 | Lu|2 = 0 where Δb is the sublaplacian of (H1 ,θ0) and L bar is the Lewy operator. We solve the linearized pseudo-Einstein equation on a bounded domain Ω ⊂H1 by applying subelliptic theory i.e. existence and regularity results for weak subelliptic harmonic maps. We determine a solution u to the linearized pseudo-Einstein equation, possessing Heisenberg spherical symmetry, and such that u(x) → - ∞ as | x | → + ∞.

  9. Analysis of heart rate and oxygen uptake kinetics studied by two different pseudo-random binary sequence work rate amplitudes.

    Science.gov (United States)

    Drescher, U; Koschate, J; Schiffer, T; Schneider, S; Hoffmann, U

    2017-06-01

    The aim of the study was to compare the kinetics responses of heart rate (HR), pulmonary (V˙O 2 pulm) and predicted muscular (V˙O 2 musc) oxygen uptake between two different pseudo-random binary sequence (PRBS) work rate (WR) amplitudes both below anaerobic threshold. Eight healthy individuals performed two PRBS WR protocols implying changes between 30W and 80W and between 30W and 110W. HR and V˙O 2 pulm were measured beat-to-beat and breath-by-breath, respectively. V˙O 2 musc was estimated applying the approach of Hoffmann et al. (Eur J Appl Physiol 113: 1745-1754, 2013) considering a circulatory model for venous return and cross-correlation functions (CCF) for the kinetics analysis. HR and V˙O 2 musc kinetics seem to be independent of WR intensity (p>0.05). V˙O 2 pulm kinetics show prominent differences in the lag of the CCF maximum (39±9s; 31±4s; p<0.05). A mean difference of 14W between the PRBS WR amplitudes impacts venous return significantly, while HR and V˙O 2 musc kinetics remain unchanged. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Kinetic investigation of the immobilization of chromotropic acid derivatives onto anion exchange resin

    Directory of Open Access Journals (Sweden)

    Savić Jasmina

    2007-01-01

    Full Text Available The adsorption kinetics of pyrazol- (РАСА and imidazol-azo-chromo-tropic acid (IACA onto Dowex 1-X8 resin, as a function of the dye concentration and temperature were investigated at pH 4.5. The pseudo-first- and second-order kinetic models and intraparticle diffusion model were used to describe the obtained kinetic data. The adsorption rate constants were found to be in the order of magnitude 10-2 min-1 for all of the used kinetics models. The adsorption capacity increases with increasing initial dye concentration. The study of adsorption kinetics at different temperatures (in the range from 5 to 25 °C reveals an increase in the rate of adsorption and adsorption capacity with increasing temperature. The activation energy (in the case of РАСА 16.6 kJ/mol, and for IACA 11.3 kJ/mol was determined using the Arrhenius dependence. Electrostatic interactions between the dye and resin beads were shown to be the adsorption mechanism.

  11. Efficient removal of cadmium using magnetic multiwalled carbon nanotube nanoadsorbents: equilibrium, kinetic, and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Pashai Gatabi, Maliheh; Milani Moghaddam, Hossain, E-mail: Milani@umz.ac.ir [University of Mazandaran, Soid State Physics Department (Iran, Islamic Republic of); Ghorbani, Mohsen [Babol Noshirvani University of Technology, Chemical Engineering Department (Iran, Islamic Republic of)

    2016-07-15

    Adsorptive potential of maghemite decorated multiwalled carbon nanotubes (MWCNTs) for the removal of cadmium ions from aqueous solution was investigated. The magnetic nanoadsorbent was synthesized using a versatile and cost effective chemical route. Structural, magnetic and surface charge properties of the adsorbent were characterized using FTIR, XRD, TEM, VSM analysis and pH{sub PZC} determination. Batch adsorption experiments were performed under varied system parameters such as pH, contact time, initial cadmium concentration and temperature. Highest cadmium adsorption was obtained at pH 8.0 and contact time of 30 min. Adsorption behavior was kinetically studied using pseudo first-order, pseudo second-order, and Weber–Morris intra particle diffusion models among which data were mostly correlated to pseudo second-order model. Adsorbate-adsorbent interactions as a function of temperature was assessed by Langmuir, Freundlich, Dubinin–Radushkevich (D-R) and Temkin isotherm models from which Freundlich model had the highest consistency with the data. The adsorption capacity increased with increasing temperature and maximum Langmuir’s adsorption capacity was found to be 78.81 mg g{sup −1} at 298 K. Thermodynamic parameters and activation energy value suggest that the process of cadmium removal was spontaneous and physical in nature, which lead to fast kinetics and high regeneration capability of the nanoadsorbent. Results of this work are of great significance for environmental applications of magnetic MWCNTs as promising adsorbent for heavy metals removal from aqueous solutions.Graphical Abstract.

  12. Theory of First Order Chemical Kinetics at the Critical Point of Solution.

    Science.gov (United States)

    Baird, James K; Lang, Joshua R

    2017-10-26

    Liquid mixtures, which have a phase diagram exhibiting a miscibility gap ending in a critical point of solution, have been used as solvents for chemical reactions. The reaction rate in the forward direction has often been observed to slow down as a function of temperature in the critical region. Theories based upon the Gibbs free energy of reaction as the driving force for chemical change have been invoked to explain this behavior. With the assumption that the reaction is proceeding under relaxation conditions, these theories expand the free energy in a Taylor series about the position of equilibrium. Since the free energy is zero at equilibrium, the leading term in the Taylor series is proportional to the first derivative of the free energy with respect to the extent of reaction. To analyze the critical behavior of this derivative, the theories exploit the principle of critical point isomorphism, which is thought to govern all critical phenomena. They find that the derivative goes to zero in the critical region, which accounts for the slowing down observed in the reaction rate. As has been pointed out, however, most experimental rate investigations have been carried out under irreversible conditions as opposed to relaxation conditions [Shen et al. J. Phys. Chem. A 2015, 119, 8784-8791]. Below, we consider a reaction governed by first order kinetics and invoke transition state theory to take into account the irreversible conditions. We express the apparent activation energy in terms of thermodynamic derivatives evaluated under standard conditions as well as the pseudoequilibrium conditions associated with the reactant and the activated complex. We show that these derivatives approach infinity in the critical region. The apparent activation energy follows this behavior, and its divergence accounts for the slowing down of the reaction rate.

  13. Kinetically Inhibited Order in a Diamond-Lattice Antiferromagnet

    International Nuclear Information System (INIS)

    MacDougall, Gregory J.; Gout, Delphine J.; Zarestky, Jerel L.; Ehlers, Georg; Podlesnyak, Andrey A.; McGuire, Michael A.; Mandrus, David; Nagler, Stephen E.

    2011-01-01

    Frustrated magnetic systems exhibit highly degenerate ground states and strong fluctuations, often leading to new physics. An intriguing example of current interest is the antiferromagnet on a diamond lattice, realized physically in the A-site spinel materials. This is a prototypical system in three dimensions where frustration arises from competing interactions rather than purely geometric constraints, and theory suggests the possibility of novel order at low temperature. Here we present a comprehensive single crystal neutron scattering study CoAl2O4, a highly frustrated A-site spinel. We observe strong diffuse scattering that peaks at wavevectors associated with Neel ordering. Below the temperature T*=6.5K, there is a dramatic change in elastic scattering lineshape accompanied by the emergence of well-defined spin-wave excitations. T* had previously been associated with the onset of glassy behavior. Our new results suggest instead that in fact T* signifies a first-order phase transition, but with true long-range order inhibited by the kinetic freezing of domain walls. This scenario might be expected to occur widely in frustrated systems containing first-order phase transitions and is a natural explanation for existing reports of anomalous glassy behavior in other materials.

  14. Application of finite difference method in the study of diffusion with chemical kinetics of first order

    Directory of Open Access Journals (Sweden)

    Beltrán-Prieto Juan Carlos

    2016-01-01

    Full Text Available The mathematical modelling of diffusion of a bleaching agent into a porous material is studied in the present paper. Law of mass conservation was applied to analize the mass transfer of a reactant from the bulk into the external surface of a solid geometrically described as a flat plate. After diffusion of the reactant, surface reaction following kinetics of first order was considered to take place. The solution of the differential equation that described the process leaded to an equation that represents the concentration profile in function of distance, porosity and Thiele modulus. The case of interfacial mass resistance is also discused. In this case, finite difference method was used for the solution of the differential equation taking into account the respective boundary conditions. The profile of concentration can be obtained after numerical especification of Thiele modulus and Biot number.

  15. Effect of cations in the background electrolyte on the adsorption kinetics of copper and cadmium and the isoelectric point of imogolite

    Energy Technology Data Exchange (ETDEWEB)

    Arancibia-Miranda, Nicolás, E-mail: nicolas.arancibia@usach.cl [Center for the Development of Nanoscience and Nanotechnology, CEDENNA, 9170124, Santiago (Chile); Facultad de Química y Biología, Universidad de Santiago de Chile, Av. B. O' Higgins, 3363, Santiago (Chile); Silva-Yumi, Jorge [Center for the Development of Nanoscience and Nanotechnology, CEDENNA, 9170124, Santiago (Chile); Escudey, Mauricio [Center for the Development of Nanoscience and Nanotechnology, CEDENNA, 9170124, Santiago (Chile); Facultad de Química y Biología, Universidad de Santiago de Chile, Av. B. O' Higgins, 3363, Santiago (Chile)

    2015-12-15

    Highlights: • Effect of various cations on the IEP of imogolite was studied. • Studied adsorption kinetics of Cd and Cu on imogolite in the presence of cations. • K{sup +} acted as an indifferent electrolyte and did not affect the IEP of imogolite. • Adsorption in the presence of K{sup +} is described well by three of the four models. • These include pseudo-second order, Elovich equation, and Weber–Morris model. - Abstract: Modification of surface charge and changes in the isoelectric point (IEP) of synthetic imogolite were studied for various cations in the background electrolyte (K{sup +}, NH{sub 4}{sup +}, Mg{sup 2+}, and Ca{sup 2+}). From the electrophoretic mobility data, it was established that the K{sup +} (KCl) concentration does not affect the IEP of imogolite; therefore, KCl is a suitable background electrolyte. In terms of the magnitude of changes in the IEP and surface charge, the cations may be ranked in the following order: Mg{sup 2+} ≈ Ca{sup 2+} >> NH{sub 4}{sup +} >> K{sup +}. Four different kinetic models were used to evaluate the influence of Mg{sup 2+}, Ca{sup 2+}, NH{sub 4}{sup +}, and K{sup +} on the adsorption of Cd and Cu on synthetic imogolite. When adsorption occurs in the presence of cations with the exception of K{sup +}, the kinetics of the process is well described by the pseudo-first order model. On the other hand, when adsorption is conducted in the presence of K{sup +}, the adsorption kinetics is well described by the pseudo-second order, Elovich, and Weber–Morris models. From the surface charge measurements, the affinity between imogolite and the cations and their effect on the adsorption of trace elements, namely Cu and Cd, were established.

  16. Heterogeneous kinetics of the reduction of chromium (VI) by elemental iron

    International Nuclear Information System (INIS)

    Fiuza, Antonio; Silva, Aurora; Carvalho, Goreti; Fuente, Antonio V. de la; Delerue-Matos, Cristina

    2010-01-01

    Zero valent iron (ZVI) has been extensively used as a reactive medium for the reduction of Cr(VI) to Cr(III) in reactive permeable barriers. The kinetic rate depends strongly on the superficial oxidation of the iron particles used and the preliminary washing of ZVI increases the rate. The reaction has been primarily modelled using a pseudo-first-order kinetics which is inappropriate for a heterogeneous reaction. We assumed a shrinking particle type model where the kinetic rate is proportional to the available iron surface area, to the initial volume of solution and to the chromium concentration raised to a power α which is the order of the chemical reaction occurring at surface. We assumed α = 2/3 based on the likeness to the shrinking particle models with spherical symmetry. Kinetics studies were performed in order to evaluate the suitability of this approach. The influence of the following parameters was experimentally studied: initial available surface area, chromium concentration, temperature and pH. The assumed order for the reaction was confirmed. In addition, the rate constant was calculated from data obtained in different operating conditions. Digital pictures of iron balls were periodically taken and the image treatment allowed for establishing the time evolution of their size distribution.

  17. Equilibrium, kinetic and thermodynamic studies for adsorption of BTEX onto Ordered Mesoporous Carbon (OMC).

    Science.gov (United States)

    Konggidinata, Mas Iwan; Chao, Bing; Lian, Qiyu; Subramaniam, Ramalingam; Zappi, Mark; Gang, Daniel Dianchen

    2017-08-15

    Chemical and petrochemical industries produce substantial amounts of wastewater everyday. This wastewater contains organic pollutants such as benzene, toluene, ethylbenzene and xylenes (BTEX) that are toxic to human and aquatic life. Ordered Mesoporous Carbon (OMC), the adsorbent that possesses the characteristics of an ideal adsorbent was investigated to understand its properties and suitability for BTEX removal. Adsorption isotherms, adsorption kinetics, the effects of initial BTEX concentrations and temperatures on the adsorption process were studied. The OMCs were characterized using surface area and pore size analyzer, transmission electron microscopy (TEM), elemental analysis, thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FTIR). The results suggested that the Langmuir Isotherm and Pseudo-Second-Order Models described the experimental data well. The thermodynamic parameters, Gibbs free energy (ΔG°), the enthalpy change (ΔH°) and the entropy change (ΔS°) of adsorption indicated that the adsorption processes were physical, endothermic, and spontaneous. In addition, OMC had 27% higher overall adsorption capacities compared to granular activated carbon (GAC). Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Thermogravimetric kinetic study of agricultural residue biomass pyrolysis based on combined kinetics.

    Science.gov (United States)

    Wang, Xun; Hu, Mian; Hu, Wanyong; Chen, Zhihua; Liu, Shiming; Hu, Zhiquan; Xiao, Bo

    2016-11-01

    Pyrolytic kinetic of an agricultural residue (AR) feedstock, a mixture of plants (cotton, wheat, rich, corn) stems, was investigated based on combined kinetics. The most suitable mechanism for AR one-step pyrolysis was f(α)=(1-α)(1.1816)α(-1.8428) with kinetic parameters of: apparent activation energy 221.7kJ/mol, pre-exponential factor 4.17E16s(-1). Pyrolysis of AR feedstock could not be described by one-step reaction attributes to heterogeneous features of pyrolysis processes. Combined kinetics three-parallel-reaction (CK-TPR) model fitted the pyrolysis experimental data very well. Reaction mechanisms for pseudo hemicelluloses, cellulose, lignin in CK-TPR model was f(α)=(1-α)(1.6244)α(-0.3371)[-ln(1-α)](-0.0515), f(α)=(1-α)(1.0597)α(-0.6909)[-ln(1-α)](0.9026) and f(α)=(1-α)(2.9577)α(-4.7719), respectively. Apparent activation energy of three pseudo components followed the order of Elignin(197.3kJ/mol)>Ecellulose(176.3kJ/mol)>Ehemicelluloses (151.1kJ/mol). Mechanism of hemicelluloses pyrolysis could be further expressed as f(α)=(1-α)(1.4). The pyrolytic mechanism of cellulose met the Nucleation well. However, mechanism of lignin pyrolysis was complex, which possibly was the combined effects of Nucleation, Diffusion, Geometrical contraction, and Power law. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Kinetics, Thermodynamics and Isotherm studies on Adsorption of Eriochrome Black-T from aqueous solution using Rutile TiO2

    Science.gov (United States)

    Priyadarshini, B.; Rath, P. P.; Behera, S. S.; Panda, S. R.; Sahoo, T. R.; Parhi, P. K.

    2018-02-01

    In this study, rutile phase of TiO2 particles have been synthesized by co-precipitation method and is used as an adsorbent for removal of toxic azo dye Eriochrome black-T (EBT) from aqueous solution. The rutile phase of TiO2 was confirmed by the X-ray powder diffraction pattern. Effect of initial dye concentration, adsorbent dose, pH, agitation speed and temperature on the adsorption process of EBT was examined. Removal of EBT was increased by increasing in adsorbent dose and decrease in initial dye concentration and pH. The optimum conditions resulted were: 25 ppm initial dye concentration, 20 mg adsorbent dose and pH of 2. Using Langmuir, Freundlich and Temkin isotherm models, equilibrium data was determined. The Freundlich model showed the best fit for uptake of the EBT dye, which evident that the process of adsorption of EBT dye onto TiO2 particles was heterogeneous. The kinetic data were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion equation. The pseudo-second order showed the best fit for the kinetic studies (R2 = 0.999), which ascertains that the adsorption process was of chemisorptions type. The intraparticle diffusion model indicated a linear relationship (R2= 0.99) suggesting the pore diffusion to be a limiting step in the overall adsorption process.

  20. Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Prakash Kumar, B.G. [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India); Shivakamy, K. [Centralised Waste Management Facility, Bhabha Atomic Research Centre, Kalpakkam 603 102 (India); Miranda, Lima Rose [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India); Velan, M. [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600 025 (India)]. E-mail: velan@annauniv.edu

    2006-08-25

    Activated carbon was produced from a biowaste product, rubberwood sawdust (RWSD) using steam in a high temperature fluidized bed reactor. Experiments were carried out to investigate the influence of various process parameters such as activation time, activation temperature, particle size and fluidising velocity on the quality of the activated carbon. The activated carbon was characterized based on its iodine number, methylene blue number, Brauner Emmet Teller (BET) surface area and surface area obtained using the ethylene glycol mono ethyl ether (EGME) retention method. The best quality activated carbon was obtained at an activation time and temperature of 1 h and 750 deg. C for an average particle size of 0.46 mm. The adsorption kinetics shows that pseudo-second-order rate fitted the adsorption kinetics better than pseudo-first-order rate equation. The adsorption capacity of carbon produced from RWSD was found to be 1250 mg g{sup -1} for the Bismark Brown dye. The rate constant and diffusion coefficient for intraparticle transport were determined for steam activated carbon. The characteristic of the prepared activated carbon was found comparable to the commercial activated carbon.

  1. Micellar effect on the kinetics of oxidation of methyl blue by Ce(IV in sulfuric acid medium

    Directory of Open Access Journals (Sweden)

    Mohammed Hassan

    2015-01-01

    Full Text Available The kinetics of oxidation of methyl blue (MB by Ce(IV in aqueous and surfactant media has been carried out to explore the micellar effect on the rate and kinetic parameters of the reaction. The reaction was found to be first order with respect to both oxidant and substrate and fractional order with respect to H+. The active kinetic species of the oxidant was found to be Ce(SO4+2 based on the effect of ionic strength and sulfate ion on the rate of the reaction. The presence of micelles was found to inhibit the reaction and this effect has been explained by the association of one of the reactants with the micelles leaving the other reactant in the bulk solution. The binding constant and first order rate constant in micellar medium has been obtained by the application of pseudo-phase model to the experimental data. Interestingly, the temperature dependence of the reaction reveals that the reaction has negative activation energy in the absence of micelles, which turns to a positive value in the presence of micelles.

  2. Equilibrium and kinetic modelling of Cd(II) biosorption by algae Gelidium and agar extraction algal waste.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2006-01-01

    In this study an industrial algal waste from agar extraction has been used as an inexpensive and effective biosorbent for cadmium (II) removal from aqueous solutions. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction. Equilibrium data follow both Langmuir and Redlich-Peterson models. The parameters of Langmuir equilibrium model are q(max)=18.0 mgg(-1), b=0.19 mgl(-1) and q(max)=9.7 mgg(-1), b=0.16 mgl(-1), respectively for Gelidium and the algal waste. Kinetic experiments were conducted at initial Cd(II) concentrations in the range 6-91 mgl(-1). Data were fitted to pseudo-first- and second-order Lagergren models. For an initial Cd(II) concentration of 91 mgl(-1) the parameters of the pseudo-first-order Lagergren model are k(1,ads)=0.17 and 0.87 min(-1); q(eq)=16.3 and 8.7 mgg(-1), respectively, for Gelidium and algal waste. Kinetic constants vary with the initial metal concentration. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model. The model successfully predicts Cd(II) concentration profiles and provides significant insights on the biosorbents performance. The homogeneous diffusivity, D(h), is in the range 0.5-2.2 x10(-8) and 2.1-10.4 x10(-8)cm(2)s(-1), respectively, for Gelidium and algal waste.

  3. Invasion-wave-induced first-order phase transition in systems of active particles.

    Science.gov (United States)

    Ihle, Thomas

    2013-10-01

    An instability near the transition to collective motion of self-propelled particles is studied numerically by Enskog-like kinetic theory. While hydrodynamics breaks down, the kinetic approach leads to steep solitonlike waves. These supersonic waves show hysteresis and lead to an abrupt jump of the global order parameter if the noise level is changed. Thus they provide a mean-field mechanism to change the second-order character of the phase transition to first order. The shape of the wave is shown to follow a scaling law and to quantitatively agree with agent-based simulations.

  4. Analysis of dechlorination kinetics of chlorinated aliphatic hydrocarbons by Fe(II) in cement slurries

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Bahngmi [Department of Earth and Environmental Sciences, Wright State University, Dayton, OH 45435-0001 (United States)], E-mail: jung.bahngmi@gmail.com; Batchelor, Bill [Department of Civil Engineering, Texas A and M University, College Station, TX 77843-3136 (United States)

    2008-03-21

    Degradative solidification/stabilization with ferrous iron (DS/S-Fe(II)) has been found to be effective in degrading a number of chlorinated aliphatic hydrocarbons including 1,1,1-trichloroethane (1,1,1-TCA), 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA), tetrachloroethylene (PCE), trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), vinyl chloride (VC), carbon tetrachloride (CT) and chloroform (CF). Previous studies have characterized degradation kinetics in DS/S-Fe(II) systems as affected by Fe(II) dose, pH and initial target organic concentration. The goal of this study is to investigate the importance of various chemical properties on degradation kinetics of DS/S-Fe(II). This was accomplished by first measuring rate constants for degradation of 1,1,1-TCA, 1,1,2,2-TeCA and 1,2-dichloroethane (1,2-DCA) in individual batch experiments. Rate constants developed in these experiments and those obtained from the literature were related to thermodynamic parameters including one-electron reduction potential, two-electron reduction potential, bond dissociation energy and lowest unoccupied molecular orbital energies. Degradation kinetics by Fe(II) in cement slurries were generally represented by a pseudo-first-order rate law. The results showed that the rate constants for chlorinated methanes (e.g. CT, CF) and chlorinated ethanes (e.g. 1,1,1-TCA) were higher than those for chlorinated ethylenes (e.g. PCE, TCE, 1,1-DCE and VC) under similar experimental conditions. The log of the pseudo-first-order rate constant (k) was found to correlate better with lowest unoccupied molecular orbital energies (E{sub LUMO}) (R{sup 2} = 0.874) than with other thermodynamic parameter descriptors.

  5. Application potential of grapefruit peel as dye sorbent: Kinetics, equilibrium and mechanism of crystal violet adsorption

    International Nuclear Information System (INIS)

    Saeed, Asma; Sharif, Mehwish; Iqbal, Muhammad

    2010-01-01

    This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation ≥0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g -1 . The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions.

  6. Application potential of grapefruit peel as dye sorbent: kinetics, equilibrium and mechanism of crystal violet adsorption.

    Science.gov (United States)

    Saeed, Asma; Sharif, Mehwish; Iqbal, Muhammad

    2010-07-15

    This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation > or = 0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g(-1). The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions. 2010 Elsevier B.V. All rights reserved.

  7. Application potential of grapefruit peel as dye sorbent: Kinetics, equilibrium and mechanism of crystal violet adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Saeed, Asma, E-mail: asmadr@wol.net.pk [Environmental Biotechnology Group, Biotechnology and Food Research Centre, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan); Sharif, Mehwish [School of Biological Sciences, University of the Punjab, Lahore 54590 (Pakistan); Iqbal, Muhammad [Environmental Biotechnology Group, Biotechnology and Food Research Centre, PCSIR Laboratories Complex, Ferozepur Road, Lahore 54600 (Pakistan)

    2010-07-15

    This study reports the sorption of crystal violet (CV) dye by grapefruit peel (GFP), which has application potential in the remediation of dye-contaminated wastewaters using a solid waste generated by the citrus fruit juice industry. Batch adsorption of CV was conducted to evaluate the effect of initial pH, contact time, temperature, initial dye concentration, GFP adsorbent dose, and removal of the adsorbate CV dye from aqueous solution to understand the mechanism of sorption involved. Sorption equilibrium reached rapidly with 96% CV removal in 60 min. Fit of the sorption experimental data was tested on the pseudo-first and pseudo-second-order kinetics mathematical equations, which was noted to follow the pseudo-second-order kinetics better, with coefficient of correlation {>=}0.992. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacity of 254.16 mg g{sup -1}. The GFP was regenerated using 1 M NaOH, with up to 98.25% recovery of CV and could be reused as a dye sorbent in repeated cycles. GFP was also shown to be highly effective in removing CV from aqueous solution in continuous-flow fixed-bed column reactors. The study shows that GFP has the potential of application as an efficient sorbent for the removal of CV from aqueous solutions.

  8. Semi-local machine-learned kinetic energy density functional with third-order gradients of electron density

    Science.gov (United States)

    Seino, Junji; Kageyama, Ryo; Fujinami, Mikito; Ikabata, Yasuhiro; Nakai, Hiromi

    2018-06-01

    A semi-local kinetic energy density functional (KEDF) was constructed based on machine learning (ML). The present scheme adopts electron densities and their gradients up to third-order as the explanatory variables for ML and the Kohn-Sham (KS) kinetic energy density as the response variable in atoms and molecules. Numerical assessments of the present scheme were performed in atomic and molecular systems, including first- and second-period elements. The results of 37 conventional KEDFs with explicit formulae were also compared with those of the ML KEDF with an implicit formula. The inclusion of the higher order gradients reduces the deviation of the total kinetic energies from the KS calculations in a stepwise manner. Furthermore, our scheme with the third-order gradient resulted in the closest kinetic energies to the KS calculations out of the presented functionals.

  9. Semiorders, Intervals Orders and Pseudo Orders Preference Structures in Multiple Criteria Decision Aid Methods

    Directory of Open Access Journals (Sweden)

    Fernández Barberis, Gabriela

    2013-06-01

    Full Text Available During the last decades, an important number of Multicriteria Decision Aid Methods (MCDA has been proposed to help the decision maker to select the best compromise alternative. Meanwhile, the PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations family of outranking method and their applications has attracted much attention from academics and practitioners. In this paper, an extension of these methods is presented, consisting of analyze its functioning under New Preference Structures (NPS. The preference structures taken into account are, namely: semiorders, intervals orders and pseudo orders. These structures outstandingly improve the modelization as they give more flexibility, amplitude and certainty at the preferences formulation, since they tend to abandon the Complete Transitive Comparability Axiom of Preferences in order to substitute it by the Partial Comparability Axiom of Preferences. It must be remarked the introduction of Incomparability relations to the analysis and the consideration of preference structures that accept the Indifference intransitivity. The NPS incorporation is carried out in three phases that the PROMETHEE Methodology takes in: preference structure enrichment, dominance relation enrichment and outranking relation exploitation for decision aid, in order to finally arrive at solving the alternatives ranking problem through the PROMETHEE I or the PROMETHEE II utilization, according to whether a partial ranking or a complete one, is respectively required under the NPS

  10. Algebra of pseudo-differential C*-operators

    International Nuclear Information System (INIS)

    Mohammad, N.

    1987-11-01

    In this paper the algebra of pseudo-differential operators is studied in the framework of C * -algebras. It is proved that every pseudo-differential operator of order m admits an adjoint operator, in this case, which is again a pseudo-differential operator. Consequently, the space of all pseudo-differential operators on a compact manifold is an involutive algebra. 10 refs

  11. Synthesis of hierarchical Ni(OH)(2) and NiO nanosheets and their adsorption kinetics and isotherms to Congo red in water.

    Science.gov (United States)

    Cheng, Bei; Le, Yao; Cai, Weiquan; Yu, Jiaguo

    2011-01-30

    Ni(OH)(2) and NiO nanosheets with hierarchical porous structures were synthesized by a simple chemical precipitation method using nickel chloride as precursors and urea as precipitating agent. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption isotherms. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The pore structure analyses indicate that Ni(OH)(2) and NiO nanosheets are composed of at least three levels of hierarchical porous organization: small mesopores (ca. 3-5 nm), large mesopores (ca. 10-50 nm) and macropores (100-500 nm). The equilibrium adsorption data of CR on the as-prepared samples were analyzed by Langmuir and Freundlich models, suggesting that the Langmuir model provides the better correlation of the experimental data. The adsorption capacities for removal of CR was determined using the Langmuir equation and found to be 82.9, 151.7 and 39.7 mg/g for Ni(OH)(2) nanosheets, NiO nanosheets and NiO nanoparticles, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The as-prepared Ni(OH)(2) and NiO nanosheets are found to be effective adsorbents for the removal of Congo red pollutant from wastewater as a result of their unique hierarchical porous structures and high specific surface areas. Copyright © 2010 Elsevier B.V. All rights reserved.

  12. Synthesis of hierarchical Ni(OH)2 and NiO nanosheets and their adsorption kinetics and isotherms to Congo red in water

    International Nuclear Information System (INIS)

    Cheng Bei; Le Yao; Cai Weiquan; Yu Jiaguo

    2011-01-01

    Ni(OH) 2 and NiO nanosheets with hierarchical porous structures were synthesized by a simple chemical precipitation method using nickel chloride as precursors and urea as precipitating agent. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption isotherms. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The pore structure analyses indicate that Ni(OH) 2 and NiO nanosheets are composed of at least three levels of hierarchical porous organization: small mesopores (ca. 3-5 nm), large mesopores (ca. 10-50 nm) and macropores (100-500 nm). The equilibrium adsorption data of CR on the as-prepared samples were analyzed by Langmuir and Freundlich models, suggesting that the Langmuir model provides the better correlation of the experimental data. The adsorption capacities for removal of CR was determined using the Langmuir equation and found to be 82.9, 151.7 and 39.7 mg/g for Ni(OH) 2 nanosheets, NiO nanosheets and NiO nanoparticles, respectively. Adsorption data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that pseudo-second-order kinetic equation and intra-particle diffusion model can better describe the adsorption kinetics. The as-prepared Ni(OH) 2 and NiO nanosheets are found to be effective adsorbents for the removal of Congo red pollutant from wastewater as a result of their unique hierarchical porous structures and high specific surface areas.

  13. Kinetic characteristics of Cu (II) adsorption on nano(poly)-cumulene

    Science.gov (United States)

    Babkin, Alexander; Neskoromnaya, Elena; Burakova, Irina; Kucherova, Ananstasia; Burakov, Alexander; Mkrtchyan, Elina

    2017-11-01

    The present paper considers the possibility of using a new type of nanocarbon materials for sorption - polycumulene modified with "Taunit-M" carbon nanotubes or graphene nanoplatelets. To evaluate the efficiency of these novel nanomodified materials as sorbents, the following studies were carried out: 1) determination of the optimum pH value to perform static batch sorption experiments, 2) identification of the onset of equilibrium for the adsorption of heavy metal ions (on the example of Cu(II) ions), and 3) elucidation of kinetic adsorption mechanisms. As a result of implementation of kinetic models such as external and internal diffusion, as well as pseudo-first- and pseudo-second-order and Elovich (to determine the contribution of chemisorption), rate constants for the Cu(II) adsorption were estimated. It was noted that the absorption process occurs in a mixed-diffusion mode with the influence of the limiting factor - "sorbate-sorbate" chemical interaction. The equilibrium time was found to be 45 min at the sorption capacity values of about 30.71 mg g-1 (in the case of the material containing carbon nanotubes) and about 24.7 mg g-1 (in the case of the material containing graphene nanoplatelets).

  14. Adsorption Equilibrium and Kinetics of Gardenia Blue on TiO2 Photoelectrode for Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Tae-Young Kim

    2014-01-01

    Full Text Available Nanostructured porous TiO2 paste was deposited on the FTO conductive glass using squeeze printing technique in order to obtain a TiO2 thin film with a thickness of 10 μm and an area of 4 cm2. Gardenia blue (GB extracted from Gardenia jasminode Ellis was employed as the natural dye for a dye-sensitized solar cell (DSSC. Adsorption studies indicated that the maximum adsorption capacity of GB on the surface of TiO2 thin film was approximately 417 mg GB/g TiO2 photoelectrode. The commercial and natural dyes, N-719 and GB, respectively, were employed to measure the adsorption kinetic data, which were analyzed by pseudo-first-order and pseudo-second-order models. The energy conversion efficiency of the TiO2 electrode with successive adsorptions of GB dye was about 0.2%.

  15. Equilibrium and kinetics study on hexavalent chromium adsorption onto diethylene triamine grafted glycidyl methacrylate based copolymers

    International Nuclear Information System (INIS)

    Maksin, Danijela D.; Nastasović, Aleksandra B.; Milutinović-Nikolić, Aleksandra D.; Suručić, Ljiljana T.; Sandić, Zvjezdana P.; Hercigonja, Radmila V.; Onjia, Antonije E.

    2012-01-01

    Highlights: ► Methacrylate based copolymers grafted with diethylene triamine as Cr(VI) sorbents. ► Chemisorption and pore diffusion are characteristics of this sorption system. ► Langmuir isotherm provided best fit and maximum adsorption capacity was 143 mg g −1 . ► Cr(VI) sorption onto amino-functionalized copolymer was endothermic and spontaneous. ► A simple, efficient and cost-effective hexavalent chromium removal method. - Abstract: Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25–70 °C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q max , at pH 1.8 and 25 °C was 143 mg g −1 for PGME2-deta (sample with the highest amino group concentration) while at 70 °C Q max reached the high value of 198 mg g −1 . Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta.

  16. Kinetics and equilibrium study for the adsorption of textile dyes on coconut shell activated carbon

    Directory of Open Access Journals (Sweden)

    Aseel M. Aljeboree

    2017-05-01

    Full Text Available The preparation of activated carbon from coconut husk with H2SO4 activation (CSAC and its ability to remove textile dyes (maxilon blue GRL, and direct yellow DY 12, from aqueous solutions were reported in this study. The adsorbent was characterized with Fourier transform infrared spectrophotometer (FT-IR, and scanning electron microscope (SEM. Various physiochemical parameters such as, contact time, initial dye concentration, adsorbent dosage, particle size, pH of dye solution and temperature were investigated in a batch-adsorption technique. Result showed that the adsorption of both GRL and DY 12 dyes was favorable at acidic pH. The adsorption uptake was found to increase with increase in initial dye concentration, and contact time but decreases with the amount of adsorbent, particle size, and temperature of the system. The chemisorption, intra-particle diffuse, pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second order exhibited the best fit for the kinetic studies, which indicates that adsorption of (GRL, and DY 12 is limited by chemisorption process. The equilibrium data were evaluated using Langmuir, Freundlich, Temkin and Fritz–Schlunder isotherms. The Fritz–Schlunder model best describes the uptake of (GRL and DY 12 dye, which implies that the adsorption of textiles dyes in this study onto coconut husk activated carbon is heterogeneous with multi-layers. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined. It was found that (GRL and DY 12 dye adsorption was spontaneous and endothermic.

  17. Fruit waste adsorbent for ammonia nitrogen removal from synthetic solution: Isotherms and kinetics

    Science.gov (United States)

    Zahrim, AY; Lija, Y.; Ricky, L. N. S.; Azreen, I.

    2016-06-01

    In this study, four types of watermelon rind (WR) adsorbents; fresh WR, modified WR with sodium hydroxide (NaOH), potassium hydroxide (KOH) and sulphuric acid (H2SO4) were used as a potential low-cost adsorbent to remove NH3-N from solution. The adsorption data were fitted with the adsorption isotherm and kinetic models to predict the mechanisms and kinetic characteristics of the adsorption process. The equilibrium data agreed well with Langmuir isotherm model with highest correlation (R2=1.00). As for kinetic modelling, the adsorption process follows pseudo-second order for all four types of adsorbents which has R2 value of 1.0 and calculated adsorption capacity, Qe of 1.2148mg/g. The calculated Qe for pseudo-second order has the smallest difference with the experimental Qe and thus suggest that this adsorption process is mainly governed by chemical process involving cations sharing or exchange between WR adsorbent and NH3-N in the solution.

  18. Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres

    International Nuclear Information System (INIS)

    Zhou Limin; Wang Yiping; Liu Zhirong; Huang Qunwu

    2009-01-01

    Magnetic chitosan microspheres were prepared and chemically modified with thiourea (TMCS) for adsorption of metal ions. TMCS obtained were investigated by means of X-ray diffraction (XRD), IR, magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of TMCS toward Hg 2+ , Cu 2+ , and Ni 2+ ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order, pseudo-second-order, and the intra-particle diffusion models. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 625.2, 66.7, and 15.3 mg/g for Hg 2+ , Cu 2+ , and Ni 2+ ions, respectively. TMCS displayed higher adsorption capacity for Hg 2+ in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded TMCS with were regenerated with an efficiency of greater than 88% using 0.01-0.1 M ethylendiamine tetraacetic acid (EDTA)

  19. The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

    Science.gov (United States)

    Basuki, Rahmat; Santosa, Sri Juari; Rusdiarso, Bambang

    2017-03-01

    Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g-1, equilibrium constant (K) was 5.651 (mol/L)-1, and multilayer sorption capacity was 2.646 × 10-2 mol g-1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. Adsorption rate constant (ka) from this novel expression was 43.178 min-1 (mol/L)-1 and desorption rate constant (kd) was 1.250 × 10-2 min-1. Application of the kinetics model on sorption Cd(II) onto HD-HA showed the nearly all of models gave a good linearity. However, only this proposed kinetics expression has good relation with Langmuir model. The novel kinetics expression proposed in this paper seems to be more realistic and reasonable and close to the experimental real condition because the value of ka/kd (3452 (mol/L)-1) was fairly close with K from Langmuir isotherm model (5651 (mol/L)-1). Comparison of this novel kinetics expression with well-known Lagergren pseudo-first order kinetics and Ho pseudo-second order kinetics was also critically discussed in this paper.

  20. an improved solution of first order kinetics for biochemical oxygen ...

    African Journals Online (AJOL)

    DELL

    Accuracies of these methods were evaluated using relative error, Akaike ... Keywords: Wastewater, Environmental Engineering, Biochemical Oxygen Demand Kinetic Parameters,. Statistical ... evaluating organic pollution level and quality of wastewaters. ... compounds ...... method can be applied on electronic devices, and.

  1. Kinetic Study on the Esterification of Palm Fatty Acid Distillate (PFAD) Using Heterogeneous Catalyst

    Science.gov (United States)

    Rofiqah, U.; Djalal, R. A.; Sutrisno, B.; Hidayat, A.

    2018-05-01

    Esterification with heterogeneous catalysts is believed to have advantages compared to homogeneous catalysts. Palm Fatty Acid Distillate (PFAD) was esterified by ZrO2 -SO4 2-/natural zeolite at temperature variation of 55°C, 60°C, and 65°C to produce biodiesel. Determination of reaction kinetics was done by experiment and modeling. Kinetic study was approached using pseudo-homogeneous model of first order. For experiment, reaction kinetics were 0.0031 s-1, 0.0054 s-1, and 0.00937 s-1 for a temperature of 55 °C, 60 °C and 65 °C, respectively. For modelling, reaction kinetics were 0.0030 s-1, 0.0055 s-1, and 0.0090 s-1 for a temperature of 55°C, 60°C and 65°C, respectively. Rate and conversion of reaction are getting increased by increasing temperature.

  2. Kinetic study of Chromium VI adsorption onto palm kernel shell activated carbon

    Science.gov (United States)

    Mohammad, Masita; Sadeghi Louyeh, Shiva; Yaakob, Zahira

    2018-04-01

    Heavy metal contamination of industrial effluent is one of the significant environmental problems due to their toxicity and its accumulation throughout the food chain. Adsorption is one of the promising methods for removal of heavy metals from aqua solution because of its simple technique, efficient, reliable and low-cost due to the utilization of residue from the agricultural industry. In this study, activated carbon from palm kernel shells has been produced through chemical activation process using zinc chloride as an activating agent and carbonized at 800 °C. Palm kernel shell activated carbon, PAC was assessed for its efficiency to remove Chromium (VI) ions from aqueous solutions through a batch adsorption process. The kinetic mechanisms have been analysed using Lagergren first-order kinetics model, second-order kinetics model and intra-particle diffusion model. The characterizations such as BET surface area, surface morphology, SEM-EDX have been done. The result shows that the activation process by ZnCl2 was successfully improved the porosity and modified the functional group of palm kernel shell. The result shows that the maximum adsorption capacity of Cr is 11.40mg/g at 30ppm initial metal ion concentration and 0.1g/50mL of adsorbent concentration. The adsorption process followed the pseudo second orders kinetic model.

  3. Pb(II) adsorption by a novel activated carbon - alginate composite material. A kinetic and equilibrium study.

    Science.gov (United States)

    Cataldo, Salvatore; Gianguzza, Antonio; Milea, Demetrio; Muratore, Nicola; Pettignano, Alberto

    2016-11-01

    The adsorption capacity of an activated carbon - calcium alginate composite material (ACAA-Ca) has been tested with the aim of developing a new and more efficient adsorbent material to remove Pb(II) ion from aqueous solution. The study was carried out at pH=5, in NaCl medium and in the ionic strength range 0.1-0.75molL -1 . Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique was used to check the amount of Pb(II) ion removed during kinetic and equilibrium experiments. Different kinetic (pseudo first order, pseudo second order and Vermuelen) and equilibrium (Langmuir and Freundlich) models were used to fit experimental data, and were statistically compared. Calcium alginate (AA-Ca) improves the adsorption capacity (q m ) of active carbon (AC) in the ACAA-Ca adsorbent material (e.g., q m =15.7 and 10.5mgg -1 at I=0.25molL -1 , for ACAA-Ca and AC, respectively). SEM-EDX and thermogravimetric (TGA) measurements were carried out in order to characterize the composite material. The results of the speciation study on the Pb(II) solution and of the characterization of the ACAA-Ca and of the pristine AA-Ca and AC were evaluated in order to explain the specific contribution of AC and AA-Ca to the adsorption of the metal ion. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Biosorption of uranium by immobilized cells of Rhodotorula glutinis

    International Nuclear Information System (INIS)

    Jing Bai; Zhan Li; Fangli Fan; Xiaolei Wu; Xiaojie Yin; Longlong Tian; Zhi Qin; Junsheng Guo

    2014-01-01

    Biosorption of uranium ions from diluted solution (≤40 mg L -1 ) onto immobilized cells of Rhodotorula glutinis was investigated in a batch system. Equilibrium, kinetic and thermodynamic studies were conducted by considering the effect of initial uranium concentration, contact time and temperature. Non-linear forms of Langmuir, Freundlich and Sips isotherm models were used to fit the equilibrium data, Sips model was designated as the best one. Kinetic data were simulated by non-linear pseudo-first-order, pseudo-second-order and intra-particle diffusion equations. Pseudo-first-order kinetic equation described the experimental data better than pseudo-second-order equation and intra-particle diffusion equation can fit the kinetic data with two independent curves. Thermodynamic parameters, including ∆H 0, ∆G 0 and ∆S 0, were evaluated, the sorption process was determined to be spontaneous and endothermic. Uranium sorption from pure uranium solutions and uranium pit wastewater by immobilized biomass and blank beads, as well as the regeneration results indicated that immobilized R. glutinis can be use to recovery uranium from uranium pit wastewater. (author)

  5. Kinetics of first order phase transformation in metals and alloys. Isothermal evolution in martensite transformation

    International Nuclear Information System (INIS)

    Iwasaki, Hiroshi; Ohshima, Ken-ichi

    2011-01-01

    The 11th lecture about microstructures and fluctuation in solids reports on the martensitic phase transformation of alkali metals and alloys. The martensitic transformation is a diffusionless first order phase transformation. Martensitic transformations are classified into two with respect to kinetics, one is isothermal transformation and the other is athermal transformation. The former transformation depends upon both temperature and time, but the latter solely depends on temperature. The former does not have a definite transformation start temperature but occurs after some finite incubation time during isothermal holding. The isothermal martensitic transformation is changed to the athermal one under high magnetic field, and also the reverse transformation occurs under the application of hydrostatic pressure. The former phenomena were observed in Fe-Ni-Mn alloys, Fe-Ni-Cr alloys and also the reverse transformation in Fe-3.1at%Ni-0.5at%Mn alloys. The athermal transformation was observed in Li and Na metals at 73 and 36 K, respectively. A neutron diffraction study has been performed on single crystals of metallic Na. On cooling the virgin sample, the incubation time to transform from the bcc structure to the low-temperature structure (9R structure) is formed to be more than 2h at 38 K, 2 K higher than the transformation temperature of 36 K. The full width of half maximum of the Bragg reflection suddenly increased, due to some deformation introduced by the nucleation of the low-temperature structure. In relation to the deformation, strong extra-diffuse scattering (Huang scattering) was observed around the Bragg reflection in addition to thermal diffuse scattering. The kinetics of the martensitic transformation in In-Tl alloys has been studied by x-ray and neutron diffraction methods. A characteristic incubation time appeared at fixed temperature above Ms, the normal martensitic transformation start temperature. (author)

  6. Parametric and kinetic study of adsorptive removal of dyes from aqueous solutions using an agriculture waste

    Science.gov (United States)

    Bencheikh, imane; el hajjaji, souad; abourouh, imane; Kitane, Said; Dahchour, Abdelmalek; El M'Rabet, Mohammadine

    2017-04-01

    Wastewater treatment is the subject of several studies through decades. Interest is continuously oriented to provide cheaper and efficient methods of treatment. Several methods of treatment exit including coagulation flocculation, filtration, precipitation, ozonation, ion exchange, reverse osmosis, advanced oxidation process. The use of these methods proved limited because of their high investment and operational cost. Adsorption can be an efficient low-cost process to remove pollutants from wastewater. This method of treatment calls for an solid adsorbent which constitutes the purification tool. Agricultural wastes have been widely exploited in this case .As we know the agricultural wastes are an important source of water pollution once discharged into the aquatic environment (river, sea ...). The valorization of such wastes and their use allows the prevention of this problem with an economic and environment benefits. In this context our study aimed testing the wastewater treatment capacity by adsorption onto holocellulose resulting from the valorization of an agriculture waste. In this study, methylene blue (MB) and methyl orange (MO) are selected as models pollutants for evaluating the holocellulose adsorbent capacity. The kinetics of adsorption is performed using UV-visible spectroscopy. In order to study the effect of the main parameters for the adsorption process and their mutual interaction, a full factorial design (type nk) has been used.23 full factorial design analysis was performed to screen the parameters affecting dye removal efficiency. Using the experimental results, a linear mathematical model representing the influence of the different parameters and their interactions was obtained. The parametric study showed that efficiency of the adsorption system (Dyes/ Holocellulose) is mainly linked to pH variation. The best yields were observed for MB at pH=10 and for MO at pH=2.The kinetic data was analyzed using different models , namely , the pseudo-first

  7. Sea of Majorana fermions from pseudo-scalar superconducting order in three dimensional Dirac materials.

    Science.gov (United States)

    Salehi, Morteza; Jafari, S A

    2017-08-15

    We suggest that spin-singlet pseudo-scalar s-wave superconducting pairing creates a two dimensional sea of Majorana fermions on the surface of three dimensional Dirac superconductors (3DDS). This pseudo-scalar superconducting order parameter Δ 5 , in competition with scalar Dirac mass m, leads to a topological phase transition due to band inversion. We find that a perfect Andreev-Klein reflection is guaranteed by presence of anomalous Andreev reflection along with the conventional one. This effect manifests itself in a resonant peak of the differential conductance. Furthermore, Josephson current of the Δ 5 |m|Δ 5 junction in the presence of anomalous Andreev reflection is fractional with 4π period. Our finding suggests another search area for condensed matter realization of Majorana fermions which are beyond the vortex-core of p-wave superconductors. The required Δ 5 pairing can be extrinsically induced by a conventional s-wave superconductor into a three dimensional Dirac material (3DDM).

  8. An atmospheric pressure flow reactor: Gas phase kinetics and mechanism in tropospheric conditions without wall effects

    Science.gov (United States)

    Koontz, Steven L.; Davis, Dennis D.; Hansen, Merrill

    1988-01-01

    A new type of gas phase flow reactor, designed to permit the study of gas phase reactions near 1 atm of pressure, is described. A general solution to the flow/diffusion/reaction equations describing reactor performance under pseudo-first-order kinetic conditions is presented along with a discussion of critical reactor parameters and reactor limitations. The results of numerical simulations of the reactions of ozone with monomethylhydrazine and hydrazine are discussed, and performance data from a prototype flow reactor are presented.

  9. Size effect on order-disorder transition kinetics of FePt nanoparticles

    International Nuclear Information System (INIS)

    Zhang, Shuaidi; Qi, Weihong; Huang, Baiyun

    2014-01-01

    The kinetics of order-disorder transition of FePt nanoparticles during high temperature annealing is theoretically investigated. A model is developed to address the influence of large surface to volume ratio of nanoparticles on both the thermodynamic and kinetic aspect of the ordering process; specifically, the nucleation and growth of L1 0 ordered domain within disordered nanoparticles. The size- and shape-dependence of transition kinetics are quantitatively addressed by a revised Johnson-Mehl-Avrami equation that included corrections for deviations caused by the domination of surface nucleation in nanoscale systems and the non-negligible size of the ordered nuclei. Calculation results based on the model suggested that smaller nanoparticles are kinetically more active but thermodynamically less transformable. The major obstacle in obtaining completely ordered nanoparticles is the elimination of antiphase boundaries. The results also quantitatively confirmed the existence of a size-limit in ordering, beyond which, inducing order-disorder transitions through annealing is impossible. A good agreement is observed between theory, experiment, and computer simulation results

  10. First-order inflation

    International Nuclear Information System (INIS)

    Kolb, E.W.

    1991-01-01

    In the original proposal, inflation occurred in the process of a strongly first-order phase transition. This model was soon demonstrated to be fatally flawed. Subsequent models for inflation involved phase transitions that were second-order, or perhaps weakly first-order; some even involved no phase transition at all. Recently the possibility of inflation during a strongly first-order phase transition has been reviewed. In this talk I will discuss some models for first-order inflation, and emphasize unique signatures that result if inflation is realized in a first-order transition. Before discussing first-order inflation, I will briefly review some of the history of inflation to demonstrate how first-order inflation differs from other models. (orig.)

  11. Type-I pseudo-first-order phase transition induced electrocaloric effect in lead-free Bi0.5Na0.5TiO3-0.06BaTiO3 ceramics

    Science.gov (United States)

    Li, Feng; Chen, Guorui; Liu, Xing; Zhai, Jiwei; Shen, Bo; Li, Shandong; Li, Peng; Yang, Ke; Zeng, Huarong; Yan, Haixue

    2017-05-01

    In this study, the electrocaloric effect (ECE) of Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-0.06BT) ceramic has been directly measured using a home-made adiabatic calorimeter. The maximum adiabatic temperature change (ΔT) approaches 0.86 K under an electric field of 5 kV/mm at 110 °C, which provides experimental evidence for optimizing the ECE near the type-I pseudo-first-order phase transition (PFOPT). Most importantly, a considerable ΔT value can be maintained over a wide temperature range well above the temperature of the PFOPT under a high electric field. In addition, ΔT is closely related to the structural transition and electric field strength. This work provides a guideline to investigate the high ECE in BNT-based ferroelectric ceramics for applications in cooling technologies.

  12. 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.

  13. First-order inflation

    International Nuclear Information System (INIS)

    Kolb, E.W.; Chicago Univ., IL

    1990-09-01

    In the original proposal, inflation occurred in the process of a strongly first-order phase transition. This model was soon demonstrated to be fatally flawed. Subsequent models for inflation involved phase transitions that were second-order, or perhaps weakly first-order; some even involved no phase transition at all. Recently the possibility of inflation during a strongly first-order phase transition has been revived. In this talk I will discuss some models for first-order inflation, and emphasize unique signatures that result in inflation is realized in a first-order transition. Before discussing first-order inflation, I will briefly review some of the history of inflation to demonstrate how first-order inflation differs from other models. 58 refs., 3 figs

  14. Heterogeneous photocatalysis of real textile wastewater: evaluation of reaction kinetics and characterization.

    Science.gov (United States)

    Sahoo, Chittaranjan; Gupta, Ashok K; Pillai, Indu M Sasidharan

    2012-01-01

    Real textile wastewater collected from the cotton dyeing bath of a fabric dyeing and finishing plant was subjected to heterogeneous photocatalysis using Ag(+) doped TiO(2) under UV irradiation in a batch reactor. The photocatalysts were characterized by FESEM, XRD, EDS, FTIR, DRS and BET analyses. The kinetics of the reaction was also evaluated. Colour removal was more than 88%, 94% and 99%, respectively for undiluted, 2 times diluted and 5 times diluted wastewater with Ag(+) doped TiO(2) (2.5 g/L) after UV irradiation for 360 minutes. The COD removal for undiluted, 2 times diluted and 5 times diluted wastewater was 47%, 70% and 92%, respectively under similar conditions. The reaction followed Langmuir-Hinshelwood pseudo first order kinetic model and the data fitted well to polynomial regression analysis.

