Cs-137 sorption and desorption in relation to properties of 17 soils

International Nuclear Information System (INIS)

Kerpen, W.

1988-01-01

For Cs-137 sorption and desorption studies material of Ap and Ah horizons from 17 soils with wide varying soil properties was selected. The soils were: Podsol, Luvisol, Chernozem, Cambisol, Phaeozem, Arenosol, Gleysol and other soils. The Cs-137 sorption and desorption experiments were carried out in aqueous solution (20 g of soil) under standardized conditions for two reasons: (1) to determine the amounts of Cs-137 sorption, desorption and remains as a function of different soils and (2) to evaluate the soil parameters which govern the sorption, desorption processes. Concerning the second point the sorption values, the amount of 137 Cs desorbed within four desorption cycles and the 137 Cs remains after four desorption cycles were correlated with pH, grain size, sorption capacity (CEC), and other soil properties. It will be shown that generally Cs-137 sorption, desorption and remains depend primarily on the pH of the soil. The middle sand proved to be an indicator for the strenght of sorption, and desorption processes. Sorption and desorption studies lead to the same results as found in biotest experiments

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-07-01

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

Oxygen Sorption and Desorption Properties of Selected Lanthanum Manganites and Lanthanum Ferrite Manganites

DEFF Research Database (Denmark)

Nielsen, Jimmi; Skou, Eivind M.; Jacobsen, Torben

2015-01-01

Temperature‐programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid‐oxide fuel cell (SOFC) cathode materials (La0.85Sr0.15)0.95MnO3+δ (LSM) and La0.60Sr0.40Fe0.80Mn0.20O3‐δ (LSFM). The powders were characterized...... by X‐ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over...... time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second‐order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate‐determining step...

Sorption and desorption of glyphosate in Mollisols and Ultisols soils of Argentina.

Science.gov (United States)

Gómez Ortiz, Ana Maria; Okada, Elena; Bedmar, Francisco; Costa, José Luis

2017-10-01

In Argentina, glyphosate use has increased exponentially in recent years as a result of the widespread adoption of no-till management combined with genetically modified glyphosate-resistant crops. This massive use of glyphosate has created concern about its potential environmental impact. Sorption-desorption of glyphosate was studied in 3 Argentinean soils with contrasting characteristics. Glyphosate sorption isotherms were modeled using the Freundlich equation to estimate the sorption coefficient (K f ). Glyphosate sorption was high, and the K f varied from 115.6 to 1612 mg 1-1/n L 1/n /kg. Cerro Azul soil had the highest glyphosate sorption capacity as a result of a combination of factors such as higher clay content, cation exchange capacity, total iron, and aluminum oxides, and lower available phosphorus and pH. Desorption isotherms were also modeled using the Freundlich equation. In general, desorption was very low (glyphosate strongly sorbs to the soils and that it is almost an irreversible process. Anguil soil had a significantly higher desorption coefficient (K fd ) than the other soils, associated with its lower clay content and higher pH and phosphorus. Glyphosate high sorption and low desorption to the studied soils may prevent groundwater contamination. However, it may also affect its bioavailability, increasing its persistence and favoring its accumulation in the environment. The results of the present study contribute to the knowledge and characterization of glyphosate retention in different soils. Environ Toxicol Chem 2017;36:2587-2592. © 2017 SETAC. © 2017 SETAC.

Effect of Pinus radiata derived biochars on soil sorption and desorption of phenanthrene

International Nuclear Information System (INIS)

Zhang Honghua; Lin Kunde; Wang Hailong; Gan, Jay

2010-01-01

Biochars are anthropogenic carbonaceous sorbent and their influences on the sorption of environmental contaminants need to be characterized. Here we evaluated the effect of Pinus radiata derived biochars on soil sorption and desorption of phenanthrene. Two biochars separately produced at 350 o C and 700 o C and three soils were tested. Biochar amendment generally enhanced the soil sorption of phenanthrene. The biochar produced at 700 o C generally showed a greater ability at enhancing a soil's sorption ability than that prepared at 350 o C. The single-step desorption measurement showed an apparent hysteresis in biochar-amended soils. After 28 d equilibration, the sorptive capacity of biochar-amended soil (with an organic carbon content of 0.16%) significantly decreased. This study clearly suggested that biochar application enhanced soil sorption of hydrophobic organic compounds, but the magnitude of enhancement depended on the preparation of biochars, the indigenous soil organic carbon levels, and the contact time between soil and biochar. - Pinus radiata derived biochars influence soil sorption and desorption of phenanthrene.

Competitive metal sorption and desorption onto Kappaphycus alvarezii, seaweed waste biomass

International Nuclear Information System (INIS)

Lee, K.O.; Nazaruddin Ramli; Mamot Said; Musa Ahmad; Suhaimi Mohd Yasir; Arbakariya Ariff

2011-01-01

Competitive metal sorption and desorption onto Kappaphycus alvarezii waste biomass were investigated. Metal sorption capacities were 0.82 mg Cr (III)/ g, 0.73 mg Ni (II)/ g, 0.67 mg Cd (II)/ g, 0.65 mg Cu( II)/ g and 0.64 mg Zn (II)/ g in multi metal system. Whereas, desorption efficiencies were 66.08 %, 71.50 % and 80.44 % using 0.1 M HNO 3 , 0.1 M HCl and 0.1 M H 2 SO 4 , respectively. The metal sorption sequence were Cr(III) > Ni(II) > Cd(II) > Cu(II) > Zn(II), while metal desorption sequence were Cd(II) > Zn(II) > Cu(II) > Ni(II) > Cr(III). Fourier transformed infrared spectroscopy (FTIR) technique was used to characterize the seaweed waste biomass. FTIR analysis shown that carbonyl (-C-O) and nitrile (-C≡N) groups interact with the metal ions. The experiments result revealed that Kappaphycus alvarezii waste biomass represent an attractive candidate to remove multi metal ions. (author)

Competitive metal sorption and desorption onto Kappaphycus alvarezii, seaweed waste biomass

Energy Technology Data Exchange (ETDEWEB)

Lee, K O; Ramli, Nazaruddin; Said, Mamot; Ahmad, Musa [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia (UKM), Bangi, selangor (Malaysia); Yasir, Suhaimi Mohd [School of Sciences and Technology, Universiti Malaysia Sabah (UMS), Sabah (Malaysia); Arbakariya Ariff, E-mail: naza@ukm.my [Faculty of Biotechnology and Biomolecular science, Universiti Putra Malaysia (UPM), Serdang, Selangor (Malaysia)

2011-07-15

Competitive metal sorption and desorption onto Kappaphycus alvarezii waste biomass were investigated. Metal sorption capacities were 0.82 mg Cr (III)/ g, 0.73 mg Ni (II)/ g, 0.67 mg Cd (II)/ g, 0.65 mg Cu( II)/ g and 0.64 mg Zn (II)/ g in multi metal system. Whereas, desorption efficiencies were 66.08 %, 71.50 % and 80.44 % using 0.1 M HNO{sub 3}, 0.1 M HCl and 0.1 M H{sub 2}SO{sub 4}, respectively. The metal sorption sequence were Cr(III) > Ni(II) > Cd(II) > Cu(II) > Zn(II), while metal desorption sequence were Cd(II) > Zn(II) > Cu(II) > Ni(II) > Cr(III). Fourier transformed infrared spectroscopy (FTIR) technique was used to characterize the seaweed waste biomass. FTIR analysis shown that carbonyl (-C-O) and nitrile (-C{identical_to}N) groups interact with the metal ions. The experiments result revealed that Kappaphycus alvarezii waste biomass represent an attractive candidate to remove multi metal ions. (author)

Sorption-desorption behavior of polybrominated diphenyl ethers in soils

International Nuclear Information System (INIS)

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

2011-01-01

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

Sorption/desorption reversibility of polycyclic aromatic hydrocarbons (PAHs) in soils and carbonaceous materials

Energy Technology Data Exchange (ETDEWEB)

Wang, Guohui

2008-07-01

Understanding sorption/desorption is an important prerequisite for the prediction of fate and transport of pollutants in the environment. During the last two decades, numerous studies have reported hysteresis phenomenon for the interaction of hydrophobic organic contaminants (HOCs) with natural organic matter (NOM). It manifests as nonsingular sorption/desorption isotherms or different rates for sorption and desorption, where during desorption a higher affinity of a compound on a given sorbent and a longer time scale for release than for sorption is observed. Other studies showed that some of the reported sorption/desorption hysteresis phenomena are due to experimental artifacts, mainly resulting from non-attainment of sorption equilibrium before desorption experiments, which result in 'pseudo-hysteresis'. Except for the hypothesis of sorbent reconfiguration, clear experimental evidence for the physical or chemical mechanisms proposed to lead to hysteresis is still lacking. In this study, sorption/desorption equilibrium and kinetics of phenanthrene sorption/desorption from two soils and three carbonaceous samples were investigated using both batch and column techniques. The main objective of this work was to monitor hysteresis phenomenon by carefully recovering the solute mass in the system and to compare sorption/desorption equilibria and kinetics thermodynamically. Nonsingular isotherms and higher desorption enthalpies as well as increased activation energies with proceeding desorption are expected if significant hysteresis exists. Sorption-desorption cycles were carried out to compare equilibrium isotherms and associated sorption/desorption enthalpies (AeH, isosteric heats). Instead of the traditional decant-and-refill batch method, the experiments were conducted using a newly designed batch protocol, which enables the determination of sorption/desorption isotherms at different temperatures using a closed batch system. This method additionally allows

Sorption/desorption reversibility of polycyclic aromatic hydrocarbons (PAHs) in soils and carbonaceous materials

Energy Technology Data Exchange (ETDEWEB)

Wang, Guohui

2008-07-01

Understanding sorption/desorption is an important prerequisite for the prediction of fate and transport of pollutants in the environment. During the last two decades, numerous studies have reported hysteresis phenomenon for the interaction of hydrophobic organic contaminants (HOCs) with natural organic matter (NOM). It manifests as nonsingular sorption/desorption isotherms or different rates for sorption and desorption, where during desorption a higher affinity of a compound on a given sorbent and a longer time scale for release than for sorption is observed. Other studies showed that some of the reported sorption/desorption hysteresis phenomena are due to experimental artifacts, mainly resulting from non-attainment of sorption equilibrium before desorption experiments, which result in 'pseudo-hysteresis'. Except for the hypothesis of sorbent reconfiguration, clear experimental evidence for the physical or chemical mechanisms proposed to lead to hysteresis is still lacking. In this study, sorption/desorption equilibrium and kinetics of phenanthrene sorption/desorption from two soils and three carbonaceous samples were investigated using both batch and column techniques. The main objective of this work was to monitor hysteresis phenomenon by carefully recovering the solute mass in the system and to compare sorption/desorption equilibria and kinetics thermodynamically. Nonsingular isotherms and higher desorption enthalpies as well as increased activation energies with proceeding desorption are expected if significant hysteresis exists. Sorption-desorption cycles were carried out to compare equilibrium isotherms and associated sorption/desorption enthalpies (AeH, isosteric heats). Instead of the traditional decant-and-refill batch method, the experiments were conducted using a newly designed batch protocol, which enables the determination of sorption/desorption isotherms at different temperatures using a closed batch system. This method additionally allows the

Kinetics and reversibility of radionuclide sorption reactions with rocks. Progress report for fiscal year 1979

International Nuclear Information System (INIS)

Barney, G.S.; Brown, G.E.

1979-01-01

Sorption-desorption reactions of cesium, strontium, neptunium, americium, and plutonium on basalt, granite, and argillite were observed for 218 days. Equilibrium in batch experiments was not reached for most radionuclides even after this long time. Reactions of the crushed rock with ground waters (dissolution, hydrolysis, precipitation, etc.) also did not reach equilibrium after 150 days. The dissolution of basalt is accompanied by the formation of colloidal particles which contain Si, Fe, Ca, and Al. These colloids sorb Cs, Sr, Am, and Pu during equilibration. Some of the colloids pass through 0.3-μm flters, are not retained even on 0.01-μm filters and, therefore, cause calculated K/sub d/ values to be too low. Samples of crushed basalt, granite, and argillite were artificially weathered by continuous leaching with distilled water for 6 months both in air and in an oxygen-free stream of nitrogen gas. The weathered rock was then characterized for surface area, surface structure, cation exchange capacity, and composition of weathered surface on the rock. Comparisons were made of radionuclide sorption (after 14 days) on fresh rock, rock weathered in air, and rock weathered in N 2 . Sorption on rocks weathered in N 2 generally is less than on rock weathered in air. This is possibly due to the lack of an Fe(OH) 3 coating on the rock weathered in N 2 . The Fe(OH) 3 is known to scavenge cations and silica from solution. Sorption of Cs, Si, Am, and Pu is strongly affected by weathering basalt and argillite. However, the cation exchange capacity is changed very little, suggesting that ion exchange plays a minor role in sorption of these radionuclides

Sorption and desorption of diuron in Oxisol under biochar application

Directory of Open Access Journals (Sweden)

Fabiano André Petter

Full Text Available ABSTRACT The objective of this study was to verify the kinetics of sorption and desorption of diuron in an Oxisol under application of biochar. The samples were collected in a field experiment conducted in randomized design blocks consisted of 2 base fertilization levels (0 and 400 kg∙ha−1 NPK 00-20-20 fertilizer formula and 3 doses of biochar (0, 8 and 16 Mg∙ha−1. In the evaluation of sorption and desorption, Batch Equilibrium method was used. The kinetics of sorption and desorption of diuron, total organic carbon, fulvic acid, humic acid and humin, pH and partition coefficient to organic carbon were evaluated. The Freundlich isotherm was adjusted appropriately to describe diuron sorption kinetics in all the studied treatments. The application of biochar provided increment in the sorption (Kf and reduction in the desorption of diuron in 64 and 44%, respectively. This effect is attributed to the biochar contribution to the total organic carbon and C-humin and of these to diuron through hydrophobic interactions and hydrogen bonds. The positive correlation between the partition coefficient to organic carbon and Kf confirms the importance of soil organic compartment in the sorption of diuron. There was no competition of NPK fertilizer for the same sorption site of diuron. The increase and reduction in sorption and desorption, respectively, show that the application of biochar is an important alternative for the remediation of soil leaching of diuron, especially in sandy soils.

Sorption and desorption of indaziflam degradates in several agricultural soils

Directory of Open Access Journals (Sweden)

Diego Gonçalves Alonso

2016-04-01

Full Text Available ABSTRACT Processes regulating pesticide fate in the environment are influenced by the physicochemical properties of pesticides and soils. Sorption and desorption are important processes as they regulate the movement of pesticides in soil. Although sorption-desorption is widely studied for herbicides, studies involving their metabolites in soil are scarce. Sorption and desorption of indaziflam metabolites (indaziflam-triazinediamine (FDAT, indaziflam-triazine-indanone (ITI and indaziflam-carboxilic acid (ICA were investigated in six Brazilian (BRA soils and three United States (USA soils with different physicochemical properties. The Freundlich equation described sorption of the metabolites for all soils (R2 > 0.98; 1/n ~ 1. Sorption order (Kf was ITI > ICA > FDAT. Mean values of Kf,oc were 453, 289, and 81 (BRA and 444, 48, and 48 (USA for metabolites ITI, ICA, and FDAT respectively. Desorption was hysteretic for all metabolites in all soils. These results suggest that these metabolites fall in the classification range of mobile to moderately mobile in soils.

Lead sorption-desorption from organic residues.

Science.gov (United States)

Duarte Zaragoza, Victor M; Carrillo, Rogelio; Gutierrez Castorena, Carmen M

2011-01-01

Sorption and desorption are mechanisms involved in the reduction of metal mobility and bioavailability in organic materials. Metal release from substrates is controlled by desorption. The capacity of coffee husk and pulp residues, vermicompost and cow manure to adsorb Pb2+ was evaluated. The mechanisms involved in the sorption process were also studied. Organic materials retained high concentrations of lead (up to 36,000 mg L(-1)); however, the mechanisms of sorption varied according to the characteristics of each material: degree of decomposition, pH, cation exchange capacity and percentage of organic matter. Vermicompost and manure removed 98% of the Pb from solution. Lead precipitated in manure and vermicompost, forming lead oxide (PbO) and lead ferrite (PbFe4O7). Adsorption isotherms did not fit to the typical Freundlich and Langmuir equations. Not only specific and non-specific adsorption was observed, but also precipitation and coprecipitation. Lead desorption from vermicompost and cow manure was less than 2%. For remediation of Pb-polluted sites, the application of vermicompost and manure is recommended in places with alkaline soils because Pb precipitation can be induced, whereas coffee pulp residue is recommended for acidic soils where Pb is adsorbed.

Sorption and desorption of diuron in Oxisol under biochar application

OpenAIRE

Petter, Fabiano André; Ferreira, Tamara Santos; Sinhorin, Adilson Paulo; Lima, Larissa Borges de; Morais, Leidimar Alves de; Pacheco, Leandro Pereira

2016-01-01

ABSTRACT The objective of this study was to verify the kinetics of sorption and desorption of diuron in an Oxisol under application of biochar. The samples were collected in a field experiment conducted in randomized design blocks consisted of 2 base fertilization levels (0 and 400 kg∙ha−1 NPK 00-20-20 fertilizer formula) and 3 doses of biochar (0, 8 and 16 Mg∙ha−1). In the evaluation of sorption and desorption, Batch Equilibrium method was used. The kinetics of sorption and desorption of diu...

Sorption-desorption of samarium in Febex bentonite

International Nuclear Information System (INIS)

Ramirez-Guinart, O.; Rigol, A.; Vidal, M.; Fernandez-Poyatos, P.; Alba, M. D.

2012-01-01

Document available in extended abstract form only. The chemical and physical nature of the clay is a key issue in the design of engineered barriers. The FEBEX bentonite is one of the clays candidates to be used in engineered barriers in deep geology repositories (DGR). Here, its performance was tested with respect to the sorption-desorption of samarium, which is a lanthanide that, besides being considered as a natural analogue of actinides, may also be present in high level radioactive waste in the form of the radioactive isotope 151 Sm. FEBEX bentonite was used in this study. This is a di-octahedral smectite, with isomorphic substitutions in tetrahedral and octahedral sheets. Its theoretical cation exchange capacity value is 1500 meq kg -1 . Sorption isotherms were obtained for Sm in the range of initial concentrations of 0.01 and 9 meq l -1 . Tests were carried out in deionized water and in a medium simulating the composition of interstitial water. Sorption tests were performed equilibrating 30 ml of the Sm solution with 0.2 g of clay. After a contact time of 24 hours, supernatants were decanted off after centrifugation. The quantification of the concentration of Sm in the initial and final solutions allowed us to quantify the Sm equilibrium concentration (C eq ), the fraction sorbed in the FEBEX bentonite (C sorb ) and to derive the sorption K d data. Desorption tests were applied to determine the desorption K d and the percentage of Sm reversibly sorbed. Desorption tests were performed with the bentonite residue from the sorption step, under the same experimental conditions, but without Sm. Powder X-ray diffractograms were obtained from 3 to 70 deg. 2θ with a step of 0.05 deg. and a counting time of 3 s. The crystalline phases were identified using the computer program X'Pert HighScore. The morphology of the samples was analyzed by SEM at 20 kV. An EDX system was fitted to the SEM equipment to perform chemical analyses of the samples using a Si/Li detector

Sorption of nitrate onto amine-crosslinked wheat straw: characteristics, column sorption and desorption properties.

Science.gov (United States)

Xing, Xu; Gao, Bao-Yu; Zhong, Qian-Qian; Yue, Qin-Yan; Li, Qian

2011-02-15

The nitrate removal process was evaluated using a fixed-bed column packed with amine-crosslinked wheat straw (AC-WS). Column sorption and desorption characteristics of nitrate were studied extensively. Solid-state (13)C NMR and zeta potential analysis validated the existence of crosslinked amine groups in AC-WS. Raman shift of the nitrate peaks suggested the electrostatic attraction between the adsorbed ions and positively charged amine sites. The column sorption capacity (q(ed)) of the AC-WS for nitrate was 87.27 mg g(-1) in comparison with the raw WS of 0.57 mg g(-1). Nitrate sorption in column was affected by bed height, influent nitrate concentration, flow rate and pH, and of all these, influent pH demonstrated an essential effect on the performance of the column. In addition, desorption and dynamic elution tests were repeated for several cycles, with high desorption rate and slight losses in its initial column sorption capacity. Copyright © 2010 Elsevier B.V. All rights reserved.

Fate and transport with material response characterization of green sorption media for copper removal via desorption process.

Science.gov (United States)

Chang, Ni-Bin; Houmann, Cameron; Lin, Kuen-Song; Wanielista, Martin

2016-07-01

Multiple adsorption and desorption cycles are required to achieve the reliable operation of copper removal and recovery. A green sorption media mixture composed of recycled tire chunk, expanded clay aggregate, and coconut coir was evaluated in this study for its desorptive characteristics as a companion study of the corresponding adsorption process in an earlier publication. We conducted a screening of potential desorbing agents, batch desorption equilibrium and kinetic studies, and batch tests through 3 adsorption/desorption cycles. The desorbing agent screening revealed that hydrochloric acid has good potential for copper desorption. Equilibrium data fit the Freundlich isotherm, whereas kinetic data had high correlation with the Lagergren pseudo second-order model and revealed a rapid desorption reaction. Batch equilibrium data over 3 adsorption/desorption cycles showed that the coconut coir and media mixture were the most resilient, demonstrating they could be used through 3 or more adsorption/desorption cycles. FE-SEM imaging, XRD, and EDS analyses supported the batch adsorption and desorption results showing significant surface sorption of CuO species in the media mixture and coconut coir, followed by partial desorption using 0.1 M HCl as a desorbing agent. Copyright © 2016 Elsevier Ltd. All rights reserved.

Waste/Rock Interactions Technology Program: the status of radionuclide sorption-desorption studies performed by the WRIT program

International Nuclear Information System (INIS)

Serne, R.J.; Relyea, J.F.

1982-04-01

The most credible means for radionuclides disposed as solid wastes in deep-geologic repositories to reach the biosphere is through dissolution of the solid waste and subsequent radionuclide transport by circulating ground water. Thus safety assessment activities must consider the physicochemical interactions between radionculides present in ground water with package components, rocks and sediments since these processes can significantly delay or constrain the mass transport of radionuclides in comparison to ground-water movement. This paper focuses on interactions between dissolved radiouclides in ground water and rocks and sediments away from the near-field repository. The primary mechanism discussed is adsorption-desorption, which has been studied using two approaches. Empirical studies of adsorption-desorption rely on distribution coefficient measurements while mechanism studies strive to identify, differentiate and quantify the processes that control nuclide retardation

Experiences of fitting isotherms to data from batch sorption experiments for radionuclides on tuffs

International Nuclear Information System (INIS)

Polzer, W.L.; Fuentes, H.R.

1989-11-01

Laboratory experiments have been performed on the sorption of radionuclides on tuff as site characterization information for the Yucca Mountain Project. This paper presents general observations on the results of curve-fitting of sorption data by isotherm equations and the effects of experimental variables on their regressional analysis. Observations are specific to the effectiveness and problems associated with fitting isotherms, the calculation and value of isotherm parameters, and the significance of experimental variables such as replication, particle size, mode of sorption, and mineralogy. These observations are important in the design of laboratory experiments to ensure that collected data are adequate for effectively characterizing sorption of radionuclides on tuffs or other materials. 13 refs., 2 figs., 4 tabs

Sorption and desorption of carbamazepine from water by smectite clays.

Science.gov (United States)

Zhang, Weihao; Ding, Yunjie; Boyd, Stephen A; Teppen, Brian J; Li, Hui

2010-11-01

Carbamazepine is a prescription anticonvulsant and mood stabilizing pharmaceutical administered to humans. Carbamazepine is persistent in the environment and frequently detected in water systems. In this study, sorption and desorption of carbamazepine from water was measured for smectite clays with the surface negative charges compensated with K+, Ca2+, NH4+, tetramethylammonium (TMA), trimethylphenylammonium (TMPA) and hexadecyltrimethylammonium (HDTMA) cations. The magnitude of sorption followed the order: TMPA-smectite≥HDTMA-smectite>NH4-smectite>K-smectite>Ca-smectite⩾TMA-smectite. The greatest sorption of carbamazepine by TMPA-smectite is attributed to the interaction of conjugate aromatic moiety in carbamazepine with the phenyl ring in TMPA through π-π interaction. Partitioning process is the primary mechanism for carbamazepine uptake by HDTMA-smectite. For NH4-smectite the urea moiety in carbamazepine interacts with exchanged cation NH4+ by H-bonding hence demonstrating relatively higher adsorption. Sorption by K-, Ca- and TMA-smectites from water occurs on aluminosilicate mineral surfaces. These results implicate that carbamazepine sorption by soils occurs primarily in soil organic matter, and soil mineral fractions play a secondary role. Desorption of carbamazepine from the sorbents manifested an apparent hysteresis. Increasing irreversibility of desorption vs. sorption was observed for K-, Ca-, TMA-, TMPA- and HDTMA-clays as aqueous carbamazepine concentrations increased. Desorption hysteresis of carbamazepine from K-, Ca-, NH4-smectites was greater than that from TMPA- and HDTMA-clays, suggesting that the sequestrated carbamazepine molecules in smectite interlayers are more resistant to desorption compared to those sorbed by organic phases in smectite clays. Copyright © 2010 Elsevier Ltd. All rights reserved.

Sorption, desorption and leaching potential of sulfonylurea herbicides in Argentinean soils.

Science.gov (United States)

Azcarate, Mariela P; Montoya, Jorgelina C; Koskinen, William C

2015-01-01

The sulfonylurea (SUs) herbicides are used to control broadleaf weeds and some grasses in a variety of crops. They have become popular because of their low application rates, low mammalian toxicity and an outstanding herbicidal activity. Sorption is a major process influencing the fate of pesticides in soil. The objective of this study was to characterize sorption-desorption of four sulfonylurea herbicides: metsulfuron-methyl (methyl 2-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)carbamoylsulfamoyl)]benzoate), sulfometuron-methyl (methyl 2-[(4,6-dimethylpyrimidin-2-yl)carbamoylsulfamoyl]benzoate), rimsulfuron (1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-pyridylsulfonyl)urea) and nicosulfuron (2-[(4,6-dimethoxypyrimidin-2-yl)carbamoylsulfamoyl]-N,N-dimethylnicotinamide) from different soil horizons of different landscape positions. Sorption was studied in the laboratory by batch equilibration method. Sorption coefficients (K(d-SE)) showed that rimsulfuron (K(d-SE) = 1.18 to 2.08 L kg(-1)) and nicosulfuron (K(d-SE) = 0.02 to 0.47 L kg(-1)) were more highly sorbed than metsulfuron-methyl (K(d-SE) = 0.00 to 0.05 L kg(-1)) and sulfometuron-methyl (K(d-SE) = 0.00 to 0.05 L kg(-1)). Sorption coefficients (K(d-SE)) were correlated with pH and organic carbon content. All four herbicides exhibited desorption hysteresis where the desorption coefficients (K(d-D)) > K(d-SE). To estimate the leaching potential, K(oc) and ground-water ubiquity score (GUS) were used to calculate the half-life (t1/2) required to be classified as "leacher" or "nonleacher". According to the results, rimsulfuron and nicosulfuron herbicides would be classified as leachers, but factors such as landscape position, soil depth and the rate of decomposition in surface and subsurface soils could change the classification. In contrast, these factors do not affect classification of sulfometuron-methyl and metsulfuron-methyl; they would rank as leachers.

Sorption-desorption dynamics of radiocaesium in organic matter soils

International Nuclear Information System (INIS)

Valcke, E.; Cremers, A.

1994-01-01

A systematic study has been carried out on the radiocaesium sorption properties of 25 soils (forest, peat) covering organic matter (OM) contents in the range of 10-97%. Predictions are made for radiocaesium partitioning between micaceous Frayed Edge Sites (FES) and regular exchange sites (RES) on the basis of specific radiocaesium interception potentials of the soil and overall exchange capacity. It is shown that for soils with a very high OM content (>80%), significant fractions are present in a readily reversible form in the OM phase. In soils of low-medium OM content (<40%), only a very minor fraction is present in the OM exchange complex. Experimental findings, based on a desorption screening with a variety of desorption agents are in agreement with these predictions. On the basis of a study of sorption kinetics, some additional tools are available for identifying problem soils. In cases of very high OM content, radiocaesium adsorption is completed within hours demonstrating the involvement of the OM sites. In soils for which interception occurs in the FES, sorption continues to proceed for periods of 2-3 weeks. In conclusion, some examples are presented on radiocaesium desorption using ion exchangers as radiocaesium sinks in promoting desorption. For a peaty soil, near quantitative desorption is accomplished. For forest soils with OM contents in a range of 10-40%, fixation levels of 30-50% are demonstrated

CHARACTERIZING SOIL/WATER SORPTION AND DESORPTION BEHAVIOR OF BTEX AND PAHS USING SELECTIVE SUPERCRITICAL FLUID EXTRACTION (SFE); TOPICAL

International Nuclear Information System (INIS)

Steve Hawthorne

1998-01-01

The first goal of the proposed study was to generate initial data to determine the ability of selective SFE behavior to mimic the soil/water sorption and desorption behavior of BTEX (benzene, toluene, and xylenes) and PAHs (polycyclic aromatic hydrocarbons).Samples generated by Professor Bill Rixey's column sorption studies (aged for 2 weeks to 8 months) and desorption studies (six weeks desorption of the aged soil columns with pure water) were extracted using sequentially-stronger SFE conditions to selectively remove different fractions of each BTEX and PAH component which range from loosely to tightly bound in the soil matrices. The selective SFE results parallel the sorption/desorption leaching behavior and mechanisms determined by Professor Rixey's investigations (under separate funding) using water desorption of soil columns previously aged with BTEX and PAHs. These results justify more intensive investigations of the use of selective SFE to mimic soil/water sorption and desorption of organic pollutants related to fossil fuels which will be performed under separate funding. The second goal of the study was to determine if selective SFE extraction behavior parallels the remediation behavior displayed by PAHs currently undergoing in-situ bioremediation at a manufactured gas plant (MGP) site. Based on soil analyses of several individual PAHs (as well as total PAHs) before remediation began, and after 147 days of remediation, selective SFE successfully mimicked remediation behavior. These results strongly support the use of selective SFE to predict remediation behavior of soils contaminated with PAHs, and are expected to provide a powerful and rapid analytical tool which will be useful for determining the remediation endpoints which are necessary for environmental protection. Based on the initial success found in the present study, additional investigations into the use of SFE for predicting and monitoring the remediation behavior of PAH-contaminated soils will be

Sorption and desorption kinetics of diuron, fluometuron, prometryn and pyrithiobac sodium in soils.

Science.gov (United States)

Baskaran, S; Kennedy, I R

1999-11-01

The sorption and desorption characteristics of four herbicides (diuron, fluometuron, prometryn and pyrithiobac-sodium) in three different cotton growing soils of Australia was investigated. Kinetics and equilibrium sorption and desorption isotherms were determined using the batch equilibrium technique. Sorption was rapid (> 80% in 2 h) and sorption equilibrium was achieved within a short period of time (ca 4 h) for all herbicides. Sorption isotherms of the four herbicides were described by Freundlich equation with an r2 value > 0.98. The herbicide sorption as measured by the distribution coefficient (Kd) values ranged from 3.24 to 5.71 L/kg for diuron, 0.44 to 1.13 L/kg for fluometuron, 1.78 to 6.04 L/kg for prometryn and 0.22 to 0.59 L/kg for pyrithiobac-sodium. Sorption of herbicides was higher in the Moree soil than in Narrabri and Wee Waa soils. When the Kd values were normalised to organic carbon content of the soils (Koc), it suggested that the affinity of the herbicides to the organic carbon increased in the order: pyrithiobac-sodium diuron. The desorption isotherms were also adequately described by the Freundlich equation. For desorption, all herbicides exhibited hysteresis and the hysteresis was stronger for highly sorbed herbicides (diuron and prometryn) than the weakly sorbed herbicides (fluometuron and pyrithiobac-sodium). Hysteresis was also quantified as the percentage of sorbed herbicides which is not released during the desorption step (omega = [nad/nde - 1] x 100). Soil type and initial concentration had significant effect on omega. The effect of sorption and desorption properties of these four herbicides on the off-site transport to contaminate surface and groundwater are also discussed in this paper.

Radionuclides sorption in clay soils

International Nuclear Information System (INIS)

Siraky, G.; Lewis, C.; Hamlat, S.; Nollmann, C.E.

1987-01-01

The sorption behaviour of clay soils is examined through a parametric study of the distribution coefficient (Kd) for the radionuclides of interest, Cs and Sr. This work is a preliminary stage of the migration studies of these nuclides in a porous medium (ground of Ezeiza, Argentina) and the evaluation of radiologic impact of the removal of low and intermediate activity wastes in shallow trenches. The determination of Kd is performed by a static technique or batch. The phases are separated by centrifugation at 20000 g during 1 hour. The activity of supernatant solution of Cs-137 and Sr-85 is measured in a detecting system of I Na(Tl) well-type. Two types of parameters were changed: a) those related to the determination method: phase separation (centrifugation vs. centrifugation plus filtration); equilibrium period, ratio solid/liquid; b) those related to the geochemical system: pH of contact solution, carrier concentration, competitive ions, ionic strength, desorption. It was observed that the modification of parameters in the Kd-measurement does not change the order of magnitude of results. (Author)

Glyphosate sorption/desorption on biochars - interactions of physical and chemical processes.

Science.gov (United States)

Hall, Kathleen E; Spokas, Kurt A; Gamiz, Beatriz; Cox, Lucia; Papiernik, Sharon K; Koskinen, William C

2018-05-01

Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350 to 900 °C to elucidate fundamental mechanisms. Glyphosate (1 mg L -1 ) sorption on biochars increased with pyrolysis temperature and was highest on 900 °C biochars; however, total sorption was low on a mass basis (glyphosate in soils, did not alter biochar sorption capacities. Glyphosate did not desorb from biochar with CaCl 2 solution; however, up to 86% of the bound glyphosate was released with a K 2 HPO 4 solution. Results from this study suggest a combined impact of surface chemistry and physical constraints on glyphosate sorption/desorption on biochar. Based on the observed phosphate-induced desorption of glyphosate, the addition of P-fertilizer to biochar-amended soils can remobilize the herbicide and damage non-target plants; therefore, improved understanding of this risk is necessary. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Sorption of prioritized elements on montmorillonite colloids and their potential to transport radionuclides

International Nuclear Information System (INIS)

Wold, Susanna

2010-04-01

, Pd, Se, Sn, Zr and U. K d -values for colloids and radionuclides are scarce as well as sorption kinetics. Sorption values were not found for the elements Ra, Nb and Pd, yet sorption of the analogues Sr, Pu and Ni are instead representing these elements. Since sorption and desorption kinetic studies are scarce, recommendations on the reversibility have been based on the elements sorption mechanisms and from their K d -values

Sorption of prioritized elements on montmorillonite colloids and their potential to transport radionuclides

Energy Technology Data Exchange (ETDEWEB)

Wold, Susanna (Royal Inst. of Technology, Stockholm (Sweden). School of Chemical Science and Engineering, Nuclear Chemistry)

2010-04-15

, Ni, Pd, Se, Sn, Zr and U. K{sub d}-values for colloids and radionuclides are scarce as well as sorption kinetics. Sorption values were not found for the elements Ra, Nb and Pd, yet sorption of the analogues Sr, Pu and Ni are instead representing these elements. Since sorption and desorption kinetic studies are scarce, recommendations on the reversibility have been based on the elements sorption mechanisms and from their K{sub d}-values

Sorption and desorption of diuron in Oxisol under biochar application

OpenAIRE

Petter,Fabiano André; Ferreira,Tamara Santos; Sinhorin,Adilson Paulo; Lima,Larissa Borges de; Morais,Leidimar Alves de; Pacheco,Leandro Pereira

2016-01-01

ABSTRACT The objective of this study was to verify the kinetics of sorption and desorption of diuron in an Oxisol under application of biochar. The samples were collected in a field experiment conducted in randomized design blocks consisted of 2 base fertilization levels (0 and 400 kg∙ha−1 NPK 00-20-20 fertilizer formula) and 3 doses of biochar (0, 8 and 16 Mg∙ha−1). In the evaluation of sorption and desorption, Batch Equilibrium method was used. The kinetics of sorpti...

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

Science.gov (United States)

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

2018-02-15

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

Sorption and desorption of tritiated water vapor on piping materials of nuclear fusion reactor

Energy Technology Data Exchange (ETDEWEB)

Tanaka, Satoru; Ohmori, Rumi [Tokyo Univ. (Japan). Faculty of Engineering

1996-10-01

Sorption and desorption of D{sub 2}O on Cr{sub 2}O{sub 3}, NiO, SS316 powders were studied at ambient temperature. When D{sub 2}O were contacted with samples after drying at 303K, broad peak was observed at 2100-2700cm{sup -1} on Cr{sub 2}O{sub 3} and NiO. Sorption and desorption rate depended on wave numbers. Isotope exchange rate with H{sub 2}O vapor was faster than dry desorption rate. By heating pretreatment, sorption amount and desorption rate for Cr{sub 2}O{sub 3} and NiO decreased. For SS316, broad peak was observed only after heating pretreatment at 673K. (author)

Sorption of radionuclides by tertiary clays

International Nuclear Information System (INIS)

Wagner, J.F.; Czurda, K.A.

1990-01-01

The sorption capacity of different clay types for some metals (Co, Cs, Sr and Zn), occurring as common radionuclides in radioactive waste deposits, had been analysed by a static (batch technique) and a dynamic method (percolation tests, in which the driving force is a hydraulic gradient). Sorption capacity generally increased with an increasing pH of solution. A decrease of sorption capacity had been observed in the order Zn > Cs ≥ Co > Sr for the batch and Cs > Zn > Sr > Co for the percolation tests. Clay marls showed a distinctly higher sorption respectively retention capacity as pure clays. Sorption capacity depends on solution parameters like type and concentration of radionuclide, pH, salt concentration, etc., and on rock parameters like mineral content (e.g. swelling clay minerals and carbonates), organic material, rock pH, micro fabric, etc. A third parameter of great influence is the contact time between clay and solution. The adsorption isotherms reflect two different adsorption mechanisms: a very rapid adsorption (a few minutes) on the external surfaces of clay minerals and a slow adsorption process (weeks and longer), due to the diffusion of metal ions into the interlayer space of clay minerals. 12 refs., 9 figs., 1 tab

Competitive sorption and desorption of heavy metals by individual soil components

International Nuclear Information System (INIS)

Covelo, E.F.; Vega, F.A.; Andrade, M.L.

2007-01-01

Knowledge of sorption and desorption of heavy metals by individual soil components should be useful for modelling the behaviour of soils of arbitrary composition when contaminated by heavy metals, and for designing amendments increasing the fixation of heavy metals by soils polluted by these species. In this study the competitive sorption and desorption of Cd, Cr, Cu, Ni, Pb and Zn by humified organic matter, Fe and Mn oxides, kaolinite, vermiculite and mica were investigated. Due to the homogeneity of the sorbents, between-metal competition for binding sites led to their preferences for one or another metal being much more manifest than in the case of whole soils. On the basis of k d100 values (distribution coefficients calculated in sorption-desorption experiments in which the initial sorption solution contained 100 mg L -1 of each metal), kaolinite and mica preferentially sorbed and retained chromium; vermiculite, copper and zinc; HOM, Fe oxide and Mn oxide, lead (HOM and Mn oxide also sorbed and retained considerable amounts of copper). Mica only retained sorbed chromium, Fe oxide sorbed cadmium and lead, and kaolinite did not retain sorbed copper. The sorbents retaining the greatest proportions of sorbed metals were vermiculite and Mn oxide, but the ratios of k d100 values for retention and sorption suggest that cations were least reversibly bound by Mn oxide, and most reversibly by vermiculite

Sorption, desorption and extraction of uranium from some sands under dynamic conditions

International Nuclear Information System (INIS)

Palagyi, S.; Laciok, A.