  15. Reactions of enolisable ketones with dichloroisocyanuric acid in absence and presence of added chloride ions – a kinetic study

    Directory of Open Access Journals (Sweden)

    Y. L. Kumar

    2015-01-01

    Full Text Available Kinetics of reactions of enolisable ketones (S = acetone/2-butanone with dichloroisocyanuric acid (DCICA were studied in aqueous acetic acid and perchloric acid media in absence and presence of added chloride ions. The reactions were found to be pseudo zero order and pseudo first order on [DCICA] in absence and presence of chloride ions respectively. Both in presence and absence of chloride ions, first order and fractional order in substrate and perchloric acid were observed respectively. An increase in the rate of reaction was observed with an increase in chloride ion concentration as well as acetic acid composition. The results were interpreted in terms of probable mechanisms involving (i rate-determining enol formation from the conjugate acid of the ketone (SH+ in the absence of added chloride ions and (ii rate-determining interaction of SH+ with the most effective molecular chlorine species produced by the hydrolysis of DCICA (rather than a rate-determining interaction of enol with chlorine in the presence of added chloride ions, prior to the rapid steps of product formation. DOI: http://dx.doi.org/10.4314/bcse.v29i1.12

  16. A Signal Decomposition Method for Ultrasonic Guided Wave Generated from Debonding Combining Smoothed Pseudo Wigner-Ville Distribution and Vold–Kalman Filter Order Tracking

    Directory of Open Access Journals (Sweden)

    Junhua Wu

    2017-01-01

    Full Text Available Carbon fibre composites have a promising application future of the vehicle, due to its excellent physical properties. Debonding is a major defect of the material. Analyses of wave packets are critical for identification of the defect on ultrasonic nondestructive evaluation and testing. In order to isolate different components of ultrasonic guided waves (GWs, a signal decomposition algorithm combining Smoothed Pseudo Wigner-Ville distribution and Vold–Kalman filter order tracking is presented. In the algorithm, the time-frequency distribution of GW is first obtained by using Smoothed Pseudo Wigner-Ville distribution. The frequencies of different modes are computed based on summation of the time-frequency coefficients in the frequency direction. On the basis of these frequencies, isolation of different modes is done by Vold–Kalman filter order tracking. The results of the simulation signal and the experimental signal reveal that the presented algorithm succeeds in decomposing the multicomponent signal into monocomponents. Even though components overlap in corresponding Fourier spectrum, they can be isolated by using the presented algorithm. So the frequency resolution of the presented method is promising. Based on this, we can do research about defect identification, calculation of the defect size, and locating the position of the defect.

  17. Monod kinetics rather than a first-order degradation model explains atrazine fate in soil mini-columns: Implications for pesticide fate modelling

    International Nuclear Information System (INIS)

    Cheyns, K.; Mertens, J.; Diels, J.; Smolders, E.; Springael, D.

    2010-01-01

    Pesticide transport models commonly assume first-order pesticide degradation kinetics for describing reactive transport in soil. This assumption was assessed in mini-column studies with associated batch degradation tests. Soil mini-columns were irrigated with atrazine in two intermittent steps of about 30 days separated by 161 days application of artificial rain water. Atrazine concentration in the effluent peaked to that of the influent concentration after initial break-through but sharply decreased while influx was sustained, suggesting a degradation lag phase. The same pattern was displayed in the second step but peak height and percentage of atrazine recovered in the effluent were lower. A Monod model with biomass decay was successfully calibrated to this data. The model was successfully evaluated against batch degradation data and mini-column experiments at lower flow rate. The study suggested that first-order degradation models may underestimate risk of pesticide leaching if the pesticide degradation potential needs amplification during degradation. - Population dynamics of pesticide degrading population should be taken into account when predictions of pesticide fate are made to avoid underestimation of pesticide break-through towards groundwater.

  18. The Oxidation of 2-(2-Methoxyethoxyethanol and 2-(2-Ethoxyethoxyethanol by Ditelluratocuprate(III: A Kinetic and Mechanistic Study

    Directory of Open Access Journals (Sweden)

    Jin-huan Shan

    2013-01-01

    Full Text Available The oxidation of 2-(2-methoxyethoxyethanol (MEE and 2-(2-ethoxyethoxyethanol (EEE by ditelluratocuprate(III (DTC had been studied spectrophotometrically in alkaline medium. The reaction between and showed first-order dependence in DTC and fractional order in MEE and EEE. The rate constant of the pseudo-first-order reaction decreased with an increase of [TeO4  2−], whereas adding [OH−] enhanced the constant. In addition, the reaction had a negative salt effect. The rate of EEE was higher than that of MEE. A suitable assumption involving preequilibriums before the rate-controlling step and a free radical mechanism was proposed, based on the kinetic data. Activation parameters and the rate constant of the rate-determining step were calculated.

  19. Adsorption of Acid Red 18 by Activated Carbon Prepared from Cedar Tree: Kinetic and Equilibrium Study

    Directory of Open Access Journals (Sweden)

    M. R. Samarghandi

    2012-10-01

    Full Text Available Introduction: Textile effluents are one of the main environmental pollution sources and contain toxic compounds which threat the environment. For that reason, the activated carbon prepared from Cedar Tree was used for removal of Acid Red 18 as an Azo Dye. Material and Methods: Activated carbon was prepared by chemical activation and was used in batch system for dye removal. Effect of various experimental parameters such as pH (3 to11, initial dye concentration (50, 75 and 100 mg/L, contact time (1 to 120 min and adsorbent dosage (2 to 10 g/L were investigated. Equilibrium data was fitted onto Langmuir and Freundlich isotherm model. In addition, pseudo first order and pseudo second order models were used to investigate the kinetic of adsorption process. Results: Results shows that dye removal was increase with increase in adsorbent dosage, contact time and initial dye concentration. In addition, higher removal efficiency was observed in low pH (pH=3. At 120 min contact time, pH=3, 6 g/L adsorbent dosage and 100 mg/L of initial dye concentration, more than 95% of dye was removed. Equilibrium data was best fitted onto Freundlich isotherm model. According to Langmuir constant, maximum sorption capacity was observed to be 51/28 mg/L. in addition pseudo second order model best describe the kinetic of adsorption of Acid Red 18 onto present adsorbent. Conclusion: The results of present work well demonstrate that prepare activated carbon from Pine Tree has higher adsorption capacity toward Acid Red 18 Azo dye and can be used for removal of dyes from textile effluents.

  20. Sorption of Th(IV) onto ZnO nanoparticles and diatomite-supported ZnO nanocomposite. Kinetics, mechanism and activation parameters

    Energy Technology Data Exchange (ETDEWEB)

    Yusan, Sabriye; Aslani, Mahmut A.A.; Aytas, Sule [Ege Univ., Izmir (Turkey). Inst. of Nuclear Sciences; Bampaiti, Anastasia; Noli, Fotini [Aristotle University of Thessaloniki (Greece). Dept. of Chemistry; Erenturk, Sema [Istanbul Technical Univ., Ayazaga Campus, Maslak-Istanbul (Turkey). Energy Inst.

    2016-11-01

    In this study, for the first time ZnO nanoparticles and diatomite-supported ZnO nanocomposite have been utilized as adsorbent for the removal of Th(IV) ions from aqueous solutions under different experimental conditions. The Langmuir, Freundlich, Temkin and Dubinin- Radushkevich (D-R) isotherms were used to analyze the equilibrium data. The sorption equilibrium data were fitted well to the Langmuir isotherm with maximum sorption capacities values was found to be 1.105 mmol/g and 0.320 mmol/g for ZnO nanoparticles and diatomite supported ZnO nanocomposite, respectively. Pseudo-first and pseudo-second order equations, Intraparticle diffusion and Bangham's models were considered to evaluate the rate parameters and sorption mechanism. Sorption kinetics were better reproduced by the pseudo-second order model (R{sup 2} > 0.999), with an activation energy (E{sub a}) of +99.74 kJ/mol and +62.95 kJ/mol for ZnO nanoparticles and diatomite-supported ZnO nanocomposite, respectively. In order to specify the type of sorption reaction, thermodynamic parameters were also determined. The evaluated ΔG* and ΔH* indicate the non-spontaneous and endothermic nature of the reactions. The results of this work suggest that both of the used materials are fast and effective adsorbents for removing Th(IV) from aqueous solutions and chemical sorption plays a role in controlling the sorption rate.

  1. 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.

  2. Pseudo LRM waveforms from CryoSat SARin acquisition

    Science.gov (United States)

    Scagliola, Michele; Fornari, Marco; Bouffard, Jerome; Parrinello, Tommaso; Féménias, Pierre

    2016-04-01

    CryoSat was launched on the 8th April 2010 and is the first European ice mission dedicated to the monitoring of precise changes in the thickness of polar ice sheets and floating sea ice. The main payload of CryoSat is a Ku-band pulsewidth limited radar altimeter, called SIRAL (Synthetic interferometric radar altimeter). When commanded in SARIn (synthetic aperture radar interferometry) mode, through coherent along-track processing of the returns received from two antennas, the interferometric phase related to the first arrival of the echo is used to retrieve the angle of arrival of the scattering in the across-track direction. When SIRAL operates in SAR or SARin mode, the obtained waveforms have an along-track resolution and a speckle reduction which is increased with respect to the pulse-limited waveforms. Anyway, in order to analyze the continuity of the geophysical retrieved parameters among different acquisition modes, techniques to transform SARin mode data to pseudo-LRM mode data are welcome. The transformation process is known as SAR reduction and it is worth recalling here that only approximate pseudo-LRM waveforms can be obtained in case of closed burst acquisitions, as SIRAL operates. A SAR reduction processing scheme has been developed to obtain pseudo-LRM waveforms from CryoSat SARin acquisition. As a trade-off between the along-track length on Earth surface contributing to one SARin pseudo-LRM waveform and the noisiness of the waveform itself, it has been chosen a SAR reduction approach based on the averaging of all the SARin echoes received each 20Hz, resulting in one pseudo-LRM waveform for each SARin burst given the SARin burst repetition period. SARin pseudo-LRM waveforms have been produced for CryoSat acquisition both on ice and sea surfaces, aiming at verifying the continuity of the retracked surface height over the ellipsoid between genuine LRM products and pseudo-LRM products. Moreover, the retracked height from the SARin pseudo-LRM has been

  3. Ordering kinetics in quasi-one-dimensional Ising-like systems

    International Nuclear Information System (INIS)

    Mueller, M.; Paul, W.

    1993-01-01

    Results are presented of a Monte Carlo simulation of the kinetics of ordering in the two-dimensional nearest-neighbor Ising model in an L x M geometry with two free boundaries of length M much-gt L. This model can be viewed as representing an adsorbant on a stepped surface with mean terrace width L. The authors follow the ordering kinetics after quenches to temperatures 0.25 ≤T/T c ≤1 starting from a random initial configuration at a coverage of Θ=0.5 in the corresponding lattice gas picture. The systems evolve in time according to a Glauber kinetics with nonconserved order parameter. The equilibrium structure is given by a one-dimensional sequence of ordered domains. The ordering process evolves from a short initial two-dimensional ordering process through a crossover region to a quasi-one-dimensional behavior. The whole process is diffusive (inverse half-width of the structure factor peak 1/Δq parallel ∝ √t), in contrast to a model proposed by Kawasaki et al., where an intermediate logarithmic growth law is expected. All results are completely describable in the picture of an annihilating random walk (ARW) of domain walls. 36 refs., 16 figs

  4. Removal of Pb(II) from aqueous solution by seed powder of Prosopis juliflora DC.

    Science.gov (United States)

    Jayaram, K; Prasad, M N V

    2009-09-30

    Biosorption potential of Prosopis juliflora seed powder (PJSP) for Pb(II) from aqueous solution was investigated. The effects of pH, contact time and different metal concentrations were studied in batch experiments. The maximum uptake of metal ions was obtained at pH 6.0. Adsorption equilibrium was established at 360 min. The pseudo-first-order and pseudo-second-order kinetic models were applied to study the kinetics of the biosorption processes. The pseudo-second-order kinetic model provided the best correlation (R(2)=0.9992) of the experimental data compared to the pseudo-first-order kinetic model. The maximum Pb(II) adsorbed was found to be 40.322 mg/g and it was found that the biosorption of Pb(II) on PJSP has correlated well (R(2)=0.9719) with the Langmuir equation compared to Freundlich isotherm equation (R(2)=0.9282) in the concentration range studied. Negative values of DeltaG indicated that the adsorption process was spontaneous and exothermic in nature. The FTIR study revealed the presence of various functional groups which are responsible for the adsorption process. The overall results show that PJSP can be envisaged as a vibrant, biosorbent for metal cleanup operations.

  5. Correlation functions in first-order phase transitions

    Science.gov (United States)

    Garrido, V.; Crespo, D.

    1997-09-01

    Most of the physical properties of systems underlying first-order phase transitions can be obtained from the spatial correlation functions. In this paper, we obtain expressions that allow us to calculate all the correlation functions from the droplet size distribution. Nucleation and growth kinetics is considered, and exact solutions are obtained for the case of isotropic growth by using self-similarity properties. The calculation is performed by using the particle size distribution obtained by a recently developed model (populational Kolmogorov-Johnson-Mehl-Avrami model). Since this model is less restrictive than that used in previously existing theories, the result is that the correlation functions can be obtained for any dependence of the kinetic parameters. The validity of the method is tested by comparison with the exact correlation functions, which had been obtained in the available cases by the time-cone method. Finally, the correlation functions corresponding to the microstructure developed in partitioning transformations are obtained.

  6. Competition kinetics - Considerations for their use with mammalian cells

    International Nuclear Information System (INIS)

    Koch, C.J.

    1987-01-01

    The mechanism of radiation protection and sensitization is thought to be based on the reaction of (DNA) target radicals with oxidizing agents, leading to damage fixation, versus reducing agents, leading to damage repair. If these reactions occur in parallel, and are pseudo-first-order, then it is very easy to develop a kinetic model which predicts a direct correspondence between the reaction rate constants and the amount of reactant (i.e. target radicals) changed along each pathway. This talk focuses on the results of direct tests of this model and concentrates on the possible reasons for its failure under several circumstances. The talk concludes with a discussion of precautions necessary for further development of the modelling process

  7. Equilibrium, kinetic and thermodynamic studies of uranium biosorption by calcium alginate beads

    International Nuclear Information System (INIS)

    Bai, Jing; Fan, Fangli; Wu, Xiaolei; Tian, Wei; Zhao, Liang; Yin, Xiaojie; Fan, Fuyou; Li, Zhan; Tian, Longlong; Wang, Yang; Qin, Zhi; Guo, Junsheng

    2013-01-01

    Calcium alginate beads are potential biosorbent for radionuclides removal as they contain carboxyl groups. However, until now limited information is available concerning the uptake behavior of uranium by this polymer gel, especially when sorption equilibrium, kinetics and thermodynamics are concerned. In present work, batch experiments were carried out to study the equilibrium, kinetics and thermodynamics of uranium sorption by calcium alginate beads. The effects of initial solution pH, sorbent amount, initial uranium concentration and temperature on uranium sorption were also investigated. The determined optimal conditions were: initial solution pH of 3.0, added sorbent amount of 40 mg, and uranium sorption capacity increased with increasing initial uranium concentration and temperature. Equilibrium data obtained under different temperatures were fitted better with Langmuir model than Freundlich model, uranium sorption was dominated by a monolayer way. The kinetic data can be well depicted by the pseudo-second-order kinetic model. The activation energy derived from Arrhenius equation was 30.0 kJ/mol and the sorption process had a chemical nature. Thermodynamic constants such as ΔH 0 , ΔS 0 and ΔG 0 were also evaluated, results of thermodynamic study showed that the sorption process was endothermic and spontaneous. -- Highlights: • Equilibrium, kinetics and thermodynamics of uranium sorption by CaAlg were studied. • Equilibrium studies show that Langmuir isotherm better fit with experimental data. • Pseudo-second-order kinetics model is found to be well depicting the kinetic data. • Thermodynamic study shows that the sorption process is endothermic and spontaneous

  8. Kinetic studies of uranyl ion adsorption on acrylonitrile (AN)/polyethylene glycol (PEG) interpenetrating networks (IPN)

    International Nuclear Information System (INIS)

    Aycik, G.A.; Gurellier, R.

    2004-01-01

    Full text: The kinetics of the adsorption of uranyl ions on amidoximated acrylonitrile (AN)/ polyethylene glycol (PEG) interpenetrating network (IPNs) from aqueous solutions was studied as a function of time and temperature. The IPNs were prepared by irradiation initiated gamma polymerisation using Co-60 gamma source. Adsorption capacities were performed for definite uranyl ion concentrations of 1x10 -2 M and at four different temperatures as 290K, 298K, 308K and 318K by gamma spectrometer. Adsorption time was increased from zero to 48 hours. The results indicate that adsorption capacity increases linearly with increasing temperature. Temperature and agitation hardly influence equilibrium and kinetics and decreasing of temperature results in a slightly greater time to reach equilibrium. The adsorption of uranyl ions has been studied in a multi step mechanism processes thus comparing chemical sorption and diffusion sorption processes. The experimental data was analysed using various kinetic models to determine the best-fit equation for the adsorption mechanisms. However, it was shown that all models, in general according to the reaction time and uranyl ion concentration in the solution, could describe the adsorption of uranyl ion onto amidoximated IPN, the adsorption kinetics was best described by zeroth order and intraparticle diffusion model whereas that of in increasing time by pseudo first and pseudo second order response respectively. External-intraparticle diffusion and zeroth order process in the IPN structure is proposed as a mass transfer mechanism and the results indicate a diffusion-controlled process. The Mean Activation Energy Of Uranyl Ions Adsorption Was Found As 4,1 Kj/Mole By Using Arrhenius Equation. The Rate Constant, The Equilibrium Adsorption Capacity And The Initial Adsorption Rate Were Calculated For All Models At Each Temperature. Kinetic Parameters Of All Models And The Normalized Standard Deviations Between The Measured And Predicted

  9. KINETIC AND EQUILIBRIUM STUDIES OF Pb(II) AND Cd(II ...

    African Journals Online (AJOL)

    and DRK isotherms and the experimental data were found to fit best the Langmuir .... The approximate surface area of the adsorbents was determined using the Sears' method [9]. ... if sorption had occurred by physical or chemical processes. ... Lagergren pseudo-first order equation, pseudo-second order equation, Elovich ...

  10. Kinetic study of olive oil degradation monitored by fourier transform infrared spectrometry. Application to oil characterization.

    Science.gov (United States)

    Román Falcó, Iván P; Grané Teruel, Nuria; Prats Moya, Soledad; Martín Carratalá, M Luisa

    2012-11-28

    A new approach for the determination of kinetic parameters of the cis/trans isomerization during the oxidation process of 24 virgin olive oils belonging to 8 different varieties is presented. The accelerated process of degradation at 100 °C was monitored by recording the Fourier transform infrared spectra. The parameters obtained confirm pseudo-first-order kinetics for the degradation of cis and the appearance of trans double bonds. The kinetic approach affords the induction time and the rate coefficient; these parameters are related to the fatty acid profile of the fresh olive oils. The data obtained were used to compare the oil stability of the samples with the help of multivariate statistical techniques. Fatty acid allowed a classification of the samples in five groups, one of them constituted by the cultivars with higher stability. Meanwhile, the kinetic parameters showed greater ability for the characterization of olive oils, allowing the classification in seven groups.

  11. Removal of Hexavalent Chromium from Aqueous Solution by Modified Holly Sawdust: A Study of Equilibrium and Kinetics

    Directory of Open Access Journals (Sweden)

    S. Azizian

    2010-01-01

    Full Text Available Introduction & Objective: Industrial wastewaters including heavy metals, are among the important sources of environmental pollution. Heavy metals such as chromium are found in plating wastewater and is harmful for human health and environment. The purpose of the present study was to investigate the absorption of heavy metals such as chromium onto modified holly sawdust as an cheaper absorbent. Materials & Methods: This study was a fundamental- application study done in Hamadan University of Medical Sciences, hygiene faculty water and wastewater chemistry laboratory. This study investigated the removal of hexavalent chromium by using modified holly sawdust with pH changes ,contact time ,absorbent dose and Cr(VI concentrations in batch system. Then the result was analyzed by Excel software.Results: The results showed that the removal efficiency decrease is accompanied by the increase of pH and initial chromium concentration. pH increase from 2 to 12(equilibrium time= 180 min, adsorbent dose= 0.6g/100CC, Cr(VI concentrations= 60 mg/L,leaded to the removal efficiency decrease from 99.67 % to 29.78 %. Also removal efficiency decreased from 99.37 % to 40.24 % after increasing the initial chromium concentrations from 20 mg/L to 100 mg/L. Moreover the results showed the removal efficiency increased after increasing the adsorbent dose and contact time. By increasing adsorbent dose from 0.2 g/100CC to 1 g/100CC, the removal efficiency increased from 34.65 % to 99.76 %.Additionally, the removal efficiency increased from 48.53%to 99.76% by increasing contact time from 5 mins to 180 mins. Experimental isotherms and kinetics models were assessed by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-order kinetics models. The results showed that the data were acceptably explained acceptably by Langmuir isotherms and pseudo-second-order kinetics models respectively.Conclusion: The results showed that the removal of hexavalent chromium

  12. Removal of cobalt from lubricant oil by the use of bentonite: equilibrium, kinetic and adsorption preliminary studies

    Energy Technology Data Exchange (ETDEWEB)

    Cuccia, Valeria; Seles, Sandro R.N.; Ladeira, Ana Cláudia Queiroz, E-mail: vc@cdtn.br, E-mail: seless@cdtn.br, E-mail: acql@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-11-01

    Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of waste has been stored in the generator's facilities, awaiting treatment alternatives. This work intends to investigate a process to treat it for final deposition, using bentonite as sorbent material. This process will result in decontaminated oil, free from radiological control, and radioactive loaded sorbent, with considerable volume reduction of the radioactive waste. The study focuses in cobalt removal from a simulated oil waste (non-active). The production of the simulated waste is described. Bentonite was used for equilibrium time determination, kinetic and adsorption studies. Cobalt adsorption equilibrium was rapidly attained after 30 minutes. The data was used for modelling the system's kinetic, applying the pseudo first and pseudo second order equation models. Experimental data fitted to pseudo second order model, supporting the assumption that the adsorption is due to chemisorption. Batch sorption tests were conducted and the results fitted to Langmuir and Freundlich sorption models. Both isotherm models chosen for this work did not fit to the experimental data. Thus, these are preliminary results and the studies must be repeated to evaluate data variability and better statistical inference. Other isotherm models must be evaluated to choose the best fitted one and describe the sorption of cobalt on bentonite in oil matrix. Even though, bentonite has considerable potential as sorbent for the removal of cobalt from lubricant oil. Finally, the results might be extended to other kinds of radioactive oils and radioactive organic wastes. (author)

  13. Thermodynamic Analysis of Chemically Reacting Mixtures-Comparison of First and Second Order Models.

    Science.gov (United States)

    Pekař, Miloslav

    2018-01-01

    Recently, a method based on non-equilibrium continuum thermodynamics which derives thermodynamically consistent reaction rate models together with thermodynamic constraints on their parameters was analyzed using a triangular reaction scheme. The scheme was kinetically of the first order. Here, the analysis is further developed for several first and second order schemes to gain a deeper insight into the thermodynamic consistency of rate equations and relationships between chemical thermodynamic and kinetics. It is shown that the thermodynamic constraints on the so-called proper rate coefficient are usually simple sign restrictions consistent with the supposed reaction directions. Constraints on the so-called coupling rate coefficients are more complex and weaker. This means more freedom in kinetic coupling between reaction steps in a scheme, i.e., in the kinetic effects of other reactions on the rate of some reaction in a reacting system. When compared with traditional mass-action rate equations, the method allows a reduction in the number of traditional rate constants to be evaluated from data, i.e., a reduction in the dimensionality of the parameter estimation problem. This is due to identifying relationships between mass-action rate constants (relationships which also include thermodynamic equilibrium constants) which have so far been unknown.

  14. Adsorptive removal of phenol from aqueous solutions on activated carbon prepared from tobacco residues: Equilibrium, kinetics and thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kilic, Murat; Apaydin-Varol, Esin [Department of Chemical Engineering, Anadolu University, Eskisehir 26470 (Turkey); Puetuen, Ayse E., E-mail: aeputun@anadolu.edu.tr [Department of Chemical Engineering, Anadolu University, Eskisehir 26470 (Turkey)

    2011-05-15

    This study consists of producing high surface area activated carbon from tobacco residues by chemical activation and its behavior of phenol removal from aqueous solutions. K{sub 2}CO{sub 3} and KOH were used as chemical activation agents and three impregnation ratios (50, 75 and 100 wt.%) were applied on biomass. Maximum BET surface areas of activated carbons were obtained from impregnation with 75 wt.% of K{sub 2}CO{sub 3} and 75 wt.% of KOH as 1635 and 1474 m{sup 2}/g, respectively. Optimum adsorption conditions were determined as a function of pH, adsorbent dosage, initial phenol concentration, contact time and temperature of solution for phenol removal. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models were used to find out the kinetic parameters and mechanism of adsorption process. The thermodynamic parameters such as {Delta}G{sup o}, {Delta}H{sup o} and {Delta}S{sup o} were calculated for predicting the nature of adsorption. According to the experimental results, activated carbon prepared from tobacco residue seems to be an effective, low-cost and alternative adsorbent precursor for the removal of phenol from aqueous solutions.

  15. Hippocrates in the pseudo-Galenic Introduction: or how was medicine taught in Roman times?

    Science.gov (United States)

    Petit, Caroline

    2010-01-01

    The Pseudo-Galenic Introduction (Introductio Sive medicus, 14.674-797 K.), a medical handbook of the Roman period, witnesses the importance of Hippocrates in medical teaching at the time. Numerous quotations, allusions and reminiscences from the Hippocratic Corpus illustrate Hippocrates' authority for Pseudo-Galen. In the light of the first critical edition of the text (C. Petit, Les Belles Lettres, Paris, 2009), this article discusses the function of Hippocrates, and the various reminiscences of the Hippocratic Corpus, in order to assess Pseudo-Galen's quotation technique and, ultimately, his reliability as a source for the history of medicine.

  16. The characterization of the adsorption of cadmium from aqueous solution using natural fibers treated with nanoparticles

    Science.gov (United States)

    Rediske, Nicole M.

    The objective of this research was to characterize natural carbon fibers from coconut husks, both bare and impregnated with metallic nanoparticles, in removing cadmium from aqueous media. The adsorbent load, kinetics, isotherm parameters, removal efficiencies, desorption capacity and possible contaminant removal mechanisms were evaluated. It was found that the fibers treated with metallic nanoparticles performed better than the bare fibers in removing cadmium from water. The ideal conditions were found to be neutral pH with low initial cadmium concentrations. Through the kinetic analyses, the adsorption process was first thought to be pseudo first order with two separate adsorption mechanisms apparent. Upon further analysis, it was seen that the first mechanism does not follow the pseudo first order kinetics model. An increase in calcium and magnesium concentrations was observed as the cadmium concentrations decreases. This increase corresponds with first mechanism. This suggests the cadmium removal in the first mechanism is due to ion exchange. The second mechanism's rate constant was consistently lower than the first mechanisms rate constant by an order of magnitude. This led to the hypothesis that the second mechanism is controlled by van de Waals forces, specifically ion-induced dipole interactions, and physical adsorption. It was also found that the cadmium does not effectively desorb from the wasted fibers in DI water. Keywords: Adsorption; kinetics; pseudo first order; cadmium; metallic nanoparticles; natural fibers; removal efficiencies; ion exchange.

  17. Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2, 3- dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex

    Directory of Open Access Journals (Sweden)

    Rajneesh Dutt Kaushik

    2015-03-01

    Full Text Available The formation of ternary intermediate unstable complex during the oxidation of aromatic amines by periodate ion catalysed by MnII has been proposed in case of some anilines. This paper is the first report on stopped-flow kinetic study and evaluation of stability constant of ternary complex forming in the MnII - catalysed periodate oxidation of 2, 3-dimethylaniline (D in acetone-water medium. Stop-flow spectrophotometric method was used to study the ternary complex formation and to determine its stability constant. The stop-flow trace shows the reaction to occur in two steps. The first step, which is presumably the formation of ternary complex, is relatively fast while the second stage is relatively quite slow. The stability constant evaluated for D - MnII - IO4- ternary complex by determining  equilibrium absorbance is (2.2 ± 1.0 × 105. Kinetics of ternary complex formation was defined by the rate law(A  under pseudo first order conditions. ln{[C2]eq / ( [C2]eq -[C2]} = kobs . t (A where, kobs is the pseudo first order rate constant, [C2] is concentration of ternary complex at given time t, and [C2]eq is the equilibrium concentration of ternary complex. © 2015 BCREC UNDIP. All rights reservedReceived: 3rd October 2014; Revised: 4th December 2014; Accepted: 15th December 2014How to Cite: Kaushik, R.D., Agarwal, R., Tyagi, P., Singh, O., Singh, J. (2015. Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2,3-dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (1: 78-87. (doi:10.9767/bcrec.10.1.7621.78-87Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.1.7621.78-87

  18. Kinetic Studies For the Removal of UO22+ and Pb2+ Ions From Aqueous Solution Using Zirconia Composite Material

    International Nuclear Information System (INIS)

    Sharaf El-Deen, G.E.

    2008-01-01

    Zirconia composite material was chemically synthesized previously and prepared by applying the sol-gel polymeric route using MgO as a stabilizer. The prepared composite material was characterized using various techniques: x-ray fluorescence (XRF), scanning electron microscope (SEM), differential thermal analysis and thermogravimetric analysis (DTA-TG), x-ray diffraction (XRD) and surface area using the BET-method. The sorption removal of UO 2 2+ and Pb 2+ ions from aqueous waste solution by zirconia composite material using batch technique was investigated. The sorption was carried out as a function of ph, particle size, shaking time and temperature. In this work, a comparison of kinetic models applied to the sorption process of each ion was evaluated for the pseudo first-order, the pseudo second-order, intra particle diffusion and homogeneous particle diffusion kinetic models, respectively. The results showed that the homogeneous particle diffusion model (HPDM) best correlate the experimental rate data and 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 thermodynamic parameters of free energy (δ G * ), enthalpy (δ H * ) and entropy (δ S * ) of activation were also computed from the linearized form of Arrhenius equation

  19. Effective Remediation of Lead Ions from Aqueous Solution by Chemically Carbonized Rubber Wood Sawdust: Equilibrium, Kinetics, and Thermodynamic Study

    Directory of Open Access Journals (Sweden)

    Swarup Biswas

    2015-01-01

    Full Text Available Rubber wood sawdust was carbonized into charcoal by chemical treatment which was used for removal of lead ion from aqueous solution. The work involves batch experiments to investigate the pH effect, initial concentration of adsorbate, contact time, and adsorbent dose. Experimental data confirmed that the adsorption capacities increased with increasing inlet concentration and bed height and decreased with increasing flow rate. Adsorption results showed a maximum adsorption capacity of 37 mg/g at 308 K. Langmuir, Freundlich, and Temkin model adsorption isotherm models were applied to analyze the process where Temkin was found as a best fitted model for present study. Simultaneously kinetics of adsorption like pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were investigated. Thermodynamic parameters were used to analyze the adsorption experiment. Fourier transform infrared spectroscopy, scanning electron microscope, and energy dispersive X-ray spectroscopy confirmed the batch adsorption of lead ion onto chemically carbonized rubber wood sawdust.

  20. Energy Budget of Cosmological First-order Phase Transitions

    CERN Document Server

    Espinosa, Jose R; No, Jose M; Servant, Geraldine

    2010-01-01

    The study of the hydrodynamics of bubble growth in first-order phase transitions is very relevant for electroweak baryogenesis, as the baryon asymmetry depends sensitively on the bubble wall velocity, and also for predicting the size of the gravity wave signal resulting from bubble collisions, which depends on both the bubble wall velocity and the plasma fluid velocity. We perform such study in different bubble expansion regimes, namely deflagrations, detonations, hybrids (steady states) and runaway solutions (accelerating wall), without relying on a specific particle physics model. We compute the efficiency of the transfer of vacuum energy to the bubble wall and the plasma in all regimes. We clarify the condition determining the runaway regime and stress that in most models of strong first-order phase transitions this will modify expectations for the gravity wave signal. Indeed, in this case, most of the kinetic energy is concentrated in the wall and almost no turbulent fluid motions are expected since the s...

  1. Statistics of fermions in the Randall-Wilkins model for kinetics of general order

    International Nuclear Information System (INIS)

    Nieto H, B.; Azorin N, J.; Vazquez C, G.A.

    2004-01-01

    As a theoretical planning of the thermoluminescence phenomena (Tl), we study the behavior of the systems formed by fermions, which are related with this phenomenon establishing a generalization of the Randall-Wilkins model, as for first order kinetics as for general order (equation of May and Partridge) in which we consider a of Fermi-Dirac statistics. As consequence of this study a new variable is manifested: the chemical potential, also we establish its relationship with some of the other magnitudes already known in Tl. (Author)

  2. The Kinetics of Joined Action of Triplet-Triplet Annihilation and First-Order Decay of Molecules in T1 State in the Case of Nondominant First-Order Process: The Kinetic Model in the Case of Spatially Periodic Excitation

    Directory of Open Access Journals (Sweden)

    Paweł Borowicz

    2013-01-01

    Full Text Available In this paper the model developed for estimation of the diffusion coefficient of the molecules in the triplet state is presented. The model is based on the intuitive modification of the Smoluchowski equation for the time-dependent rate parameter. Since the sample is irradiated with the spatially periodic pattern nonexponential effects can be expected in the areas of the constructive interference of the exciting laser beams. This nonexponential effects introduce changes in the observed kinetics of the diffusion-controlled triplet-triplet annihilation. Due to irradiation with so-called long excitation pulse these non-exponential effects are very weak, so they can be described with introducing very simple correction to the kinetic model described in the first paper of this series. The values of diffusion coefficient of anthracene are used to calculate the annihilation radius from the data for spatially homogeneous excitation.

  3. The Flavor of the Composite Pseudo-Goldstone Higgs

    CERN Document Server

    Csaki, Csaba; Weiler, Andreas

    2008-01-01

    We study the flavor structure of 5D warped models that provide a dual description of a composite pseudo-Goldstone Higgs. We first carefully re-examine the flavor constraints on the mass scale of new physics in the standard Randall-Sundrum-type scenarios, and find that the KK gluon mass should generically be heavier than about 21 TeV. We then compare the flavor structure of the composite Higgs models to those in the RS model. We find new contributions to flavor violation, which while still are suppressed by the RS-GIM mechanism, will enhance the amplitudes of flavor violations. In particular, there is a kinetic mixing term among the SM fields which (although parametrically not enhanced) will make the flavor bounds even more stringent than in RS, and imply the KK gluon mass to be at least about 33 TeV. For both the RS and the composite Higgs models the flavor bounds could be stronger or weaker depending on the assumption on the value of the gluon boundary kinetic term. These strong bounds seem to imply that the...

  4. Kinetics and Mechanism of Oxidation of Triethylene Glycol and Tetraethylene Glycol by Ditelluratoargentate (III in Alkaline Medium

    Directory of Open Access Journals (Sweden)

    Jinhuan Shan

    2013-01-01

    Full Text Available The kinetics of oxidation of triethylene glycol and tetraethylene glycol by ditelluratoargentate (III (DTA in alkaline liquids has been studied spectrophotometrically in the temperature range of 293.2 K–313.2 K. The reaction rate showed first-order dependence in DTA and fractional order with respect to triethylene glycol or tetraethylene glycol. It was found that the pseudo-first-order rate constant (kobs increased with an increase in concentration of OH− and a decrease in concentration of H4TeO6 2−. There was a negative salt effect and no free radicals were detected. A plausible mechanism involving a two-electron transfer was proposed, and the rate equations derived from the mechanism explained all the experimental results and observations. The activation parameters along with the rate constants of the rate-determining step were calculated.

  5. Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot

    Directory of Open Access Journals (Sweden)

    R. Prasad

    2011-01-01

    Full Text Available To comply with the stringent emission regulations on soot, diesel vehicles manufacturers more and more commonly use diesel particulate filters (DPF. These systems need to be regenerated periodically by burning soot that has been accumulated during the loading of the DPF. Design of the DPF requires rate of soot oxidation. This paper describes the kinetics of catalytic oxidation of diesel soot with air under isothermal conditions. Kinetics data were collected in a specially designed mini-semi-batch reactor. Under the high air flow rate assuming pseudo first order reaction the activation energy of soot oxidation was found to be, Ea = 160 kJ/ mol. ©2010 BCREC UNDIP. All rights reserved(Received: 14th June 2010, Revised: 18th July 2010, Accepted: 9th August 2010[How to Cite: R. Prasad, V.R. Bella. (2010. Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot. Bulletin of Chemical Reaction Engineering and Catalysis, 5(2: 95-101. doi:10.9767/bcrec.5.2.796.95-101][DOI:http://dx.doi.org/10.9767/bcrec.5.2.796.95-101 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/796]Cited by in: ACS 1 |

  6. Concentration-dependent photodegradation kinetics and hydroxyl-radical oxidation of phenicol antibiotics.

    Science.gov (United States)

    Li, Kai; Zhang, Peng; Ge, Linke; Ren, Honglei; Yu, Chunyan; Chen, Xiaoyang; Zhao, Yuanfeng

    2014-09-01

    Thiamphenicol and florfenicol are two phenicol antibiotics widely used in aquaculture and are ubiquitous as micropollutants in surface waters. The present study investigated their photodegradation kinetics, hydroxyl-radical (OH) oxidation reactivities and products. Firstly, the photolytic kinetics of the phenicols in pure water was studied as a function of initial concentrations (C0) under UV-vis irradiation (λ>200nm). It was found that the kinetics was influenced by C0. A linear plot of the pseudo-first-order rate constant vs C0 was observed with a negative slope. Secondly, the reaction between the phenicol antibiotics and OH was examined with a competition kinetic method under simulated solar irradiation (λ>290nm), which quantified their bimolecular reaction rate constants of (2.13±0.02)×10(9)M(-1)s(-1) and (1.82±0.10)×10(9)M(-1)s(-1) for thiamphenicol and florfenicol, respectively. Then the corresponding OH oxidated half-lives in sunlit surface waters were calculated to be 90.5-106.1h. Some main intermediates were formed from the reaction, which suggested that the two phenicols underwent hydroxylation, oxygenation and dehydrogenation when OH existed. These results are of importance to assess the phenicol persistence in wastewater treatment and sunlit surface waters. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Structural changes of small amplitude kinetic Alfvén solitary waves due to second-order corrections

    International Nuclear Information System (INIS)

    Choi, Cheong R.

    2015-01-01

    The structural changes of kinetic Alfvén solitary waves (KASWs) due to higher-order terms are investigated. While the first-order differential equation for KASWs provides the dispersion relation for kinetic Alfvén waves, the second-order differential equation describes the structural changes of the solitary waves due to higher-order nonlinearity. The reductive perturbation method is used to obtain the second-order and third-order partial differential equations; then, Kodama and Taniuti's technique [J. Phys. Soc. Jpn. 45, 298 (1978)] is applied in order to remove the secularities in the third-order differential equations and derive a linear second-order inhomogeneous differential equation. The solution to this new second-order equation indicates that, as the amplitude increases, the hump-type Korteweg-de Vries solution is concentrated more around the center position of the soliton and that dip-type structures form near the two edges of the soliton. This result has a close relationship with the interpretation of the complex KASW structures observed in space with satellites

  8. A simple UV-ozone surface treatment to enhance photocatalytic performance of TiO 2 loaded polymer nanofiber membranes

    KAUST Repository

    Dilpazir, S.; Usman, M.; Rasul, Shahid; Arshad, S. N.

    2016-01-01

    . The photocatalytic activity improved by a factor of ∼2 and the kinetics of photodegradation switched from pseudo-first order to pseudo-second order with increasing TiO2 content with a maximum rate constant of 20.7 h-1. © The Royal Society of Chemistry 2016.

  9. Role of pseudo-turbulent stresses in shocked particle clouds and construction of surrogate models for closure

    Science.gov (United States)

    Sen, O.; Gaul, N. J.; Davis, S.; Choi, K. K.; Jacobs, G.; Udaykumar, H. S.

    2018-05-01

    Macroscale models of shock-particle interactions require closure terms for unresolved solid-fluid momentum and energy transfer. These comprise the effects of mean as well as fluctuating fluid-phase velocity fields in the particle cloud. Mean drag and Reynolds stress equivalent terms (also known as pseudo-turbulent terms) appear in the macroscale equations. Closure laws for the pseudo-turbulent terms are constructed in this work from ensembles of high-fidelity mesoscale simulations. The computations are performed over a wide range of Mach numbers ( M) and particle volume fractions (φ ) and are used to explicitly compute the pseudo-turbulent stresses from the Favre average of the velocity fluctuations in the flow field. The computed stresses are then used as inputs to a Modified Bayesian Kriging method to generate surrogate models. The surrogates can be used as closure models for the pseudo-turbulent terms in macroscale computations of shock-particle interactions. It is found that the kinetic energy associated with the velocity fluctuations is comparable to that of the mean flow—especially for increasing M and φ . This work is a first attempt to quantify and evaluate the effect of velocity fluctuations for problems of shock-particle interactions.

  10. Out-of-order event processing in kinetic data structures

    DEFF Research Database (Denmark)

    Abam, Mohammad; de Berg, Mark; Agrawal, Pankaj

    2011-01-01

    ’s for the maintenance of several fundamental structures such as kinetic sorting and kinetic tournament trees, which overcome the difficulty by employing a refined event scheduling and processing technique. We prove that the new event scheduling mechanism leads to a KDS that is correct except for finitely many short......We study the problem of designing kinetic data structures (KDS’s for short) when event times cannot be computed exactly and events may be processed in a wrong order. In traditional KDS’s this can lead to major inconsistencies from which the KDS cannot recover. We present more robust KDS...

  11. Ordering kinetics in model systems with inhibited interfacial adsorption

    DEFF Research Database (Denmark)

    Willart, J.-F.; Mouritsen, Ole G.; Naudts, J.

    1992-01-01

    . The results are related to experimental work on ordering processes in orientational glasses. It is suggested that the experimental observation of very slow ordering kinetics in, e.g., glassy crystals of cyanoadamantane may be a consequence of low-temperature activated processes which ultimately lead...

  12. Introduction to fractional and pseudo-differential equations with singular symbols

    CERN Document Server

    Umarov, Sabir

    2015-01-01

    The book systematically presents the theories of pseudo-differential operators with symbols singular in dual variables, fractional order derivatives, distributed and variable order fractional derivatives, random walk approximants, and applications of these theories to various initial and multi-point boundary value problems for pseudo-differential equations. Fractional Fokker-Planck-Kolmogorov equations associated with a large class of stochastic processes are presented. A complex version of the theory of pseudo-differential operators with meromorphic symbols based on the recently introduced complex Fourier transform is developed and applied for initial and boundary value problems for systems of complex differential and pseudo-differential equations.

  13. Application of first order rate kinetics to explain changes in bloom toxicity—the importance of understanding cell toxin quotas

    Science.gov (United States)

    Orr, Philip T.; Willis, Anusuya; Burford, Michele A.

    2018-04-01

    Cyanobacteria are oxygenic photosynthetic Gram-negative bacteria that can form potentially toxic blooms in eutrophic and slow flowing aquatic ecosystems. Bloom toxicity varies spatially and temporally, but understanding the mechanisms that drive these changes remains largely a mystery. Changes in bloom toxicity may result from changes in intracellular toxin pool sizes of cyanotoxins with differing molecular toxicities, and/or from changes in the cell concentrations of toxic and non-toxic cyanobacterial species or strains within bloom populations. We show here how first-order rate kinetics at the cellular level can be used to explain how environmental conditions drive changes in bloom toxicity at the ecological level. First order rate constants can be calculated for changes in cell concentration (μ c: specific cell division rate) or the volumetric biomass concentration (μ g: specific growth rate) between short time intervals throughout the cell cycle. Similar first order rate constants can be calculated for changes in nett volumetric cyanotoxin concentration (μ tox: specific cyanotoxin production rate) over similar time intervals. How μ c (or μ g ) covaries with μ tox over the cell cycle shows conclusively when cyanotoxins are being produced and metabolised, and how the toxicity of cells change in response to environment stressors. When μ tox/μ c>1, cyanotoxin cell quotas increase and individual cells become more toxic because the nett cyanotoxin production rate is higher than the cell division rate. When μ tox/μ c=1, cell cyanotoxin quotas remains fixed because the nett cyanotoxin production rate matches the cell division rate. When μ tox/μ ccyanotoxin cell quota decreases because either the nett cyanotoxin production rate is lower than the cell division rate, or metabolic breakdown and/or secretion of cyanotoxins is occurring. These fundamental equations describe cyanotoxin metabolism dynamics at the cellular level and provide the necessary

  14. The flavor of the composite pseudo-goldstone Higgs

    International Nuclear Information System (INIS)

    Csaki, Csaba; Weiler, Andreas; Falkowski, Adam

    2008-01-01

    We study the flavor structure of 5D warped models that provide a dual description of a composite pseudo-Goldstone Higgs. We first carefully re-examine the flavor constraints on the mass scale of new physics in the standard Randall-Sundrum-type scenarios, and find that the KK gluon mass should generically be heavier than about 21 TeV. We then compare the flavor structure of the composite Higgs models to those in the RS model. We find new contributions to flavor violation, which while still are suppressed by the RS-GIM mechanism, will enhance the amplitudes of flavor violations. In particular, there is a kinetic mixing term among the SM fields which (although parametrically not enhanced) will make the flavor bounds even more stringent than in RS. This together with the fact that in the pseudo-Goldstone scenario Yukawa couplings are set by a gauge coupling implies the KK gluon mass to be at least about 33 TeV. For both the RS and the composite Higgs models the flavor bounds could be stronger or weaker depending on the assumption on the value of the gluon boundary kinetic term. These strong bounds seem to imply that the fully anarchic approach to flavor in warped extra dimensions is implausible, and there have to be at least some partial flavor symmetries appearing that eliminate part of the sources for flavor violation. We also present complete expressions for the radiatively generated Higgs potential of various 5D implementations of the composite Higgs model, and comment on the 1-5 percent level tuning needed in the top sector to achieve a phenomenologically acceptable vacuum state.

  15. Measuring order in disordered systems and disorder in ordered systems: Random matrix theory for isotropic and nematic liquid crystals and its perspective on pseudo-nematic domains

    Science.gov (United States)

    Zhao, Yan; Stratt, Richard M.

    2018-05-01

    Surprisingly long-ranged intermolecular correlations begin to appear in isotropic (orientationally disordered) phases of liquid crystal forming molecules when the temperature or density starts to close in on the boundary with the nematic (ordered) phase. Indeed, the presence of slowly relaxing, strongly orientationally correlated, sets of molecules under putatively disordered conditions ("pseudo-nematic domains") has been apparent for some time from light-scattering and optical-Kerr experiments. Still, a fully microscopic characterization of these domains has been lacking. We illustrate in this paper how pseudo-nematic domains can be studied in even relatively small computer simulations by looking for order-parameter tensor fluctuations much larger than one would expect from random matrix theory. To develop this idea, we show that random matrix theory offers an exact description of how the probability distribution for liquid-crystal order parameter tensors converges to its macroscopic-system limit. We then illustrate how domain properties can be inferred from finite-size-induced deviations from these random matrix predictions. A straightforward generalization of time-independent random matrix theory also allows us to prove that the analogous random matrix predictions for the time dependence of the order-parameter tensor are similarly exact in the macroscopic limit, and that relaxation behavior of the domains can be seen in the breakdown of the finite-size scaling required by that random-matrix theory.

  16. Scaphoid pseudo-arthrosis: Frequency, pathogenesis and course

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, K.; Teifke, A.; Benning, R.; Dahm, M.; Thelen, R.; Schild, H.

    1989-06-01

    Eighty-three scaphoid pseudo-arthroses were found amongst 1.104 scaphoid examinations. Sixtyseven were present at the first examination and 16 pseudo-arthroses developed amongst 252 scaphoid fractures. Men were affected predominantly, particularly in the 20 to 40-year old group. Fractures in the proximal third of the scaphoid and vertical oblique fractures had a particular tendency to pseudo-arthrosis formation. The operative treatment of choice is a Matti-Russe bone graft. Only one patient in seven with definite scaphoid pseudo-arthrosis showed firm fusion. (orig.).

  17. Scaphoid pseudo-arthrosis: Frequency, pathogenesis and course

    International Nuclear Information System (INIS)

    Schunk, K.; Teifke, A.; Benning, R.; Dahm, M.; Thelen, R.; Schild, H.; Mainz Univ.

    1989-01-01

    Eighty-three scaphoid pseudo-arthroses were found amongst 1.104 scaphoid examinations. Sixtyseven were present at the first examination and 16 pseudo-arthroses developed amongst 252 scaphoid fractures. Men were affected predominantly, particularly in the 20 to 40-year old group. Fractures in the proximal third of the scaphoid and vertical oblique fractures had a particular tendency to pseudo-arthrosis formation. The operative treatment of choice is a Matti-Russe bone graft. Only one patient in seven with definite scaphoid pseudo-arthrosis showed firm fusion. (orig.) [de

  18. Adsorption Kinetics and intra particulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber

    International Nuclear Information System (INIS)

    Igwe, J. C.; Abia, A. A.; Ibeh, C. A.

    2008-01-01

    As, Hg and Pb are examples of heavy metals which are present in different types of industrial effluents responsible for environmental pollution. Their removal is traditionally made by chemical precipitation, ion-exchange and so on. However, this is expensive and not completely feasible to reduce their concentrations to the levels as low as required by the environmental legislation. Bio sorption is a process in which solids of natural origin are employed for binding the heavy metal. It is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. The kinetics was studied for bio sorption experiments using coconut fiber for As (III), Hg (II) and Pb (II) ions adsorption. The specific surface area and surface charge density of the coconut fiber are 1.186x10 25 (m 2 /g) and 5.39 xI0 24 (meq/m 2 ), respectively. The maximum adsorption capacity was found to be the highest for Pb (II) followed by Hg (II) and As (Ill). The modification of the adsorbent by thiolation affected the adsorption capacity. Equilibrium sorption was reached for the metal ions at about 60 min. The equilibrium constant and free energy of the adsorption at 30 degree were calculated. The mechanism of sorption was found to obey the particle-diffusion model. The kinetic studies showed that the sorption rates could be described by both pseudo first-order and pseudo second-order models. The pseudo second-order model showed a better fit with a rate constant value of 1.16x10 -4 /min. for all three metal ions.Therefore, the results of this study show that coconut fiber, both modified and unmodified, is an efficient adsorbent for the removal of toxic and valuable metals from industrial effluents

  19. Kinetics of transformation of 1,1,1-trichloroethane by Fe(II) in cement slurries

    International Nuclear Information System (INIS)

    Jung, Bahngmi; Batchelor, Bill

    2009-01-01

    This study examines the applicability of the iron-based degradative solidification/stabilization (DS/S-Fe(II)) process to 1,1,1-trichloroethane (1,1,1-TCA), which is one of common chlorinated aliphatic hydrocarbons (CAHs) of concern at contaminated sites. DS/S-Fe(II) combines contaminant degradation by Fe(II) and immobilization by the hydration reactions of Portland cement. The transformation of 1,1,1-TCA by Fe(II) in 10% Portland cement slurries was studied using a batch slurry reactor system. The effects of Fe(II) dose, pH, and initial concentration of 1,1,1-TCA on the kinetics of 1,1,1-TCA degradation were evaluated. Degradation of 1,1,1-TCA in cement slurries including Fe(II) was very rapid and could be described by a pseudo-first-order rate law. The half-lives for 1,1,1-TCA were measured between 0.4 and 5 h when Fe(II) dose ranged from 4.9 to 39.2 mM. The pseudo-first-order rate constant increased with pH to a maximum near pH 12.5. A saturation rate equation was able to predict degradation kinetics over a wide range of target organic concentrations and at higher Fe(II) doses. The major transformation product of 1,1,1-TCA in mixtures of Fe(II) and cement was 1,1-dichloroethane (1,1-DCA), which indicates that degradation occurred by a hydrogenolysis pathway. A small amount of ethane was observed. The conversion of 1,1,1-TCA to ethane was better described by a parallel reaction model than by a consecutive reaction model

  20. Determination of kinetic parameters in the pyrolysis operation and thermal behavior of Prosopis juliflora using thermogravimetric analysis.