2006-01-01

Sorption, desorption and extraction behavior of uranium in various fluvial sands of domestic origin were investigated in continuous dynamic column experiments. For the sorption of U(VI) an aqueous 10 -4 M UO 2 (NO 3 ) 2 solution was used at a flow rate of about 0.3 cm 3 /min. Desorption was carried out with demineralized water, and the extraction with 10 -2 M Na 2 CO 3 solution following desorption. The retardation coefficients (R) and hydrodynamic dispersion coefficients (D d ), were determined using an ADE equation. From the experimentally determined values of R, bulk density and porosity, the distribution coefficients (K d ) of the UO 2 2+ species have been calculated for the respective processes. The extent of U sorption in sands, as well as the proportion of desorbed and extracted U from these sands, was also calculated. (author)

Glyphosate sorption and desorption in soils with distinct phosphorus levels

International Nuclear Information System (INIS)

Prata, Fabio; Cardinali, Vanessa Camponez do Brasil; Tornisielo, Valdemar Luiz; Regitano, Jussara Borges; Lavorenti, Arquimedes

2003-01-01

The sorption of glyphosate by soils occurs due to the inner sphere complex formation with metals of soil oxides, which are related to the soil phosphate adsorption capacity. The aim of this study was to evaluate the effects of increasing rates of phosphorus on sorption and desorption of glyphosate in three soils with different mineralogical attributes. Soils were a Rhodic Kandiudalf, an Anionic Acrudox and a Typic Humaquept. Soil samples were amended with Kh 2 PO 4 at equivalent rates of 0; 1,000; 5,000; 20,000 and 50,000 kg ha -1 of P 2 O 5 , which are high from the agricultural point of view, but necessary in order to perform sorption and desorption studies. The experimental design consisted of a completely randomized factorial: 2 soils x 5 phosphorus rates and 3 replicates. For the sorption experiments, five glyphosate solutions were employed (0.42; 0.84; 1.68; 3.36 and 6.72 mg L -1 ), with a 14 C radioactivity of 0.233 kBq mL -1 . Four steps of the desorption procedures withCaCl 2 0.01 mol L -1 and one extraction with Mehlich 3 were performed only at one concentration (0.84 mol L -1 ). Soil samples were afterwards biologically oxidized to establish the radioactive balance. Glyphosate competes with phosphorus for specific sorption sites, but this competition becomes important when phosphorus is present at rates higher than 1,000 mg dm -3 . Moreover, a small amount of applied glyphosate was extracted (<10%), and the extraction increased with increasing soil phosphorus content. (author)

Glyphosate sorption and desorption in soils with distinct phosphorus levels

Directory of Open Access Journals (Sweden)

Prata Fábio

2003-01-01

Full Text Available The sorption of glyphosate by soils occurs due to the inner sphere complex formation with metals of soil oxides, which are related to the soil phosphate adsorption capacity. The aim of this study was to evaluate the effects of increasing rates of phosphorus on sorption and desorption of glyphosate in three soils with different mineralogical attributes. Soils were a Rhodic Kandiudalf, an Anionic Acrudox and a Typic Humaquept. Soil samples were amended with KH2PO4 at equivalent rates of 0; 1,000; 5,000; 20,000 and 50,000 kg ha-1 of P2O5, which are high from the agricultural point of view, but necessary in order to perform sorption and desorption studies. The experimental design consisted of a completely randomized factorial: 2 soils x 5 phosphorus rates and 3 replicates. For the sorption experiments, five glyphosate solutions were employed (0.42; 0.84; 1.68; 3.36 and 6.72 mg L-1, with a 14C radioactivity of 0.233 kBq mL-1. Four steps of the desorption procedure with CaCl2 0.01 mol L-1 and one extraction with Mehlich 3 were performed only at one concentration (0.84 mol L-1. Soil samples were afterwards biologically oxidized to establish the radioactive balance. Glyphosate competes with phosphorus for specific sorption sites, but this competition becomes important when phosphorus is present at rates higher than 1,000 mg dm-3. Moreover, a small amount of applied glyphosate was extracted (<10%, and the extraction increased with increasing soil phosphorus content.

Sorption – desorption of imidacloprid insecticide on Indian soils of five different locations

Directory of Open Access Journals (Sweden)

Shailendra Singh Chauhan

2013-07-01

Full Text Available Sorption-desorption processes govern the movement of all chemicals including pesticides in soils. The present investigation was undertaken to study the sorption-desorption of imidacloprid, using a batch method, on soils of five different location of India. Sorption data were fitted to Freundlich isotherm. The log K value was the highest for loam type soil (1.830 and the lowest for clay type soil (1.661. The value of 1/n was the maximum for silt loam soil (0.909 but minimum for loam soil (0.723. Simple correlation analysis indicated that among soil properties only electrical conductivity showed a higher but marginally non-significant negative correlation with log K (r = -0.826 indicating that higher concentration of solutes solutes are conducive to low sorption capacity of soil. The desorption data conformed to two surfaces Freundlich desorption isotherm. The values of 1/n1' corresponding to easily desorbed fraction of imidacloprid showed significant negative correlation with soil pH (r = -0.886, significant at p ≤0.05 but significant positive correlation with clay content (r = 0.980, significant at p ≤0.01. The desorption index for easily desorbed fraction of imidacloprid (n1’/n also had significant negative correlation with soil pH (r = 0.953, significant at p ≤0.05. From cumulative desorption data, it appeared that bioavailability of imidacloprid would be lower in neutral soil than acidic or alkaline soils.

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

International Nuclear Information System (INIS)

Karlin, Yu.V.

1993-01-01

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

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

Science.gov (United States)

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

2017-12-01

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

Glyphosate sorption and desorption in soils with distinct phosphorus levels

Energy Technology Data Exchange (ETDEWEB)

Prata, Fabio [BIOAGRI Labs., Piracicaba, SP (Brazil). Div. de Quimica. Lab. de Radioquimica; Cardinali, Vanessa Camponez do Brasil; Tornisielo, Valdemar Luiz; Regitano, Jussara Borges [Sao Paulo Univ., Piracicaba, SP (Brazil). Escola Superior de Agricultura Luiz de Queiroz. Dept. de Ciencias Exatas; Lavorenti, Arquimedes [Centro de Energia Nuclear na Agricultura (CENA), Piracicaba, SP (Brazil). Secao de Toxicologia

2003-03-01

The sorption of glyphosate by soils occurs due to the inner sphere complex formation with metals of soil oxides, which are related to the soil phosphate adsorption capacity. The aim of this study was to evaluate the effects of increasing rates of phosphorus on sorption and desorption of glyphosate in three soils with different mineralogical attributes. Soils were a Rhodic Kandiudalf, an Anionic Acrudox and a Typic Humaquept. Soil samples were amended with Kh{sub 2}PO{sub 4} at equivalent rates of 0; 1,000; 5,000; 20,000 and 50,000 kg ha{sup -1} of P{sub 2}O{sub 5}, which are high from the agricultural point of view, but necessary in order to perform sorption and desorption studies. The experimental design consisted of a completely randomized factorial: 2 soils x 5 phosphorus rates and 3 replicates. For the sorption experiments, five glyphosate solutions were employed (0.42; 0.84; 1.68; 3.36 and 6.72 mg L{sup -1}), with a {sup 14}C radioactivity of 0.233 kBq mL{sup -1}. Four steps of the desorption procedures withCaCl{sub 2} 0.01 mol L{sup -1} and one extraction with Mehlich 3 were performed only at one concentration (0.84 mol L{sup -1}). Soil samples were afterwards biologically oxidized to establish the radioactive balance. Glyphosate competes with phosphorus for specific sorption sites, but this competition becomes important when phosphorus is present at rates higher than 1,000 mg dm{sup -3}. Moreover, a small amount of applied glyphosate was extracted (<10%), and the extraction increased with increasing soil phosphorus content. (author)

Sorption and desorption of insecticides in Brazilian soils

International Nuclear Information System (INIS)

Luchini, L.C.; Lord, K.A.; Ruegg, E.F.

1980-01-01

The sorption from aqueous solution of ten Brazilian soil types of four organochlorine, two organophosphorus and one carbamate insecticide was determined in the laboratory using gas chromatographic and radiometric techniques. Measurements showed that soils richest in organic matter, sorbed all substances except aldrin more strongly than the other soils. DDT was the most and aldrin the least sorbed organochlorine pesticide, being dieldrin sorbed two to four times more strongly than aldrin. Sorption of lindane varied in different soils. The organophosphate insecticides malathion and parathion were strongly sorbed in the soils richest in organic matter and weakly sorbed in the poorest soils heing moderately sorbed by the other soils. Sorption of carbaryl by all soils is small. Lindane was desorbed from the soil richest in organic matter and the extent of desorption was dependent on the sorption time. (Author) [pt

A literature survey of mineral-specific sorption data on radionuclides with relevance to the disposal of radioactive waste

International Nuclear Information System (INIS)

Delakowitz, B.; Meinrath, G.; Spiegel, W.

1996-01-01

A comparative review of mineral-specific radionuclide sorption databases created for performance assessment and reported in both the open literature and 'grey literature' (e.g. technical reports) has in part shown poor quality of documentation describing the database selection procedures. Inadequate information is available on the chemical species of the radionuclide under consideration and the laboratory conditions for determining K d -values. Sorption data derived from literature are neither comparable nor generally applicable due to the wide range in the composition of the aqueous and the solid phase applied in migration experiments. Subsequently, standardized characterization and determination procedures are needed. To improve the reliability of a mathematical model for the prediction of radionuclide sorption on cementitious and ash-type binder materials, determination of mineral-specific sorption coefficients is indispensable. (author). 31 refs., 1 fig., 2 tabs

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

International Nuclear Information System (INIS)

Chen Wei; Hou Lei; Luo Xiaoli; Zhu Lingyan

2009-01-01

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

Sorption and desorption behaviors of diuron in soils amended with charcoal.

Science.gov (United States)

Yu, Xiang-Yang; Ying, Guang-Guo; Kookana, Rai S

2006-11-01

Charcoal derived from the partial combustion of vegetation is ubiquitous in soils and sediments and can potentially sequester organic contaminants. To examine the role of charcoal in the sorption and desorption behaviors of diuron pesticide in soil, synthetic charcoals were produced through carbonization of red gum (Eucalyptus spp.) wood chips at 450 and 850 degrees C (referred to as charcoals BC450 and BC850, respectively, in this paper). Pore size distribution analyses revealed that BC850 contained mainly micropores (pores approximately 0.49 nm mean width), whereas BC450 was essentially not a microporous material. Short-term equilibration (diuron in a soil amended with various amounts of charcoals of both types. The sorption coefficients, isotherm nonlinearity, and apparent sorption-desorption hysteresis markedly increased with increasing content of charcoal in the soil, more prominently in the case of BC850, presumably due to the presence of micropores and its relatively higher specific surface area. The degree of apparent sorption-desorption hystersis (hysteresis index) showed a good correlation with the micropore volume of the charcoal-amended soils. This study indicates that the presence of small amounts of charcoal produced at high temperatures (e.g., interior of wood logs during a fire) in soil can have a marked effect on the release behavior of organic compounds. Mechanisms of this apparent hysteretic behavior need to be further investigated.

Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass

Energy Technology Data Exchange (ETDEWEB)

Gupta, V.K. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)], E-mail: vinodfcy@iitr.ernet.in; Rastogi, A. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

2008-06-15

This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 {sup o}C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO{sub 3} and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater.

Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass

International Nuclear Information System (INIS)

Gupta, V.K.; Rastogi, A.

2008-01-01

This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 o C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO 3 and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater

Annealing effect reversal by water sorption-desorption and heating above the glass transition temperature-comparison of properties.

Science.gov (United States)

Saxena, A; Jean, Y C; Suryanarayanan, R

2013-08-05

Our objective is to compare the physical properties of materials obtained from two different methods of annealing reversal, that is, water sorption-desorption (WSD) and heating above glass transition temperature (HAT). Trehalose was annealed by storing at 100 °C for 120 h. The annealing effect was reversed either by WSD or HAT, and the resulting materials were characterized by differential scanning calorimetry (DSC), water sorption studies, and positron annihilation spectroscopy (PAS). While the products obtained by the two methods of annealing reversal appeared to be identical by conventional characterization methods, they exhibited pronounced differences in their water sorption behavior. Positron annihilation spectroscopy (PAS), by measuring the fractional free volume changes in the processed samples, provided a mechanistic explanation for the differences in the observed behavior.

Influence of temperature on pentavalent Np Sorption and desorption onto Goethite, Montmorillonite

International Nuclear Information System (INIS)

Vial, M.A.; Sherman, C; Czerwinski, K.R.; Reed, D.

2002-01-01

Yucca Mountain Site has been selected by the United States Department of Energy as the repository for disposing the US HLW. The performance allocation analysis on a multi-barrier system for high-level radioactive waste disposal has pointed 237 Np as the dominant hazard at the inlet of the biosphere [1J. 2JNp is present in high-level radioactive wastes (HLW), although in smaller amounts in comparison to other radionuclides. Because of its long half-life of 2.14 million years and its mobile nature under aerobic conditions due to the high chemical stability of its pentavalent state, it is considered a possible long-term pollutant of the ecosystem. Understanding Np behavior is required in order to quantitatively describe its transport in surface groundwater systems. In the repository, many components are known to play an important role in Np and other actinides speciation through adsorption-, complexation-, dissolution-, precipitation- and, colloids or pseudocolloids generation reactions [1]. Inorganic Ligands (C0 3 - , OH - ), present in nearly all natural water at various degree, and organic ligands (humic acid) can react with Np and consequently affect its leachability through the formation of numerous compounds. The solubility limits of radionuclides may act as an initial barrier to radionuclide migration from the potential repository at Yucca Mountain for some radionuclides. However, once radionuclides have dissolved in water infiltrating the site, sorption of these radionuclides onto the surrounding mineral phases becomes a potentially important second barrier. The study of retardation of Np and other key actinides is of major importance in assessing the performance of the potential repository. Among the soil of interest montmorillonite and iron-based materials have generated lots of researches. Nagasaki et al. [2] recent researches on sorption equilibrium and kinetics of NpO 2 + on dispersed particles of Na-montmorillonite and Na-illite (batch experiments at p

Uranium and Cesium sorption to bentonite colloids in high salinity and carbonate-rich environments: Implications for radionuclide transport

Science.gov (United States)

Tran, E. L.; Teutsch, N.; Klein-BenDavid, O.; Weisbrod, N.

2017-12-01

When radionuclides are leaked into the subsurface due to engineered waste disposal container failure, the ultimate barrier to migration of radionuclides into local aquifers is sorption to the surrounding rock matrix and sediments, which often includes a bentonite backfill. The extent of this sorption is dependent on pH, ionic strength, surface area availability, radionuclide concentration, surface mineral composition, and solution chemistry. Colloidal-sized bentonite particles eroded from the backfill have been shown to facilitate the transport of radionuclides sorbed to them away from their source. Thus, sorption of radionuclides such as uranium and cesium to bentonite surfaces can be both a mobilization or retardation factor. Though numerous studies have been conducted to-date on sorption of radionuclides under low ionic strength and carbonate-poor conditions, there has been little research conducted on the behavior of radionuclides in high salinities and carbonate rich conditions typical of aquifers in the vicinity of some potential nuclear repositories. This study attempts to characterize the sorption properties of U(VI) and Cs to bentonite colloids under these conditions using controlled batch experiments. Results indicated that U(VI) undergoes little to no sorption to bentonite colloids in a high-salinity (TDS= 9000 mg/L) artificial groundwater. This lack of sorption was attributed to the formation of CaUO2(CO3)22- and Ca2UO2(CO3)3 aqueous ions which stabilize the UO22+ ions in solution. In contrast, Cs exhibited greater sorption, the extent to which was influenced greatly by the matrix water's ionic strength and the colloid concentration used. Surprisingly, when both U and Cs were together, the presence of U(VI) in solution decreased Cs sorption, possibly due to the formation of stabilizing CaUO2(CO3)22- anions. The implications of this research are that rather than undergoing colloid-facilitated transport, U(VI) is expected to migrate similarly to a

Radionuclide sorption on crushed and intact granitic rock

International Nuclear Information System (INIS)

Eriksen, Tryggve E.; Locklund, Birgitta

1989-05-01

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

Particle-size dependent sorption and desorption of pesticides within a water-soil-nonionic surfactant system.

Science.gov (United States)

Wang, Peng; Keller, Arturo A

2008-05-01

Although nonionic surfactants have been considered in surfactant-aided soil washing systems, there is little information on the particle-size dependence of these processes, and this may have significant implications for the design of these systems. In this study, Triton-100 (TX) was selected to study its effect on the sorption and desorption of two pesticides (Atrazine and Diuron) from different primary soil size fractions (clay, silt, and sand fractions) under equilibrium sorption and sequential desorption. Soil properties, TX sorption, and pesticide sorption and desorption all exhibited significant particle-size dependence. The cation exchange capacity (CEC) of the bulk soils and the soil fractions determined TX sorption capacity, which in turn determined the desorption efficiency. Desorption of pesticide out of the clay raction is the limiting factor in a surfactant-aided washing system. The solubilization efficiency of the individual surfactant micelles decreased as the amount of surfactant added to the systems increased. Thus, instead of attempting to wash the bulk soil, a better strategy might be to either (1) use only the amount of surfactant that is sufficient to clean the coarse fraction, then separate the fine fraction, and dispose or treat it separately, or (2) to separate the coarse fractions mechanically and then treatthe coarse and fine fractions separately. These results may be applicable to many other hydrophobic organic compounds such as polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) strongly sorbed onto soils and sediments.

Study of boric acid sorption and desorption processes

International Nuclear Information System (INIS)

Czosnowska, B.; Laren, E.

1978-01-01

The results are given of the experimental determination of the effect on the boric acid flow and sorption and desorption efficiency of the flow rate of boric acid at different concentrations through an ion exchange column 10.2 cm 2 in cross section. The strongly alkaline VOFATIT RO ion exchanger was used. (B.S.)

Sorption behavior of cesium onto bentonite colloid

International Nuclear Information System (INIS)

Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

2004-01-01

It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

Sorption/desorption of Cs on clay and soil fractions from various regions of Turkey

International Nuclear Information System (INIS)

Erten, H.N.

1988-01-01

The sorption/desorption behaviour of Cs ion in the concentration region of 10 -8 to 10 -4 meqml -1 have been studied using clay and soil fractions from various regions of Turkey. The sorption curves for all the material studied show similar behaviour indicating at least two different sorption processes. One with high and the other with low distribution coefficients. The results of desorption studies indicate that Cs cation is to a large extent attached to the solid material in a reversible manner. The adsorption isotherms were found to be nonlinear in all cases. The increase of R D values with decreasing particle size in most cases, suggests that sorption and/or exchange is primarily a surface phenomenon in the clay and soil fractions studied. 14 figs.; 4 tabs

Sorption of radionuclides from Pb-Bi melt. Report 1

International Nuclear Information System (INIS)

Konovalov, Eh.E.; Il'icheva, N.S.; Trifonova, O.E.

2015-01-01

Results of laboratory investigations of sorption and interfacial distribution of 54 Mn, 59 Fe, 60 Co, 106 Ru, 125 Sb, 137 Cs, 144 Ce, 154,155 Eu and 235,238 U radionuclides in the system Pb-Bi melt - steel surface are analyzed. It is shown that 106 Ru and 125 Sb are concentrated in Pb-Bi melt and other radionuclides with higher oxygen affinity are sorbed on oxide deposits on structural materials. Temperature dependences of sorption efficiency of radionuclides are studied. It is shown that there is sharp increase of this value for all radionuclides near the temperature range 350-400 deg C. Recommendations are given on the use of 106 Ru and 125 Sb as a reference for fuel element rupture detection system with radiometric monitoring of coolant melt samples and 137 Cs, 134 Cs, 134m Cs with radiometric monitoring of sorbing samples [ru

The effect of carbonate on neptunium sorption by hydroxyapatite

International Nuclear Information System (INIS)

Moore, R.C.; Holt, K.

2005-01-01

Full text of publication follows: Hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 , is a common mineral, the main inorganic compound in bone and exhibits strong sorptive properties for many radionuclides. It has been widely studied and proposed as a backfill material for nuclear waste repositories. Neptunium is one the radionuclides sorbed by hydroxyapatite. Neptunium is of particular importance to nuclear waste repository performance because of its relatively high aqueous solubility, high mobility in the environment and long half-life. In this work, we report on the effects of carbonate on sorption of neptunium by hydroxyapatite. Batch sorption and desorption studies for neptunium were performed as a function of carbonate concentration in water using a synthetic hydroxyapatite. The results indicate even low concentrations of carbonate significantly reduce neptunium sorption and enhance desorption. The data were fit to several simple isotherm equations with the Langmuir equation giving the best results. The results of the work are discussed with respect to nuclear waste repository performance. (authors)

Description of the phosphorus sorption and desorption processes in lowland peaty clay soils

NARCIS (Netherlands)

Schoumans, O.F.

2013-01-01

To determine phosphorus (P) losses from agricultural land to surface water, information is needed about the behavior of P in soils. In this study, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies. The maximum P sorption

Sorption-capacity limited retardation of radionuclides transport in water-saturated packing materials

International Nuclear Information System (INIS)

Pescatore, C.; Sullivan, T.

1984-01-01

Radionuclides breakthrough times as calculated through constant retardation factors obtained in dilute solutions are non-conservative. The constant retardation approach regards the solid as having infinite sorption capacity throughout the solid. However, as the solid become locally saturated, such as in the proximity of the waste form-packing materials interface, it will exhibit no retardation properties, and transport will take place as if the radionuclides were locally non-reactive. The magnitude of the effect of finite sorption capacity of the packing materials on radionuclide transport is discussed with reference to high-level waste package performance. An example based on literature sorption data indicated that the breakthrough time may be overpredicted by orders of magnitude using a constant retardation factor as compared to using the entire sorption isotherm to obtain a concentration-dependent retardation factor. 8 refs., 3 figs., 3 tabs

Sorption-capacity limited retardation of radionuclides transport in water-saturated packing materials

International Nuclear Information System (INIS)

Pescatore, C.; Sullivan, T.

1984-01-01

Radionuclides breakthrough times as calculated through constant retardation factors obtained in dilute solutions are non-conservative. The constant retardation approach regards the solid as having infinite sorption capacity throughout the solid. However, as the solid becomes locally saturated, such as in the proximity of the waste form-packing materials interface, it will exhibit no retardation properties, and transport will take place as if the radionuclides were locally non-reactive. The magnitude of the effect of finite sorption capacity of the packing materials on radionuclide transport is discussed with reference to high-level waste package performance. An example based on literature sorption data indicates that the breakthrough time may be overpredicted by orders of magnitude using a constant retardation factor as compared to using the entire sorption isotherm to obtain a concentration-dependent retardation factor. 8 references, 3 figures, 3 tables

Comparative sorption and desorption behaviors of PFHxS and PFOS on sequentially extracted humic substances

Institute of Scientific and Technical Information of China (English)

Lixia Zhao; Yifeng Zhang; Shuhong Fang; Lingyan Zhu; Zhengtao Liu

2014-01-01

The sorption and desorption behaviors of two perfluoroalkane sulfonates (PFSAs),including perfluorohexane sulfonate (PFHxS) and perfluorooctane sulfonate (PFOS) on two humic acids (HAs) and humin (HM),which were extracted from a peat soil,were investigated.The sorption kinetics and isotherms showed that the sorption of PFOS on the humic substances (HSs) was much higher than PFHxS.For the same PFSA compound,the sorption on HSs followed the order of HM ＞ HA2 ＞ HA1.These suggest that hydrophobic interaction plays a key role in the sorption of PFSAs on HSs.The sorption capacities of PFSAs on HSs were significantly related to their aliphaticity,but negatively correlated to aromatic carbons,indicating the importance of aliphatic groups in the sorption of PFSAs.Compared to PFOS,PFHxS displayed distinct desorption hysteresis,probably due to irreversible pore deformation after sorption of PFHxS.The sorption of the two PFSAs on HSs decreased with an increase in pH in the solution.This is ascribed to the electrostatic interaction and hydrogen bonding at lower pH.Hydrophobic interaction might also be stronger at lower pH due to the aggregation of HSs.

Sorption and desorption of 125I-, 137Cs+, 85Sr2+ and 152,154Eu3+ on disturbed soils under dynamic flow and static batch conditions

International Nuclear Information System (INIS)

Palagyi, S.; Vodickova, H.

2009-01-01

Sorption of radionuclides on homogenized soils (under 2.5 mm grain size) from synthetic groundwater of 8 x 10 -3 M ionic strength and pH 8.5 has been studied under dynamic (flow) and static (batch) conditions. The corresponding water-soluble compounds, as carriers in the 10 -6 mol/dm 3 concentration, ere added into the SGW prior to the experiments. Soil samples were taken rom several locations around the environment of the High Level Waste Storage facility at Nuclear Research Institute Rez plc in 5-100 cm depth. The dynamic experiments were carried out in columns made of PP+PE injection syringes of 7.8 cm length and 2.1 cm in diameter. A multi-head peristaltic pump was used or pumping the water upward through the columns at a seepage velocity of bout 0.06 cm/min in average. The radioactive nuclides were added into the water stream individually in a form of a short pulse in 0.1 cm 3 of demineralized water. Dynamic desorption experiments were performed with the same experimental arrangement using a mixture of 10 -2 N H 2 SO 4 and 10 -2 N NO 3 in a volume ratio of 2 : 1. Retardation, distribution and hydrodynamic dispersion coefficients during transport of radionuclides were determined by he evaluation of the integral form of a simple advection-dispersion equation, used for fitting experimental data and modeling the theoretical sorption breakthrough and desorption displacement curves. The static experiments were realized in 100 cm 3 plastic bottles stirring 5 g of soil samples with SGW occasionally in a soil to SGW ratio of 1 : 10 (m/V). Kinetic parameters including equilibrium sorption activity, activity transfer rate constants and sorption half-times were also determined. The results of dynamic experiments were compared with static sorption experiments. (author)

Application of biomass for the sorption of radionuclides from low level Purex aqueous wastes

International Nuclear Information System (INIS)

Ramanujam, A.; Gopalakrishnan, V.; Dhami, P.S.; Kannan, R.; Udupa, S.R.; Salvi, N.A.

1997-05-01

Microbial biomass have been found to be good biological adsorbents for radioactive nuclides such as uranium and thorium with comparatively easy desorption and recovery. Based on this, sorption studies have been carried out to assess the feasibility of using biomass Rhizopus arrhizus (RA) for the removal of radionuclides present in Purex low level waste streams. Biomass Rhizopus arrhizus (RA) appears effective for the removal of actinides and fission products from low level Purex plant waste/effluent solutions. Maximum sorption for uranium and plutonium is observed at 6-7 pH whereas for Am, Eu, Pm, Ce and Zr the sorption is maximum at pH 2 with high D values and fast kinetics in both cases. Sorption for Ru and Cs are negligible. Sorbed nuclides are recoverable by elution with 1 M HNO 3 , on once through basis. The method can be used for treating the evaporator condensates from the plant and the hold-up delay tank solution. The sodium nitrate salt concentration in the aqueous solution beyond 0.14 M seriously affects the metal uptake. The results from column experiments indicate a limited loading capacity in terms of mg of Am/U/Pu etc. per gm of RA. However, as the Purex low level effluents contain only trace level activities whose absolute ionic concentrations are much lower, the capacities observed with the present form of biomass may still be satisfactory

Sorption and desorption of 17α-ethinylestradiol onto sediments affected by rhamnolipidic biosurfactants.

Science.gov (United States)

Guo, Yan-Ping; Hu, Yong-You; Lin, Hui; Ou, Xue-Lian

2018-02-15

Many studies have addressed the desorption and mobilization performances of sorbed contaminants affected by different rhamnolipidic biosurfactants. Study results have been mixed and complicated. Rhamnolipids are always microbial produced with variable homologues. In this study, two representative rhamnolipidic fractions (i.e., RL-F1 and RL-F2, which are mono- and di-rhamnolipids, respectively) were investigated and compared to determine their influence on 17α-ethynylestradiol (EE2) distribution within sediment-water sorption and desorption systems. In general, the coexistence of RL-F1 and EE2 enhanced EE2 sorption in a wider monorhamnolipidic dosage range when freshly treated sorbate was used. The sorbed EE2 concentration decreased as the RL-F1 dosage increased in the aged sorbate desorption systems. However, RL-F2 facilitated EE2 mobilization in both sorption and desorption processes. Experimental data were estimated using a conceptual model that considered the sorbed rhamnolipids and aqueous micelles for organic partitioning. The model results indicated that the rhamnolipid type is an important factor influencing organic distribution, in addition to sorbate aging process and sediment characteristics. The use of a rhamnolipidic mixture containing both mono- and di-rhamnosyl components may not achieve the desired effect when the biosurfactant-enhanced mobilization or immobilization approach is selected. These results are significant for selecting and applying rhamnolipids to remediate contaminants. Copyright © 2017. Published by Elsevier B.V.

Humidity scanning quartz crystal microbalance with dissipation monitoring setup for determination of sorption-desorption isotherms and rheological changes

Energy Technology Data Exchange (ETDEWEB)

Björklund, Sebastian, E-mail: sebastianbjorklund@gmail.com; Kocherbitov, Vitaly [Department of Biomedical Science, Faculty of Health and Society, Malmö University, Malmö (Sweden); Biofilms—Research Center for Biointerfaces, Malmö University, Malmö (Sweden)

2015-05-15

A new method to determine water sorption-desorption isotherms with high resolution in the complete range of water activities (relative humidities) is presented. The method is based on quartz crystal microbalance with dissipation monitoring (QCM-D). The QCM-D is equipped with a humidity module in which the sample film is kept in air with controlled humidity. The experimental setup allows for continuous scanning of the relative humidity from either dry to humid conditions or vice versa. The amount of water sorbed or desorbed from the sample is determined from the resonance frequencies of the coated quartz sensor, via analysis of the overtone dependence. In addition, the method allows for characterization of hydration induced changes of the rheological properties from the dissipation data, which is closely connected to the viscoelasticity of the film. The accuracy of the humidity scanning setup is confirmed in control experiments. Sorption-desorption isotherms of pig gastric mucin and lysozyme, obtained by the new method, show good agreement with previous results. Finally, we show that the deposition technique used to coat the quartz sensor influences the QCM-D data and how this issue can be used to obtain further information on the effect of hydration. In particular, we demonstrate that spin-coating represents an attractive alternative to obtain sorption-desorption isotherms, while drop-coating provides additional information on changes of the rheological properties during hydration.

Radionuclide sorption from the safety evaluation perspective

International Nuclear Information System (INIS)

1992-01-01

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

Sorption and desorption of glyphosate, MCPA and tetracycline and their mixtures in soil as influenced by phosphate.

Science.gov (United States)

Munira, Sirajum; Farenhorst, Annemieke

2017-12-02

Phosphate fertilizers and herbicides such as glyphosate and MCPA are commonly applied to agricultural land, and antibiotics such as tetracycline have been detected in soils following the application of livestock manures and biosolids to agricultural land. Utilizing a range of batch equilibrium experiments, this research examined the competitive sorption interactions of these chemicals in soil. Soil samples (0-15 cm) collected from long-term experimental plots contained Olsen P concentrations in the typical (13 to 20 mg kg -1 ) and elevated (81 to 99 mg kg -1 ) range of build-up phosphate in agricultural soils. The elevated Olsen P concentrations in field soils significantly reduced glyphosate sorption up to 50%, but had no significant impact on MCPA and tetracycline sorption. Fresh phosphate additions in the laboratory, introduced to soil prior to, or at the same time with the other chemical applications, had a greater impact on reducing glyphosate sorption (up to 45%) than on reducing tetracycline (up to 13%) and MCPA (up to 8%) sorption. The impact of fresh phosphate additions on the desorption of these three chemicals was also statistically significant, but numerically very small namely glyphosate and tetracycline and 3% for MCPA. The presence of MCPA significantly reduced sorption and increased desorption of glyphosate, but only when MCPA was present at concentrations much greater than environmentally relevant and there was no phosphate added to the MCPA solution. Tetracycline addition had no significant effect on glyphosate sorption and desorption in soil. For the four chemicals studied, we conclude that when mixtures of phosphate, herbicides and antibiotics are present in soil, the greatest influence of their competitive interactions is phosphate decreasing glyphosate sorption and the presence of phosphate in solution lessens the potential impact of MCPA on glyphosate sorption. The presence of chemical mixtures in soil solution has an overall greater impact

Application of biomass for the sorption of radionuclides from low level Purex aqueous wastes

Energy Technology Data Exchange (ETDEWEB)

Ramanujam, A; Gopalakrishnan, V; Dhami, P S; Kannan, R [Fuel Reprocessing Div., Bhabha Atomic Research Centre, Mumbai (India); Udupa, S R; Salvi, N A [Bio-Organic Div., Bhabha Atomic Research Centre, Mumbai (India)

1997-05-01

Microbial biomass have been found to be good biological adsorbents for radioactive nuclides such as uranium and thorium with comparatively easy desorption and recovery. Based on this, sorption studies have been carried out to assess the feasibility of using biomass Rhizopus arrhizus (RA) for the removal of radionuclides present in Purex low level waste streams. Biomass Rhizopus arrhizus (RA) appears effective for the removal of actinides and fission products from low level Purex plant waste/effluent solutions. Maximum sorption for uranium and plutonium is observed at 6-7 pH whereas for Am, Eu, Pm, Ce and Zr the sorption is maximum at pH 2 with high D values and fast kinetics in both cases. Sorption for Ru and Cs are negligible. Sorbed nuclides are recoverable by elution with 1 M HNO{sub 3}, on once through basis. The method can be used for treating the evaporator condensates from the plant and the hold-up delay tank solution. The sodium nitrate salt concentration in the aqueous solution beyond 0.14 M seriously affects the metal uptake. The results from column experiments indicate a limited loading capacity in terms of mg of Am/U/Pu etc. per gm of RA. However, as the Purex low level effluents contain only trace level activities whose absolute ionic concentrations are much lower, the capacities observed with the present form of biomass may still be satisfactory. 15 refs., 12 tabs.

Barriers to migration of radionuclides from radioactive waste repositories

International Nuclear Information System (INIS)

Stefanova, I.

1999-01-01

Natural inorganic sorbents are known as effective barriers that reduce the migration of radionuclides from radioactive waste repositories and contaminated sites. They could be used as buffer, backfill and sealing materials in the repository and their presence in the host rock and the surrounding geological formations increases the retention properties of the strata. Natural occurring minerals from local origin are used in the study - zeolites (clinoptilolite and mordenite), celadonite and loess. Sorption of wide range of radionuclides is studies. Batch capacity is determined. Sorption of radionuclides from simulated natural solution is studied. Distribution coefficients are calculated from sorption isotherms. Desorption in presence of different natural solutions is studied. Sorption properties are compared. It is shown that clinoptilolite acts as effective barrier against migration of radionuclides from repositories. The presence of celadonite in the clinoptilolite rock increases the retention of polyvalent ions. The retention of radionuclides on loess samples fulfils the requirements for host media for repository for low and intermediate level waste. A method for construction of additional barrier to the existing in the country disposal vault for spent sealed sources is proposed

Critical review: Radionuclide transport, sediment transport, and water quality mathematical modeling; and radionuclide adsorption/desorption mechanisms

Energy Technology Data Exchange (ETDEWEB)

Onishi, Y.; Serne, R.J.; Arnold, E.M.; Cowan, C.E.; Thompson, F.L. [Pacific Northwest Lab., Richland, WA (United States)

1981-01-01

This report describes the results of a detailed literature review of radionuclide transport models applicable to rivers, estuaries, coastal waters, the Great Lakes, and impoundments. Some representatives sediment transport and water quality models were also reviewed to evaluate if they can be readily adapted to radionuclide transport modeling. The review showed that most available transport models were developed for dissolved radionuclide in rivers. These models include the mechanisms of advection, dispersion, and radionuclide decay. Since the models do not include sediment and radionuclide interactions, they are best suited for simulating short-term radionuclide migration where: (1) radionuclides have small distribution coefficients; (2) sediment concentrations in receiving water bodies are very low. Only 5 of the reviewed models include full sediment and radionuclide interactions: CHMSED developed by Fields; FETRA SERATRA, and TODAM developed by Onishi et al, and a model developed by Shull and Gloyna. The 5 models are applicable to cases where: (1) the distribution coefficient is large; (2) sediment concentrations are high; or (3) long-term migration and accumulation are under consideration. The report also discusses radionuclide absorption/desorption distribution ratios and addresses adsorption/desorption mechanisms and their controlling processes for 25 elements under surface water conditions. These elements are: Am, Sb, C, Ce, Cm, Co, Cr, Cs, Eu, I, Fe, Mn, Np, P, Pu, Pm, Ra, Ru, Sr, Tc, Th, {sup 3}H, U, Zn and Zr.

Examination of competitive lanthanide sorption onto smectites and its significance in the management of radioactive waste

Energy Technology Data Exchange (ETDEWEB)

Galunin, Evgeny [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain); Alba, Maria D. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Cientificas - Universidad de Sevilla, Av. Americo Vespucio 49, 41092 Sevilla (Spain); Santos, Maria J. [Departamento de Quimica, Universidade Estadual de Londrina, Londrina, PR 86051-990 (Brazil); Abrao, Taufik [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Cientificas - Universidad de Sevilla, Av. Americo Vespucio 49, 41092 Sevilla (Spain); Vidal, Miquel, E-mail: miquel.vidal@ub.edu [Departament de Quimica Analitica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)

2011-02-28

The competitive effect of La and Lu (analogues of radionuclides appearing in radioactive waste) in the sorption in four smectites was examined. Sorption and desorption distribution coefficients (K{sub d}; K{sub d,des}), and desorption rates (R{sub des}) were determined from batch tests in two media: deionized water and, to consider the influence of cement leachates, 0.02 mol L{sup -1} Ca. The competitive effect was lower when high-affinity sites were available, as in the water medium at the lowest range of initial lanthanide concentration, with high K{sub d} for La and for Lu (5-63 x 10{sup 4} L kg{sup -1}). Lower K{sub d} was measured at higher initial concentrations and in the Ca medium, where Lu showed a stronger competitive effect. This was confirmed by fitting the sorption data to a two-solute Langmuir isotherm. The desorption data indicated that sorption was virtually irreversible for the scenarios with high sorption, with an excellent correlation between K{sub d} and K{sub d,des} (R{sup 2} around 0.9 for the two lanthanides). Assuming that radioactive waste is a mixture of radionuclides, and that Ca ions will be provided by the cement leachates, this would reduce the retention capacity of clay engineered barriers.

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

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Iip Izul Falah

2015-11-01

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

Sorption of radionuclides from spent fuel in crystalline rocks

International Nuclear Information System (INIS)

Nikula, A.

1982-10-01

The safe disposal of spent nuclear fuel or reprocessed waste is an essential element in the expansion of the nuclear power industry. Stable rock formations e.g. granite are considered to be potential sites for disposal. A major factor in evaluating the degree of safety of the disposal is the sorption of radionuclides in rock, which affects their retardation. The report considers the chemical forms of the hazardous radionuclides of spent nuclear fuel in groundwater and the effects of the water's properties on them. In the groundwater near the Olkiluoto power plant site cesium, strontium and radium are in cationic form, iodine as I - . Technetium would occur as TcO +2 , but the pertechnetate form is also possible. Uranium most probably would be as U(VI) plutonium and neptunium as Np(IV) or Np(V). The valences for thorium, americium and curium are not changed in this groundwater and would be +4, +3 and +3, respectively. The actinides in groundwater are all in hydrated or complex form. An increase on the ionic stregth of the groundwater in most instances causes a decrease in the sorption of nuclides since the ion exchange capacity of the rock is limited. Anionic ligands also decrease sorption of cations by complex formation. In some case, on the other hand, high salt concentrations may cause formation of radiocolloids of lanthanides and neptunium and thus increase sorption. In all cases the degree of sorption described by the distribution ratio Ksub(d) was influenced by the pH of the groundwater. Sorption of cesium and strontium increased with growing pH. The sorption behaviour of actinides was in positive correlation with formation of hydroxide complexes at different pH values. The Ksub(d) values of Cs, Sr, Co, Ni and Am for Olkiluoto granites were found to agree with Swedish values, also determined at ambient atmospheric conditions

Prediction of metal sorption in soils

International Nuclear Information System (INIS)

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

2000-01-01

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

Glyphosate sorption/desorption on biochars – Interactions of physical and chemical processes

Science.gov (United States)

BACKGROUND: Biochar, a carbon-rich product of biomass pyrolysis, could limit glyphosate transport in soil and remediate contaminated water. The present study investigates the sorption/desorption behavior of glyphosate on biochars prepared from different hardwoods at temperatures ranging from 350°C t...