    Science.gov (United States)

    Chandrasekaran, Arunkumar; Ramachandran, Sethumadhavan; Subbiah, Senthilmurugan

    2017-06-01

    This paper deals with the pyrolysis of Prosopis juliflora fuelwood using thermogravimetric analysis to determine the kinetic parameters at six different heating rates of 2, 5, 10, 15, 20 and 25°C/min. The activation energy of pyrolysis was calculated using different methods, namely Kissinger, Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall and Friedman model and corresponding calculated activation energy were found to be 164.6, 204, 203.2, and 219.3kJ/mol, respectively for each method. The three-pseudo component model was applied to calculate the following three kinetic parameters: activation energy, pre-exponential factor and order of reaction. The experimental results were validated with model prediction for all the six heating rates. The three-pseudo component model is able to predict experimental results much accurately while considering variable order reaction model (n≠1). Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. VOLUME 9 (2004)

    African Journals Online (AJOL)

    denise

    2004). Kinetics And Mechanism Of The Redox Reaction Between Catechol And ... Kinetics. All kinetics measurements were made under pseudo-first order conditions with the catechol in at least 100-fold excess at 605nm and constant ionic.

  2. Influencing factors and kinetic studies of imidacloprid degradation by ozonation.

    Science.gov (United States)

    Chen, Shi; Deng, Jing; Deng, Yang; Gao, Naiyun

    2018-03-02

    Batch kinetic tests in ozonation of imidacloprid from water were performed in this study. The pseudo-first-order rate constant of imidacloprid degradation was increased from 0.079 to 0.326 min -1 with the increasing pH from 6.02 to 8.64 at an average ozone dose of 1.149 mg L -1 . When the alkalinity was increased from 0 to 250 mg L -1 NaHCO 3 , the pseudo-first-order rate constants decreased from 0.121 to 0.034 min -1 . These results suggested that the predominant oxidant gradually switched from ozone to hydroxyl radicals ([Formula: see text]) with the increase in solution pH. The secondary rate constant [Formula: see text] (10.92 ± 0.12 M -1 s -1 ) for the reaction of imidacloprid and molecular ozone was determined at pH 2.0 and in the presence of 50 mM ter-butyl alcohol (p-chlorobenzoic acid, pCBA), respectively. An indirect competition method was used to determine the secondary rate constant for [Formula: see text] oxidation of imidacloprid in the presence of pCBA as the reference compound. The rate constants [Formula: see text] were estimated to range 2.65-3.79 M -1 s -1 at pH 6.02-8.64. Results obtained from this study demonstrate that ozonation appears to be an effective method to remove imidacloprid from water.

  3. Heavy Metal Adsorption onto Kappaphycus sp. from Aqueous Solutions: The Use of Error Functions for Validation of Isotherm and Kinetics Models.

    Science.gov (United States)

    Rahman, Md Sayedur; Sathasivam, Kathiresan V

    2015-01-01

    Biosorption process is a promising technology for the removal of heavy metals from industrial wastes and effluents using low-cost and effective biosorbents. In the present study, adsorption of Pb(2+), Cu(2+), Fe(2+), and Zn(2+) onto dried biomass of red seaweed Kappaphycus sp. was investigated as a function of pH, contact time, initial metal ion concentration, and temperature. The experimental data were evaluated by four isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and four kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models). The adsorption process was feasible, spontaneous, and endothermic in nature. Functional groups in the biomass involved in metal adsorption process were revealed as carboxylic and sulfonic acids and sulfonate by Fourier transform infrared analysis. A total of nine error functions were applied to validate the models. We strongly suggest the analysis of error functions for validating adsorption isotherm and kinetic models using linear methods. The present work shows that the red seaweed Kappaphycus sp. can be used as a potentially low-cost biosorbent for the removal of heavy metal ions from aqueous solutions. Further study is warranted to evaluate its feasibility for the removal of heavy metals from the real environment.

  4. Defluoridation using biomimetically synthesized nano zirconium chitosan composite: Kinetic and equilibrium studies

    International Nuclear Information System (INIS)

    Prasad, Kumar Suranjit; Amin, Yesha; Selvaraj, Kaliaperumal

    2014-01-01

    Highlights: • Colloidal Zr nanoparticles, synthesized using Aloe vera extract were entrapped in chitosan beads. • Zr loaded beads were employed for removal of F − ion and showed excellent removal efficiency. • Zr and chitosan are cost effective materials hence can be a good adsorbent for removal of fluoride. - Abstract: The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV–vis absorption peak at 420 nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18 nm to 42 nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like -NH, -C=O, -C=N and -C=C were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R 2 value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F − onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water

  5. Two-order parameters theory of the metal-insulator phase transition kinetics in the magnetic field

    Science.gov (United States)

    Dubovskii, L. B.

    2018-05-01

    The metal-insulator phase transition is considered within the framework of the Ginzburg-Landau approach for the phase transition described with two coupled order parameters. One of the order parameters is the mass density which variation is responsible for the origin of nonzero overlapping of the two different electron bands and the appearance of free electron carriers. This transition is assumed to be a first-order phase one. The free electron carriers are described with the vector-function representing the second-order parameter responsible for the continuous phase transition. This order parameter determines mostly the physical properties of the metal-insulator transition and leads to a singularity of the surface tension at the metal-insulator interface. The magnetic field is involved into the consideration of the system. The magnetic field leads to new singularities of the surface tension at the metal-insulator interface and results in a drastic variation of the phase transition kinetics. A strong singularity in the surface tension results from the Landau diamagnetism and determines anomalous features of the metal-insulator transition kinetics.

  6. Fluctuation effects in first-order phase transitions: Theory and model for martensitic transformations

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Mouritsen, Ole G.

    1990-01-01

    We discuss central questions in weak, first-order structural transitions by means of a magnetic analog model. A theory including fluctuation effects is developed for the model, showing a dynamical response with softening, fading modes and a growing central peak. The model is also analyzed by a two......-dimensional Monte Carlo simulation, showing clear precursor phenomena near the first-order transition and spontaneous nucleation. The kinetics of the domain growth is studied and found to be exceedingly slow. The results are applicable for martensitic transformations and structural surface...

  7. Theory of pseudo-differential operators over C*-Algebras

    International Nuclear Information System (INIS)

    Mohammad, N.

    1987-06-01

    In this article the behaviour of adjoints and composition of pseudo-differential operators in the framework of a C*-algebra is studied. It results that the class of pseudo-differential operators of order zero is a C*-algebra. 8 refs

  8. Postoperative ocular higher-order aberrations and contrast sensitivity: femtosecond lenticule extraction versus pseudo small-incision lenticule extraction.

    Science.gov (United States)

    Tan, Deborah K L; Tay, Wan Ting; Chan, Cordelia; Tan, Donald T H; Mehta, Jodhbir S

    2015-03-01

    To evaluate and compare changes in contrast sensitivity and ocular higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEx) and pseudo small-incision lenticule extraction (SMILE). Singapore National Eye Centre, Singapore. Retrospective case series. Patients had femtosecond lenticule extraction (Group 1) or pseudo small-incision lenticule extraction (Group 2) between March 2010 and December 2011. The main outcome measures were manifest refraction, HOAs, and contrast sensitivity 1, 3, 6, and 12 months postoperatively. Fifty-two consecutive patients (102 eyes) were recruited, 21 patients (42 eyes) in Group 1 and the 31 patients (60 eyes) in Group 2. The uncorrected and corrected distance visual acuities were significantly better in Group 2 than in Group 1 at 12 months (P = .032). There was no significant increase in 3rd- or 4th-order aberrations at 1 year and no significant difference between the 2 groups preoperatively or postoperatively. At 1 year, there was a significant increase in mesopic contrast sensitivity in Group 2 at 1.5 cycles per degree (cpd) (P = .008) that was not found in Group 1, and photopic contrast sensitivity at 6.0 cpd was higher in Group 2 (P = .027). These results indicate that refractive lenticule extraction is safe and effective with no significant induction of HOAs or deterioration in contrast sensitivity at 1 year. Induction of HOAs was not significantly different between both variants of refractive lenticule extraction. However, there was significant improvement in photopic contrast sensitivity after pseudo small-incision lenticule extraction, which persisted through 1 year. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  9. Almost Automorphic and Pseudo-Almost Automorphic Solutions to Semilinear Evolution Equations with Nondense Domain

    Directory of Open Access Journals (Sweden)

    Bruno de Andrade

    2009-01-01

    Full Text Available We study the existence and uniqueness of almost automorphic (resp., pseudo-almost automorphic solutions to a first-order differential equation with linear part dominated by a Hille-Yosida type operator with nondense domain.

  10. Performance, kinetics, and equilibrium of methylene blue adsorption on biochar derived from eucalyptus saw dust modified with citric, tartaric, and acetic acids.

    Science.gov (United States)

    Sun, Lei; Chen, Dongmei; Wan, Shungang; Yu, Zebin

    2015-12-01

    Biochar derived from eucalyptus saw dust modified with citric, tartaric, and acetic acids at low temperatures was utilized as adsorbent to remove methylene blue (MB) from aqueous solutions. Fourier transform infrared spectroscopy analysis showed that the carboxyl group was introduced on the biochar surface. Adsorption experiment data indicated that eucalyptus saw dust modified with citric acid showed higher MB adsorption efficiency than that modified with tartaric and acetic acids. Pseudo-second-order kinetics was the most suitable model for describing MB adsorption on biochar compared with pseudo-first-order, Elovich, and intraparticle diffusion models. The calculated values of ΔG(0) and ΔH(0) indicated the spontaneous and endothermic nature of the adsorption process. MB adsorption on biochar followed the Langmuir isotherm. The maximum adsorption capacities for eucalyptus saw dust modified with citric, tartaric, and acetic acids were 178.57, 99.01, and 29.94 mg g(-1), respectively, at 35°C. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Removal of three nitrophenols from aqueous solutions by adsorption onto char ash: equilibrium and kinetic modeling

    Science.gov (United States)

    Magdy, Yehia M.; Altaher, Hossam; ElQada, E.

    2018-03-01

    In this research, the removal of 2,4 dinitrophenol, 2 nitrophenol and 4 nitrophenol from aqueous solution using char ash from animal bones was investigated using batch technique. Three 2-parameter isotherms (Freundlich, Langmuir, and Temkin) were applied to analyze the experimental data. Both linear and nonlinear regression analyses were performed for these models to estimate the isotherm parameters. Three 3-parameter isotherms (Redlich-Peterson, Sips, Toth) were also tested. Moreover, the kinetic data were tested using pseudo-first order, pseudo-second order, Elovich, Intraparticle diffusion and Boyd methods. Langmuir adsorption isotherm provided the best fit for the experimental data indicating monolayer adsorption. The maximum adsorption capacity was 8.624, 7.55, 7.384 mg/g for 2 nitrophenol, 2,4 dinitrophenol, and 4 nitrophenol, respectively. The experimental data fitted well to pseudo-second order model suggested a chemical nature of the adsorption process. The R 2 values for this model were 0.973 up to 0.999. This result with supported by the Temkin model indicating heat of adsorption to be greater than 10 kJ/mol. The rate controlling step was intraparticle diffusion for 2 nitrophenol, and a combination of intraparticle diffusion and film diffusion for the other two phenols. The pH and temperature of solution were found to have a considerable effect, and the temperature indicated the exothermic nature of the adsorption process. The highest adsorption capacity was obtained at pH 9 and 25 °C.

  12. Removal of tartrazine from aqueous solutions by strongly basic polystyrene anion exchange resins.

    Science.gov (United States)

    Wawrzkiewicz, Monika; Hubicki, Zbigniew

    2009-05-30

    The removal of tartrazine from aqueous solutions onto the strongly basic polystyrene anion exchangers of type 1 (Amberlite IRA-900) and type 2 (Amberlite IRA-910) was investigated. The experimental data obtained at 100, 200, 300 and 500 mg/dm(3) initial concentrations at 20 degrees C were applied to the pseudo-first order, pseudo-second order and Weber-Morris kinetic models. The calculated sorption capacities (q(e,cal)) and the rate constant of the first order adsorption (k(1)) were determined. The pseudo-second order kinetic constants (k(2)) and capacities were calculated from the plots of t/q(t) vs. t, 1/q(t) vs. 1/t, 1/t vs. 1/q(t) and q(t)/t vs. q(t) for type 1, type 2, type 3 and type 4 of the pseudo-second order expression, respectively. The influence of phase contact time, solution pH and temperature on tartrazine removal was also discussed. The FTIR spectra of pure anion exchangers and those loaded with tartrazine were recorded, too.

  13. SEARCHING FOR LOW WEIGHT PSEUDO-CODEWORDS

    International Nuclear Information System (INIS)

    Chertkov, Michael; Stepanov, Mikhail

    2007-01-01

    Belief Propagation (BP) and Linear Programming (LP) decodings of LDPC codes are discussed. The authors summarize results of instanton/pseudo-codeword approach developed for analysis of the error-floor domain of the codes. Instantons are special, code and decoding specific, configurations of the channel noise contributing most to the Frame-Error-Rate (FER). Instantons are decoded into pseudo-codewords. Instanton/pseudo-codeword with the lowest weight describes the largest Signal-to-Noise-Ratio (SNR) asymptotic of FER, while the whole spectra of the low weight instantons is descriptive of the FER vs. SNR profile in the extended error-floor domain. First, they describe a general optimization method that allows to find the instantons for any coding/decoding. Second, they introduce LP-specific pseudo-codeword search algorithm that allows efficient calculations of the pseudo-codeword spectra. Finally, they discuss results of combined BP/LP error-floor exploration experiments for two mode codes.

  14. SEARCHING FOR LOW WEIGHT PSEUDO-CODEWORDS

    Energy Technology Data Exchange (ETDEWEB)

    CHERTKOV, MICHAEL [Los Alamos National Laboratory; STEPANOV, MIKHAIL [Los Alamos National Laboratory

    2007-01-23

    Belief Propagation (BP) and Linear Programming (LP) decodings of LDPC codes are discussed. The authors summarize results of instanton/pseudo-codeword approach developed for analysis of the error-floor domain of the codes. Instantons are special, code and decoding specific, configurations of the channel noise contributing most to the Frame-Error-Rate (FER). Instantons are decoded into pseudo-codewords. Instanton/pseudo-codeword with the lowest weight describes the largest Signal-to-Noise-Ratio (SNR) asymptotic of FER, while the whole spectra of the low weight instantons is descriptive of the FER vs. SNR profile in the extended error-floor domain. First, they describe a general optimization method that allows to find the instantons for any coding/decoding. Second, they introduce LP-specific pseudo-codeword search algorithm that allows efficient calculations of the pseudo-codeword spectra. Finally, they discuss results of combined BP/LP error-floor exploration experiments for two mode codes.

  15. KINETICS OF PALM OIL TRANSESTERIFICATION IN METHANOL WITH POTASSIUM HYDROXIDE AS A CATALYST

    Directory of Open Access Journals (Sweden)

    Yoeswono Yoeswono

    2010-06-01

    Full Text Available A study on palm oil transesterification to evaluate the effect of some parameters in the reaction on the reaction kinetics has been carried out. Transesterification was started by preparing potassium methoxide from potassium hydroxide and methanol and then mixed it with the palm oil. An aliquot was taken at certain time interval during transesterification and poured into test tube filled with distilled water to stop the reaction immediately. The oil phase that separated from the glycerol phase by centrifugation was analyzed by 1H-NMR spectrometer to determine the percentage of methyl ester conversion. Temperature and catalyst concentration were varied in order to determine the reaction rate constants, activation energies, pre-exponential factors, and effective collisions. The results showed that palm oil transesterification in methanol with 0.5 and 1 % w/w KOH/palm oil catalyst concentration appeared to follow pseudo-first order reaction. The rate constants increase with temperature. After 13 min of reaction, More methyl esters were formed using KOH 1 % than using 0.5 % w/w KOH/palm oil catalyst concentration. The activation energy (Ea and pre-exponential factor (A for reaction using 1 % w/w KOH was lower than those using 0.5 % w/w KOH.   Keywords: palm oil, transesterification, catalyst, first order kinetics, activation energy, pre-exponential factor

  16. Adsorption kinetics of malachite green onto activated carbon prepared from Tuncbilek lignite

    International Nuclear Information System (INIS)

    Onal, Y.; Akmil-Basar, C.; Eren, Didem; Sarici-Ozdemir, Cigdem; Depci, Tolga

    2006-01-01

    Adsorbent (T 3 K618) has been prepared from Tuncbilek lignite by chemical activation with KOH. Pore properties of the activated carbon such as BET surface area, pore volume, pore size distribution, and pore diameter were characterized by t-plot based on N 2 adsorption isotherm. The N 2 adsorption isotherm of malachite green on T 3 K618 is type I. The BET surface area of the adsorbent which was primarily contributed by micropores was determined 1000 m 2 /g. T 3 K618 was used to adsorb malachite green (MG) from an aqueous solution in a batch reactor. The effects of initial dye concentration, agitation time, initial pH and adsorption temperature have been studied. It was also found that the adsorption isotherm followed both Freundlich and Dubinin-Radushkevich models. However, the Freundlich gave a better fit to all adsorption isotherms than the Dubinin-Radushkevich. The kinetics of adsorption of MG has been tested using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Results show that the adsorption of MG from aqueous solution onto micropores T 3 K618 proceeds according to the pseudo-second-order model. The intraparticle diffusion of MG molecules within the carbon particles was identified to be the rate-limiting step. The adsorption of the MG was endothermic (ΔH o = 6.55-62.37 kJ/mol) and was accompanied by an increase in entropy (ΔS o = 74-223 J/mol K) and a decrease in mean value of Gibbs energy (ΔG o = -6.48 to -10.32 kJ/mol) in the temperature range of 20-50 deg. C

  17. Kinetics and mechanism of reduction of iron(iii) kojic acid complex by hydroquinone and l-cysteine

    International Nuclear Information System (INIS)

    Hussain, Z.; Perviaz, M.; Kazmi, S.A.; Johnson, A.S.; Offiong, O.E.

    2014-01-01

    The effect of pH on the kinetics of reduction of iron(III) kojic acid complex by hydroquinone (H/sub 2/Q) and L-cysteine (L-Cys) was studied in the pH range of 2.34 - 4.03 for H/sub 2/Q and 3.04 - 5.5 for L-cysteine at ionic strength of 0.5 M and at 35 degree C. The pseudo-first order rate constants for the reduction of Fe(KA)3 by L-cysteine and hydroquinone increase linearly with increasing reductant concentration, indicating first-order kinetics in reductant concentration. However, whereas the rate of reduction by H2Q increases with increasing pH, an opposite trend was observed in the case of reduction by L-cysteine. Plausible rate laws and mechanisms have been proposed in line with these observations. Activation parameters (delta H no and delta S no) were evaluated for the reduction of iron (III) kojic acid complex by cysteine and the values obtained are 35.25 kJmol-1, -141.4 JK-1mol-1 and 28.14 kJmol-1 , 161.2 JK-1mol-1 for pH 4.5 and 3.52 respectively. (author)

  18. Kinetic study of microwave-assisted alkaline hydrolysis of Jatropha curcas oil

    Science.gov (United States)

    Yusuf, Nur'aini Raman; Kamil, Ruzaimah Nik Mohamad; Yusup, Suzana

    2016-11-01

    The kinetics of hydrolysis of Jatropha curcas oil under microwave irradation in the presence of alkaline solution was studied. The temperature of 50°C, 65°C and 80°C were studied in the range of optimum condition of 1.75 M catalyst, solvent/oil ratio of (1: 68) and 15 minutes reaction time. The rate constants of oil hydrolysis are corresponding to triglyceride disappearance concentration. The rates of reaction for fatty acids production was determined by pseudo first order. The activation energy (Ea) achieved at 30.61 kJ/mol is lower using conventional method. This conclude that the rate of reaction via microwave heating is less temperature sensitive therefore reaction can be obtained at lower temperature.

  19. Kinetics of two simultaneous second-order reactions occurring in different zones

    International Nuclear Information System (INIS)

    Dole, M.; Hsu, C.S.; Patel, V.M.; Patel, G.N.

    1975-01-01

    Equations have been derived for the case of free radicals recombining according to the second-order kinetics with or without diffusion control under the conditions that there are two simultaneous spatially separated recombination reactions but that only the overall free-radical concentration can be observed. The properties of these equations are discussed and methods for determining the three independent parameters in the first case and five in the second developed. The resulting equations have been applied to the interpretation of data obtained in studying the decay of allyl chain free radicals in irradiated extended chain crystalline polyethylene

  20. Adsorption of 2,4-dichlorophenoxyacetic acid and 4-chloro-2-metylphenoxyacetic acid onto activated carbons derived from various lignocellulosic materials.

    Science.gov (United States)

    Doczekalska, Beata; Kuśmierek, Krzysztof; Świątkowski, Andrzej; Bartkowiak, Monika

    2018-05-04

    Adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-metylphenoxyacetic acid (MCPA) from aqueous solution onto activated carbons derived from various lignocellulosic materials including willow, miscanthus, flax, and hemp shives was investigated. The adsorption kinetic data were analyzed using two kinetic models: the pseudo-first order and pseudo-second order equations. The adsorption kinetics of both herbicides was better represented by the pseudo-second order model. The adsorption isotherms of 2,4-D and MCPA on the activated carbons were analyzed using the Freundlich and Langmuir isotherm models. The equilibrium data followed the Langmuir isotherm. The effect of pH on the adsorption was also studied. The results showed that the activated carbons prepared from the lignocellulosic materials are efficient adsorbents for the removal of 2,4-D and MCPA from aqueous solutions.

  1. Structure and properties of cotton fabrics treated with functionalized dialdehyde chitosan.

    Science.gov (United States)

    He, Xuemei; Tao, Ran; Zhou, Tianchi; Wang, Chunxia; Xie, Kongliang

    2014-03-15

    In this research, modified cotton fabrics were prepared by pad-dry-cure technique from the aldehyde chitosan solution containing 3-aminopropyltriethoxysilane (APTES) and 1,2-ethanediamine (EDA) respectively. The structural characterization of the modified cotton fabrics was performed by attenuated total reflection ATR, scanning electron microscopy (SEM) and thermogravimetry (TG) analysis and physical mechanical properties were measured. The adsorption kinetics of modified cotton fabrics were also investigated by using the pseudo first-order and pseudo second-order kinetic model. The dyeing rate constant k1, k2 and half adsorption time t1/2 were calculated, respectively. The results show that the mechanical properties of different modified cotton fabrics were improved, and the surface color depth values (K/S), UV index UPF and anti-wrinkle properties were better than those of untreated cotton. Dyeing kinetics data at different temperatures indicate that Direct Pink 12B up-take on the modified cotton fabrics fitted to pseudo second-order kinetic model. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Pseudo-simple heteroclinic cycles in R4

    Science.gov (United States)

    Chossat, Pascal; Lohse, Alexander; Podvigina, Olga

    2018-06-01

    We study pseudo-simple heteroclinic cycles for a Γ-equivariant system in R4 with finite Γ ⊂ O(4) , and their nearby dynamics. In particular, in a first step towards a full classification - analogous to that which exists already for the class of simple cycles - we identify all finite subgroups of O(4) admitting pseudo-simple cycles. To this end we introduce a constructive method to build equivariant dynamical systems possessing a robust heteroclinic cycle. Extending a previous study we also investigate the existence of periodic orbits close to a pseudo-simple cycle, which depends on the symmetry groups of equilibria in the cycle. Moreover, we identify subgroups Γ ⊂ O(4) , Γ ⊄ SO(4) , admitting fragmentarily asymptotically stable pseudo-simple heteroclinic cycles. (It has been previously shown that for Γ ⊂ SO(4) pseudo-simple cycles generically are completely unstable.) Finally, we study a generalized heteroclinic cycle, which involves a pseudo-simple cycle as a subset.

  3. Quantitative production of compound I from a cytochrome P450 enzyme at low temperatures. Kinetics, activation parameters, and kinetic isotope effects for oxidation of benzyl alcohol.

    Science.gov (United States)

    Wang, Qin; Sheng, Xin; Horner, John H; Newcomb, Martin

    2009-08-05

    Cytochrome P450 enzymes are commonly thought to oxidize substrates via an iron(IV)-oxo porphyrin radical cation transient termed Compound I, but kinetic studies of P450 Compounds I are essentially nonexistent. We report production of Compound I from cytochrome P450 119 (CYP119) in high conversion from the corresponding Compound II species at low temperatures in buffer mixtures containing 50% glycerol by photolysis with 365 nm light from a pulsed lamp. Compound I was studied as a reagent in oxidations of benzyl alcohol and its benzylic mono- and dideuterio isotopomers. Pseudo-first-order rate constants obtained at -50 degrees C with concentrations of substrates between 1.0 and 6.0 mM displayed saturation kinetics that gave binding constants for the substrate in the Compound I species (K(bind)) and first-order rate constants for the oxidation reactions (k(ox)). Representative results are K(bind) = 214 M(-1) and k(ox) = 0.48 s(-1) for oxidation of benzyl alcohol. For the dideuterated substrate C(6)H(5)CD(2)OH, kinetics were studied between -50 and -25 degrees C, and a van't Hoff plot for complexation and an Arrhenius plot for the oxidation reaction were constructed. The H/D kinetic isotope effects (KIEs) at -50 degrees C were resolved into a large primary KIE (P = 11.9) and a small, inverse secondary KIE (S = 0.96). Comparison of values extrapolated to 22 degrees C of both the rate constant for oxidation of C(6)H(5)CD(2)OH and the KIE for the nondeuterated and dideuterated substrates to values obtained previously in laser flash photolysis experiments suggested that tunneling could be a significant component of the total rate constant at -50 degrees C.

  4. Defluoridation using biomimetically synthesized nano zirconium chitosan composite: Kinetic and equilibrium studies

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Kumar Suranjit, E-mail: suranjit@gmail.com [Department of Environmental Biotechnology, Ashok and Rita Patel Institute of Integrated Study and Research in Biotechnology and Allied Sciences (ARIBAS), New Vallabh Vidyanagar, Anand, 388121 Gujarat (India); Amin, Yesha, E-mail: yesha_2879@yahoo.co.in [Department of Environmental Biotechnology, Ashok and Rita Patel Institute of Integrated Study and Research in Biotechnology and Allied Sciences (ARIBAS), New Vallabh Vidyanagar, Anand, 388121 Gujarat (India); Selvaraj, Kaliaperumal, E-mail: k.selvaraj@ncl.res.in [Nano and Computational Materials Lab, Catalysis Division, National Chemical Laboratory, Council of Scientific and Industrial Research, Pune 411008 (India)

    2014-07-15

    Highlights: • Colloidal Zr nanoparticles, synthesized using Aloe vera extract were entrapped in chitosan beads. • Zr loaded beads were employed for removal of F{sup −} ion and showed excellent removal efficiency. • Zr and chitosan are cost effective materials hence can be a good adsorbent for removal of fluoride. - Abstract: The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV–vis absorption peak at 420 nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18 nm to 42 nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like -NH, -C=O, -C=N and -C=C were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R{sup 2} value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F{sup −} onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water.

  5. CO2 adsorption using TiO2 composite polymeric membranes: A kinetic study.

    Science.gov (United States)

    Hafeez, Sarah; Fan, X; Hussain, Arshad; Martín, C F

    2015-09-01

    CO2 is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO2. Membrane gas separation is a fast growing CO2 capture technique, particularly gas separation by composite membranes. The separation of CO2 by a membrane is not just a process to physically sieve out of CO2 through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO2. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO2 in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO2 through membranes. Pure cellulose acetate (CA) and cellulose acetate-titania nanoparticle (CA-TiO2) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO2 membrane adsorbed more quantity of CO2 gas as compared to pure CA membrane. The high CO2 adsorption capacity may enhance the diffusion and solubility of CO2 in the CA-TiO2 composite membrane, which results in a better CO2 separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models. According to correlation factor R(2), the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion. Copyright © 2015. Published by Elsevier B.V.

  6. Pseudo-nitzschia simulans sp. nov. (Bacillariophyceae), the first domoic acid producer from Chinese waters

    DEFF Research Database (Denmark)

    Li, Yang; Huang, Chun Xiu; Xu, Guo Shuang

    2017-01-01

    The genus Pseudo-nitzschia has attracted attention because of production of the toxin, domoic acid (DA), causing Amnesic Shellfish Poisoning (ASP). Pseudo-nitzschia blooms occur frequently in Chinese coastal waters, and DA has been detected in several marine organisms, but so far no Pseudo-nitzsc...

  7. Feasibility of treating aged polycyclic aromatic hydrocarbons (PAHs)-contaminated soils using ethyl lactate-based Fenton treatment via parametric and kinetic studies.

    Science.gov (United States)

    Yap, Chiew Lin; Gan, Suyin; Ng, Hoon Kiat

    2015-01-01

    This study focuses on the feasibility of treating aged polycyclic aromatic hydrocarbons (PAHs)-contaminated soils using ethyl lactate (EL)-based Fenton treatment via a combination of parametric and kinetic studies. An optimised operating condition was observed at 66.7 M H2O2 with H2O2/Fe(2+) of 40:1 for low soil organic carbon (SOC) content and mildly acidic soil (pH 6.2), and 10:1 for high SOC and very acidic soil (pH 4.4) with no soil pH adjustment. The desorption kinetic was only mildly shifted from single equilibrium to dual equilibrium of the first-order kinetic model upon ageing. Pretreatment with EL fc = 0.60 greatly reduced the mass transfer coefficient especially for the slow desorbed fraction (kslow) of high molecular weight (HMW) PAHs, largely contributed by the concentration gradient created by EL-enhanced solubility. As the major desorption obstacle was almost fully overcome by the pretreatment, the pseudo-first-order kinetic reaction rate constant of PAHs degradation of aged soils was statistically discernible from that of freshly contaminated soils but slightly reduced in high SOC and high acidity soil. Stabilisation of H2O2 by EL addition in combination with reduced Fe(2+) catalyst were able to slow the decomposition rate of H2O2 even at higher soil pH.

  8. Adsorptive Removal of Malachite Green with Activated Carbon ...

    African Journals Online (AJOL)

    NICO

    2012-11-22

    Nov 22, 2012 ... The kinetics of the adsorption process was tested by means of pseudo-first-order, pseudo-second-order and ... the production of activated carbon by using agricultural ... tion Number 42 000, with the chemical formula C52H54N4O12, and ...... 40 S. Lagergren and B. K. Svenska, Band., 1893, 24, 1–13.

  9. Kinetic and mechanistic investigations of the degradation of sulfamethazine in heat-activated persulfate oxidation process.

    Science.gov (United States)

    Fan, Yan; Ji, Yuefei; Kong, Deyang; Lu, Junhe; Zhou, Quansuo

    2015-12-30

    Sulfamethazine (SMZ) is widely used in livestock feeding and aquaculture as an antibiotic agent and growth promoter. Widespread occurrence of SMZ in surface water, groundwater, soil and sediment has been reported. In this study, degradation of SMZ by heat-activated persulfate (PS) oxidation was investigated in aqueous solution. Experimental results demonstrated that SMZ degradation followed pseudo-first-order reaction kinetics. The pseudo-first-order rate constant (kobs) was increased markedly with increasing concentration of PS and temperature. Radical scavenging tests revealed that the predominant oxidizing species was SO4·(-) with HO playing a less important role. Aniline moiety in SMZ molecule was confirmed to be the reactive site for SO4·(-) attack by comparison with substructural analogs. Nontarget natural water constituents affected SMZ removal significantly, e.g., Cl(-) and HCO3(-) improved the degradation while fulvic acid reduced it. Reaction products were enriched by solid phase extraction (SPE) and analyzed by liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MS/MS). 6 products derived from sulfonamide S--N bond cleavage, aniline moiety oxidation and Smiles-type rearrangement were identified, and transformation pathways of SMZ oxidation were proposed. Results reveal that heat-activated PS oxidation could be an efficient approach for remediation of water contaminated by SMZ and related sulfonamides. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Pseudo color ghost coding imaging with pseudo thermal light

    Science.gov (United States)

    Duan, De-yang; Xia, Yun-jie

    2018-04-01

    We present a new pseudo color imaging scheme named pseudo color ghost coding imaging based on ghost imaging but with multiwavelength source modulated by a spatial light modulator. Compared with conventional pseudo color imaging where there is no nondegenerate wavelength spatial correlations resulting in extra monochromatic images, the degenerate wavelength and nondegenerate wavelength spatial correlations between the idle beam and signal beam can be obtained simultaneously. This scheme can obtain more colorful image with higher quality than that in conventional pseudo color coding techniques. More importantly, a significant advantage of the scheme compared to the conventional pseudo color coding imaging techniques is the image with different colors can be obtained without changing the light source and spatial filter.

  11. First-order reversal curves of single domain particles: diluted random assemblages and chains

    Science.gov (United States)

    Egli, R.

    2009-04-01

    Exact magnetic models can be used to calculate first-order reversal curves (FORC) of single domain (SD) particle assemblages, as shown by Newell [2005] for the case of isolated Stoner-Wohlfarth particles. After overcoming experimental difficulties, a FORC diagram sharing many similarities to Newell's model has been measured on a lake sediment sample (see A.P. Chen et al., "Quantification of magnetofossils using first-order reversal curves", EGU General Assembly 2009, Abstracts Vol. 11, EGU2009-10719). This sample contains abundant magnetofossils, as shown by coercivity analysis and electron microscopy, therefore suggesting that well dispersed, intact magnetosome chains are the main SD carriers. Subtle differences between the reversible and the irreversible contributions of the measured FORC distribution suggest that magnetosome chains might not be correctly described by the Stoner-Wohlfarth model. To better understand the hysteresis properties of such chains, a simple magnetic model has been implemented, taking dipole-dipole interactions between particles within the same chain into account. The model results depend on the magnetosome elongation, the number of magnetosomes in a chain, and the gap between them. If the chain axis is subparallel to the applied field, the magnetic moment reverses by a pseudo-fanning mode, which is replaced by a pseudo-coherent rotation mode at greater angles. These reversal modes are intrinsically different from coherent rotation assumed Stoner-Wohlfarth model, resulting in FORC diagrams with a smaller reversible component. On the other hand, isolated authigenic SD particles can precipitate in the sediment matrix, as it might occur for pedogenic magnetite. In this case, an assembly of randomly located particles provides a possible model for the resulting FORC diagram. If the concentration of the particles is small, each particle is affected by a random interaction field whose statistical distribution can be calculated from first

  12. Tannins and Tannin-Related Derivatives Enhance the (Pseudo-)Halogenating Activity of Lactoperoxidase.

    Science.gov (United States)

    Gau, Jana; Prévost, Martine; Van Antwerpen, Pierre; Sarosi, Menyhárt-Botond; Rodewald, Steffen; Arnhold, Jürgen; Flemmig, Jörg

    2017-05-26

    Several hydrolyzable tannins, proanthocyanidins, tannin derivatives, and a tannin-rich plant extract of tormentil rhizome were tested for their potential to regenerate the (pseudo-)halogenating activity, i.e., the oxidation of SCN - to hypothiocyanite - OSCN, of lactoperoxidase (LPO) after hydrogen peroxide-mediated enzyme inactivation. Measurements were performed using 5-thio-2-nitrobenzoic acid in the presence of tannins and related substances in order to determine kinetic parameters and to trace the LPO-mediated - OSCN formation. The results were combined with docking studies and molecular orbital analysis. The - OSCN-regenerating effect of tannin derivatives relates well with their binding properties toward LPO as well as their occupied molecular orbitals. Especially simple compounds like ellagic acid or methyl gallate and the complex plant extract were found as potent enzyme-regenerating compounds. As the (pseudo-)halogenating activity of LPO contributes to the maintenance of oral bacterial homeostasis, the results provide new insights into the antibacterial mode of action of tannins and related compounds. Furthermore, chemical properties of the tested compounds that are important for efficient enzyme-substrate interaction and regeneration of the - OSCN formation by LPO were identified.

  13. Pseudo-extravasation rate constant of dynamic susceptibility contrast-MRI determined from pharmacokinetic first principles.

    Science.gov (United States)

    Li, Xin; Varallyay, Csanad G; Gahramanov, Seymur; Fu, Rongwei; Rooney, William D; Neuwelt, Edward A

    2017-11-01

    Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) is widely used to obtain informative perfusion imaging biomarkers, such as the relative cerebral blood volume (rCBV). The related post-processing software packages for DSC-MRI are available from major MRI instrument manufacturers and third-party vendors. One unique aspect of DSC-MRI with low-molecular-weight gadolinium (Gd)-based contrast reagent (CR) is that CR molecules leak into the interstitium space and therefore confound the DSC signal detected. Several approaches to correct this leakage effect have been proposed throughout the years. Amongst the most popular is the Boxerman-Schmainda-Weisskoff (BSW) K 2 leakage correction approach, in which the K 2 pseudo-first-order rate constant quantifies the leakage. In this work, we propose a new method for the BSW leakage correction approach. Based on the pharmacokinetic interpretation of the data, the commonly adopted R 2 * expression accounting for contributions from both intravascular and extravasating CR components is transformed using a method mathematically similar to Gjedde-Patlak linearization. Then, the leakage rate constant (K L ) can be determined as the slope of the linear portion of a plot of the transformed data. Using the DSC data of high-molecular-weight (~750 kDa), iron-based, intravascular Ferumoxytol (FeO), the pharmacokinetic interpretation of the new paradigm is empirically validated. The primary objective of this work is to empirically demonstrate that a linear portion often exists in the graph of the transformed data. This linear portion provides a clear definition of the Gd CR pseudo-leakage rate constant, which equals the slope derived from the linear segment. A secondary objective is to demonstrate that transformed points from the initial transient period during the CR wash-in often deviate from the linear trend of the linearized graph. The inclusion of these points will have a negative impact on the accuracy of the leakage

  14. Fabrication and Characterization of Ultrathin-ring Electrodes for Pseudo-steady-state Amperometric Detection.

    Science.gov (United States)

    Kitazumi, Yuki; Hamamoto, Katsumi; Noda, Tatsuo; Shirai, Osamu; Kano, Kenji

    2015-01-01

    The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.

  15. Isothermal Kinetics of Diesel Soot Oxidation over La0.7K0.3ZnOy Catalysts

    Directory of Open Access Journals (Sweden)

    Ram Prasad

    2014-10-01

    Full Text Available This paper describes the kinetics of catalytic oxidation of diesel soot with air under isothermal conditions (320-350 oC. Isothermal kinetics data were collected in a mini-semi-batch reactor. Experiments were performed over the best selected catalyst composition La0.7K0.3ZnOy prepared by sol-gel method. Characterization of the catalyst by XRD and FTIR confirmed that La1-xKxZnOy did not exhibit perovskite phase but formed mixed metal oxides. 110 mg of the catalyst-soot mixture in tight contact (10:1 ratio was taken in order to determine the kinetic model, activation energy and Arrhenius constant of the oxidation reaction under the high air flow rate assuming pseudo first order reaction. The activation energy and Arrhenius constant were found to be 138 kJ/mol and 6.46x1010 min-1, respectively. © 2014 BCREC UNDIP. All rights reservedReceived: 26th April 2014; Revised: 27th May 2014; Accepted: 28th June 2014How to Cite: Prasad, R., Kumar, A., Mishra, A. (2014. Isothermal Kinetics of Diesel Soot Oxidation over La0.7K0.3ZnOy Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 9(3: 192-200. (doi: 10.9767/bcrec.9.3.6773.192-200Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.3.6773.192-200

  16. Glycerol acetals, kinetic study of the reaction between glycerol and formaldehyde

    International Nuclear Information System (INIS)

    Agirre, I.; Garcia, I.; Requies, J.; Barrio, V.L.; Gueemez, M.B.; Cambra, J.F.; Arias, P.L.

    2011-01-01

    The acetalization reaction between glycerol and formaldehyde using Amberlyst 47 acidic ion exchange resin was studied. These acetals can be obtained from renewable sources (bioalcohols and bioalcohol derived aldehydes) and seem to be good candidates for different applications such as oxygenated diesel additives. A preliminary kinetic study was performed in a batch stirred tank reactor studying the influence of different process parameters like temperature, feed composition and the stirring speed. A pseudo homogenous kinetic model able to explain the reaction mechanism was adjusted. Thus, the corresponding order of reaction was determined. Amberlyst 47 acidic ion exchange resin showed a fairly good behavior allowing 100% of selectivity towards acetals formation. However, the studied acetalization reaction showed high thermodynamic limitations achieving glycerol conversions around 50% using a stoichiometric feed ratio at 353 K. The product is a mixture of two isomers (1,3-Dioxan-5-ol and 1,3-dioxolane-4-methanol) and the conversion of 1,3-dioxolane-4-methanol into 1,3-Dioxan-5-ol was also observed. -- Highlights: → The reaction between glycerol and acetaldehyde shows thermodynamic limitations. → Amberlyst 47 ion exchange resins show 100% of selectivity. → A pseudo-homogeneous kinetic model is able to predict the reaction progress. → Isomerization reactions were observed from dioxalanes to dioxanes.

  17. Chaos-based Pseudo-random Number Generation

    KAUST Repository

    Barakat, Mohamed L.

    2014-04-10

    Various methods and systems related to chaos-based pseudo-random number generation are presented. In one example, among others, a system includes a pseudo-random number generator (PRNG) to generate a series of digital outputs and a nonlinear post processing circuit to perform an exclusive OR (XOR) operation on a first portion of a current digital output of the PRNG and a permutated version of a corresponding first portion of a previous post processed output to generate a corresponding first portion of a current post processed output. In another example, a method includes receiving at least a first portion of a current output from a PRNG and performing an XOR operation on the first portion of the current PRNG output with a permutated version of a corresponding first portion of a previous post processed output to generate a corresponding first portion of a current post processed output.

  18. Chaos-based Pseudo-random Number Generation

    KAUST Repository

    Barakat, Mohamed L.; Mansingka, Abhinav S.; Radwan, Ahmed Gomaa Ahmed; Salama, Khaled N.

    2014-01-01

    Various methods and systems related to chaos-based pseudo-random number generation are presented. In one example, among others, a system includes a pseudo-random number generator (PRNG) to generate a series of digital outputs and a nonlinear post processing circuit to perform an exclusive OR (XOR) operation on a first portion of a current digital output of the PRNG and a permutated version of a corresponding first portion of a previous post processed output to generate a corresponding first portion of a current post processed output. In another example, a method includes receiving at least a first portion of a current output from a PRNG and performing an XOR operation on the first portion of the current PRNG output with a permutated version of a corresponding first portion of a previous post processed output to generate a corresponding first portion of a current post processed output.

  19. Adsorption removal of acid black 1 from aqueous solution using ordered mesoporous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Xiaoming, E-mail: pengxiaoming70@126.com [School of Civil Engineering, Southeast University, Nanjing 210096 (China); Hu, Xijun [Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong,China (China); Fu, Dafang, E-mail: fdf@seu.edu.cn [School of Civil Engineering, Southeast University, Nanjing 210096 (China); Lam, Frank L.Y. [Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong,China (China)

    2014-03-01

    Highlights: • Ordered mesoporous carbon was prepared using template. • Ordered mesoporous carbon was introduced of N-containing group by Chemical vapor deposition method. • Modified CMK-3 have better adsorption capacity and efficiency than virgin CMK-3 to removal AB1 dye. - Abstract: A novel ordered mesoporous carbon CMK-3 and synthetic CMK-3 containing nitrogen functional groups by ammonia-treated were applied for acid black 1(AB1) dye adsorption. The ammonia-treated(chemical vapor deposition method) before and after CMK-3 were characterized by using a Micrometitics ASAP 2020 surface area analyzer (ASAP 2020), Fourier transform infrared spectrophotometer (FT–IR), X-ray Photoelectron Spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM) and equilibrium studies. This result indicates that the prepared CMK-3 and modified CMK-3 were almost uniform, as rope-like domains and their uniform mesopore with diameter centered at 3.2 nm and 3.7 nm. The FIIR analysis depicted that the presence of a variety of new basic functional groups on the modified CMK-3 surface. Several effect variables of pH, dye concentration and temperature were studied. The pseudo second-order model showed the fitter well to agree with the kinetic data. The experimental data were analyzed by the Langmuir and Freundlich models, with the latter found to closely the isotherm model. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The results show that CMK-3 using ammonia gas modified by thermal treatment system is an effective method to improvement capacity as it shows the highest adsorption capacity of AB1, as compared to the unmodified CMK-3 and the bamboo-based carbon, respectively.

  20. Kinetics and adsorption isotherm of lactic acid from fermentation broth onto activated charcoal

    Directory of Open Access Journals (Sweden)

    Seankham Soraya

    2017-01-01

    Full Text Available Activated charcoal was applied for the recovery of lactic acid in undissociated form from fermentation broth. Lactic acid was obtained from the fermentation of Lactobacillus casei TISTR 1340 using acid hydrolyzed Jerusalem artichoke as a carbon source. The equilibrium adsorption isotherm and kinetics for the lactic acid separation were investigated. The experimental data for lactic acid adsorption from fermentation broth were best described by the Freundlich isotherm and the pseudo-second order kinetics with R2 values of 0.99. The initial adsorption rate was 41.32 mg/g⋅min at the initial lactic acid concentration of 40 g/L.

  1. Adsorption of Reactive Blue 171 from Aqueous Solution using Low Cost Activated Carbon Prepared from Agricultural Solid Waste: Albizia amara

    Directory of Open Access Journals (Sweden)

    K. Anitha

    2015-07-01

    Full Text Available The adsorption of Reactive Blue 171 (Reactive Dye from aqueous solution using activated carbon prepared from Albizia amara pod shell waste as an adsorbent have been carried out. The experimental adsorption data fitted reasonably well to Langmuir and Freundlich adsorption isotherms. Kinetic parameters as a function of Initial dye concentration have been calculated and the kinetic data were substituted in Pseudo First Order, Elovich and Pseudo Second order equations. A probable explanation is offered to account for the results of kinetic study. The thermodynamic parameter enthalpy change (∆H suggests the exothermic nature of absorption of Reactive Blue 171 onto activated Albizia amara pod shell waste carbon.

  2. [CoCuMnOx Photocatalyzed Oxidation of Multi-component VOCs and Kinetic Analysis].

    Science.gov (United States)

    Meng, Hai-long; Bo, Long-li; Liu, Jia-dong; Gao, Bo; Feng, Qi-qi; Tan, Na; Xie, Shuai

    2016-05-15

    Solar energy absorption coating CoCuMnOx was prepared by co-precipitation method and applied to photodegrade multi- component VOCs including toluene, ethyl acetate and acetone under visible light irradiation. The photocatalytic oxidation performance of toluene, ethyl acetate and acetone was analyzed and reaction kinetics of VOCs were investigated synchronously. The research indicated that removal rates of single-component toluene, ethyl acetate and acetone were 57%, 62% and 58% respectively under conditions of 400 mg · m⁻³ initial concentration, 120 mm illumination distance, 1 g/350 cm² dosage of CoCuMnOx and 6 h of irradiation time by 100 W tungsten halogen lamp. Due to the competition among different VOCs, removal efficiencies in three-component mixture were reduced by 5%-26% as compared with single VOC. Degradation processes of single-component VOC and three-component VOCs both fitted pseudo first order reaction kinetics, and kinetic constants of toluene, ethyl acetate and acetone were 0.002, 0.002 8 and 0.002 33 min⁻¹ respectively under single-component condition. Reaction rates of VOCs in three-component mixture were 0.49-0.88 times of single components.

  3. Kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain from aqueous solutions

    International Nuclear Information System (INIS)

    Li Qingzhu; Chai Liyuan; Yang Zhihui; Wang Qingwei

    2009-01-01

    Spent grain, a main by-product of the brewing industry, is available in large quantities, but its main application has been limited to animal feeding. Nevertheless, in this study, spent grain modified with 1 M NaCl solution as a novel adsorbent has been used for the adsorption of Pb(II) in aqueous solutions. Isotherms, kinetics and thermodynamics of Pb(II) adsorption onto modified spent grain were studied. The equilibrium data were well fitted with Langmuir, Freundlich and Dubinin-Radushkevick (D-R) isotherm models. The kinetics of Pb(II) adsorption followed pseudo-second-order model, using the rate constants of pseudo-second-order model, the activation energy (E a ) of Pb(II) adsorption was determined as 12.33 kJ mol -1 according to the Arrhenius equation. Various thermodynamic parameters such as ΔG ads , ΔH ads and ΔS ads were also calculated. Thermodynamic results indicate that Pb(II) adsorption onto modified spent grain is a spontaneous and endothermic process. Therefore, it can be concluded that modified spent grain as a new effective adsorbent has potential for Pb(II) removal from aqueous solutions.

  4. Evaluation of the potential cationic dye removal using adsorption by graphene and carbon nanotubes as adsorbents surfaces

    Directory of Open Access Journals (Sweden)

    Akbar Elsagh

    2017-05-01

    Full Text Available We are employed in the present study of single-walled carbon nanotubes (SWCNTs, carboxylate group functionalized single-walled carbon nanotubes (SWCNT-COOH, graphene (G and graphene oxide (GO as alternative adsorbents for the removal of cationic dye Basic Red 46 (BR 46, from aqueous solution. Various physico-chemical parameters were studied such as electrical conductivity behaviors, contact time, solution pH, and dye concentration. The experimental results show that SWCNTs, SWCNT-COOH, G and GO are promising adsorbents for removing BR 46. The adsorption equilibrium data were analyzed using various adsorption isotherms, and the results have shown that adsorption behavior of BR 46 could be described reasonably well by the Langmuir isotherm. Results showed that the removal of BR 46 increased with increasing initial dye concentration, contact time and pH. Adsorption kinetics data were modeled using the pseudo-first and pseudo-second order, and intra-particle diffusion models. Results show that the pseudo-first order kinetic model for SWCNTs, SWCNT-COOH and the pseudo-second order for G and GO were found to correlate the experimental data well.

  5. Valorization of two waste streams into activated carbon and studying its adsorption kinetics, equilibrium isotherms and thermodynamics for methylene blue removal

    Directory of Open Access Journals (Sweden)

    Zeid Abdullah AlOthman

    2014-12-01

    Full Text Available Wastes must be managed properly to avoid negative impacts that may result. Open burning of waste causes air pollution which is particularly hazardous. Flies, mosquitoes and rats are major problems in poorly managed surroundings. Uncollected wastes often cause unsanitary conditions and hinder the efforts to keep streets and open spaces in a clean and attractive condition. During final disposal methane is generated, it is much more effective than carbon dioxide as a greenhouse gas, leading to climate change. Therefore, this study describes the possible valorization of two waste streams into activated carbon (AC with added value due to copyrolysis. High efficiency activated carbon was prepared by the copyrolysis of palm stem waste and lubricating oil waste. The effects of the lubricating oil waste to palm stem ratio and the carbonization temperature on the yield and adsorption capacity of the activated carbon were investigated. The results indicated that the carbon yield depended strongly on both the carbonization temperature and the lubricating oil to palm stem ratio. The efficiency of the adsorption of methylene blue (MB onto the prepared carbons increased when the lubricating oil to palm stem ratio increased due to synergistic effect. The effects of pH, contact time, and the initial adsorbate concentration on the adsorption of methylene blue were investigated. The maximum adsorption capacity (128.89 mg/g of MB occurred at pH 8.0. The MB adsorption kinetics were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The results indicated that the adsorption of MB onto activated carbon is best described using a second order kinetic model. Adsorption data are well fitted with Langmuir and Freundlich isotherms. The thermodynamic parameters; ΔG°, ΔH° and ΔS° indicate that the adsorption is spontaneous and endothermic.

  6. Copper removal by algae Gelidium, agar extraction algal waste and granulated algal waste: kinetics and equilibrium.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2008-03-01

    Biosorption of copper ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). The effects of contact time, pH, ionic strength (IS) and temperature on the biosorption process have been studied. Equilibrium data follow both Langmuir and Langmuir-Freundlich models. The parameters of Langmuir equilibrium model were: q(max)=33.0mgg(-1), K(L)=0.015mgl(-1); q(max)=16.7mgg(-1), K(L)=0.028mgl(-1) and q(max)=10.3mgg(-1), K(L)=0.160mgl(-1) respectively for Gelidium, algal waste and composite material at pH=5.3, T=20 degrees C and IS=0.001M. Increasing the pH, the number of deprotonated active sites increases and so the uptake capacity of copper ions. In the case of high ionic strengths, the contribution of the electrostatic component to the overall binding decreases, and so the uptake capacity. The temperature has little influence on the uptake capacity principally for low equilibrium copper concentrations. Changes in standard enthalpy, Gibbs energy and entropy during biosorption were determined. Kinetic data at different solution pH (3, 4 and 5.3) were fitted to pseudo-first-order and pseudo-second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model, which successfully predicts Cu(II) concentration profiles.

  7. KINETICS OF THE PHOTOCATALYTIC DEGRADATION OF SELECTED ORGANIC MICROPOLLUTANTS IN THE WATER ENVIROMENT

    Directory of Open Access Journals (Sweden)

    Edyta Anna Kudlek

    2017-04-01

    Full Text Available The paper presents an assessment of the removal degree of selected polycyclic aromatic hydrocarbons (anthracene, benzo(apyrene, xenoestrogens (octylphenol, pentachlorophenol and pharmaceutical compounds (diclofenac in the process of heterogeneous photocatalysis of their water solutions, which were prepared on the base of deionized water. Titanium dioxide at a dose of 100 mg/dm3 was used as a photocatalyst of the process. The kinetics of the process was determined based on the Langmuir-Hinsherlwood equation, assuming the pseudo-first-order reaction of micropollutants decomposition. Furthermore a toxicological analysis of water samples of test compounds was performed by the use of the Microtox® test. It has been found that the micropollutant concentrations decreased with the increase of process time and their removal degree after 60 minutes exceeds 90%. The analysis of the proces kinetic showed that the oxidation of the compounds occurred with the greatest intensity in the first stage of the process up to 10 min. The preformed toxicological assessment confirmed the incomplete decomposition of pollutants and the generation of by-products, which contribute to the increase of the toxicity of treated water solutions.