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

Science.gov (United States)

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

2006-01-01

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

Effect of humic acid & bacterial exudates on sorption-desorption interactions of 90Sr with brucite.

Science.gov (United States)

Ashworth, Hollie; Abrahamsen-Mills, Liam; Bryan, Nick; Foster, Lynn; Lloyd, Jonathan R; Kellet, Simon; Heath, Sarah

2018-05-18

One of the nuclear fuel storage ponds at Sellafield (United Kingdom) is open to the air, and has contained a significant inventory of corroded magnox fuel and sludge for several decades. As a result, some fission products have also been released into solution. 90Sr is known to constitute a small mass of the radionuclides present in the pond, but due to its solubility and activity, it is at risk of challenging effluent discharge limits. The sludge is predominantly composed of brucite (Mg(OH)2), and organic molecules are known to be present in the pond liquor with occasional algal blooms restricting visibility. Understanding the chemical interactions of these components is important to inform ongoing sludge retrievals and effluent management. Additionally, interactions of radionuclides with organics at high pH will be an important consideration for the evolution of cementitious backfilled disposal sites in the UK. Batch sorption-desorption experiments were performed with brucite, 90Sr and natural organic matter (NOM) (humic acid (HA) and Pseudanabaena catenata cyanobacterial growth supernatant) in both binary and ternary systems at high pH. Ionic strength, pH and order of addition of components were varied. 90Sr was shown not to interact strongly with the bulk brucite surface in binary systems under pH conditions relevant to the pond. HA in both binary and ternary systems demonstrated a strong affinity for the brucite surface. Ternary systems containing HA demonstrated enhanced sorption of 90Sr at pH 11.5 and vice versa, likely via formation of strontium-humate complexes regardless of the order of addition of components. The distribution coefficients show HA sorption to be reversible at all pH values studied, and it appeared to control 90Sr behaviour at pH 11.5. Ternary systems containing cyanobacterial supernatant demonstrated a difference in 90Sr behaviour when the culture had been subjected to irradiation in the first stages of its growth.

Effect of the cationic composition of sorption solution on the quantification of sorption-desorption parameters of heavy metals in soils

International Nuclear Information System (INIS)

Sastre, J.; Rauret, G.; Vidal, M.

2006-01-01

We obtained the sorption isotherms of Cd, Cu, Pb and Zn in clay, clay saline and organic soils. The distribution coefficients (K d ) were determined in 0.02 eq l -1 CaCl 2 and in a solution that simulated the soil solution cationic composition. The K d values greatly varied with the composition of the sorption solution and the initial metal concentration. The sorption experiments were complemented with the quantification of the extractable metal, to estimate the reversibility of metal sorption. The extraction yields depended on the metal-soil combination, and the initial metal concentration, showing no correlation with previous K d values. The effect of the solution composition in mobility predictions was estimated through a Retention Factor, defined as the ratio of the K d versus the extraction yield. Results showed that risk was over- or underestimated using the CaCl 2 medium in soils with a markedly different soil solution composition. - Sorption solution composition modifies metal sorption-desorption pattern in soils

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

Science.gov (United States)

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

2015-01-01

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

Reversibility of sorption of plutonium-239 onto hematite and goethite colloids

International Nuclear Information System (INIS)

Lu, N.; Cotter, C.R.; Kitten, H.D.; Bentley, J.; Triay, I.R.

1998-01-01

Laboratory batch sorption experiments were conducted to evaluate: (1) sorption of plutonium-239 ( 239 Pu) on different iron oxide colloids (hematite and geothite), (2) sorption kinetics of colloidal Pu(IV) and soluble Pu(V) onto these two colloids, and (3) desorption of colloidal Pu(IV) and soluble Pu(V) from 239 Pu-loaded colloids as a function of time. Natural groundwater and carbonate-rich synthetic groundwater were used in this study. To examine the possible influence of bicarbonate on 239 Pu sorption, an additional set of experiments was conducted in sodium nitrate (NaNO 3 ) solutions under carbon dioxide free environments. Our results show that colloidal Pu(IV) as well as soluble Pu(V) was rapidly adsorbed by hematite and goethite colloids in both natural and synthetic groundwater. The amount of 239 Pu adsorbed by both iron oxide colloids in synthetic groundwater was higher than in natural groundwater. The presence of carbonate did not influence the sorption of 239 Pu. While sorption of soluble Pu(V) is a slow process, sorption of colloidal Pu(IV) occurs rapidly. Desorption of Pu from iron oxide colloids is much slower than the sorption processes. Our findings suggest that different sorption and desorption behaviors of 239 Pu by iron oxide colloids in groundwater may facilitate the transport of 239 Pu along potential flowpaths from the areas contaminated by radionuclide and release to the accessible environment. (orig.)

Separation of radionuclides from gas by sorption on activated charcoal and inorganic sorbents

International Nuclear Information System (INIS)

Kepak, F.

1988-01-01

The review deals with the sorption and ion exchange of gaseous radionuclides on activated charcoal and on inorganic sorbents. It presents the physical and chemical characteristics of radionuclides, the sources of gaseous forms of radionuclides as well as the composition of radioactive gases from some nuclear facilities. 79 refs. (author)

Clinoptilolite and palygorskite as sorbents of neutral emerging organic contaminants in treated wastewater: Sorption-desorption studies.

Science.gov (United States)

Leal, María; Martínez-Hernández, Virtudes; Meffe, Raffaella; Lillo, Javier; de Bustamante, Irene

2017-05-01

Water reuse for aquifer recharge could be an important route for the introduction of emerging organic contaminants (EOCs) into the environment. The installation of a Horizontal Permeable Reactive Barrier (H-PRB) could constitute a tertiary treatment process to remove EOCs from treated domestic wastewater prior to recharge activities. The sorption-desorption behaviour of six neutral EOCs present in treated domestic wastewater (acetaminophen, caffeine, carbamazepine, cotinine, 4-acetamidoantipyrine (4-AAA) and 4-formylaminoantipyrine (4-FAA)) has been evaluated. Clinoptilolite and palygorskite have been studied as sorbents to be installed in the H-PRB. Batch tests were carried out using an EOC initial concentration ranging from 5 to 100 μg L -1 . Apart from acetaminophen and caffeine, both materials showed a limited sorption capacity of neutral EOCs (K d  = 0.63-5.42 L kg -1 ). In general, the experimental results show that EOCs exhibit a higher sorption affinity for clinoptilolite than for palygorskite. With the exception of carbamazepine, the sorption of the compounds occurs mainly by interactions with mineral surfaces as indicated by the comparison of the partition coefficients into organic matter and into mineral surfaces. According to the molecular geometry of the compounds and the sorption sequences observed, it appears that the dimensions of the organic molecules play a key role in the sorption process. All the studied EOCs exhibit irreversible sorption and sorption-desorption hysteresis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Geochemical studies of sorption and transport of radionuclides in rock media

International Nuclear Information System (INIS)

Coles, D.G.; Weed, H.C.; Tewhey, J.D.

1980-01-01

Four studies, which supported the goals of the WISAP Program at Battelle PNL, were undertaken by the Lawrence Livermore Laboratory during FY 1979. These were: (1) Batch K/sub d/ experiments, (2) Dynamic sorption experiments on rock cores, (3) Feasibility study for an in situ tracer test at the Climax Stock, NTS, and (4) Geochemical equilibrium code development. Only the equilibrium code development was not funded by the WISAP during FY 1979. The emphasis for the batch K/sub d/ studies was on various (15) sandstones in brine using 75 Se, 85 Sr, 125 Sb, 137 Cs, 141 Ce, and 237 Pu tracers. These sandstone samples were well-characterized for their physical and mineralogical nature. Complex K/sub d/ behavior was observed for the radionuclides studied but 85 Sr showed K/sub d/ values near zero for all samples. Both 141 Ce and 239 Pu K/sub d/ values ranged from 20 to upper limits of greater than or equal to 17,000. Dynamic sorption studies were done on NTS tuff and St. Peter sandstone core using 3 H, 85 Sr, and /sup 95m/Tc. These radionuclides were injected as a short pulse into the rock-equilibrated water that was flowing through the core. Tracer-free water was then continually flowed through the core until elution curves for the mobile radionuclides were established. Tritium and /sup 95m/Tc both traveled through the cores at the same rate, indicating no sorption for the mobile fraction of /sup 95m/Tc ( 95 TcO 4 - ). Strontium-85 did not exit the tuff cores but did exit the sandstone core although the elution curves showed definite retardation relative to the movement of 3 H and /sup 95m/Tc. Post-elution sectioning of the cores indicated that a fraction of the /sup 95m/Tc remained in the cores and was evenly distributed through the tuff cores. Strontium-85 showed a generally decreasing distribution from the inlet side to the outlet side of the tuff cores

Sorption of radionuclides on London clay

International Nuclear Information System (INIS)

Berry, J.A.; Bourke, P.J.; Green, A.; Littleboy, A.K.

1989-02-01

Techniques for studying the sorption of radionuclides on London clay have been investigated. This work involved the use of through-diffusion, in-diffusion, high-pressure convection and batch methods to study the sorption of iodide, strontium, caesium and americium. Through-diffusion and high-pressure convection methods were found to be most useful for investigating weakly and moderately sorbing nuclides and give realistic values for sorptivity. The batch technique remains the most practical method of obtaining large quantities of data within a relatively short timescale but gives very high sorptivity values. It is however very useful for intercomparisons of nuclides or geological media. The in-diffusion method requires further refinement for use with strongly sorbing nuclides. Good agreement between through-diffusion and high-pressure convection methods was obtained for the sorptivity of strontium, whilst trends observed for caesium by through-diffusion were confirmed by batch measurements. (author)

Sorption studies of radionuclides on a modified mesoporous cerium(IV) silicate

International Nuclear Information System (INIS)

Sepehrian, H.; Tarbiat Moallem University, Tehran; Ghannadi-Maragheh, M.; Yavari, R.; Khanchi, A.R.; Waqif-Husain, S.

2008-01-01

Five different samples of a new sorbent, modified mesoporous cerium(IV) silicate have been prepared with various mole ratios of Si/Ce and Cetyltrimethylammonium bromide (CTMABr) as template. XRD, nitrogen sorption, SEM, IR, thermogravimetry and sorption of radionuclides have been studied. Separation of Hg(II)-Th(IV), Hg(II)-Zr(IV) and Rb(I)-Zr(IV) have been developed on columns of this novel sorbent. (author)

Radionuclide and metal sorption on cement and concrete

CERN Document Server

Ochs, Michael; Wang, Lian

2016-01-01

Cementitious materials are being widely used as solidification/stabilisation and barrier materials for a variety of chemical and radioactive wastes, primarily due to their favourable retention properties for metals, radionuclides and other contaminants. The retention properties result from various mineral phases in hydrated cement that possess a high density and diversity of reactive sites for the fixation of contaminants through a variety of sorption and incorporation reactions. This book presents a state of the art review and critical evaluation of the type and magnitude of the various sorption and incorporation processes in hydrated cement systems for twenty-five elements relevant for a broad range of radioactive and industrial wastes. Effects of cement evolution or ageing on sorption/incorporation processes are explicitly evaluated and quantified. While the immobilisation of contaminants by mixing-in during hydration is not explicitly addressed, the underlying chemical processes are similar. A quantitativ...

Sorption and desorption of Sr-90 and Cs-137 by sediments of the Sozh-river valley and border water collections

International Nuclear Information System (INIS)

Onoshko, M.P.

2001-01-01

From the last literature analysis it follows, that to studying of sorption and desorption soil, some rocks and minerals properties concerning radioisotopes the steadfast attention of researchers is paid nowadays. The materials of heavy particles sorption kinetics, the action of adsorption molecules and ions from solutions on leaching products are examined. Sr-90, Cs-137, Pu-239,240 diffusion is estimated. It is found out, that sorbed and desorbed amount of radioisotopes is proportionally to their concentration in soil, and sorption (S) and distributions (Cd) factors do not depend on soil contamination density, and are determined by its physical and chemical properties, parity of firm and liquid phases. It is judged, that increase of soil absorbing properties by the increase of sorbent entering are unpromising, as sorption soil capacity is filled by Cs-137 only in thousand shares of per cent from the sorbent amount, which can be absorbed by soil. With the reference to the conditions of Belarus, experiments and natural supervision on Sr-90 and Cs-137 sorption by Fe, Mn, Si, Al, Ti hydroxides were executed. At experimental researches of electrolyte influence on radioisotope sorption by peat soils Cd amount lines were established. Sediments under certain conditions, due to desorption, become a source of the secondary contamination of natural waters up to ecologically dangerous concentration. Radioisotopes desorption ambiguity is connected to many parallel proceeding processes: exchange sorption on organic and mineral components, co-sedimentation with one-and-a-half Fe, Al and Mn hydroxides and also depends on solutions structure, cationic exchange rocks and soil capacities, concentration of competing ions. At low radioisotopes contents desorption is insignificant, at high - their extraction does not depend on reagent concentration. We carried out the experiment on studying Cs-137 and Sr-90 sorption-desorption from sediments Sozh-river valley and border water

Silica colloids and their effect on radionuclide sorption. A literature review

International Nuclear Information System (INIS)

Hoelttae, P.; Hakanen, M.

2008-05-01

Silica sol, commercial colloidal silica manufactured by Eka Chemicals in Bohus, Sweden is a promising inorganic grout material for sealing small fractures in low permeable rock. This literature review collects information about the use of silica sol as an injection grout material, the properties of inorganic, especially silica colloids, colloid contents in granitic groundwater conditions, essential characterization methods and colloid-mediated transport of radionuclides. Objective was to evaluate the release and mobility of silica sol colloids, the effect of the groundwater conditions, the amount of colloids compared with natural colloids in Olkiluoto conditions, radionuclide sorption on colloids and their contribution to radionuclide transport. Silica sol seems to be a feasible material to seal fractures with an aperture as small as 10 μm in low permeable rock. The silica sol gel is sufficiently stable to limit to water ingress during the operational phase, the requirement that the pH should be below 11 is fulfilled and the compatibility with Engineered Barrier System (EBS) materials is expected to be good. No significant influence on the bentonite properties caused by the silica sol is expected when calcium chloride is used as an accelerator but the influence of sodium chloride has not been examined. No significant release of colloids is expected under prevailing groundwater conditions. The long-term (100 y) stability of silica sol gel has not yet been clearly demonstrated and a long-term release of silica colloids cannot be excluded. The question is the amount of colloids, how mobile they are and the influence of possible glacial melt waters. The bentonite buffer used in the EBS system is assumed to be a potential source of colloids. In a study in Olkiluoto, bentonite colloids were found only in low salinity groundwater. In general, low salinity water (total dissolved solids -1 ) favours colloid stability and bentonite colloids can remain stable over long

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Combined effects of DOM extracted from site soil/compost and biosurfactant on the sorption and desorption of PAHs in a soil-water system

Energy Technology Data Exchange (ETDEWEB)

Yu Hui, E-mail: yuhui200@uregina.ca [Environmental Systems Engineering Program, Faculty of Engineering and Applied Science, University of Regina, Regina, SK S4S 0A2 (Canada); Huang Guohe, E-mail: gordon.huang@uregina.ca [Environmental Systems Engineering Program, Faculty of Engineering and Applied Science, University of Regina, Regina, SK S4S 0A2 (Canada); An Chunjiang, E-mail: an209@uregina.ca [Environmental Systems Engineering Program, Faculty of Engineering and Applied Science, University of Regina, Regina, SK S4S 0A2 (Canada); Wei Jia, E-mail: jia.wei@iseis.org [Environmental Systems Engineering Program, Faculty of Engineering and Applied Science, University of Regina, Regina, SK S4S 0A2 (Canada)

2011-06-15

Highlights: {yields} The combined DOM and biosurfactant significantly enhanced desorption of PAHs. {yields} Compost DOM exhibited higher desorption enhancement capacity than the soil DOM. {yields} Competition among PAHs, DOM and biosurfactant for sorption site determined desorption of PAHs from soil. {yields} Formation of DOM-biosurfactant complex enhance desorption extent of PAHs. - Abstract: The combined effects of DOM and biosurfactant on the sorption/desorption behavior of phenanthrene (PHE) and pyrene (PYR) in soil water systems were systematically investigated. Two origins of DOMs (extracted from soil and extracted from food waste compost) and an anionic biosurfactant (rhamnolipid) were introduced. The presence of DOM in the aqueous phase could decrease the sorption of PAHs, thus influence their mobility. Desorption enhancement for both PHE and PYR in the system with compost DOM was greater than that in the soil DOM system. This is due to the differences in specific molecular structures and functional groups of two DOMs. With the co-existence of biosurfactant and DOM, partitioning is the predominant process and the desorption extent was much higher than the system with DOM or biosurfactant individually. For PHE, the desorption enhancement of combined DOM and biosurfactant was larger than the sum of DOM or biosurfactant; however desorption enhancement for PYR in the combined system was less than the additive enhancement in two individual system under low PAH concentration. This could be explained as the competition sorption among PAHs, DOM and biosurfactant. The results of this study will help to clarify the transport of petroleum pollutants in the remediation of HOCs-contaminated soils.

Combined effects of DOM extracted from site soil/compost and biosurfactant on the sorption and desorption of PAHs in a soil-water system

International Nuclear Information System (INIS)

Yu Hui; Huang Guohe; An Chunjiang; Wei Jia

2011-01-01

Highlights: → The combined DOM and biosurfactant significantly enhanced desorption of PAHs. → Compost DOM exhibited higher desorption enhancement capacity than the soil DOM. → Competition among PAHs, DOM and biosurfactant for sorption site determined desorption of PAHs from soil. → Formation of DOM-biosurfactant complex enhance desorption extent of PAHs. - Abstract: The combined effects of DOM and biosurfactant on the sorption/desorption behavior of phenanthrene (PHE) and pyrene (PYR) in soil water systems were systematically investigated. Two origins of DOMs (extracted from soil and extracted from food waste compost) and an anionic biosurfactant (rhamnolipid) were introduced. The presence of DOM in the aqueous phase could decrease the sorption of PAHs, thus influence their mobility. Desorption enhancement for both PHE and PYR in the system with compost DOM was greater than that in the soil DOM system. This is due to the differences in specific molecular structures and functional groups of two DOMs. With the co-existence of biosurfactant and DOM, partitioning is the predominant process and the desorption extent was much higher than the system with DOM or biosurfactant individually. For PHE, the desorption enhancement of combined DOM and biosurfactant was larger than the sum of DOM or biosurfactant; however desorption enhancement for PYR in the combined system was less than the additive enhancement in two individual system under low PAH concentration. This could be explained as the competition sorption among PAHs, DOM and biosurfactant. The results of this study will help to clarify the transport of petroleum pollutants in the remediation of HOCs-contaminated soils.

Sorption Behavior of Strontium-85 Onto Colloids of Silica and Smectite

International Nuclear Information System (INIS)

Lu, N.; Triay, I.R.; Mason, C.F.V.; Longmire, P.A.

1998-01-01

Strontium-90 is one of the sizable radioactive contaminants found in DP Canyon at Los Alamos, New Mexico. Radioactive surveys found the 90 Sr is present in surface and groundwater in DP Canyon and Los Alamos Canyon. Colloids may influence the transport of this radionuclide in surface water and groundwater environments in both canyons. In this study, we investigated the sorption/desorption behavior of Sr on colloids of smectite and silica. Laboratory batch sorption experiments were conducted using 85 Sr as a surrogate to 90 Sr. Groundwater, collected from DP Canyon and from Well J-13 at Yucca Mountain, Nevada, and deionized water were used in this study. Our results show that 92% to 100% of 85 Sr was rapidly adsorbed onto smectite colloids in all three waters. The concentrations of Ca 2+ significantly influence the adsorption of 85 Sr onto silica colloids. Desorption of 85 Sr from smectite colloids is much slower than the sorption process. Desorption of 85 Sr from silica colloids was rapid in DP groundwater and slow using J-13 groundwater and deionized water

Sorption behavior of cesium, cobalt and europium radionuclides onto hydroxyl magnesium silicate

Energy Technology Data Exchange (ETDEWEB)

Hamed, Mostafa M.; Holiel, M.; Ahmed, I.M. [Atomic Energy Authority, Cairo (Egypt). Hot Laboratories and Waste Management Center

2016-07-01

The radioactive wastes from different activities have to be safely disposed of and isolated from the human environment. The retardation of radioactive materials by designed barriers is originally controlled by the sorption ability of the mineral compositions. In this work, a naturally available mineral composite, a hydroxyl magnesium silicate (HMS) was investigated as potential natural inorganic sorbent for the retention of long-lived radionuclides ({sup 134}Cs, {sup 60}Co and {sup 152+154}Eu) from aqueous solutions. The factors affecting the sorption process, such as contact time and pH were evaluated. Furthermore X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential thermal and thermogravimetry analyses (DTA/TGA) measurements were examined in order to assess the physicochemical properties of the magnesium silicate mineral. Langmuir and Freundlich isotherms fitted the result s substantially better than the Flory-Huggins isotherm and the sorption was found to follow pseudo-first order kinetic model. The proposed mineral has been successfully applied for the sorption of {sup 134}Cs, {sup 60}Co and {sup 152+154}Eu radionuclides from real radioactive waste. The results indicated that about 97.4-99% of {sup 134}Cs, {sup 60}Co and {sup 152+154}Eu radionuclides were efficiently retained onto the HMS mineral. Based on the results obtained, it can be concluded that the HMS mineral is an economic and efficient retaining material for environmental hazardous migration and/or leakage of some radionuclides such as {sup 134}Cs, {sup 60}Co and {sup 152+154}Eu and trivalent actinide ({sup 241}Am, {sup 242m}Am and {sup 243}Am) ions. Therefore, this study could be used as a starting point to establish and consider that mineral as an engineered barrier around the disposal facilities at the nuclear activity centres.

Influence of mineral characteristics on the retention of low molecular weight organic compounds: a batch sorption-desorption and ATR-FTIR study.

Science.gov (United States)

Yeasmin, Sabina; Singh, Balwant; Kookana, Rai S; Farrell, Mark; Sparks, Donald L; Johnston, Cliff T

2014-10-15

Batch experiments were conducted to evaluate the sorption-desorption behaviour of (14)C-labelled carboxylic acids (citric and oxalic) and amino acids (glutamic, alanine, phenylalanine and lysine) on pure minerals (kaolinite, illite, montmorillonite, ferrihydrite and goethite). The sorption experiments were complemented by ATR-FTIR spectroscopy to gain possible mechanistic insight into the organic acids-mineral interactions. In terms of charge, the organic solutes ranged from strongly negative (i.e., citric) to positively charged solutes (i.e., lysine); similarly the mineral phases also ranged from positively to negatively charged surfaces. In general, sorption of anionic carboxylic and glutamic acids was higher compared to the other compounds (except lysine). Cationic lysine showed a stronger affinity to permanently charged phyllosilicates than Fe oxides. The sorption of alanine and phenylalanine was consistently low for all minerals, with relatively higher sorption and lower desorption of phenylalanine than alanine. Overall, the role of carboxylic functional groups for the sorption and retention of these carboxylic and amino acids on Fe oxides (and kaolinite) and of amino group on 2:1 phyllosilicates was noticeable. Mineral properties (surface chemistry, specific surface area), chemistry of the organic compounds (pKa value, functional groups) and the equilibrium pH of the system together controlled the differences in sorption-desorption patterns. The results of this study aid to understand the effects of mineralogical and chemical factors that affect naturally occurring low molecular weight organic compounds sorption under field conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

Sorption-desorption characteristics of benzimidazole based fungicide 2-(4-fluorophenyl)-1h-benzimidazole on physicochemical properties of selected pakistani soils

International Nuclear Information System (INIS)

Ahmad, K.S.

2014-01-01

A batch equilibrium method has been utilized to investigate the sorption-desorption behavior of a versatile cost-effective fungicide2-(4-fluorophenyl)-1H-benzimidazole) FBNZ on four Pakistani soils geographically distant, from hilly to desert areas. FBNZ is a newly synthesized fungicide prepared in the laboratory and is cost effective than the commercially available fungicides. The adsorption and desorption data were fitted to the Freundlich equation, with values of na = 1, which points to a C-type isotherm. Sorption increases with soil organic carbon content, with greater degree of adsorption for hilly soil and least adsorption on sandy soil of Multan, Punjab. Desorption studies reveal that the adsorbed fungicide are firmly retained by soil particles and present a certain degree of irreversibility. The results indicate that the soil organic matters followed by clay content are the most important soil properties governing the fungicide sorption capacity. (author)

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

International Nuclear Information System (INIS)

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

2002-01-01

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

Sorption of radionuclides on a soil

International Nuclear Information System (INIS)

Fukui, Masami

1979-01-01

Disposal of radioactive wastes into the ground has been discussed, and this paper emphasized significance of the investigation for underground water flow and for the prediction of radionuclides through a stratified aquifer using column experiments to evaluate the internal radiation dose. Distributions and redistributions of radionuclides in a sandy layer were observed to identify the sorption model which predicts the behavior, and the underground water flow in the Plio-Pleistocene Osaka Group was investigated as an example, by mean of the measurement of 222 Rn concentration, the pumping technique and the tracer technique using the activation analysis. Then, the estimation of radioactive concentration in the underground water was worked out for the boundary condition of steady state inflow of liquid wastes and of which the 90 Sr are leached from the solidified body, moreover, the equation which easily evaluates the suitability of the disposal site was proposed. These approach may be useful for the actual site selection of radioactive wastes disposal. (author)

Effects of human management on black carbon sorption/desorption during a water transfer project: Recognizing impacts and identifying mitigation possibilities.

Science.gov (United States)

Hao, Rong; Zhang, Jinliang; Wang, Peichao; Hu, Ronggui; Song, Yantun; Wu, Yupeng; Qiu, Guohong

2018-05-15

Water resources management is an important public concern. In this study, we examined the extent of sorption/desorption of trace pollutants to soil black carbon (BC) in the water level fluctuation zone (WLFZ) of the middle route of the South to North Water Transfer Project in China. In addition, we investigated the main management measures affecting these processes during the project. The results showed that the pseudo second-order model adequately describes the sorption/desorption of phenanthrene on the soil BC in the WLFZ. Water level fluctuation may indirectly influenced BC sorption/desorption by altering water chemistry. Water level residence time had negative effects on BC sorption in short-term experiments (days to months), but the impact gradually diminished with increased residence time. The results suggested that long-term field monitoring of water chemistry is urgent. During the initial period of water transfer, delaying the water supplies as drinking water source or directly irrigating crops could mitigate the adverse impacts. Future research should focus on the water-soluble products of BC degradation. The findings of this study should be useful in improving sustainable management of water resources for water transfer projects. Copyright © 2018 Elsevier Ltd. All rights reserved.

An overview of BORIS: Bioavailability of Radionuclides in Soils

International Nuclear Information System (INIS)

Tamponnet, C.; Martin-Garin, A.; Gonze, M.-A.; Parekh, N.; Vallejo, R.; Sauras-Yera, T.; Casadesus, J.; Plassard, C.; Staunton, S.; Norden, M.; Avila, R.; Shaw, G.

2008-01-01

The ability to predict the consequences of an accidental release of radionuclides relies mainly on the level of understanding of the mechanisms involved in radionuclide interactions with different components of agricultural and natural ecosystems and their formalisation into predictive models. Numerous studies and databases on contaminated agricultural and natural areas have been obtained, but their use to enhance our prediction ability has been largely limited by their unresolved variability. Such variability seems to stem from incomplete knowledge about radionuclide interactions with the soil matrix, soil moisture, and biological elements in the soil and additional pollutants, which may be found in such soils. In the 5th European Framework Programme entitled Bioavailability of Radionuclides in Soils (BORIS), we investigated the role of the abiotic (soil components and soil structure) and biological elements (organic compounds, plants, mycorrhiza, and microbes) in radionuclide sorption/desorption in soils and radionuclide uptake/release by plants. Because of the importance of their radioisotopes, the bioavailability of three elements, caesium, strontium, and technetium has been followed. The role of one additional non-radioactive pollutant (copper) has been scrutinised in some cases. Role of microorganisms (e.g., K d for caesium and strontium in organic soils is much greater in the presence of microorganisms than in their absence), plant physiology (e.g., changes in plant physiology affect radionuclide uptake by plants), and the presence of mycorrhizal fungi (e.g., interferes with the uptake of radionuclides by plants) have been demonstrated. Knowledge acquired from these experiments has been incorporated into two mechanistic models CHEMFAST and BIORUR, specifically modelling radionuclide sorption/desorption from soil matrices and radionuclide uptake by/release from plants. These mechanistic models have been incorporated into an assessment model to enhance its

An overview of BORIS: Bioavailability of Radionuclides in Soils

Energy Technology Data Exchange (ETDEWEB)

Tamponnet, C. [Institute of Radioprotection and Nuclear Safety, DEI/SECRE, CADARACHE, B.P. 1, 13108 Saint-Paul-lez-Durance, Cedex (France)], E-mail: christian.tamponnet@irsn.fr; Martin-Garin, A.; Gonze, M.-A. [Institute of Radioprotection and Nuclear Safety, DEI/SECRE, CADARACHE, B.P. 1, 13108 Saint-Paul-lez-Durance, Cedex (France); Parekh, N. [Center for Ecology and Hydrology, Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ (United Kingdom); Vallejo, R.; Sauras-Yera, T.; Casadesus, J. [Department of Plant Biology, University of Barcelona, 08028 Barcelona (Spain); Plassard, C.; Staunton, S. [INRA, UMR Rhizosphere and Symbiosis, Place Viala, 34060 Montpellier (France); Norden, M. [Swedish Radiation Protection Institute, 171 16 Stockholm (Sweden); Avila, R. [Facilia AB, Valsgaerdevaegen 12, 168 53 Bromma, Stockholm (Sweden); Shaw, G. [Division of Agricultural and Environmental Sciences University Park, Nottingham NG7 2RD (United Kingdom)

2008-05-15

The ability to predict the consequences of an accidental release of radionuclides relies mainly on the level of understanding of the mechanisms involved in radionuclide interactions with different components of agricultural and natural ecosystems and their formalisation into predictive models. Numerous studies and databases on contaminated agricultural and natural areas have been obtained, but their use to enhance our prediction ability has been largely limited by their unresolved variability. Such variability seems to stem from incomplete knowledge about radionuclide interactions with the soil matrix, soil moisture, and biological elements in the soil and additional pollutants, which may be found in such soils. In the 5th European Framework Programme entitled Bioavailability of Radionuclides in Soils (BORIS), we investigated the role of the abiotic (soil components and soil structure) and biological elements (organic compounds, plants, mycorrhiza, and microbes) in radionuclide sorption/desorption in soils and radionuclide uptake/release by plants. Because of the importance of their radioisotopes, the bioavailability of three elements, caesium, strontium, and technetium has been followed. The role of one additional non-radioactive pollutant (copper) has been scrutinised in some cases. Role of microorganisms (e.g., K{sub d} for caesium and strontium in organic soils is much greater in the presence of microorganisms than in their absence), plant physiology (e.g., changes in plant physiology affect radionuclide uptake by plants), and the presence of mycorrhizal fungi (e.g., interferes with the uptake of radionuclides by plants) have been demonstrated. Knowledge acquired from these experiments has been incorporated into two mechanistic models CHEMFAST and BIORUR, specifically modelling radionuclide sorption/desorption from soil matrices and radionuclide uptake by/release from plants. These mechanistic models have been incorporated into an assessment model to enhance

Adsorption-desorption isotherms and heat of sorption of prickly pear fruit (Opuntia ficus indica)

International Nuclear Information System (INIS)

Lahsasni, S.; Kouhila, M.; Mahrouz, M.

2004-01-01

The equilibrium moisture contents were determined for prickly pear fruit using the gravimetric static method at t=30, 40 and 50 deg. C over a range of relative humidities from 0.05 to 0.9. The sorption curves of prickly pear fruit decreased with increase in temperature at constant relative humidity. The hysteresis effect was observed. The GAB, modified Halsey, modified Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures are calculated using a modified BET equation. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures

Adsorption-desorption isotherms and heat of sorption of prickly pear fruit (Opuntia ficus indica)

Energy Technology Data Exchange (ETDEWEB)

Lahsasni, S.; Kouhila, M. E-mail: kouhila@hotmail.com; Mahrouz, M

2004-01-01

The equilibrium moisture contents were determined for prickly pear fruit using the gravimetric static method at t=30, 40 and 50 deg. C over a range of relative humidities from 0.05 to 0.9. The sorption curves of prickly pear fruit decreased with increase in temperature at constant relative humidity. The hysteresis effect was observed. The GAB, modified Halsey, modified Chung-Pfost, modified Oswin and modified Henderson models were tested to fit the experimental data. The GAB model was found to be the most suitable for describing the sorption curves. The monolayer moisture content values for the sorption at different temperatures are calculated using a modified BET equation. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures.

Effect of salinity and sediment characteristics on the sorption and desorption of perfluorooctane sulfonate at sediment-water interface

International Nuclear Information System (INIS)

You Chun; Jia Chengxia; Pan Gang

2010-01-01

This study investigated the influence of solution salinity, pH and the sediment characteristics on the sorption and desorption of perfluorooctane sulfonate (PFOS). The results showed that the sorption of PFOS onto sediment increased by a factor of 3 as the CaCl 2 concentration increased from 0.005 to 0.5 mol L -1 at pH 7.0, and nearly 6 at pH 8.0. Desorption hysteresis occurred over all salinity. The thermodynamic index of irreversibility (TII) values increased with increasing concentration of CaCl 2 . Maximum irreversibility was found in the sorption systems with CaCl 2 in the concentration of 0.5 mol L -1 . The results suggested that PFOS can be largely removed from the water with increasing salinity, and get trapped onto sediments irreversibly. These phenomena could be explained by salting-out effect and Ca-bridging effect. Studies also suggested that the content of total organic carbon is the dominant psychochemical properties of sediment controlling the sorption of PFOS. - Salinity is an important environmental parameter affecting the transport and fate of PFOS in aquatic environment.

Radionuclide sorption studies on abyssal red clays

International Nuclear Information System (INIS)

Erickson, K.L.

1979-01-01

The radionuclide sorption properties of a widely distributed abyssal red clay are being experimentally investigated using batch equilibration techniques. This paper summarizes sorption equilibrium data obtained when 0.68 N NaCl solutions containing either Tc, U, Pu, Am or Cm were contacted with samples of the red clay and also summarizes some initial results from experiments designed to determine the relative selectivity of the clay for various nuclides. Under mildly oxidizing conditions, the sorption equilibrium distribution coefficients for technetium were essentially zero. At solution-phase nuclide concentrations on the order of 10 -6 M and less and at solution pH values of about 6.9, the distribution coefficients for plutonium were about 3 x 10 3 m1/gm and for uranium, americium, and curium were about 10 5 ml/gm or greater. However, at solution pH values of about 2.7, the distribution coefficients for each of the nuclides were greatly diminished. Initial experiments conducted in order to determine the relative selectivity of the clay for cesium, barium, and cerium, indicated that the silicate phases in the clay were selective for cesium over barium and cerium. These experiments also indicated that the hydrous oxide phases were selective for cerium over barium and for barium over cesium

Continuous cadmium removal from aqueous solutions by seaweed in a packed-bed column under consecutive sorption-desorption cycles

International Nuclear Information System (INIS)

Jafari, Seyed Ali; Jamali, Abbas

2016-01-01

Packed-bed column process efficiency for cadmium adsorption from aqueous solution was investigated under different bed heights (2.6 to 7.5 cm) and feed flow rates (15 to 30 ml min -1 ). The column was filled with brown seaweed, Sargassum angustifolium. Three simplified models, including Bed Depth Service Time, Thomas, and Yoon- Nelson were employed for describing the experimental breakthrough curves as well as achieving design parameters. Bed lifetime was also evaluated in several consecutive sorption-desorption cycles. Cadmium concentration of 0.005mg l−1, as a standard limit for potable water, was considered as the breakthrough concentration. The maximum column performance was achieved 81% at 7.5 cm bed length and flow rate of 15 ml min -1 . Indeed, increasing the bed height increased the sorption performance and service time, while increasing the feed flow rate had a negative effect. Maximum sorption capacity value remained almost constant by the bed height changes; however, increase in the feed flow rate slightly decreased it. The modeling results revealed that the Yoon-Nelson model was more accurate than Thomas for describing the experimental breakthrough data, especially at low flow rates. Column service time predictions were surprisingly achieved using the Bed Depth Service Time model even at extrapolations. 20% reduction in column adsorption efficiency was observed at the end of four consecutive sorption-desorption cycles; however, desorption efficiencies were achieved more than 99% in each cycle.

Continuous cadmium removal from aqueous solutions by seaweed in a packed-bed column under consecutive sorption-desorption cycles

Energy Technology Data Exchange (ETDEWEB)

Jafari, Seyed Ali; Jamali, Abbas [Persian Gulf Research Institute, Persian Gulf University, 75169, Bushehr (Iran, Islamic Republic of)

2016-04-15

Packed-bed column process efficiency for cadmium adsorption from aqueous solution was investigated under different bed heights (2.6 to 7.5 cm) and feed flow rates (15 to 30 ml min{sup -1}). The column was filled with brown seaweed, Sargassum angustifolium. Three simplified models, including Bed Depth Service Time, Thomas, and Yoon- Nelson were employed for describing the experimental breakthrough curves as well as achieving design parameters. Bed lifetime was also evaluated in several consecutive sorption-desorption cycles. Cadmium concentration of 0.005mg l−1, as a standard limit for potable water, was considered as the breakthrough concentration. The maximum column performance was achieved 81% at 7.5 cm bed length and flow rate of 15 ml min{sup -1}. Indeed, increasing the bed height increased the sorption performance and service time, while increasing the feed flow rate had a negative effect. Maximum sorption capacity value remained almost constant by the bed height changes; however, increase in the feed flow rate slightly decreased it. The modeling results revealed that the Yoon-Nelson model was more accurate than Thomas for describing the experimental breakthrough data, especially at low flow rates. Column service time predictions were surprisingly achieved using the Bed Depth Service Time model even at extrapolations. 20% reduction in column adsorption efficiency was observed at the end of four consecutive sorption-desorption cycles; however, desorption efficiencies were achieved more than 99% in each cycle.

Approach for predicting P sorption/desorption behaviour of potentially eroded topsoil in watercourses

Czech Academy of Sciences Publication Activity Database

Borovec, Jakub; Jan, Jiří

2018-01-01

Roč. 624, May (2018), s. 1316-1324 ISSN 0048-9697 R&D Projects: GA TA ČR TA04021342; GA MZe QI102A265; GA MŠk(CZ) EF16_013/0001782 Institutional support: RVO:60077344 Keywords : erosion * Mehlich 3 * sorption/desorption Subject RIV: DJ - Water Pollution ; Quality OBOR OECD: Water resources Impact factor: 4.900, year: 2016

Ellipsometry-based combination of isothermal sorption-desorption measurement and temperature programmed desorption technique: A probe for interaction of thin polymer films with solvent vapor

Science.gov (United States)

Efremov, Mikhail Yu.; Nealey, Paul F.

2018-05-01

An environmental chamber equipped with an in situ spectroscopic ellipsometer, programmatic vapor pressure control, and variable temperature substrate holder has been designed for studying polymer coating behavior during an exposure to a solvent vapor and also for probing the residual solvent in the film afterwards. Both sorption-desorption cycle at a constant temperature and temperature programmed desorption (TPD) of the residual solvent manifest themselves as a change of the film thickness. Monitoring of ellipsometric angles of the coating allows us to determine the thickness as a function of the vapor pressure or sample temperature. The solvent vapor pressure is precisely regulated by a computer-controlled pneumatics. TPD spectra are recorded during heating of the film in an oil-free vacuum. The vapor pressure control system is described in detail. The system has been tested on 6-170 nm thick polystyrene, poly(methyl methacrylate), and poly(2-vinyl pyridine) films deposited on silicon substrates. Liquid toluene, water, ethanol, isopropanol, cyclohexane, 1,2-dichloroethane, and chlorobenzene were used to create a vapor atmosphere. Typical sorption-desorption and TPD curves are shown. The instrument achieves sub-monolayer sensitivity for adsorption studies on flat surfaces. Polymer-solvent vapor systems with strong interaction demonstrate characteristic absorption-desorption hysteresis spanning from vacuum to the glass transition pressure. Features on the TPD curves can be classified as either glass transition related film contraction or low temperature broad contraction peak. Typical absorption-desorption and TPD dependencies recorded for the 6 nm thick polystyrene film demonstrate the possibility to apply the presented technique for probing size effects in extremely thin coatings.

Research on sorption behavior of radionuclides under shallow land environment. Mechanism and standard methodologies for measurement of distribution coefficients of radionuclides

International Nuclear Information System (INIS)

Sakamoto, Yoshiaki; Tanaka, Tadao; Takebe, Shinichi; Nagao, Seiya; Ogawa, Hiromichi; Komiya, Tomokazu; Hagiwara, Shigeru

2001-01-01

This study consists of two categories' research works. One is research on sorption mechanism of radionuclides with long half-life, which are Technetium-99, TRU elements and U series radionuclides, on soil and rocks, including a development of database of distribution coefficients of radionuclides. The database on the distribution coefficients of radionuclides with information about measurement conditions, such as shaking method, soil characteristics and solution composition, has been already opened to the public (JAERI-DATABASE 20001003). Another study is investigation on a standard methodology of the distribution coefficient of radionuclide on soils, rocks and engineering materials in Japan. (author)

Metal sorption on kaolinite

International Nuclear Information System (INIS)

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

1997-01-01

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

Migration behavior and sorption mechanisms of radionuclides in sedimentary sand stones

International Nuclear Information System (INIS)

Tanaka, Tadao; Kamiyama, Hideo; Sriyotha, K.

1993-05-01

The influence of crushed particle size and weathering of sedimentary rock on migration behavior and sorption mechanisms of 60 Co, 85 Sr and 137 Cs has been investigated by using the fresh sand stones (classified into two particle size ranges of 1 ∼ 3 mm and 2 , KCl, NH 2 OH-HCl, K-oxalate and H 2 O 2 solutions were carried out, to elucidate their dominated sorption mechanisms. Distribution coefficient values of the all three radionuclides, Kds, for the sand stone of 1 ∼ 3 mm was smaller than that of 85 Sr, and the same irreversible sorptions as the selective sorption of Co onto manganese oxides and fixation of Cs by the layer silicate for 60 Co and 137 Cs, respectively. Larger sorbability of the weathered sand stone was explained to be related to an increase of amounts of the effective sorption site, such as cation exchangeable site, calcite, smectite and manganese oxides, which was possibly caused from metamorphism induced by weathering the fresh sand stone. (author)

Effect of salinity and sediment characteristics on the sorption and desorption of perfluorooctane sulfonate at sediment-water interface

Energy Technology Data Exchange (ETDEWEB)

You Chun; Jia Chengxia [State Key Lab of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China); Pan Gang, E-mail: gpan@rcees.ac.c [State Key Lab of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China)

2010-05-15

This study investigated the influence of solution salinity, pH and the sediment characteristics on the sorption and desorption of perfluorooctane sulfonate (PFOS). The results showed that the sorption of PFOS onto sediment increased by a factor of 3 as the CaCl{sub 2} concentration increased from 0.005 to 0.5 mol L{sup -1} at pH 7.0, and nearly 6 at pH 8.0. Desorption hysteresis occurred over all salinity. The thermodynamic index of irreversibility (TII) values increased with increasing concentration of CaCl{sub 2}. Maximum irreversibility was found in the sorption systems with CaCl{sub 2} in the concentration of 0.5 mol L{sup -1}. The results suggested that PFOS can be largely removed from the water with increasing salinity, and get trapped onto sediments irreversibly. These phenomena could be explained by salting-out effect and Ca-bridging effect. Studies also suggested that the content of total organic carbon is the dominant psychochemical properties of sediment controlling the sorption of PFOS. - Salinity is an important environmental parameter affecting the transport and fate of PFOS in aquatic environment.

Determination of sorption mechanisms of radionuclides onto clay minerals using extended x-ray absorption fine structure (EXAFS) spectroscopy

Energy Technology Data Exchange (ETDEWEB)

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

2001-03-01

Much of the experimental work in the Waste Management Laboratory at PSI concentrates on trying to understand the processes and mechanisms which govern the release of safety-relevant radionuclides from waste matrices, and their transport through engineered barrier systems and the surrounding geosphere. For this reason, detailed sorption studies of radionuclides (Cs, Sr, Ni, Zn, Eu, Am, Th and Se) in clay and cement systems are being conducted. The sorption and modelling studies are combined with kinetic investigations and advanced spectroscopic and microscopic methods in order to understand the sorption mechanism on an atomic level. This approach is part of a new multidisciplinary research field called Molecular Environmental Science (MES). In this paper, a case study of Ni sorption on montmorillonite is presented to illustrate how EXAFS can be used successfully to better understand sorption processes. (author)

Determination of sorption mechanisms of radionuclides onto clay minerals using extended x-ray absorption fine structure (EXAFS) spectroscopy

International Nuclear Information System (INIS)

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

2001-01-01

Much of the experimental work in the Waste Management Laboratory at PSI concentrates on trying to understand the processes and mechanisms which govern the release of safety-relevant radionuclides from waste matrices, and their transport through engineered barrier systems and the surrounding geosphere. For this reason, detailed sorption studies of radionuclides (Cs, Sr, Ni, Zn, Eu, Am, Th and Se) in clay and cement systems are being conducted. The sorption and modelling studies are combined with kinetic investigations and advanced spectroscopic and microscopic methods in order to understand the sorption mechanism on an atomic level. This approach is part of a new multidisciplinary research field called Molecular Environmental Science (MES). In this paper, a case study of Ni sorption on montmorillonite is presented to illustrate how EXAFS can be used successfully to better understand sorption processes. (author)

Sorption of long-lived radionuclides in clay and rock

International Nuclear Information System (INIS)

Allard, B.; Kipatsi, H.; Rydberg, J.

1977-10-01

The mechanism of sorption of water soluble species in the natural environment has been discussed. The radiochemical and radiobiological properties of the elements in spent nuclear fuel have been briefly discussed, and 14 of the radioactive products have been selected for studies of the sorption behaviour in contact with natural rock and clay minerals. These 14 elements are Sr, Zr, Tc, I, Cs, Ce, Nd, Eu, Ra, Th, U, Np, Pu and Am. From data available concerning composition and equilibria in natural subsoil waters two standard water compositions have been suggested for the laboratory measurements. Suitable concentrations of the radionuclides and experimental temperatures have been proposed. A batch technique has been used for determination of distribution coefficients for powdered solid materials. Measurements have been performed for all of the 14 elements with granite and bentonite/quartz mixture (10:90) with variation of water composition, nuclide concentration and temperature. Moreover, the effect of variation of the particle size has been studied for granite with Sr, Cs and Am, as well as the sorption in powdered granodiorite, chlorite and silt and on fresh and old rock surfaces (granite). The presence of organic components in bentonite has been confirmed and a preliminary complex formation study with these organics has been performed. An estimation of the valencestate of the actinides U, Np and Pu has been suggested using reasonable assumptions regarding the hydrolysis of the actinides and the presence of Fe(IIE/Fe(IE in natural waters. Using measured or calculated distribution coefficients and considering the chemical properties of the natural water system, relevant retention factors of the radionuclides have been proposed. (author)

Effect of exchangeable cation concentration on sorption and desorption of dissolved organic carbon in saline soils.

Science.gov (United States)

Setia, Raj; Rengasamy, Pichu; Marschner, Petra

2013-11-01

Sorption is a very important factor in stabilization of dissolved organic carbon (DOC) in soils and thus C sequestration. Saline soils have significant potential for C sequestration but little is known about the effect of type and concentration of cations on sorption and release of DOC in salt-affected soils. To close this knowledge gap, three batch sorption and desorption experiments were conducted using soils treated with solutions either low or high in salinity. In Experiment 1, salinity was developed with either NaCl or CaCl2 to obtain an electrical conductivity (EC) in a 1:5 soil: water extract (EC1:5) of 2 and 4 dS m(-1). In Experiments 2 and 3, NaCl and CaCl2 were added in various proportions (between 25 and 100%) to obtain an EC1:5 of 0.5 and 4 dS m(-1), respectively. At EC1:5 of 4 dS m(-1), the sorption of DOC (derived from wheat straw) was high even at a low proportion of added Ca(2+) and did not change with proportion of Ca added, but at EC1:5 of 0.5 dS m(-1) increasing proportion of Ca(2+) added increased DOC sorption. This can be explained by the differences in exchangeable Ca(2+) at the two salinity levels. At EC1:5 of 4 dS m(-1), the exchangeable Ca(2+) concentration did not increase beyond a proportion of 25% Ca(2+), whereas it increased with increasing Ca(2+) proportion in the treatments at EC1:5 of 0.5 dS m(-1). The DOC sorption was lowest with a proportion of 100% as Na(+). When Ca(2+) was added, DOC sorption was highest, but least was desorbed (with deionised water), thus sorption and desorption of added DOC were inversely related. The results of this study suggest that DOC sorption in salt-affected soils is mainly controlled by the levels of exchangeable Ca(2+) irrespective of the Ca(2+) concentration in the soil solution which has implications on carbon stabilization in salt-affected soils. Copyright © 2013 Elsevier B.V. All rights reserved.

Comparative study on sorption/desorption of radioeuropium on alumina, bentonite and red earth: effects of pH, ionic strength, fulvic acid, and iron oxides in red earth

International Nuclear Information System (INIS)

Dong Wenming; Wang Xiangke; Bian Xiaoyan; Wang Aixia; Du Jingzhou; Tao, Z.Y.

2001-01-01

The sorption and desorption of Eu(III) as a representative of trivalent lanthanides and actinides on bentonite, alumina, red earth and red earth treated to remove free iron oxides were comparatively investigated by using batch technique and radiotracer 152+154 Eu. The effects of pH, ionic strength, fulvic acid, iron oxides in red earth and the sorption mechanism were also discussed. As compared to alumina and red earth, Eu(III) presents a considerable distribution coefficient (K d ) onto bentonite. It was found that the pH and the presence of clay minerals are the main factors dominating the sorption/desorption characteristic of Eu 3+ in the soil, and that a sorption-desorption hysteresis on bentonite and red earth actually occurs. Furthermore, the main sorption mechanism of lanthanides onto bentonite, alumina and red earth is the formation of bridged hydroxo complexes with the surface, and there are negative effects of fulvic acid and free iron oxides in red earth on the sorption of Eu(III). The results of this paper indicate that the additivity rule on the sorption characteristic of a soil from the individual component's characteristics is not general

Elimination of radionuclides and heavy metals from soils

International Nuclear Information System (INIS)

Navarcik, I.; Cipakova, A.; Palagyi, S.

1994-01-01

At present increased attention is devoted to occurrence of radionuclides and heavy metals in soils, that enter them, owing to a development of power supply, industry, agriculture, traffic etc. These pollutants can cumulate in soils and therefore it is necessary to know to what extent and under which conditions they are held by soil material, so their transfer into plants and so enter into foodchains and their penetration into underground waters could be stopped. Sorption and desorption processes are the basic ones that can determine migration range of radionuclides and heavy metals. Distribution coefficients (K D ) characterize division of pollutants between soil and soil solution. There is connection between K D and soil characteristics and therefore it is possible to use this quantity for observation of factors influencing sorption of pollutants in soils. In the first period of our work sorption and desorption of radionuclides (RN) and heavy metals (HM) in soils, their vertical migration and gradual extraction from soils were verified. In experiments samples of arable and forest soils of the Slovak Republic (black earth, brown soil and sandy soil) were used. Tessier sequential extraction method was used for determination of RN and HM physico-chemical forms. On the base of obtained experimental results we can claim: From the point of view of RN and HM receipt by root system of plants and their appropriate leaching into ground waters, fixed forms (unavailable) are prevailing in soils. Ratio of their unavailable forms are increasing with content of organic matter and clay minerals in soils. As to artificial RN ( 90 Sr, 137 Cs) ratio of firmly bound forms with soil compartments is higher for 137 Cs (black earth - about 95 % , sandy soil - 62 %). Higher measure of 90 Sr depth migration and higher ratio of its availability for plants follow from it. From studied HM, Cd is more mobile, because of its not firm linkage with soil compartments. Ratio of Cd easily available

Sorption behaviour of Cs, Sr radionuclides in the presence of various anions and surfactants in solutions

International Nuclear Information System (INIS)

Davydov, Yu.P.; Toropov, I.G.; Vasilevskaya, T.V.

1997-01-01

The state of 137 Cs and 90 Sr radionuclides was studied in solutions of different compositions to develop appropriate methodology and technology for treatment of spent decontamination solutions. Complex physico-chemical methods were used for this study. Particular attention was paid to the sorption of 137 Cs and 90 Sr on different natural and synthetic inorganic sorbents, as the most specific and selective sorbents for separation of these radionuclides from different solutions. Sorption of CS and Sr on different fractions of soil was also studied in connection with development of rehabilitation methods for contaminated territories. (author). 2 refs, 20 tabs

4-MCHM sorption to and desorption from granular activated carbon and raw coal.

Science.gov (United States)

Jeter, T Scott; Sarver, Emily A; McNair, Harold M; Rezaee, Mohammad

2016-08-01

4-Methylcyclohexanemethanol (4-MCHM) is a saturated higher alicyclic primary alcohol that is used in the froth flotation process for cleaning coal. In early 2014, a large spill of crude chemical (containing primarily 4-MCHM) to the Elk River near Charleston, WV contaminated the local water supply. Carbon filters at the affected water treatment facility quickly became saturated, and the contaminated water was distributed to nearby homes and businesses. Sorption of 4-MCHM to granular activated carbon (GAC) was studied in the laboratory using head space (HS) analysis via gas chromatography with a flame ionization detector (GC-FID). Sorption to raw coal was also investigated, since this material may be of interest as a sorbent in the case of an on-site spill. As expected, sorption to both materials increased with decreased particle size and with increased exposure time; although exposure time proved to be much more important in the case of GAC than for coal. Under similar conditions, GAC sorbed more 4-MCHM than raw coal (e.g., 84.9 vs. 63.1 mg/g, respectively, for 20 × 30 mesh particles exposed to 860 mg/L 4-MCHM solution for 24 h). Desorption from both materials was additionally evaluated. Interestingly, desorption of 4-MCHM on a mass per mass basis was also higher for GAC than for raw coal. Overall, results indicated that GAC readily sorbs 4-MCHM but can also readily release a portion of the chemical, whereas coal sorbs somewhat less 4-MCHM but holds it tightly. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling of radionuclide migration and a temperature dynamics in underground disposal of liquid radioactive waste

International Nuclear Information System (INIS)

Larin, V.K.; Zubkov, A.A.; Balakhonov, V.G.; Sukhorukov, V.A.; Zhiganov, A.N.; Noskov, M.D.; Istomin, A.D.; Kesler, A.G.

2002-01-01

Mathematical model of radionuclide migration and temperature field dynamics during underground disposal of liquid radioactive wastes is presented. The model involves the description of filtration, convective-dispersion mass transfer, sorption and desorption of radionuclides, radioactive decay, convective heat transport and hear transfer. Software making possible to conduct prognosis calculations of changing state of stratum-collector of radioactive wastes was made. Results of the simulation of temperature field dynamics and behaviour of radionuclides on underground disposal of liquid radioactive wastes of the Siberian chemical plant are performed [ru

Radionuclide getters in the near-field chemistry of repositories

International Nuclear Information System (INIS)

Holland, T.R.; Lee, D.J.

1990-08-01

This programme of work has assessed the radionuclide sorption efficiency of selected inorganic 'getters' incorporated into cement as a means of enhancing the retention of radioactive species by the proposed repository backfill. The study has shown that most of the materials tested retained considerable sorptive properties for radium and caesium after incorporation into cement. However, poor retention of iodine prompted a search for a specific iodine getter. Apart from encapsulated activated carbon, the specific getters tested showed no improved sorption above that of the cement matrix. A study of factors influencing sorption, showed that the getter concentration was the only factor causing a major change in sorption efficiency. Retesting of samples after 12 months sorption indicated that, in general, a slight degree of desorption had taken place. An engineering assessment, examining the physical characteristics of a selected backfill formulation, was carried out, demonstrating the practicability of the process. (author)

Sorption, desorption and mineralisation of the herbicides glyphosate and MCPA in samples from two Danish soil and subsurface profiles

International Nuclear Information System (INIS)

Sorensen, Sebastian R.; Schultz, Anne; Jacobsen, Ole S.; Aamand, Jens

2006-01-01

The vertical distribution of the sorption, desorption and mineralisation of glyphosate and MCPA was examined in samples from two contrasting soil and subsurface profiles, obtained from a sandy agricultural site and a non-agricultural clay rich site. The highest mineralisation of [ 14 C-methylen]glyphosate, with 9.3-14.7% degraded to 14 CO 2 within 3 months was found in the deepest sample from the clay site. In the deeper parts of the sandy profile high sorption and low desorption of glyphosate coincided with no or minor mineralisation indicating a limited glyphosate bioavailability. MCPA was readily mineralised except in the deepest samples from both sites. The highest MCPA mineralisation was detected just below the surface layers with 72% or 44% degraded to 14 CO 2 at the sandy or the clay sites, respectively. MCPA sorped to a minor extent in all samples and no indications of sorption-controlled mineralisation was revealed. None of the herbicides were mineralised under anoxic conditions. - Natural attenuation potential of the herbicides glyphosate and MCPA was assessed in soil and subsurface profiles

Sorption, desorption and mineralisation of the herbicides glyphosate and MCPA in samples from two Danish soil and subsurface profiles

Energy Technology Data Exchange (ETDEWEB)

Sorensen, Sebastian R. [Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Oster Voldgade 10, DK-1350 Copenhagen K (Denmark)]. E-mail: srs@geus.dk; Schultz, Anne [Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Oster Voldgade 10, DK-1350 Copenhagen K (Denmark); Jacobsen, Ole S. [Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Oster Voldgade 10, DK-1350 Copenhagen K (Denmark); Aamand, Jens [Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Oster Voldgade 10, DK-1350 Copenhagen K (Denmark)

2006-05-15

The vertical distribution of the sorption, desorption and mineralisation of glyphosate and MCPA was examined in samples from two contrasting soil and subsurface profiles, obtained from a sandy agricultural site and a non-agricultural clay rich site. The highest mineralisation of [{sup 14}C-methylen]glyphosate, with 9.3-14.7% degraded to {sup 14}CO{sub 2} within 3 months was found in the deepest sample from the clay site. In the deeper parts of the sandy profile high sorption and low desorption of glyphosate coincided with no or minor mineralisation indicating a limited glyphosate bioavailability. MCPA was readily mineralised except in the deepest samples from both sites. The highest MCPA mineralisation was detected just below the surface layers with 72% or 44% degraded to {sup 14}CO{sub 2} at the sandy or the clay sites, respectively. MCPA sorped to a minor extent in all samples and no indications of sorption-controlled mineralisation was revealed. None of the herbicides were mineralised under anoxic conditions. - Natural attenuation potential of the herbicides glyphosate and MCPA was assessed in soil and subsurface profiles.

Sorption data bases and mechanistic sorption studies

International Nuclear Information System (INIS)

Bradbury, M.H.

2000-01-01

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

Sorption/Desorption Behavior and Mechanism of NH4(+) by Biochar as a Nitrogen Fertilizer Sustained-Release Material.

Science.gov (United States)

Cai, Yanxue; Qi, Hejinyan; Liu, Yujia; He, Xiaowei

2016-06-22

Biochar, the pyrolysis product of biomass material with limited oxygen, has the potential to increase crop production and sustained-release fertilizer, but the understanding of the reason for improving soil fertility is insufficient, especially the behavior and mechanism of ammonium sulfate. In this study, the sorption/desorption effect of NH4(+) by biochar deriving from common agricultural wastes under different preparation temperatures from 200 to 500 °C was studied and its mechanism was discussed. The results showed that biochar displayed excellent retention ability in holding NH4(+) above 90% after 21 days under 200 °C preparation temperature, and it can be deduced that the oxygen functional groups, such as carboxyl and keto group, played the primary role in adsorbing NH4(+) due to hydrogen bonding and electrostatic interaction. The sorption/desorption effect and mechanism were studied for providing an optional way to dispose of agricultural residues into biochar as a nitrogen fertilizer sustained-release material under suitable preparation temperature.

SiO2, TiO2 and Al2O3 colloid characterization and their cesium and iodine sorption part

International Nuclear Information System (INIS)

Hakem, N.

1995-03-01

Recent studies have shown the important role played by colloids in the transport behaviour of radionuclides. In the present study, we have investigated the sorption, at tracer level, to two radionuclides 131 I and 137 Cs on some mineral oxide colloids (100 to 500 nm in size) chosen as ''models'' owing to their very distinct isoelectric points; SiO 2 , TiO 2 and A1 2 O 3 (i.e.p. = 2, 6,25, 9,5 respectively). These colloids have first been characterized, under various pH and ionic strength conditions, by potentiometric and electro kinetic measurements. We have then measured the sorption ratios R, resulting from the partition, at equilibrium, of each radionuclide between the colloidal and aqueous phases in the contact. In a second step, we have attempted to describe the sorption mechanisms of iodine and cesium on the three oxide colloids under investigation, using following models: ion-exchange reaction, physical adsorption, Langmuir and Freundlich isotherms and surface complexation theories. (author). 53 refs., 13 tabs., 43 figs., 4 appendixes

A Generic Procedure for the Assessment of the Effect of Concrete Admixtures on the Sorption of Radionuclides on Cement: Concept and Selected Results

International Nuclear Information System (INIS)

Glaus, M.A.; Laube, A.; Van Loon, L.R.

2004-01-01

A screening procedure is proposed for the assessment of the effect of concrete admixtures on the sorption of radionuclides by cement. The procedure is both broad and generic, and can thus be used as input for the assessment of concrete admixtures which might be used in the future. The experimental feasibility and significance of the screening procedure are tested using selected concrete admixtures: i.e. sulfonated naphthalene-formaldehyde condensates, lignosulfonates, and a plasticiser used at PSI for waste conditioning. The effect of these on the sorption properties of Ni(II), Eu(III) and Th(IV) in cement is investigated using crushed Hardened Cement Paste (HCP), as well as cement pastes prepared in the presence of these admixtures. Strongly adverse effects on the sorption of the radionuclides tested are observed only in single cases, and under extreme conditions: i.e. at high ratios of concrete admixtures to HCP, and at low ratios of HCP to cement pore water. Under realistic conditions, both radionuclide sorption and the sorption of isosaccharinic acid (a strong complexant produced in cement-conditioned wastes containing cellulose) remain unaffected by the presence of concrete admixtures, which can be explained by the sorption of them onto the HCP. The pore-water concentrations of the concrete admixtures tested are thereby reduced to levels at which the formation of radionuclide complexes is no longer of importance. Further, the Langmuir sorption model, proposed for the sorption of concrete admixtures on HCP, suggests that the HCP surface does not become saturated, at least for those concrete admixtures tested. (author)

A Generic Procedure for the Assessment of the Effect of Concrete Admixtures on the Sorption of Radionuclides on Cement: Concept and Selected Results

Energy Technology Data Exchange (ETDEWEB)

Glaus, M.A.; Laube, A.; Van Loon, L.R

2004-03-01

A screening procedure is proposed for the assessment of the effect of concrete admixtures on the sorption of radionuclides by cement. The procedure is both broad and generic, and can thus be used as input for the assessment of concrete admixtures which might be used in the future. The experimental feasibility and significance of the screening procedure are tested using selected concrete admixtures: i.e. sulfonated naphthalene-formaldehyde condensates, lignosulfonates, and a plasticiser used at PSI for waste conditioning. The effect of these on the sorption properties of Ni(II), Eu(III) and Th(IV) in cement is investigated using crushed Hardened Cement Paste (HCP), as well as cement pastes prepared in the presence of these admixtures. Strongly adverse effects on the sorption of the radionuclides tested are observed only in single cases, and under extreme conditions: i.e. at high ratios of concrete admixtures to HCP, and at low ratios of HCP to cement pore water. Under realistic conditions, both radionuclide sorption and the sorption of isosaccharinic acid (a strong complexant produced in cement-conditioned wastes containing cellulose) remain unaffected by the presence of concrete admixtures, which can be explained by the sorption of them onto the HCP. The pore-water concentrations of the concrete admixtures tested are thereby reduced to levels at which the formation of radionuclide complexes is no longer of importance. Further, the Langmuir sorption model, proposed for the sorption of concrete admixtures on HCP, suggests that the HCP surface does not become saturated, at least for those concrete admixtures tested. (author)

Influence of selected factors on strontium sorption on bentonites

International Nuclear Information System (INIS)

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

2007-01-01

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

Radionuclide distributions and sorption behavior in the Susquehanna--Chesapeake Bay System

International Nuclear Information System (INIS)

Olsen, C.R.; Larsen, I.L.; Lowry, P.D.; McLean, R.I.; Domotor, S.L.

1989-01-01

Radionuclides released into the Susquehanna--Chesapeake System from the Three Mile Island, Peach Bottom, and Calvert Cliffs nuclear power plants are partitioned among dissolved, particulate, and biological phases and may thus exist in a number of physical and chemical forms. In this project, we have measured the dissolved and particulate distributions of fallout 137 Cs; reactor-released 137 Cs, 134 Cs, 65 Zn, 60 Co, and 58 Co; and naturally occurring 7 Be and 210 Pb in the lower Susquehanna River and Upper Chesapeake Bay. In addition, we chemically leached suspended particles and bottom sediments in the laboratory to determine radionuclide partitioning among different particulate-sorbing phases to complement the site-specific field data. This information has been used to document the important geochemical processes that affect the transport, sorption, distribution, and fate of reactor-released radionuclides (and by analogy, other trace contaminants) in this river-estuarine system. Knowledge of the mechanisms, kinetic factors, and processes that affect radionuclide distributions is crucial for predicting their biological availability, toxicity, chemical behavior, physical transport, and accumulation in aquatic systems. The results from this project provide the information necessary for developing accurate radionuclide-transport and biological-uptake models. 76 refs., 12 figs

SORPTION OF Au(III BY Saccharomyces cerevisiae BIOMASS

Directory of Open Access Journals (Sweden)

Amaria Amaria

2010-07-01

Full Text Available Au(III sorption by S. cerevisiae biomass extracted from beer waste industry was investigated. Experimentally, the sorption was conducted in batch method. This research involved five steps: 1 identification the functional groups present in the S. cerevisiae biomass by infrared spectroscopic technique, 2 determination of optimum pH, 3 determination of the sorption capacity and energy, 4 determination of the sorption type by conducting desorption of sorbed Au(III using specific eluents having different desorption capacity such as H2O (van der Waals, KNO3 (ion exchange, HNO3 (hydrogen bond, and tiourea (coordination bond, 5 determination of effective eluents in Au(III desorption by partial desorption of sorbed Au(III using thiourea, NaCN and KI. The remaining Au(III concentrations in filtrate were analyzed using Atomic Absorption Spectrophotometer. The results showed that: 1 Functional groups of S. cerevisiae biomass that involved in the sorption processes were hydroxyl (-OH, carboxylate (-COO- and amine (-NH2, 2 maximum sorption was occurred at pH 4, equal to 98.19% of total sorption, 3 The sorption capacity of biomass was 133.33 mg/g (6.7682E-04 mol/g and was involved sorption energy 23.03 kJ mol-1, 4 Sorption type was dominated by coordination bond, 5 NaCN was effective eluent to strip Au(III close to 100%.   Keywords: sorption, desorption, S. cerevisiae biomass, Au(III

Kinetics and reversibility of micropollutant sorption in sludge.

Science.gov (United States)

Barret, Maialen; Carrère, Hélène; Patau, Mathieu; Patureau, Dominique

2011-10-01

The fate of micropollutants throughout wastewater treatment systems is highly dependent on their sorption interactions with sludge matter. In this study, both the sorption and desorption kinetics of polycyclic aromatic hydrocarbons (PAHs) in activated sludge were shown to be very rapid in comparison to biodegradation kinetics. It was concluded that PAH transfer does not limit their biodegradation and that their fate is governed by the sorption/desorption equilibrium state. The effect of contact time between sludge and PAHs was also investigated. It was shown that aging did not influence the sorption/desorption equilibrium although PAH losses during aging suggest that sequestration phenomena had occurred. This implies that for PAH sorption assessment within treatment processes there is no need to include a contact time dimension. As a consequence, thanks to an innovative approach taking into account sorption equilibria and sequestration, this work has demonstrated that studies in the literature which, in main, deal with micropollutant sorption in sewage sludge with only a short contact time can be extrapolated to real systems in which sorption, desorption and aging occur.

Diffusion and sorption properties of radionuclides in compacted bentonite

Energy Technology Data Exchange (ETDEWEB)

Yu Ji-Wei; Neretnieks, I. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Engineering and Technology

1997-07-01

In this report, recent studies on sorption and diffusion of radionuclides in compacted bentonite have been reviewed. The sorption distribution coefficient and diffusion coefficient data obtained from experiments in the literature have been compiled. Based on these experimental data and the report SKB-TR--91-16 (Brandberg and Skagius, 1991), this report proposes a set of sorption distribution coefficient and diffusion coefficient values for modelling purpose for safety analysis of nuclear waste repositories. The variability and uncertainty of the diffusivity data span somewhat more than an order or magnitude up and down. Most of the nuclides have an effective diffusivity in around 10{sup -10} m{sup 2}/s. Ion exclusion effects are observed for C, Cl and for Tc in oxidizing waters. Effective diffusivities are nearly tow orders of magnitude lower for these elements and of the order of 10{sup -12} m{sup 2}/s. Surface diffusion effects are found for Cs, Ni, Pa, Pb, Ra, Sn, Sr and Zr. Effective diffusivities for these elements are of the order of 10{sup -8} m{sup 2}/s. The surface diffusion effect should decrease in saline waters which is seen for Cs and Sr where there are data available. It is also deemed that Ra will have this effect because of its similarity with Sr. The other nuclides should also show this decrease but no data is available. Sorption and diffusion mechanisms in compacted bentonite are discussed in the report. In highly compacted bentonite, sorption and hence its distribution coefficient is not well defined, and a pore diffusion coefficient or a surface diffusion coefficient is not well defined either. Therefore, an apparent diffusion coefficient and a total concentration gradient should be more relevant in describing the diffusion process in compacted bentonite. 99 refs.

Sorption data bases and mechanistic sorption studies

Energy Technology Data Exchange (ETDEWEB)

Bradbury, M.H

2000-07-01

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

Sorption of radionuclides on mesoporous Sn(IV) silicate: a new sorbent

Energy Technology Data Exchange (ETDEWEB)

Sepehrian, H. [Jaber Ibn Hayan Research Labs., Nuclear Science and Technology Research Inst., AEOI, Tehran (Iran); Dept. of Applied Chemistry, Univ. of Tarbiat Moallem, Tehran (Iran); Yavari, R.; Ghannadi Maragheh, M. [Jaber Ibn Hayan Research Labs., Nuclear Science and Technology Research Inst., AEOI, Tehran (Iran); Husain, S.W. [Dept. of Applied Chemistry, Univ. of Tarbiat Moallem, Tehran (Iran)

2008-07-01

Four different samples of mesoporous Sn(IV) silicate with varying mole ratio of Si/Sn have been used to study the sorption behavior of 18 radionuclides on these materials. Ion-exchange capacity, SEM, distribution coefficient and chemical stability have been studied and discussed. Separation of Tl(I) from Th(IV), Cs(I) from Th(IV) and Cs(I) from Zr(IV) have been developed on columns of this sorbent. (orig.)

Sorption of radionuclides on mesoporous Sn(IV) silicate: a new sorbent

International Nuclear Information System (INIS)

Sepehrian, H.; Yavari, R.; Ghannadi Maragheh, M.; Husain, S.W.

2008-01-01

Four different samples of mesoporous Sn(IV) silicate with varying mole ratio of Si/Sn have been used to study the sorption behavior of 18 radionuclides on these materials. Ion-exchange capacity, SEM, distribution coefficient and chemical stability have been studied and discussed. Separation of Tl(I) from Th(IV), Cs(I) from Th(IV) and Cs(I) from Zr(IV) have been developed on columns of this sorbent. (orig.)

Behavior of sorption and thermal desorption of fission products from loaded metal oxide exchangers

International Nuclear Information System (INIS)

Buerck, J.

1986-08-01

A new sublimation method for the concentration and purification of 99 Mo, produced by the fission of 235 U with thermal neutrons, has been developed to replace the present final decontamination steps in the various well established 99 Mo separation processes. A distinct simplification and shortening of the actual procedure is obtained by combining the chromatographic sorption on the SnO 2 -exchanger with the direct thermal desorption of the Mo product from the oxide. (orig./PW) [de

Characterization of aqueous interactions of copper-doped phosphate-based glasses by vapour sorption.

Science.gov (United States)

Stähli, Christoph; Shah Mohammadi, Maziar; Waters, Kristian E; Nazhat, Showan N

2014-07-01

Owing to their adjustable dissolution properties, phosphate-based glasses (PGs) are promising materials for the controlled release of bioinorganics, such as copper ions. This study describes a vapour sorption method that allowed for the investigation of the kinetics and mechanisms of aqueous interactions of PGs of the formulation 50P2O5-30CaO-(20-x)Na2O-xCuO (x=0, 1, 5 and 10mol.%). Initial characterization was performed using (31)P magic angle spinning nuclear magnetic resonance and attenuated total reflectance-Fourier transform infrared spectroscopy. Increasing CuO content resulted in chemical shifts of the predominant Q(2) NMR peak and of the (POP)as and (PO(-)) Fourier transform infrared absorptions, owing to the higher strength of the POCu bond compared to PONa. Vapour sorption and desorption were gravimetrically measured in PG powders exposed to variable relative humidity (RH). Sorption was negligible below 70% RH and increased exponentially with RH from 70 to 90%, where it exhibited a negative correlation with CuO content. Vapour sorption in 0% and 1% CuO glasses resulted in phosphate chain hydration and hydrolysis, as evidenced by protonated Q(0)(1H) and Q(1)(1H) species. Dissolution rates in deionized water showed a linear correlation (R(2)>0.99) with vapour sorption. Furthermore, cation release rates could be predicted based on dissolution rates and PG composition. The release of orthophosphate and short polyphosphate species corroborates the action of hydrolysis and was correlated with pH changes. In conclusion, the agreement between vapour sorption and routine characterization techniques in water demonstrates the potential of this method for the study of PG aqueous reactions. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Assessment of Management Oxides for the Sorption of Radionuclides

International Nuclear Information System (INIS)

D.R. Learman; M.F. Hochella, Jr.

2005-01-01

Recent research has shown that certain manganese oxides have the ability to sorb aqueous metal cations much more efficiently than any of the naturally occurring iron oxides when normalized to surface area. This ability is, at least in part, related to the internal sites available in many manganese oxide structures, including those within tunnels and between sheets. Additionally, a new naturally-occurring manganese oxide structurally related to vernadite ((delta)-MnO 2 ), collected along the Clark Fork River in western Montana, USA, has shown the ability to sorb arsenate, an anionic complex. The potential for manganese oxides to sorb anions has made it an attractive material as a radionuclide ''getter''. According to the US Department of Energy's Total Systems Performance Assessment, technetium and iodine are two major anionic radionuclides contributing to the list of potential contaminants released from Yucca Mountain repository, Nevada, USA. These two radionuclides are extremely problematic because they are very mobile in the environment. This project involves running flow-through sorption experiments using rhenium (a surrogate for technetium) and stable iodine as sorbates and several synthetic manganese oxides, including birnessite, vernadite, cryptomelane, and possibly the new vernadite-like phase mentioned earlier, as sorbants. For all synthesis reactions, manganese (VII) salts are reduced to manganese (III,IV) oxides. The different oxides are produced from specific reductants and/or the addition of heat, followed by multiple washing steps. To verify that the proper phases have been synthesized, all oxides are analyzed using transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). The sorption experiments will be run in flow-through reactors bearing the aqueous complex of interest, where solutions, at various temperatures, pH's, and ionic strengths, will pass through a bed of one of the manganese oxides. The effluent solution will be analyzed

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

International Nuclear Information System (INIS)

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

1996-08-01

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

Sorption and desorption of the industrial chemical MCHM into polymer pipes, liners and activated carbon

OpenAIRE

Ahart, Megan Leanne

2015-01-01

Polyethylene pipes and epoxy or polyurethane linings are increasingly used in drinking water infrastructure. As a recent introduction to the water industry, there are still many unknowns about how polymers will behave in the distribution system specifically relating to sorption and desorption of chemical contaminants. This study is in response to a spill of 4-methylcyclohexane methanol (MCHM) that occurred in January 2014 contaminating the drinking water of nine counties in West Virginia. Thi...

Radionuclide sorption behavior in particulate matter in near coastal marine environments

International Nuclear Information System (INIS)

Hansen, A.M.; Ortega-Lara, V.; Leckie, J.O.

1997-01-01

Full text: In order to evaluate the migration behavior of radioactive cesium and strontium while transported from continental aquatic systems to marine environments, the sorption behaviors for these metals were evaluated in several different environments. Laboratory experiments using radioactive tracers, and equilibrium as well as time dependent modeling were used to evaluate and quantify the distribution of the two elements as a function of element chemistry, solid substrate characteristics and solution composition. The experimental conditions reflected salinities ranging from those found in rivers and lakes through estuaries to the ocean. Adsorption constants were obtained for strontium in natural sediments from these aquatic environments. The strontium specification was evaluated in solution as well as in the adsorbed state. Sorption of strontium occurred mainly as outer sphere complexes. Major cations, ligands (soluble and particulate), ionic strength, and pH were among parameters that affected the distribution of cesium and strontium between adsorbed and dissolved forms. Time-dependent sorption behaviors were observed under study dissolved salt and suspended sediment conditions. Desorption occurred to some degree for all sediment types. Cesium was exchanged with potassium and sodium in clay minerals and was therefore less desorbed than would be expected. The results allowed the description of migration behaviors of two important pollutants from the atomic energy industry

Experimental methodology to study radionuclide sorption and migration in geological formations and engineered barriers of waste repositories

International Nuclear Information System (INIS)

Rojo Sanz, H.

2010-01-01

In Spain, the waste management options include either the possibility of a final storage in a deep geological repository (DGR) or the centralized temporal surface disposal (CTS). DGRs are based in a multi-barrier concept with the geological barrier and including the vitrified waste, the metal containers and engineered barriers such as compacted bentonite and cement-based materials. On the other hand, CTS mainly considers concrete and cement to confine the metal canisters containing the waste. Radionuclide migration will mainly take place by the existence of chemical concentration gradients being thus diffusion the main transport mechanism or by the existence of hydraulic gradients due to the existence of water-conductive fractures. Radionuclide sorption/retention on the materials composing the natural and engineered barriers is the fundamental process controlling contaminant migration. The evaluation of sorption parameters and the understanding of the different mechanisms leading to radionuclide retention are very important issues. The study of diffusion processes is very relevant as well. This paper describes the main experimental methodologies applied to analyse radionuclide transport in the different barriers of radioactive repositories. Particularly we focused on obtaining of retention parameters as distribution coefficients, kd, or retardation factors, Rf, and diffusion coefficients of radionuclides. (Author) 6 refs.

Geochemical behavior of disposed radioactive waste

International Nuclear Information System (INIS)

Barney, G.S.; Navratil, J.D.; Schulz, W.W.