  8. On the analysis of glow curves with the general order kinetics: Reliability of the computed trap parameters

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, F. [Facultad de Ingeniería (UNCPBA) and CIFICEN (UNCPBA – CICPBA – CONICET), Av. del Valle 5737, 7400 Olavarría (Argentina); Santiago, M.; Martinez, N.; Marcazzó, J.; Molina, P.; Caselli, E. [Instituto de Física Arroyo Seco (UNCPBA) and CIFICEN (UNCPBA – CICPBA – CONICET), Pinto 399, 7000 Tandil (Argentina)

    2017-04-15

    Nowadays the most employed kinetics for analyzing glow curves is the general order kinetics (GO) proposed by C. E. May and J. A. Partridge. As shown in many articles this kinetics might yield wrong parameters characterizing trap and recombination centers. In this article this kinetics is compared with the modified general order kinetics put forward by M. S. Rasheedy by analyzing synthetic glow curves. The results show that the modified kinetics gives parameters, which are more accurate than that yield by the original general order kinetics. A criterion is reported to evaluate the accuracy of the trap parameters found by deconvolving glow curves. This criterion was employed to assess the reliability of the trap parameters of the YVO{sub 4}: Eu{sup 3+} compounds.

  9. Transition state kinetics of Hg(II) adsorption at gibbsite-water interface

    International Nuclear Information System (INIS)

    Weerasooriya, Rohan; Tobschall, Heinz J.; Seneviratne, Wasana; Bandara, Atula

    2007-01-01

    Kinetics of adsorption plays a pivotal factor in determining the bio-availability and mobility of Hg(II) in the environment. The kinetics of Hg(II) adsorption on gibbsite was examined as a function of pH, temperature and electrolyte type. Adsorption of Hg(II) was highly non-linear where the rate of Hg(II) retention was rapid initially and was followed by gradual or somewhat slow retention behavior with increasing contact time. The respective rate constants designated as k 1 (S-1: fast step) and k 2 (S-2: slow step). Always k 1 follows the order: k 1 ClO 4 >=k 1 (NO 3 ) 4 >>k 1 Cl . Such a relationship was not observed for the S-2 route. A two-step reaction model with pseudo-first order kinetics successfully described the adsorption rates of Hg(II) on gibbsite. Arrhenius and Erying models determined the thermodynamic parameters at activation states, which correspond to S-1 and S-2 routes. In a given system, always the activation energies showed a decrease with the pH. Gibbs free energy (ΔG numbersign ), enthalpy (ΔH numbersign ), and entropy (ΔS numbersign ) values of activation states were almost similar both in NaClO 4 and NaNO 3 which signal a similar Hg(II) adsorptive mechanism on gibbsite. The configurations of different Hg(II)-surface complexes were elucidated by transmission vibration spectroscopy

  10. Role of Ru(IlI) as an inhibitor in oxidation of lactose by (Cu(bipy)2)2+ in alkaline medium: spectrophotometric and kinetic studies

    International Nuclear Information System (INIS)

    Singh, Ashok Kumar; Singh, Manjula; Srivastava, Jaya; Rahmani, Shahla

    2013-01-01

    Kinetics of oxidation of lactose by (Cu(bipy) 2 ) 2+ in alkaline medium using Ru(III) as an inhibitor has been studied spectrophotometrically at 40 °C. The studies show that the rate of the reaction is zero order with respect to (Cu(bipy) 2 ) 2+ and first order with respect to (lactose). The order of reaction is found to be two at low concentrations of OH - (from 1.48×10 5 to 3.47×10 5 M) and less than two at its high concentrations (from 4.27×10 5 to 6.31×10 5 M). There is a substantial decrease in the pseudo-zero order rate constant with increase in the concentration of Ru(III) chloride, indicating the role of Ru(III) chloride as an inhibitor. Decrease in the rate with increase in dielectric constant of the medium is observed, while ionic strength of the medium and bipyridyl concentration has no influence on the rate. Based on kinetic data and spectrophotometric evidences, a suitable mechanism is proposed for the studied reaction. (author)

  11. Reaction kinetics of resveratrol with thiyl and alkoxyl radicals

    International Nuclear Information System (INIS)

    Dzeba, I.; Mihaljevic, B.

    2011-01-01

    Complete text of publication follows. Plant derived resveratrol (trans-3,5,4'-trihydroxystilbene) possesses a broad spectrum of biological activities, one of them are very well known its antioxidative properties. Our work aims to provide kinetic data with regard to the reactivity of resveratrol with uninvestigated short-lived bioradicals, identified as mediators in oxidative lipid degradation processes. Radicals of our interest are alkoxyl radicals, well known propagators of the chain free radical reactions in lipids, and thiyl radicals which protect lipids from their degradation pathway, but at the same time cause the isomerization of the double bonds. In order to investigate these reactions of resveratrol laser flash photolysis was used. On the basis of competitive kinetics the rate constants were determined under pseudo-first order conditions in acetonitrile solutions at room temperature. Thiyl radicals were generated indirectly in solution containing 1-octadecanthiol and photosensitive benzophenone in acetonitrile using the light pulses at 347 nm from ruby laser. Tert-butoxyl radicals were generated directly by peroxide bond cleavage from di-tert-butyl peroxide in acetonitrile by light pulses of Nd:YAG at 355 nm, and ruby at 347 nm. Obtained rate constants for the reactions of resveratrol and radicals generated by laser flash photolysis will be summarized and compared with rare literature data for the rate constants of investigated reactions of resveratrol and other radicals generated by pulse radiolysis.

  12. Evaluating the potential of a Nigerian soil as an adsorbent for tartrazine dye: Isotherm, kinetic and thermodynamic studies

    Directory of Open Access Journals (Sweden)

    M.O. Dawodu

    2016-12-01

    Full Text Available The release of toxic tartrazine dye from industrial effluent into the environment is of public health concern. This study therefore aimed at the removal of tartrazine from solution using Nigerian soil as a low cost potential sorbent. The sorbent was characterized by the Fourier transform infrared spectrophotometer and Scanning electron microscope. Batch sorption methodology was used to investigate the effect of pH, adsorbent dose, dye concentration, contact time and temperature. The sorbent recorded a Brunauer, Emmett and Teller surface area of 9.8 m2/g and pH point of zero charge of 5.8. Optimum sorption was achieved at pH 2.0, contact time of 120 min, adsorbent dose of 0.05 g and tartrazine concentration of 50 mg/L. Equilibrium isotherms were analyzed by the Langmuir, Freundlich, Scatchard and Flory-Huggins isotherm models. The pseudo-first-order, pseudo-second-order, Elovich and Bangham models were used for kinetic analysis. Thermodynamics revealed a spontaneous, feasible and endothermic sorption process. The soil was found to be suitable as a low cost sorbent for tartrazine from contaminated solution.

  13. Degradation of oxcarbazepine by UV-activated persulfate oxidation: kinetics, mechanisms, and pathways.

    Science.gov (United States)

    Bu, Lingjun; Zhou, Shiqing; Shi, Zhou; Deng, Lin; Li, Guangchao; Yi, Qihang; Gao, Naiyun

    2016-02-01

    The degradation kinetics and mechanism of the antiepileptic drug oxcarbazepine (OXC) by UV-activated persulfate oxidation were investigated in this study. Results showed that UV/persulfate (UV/PS) process appeared to be more effective in degrading OXC than UV or PS alone. The OXC degradation exhibited a pseudo-first order kinetics pattern and the degradation rate constants (k obs) were affected by initial OXC concentration, PS dosage, initial pH, and humic acid concentration to different degrees. It was found that low initial OXC concentration, high persulfate dosage, and initial pH enhanced the OXC degradation. Additionally, the presence of humic acid in the solution could greatly inhibit the degradation of OXC. Moreover, hydroxyl radical (OH•) and sulfate radical (SO4 (-)••) were identified to be responsible for OXC degradation and SO4 (-)• made the predominant contribution in this study. Finally, major intermediate products were identified and a preliminary degradation pathway was proposed. Results demonstrated that UV/PS system is a potential technology to control the water pollution caused by emerging contaminants such as OXC.

  14. Phototransformation of amlodipine: degradation kinetics and identification of its photoproducts.

    Directory of Open Access Journals (Sweden)

    Anna Jakimska

    Full Text Available Nowadays, monitoring focuses on the primary compounds and does not include degradation products formed during various biological and chemical processes. Transformation products may have the same effects to human health and the environment or sometimes they can be more toxic than the parent compound. Unfortunately, knowledge about the formation of degradation products is still limited, however, can be very important for the environmental risk assessment. Firstly, the photodegradation kinetic of amlodipine was investigated in two experimental conditions: during the exposure to solar radiation and during the exposure to the light emitted by the xenon lamp. In all cases degradation of amlodipine followed a pseudo-first-order kinetics. In the next step, identification of transformation products of amlodipine formed during the exposure to xenon lamp irradiation was performed using ultra high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS. As a result sixteen photoproducts were identified, their structures were elucidated and ultimately the transformation pathway was proposed. Fifteen compounds (out of 16 photoproducts were newly identified and reported here for the first time; some of those compounds were formed from the first photoproduct, amlodipine pyridine derivative. Several analytes were formed only in acidic or basic conditions. Furthermore, the occurrence of amlodipine and its identified degradation products was investigated in environmental waters. Only one out of 16 compounds was found in wastewater effluent. The possibility of the sorption of examined analytes to sewage sludge particles was discussed based on QSAR.

  15. Pseudo-populations a basic concept in statistical surveys

    CERN Document Server

    Quatember, Andreas

    2015-01-01

    This book emphasizes that artificial or pseudo-populations play an important role in statistical surveys from finite universes in two manners: firstly, the concept of pseudo-populations may substantially improve users’ understanding of various aspects in the sampling theory and survey methodology; an example of this scenario is the Horvitz-Thompson estimator. Secondly, statistical procedures exist in which pseudo-populations actually have to be generated. An example of such a scenario can be found in simulation studies in the field of survey sampling, where close-to-reality pseudo-populations are generated from known sample and population data to form the basis for the simulation process. The chapters focus on estimation methods, sampling techniques, nonresponse, questioning designs and statistical disclosure control.This book is a valuable reference in understanding the importance of the pseudo-population concept and applying it in teaching and research.

  16. Determining Li+-Coupled Redox Targeting Reaction Kinetics of Battery Materials with Scanning Electrochemical Microscopy.

    Science.gov (United States)

    Yan, Ruiting; Ghilane, Jalal; Phuah, Kia Chai; Pham Truong, Thuan Nguyen; Adams, Stefan; Randriamahazaka, Hyacinthe; Wang, Qing

    2018-02-01

    The redox targeting reaction of Li + -storage materials with redox mediators is the key process in redox flow lithium batteries, a promising technology for next-generation large-scale energy storage. The kinetics of the Li + -coupled heterogeneous charge transfer between the energy storage material and redox mediator dictates the performance of the device, while as a new type of charge transfer process it has been rarely studied. Here, scanning electrochemical microscopy (SECM) was employed for the first time to determine the interfacial charge transfer kinetics of LiFePO 4 /FePO 4 upon delithiation and lithiation by a pair of redox shuttle molecules FcBr 2 + and Fc. The effective rate constant k eff was determined to be around 3.70-6.57 × 10 -3 cm/s for the two-way pseudo-first-order reactions, which feature a linear dependence on the composition of LiFePO 4 , validating the kinetic process of interfacial charge transfer rather than bulk solid diffusion. In addition, in conjunction with chronoamperometry measurement, the SECM study disproves the conventional "shrinking-core" model for the delithiation of LiFePO 4 and presents an intriguing way of probing the phase boundary propagations induced by interfacial redox reactions. This study demonstrates a reliable method for the kinetics of redox targeting reactions, and the results provide useful guidance for the optimization of redox targeting systems for large-scale energy storage.

  17. Phosphate cellulose with metaphosphoric acid for dye removal

    International Nuclear Information System (INIS)

    Silva, S.C.C.; Silva, F.C.; Lima, L.C.B.; Santos, M.R.M.C.; Osajima, J.A.; Silva Filho, E.C. da

    2014-01-01

    The chemical modification of cellulose is a suitable method used for producing value-added products, making them more efficient and selective for certain applications such as adsorption of dye. Thus the aim of this study was to modify the natural cellulose with metaphosphoric acid, characterized it through the techniques of FTIR and "3"1P NMR and applies it in the adsorption of brilliant green dye, evaluating the kinetic models of pseudo first-order and pseudo second-order and the theoretical models of the Langmuir, Freundlich and Temkin isotherms. The characterizations demonstrated the effectiveness of the modification, the maximum adsorption capacity was 150.0 mg g-1, adjusting better to the kinetic model of pseudo-second order and the theoretical model of Temkin, with the adsorbent showing efficient for removal of brilliant green dye. (author)

  18. Removal of Methylene Blue from Aqueous Solution by Activated Carbon Prepared from Pea Shells (Pisum sativum

    Directory of Open Access Journals (Sweden)

    Ünal Geçgel

    2013-01-01

    Full Text Available An activated carbon was prepared from pea shells and used for the removal of methylene blue (MB from aqueous solutions. The influence of various factors such as adsorbent concentration, initial dye concentration, temperature, contact time, pH, and surfactant was studied. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. The adsorption isotherm was found to follow the Langmuir model. The monolayer sorption capacity of activated carbon prepared from pea shell for MB was found to be 246.91 mg g−1 at 25 ∘C. Two simplified kinetic models including pseudo-first-order and pseudo-second-order equation were selected to follow the adsorption processes. Kinetic studies showed that the adsorption followed pseudo-second-order kinetic model. Various thermodynamic parameters such as , , and were evaluated. The results in this study indicated that activated carbon prepared from pea shell could be employed as an adsorbent for the removal of MB from aqueous solutions.

  19. Magnesite tailing as low-cost adsorbent for the removal of copper (II) ions from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Kipcak, Ilker; Isiyel, Turgut Giray [Eskisehir Osmangazi University, Eskisehir (Turkmenistan)

    2015-08-15

    The removal of Cu(II) ions from aqueous solution using magnesite tailing was investigated. Batch kinetic and equilibrium experiments were conducted to study the effects of initial pH, adsorbent dosage, contact time, initial concentration and temperature. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to study the kinetic data. The experimental data were best fitted by the pseudo-second-order kinetic model. The linear Langmuir and Freundlich adsorption equations were applied to describe the equilibrium isotherms. The equilibrium data fit very well the Langmuir model, and the maximum adsorption capacity was estimated as 12.18mg/g at 45 .deg. C. Thermodynamic parameters such as enthalpy change (ΔH{sup o}), free energy change (ΔG{sup o}) and entropy change (ΔS{sup o}) were calculated, and it was found that the adsorption process was spontaneous and endothermic. The results showed that magnesite tailing is a suitable adsorbent for the removal of Cu(II) ions from aqueous solutions.

  20. Nitrogen Removal in a Horizontal Subsurface Flow Constructed Wetland Estimated Using the First-Order Kinetic Model

    Directory of Open Access Journals (Sweden)

    Lijuan Cui

    2016-11-01

    Full Text Available We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW in Beijing, China, for two years. We simulated the area-based constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N removal rate, N load, seasonal variations in the N removal rate, and environmental factors—such as the area-based constant, temperature, and dissolved oxygen (DO. The effluent ammonia (NH4+-N and nitrate (NO3−-N concentrations were significantly lower than the influent concentrations (p < 0.01, n = 38. The NO3−-N load was significantly correlated with the removal rate (R2 = 0.96, p < 0.01, but the NH4+-N load was not correlated with the removal rate (R2 = 0.02, p > 0.01. The area-based constants of NO3−-N and NH4+-N at 20 °C were 27 ± 26 (mean ± SD and 14 ± 10 m∙year−1, respectively. The temperature coefficients for NO3−-N and NH4+-N were estimated at 1.004 and 0.960, respectively. The area-based constants for NO3−-N and NH4+-N were not correlated with temperature (p > 0.01. The NO3−-N area-based constant was correlated with the corresponding load (R2 = 0.96, p < 0.01. The NH4+-N area rate was correlated with DO (R2 = 0.69, p < 0.01, suggesting that the factors that influenced the N removal rate in this wetland met Liebig’s law of the minimum.

  1. Kinetics in radiation chemistry

    International Nuclear Information System (INIS)

    Hummel, A.

    1987-01-01

    In this chapter the authors first briefly review the kinetics of first- and second-order processes for continuous and pulsed irradiation, without taking the effects of nonhomogeneous formation of the species into consideration. They also discuss diffusion controlled reactions under conditions where interactions of more than two particles can be neglected, first the kinetics of the diffusion-controlled reaction of randomly generated species (homogeneous reaction) and then that of isolated pairs of reactants. The latter is often called geminate kinetics when dealing with pairs of oppositely charged species; they shall use this term for the kinetics of isolated pairs in general. In the last section they discuss briefly the kinetics of groups of more than two reactants

  2. Pseudo-differential operators on manifolds with singularities

    CERN Document Server

    Schulze, B-W

    1991-01-01

    The analysis of differential equations in domains and on manifolds with singularities belongs to the main streams of recent developments in applied and pure mathematics. The applications and concrete models from engineering and physics are often classical but the modern structure calculus was only possible since the achievements of pseudo-differential operators. This led to deep connections with index theory, topology and mathematical physics. The present book is devoted to elliptic partial differential equations in the framework of pseudo-differential operators. The first chapter contains the Mellin pseudo-differential calculus on R+ and the functional analysis of weighted Sobolev spaces with discrete and continuous asymptotics. Chapter 2 is devoted to the analogous theory on manifolds with conical singularities, Chapter 3 to manifolds with edges. Employed are pseudo-differential operators along edges with cone-operator-valued symbols.

  3. Removal of ammonium ion from aqueous solution using natural Turkish clinoptilolite

    International Nuclear Information System (INIS)

    Karadag, Dogan; Koc, Yunus; Turan, Mustafa; Armagan, Bulent

    2006-01-01

    A study on ion exchange kinetics and equilibrium isotherms of ammonium ion on natural Turkish clinoptilolite (zeolite) was conducted using a batch experiment technique. The effects of relevant parameters, such as temperature, contact time and initial ammonium (NH 4 + ) concentration were examined, respectively. The pseudo first-order, pseudo second-order kinetic models and intraparticle diffusion model were used to describe the kinetic data. The pseudo second-order kinetic model provided excellent kinetic data fitting (R 2 > 0.990) and intraparticle diffusion effects ammonium uptake. The Langmuir and Freundlich models were applied to describe the equilibrium isotherms for ammonium uptake and the Langmuir model agrees very well with experimental data. Thermodynamic parameters such as change in free energy (ΔG 0 ), enthalpy (ΔH 0 ) and entropy (ΔS 0 ) were also determined. An examination of the thermodynamic parameters shows that the exchange of ammonium ion by clinoptilolite is a process occurring spontaneously and physical in nature at ambient conditions (25 deg. C). The process is also found to be exothermic. The results indicate that there is a significant potential for the natural Turkish clinoptilolite as an adsorbent material for ammonium removal from aqueous solutions

  4. 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

  5. Direct determination of the rate constant of propagation by pseudo-stationary polymerization technique: screening investigation for the (implicit) penultimate effect

    International Nuclear Information System (INIS)

    Schnoll-Bitai, I.; Friedrich Olaj, O.; Liu Song Yu

    1999-01-01

    The systems styrene-p-methylstyrene, styrene-p-chlorostyrene, methyl methacrylate-p-methylstyrene and methyl methacrylate-p-chlorostyrene were polymerized under pseudo-stationary conditions (rotating sector or pulsed laser) at 25 degree C, 40 degree C and 50 degree C. The respective molecular weight distributions measured by GPC were analysed in order to derive directly the phenomenological rate constant of propagation, κ sub ρ. Copolymer compositions as a function of monomer feed could be described by the terminal model, whereas the kinetic results could only be interpreted in terms of the restricted penultimate model

  6. Eros in the first century’s Christian theology. Pseudo-Dionysius the Areopagite

    Directory of Open Access Journals (Sweden)

    Mircea Adrian Marica

    2015-11-01

    Full Text Available For among most contemporaries, the concept of Eros seems to have nothing to do with Christianity. Sifting through the psychoanalysis of sexual fantasy, theologically it says nothing. Our study gives reasons showing that for theologians since the dawn of the Christian era, Eros-love plays a fundamental role.. The connotations of this concept, however, are different from those of today, when its sensory meaning is more restricted to sexuality. Greek theologians of the first centuries after Christ, taught the concept of Plato enshrined as a unifying enthusiasm, the attraction of inferior to superior states, as “hungry and thirsty” for something continuously higher, developing, and enriching the connotation. The work of Dionysius ((Pseudo Areopagite, the Idea of Good, leads us step by step up the ascent of the erotically chaste, and is identified with the One-God, who is the very source of love. Consequently, Eros-love originates from God, Eros- love being not only an ascending but firstly a descending love, which calls for a reciprocal communion.

  7. Kinetics of soybean oil epoxidation with peracetic acid formed in situ in the presence of an ion exchange resin: Pseudo-homogeneous model

    Directory of Open Access Journals (Sweden)

    Janković Milovan

    2017-01-01

    Full Text Available A kinetic model was proposed for the epoxidation of vegetable oils with peracetic acid formed in situ from acetic acid and hydrogen peroxide in the presence of an acidic ion exchange resin as a catalyst. The model is pseudo-homogeneous with respect to the catalyst. Besides the main reactions of peracetic acid and epoxy ring formation, the model takes into account the side reaction of epoxy ring opening with acetic acid. The partitioning of acetic acid and peracetic acid between the aqueous and organic phases and the change in the phases’ volumes during the process were considered. The temperature dependency of the apparent reaction rate coefficients is described by a reparameterized Arrhenius equation. The constants in the proposed model were estimated by fitting the experimental data obtained for the epoxidations of soybean oil conducted under defined reaction conditions. The highest epoxy yield of 87.73% was obtained at 338 K when the mole ratio of oil unsaturation:acetic acid:hydrogen peroxide was 1:0.5:1.35 and when the amount of the catalyst Amberlite IR-120H was 4.04 wt.% of oil. Compared to the other reported pseudo-homogeneous models, the model proposed in this study better correlates the change of double bond and epoxy group contents during the epoxidation process. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45022

  8. Kinetic modeling of the biosorption of Cd2+ ions from aqueous solutions onto Eichhornia crassipes roots using potentiometry: low-cost alternative to conventional methods

    Directory of Open Access Journals (Sweden)

    Carolina Martínez-Sánchez

    2013-01-01

    Full Text Available This work presents the use of potentiometric measurements for kinetic studies of biosorption of Cd2+ ions from aqueous solutions on Eichhornia crassipes roots. The open circuit potential of the Cd/Cd2+ electrode of the first kind was measured during the bioadsorption process. The amount of Cd2+ ions accumulated was determined in real time. The data were fit to different models, with the pseudo-second-order model proving to be the best in describing the data. The advantages and limitations of the methodology proposed relative to the traditional method are discussed.

  9. Remoção de azul de metileno de solução aquosa usando zeólitas sintetizadas com amostras de cinzas de carvão diferentes Removal of methylene blue from aqueous solution using zeolite synthesized from different coal fly ashes samples

    Directory of Open Access Journals (Sweden)

    Denise Alves Fungaro

    2009-01-01

    Full Text Available Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using zeolites synthesized from fly ashes as an adsorbent. The adsorbents were characterized by XFR, XRD and SEM. Nearly 90 min of contact time are found to be sufficient for the adsorption of dye to reach equilibrium. Equilibrium data have been analyzed using Langmuir and Freundlich isotherms and the results were found to be well represented by the Freundlich isotherm equation. Adsorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics.

  10. Pseudo-periodic maps and degeneration of Riemann surfaces

    CERN Document Server

    Matsumoto, Yukio

    2011-01-01

    The first part of the book studies pseudo-periodic maps of a closed surface of genus greater than or equal to two. This class of homeomorphisms was originally introduced by J. Nielsen in 1944 as an extension of periodic maps. In this book, the conjugacy classes of the (chiral) pseudo-periodic mapping classes are completely classified, and Nielsen’s incomplete classification is corrected. The second part applies the results of the first part to the topology of degeneration of Riemann surfaces. It is shown that the set of topological types of all the singular fibers appearing in one-parameter holomorphic families of Riemann surfaces is in a bijective correspondence with the set of conjugacy classes of the pseudo-periodic maps of negative twists. The correspondence is given by the topological monodromy.

  11. Pseudo-Glassification Material for G-Demption

    Energy Technology Data Exchange (ETDEWEB)

    Casella, Andrew M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Buck, Edgar C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gates, Robert O. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Riley, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    G-Demption, LLC has requested that PPNL provide design input for a “pseudo-glassification” process associated with their proposed technology for generating gamma irradiation stations from used nuclear fuel. The irradiation design currently consists of an aluminum enclosure designed to allow for proper encapsulation of and heat flow from a used fuel rod while minimally impacting the streaming of gamma rays from the fuel. In order to make their design more robust, G-Demption is investigating the benefits of backfilling this aluminum enclosure with a setting material once the used fuel rod is properly placed. This process has been initially referred to as “pseudo-glassification”, and strives not to impact heat transport or gamma streaming from the used fuel rod while providing increased fuel rod protection and fission gas retention. PNNL has compiled an internal material evaluation and discussion for the “pseudo-glassification” process in this report.

  12. Non-isothermal cold crystallization kinetics of poly(3-hydoxybutyrate) filled with zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ries, Andreas, E-mail: ries750@yahoo.com.br [Electrical Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil); Canedo, Eduardo L. [Materials Engineering Department, Federal University of Campina Grande, Campina Grande, PB 58429-900 (Brazil); Souto, Cícero R. [Electrical Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil); Wellen, Renate M.R. [Materials Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil)

    2016-08-10

    Highlights: • Non-isothermal cold crystallization kinetics of PHB filled with ZnO is presented. • Pseudo-Avrami model is best for describing an individual crystallization condition. • Mo model is allows to judge the kinetics of a condition untested in this work. • ZnO affects the kinetics irregularly. - Abstract: The non-isothermal cold crystallization kinetics of poly(3-hydroxybutyrate) (PHB) and PHB-ZnO composites, with ZnO content of 1%, 5% and 10% per weight, was investigated at different heating rates (5, 7.5, 10, 15, 20 and 30 °C/min) using differential scanning calorimetry. Both, Kissinger and Friedman activation energies predict correctly the slowest and fastest crystallizing composition. It was further found, that ZnO can neither be classified as a crystallization accelerator, nor as a crystallization inhibitor; its action is strongly concentration dependent. The empirical Pseudo-Avrami model has the best overall capability for fitting the experimental kinetic data. However, since the Pseudo-Avrami exponent was found to vary irregularly with heating rate and filler content, this model should not be applied for kinetic predictions of an arbitrary composition or an untested heating rate. In such cases, Mo's model should be used.

  13. Determination of kinetic parameters of Phlomis bovei de Noé using thermogravimetric analysis.

    Science.gov (United States)

    Yahiaoui, Meriem; Hadoun, Hocine; Toumert, Idir; Hassani, Aicha

    2015-11-01

    This paper reports the pyrolysis study of Phlomis bovei biomass by thermogravimetric experiments in order to determine the thermal degradation behavior and kinetic parameters. The weight losses were found to occur in three stages. In the DTG thermograms, an increase of the heating rate tended to delay thermal degradation processes towards higher temperatures. The average values of activation energy and pre-exponential factor calculated from Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Kissinger methods are 134.83, 134.06, 223.31kJ/mol and 4.1610(13), 1.1810(10), 2.8110(11)/s, respectively. The three-pseudo-component method shows that the activation energy increases with increasing the heating rate for hemicellulose and cellulose while the activation energy of the lignin decreased with an increase of the heating rate. Predicted results and experimental data exhibit similar tendencies and the three pseudo-components model with n different from unity 1 is recommended as the most suitable for prediction of kinetic behavior of Phlomis bovei de Noé. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Pseudo-set framing.

    Science.gov (United States)

    Barasz, Kate; John, Leslie K; Keenan, Elizabeth A; Norton, Michael I

    2017-10-01

    Pseudo-set framing-arbitrarily grouping items or tasks together as part of an apparent "set"-motivates people to reach perceived completion points. Pseudo-set framing changes gambling choices (Study 1), effort (Studies 2 and 3), giving behavior (Field Data and Study 4), and purchase decisions (Study 5). These effects persist in the absence of any reward, when a cost must be incurred, and after participants are explicitly informed of the arbitrariness of the set. Drawing on Gestalt psychology, we develop a conceptual account that predicts what will-and will not-act as a pseudo-set, and defines the psychological process through which these pseudo-sets affect behavior: over and above typical reference points, pseudo-set framing alters perceptions of (in)completeness, making intermediate progress seem less complete. In turn, these feelings of incompleteness motivate people to persist until the pseudo-set has been fulfilled. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  15. Pseudo-spectral method using rotated staggered grid for elastic wave propagation in 3D arbitrary anisotropic media

    KAUST Repository

    Zou, Peng

    2017-05-10

    Staggering grid is a very effective way to reduce the Nyquist errors and to suppress the non-causal ringing artefacts in the pseudo-spectral solution of first-order elastic wave equations. However, the straightforward use of a staggered-grid pseudo-spectral method is problematic for simulating wave propagation when the anisotropy level is greater than orthorhombic or when the anisotropic symmetries are not aligned with the computational grids. Inspired by the idea of rotated staggered-grid finite-difference method, we propose a modified pseudo-spectral method for wave propagation in arbitrary anisotropic media. Compared with an existing remedy of staggered-grid pseudo-spectral method based on stiffness matrix decomposition and a possible alternative using the Lebedev grids, the rotated staggered-grid-based pseudo-spectral method possesses the best balance between the mitigation of artefacts and efficiency. A 2D example on a transversely isotropic model with tilted symmetry axis verifies its effectiveness to suppress the ringing artefacts. Two 3D examples of increasing anisotropy levels demonstrate that the rotated staggered-grid-based pseudo-spectral method can successfully simulate complex wavefields in such anisotropic formations.

  16. OXYGEN UPTAKE KINETICS DURING INCREMENTAL- AND DECREMENTAL-RAMP CYCLE ERGOMETRY

    Directory of Open Access Journals (Sweden)

    Fadıl Özyener

    2011-09-01

    Full Text Available The pulmonary oxygen uptake (VO2 response to incremental-ramp cycle ergometry typically demonstrates lagged-linear first-order kinetics with a slope of ~10-11 ml·min-1·W-1, both above and below the lactate threshold (ӨL, i.e. there is no discernible VO2 slow component (or "excess" VO2 above ӨL. We were interested in determining whether a reverse ramp profile would yield the same response dynamics. Ten healthy males performed a maximum incremental -ramp (15-30 W·min-1, depending on fitness. On another day, the work rate (WR was increased abruptly to the incremental maximum and then decremented at the same rate of 15-30 W.min-1 (step-decremental ramp. Five subjects also performed a sub-maximal ramp-decremental test from 90% of ӨL. VO2 was determined breath-by-breath from continuous monitoring of respired volumes (turbine and gas concentrations (mass spectrometer. The incremental-ramp VO2-WR slope was 10.3 ± 0.7 ml·min-1·W-1, whereas that of the descending limb of the decremental ramp was 14.2 ± 1.1 ml·min-1·W-1 (p < 0.005. The sub-maximal decremental-ramp slope, however, was only 9. 8 ± 0.9 ml·min-1·W-1: not significantly different from that of the incremental-ramp. This suggests that the VO2 response in the supra-ӨL domain of incremental-ramp exercise manifest not actual, but pseudo, first-order kinetics

  17. Utilization of cocoa pod husk waste as potential adsorbents for Remazol Brilliant Violet 5R removal

    International Nuclear Information System (INIS)

    Tan Tong Siang; Mohd Azmier Ahmad

    2010-01-01

    Removal of Remazol Brilliant Violet 5R (RBV5R) dye from aqueous solution by adsorption onto activated carbon produced from cocoa pod husk (CPH) waste was investigated. Adsorption isotherms were derived at 30 degree Celsius on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundlich models. Kinetics of adsorption was followed by in situ UV-spectroscopy and the data were treated according to pseudo-first-order and pseudo-second-order models. The fits of experimental data to these equations were examined. It was found that the adsorption process by RVB5R dye onto activated carbon (AC) follows the Freundlich and pseudo-first-order model. (author)

  18. Pseudo-random bit generator based on lag time series

    Science.gov (United States)

    García-Martínez, M.; Campos-Cantón, E.

    2014-12-01

    In this paper, we present a pseudo-random bit generator (PRBG) based on two lag time series of the logistic map using positive and negative values in the bifurcation parameter. In order to hidden the map used to build the pseudo-random series we have used a delay in the generation of time series. These new series when they are mapped xn against xn+1 present a cloud of points unrelated to the logistic map. Finally, the pseudo-random sequences have been tested with the suite of NIST giving satisfactory results for use in stream ciphers.

  19. Equilibrium, kinetics and mechanism of Au3+, Pd2+ and Ag+ ions adsorption from aqueous solutions by graphene oxide functionalized persimmon tannin.

    Science.gov (United States)

    Wang, Zhongmin; Li, Xiaojuan; Liang, Haijun; Ning, Jingliang; Zhou, Zhide; Li, Guiyin

    2017-10-01

    In this study, a novel bio-adsorbent (PT-GO) was prepared by functionalization persimmon tannin (PT) with graphene oxide (GO) and the effective adsorption behaviors of Au 3+ , Pd 2+ and Ag + ions from aqueous solution was investigated. The PT-GO was characterized by Fourier transform infrared spectrometer (FTIR), scanning electronic microscope (SEM), thermogravimetric analysis (TGA) and Zeta potential. Many influence factors such as pH value, bio-adsorbent dosage, initial concentration of metal ions and contact time were optimized. The maximum adsorption capacity for Au 3+ , Pd 2+ and Ag + was 1325.09mg/g, 797.66mg/g and 421.01mg/g, respectively. The equilibrium isotherm for the adsorption of Au 3+ and Ag + on PT-GO were found to obey the Langmuir model, while the Freundlich model fitted better for Pd 2+ . The adsorption process of Au 3+ , Pd 2+ presented relatively fast adsorption kinetics with pseudo-second-order equation as the best fitting model, while the pseudo-first-order kinetic model was suitable for describing the adsorption of Ag + . Combination of ion exchange, electrostatic interaction and physical adsorption was the mechanism for adsorption of Au 3+ , Pd 2+ and Ag + onto PT-GO bio-adsorbent. Therefore, the PT-GO bio-adsorbent would be an ideal adsorbent for removal of precious metal ions and broaden the potential applications of persimmon tannin in environmental research. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Thermodynamic, Kinetic, and Equilibrium Parameters for the Removal of Lead and Cadmium from Aqueous Solutions with Calcium Alginate Beads

    Directory of Open Access Journals (Sweden)

    Ruth Alfaro-Cuevas-Villanueva

    2014-01-01

    Full Text Available The sorption of cadmium (Cd and lead (Pb by calcium alginate beads (CAB from aqueous solutions in batch systems was investigated. The kinetic and thermodynamic parameters, as well as the sorption capacities of CAB in each system at different temperatures, were evaluated. The rate of sorption for both metals was rapid in the first 10 minutes and reached a maximum in 50 minutes. Sorption kinetic data were fitted to Lagergren, pseudo-second-order and Elovich models and it was found that the second-order kinetic model describes these data for the two metals; comparing kinetic parameters for Cd and Pb sorption a higher kinetic rate (K2 for Pb was observed, indicating that the interaction between lead cations and alginate beads was faster than for cadmium. Similarly, isotherm data were fitted to different models reported in literature and it was found that the Langmuir-Freundlich (L-F and Dubinin-Radushkevich (D-R models describe the isotherms in all cases. CAB sorption capacity for cadmium was 27.4 mg/g and 150.4 mg/g for lead, at 25°C. Sorption capacities of Cd and Pb increase as temperature rises. According to the thermodynamic parameters, the cadmium and lead adsorption process was spontaneous and endothermic. It was also found that pH has an important effect on the adsorption of these metals by CAB, as more were removed at pH values between 6 and 7.

  1. First-Order Twistor Lifts

    Directory of Open Access Journals (Sweden)

    Simões BrunoAscenso

    2010-01-01

    Full Text Available The use of twistor methods in the study of Jacobi fields has proved quite fruitful, leading to a series of results. L. Lemaire and J. C. Wood proved several properties of Jacobi fields along harmonic maps from the two-sphere to the complex projective plane and to the three- and four-dimensional spheres, by carefully relating the infinitesimal deformations of the harmonic maps to those of the holomorphic data describing them. In order to advance this programme, we prove a series of relations between infinitesimal properties of the map and those of its twistor lift. Namely, we prove that isotropy and harmonicity to first order of the map correspond to holomorphicity to first order of its lift into the twistor space, relatively to the standard almost complex structures and . This is done by obtaining first-order analogues of classical twistorial constructions.

  2. First-Order Twistor Lifts

    Directory of Open Access Journals (Sweden)

    Bruno Ascenso Simões

    2010-01-01

    Full Text Available The use of twistor methods in the study of Jacobi fields has proved quite fruitful, leading to a series of results. L. Lemaire and J. C. Wood proved several properties of Jacobi fields along harmonic maps from the two-sphere to the complex projective plane and to the three- and four-dimensional spheres, by carefully relating the infinitesimal deformations of the harmonic maps to those of the holomorphic data describing them. In order to advance this programme, we prove a series of relations between infinitesimal properties of the map and those of its twistor lift. Namely, we prove that isotropy and harmonicity to first order of the map correspond to holomorphicity to first order of its lift into the twistor space, relatively to the standard almost complex structures J1 and J2. This is done by obtaining first-order analogues of classical twistorial constructions.

  3. Kinetic theory of oxygen isotopic exchange between minerals and water

    Science.gov (United States)

    Criss, R.E.; Gregory, R.T.; Taylor, H.P.

    1987-01-01

    Kinetic and mass conservation equations are used to describe oxygen isotopic exchange between minerals and water in "closed" and open hydrothermal systems. In cases where n coexisting mineral phases having different reaction rates are present, the exchange process is described by a system of n + 1 simultaneous differential equations consisting of n pseudo first-order rate equations and a conservation of mass equation. The simultaneous solutions to these equations generate curved exchange trajectories on ??-?? plots. Families of such trajectories generated under conditions allowing for different fluid mole fractions, different fluid isotopic compositions, or different fluid flow rates are connected by positive-sloped isochronous lines. These isochrons reproduce the effects observed in hydrothermally exchanged mineral pairs including 1) steep positive slopes, 2) common reversals in the measured fractionation factors (??), and 3) measured fractionations that are highly variable over short distances where no thermal gradient can be geologically demonstrated. ?? 1987.

  4. Removal of ammonium ions by laboratory-synthesized zeolite linde type A adsorption from water samples affected by mining activities in Ghana.

    Science.gov (United States)

    Kwakye-Awuah, Bright; Labik, Linus Kweku; Nkrumah, Isaac; Williams, Craig

    2014-03-01

    Ammonium ion adsorption by laboratory-synthesized zeolite (linde type A; LTA) was investigated in batch kinetics experiments. Synthesized zeolite LTA was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and particle size analysis. Water samples were taken from the Nyam and Tano rivers in Ghana, and 0.8 g of zeolite was added to 100 ml portions of each sample. Portions of the samples were withdrawn every 30 min for 150 min and the concentration of ammonia in each sample was determined. The removal efficiency of zeolite LTA was evaluated by retrieving the zeolite from the water samples and adding to a fresh sample to repeat the process. Equilibrium data were fitted by Langmuir and Freundlich isotherms. Maximum adsorption capacities were 72.99 mg g(-1) for samples from the River Nyam and 72.87 mg g(-1) for samples from the River Tano. The equilibrium kinetic data were analysed using adsorption kinetic models: pseudo-first order and pseudo-second order kinetic models. Linear regression was used to estimate the adsorption and kinetic parameters. The results showed that the adsorption followed pseudo-second order kinetics and suggest that zeolite LTA is a good adsorbent for the removal of nitrogen ammonia from water.

  5. Dye removal from wastewater using activated carbon developed from sawdust: adsorption equilibrium and kinetics.

    Science.gov (United States)

    Malik, P K

    2004-09-10

    Mahogany sawdust was used to develop an effective carbon adsorbent. This adsorbent was employed for the removal of direct dyes from spent textile dyeing wastewater. The experimental data were analysed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The equilibrium adsorption capacity of the sawdust carbon was determined with the Langmuir equation as well as the pseudo-second-order rate equation and found to be >300 mg dye per gram of the adsorbent. The most ideal pH for adsorption of direct dyes onto sawdust carbon was found to be 3 and below. The results indicate that the Mahogany sawdust carbon could be employed as a low cost alternative to commercial activated carbon in the removal of dyes from wastewater.

  6. Removal of hazardous pharmaceutical dyes by adsorption onto papaya seeds.

    Science.gov (United States)

    Weber, Caroline Trevisan; Collazzo, Gabriela Carvalho; Mazutti, Marcio Antonio; Foletto, Edson Luiz; Dotto, Guilherme Luiz

    2014-01-01

    Papaya (Carica papaya L.) seeds were used as adsorbent to remove toxic pharmaceutical dyes (tartrazine and amaranth) from aqueous solutions, in order to extend application range. The effects of pH, initial dye concentration, contact time and temperature were investigated. The kinetic data were evaluated by the pseudo first-order, pseudo second-order and Elovich models. The equilibrium was evaluated by the Langmuir, Freundlich and Temkin isotherm models. It was found that adsorption favored a pH of 2.5, temperature of 298 K and equilibrium was attained at 180-200 min. The adsorption kinetics followed the pseudo second-order model, and the equilibrium was well represented by the Langmuir model. The maximum adsorption capacities were 51.0 and 37.4 mg g(-1) for tartrazine and amaranth, respectively. These results revealed that papaya seeds can be used as an alternative adsorbent to remove pharmaceutical dyes from aqueous solutions.

  7. Heavy metal ion adsorption behavior in nitrogen-doped magnetic carbon nanoparticles: Isotherms and kinetic study

    International Nuclear Information System (INIS)

    Shin, Keun-Young; Hong, Jin-Yong; Jang, Jyongsik

    2011-01-01

    Graphical abstract: Display Omitted Research highlights: → The monodisperse and multigram-scale N-MCNPs are fabricated by carbonization of polypyrrole as a carbon precursor. → The synthesized N-MCNPs provide an enhanced adsorption uptake for various heavy metal ions. → The N-MCNPs can be applied to the Langmuir model and pseudo-second-order kinetics. → The iron-impregnated N-MCNPs are reused up to 5 times with no loss of removal efficiency. - Abstract: To clarify the heavy metal adsorption mechanism of nitrogen-doped magnetic carbon nanoparticles (N-MCNPs), adsorption capacity was investigated from the adsorption isotherms, kinetics and thermodynamics points of view. The obtained results showed that the equilibrium adsorption behavior of Cr 3+ ion onto the N-MCNPs can be applied to the Langmuir model and pseudo-second-order kinetics. It indicated that the fabricated N-MCNPs had the homogenous surface for adsorption and all adsorption sites had equal adsorption energies. Furthermore, the adsorption onto N-MCNPs taken place through a chemical process involving the valence forces. According to the thermodynamics, the adsorption process is spontaneous and endothermic in nature which means that the adsorption capacity increases with increasing temperature due to the enhanced mobility of adsorbate molecules. The effects of the solution pH and the species of heavy metal ion on the adsorption uptake were also studied. The synthesized N-MCNPs exhibited an enhanced adsorption capacity for the heavy metal ions due to the high surface area and large amount of nitrogen contents.

  8. Discrete pseudo-integrals

    Czech Academy of Sciences Publication Activity Database

    Mesiar, Radko; Li, J.; Pap, E.

    2013-01-01

    Roč. 54, č. 3 (2013), s. 357-364 ISSN 0888-613X R&D Projects: GA ČR GAP402/11/0378 Institutional support: RVO:67985556 Keywords : concave integral * pseudo-addition * pseudo-multiplication Subject RIV: BA - General Mathematics Impact factor: 1.977, year: 2013 http://library.utia.cas.cz/separaty/2013/E/mesiar-discrete pseudo-integrals.pdf

  9. Deconvolution of the thermoluminescent emission curve. Second order kinetics

    International Nuclear Information System (INIS)

    Moreno y M, A.; Moreno B, A.

    1999-01-01

    In this work it is described the Randall and Wilkins second order kinetics in Microsoft Excel language, which allows its expression as the sum of Gaussian and the correction factors corresponding. These factors are obtained of the differences between the real thermoluminescent curve and the Gaussian proposed. The results obtained justify the Gaussian expression added to the correction factor. (Author)

  10. Biphasic kinetics in the reaction between amino acids or glutathione and the chromium acetate cluster, [Cr3O(OAc)6]+.

    Science.gov (United States)

    Chaudhary, Shveta; Van Horn, J David

    2006-11-07

    Kinetics for the breakdown of the trinuclear chromium acetate cluster with a series of monoprotic and diprotic amino acid ligands and with glutathione in aqueous media have been investigated spectrophotometrically at pH 3.5-5.5 and in a temperature range of 45-60 degrees C. Under pseudo-first-order conditions, reactions with these ligands exhibited biphasic kinetic behavior that can be accounted for by a consecutive two-step reaction, A-->B-->C, where A is assumed to be a forced ion pair, B an intermediate and C is the product; experimental data fit to a biexponential equation for the transformation. Rates for k(short), k(long), and k(obs) were determined by manual extrapolation of absorbance data or curve-fitting routines; associated activation parameters for each step of the reaction were calculated using the Eyring equation. Rates for the first and second steps of the reaction are on the order of approximately 10(-4) and approximately 10(-5)s(-1), respectively. The large negative values of DeltaS++ and smaller DeltaH++ in the first step indicate an associative step, while high positive values of DeltaS(double dagger) in the second step indicate dissociation. To account for the results mechanistically, the results are interpreted to be a first step of ligand exchange with a pseudo-axial aqua ligand, followed by a dissociative step involving acetate or oxo ligand displacement. The dissociative step is the rate determining step, with k(obs) approximately k(long). The results demonstrate reaction pathways that are available to the Cr(III) metal centers that may be physiologically relevant in the ligand-rich environment of biological systems. Under general conditions Cr(III) clusters may be expected to be broken down, unless some unique biological environment stabilizes the cluster. The present study has application to the processes related to Cr(III) transport and excretion, to potential mechanisms of Cr(III) action in a biological setting, and to the

  11. Electrochemical degradation of sulfonamides at BDD electrode: Kinetics, reaction pathway and eco-toxicity evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Fabiańska, Aleksandra; Białk-Bielińska, Anna; Stepnowski, Piotr [Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-952 Gdansk (Poland); Stolte, Stefan [Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-952 Gdansk (Poland); UFT-Centre of Environmental Research and Sustainable Technology, University of Bremen, Leobener Straße UFT, D-28359 Bremen (Germany); Siedlecka, Ewa Maria, E-mail: ewa.siedlecka@ug.edu.pl [Faculty of Chemistry, University of Gdansk, ul. Wita Stwosza 63, 80-952 Gdansk (Poland)

    2014-09-15

    Highlights: • SNs were electrochemically oxidized at BDD in one compartment reactor. • The efficiency of SN degradation was the highest in effluents from municipal WWTP. • The electro-degradation SNs based on oxidation but reduction was also possible. • Electrochemical oxidation of SNs led in some cases to mixtures toxic to L. minor. - Abstract: The investigation dealt with electrochemical oxidation of five sulfonamides (SNs): sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMN) and sulfadimethoxine (SDM) in aqueous solution at boron-doped diamond (BDD) electrode. All studied sulfonamides were degraded according to a pseudo first order kinetics. The structure of SNs had no significant effect on the values of pseudo first order rate constants. Increased degradation efficiency was observed in higher temperature and in acidic pH. Due to the presence of chlorine and nitrate SNs were more effectively oxidized from municipal wastewater treatment plant (WWTP) effluents than from pure supporting electrolyte Na{sub 2}SO{sub 4}. The intermediates identified by LC–MS and GC–MS analysis suggested that the hydroxyl radicals attack mainly the S-N bond, but also the aromatic ring systems (aniline, pyrimidine or triazole) of SNs. Finally, the toxicity of the SNs solutions and effluents after electrochemical treatment was assessed through the measurement of growth inhibition of green algae (Scenedesmus vacualatus) and duckweed (Lemna minor). Toxicity of SMR, STZ, SMN solutions before and after electrochemical oxidation and SDM solution after the process in L. minor test was observed. No significant toxicity of studied SNs was observed in algae test.

  12. Electrochemical degradation of sulfonamides at BDD electrode: Kinetics, reaction pathway and eco-toxicity evaluation

    International Nuclear Information System (INIS)

    Fabiańska, Aleksandra; Białk-Bielińska, Anna; Stepnowski, Piotr; Stolte, Stefan; Siedlecka, Ewa Maria

    2014-01-01

    Highlights: • SNs were electrochemically oxidized at BDD in one compartment reactor. • The efficiency of SN degradation was the highest in effluents from municipal WWTP. • The electro-degradation SNs based on oxidation but reduction was also possible. • Electrochemical oxidation of SNs led in some cases to mixtures toxic to L. minor. - Abstract: The investigation dealt with electrochemical oxidation of five sulfonamides (SNs): sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMN) and sulfadimethoxine (SDM) in aqueous solution at boron-doped diamond (BDD) electrode. All studied sulfonamides were degraded according to a pseudo first order kinetics. The structure of SNs had no significant effect on the values of pseudo first order rate constants. Increased degradation efficiency was observed in higher temperature and in acidic pH. Due to the presence of chlorine and nitrate SNs were more effectively oxidized from municipal wastewater treatment plant (WWTP) effluents than from pure supporting electrolyte Na 2 SO 4 . The intermediates identified by LC–MS and GC–MS analysis suggested that the hydroxyl radicals attack mainly the S-N bond, but also the aromatic ring systems (aniline, pyrimidine or triazole) of SNs. Finally, the toxicity of the SNs solutions and effluents after electrochemical treatment was assessed through the measurement of growth inhibition of green algae (Scenedesmus vacualatus) and duckweed (Lemna minor). Toxicity of SMR, STZ, SMN solutions before and after electrochemical oxidation and SDM solution after the process in L. minor test was observed. No significant toxicity of studied SNs was observed in algae test

  13. A comprehensive investigation of the pseudo-skin factor for partially completed vertical wells

    International Nuclear Information System (INIS)

    Farokhi, Vahid; Gerami, Shahab

    2012-01-01

    To prohibit gas and/or water coning, it is very common for wells to be completed over only a portion of their productive zone. Such a procedure causes an additional pressure drop, termed the pseudo-skin factor, which reduces the well productivity. In order to ascertain whether or not a partially penetrated well requires stimulation, one has to quantitatively determine the different components of the total skin. Hence, an accurate evaluation of the pseudo-skin factor as one of the main components of the total skin is critical. Many authors have employed different mathematics to find expressions for estimating the pseudo-skin factor, however, since a comprehensive investigation of the available models has not as yet been performed, the diversity of these expressions could be very confusing. This paper first aims to propose an analytical model which accurately estimates the pseudo-skin factor in a partially penetrated well. In model development, the impacts of anisotropy and the arbitrariness of the open interval location are all taken into account, and the model is validated against a numerical simulator (ECLIPSE). Its second aim is to take the results of the numerical simulator as the comparison basis, and make a comprehensive investigation of the available models to check their accuracy for estimating the pseudo-skin factor. The results of the investigation show that, in comparison to other methods, this proposed model, Streltsova's method and that of Yeh and Reynolds, estimate the pseudo-skin factor favourably close to that obtained by the simulator. (paper)

  14. Photodegradation of gemfibrozil in aqueous solution under UV irradiation: kinetics, mechanism, toxicity, and degradation pathways.

    Science.gov (United States)

    Ma, Jingshuai; Lv, Wenying; Chen, Ping; Lu, Yida; Wang, Fengliang; Li, Fuhua; Yao, Kun; Liu, Guoguang

    2016-07-01

    The lipid regulator gemfibrozil (GEM) has been reported to be persistent in conventional wastewater treatment plants. This study investigated the photolytic behavior, toxicity of intermediate products, and degradation pathways of GEM in aqueous solutions under UV irradiation. The results demonstrated that the photodegradation of GEM followed pseudo-first-order kinetics, and the pseudo-first-order rate constant was decreased markedly with increasing initial concentrations of GEM and initial pH. The photodegradation of GEM included direct photolysis via (3)GEM(*) and self-sensitization via ROS, where the contribution rates of degradation were 0.52, 90.05, and 8.38 % for ·OH, (1)O2, and (3)GEM(*), respectively. Singlet oxygen ((1)O2) was evidenced by the molecular probe compound, furfuryl alcohol (FFA), and was identified as the primary reactive species in the photolytic process. The steady-state concentrations of (1)O2 increased from (0.324 ± 0.014) × 10(-12) to (1.021 ± 0.040) × 10(-12) mol L(-1), as the initial concentrations of GEM were increased from 5 to 20 mg L(-1). The second-order rate constant for the reaction of GEM with (1)O2 was calculated to be 2.55 × 10(6) M(-1) s(-1). The primary transformation products were identified using HPLC-MS/MS, and possible photodegradation pathways were proposed by hydroxylation, aldehydes reactions, as well as the cleavage of ether side chains. The toxicity of phototransformation product evaluation revealed that photolysis potentially provides a critical pathway for GEM toxicity reduction in potable water and wastewater treatment facilities.

  15. First- and second-order metal-insulator phase transitions and topological aspects of a Hubbard-Rashba system

    Science.gov (United States)

    Marcelino, Edgar

    2017-05-01

    This paper considers a model consisting of a kinetic term, Rashba spin-orbit coupling and short-range Coulomb interaction at zero temperature. The Coulomb interaction is decoupled by a mean-field approximation in the spin channel using field theory methods. The results feature a first-order phase transition for any finite value of the chemical potential and quantum criticality for vanishing chemical potential. The Hall conductivity is also computed using the Kubo formula in a mean-field effective Hamiltonian. In the limit of infinite mass the kinetic term vanishes and all the phase transitions are of second order; in this case the spontaneous symmetry-breaking mechanism adds a ferromagnetic metallic phase to the system and features a zero-temperature quantization of the Hall conductivity in the insulating one.

  16. Difference method for solving a nonlocal boundary value problem for a degenerating third-order pseudo-parabolic equation with variable coefficients

    Science.gov (United States)

    Beshtokov, M. Kh.

    2016-10-01

    A nonlocal boundary value problem for a degenerating third-order pseudo-parabolic equation with variable coefficients is considered. For solving this problem, a priori estimates in the differential and difference forms are obtained. The a priori estimates imply the uniqueness and stability of the solution on a layer with respect to the initial data and the right-hand side and the convergence of the solution of the difference problem to the solution of the differential problem.

  17. Effect of Humic Acid on As Redox Transformation and Kinetic Adsorption onto Iron Oxide Based Adsorbent (IBA

    Directory of Open Access Journals (Sweden)

    Hoda Fakour

    2014-10-01

    Full Text Available Due to the importance of adsorption kinetics and redox transformation of arsenic (As during the adsorption process, the present study elucidated natural organic matter (NOM effects on As adsorption-desorption kinetics and speciation transformation. The experimental procedures were conducted by examining interactions of arsenate and arsenite with different concentrations of humic acid (HA as a model representative of NOM, in the presence of iron oxide based adsorbent (IBA, as a model solid surface in three environmentally relevant conditions, including the simultaneous adsorption of both As and HA onto IBA, HA adsorption onto As-presorbed IBA, and As adsorption onto HA-presorbed IBA. Experimental adsorption-desorption data were all fitted by original and modified Lagergren pseudo-first and -second order adsorption kinetic models, respectively. Weber’s intraparticle diffusion was also used to gain insight into the mechanisms and rate controlling steps, which the results suggested that intraparticle diffusion of As species onto IBA is the main rate-controlling step. Different concentrations of HA mediated the redox transformation of As species, with a higher oxidation ability than reduction. The overall results indicated the significant effect of organic matter on the adsorption kinetics and redox transformation of As species, and consequently, the fate, transport and mobility of As in different environmentally relevant conditions.

  18. Three-dimensional cross-linked carbon network wrapped with ordered polyaniline nanowires for high-performance pseudo-supercapacitors

    Science.gov (United States)

    Hu, Huan; Liu, Shuwu; Hanif, Muddasir; Chen, Shuiliang; Hou, Haoqing

    2014-12-01

    The polyaniline (PANI)-based pseudo-supercapacitor has been extensively studied due to its good conductivity, ease of synthesis, low-cost monomer, tunable properties and remarkable specific capacitance. In this work, a three-dimensional cross-linked carbon network (3D-CCN) was used as a contact-resistance-free substrate for PANI-based pseudo-supercapacitors. The ordered PANI nanowires (PaNWs) were grown on the 3D-CCN to form PaNWs/3D-CCN composites by in-situ polymerization. The PaNWs/3D-CCN composites exhibited a specific capacitance (Cs) of 1191.8 F g-1 at a current density of 0.5 A g-1 and a superior rate capability with 66.4% capacitance retention at 100.0 A g-1. The high specific capacitance is attributed to the thin PaNW coating and the spaced PANI nanowire array, which ensure a higher utilization of PANI due to the ease of diffusion of protons through/on the PANI nanowires. In addition, the unique 3D-CCN was used as a high-conductivity platform (or skeleton) with no contact resistance for fast electron transfer and facile charge transport within the composites. Therefore, the binder-free composites can process rapid gains or losses of electrons and ions, even at a high current density. As a result, the specific capacitance and rate capability of our composites are remarkably higher than those of other PANI composites.

  19. Peroxone mineralization of chemical oxygen demand for direct potable water reuse: Kinetics and process control.

    Science.gov (United States)

    Wu, Tingting; Englehardt, James D

    2015-04-15

    Mineralization of organics in secondary effluent by the peroxone process was studied at a direct potable water reuse research treatment system serving an occupied four-bedroom, four bath university residence hall apartment. Organic concentrations were measured as chemical oxygen demand (COD) and kinetic runs were monitored at varying O3/H2O2 dosages and ratios. COD degradation could be accurately described as the parallel pseudo-1st order decay of rapidly and slowly-oxidizable fractions, and effluent COD was reduced to below the detection limit (<0.7 mg/L). At dosages ≥4.6 mg L(-1) h(-1), an O3/H2O2 mass ratio of 3.4-3.8, and initial COD <20 mg/L, a simple first order decay was indicated for both single-passed treated wastewater and recycled mineral water, and a relationship is proposed and demonstrated to estimate the pseudo-first order rate constant for design purposes. At this O3/H2O2 mass ratio, ORP and dissolved ozone were found to be useful process control indicators for monitoring COD mineralization in secondary effluent. Moreover, an average second order rate constant for OH oxidation of secondary effluent organics (measured as MCOD) was found to be 1.24 × 10(7) ± 0.64 × 10(7) M(-1) S(-1). The electric energy demand of the peroxone process is estimated at 1.73-2.49 kW h electric energy for removal of one log COD in 1 m(3) secondary effluent, comparable to the energy required for desalination of medium strength seawater. Advantages/disadvantages of the two processes for municipal wastewater reuse are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Picolinic acid promoted oxidative decarboxylation of ...

    African Journals Online (AJOL)

    The kinetics and mechanism of picolinic acid promoted reaction of phenylsulfinylacetic acid (PSAA) with Cr(VI) was carried out in aqueous acetonitrile medium under pseudo first order conditions. The reaction follows Michaelis-Menten type of kinetics with respect to PSAA. The catalytic activity by picolinic acid can be ...

  1. Powdered activated carbon adsorption of two fishy odorants in water: Trans,trans-2,4-heptadienal and trans,trans-2,4-decadienal.

    Science.gov (United States)

    Li, Xin; Wang, Jun; Zhang, Xiaojian; Chen, Chao

    2015-06-01

    Powdered activated carbon (PAC) adsorption of two fishy odorants, trans,trans-2,4-heptadienal (HDE) and trans,trans-2,4-decadienal (DDE), was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters (ΔG0, ΔH0, and ΔS0) indicated an exothermic and spontaneous adsorption process. PAC dosage, pH, and natural organic matter (NOM) presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of pH had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at pH9. The presence of NOM, especially the fraction with molecular weight less than 1k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did. Copyright © 2015. Published by Elsevier B.V.

  2. Kinetic study on adsorption of Cr(VI), Ni(II), Cd(II) and Pb(II) ions from aqueous solutions using activated carbon prepared from Cucumis melo peel

    Science.gov (United States)

    Manjuladevi, M.; Anitha, R.; Manonmani, S.

    2018-03-01

    The adsorption of Cr(VI), Ni(II), Cd(II) and Pb(II), ions from aqueous solutions by Cucumis melo peel-activated carbon was investigated under laboratory conditions to assess its potential in removing metal ions. The adsorption behavior of metal ions onto CMAC was analyzed with Elovich, intra-particle diffusion rate equations and pseudo-first-order model. The rate constant of Elovich and intra-particle diffusion on CMAC increased in the sequence of Cr(VI) > Ni(II) > Cd(II) > Pb(II). According to the regression coefficients, it was observed that the kinetic adsorption data can fit better by the pseudo-first-order model compared to the second-order Lagergren's model with R 2 > 0.957. The maximum adsorption of metal ions onto the CMAC was found to be 97.95% for Chromium(VI), 98.78% for Ni(II), 98.55% for Pb(II) and 97.96% for Cd(II) at CMAC dose of 250 mg. The adsorption capacities followed the sequence Ni(II) ≈ Pb(II) > Cr(VI) ≈ Cd(II) and Ni(II) > Pb(II) > Cd(II) > Cr(VI). The optimum adsorption conditions selected were adsorbent dosage of 250 mg, pH of 3.0 for Cr(VI) and 6.0 for Ni(II), Cd(II) and Pb(II), adsorption concentration of 250 mg/L and contact time of 180.

  3. Download this PDF file

    African Journals Online (AJOL)

    Rates of reaction of l-aryl-3,3-diethyltriazines with. B-naphthol in acid media to yield azo ayes have been measured in dimethylformamide solution at 25°. For a series of four acids of different acid strengths, pseudo-first-order rate constants were obtained, and the reaction was found to be follow third order kinetics, first order ...

  4. Magnetic vinylphenyl boronic acid microparticles for Cr(VI) adsorption: Kinetic, isotherm and thermodynamic studies

    International Nuclear Information System (INIS)

    Kara, Ali; Demirbel, Emel; Tekin, Nalan; Osman, Bilgen; Beşirli, Necati

    2015-01-01

    Highlights: • Cr(VI) can oxidize biological molecules and be one of the most harmful substance. • Magnetic seperation techniques are used on different applications in many fields. • Magnetic systems can be used for rapid and selective removal as a magnetic processor. • We investigate properties of both new material and other magnetic adsorbents reported in the literatures on the adsorption of Cr(VI) ions. • No researchments were reported on adsorption of Cr(VI) with magnetic vinylphenyl boronic acid microparticles. - Abstract: Magnetic vinylphenyl boronic acid microparticles, poly(ethylene glycol dimethacrylate(EG)–vinylphenyl boronic acid(VPBA)) [m-poly(EG–VPBA)], produced by suspension polymerization and characterized, was found to be an efficient solid polymer for Cr(VI) adsorption. The m-poly(EG–VPBA) microparticles were prepared by copolymerizing of ethylene glycol dimethylacrylate (EG) with 4-vinyl phenyl boronic acid (VPBA). The m-poly(EG–VPBA) microparticles were characterized by N 2 adsorption/desorption isotherms, electron spin resonance (ESR), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), elemental analysis, scanning electron microscope (SEM) and swelling studies. The m-poly(EG–VPBA) microparticles were used at adsorbent/Cr(VI) ion ratios. The influence of pH, Cr(VI) initial concentration, temperature of the removal process was investigated. The maximum removal of Cr(VI) was observed at pH 2. Langmuir isotherm and Dubinin–Radushkvich isotherm were found to better fit the experiment data rather than Fruendlich isotherm. The kinetics of the adsorption process of Cr(VI) on the m-poly(EG–VPBA) microparticles were investigated using the pseudo first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models, results showed that the pseudo-second order equation model provided the best correlation with the experimental results. The thermodynamic

  5. Effect of light on the kinetics and equilibrium of the textile dye (Reactive Red 120) adsorption by Helianthus annuus hairy roots.

    Science.gov (United States)

    Srikantan, Chitra; Suraishkumar, G K; Srivastava, Smita

    2018-06-01

    The study demonstrates for the first time that light influences the adsorption equilibrium and kinetics of a dye by root culture system. The azo dye (Reactive Red 120) adsorption by the hairy roots of H. annuus followed a pseudo first-order kinetic model and the adsorption equilibrium parameters were best estimated using Langmuir isotherm. The maximum dye adsorption capacity of the roots increased 6-fold, from 0.26 mg g -1 under complete dark conditions to 1.51 mg g -1 under 16/8 h light/dark photoperiod. Similarly, adsorption rate of the dye and removal (%) also increased in the presence of light, irrespective of the initial concentration of the dye (20-110 mg L -1 ). The degradation of the azo dye upon adsorption by the hairy roots of H. annuus was also confirmed. In addition, a strategy for simultaneous dye removal and increased alpha-tocopherol (industrially relevant) production by H. annuus hairy root cultures has been proposed and demonstrated. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. A family of high-order gas-kinetic schemes and its comparison with Riemann solver based high-order methods

    Science.gov (United States)

    Ji, Xing; Zhao, Fengxiang; Shyy, Wei; Xu, Kun

    2018-03-01

    Most high order computational fluid dynamics (CFD) methods for compressible flows are based on Riemann solver for the flux evaluation and Runge-Kutta (RK) time stepping technique for temporal accuracy. The advantage of this kind of space-time separation approach is the easy implementation and stability enhancement by introducing more middle stages. However, the nth-order time accuracy needs no less than n stages for the RK method, which can be very time and memory consuming due to the reconstruction at each stage for a high order method. On the other hand, the multi-stage multi-derivative (MSMD) method can be used to achieve the same order of time accuracy using less middle stages with the use of the time derivatives of the flux function. For traditional Riemann solver based CFD methods, the lack of time derivatives in the flux function prevents its direct implementation of the MSMD method. However, the gas kinetic scheme (GKS) provides such a time accurate evolution model. By combining the second-order or third-order GKS flux functions with the MSMD technique, a family of high order gas kinetic methods can be constructed. As an extension of the previous 2-stage 4th-order GKS, the 5th-order schemes with 2 and 3 stages will be developed in this paper. Based on the same 5th-order WENO reconstruction, the performance of gas kinetic schemes from the 2nd- to the 5th-order time accurate methods will be evaluated. The results show that the 5th-order scheme can achieve the theoretical order of accuracy for the Euler equations, and present accurate Navier-Stokes solutions as well due to the coupling of inviscid and viscous terms in the GKS formulation. In comparison with Riemann solver based 5th-order RK method, the high order GKS has advantages in terms of efficiency, accuracy, and robustness, for all test cases. The 4th- and 5th-order GKS have the same robustness as the 2nd-order scheme for the capturing of discontinuous solutions. The current high order MSMD GKS is a

  7. Anaerobic digestion of amine-oxide-based surfactants: biodegradation kinetics and inhibitory effects.

    Science.gov (United States)

    Ríos, Francisco; Lechuga, Manuela; Fernández-Arteaga, Alejandro; Jurado, Encarnación; Fernández-Serrano, Mercedes

    2017-08-01

    Recently, anaerobic degradation has become a prevalent alternative for the treatment of wastewater and activated sludge. Consequently, the anaerobic biodegradability of recalcitrant compounds such as some surfactants require a thorough study to avoid their presence in the environment. In this work, the anaerobic biodegradation of amine-oxide-based surfactants, which are toxic to several organisms, was studied by measuring of the biogas production in digested sludge. Three amine-oxide-based surfactants with structural differences in their hydrophobic alkyl chain were tested: Lauramine oxide (AO-R 12 ), Myristamine oxide (AO-R 14 ) and Cocamidopropylamine oxide (AO-cocoamido). Results show that AO-R 12 and AO-R 14 inhibit biogas production, inhibition percentages were around 90%. AO-cocoamido did not cause inhibition and it was biodegraded until reaching a percentage of 60.8%. Otherwise, we fitted the production of biogas to two kinetic models, to a pseudo first-order model and to a logistic model. Production of biogas during the anaerobic biodegradation of AO-cocoamido was pretty good adjusted to the logistics model. Kinetic parameters were also determined. This modelling is useful to predict their behaviour in wastewater treatment plants and under anaerobic conditions in the environment.

  8. A note on Lorentz transformation and pseudo-rapidity distributions

    International Nuclear Information System (INIS)

    Hama, Y.

    1980-07-01

    It is shown that although rapidity and pseudo-rapidity are almost equivalent variables, their difference may in pratice become quite remarkable. Non Lorentz invariance of pseudo-rapidity distributions may cause appearance of strange effects at first sight, such as deformation of a perfectly symmetric particle distribution into an asymmetric one when going to another frame. (Author) [pt

  9. Thermoluminescence glow-curve deconvolution functions for mixed order of kinetics and continuous trap distribution

    International Nuclear Information System (INIS)

    Kitis, G.; Gomez-Ros, J.M.

    2000-01-01

    New glow-curve deconvolution functions are proposed for mixed order of kinetics and for continuous-trap distribution. The only free parameters of the presented glow-curve deconvolution functions are the maximum peak intensity (I m ) and the maximum peak temperature (T m ), which can be estimated experimentally together with the activation energy (E). The other free parameter is the activation energy range (ΔE) for the case of the continuous-trap distribution or a constant α for the case of mixed-order kinetics

  10. Removal of Basic Red 46 dye from aqueous solution by adsorption onto Moroccan clay

    International Nuclear Information System (INIS)

    Karim, A. Bennani; Mounir, B.; Hachkar, M.; Bakasse, M.; Yaacoubi, A.

    2009-01-01

    In this study, Moroccan crude clay of Safi, which was characterized by X-ray diffraction, is used as adsorbent for the investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the Basic Red 46 (BR46) in aqueous solutions at various dye concentrations, adsorbent masses and pH values. The results showed that the adsorption capacity of the dye increased by initial dye concentration and pH values. Two kinetic models (the pseudo-first-order and the pseudo-second-order) were used to calculate the adsorption rate constants. The adsorption kinetics of the basic dye followed pseudo-second-order model. The experimental data isotherms were analyzed using the Langmuir, Freundlich and Dubinin-Radushkevish equations. The monolayer adsorption capacity for BR46 dye is 54 mg/g of crude clay. Nearly 20 min of contact time was found to be sufficient for the dye adsorption to reach equilibrium. Thermodynamical parameters were also evaluated for the dye-adsorbent system and revealed that the adsorption process is exothermic in nature.

  11. Removal of Disperse Blue 56 and Disperse Red 135 dyes from aqueous dispersions by modified montmorillonite nanoclay

    Directory of Open Access Journals (Sweden)

    Ahmadishoar Javad

    2017-01-01

    Full Text Available In this study modified montmorillonite was used as an adsorbent for the removal of two selected disperse dyes i.e., Disperse Blue 56 (DB and Disperse Red 135 (DR from dye dispersions. The adsorption equilibrium data of dyes adsorption were investigated by using Nernst, Freundlich and Langmuir isotherm models. The adsorption kinetics was analyzed by using different models including pseudo-first-order, pseudo-second-order, Elovich and Intraparticle diffusion model. The Freundlich isotherm was found to be the most appropriate model for describing the sorption of the dyes on modified nanoclay. The best fit to the experimental results was obtained by using the pseudo-second-order kinetic equation, which satisfactorily described the process of dye adsorption. Although different kinetic models may control the rate of the adsorption process, the results indicated that the main rate limiting step was the intraparticle diffusion. The results showed that the proposed modified montmorillonite could be used as an effective adsorbent for the removal of disperse dyes even from highly concentrated dispersions.

  12. Adsorptive removal of nickel from aqueous solutions by activated carbons from doum seed (Hyphaenethebaica coat

    Directory of Open Access Journals (Sweden)

    Manal El-Sadaawy

    2014-06-01

    Full Text Available The present study investigates the possibility of using low cost agriculture waste as doum-palm seed coat for the removal of nickel ions from aqueous solutions. Two activated carbons had been prepared from raw doum-palm seed coat (DACI and DACII; as well, the raw material was used as an adsorbent (RD. Batch adsorption experiments were performed as a function of pH of solution, initial nickel ions concentration, dose of adsorbent and contact time. Adsorption data were modeled using Langmuir, Freundlich, Temkin and D–R Models. Different error analysis conforms that the isotherm data followed Freundlich models for all adsorbents. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order and Elovich model. Adsorption mechanism was investigated using the intra-particle diffusion model. Diffusion coefficients were calculated using the film and intraparticle diffusion models. Kinetic studies showed that the adsorption of Ni2+ ions onto RD, DACI and DACII followed pseudo-second order kinetic model, and indicates that the intra-particle diffusion controls the rate of adsorption but it is not the rate limiting step.

  13. Dye adsorption mechanisms in TiO2 films, and their effects on the photodynamic and photovoltaic properties in dye-sensitized solar cells.

    Science.gov (United States)

    Hwang, Kyung-Jun; Shim, Wang-Geun; Kim, Youngjin; Kim, Gunwoo; Choi, Chulmin; Kang, Sang Ook; Cho, Dae Won

    2015-09-14

    The adsorption mechanism for the N719 dye on a TiO2 electrode was examined by the kinetic and diffusion models (pseudo-first order, pseudo-second order, and intra-particle diffusion models). Among these methods, the observed adsorption kinetics are well-described using the pseudo-second order model. Moreover, the film diffusion process was the main controlling step of adsorption, which was analysed using a diffusion-based model. The photodynamic properties in dye-sensitized solar cells (DSSCs) were investigated using time-resolved transient absorption techniques. The photodynamics of the oxidized N719 species were shown to be dependent on the adsorption time, and also the adsorbed concentration of N719. The photovoltaic parameters (Jsc, Voc, FF and η) of this DSSC were determined in terms of the dye adsorption amounts. The solar cell performance correlates significantly with charge recombination and dye regeneration dynamics, which are also affected by the dye adsorption amounts. Therefore, the photovoltaic performance of this DSSC can be interpreted in terms of the adsorption kinetics and the photodynamics of oxidized N719.

  14. Reaction rate constants of H-abstraction by OH from large ketones: Measurements and site-specific rate rules

    KAUST Repository

    Badra, Jihad; Elwardani, Ahmed Elsaid; Farooq, Aamir

    2014-01-01

    -pentanone, and 4-methl-2-pentanone. Rate constants are measured under pseudo-first-order kinetics at temperatures ranging from 866 K to 1375 K and pressures near 1.5 atm. The reported high-temperature rate constant measurements are the first direct

  15. The catalytic oxidation of 1-butene over bismuth molybdate catalysts : V. The kinetics of the oxidation: A. Pulse reaction kinetics; exploratory experiments for a kinetic investigation

    NARCIS (Netherlands)

    Keizer, K.; Batist, P.A.; Schuit, G.C.A.

    1969-01-01

    The kinetics of oxidn. of 1-butene with O on three types of bismuth molybdate catalysts were investigated in pulse expts. For all the catalysts mentioned the kinetics can be expressed by a first-order dependency on the butene pressure and a zero-order dependency on the O pressure. A slight deviation

  16. Kinetics, mechanism and thermodynamics of bisulfite-aldehyde adduct formation

    Energy Technology Data Exchange (ETDEWEB)

    Olson, T.M.; Boyce, S.D.; Hoffmann, M.R.

    1986-04-01

    The kinetics and mechanism of bisulfite addition to benzaldehyde were studied at low pH in order to assess the importance of this reaction in stabilizing S(IV) in fog-, cloud-, and rainwater. Previously, the authors established that appreciable concentrations of the formaldehyde-bisulfite adduct (HMSA) are often present in fogwater. Measured HMSA concentrations in fogwater often do not fully account for observed excess S(IV) concentrations, however, so that other S(IV)-aldehyde adducts may be present. Reaction rates were determined by monitoring the disappearance of benzaldehyde by U.V. spectrophotometry under pseudo-first order conditions, (S(IV))/sub T/ >>(phi-CHO)/sub T/, in the pH range 0 - 4.4 at 25/sup 0/C. The equilibrium constant was determined by dissolving the sodium salt of the addition compound in a solution adjusted to pH 3.9, and measuring the absorbance of the equilibrated solution at 250 nm. A literature value of the extinction coefficient for benzaldehyde was used to calculate the concentration of free benzaldehyde. All solutions were prepared under an N/sub 2/ atmosphere using deoxygenated, deionized water and ionic strength was maintained at 1.0 M with sodium chloride.

  17. Degradation kinetics of reactive dye by UV/H2O2/US process under continuous mode operation.

    Science.gov (United States)

    Fung, P C; Poon, C S; Chu, C W; Tsui, S M

    2001-01-01

    Degradation of a dye, C. I . Reactive Red 120, in dyeing waatewater by the process o UV/H2O2/US was studied with a bench-scale reactor under the continuous mode of operation. The effects of dyeing wastewater flow rate and the feeding rate of an oxidant, H2O2, on the color removal efficiency of the process were investigated. The significance of ultrasonic (US) combined with UV irradiation was also investigated and the performances of the process on color removal were evaluated. The results showed that the decoloration process followed a pseudo first-order kinetic model and the UV light is the most significant factor on dye removal. Besides, at higher flow rates, incomplete color removal was observed due to relatively insufficient irradiation time (low degradation rate). In order to achieve a higher degradation rate, the feeding rate of H2O2 should be increased.

  18. Adsorption kinetics of c-Fos and c-Jun to air-water interfaces.

    Science.gov (United States)

    Del Boca, Maximiliano; Nobre, Thatyane Morimoto; Zaniquelli, Maria Elisabete Darbello; Maggio, Bruno; Borioli, Graciela A

    2007-11-01

    The kinetics of adsorption to air-water interfaces of the biomembrane active transcription factors c-Fos, c-Jun and their mixtures is investigated. The adsorption process shows three distinct stages: a lag time, a fast pseudo zero-order stage, and a halting stage. The initial stage determines the course of the process, which is concentration dependent until the end of the fast stage. We show that c-Fos has faster adsorption kinetics than c-Jun over all three stages and that the interaction between both proteins is apparent in the adsorption profiles of the mixtures. Protein molecular reorganization at the interface determines the transition to the final adsorption stage of the pure proteins as well as that of the mixtures.

  19. Phototransformation of iodate by UV irradiation: Kinetics and iodinated trihalomethane formation during subsequent chlor(am)ination

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Fu-Xiang [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Hu, Xiao-Jun, E-mail: hu-xj@mail.tsinghua.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Xu, Bin; Zhang, Tian-Yang; Gao, Yu-Qiong [State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China)

    2017-03-15

    Highlights: • IO{sub 3}{sup −} can be photodegraded by UV irradiation with pseudo-first order kinetics. • Solution pH has no remarkable influence on the photodegradation rate of IO{sub 3}{sup −}. • The I{sup −} and HOI derived from the photoreduction of IO{sub 3}{sup −} were determined. • The presence of NOM greatly enhanced the photolysis rate of IO{sub 3}{sup −}. • NOM sources can affect the formation of I-THMs in UV-chlor(am)ination of IO{sub 3}{sup −}. - Abstract: The photodegradation of IO{sub 3}{sup −} at 254 nm and the formation of iodinated trihalomethanes (I-THMs) during subsequent chlorination or chloramination in the presence of natural organic matter (NOM) were investigated in this study. The thermodynamically stable IO{sub 3}{sup −} can be degraded by UV irradiation with pseudo-first order kinetics and the quantum yield was calculated as 0.0591 mol einstein{sup −1}. Solution pH posed no remarkable influence on the photolysis rate of IO{sub 3}{sup −}. The UV phototransformation of IO{sub 3}{sup −} was evidenced by the determination of iodide (I{sup −}) and hypoiodous acid (HOI) in solution. NOM sources not only enhanced the photodegradation rate of IO{sub 3}{sup −} by photoejecting solvated electrons, but also greatly influenced the production I-THMs in subsequent chlor(am)ination processes. In UV irradiation and sequential oxidation processes by chlorine or chloramine, the I-THMs formation was susceptible to NOM sources, especially the two major fractions of aqueous humic substances (humic acid and fulvic acid). The toxicity of disinfected waters greatly increased in chloramination over chlorination of the UV photodecomposed IO{sub 3}{sup −}, as far more I-THMs especially CHI{sub 3}, were formed. As “the fourth iodine source” of iodinated disinfection by-products, the occurrence, transportation and fate of IO{sub 3}{sup −} in aquatic environment should be of concern instead of being considered a desired

  20. Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

    International Nuclear Information System (INIS)

    Solgy, Mostafa; Taghizadeh, Majid; Ghoddocynejad, Davood

    2015-01-01

    Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

  1. Episodic seasonal Pseudo-Bartter syndrome in cystic fibrosis.

    Science.gov (United States)

    Kintu, Brett; Brightwell, Alex

    2014-06-01

    Pseudo-Bartter syndrome (PBS) describes an uncommon but well recognised complication of cystic fibrosis leading to hypochloraemic, hypokalaemic metabolic alkalosis. Pseudo-Bartter syndrome is usually seen at initial presentation or within the first two years of life in children with cystic fibrosis. Risk factors for development of PBS include warm weather conditions, severe respiratory or pancreatic disease and gastrointestinal losses (e.g. vomiting and diarrhoea). PBS is rare in older children and adolescents although epidemics have been associated with heat wave conditions in warmer climates. In this era of climate change, it is crucial that clinicians consider Pseudo-Bartter syndrome when patients with cystic fibrosis present unwell during summer. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Graphical analysis of some pseudo-random number generators

    OpenAIRE

    Lewis, Peter A. W.

    1986-01-01

    There exist today many 'good' pseudo-random number generators; the problem is to retrieve them. This document discusses three commonly used pseudo- random number generators, the first being RANDU, a notoriously bad generator, but one which is still occasionally used. The next is the widely used prime modulus, multiplicative congruential generator used in LL-RANDOMII, the Naval Postgraduate School random number package, and the last is the random number generator provided for microcomputers wi...

  3. Radiation-induced recurrent intestinal pseudo-obstruction

    International Nuclear Information System (INIS)

    Conklin, J.L.; Anuras, S.

    1981-01-01

    The syndrome of intestinal pseudo-obstruction is a complex of signs and symptoms of intestinal obstruction without evidence of mechanical obstruction of the intestinal lumen. A patient with radiation-induced intestinal pseudoobstruction is described. The patient is a 74-year old woman with a history of chronic diarrhea, recurrent episodes of crampy abdominal pain, nausea and vomiting since receiving a 13,000 rad radiation dose to the pelvis in 1954. She has been hospitalized on many occasions for symptoms and signs of bowel obstruction. Upper gastrointestinal contrast roentgenograms with small bowel follow-through done during these episodes revealed multiple dilated loops of small bowel with no obstructing lesion. Barium enemas revealed no obstructing lesion. Each episode resolved with conservative therapy. Other secondary causes for intestinal pseudo-obstruction were ruled out in our patient. She gave no history of familial gastrointestinal disorders. Although postirradiation motility abnormalities have been demonstrated experimentally this is the first report of radiation induced intestinal pseudo-obstruction

  4. Defect ordering in aliovalently doped cubic zirconia from first principles

    International Nuclear Information System (INIS)

    Bogicevic, A.; Wolverton, C.; Crosbie, G.M.; Stechel, E.B.

    2001-01-01

    Defect ordering in aliovalently doped cubic-stabilized zirconia is studied using gradient corrected density-functional calculations. Intra- and intersublattice ordering interactions are investigated for both cation (Zr and dopant ions) and anion (oxygen ions and vacancies) species. For yttria-stabilized zirconia, the crystal structure of the experimentally identified, ordered compound δ-Zr 3 Y 4 O 12 is established, and we predict metastable zirconia-rich ordered phases. Anion vacancies repel each other at short separations, but show an energetic tendency to align as third-nearest neighbors along directions. Calculations with divalent (Be, Mg, Ca, Sr, Ba) and trivalent (Y, Sc, B, Al, Ga, In) oxides show that anion vacancies prefer to be close to the smaller of the cations (Zr or dopant ion). When the dopant cation is close in size to Zr, the vacancies show no particular preference, and are thus less prone to be bound preferentially to any particular cation type when the vacancies traverse such oxides. This ordering tendency offers insight into the observed high conductivity of Y 2 O 3 - and Sc 2 O 3 -stabilized zirconia, as well as recent results using, e.g., lanthanide oxides. The calculations point to In 2 O 3 as a particularly promising stabilizer for high ionic conductivity. Thus we are able to directly link (thermodynamic) defect ordering to (kinetic) ionic conductivity in cubic-stabilized zirconia using first-principles atomistic calculations

  5. Electrochemical oxidation of COD from real textile wastewaters: Kinetic study and energy consumption.

    Science.gov (United States)

    Zou, Jiaxiu; Peng, Xiaolan; Li, Miao; Xiong, Ying; Wang, Bing; Dong, Faqin; Wang, Bin

    2017-03-01

    In the present study, the electrochemical oxidation of real wastewaters discharged by textile industry was carried out using a boron-doped diamond (BDD) anode. The effect of operational variables, such as applied current density (20-100 mA·cm -2 ), NaCl concentration added to the real wastewaters (0-3 g·L -1 ), and pH value (2.0-10.0), on the kinetics of COD oxidation and on the energy consumption was carefully investigated. The obtained experimental results could be well matched with a proposed kinetic model, in which the indirect oxidation mediated by electrogenerated strong oxidants would be described through a pseudo-first-order kinetic constant k. Values of k exhibited a linear increase with increasing applied current density and decreasing pH value, and an exponential increase with NaCl concentration. Furthermore, high oxidation kinetics resulted in low specific energy consumption, but this conclusion was not suitable to the results obtained under different applied current density. Under the optimum operational conditions, it only took 3 h to complete remove the COD in the real textile wastewaters and the specific energy consumption could be as low as 11.12 kWh·kg -1  COD. The obtained results, low energy consumption and short electrolysis time, allowed to conclude that the electrochemical oxidation based on BDD anodes would have practical industrial application for the treatment of real textile wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Thermodynamic and kinetic studies on CO2 capture with Poly[VBTMA][Arg

    Science.gov (United States)

    Raja Shahrom, Maisara Shahrom; Wilfred, Cecilia Devi; Chong, Fai Kait

    2018-05-01

    This paper discusses the technologies for capturing CO2 from the natural gas using poly[VBTMA][Arg], a type of poly(ionic liquids) with an amino acid as the anion. The results revealed that the CO2 uptake increased from 3.23 mmol/g to 7.91 mmol/g at 1-10 bar, 298 K due to both chemical absorption and physical adsorption increments. Four adsorption isotherm models were applied to study the interaction between adsorbate and adsorbent to study the physical adsorption i.e. Freundlich, Langmuir, Dubinin Raduschkevich and Temkin isotherms at 298 K, 313 K and 333 K. Promising results were obtained that suggested the Freundlich model and the pseudo-first order model are well fitted with the kinetic data at 298 K with a 0.9943 R2 value. This study has provided empirical evidence to the current body of knowledge pertaining to CO2 capture technologies.

  7. An efficient and accurate two-stage fourth-order gas-kinetic scheme for the Euler and Navier-Stokes equations

    Science.gov (United States)

    Pan, Liang; Xu, Kun; Li, Qibing; Li, Jiequan

    2016-12-01

    provides a dynamic process of evolution from the kinetic scale particle free transport to the hydrodynamic scale wave propagation, which provides the physics for the non-equilibrium numerical shock structure construction to the near equilibrium NS solution. As a result, with the implementation of the fifth-order WENO initial reconstruction, in the smooth region the current two-stage GKS provides an accuracy of O ((Δx) 5 ,(Δt) 4) for the Euler equations, and O ((Δx) 5 ,τ2 Δt) for the NS equations, where τ is the time between particle collisions. Many numerical tests, including difficult ones for the Navier-Stokes solvers, have been used to validate the current method. Perfect numerical solutions can be obtained from the high Reynolds number boundary layer to the hypersonic viscous heat conducting flow. Following the two-stage time-stepping framework, the third-order GKS flux function can be used as well to construct a fifth-order method with the usage of both first-order and second-order time derivatives of the flux function. The use of time-accurate flux function may have great advantages on the development of higher-order CFD methods.

  8. Wetting transitions: First order or second order

    International Nuclear Information System (INIS)

    Teletzke, G.F.; Scriven, L.E.; Davis, H.T.

    1982-01-01

    A generalization of Sullivan's recently proposed theory of the equilibrium contact angle, the angle at which a fluid interface meets a solid surface, is investigated. The generalized theory admits either a first-order or second-order transition from a nonzero contact angle to perfect wetting as a critical point is approached, in contrast to Sullivan's original theory, which predicts only a second-order transition. The predictions of this computationally convenient theory are in qualitative agreement with a more rigorous theory to be presented in a future publication

  9. Cadmium telluride nanoparticles loaded on activated carbon as adsorbent for removal of sunset yellow

    Science.gov (United States)

    Ghaedi, M.; Hekmati Jah, A.; Khodadoust, S.; Sahraei, R.; Daneshfar, A.; Mihandoost, A.; Purkait, M. K.

    2012-05-01

    Adsorption is a promising technique for decolorization of effluents of textile dyeing industries but its application is limited due to requirement of high amounts of adsorbent required. The objective of this study was to assess the potential of cadmium telluride nanoparticles loaded onto activated carbon (CdTN-AC) for the removal of sunset yellow (SY) dye from aqueous solution. Adsorption studies were conducted in a batch mode varying solution pH, contact time, initial dye concentration, CdTN-AC dose, and temperature. In order to investigate the efficiency of SY adsorption on CdTN-AC, pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion kinetic models were studied. It was observed that the pseudo-second-order kinetic model fits better than other kinetic models with good correlation coefficient. Equilibrium data were fitted to the Langmuir model. Thermodynamic parameters such as enthalpy, entropy, activation energy, and sticking probability were also calculated. It was found that the sorption of SY onto CdTN-AC was spontaneous and endothermic in nature. The proposed adsorbent is applicable for SY removal from waste of real effluents including pea-shooter, orange drink and jelly banana with efficiency more than 97%.

  10. Differential and Difference Boundary Value Problem for Loaded Third-Order Pseudo-Parabolic Differential Equations and Difference Methods for Their Numerical Solution

    Science.gov (United States)

    Beshtokov, M. Kh.

    2017-12-01

    Boundary value problems for loaded third-order pseudo-parabolic equations with variable coefficients are considered. A priori estimates for the solutions of the problems in the differential and difference formulations are obtained. These a priori estimates imply the uniqueness and stability of the solution with respect to the initial data and the right-hand side on a layer, as well as the convergence of the solution of each difference problem to the solution of the corresponding differential problem.

  11. Kinetic Re-Evaluation of Fuel Neutralization by AKGA

    Science.gov (United States)

    Oropeza Cristina; Kosiba, Mike; Davis, Chuck

    2010-01-01

    Baseline characterization testing previously identified alpha-ketoglutaric acid (AKGA) cis a potential alternative to the current standard hydrazine (HZ) family fuel neutralization techniques in use at Kennedy Space Center (KSC). Thus far, the reagent shows promise for use in hardware decontamination operations and as a drop-in replacement for the scrubber liquor currently used in KSC four tower vapor scrubbers. Implementation of AKGA could improve process safety and reduce or eliminate generation of hydrazine-Iaden waste streams. This paper focuses on evaluation of the kinetics of these decontamination reactions in solution. Pseudo first order reaction rate constants with respect to the pyridazine products (6-oxo-4,5-dihydro-1H-pyridazine-3-carboxylic acid, (PCA) and 1-methyl-6-oxo-4,5-dihydro-pyridazine-3-carboxylic acid (mPCA)) in the presence of excess AKGA were determined by monitoring product formation using a ultra-violet visible absorption spectroscopy method. The results are presented here in comparison to previous data obtained by monitoring reactant depletion by gas chromatography with nitrogen phosphorus detector (GC-NPD).

  12. A simple UV-ozone surface treatment to enhance photocatalytic performance of TiO 2 loaded polymer nanofiber membranes

    KAUST Repository

    Dilpazir, S.

    2016-01-29

    Homogeneously dispersed titanium dioxide loaded polyacrylonitrile nanofiber membranes with increased active mass loading, Ti3+ surface defects and hydrophilicity were fabricated by combining electrospinning and UV-ozone surface treatment. The photocatalytic activity improved by a factor of ∼2 and the kinetics of photodegradation switched from pseudo-first order to pseudo-second order with increasing TiO2 content with a maximum rate constant of 20.7 h-1. © The Royal Society of Chemistry 2016.

  13. Perisplenic Pseudo

    International Nuclear Information System (INIS)

    Kim, Hyo Heon; Cho, Sin Young; Suh, Hong Kil; Kim, Ji Hyeon; Choi, Chul Soon; Lee, Eil Seong; Kang, Ik Won

    1995-01-01

    Perisplenic pseudo 'fluid collection' is one of the rare normal variations. Its frequency and sonographic findings for the differentiation from true perisplenic fluid collection have not been well described. Thus, we performed this study. The examination was performed with special attention to the splenic and perisplenic areas. We excluded patients with proved or suspected liver cirrhosis, pancreatic diseases,and abdominal trauma from the study population, but did not exclude the patients with chronic hepatitis and the carriers of hepatitis B virus. Of the examined 4794 patients, 8 cases showed perisplenic pseudo 'fluid collection'. Two of them were confirmed with computed tomography and liver scan, and six were inferred from the fact proved to be a part of the left lobe extension of the liver by tracing with the transducer. All cases ofperisplenic pseudo 'fluid collection' showed hypoechoic crescent area with hepatic ductal echoes. Perisplenic pseudo 'fluid collection' is very rare. The helpful findings for the differentiation from true fluid collection are the hepatic ductal echoes seen in the normal liver, proof of continuation into remained voluminous liver by tracing with the transducer. High awareness of it would prevent further unnecessary studies such as computed tomography and liver scan

  14. Zero-Shot Learning by Generating Pseudo Feature Representations

    OpenAIRE

    Lu, Jiang; Li, Jin; Yan, Ziang; Zhang, Changshui

    2017-01-01

    Zero-shot learning (ZSL) is a challenging task aiming at recognizing novel classes without any training instances. In this paper we present a simple but high-performance ZSL approach by generating pseudo feature representations (GPFR). Given the dataset of seen classes and side information of unseen classes (e.g. attributes), we synthesize feature-level pseudo representations for novel concepts, which allows us access to the formulation of unseen class predictor. Firstly we design a Joint Att...

  15. Kinetic competitivity between ordering and solute segregation to dislocations in Cu-20% at. Mn

    International Nuclear Information System (INIS)

    Donoso, E.; Varschavsky, A.

    1997-01-01

    By using differential scanning calorimetry (DSC) energetic measurements associated with the different peaks displayed during linear heating of Cu-20% at. Mn were made, employing quenched and cold-worked materials. Unique to the situation observed in the quenched alloy in which disperse order is developed, in the deformed alloy such process is inhibited by the segregation of solute atoms to partial dislocations. An appropriate model for calculation the energy evolved during the pinning process was applied in order to determine the dislocation density from the exothermic peak designated as stage 4. The computed value, which is in excellent agreement with the one obtained from expressions governing the energy release accompanying recrystallization allows to verify together with microhardness measurements and kinetic analysis that the first observed thermal effect in the deformed materials effectively corresponds a solute segregation process. (Author) 35 refs

  16. Kinetic studies of potassium permanganate adsorption by activated carbon and its ability as ethylene oxidation material

    Science.gov (United States)

    Aprilliani, F.; Warsiki, E.; Iskandar, A.

    2018-03-01

    Generally, ethylene production in many horticultural products has been seen to be detrimental to the quality during storage and distribution process. For this reason, removing ethylene from storage or distribution atmosphere is needed to maintain the quality. One of the technologies that can be applied is the use of potassium permanganate (KMnO4). KMnO4 is an active compound that can be used as an oxidizing agent on ethylene removal process. KMnO4 is not recommended for direct used application. As the result, additional material is required to impregnate the potassium permanganate. The inert materials used are commercial activated carbon. Activated carbon is chosen because it has high surface area. The purpose of this research is to determine kinetics adsorption and oxidation model of ethylene removal material. The kinetics adsorption was determined using the pseudo-first and second-order kinetic models. The data on adsorption process show that the second-order equation is more suitable to express the adsorption process on this research. The analyzing of the ethylene oxidation capacity increased with time until it reaches an optimal value. The ethylene oxidation rate is able to be estimated by the formula r = 0.1967 [C2H4]0.99 [KMnO4]0.01; MSE = 0.44 %. The actual and estimation data of ethylene oxidation show that the model is fitted to describe the actual ethylene oxidation under same experimental conditions.

  17. Stochastic cooling of bunched beams from fluctuation and kinetic theory

    International Nuclear Information System (INIS)

    Chattopadhyay, S.

    1982-09-01

    A theoretical formalism for stochastic phase-space cooling of bunched beams in storage rings is developed on the dual basis of classical fluctuation theory and kinetic theory of many-body systems in phase-space. The physics is that of a collection of three-dimensional oscillators coupled via retarded nonconservative interactions determined by an electronic feedback loop. At the heart of the formulation is the existence of several disparate time-scales characterizing the cooling process. Both theoretical approaches describe the cooling process in the form of a Fokker-Planck transport equation in phase-space valid up to second order in the strength and first order in the auto-correlation of the cooling signal. With neglect of the collective correlations induced by the feedback loop, identical expressions are obtained in both cases for the coherent damping and Schottky noise diffusion coefficients. These are expressed in terms of Fourier coefficients in a harmonic decomposition in angle of the generalized nonconservative cooling force written in canonical action-angle variables of the particles in six-dimensional phase-space. Comparison of analytic results to a numerical simulation study with 90 pseudo-particles in a model cooling system is presented

  18. Kinetic and equilibrium study of uranium(VI) adsorption by Bacillus licheniformis

    International Nuclear Information System (INIS)

    Zheng-ji Yi; University of Science and Technology Beijing, Beijing; Jun Yao

    2012-01-01

    Uranium pollution is a severe problem worldwide. Biosorption has been proposed as one of the most promising technologies for the removal of uranyl cations. Here we report on the adsorption behavior of uranium(VI) [U(VI)] on Bacillus licheniformis biomass to explore the potentiality of its application in uranium contamination control. The adsorption equilibrium, adsorption kinetics, and effects of temperature, pH and initial biosorbent dosage on the adsorption equilibrium were investigated in detail through batch experiments. The adsorption process is pronouncedly affected by the solution pH and the optimum pH range should be 4.5-5.0.Temperature range from 25 to 45 deg C has a certain effect on the rate of biosorption, but little effect on the equilibrium adsorption capacity. The U(VI) percentage removal increased concurrently with increasing biomass dosage, whereas the adsorption capacity decreased. The process follows the Langmuir isotherm model. The adsorption kinetics data were fitted very well by the pseudo-first-order rate model. Finally, the calculation results of thermodynamic constant (ΔG a = 9.98 kJ/mol) reveal that the adsorption process can be identified as a spontaneous chemical process. The present results suggest that B. licheniformis has considerable potential for the removal of uranyl from aqueous solution. (author)

  19. Thermogravimetric pyrolysis kinetics of bamboo waste via Asymmetric Double Sigmoidal (Asym2sig) function deconvolution.

    Science.gov (United States)

    Chen, Chuihan; Miao, Wei; Zhou, Cheng; Wu, Hongjuan

    2017-02-01

    Thermogravimetric kinetic of bamboo waste (BW) pyrolysis has been studied using Asymmetric Double Sigmoidal (Asym2sig) function deconvolution. Through deconvolution, BW pyrolytic profiles could be separated into three reactions well, each of which corresponded to pseudo hemicelluloses (P-HC), pseudo cellulose (P-CL), and pseudo lignin (P-LG) decomposition. Based on Friedman method, apparent activation energy of P-HC, P-CL, P-LG was found to be 175.6kJ/mol, 199.7kJ/mol, and 158.4kJ/mol, respectively. Energy compensation effects (lnk 0, z vs. E z ) of pseudo components were in well linearity, from which pre-exponential factors (k 0 ) were determined as 6.22E+11s -1 (P-HC), 4.50E+14s -1 (P-CL) and 1.3E+10s -1 (P-LG). Integral master-plots results showed pyrolytic mechanism of P-HC, P-CL, and P-LG was reaction order of f(α)=(1-α) 2 , f(α)=1-α and f(α)=(1-α) n (n=6-8), respectively. Mechanism of P-HC and P-CL could be further reconstructed to n-th order Avrami-Erofeyev model of f(α)=0.62(1-α)[-ln(1-α)] -0.61 (n=0.62) and f(α)=1.08(1-α)[-ln(1-α)] 0.074 (n=1.08). Two-steps reaction was more suitable for P-LG pyrolysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Decomposition of clofibric acid in aqueous media by advance oxidation techniques: kinetics study and degradation pathway

    International Nuclear Information System (INIS)

    Syed, M.; Khan, A.M.; Khan, R.A.

    2016-01-01

    This study investigates the decomposition of clofibric acid (CLF) by different advanced oxidation processes (AOPs), such as UV (254 nm), VUV (185 nm), UV / TiO/sub 2/ and VUV / TiO/sub 2/. The removal efficiencies of applied AOPs were compared in the presence and absence of dissolved oxygen. The removal efficiency of the studied AOPs towards degradation of CLF were found in the order of VUV / TiO/sub 2/ + O/sub 2/ > VUV/TiO/sub 2/ + N/sub 2/ > VUV alone > UV / TiO/sub 2/ + O/sub 2/ > UV / TiO/sub 2/ +N/sub 2/ > UV alone. The decomposition kinetics of CLF was found to follow pseudo-first order rate law. VUV / TiO2 process was found to be most cheap and effective one for decomposition of CLF as compared to other applied AOPs in terms of electrical energy per order. Degradation products resulting from the degradation processes were also investigated using UPLC-MS /MS, accordingly degradation pathway was proposed. (author)

  1. Ordered Mesoporous Carbons as Novel and Efficient Adsorbent for Dye Removal from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Phuong T. Dang

    2016-01-01

    Full Text Available Ordered mesoporous carbons (OMCs were successfully synthesized by using hard template and soft template methods. These materials were characterized by XRD, TEM, and N2 adsorption-desorption Brunauer-Emmett-Teller (BET. From the obtained results, it is revealed that the obtained OMCs samples showed high surface area (>1000 m2/g with high pore volume, mainly mesopore volume (1.2–2.4 cm3/g. Moreover, OMCs samples had similar structure of the SBA-15 silica and exhibited high MB adsorption capacity with qm of 398 mg·g−1 for OMCs synthesis with hard template and 476 mg·g−1 for OMCs synthesis with soft template, respectively. From kinetics investigation, it is confirmed that MB adsorption from aqueous solution obeys the pseudo-second-order kinetic equation.

  2. Fluoride sorption using Cynodon dactylon based activated carbon

    Directory of Open Access Journals (Sweden)

    Alagumuthu G.

    2011-01-01

    Full Text Available This study deals the application of Cynodon dactylon based thermally activated carbon for fluoride toxicity. The batch adsorption techniques was followed at neutral pH as the functions of contact time, adsorbent dose, adsorbate concentration, temperature and the effect of co-anions. The data indicate that the prepared adsorbent surface sites are heterogeneous in nature and that fits into a heterogeneous site-binding model. The present system followed the Redlich-Peterson isotherm as well as Langmuir adsorption isotherm model. Lagergren pseudo-first-order, pseudo-second-order, intra particle diffusion and Elovich kinetics were modeled to describe the adsorption rate of fluoride and determined as this scheme followed pseudo-second-order kinetics. The calculated enthalpy change, ΔH°, and entropy change, ΔS°, for the adsorption process are +8.725 kJ/mol and +0.033 J/mol K respectively and shows endothermic experience. Instrumental analysis of XRD, FTIR and SEM gives the idea about the fluoride binding ability of adsorbent.

  3. Adsorption of gold onto γ-aminopropyltriethoxysilane grafted coconut pith

    International Nuclear Information System (INIS)

    Usman, M.; Akhtar, J.

    2017-01-01

    This study was carried out to investigate adsorption kinetic and adsorption thermodynamics of Au(III) ions onto γ-aminopropyltriethoxysilane grafted coconut pith. The results from equilibrium adsorption were fitted in various adsorption isotherm models such as Langmuir, Freundlich, Temkin and Dubinin-Radushkevich and the best fit for the experimental data was Langmuir isotherm. The maximum adsorption capacity for virgin coconut pith (VCP) and the grafted coconut pith (GCP) were 256.41 and 285.59 mg/g, respectively. The kinetic data was verified using pseudo-first-order, pseudo-second-order, elovich equation and intraparticle diffusion model. The correlation results suggested that the pseudo-second-order model fits the experimental data well. A thermodynamic study revealed the endothermic nature of reaction due to positive enthalpy (?Ho) values and negative values of Gibbs free energy (?Go) describes the spontaneity of adsorption process. The regenerability of VCP and GCP adsorbents were investigated with NaOH (1.0 M).