1984-01-01

The papers in this book are organized to cover the chemical aspects that are important to understanding the behavior of disposed radioactive wastes. These aspects include radionuclide sorption and desorption, solubility of radionuclide compounds, chemical species of radionuclides in natural waters, hydrothermal geochemical reactions, measurements of radionuclide migration, solid state chemistry of wastes, and waste-form leaching behavior. The information in each of the papers is necessary to predict the transport of radionuclides from wastes via natural waters and thus to predict the safety of the disposed waste. Radionuclide transport in natural waters is strongly dependent on sorption, desorption, dissolution, and precipitation processes. The first two papers discuss laboratory investigations of these processes. Descriptions of sorption and desorption behavior of important radionuclides under a wide range of environmental conditions are presented in the first section. Among the sorbents studied are basalt interbed solids, granites, clays, sediments, hydrous oxides, and pure minerals. Effects of redox conditions, groundwater composition and pH on sorption reactions are described

Sorption-desorption studies on tuff III. A continuation of studies with samples from Jackass Flats and Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Wolfsberg, K.; Aguilar, R.D.; Bayhurst, B.P.

1981-05-01

This report is the third in a series of reports describing studies of sorption and migration of radionuclides in tuff. The investigations were extended to lithologies of tuff not previously studied. Continuing experiments with uranium, plutonium, and americium are described. The dependence of sorption on the concentration of the sorbing element and on the solution-to-solid ratio was investigated for a number of nuclides and two lithologies. A circulating system was designed for measuring sorption ratios. Values obtained from this system, batch measurements, and column elutions are compared. Progress on measuring and controlling Eh is described

Characterization of 200-UP-1 Aquifer Sediments and Results of Sorption-Desorption Tests Using Spiked Uncontaminated Groundwater

Energy Technology Data Exchange (ETDEWEB)

Um, Wooyong; Serne, R JEFFREY.; Bjornstad, Bruce N.; Schaef, Herbert T.; Brown, Christopher F.; Legore, Virginia L.; Geiszler, Keith N.; Baum, Steven R.; Valenta, Michelle M.; Kutnyakov, Igor V.; Vickerman, Tanya S.; Lindberg, Michael J.

2005-11-16

Core characterization showed only 4 out of 13 core liner samples were intact samples and that the others were slough material. The intact samples showed typical Ringold Unit E characteristics such as being dominated by gravel and sand. Moderately reducing conditions are inferred in some core from borehole C4299. This reducing condition was caused by the hard tool process used to drill the wells. One core showed significant presence of ferric iron oxide/clay coatings on the gravels. There were no highly contaminated sediments found in the cores from the three new boreholes in UP-1 operable unit, especially for uranium. The presence of slough and ''flour'' caused by hard tooling is a serious challenge to obtaining field relevant sediments for use in geochemical experiments to determine the adsorption-desorption tendencies of redox sensitive elements such as uranium. The adsorption of COCs on intact Ringold Formation sediments and Fe/clay coatings showed that most of the anionic contaminants [Tc(VII), Se(VI), U(VI), Cr(VI), and I(-I)] did not adsorbed very well compared to cationic [Np(V), Sr(II), and Cs(I)] radionuclides. The high hydrous iron oxide content in Fe/clay coatings caused the highest Kd values for U and Np, suggesting these hydrous oxides are the key solid adsorbent in the sediments. Enhanced adsorption behavior for Tc, and Cr and perhaps Se on the sediments was considered an ?artifact? result caused by the induced reducing conditions from the hard tool drilling. Additional U(VI) adsorption Kd studies were performed on Ringold Formation sediments to develop more robust Kd data base for U. The <2 mm size separates of three UP-1 sediments showed a linear U(VI) adsorption isotherm up 1 ppm of total U(VI) concentration in solution. The additional U(VI) Kds obtained from varying carbonate concentration indicated that U(VI) adsorption was strongly influenced by the concentration of carbonate in solution. U(VI) adsorption decreased with

Experimental and Theoretical Studies on Alkaline Degradation of Cellulose and its Impact on the Sorption of Radionuclides

International Nuclear Information System (INIS)

Loon, L.R. van; Glaus, M.A.

1998-08-01

For more than ten years, cellulose degradation has been regarded as an important process which can adversely effect the sorption of radionuclides on cement in a radioactive waste repository. However, so far, it was not possible to quantify this effect. This study reports new experimental data on alkaline degradation of cellulose, together with a re-evaluation of old literature data. For the first time now, it becomes possible to quantitatively estimate the potential role of cellulose degradation in performance assessment studies. In the first part of this study, a literature overview of other studies on alkaline degradation of cellulose is given, together with a general discussion on the effect of organic ligands on the sorption of radionuclides. Further, an overview of the important mechanisms of alkaline degradation of cellulose and some kinetic aspects of the main reactions taking place is presented. The relevance of the processes for performance assessment is explained in detail. The discussion forms the starting-point for a detailed experimental program for evaluating the role of alkaline degradation of cellulose in performance assessment. In the second part, experimental studies on alkaline degradation are presented. Different cellulosic materials were degraded in an artificial cement pore water, representing the first stage of cement degradation. The most important degradation products (α- and β-isosaccharinic acid) were characterised and the results compared with other studies. Kinetic parameters for the main reactions were measured and discussed. A good agreement was found between the measured values and values extrapolated from the literature. The solubility of the sparingly soluble Ca-salt of α-isosaccharinic acid (ISA) was studied as well as the interaction of ISA with cement. Sorption of ISA on cement can keep the ISA concentration in the pore water of a repository at a low level. The effect of pure ISA and degradation products on the sorption of

Experimental and Theoretical Studies on Alkaline Degradation of Cellulose and its Impact on the Sorption of Radionuclides

Energy Technology Data Exchange (ETDEWEB)

Loon, L.R. van; Glaus, M A

1998-08-01

For more than ten years, cellulose degradation has been regarded as an important process which can adversely effect the sorption of radionuclides on cement in a radioactive waste repository. However, so far, it was not possible to quantify this effect. This study reports new experimental data on alkaline degradation of cellulose, together with a re-evaluation of old literature data. For the first time now, it becomes possible to quantitatively estimate the potential role of cellulose degradation in performance assessment studies. In the first part of this study, a literature overview of other studies on alkaline degradation of cellulose is given, together with a general discussion on the effect of organic ligands on the sorption of radionuclides. Further, an overview of the important mechanisms of alkaline degradation of cellulose and some kinetic aspects of the main reactions taking place is presented. The relevance of the processes for performance assessment is explained in detail. The discussion forms the starting-point for a detailed experimental program for evaluating the role of alkaline degradation of cellulose in performance assessment. In the second part, experimental studies on alkaline degradation are presented. Different cellulosic materials were degraded in an artificial cement pore water, representing the first stage of cement degradation. The most important degradation products ({alpha}- and {beta}-isosaccharinic acid) were characterised and the results compared with other studies. Kinetic parameters for the main reactions were measured and discussed. A good agreement was found between the measured values and values extrapolated from the literature. The solubility of the sparingly soluble Ca-salt of {alpha}-isosaccharinic acid (ISA) was studied as well as the interaction of ISA with cement. Sorption of ISA on cement can keep the ISA concentration in the pore water of a repository at a low level. The effect of pure ISA and degradation products on the

Soil microorganisms determine the sorption of radionuclides within organic soil systems

International Nuclear Information System (INIS)

Parekh, N.R.; Poskitt, J.M.; Dodd, B.A.; Potter, E.D.; Sanchez, A.

2008-01-01

The potential of soil microorganisms to enhance the retention of 137 Cs and 85 Sr in organic systems was assessed in a series of experiments. A biologically active, 'mineral-free', organic material, produced under laboratory conditions from leaves, was used as the uptake matrix in all experiments to minimise potential interference from competing clay minerals. Biological uptake and release were differentiated from abiotic processes by comparing the sorption of radionuclides in sterilised organic material with sterile material inoculated with soil extracts or single fungal strains. Our results show conclusively that living components of soil systems are of primary importance in the uptake of radionuclides in organic material. The presence of soil microorganisms significantly enhanced the retention of Cs in organic systems and ∼70% of the Cs spike was strongly (irreversibly) bound (remained non-extractable) in the presence of microorganisms compared to only ∼10% in abiotic systems. Sorption of 85 Sr was not significantly influenced by the presence of soil microorganisms. A non-linear temperature response was observed for the retention in biotic systems with increased uptake at between 10 and 30 deg. C and lower retention at temperatures above or below the optimum range. The optimum temperatures for biological uptake were between 15 and 20 deg. C for Cs, and 25 and 30 deg. C for Sr. Our results indicate that single strains of soil and saprotrophic fungi make an important contribution to the sorption of Cs and Sr in organic systems, but can only account for part of the strong, irreversible binding observed in biotic systems. Single strains of soil fungi increased the amount of non-extractable 137 Cs (by ∼30%) and 85 Sr (by ∼20%) in the organic systems as compared to abiotic systems, but the major fraction of 137 Cs and 85 Sr sorbed in systems inoculated with saprotrophic fungi remained extractable

In-situ radionuclide transport and preferential groundwater flows at INEEL (Idaho): Decay-series disequilibrium studies

International Nuclear Information System (INIS)

Luo, S.; Ku, T.L.; Roback, R.; Murrell, M.; McLing, T.L.

2000-01-01

Uranium and thorium-decay series disequilibria in groundwater occur as a result of water-rock interactions, and they provide site-specific, natural analog information for assessment of in-situ, long-term migration of radionuclides in the far field of a nuclear waste disposal site. In this study, a mass balance model was used to relate the decay-series radionuclide distributions among solution, sorbed and solid phases in an aquifer system to processes of water transport, sorption-desorption, dissolution-precipitation, radioactive ingrowth-decay, and α recoil. Isotopes of U and Rn were measured in 23 groundwater samples collected from a basaltic aquifer at the Idaho National Engineering and Environmental Laboratory (INEEL), Idaho. The results show that groundwater activities of Th and Ra isotopes are 2--4 orders lower than those of their U progenitors. Modeling of the observed disequilibria places the following constraints on the time scale of radionuclide migration and water-rock interaction at INEEL: (1) Time for sorption is minutes for Ra and Th; time for desorption is days for Ra and years for Th; and time for precipitation is days for Th, years for Ra, and centuries for U. (2) Retardation factors due to sorption average > 10 6 for 232 Th, approximately10 4 for 226 Ra, and approximately10 3 for 238 U. (3) Dissolution rates of rocks are approximately70 to 800 mg/L/y. (4) Ages of groundwater range from 222 Rn occur near the groundwater recharging sites as well as in the major flow pathways. Decay of the sorbed parent radionuclides (e.g., 226 Ra and 228 Ra) on micro-fracture surfaces constitutes an important source of their daughter ( 222 Rn and 228 Th) activities in groundwater

Sorption-Desorption Behavior of Newly synthesized N-(1H-Benzimidazole -2 ylmethyl) Acetamide (ABNZ) on Selected Soils and its Antifungal activity

International Nuclear Information System (INIS)

Ahmad, K. S.; Rashid, N.

2015-01-01

A batch equilibrium method has been utilized to investigate the adsorption-desorption behavior of a versatile commercially available fungicide N-(1H-benzimidazole-2ylmethyl) acetamide (ABNZ) on four Pakistani soils geographically distant, from hilly to desert areas. Both qualitative and quantitative analysis has been done for sorption-desorption behavior of ABNZ. These analyses are done in the different concentration of fungicide (0-0.25, 0.25-0.5, 0.5-0.75). Based on statistical analysis ABNZ execute the Freundlich adsorption isotherm in all four tested soils having values of slope n<1 resembling the L-type curve. The distribution co-efficient K/sub d(ads)/ ranges from (2.66 to 12.42 ml/meu g/sup -1/) indicating low adsorption of ABNZ overall. Sorption increases with soil organic carbon content, exhibited greater degree of adsorption for hilly soil and least adsorption on sandy soil of Multan, Punjab. Desorption studies reveal that the adsorbed fungicide is firmly retained by soil particles and present a certain degree of irreversibility. The results indicate that the soil organic matters followed by clay content are the most important soil properties governing the fungicide sorption capacity. Compound N-(1H- benzimidazole -2-ylmethyl) acetamide (ABNZ) showed maximum antifungal activity compared to rest of the tested compound. This anti-fungal activity is substantial in comparison to other pesticides. It causes 40% inhibition of Microsporum canis and Fusarium solani. (author)

Chancellor Water Colloids: Characterization and Radionuclide Associated Transport

Energy Technology Data Exchange (ETDEWEB)

Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Boukhalfa, Hakim [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-09-26

Column transport experiments were conducted in which water from the Chancellor nuclear test cavity was transported through crushed volcanic tuff from Pahute Mesa. In one experiment, the cavity water was spiked with solute ¹³⁷Cs, and in another it was spiked with ^239/240Pu(IV) nanocolloids. A third column experiment was conducted with no radionuclide spike at all, although the ¹³⁷Cs concentrations in the water were still high enough to quantify in the column effluent. The radionuclides strongly partitioned to natural colloids present in the water, which were characterized for size distribution, mass concentration, zeta potential/surface charge, critical coagulation concentration, and qualitative mineralogy. In the spiked water experiments, the unanalyzed portion of the high-concentration column effluent samples were combined and re-injected into the respective columns as a second pulse. This procedure was repeated again for a third injection. Measurable filtration of the colloids was observed after each initial injection of the Chancellor water into the columns, but the subsequent injections (spiked water experiments only) exhibited no apparent filtration, suggesting that the colloids that remained mobile after relatively short transport distances were more resistant to filtration than the initial population of colloids. It was also observed that while significant desorption of ¹³⁷Cs from the colloids occurred after the first injection in both the spiked and unspiked waters, subsequent injections of the spiked water exhibited much less ¹³⁷Cs desorption (much greater ¹³⁷Cs colloid-associated transport). This result suggests that the ¹³⁷Cs that remained associated with colloids during the first injection represented a fraction that was more strongly adsorbed to the mobile colloids than the initial ¹³⁷Cs associated with the colloids. A greater amount of the ^239/240

Compilation and comparison of radionuclide sorption databases used in recent performance assessments

International Nuclear Information System (INIS)

McKinley, I.G.; Scholtis, A.

1992-01-01

The aim of this paper is to review the radionuclide sorption databases which have been used in performance assessments published within the last decade. It was hoped that such a review would allow areas of consistency to be identified, possibly indicating nuclide/rock/water systems which are now well characterised. Inconsistencies, on the other hand, might indicate areas in which further work is required. This study followed on from a prior review of the various databases which had been used in Swiss performance assessments. The latter was, however, considerably simplified by the fact that the authors had been heavily involved in sorption database definition for these assessments. The first phase of the current study was based entirely on available literature and it was quickly evident that the analyses would be much more complex (and time consuming) than initially envisaged. While some assessments clearly list all sorption data used, others depend on secondary literature (which may or may not be clearly referenced) or present sorption data which has been transmogrified into another form (e.g. into a retardation factor -c.f. following section). This study focused on database used (or intended) for performance assessment which have been published within the last 10 years or so. 45 refs., 12 tabs., 1 fig

Natural sorbents as barriers against migration of radionuclides from radioactive waste repositories

International Nuclear Information System (INIS)

Stefanova, I.; Gradev, G.D.

1993-01-01

The sorption properties of Bulgarian inorganic sorbents - clinoptilolite, vermiculite, bentonite, glauconite, celadonite and loess, which can be used as buffer, backfill and sealing materials in radwaste repository are studied. Experimental data about sorption and desorption capacities, radiation and thermal stability of sorbents from different Bulgarian deposits are reported and compared. Clinoptilolite from Beli Plast and its sodium variety from Kostino and Moryantsi is recommended as a barrier against radionuclide migration from radwaste repository due to their high sorption capacity of 137 Ce, 90 Sr and 60 Co. The high selectivity of vermiculite for polyvalent ions ( 144 Ce, 59 Fe and 90 Sr) gives grounds to include the sorption on vermiculite as a second step in the ion exchange technology for low level laundry waste decontamination. Bentonite is studied as a proposed buffer, backfill and sealing material. Its selectivity for cesium is lower compared to those of clinoptilolite. Thus a tailored-made mixture of bentonite and clinoptilolite will act as a barrier against radionuclides in different oxidation state. Glauconite can be successfully used as a barrier against migration of 144 Ce, 90 Sr, 54 Mn and 65 Zn. Loess is also included in the study, as the Kozloduy NPP is sited on loess formation and it is a natural potential site for low and intermediate level waste burial. It is concludes that zeolites and clays of Bulgarian deposits can be used effectively against radionuclide migration from radioactive waste repositories. 59 refs., 5 tabs. (author)

Sorption of polycyclic aromatic hydrocarbons on particulate organic matters

International Nuclear Information System (INIS)

Guo Xueyan; Luo Lei; Ma Yibing; Zhang Shuzhen

2010-01-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Science.gov (United States)

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

2016-01-01

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

Characterization of sorption properties of selected soils from Lublin region by using water vapour adsorption method

Science.gov (United States)

Skic, Kamil; Boguta, Patrycja; Sokołowska, Zofia

2016-04-01

*The studies were carried out within the framework of a research project. The project was financed from funds of National Science Center on the base of decision number DEC-2013/11/D/NZ9/02545 Among many methods proposed to study sorption properties of soils an analysis of adsorption/ desorption isotherm is probably the easiest and most convenient one. It characterizes both quantity and quality of mineral and organic components and also their physical and physicochemical properties. The main aim of this study is comparison of sorption properties of selected Polish soils by using water vapour adsorption method. Samples were taken from the depth of 0-20 cm, from the Lublin region, eastern Poland. Soils were selected on the basis of their different physicochemical properties and were classified as: Haplic Fluvisol, Haplic Chernozem, Mollic Gleysol, Rendzic Phaeozem, Stagnic Luvisol, Haplic Cambisol (WG WRB 2006). Data taken from experimental adsorption isotherms were used to determine parameters of monolayer capacity, specific surface area and the total amount of vapour adsorbed at relative pressure of 0.974. Obtained adsorption and desorption isotherms reviled that adsorbate molecules interacted with the soil particles in different extent. Similar monolayer capacity was observed for Haplic Fluvisol, Haplic Chernozem and Stagnic Luvisol, while for Mollic Gleysol was more than 4 times higher. Mollic Gleysol was also characterized by highest values of specific surface area as well as quantity of adsorbed vapour at relative pressure of 0.974. Higher sorption was caused by presence of soil colloids which contains functional groups of a polar nature (mainly hydroxyls, phenolic and carboxyls). These groups similarly to silicates, oxides, hydratable cations as well as electric charge form adsorption centres for water vapour molecules.

Sorption of strontium by magnetically modified yeast cells

International Nuclear Information System (INIS)

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

2008-01-01

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

Immobilization of metal hexa-cyanoferrates in chitin beads for cesium sorption: synthesis and characterization

International Nuclear Information System (INIS)

Vincent, T.; Guibal, E.; Vincent, C.; Barre, Y.; Guari, Y.; Le Saout, G.

2014-01-01

Five metal-potassium hexacyanoferrate/chitin composites (based on Cu, Ni, Zn, Co or Fe co-metal) have been prepared and characterized, using SEM-EDX, TEM, X-ray diffraction and FT-IR, before being compared for Cs(I) and 137 Cs(I) sorption. The Zn-ion exchanger was characterized by a much larger crystal size of about 250 nm compared with a few tens of nm for other ion-exchangers. The ion exchangers are well distributed in the whole mass of the composite and they are fully accessible to Cs(I), as evidenced by Cs(I) distribution after metal sorption. Uptake kinetics can be modeled using both the pseudo-second order rate equation and the Crank equation (resistance to intra-particle diffusion coefficient). Sorption isotherms showed substantial differences in the sorbents that can be ranked as Cu ≥ Ni ≥ Zn ≥ Co ≥ Fe. However, based on 137 Cs K d values, the sorbents can be ranked as Co≥≥Fe≥≥Cu≥≥Ni≥Zn. Taking into account the cost and toxicity of metals (both in terms of manufacturing and potential metal release) a Prussian Blue based sorbent (i.e., iron-potassium hexacyanoferrate/chitin composite) sounds to be a good composite for Cs(I) recovery from radionuclide-containing effluents. (authors)

Sorption-desorption processes of radioisotopes with solid materials from liquid releases and atmosphere deposits. The distribution coefficient (Ksub(d)), its uses, limitations, and practical applications

International Nuclear Information System (INIS)

Saas, Arsene

1979-03-01

The various sorption-desorption processes of radionuclides with environmental materials are presented. The parameters governing the distribution coefficient are reviewed in the light of various examples. The factors affecting equilibria between the different phases are: reaction time, concentration of the solid phase, water quality, salinity, competition between ions, concentration of radioisotopes or stable isotopes, pH of the mobile phase, particle diameter, chemical form of the radioisotopes, nature of the solid phase, temperature. The effects of the biological parameters on the distribution coefficient are discussed. Biological processes affect the main chemical transformations: mineralization, insolubilization, oxidation-reduction, complexation, ... The importance of these processes is demonstrated by a number of examples in various media. Finally, the practical use of Ksub(d) in the assessment of the environmental impact of radioactive releases is developed, with special emphasis on the limits of its use in siting studies and its essential interest in specifying pathways and capacity of a river system [fr

Batch desorption studies and multiple sorption-regeneration cycles in a fixed-bed column for Cd(II) elimination by protonated Sargassum muticum

International Nuclear Information System (INIS)

Lodeiro, P.; Herrero, R.; Sastre de Vicente, M.E.

2006-01-01

The protonated alga Sargassum muticum was employed in batch desorption studies to find the most appropriate eluting agent for Cd(II)-laden biomass regeneration. Eleven types of eluting solutions at different concentrations were tested, finding elution efficiencies higher than 90% for most of the desorbents studied. Total organic carbon and biomass weight loss measurements were made. The reusability of the protonated alga was also studied using a fixed-bed column. Eleven consecutive sorption-regeneration cycles at a flow rate of 10 mL min -1 were carried out for the removal of 50 mg L -1 Cd(II) solution. A 0.1 M HNO 3 solution was employed as desorbing agent. The column was operated during 605 h for sorption and 66 h for desorption, equivalent to a continuous use during 28 days, with no apparent loss of sorption performance. In these cycles, no diminution of the breakthrough time was found; although, a relative loss of sorption capacity, regarding the found in the first cycle, was observed. The slope of the breakthrough curves experiments a gradual increase reaching its maximum value for the last cycle tested (40% greater than for the first one). The maximum Cd(II) concentration elution peak was achieved in 5 min or less, and the metal effluent concentration was always lower than 0.9 mg L -1 after 1 h of elution. The maximum concentration factor was determined to be between 55 and 109

Laboratory studies of radionuclide distributions between selected groundwaters and geologic media. Progress report, October 1, 1979-September 30, 1980

International Nuclear Information System (INIS)

Daniels, W.R.

1981-01-01

During FY-1980, Los Alamos Scientific Laboratory contributions to the Waste/Rock Interactions Technology program were primarily in the areas of migration-rate studies using crushed rock, whole core, and fractured core columns; parametric studies of variables which may influence radionuclide sorption-desorption behavior; and initial studies of actinide chemistry in near-neutral solutions and Eh control. Batch experiments in both air and a controlled atmosphere (nitrogen, less than or equal to 0.2 ppM oxygen, less than or equal to 20 ppM carbon dioxide) for the sorption of several radionuclides on granite and argillite were completed. These data also provided informaton on the effects of other parameters, such as particle size and contact time. All nine elements studied had different sorption ratios for argillite when measured under the controlled atmosphere than when measured in air, except possibly for americium where any effect was smaller than the standard deviations. As expected, strontium, cesium, and barium are least affected by the presence or absence of oxygen and carbon dioxide. Columns of crushed rock and solid and cracked cores were used to study the migration of radionuclides through such materials. In general, sorption ratios measured by batch techniques are 2 to 3 times greater than those for columns; however, a wide variation in behavior was observed, depending upon the element and the mineralogy. Work has begun on a system wherein traced groundwater is circulated through a crushed rock column; this should provide a link between the usual, single-pass, crushed rock columns and the batch experiments. Materials characterization has continued, and techniques for the determination of Fe(II) in silicate rocks and groundwater have been made operational. Work on the fundamental solution chemistry of the actinides has been started

Sorption characteristics of radioactive cesium and strontium on smectite

International Nuclear Information System (INIS)

Ohnuki, Toshihiko; Kozai, Naofumi

1994-01-01

Sorption of 137 Cs and 85 Sr on smectite has been studied by combining sorption and desorption experiments. In the desorption experiments, the 137 Cs and 85 Sr were desorbed from the smectite by 0.1 N different desorption reagents solution of Li + , Na + , K + , Rb + , Cs + , Mg 2+ , Ca 2+ and Ba 2+ . The effects of Cs and Sr concentrations on sorption were examined by desorption experiments using 1 N KCl as a desorption reagent over a Cs and Sr concentrations range from 10 -8 to 1 N (saturated). All of Sr sorbed was desorbed with a 1 N KCl solution over Sr concentrations range of 10 -8 and 1 M. Approximately 50% of the 137 Cs sorbed at a concentration of 10 -8 M was desorbed with a 1 N KCl solution, and the fraction desorbed increased with increasing a Cs concentration. These results show that all Sr was reversibly sorbed on smectite, and a fraction of Cs was irreversibly sorbed on smectite. Thus, smectite has reversible sorption sites for Sr and both reversible and irreversible sorption sites for Cs. The fractions of Sr desorbed were related to the products of an ionic radius and charge of a desorption reagent, and those of Cs were related to the hydration energy. These results suggest that sorbed Sr and Cs reversibly on smectite form hydrated and dehydrated ions, respectively. (orig.)

New sorption-reagent materials for decontamination of liquid radioactive waste

International Nuclear Information System (INIS)

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

2001-01-01

Full text: Use of selective sorbents in liquid radioactive waste (LRW) management is widely spread in the field of nuclear power objects liquid waste decontamination, since the main objective there is to remove long-lived radionuclides of the nuclear cycle. The latter include, first of all, cesium-137, strontium-90, cobalt-60 and a number of α-irradiators. In this case LRW composition for most of the nuclear power objects is rather simple, except acidic deactivation solutions. At the same time, liquid radioactive wastes of different research centers have a variable chemical and radiochemical composition depending on objectives and tasks of a given center research activities. As a result, application of sorption technologies in such waste decontamination determines special requirements to these sorbents selectivity: a wide spectrum of radionuclides that can be removed and fairly high selectivity enabling to remove radionuclides from solutions of complex chemical composition (containing surfactants, complexing agents etc.). This paper is concerned with studying properties of new materials selective to different radionuclides. These materials are capable to interact with solution components whether already contained in the waste or deliberately added into resulting solution. Such sorption-reagent materials combine universal character of co-precipitation methods with simplicity of sorption methods. In this work we studied sorption-reagent inorganic ion-exchange materials interacting with sulfate-, carbonate-, oxalate-, sulfide-, and permanganate-ions. Insoluble compounds formed as a result of this interaction increase tens- and hundreds-fold the sorption selectivity of different radionuclides - strontium, cobalt, mercury, iron, and manganese as compared to conventional ion-exchange system. By means of X-ray phase analysis, IR-spectroscopy, chemical and radiochemical analysis, we have studied the mechanism of radionuclide sorption on different sorption

Raw or incubated olive-mill wastes and its biotransformed products as agricultural soil amendments-effect on sorption-desorption of triazine herbicides.

Science.gov (United States)

Delgado-Moreno, Laura; Almendros, Gonzalo; Peña, Aránzazu

2007-02-07

Raw olive-mill waste and soil amendments obtained from their traditional composting or vermicomposting were added, at rates equivalent to 200 Mg ha-1, to a calcareous silty clay loam soil in a laboratory test, in order to improve its fertility and physicochemical characteristics. In particular, the effects on the sorption-desorption processes of four triazine herbicides have been examined. We found that comparatively hydrophobic herbicides terbuthylazine and prometryn increased their retention on amended soil whereas the more polar herbicides simazine and cyanazine were less affected. Soil application of olive cake, without transformation, resulted in the highest herbicide retention. Its relatively high content in aliphatic fractions and lipids could explain the increased herbicide retention through hydrophobic bonding and herbicide diffusion favored by poorly condensed macromolecular structures. On the other hand, the condensed aromatic structure of the compost and vermicompost from olive cake could hinder diffusion processes, resulting in lower herbicide sorption. In fact, the progressive humification in soil of olive-mill solid waste led to a decrease of sorption capacity, which suggested important changes in organic matter quality and interactions during the mineralization process. When soil amended with vermicompost was incubated for different periods of time, the enhanced herbicide sorption capacity persisted for 2 months. Pesticide desorption was reduced by the addition of fresh amendments but was enhanced during the transformation process of amendments in soil. Our results indicate the potential of soil amendments based on olive-mill wastes in the controlled, selective release of triazine herbicides, which varies depending on the maturity achieved by their biological transformation.

Impact of kinetics and flow path heterogeneity on nanoparticle/radionuclide migration

International Nuclear Information System (INIS)

Huber, Florian M.

2011-01-01

The prevailing PhD thesis experimentally investigates the impact of both sorption/desorption (reversibility) and reduction kinetics on radionuclide migration in synthetic and natural systems from the nano-to the centimeter scale. Furthermore, the impact of fracture heterogeneity on flow and solute/nanoparticle transport as a potential additional retardation mechanism is examined both on an experimental and numerical basis. The process of sorptive reduction of U(VI) to sparingly soluble tetravalent uranium by structural bound Fe(II) in magnetite shows fast kinetics (hours to a few days contact time). A clear correlation between the Fe(II) content on the magnetite surface and the amount of U(VI) was observed, that is, increasing U(IV) with increasing Fe(II). Moreover, a congruency between the measured Eh(SHE) and the U valence state can partly been derived within the analytical uncertainties of the redox potential measurements. Thus, secondary phases as the stainless steel corrosion product magnetite can have beneficial effects on radionuclide migration as an effective retardation pathway for redox sensitive radionuclides. Beside, the studies on U(VI) maghemite sorption show that oxidized surfaces can possess long-term reduction capacities further enhancing radionuclide retention. Concerning the colloid-facilitated radionuclide transport, the batch sorption reversibility studies revealed the significance of kinetically controlled radionuclide desorption from the colloidal phase and subsequent sorption to the fracture filling materials (independent of the mineralogy and/or size fraction). By this process, initially colloidal associated radionuclides like the tri-and tetravalent radionuclides Th, Pu and Am are effectively retarded leading to an increase in the residence time. These reversibility results need to be included in codes for simulating colloid-facilitated radionuclide transport to reduce the conservatism and degree of uncertainties in input parameters

Impact of kinetics and flow path heterogeneity on nanoparticle/radionuclide migration

Energy Technology Data Exchange (ETDEWEB)

Huber, Florian M.

2011-11-29

The prevailing PhD thesis experimentally investigates the impact of both sorption/desorption (reversibility) and reduction kinetics on radionuclide migration in synthetic and natural systems from the nano-to the centimeter scale. Furthermore, the impact of fracture heterogeneity on flow and solute/nanoparticle transport as a potential additional retardation mechanism is examined both on an experimental and numerical basis. The process of sorptive reduction of U(VI) to sparingly soluble tetravalent uranium by structural bound Fe(II) in magnetite shows fast kinetics (hours to a few days contact time). A clear correlation between the Fe(II) content on the magnetite surface and the amount of U(VI) was observed, that is, increasing U(IV) with increasing Fe(II). Moreover, a congruency between the measured Eh(SHE) and the U valence state can partly been derived within the analytical uncertainties of the redox potential measurements. Thus, secondary phases as the stainless steel corrosion product magnetite can have beneficial effects on radionuclide migration as an effective retardation pathway for redox sensitive radionuclides. Beside, the studies on U(VI) maghemite sorption show that oxidized surfaces can possess long-term reduction capacities further enhancing radionuclide retention. Concerning the colloid-facilitated radionuclide transport, the batch sorption reversibility studies revealed the significance of kinetically controlled radionuclide desorption from the colloidal phase and subsequent sorption to the fracture filling materials (independent of the mineralogy and/or size fraction). By this process, initially colloidal associated radionuclides like the tri-and tetravalent radionuclides Th, Pu and Am are effectively retarded leading to an increase in the residence time. These reversibility results need to be included in codes for simulating colloid-facilitated radionuclide transport to reduce the conservatism and degree of uncertainties in input parameters

Recent developments in the integrated approach toward characterization of radionuclide transport, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Simmons, A.M.; Canepa, J.A.

1992-01-01

The radionuclide migration program for the Yucca Mountain Site Characterization Project (YMP) includes studies of radionuclide solubility, sorption, diffusion, and transport. The study plans incorporate all possible parameters of investigation; decision-making strategies for prioritizing the parameters and evaluating their significance were developed in conjunction with the study plans. After definition of explicit research goals for each study, YMP evaluated the applicability of existing data and formulated experimental approaches for obtaining additional data. This resulted in development of individual testing strategies that were integrated into an overall strategy for the radionuclide migration program designed to provide input to credible performance assessments. The strategies allow for decision points at various steps of data collection and testing. They provide a streamlined process toward a defensible level of understanding of chemical retardation and transport processes that will be used to predict the mountain's ability to isolate waste. (author)

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

International Nuclear Information System (INIS)

2012-01-01

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

Sorção e dessorção do ametryn em Latossolos brasileiros Sorption and desorption of ametryn in Brazilian Latosols

Directory of Open Access Journals (Sweden)

L.O.C. Silva

2012-09-01

Full Text Available O conhecimento dos processos de retenção de herbicidas em solo é fundamental para se prever o potencial de lixiviação e degradação e a eficiência no controle das plantas daninhas. Objetivou-se com este trabalho avaliar os processos de sorção e dessorção do ametryn em quatro solos brasileiros: Latossolo Vermelho-Amarelo (LVA, Latossolo Vermelho-Amarelo húmico (LVAh, Latossolo Vermelho (LV e Latossolo Amarelo (LA, com diferentes valores de pH. Para isso, utilizou-se o método Batch Equilibrium em condições controladas de laboratório e análise por cromatografia líquida de alta eficiência, com detector UV-Vis a 245 nm. Considerando os valores da constante de Freundlich modificada (K'f, verificou-se, entre os solos estudados, a ordem crescente de sorção do ametryn: LV pH 6,06 Knowledge of herbicide retention processes in soil is fundamental to predict leaching potential, degradation, and weed control efficiency. The objective of this study was to evaluate the processes of sorption and desorption of ametryn in four Brazilian soils: Red-Yellow Latosol (LVA, Red-Yellow humic Latosol (LVAh, Red Latosol (LV, and Yellow Latosol (LA, with different pH values. Thus, the method "Batch Equilibrium" was applied under controlled laboratory conditions, and analysis by high performance liquid chromatography using UV-Vis detector at 245 nm. Considering the values of the modified Freundlich constant (K'f, the following increasing sorption order of ametryn was verified: LV pH 6.06 <5.00 LV pH <6.30 LA pH <6.11 pH LVA sorption and desorption, and that soils with higher organic matter content showed the highest rates of sorption, besides smaller percentages of desorption, indicating the occurrence of hysteresis.

Mucilage from seeds of chia (Salvia hispanica L.) used as soil conditioner; effects on the sorption-desorption of four herbicides in three different soils.

Science.gov (United States)

Di Marsico, A; Scrano, L; Amato, M; Gàmiz, B; Real, M; Cox, L

2018-06-01

The objective of this work was to determine the effect of the mucilage extracted from Chia seeds (Salvia hispanica L.) as soil amendment on soil physical properties and on the sorption-desorption behaviour of four herbicides (MCPA, Diuron, Clomazone and Terbuthylazine) used in cereal crops. Three soils of different texture (sandy-loam, loam and clay-loam) were selected, and mercury intrusion porosimetry and surface area analysis were used to examine changes in the microstructural characteristics caused by the reactions that occur between the mucilage and soil particles. Laboratory studies were conducted to characterise the selected herbicides with regard their sorption on tested soils added or not with the mucilage. Mucilage amendment resulted in a reduction in soil porosity, basically due to a reduction in larger pores (radius>10μm) and an important increase in finer pores (radius<10μm) and in partcles' surface. A higher herbicide sorption in the amended soils was ascertained when compared to unamended soils. The sorption percentage of herbicides in soils treated with mucilage increased in the order; sandy-loamDesorption of the herbicides was highly inhibited in the soils treated with mucilage; only Terbuthylazine showed a slight desorption in the case of loam and clay loam-soils. This study leads to the conclusion that mucilage from Chia seeds used as soil conditioner can reduce the mobility of herbicides tested in agricultural soils with different physico-chemical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Sorption and desorption of remazol yellow by a Fe-zeolitic tuff

International Nuclear Information System (INIS)

Solache R, M. J.; Villalva C, R.; Diaz N, M. C.

2010-01-01

The adsorption of remazol yellow from aqueous solution was evaluated using a Fe-zeolitic tuff. The adsorbent was characterized by scanning electron microscopy, IR spectroscopy and X-ray diffraction. Sorption kinetic and isotherms were determined and the adsorption behavior was analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results, indicating chemisorption on a heterogeneous material. The regeneration of the material was best accomplished by using a H 2 O 2 solution. The sorption capacity of the Fe-zeolitic tuff increased when the saturated samples were treated with a H 2O2 or FeCl 3 solution. (Author)

Sorption and desorption of remazol yellow by a Fe-zeolitic tuff

Energy Technology Data Exchange (ETDEWEB)

Solache R, M. J. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Villalva C, R.; Diaz N, M. C., E-mail: marcos.solache@inin.gob.m [Instituto Tecnologico de Toluca, Division de Estudios del Posgrado, Av. Tecnologico s/n, Ex-Rancho La Virgen, 52140 Metepec, Estado de Mexico (Mexico)

2010-07-01

The adsorption of remazol yellow from aqueous solution was evaluated using a Fe-zeolitic tuff. The adsorbent was characterized by scanning electron microscopy, IR spectroscopy and X-ray diffraction. Sorption kinetic and isotherms were determined and the adsorption behavior was analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results, indicating chemisorption on a heterogeneous material. The regeneration of the material was best accomplished by using a H{sub 2}O{sub 2} solution. The sorption capacity of the Fe-zeolitic tuff increased when the saturated samples were treated with a H{sub 2O2} or FeCl{sub 3} solution. (Author)

Investigation into kinetics of sorption of some radionuclides by mixed sorbents based on amorphous niobium phosphate

International Nuclear Information System (INIS)

Belkina, R.M.; Sukharev, Yu.I.; Egorov, Yu.V.; Plotnikov, V.I.

1977-01-01

A study has been made of kinetics of sorption of radionuclides 110 Ag, 60 Co, and 51 Cr by samples of amorphous stoichiometric niobium (5) phosphate. Ratios of the concentration conductivity to the mean radius of sorbent particles were calculated which are proportional to diffusivities. Increased specificity towards Cr 3+ ions of samples of ion exchangeable niobium phosphate containing cerium and treated with 0.1N HCl was established. This effect was explained by formation and subsequent destruction of the copolymer oxo-ol matrix of niobium and cerium, as a result of which a gel is formed with mosaic structure being favourable for sorption of three-charged ions

Sorbent application on the base of chitosan for radionuclides separation

International Nuclear Information System (INIS)

Pivarciova, L.