  4. Pseudo-Riemannian Novikov algebras

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhiqi; Zhu Fuhai [School of Mathematical Sciences and LPMC, Nankai University, Tianjin 300071 (China)], E-mail: chenzhiqi@nankai.edu.cn, E-mail: zhufuhai@nankai.edu.cn

    2008-08-08

    Novikov algebras were introduced in connection with the Poisson brackets of hydrodynamic-type and Hamiltonian operators in formal variational calculus. Pseudo-Riemannian Novikov algebras denote Novikov algebras with non-degenerate invariant symmetric bilinear forms. In this paper, we find that there is a remarkable geometry on pseudo-Riemannian Novikov algebras, and give a special class of pseudo-Riemannian Novikov algebras.

  5. Kinetics and

    Directory of Open Access Journals (Sweden)

    Mojtaba Ahmadi

    2016-11-01

    Full Text Available The aqueous degradation of Reactive Yellow 84 (RY84 by potassium peroxydisulfate (K2S2O8 has been studied in laboratory scale experiments. The effect of the initial concentrations of potassium peroxydisulfate and RY84, pH and temperature on RY84 degradation were also examined. Experimental data were analyzed using first and second-order kinetics. The degradation kinetics of RY84 of the potassium peroxydisulfate process followed the second-order reaction kinetics. These rate constants have an extreme values similar to of 9.493 mM−1min−1 at a peroxydisulfate dose of 4 mmol/L. Thermodynamic parameters such as activation (Ea and Gibbs free energy (ΔG° were also evaluated. The negative value of ΔGo and Ea shows the spontaneous reaction natural conditions and exothermic nature.

  6. Cold Incineration of Chlorophenols in Aqueous Solution by Advanced Electrochemical Process Electro-Fenton. Effect of Number and Position of Chlorine Atoms on the Degradation Kinetics

    Science.gov (United States)

    Oturan, Nihal; Panizza, Marco; Oturan, Mehmet A.

    2009-09-01

    This study reports the kinetics of the degradation of several chlorophenols (CPs), such as monochlorophenols (2-chlorophenol and 4-chlorophenol), dichlorophenols (2,4-dichlorophenol and 2,6- dichlorophenol), trichlorophenols (2,3,5- trichlorophenol and 2,4,5-trichlorophenol), 2,3,5,6-tetrachlorophenol, and pentachlorophenol, by the electro-Fenton process using a carbon felt cathode and a Pt anode. The effect of number and the position of the chlorine atoms in the aromatic ring on the oxidative degradation rate was evaluated and discussed. The oxidation reaction of all the CPs with hydroxyl radicals evidenced a pseudo-first-order kinetics and the rate constant decreased with increasing the number of chlorine atoms. The absolute rate constant of second-order reaction kinetics between CPs and •OH was determined by the competition kinetics method in the range of (3.56-7.75) × 109 M-1 s-1 and follows the same sequence of the apparent rate constants. The mineralization of several CPs and of a mixture of all CPs under study was monitored by the total organic carbon (TOC) removal and the chlorine release during mineralization was followed by ion chromatography. Our results demonstrated that more chlorinated phenols are more difficult to mineralize; however for all the tested CPs, almost quantitative release of chloride ions was obtained after 6 h of treatment.

  7. Copper adsorption on magnetite-loaded chitosan microspheres: A kinetic and equilibrium study

    Energy Technology Data Exchange (ETDEWEB)

    Podzus, P.E., E-mail: ppodzus@gmail.com [Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Debandi, M.V. [Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina); Daraio, M.E., E-mail: medit@fi.uba.ar [Grupo de Aplicaciones de Materiales Biocompatibles, Departamento de Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV Buenos Aires (Argentina)

    2012-08-15

    A composite of Fe{sub 3}O{sub 4} nanoparticles and the biopolymer chitosan, chemically crosslinked, was prepared as microspheres and used to adsorb copper ions, which were chosen as a model of contaminant metal in water. The adsorption of copper on the magnetic microspheres was studied in a batch process, with different aqueous solutions of Cu (II) at concentrations ranging from 40 to 1100 ppm. Kinetic and equilibrium aspects of the adsorption process were studied. The time-dependent Cu (II) adsorption data were well described by a pseudo-second-order kinetic model. It was found that the equilibrium data follow the Langmuir isotherm, with a maximum adsorption capacity of around 500 mg Cu/g chitosan. The used microspheres were removed and after desorption the material was able to be reused as an adsorbent. The prepared microspheres proved efficient in the removal of copper ions through an adsorption process whose kinetic and equilibrium characteristics were analyzed.

  8. Complexes between ovalbumin nanoparticles and linoleic acid: Stoichiometric, kinetic and thermodynamic aspects.

    Science.gov (United States)

    Sponton, Osvaldo E; Perez, Adrián A; Carrara, Carlos R; Santiago, Liliana G

    2016-11-15

    Stoichiometric, kinetic and thermodynamic aspects of complex formation between heat-induced aggregates of ovalbumin (ovalbumin nanoparticles, OVAn) and linoleic acid (LA) were evaluated. Extrinsic fluorescence data were fitted to modified Scatchard model yielding the following results: n: 49±2 LA molecules bound per OVA monomer unit and Ka: 9.80±2.53×10(5)M. Kinetic and thermodynamic properties were analyzed by turbidity measurements at different LA/OVA monomer molar ratios (21.5-172) and temperatures (20-40°C). An adsorption approach was used and a pseudo-second-order kinetics was found for LA-OVAn complex formation. This adsorption process took place within 1h. Thermodynamic parameters indicated that LA adsorption on OVAn was a spontaneous, endothermic and entropically-driven process, highlighting the hydrophobic nature of the LA and OVAn interaction. Finally, Atomic Force Microscopy imaging revealed that both OVAn and LA-OVAn complexes have a roughly rounded form with size lower than 100nm. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Copper adsorption on magnetite-loaded chitosan microspheres: A kinetic and equilibrium study

    International Nuclear Information System (INIS)

    Podzus, P.E.; Debandi, M.V.; Daraio, M.E.

    2012-01-01

    A composite of Fe 3 O 4 nanoparticles and the biopolymer chitosan, chemically crosslinked, was prepared as microspheres and used to adsorb copper ions, which were chosen as a model of contaminant metal in water. The adsorption of copper on the magnetic microspheres was studied in a batch process, with different aqueous solutions of Cu (II) at concentrations ranging from 40 to 1100 ppm. Kinetic and equilibrium aspects of the adsorption process were studied. The time-dependent Cu (II) adsorption data were well described by a pseudo-second-order kinetic model. It was found that the equilibrium data follow the Langmuir isotherm, with a maximum adsorption capacity of around 500 mg Cu/g chitosan. The used microspheres were removed and after desorption the material was able to be reused as an adsorbent. The prepared microspheres proved efficient in the removal of copper ions through an adsorption process whose kinetic and equilibrium characteristics were analyzed.

  10. A kinetic model of the formation of organic monolayers on hydrogen-terminated silicon by hydrosilation of alkenes.

    Science.gov (United States)

    Woods, M; Carlsson, S; Hong, Q; Patole, S N; Lie, L H; Houlton, A; Horrocks, B R

    2005-12-22

    We have analyzed a kinetic model for the formation of organic monolayers based on a previously suggested free radical chain mechanism for the reaction of unsaturated molecules with hydrogen-terminated silicon surfaces (Linford, M. R.; Fenter, P. M.; Chidsey, C. E. D. J. Am. Chem. Soc 1995, 117, 3145). A direct consequence of this mechanism is the nonexponential growth of the monolayer, and this has been observed spectroscopically. In the model, the initiation of silyl radicals on the surface is pseudo first order with rate constant, ki, and the rate of propagation is determined by the concentration of radicals and unreacted Si-H nearest neighbor sites with a rate constant, kp. This propagation step determines the rate at which the monolayer forms by addition of alkene molecules to form a track of molecules that constitute a self-avoiding random walk on the surface. The initiation step describes how frequently new random walks commence. A termination step by which the radicals are destroyed is also included. The solution of the kinetic equations yields the fraction of alkylated surface sites and the mean length of the random walks as a function of time. In mean-field approximation we show that (1) the average length of the random walk is proportional to (kp/ki)1/2, (2) the monolayer surface coverage grows exponentially only after an induction period, (3) the effective first-order rate constant describing the growth of the monolayer and the induction period (kt) is k = (2ki kp)1/2, (4) at long times the effective first-order rate constant drops to ki, and (5) the overall activation energy for the growth kinetics is the mean of the activation energies for the initiation and propagation steps. Monte Carlo simulations of the mechanism produce qualitatively similar kinetic plots, but the mean random walk length (and effective rate constant) is overestimated by the mean field approximation and when kp > ki, we find k approximately ki0.7kp0.3 and Ea = (0.7Ei+ 0.3Ep

  11. Removal of Cu(II) from leachate using natural zeolite as a landfill liner material.

    Science.gov (United States)

    Turan, N Gamze; Ergun, Osman Nuri

    2009-08-15

    All hazardous waste disposal facilities require composite liner systems to act as a barrier against migration of contaminated leachate into the subsurface environment. Removal of copper(II) from leachate was studied using natural zeolite. A serial of laboratory systems on bentonite added natural zeolite was conducted and copper flotation waste was used as hazardous waste. The adsorption capacities and sorption efficiencies were determined. The sorption efficiencies increased with increasing natural zeolite ratio. The pseudo-first-order, the pseudo-second-order, Elovich and the intra-particle diffusion kinetic models were used to describe the kinetic data to estimate the rate constants. The second-order model best described adsorption kinetic data. The results indicated that natural zeolite showed excellent adsorptive characteristics for the removal of copper(II) from leachate and could be used as very good liner materials due to its high uptake capacity and the abundance in availability.

  12. Removal of Cu(II) from leachate using natural zeolite as a landfill liner material

    International Nuclear Information System (INIS)

    Turan, N. Gamze; Ergun, Osman Nuri

    2009-01-01

    All hazardous waste disposal facilities require composite liner systems to act as a barrier against migration of contaminated leachate into the subsurface environment. Removal of copper(II) from leachate was studied using natural zeolite. A serial of laboratory systems on bentonite added natural zeolite was conducted and copper flotation waste was used as hazardous waste. The adsorption capacities and sorption efficiencies were determined. The sorption efficiencies increased with increasing natural zeolite ratio. The pseudo-first-order, the pseudo-second-order, Elovich and the intra-particle diffusion kinetic models were used to describe the kinetic data to estimate the rate constants. The second-order model best described adsorption kinetic data. The results indicated that natural zeolite showed excellent adsorptive characteristics for the removal of copper(II) from leachate and could be used as very good liner materials due to its high uptake capacity and the abundance in availability.

  13. Study on Selective Removal of Impurity Iron from Leached Copper-Bearing Solution Using a Chelating Resin

    Directory of Open Access Journals (Sweden)

    Yubiao Li

    2016-10-01

    Full Text Available In order to selectively remove iron from copper laden solution after leaching but prior to electrowinning, equilibrium, kinetic, and thermodynamic studies have been conducted on an a chelating resin of Rexp-501 at pH 1.0 and at various temperatures. Both Langmuir and Freundlich models were investigated, with the Langmuir model proving to be more suitable for fitting iron removal performance, with little influence from copper concentration. Compared with the pseudo first order kinetic model, the pseudo second order kinetic model fitted the dynamic adsorption process better, indicating a chemisorption mechanism. Fourier transform infrared spectroscopy (FT-IR results indicated that C=O from carbonyl group played a key role in combining with iron and can be regenerated and reused. However, the C=O of the acylamino group combining with iron was not able to be released after oxalic acid was applied.

  14. Perisplenic Pseudo

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyo Heon; Cho, Sin Young; Suh, Hong Kil; Kim, Ji Hyeon; Choi, Chul Soon; Lee, Eil Seong; Kang, Ik Won [Hallym University College of Medicine, Chuncheon (Korea, Republic of)

    1995-12-15

    Perisplenic pseudo 'fluid collection' is one of the rare normal variations. Its frequency and sonographic findings for the differentiation from true perisplenic fluid collection have not been well described. Thus, we performed this study. The examination was performed with special attention to the splenic and perisplenic areas. We excluded patients with proved or suspected liver cirrhosis, pancreatic diseases,and abdominal trauma from the study population, but did not exclude the patients with chronic hepatitis and the carriers of hepatitis B virus. Of the examined 4794 patients, 8 cases showed perisplenic pseudo 'fluid collection'. Two of them were confirmed with computed tomography and liver scan, and six were inferred from the fact proved to be a part of the left lobe extension of the liver by tracing with the transducer. All cases ofperisplenic pseudo 'fluid collection' showed hypoechoic crescent area with hepatic ductal echoes. Perisplenic pseudo 'fluid collection' is very rare. The helpful findings for the differentiation from true fluid collection are the hepatic ductal echoes seen in the normal liver, proof of continuation into remained voluminous liver by tracing with the transducer. High awareness of it would prevent further unnecessary studies such as computed tomography and liver scan

  15. Equilibrium and kinetic study for the adsorption of p-nitrophenol from wastewater using olive cake based activated carbon

    International Nuclear Information System (INIS)

    Abdel-Ghani, N. T.; Rawash, E. S. A.; El-Chaghaby, G. A.

    2016-01-01

    The present work was carried out to evaluate the removal of p-nitrophenol by adsorption onto olive cake based activated carbon having a BET surface area of 672 m²/g. The batch adsorption experimental results indicated that the equilibrium time for nitrophenol adsorption by olive cake-based activated carbon was 120 minutes. The adsorption data was modeled by equilibrium and kinetic models. The pseudo- first and second order as well as the Elovichkinetic models were applied to fit the experimental data and the intra particle diffusion model was assessed for describing the mechanism of adsorption. The data were found to be best fitted to the pseudo-second order model with a correlation coefficient (R2=0.986). The intra particle diffusion mechanism also showed a good fit to the experimental data, showing two distinct linear parts assuming that more than one step could be involved in the adsorption of nitrophenol by the activated carbon. The equilibrium study was performed using three models including Langmuir, Freundlich and Temkin. The results revealed that the Temkin equilibrium model is the best model fitting the experimental data (R2=0.944). The results of the present study proved the efficiency of using olive cake based activated carbon as a novel adsorbent for the removal of nitrophenol from aqueous solution.

  16. Ranking nano-enabled hybrid media for simultaneous removal of contaminants with different chemistries: Pseudo-equilibrium sorption tests versus column tests.

    Science.gov (United States)

    Custodio, Tomas; Garcia, Jose; Markovski, Jasmina; McKay Gifford, James; Hristovski, Kiril D; Olson, Larry W

    2017-12-15

    The underlying hypothesis of this study was that pseudo-equilibrium and column testing conditions would provide the same sorbent ranking trends although the values of sorbents' performance descriptors (e.g. sorption capacity) may vary because of different kinetics and competition effects induced by the two testing approaches. To address this hypothesis, nano-enabled hybrid media were fabricated and its removal performances were assessed for two model contaminants under multi-point batch pseudo-equilibrium and continuous-flow conditions. Calculation of simultaneous removal capacity indices (SRC) demonstrated that the more resource demanding continuous-flow tests are able to generate the same performance rankings as the ones obtained by conducing the simpler pseudo-equilibrium tests. Furthermore, continuous overlap between the 98% confidence boundaries for each SRC index trend, not only validated the hypothesis that both testing conditions provide the same ranking trends, but also pointed that SRC indices are statistically the same for each media, regardless of employed method. In scenarios where rapid screening of new media is required to obtain the best performing synthesis formulation, use of pseudo-equilibrium tests proved to be reliable. Considering that kinetics induced effects on sorption capacity must not be neglected, more resource demanding column test could be conducted only with the top performing media that exhibit the highest sorption capacity. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Effect of sorbic acid and some other food preservatives on human ...

    African Journals Online (AJOL)

    Arif

    2012-06-26

    Jun 26, 2012 ... and certain fruit and vegetable products, including wines. Sorbates are generally ... the enzyme that follows pseudo first order kinetics (Odani et al., 1982 ..... Inhibition of alcoholic fermentation by sorbic acid. J. Bacteriol., 81: ...

  18. Kinetics of phase transformations

    International Nuclear Information System (INIS)

    Thompson, M.O.; Aziz, M.J.; Stephenson, G.B.

    1992-01-01

    This volume contains papers presented at the Materials Research Society symposium on Kinetics of Phase Transformations held in Boston, Massachusetts from November 26-29, 1990. The symposium provided a forum for research results in an exceptionally broad and interdisciplinary field. Presentations covered nearly every major class of transformations including solid-solid, liquid-solid, transport phenomena and kinetics modeling. Papers involving amorphous Si, a dominant topic at the symposium, are collected in the first section followed by sections on four major areas of transformation kinetics. The symposium opened with joint sessions on ion and electron beam induced transformations in conjunction with the Surface Chemistry and Beam-Solid Interactions: symposium. Subsequent sessions focused on the areas of ordering and nonlinear diffusion kinetics, solid state reactions and amorphization, kinetics and defects of amorphous silicon, and kinetics of melting and solidification. Seven internationally recognized invited speakers reviewed many of the important problems and recent results in these areas, including defects in amorphous Si, crystal to glass transformations, ordering kinetics, solid-state amorphization, computer modeling, and liquid/solid transformations

  19. A Classical Based Derivation of Time Dilation Providing First Order Accuracy to Schwarzschild's Solution of Einstein's Field Equations

    Science.gov (United States)

    Austin, Rickey W.

    In Einstein's theory of Special Relativity (SR), one method to derive relativistic kinetic energy is via applying the classical work-energy theorem to relativistic momentum. This approach starts with a classical based work-energy theorem and applies SR's momentum to the derivation. One outcome of this derivation is relativistic kinetic energy. From this derivation, it is rather straight forward to form a kinetic energy based time dilation function. In the derivation of General Relativity a common approach is to bypass classical laws as a starting point. Instead a rigorous development of differential geometry and Riemannian space is constructed, from which classical based laws are derived. This is in contrast to SR's approach of starting with classical laws and applying the consequences of the universal speed of light by all observers. A possible method to derive time dilation due to Newtonian gravitational potential energy (NGPE) is to apply SR's approach to deriving relativistic kinetic energy. It will be shown this method gives a first order accuracy compared to Schwarzschild's metric. The SR's kinetic energy and the newly derived NGPE derivation are combined to form a Riemannian metric based on these two energies. A geodesic is derived and calculations compared to Schwarzschild's geodesic for an orbiting test mass about a central, non-rotating, non-charged massive body. The new metric results in high accuracy calculations when compared to Einsteins General Relativity's prediction. The new method provides a candidate approach for starting with classical laws and deriving General Relativity effects. This approach mimics SR's method of starting with classical mechanics when deriving relativistic equations. As a compliment to introducing General Relativity, it provides a plausible scaffolding method from classical physics when teaching introductory General Relativity. A straight forward path from classical laws to General Relativity will be derived. This derivation

  20. UV and solar photo-degradation of naproxen: TiO₂ catalyst effect, reaction kinetics, products identification and toxicity assessment.

    Science.gov (United States)

    Jallouli, Nabil; Elghniji, Kais; Hentati, Olfa; Ribeiro, Ana R; Silva, Adrián M T; Ksibi, Mohamed

    2016-03-05

    Direct photolysis and TiO2-photocatalytic degradation of naproxen (NPX) in aqueous solution were studied using a UV lamp and solar irradiation. The degradation of NPX was found to be in accordance with pseudo-first order kinetics, the photocatalytic process being more efficient than photolysis. The NPX removal by photolysis (pHinitial 6.5) was 83% after 3h, with 11% of chemical oxygen demand (COD) reduction, whereas the TiO2-UV process led to higher removals of both NPX (98%) and COD (25%). The apparent pseudo-first-order rate constant (kapp) for NPX degradation by photolysis ranged from 0.0050 min(-1) at pH 3.5 to 0.0095 min(-1) at pH 6.5, while it was estimated to be 0.0063 min(-1) under acidic conditions in photocatalysis, increasing by 4-fold at pH 6.5. Ultra High Performance Liquid chromatography (UHPLC) coupled with a triple quadrupole detector and also a hybrid mass spectrometer which combines the linear ion trap triple quadrupole (LTQ) and OrbiTrap mass analyser, were used to identify NPX degradation products. The main intermediates detected were 1-(6-methoxynaphtalene-2-yl) ethylhydroperoxide, 2-ethyl-6-methoxynaphthalene, 1-(6-methoxynaphtalen-2-yl) ethanol, 1-(6-methoxynaphtalen-2-yl) ethanone and malic acid. Solar photocatalysis of NPX showed COD removals of 33% and 65% after 3 and 4h of treatment, respectively, and some reduction of acute toxicity, evaluated by the exposure of Eisenia andrei to OECD soils spiked with NPX-treated solutions. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Kinetics and thermodynamics of aqueous Cu(II adsorption on heat regenerated spent bleaching earth

    Directory of Open Access Journals (Sweden)

    Enos W. Wambu

    2011-08-01

    Full Text Available This study investigated the kinetics and thermodynamics of copper(II removal from aqueous solutions using spent bleaching earth (SBE. The spent bleaching earth, a waste material from edible oil processing industries, was reactivated by heat treatment at 370 oC after residual oil extraction in excess methyl-ethyl ketone. Copper adsorption tests were carried out at room temperature (22±3 oC using 5.4 x 10-3C M metal concentrations. More than 70% metal removal was recorded in the first four hours although adsorption continued to rise to within 90% at 42 hours. The pH, adsorbent dosage and initial concentrations were master variables affecting RSBE adsorption of Cu(II ions. The adsorption equilibrium was adequately described by the Dubinin-Radushkevich (D-R and the Temkin isotherms and the maximum sorption capacity derived from the D-R isotherm was compared with those of some other low cost adsorbents. The adsorption process was found to follow Lagergren Pseudo-second order kinetics complimented by intra-particle diffusion kinetics at prolonged periods of equilibration. Based on the D-R isotherm adsorption energy and the thermodynamic adsorption free energy ∆G, it was suggested that the process is spontaneous and based on electrostatic interactions between the metal ions and exposed active sites in the adsorbent surface.

  2. Conformal maps between pseudo-Finsler spaces

    Science.gov (United States)

    Voicu, Nicoleta

    The paper aims to initiate a systematic study of conformal mappings between Finsler spacetimes and, more generally, between pseudo-Finsler spaces. This is done by extending several results in pseudo-Riemannian geometry which are necessary for field-theoretical applications and by proposing a technique that reduces some problems involving pseudo-Finslerian conformal vector fields to their pseudo-Riemannian counterparts. Also, we point out, by constructing classes of examples, that conformal groups of flat (locally Minkowskian) pseudo-Finsler spaces can be much richer than both flat Finslerian and pseudo-Euclidean conformal groups.

  3. First-order dynamical phase transition in models of glasses: an approach based on ensembles of histories

    International Nuclear Information System (INIS)

    Garrahan, Juan P; Jack, Robert L; Lecomte, Vivien; Duijvendijk, Kristina van; Wijland, Frederic van; Pitard, Estelle

    2009-01-01

    We investigate the dynamics of kinetically constrained models of glass formers by analysing the statistics of trajectories of the dynamics, or histories, using large deviation function methods. We show that, in general, these models exhibit a first-order dynamical transition between active and inactive dynamical phases. We argue that the dynamical heterogeneities displayed by these systems are a manifestation of dynamical first-order phase coexistence. In particular, we calculate dynamical large deviation functions, both analytically and numerically, for the Fredrickson-Andersen model, the East model, and constrained lattice gas models. We also show how large deviation functions can be obtained from a Landau-like theory for dynamical fluctuations. We discuss possibilities for similar dynamical phase-coexistence behaviour in other systems with heterogeneous dynamics

  4. Sorption of uranium cationic species from aqueous solutions on Slovak bentonite Jelsovy potok

    Energy Technology Data Exchange (ETDEWEB)

    Krajnak, A.; Viglasova, E.; Galambos, M.; Rosskopfova, O. [Comenius University in Bratislava, Faculty of Natural Sciences, Department of Nuclear Chemistry, 842 15 Bratislava (Slovakia)

    2013-04-16

    Bentonite deposit Jelsovy potok in Slovakia has great potential for use as a engineering barrier in the multi-barrier system of deep geological repository for high level radioactive waste and spent nuclear fuel. In this study, the adsorption equilibrium and kinetics of U(VI) ions on Slovak bentonite Jelsovy potok (J15) was examined. The removal of uranium cationic species from aqueous solutions (initial concentration: 10-1,000 mg/L) by J15 was studied in the absence of background electrolytes at initial pH (pH{sub init}) 2.5. The amount of the sorbed U was determined spectrophotometrically using the Arsenazo III method. The maximum uptake capacity observed was 30.15 (mg/g) at 298 K. Experimental results were analysed by the Langmuir, Freundlich and Dubinin-Redushkevich isotherm. The kinetics of adsorption of U(VI) ions was also discussed using the pseudo-first-order and the pseudo-second-order at three different temperatures. The experimental data fitted very well the pseudo-second-order kinetic model. The activation energy of the sorption was calculated as 11.316 kJ.mol{sup -}1 for J15. (authors)

  5. Effect of the humic acids in the adsorption of U (Vi) in a Mexican natural zeolite; Efecto de los acidos humicos en la adsorcion de U (VI) en una zeolita natural mexicana

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval G, H. A.; Lopez del R, H.; Davila R, J. I.; Mireles G, F., E-mail: hlopezdelrio@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2012-10-15

    The uranium adsorption was studied in a Mexican natural zeolite of the clinoptilolite type in presence and absence of humic acids (Ha). The adsorption kinetics of the binary U-zeolite and ternary U-Ha-zeolite systems were compared, and the effect of the humic matter impregnated in the zeolite in the uranium removal in function of the solution ph was studied. The experiments were made to environmental conditions and lightly acid ph, with fixed concentrations of uranium and Ha of 1 x 10{sup -5} M and 20 ppm, respectively, and a reason m/V of 5 mg/ml. The uranium adsorption in absence of Ha was of 96% and decreased to 45% in the ternary system U-Ha-zeolite. The data of the binary system U-zeolite were analyzed with three kinetic models of adsorption (pseudo-first order, pseudo-second order and Elovich). By means of non lineal regression was found that the uranium adsorption obeys a kinetic of pseudo-second order. It was observed that the uranium adsorption in the zeolite impregnated with Ha is favored to more ph at 5. (Author)

  6. Poly(acrylic acid) modifying bentonite with in-situ polymerization for removing lead ions.

    Science.gov (United States)

    He, Y F; Zhang, L; Yan, D Z; Liu, S L; Wang, H; Li, H R; Wang, R M

    2012-01-01

    In this paper, a new kind of poly(acrylic acid) modified clay adsorbent, the poly(acrylic acid)/bentonite composite (PAA/HB) was prepared by in-situ polymerization, and utilized to remove lead(II) ions from solutions. The maximum adsorption of adsorbent is at pH 5 for metal ions, whereas the adsorption starts at pH 2. The effects of contact time (5-60 min), initial concentration of metal ions (200-1,000 mg/L) and adsorbent dosage (0.04-0.12 g/100 mL) have been reported in this article. The experimental data were investigated by means of kinetic and equilibrium adsorption isotherms. The kinetic data were analyzed by the pseudo-first-order and pseudo-second-order equation. The experimental data fitted the pseudo-second-order kinetic model very well. Langmuir and Freundlich isotherms were tried for the system to better understand the adsorption isotherm process. The maximal adsorption capacity of the lead(II) ions on the PAA/HB, as calculated from the Langmuir model, was 769.2 mg/g. The results in this study indicated that PAA/HB was an attractive candidate for removing lead(II) (99%).

  7. Calculated Third Order Rate Constants for Interpreting the Mechanisms of Hydrolyses of Chloroformates, Carboxylic Acid Halides, Sulfonyl Chlorides and Phosphorochloridates

    Directory of Open Access Journals (Sweden)

    T. William Bentley

    2015-05-01

    Full Text Available Hydrolyses of acid derivatives (e.g., carboxylic acid chlorides and fluorides, fluoro- and chloroformates, sulfonyl chlorides, phosphorochloridates, anhydrides exhibit pseudo-first order kinetics. Reaction mechanisms vary from those involving a cationic intermediate (SN1 to concerted SN2 processes, and further to third order reactions, in which one solvent molecule acts as the attacking nucleophile and a second molecule acts as a general base catalyst. A unified framework is discussed, in which there are two reaction channels—an SN1-SN2 spectrum and an SN2-SN3 spectrum. Third order rate constants (k3 are calculated for solvolytic reactions in a wide range of compositions of acetone-water mixtures, and are shown to be either approximately constant or correlated with the Grunwald-Winstein Y parameter. These data and kinetic solvent isotope effects, provide the experimental evidence for the SN2-SN3 spectrum (e.g., for chloro- and fluoroformates, chloroacetyl chloride, p-nitrobenzoyl p-toluenesulfonate, sulfonyl chlorides. Deviations from linearity lead to U- or V-shaped plots, which assist in the identification of the point at which the reaction channel changes from SN2-SN3 to SN1-SN2 (e.g., for benzoyl chloride.

  8. Mechanism and kinetics of uranium adsorption onto soil around coal-fired power plant

    Science.gov (United States)

    Yasim, Nurzulaifa Shaheera Erne Mohd; Ariffin, Nik Azlin Nik; Mohammed, Noradila; Ayob, Syafina

    2017-11-01

    Coal is the largest source of energy in Malaysia providing approximately 80 % of all entire power needs. The combustion of coal concentrates a high content of heavy metals and radioactive elements in the ashes and sludge. Hazardous emissions from coal combustion were deposited into the soil and most likely transported into the groundwater system. The presence of radioactive materials in the ground water system can cause a wide range of environmental impacts and adverse health effects like cancer, impairment of neurological function and cardiovascular disease. However, the soil has a natural capability in adsorption of radioactive materials. Thus, this study was evaluated the adsorption capacity of Uranium onto the soil samples collected nearby the coal-fired power plants. In the batch experiment, parameters that were set constant include pH, the amount of soil and contact time. Various initial concentrations of radionuclides elements in the range of 2 mg/L - 10 mg/L were used. The equilibrium adsorption data was analyzed by the Freundlich isotherm and Langmuir isotherms. Then, the influences of solution pH, contact time and temperature on the adsorption process were investigated. The kinetics of radioactive materials was discussed by pseudo-first-order and pseudo-second-order rate equation. Thus, the data from this study could provide information about the potentiality of soil in sorption of radioactive materials that can be leached into groundwater. Besides that, this study could also be used as baseline data for future reference in the development of adsorption modeling in the calculation of distribution coefficient.

  9. UV and solar photo-degradation of naproxen: TiO_2 catalyst effect, reaction kinetics, products identification and toxicity assessment

    International Nuclear Information System (INIS)

    Jallouli, Nabil; Elghniji, Kais; Hentati, Olfa; Ribeiro, Ana R.; Silva, Adrián M.T.; Ksibi, Mohamed

    2016-01-01

    Highlights: • Degradation kinetics and mineralization rate of naproxen (NPX) were studied. • Direct photolysis and TiO_2/UV approaches were evaluated. • The formation of by-products was followed by UHPLC-DAD-MS. • Ecological risk assessment of NPX-treated solutions was assessed using E. andrei. - Abstract: Direct photolysis and TiO_2-photocatalytic degradation of naproxen (NPX) in aqueous solution were studied using a UV lamp and solar irradiation. The degradation of NPX was found to be in accordance with pseudo-first order kinetics, the photocatalytic process being more efficient than photolysis. The NPX removal by photolysis (pH_i_n_i_t_i_a_l 6.5) was 83% after 3 h, with 11% of chemical oxygen demand (COD) reduction, whereas the TiO_2-UV process led to higher removals of both NPX (98%) and COD (25%). The apparent pseudo-first-order rate constant (k_a_p_p) for NPX degradation by photolysis ranged from 0.0050 min"−"1 at pH 3.5 to 0.0095 min"−"1 at pH 6.5, while it was estimated to be 0.0063 min"−"1 under acidic conditions in photocatalysis, increasing by 4-fold at pH 6.5. Ultra High Performance Liquid chromatography (UHPLC) coupled with a triple quadrupole detector and also a hybrid mass spectrometer which combines the linear ion trap triple quadrupole (LTQ) and OrbiTrap mass analyser, were used to identify NPX degradation products. The main intermediates detected were 1-(6-methoxynaphtalene-2-yl) ethylhydroperoxide, 2-ethyl-6-methoxynaphthalene, 1-(6-methoxynaphtalen-2-yl) ethanol, 1-(6-methoxynaphtalen-2-yl) ethanone and malic acid. Solar photocatalysis of NPX showed COD removals of 33% and 65% after 3 and 4 h of treatment, respectively, and some reduction of acute toxicity, evaluated by the exposure of Eisenia andrei to OECD soils spiked with NPX-treated solutions.

  10. 10.23  Mcps laser pseudo-code ranging system with 0.33  mm (1σ) pseudo-range measurement precision.

    Science.gov (United States)

    Yu, Xiaonan; Tong, Shoufeng; Zhang, Lei; Dong, Yan; Zhao, Xin; Qiao, Yue

    2017-07-01

    The inter-satellite laser link is the backbone of the next inter-satellite information network, and ranging and communication are the main functions of the inter-satellite laser link. This study focuses on the inter-satellite laser ranging based on the pseudo-code correlation technology. In this paper, several typical laser-ranging methods have been compared and we determined that the laser pseudo-code ranging architecture is more suitable for the inter-satellite laser communication link. The pseudo-code ranging system is easy to combine with a digital communication system, and we used it to calculate integer ambiguity by modulating the time information. The main challenge of the ranging system is range precision, which is the main focus of this paper. First, the framework of the pseudo-code ranging system is introduced; the ranging architecture of dual one-way ranging is used to eliminate the clock error between the two transceivers, and then the uncertainty of the phase detector is analyzed. In the analysis, the carrier to noise ratio and the ranging code rate are constrained by the laser communication link margin and the electronic hardware limitation. Therefore, the relationship between the sampling depth and the phase detector uncertainty is verified. A series of optical fiber channel laser pseudo-code ranging experiments demonstrated the effects of sampling depth on the ranging precision. By adjusting the depth of storage, such as the depth of 1.6 Mb, we obtained a pseudo-range measurement precision of 0.33 mm (1σ), which is equivalent to 0.0001 times code subdivision of 10.23 Mcps pseudo-code. This paper has achieved high precision in a pseudo-range measurements, which is the foundation of the inter-satellite laser link.

  11. Effect of Process Variables, Adsorption Kinetics and Equilibrium Studies of Hexavalent Chromium Removal from Aqueous Solution by Date Seeds and its Activated Carbon by ZnCl2

    Directory of Open Access Journals (Sweden)

    Samar K. Theydan

    2018-03-01

    Full Text Available The adsorption of hexavalent chromium by preparing activated carbon from date seeds with zinc chloride as chemical activator and granular date seeds was studied in a batch system. The characteristics of date seeds and prepared activated carbon (ZAC were determined and found to have a surface area 500.01 m2/g and 1050.01 m2/g , respectively and iodine number of 485.78 mg/g and 1012.91 mg/g, respectively. The effects of PH value (2-12, initial sorbate concentration(50-450mg/L, adsorbent weight (0.004-0.036g and contact time (30-150 min on the adsorption process were studied . For Cr(VI adsorption on ZAC, at 120 min time contact, pH solution 2 and 0.02 adsorbent weight will achieve an amount of 35.6 mg/g adsorbed . While when use date seeds as adsorbent , conditions of 3 solution pH, 0.02 absorbent weight , and 120 contact time gave 26.49 mg/g adsorbed amount. Using both Langmuir, Freundlich and Sips models were explain the dsorption isotherms. It declare that the Sips model fits well with the experimental data with a maximum Cr( VI adsorption capacity for (ZAC and granular date stone 233.493 and 208.055 mg/g, respectively . The kinetics data which obtained at different initial Cr(VI concentrations were examined by using pseudo-first-order, pseudo-second-order, and intra-particle diffusion models . The result gained showed that the second-order model was only describing well the empirical kinetics data of both (ZAC and granular date seeds. It was noticed that the granular date seeds has adsorption performance lower than the (ZAC.

  12. Brain MR image segmentation using NAMS in pseudo-color.

    Science.gov (United States)

    Li, Hua; Chen, Chuanbo; Fang, Shaohong; Zhao, Shengrong

    2017-12-01

    Image segmentation plays a crucial role in various biomedical applications. In general, the segmentation of brain Magnetic Resonance (MR) images is mainly used to represent the image with several homogeneous regions instead of pixels for surgical analyzing and planning. This paper proposes a new approach for segmenting MR brain images by using pseudo-color based segmentation with Non-symmetry and Anti-packing Model with Squares (NAMS). First of all, the NAMS model is presented. The model can represent the image with sub-patterns to keep the image content and largely reduce the data redundancy. Second, the key idea is proposed that convert the original gray-scale brain MR image into a pseudo-colored image and then segment the pseudo-colored image with NAMS model. The pseudo-colored image can enhance the color contrast in different tissues in brain MR images, which can improve the precision of segmentation as well as directly visual perceptional distinction. Experimental results indicate that compared with other brain MR image segmentation methods, the proposed NAMS based pseudo-color segmentation method performs more excellent in not only segmenting precisely but also saving storage.

  13. Kinetic modelling and mechanism of dye adsorption on unburned carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S.B.; Li, H.T. [Curtin University of Technology, Perth, WA (Australia). Dept. of Chemical Engineering

    2007-07-01

    Textile dyeing processes are among the most environmentally unfriendly industrial processes by producing coloured wastewaters. The adsorption method using unburned carbon from coal combustion residue was studied for the decolourisation of typical acidic and basic dyes. It was discovered that the unburned carbon showed high adsorption capacity at 1.97 x 10{sup -4} and 5.27 x 10{sup -4} mol/g for Basic Violet 3 and Acid Black 1, respectively. The solution pH, particle size and temperature significantly influenced the adsorption capacity. Higher solution pH favoured the adsorption of basic dye while reduced the adsorption of acid dye. The adsorption of dye increased with increasing temperature but decreased with increasing particle size. Sorption kinetic data indicated that the adsorption kinetics followed the pseudo-second-order model. The adsorption mechanism consisted of two processes, external diffusion and intraparticle diffusion, and the external diffusion was the dominating process.

  14. Kinetic and mechanistic study of microcystin-LR degradation by nitrous acid under ultraviolet irradiation

    International Nuclear Information System (INIS)

    Ma, Qingwei; Ren, Jing; Huang, Honghui; Wang, Shoubing; Wang, Xiangrong; Fan, Zhengqiu

    2012-01-01

    Highlights: ► For the first time, degradation of MC-LR by nitrous acid under UV 365 nm was discovered. ► The effects of factors on MC-LR degradation were analyzed based on kinetic study. ► Mass spectrometry was applied for identification of intermediates and products. ► Special intermediates involved in this study were identified. ► Degradation mechanisms were proposed according to the results of LC–MS analysis. - Abstract: Degradation of microcystin-LR (MC-LR) in the presence of nitrous acid (HNO 2 ) under irradiation of 365 nm ultraviolet (UV) was studied for the first time. The influence of initial conditions including pH value, NaNO 2 concentration, MC-LR concentration and UV intensity were studied. MC-LR was degraded in the presence of HNO 2 ; enhanced degradation of MC-LR was observed with 365 nm UV irradiation, caused by the generation of hydroxyl radicals through the photolysis of HNO 2 . The degradation processes of MC-LR could well fit the pseudo-first-order kinetics. Mass spectrometry was applied for identification of the byproducts and the analysis of degradation mechanisms. Major degradation pathways were proposed according to the results of LC–MS analysis. The degradation of MC-LR was initiated via three major pathways: attack of hydroxyl radicals on the conjugated carbon double bonds of Adda, attack of hydroxyl radicals on the benzene ring of Adda, and attack of nitrosonium ion on the benzene ring of Adda.

  15. [Effect of SO2 volume fraction in flue gas on the adsorption behaviors adsorbed by ZL50 activated carbon and kinetic analysis].

    Science.gov (United States)

    Gao, Ji-xian; Wang, Tie-feng; Wang, Jin-fu

    2010-05-01

    The influence of SO2 dynamic adsorption behaviors using ZL50 activated carbon for flue gas desulphurization and denitrification under different SO2 volume fraction was investigated experimentally, and the kinetic analysis was conducted by kinetic models. With the increase of SO2 volume fraction in flue gas, the SO2 removal ratio and the activity ratio of ZL50 activated carbon decreased, respectively, and SO2 adsorption rate and capacity increased correspondingly. The calculated results indicate that Bangham model has the best prediction effect, the chemisorption processes of SO2 was significantly affected by catalytic oxidative reaction. The adsorption rate constant of Lagergren's pseudo first order model increased with the increase of inlet SO, volume fraction, which indicated that catalytic oxidative reaction of SO2 adsorbed by ZL50 activated carbon may be the rate controlling step in earlier adsorption stage. The Lagergren's and Bangham's initial adsorption rate were deduced and defined, respectively. The Ho's and Elovich's initial adsorption rate were also deduced in this paper. The Bangham's initial adsorption rate values were defined in good agreement with those of experiments. The defined Bangham's adsorptive reaction kinetic model can describe the SO2 dynamic adsorption rate well. The studied results indicated that the SO2 partial order of initial reaction rate was one or adjacent to one, while the O2 and water vapor partial order of initial reaction rate were constants ranging from 0.15-0.20 and 0.45-0.50, respectively.

  16. Uptake of selenate on hydrated and degraded cement: batch and dynamic experiments

    International Nuclear Information System (INIS)

    Rojo, I.; Rovira, I.; Marti, V.; Pablo, J. de; Duro, L.; Gaona, X.; Colas, E.; Grive, M.

    2009-01-01

    The evaluation of selenate sorption and retardation in batch and dynamic experiments on hydrated and degraded cement has been studied. Desorption studies have also been carried in order to assess the reversibility of the sorption process. Sorption data onto degraded cement have been treated assuming the formation of surface complexes, whereas sorption kinetics has been fitted by using a pseudo-first order kinetic equation. Dynamic flow experiments have also been modelled. (authors)

  17. The removal of COD and NH3-N from atrazine production wastewater treatment using UV/O3: experimental investigation and kinetic modeling.

    Science.gov (United States)

    Jing, Liang; Chen, Bing; Wen, Diya; Zheng, Jisi; Zhang, Baiyu

    2018-01-01

    In this study, a UV/O 3 hybrid advanced oxidation system was used to remove chemical oxygen demand (COD), ammonia nitrogen (NH 3 -N), and atrazine (ATZ) from ATZ production wastewater. The removal of COD and NH 3 -N, under different UV and O 3 conditions, was found to follow pseudo-first-order kinetics with rate constants ranging from 0.0001-0.0048 and 0.0015-0.0056 min -1 , respectively. The removal efficiency of ATZ was over 95% after 180 min treatment, regardless the level of UV power. A kinetic model was further proposed to simulate the removal processes and to quantify the individual roles and contributions of photolysis, direct O 3 oxidation, and hydroxyl radical (OH·) induced oxidation. The experimental and kinetic modeling results agreed reasonably well with deviations of 12.2 and 13.1% for the removal of COD and NH 3 -N, respectively. Photolysis contributed appreciably to the degradation of ATZ, while OH· played a dominant role for the removal of both COD and NH 3 -N, especially in alkaline environments. This study provides insights into the treatment of ATZ containing wastewater using UV/O 3 and broadens the knowledge of kinetics of ozone-based advanced oxidation processes.

  18. Adsorption kinetics of ion of Pb2+ using Tricalcium Phosphate particles

    Science.gov (United States)

    Fadli, A.; Yenti, S. R.; Akbar, F.; Maihendra; Mawarni, F.

    2018-04-01

    One of the heavy metals that can pollute water is Pb2+. The concentration of ion Pb2+ can be removed using the adsorption method. The purpose of this research is to determine the adsorption kinetics model of ions Pb2+ using tricalcium phosphate (TCP) particles with variation of the temperature and adsorbent dosage. Five hundred mililiter Pb2+ solution with of 3 mg/L were added 0,5 gr, 1 gr and 1,5 gr of TCP in a glass beaker and stirred with rate of 300 rpm at a temperature of 30 °C, 40 °C and 50 °C. Pb2+ concentration in solution was analyzed by AAS (Atomic Adsorption Spectroscopy). The results showed that the rate of adsorption increased with the increasing of the temperature and adsorbent dosage. Minimum constant value of adsorption kinetic was 1,720 g/mg.min obtained at temperature of 30 °C and adsorbent dosageof 0,5 gr. The maximum value of adsorption kinetic constant was 9,755 g/mg.min obtained at temperature of 50 °C and adsorbent dosage of 1,5 gr. The appropriate model for adsorption kinetics followed the pseudo second order.

  19. Equilibrium, kinetic and thermodynamic studies on the adsorption of m-cresol onto micro- and mesoporous carbon

    International Nuclear Information System (INIS)

    Kennedy, L. John; Vijaya, J. Judith; Sekaran, G.; Kayalvizhi, K.

    2007-01-01

    Investigations were conducted in batch mode to study the adsorption behaviour of m-cresol on a porous carbon prepared from rice husk (RHAC) by varying the parameters such as agitation time, m-cresol concentration (50-300 mg/l), pH (2.5-10) and temperature (293-323 K). Studies showed that the adsorption decreased with increase in pH and temperature. The isotherm data were fitted to Langmuir, Freundlich, and Dubinin-Radushkevic (D-R) models. The kinetic models such as pseudo-first-order, pseudo-second-order and intraparticle diffusion models were selected to understand the reaction pathways and mechanism of adsorption process. The thermodynamic equilibrium coefficients obtained at different temperatures were used to evaluate the thermodynamic constants ΔG o , ΔH o and ΔS o . The sorption process was found to be exothermic in nature (ΔH o : -23.46 to -25.40 kJ/mol) with a decrease in entropy (ΔS o : -19.44 to -35.87 J/(mol K)). The negative value of Gibbs free energy, ΔG o indicates that the adsorption occurs via a spontaneous process. The decrease in the value of -ΔG o from 17.70 to 13.54 kJ/mol with increase in pH and temperature indicates that the adsorption of m-cresol onto activated carbon is less favourable at higher temperature and pH range. The influence of mesopore and a possible mechanism of adsorption is also suggested

  20. Competitive adsorption characteristics of fluoride and phosphate on calcined Mg-Al-CO{sub 3} layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Peng [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Zheng, Hong, E-mail: zhengh@cugb.edu.cn [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Wang, Chong; Ma, Hongwen; Hu, Jianchao; Pu, Yubing; Liang, Peng [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China)

    2012-04-30

    Highlights: Black-Right-Pointing-Pointer The influences of pH, contact time and order of addition of the anions were obtained. Black-Right-Pointing-Pointer The kinetic data were found to fit very well the pseudo second-order kinetic model. Black-Right-Pointing-Pointer Data of equilibrium experiments were fitted well to Langmuir isotherm. Black-Right-Pointing-Pointer The competitive monolayer adsorption capacities obviously decreased. Black-Right-Pointing-Pointer ATR-FTIR proofs of competitive adsorption were obtained. - Abstract: With synthetic wastewater, competitive adsorption characteristics of fluoride and phosphate on calcined Mg-Al-CO{sub 3} layered double hydroxides (CLDH) were investigated. A series of batch experiments were performed to study the influence of various experimental parameters, such as pH, contact time, and order of addition of the anions on the competitive adsorption of fluoride and phosphate on CLDH. It was found that the optimal pH is around 6 and it took 24 h to attain equilibrium when fluoride and phosphate were simultaneous added. The order of addition of anions influenced the adsorption of fluoride and phosphate on CLDH. The kinetic data were analyzed using the pseudo first-order and pseudo second-order models and they were found to fit very well the pseudo second-order kinetic model. Data of equilibrium experiments were fitted well to Langmuir isotherm and the competitive monolayer adsorption capacities of fluoride and phosphate were found to be obviously lower than those of single anion at 25 Degree-Sign C. The results of X-ray diffraction, Scanning Electron Microscopy with energy-dispersive X-ray analyses, and ATR-FTIR demonstrate that the adsorption mechanism involves the rehydration of mixed metal oxides and concomitant intercalation of fluoride and phosphate ions into the interlayer to reconstruct the initial LDHs structure.

  1. 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

  2. THE PSEUDO-SMARANDACHE FUNCTION

    OpenAIRE

    David Gorski

    2007-01-01

    The Pseudo-Smarandache Function is part of number theory. The function comes from the Smarandache Function. The Pseudo-Smarandache Function is represented by Z(n) where n represents any natural number.

  3. Mathematical modelling of oil spill fate and transport in the marine environment incorporating biodegradation kinetics of oil droplets

    Science.gov (United States)

    Spanoudaki, Katerina

    2016-04-01

    Oil biodegradation by native bacteria is one of the most important natural processes that can attenuate the environmental impacts of marine oil spills. However, very few numerical models of oil spill fate and transport include biodegradation kinetics of spilled oil. Furthermore, in models where biodegradation is included amongst the oil transformation processes simulated, it is mostly represented as a first order decay process neglecting the effect of several important parameters that can limit biodegradation rate, such as oil composition and oil droplets-water interface. To this end, the open source numerical model MEDSKIL-II, which simulates oil spill fate and transport in the marine environment, has been modified to include biodegradation kinetics of oil droplets dispersed in the water column. MEDSLIK-II predicts the transport and weathering of oil spills following a Lagrangian approach for the solution of the advection-diffusion equation. Transport is governed by the 3D sea currents and wave field provided by ocean circulation models. In addition to advective and diffusive displacements, the model simulates several physical and chemical processes that transform the oil (evaporation, emulsification, dispersion in the water column, adhesion to coast). The fate algorithms employed in MEDSLIK-II consider the oil as a uniform substance whose properties change as the slick weathers, an approach that can lead to reduced accuracy, especially in the estimation of oil evaporation and biodegradation. Therefore MEDSLIK-II has been modified by adopting the "pseudo-component" approach for simulating weathering processes. Spilled oil is modelled as a relatively small number of discrete, non-interacting components (pseudo-components). Chemicals in the oil mixture are grouped by physical-chemical properties and the resulting pseudo-component behaves as if it were a single substance with characteristics typical of the chemical group. The fate (evaporation, dispersion

  4. Kinetic and mechanistic study of microcystin-LR degradation by nitrous acid under ultraviolet irradiation.

    Science.gov (United States)

    Ma, Qingwei; Ren, Jing; Huang, Honghui; Wang, Shoubing; Wang, Xiangrong; Fan, Zhengqiu

    2012-05-15

    Degradation of microcystin-LR (MC-LR) in the presence of nitrous acid (HNO(2)) under irradiation of 365nm ultraviolet (UV) was studied for the first time. The influence of initial conditions including pH value, NaNO(2) concentration, MC-LR concentration and UV intensity were studied. MC-LR was degraded in the presence of HNO(2); enhanced degradation of MC-LR was observed with 365nm UV irradiation, caused by the generation of hydroxyl radicals through the photolysis of HNO(2). The degradation processes of MC-LR could well fit the pseudo-first-order kinetics. Mass spectrometry was applied for identification of the byproducts and the analysis of degradation mechanisms. Major degradation pathways were proposed according to the results of LC-MS analysis. The degradation of MC-LR was initiated via three major pathways: attack of hydroxyl radicals on the conjugated carbon double bonds of Adda, attack of hydroxyl radicals on the benzene ring of Adda, and attack of nitrosonium ion on the benzene ring of Adda. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Kinetics of nickel bioaccumulation and its relevance to selected cellular processes in leaves of Elodea canadensis during short-term exposure.

    Science.gov (United States)

    Maleva, Maria G; Malec, Przemysław; Prasad, Majeti Narasimha Vara; Strzałka, Kazimierz

    2016-03-01

    Elodea canadensis is an aquatic macrophyte used widely as a bioindicator for the monitoring of water quality and in the phytoremediation of metal-contaminated waters. This study considers the kinetics of nickel bioaccumulation and changes in accompanying metabolic and stress-related physiological parameters. These include photosynthetic activity, pigment content, the accumulation of thiol-containing compounds, thiobarbituric acid-reactive substance (TBARS) products, and the activity of selected antioxidant enzymes (catalase, glutathione reductase, superoxide dismutase). Elodea leaves accumulated nickel according to pseudo-second-order kinetics, and the protective responses followed a time sequence which was related to the apparent rates of nickel accumulation. The applicability of second-order kinetics to the Ni uptake by Elodea leaves during the first 8 h of exposure to the metal suggested that the passive binding of metal ions (chemisorption) was a rate-limiting step at the initial phase of Ni accumulation. This phase was accompanied by an increase in photosynthetic activity together with elevated photosynthetic pigments and protein synthesis, the enhanced activity of antioxidant enzymes, and increased thiol concentration. In contrast, there was a decrease in metabolic activity upon the accumulation of TBARS, and the decline in enzyme activity was observed in the saturation phase of Ni accumulation (8-24 h). These results show that a correlation exists between the protective response and the apparent kinetic rate of Ni uptake. Thus, the time of exposure to the toxicant is a crucial factor in the activation of specific mechanisms of Ni detoxification and stress alleviation.