2016-01-01

Radioactive waste contains enormous amounts of radionuclides, which pollute the environment and can cause serious chemical and radiological toxicity threats to lower and higher living organism. Alternative process for the removal of heavy metal ions and radionuclides is sorption, which utilizes various certain natural materials of biological origin. Amino-polysaccharide-based sorbents e.g. chitosan represent suitable materials for binding of metal oxo-anion species because of numerous functional groups -OH and -NH_2 because of their suitable H-bond donor and acceptor sites. The sorbents on the base chitosan prepared through chemical modification were used for removal and separation certain radionuclides from aqueous media. The aim of this work was the study of physicochemical properties of prepared sorbents. The specific surface of sorbents was characterized with BET methods. Point of zero charge was identified with potentiometric titration. The size of particles and shape of sorbents were determined by scanning electron microscope. The sorption experiments for selected radionuclides were conducted under static and dynamic conditions. The effect of various parameters on the sorption "9"9"mTc, "6"0Co and the effect of pH on the separation of radionuclide mixture in the solution were studied. (author)

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

DEFF Research Database (Denmark)

Arthur, Emmanuel; Tuller, Markus; Moldrup, Per

2016-01-01

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

Simulation of radionuclide chemistry and sorption characteristics in the geosphere by artificial intelligence technique

International Nuclear Information System (INIS)

Liu Shangjyh; National Tsing Hua Univ., Hsinchu; Wang Shigang; Ho Liwei

1988-01-01

An expert system operated in a personal computer is employed to simulate chemistry and sorption phenomena of radionuclides in the geosphere. The system handles both qualitative and quantitative analyses primarily for the actinides and fission products. The system also incorporates data bases of several groundwater and rock types with mineral and chemical compositions, the distribution coefficients of nuclides for minerals, etc. The decision rule base facilitates this system to carry out the reasoning procedures to predict the solubility-limiting phase, solute species, oxidation states and possible complex formations of radionuclides, as well as to calculate the distribution coefficients and retardation factors in a geological formation, provided that the essential groundwater and host rock information are available. It is concluded that this device of artificial intelligence provides a vehicle to accumulate developed human knowledge and serves as a tool not only for simulating the complicated radionuclide behaviour in the geosphere, but also for instructional or educational purpose in this field. (orig.)

Influence of fracture networks on radionuclide transport from solidified waste forms

Energy Technology Data Exchange (ETDEWEB)

Seetharam, S.C., E-mail: suresh.seetharam@sckcen.be [Performance Assessments Unit, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK CEN), Boeretang 200, B-2400 Mol (Belgium); Perko, J.; Jacques, D. [Performance Assessments Unit, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK CEN), Boeretang 200, B-2400 Mol (Belgium); Mallants, D. [CSIRO Land and Water, Waite Road – Gate 4, Glen Osmond, SA 5064 (Australia)

2014-04-01

Highlights: • Magnitude of peak radionuclide fluxes is less sensitive to the fracture network geometry. • Time of peak radionuclide fluxes is sensitive to the fracture networks. • Uniform flow model mimics a limiting case of a porous medium with large number of fine fractures. • Effect of fracture width on radionuclide flux depends on the ratio of fracture to matrix conductivity. • Effect of increased dispersivity in fractured media does not always result in a lower peak flux for specific fracture networks due to higher concentrations adjacent to the fracture plane. - Abstract: Analysis of the effect of fractures in porous media on fluid flow and mass transport is of great interest in many fields including geotechnical, petroleum, hydrogeology and waste management. This paper presents sensitivity analyses examining the effect of various hypothetical fracture networks on the performance of a planned near surface disposal facility in terms of radionuclide transport behaviour. As it is impossible to predict the initiation and evolution of fracture networks and their characteristics in concrete structures over time scales of interest, several fracture networks have been postulated to test the sensitivity of radionuclide release from a disposal facility. Fluid flow through concrete matrix and fracture networks are modelled via Darcy's law. A single species radionuclide transport equation is employed for both matrix and fracture networks, which include the processes advection, diffusion, dispersion, sorption/desorption and radioactive decay. The sensitivity study evaluates variations in fracture network configuration and fracture width together with different sorption/desorption characteristics of radionuclides in a cement matrix, radioactive decay constants and matrix dispersivity. The effect of the fractures is illustrated via radionuclide breakthrough curves, magnitude and time of peak mass flux, cumulative mass flux and concentration profiles. For the

Influence of fracture networks on radionuclide transport from solidified waste forms

International Nuclear Information System (INIS)

Seetharam, S.C.; Perko, J.; Jacques, D.; Mallants, D.

2014-01-01

Highlights: • Magnitude of peak radionuclide fluxes is less sensitive to the fracture network geometry. • Time of peak radionuclide fluxes is sensitive to the fracture networks. • Uniform flow model mimics a limiting case of a porous medium with large number of fine fractures. • Effect of fracture width on radionuclide flux depends on the ratio of fracture to matrix conductivity. • Effect of increased dispersivity in fractured media does not always result in a lower peak flux for specific fracture networks due to higher concentrations adjacent to the fracture plane. - Abstract: Analysis of the effect of fractures in porous media on fluid flow and mass transport is of great interest in many fields including geotechnical, petroleum, hydrogeology and waste management. This paper presents sensitivity analyses examining the effect of various hypothetical fracture networks on the performance of a planned near surface disposal facility in terms of radionuclide transport behaviour. As it is impossible to predict the initiation and evolution of fracture networks and their characteristics in concrete structures over time scales of interest, several fracture networks have been postulated to test the sensitivity of radionuclide release from a disposal facility. Fluid flow through concrete matrix and fracture networks are modelled via Darcy's law. A single species radionuclide transport equation is employed for both matrix and fracture networks, which include the processes advection, diffusion, dispersion, sorption/desorption and radioactive decay. The sensitivity study evaluates variations in fracture network configuration and fracture width together with different sorption/desorption characteristics of radionuclides in a cement matrix, radioactive decay constants and matrix dispersivity. The effect of the fractures is illustrated via radionuclide breakthrough curves, magnitude and time of peak mass flux, cumulative mass flux and concentration profiles. For the

Study of sorption of technetium on pyrrhotine

International Nuclear Information System (INIS)

Shen Dong; Fan Xianhua; Su Xiguang; Zeng Jishu

2001-01-01

The sorption behaviors of technetium on pyrrhotine are studied with batch experiment and dilute sulfuric acid is used to dissolve the technetium adsorbed on pyrrhotine. Sorption and desorption experiment are performed under aerobic and anaerobic conditions (inert gas box). The results show that a significant sorption of technetium on pyrrhotine is found under aerobic and anaerobic conditions, and the sorption on the mineral is supposed to be due to the reduction of TcO 4 - to insoluble TcO 2 ·nH 2 O. Desorption process of the sorbed technetium into dilute sulfuric acid is found to be different under aerobic and anaerobic conditions. On addition of H 2 O 2 to the leach solution a sudden increase of the technetium concentration is observed

Capacity study of sorption of radionuclides 137Cs, 233U, 75Se and 60Co in concrete and mortar

International Nuclear Information System (INIS)

Rojo, H.; Garcia-Gutierrez, M.; Missana, T.; Mingarro, M.; Alonso, U.; Morejon, J.; Gil, P.; Lopez, T.

2010-01-01

In this paper we consider and mortar similar in composition to those used in the storage of radioactive waste of low and intermediate level of the Cabril (Cordoba) and presents the results of tests of selected radionuclides sorption.

Sorption equilibria of ethanol on cork.

Science.gov (United States)

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

2013-06-05

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

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Sorption of actinides onto nanodiamonds

Energy Technology Data Exchange (ETDEWEB)

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

2015-06-01

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

Sorption of actinides onto nanodiamonds

International Nuclear Information System (INIS)

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

2015-01-01

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

Sorption mechanisms and sorption models

International Nuclear Information System (INIS)

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

2004-01-01

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

Batch experiments for assessing the sorption/desorption characteristics of 152Eu in systems of loose sediments and water containing humic acids

International Nuclear Information System (INIS)

Klotz, D.

2001-01-01

The 152 Eu distribution coefficients of the sorption and desorption of non-binding loose sediments of different grain sizes are investigated using a groundwater of tertiary lignite from Northern Germany which contains high concentrations of humic acids. The batch experiments were carried out with a ratio of 2.5cm 3 /g of solution volume to sediment mass, without mixing [de

Contribution to the study of sorption mechanisms at solid-liquid interfaces: application to the cases of apatites and oxy-hydroxides; Contribution a l'etude des mecanismes de sorption aux interfaces solide-liquide: application aux cas des apatites et des oxy-hydroxydes

Energy Technology Data Exchange (ETDEWEB)

Duc, M

2002-11-15

Sorption-desorption phenomena play an important role in the transport of toxic and radioactive elements in surface and underground water in contact with solid matter. Selenium, which is one of the long-lived radionuclides present in radioactive waste, is characterized by several oxidation states and by anionic species in aqueous solutions. In order to predict its transport, we need a good knowledge of its sorption processes. We have studied the sorption of Se(IV) and Se(VI) on two types of solids present in natural media or which have been proposed as additives to active barriers: hydroxy-apatites, fluoro-apatite and iron oxi-hydroxides (goethite and hematite). Sorption mechanisms have been studied through an approach including several different and complementary methods: titrimetry, zeta-metry, scanning and transmission electron microscopy, infrared spectroscopy, X-ray diffraction, X-ray photo electron spectroscopy, etc... Results showed that Se(VI) is much less sorbed than Se(VI) on both types of solids. For Se(IV) the sorption mechanisms are different for iron oxides and apatites. On oxides, sorption increases when pH decreases. It can be interpreted by a surface complexation model, essentially through an inner sphere complex (monodentate or bidentate). Modelling of Se sorption curves was performed after the determination of acido-basic properties of oxides. However, the determination of the intrinsic properties of oxides is disturbed by several parameters identified as impurities, evolution of the solid in solution, kinetic and solubility of the solid. For apatites, selenium sorption proceeds by exchange with superficial groups, with a maximum of fixation at approximately pH 8. Thanks to XPS measurements and the elaboration of a mathematical model, we could determine the depth of penetration of both selenium and cadmium on apatites. (author)

Modeling Fission Product Sorption in Graphite Structures

International Nuclear Information System (INIS)

Szlufarska, Izabela; Morgan, Dane; Allen, Todd

2013-01-01

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

Sorption of radioactive technetium on pyrrhotine

International Nuclear Information System (INIS)

Shen, D.; Fan, X.H.; Su, X.G.; Zeng, J.S.; Dong, Y.

2002-01-01

The sorption behavior of technetium on pyrrhotine was studied with batch experiments and diluted sulfuric acid (less than 2.88 mol/l) was used to dissolve the technetium adsorbed on pyrrhotine. A significant sorption of technetium on pyrrhotine was observed under aerobic and anaerobic conditions, and the sorption on the mineral was supposed to be due to the reduction of TcO 4 - to insoluble TcO 2 x nH 2 O. Sorbed technetium on the mineral could be desorbed by diluted sulfuric acid. The maximum desorption ratio under aerobic conditions was much higher than that of under anaerobic conditions, meanwhile, the desorption rates under anaerobic conditions were higher than that of under aerobic conditions in the initial stage of the experiments. (author)

Sorption of radionuclides on inorganic sorbents

International Nuclear Information System (INIS)

Rajec, P.; Matel, L.

1995-01-01

The sorption of cesium, strontium, plutonium and americium from water solution on natural zeolite, clay minerals, synthetic zeolites and ferrocyanides in silica gel matrix was studied. The same experiments but with synthetic zeolites irradiated by the dose 100 kGy proved no change in sorption properties. 1 tab., 4 refs

Research summary: characterization of radionuclide and moisture movement through arid region sediments

International Nuclear Information System (INIS)

Gee, G.W.; Jones, T.L.; Rai, D.

1981-09-01

This project has the task of understanding the movement of moisture and radionuclides under arid region conditions. This understanding will be used to maximize the isolation of low level waste from the environment. Specific objectives include: field monitoring of moisture and radionuclide transport at an arid region site; assessment of the interaction of radionuclides with unsaturated soils in arid regions; evaluation of radionuclide transport in unsaturated soils by appropriate mathematical models; and assessment of the importance of upward migration of radionuclides by evaporation and diffusion processes. The Burial Waste Test Facility (BWTF) located near Richland, Washington, on the Department of Energy (DOE) Hanford Site has been monitored for water content and radionuclide transport for the past two years. Tritium movement has been observed to depths of 7.6 m in both irrigated and nonirrigated lysimeters. Laboratory tests were conducted to determine how leachate from uranium tailings interacts with geologic materials. Acid leach tailings and tailings solution and geologic materials typical of mill site tailing pits were physically and chemically characterized. Investigation was made of the sorption characteristics of heavy metals and radionuclides on the geologic materials under low and neutral pH conditions. From solubility tests conducted at Pacific Northwest Laboratory, thermodynamic considerations predicted that for the Eh-pH range of natural aqueous environment, the dominant species of Pu is likely to be Pu(V) in relatively oxidizing environments and Pu(III) in reducing environments. Radionuclide transport through unsaturated media was investigated by using two solute transport models to describe the transport of tritium and strontium-85 in laboratory columns. A new approach was used to analyze radon emissions from uranium mill tailings

Development of autoradiographic method for measuring sorption of radionuclides on natural fracture surfaces

International Nuclear Information System (INIS)

Muuronen, S.

1983-11-01

On the basis of positive results about sorption of radionuclides in rock thin sections an autoradiographic method applicable for measurement sorption of radionuclides on rough rock surfaces was developed. There is no method available because 1) a plane film cannot be used because due to the roughness of rock surfaces 2) rock samples used in this investigation cannot be studied with microscopes and 3) autoradiogram cannot be studied fixed on the surface of a rock sample because the colours of the minerals in the sample will interfere with the interpretation. This report discusses experimental work done to find an useful proedure. In the development of the method main emphasis was put on investigation of the following steps: 1) preparation of the sample for equilibration and spiking; 2) properties of the covering paint for the rock surface and 3) testing of autoradiographic methods using different nuclear emulsions. As the result of these experiments promising autoradiograms with gel emulsion for sawed rock surfaces and with stripping film for rough rock surfaces were obtained. The mineralogic disribution of sorbed activity is easily seen in autoradiograms. Much work must still be done to get reliable quantitative information from autoradiograms. For developing of the autoradiographic method sawed plane rock samples of quartz feldspar intergrowth, pegmatite and limestone were used. In addition core samples of tonalite and mica gneiss from Olkiluoto were utilized. The distribution coefficients (Ksub(a)) obtained for cesium were 560 x 10 -4 and 620 x 10 -4 m 3 /m 2 for tonalite and mica gneiss, respectively. The results are little higher but of the same order of magnitude as obtained by the autoradiographic method using rock thin sections and by the batch method using crused samples. The natural fracture surface sorption study is a logical step in determining the scaling factor from laboratory to field studies. Field data will be needed to determine whether laboratory

Radionuclide fixation mechanisms in rocks

International Nuclear Information System (INIS)

Nakashima, S.

1991-01-01

In the safety evaluation of the radioactive waste disposal in geological environment, the mass balance equation for radionuclide migration is given. The sorption of radionuclides by geological formations is conventionally represented by the retardation of the radionuclides as compared with water movement. In order to quantify the sorption of radionuclides by rocks and sediments, the distribution ratio is used. In order to study quantitatively the long term behavior of waste radionuclides in geological environment, besides the distribution ratio concept in short term, slower radionuclide retention reaction involving mineral transformation should be considered. The development of microspectroscopic method for long term reaction path modeling, the behavior of iron during granite and water interaction, the reduction precipitation of radionuclides, radionuclide migration pathways, and the representative scheme of radionuclide migration and fixation in rocks are discussed. (K.I.)

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

International Nuclear Information System (INIS)

Harvey, K.B.

1997-02-01

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

Contribution to the study of sorption mechanisms at solid-liquid interfaces: application to the cases of apatites and oxy-hydroxides

International Nuclear Information System (INIS)

Duc, M.

2002-11-01

Sorption-desorption phenomena play an important role in the transport of toxic and radioactive elements in surface and underground water in contact with solid matter. Selenium, which is one of the long-lived radionuclides present in radioactive waste, is characterized by several oxidation states and by anionic species in aqueous solutions. In order to predict its transport, we need a good knowledge of its sorption processes. We have studied the sorption of Se(IV) and Se(VI) on two types of solids present in natural media or which have been proposed as additives to active barriers: hydroxy-apatites, fluoro-apatite and iron oxi-hydroxides (goethite and hematite). Sorption mechanisms have been studied through an approach including several different and complementary methods: titrimetry, zeta-metry, scanning and transmission electron microscopy, infrared spectroscopy, X-ray diffraction, X-ray photo electron spectroscopy, etc... Results showed that Se(VI) is much less sorbed than Se(VI) on both types of solids. For Se(IV) the sorption mechanisms are different for iron oxides and apatites. On oxides, sorption increases when pH decreases. It can be interpreted by a surface complexation model, essentially through an inner sphere complex (monodentate or bidentate). Modelling of Se sorption curves was performed after the determination of acido-basic properties of oxides. However, the determination of the intrinsic properties of oxides is disturbed by several parameters identified as impurities, evolution of the solid in solution, kinetic and solubility of the solid. For apatites, selenium sorption proceeds by exchange with superficial groups, with a maximum of fixation at approximately pH 8. Thanks to XPS measurements and the elaboration of a mathematical model, we could determine the depth of penetration of both selenium and cadmium on apatites. (author)

Study of 137Cs e 60Co sorption in sediments from Saco de Piraquara de Fora, Angra dos Reis and its application for environmental monitoring

International Nuclear Information System (INIS)

Ferreira, Ingryd Marques

2016-01-01

Both the suspended solid particles and the bed sediments sorb radionuclides, released in water systems. Sorption is usually represented mathematically by the distribution coefficient that is based in equilibrium between phases. Here the adsorption/desorption kinetics of 60 Co and 137 Cs in sea water were simulated by batch equilibrium experiments with sediments in two points (PT - 01, PT - 02) from Saco de Piraquara de Fora inlet (SPF). For both radionuclides, partition coefficient values (Kd) for the sampling point PT - 02 (509 and 385 L/kg for 60 Co and 137 Cs, respectively) were higher than the values determined for PT - 01 one (426 and 182 L/kg for 137 Cs and 60 Co, respectively). The higher values of Kd of PT-02 reflects the higher CEC (71,4 cmolc.dm 3 ) and content of mud < 63 μm (87%) when compared to PT-01 (CEC of 39,5 cmol c .dm 3 ) and mud (55%). In comparison with the values reported in the literature, the found Kd values are low, which may be related to the predominance of kaolinite, which is a clay of low sorption capacity. The Kd values with an increase in temperature of 23 deg C to 27 deg C were similar ( 60 Co in PT-02 and 137 Cs in both sediment) or 27 ° C values were higher ( 60 Co the PT-01). With increasing temperature to 31 °C Kd values for the two radionuclides showed a decrease. However, increasing temperature increases the desorption of the two radionuclides for both sediments The sorption process is spontaneous and favorable for both sediments and the model of sorption can be fitted by both Freundlich and Langmuir sorption isotherms. The maximum amount of 60 Co that can be sorbed on sediments were 1,64 10 -5 moles/g (4,12 10 10 Bq/g) and 2,79 10 -5 moles/g (7,03 10 10 Bq/g) to PT-01 and PT-02, respectively, and of 137 Cs 1,99 10 -6 moles/g (9,70 10 8 Bq/g) and 6,60 10 -6 mol/g (2,87 10 9 Bq/g ) to PT-01 and PT-02. Two areas in SPF can potentially accumulate 137 Cs: sediments located near the effluent discharge and the area located north

Radionuclide sorption on granitic drill core material

International Nuclear Information System (INIS)

Eriksen, T.E.; Locklund, B.

1987-11-01

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

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

Directory of Open Access Journals (Sweden)

Amel Saad

2014-01-01

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

Sorption of DNA by diatomite-Zn(II) embedded supermacroporous monolithic p(HEMA) cryogels.

Science.gov (United States)

Tozak, Kabil Özcan; Erzengin, Mahmut; Sargin, Idris; Ünlü, Nuri

2013-01-01

In this study, the DNA sorption performance of diatomite-Zn(II) embedded supermacroporous monolithic p(HEMA) cryogels were investigated for the purpose of designing a novel adsorbent that can be utilized for DNA purification, separation and immunoadsorption studies such as removal of anti-dsDNA antibodies from systemic lupus erythematosus (SLE) patient plasma. Poly(2-hydroxyethyl methacrylate) [p(HEMA)]-based monolithic cryogel column embedded with Zn(2+)-diatomite particles was prepared by free radical cryo-copolymerization of 2-hydroxyethyl methacrylate (HEMA) with N,N'-methylene-bis-acrylamide (MBAAm). The polymerization reaction was initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) pair in an ice bath. After thawing, the monolithic composite cryogels were used for affinity sorption and then subsequent desorption of DNA molecules from aqueous solutions. Diatomite (DA) particles were characterized by XRF and BET method. The characterization of composite cryogel was done through SEM imaging. The effects of pH of the solution, initial DNA concentration, ionic strength, temperature and flow rates on adsorption were investigated to determine the optimum conditions for adsorption/desorption experiments. The particle embedding procedure was shown to yield significantly enhanced adsorption of DNA on the adsorbent. Furthermore, considering its excellent bio-compatibility, p(HEMA) cryogels are promising a candidate for further DNA sorption studies.

Role of soil micro-organisms in the sorption of radionuclides in organic systems

International Nuclear Information System (INIS)

Parekh, N.R.; Potter, E.D.; Poskitt, J.M.; Dodd, B.A.; Sanchez, A.

2004-01-01

Although the fraction of radionuclides linked to soil organic matter and soil microorganisms may be relatively small when compared to the amount bound to the mineral constituents, (mostly irreversibly bound), this fraction is of great importance as it remains readily exchangeable and is thus available for plant uptake. Many studies have measured the uptake of radionuclides by organic soils but the role of soil micro-organisms may have been masked by the presence of even small amounts of clay minerals occurring in these soils. We have carried out a series of experiments using a biologically active, 'mineral-free' organic soil produced under laboratory conditions, to determine the potential of soil micro-organisms to accumulate radionuclides Cs-134 and Sr-85. Biological uptake and release was differentiated from abiotic processes by comparing experimental results with inoculated and non-inoculated sterile organic material. We have investigated the role of different clay minerals, competing potassium and calcium ions, and changes in temperature on the sorption of Cs and Sr isotopes. The results from studies so far show conclusively that living components of soil systems are of primary importance in the uptake of radionuclides in organic material, microorganisms also influence the importance of chemical factors (e.g. adsorption to clay minerals) which may play a secondary role in these highly organic systems. In further experiments we hope to define the precise role of specific soil micro-organisms in these organic systems. (author)

Preparation, characterization and application of superparamagnetic iron oxide nanoparticles modified with natural polymers for removal of {sup 60}Co-radionuclides from aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Sharaf El-Deen, Gehan E. [Atomic Energy Authority, Cairo (Egypt). Radioactive Waste Management Dept.; Imam, Neama G. [Atomic Energy Authority, Cairo (Egypt). Experimental Physics Dept.; Elettra, Sincrotrone, Trieste (Italy); Ayoub, Refaat R. [Atomic Energy Authority, Cairo (Egypt). Nuclear Chemistry Dept.

2017-04-01

Superparamagnetic iron oxide nanoparticles (IO-MNPs) coated with natural polymers, starch (IO-S MNPs) and dextrin (IO-D MNPs), were synthesized by modified co-precipitation method. IO and hybrid-IO-MNPs were characterized by XRD, SEM, HRTEM, FT-IR spectroscopy, vibrating sample magnetometer (VSM) and zeta potential (ZP). IO-S MNPs and IO-D MNPs have IO core-shell structure with core of 10.8 nm and 13.8 nm and shell of 7.5 nm and 5.9 nm, respectively. The efficiency of the hybrid IO-MNPs for sorption of {sup 60}Co(II)-radionuclides from aqueous solution was investigated under varying experimental conditions. Kinetic data were described well by pseudo-second-order mode, sorption isotherms were fitted quite with Freundlich model with maximum adsorption capacity 36.89 (mmol.g{sup -1})/(L.mmol{sup -1}){sup n} for IO-S MNPs and 24.9 (mmol.g{sup -1})/(L.mmol{sup -1}){sup n} for IO-D MNPs. Sorption of {sup 60}Co-radionuclides by IO-S MNPs was suppressed with salinity and most of the adsorbed {sup 60}Co onto IO-S MNPs could be remove with 0.1 M HCl solution. IO-S MNPs exhibits superparamagnetic properties, easier separation according to higher saturation magnetization (47 emu/g) and better adsorption for {sup 60}CO-radionuclides than IO-D MNPs.

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

International Nuclear Information System (INIS)

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

2011-02-01

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

Moisture sorption–desorption characteristics and the corresponding thermodynamic properties of carvedilol phosphate

Directory of Open Access Journals (Sweden)

Ravikiran Allada

2017-01-01

Full Text Available Aims: Carvedilol phosphate (CDP is a nonselective beta-blocker used for the treatment of heart failures and hypertension. In this work, moisture sorption–desorption characteristics and thermodynamic properties of CDP have been investigated. Materials and Methods: The isotherms were determined using dynamic vapor sorption analyzer at different humidity conditions (0%–90% relative humidity and three pharmaceutically relevant temperatures (20°C, 30°C, and 40°C. The experimental sorption data determined were fitted to various models, namely, Brunauer–Emmett–Teller; Guggenheim-Anderson-De Boer (GAB; Peleg; and modified GAB. Isosteric heats of sorption were evaluated through the direct use of sorption isotherms by means of the Clausius-Clapeyron equation. Statistical Analysis Used: The sorption model parameters were determined from the experimental sorption data using nonlinear regression analysis, and mean relative percentage deviation (P, correlation (Correl, root mean square error, and model efficiency were considered as the criteria to select the best fit model. Results: The sorption–desorption isotherms have sigmoidal shape – confirming to Type II isotherms. Based on the statistical data analysis, modified GAB model was found to be more adequate to explain sorption characteristics of CDP. It is noted that the rate of adsorption and desorption is specific to the temperature at which it was being studied. It is observed that isosteric heat of sorption decreased with increasing equilibrium moisture content. Conclusions: The calculation of the thermodynamic properties was further used to draw an understanding of the properties of water and energy requirements associated with the sorption behavior. The sorption–desorption data and the set of equations are useful in the simulation of processing, handling, and storage of CDP and further behavior during manufacture and storage of CDP formulations.

Radionuclide transport and retardation in tuff

International Nuclear Information System (INIS)

Vine, E.N.; Bayhurst, B.P.; Daniels, W.R.; DeVilliers, S.J.; Erdal, B.R.; Lawrence, F.O.; Wolfsberg, K.

1980-01-01

Batch measurements provide an understanding of which experimental variables are important. For example, sorption ratios vary little with particle size (and surface area); however, groundwater composition and rock composition are quite important. A general correlation has been identified between mineralogy (major phases) and degree of sorption for strontium, cesium, and barium. Although these are approximate, a more detailed analysis may be possible as more samples are studied and the data base increased. Data from crushed tuff columns indicate that, except in simple cases where sorption coefficients are relatively low, and ion-exchange equilibria not only exist but are the dominant mechanism for removal of radioisotopes from solution, the simple relation between the sorption ratio R/sub d/ (or K/sub d/) and the relative velocity of radionuclides with respect to groundwater velocity may be insufficient to permit accurate modeling of the retardation of radionuclides. Additional work on whole core columns and larger blocks of intact material is required to better understand radionuclide sorption and transport through rock

Pesticide sorption and desorption from soils having different land use

Directory of Open Access Journals (Sweden)

Ismael Madrigal Monárrez

2008-09-01

Full Text Available This study was carried out within the framework of a multidisciplinary project for evaluating buffer zones for combating pesticide contamination of surface water. Such areas are effective in removing pesticides transported by run-off; however, little information is available about the fate of the pesticides so intercepted. Two herbicides having contrasting properties (isoproturon, moderately hydrophobic (log Kow = 2.5, diflufenican, strongly hydrophobic (log K ow = 4.9 and isopropylaniline (an isoproturon metabolite were used for characterising sorption and desorption from soil having three different land uses: grass buffer strip, woodland and cultivated plot. The experiments were carried out in controlled laboratory conditions using isoproturon labelled with 14C in the benzene ring. The results demonstrated that diflufenican and isopropilaniline retention was more significant than isoproturon in three soils. The three molecules’ Kd values revealed that isoproturon and diflufenicanil retention was more important in woodland soil where carbon content was more significant (ZB 0-2: Kd IPU = 15.1 Ls kg-1; Kd DFF = 169.2 Ls kg-1. Isopropilanilina Kd was higher in grass buffer strip soil (BE 0-2: Kd IPA = 53.1 L kg-1. These differences were related to different organic matter content and nature according to the type of land use.

Modeling and Prediction of Soil Water Vapor Sorption Isotherms

DEFF Research Database (Denmark)

Arthur, Emmanuel; Tuller, Markus; Moldrup, Per

2015-01-01

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

The European programme boris (bioavailability of radionuclides in soils): a global analysis of results

International Nuclear Information System (INIS)

Tamponnet, C.; Martin-Garin, A.; Gonzr, M.A.; Parekh, N.; Vallejo, R.; Sauras, T.; Casadesus, J.; Plassard, C.; Staunton, S.; Norden, M.; Avila, R.; Shaw, G.; Wells, C.

2004-01-01

The ability to predict the consequences of an accidental release of radioactive nuclides relies mainly on the level of understanding of the mechanisms involved in radioactive nuclides interactions with different components of agricultural and natural ecosystems and their formalization into predictive models. Numerous studies and databases about contaminated agricultural and natural areas have been obtained but their use to enhance our prediction ability has been largely limited by their unresolved variability. Such variability seems to stem from an incomplete knowledge about radioactive nuclide interactions with the soil matrix, soil moisture, biological elements in the soil and additional pollutants, which may be found in such soils. In this project, we investigated mainly the role of the biological elements (plants, mycorrhizas, microbes) in: radioactive nuclide sorption/desorption in soils and radioactive nuclide uptake/release by plants. Because of the importance of the chemical nature of the involved radioactive nuclides, we followed the bioavailability of three radioactive nuclides: caesium, strontium, and technetium. The role of one additional non-radioactive pollutant (copper) has been scrutinised. Role of microorganisms (K d for caesium and strontium in organic soils is much greater in the presence of microorganisms than in their absence), plant physiology (changes in plant physiology affect radionuclide uptake by plants), the presence of mycorrhizal fungi (interferes with the uptake of radionuclides by plants), have been demonstrated. Knowledge acquired from these experiments has been incorporated into two mechanistic models CHEMFAST (a soil Column Heuristic Model of radionuclide Fixation and Solution Transport) and BIORUR specifically modelling radioactive nuclide sorption/desorption from soil matrices and radioactive nuclide uptake by/release from plants. These mechanistic models have been incorporated into an assessment model to enhance its prediction

Sorption of americium and neptunium by deep-sea sediments

International Nuclear Information System (INIS)

Higgo, J.J.W.; Rees, L.V.C.; Cronan, D.S.

1983-01-01

The sorption and desorption of americium and neptunium by a wide range of deep-sea sediments from natural sea water at 4 0 C has been studied using a carefully controlled batch technique. All the sediments studied should form an excellent barrier to the migration of americium since distribution coefficients were uniformly greater than 10 5 and the sorption-desorption reaction may not be reversible. The sorption of neptunium was reversible and, except for one red clay, the distribution coefficients were greater than 10 3 for all the sediments investigated. Nevertheless the migration of neptunium should also be effectively retarded by most deep-sea sediments even under relatively oxidizing conditions. The neptunium in solution remained in the V oxidation state throughout the experiments. Under the experimental conditions used colloidal americium was trapped by the sediment and solubility did not seem to be the controlling factor in the desorption of americium. (Auth.)

Radionuclide sorption database for Swiss safety assessment

International Nuclear Information System (INIS)

McKinley, I.G.; Hadermann, J.

1984-10-01

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

Compilation of radionuclide sorption coefficients for performance assessment

International Nuclear Information System (INIS)

Carbol, P.; Engkvist, I.

1997-09-01

The report presents four possible site-specific conditions in Sweden. The different sorption mechanisms applicable to the studied elements together with the K d concept are shortly summarised. The influence of organic substances present in the groundwater on the element's sorption and mobility is also discussed. Criteria for selection of K d values are presented together with sensitivity of the values to pH, E h and salinity. Sorption coefficients are recommended for elements in the repository with half-life above 5.3 years. The elements reviewed are: Cs, Sr, Ra, Ln, Ac, Th, Pa, U, Np, Pu, Am, Cm, Co, Ni, Cd, Zr, Nb, Tc, Pd, Ag, Sn, C, I, Cl, Se and Kr. For every element there is a recommendation of a realistic K d value with an uncertainty limit. The selection is based on experimental investigations or chemical analogues. In some cases few or no K d data were found, and it is recommended that sorption studies be performed on elements such as Cd, Pa, Cm, Zr, Nb, Pd, Ag and Sn. The recommended K d values for the different element's sorption on granitic rock, serve as a guidance of the sorption performance

Sorption of radionuclides on hard rocks

International Nuclear Information System (INIS)

Berry, J.A.; Bourke, P.J.; Green, A.; Littleboy, A.K.

1987-09-01

Methods for measuring sorption on hard rocks, particularly of strontium, caesium, neptunium and americium on Darley Dale sandstone and Welsh slate have been investigated. The methods tried included batch tests with crushed rock and tests of simultaneous diffusion and convection with sorption on intact rock. High pressures (800m H 2 O) were used in the convective tests to pump water quickly through the rock samples and to measure high sorptivities in times shorter than those needed in the diffusive methods with intact samples. (author)

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

International Nuclear Information System (INIS)

Rundberg, R.S.

1992-01-01

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

Construction of predictive models for radionuclide sorption applied to radioactive waste deep storage: an overview of the CEA research program

International Nuclear Information System (INIS)

Christophe Poinssot; Etienne Tevissen; Jacques Ly; Michael Descostes; Virginie Blin; Catherine Beaucaire; Florence Goutelard; Christelle Latrille; Philippe Jacquier

2006-01-01

set on the sorption of major ions and radionuclides on many clay minerals and some other mineral phases such as iron oxides. These data allows one to build predictive models of radionuclides sorption on complex rocks. Furthermore, this work is completed by batch Kd measurements on the whole rocks for specific radionuclides in particular in the low concentration domain. In a second approach, the question of compatibility between sorption values obtained with dispersed systems in batch tests, and retardation during a diffusive process in the compacted material, has then to be assessed. Indeed, intact argillaceous rocks and compacted bentonite or cements are complex chemical and physical systems in which the pore water chemistry and the accessibility of retention site are still poorly understood. In that purpose, CEA-DPC is currently developing a full set of experimental means (diffusion cells, columns and μLIBS) dedicated to the direct investigation of radionuclide behavior affected by the coupled effect of sorption and diffusion. Finally, the behaviour of radioactive tracers is currently being validated by the in-situ measurements performed within the URL of Meuse/Haute-Marne with ANDRA. (authors)

Compilation of radionuclide sorption coefficients for performance assessment

Energy Technology Data Exchange (ETDEWEB)

Carbol, P.; Engkvist, I. [PI Chemical Consulting HB, Landvetter (Sweden)

1997-09-01

The report presents four possible site-specific conditions in Sweden. The different sorption mechanisms applicable to the studied elements together with the K{sub d} concept are shortly summarised. The influence of organic substances present in the groundwater on the element`s sorption and mobility is also discussed. Criteria for selection of K{sub d} values are presented together with sensitivity of the values to pH, E{sub h} and salinity. Sorption coefficients are recommended for elements in the repository with half-life above 5.3 years. The elements reviewed are: Cs, Sr, Ra, Ln, Ac, Th, Pa, U, Np, Pu, Am, Cm, Co, Ni, Cd, Zr, Nb, Tc, Pd, Ag, Sn, C, I, Cl, Se and Kr. For every element there is a recommendation of a realistic K{sub d} value with an uncertainty limit. The selection is based on experimental investigations or chemical analogues. In some cases few or no K{sub d} data were found, and it is recommended that sorption studies be performed on elements such as Cd, Pa, Cm, Zr, Nb, Pd, Ag and Sn. The recommended K{sub d} values for the different element`s sorption on granitic rock, serve as a guidance of the sorption performance 87 refs, 18 tabs

The effect of organic amendment on mobility of cesium in tropical soils - The effect of organic amendment on sorption mechanisms for cesium and cobalt in tropical soils

Energy Technology Data Exchange (ETDEWEB)

Wasserman, M.A.V.; Santos-Oliveira, R. [Instituto de Engenharia nuclear/CNEN. Rua Helio de Almeida, 75. Cidade Universitaria - Ilha do Fundao, Rio de Janeiro, RJ. CEP 21941-906 (Brazil); Garcia, R.J.L.; Ferreira, A.C.M.; Rochedo, E.R.R.; Sobrinho, G.A.N. [Instituto de Radioprotecao e Dosimetria/CNEN. Av. Salvador Allende s /no. Rio de Janeiro, RJ. CEP: 22780-160 (Brazil); Perez, D.V. [Centro Nacional de Pesquisa de Solos/EMBRAPA. R. Jardim Botanico, 1024.Rio de Janeiro, RJ, CEP: 22460-000 (Brazil); Wasserman, J.C. [dUFF Network of Environment and Sustainable Development (REMADS-UFF), University Federal Fluminense, Niteroi, RJ (Brazil)

2014-07-01

This work aimed to investigate the mechanisms involved in the sorption of {sup 137}Cs and {sup 60}Co as a function of the physico-chemical properties of some types of Brazilian soils and the changes on the behavior of these radionuclides due to changes in soil properties promoted by organic amendment. The experimental study was conducted in a controlled area, where pots containing different types of soils (Ferralsol, Nitisol and Histosol) and different doses of organic amendment (no amendment; 2 kg.m{sup -2} and 4 kg.m{sup -2}) were spiked with {sup 137}Cs and {sup 60}Co. The organic amendment used in this experiment was obtained in the Unit of Compost of the Organic Material of Pinheiral (RJ, Brazil), where the compost is made up from the leaves swept from the streets of the Pinheiral city. The mobility of these radionuclides in the soil was assessed through sequential chemical extraction and desorption studies as a function of pH. The bioavailability was evaluated through the effective absorption of radionuclide by root crops (Raphanus sativus, L). This study evidenced that the organic amendment plays an important role in the desorption processes of cobalt and cesium, reducing desorption of both nuclides beneath higher organic amendment dose. This behavior was observed in acid conditions as well in alkaline. However extreme acid conditions may mobilize both radionuclides, although cobalt mobility was shown to be more sensitive to low pH than cesium. (authors)

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

Directory of Open Access Journals (Sweden)

Silvio José Ferreira de Souza

2015-03-01

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

Long-term batch study of sorption, transformation and extractability to characterize the fate of the veterinary antibiotic sulfadiazine

Science.gov (United States)

Sittig, Stephan; Kasteel, Roy; Groeneweg, Joost; Vereecken, Harry

2010-05-01

The occurrence of veterinary antibiotic substances in various environmental compartments is of growing concern. Once released into the environment (e.g. via manure), these organic substances can cause changes in the composition of microbial populations, provoke the development and spreading of resistance genes and finally reach the food chain. The substance under study is the veterinary antibiotic sulfadiazine (SDZ), which belongs to the chemical group of the sulfonamides. These compounds are widely applied in animal husbandry. There are hardly any studies on the macroscopic sorption and desorption behaviour in combination with transformation processes, particularly investigating the sorbed fraction. We are conducting long-term batch sorption experiments to characterize the partitioning between the liquid and the solid phases as well as formation of transformation products. A sequential extraction procedure enables us to analyse the composition of the various sorbed fractions. We applied 14C-labelled SDZ in aqueous solution to fresh soil, originating from an agricultural field (silty loam). Adsorption and desorption studies are conducted for the duration of 60 d and 80 d, respectively. Unique setups for single time-steps allow us to trace the development of the partition process between the liquid and the solid phase and also partitioning within the solid phase. The composition of these liquid phases concerning the parent substance and the transformation products is analyzed. Using Radio-HPLC we find at least five transformation products: 4-hydroxy-sulfadiazine (4-OH-SDZ), 4-(2-iminopyrimidin-1(2H)-yl)-aniline (An-SDZ) and additionally three yet unknown products. By means of a sequential extraction, differently strong bound fractions of the compound can be distinguished. Extractions consist of a mild method (0.01 M CaCl2-solution; 24 h) followed by a methanol extraction (4 h). Finally, a residual fraction is gained by microwave extraction at an elevated temperature

Kinetic approach for interactive reactions of radionuclide, bacteria and granitic crushed rock

International Nuclear Information System (INIS)

Kim, Jung Woo; Baik, Min Hoon; Lee, Seung Yeop; Lee, Jae Kwang; Kim, Seung Soo; Oh, Jong Min; Lee, Tae Yup

2011-01-01

For many radionuclides, sorption is an important phenomenon as their migration rates in groundwater are reduced in both engineered barrier and fractured rock matrix. Sorption of radionuclides is strongly dependent on the chemistry of the surrounding groundwater, such as pH, Eh, ionic strength, etc., by changing their valence states (e.g.,). In addition, it is also known that some bacteria can change the mobility and speciation of a radionuclide in groundwater. Biological immobilization mechanisms of radionuclides include precipitation, transformation to less soluble forms and so on. On the other hand, bacteria can also play a role of sorbent for radionuclides. Since bacteria can not only be mobile as a colloid but also be immobile as biofilm in the rock fracture, the bacteria as the sorbents of radionuclides in the groundwater can have both positive and negative effects on the radionuclide migration. In this study, therefore, sorption of radionuclide onto rock surface in the presence of bacteria was investigated via batch experiments. Although sorption equilibrium state can be expected in the transport of weakly sorbing (distribution coefficient, K d -3 m 3 kg -1 ) or strongly adsorbing (K d > ∼4.6 m 3 kg -1 ) nuclides in fractured rock, sorption kinetics needs to be considered in the intermediate range. Therefore, the sorption of radionuclide whose valence state is expected to be changed by biological reduction was evaluated in a kinetic approach

Modeling of radionuclide and heavy metal sorption around low and high pH waste disposal sites at Oak Ridge, Tennessee: Classification review package

International Nuclear Information System (INIS)

Saunders, J.A.