  6. Pseudo one-dimensional analysis of polymer electrolyte fuel cell cold-start

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Partha P [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory; Borup, Rodney L [Los Alamos National Laboratory; Wang, Yun [NON LANL; Mishlera, Jeff [NON LANL

    2009-01-01

    This paper investigates the electrochemical kinetics, oxygen transport, and solid water formation in polymer electrolyte fuel cell (PEFC) during cold start. Following [Yo Wang, J. Electrochem. Soc., 154 (2007) B1041-B1048], we develop a pseudo one-dimensional analysis, which enables the evaluation of the impact of ice volume fraction and temperature variations on cell performance during cold-start. The oxygen profile, starvation ice volume fraction, and relevant overpotentials are obtained. This study is valuable for studying the characteristics of PEFC cold-start.

  7. A third-order gas-kinetic CPR method for the Euler and Navier-Stokes equations on triangular meshes

    Science.gov (United States)

    Zhang, Chao; Li, Qibing; Fu, Song; Wang, Z. J.

    2018-06-01

    A third-order accurate gas-kinetic scheme based on the correction procedure via reconstruction (CPR) framework is developed for the Euler and Navier-Stokes equations on triangular meshes. The scheme combines the accuracy and efficiency of the CPR formulation with the multidimensional characteristics and robustness of the gas-kinetic flux solver. Comparing with high-order finite volume gas-kinetic methods, the current scheme is more compact and efficient by avoiding wide stencils on unstructured meshes. Unlike the traditional CPR method where the inviscid and viscous terms are treated differently, the inviscid and viscous fluxes in the current scheme are coupled and computed uniformly through the kinetic evolution model. In addition, the present scheme adopts a fully coupled spatial and temporal gas distribution function for the flux evaluation, achieving high-order accuracy in both space and time within a single step. Numerical tests with a wide range of flow problems, from nearly incompressible to supersonic flows with strong shocks, for both inviscid and viscous problems, demonstrate the high accuracy and efficiency of the present scheme.

  8. On Generalized Fractional Kinetic Equations Involving Generalized Bessel Function of the First Kind

    Directory of Open Access Journals (Sweden)

    Dinesh Kumar

    2015-01-01

    Full Text Available We develop a new and further generalized form of the fractional kinetic equation involving generalized Bessel function of the first kind. The manifold generality of the generalized Bessel function of the first kind is discussed in terms of the solution of the fractional kinetic equation in the paper. The results obtained here are quite general in nature and capable of yielding a very large number of known and (presumably new results.

  9. Multivariate Discrete First Order Stochastic Dominance

    DEFF Research Database (Denmark)

    Tarp, Finn; Østerdal, Lars Peter

    This paper characterizes the principle of first order stochastic dominance in a multivariate discrete setting. We show that a distribution  f first order stochastic dominates distribution g if and only if  f can be obtained from g by iteratively shifting density from one outcome to another...

  10. Analytical Expressions for the Mixed-Order Kinetics Parameters of TL Glow Peaks Based on the two Heating Rates Method.

    Science.gov (United States)

    Maghrabi, Mufeed; Al-Abdullah, Tariq; Khattari, Ziad

    2018-03-24

    The two heating rates method (originally developed for first-order glow peaks) was used for the first time to evaluate the activation energy (E) from glow peaks obeying mixed-order (MO) kinetics. The derived expression for E has an insignificant additional term (on the scale of a few meV) when compared with the first-order case. Hence, the original expression for E using the two heating rates method can be used with excellent accuracy in the case of MO glow peaks. In addition, we derived a simple analytical expression for the MO parameter. The present procedure has the advantage that the MO parameter can now be evaluated using analytical expression instead of using the graphical representation between the geometrical factor and the MO parameter as given by the existing peak shape methods. The applicability of the derived expressions for real samples was demonstrated for the glow curve of Li 2 B 4 O 7 :Mn single crystal. The obtained parameters compare very well with those obtained by glow curve fitting and with the available published data.

  11. Pseudo Boolean Programming for Partially Ordered Genomes

    Science.gov (United States)

    Angibaud, Sébastien; Fertin, Guillaume; Thévenin, Annelyse; Vialette, Stéphane

    Comparing genomes of different species is a crucial problem in comparative genomics. Different measures have been proposed to compare two genomes: number of common intervals, number of adjacencies, number of reversals, etc. These measures are classically used between two totally ordered genomes. However, genetic mapping techniques often give rise to different maps with some unordered genes. Starting from a partial order between genes of a genome, one method to find a total order consists in optimizing a given measure between a linear extension of this partial order and a given total order of a close and well-known genome. However, for most common measures, the problem turns out to be NP-hard. In this paper, we propose a (0,1)-linear programming approach to compute a linear extension of one genome that maximizes the number of common intervals (resp. the number of adjacencies) between this linear extension and a given total order. Next, we propose an algorithm to find linear extensions of two partial orders that maximize the number of adjacencies.

  12. Existence of pseudo almost periodic solutions for a class of partial functional differential equations

    Directory of Open Access Journals (Sweden)

    Hui-Sheng Ding

    2013-04-01

    Full Text Available In this paper, we first introduce a new class of pseudo almost periodic type functions and investigate some properties of pseudo almost periodic type functions; and then we discuss the existence of pseudo almost periodic solutions to the class of abstract partial functional differential equations $x'(t=Ax(t+f(t,x_t$ with finite delay in a Banach space X.

  13. A kinetic model for the first stage of pygas upgrading

    Directory of Open Access Journals (Sweden)

    J. L. de Medeiros

    2007-03-01

    Full Text Available Pyrolysis gasoline - PYGAS - is an intermediate boiling product of naphtha steam cracking with a high octane number and high aromatic/unsaturated contents. Due to stabilization concerns, PYGAS must be hydrotreated in two stages. The first stage uses a mild trickle-bed conversion for removing extremely reactive species (styrene, dienes and olefins prior to the more severe second stage where sulfured and remaining olefins are hydrogenated in gas phase. This work addresses the reaction network and two-phase kinetic model for the first stage of PYGAS upgrading. Nonlinear estimation was used for model tuning with kinetic data obtained in bench-scale trickle-bed hydrogenation with a commercial Pd/Al2O3 catalyst. On-line sampling experiments were designed to study the influence of variables - temperature and spatial velocity - on the conversion of styrene, dienes and olefins.

  14. Kinetics and thermodynamics of textile dye adsorption from aqueous solutions using babassu coconut mesocarp

    International Nuclear Information System (INIS)

    Vieira, Adriana P.; Santana, Sirlane A.A.; Bezerra, Cicero W.B.; Silva, Hildo A.S.; Chaves, Jose A.P.; Melo, Julio C.P. de; Silva Filho, Edson C. da; Airoldi, Claudio

    2009-01-01

    Extracted babassu coconut (Orbignya speciosa) mesocarp (BCM) was applied as a biosorbent for aqueous Blue Remazol R160 (BR 160), Rubi S2G (R S2G), Red Remazol 5R (RR 5), Violet Remazol 5R (VR 5) and Indanthrene Olive Green (IOG) dye solutions. The natural sorbent was processed batchwise while varying several system parameters such as stirring time, pH and temperature. The interactions were assayed with respect to both pseudo-first-order and second-order reaction kinetics, with the latter the more suitable kinetic model. The maximum adsorption was obtained at pH 1.0 for all dyes due to available anionic groups attached to the structures, which can be justified by pH pzc 6.7 for the biosorbent BCM. The ability of babassu coconut mesocarp to adsorb dyes gave the order R S2G > VR 5 > BR 160 > IOG > RR 5, which data were best fit to Freundlich model, but did not well-adjusted for all dyes. The dye/biopolymer interactions at the solid/liquid interface are all spontaneous as given by free Gibbs energy, with exothermic enthalpic values of -26.1, -15.8, -17.8, -15.8 and -23.7 kJ mol -1 for BR 160, R S2G, RR 5, IOG and VR 5, respectively. In spite of the negative entropic values contribution, the set of thermodynamic data is favorable for all dyes removal. However, the results pointed to the effectiveness of the mesocarp of babassu coconut as a biosorbent for removing textile dyes from aqueous solutions.

  15. Pseudo-scalar Higgs boson production at N"3LO_A+N"3LL"'

    International Nuclear Information System (INIS)

    Ahmed, Taushif; Rana, Narayan; Ravindran, V.; Bonvini, Marco; Rottoli, Luca; Kumar, M.C.; Mathews, Prakash

    2016-01-01

    We consider the production of a pseudo-scalar particle A at the LHC, and present accurate theoretical predictions for its inclusive cross section in gluon fusion. The prediction is based on combining fixed-order perturbation theory and all-order threshold resummation. At fixed order we include the exact next-to-next-to-leading order (NNLO) plus an approximate next-to-next-to-next-to-leading order (N"3LO_A) which is based on the recent computation at this order for the scalar case. We then add threshold resummation at next-to-next-to-next-to leading logarithmic accuracy (N"3LL"'). Various forms of threshold resummation are considered, differing by the treatment of subleading terms, allowing a robust estimate of the theoretical uncertainties due to missing higher orders. With particular attention to pseudo-scalar masses of 200 and 750 GeV, we also observe that perturbative convergence is much improved when resummation is included. Additionally, results obtained with threshold resummation in direct QCD are compared with analogous results as computed in soft-collinear effective theory, which turn out to be in good agreement. We provide precise predictions for pseudo-scalar inclusive cross section at 13 TeV LHC for a wide range of masses. The results are available through updated versions of the public codes ggHiggs and TROLL. (orig.)

  16. Chromium and zinc uptake by algae Gelidium and agar extraction algal waste: kinetics and equilibrium.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-11-19

    Biosorption of chromium and zinc ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). Langmuir and Langmuir-Freundlich equilibrium models describe well the equilibrium data. The parameters of Langmuir equilibrium model at pH 5.3 and 20 degrees C were for the algae, q(L)=18 mg Cr(III)g(-1) and 13 mgZn(II)g(-1), K(L) = 0.021l mg(-1)Cr(III) and 0.026l mg(-1) Zn(II); for the algal waste, q(L)=12 mgCr(III)g(-1) and 7mgZn(II)g(-1), K(L)=0.033lmg(-1) Cr(III) and 0.042l mg(-1) Zn(II); for the composite material, q(L) = 9 mgCr(III)g(-1) and 6 mgZn(II)g(-1), K(L)=0.032l mg(-1)Cr(III) and 0.034l mg(-1)Zn(II). The biosorbents exhibited a higher preference for Cr(III) ions and algae Gelidium is the best one. The pseudo-first-order Lagergren and pseudo-second-order models fitted well the kinetic data for the two metal ions. Kinetic constants and equilibrium uptake concentrations given by the pseudo-second-order model for an initial Cr(III) and Zn(II) concentration of approximately 100 mgl(-1), at pH 5.3 and 20 degrees C were k(2,ads)=0.04 g mg(-1)Cr(III)min(-1) and 0.07 g mg(-1)Zn(II)min(-1), q(eq)=11.9 mgCr(III)g(-1) and 9.5 mgZn(II)g(-1) for algae; k(2,ads)=0.17 g mg(-1)Cr(III)min(-1) and 0.19 g mg(-1)Zn(II)min(-1), q(eq)=8.3 mgCr(III)g(-1) and 5.6 mgZn(II)g(-1) for algal waste; k(2,ads)=0.01 g mg(-1)Cr(III)min(-1) and 0.18 g mg(-1)Zn(II)min(-1), q(eq)=8.0 mgCr(III)g(-1) and 4.4 mgZn(II)g(-1) for composite material. Biosorption was modelled using a batch adsorber mass transfer kinetic model, which successfully predicts Cr(III) and Zn(II) concentration profiles. The calculated average homogeneous diffusivities, D(h), were 4.2 x 10(-8), 8.3 x 10(-8) and 1.4 x 10(-8)cm(2)s(-1) for Cr(III) and 4.8 x 10(-8), 9.7 x 10(-8) and 6.2 x 10(-8)cm(2)s(-1

  17. 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)

  18. Adsorption Removal of Glycidyl Esters from Palm Oil and Oil Model Solution by Using Acid-Washed Oil Palm Wood-Based Activated Carbon: Kinetic and Mechanism Study.

    Science.gov (United States)

    Cheng, Weiwei; Liu, Guoqin; Wang, Xuede; Han, Lipeng

    2017-11-08

    Acid-washed oil palm wood-based activated carbon (OPAC) has been investigated for its potential application as a promising adsorbent in the removal of glycidyl esters (GEs) from both palm oil and oil model (hexadecane) solution. It was observed that the removal rate of GEs in palm oil was up to >95%, which was significantly higher than other adsorbents used in this study. In batch adsorption system, the adsorption efficiency and performance of acid-washed OPAC were evaluated as a function of several experimental parameters such as contact time, initial glycidyl palmitate (PGE) concentration, adsorbent dose, and temperature. The Langmuir, Freundlich, and Dubinin-Radushkevich models were used to describe the adsorption equilibrium isotherm, and the equilibrium data were fitted best by the Langmuir model. The maximum adsorption capacity of acid-washed OPAC was found to be 36.23 mg/g by using the Langmuir model. The thermodynamic analysis indicated that the adsorption of PGE on acid-washed OPAC was an endothermic and physical process in nature. The experimental data were fitted by using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. It was found that the kinetic of PGE adsorption onto acid-washed OPAC followed well the pseudo-second-order model for various initial PGE concentrations and the adsorption process was controlled by both film diffusion and intraparticle diffusion. The desorption test indicated the removal of GEs from palm oil was attributed to not only the adsorption of GEs on acid-washed OPAC, but also the degradation of GEs adsorbed at activated sites with acidic character. Furthermore, no significant difference between before and after PGE adsorption in oil quality was observed.

  19. Stepanov-like weighted pseudo almost automorphic solutions to ...

    Indian Academy of Sciences (India)

    Abstract. In this article, we study the concept of Stepanov-like weighted pseudo almost automorphic solutions to fractional order abstract integro-differential equations. We establish the results with Lipschitz condition and without Lipschitz condition on the forcing term. An interesting example is presented to illustrate the main ...

  20. Kinetics and thermodynamics of oxidation mediated reaction in L-cysteine and its methyl and ethyl esters in dimethyl sulfoxide-d6 by NMR spectroscopy

    Science.gov (United States)

    Dougherty, Ryan J.; Singh, Jaideep; Krishnan, V. V.

    2017-03-01

    L-Cysteine (L-Cys), L-Cysteine methyl ester (L-CysME) or L-Cysteine ethyl ester (L-CysEE), when dissolved in dimethyl sulfoxide, undergoes an oxidation process. This process is slow enough and leads to nuclear magnetic resonance (NMR) spectral changes that could be monitored in real time. The oxidation mediated transition is modeled as a pseudo-first order kinetics and the thermodynamic parameters are estimated using the Eyring's formulation. L-Cysteine and their esters are often used as biological models due to the remarkable thiol group that can be found in different oxidation states. This oxidation mediated transition is due to the combination of thiol oxidation to a disulfide followed by solvent-induced effects may be relevant in designing cysteine-based molecular models.

  1. Photocatalytic degradation kinetics and mechanism of environmental pharmaceuticals in aqueous suspension of TiO{sub 2}: A case of {beta}-blockers

    Energy Technology Data Exchange (ETDEWEB)

    Yang Hai [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); An Taicheng, E-mail: antc99@gig.ac.cn [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Li Guiying [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Song Weihua; Cooper, William J. [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175 (United States); Luo Haiying [State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Kehua Street, Tianhe District, Guangzhou 510640 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Guangzhou Product Quality Supervision and Testing Institute, National Centre for Quality Supervision and Testing of Processed Food (Guangzhou), Guangzhou 510110 (China); Guo Xindong [Guangzhou Product Quality Supervision and Testing Institute, National Centre for Quality Supervision and Testing of Processed Food (Guangzhou), Guangzhou 510110 (China)

    2010-07-15

    This study investigated the photocatalytic degradation of three {beta}-blockers in TiO{sub 2} suspensions. The disappearance of the compounds followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model and the rate constants were 0.075, 0.072 and 0.182 min{sup -1} for atenolol, metoprolol and propranolol, respectively. After 240 min irradiation, the reaction intermediates were completely mineralized to CO{sub 2} and the nitrogen was predominantly as NH{sub 4}{sup +}. The influence of initial pH and {beta}-blocker concentration on the kinetics was also studied. From adsorption studies it appears that the photocatalytic degradation occurred mainly on the surface of TiO{sub 2}. Further studies indicated that surface reaction with {center_dot}OH radical was principally responsible for the degradation of these three {beta}-blockers. The major degradation intermediates were identified by HPLC/MS analysis. Cleavage of the side chain and the addition of the hydroxyl group to the parent compounds were found to be the two main degradation pathways for all three {beta}-blockers.

  2. Kinetics and thermodynamics of adsorption of azinphosmethyl from aqueous solution onto pyrolyzed (at 600 deg. C) ocean peat moss (Sphagnum sp.)

    International Nuclear Information System (INIS)

    Aroguz, A.Z.

    2006-01-01

    The removal of azinphosmethyl from aqueous solution onto pyrolyzed ocean peat moss (Sphagnum sp.), as a residue, from the Rhode Island coast (USA), has been investigated at different temperatures and initial concentrations. The ocean peat moss had been pyrolyzed at 600 deg. C in nitrogen atmosphere before the adsorption process. The kinetic data obtained from batch studies have been analyzed using pseudo-first order kinetic model. The rate constants were evaluated at different temperatures. The thermodynamic parameters (ΔG o , ΔH o , ΔS o ) for the adsorption process were calculated and the results suggest that the nature of adsorption is endothermic and the process is spontaneous and favorable. The activation energy for adsorption process was estimated, about 18.3 kJ mol -1 . According to this value the adsorption of azinphosmethyl onto pyrolyzed ocean peat moss is in the range of physical adsorption. The experimental data have been modeled using Langmuir, Freundlich and Temkin isotherms. It was found that Langmuir and Freundlich isotherms give the best correlation with the experimental data

  3. Amino-functionalized mesoporous MCM-41 silica as an efficient adsorbent for water treatment: batch and fixed-bed column adsorption of the nitrate anion

    Science.gov (United States)

    Ebrahimi-Gatkash, Mehdi; Younesi, Habibollah; Shahbazi, Afsaneh; Heidari, Ava

    2017-07-01

    In the present study, amino-functionalized Mobil Composite Material No. 41 (MCM-41) was used as an adsorbent to remove nitrate anions from aqueous solutions. Mono-, di- and tri-amino functioned silicas (N-MCM-41, NN-MCM-41 and NNN-MCM-41) were prepared by post-synthesis grafting method. The samples were characterized by means of X-ray powder diffraction, FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption-desorption. The effects of pH, initial concentration of anions, and adsorbent loading were examined in batch adsorption system. Results of adsorption experiments showed that the adsorption capacity increased with increasing adsorbent loading and initial anion concentration. It was found that the Langmuir mathematical model indicated better fit to the experimental data than the Freundlich. According to the constants of the Langmuir equation, the maximum adsorption capacity for nitrate anion by N-MCM-41, NN-MCM-41 and NNN-MCM-41 was found to be 31.68, 38.58 and 36.81 mg/g, respectively. The adsorption kinetics were investigated with pseudo-first-order and pseudo-second-order model. Adsorption followed the pseudo-second-order rate kinetics. The coefficients of determination for pseudo-second-order kinetic model are >0.99. For continuous adsorption experiments, NNN-MCM-41 adsorbent was used for the removal of nitrate anion from solutions. Breakthrough curves were investigated at different bed heights, flow rates and initial nitrate anion concentrations. The Thomas and Yan models were utilized to calculate the kinetic parameters and to predict the breakthrough curves of different bed height. Results from this study illustrated the potential utility of these adsorbents for nitrate removal from water solution.

  4. peroxo complexes

    Indian Academy of Sciences (India)

    Administrator

    present kinetic studies of the decomposition of a group of closely related ... tuted benzoic acid; n = 1 or 2) at low temperature shows a pseudo first order rate of decay. ... species. References. 1. Que Jr L 1997 J. Chem. Soc., Dalton Trans. 3933.

  5. First- and second-order processing in transient stereopsis.

    Science.gov (United States)

    Edwards, M; Pope, D R; Schor, C M

    2000-01-01

    Large-field stimuli were used to investigate the interaction of first- and second-order pathways in transient-stereo processing. Stimuli consisted of sinewave modulations in either the mean luminance (first-order stimulus) or the contrast (second-order stimulus) of a dynamic-random-dot field. The main results of the present study are that: (1) Depth could be extracted with both the first-order and second-order stimuli; (2) Depth could be extracted from dichoptically mixed first- and second-order stimuli, however, the same stimuli, when presented as a motion sequence, did not result in a motion percept. Based upon these findings we conclude that the transient-stereo system processes both first- and second-order signals, and that these two signals are pooled prior to the extraction of transient depth. This finding of interaction between first- and second-order stereoscopic processing is different from the independence that has been found with the motion system.

  6. Removal of malachite green by using an invasive marine alga Caulerpa racemosa var. cylindracea

    International Nuclear Information System (INIS)

    Bekci, Zehra; Seki, Yoldas; Cavas, Levent

    2009-01-01

    The biosorption of a cationic dye, malachite green oxalate (MG) from aqueous solution onto an invasive marine alga Caulerpa racemosa var. cylindracea (CRC) was investigated at different temperatures (298, 308 and 318 K). The dye adsorption onto CRC was confirmed by FTIR analysis. Equilibrium data were analyzed using Freundlich, Langmuir and Dubinin-Radushkevich (DR) equations. All of the isotherm parameters were calculated. The Freundlich model gave a better conformity than Langmuir equation. The mean free energy values (E) from DR isotherm were also estimated. In order to clarify the sorption kinetic, the fit of pseudo-first-order kinetic model, second-order kinetic model and intraparticle diffusion model were investigated. It was obtained that the biosorption process followed the pseudo-second-order rate kinetics. From thermodynamic studies the free energy changes were found to be -7.078, -9.848 and -10.864 kJ mol -1 for 298, 308 and 318 K, respectively. This implied the spontaneous nature of biosorption and the type of adsorption as physisorption. Activation energy value for MG sorption (E a ) was found to be 37.14 kJ mol -1 . It could be also derived that this result supported physisorption as a type of adsorption

  7. Pseudo-color processing in nuclear medical image

    International Nuclear Information System (INIS)

    Wang Zhiqian; Jin Yongjie

    1992-01-01

    The application of pseudo-color technology in nuclear medical image processing is discussed. It includes selection of the number of pseudo-colors, method of realizing pseudo-color transformation, function of pseudo-color transformation and operation on the function

  8. Effect of hydrophobicity of pharmaceuticals and personal care products for adsorption on activated carbon: Adsorption isotherms, kinetics and mechanism.

    Science.gov (United States)

    Kaur, Harkirat; Bansiwal, Amit; Hippargi, Girivyankatesh; Pophali, Girish R

    2017-09-11

    Adsorption of three pharmaceuticals and personal care products (PPCPs), namely caffeine, ibuprofen and triclosan on commercial powdered activated carbon was examined in aqueous medium. The contaminants were chosen based on their diverse log K ow (octanol-water partition coefficient) viz. - 0.07 for caffeine, 3.97 for ibuprofen and 4.76 for triclosan to examine the role of hydrophobicity on adsorption process. The adsorbent characterisation was achieved using BET surface area, SEM, pore size distribution studies and FTIR. Influence of mass of PAC, contact time, solution pH and initial concentration on adsorption capacity of PAC was studied. Adsorption isotherms and kinetics were applied to establish the mechanism of adsorption. The kinetics followed pseudo-second order with physisorption occurring through particle diffusion. The Freundlich model fitted best among the isotherm models. The adsorption capacity increased in the order CFN activated carbon.

  9. Spin dynamics in the pseudo-gap state of a high-temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Hinkov, V; Lin, C T; Chen, D P; Keimer, B [Max Planck Inst Solid State Res, D-70569 Stuttgart, (Germany); Bourges, P; Pailhes, S; Sidis, Y [CEA, CNRS, CE Saclay, Lab Leon Brillouin, F-91191 Gif Sur Yvette, (France); Ivanov, A [Inst Max Von Laue Paul Langevin, F-38042 Grenoble, (France); Frost, C D; Perring, T G [Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, (United Kingdom)

    2007-07-01

    The pseudo-gap is one of the most pervasive phenomena of high-temperature superconductors. It is attributed either to incoherent Cooper pairing setting in above the superconducting transition temperature, Tc, or to a hidden order parameter competing with superconductivity. Here, we use inelastic neutron scattering from under-doped YBa{sub 2}Cu{sub 3}O{sub 6.6} to show that the dispersion relations of spin excitations in the superconducting and pseudo-gap states are qualitatively different. Specifically, the extensively studied 'hour glass' shape of the magnetic dispersions in the superconducting state is no longer discernible in the pseudo-gap state and we observe an unusual 'vertical' dispersion with pronounced in-plane anisotropy. The differences between superconducting and pseudo-gap states are thus more profound than generally believed, suggesting a competition between these two states. Whereas the high-energy excitations are common to both states and obey the symmetry of the copper oxide square lattice, the low-energy excitations in the pseudo-gap state may be indicative of collective fluctuations towards a state with broken orientational symmetry predicted in theoretical work. (authors)

  10. Riemann-Liouville integrals of fractional order and extended KP hierarchy

    International Nuclear Information System (INIS)

    Kamata, Masaru; Nakamula, Atsushi

    2002-01-01

    An attempt to formulate the extensions of the KP hierarchy by introducing fractional-order pseudo-differential operators is given. In the case of the extension with the half-order pseudo-differential operators, a system analogous to the supersymmetric extensions of the KP hierarchy is obtained. Unlike the supersymmetric extensions, no Grassmannian variable appears in the hierarchy considered here. More general hierarchies constructed by the 1/Nth-order pseudo-differential operators, their integrability and the reduction procedure are also investigated. In addition to finding the new extensions of the KP hierarchy, a brief introduction to the Riemann-Liouville integral is provided to yield a candidate for the fractional-order pseudo-differential operators

  11. Equilibrium models and kinetic for the adsorption of methylene blue on Co-hectorites

    International Nuclear Information System (INIS)

    Ma Jun; Jia Yongzhong; Jing Yan; Sun Jinhe; Yao Ying; Wang Xiaohua

    2010-01-01

    The adsorption of methylene blue (MB) onto the surface of cobalt doping hectorite (Co-hectorite) was systematically studied. The physical properties of Co-hectorites were investigated, where characterizations were carried out by X-ray diffraction (XRD) and Electron Diffraction Spectrum (EDS) techniques, and morphology was examined by nitrogen adsorption. The sample with a Co content 5% (m/m) had a higher specific surface area than other Co-hectorites. The pore diameters were distributed between 2.5 and 5.0 nm. The adsorption results revealed that Co-hectorite surfaces possessed effective interactions with MB and bases, and greatest adsorption capacity achieved with Co content 5%, where the best-fit isotherm model was the Langmuir adsorption model. Kinetic studies were fitted to the pseudo-second-order kinetic model. The intraparticle diffusion was not the rate-limiting step for the whole reaction.

  12. The effect of the textile industry dye bath additive EDTMPA on colour removal characteristics by ozone oxidation.

    Science.gov (United States)

    Olmez, T; Kabdaşli, I; Tünay, O

    2007-01-01

    In this study, the effects of the phosphonic acid based sequestering agent EDTMPA used in the textile dye baths on colour and organic matter removal by ozone oxidation was experimentally investigated. Procion Navy HEXL dyestuff that has been commonly used for the reactive dyeing of cellulose fibers was selected as the model component. The organic matter oxidation by ozone was determined to obey the pseudo-first order kinetics as they are treated singly or in combination. COD removal rates obtained from pseudo-first order reaction kinetics showed that oxidation of Navy HEXL alone (0.0947 L/min) was faster than that of EDTMPA (0.0171 L/min) and EDTMPA with dye (0.0155 L/min) at pH 3.0. It was also found that reaction rates of single EDTMPA removal and EDTMPA and dye mixture removal increased as the reaction pH was increased from 3.0 to 10.5.

  13. Removal of acid blue 062 on aqueous solution using calcinated colemanite ore waste

    Energy Technology Data Exchange (ETDEWEB)

    Atar, Necip [Department of Chemistry, Faculty of Arts and Science, University of Dumlupinar, Kuetahya (Turkey); Olgun, Asim [Department of Chemistry, Faculty of Arts and Science, University of Dumlupinar, Kuetahya (Turkey)]. E-mail: aolgun@dumlupinar.edu.tr

    2007-07-19

    Colemanite ore waste (CW) has been employed as adsorbent for the removal of acid blue 062 anionic dye (AB 062) from aqueous solution. The adsorption of AB 062 onto CW was examined with respect to contact time, calcination temperature, particle size, pH, adsorbent dosage and temperature. The physical and chemical properties of the CW, such as particle sizes and calcinations temperature, play important roles in dye adsorption. The dye adsorption largely depends on the initial pH of the solution with maximum uptake occurring at pH 1.Three simplified kinetics models, namely, pseudo-first order, pseudo-second order, and intraparticle diffusion models were tested to investigate the adsorption mechanisms. The kinetic adsorption of AB 062 on CW follows a pseudo-second order equation. The adsorption data have been analyzed using Langmuir and Freundlich isotherms. The results indicate that the Langmuir model provides the best correlation of the experimental data. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of the adsorption of dye onto CW.

  14. Removal of acid blue 062 on aqueous solution using calcinated colemanite ore waste

    International Nuclear Information System (INIS)

    Atar, Necip; Olgun, Asim

    2007-01-01

    Colemanite ore waste (CW) has been employed as adsorbent for the removal of acid blue 062 anionic dye (AB 062) from aqueous solution. The adsorption of AB 062 onto CW was examined with respect to contact time, calcination temperature, particle size, pH, adsorbent dosage and temperature. The physical and chemical properties of the CW, such as particle sizes and calcinations temperature, play important roles in dye adsorption. The dye adsorption largely depends on the initial pH of the solution with maximum uptake occurring at pH 1.Three simplified kinetics models, namely, pseudo-first order, pseudo-second order, and intraparticle diffusion models were tested to investigate the adsorption mechanisms. The kinetic adsorption of AB 062 on CW follows a pseudo-second order equation. The adsorption data have been analyzed using Langmuir and Freundlich isotherms. The results indicate that the Langmuir model provides the best correlation of the experimental data. Isotherms have also been used to obtain the thermodynamic parameters such as free energy, enthalpy and entropy of the adsorption of dye onto CW

  15. Application of potato (Solanum tuberosum plant wastes for the removal of methylene blue and malachite green dye from aqueous solution

    Directory of Open Access Journals (Sweden)

    Neha Gupta

    2016-09-01

    Full Text Available Dye pollutants from the textile, paper, and leather industries are important sources of environmental contamination. In the present study an agricultural waste from potato plant (potato stem powder, PSP and potato leaves powder, PLP was used as an adsorbent for removal of the methylene blue (MB and malachite green (MG dyes from aqueous solution. The adsorbent materials were characterized by scanning electron microscope (SEM and Fourier transform infrared (FTIR spectroscopy. Batch experiments were performed to investigate the effect of physico-chemical parameters, such as pHpzc, ionic strength, adsorbent dose, contact time, initial dyes concentration and temperature. The kinetics of adsorption was studied by applying the pseudo-first order, pseudo-second order and intraparticle diffusion models. The pseudo-second order model better represented the adsorption kinetics and the mechanism was controlled by surface adsorption and intraparticle diffusion. Equilibrium data were analyzed using Langmuir and Freundlich isotherm models. The thermodynamic parameters such as change in enthalpy (ΔH°, entropy (ΔS° and Gibb’s free energy (ΔG° of adsorption systems were also determined and evaluated.

  16. Algebra of pseudo-differential operators over C*-algebra

    International Nuclear Information System (INIS)

    Mohammad, N.

    1982-08-01

    Algebras of pseudo-differential operators over C*-algebras are studied for the special case when in Hormander class Ssub(rho,delta)sup(m)(Ω) Ω = Rsup(n); rho = 1, delta = 0, m any real number, and the C*-algebra is infinite dimensional non-commutative. The space B, i.e. the set of A-valued C*-functions in Rsup(n) (or Rsup(n) x Rsup(n)) whose derivatives are all bounded, plays an important role. A denotes C*-algebra. First the operator class Ssub(phi,0)sup(m) is defined, and through it, the class Lsub(1,0)sup(m) of pseudo-differential operators. Then the basic asymptotic expansion theorems concerning adjoint and product of operators of class Ssub(1,0)sup(m) are stated. Finally, proofs are given of L 2 -continuity theorem and the main theorem, which states that algebra of all pseudo-differential operators over C*-algebras is itself C*-algebra

  17. Estados de pseudo-Cushing

    OpenAIRE

    Romanholi, Daniella J.P.C.; Salgado, Luiz Roberto

    2007-01-01

    Síndromes de pseudo-Cushing são um grupo heterogêneo de doenças, incluindo alcoolismo, anorexia nervosa, obesidade visceral e depressão, que compartilham muitas das características clínicas e bioquímicas da síndrome de Cushing. Os mecanismos responsáveis para a gênese da síndrome de pseudo-Cushing são fracamente compreendidos. Tem sido sugerido que o hipercortisolismo da síndrome de pseudo-Cushing pode ser resultante do aumento da secreção do hormônio liberador de corticotrofina (CRH) hipotal...

  18. Fenton and Fenton-like oxidation of pesticide acetamiprid in water samples: kinetic study of the degradation and optimization using response surface methodology.

    Science.gov (United States)

    Mitsika, Elena E; Christophoridis, Christophoros; Fytianos, Konstantinos

    2013-11-01

    The aims of this study were (a) to evaluate the degradation of acetamiprid with the use of Fenton reaction, (b) to investigate the effect of different concentrations of H2O2 and Fe(2+), initial pH and various iron salts, on the degradation of acetamiprid and (c) to apply response surface methodology for the evaluation of degradation kinetics. The kinetic study revealed a two-stage process, described by pseudo- first and second order kinetics. Different H2O2:Fe(2+) molar ratios were examined for their effect on acetamiprid degradation kinetics. The ratio of 3 mg L(-1) Fe(2+): 40 mg L(-1) H2O2 was found to completely remove acetamiprid at less than 10 min. Degradation rate was faster at lower pH, with the optimal value at pH 2.9, while Mohr salt appeared to degrade acetamiprid faster. A central composite design was selected in order to observe the effects of Fe(2+) and H2O2 initial concentration on acetamiprid degradation kinetics. A quadratic model fitted the experimental data, with satisfactory regression and fit. The most significant effect on the degradation of acetamiprid, was induced by ferrous iron concentration followed by H2O2. Optimization, aiming to minimize the applied ferrous concentration and the process time, proposed a ratio of 7.76 mg L(-1) Fe(II): 19.78 mg L(-1) H2O2. DOC is reduced much more slowly and requires more than 6h of processing for 50% degradation. The use to zero valent iron, demonstrated fast kinetic rates with acetamiprid degradation occurring in 10 min and effective DOC removal. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Design of a new integrated chitosan-PAMAM dendrimer biosorbent for heavy metals removing and study of its adsorption kinetics and thermodynamics.

    Science.gov (United States)

    Zarghami, Zabihullah; Akbari, Ahmad; Latifi, Ali Mohammad; Amani, Mohammad Ali

    2016-04-01

    In this research, different generations of PAMAM-grafted chitosan as integrated biosorbents were successfully synthesized via step by step divergent growth approach of dendrimer. The synthesized products were utilized as adsorbents for heavy metals (Pb(2+) in this study) removing from aqueous solution and their reactive Pb(2+) removal potential was evaluated. The results showed that as-synthesized products with higher generations of dendrimer, have more adsorption capacity compared to products with lower generations of dendrimer and sole chitosan. Adsorption capacity of as-prepared product with generation 3 of dendrimer is 18times more than sole chitosan. Thermodynamic and kinetic studies were performed for understanding equilibrium data of the uptake capacity and kinetic rate uptake, respectively. Thermodynamic and kinetic studies showed that Langmuir isotherm model and pseudo second order kinetic model are more compatible for describing equilibrium data of the uptake capacity and kinetic rate of the Pb(2+) uptake, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Equilibrium, kinetic and thermodynamic studies of adsorption of Th(IV) from aqueous solution onto kaolin

    International Nuclear Information System (INIS)

    Hongxia Zhang; Zhiwei Niu; Zhi Liu; Zhaodong Wen; Weiping Li; Xiaoyun Wang; Wangsuo Wu

    2015-01-01

    The kinetics and thermodynamics of the adsorption of Th(IV) on the kaolin were studied by using batch method. In addition, the experimental data were studied by dynamic and thermodynamic models. The results showed that the adsorption capacity of the adsorbent increased with increasing temperature and solid liquid ratio, but decreased with increasing initial Th(IV) ion concentration, and the best fit was obtained for the pseudo-second-order kinetics model. The calculated activation energy for adsorption was about 45 kJ/mol, which indicated the adsorption process to be chemisorption. The adsorption isotherm data could be well described by the Langmuir as well as Dubinin-Radushkevich model. The mean free energy (E) of adsorption was calculated to be about 15 kJ/mol. The thermodynamic data calculated showed that the adsorption was spontaneous and enhanced at higher temperature. Considering kinetics and equilibrium studies, the adsorption on the sites was the rate-limiting step and that adsorption was mainly a chemisorption process through cation exchange. (author)

  1. Biosorption of Cu (II onto chemically modified waste mycelium of Aspergillus awamori: Equilibrium, kinetics and modeling studies

    Directory of Open Access Journals (Sweden)

    ZDRAVKA VELKOVA

    2012-01-01

    Full Text Available The biosorption potential of chemically modified waste mycelium of industrial xylanase-producing strain Aspergillus awamori for Cu (II removal from aqueous solutions was evaluated. The influence of pH, contact time and initial Cu (II concentration on the removal efficiency was evaluated. Maximum biosorption capacity was reached by sodium hydroxide treated waste fungal mycelium at pH 5.0. The Langmuir adsorption equation matched very well the adsorption equilibrium data in the studied conditions. The process kinetic followed the pseudo-firs order model.

  2. The nature of pseudo-twinning modes on the basis of a twin classification scheme

    International Nuclear Information System (INIS)

    Singh, Jung B.; Sundararaman, M.; Krishnan, M.

    2011-01-01

    Pseudo-twins can form in ordered structures under high stress conditions. These twins are defined by lattice sites that are at twin positions but are incorrectly occupied by different species of atoms. The present note discusses if it is possible to further classify pseudo-twins into different modes based on the nature of associated twinning elements.

  3. Adsorption removal of tartrazine by chitosan/polyaniline composite: Kinetics and equilibrium studies.

    Science.gov (United States)

    Sahnoun, Sousna; Boutahala, Mokhtar

    2018-02-24

    The present work focused on the performance of chitosan/polyaniline (Cht-PANI) composite for removing tartrazine dye from aqueous solutions. The adsorbent was characterized using SEM, XRD, FTIR, and TGA/DTA techniques. The effects of pH, initial dye concentration, contact time, and temperature on azo dye removal were studied. The kinetics and isotherm of tartrazine removal follow pseudo-second-order kinetics and the Freundlich isotherm, respectively. The Langmiur isotherm model exhibted a maximum adsorption capacity of 584.0 mg/g. The thermodynamic parameters were calculated and the negative values of ΔG° and positive value of ΔH° indicate that the adsorption processes are spontaneous and endothermic in nature. In addition, the resulting adsorbent reusability was demonstrated over four cycles, indicating that the Cht-PANI is a very promising adsorbent for removal of toxic pollutants from aqueous solutions. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Preparation and characterization of poly(AA co PVP)/PGS composite and its application for methylene blue adsorption.

    Science.gov (United States)

    Yang, Cai-xia; Lei, Lei; Zhou, Peng-xin; Zhang, Zhe; Lei, Zi-qiang

    2015-04-01

    Poly (AA co PVP)/PGS (PAPP) composite adsorbent was prepared by radical polymerization from Acrylic acid (AA), Polyvinylpyrrolidone (PVP) and Palygorskite (PGS), using N,N-methylenebisacrylamide (MBA) as cross-linker and potassium persulfate (KPS) as initiator. The PAPP was characterized with Fourier transform infrared (FT-IR), thermogravimetric analysis (TG), scanning electron microscope (SEM) and transmission electron microscopy (TEM). PAPP was used as adsorbent for the removal of methylene blue from aqueous solutions. The influences of pH, adsorption temperature and adsorption time on the adsorption properties of the composite to the dye were also investigated. Meanwhile, the adsorption rate data and adsorption equilibrium date were analyzed based on the pseudo-first-order and pseudo-second-order kinetic model, Langmuir and Freundlich isotherm models, respectively. The results indicating that the kinetic behavior better fit with the pseudo-second-order kinetic model. The maximum equilibrium adsorption capacity (q(m)) is 1815 mg/g at 289 K. The isotherm behavior can be explained by the Langmuir isotherm models. The activation energy was also evaluated for the removal of methylene blue onto PAPP. These results demonstrate that this composite material could be used as a good adsorbent for the removal of cationic dyes from wastewater. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Comparative Study of Ni-Zn LHS and Mg-Al LDH Adsorbents of Navy Blue and Yellow F3G Dye

    Directory of Open Access Journals (Sweden)

    Idha Yulia Ikhsani

    2016-03-01

    Full Text Available Adsorption of disperse dyes from wastewater onto Ni-Zn LHS (layered hydroxide salts and Mg-Al LDH (layered double hydroxides has been compared in this study. Effects of initial pH solution, contact time and initial dye concentration were investigated. The ability of the adsorbent to be reused was also studied. The results showed that acidic condition was favorable for the adsorption of each dyes onto both adsorbent. The adsorption kinetics was studied using pseudo-first-order, pseudo-second-order and Santosa’s kinetics models. The experimental data fits well with the pseudo-second order kinetic model. The equilibrium adsorption data were analyzed using Langmuir and Freundlich isotherm models. The results showed that adsorption of navy blue onto both adsorbent followed Freundlich isotherm adsorption, while yellow F3G followed Langmuir isotherm adsorption. In the application for the adsorption the wastewater containing dyes, Ni-Zn LHS has a better adsorption capacity of 52.33 mg/g than that of Mg-Al LDH that 30.54 mg/g. Calcination of the adsorbent which has already been used increased the adsorption capacity of Mg-Al LDH to 84.75 mg/g, but decreased the adsorption capacity of the Ni-Zn LHS to 42.65 mg/g.

  6. The sorption of lead, cadmium, copper and zinc ions from aqueous solutions on a raw diatomite from Algeria.

    Science.gov (United States)

    Safa, Messaouda; Larouci, Mohammed; Meddah, Boumediene; Valemens, Pierre

    2012-01-01

    The adsorption of Cu(2+), Zn(2+), Cd(2+) and Pb(2+) ions from aqueous solution by Algerian raw diatomite was studied. The influences of different sorption parameters such as contact pH solution, contact time and initial metal ions concentration were studied to optimize the reaction conditions. The metals ions adsorption was strictly pH dependent. The maximum adsorption capacities towards Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were 0.319, 0.311, 0.18 and 0.096 mmol g(-1), respectively. The kinetic data were modelled using the pseudo-first-order and pseudo-second-order kinetic equations. Among the kinetic models studied, the pseudo-second-order equation was the best applicable model to describe the sorption process. Equilibrium isotherm data were analysed using the Langmuir and the Freundlich isotherms; the results showed that the adsorption equilibrium was well described by both model isotherms. The negative value of free energy change ΔG indicates feasible and spontaneous adsorption of four metal ions on raw diatomite. According to these results, the high exchange capacities of different metal ions at high and low concentration levels, and given the low cost of the investigated adsorbent in this work, Algerian diatomite was considered to be an excellent adsorbent.

  7. Kinetics and mechanism of oxidation of chloramphenicol by 1

    Indian Academy of Sciences (India)

    Chloramphenicol (CAP) is an antibiotic drug having a wide spectrum of activity. The kinetics of oxidation of chloramphenicol by 1-chlorobenzotriazole (CBT) in HClO4 medium over the temperature range 293-323 K has been investigated. The reaction exhibits first-order kinetics with respect to [CBT]o and zero-order with ...

  8. Kinetic and mechanistic study of microcystin-LR degradation by nitrous acid under ultraviolet irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Qingwei; Ren, Jing [Department of Environmental Science and Engineering, Fudan University, Shanghai 200433 (China); Huang, Honghui [Key Laboratory of Fisheries Ecology Environment, Ministry of Agriculture, Guangzhou 510300 (China); Wang, Shoubing [Department of Environmental Science and Engineering, Fudan University, Shanghai 200433 (China); Wang, Xiangrong, E-mail: xrxrwang@vip.sina.com [Department of Environmental Science and Engineering, Fudan University, Shanghai 200433 (China); Fan, Zhengqiu, E-mail: zhqfan@fudan.edu.cn [Department of Environmental Science and Engineering, Fudan University, Shanghai 200433 (China)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer For the first time, degradation of MC-LR by nitrous acid under UV 365 nm was discovered. Black-Right-Pointing-Pointer The effects of factors on MC-LR degradation were analyzed based on kinetic study. Black-Right-Pointing-Pointer Mass spectrometry was applied for identification of intermediates and products. Black-Right-Pointing-Pointer Special intermediates involved in this study were identified. Black-Right-Pointing-Pointer Degradation mechanisms were proposed according to the results of LC-MS analysis. - Abstract: Degradation of microcystin-LR (MC-LR) in the presence of nitrous acid (HNO{sub 2}) under irradiation of 365 nm ultraviolet (UV) was studied for the first time. The influence of initial conditions including pH value, NaNO{sub 2} concentration, MC-LR concentration and UV intensity were studied. MC-LR was degraded in the presence of HNO{sub 2}; enhanced degradation of MC-LR was observed with 365 nm UV irradiation, caused by the generation of hydroxyl radicals through the photolysis of HNO{sub 2}. The degradation processes of MC-LR could well fit the pseudo-first-order kinetics. Mass spectrometry was applied for identification of the byproducts and the analysis of degradation mechanisms. Major degradation pathways were proposed according to the results of LC-MS analysis. The degradation of MC-LR was initiated via three major pathways: attack of hydroxyl radicals on the conjugated carbon double bonds of Adda, attack of hydroxyl radicals on the benzene ring of Adda, and attack of nitrosonium ion on the benzene ring of Adda.

  9. Viriato: a Fourier-Hermite spectral code for strongly magnetised fluid-kinetic plasma dynamics

    Science.gov (United States)

    Loureiro, Nuno; Dorland, William; Fazendeiro, Luis; Kanekar, Anjor; Mallet, Alfred; Zocco, Alessandro

    2015-11-01

    We report on the algorithms and numerical methods used in Viriato, a novel fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic Reduced Electron Heating Model equations [Zocco & Schekochihin, 2011] and (ii) the kinetic reduced MHD (KRMHD) equations [Schekochihin et al., 2009]. Two main applications of these equations are magnetised (Alfvnénic) plasma turbulence and magnetic reconnection. Viriato uses operator splitting to separate the dynamics parallel and perpendicular to the ambient magnetic field (assumed strong). Along the magnetic field, Viriato allows for either a second-order accurate MacCormack method or, for higher accuracy, a spectral-like scheme. Perpendicular to the field Viriato is pseudo-spectral, and the time integration is performed by means of an iterative predictor-corrector scheme. In addition, a distinctive feature of Viriato is its spectral representation of the parallel velocity-space dependence, achieved by means of a Hermite representation of the perturbed distribution function. A series of linear and nonlinear benchmarks and tests are presented, with focus on 3D decaying kinetic turbulence. Work partially supported by Fundação para a Ciência e Tecnologia via Grants UID/FIS/50010/2013 and IF/00530/2013.

  10. Study of the lifetime of the TL peaks of quartz: comparison of the deconvolution using the first order kinetic with the initial rise method

    International Nuclear Information System (INIS)

    RATOVONJANAHARY, A.J.F.

    2005-01-01

    Quartz is a thermoluminescent material which can be used for dating and/or for dosimetry. This material has been used since 60s for dating samples like pottery, flint, etc., but the method is still subject to some improvement. One of the problem of thermoluminescence dating is the estimation of the lifetime of the ''used peak'' . The application of the glow-curve deconvolution (GCD) technique for the analysis of a composite thermoluminescence glow curve into its individual glow peaks has been applied widely since the 80s. Many functions describing a single glow peak have been proposed. For analysing quartz behaviour, thermoluminescence glow-curve deconvolution (GCD) functions are compared for first order of kinetic. The free parameters of the GCD functions are the maximum peak intensity (I m ) and the maximum peak temperature (T m ), which can be obtained experimentally. The activation energy (E) is the additional free parameter. The lifetime (τ) of each glow peak, which is an important factor for dating, is calculated from these three parameters. For ''used'' ''peak'' lifetime analysis, GCD results are compared to those from initial rise method (IRM). Results vary fairly from method to method. [fr

  11. A potential low cost adsorbent for the removal of cationic dyes from aqueous solutions

    Science.gov (United States)

    Uddin, Md. Tamez; Rahman, Md. Arifur; Rukanuzzaman, Md.; Islam, Md. Akhtarul

    2017-10-01

    This study was aimed at using mango leaf powder (MLP) as a potential adsorbent for the removal of methylene blue (MB) from aqueous solutions. Characterization of the adsorbent was carried out with scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The pH at the point of zero charge of the adsorbent was determined by titration method and was found a value to be 5.6 ± 0.2. Batch studies were performed to evaluate the influence of various experimental parameters like initial solution pH, contact time, initial concentration of dye and adsorbent dosage on the removal of MB. An adsorption-desorption study was carried out resulting the mechanism of adsorption was carried out by electrostatic force of attraction. The adsorption equilibrium time required for the adsorption of MB on MLP was almost 2 h and 85 ± 5% of the total amount of dye uptake was found to occur in the first rapid phase (30 min). The Langmuir and Freundlich isotherm models were used for modeling the adsorption equilibrium. The experimental equilibrium data could be well interpreted by Langmuir isotherm with maximum adsorption capacity of 156 mg/g. To state the sorption kinetics, the fits of pseudo-first-order and pseudo-second-order kinetic models were investigated. It was obtained that the adsorption process followed the pseudo-second-order rate kinetics. The above findings suggest that MLP can be effectively used for decontamination of dye containing wastewater.

  12. Treatment of textile effluents by chloride-intercalated Zn-, Mg- and Ni-Al layered double hydroxides

    Directory of Open Access Journals (Sweden)

    F. Z. Mahjoubi

    2017-09-01

    Full Text Available This work involved the preparation, characterization and dyes removal ability of Zn-Al, Mg-Al and Ni-Al layered double hydroxide (LDH minerals intercalated by chloride ions. The materials were synthetized by the co-precipitation method. X-ray diffraction, Fourier transform infrared, thermogravimetric-differential thermal analysis and transmission electron microscopy characterization exhibited a typical hydrotalcite structure for all the samples. Adsorption experiments for methyl orange were performed in terms of solution pH, contact time and initial dye concentration. Experimental results indicate that the capacity of dye uptake augmented rapidly within the first 60 min and then stayed practically the same regardless of the concentration. Maximum adsorption occurred with acidic pH medium. Kinetic data were studied using pseudo-first-order and pseudo-second-order kinetic models. Suitable correlation was acquired with the pseudo-second-order kinetic model. Equilibrium data were fitted to Langmuir and Freundlich isotherm models. The maximum Langmuir monolayer adsorption capacities were 2,758, 1,622 and 800 mg/g, respectively, for Zn-Al-Cl, Mg-Al-Cl and Ni-Al-Cl. The materials were later examined for the elimination of color and chemical oxygen demand (COD from a real textile effluent wastewater. The results indicated that the suitable conditions for color and COD removal were acquired at pH of 5. The maximum COD removal efficiency from the effluent was noted as 92.84% for Zn-Al-Cl LDH.

  13. First kinetic discrimination between carbon and oxygen reactivity of enols.

    Science.gov (United States)

    García-Río, Luis; Mejuto, Juan C; Parajó, Mercedes; Pérez-Lorenzo, Moisés

    2008-11-07

    Nitrosation of enols shows a well-differentiated behavior depending on whether the reaction proceeds through the carbon (nucleophilic catalysis is observed) or the oxygen atom (general acid-base catalysis is observed). This is due to the different operating mechanisms for C- and O-nitrosation. Nitrosation of acetylacetone (AcAc) shows a simultaneous nucleophilic and acid-base catalysis. This simultaneous catalysis constitutes the first kinetic evidence of two independent reactions on the carbon and oxygen atom of an enol. The following kinetic study allows us to determine the rate constants for both reaction pathways. A similar reactivity of the nucleophilic centers with the nitrosonium ion is observed.

  14. a Time-Resolved X-Ray Scattering Study of the Ordering Kinetics in COPPER(3)-GOLD

    Science.gov (United States)

    Shannon, Robert Francis, Jr.