1994-10-01

Modeling of mineral precipitation and metal sorption reactions using MINTEQA2 and the iron oxyhydroxide diffuse-layer model has provided insights into geochemical processes governing contaminant migration from low-level radioactive waste disposal sites at the US Department of Energy's Oak Ridge National Laboratory and Y-12 Plant at Oak Ridge, Tennessee. Both acidic and basic nuclear-fuel reprocessing wastes, locally mixed with decontamination solvents, were disposed of in unlined trenches and lagoons. Model results show that as wastes move toward neutral pH due to reactions with surrounding soils and saprolite, mineral precipitation and sorption can limit the solubility of heavy metals and radionuclides. However, observed contaminant levels in monitoring wells indicate that at least locally, wastes are moving in faults and fractures and are not retarded by sorption reactions along such flow paths. Model results also support previous studies that have indicated organic complexing agents used in decontamination procedures can enhance radionuclide and heavy metal solubility when mixed with nuclear fuel reprocessing wastes. However, complex interactions between metal-organic complexes and mineral surfaces and natural organic matter, biodegradation, and fracture flow complicate the interpretation of contaminant mobility

Experimental studies on the migration of radionuclides of the elements I, Sr, Cs, Co and Pd in the roof rock of the projected waste repository at Gorleben

International Nuclear Information System (INIS)

Klotz, D.; Lang, H.; Moser, H.

1985-07-01

The studies were intended to provide information on the sorptive properties of 15 samples of fine-grain and medium-grain sands with regard to the radionuclides of I, Sr, Cs, Co, and Pd, and on their hydraulic properties. The samples were taken from the geologic formations in the area surrounding the projected waste repository in the Gorleben salt mine, at depth of up to 250 m down from terrain surface, and were analysed by means of column and batch experiments. Further goals were to determine the radionuclide migration as a function of flow velocity of the groundwater, and of sand compactness, as well as the effects of carrier ions and main groundwater contituents. The margins of retardation factors for the various radionuclides are given. One important result of the studies is that it could be expeimentally verified that there is the process of quasi irreversible sorption, i.e. it could be shown that desorption of radionuclides from natural, unconsolidated rock proceeds very much slowlier than sorption, so that this finding is of great significance to the safety assessment of a radioactive waste repository in geologic formations. (orig./HP) [de

A review of sorption of radionuclides under the near- and far-field conditions of an underground radioactive waste repository. Pt. 2

International Nuclear Information System (INIS)

Berry, J.A.

1992-01-01

This report, a bibliography, has been prepared, presenting work carried out world-wide since 1970 on the sorption of radionuclides under near- and far-field conditions. Work has been included where the results are relevant to the disposal of low- and intermediate-level radioactive waste in a cementitious repository in the UK. The bibliography has been prepared using the INIS database and includes eight hundred references, listed both by subject and by country. In addition to these indexes, full abstracts are presented in reverse chronological order. A brief description of the relevance and measurement of sorption parameters is included. (author)

Corrigendum to “Sorption/desorption of non-hydrophobic and ionisable pharmaceutical and personal care products from reclaimed water onto/from a natural sediment” Sci Total Environ 472 (2014) 273–281

Energy Technology Data Exchange (ETDEWEB)

Martínez-Hernández, Virtudes, E-mail: virtudes.martinez@imdea.org [IMDEA Agua, Madrid Institute for Advanced Studies in Water, Parque Científico Tecnológico de la Universidad de Alcalá, 28805 Alcalá de Henares, Madrid (Spain); Meffe, Raffaella; Herrera, Sonia [IMDEA Agua, Madrid Institute for Advanced Studies in Water, Parque Científico Tecnológico de la Universidad de Alcalá, 28805 Alcalá de Henares, Madrid (Spain); Arranz, Elena [University of Alcalá, Geography and Geology Department, 28871 Alcalá de Henares, Madrid (Spain); Bustamante, Irene de [IMDEA Agua, Madrid Institute for Advanced Studies in Water, Parque Científico Tecnológico de la Universidad de Alcalá, 28805 Alcalá de Henares, Madrid (Spain); University of Alcalá, Geography and Geology Department, 28871 Alcalá de Henares, Madrid (Spain)

2015-02-01

In the present work, the sorption of pharmaceutical and personal care products (PPCPs) (acetaminophen, atenolol, carbamazepine, caffeine, naproxen and sulphamethoxazole) onto the natural organic matter (NOM) and the inorganic surfaces of a natural sandy loam sediment was quantified separately. The quantification was based on the PPCP charge, their degree of ionisation, their octanol-water partitioning coefficient (K{sub OW}) and the sediment organic carbon fraction (ƒ{sub OC}). PPCP desorption from the sediment was examined under conditions of infiltrating water containing a high concentration of inorganic ions (mimicking infiltrating reclaimed water), and a low concentration (and smaller diversity) of inorganic ions (mimicking rainwater infiltration). Batch tests were performed using a sediment/water ratio of 1:4 and a PPCP initial concentration ranging from 1 to 100 μg L{sup −1}. The results showed the type and degree of PPCP ionisation to strongly influence the sorption of these compounds onto the sediment. The sorption of cationic species onto the sediment was higher than that of anionic species and mostly reversible; the sorption of neutral species was negligible with the exception of caffeine. The anionic species sorbed less onto the sediment, but also desorbed less easily. Most of the compounds showed a sorption that was highly influenced by interaction with mineral surfaces. The presence of inorganic ions had no impact on the desorption of the PPCPs from the sediment. According to the calculated percentages of removal, the mobility followed the order: carbamazepine > acetaminophen > naproxen > atenolol > sulphamethoxazole > caffeine.

Corrigendum to “Sorption/desorption of non-hydrophobic and ionisable pharmaceutical and personal care products from reclaimed water onto/from a natural sediment” Sci Total Environ 472 (2014) 273–281

International Nuclear Information System (INIS)

Martínez-Hernández, Virtudes; Meffe, Raffaella; Herrera, Sonia; Arranz, Elena; Bustamante, Irene de

2015-01-01

In the present work, the sorption of pharmaceutical and personal care products (PPCPs) (acetaminophen, atenolol, carbamazepine, caffeine, naproxen and sulphamethoxazole) onto the natural organic matter (NOM) and the inorganic surfaces of a natural sandy loam sediment was quantified separately. The quantification was based on the PPCP charge, their degree of ionisation, their octanol-water partitioning coefficient (K OW ) and the sediment organic carbon fraction (ƒ OC ). PPCP desorption from the sediment was examined under conditions of infiltrating water containing a high concentration of inorganic ions (mimicking infiltrating reclaimed water), and a low concentration (and smaller diversity) of inorganic ions (mimicking rainwater infiltration). Batch tests were performed using a sediment/water ratio of 1:4 and a PPCP initial concentration ranging from 1 to 100 μg L −1 . The results showed the type and degree of PPCP ionisation to strongly influence the sorption of these compounds onto the sediment. The sorption of cationic species onto the sediment was higher than that of anionic species and mostly reversible; the sorption of neutral species was negligible with the exception of caffeine. The anionic species sorbed less onto the sediment, but also desorbed less easily. Most of the compounds showed a sorption that was highly influenced by interaction with mineral surfaces. The presence of inorganic ions had no impact on the desorption of the PPCPs from the sediment. According to the calculated percentages of removal, the mobility followed the order: carbamazepine > acetaminophen > naproxen > atenolol > sulphamethoxazole > caffeine

Sorption and desorption of arsenic to ferrihydrite in a sand filter.

Science.gov (United States)

Jessen, Soren; Larsen, Flemming; Koch, Christian Bender; Arvin, Erik

2005-10-15

Elevated arsenic concentrations in drinking water occur in many places around the world. Arsenic is deleterious to humans, and consequently, As water treatment techniques are sought. To optimize arsenic removal, sorption and desorption processes were studied at a drinking water treatment plant with aeration and sand filtration of ferrous iron rich groundwater at Elmevej Water Works, Fensmark, Denmark. Filter sand and pore water were sampled along depth profiles in the filters. The sand was coated with a 100-300 microm thick layer of porous Si-Ca-As-contaning iron oxide (As/Fe = 0.17) with locally some manganese oxide. The iron oxide was identified as a Si-stabilized abiotically formed two-line ferrihydrite with a magnetic hyperfine field of 45.8 T at 5 K. The raw water has an As concentration of 25 microg/L, predominantly as As(II). As the water passes through the filters, As(III) is oxidized to As(V) and the total concentrations drop asymptotically to a approximately 15 microg/L equilibrium concentration. Mn is released to the pore water, indicating the existence of reactive manganese oxides within the oxide coating, which probably play a role for the rapid As(III) oxidation. The As removal in the sand filters appears controlled by sorption equilibrium onto the ferrihydrite. By addition of ferrous chloride (3.65 mg of Fe(II)/L) to the water stream between two serially connected filters, a 3 microg/L As concentration is created in the water that infiltrates into the second sand filter. However, as water flow is reestablished through the second filter, As desorbs from the ferrihydrite and increases until the 15 microg/L equilibrium concentration. Sequential chemical extractions and geometrical estimates of the fraction of surface-associated As suggest that up to 40% of the total As can be remobilized in response to changes in the water chemistry in the sand filter.

Radionuclides incorporation in activated natural nanotubes

International Nuclear Information System (INIS)

Silva, Jose Parra

2016-01-01

Natural palygorskite nanotubes show suitable physical and chemical properties and characteristics to be use as potential nanosorbent and immobilization matrix for the concentration and solidification of radionuclides present in nuclear wastes. In the development process of materials with sorption properties for the incorporation and subsequent immobilization of radionuclides, the most important steps are related with the generation of active sites simultaneously to the increase of the specific surface area and suitable heat treatment to producing the structural folding. This study evaluated the determining parameters and conditions for the activation process of the natural palygorskite nanotubes aiming at the sorption of radionuclides in the nanotubes structure and subsequent evaluation of the parameters involve in the structural folding by heat treatments. The optimized results about the maximum sorption capacity of nickel in activated natural nanotubes show that these structures are apt and suitable for incorporation of radionuclides similar to nickel. By this study is verified that the optimization of the acid activation process is fundamental to improve the sorption capacities for specifics radionuclides by activated natural nanotubes. Acid activation condition optimized maintaining structural integrity was able to remove around 33.3 wt.% of magnesium cations, equivalent to 6.30·10 -4 g·mol -1 , increasing in 42.8% the specific surface area and incorporating the same molar concentration of nickel present in the liquid radioactive waste at 80 min. (author)

Sorption of a nonionic surfactant Tween 80 by minerals and soils

Energy Technology Data Exchange (ETDEWEB)

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

2015-03-02

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

An investigation of the sorption/desorption of organics from natural waters by solid adsorbents and anion exchangers

International Nuclear Information System (INIS)

Larin, B.M.; Sedlov, A.S.

2006-01-01

The results of laboratory and operational tests at thermal and nuclear power stations on anion exchangers and solid adsorbents of makeup water treatment plants with regard to the sorption/desorption of organic substances in natural water and condensate are presented. The resins Amberlite trademark IRA-67, IRA-900, IRA-958Cl, Purolite registered 2 A-500P, Dowex TM3 Marathon, and others were tested. Retention of up to 60-80% of the ''organic'' material on the anion exchangers and organic absorbers installed at different places in the technological scheme of the water processing unit was attained. The possibility of a partial ''poisoning'' of the resins and the degradation of the working characteristics over the first year of operation are discussed. (orig.)

Assessment of the important radionuclides in nuclear waste

International Nuclear Information System (INIS)

Kerrisk, J.F.

1985-10-01

The relative importance of the various radionuclides contained in nuclear waste has been assessed by consideration of (1) the quantity of each radionuclide present, (2) the Environmental Protection Agency's release limits for radionuclides, (3) how retardation processes such as solubility and sorption affect radionuclie transport, and (4) the physical and chemical forms of radionuclides in the waste. Three types of waste were reviewed: spent fuel, high-level waste, and defense high-level waste. Conditions specific to the Nevada Nuclear Waste Storage Investigations project potential site at Yucca Mountain were used to describe radionuclide transport. The actinides Am, Pu, Np, and U were identified as the waste elements for which solubility and sorption data were most urgently needed. Other important waste elements were identified as Sr, Cs, C, Ni, Zr, Tc, Th, Ra, and Sn. Under some conditions, radionuclides of three elements (C, Tc, and I) may have high solubility and negligible sorption. The potential for transport of some waste elements (C and I) in the gas phase must also be evaluated for the Yucca Mountain Site. 12 refs., 17 tabs

Quantifying the effect of sorption and bioavailability of hydrophobic organic contaminants

International Nuclear Information System (INIS)

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

1994-01-01

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

Models of sorption and migration of radionuclides in geologic media

International Nuclear Information System (INIS)

Fukui, Masami

1987-01-01

Full understanding of the transportation of nuclides by groundwater is essential in designing an underground radioactive waste disposal site. What is the most important is to clarify in detail the process of sorption of nuclides by rock and soil. This report outlines various theories and experimental data that are currently available. In addition, studies made in various countries are reviewed and some problems are pointed out. First, a review is made of studies that deal with adsorption and behaviors of contaminants in natural barriers (rock, soil). Next, migration models that have been developed in studying migration processes in the field of chemical engineering or behaviors of agricultural chemicals in the field of soil physics are examined to see if they can be applied to investigations of the migration of radioactive contaminants in a porous medium. Finally, a review is made of basic underground migration models that are used in various countries in studying deep underground disposal of long-life radionuclides. Some laboratory experiments on TRU nuclides in rock are also outlined. (Nogami, K.)

Sorption behaviour of herbicides in soils

International Nuclear Information System (INIS)

Luchini, L.C.; Wiendl, F.M.; Ruegg, E.F.; Instituto Biologico, Sao Paulo

1988-01-01

Environmental contamination by herbicides is related with the sorption phenomenon of these compounds in the soils. The behaviour of paraquat, 2,4-D and diuron was studied in soils with different physico-chemical properties, through the Freundlich adsorption and desorption isotherms, using 14 C-radiolabeled herbicides. Results of the range of the adsorption-desorption of each herbicide was related mainly with the chemical characteristics of these compounds. (author) [pt

Mechanisms controlling radionuclide mobility in forest soils

International Nuclear Information System (INIS)

Delvaux, B.; Kruyts, N.; Maes, E.; Agapkina, G.I.; Kliashtorin, A.; Bunzl, K.; Rafferty, B.

1996-01-01

Soil processes strongly influence the radionuclide mobility in soils. The mobility of radionuclides in forest soils is governed by several processes involving both abiotic and biotic factors. The sorption-desorption process chiefly governs the activity of radionuclides in the soil solution, hence thereby their mobility and biological availability. Radiocaesium exhibits a very low mobility in mineral soils. Both mobility and bioavailability however increase as the thickness of organic layers and their content in organic matter increases. Clay minerals of micaceous origin strongly act as slinks for radiocaesium in forest soils. The magnitude of cesium mineral fixation in topsoils is expected to be the highest in mineral soils of Eutric cambisol type, and, to a lesser extent, of type of Distric cambisol and Podzoluvisol. A low mobility of radiocaesium in the surface horizons of forest soils may also be partially explained by a biological mobilization: fungi absorb radiocaesium and transport it to upper layers, thereby contributing to constantly recycle the radioelement in the organic horizons. This mechanism is probably important in soils with thick organic layers (Podsol, Histosol, and, to a lesser extent, Distric cambisol and Podzoluvisol). Radionuclides can be associated with soluble organic anions in the soil solution of forest acid soils. Such associations are highly mobile: they are stable in conditions of poor biological activity (low temperatures, acid soil infertility, water excess, etc.). Their magnitude is expected to be the highest in thick acid organic layers (soils of type Podzol and Histosol)

Radiocaesium forms in soil - problems of experimental determination

International Nuclear Information System (INIS)

Davydov, D.; Davydov, Yu.; Voronik, N.; Titov, A.; Toropova, N.

2006-01-01

A method for determining Cs form in soil is proposed based on the comparison of the experimental data on desorption of Cs radionuclide from the soil contaminated as a result of the Chernobyl accident and from the soil samples on which Cs was absorbed in laboratory (Cs was introduced in ionic form in solution). The data obtained on desorption of Cs from different soils show that Cs radionuclide is present in the soil contaminated as a result of the Chernobyl accident predominantly in an ionic form (sorbed on the different soil fractions). It has also been found that the ratio of 144 Ce/ 137 Cs radionuclides is much higher in solution than in the soil. At the same time the data on sorption of Cs and Ce radionuclides on different soils from solution 0.1M HCI + 0.1M KCI + 0.1M FeCI 3 show that the sorption ability of Cs is higher than the sorption ability of Ce for all the soil types investigated. Hence, it can be assumed that the mechanism of the radionuclides extraction is desorption rather than dissolution of the matrix particles, since in the letter case extraction value of the radionuclides would not be different. The fact that the ratio of 144 Ce/ 137 Cs radionuclides in solution remains higher than in soil independent on the distance from the Chernobyl NPP indicates that the form of the radionuclides does not change with the distance from the reactor. In order to determine what type of molecules Cs radionuclide can be bound to in soil the experiments on sorption of Cs on sandy soil in the presence of humic acid in solution has been carried out. The data obtained show that the presence of humic acids has none or little effect on the sorption of Cs. This indicates that interaction of Cs radionuclides with humic acid is week and these molecules can not be responsible for binding Cs in soil. (author)

The NEA sorption data base (SDB)

International Nuclear Information System (INIS)

Ruegger, B.; Ticknor, K.

1992-01-01

The current NEA Sorption Data Base is developed to replace the former International Sorption Information Retrieval System (ISIRS) initiated at Pacific Northwest Laboratory and contains about 11,000 distribution coefficients with corresponding experimental condition parameters describing sorption of key nuclides for a large variety of solid and liquid phases. The SDB is designed to run on a micro-computer using the commercially available database software dBASE III Plus. For each recorded sorption experiment, the SDB provides a bibliographical reference, the most complete characterization of the solid and liquid phases available, a description of the experimental conditions and the distribution coefficient or retardation factor for each element studied. When available, parameters such as temperature, initial radionuclide concentration, pH, Eh, contact time, solid to solution ratio, sample origin, oxidation state and type of solution are included. The SDB provides information for a wide variety of rocks or geological materials, buffer backfill candidates, concretes/cements, elements (Am, Cs, Co, I, Np, Pu, Ra, Sr, Se, Tc, U and, to a lesser extent, Ag, Ba, C, Ce, Eu, Fe, Mn, Mo, Na, Nb, Ni, Pd, Pm, Ru, Sb, Sn, Y, Zn, and Zr), or radioisotopes. A compilation of sorption data like SDB provide a readily available source of data for radioactive waste repository performance assessments when site specific data are not available or essential, for example, during a site selection phase. 2 appendices

Investigation of biotransformation, sorption, and desorption of multiple chemical contaminants in pilot-scale drinking water biofilters.

Science.gov (United States)

Greenstein, Katherine E; Lew, Julia; Dickenson, Eric R V; Wert, Eric C

2018-06-01

The evolving demands of drinking water treatment necessitate processes capable of removing a diverse suite of contaminants. Biofiltration can employ biotransformation and sorption to remove various classes of chemicals from water. Here, pilot-scale virgin anthracite-sand and previously used biological activated carbon (BAC)-sand dual media filters were operated for ∼250 days to assess removals of 0.4 mg/L ammonia as nitrogen, 50-140 μg/L manganese, and ∼100 ng/L each of trace organic compounds (TOrCs) spiked into pre-ozonated Colorado River water. Anthracite achieved complete nitrification within 200 days and started removing ibuprofen at 85 days. Limited manganese (10%) removal occurred. In contrast, BAC completely nitrified ammonia within 113 days, removed all manganese at 43 days, and exhibited steady state removal of most TOrCs by 140 days. However, during the first 140 days, removal of caffeine, DEET, gemfibrozil, naproxen, and trimethoprim decreased, suggesting a shift from sorption to biotransformation. Acetaminophen and sulfamethoxazole were removed at consistent levels, with complete removal of acetaminophen achieved throughout the study; ibuprofen removal increased with time. When subjected to elevated (1 μg/L) concentrations of TOrCs, BAC removed larger masses of chemicals; with a subsequent decrease and ultimate cease in the TOrCs spike, caffeine, DEET, gemfibrozil, and trimethoprim notably desorbed. By the end of operation, anthracite and BAC exhibited equivalent quantities of biomass measured as adenosine triphosphate, but BAC harbored greater microbial diversity (examined with 16S rRNA sequencing). Improved insight was gained regarding concurrent biotransformation, sorption, and desorption of multiple organic and inorganic contaminants in pilot-scale drinking water biofilters. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

A review of sorption of radionuclides under the near- and far-field conditions of an underground radioactive waste repository. Pt. 1

International Nuclear Information System (INIS)

Berry, J.A.

1992-01-01

This report presents and discusses work funded by the Department of the Environment and UK Nirex Ltd in the area of sorption of radionuclides under near-field and far-field conditions as related to the underground disposal of radioactive waste in the UK. It is intended as a basis for comparison with work undertaken world-wide in the sorption area, presented in Part II of this review. The UK and overseas work are compared in Part III. From lists of reports and papers supplied by DOE (HMIP) and Nirex, those publications believed to be relevant were selected and are listed here by subject. Summaries of all these reports are included in the form of abstracts, or where available, executive summaries. The work presented is further summarised and discussed. Sections on sorption and laboratory experimental methods are included, along with a section on the level of understanding and outstanding issues. (Author)

Tritium sorption on protective coatings for concrete

International Nuclear Information System (INIS)

Miller, J.M.; Senohrabek, J.A.; Allsop, P.A.

1992-11-01

Because of the high sorption level of tritium on unprotected concrete, a program to examine the effectiveness of various concrete coatings and sealants in reducing tritium sorption was undertaken, and various exposure conditions were examined. Coatings of epoxy, polyurethane, bituminous sealant, bituminous sealant covered with polyvinylidene chloride wrap, alkyd paint, and sodium silicate were investigated with tritium (HTO) vapor concentration, humidity and contact time being varied. An exposure to HT was also carried out, and the effect of humidity on the tritium desorption rate was investigated. The relative effectiveness of the coatings was in the order of bituminous sealant + wrap > bituminous sealant > solvent-based epoxy > 100%-solids epoxy > alkyd paint > sodium silicate. The commercially available coatings for concrete resulted in tritium sorption being reduced to less than 7% of unprotected concrete. This was improved to ∼0.1% with the use of the Saran wrap (polyvinylidene chloride). The amount of tritium sorbed was proportional to tritium concentration. The total tritium sorbed decreased with an increase in humidity. A saturation effect was observed with increasing exposure time for both the coated and unprotected samples. Under the test conditions, complete saturation was not achieved within the maximum 8-hour contact time, except for the solvent-based epoxy. The desorption rate increased with a higher-humidity air purge stream. HT desorbed more rapidly than HTO, but the amount sorbed was smaller. The experimental program showed that HTO sorption by concrete can be significantly reduced with the proper choice of coating. However, tritium sorption on concrete and proposed coatings will continue to be a concern until the effects of the various conditions that affect the adsorption and desorption of tritium are firmly established for both chronic and acute tritium release conditions. Material sorption characteristics must also be considered in

Sorption of samarium in soils: influence of soil properties and Sm concentration

Energy Technology Data Exchange (ETDEWEB)

Ramirez-Guinart, Oriol; Salaberria, Aitor; Rigol, Anna; Vidal, Miquel [Analytical Chemistry department, Faculty of Chemistry, University of Barcelona, Marti i Franques 1-11, 08028, Barcelona (Spain)

2014-07-01

Due to the fact that barriers of Deep Geological Repositories (DGR) may lose efficiency before the radioisotopes present in the High Level Radioactive Waste (HLRW) completely decay, it is possible that, in the long-term, radioactive leachates may escape from the DGR and reach the soil and water compartments in the biosphere. Therefore, it is required to examine the interaction and mobility of radionuclides present in the HLRW, or their chemical analogues, to predict the impact of their eventual incorporation in the biosphere and to assess the derived risk. Although relevant data have been recently obtained for a few radionuclides in soils, there are still some important gaps for some radionuclides, such us for samarium (Sm). Sm is a lanthanide that, besides being considered as a natural analogue of actinides, may also be present in HLRW in the form of the radioactive isotope {sup 151}Sm. The main objective of this work was to obtain sorption data (K{sub d}) of {sup 151}Sm gathered from a set of soil samples physicochemical fully-characterized (pH, texture, cationic exchange capacity, soil solution cationic composition, organic matter, carbonate and metallic oxides content, etc.). Additionally, as an alternative for testing sorption capacity of radionuclides in soils is the use of the corresponding stable isotope or a chemical analogue, the influence of Sm concentration was also checked. To evaluate {sup 151}Sm sorption, batch assays were carried out for each soil sample, which consisted in a pre-equilibration step of 2 g of each soil with 50 ml of double deionised water, and a subsequent equilibration step with the same solution, but labelled with {sup 151}Sm. The activity of {sup 151}Sm in initial and final solutions was measured by liquid scintillation and K{sub d} ({sup 151}Sm) data were calculated. The reversibly sorbed fraction was estimated by the application of a single extraction test, with double deionised water, to soil residues coming from the previous

Sorption of tritium and tritiated water on construction materials

International Nuclear Information System (INIS)

Dickson, R.S.; Miller, J.M.

1991-11-01

Sorption and desorption of tritium (HT) and tritiated water (HTO) on materials to be used in the construction of fusion facilities were studied. In ∼ 24-hour exposures in argon or room air, metal samples sorbed 8-200 μCi/m 2 of tritium from atmospheres of 5-9 Ci/m 3 HT, and non-metallic samples sorbed 60-800 μCi/m 2 from atmospheres of 14 Ci/m 3 HT. Sorption of HTO varied much more widely than HT sorption for different samples, ranging from 4 μCi/m 2 for glass to 1,300,000 μCi/m 2 for concrete samples, in 24-hour exposures to 1 Ci/m 3 HTO in room air. Time dependence of desorption in dry air showed a rapid initial process and a slower secondary process. (Author) (10 refs., 4 figs., 2 tabs.)

Radionuclide characterization of environmental air around nuclear facilities

International Nuclear Information System (INIS)

Gede Sutresna Wijaya; Anung Muharini

2015-01-01

Air is an important environmental component in human life. Presence of air pollutants or contaminants will have a negative impact on human health. According to the existence of a nuclear facility in Yogyakarta, the characterization of radionuclides in the air is absolutely necessary to ensure the safety of people and the environment and also to supervise the safe operation of the facility. In this research the characterization of radionuclides in the air was carried through the air sampling by using High Volume Air Sampler equipped with filter TFA 2133, followed by analysis using combination of a gamma and alpha spectrometers. The concentration of radioactivity in the air fluctuates depending on the time and duration of sampling. Characterization of gamma emitting radionuclides in the air is dominated by radon progeny radionuclides such as 214 Pb, 214 Bi with activity 20.09 ± 1.23 until 32.91 ± 4.87 Bq/m 3 and 31.22 ± 1.76 until 44.25 ± 4.91 Bq/m 3 . Alpha emitter radionuclide was dominated by 214 Po (7.69 MeV) which is also radon progeny and a primordial radionuclides. It can be concluded that the presence of radionuclides in the environmental air not as a product resulting from the operation of nuclear facilities in Yogyakarta. (author)

Development of a web-based sorption database (KAERI-SDB) and application to the safety assessment of a radioactive waste disposal

International Nuclear Information System (INIS)

Lee, Jae-Kwang; Baik, Min-Hoon; Choi, Jong-Won; Seo, Min-Seok

2011-01-01

Sorption plays a key role in a retardation of radionuclide migration in various geological environments. Hence sorption of radionuclides onto geological media is one of the important factors for the safety assessment of radioactive waste disposal. A web-based radionuclide sorption database program named KAERI-SDB has been developed to provide a database for the sorption of radionuclides onto geological media at various geochemical conditions. The KAERI-SDB is designed to determine the distribution coefficient (K d ) of a radionuclide and evaluate sorption properties by easily accessing an internet web-site ( (http://sdb.kaeri.re.kr)). The KAERI-SDB provides a useful output and search result as a scatter plot chart or an index chart. The KAEI-SDB was designed to show the search results in a statistical way by representing the mean K d value at 95% of confidence as a function of major geochemical indices. Several case studies were carried out to demonstrate the applicability of the KAERI-SDB and the result showed a successful applicability of the KAERI-SDB to various radionuclide sorption cases.

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

International Nuclear Information System (INIS)

Kulik, D.A.

2005-01-01

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

A review of sorption of radionuclides under the near- and far-field conditions of an underground radioactive waste repository. Pt. 3

International Nuclear Information System (INIS)

Berry, J.A.

1992-01-01

This report summarises work funded by the Department of the Environment and UK Nirex Ltd in the area of sorption of radionuclides under the near-field and far-field conditions pertaining to the underground disposal of radioactive waste in the UK that was presented and discussed in Part I. The report also summarises comparable research undertaken overseas (presented in Part II). (author)

Applicability of microautoradiography to sorption studies

International Nuclear Information System (INIS)

Thompson, J.L.; Wolfsberg, K.

1979-01-01

The technique of microautoradiography was applied to the study of the sorption of uranium and americium on five rock types which exist at the Nevada Test Site. It was found that autoradiograms could be prepared in a few days which would allow the specific minerals responsible for sorption to be identified. Furthermore, the state of aggregation of the sorbed species was clearly indicated. It was concluded that microautoradiography was a useful adjunct to currently used methods for studying sorption of certain radionuclides

Sorption of microamount of colloidal silver iodide on hydrated iron(III) oxide

International Nuclear Information System (INIS)

Kepak, F.; Nova, J.

1975-01-01

Sorption of a microamount of colloidal silver iodide labelled with 131 I on hydrated iron/III/ oxide suspension was studied. The sorption dependence upon pH, sorbent amount, and inert electrolyte concentration has revealed that sorption of silver iodide reaches no more than 63%. The sorption lasted one hour during which the maximum value was reached. Desorption time was one hour, as well. Except for measuring the sorption dependence on pH, the sorption pH was 7.0, temperature 24+-2 0 C. (F.G.)

Elimination of radionuclides and heavy metals from soils

International Nuclear Information System (INIS)

Navarcik, I.; Cipakova, A.; Palagyl, S.

1994-01-01

Sorption and desorption of radionuclides and heavy metals, their vertical migration and gradual extraction from soils were studied. Tessier sequential extraction method was used for determination the physicochemical forms of radionuclides and heavy metals absorbed by root system of plants and leached into ground water. Fixed forms of heavy metals and radionuclides are prevailing in soils. As to artificial ( 90 Sr, 137 Cs) isotope ratio of fixed forms bound with soil components, it is higher for 137 Cs (black earth - 95%, sandy soil - 62%) as compared to 90 Sr. Mobilization procedures for elimination of unfavourable influence of these pollutants in soils were used. The bacteria Pseudomonas sp. and Micrococcus l. are applied for this purpose. At the same time the growing of technical plants (Linum usitatissimum L. and Brassica napus L. var.) was studied as a method for mobilizing the heavy metals and radionuclides from soils. Retardation influence of bacteria on 85 Sr was noticed after as much as 3 months. The sum of water-soluble and exchangeable fractions reached 60%. Values of Cs distribution proved that microorganisms or plants used had no appreciable influence on Cs-mobility. After 3 months the relative ratio of accessible fraction increased with about 5%. As to heavy metals, both bacteria and plant growing influenced their retardation. In the case of Cd, one month operation of microorganisms resulted in important increase of easily available Cd-ratio (about 25%) in soils. (author)

Sorption and migration of neptunium in porous sedimentary materials

International Nuclear Information System (INIS)

Tanaka, Tadao; Mukai, Masayuki; Nakayama, Shinichi

2005-01-01

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

The effect of organics on the sorption of cobalt by glacial sand in laboratory batch experiments

International Nuclear Information System (INIS)

Haigh, D.G.; Williams, G.M.; Hooker, P.J.; Ross, C.A.M.; Allen, M.R.; Warwick, P.

1989-01-01

Acetate, EDTA and organic compounds naturally present in groundwater at the Drigg in situ radionuclide migration experimental site, have been studied to assess their effect on the sorption of cobalt by glacial sand in a series of batch experiments. Removing 56% of the natural organic material from the grounwater with DEAE cellulose increased the distribution ratio (R d ) of cobalt by a factor of about two. EDTA had a dramatic effect on the sorption of Co even at low concentrations, reducing the R d by up to two orders of magnitude. At EDTA concentrations greater than 5 mg/l, there was no further reduction in sorption. EDTA was not itself sorbed, but formed a mobile complex with Co. Differences in distribution ratios were observed depending on whether the cobalt was added before or after EDTA. Within the same period of equilibrium, the R d values were higher when cobalt was allowed to equilibrate with the sand before adding EDTA. The desorption of cobalt from the mineral surface may be a rate-limiting step such that equilibrium was not achieved within the 14-day period of these experiments. Acetate had no effect on cobalt sorption in any of the experiments undertaken. This work is part of the Commission Mirage project, Phase 2, research area Geochemistry of actinides and fission products in natural aquifer systems

Erosion of atmospherically deposited radionuclides as affected by soil disaggregation mechanisms

International Nuclear Information System (INIS)

Claval, D.; Garcia-Sanchez, L.; Real, J.; Rouxel, R.; Mauger, S.; Sellier, L.

2004-01-01

The interactions of soil disaggregation with radionuclide erosion were studied under controlled conditions in the laboratory on samples from a loamy silty-sandy soil. The fate of 134 Cs and 85 Sr was monitored on soil aggregates and on small plots, with time resolution ranging from minutes to hours after contamination. Analytical experiments reproducing disaggregation mechanisms on aggregates showed that disaggregation controls both erosion and sorption. Compared to differential swelling, air explosion mobilized the most by producing finer particles and increasing five-fold sorption. For all the mechanisms studied, a significant part of the contamination was still unsorbed on the aggregates after an hour. Global experiments on contaminated sloping plots submitted to artificial rainfalls showed radionuclide erosion fluctuations and their origin. Wet radionuclide deposition increased short-term erosion by 50% compared to dry deposition. A developed soil crust when contaminated decreased radionuclide erosion by a factor 2 compared to other initial soil states. These erosion fluctuations were more significant for 134 Cs than 85 Sr, known to have better affinity to soil matrix. These findings confirm the role of disaggregation on radionuclide erosion. Our data support a conceptual model of radionuclide erosion at the small plot scale in two steps: (1) radionuclide non-equilibrium sorption on mobile particles, resulting from simultaneous sorption and disaggregation during wet deposition and (2) later radionuclide transport by runoff with suspended matter

Study on the effects of titanium oxide based nanomaterials as catalysts on the hydrogen sorption kinetics of magnesium hydride

Energy Technology Data Exchange (ETDEWEB)

Pereira, Anderson de Farias; Jardim, Paula Mendes; Santos, Dilson Silva dos, E-mail: anderso.n@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Conceicao, Monique Osorio Talarico da [Centro Universitario de Volta Redonda (UniFOA), RJ (Brazil)

2016-07-01

Full text: Magnesium hydride is highly attractive for hydrogen storage in solid state in reason of its high gravimetric capacity (7,6 wt% of H{sub 2}) and low density (1,7 g/cm³), making it a promissory candidate for mobile applications [1]. However, its low sorption kinetics and desorption temperature are the main obstacles for its application. In the present study the catalytic role of TiO{sub 2} based nanomaterials with different morphologies on the sorption kinetics of MgH{sub 2} was evaluated. The additions consisted on titanate nanotubes (TTNT-Low), TiO{sub 2} nanorods (TTNT-550) and nanoparticles (KA-100, TTNT-ACID). Transmission and Scanning Transmission Electron Microscopy (S/TEM) associated with X-ray Energy Dispersive Spectroscopy (XEDS) mapping was used to characterize the catalysts' morphology and crystalline structure and their dispersion within magnesium hydride, altogether with other characterization techniques such as X-ray diffraction (XRD) and BET technique for structure and surface area analysis. The sorption kinetics were evaluated by means of a volumetric gas absorption/desorption (Sievert-type) apparatus. The results indicated that all additives improved the sorption kinetics of MgH{sub 2}, but the samples with TTNT-550 (TiO{sub 2} nanorods) and TTNT-ACID (TiO{sub 2} nanoparticles) presented the best and the second best performances, respectively, suggesting that the 1D morphology may promote a slightly superior kinetics than particulate catalysts. (author)

Sorption of iodine, chlorine, technetium and cesium in soil

International Nuclear Information System (INIS)

Soederlund, M.; Lusa, M.; Lehto, J.; Hakanen, M.; Vaaramaa, K.

2011-01-01

The safety assessment of final disposal of spent nuclear fuel will include an estimate for the behavior of waste nuclides in the biosphere. As a part of this estimate also the sorption of radioactive iodine, chlorine, technetium and cesium in soil is to be considered. The chemistry and the sorption of these radionuclides in soils are described in this literature survey. Behavior of I-129, Cl-36 and Tc-99 in the environment is of great interest because of their long half-lives and relatively high mobilities. The importance of Cs-135 arises from its high content in spent nuclear fuel and long physical half-life, even though it is considered relatively immobile in soil. Factors affecting the migration and sorption of radionuclides in soils can be divided into elemental and soil specific parameters. The most important elemental factor is the speciation of the element, which is influenced by the soil redox potential, pH and complex forming ligands. Soil micro-organisms can either serve as sorbents for radionuclides or affect their speciation by altering the prevailing soil redox conditions. Soil organic matter content and mineral properties have a marked influence on the retention of radionuclides. The sorption of anionic radionuclides such as I-, Cl- and TcO 4 - is pronounced in the presence of organic matter. Clay minerals are known to bound cesium effectively. The effect of speciation of radioactive iodine, chlorine, technetium and cesium in soil is considered in this study, as well as the effect of soil micro-organisms, organic matter and mineral properties. (orig.)

Thermodynamics of imidacloprid sorption in Croatian soils

Science.gov (United States)

Milin, Čedomila; Broznic, Dalibor

2015-04-01

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

THE SORPTION OF OFLOXACIN BY HYDRATED ALUMINA AND SILICON

Directory of Open Access Journals (Sweden)

A. N. Chebotarev

2016-11-01

Full Text Available The sorption of ofloxacin (OFL – the antibiotic from class of fluoroquinolones has been studied on alumina (γ-Al2O3 different acid-base modifications – acidic Al2O3(acidic, neutral Al2O3 (Neutral and the basic Al2O3 (core and amorphous silica – silica gel (SG L 5/40 and aerosil A-300. Determination of ofloxacin in solutions has been carried out by spectrophotometry on spectrophotometer SF-46 at λ = 291 nm and acidity 7. To clarify the nature of the sorption surfaces of OFL hydrated on aluminum and silicon oxides were studied according to the degree of extraction (S% from pH, contact time of the phases (min. sample from the sorbent mass (g; sorption isotherms were built and antibiotic desorption was studied. The OFL significant recovery (~ 60% is observed at the pH range of 4 ÷ 8, and reaches its maximum (80-85% at pH 7. The maximum degree of extraction of the antibiotic on aerosil A-300 and L 5/40 silica realized at pH 6 and it was ~ 80%. Comparative analysis of the forms constructed isotherms (L – type indicates a significant affinity investigated hydrated oxides to sorbate. The value of the static exchange capacity and concentration ratios can proof that. Differences in the quantitative characteristics of sorption of aluminum and silicon oxides are associated with nature and the acid-base properties of adsorption sites. In the study of the OFL concentrates desorption in static mode dilute NaOH and HNO3 solutions it was found that growth desorption degree occured with increasing concentration. Desorption was 2-3 times better in the case of aluminum oxide than silicon oxide when there were the same concentrations of acid and alkali. This is another confirmation of the participation in various sorption interactions forces of physical and chemical nature.