    Time-resolved x-ray scattering has been used to study ordering kinetics in single crystal bulk Cu _3Au, as well as in sputtered and molecular beam epitaxy grown films. After annealing at high temperatures the sample is rapidly quenched to fixed temperatures below the order-disorder transition temperature. The development of order is monitored in real time using scattering techniques. The bulk sample clearly showed three regimes: nucleation, ordering, and coarsening. The anisotropic superlattice peaks that reflect the domains structure are investigated in connection with the ordering kinetics. The line shape of the scattering function exhibits a crossover from gaussian to lorentzian-squared as the system goes from the ordering regime to the coarsening regime. Coarsening in Cu_3Au is consistent with curvature driven growth. Domain coarsening in stoichiometric sputtered films is also consistent with curvature driven growth. However, coarsening in copper rich films proceeds much more slowly. The results suggest the extra copper affects the ordering kinetics in the same way diffusive impurities would, resulting in a logarithmic like time dependence. The M.B.E. films show a slowing of the growth at late times. The 4500A film starts out with curvature driven growth but then continuously slows down as the domains grow. The 710A film shows an interesting temperature dependence for the growth, in such a way that at temperatures close to the transition, the domain growth almost freezes at late times. The dominate factor is probably strain, all of the trends for slower growth are consistent with greater strain. The dimensionality in the M.B.E. film systems is considered. The scaling in the 4500A and 710A films is clearly three dimensional. However, the dimension of the scaling in the 260A film is unclear.

  15. Second-order advantage from kinetic-spectroscopic data matrices in the presence of extreme spectral overlapping

    International Nuclear Information System (INIS)

    Culzoni, Maria J.; Goicoechea, Hector C.; Ibanez, Gabriela A.; Lozano, Valeria A.; Marsili, Nilda R.; Olivieri, Alejandro C.; Pagani, Ariana P.

    2008-01-01

    Multivariate curve resolution coupled to alternating least-squares (MCR-ALS) has been employed to model kinetic-spectroscopic second-order data, with focus on the achievement of the important second-order advantage, under conditions of extreme spectral overlapping among sample components. A series of simulated examples shows that MCR-ALS can conveniently handle the studied analytical problem unlike other second-order multivariate calibration algorithms, provided matrix augmentation is implemented in the spectral mode instead of in the usual kinetic mode. The approach has also been applied to three experimental examples, which involve the determination of: (1) the antiparkinsonian carbidopa (analyte) in the presence of levodopa as a potential interferent, both reacting with cerium (IV) to produce the fluorescent species cerium (III) with different kinetics; (2) Fe(II) (analyte) in the presence of the interferent Zn(II), both catalyzing the oxidation of methyl orange with potassium bromate; and (3) tartrazine (analyte) in the presence of the interferent brilliant blue, both oxidized with potassium bromate, with the interferent leading to a product with an absorption spectrum very similar to tartrazine. The results indicate good analytical performance towards the analytes, despite the intense spectral overlapping and the presence of unexpected constituents in the test samples

  16. Second-order advantage from kinetic-spectroscopic data matrices in the presence of extreme spectral overlapping

    Energy Technology Data Exchange (ETDEWEB)

    Culzoni, Maria J. [Laboratorio de Desarrollo Analitico y Quimiometria (LADAQ), Catedra de Quimica Analitica I, Facultad de Bioquimica y Ciencias Biologicas, Universidad Nacional del Litoral, Ciudad Universitaria, Santa Fe S3000ZAA (Argentina); Goicoechea, Hector C. [Laboratorio de Desarrollo Analitico y Quimiometria (LADAQ), Catedra de Quimica Analitica I, Facultad de Bioquimica y Ciencias Biologicas, Universidad Nacional del Litoral, Ciudad Universitaria, Santa Fe S3000ZAA (Argentina)], E-mail: hgoico@fbcb.unl.edu.ar; Ibanez, Gabriela A.; Lozano, Valeria A. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario and Instituto de Quimica Rosario (IQUIR-CONICET), Suipacha 531, Rosario S2002LRK (Argentina); Marsili, Nilda R. [Laboratorio de Desarrollo Analitico y Quimiometria (LADAQ), Catedra de Quimica Analitica I, Facultad de Bioquimica y Ciencias Biologicas, Universidad Nacional del Litoral, Ciudad Universitaria, Santa Fe S3000ZAA (Argentina); Olivieri, Alejandro C. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario and Instituto de Quimica Rosario (IQUIR-CONICET), Suipacha 531, Rosario S2002LRK (Argentina)], E-mail: aolivier@fbioyf.unr.edu.ar; Pagani, Ariana P. [Departamento de Quimica Analitica, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario and Instituto de Quimica Rosario (IQUIR-CONICET), Suipacha 531, Rosario S2002LRK (Argentina)

    2008-04-28

    Multivariate curve resolution coupled to alternating least-squares (MCR-ALS) has been employed to model kinetic-spectroscopic second-order data, with focus on the achievement of the important second-order advantage, under conditions of extreme spectral overlapping among sample components. A series of simulated examples shows that MCR-ALS can conveniently handle the studied analytical problem unlike other second-order multivariate calibration algorithms, provided matrix augmentation is implemented in the spectral mode instead of in the usual kinetic mode. The approach has also been applied to three experimental examples, which involve the determination of: (1) the antiparkinsonian carbidopa (analyte) in the presence of levodopa as a potential interferent, both reacting with cerium (IV) to produce the fluorescent species cerium (III) with different kinetics; (2) Fe(II) (analyte) in the presence of the interferent Zn(II), both catalyzing the oxidation of methyl orange with potassium bromate; and (3) tartrazine (analyte) in the presence of the interferent brilliant blue, both oxidized with potassium bromate, with the interferent leading to a product with an absorption spectrum very similar to tartrazine. The results indicate good analytical performance towards the analytes, despite the intense spectral overlapping and the presence of unexpected constituents in the test samples.

  17. Brane-worlds pseudo-Goldstinos

    International Nuclear Information System (INIS)

    Benakli, Karim; Moura, Cesar

    2008-01-01

    We consider a space-time with extra dimensions containing sectors, branes and bulk, that communicate only through gravitational interactions. In each sector, if considered separately, supersymmetry could be spontaneously broken, leading to the appearance of Goldstinos. However, when taken all together, only certain combinations of the latter states turn out to be true 'would-be-Goldstinos', eaten by the gravitinos. The other (orthogonal) combinations, we call pseudo-Goldstinos, remain in the low energy spectrum. We discuss explicitly how this happen in the simplest set-up of five-dimensional space compactified on S 1 /Z 2 . Our results divide into two parts that can be considered separately. First, we build an extension of the bulk five-dimensional supergravity, by a set of new auxiliary fields, that allows coupling it to branes where supersymmetry is spontaneously broken. Second, we discuss in details the super-Higgs mechanism in the R ξ and unitary gauges, in the presence of both of a bulk Scherk-Schwarz mechanism and brane localized F-terms. This leads us to compute the gravitino mass and provide explicit formulae for the pseudo-Goldstinos spectrum

  18. Discriminating between first- and second-order cognition in first-episode paranoid schizophrenia.

    Science.gov (United States)

    Bliksted, Vibeke; Samuelsen, Erla; Sandberg, Kristian; Bibby, Bo Martin; Overgaard, Morten Storm

    2017-03-01

    An impairment of visually perceiving backward masked stimuli is commonly observed in patients with schizophrenia, yet it is unclear whether this impairment is the result of a deficiency in first or higher order processing and for which subtypes of schizophrenia it is present. Here, we compare identification (first order) and metacognitive (higher order) performance in a visual masking paradigm between a highly homogenous group of young first-episode patients diagnosed with paranoid schizophrenia (N = 11) to that of carefully matched healthy controls (N = 13). We find no difference across groups in first-order performance, but find a difference in metacognitive performance, particularly for stimuli with relatively high visibility. These results indicate that the masking deficit is present in first-episode patients with paranoid schizophrenia, but that it is primarily an impairment of metacognition.

  19. Removing polycyclic aromatic hydrocarbons from water using granular activated carbon: kinetic and equilibrium adsorption studies.

    Science.gov (United States)

    Eeshwarasinghe, Dinushika; Loganathan, Paripurnanda; Kalaruban, Mahatheva; Sounthararajah, Danious Pratheep; Kandasamy, Jaya; Vigneswaran, Saravanamuthu

    2018-05-01

    Polycyclic aromatic hydrocarbons (PAHs) constitute a group of highly persistent, toxic and widespread environmental micropollutants that are increasingly found in water. A study was conducted in removing five PAHs, specifically naphthalene, acenaphthylene, acenaphthene, fluorene and phenanthrene, from water by adsorption onto granular activated carbon (GAC). The pseudo-first-order (PFO) model satisfactorily described the kinetics of adsorption of the PAHs. The Weber and Morris diffusion model's fit to the data showed that there were faster and slower rates of intra-particle diffusion probably into the mesopores and micropores of the GAC, respectively. These rates were negatively related to the molar volumes of the PAHs. Batch equilibrium adsorption data fitted well to the Langmuir, Freundlich and Dubinin-Radushkevich models, of which the Freundlich model exhibited the best fit. The adsorption affinities were related to the hydrophobicity of the PAHs as determined by the log K ow values. Free energies of adsorption calculated from the Dubinin-Radushkevich model and the satisfactory kinetic data fitting to the PFO model suggested physical adsorption of the PAHs. Adsorption of naphthalene, acenaphthylene and acenaphthene in fixed-bed columns containing a mixture of GAC (0.5 g) + sand (24.5 g) was satisfactorily simulated by the Thomas model.

  20. Selective adsorption behavior of Cd(II) ion imprinted polymers synthesized by microwave-assisted inverse emulsion polymerization: Adsorption performance and mechanism

    International Nuclear Information System (INIS)

    Zhu, Fang; Li, Luwei; Xing, Junde

    2017-01-01

    Highlights: • Microwave assisted inverse emulsion polymerization was applied to prepare Cd(II) imprinted polymers. • The adsorption capacity was evaluated by static adsorption experiments. • Pseudo-second-order model and Langmuir adsorption isotherm model had the best agreement with the experimental data. • The adsorption was a spontaneous and endothermic process. • Cd(II) imprinted polymers have specific identification for Cd(II). - Abstract: Microwave-assisted inverse emulsion polymerization method was used to prepare Cd(II) imprinted polymer (IIP) by using β-cyclodextrin (β-CD) and acrylamide (AM) as functional monomer, epichlorohydrin (ECH) as crossing-linking agent, ammonium persulfate as initiator. The Cd(II) imprinted polymer was characterized by SEM, FTIR and TGA. The influences of initial concentration of Cd(II), pH values, temperature, time and competitive ions on adsorption capacity and recognition properties are investigated. Under the optimal conditions, the adsorption capacity could reach 107 mg/g. Furthermore, pseudo first order kinetic model, pseudo second order kinetic model and intra-particular diffusion model were used to describe the adsorption kinetic behavior. Results showed that the pseudo-second-order model (R"2 0.9928–0.9961) had the best agreement with the experimental data. Langmuir adsorption isotherm model described the experimental data well, which indicated that adsorption was mainly monolayer absorption. Moreover, the study of adsorption thermodynamics (ΔG"0 0, ΔS"0 > 0) suggested that the adsorption process was a spontaneous and endothermic process. Competitive selectivity experiment revealed that imprinted polymer could selectively recognize Cd(II). It provides a new idea for removing Cd(II) from aqueous solution.

  1. Scavenging remazol brilliant blue R dye using microwave-assisted activated carbon from acacia sawdust: Equilibrium and kinetics studies

    Science.gov (United States)

    Yusop, M. F. M.; Aziz, H. A.; Ahmad, M. A.

    2017-10-01

    This work explores the feasibility of microwave-assisted acacia wood based activated carbon (AWAC) for remazol brilliant blue R (RBBR) dye removal from synthetic wastewater. Acacia wood (AW) was impregnated with potassium hydroxide (KOH) and heated using microwave, resulting tremendously high fixed carbon content, surface area, total pore volume and adsorption capacity of 81.14%, 1045.56m2/g, 0.535cm3/g and 263.16mg/g respectively. Batch study conducted divulged an increasing trend in RBBR uptake when initial RBBR concentration and contact time were increased. pH study revealed that RBBR adsorption was best at acidic condition. Langmuir isotherm model fitted well the adsorption equilibrium data while the adsorption kinetic was found to follow the pseudo-second-order kinetic model.

  2. Adsorption Behavior and Kinetic Characteristic of Cibacron Brilliant Red 3B-A by Granular Activated Carbon

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Jib [Kongju National University, Cheonan (Korea, Republic of)

    2014-08-15

    In this paper, the adsorption behavior and kinetic characteristics of cibacron brilliant red 3B-A from aqueous solution using granular activated carbon were investigated. The effect of various parameters such as adsorbent dose, pH, initial concentration, contact time and temperature on the adsorption system were studied. Base on the estimated Langmuir constant (R{sub L}) and Freundlich constant (1/n), This process could be employed as effective treatment method. From the Temkin constant (B) and Dubinin-Radushkevich constant (E), This adsorption process is physical adsorption. From kinetic experiments, the adsorption process followed the pseudo second order model with good correlation. Base on the Gibbs free energy and enthalpy, the adsorption of cibacron brilliant red 3B-A onto granular activated carbon was physisorption and endothermic in nature.

  3. Adsorption Behavior and Kinetic Characteristic of Cibacron Brilliant Red 3B-A by Granular Activated Carbon

    International Nuclear Information System (INIS)

    Lee, Jong Jib

    2014-01-01

    In this paper, the adsorption behavior and kinetic characteristics of cibacron brilliant red 3B-A from aqueous solution using granular activated carbon were investigated. The effect of various parameters such as adsorbent dose, pH, initial concentration, contact time and temperature on the adsorption system were studied. Base on the estimated Langmuir constant (R L ) and Freundlich constant (1/n), This process could be employed as effective treatment method. From the Temkin constant (B) and Dubinin-Radushkevich constant (E), This adsorption process is physical adsorption. From kinetic experiments, the adsorption process followed the pseudo second order model with good correlation. Base on the Gibbs free energy and enthalpy, the adsorption of cibacron brilliant red 3B-A onto granular activated carbon was physisorption and endothermic in nature

  4. Slow coarsening of B2-ordered domains at low temperatures: A kinetic Monte Carlo study

    International Nuclear Information System (INIS)

    Le Floc'h, D.; Bellon, P.; Athenes, M.

    2000-01-01

    The kinetics of the ordering and coarsening of B2-ordered domains is studied using atomistic kinetic Monte Carlo simulations. Special emphasis is put on the effect of annealing temperature, alloy composition, and atom dynamics on the coarsening behavior. When atomic diffusion proceeds by vacancy jumps to nearest-neighbor sites, a transient slow coarsening regime is observed at temperatures below half the order-disorder transition temperature T c . It results in apparent coarsening exponents that decrease with decreasing the annealing temperature. Values as low as 0.14 are measured at 0.25T c . Slow transients take place in both stoichiometric and nonstoichiometric alloys. These regimes are correlated with the transient creation of excess antisites during domain disappearance. Since antiphase boundary mobility decreases with increasing antisite concentration, this transient excess results in the slow coarsening observed in simulations. (c) 2000 The American Physical Society

  5. Factors impacting biotransformation kinetics of trace organic compounds in lab-scale activated sludge systems performing nitrification and denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Su, Lijuan; Aga, Diana [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260 (United States); Chandran, Kartik [Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027 (United States); Khunjar, Wendell O., E-mail: wkhunjar@hazenandsawyer.com [Hazen and Sawyer P.C., Fairfax, VA 22030 (United States)

    2015-01-23

    Highlights: • We examined TOrC biotransformation kinetics in nitrifying and denitrifying reators. • TOrC biotransformation was linked to heterotrophic and autotrophic activity. • TOrC biotransformation rates were not sensitive to the initial TOrC concentration. • Readily biodegradable organic matter suppressed TOrC biotransformation rates. - Abstract: To predict TOrC fate in biological activated sludge systems, there is a need to accurately determine TOrC biodegradation kinetics in mixed microbial cultures. Short-term batch tests with salicylic acid, 17α-ethinylestradiol, nonylphenol, trimethoprim and carbamazepine were conducted with lab-scale activated sludge cultures in which the initial TOrC concentration (1 mg/L and 0.0005 mg/L) and readily biodegradable substrate concentrations were varied. The results indicate that pseudo-first order kinetic estimates of TOrC are not sensitive (p > 0.05) to the initial TOrC concentration as long as the initial TOrC concentration (S{sub 0}) to biomass (X{sub 0}) ratio (on COD basis) is below 2 × 10{sup −3}. The presence of readily biodegradable organic matter suppresses TOrC biotransformation rates under nitrifying and denitrifying conditions, and this impact can be adequately described using a reversible non-competitive inhibition equation. These results demonstrate the importance of closely mimicking parent reactor conditions in batch testing because biotransformation parameters are impacted by in-situ carbon loading and redox conditions.

  6. Factors impacting biotransformation kinetics of trace organic compounds in lab-scale activated sludge systems performing nitrification and denitrification

    International Nuclear Information System (INIS)

    Su, Lijuan; Aga, Diana; Chandran, Kartik; Khunjar, Wendell O.

    2015-01-01

    Highlights: • We examined TOrC biotransformation kinetics in nitrifying and denitrifying reators. • TOrC biotransformation was linked to heterotrophic and autotrophic activity. • TOrC biotransformation rates were not sensitive to the initial TOrC concentration. • Readily biodegradable organic matter suppressed TOrC biotransformation rates. - Abstract: To predict TOrC fate in biological activated sludge systems, there is a need to accurately determine TOrC biodegradation kinetics in mixed microbial cultures. Short-term batch tests with salicylic acid, 17α-ethinylestradiol, nonylphenol, trimethoprim and carbamazepine were conducted with lab-scale activated sludge cultures in which the initial TOrC concentration (1 mg/L and 0.0005 mg/L) and readily biodegradable substrate concentrations were varied. The results indicate that pseudo-first order kinetic estimates of TOrC are not sensitive (p > 0.05) to the initial TOrC concentration as long as the initial TOrC concentration (S 0 ) to biomass (X 0 ) ratio (on COD basis) is below 2 × 10 −3 . The presence of readily biodegradable organic matter suppresses TOrC biotransformation rates under nitrifying and denitrifying conditions, and this impact can be adequately described using a reversible non-competitive inhibition equation. These results demonstrate the importance of closely mimicking parent reactor conditions in batch testing because biotransformation parameters are impacted by in-situ carbon loading and redox conditions

  7. Empiricism or self-consistent theory in chemical kinetics?

    International Nuclear Information System (INIS)

    Gutman, E.M.

    2007-01-01

    To give theoretical background for mechanochemical kinetics, we need first of all to find a possibility to predict the kinetic parameters for real chemical processes by determining rate constants and reaction orders without developing strictly specialized and, to a great extent, artificial models, i.e. to derive the kinetic law of mass action from 'first principles'. However, the kinetic law of mass action has had only an empirical basis from the first experiments of Gulberg and Waage until now, in contrast to the classical law of mass action for chemical equilibrium rigorously derived in chemical thermodynamics from equilibrium condition. Nevertheless, in this paper, an attempt to derive the kinetic law of mass action from 'first principles' is made in macroscopic formulation. It has turned out to be possible owing to the methods of thermodynamics of irreversible processes that were unknown in Gulberg and Waage's time

  8. High performance maleated lignocellulose epicarp fibers for copper ion removal

    Directory of Open Access Journals (Sweden)

    A. P. Vieira

    2014-03-01

    Full Text Available Natural lignocellulosic fiber epicarp extracted from the babassu coconut (Orbignya speciosa was chemically modified through reaction with molten maleic anhydride without solvent, with incorporation of 189.34 mg g-1 of carboxylic acid groups into the biopolymer structure. The success of this reaction was also confirmed by the presence of carboxylic acid bands at 1741 and 1164 cm-1 in the infrared spectrum. Identically, the same group is observed through 13C NMR CP/MAS in the solid state, via high field signals in the 167 pm region. Both the precursor and the immobilized maleated biopolymers presented nearly the same thermal stability and similar crystallinity to cellulose. However, the pendant carboxylic groups have the ability to remove copper with maximum sorption through a batchwise process at pH 6.0, as expected from the point of zero charge, determined to be 6.45. The sorption kinetic data were fitted to pseudo-first order, pseudo-second order, Elovich-chemisorption and intra-particle diffusion models and the equilibrium data were fitted to the Langmuir, the Freundlich and Tenkim isotherm models. Taking into account a statistical error function and determination coefficients, the data were fit to the pseudo-first and pseudo-second order kinetic and Langmuir isotherm models, with a maximum sorption capacity of copper ions of 55.09 mg g-1. This value suggests the application of this biopolymer with incorporated carboxylate groups as a favorable agent for copper removal from appropriate systems.

  9. Rapid removal of bisphenol A on highly ordered mesoporous carbon.

    Science.gov (United States)

    Sui, Qian; Huang, Jun; Liu, Yousong; Chang, Xiaofeng; Ji, Guangbin; Deng, Shubo; Xie, Tao; Yu, Gang

    2011-01-01

    Bisphenol A (BPA) is of global concern due to its disruption of endocrine systems and ubiquity in the aquatic environment. It is important, therefore, that efforts are made to remove it from the aqueous phase. A novel adsorbent, mesoporous carbon CMK-3, prepared from hexagonal SBA-15 mesoporous silica was studied for BPA removal from aqueous phase, and compared with conventional powdered activated carbon (PAC). Characterization of CMK-3 by transmission electron microscopy (TEM), X-ray diffraction, and nitrogen adsorption indicated that prepared CMK-3 had an ordered mesoporous structure with a high specific surface area of 920 m2/g and a pore-size of about 4.9 nm. The adsorption of BPA on CMK-3 followed a pseudo second-order kinetic model. The kinetic constant was 0.00049 g/(mg x min), much higher than the adsorption of BPA on PAC. The adsorption isotherm fitted slightly better with the Freundlich model than the Langmuir model, and adsorption capacity decreased as temperature increased from 10 to 40 degrees C. No significant influence of pH on adsorption was observed at pH 3 to 9; however, adsorption capacity decreased dramatically from pH 9 to 13.

  10. KINETIC MODELING AND ISOTHERM STUDIES ON A BATCH REMOVAL OF ACID RED 114 BY AN ACTIVATED PLANT BIOMASS

    Directory of Open Access Journals (Sweden)

    N. RAJAMOHAN

    2013-12-01

    Full Text Available In this paper, the dye Acid Red 114(AR 114 was removed from aqueous solutions using Acid-Activated Eichornia Crassipes (AAEC under batch conditions. The optimum conditions for AR 114 removal were found to be pH 1.5, adsorbent dosage = 1.25 g/L of solution and equilibrium time = 3 h. The equilibrium data were evaluated for compliance with Langmuir, Freundlich and Temkin isotherms and Langmuir isotherm was found to fit well. The maximum sorption capacity was estimated as 112.34 mg/g of adsorbent. Also, adsorption kinetics of the dye was studied and the rates of sorption were found to follow pseudo-second order kinetics with good correlation (R2 ≥ 0.997.The kinetic study at different temperatures revealed that the sorption was an endothermic process. The activation energy of the sorption process was estimated as 9.722 kJ/mol.

  11. Self-imaging in first-order optical systems

    NARCIS (Netherlands)

    Alieva, T.; Bastiaans, M.J.; Nijhawan, O.P.; Guota, A.K.; Musla, A.K.; Singh, Kehar

    1998-01-01

    The structure and main properties of coherent and partially coherent optical fields that are self-reproducible under propagation through a first-order optical system are investigated. A phase space description of self-imaging in first-order optical systems is presented. The Wigner distribution

  12. Oxidation of L-cystine by chromium(VI) - a kinetic study | Kumar ...

    African Journals Online (AJOL)

    The kinetics of the title reaction was studied spectrophotometrically in HClO4 medium at 380 nm. The data suggested that the order with respect to cystine is fractional, whereas chromium(VI) follows first order kinetics. The reaction was second order in [H+]. Cysteic acid was found to be the main product of oxidation.

  13. A high-order method for the integration of the Galerkin semi-discretized nuclear reactor kinetics equations

    International Nuclear Information System (INIS)

    Vargas, L.

    1988-01-01

    The numerical approximate solution of the space-time nuclear reactor kinetics equation is investigated using a finite-element discretization of the space variable and a high order integration scheme for the resulting semi-discretized parabolic equation. The Galerkin method with spatial piecewise polynomial Lagrange basis functions are used to obtained a continuous time semi-discretized form of the space-time reactor kinetics equation. A temporal discretization is then carried out with a numerical scheme based on the Iterated Defect Correction (IDC) method using piecewise quadratic polynomials or exponential functions. The kinetics equations are thus solved with in a general finite element framework with respect to space as well as time variables in which the order of convergence of the spatial and temporal discretizations is consistently high. A computer code GALFEM/IDC is developed, to implement the numerical schemes described above. This issued to solve a one space dimensional benchmark problem. The results of the numerical experiments confirm the theoretical arguments and show that the convergence is very fast and the overall procedure is quite efficient. This is due to the good asymptotic properties of the numerical scheme which is of third order in the time interval

  14. Field Method for Integrating the First Order Differential Equation

    Institute of Scientific and Technical Information of China (English)

    JIA Li-qun; ZHENG Shi-wang; ZHANG Yao-yu

    2007-01-01

    An important modern method in analytical mechanics for finding the integral, which is called the field-method, is used to research the solution of a differential equation of the first order. First, by introducing an intermediate variable, a more complicated differential equation of the first order can be expressed by two simple differential equations of the first order, then the field-method in analytical mechanics is introduced for solving the two differential equations of the first order. The conclusion shows that the field-method in analytical mechanics can be fully used to find the solutions of a differential equation of the first order, thus a new method for finding the solutions of the first order is provided.

  15. Evaluation of Zirconium Silico phosphate Material for the Removal of Copper Ions from Waste Water

    International Nuclear Information System (INIS)

    Abd El-Mohsen, E.S.; El-Naggar, M.R.; EI-Naggar, I.M.; El-Shahhat, M.F.

    2014-01-01

    Zirconium silico phosphate/polyacrylamide (ZrSP/PAA) nano composite was synthesized. Synthesis process was based on the intercalation polymerization technique. The obtained nano product was characterized using XRF, XRD, FTIR, TG-DTA, SEM and TEM techniques. The physicochemical properties indicated that the synthesized material was semicrystalline in nature with a particle size in the nan orange (45 nm). FTIR analysis suggested that the intercalation polymerization was achieved via hydrogen bonding. The kinetics of copper retention at different temperatures were analyzed using pseudo first-order, pseudo second-order and Helfferich kinetic models. Kinetic modeling of the experimentally obtained data indicated that the intra-particle diffusion was the controlled mechanism of the sorption process. Various parameters such as effective diffusion coefficient and activation energy were evaluated. The mean free energy was in the range corresponding to the ion exchange type of sorption. Results indicated that synthetic ZrSP/PAA nano composite can be used as an efficient ion exchange material for the removal of cupper ions from waste water

  16. Rarefied gas flow simulations using high-order gas-kinetic unified algorithms for Boltzmann model equations

    Science.gov (United States)

    Li, Zhi-Hui; Peng, Ao-Ping; Zhang, Han-Xin; Yang, Jaw-Yen

    2015-04-01

    This article reviews rarefied gas flow computations based on nonlinear model Boltzmann equations using deterministic high-order gas-kinetic unified algorithms (GKUA) in phase space. The nonlinear Boltzmann model equations considered include the BGK model, the Shakhov model, the Ellipsoidal Statistical model and the Morse model. Several high-order gas-kinetic unified algorithms, which combine the discrete velocity ordinate method in velocity space and the compact high-order finite-difference schemes in physical space, are developed. The parallel strategies implemented with the accompanying algorithms are of equal importance. Accurate computations of rarefied gas flow problems using various kinetic models over wide ranges of Mach numbers 1.2-20 and Knudsen numbers 0.0001-5 are reported. The effects of different high resolution schemes on the flow resolution under the same discrete velocity ordinate method are studied. A conservative discrete velocity ordinate method to ensure the kinetic compatibility condition is also implemented. The present algorithms are tested for the one-dimensional unsteady shock-tube problems with various Knudsen numbers, the steady normal shock wave structures for different Mach numbers, the two-dimensional flows past a circular cylinder and a NACA 0012 airfoil to verify the present methodology and to simulate gas transport phenomena covering various flow regimes. Illustrations of large scale parallel computations of three-dimensional hypersonic rarefied flows over the reusable sphere-cone satellite and the re-entry spacecraft using almost the largest computer systems available in China are also reported. The present computed results are compared with the theoretical prediction from gas dynamics, related DSMC results, slip N-S solutions and experimental data, and good agreement can be found. The numerical experience indicates that although the direct model Boltzmann equation solver in phase space can be computationally expensive

  17. Removal of 2,4-dichlorophenol using cyclodextrin-ionic liquid polymer as a macroporous material: Characterization, adsorption isotherm, kinetic study, thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Raoov, Muggundha [University of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Advanced Medical and Dental Institute, University of Science Malaysia, No. 1–8 (Lot 8), Persiaran Seksyen 4/1, Bandar Putra Bertam, Kepala Batas, Pulau Pinang 13200 (Malaysia); Mohamad, Sharifah, E-mail: sharifahm@um.edu.my [University of Malaya Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia); Abas, Mohd Radzi [Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia)

    2013-12-15

    Highlights: • βCD-BIMOTs-TDI exhibits macropore size (77.66 nm) with 1.254 m{sup 2} g{sup −1} surface area. • Freundlich isotherm and pseudo-second order kinetics fit well the adsorption process. • Removal was optimum at pH 6 with 83% and reached equilibrium at 80 mg L{sup −1}. • Entropy (ΔS°) and heat of adsorption (ΔH°) estimated as −55.99 J/K mol and −18.10 J/mol. • Inclusion complex and π–π interaction were found to be dominant at pH 6. -- Abstract: Cyclodextrin-ionic liquid polymer (βCD-BIMOTs-TDI) was firstly synthesized using functionalized β-Cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using toluene diisocyanate (TDI) linker to form insoluble βCD-BIMOTs-TDI. SEM characterization result shows that βCD-BIMOTs-TDI exhibits macropore size while the BET result shows low surface area (1.254 m{sup 2} g{sup −1}). The unique properties of the ILs allow us to produce materials with different morphologies. The adsorption isotherm and kinetics of 2,4-dichlorophenol (2,4-DCP) onto βCD-BIMOTs-TDI is studied. Freundlich isotherm and pseudo-second order kinetics are found to be the best to represent the data for 2,4-DCP adsorption on the βCD-BIMOTs-TDI. The presence of macropores decreases the mass transfer resistance and increases the adsorption process by reducing the diffusion distance. The change in entropy (ΔS°) and heat of adsorption (ΔH°) for 2,4-DCP on βCD-BIMOTs-TDI were estimated as −55.99 J/Kmol and −18.10 J/mol, respectively. The negative value of Gibbs free energy (ΔG°) indicates that the adsorption process is thermodynamically feasible, spontaneous and chemically controlled. Finally, the interactions between the cavity of βCD-BIMOTs and 2,4-DCP are investigated and the results shows that the inclusion of the complex formation and π–π interaction are the main processes involved in the adsorption process.

  18. First order actions for gravitational systems, strings and membranes

    International Nuclear Information System (INIS)

    Lindstrom, U.

    1988-01-01

    The authors discuss first order actions in general and the construction of first order actions by eliminating Lagrange multipliers in particular. A number of first order actions for gravitational theories are presented. Part of the article reviews first order actions, some of them well-known and some lesser known. New examples of first order actions include Weyl-invariant actions for membranes, with and without rigidity terms, as well as for Abelian and non-Abelian Born-Infeld actions in two dimensions

  19. Prediction and validation of burnout curves for Goettelborn char using reaction kinetics determined in shock tube experiments

    Energy Technology Data Exchange (ETDEWEB)

    Moors, J.H.J.; Banin, V.E.; Haas, J.H.P.; Weber, R.; Veefkind, A. [Eindhoven University of Technology, Eindhoven (Netherlands). Dept. of Applied Physics

    1999-01-01

    Using a shock tube facility the combustion characteristics of pulverised char ({lt} 10 {mu}m) were measured. A prediction was made for the burnout behaviour of a commercial sized char particle (75-90 {mu}m) in different ambient conditions using a `pseudo kinetic` approach. In this approach the kinetic rate of a surface containing micro pores is determined and these `pseudo kinetics` are then applied to the larger particle not taking into account the micro pores. Comparison of the predictions with measurements done with an isothermal plug flow reactor showed this approach to be valid within experimental error for low burnout. A linear decrease of the kinetic reaction rate with burnout is shown to predict the burnout behaviour in the complete range of burnout. A possible explanation for this linear decrease could be a growing fraction of non-combustible material in the char particles during burnout. 11 refs., 6 figs., 2 tabs.

  20. Waste Plant Material as a Potential Adsorbent of a Selected Azo Dye

    Directory of Open Access Journals (Sweden)

    Tomczak Elwira

    2017-06-01

    Full Text Available This paper discusses the adsorption of Direct Orange 26 azo dye on sunflower husk - an agricultural waste product. During the study, sorption kinetics and equilibrium as well as sorption capacity of the husk were investigated. The adsorption kinetics was analyzed using pseudo-first and pseudo-second order equations, which indicated a chemical sorption mechanism. The sorption equilibrium was approximated with the two-parameter Freundlich and Langmuir equations and the three-parameter Redlich-Peterson equation. The main experiments were carried out in a laboratory adsorption column under different process conditions. Experimental data were interpreted with the Thomas model, based on the volumetric flow rate, initial composition of the feed solution and mass of the adsorbent. The results of modeling the adsorption equilibrium, adsorption kinetics and adsorption dynamics were evaluated statistically.

  1. Observations on the properties of second and general-order kinetics equations describing the thermoluminescence processes

    International Nuclear Information System (INIS)

    Kitis, G.; Furetta, C.; Azorin, J.

    2003-01-01

    Synthetic thermoluminescent (Tl) glow peaks, following a second and general kinetics order have been generated by computer. The general properties of the so generated peaks have been investigated over several order of magnitude of simulated doses. Some non usual results which, at the best knowledge of the authors, are not reported in the literature, are obtained and discussed. (Author)

  2. Pseudo-Random Number Generators for Vector Processors and Multicore Processors

    DEFF Research Database (Denmark)

    Fog, Agner

    2015-01-01

    Large scale Monte Carlo applications need a good pseudo-random number generator capable of utilizing both the vector processing capabilities and multiprocessing capabilities of modern computers in order to get the maximum performance. The requirements for such a generator are discussed. New ways...

  3. Kinetics and equilibrium adsorption studies of dimethylamine (DMA) onto ion-exchange resin

    International Nuclear Information System (INIS)

    Hu Qinhai; Meng Yuanyuan; Sun Tongxi; Mahmood, Qaisar; Wu Donglei; Zhu Jianhang; Lu, George

    2011-01-01

    The fine grained resin ZGSPC106 was used to adsorb dimethylamine (DMA) from aqueous solution in the present research. Batch experiments were performed to examine the effects of initial pH of solution and agitation time on the adsorption process. The thermodynamics and kinetics of adsorption were also analyzed. The maximum adsorption was found at natural pH of DMA solution and equilibrium could be attained within 12 min. The equilibrium adsorption data were conformed satisfactorily to the Langmuir equation. The evaluation based on Langmuir isotherm gave the maximal static saturated adsorption capacity of 138.89 mg/g at 293 K. Various thermodynamic parameters such as free energy (ΔG o ), enthalpy (ΔH o ) and entropy (ΔS o ) showed that the adsorption was spontaneous, endothermic and feasible. DMA adsorption on ZGSPC106 fitted well to the pseudo-second-order kinetic model. Furthermore, the adsorption mechanism was discussed by Fourier transform infrared spectroscopy (FT-IR) analysis.

  4. Malonic acid concentration as a control parameter in the kinetic analysis of the Belousov-Zhabotinsky reaction under batch conditions.

    Science.gov (United States)

    Blagojević, Slavica M; Anić, Slobodan R; Cupić, Zeljko D; Pejić, Natasa D; Kolar-Anić, Ljiljana Z

    2008-11-28

    The influence of the initial malonic acid concentration [MA]0 (8.00 x 10(-3) sulfuric acid (1.00 mol dm(-3)) and cerium sulfate (2.50 x 10(-3) mol dm(-3)) on the dynamics and the kinetics of the Belousov-Zhabotinsky (BZ) reactions was examined under batch conditions at 30.0 degrees C. The kinetics of the BZ reaction was analyzed by the earlier proposed method convenient for the examinations of the oscillatory reactions. In the defined region of parameters where oscillograms with only large-amplitude relaxation oscillations appeared, the pseudo-first order of the overall malonic acid decomposition with a corresponding rate constant of 2.14 x 10(-2) min(-1) was established. The numerical results on the dynamics and kinetics of the BZ reaction, carried out by the known skeleton model including the Br2O species, were in good agreement with the experimental ones. The already found saddle node infinite period (SNIPER) bifurcation point in transition from a stable quasi-steady state to periodic orbits and vice versa is confirmed by both experimental and numerical investigations of the system under consideration. Namely, the large-amplitude relaxation oscillations with increasing periods between oscillations in approaching the bifurcation points at the beginning and the end of the oscillatory domain, together with excitability of the stable quasi-steady states in their vicinity are obtained.

  5. In situ and laboratory determined first-order degradation rate constants of specific organic compounds in an aerobic aquifer

    DEFF Research Database (Denmark)

    Nielsen, P.H.; Bjerg, P.L.; Nielsen, P.

    1996-01-01

    In situ microcosms (ISM) and laboratory batch microcosms (LBM) were used for determination of the first-order degradation rate constants of benzene, toluene, o-xylene, nitrobenzene, naphthalene, biphenyl, o- and p-dichlorobenzene, 1,1,1 -trichloroethane, tetrachlorometane, trichloroethene......, tetrachloroethene, phenol, o-cresol, 2,4- and 2,6-dichlorophenol, 4,6-o-dichlorocresol, and o- and p-nitrophenol in an aerobic aquifer, All aromatic hydrocarbons were degraded in ISM and LBM experiments. The phenolic hydrocarbons were ail degraded in ISM experiments, but some failed to degrade in LBM experiments....... Chlorinated aliphatic hydrocarbons were degraded neither in ISM nor LBM experiments. Degradation rate constants were determined by a model accounting for kinetic sorption (bicontinuum model), lag phases, and first-order degradation. With a few exceptions, lag phases were less than 2 weeks in both ISM and LBM...

  6. Fast and calibration free determination of first order reaction kinetics in API synthesis using in-situ ATR-FTIR.

    Science.gov (United States)

    Rehbein, Moritz C; Husmann, Sascha; Lechner, Christian; Kunick, Conrad; Scholl, Stephan

    2018-05-01

    In early stages of drug development only sparse amounts of the key substances are available, which is problematic for the determination of important process data like reaction kinetics. Therefore, it is important to perform experiments as economically as possible, especially in regards to limiting compounds. Here we demonstrate the use of a temperature step experiment enabling the determination of complete reaction kinetics in a single non-isothermal experiment. In contrast to the traditionally used HPLC, the method takes advantage of the high measuring rate and the low amount of labor involved in using in-situ ATR-FTIR to determine time-dependent concentration-equivalent data. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Isolation, identification, Pb(II) biosorption isotherms and kinetics of a lead adsorbing penicillium sp. MRF-1 from South Korean mine soil.

    Science.gov (United States)

    Velmurugan, Natarajan; Hwang, Grim; Sathishkumar, Muthuswamy; Choi, Tae Kie; Lee, Kui-Jae; Oh, Byung-Taek; Lee, Yang-Soo

    2010-01-01

    A heavy metal contaminated soil sample collected from a mine in Chonnam Province of South Korea was found to be a source of heavy metal adsorbing biosorbents. Chemical analyses showed high contents of lead (Pb) at 357 mg/kg and cyanide (CN) at 14.6 mg/kg in the soil. The experimental results showed that Penicillium sp. MRF-1 was the best lead resistant fungus among the four individual metal tolerant fungal species isolated from the soil. Molecular characterization of Penicillium sp. MRF-1 was determined using ITS regions sequences. Effects of pH, temperature and contact time on adsorption of Pb(II) by Penicillium sp. MRF-1 were studied. Favorable conditions for maximum biosportion were found at pH 4 with 3 hr contact time. Biosorption of Pb(II) gradually increased with increasing temperature. Efficient performance of the biosorbent was described using Langmuir and Freundlich isotherms. Adsorption kinetics was studied using pseudo first-order and pseudo second-order models. Biosorbent Penicillium sp. MRF-1 showed the maximum desorption in alkali conditions. Consistent adsorption/desorption potential of the biosorbent in repetitive cycles validated the efficacy of it in large scale. SEM studies given notes on surface modification of fungal biomass under metal stress and FT-IR results showed the presence of amino groups in the surface structure of the biosorbent. In conclusion, the new biosorbent Penicillium sp. MRF-1 may potentially be used as an inexpensive, easily cultivatable material for the removal of lead from aqueous solution.

  8. Order-disorder transitions govern kinetic cooperativity and allostery of monomeric human glucokinase.

    Directory of Open Access Journals (Sweden)

    Mioara Larion

    Full Text Available Glucokinase (GCK catalyzes the rate-limiting step of glucose catabolism in the pancreas, where it functions as the body's principal glucose sensor. GCK dysfunction leads to several potentially fatal diseases including maturity-onset diabetes of the young type II (MODY-II and persistent hypoglycemic hyperinsulinemia of infancy (PHHI. GCK maintains glucose homeostasis by displaying a sigmoidal kinetic response to increasing blood glucose levels. This positive cooperativity is unique because the enzyme functions exclusively as a monomer and possesses only a single glucose binding site. Despite nearly a half century of research, the mechanistic basis for GCK's homotropic allostery remains unresolved. Here we explain GCK cooperativity in terms of large-scale, glucose-mediated disorder-order transitions using 17 isotopically labeled isoleucine methyl groups and three tryptophan side chains as sensitive nuclear magnetic resonance (NMR probes. We find that the small domain of unliganded GCK is intrinsically disordered and samples a broad conformational ensemble. We also demonstrate that small-molecule diabetes therapeutic agents and hyperinsulinemia-associated GCK mutations share a strikingly similar activation mechanism, characterized by a population shift toward a more narrow, well-ordered ensemble resembling the glucose-bound conformation. Our results support a model in which GCK generates its cooperative kinetic response at low glucose concentrations by using a millisecond disorder-order cycle of the small domain as a "time-delay loop," which is bypassed at high glucose concentrations, providing a unique mechanism to allosterically regulate the activity of human GCK under physiological conditions.

  9. Equilibrium and Kinetics Study of Adsorption of Crystal Violet onto the Peel of Cucumis sativa Fruit from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    T. Smitha

    2012-01-01

    Full Text Available The use of low-cost, locally available, high efficiency and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This study investigates the potential use of the peel of Cucumis sativa fruit for the removal of crystal violet (CV dye from simulated wastewater. The effects of different system variables, adsorbent dosage, initial dye concentration, pH and contact time were investigated and optimal experimental conditions were ascertained. The results showed that as the amount of the adsorbent increased, the percentage of dye removal increased accordingly. Optimum pH value for dye adsorption was determined as 7.0. The adsorption of crystal violet followed pseudo-second order rate equation and fit well Langmuir and Freundlich equations. The maximum removal of CV was obtained at pH 7 as 92.15% for adsorbent dose of 0.2 g/50 mL and 25 mg L-1 initial dye concentration at room temperature. The maximum adsorption capacity obtained from Langmuir equation was 34.24 mg g-1. Furthermore, adsorption kinetics of (CV was studied and the rate of adsorption was found to conform to pseudo-second order kinetics with a good correlation (R2 > 0.9739. The peel of Cucumis sativa fruit can be attractive options for dye removal from diluted industrial effluents since test reaction made on simulated dyeing wastewater show better removal percentage of (CV.

  10. Essaying a Pseudo-Panel Approach: Studies on Education, Women, and Income Inequality in Thailand

    Science.gov (United States)

    Warunsiri, Sasiwimon

    2010-01-01

    This dissertation is composed of three studies on Thai labor markets using a pseudo-panel data set: The first chapter estimates the rate of return to education in Thailand, while treating the endogeneity bias common to estimates from data on individuals. Pseudo-panel data are constructed from repeated cross sections of Labor Force Surveys…

  11. Fuzzy Reasoning Based on First-Order Modal Logic,

    NARCIS (Netherlands)

    Zhang, Xiaoru; Zhang, Z.; Sui, Y.; Huang, Z.

    2008-01-01

    As an extension of traditional modal logics, this paper proposes a fuzzy first-order modal logic based on believable degree, and gives out a description of the fuzzy first-order modal logic based on constant domain semantics. In order to make the reasoning procedure between the fuzzy assertions

  12. Interaction of 2-aminopyrimidine with dichloro-[1-alkyl-2-(naphthylazo imidazole]palladium(II complexes : Kinetic and mechanistic studies

    Directory of Open Access Journals (Sweden)

    Saha Sushanta

    2007-10-01

    rate constant, k2, at 298 K, was shown to increase thus: b a c as well as 1 2. Conclusion The kinetics of the reaction between Pd(II complexes (1 and 2 and 2-NH2-Pym were examined spectrophotometrically at 530 nm in MeCN under pseudo-first-order conditions. The reaction rate is largely influenced by the π-acidity of the chelating ligand, with substitution in the naphthyl azoimidazole backbone influencing the rate of the substitution process. The activation parameters, Δ‡H° and Δ‡S°, were determined and support the kinetic rate data.

  13. Biosorption of lead ions on biosorbent prepared from plumb shells (spondias mombin): kinetics and equilibrium studies

    International Nuclear Information System (INIS)

    Adeogen, A.I.; Bello, O.S.; Adeboye, M.D.

    2010-01-01

    Plumb shell was used to prepare an adsorbent for biosorption of lead ions in aqueous solution at 25 degree C. The adsorption capacity of the adsorbent at equilibrium was found to increase from 2.8 to 49.0 mg/g with an increase in the initial lead ion concentration from 50 to 200 mg/L. Using the equilibrium and kinetics studies, isotherm of the lead ions on the biosorbent was determined and correlated with common isotherm equations. The equilibrium data for lead ion adsorption fitted well into the Freundlich equation, with a value of 0.76 (R2 = 0.9), with distribution coefficient of 4.90. The biosorption of lead ions on the adsorbent from plumb shells could best be described by the pseudo-second-order equation. The kinetic parameters of this best-fit model were calculated and discussed. (author)

  14. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry.

    Science.gov (United States)

    Vilar, Vítor J P; Botelho, Cidália M S; Boaventura, Rui A R

    2007-05-08

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mgl(-1) and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D(h), are 3.6 x 10(-8); 6.1 x 10(-8) and 2.4 x 10(-8)cm(2)s(-1), respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

  15. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry

    International Nuclear Information System (INIS)

    Vilar, Vitor J.P.; Botelho, Cidalia M.S.; Boaventura, Rui A.R.

    2007-01-01

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mg l -1 and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D h , are 3.6 x 10 -8 ; 6.1 x 10 -8 and 2.4 x 10 -8 cm 2 s -1 , respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium

  16. Kinetics and equilibrium modelling of lead uptake by algae Gelidium and algal waste from agar extraction industry

    Energy Technology Data Exchange (ETDEWEB)

    Vilar, Vitor J.P. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Botelho, Cidalia M.S. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Boaventura, Rui A.R. [Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal)]. E-mail: bventura@fe.up.pt

    2007-05-08

    Pb(II) biosorption onto algae Gelidium, algal waste from agar extraction industry and a composite material was studied. Discrete and continuous site distribution models were used to describe the biosorption equilibrium at different pH (5.3, 4 and 3), considering competition among Pb(II) ions and protons. The affinity distribution function of Pb(II) on the active sites was calculated by the Sips distribution. The Langmuir equilibrium constant was compared with the apparent affinity calculated by the discrete model, showing higher affinity for lead ions at higher pH values. Kinetic experiments were conducted at initial Pb(II) concentrations of 29-104 mg l{sup -1} and data fitted to pseudo-first Lagergren and second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch mass transfer kinetic model, which successfully predicts Pb(II) concentration profiles at different initial lead concentration and pH, and provides significant insights on the biosorbents performance. Average values of homogeneous diffusivity, D {sub h}, are 3.6 x 10{sup -8}; 6.1 x 10{sup -8} and 2.4 x 10{sup -8} cm{sup 2} s{sup -1}, respectively, for Gelidium, algal waste and composite material. The concentration of lead inside biosorbent particles follows a parabolic profile that becomes linear near equilibrium.

  17. Adsorption kinetics, isotherm, and thermodynamics studies of acetyl-11-keto-β-boswellic acids (AKBA) from Boswellia serrata extract using macroporous resin.

    Science.gov (United States)

    Niphadkar, Sonali S; Rathod, Virendra K

    2017-09-14

    An acetyl-11-keto-β-boswellic acid (AKBA) is potent anti-inflammatory agent found in Boswellia serrata oleogum resin. Adsorption characteristics of AKBA from B. serrata were studied using macroporous adsorbent resin to understand separation and adsorption mechanism of targeted molecules. Different macroporous resins were screened for adsorption and desorption of AKBA and Indion 830 was screened as it showed higher adsorption capacity. The kinetic equations were studied and results showed that the adsorption of AKBA on Indion 830 was well fitted to the pseudo first-order kinetic model. The influence of two parameters such as temperature (298, 303, and 308 K) and pH (5-8) on the adsorption process was also studied. The experimental data was further investigated using Langmuir, Freundlich, and Temkin isotherm models. It was observed that Langmuir isotherm model was found to be the best fit for AKBA adsorption by Indion 830 and highest adsorption capacity (50.34 mg/g) was obtained at temperature of 303 K. The values of thermodynamic parameters such as the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), indicated that the process of adsorption was spontaneous, favourable, and exothermic.

  18. A natural sorbent, Luffa cylindrica for the removal of a model basic dye

    International Nuclear Information System (INIS)

    Altinisik, Aylin; Guer, Emel; Seki, Yoldas

    2010-01-01

    In this work, application of Luffa cylindrica in malachite green (MG) removal from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on removal of malachite green was also investigated. By the time pH was increased from 3 to 5, the amount of sorbed malachite green also increased. Beyond the pH value of 5, the amount of sorbed malachite green remains constant. The fits of equilibrium sorption data to Langmuir, Freundlich and Dubinin-Radushkevich equations were investigated. Langmuir isotherm exhibited best fit with the experimental data. Monolayer sorption capacity increased with the increasing of temperature. Sorption kinetic was evaluated by pseudo-first-order, pseudo-second-order, Elovich rate equations and intraparticle diffusion models. It was inferred that sorption follows pseudo-second-order kinetic model. Thermodynamic parameters for sorption process were also found out. Spontaneous and endothermic nature of sorption was obtained due to negative value of free energy (ΔG o ) and positive value of enthalpy (ΔH o ) changes. FTIR analyses were also conducted to confirm the sorption of malachite green onto L. cylindrica.

  19. Utilization of unconventional lignocellulosic waste biomass for the biosorption of toxic triphenylmethane dye malachite green from aqueous solution.

    Science.gov (United States)

    Selvasembian, Rangabhashiyam; P, Balasubramanian

    2018-05-12

    Biosorption potential of novel lignocellulosic biosorbents Musa sp. peel (MSP) and Aegle marmelos shell (AMS) was investigated for the removal of toxic triphenylmethane dye malachite green (MG), from aqueous solution. Batch experiments were performed to study the biosorption characteristics of malachite green onto lignocellulosic biosorbents as a function of initial solution pH, initial malachite green concentration, biosorbents dosage, and temperature. Biosorption equilibrium data were fitted to two and three parameters isotherm models. Three-parameter isotherm models better described the equilibrium data. The maximum monolayer biosorption capacities obtained using the Langmuir model for MG removal using MSP and AMS was 47.61 and 18.86 mg/g, respectively. The biosorption kinetic data were analyzed using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The pseudo-second-order kinetic model best fitted the experimental data, indicated the MG biosorption using MSP and AMS as chemisorption process. The removal of MG using AMS was found as highly dependent on the process temperature. The removal efficiency of MG showed declined effect at the higher concentrations of NaCl and CaCl 2 . The regeneration test of the biosorbents toward MG removal was successful up to three cycles.

  20. Bioadsorption of a reactive dye from aqueous solution by municipal solid waste

    Directory of Open Access Journals (Sweden)

    Abdelkader Berrazoum

    2015-09-01

    Full Text Available The biosorbent was obtained from municipal solid waste (MSW of the Mostaganem city. Before use the MSW was dried in air for three days and washed several times. The sorption of yellow procion reactive dye MX-3R onto biomass from aqueous solution was investigated as function of pH, contact time and temperature. The adsorption capacity of MX-3R was 45.84 mg/g at pH 2–3 and room temperature. MX-3R adsorption decreases with increasing temperature. The Langmuir, Freundlich and Langmuir–Freundlich adsorption models were applied to describe the related isotherms. Langmuir–Freundlich equation has shown the best fitting with the experimental data. The pseudo first-order, pseudo second-order and intra-particle diffusion kinetic models were used to describe the kinetic sorption. The results clearly showed that the adsorption of MX-3R onto biosorbent followed the pseudo second-order model. The enthalpy (ΔH°, entropy (ΔS° and Gibbs free energy (ΔG° changes of adsorption were calculated. The results indicated that the adsorption of MX-3R occurs spontaneously as an exothermic process.