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

International Nuclear Information System (INIS)

Kozai, Naofumi; Ohnuki, Toshihiko; Muraoka, Susumu

1995-01-01

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

Influence of speciation on the geospheric migration of radionuclides

International Nuclear Information System (INIS)

Hadermann, J.; Schweingruber, M.

1982-01-01

For geosphere transport calculations in safety analyses of waste repositories it is generally assumed that the retardation of a migrating radionuclide is characterized by a single retention factor. However, in groundwater, radionuclides exist in various chemical forms with strongly differing sorption properties. We consider the effect of pseudo first order chemical reactions in liquid phase on migration. Conditions are derived under which local equilibrium in liquid phase is well fulfilled and migration is governed by a single effective retention factor. It is argued that in geosphere transport, equilibrium is likely to exist even when laboratory measurements show chromatographic separations. (author)

Adsorption and desorption of radionuclide europium(III) on multiwalled carbon nanotubes studied by batch techniques

International Nuclear Information System (INIS)

Songsheng Lu; Junzheng Xu; Caicai Zhang; Zhiwei Niu

2011-01-01

The adsorption of Eu(III) on multiwalled carbon nanotubes (MWCNTs) as a function of pH, ionic strength and solid contents are studied by batch technique. The results indicate that the adsorption of Eu(III) on MWCNTs is strongly dependent on pH values, dependent on ionic strength at low pH values and independent of ionic strength at high pH values. Strong surface complexation and ion exchange contribute to the adsorption of Eu(III) on MWCNTs at low pH values, whereas surface complexation and surface precipitation are the main adsorption mechanism of Eu(III) on MWCNTs. The desorption of adsorbed Eu(III) from MWCNTs by adding HCl is also studied and the recycling use of MWCNTs in the removal of Eu(III) is investigated after the desorption of Eu(III) at low pH values. The results indicate that adsorbed Eu(III) can be easily desorbed from MWCNTs at low pH values, and MWCNTs can be repeatedly used to remove Eu(III) from aqueous solutions. MWCNTs are suitable material in the preconcentration and solidification of radionuclides from large volumes of aqueous solutions in nuclear waste management. (author)

Characterization of the sorption of uranium(VI) on different complexing resins

Energy Technology Data Exchange (ETDEWEB)

Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela [Dipartimento di Chimica Generale dell' Universita degli Studi di Pavia, Via Taramelli 12, 27100, Pavia (Italy)

2003-08-01

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with log{beta}{sub 110i}=-1.16, in more acidic solution, and ML{sub 2}with log {beta}{sub 120i}=-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML {sub 2}, in more acidic solution, with log {beta}{sub 120i}=-3.16. In the presence of the ligand EDTA, the complex ML {sub 2}(OH) {sub 2}was characterized with log {beta}{sub 12-2i}=-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

Characterization of the sorption of uranium(VI) on different complexing resins

International Nuclear Information System (INIS)

Pesavento, Maria; Biesuz, Raffaela; Alberti, Giancarla; Sturini, Michela

2003-01-01

The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with logβ 110i =-1.16, in more acidic solution, and ML 2 with log β 120i =-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML 2 , in more acidic solution, with log β 120i =-3.16. In the presence of the ligand EDTA, the complex ML 2 (OH) 2 was characterized with log β 12-2i =-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)

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

International Nuclear Information System (INIS)

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

1987-01-01

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

Experimental study of strontium sorption on fissure filling material

Energy Technology Data Exchange (ETDEWEB)

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

1994-12-01

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

Experimental study of strontium sorption on fissure filling material

International Nuclear Information System (INIS)

Eriksen, T.E.; Cui, Daqing

1994-12-01

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

Impact of long-term wastewater irrigation on sorption and transport of atrazine in Mexican agricultural soils.

Science.gov (United States)

Müller, K; Duwig, C; Prado, B; Siebe, C; Hidalgo, C; Etchevers, J

2012-01-01

In the Mezquital Valley, Mexico, crops have been irrigated with untreated municipal wastewater for more than a century. Atrazine has been applied to maize and alfalfa grown in the area for weed control for 15 years. Our objectives were to analyse (i) how wastewater irrigation affects the filtering of atrazine, and (ii) if the length of irrigation has a significant impact. We compared atrazine sorption to Phaeozems that have been irrigated with raw wastewater for 35 (P35) and 85 (P85) years with sorption to a non-irrigated (P0) Phaeozem soil under rainfed agriculture. The use of bromide as an inert water tracer in column experiments and the subsequent analysis of the tracers' breakthrough curves allowed the calibration of the hydrodynamic parameters of a two-site non equilibrium convection-dispersion model. The quality of the irrigation water significantly altered the soils' hydrodynamic properties (hydraulic conductivity, dispersivity and the size of pores that are hydraulically active). The impacts on soil chemical properties (total organic carbon content and pH) were not significant, while the sodium adsorption ratio was significantly increased. Sorption and desorption isotherms, determined in batch and column experiments, showed enhanced atrazine sorption and reduced and slower desorption in wastewater-irrigated soils. These effects increased with the length of irrigation. The intensified sorption-desorption hysteresis in wastewater-irrigated soils indicated that the soil organic matter developed in these soils had fewer high-energy, easily accessible sorption sites available, leading to lower and slower atrazine desorption rates. This study leads to the conclusion that wastewater irrigation decreases atrazine mobility in the Mezquital valley Phaeozems by decreasing the hydraulic conductivity and increasing the soil's sorption capacity.

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

Science.gov (United States)

Glynn, P.D.

2003-01-01

simulation conditions. Functional behaviors that cannot be fit include concentration trend reversals and radionuclide desorption spikes. Other simulation results are fit successfully but the fitted parameters (Kd and dispersivity) vary significantly depending on simulation conditions (e.g. "infiltration" vs. "cleanup" conditions). Notably, an increase in the variance of the specified sorption capacities results in a marked increase in the dispersion of the radionuclides. The results presented have implications for the simulation of radionuclide migration in performance assessments of nuclear waste-disposal sites, for the future monitoring of those sites, and more generally for modeling contaminant transport in ground-water environments. ?? 2003 Published by Elsevier Science Ltd.

Yucca Mountain Project far-field sorption studies and data needs

International Nuclear Information System (INIS)

Meijer, A.

1990-09-01

Batch sorption experiments in which radionuclides dissolved in groundwaters from Yucca Mountain were sorbed onto samples of crushed tuff have resulted in a substantial database of sorption coefficients for radionuclides of interest to the repository program. Although this database has been useful in preliminary evaluations of Yucca Mountain as a potential site for a nuclear waste repository, the database has limitations that must be addressed before it can be used for performance assessment calculations in support of a license application for a waste repository. The purpose of this paper is to: review the applicability of simple (constant) sorption coefficients in transport calculations; review and evaluate alternative methods for the derivation of sorption coefficients; summarize and evaluate the present YMP sorption database to identify areas of data sufficiency and significant data gaps; summarize our current understanding of pertinent sorption mechanisms and associated kinetic parameters; evaluate the significance to the YMP of potential problems in the experimental determination and field application of sorption coefficients as enumerated by the NRC (Nuclear Regulatory Commission, 1987) in its technical position paper on sorption; formulate and evaluate strategies for the resolution of NRC concerns regarding experimental problems; and formulate a position on the sorption coefficient database and the level of understanding of sorption mechanisms likely to be required in the licensing application. 75 refs., 1 fig., 2 tabs

Sorption/Desorption Interactions of Plutonium with Montmorillonite

Science.gov (United States)

Begg, J.; Zavarin, M.; Zhao, P.; Kersting, A. B.

2012-12-01

Plutonium (Pu) release to the environment through nuclear weapon development and the nuclear fuel cycle is an unfortunate legacy of the nuclear age. In part due to public health concerns over the risk of Pu contamination of drinking water, predicting the behavior of Pu in both surface and sub-surface water is a topic of continued interest. Typically it was assumed that Pu mobility in groundwater would be severely restricted, as laboratory adsorption studies commonly show that naturally occurring minerals can effectively remove plutonium from solution. However, evidence for the transport of Pu over significant distances at field sites highlights a relative lack of understanding of the fundamental processes controlling plutonium behavior in natural systems. At several field locations, enhanced mobility is due to Pu association with colloidal particles that serve to increase the transport of sorbed contaminants (Kersting et al., 1999; Santschi et al., 2002, Novikov et al., 2006). The ability for mineral colloids to transport Pu is in part controlled by its oxidation state and the rate of plutonium adsorption to, and desorption from, the mineral surface. Previously we have investigated the adsorption affinity of Pu for montmorillonite colloids, finding affinities to be similar over a wide range of Pu concentrations. In the present study we examine the stability of adsorbed Pu on the mineral surface. Pu(IV) at an initial concentration of 10-10 M was pre-equilibrated with montmorillonite in a background electrolyte at pH values of 4, 6 and 8. Following equilibration, aliquots of the suspensions were placed in a flow cell and Pu-free background electrolyte at the relevant pH was passed through the system. Flow rates were varied in order to investigate the kinetics of desorption and hence gain a mechanistic understanding of the desorption process. The flow cell experiments demonstrate that desorption of Pu from the montmorillonite surface cannot be modeled as a simple

Transfer parameters of radionuclides in the marine environment

International Nuclear Information System (INIS)

1996-03-01

To increase the accuracy of estimation of exposure dose by radionuclides in the marine, the informations of environmental parameter data in the marine were collected, arranged and discussed. The informations were discussed by 'a sectional committee of marine suspended solids and sediment'. The following problems were investigated and the studies were recorded in this report, clear explanation about the distribution factor (kd), the estimation method of kd, the fluctuating factor of kd data (properties of suspension and sediment, differences among the experimental methods), the physical and chemical behavior of radionuclides, sediment of radionuclides by means of sorption to the suspended particles in the marine, sorption of radionuclides into the marine soil (sediment), re-eluent of radionuclides sorpted in the marine soil (sediment), and relation between marine organism and marine suspended materials and sediment. (S.Y.)

A study of sorption mechanism onto cement hydrates by isotherm measurements

International Nuclear Information System (INIS)

Sugiyama, Daisuke; Fujita, Tomonari

2003-01-01

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

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

International Nuclear Information System (INIS)

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

1992-01-01

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

Kinetics of strontium sorption in calcium phosphate

International Nuclear Information System (INIS)

Bacic, S.; Komarov, V.F.; Vukovic, Z.

1989-01-01

Kinetics of strontium sorption by highly dispersed solids: tricalcium phosphate (Ca 3 (PO 4 ) 2 , TCP) and hydroxyapatite (Ca 5 (PO 4 ) 3 )H, HAP) were investigated. Analysis of sorption data was made taking into consideration composition and morphology of ultra micro particles. Conclusion is that the isomorphous strontium impurity is structurally sensitive element for calcium phosphate. It was determined that the beginning of strontium desorption corresponds to the beginning of transformation of the TCP - HAP (author)

Hysteresis and Temperature Dependency of Moisture Sorption – New Measurements

DEFF Research Database (Denmark)

Rode, Carsten; Hansen, Kurt Kielsgaard

2011-01-01

measurements of hysteresis and temperature dependency of the moisture sorption characteristics of three different porous building materials: aerated concrete, cement paste and spruce. Scanning curves are measured for all three materials where periods with adsorption and desorption interrupt each other...... intermittently. For one of the materials, aerated concrete, the sorption curves are determined at three different temperatures....

Sorption of benzothiazoles onto sandy aquifer material under equilibrium and nonequlibrium conditions

Directory of Open Access Journals (Sweden)

Kragulj Marijana M.

2014-01-01

Full Text Available In this study, the sorption behaviour of 1,3-benzothiazole (BT and 2-(methylthiobenzothiazole (MTBT was investigated on Danube geosorbent under equilibrium and nonequilibrium conditions. All sorption isotherms fitted well with the Freundlich model (R2=0.932-0.993. The results showed that organic matter of the Danube geosorbent has a higher sorption affinity for the more hydrophobic MTBT compared to BT. However, sorption-desorption experiments showed that MTBT was more easily desorbed than BT molecules, which indicates the importance of absorption relative to adsorption in the overall sorption mechanism of MTBT. In general, molecules of BT and MTBT were more easily desorbed in the lower concentration range, which resulted in an increase in the hysteresis indices with increasing concentrations. Column experiments revealed that retention of the investigated compounds on the aquifer material followed the compound’s hydrophobicity. BT showed a lower retention, in accordance with its lower sorption affinity obtained in the static experiments, while MTBT showed a greater sorption affinity, and thus had a longer retention time on the column. Thus during transport BT represent greater risk for groundwaters than MTBT. These results have increased our understanding of benzothiazoles sorption and desorption process which represent one of the most important factors which influence the behaviour of organic compounds in the environment.

Web-based sorption database (KAERI-SDB)

International Nuclear Information System (INIS)

Lee, Jae Kwang; Baik, Min Hoon

2010-10-01

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

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

International Nuclear Information System (INIS)

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

1984-01-01

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

Sorption of thiabendazole in sub-tropical Brazilian soils.

Science.gov (United States)

de Oliveira Neto, Odilon França; Arenas, Alejandro Yopasa; Fostier, Anne Hélène

2017-07-01

Thiabendazole (TBZ) is an ionizable anthelmintic agent that belongs to the class of benzimidazoles. It is widely used in veterinary medicine and as a fungicide in agriculture. Sorption and desorption are important processes influencing transport, transformation, and bioavailability of xenobiotic compounds in soils; data related to sorption capacity are therefore needed for environmental risk assessments. The aim of this work was to assess the sorption potential of TBZ in four Brazilians soils (sandy, sandy-clay, and clay soils), using batch equilibrium experiments at three pH ranges (2.3-3.0, 3.8-4.2, and 5.5-5.7). The Freundlich sorption coefficient (K F ) ranged from 9.0 to 58 μg 1-1/n  (mL) 1/n  g -1 , with higher values generally observed at the lower pH ranges (2.3-3.0 and 3.8-4.2) and for clay soils. The highest organic carbon-normalized sorption coefficients (K OC ) obtained at pH 3.8-5.7 (around the natural pH range of 4.1-5.0) for both clay soils and sandy-clay soil were 3255 and 2015 mL g -1 , respectively. The highest correlations K F vs SOM (r = 0.70) and K F vs clay content (r = 0.91) were observed at pH 3.8-4.2. Our results suggest that TBZ sorption/desorption is strongly pH dependent and that its mobility could be higher in the studied soils than previously reported in soils from temperate regions.

Sorption of cesium and uranium to Feldspar

International Nuclear Information System (INIS)

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

1990-07-01

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

2.6. Sorption of serum albumin by ethynyl-piperidol hydrogels

International Nuclear Information System (INIS)

Khalikov, D.Kh.

2012-01-01

The sorption of serum albumin by ethynyl-piperidol hydrogels was studied in this article. Albumins adsorption on the surface of solids was considered. The capacity of cross-linked ethynyl piperidol polymers to the serum albumin was considered as well. The kinetic curves of sorption of human serum albumin by triple copolymer of isopropenyl trimethyl ethynyl piperidol were constructed. Sorption activity of ethynyl-piperidol polymers depending on ph of solution of human serum albumin were defined. Influence of solution ionic strength on sorption of human serum albumin was defined as well. The desorption of human serum albumin from the complexes with hydrogels was examined.

Sorption heat engines: simple inanimate negative entropy generators

OpenAIRE

Muller, Anthonie W. J.; Schulze-Makuch, Dirk

2005-01-01

The name 'sorption heat engines' is proposed for simple negative entropy generators that are driven by thermal cycling and work on alternating adsorption and desorption. These generators are in general not explicitly recognized as heat engines. Their mechanism is applicable to the fields of engineering, physics, chemistry, geology, and biology, in particular the origin of life. Four kinds of sorption heat engines are distinguished depending on the occurrence of changes in the adsorbent or ads...

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

Energy Technology Data Exchange (ETDEWEB)

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

1995-07-01

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

Status of subseabed repository design concepts and radionuclide

International Nuclear Information System (INIS)

Brush, L.H.

1980-01-01

Various projects underway in support of the marine disposal of radioactive wastes are described. These include: geochemical studies on sediments; canister-related research and development activities; radionuclide transport studies through smectitic sediments; seawater-sediment interactions under near-field conditions; effects of a radiation field on high temperature, seawater-sediment interactions; sorption of fission products and actinides by deep-sea sediments under far-field (below 100 0 C) conditions; sorption experiments using column diffusion; development of a computer code, IONMIG, to model the migration of radionuclides through undisturbed deep-sea sediments; and planning for a field test of the laboratory measurements and computer models of radionuclide transport

Sorption Enhanced Reaction Process (SERP) for production of hydrogen

Energy Technology Data Exchange (ETDEWEB)

Anand, M.; Hufton, J.; Mayorga, S. [Air Products and Chemicals, Inc., Allentown, PA (United States)] [and others

1996-10-01

Sorption Enhanced Reaction Process (SERP) is a novel process that is being developed for the production of lower cost hydrogen by steam-methane reforming (SMR). In this process the reaction of methane with steam is carried out in the presence of an admixture of a catalyst and a selective adsorbent for carbon dioxide. The key consequences of SERP are: (i) reformation reaction is carried out at a significantly lower temperature (300-500{degrees}C) than that in a conventional SMR reactor (800-1100{degrees}C), while achieving the same conversion of methane to hydrogen, (ii) the product hydrogen is obtained at reactor pressure (200-400 psig) and at 98+% purity directly from the reactor (compared to only 70-75% H{sub 2} from conventional SMR reactor), (iii) downstream hydrogen purification step is either eliminated or significantly reduced in size. The first phase of the program has focused on the development of a sorbent for CO{sub 2} which has (a) reversible CO{sub 2} capacity >0.3 mmol/g at low partial pressures of CO{sub 2} (0.1 - 1.0 atm) in the presence of excess steam (pH{sub 2}O/pCO{sub 2}>20) at 400-500{degrees}C and (b) fast sorption-desorption kinetics for CO{sub 2}, at 400-500{degrees}C. Several families of supported sorbents have been identified that meet the target CO{sub 2} capacity. A few of these sorbents have been tested under repeated sorption/desorption cycles and extended exposure to high pressure steam at 400-500{degrees}C. One sorbent has been scaled up to larger quantities (2-3 kg) and tested in the laboratory process equipment for sorption and desorption kinetics of CO{sub 2}. The CO{sub 2}, sorption and desorption kinetics are desirably fast. This was a critical path item for the first phase of the program and now has been successfully demonstrated. A reactor has been designed that will allow nearly isothermal operation for SERP-SMR. This reactor was integrated into an overall process flow diagram for the SERP-SMR process.

Investigations for the influence of geochemical parameters on the sorption and desorption of lanthanides and uranium onto opalinus clay as potential host rock for a repository

International Nuclear Information System (INIS)

Moeser, Christina

2010-01-01

The development of a disposal in deep geological formations for radioactive waste is a very important task for the future. The safety assessment for more than a hundred thousand years needs a full understanding of all processes of interaction between the radioactive waste and the surrounded formations. This work contributes to this understanding. The interaction between lanthanides (homologues of the actinides americium, curium and berkelium) / uranium and the host rock opalinus clay under influence of organic substances (NOM) have been analyzed and discussed. The complex system was split into 3 binary basic systems with the following interactions - Interactions between lanthanides / uranium and NOM - Interactions between lanthanides / uranium and the opalinus clay - Interactions between NOM and opalinus clay All binary systems can be influenced by geological parameters like pH, ion strength and competing cations. The sorption / desorption of the lanthanides onto the opalinus clay is analyzed via inductively coupled plasma mass spectrometry. For the investigation of the complexation behavior of metals with NOM we used capillary electrophoresis coupled with inductively coupled plasma mass spectrometry. Under these conditions the chosen model organic humic acid affected the sorption of the lanthanides onto opalinus clay favorably. The smaller organic compounds, which dominate in the composition of the clay organics, remobilized the metals after sorption onto clay and the sorption can be inhibited by NOM. Due to the reduced metal sorption onto Opalinus clay by NOM, a migration through the clay may be possible.

Sorption of environmentally relevant radionuclides (U(VI), Np(V)) and lanthanides (Nd(III)) on feldspar and mica

Energy Technology Data Exchange (ETDEWEB)

Richter, Constanze

2015-11-05

A safe storage of radioactive waste in repositories is an important task to protect humans and the environment from radio- and chemotoxicity. Long-term safety assessments predict the behavior of potential environmental contaminants like the actinides plutonium, uranium, or neptunium, in the near and far field of repositories. For such safety assessments, it is necessary to know the migration behavior of the contaminants in the environment, which is mainly dependent on the aquatic speciation, the solubility product of relevant solid phases, and the retardation due to sorption on surrounding minerals. Thus, an investigation of sorption processes of contaminants onto different minerals as well as the derivation of mineral specific surface complexation model (SCM) parameters is of great importance. Feldspar and mica are widely distributed in nature. They occur as components of granite, which is considered as a potential host rock for a repository in Germany, and in numerous other rocks, and thus also in the far field of nearly all repositories. However, their sorption behavior with actinides has only been scarcely investigated until now. In order to better characterize these systems and subsequently to integrate these minerals into the long-term safety assessments, this work focuses on the investigation of the sorption behavior of U(VI), Np(V), and Nd(III) as analogue for An(III) onto the minerals orthoclase and muscovite, representing feldspars and mica, respectively. All investigations were performed under conditions relevant to the far field of a repository. In addition to the extensive characterization of the minerals, batch sorption experiments, spectroscopic investigations, and surface complexation modeling were performed to elucidate the uptake and speciation of actinides on the mineral surfaces. In addition, the influence of microorganisms naturally occurring on the mineral surfaces and the effect of Ca{sup 2+} on U(VI) uptake on the minerals was studied. The

Sorption of environmentally relevant radionuclides (U(VI), Np(V)) and lanthanides (Nd(III)) on feldspar and mica

International Nuclear Information System (INIS)

Richter, Constanze

2015-01-01

A safe storage of radioactive waste in repositories is an important task to protect humans and the environment from radio- and chemotoxicity. Long-term safety assessments predict the behavior of potential environmental contaminants like the actinides plutonium, uranium, or neptunium, in the near and far field of repositories. For such safety assessments, it is necessary to know the migration behavior of the contaminants in the environment, which is mainly dependent on the aquatic speciation, the solubility product of relevant solid phases, and the retardation due to sorption on surrounding minerals. Thus, an investigation of sorption processes of contaminants onto different minerals as well as the derivation of mineral specific surface complexation model (SCM) parameters is of great importance. Feldspar and mica are widely distributed in nature. They occur as components of granite, which is considered as a potential host rock for a repository in Germany, and in numerous other rocks, and thus also in the far field of nearly all repositories. However, their sorption behavior with actinides has only been scarcely investigated until now. In order to better characterize these systems and subsequently to integrate these minerals into the long-term safety assessments, this work focuses on the investigation of the sorption behavior of U(VI), Np(V), and Nd(III) as analogue for An(III) onto the minerals orthoclase and muscovite, representing feldspars and mica, respectively. All investigations were performed under conditions relevant to the far field of a repository. In addition to the extensive characterization of the minerals, batch sorption experiments, spectroscopic investigations, and surface complexation modeling were performed to elucidate the uptake and speciation of actinides on the mineral surfaces. In addition, the influence of microorganisms naturally occurring on the mineral surfaces and the effect of Ca 2+ on U(VI) uptake on the minerals was studied. The

Review of the sorption of radionuclides on the bedrock of Haestholmen and on construction and backfill materials of a final repository for reactor wastes

International Nuclear Information System (INIS)

Kulmala, S.; Hakanen, M.

1992-10-01

Imatran Voima Oy (IVO) has plans to build a final repository for reactor wastes in the bedrock of the nuclear power plant site at Haestholmen, Loviisa. This report summarizes the sorption studies of radionuclides in Finnish bedrock performed at the Department of Radiochemistry, University of Helsinki. The values of mass distribution ratios, K d , and surface distribution ratios, K a ; of carbon, calsium, Zirconium, niobium, cobalt, nickel, strontium, cesium, uranium, plutonium, americium, thorium, chlorine, iodine and technetium are surveyed. Special attention is paid to the sorption data for construction and backfill materials of rector waste repository and the bedrock of Haestholmen. Safety assessment of a repository includes calculations of migration of the waste element in construction materials and backfill in the nearfield and in bedrock. Retardation by sorption of waste nuclides compared to groundwater flow is described by using distribution ratios between solid materials and water. (orig.)

Sorption Isotherm of Southern Yellow Pine—High Density Polyethylene Composites

Directory of Open Access Journals (Sweden)

Feihong Liu

2015-01-01

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

Sorption of radionuclides on geologic media - A literature survey. I: Fission Products

International Nuclear Information System (INIS)

Andersson, K.; Allard, B.

1983-01-01

The fission products investigated were cobalt, nickel, strontium, cesium, technetium and iodine. Parameters of importance to sorption have been identified and a tabulation of distribution coefficients for groundwater conditions (pH 7-9, low to medium ionic strength) is included in the report. For cobalt and nickel the sorption is related to hydrolysis. High sorption is observed at a pH where hydrolysis become important and the sorption is high as long as cationic hydrolysis products are formed. When pH is increased or negatively charged hydrolysis products may be formed and the sorption decreases. For strontium hydrolysis is of no importance at the normal pH of groundwater, but in groundwater above pH 9 carbonate complexation may occur. For most minerals, the sorption is low, ususally with a pronounced pH dependence. Other important parameters are ionic strength and CEC. A nonselective sorption due to electrostatic interactions between negatively charged mineral surfaces and Sr 2+ seems to occur. For cesium no hydrolysis may be expected and pH has less importance than for Sr. For most minerals, however, the sorption of Cs is higher than for Sr. Important parameters are nuclide concentration and ionic strength. A selective for Cs-sorption is found for some minerals, mostly sheet-silicates. For technetium sorption is due to a reduction of TcO 4 - TcO 2 (s) and as anions are poorly sorbed, the sorption is dependent on the redox potential. Iodine is also anionic and poorly sorbed. Minerals containing ions capable of forming iodides with low solubility (Ag, Mg, Pb etc) are, however, sorbing I - . (Author)

Sorption and diffusion of Cs and I in concrete

International Nuclear Information System (INIS)

Andersson, K.; Torstenfelt, B.; Allard, B.

1983-01-01

Concrete has been suggested as a possible encapsulation material for long-term storage of low and medium level radioactive waste. At an underground storage of concrete encapsulated waste, a slow release of radioactive elements into the groundwater by diffusion through the concrete must be considered in the safety analysis. The diffusion may be delayed by sorption reactions on the solid. A wide range of long-lived radionuclides may be present in the low and medium level radioactive waste. Here, the sorption and diffusion of iodide and cesium on slag cement paste and concrete has been studied. The influence of four different water phases (pore water, groundwater, Baltic Sea water and sea water) as well as the influence of some added species (carbonate, sulphate and magnesium) has been investigated. A significant sorption of iodide on cement paste in contact with pore water was observed, indicating that the diffusion may be expected to be retarded in this medium. For cesium the highest sorption was found for concrete and groundwater. This means that the sorption increases as the concrete is weathered. Low or insignificant sorption was found for the cement paste, indicating that the ballast is responsible for the Cs-sorption. Carbonatization enhances the Cs-sorption by about a factor of 3. The diffusivity of Cs in concrete and cement paste was determined to between 2x10 - 14 and 8x10 - 14 m 2 /s in pore water (where an insignificant sorption was observed). The choice of ballast as well as addition of suitable getters with high sorption of the long-lived radionuclides might decrease the mass transfer rate through the cement. (Authors)

Sorption properties of bentonite clays towards Pu(IV), U(VI), Np(V) and Cs: experimental and surface complexation study

Energy Technology Data Exchange (ETDEWEB)

Sabodina, M.N. [Institute of Physical Chemistry of Russian Academy of Science, Moscow 119192 (Russian Federation); Kalmykov, St.N.; Sapozhnikov, Yu.A. [Radiochemistry div., Chemistry dept., Lomonosov Moscow State University, Moscow 119992, (Russian Federation); Gupalo, T.A.; Beigul, V.P. [VNIPI Promtechnology, Moscow (Russian Federation)

2005-07-01

Full text of publication follows: Sorption of radionuclides, their diffusion in bentonite as well as its solubility are the major factors that define bentonite as a geochemical barrier. Sorption of cations by bentonite could be governed by two mechanisms including ion exchange with interlayer cations and formation of surface complexes with either silanol or aluminol groups. The aim of this work was to study mechanisms of {sup 137}Cs, Pu(IV), Np(V) and U(VI) sorption by bentonite and their solubility in bentonite pore waters. Bentonite (Khakassiya deposit) used in the experiments was taken in Na-form and characterized by powder X-ray diffraction, scanning electron microscopy, potentiometric titration. The cation exchange capacities of bentonite at pH=6 were measured by isotopic exchange with {sup 22}Na{sup +} and Cs{sup +} saturation. Sorption experiments were performed in N{sub 2} atmosphere in plastic vials. Bentonite samples were left in the working solutions to swell for few days before sorption experiments were performed. After the desired concentration of radionuclide ({sup 137}Cs, {sup 238}Pu, {sup 239}Pu, {sup 237}Np, {sup 239}Np, {sup 238}U) was added to the suspension, the required pH values are established and samples were left until the equilibrium was reached. Separation of solution after the sorption was performed using micro- and ultrafiltration techniques. The sorption of Pu(IV), U(VI) and Np(V) was highly pH dependent that indicates predominant surface complexation mechanism of sorption. For {sup 137}Cs the pH dependence of sorption was less pronounced and significant decrease of sorption occurs at pH<1.7 that indicate the ion exchange as the major mechanism. The equilibrium constant of Na{sup +}/Cs{sup +} exchange was calculated form sorption isotherms and pH dependence of sorption. It is established using micro- and ultra-filtrations, that sorption of radionuclides onto bentonite nano colloids is essential. Surface complexation modeling exercises

Sorptive and desorptive fractionation of dissolved organic matter by mineral soil matrices.

Science.gov (United States)

Oren, Adi; Chefetz, Benny

2012-01-01

Interactions of dissolved organic matter (DOM) with soil minerals, such as metal oxides and clays, involve various sorption mechanisms and may lead to sorptive fractionation of certain organic moieties. While sorption of DOM to soil minerals typically involves a degree of irreversibility, it is unclear which structural components of DOM correspond to the irreversibly bound fraction and which factors may be considered determinants. To assist in elucidating that, the current study aimed at investigating fractionation of DOM during sorption and desorption processes in soil. Batch DOM sorption and desorption experiments were conducted with organic matter poor, alkaline soils. Fourier-transform infrared (FTIR) and UV-Vis spectroscopy were used to analyze bulk DOM, sorbed DOM, and desorbed DOM fractions. Sorptive fractionation resulted mainly from the preferential uptake of aromatic, carboxylic, and phenolic moieties of DOM. Soil metal-oxide content positively affected DOM sorption and binding of some specific carboxylate and phenolate functional groups. Desorptive fractionation of DOM was expressed by the irreversible-binding nature of some carboxylic moieties, whereas other bound carboxylic moieties were readily desorbed. Inner-sphere, as opposed to outer-sphere, ligand-exchange complexation mechanisms may be responsible for these irreversible, as opposed to reversible, interactions, respectively. The interaction of aliphatic DOM constituents with soil, presumably through weak van der Waals forces, was minor and increased with increasing proportion of clay minerals in the soil. Revealing the nature of DOM-fractionation processes is of great importance to understanding carbon stabilization mechanisms in soils, as well as the overall fate of contaminants that might be associated with DOM. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Determination of persistent organic pollutants in solid environmental samples using accelerated solvent extraction and supercritical fluid extraction. Exhaustive extraction and sorption/desorption studies of PCBs

Energy Technology Data Exchange (ETDEWEB)

Bjoerklund, E.

1998-10-01

to verify that the developed SFE methods are exhaustive. It is quite clear though that there is no reason to continue using for example Soxhlet extraction, which should be replaced in routine laboratories. The possibility of utilizing SFE as a selective tool in sorption/desorption studies of POPs in natural sediments was also addressed. This second objective was proven successful and sediments could be characterized in terms of resistance towards desorption of bound analytes under supercritical conditions. These data could be correlated to desorption processes occurring under natural conditions. Additionally it could be verified that sorption of POPs from water to sediment is a very slow process requiring months or even years. This supports recent research results, demonstrating that distribution coefficients many times are underestimated since the system has not reached equilibrium 205 refs, 10 figs, 3 tabs

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

International Nuclear Information System (INIS)

Tachi, Yukio; Suyama, Tadahiro

2016-03-01

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

Radionuclide and heavy metal biosorption by Pseudomonas biomass

International Nuclear Information System (INIS)

Sar, Pinaki; D'Souza, S.F.; Kazy, Sufia K.; Singh, S.P.

2001-01-01

Biosorptive metal (nickel and copper) and radionuclide (uranium) uptake capacity of two Pseudomonas strains was investigated in order to develop biotechnological strategies for toxic metals remediation. Lyophilized Pseudomonas biomass showed a very high uranium loading of 541 mg g -1 dry wt. Compared to this, the other bacterial strain of Pseudomonas aeruginosa used for nickel and copper removal yielded a maximum value of 265 mg g -1 and 137 mg g -1 respectively. Cation binding by both the biomass was fast saturating, pH -dependent process with optimum pH for U, Cu and Ni was pH 5.0, 7.0 and 8.0, respectively. In bimetallic combination, U sorption was inhibited only by Fe 3+ , Al 3+ and Cu 2+ suggesting a selective cation binding by the Pseudomonas biomass. In case of Ni and Cu, presence of Na, K or Ca increased the metal binding while Cd and Pb was antagonistic. Mineral acids could recover more than 75% (on average) of sorbed Ni or Cu. Noticeably, uranium and copper desorption was specifically high (88-90%) with sodium carbonate while calcium carbonate showed a good result for nickel. The overall data are in favour of deployment of the test biomass as efficient metal/radionuclide removal/recovery system. (author)

Sorption of U(VI) and Am(III) on Eucalyptus Biochar

International Nuclear Information System (INIS)

Mishra, Vijayakriti; Sureshkumar, M.K.; Kaushik, C.P.

2016-01-01

Biochar is partially oxidized residues from substrates of biological origin. Due to their binding properties with various organic and inorganic pollutants, these materials are widely studied for pollutant abatement both in field studies and laboratory investigations. Though large quantity of information is available on the use of biochar of various origin for heavy metals, studies pertaining to their use in radionuclide sorption are scarce in literature. Here we are reporting the sorption characteristics of U(VI) and Am(III) on to eucalyptus biochar as a function of various operating parameters such as solution pH, initial metal ion concentration, contact time and ionic strength of the medium. Overall the present studies shows that eucalyptus biochar is a suitable sorbent for the sorption of heavy radionuclides from aqueous solutions

Effects of mineralogy on sorption of strontium and cesium onto Calico Hills Tuff

International Nuclear Information System (INIS)

Meyer, R.E.; Arnold, W.D.; Case, F.I.; O'Kelley, G.D.; Land, J.F.

1990-04-01

The sorption properties of tuff formations at the proposed site for the high-level nuclear waste repository at Yucca Mountain, Nevada, have been extensively studied. Sorption and desorption measurements were made of strontium and cesium onto clinoptilolite and Calico Hills Tuff. The object was to see whether there was a correlation between sorption of strontium and cesium onto Calico Hills Tuff and the sorption of strontium and cesium onto clinoptilolite based on the content of clinoptilolite in the Calico Hills Tuff. 13 refs., 10 figs., 6 tabs

Cementitious Near-Field Sorption Data Base for Performance Assessment of an ILW Repository in Opalinus Clay

Energy Technology Data Exchange (ETDEWEB)

Wieland, E.; Van Loon, L. R

2003-08-01

The present report describes a cement sorption database (SDB) for the safety-relevant radionuclides to be disposed of in the planned Swiss repository for long-lived intermediate-level radioactive wastes (ILW). This report is an update on earlier SDBs, which were compiled for the cementitious near field of a repository for low- and intermediate-level radioactive wastes (L/ILW) by BRADBURY + SAROTT (1995) and BRADBURY + VAN LOON (1998). The radionuclide inventories are determined by the waste streams to be disposed of in the ILW repository. A list of the safety-relevant radionuclides was provided based on the currently available information on ILW inventories. The compositions of the cement porewaters in the near fields of the L/ILW and ILW repositories, which had been calculated using well-established codes for modelling cement degradation, were compared to identify any differences in the near-field conditions and to assess their influence on radionuclide sorption. Sorption values were selected based on the previously reported SDBs for the near field of the L/ILW repository. Sorption values were revised if new information and/or data were available which allowed changes to or re-appraisals of the data to be made. The sorption values recommended in this report were either selected on the basis of data from in-house experimental studies or from literature data. For some key radioelements, i.e., Cs(l), Sr(II), Ni(II), Eu(lll), Th(IV) and Sn(IV), new data were available from in-house measurements. These elements had been selected for experimental studies due to their relevance to safety assessment and/or their importance as appropriate chemical analogues. Degradation products of bitumen and cellulose, concrete admixtures and cement-derived near-field colloids were taken into account as the main potential perturbations, which could reduce radionuclide sorption in the near field. Possible impacts of the perturbing factors on radionuclide mobility were considered and

Recent progress in sorption mechanisms and models

International Nuclear Information System (INIS)

Fedoroff, M.; Lefevre, G.

2005-01-01

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

Sorption of organic gases in a furnished room

Energy Technology Data Exchange (ETDEWEB)

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

2003-11-30

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

Sorption of selenium on Mg-Al and Mg-Al-Eu layered double hydroxides

International Nuclear Information System (INIS)

Curtius, H.; Paparigas, Z.; Kaiser, G.

2008-01-01

Salt domes represent deep geological formations which are under consideration as final repositories for irradiated research reactor fuel elements. For long-term safety aspects the mobilisation of the radionuclides due to a water ingress is intensively investigated. At the Institute of Energy Research (IEF-6), leaching experiments were performed in a hot cell facility with UAl x -Al and U 3 Si 2 -Al dispersed research reactor fuel elements in repository-relevant MgCl 2 -rich salt brines under anaerobic conditions. The fuel plates corroded completely within one year and a Mg-Al-layered double hydroxide (LDH) with chloride as interlayer anion was identified as one crystalline phase component of the corrosion products (secondary phases). This Mg-Al-LDH was synthesized, characterized, and the ability to retard europium by an incorporation process was investigated. Europium, as a representative for lanthanides, was identified to be one of the radionuclides which were found in the corrosion products. We could show that europium was incorporated in the lattice structure. LDHs have high anion exchange capacities that enhance their potential to remove anionic contaminants from aqueous systems. In this work the sorption behaviour of selenium in the chemical form as selenite (SeO 3 2- ) on Mg-Al-LDH and on Mg-Al-Eu-LDH was investigated. Especially the influence of the larger europium-III ion was of interest. It represents in the Mg-Al-Eu-LDH about 10% of the molar aluminium amount. The sorption has been experimentally studied in a wide range of pH, ionic strength, radionuclide and sorbent concentration. Both LDHs with chloride as interlayer anion were synthesized by a coprecipitation method under controlled conditions, and their main physico-chemical properties were analyzed prior to the sorption experiments. The sorption kinetics of selenite on the LDHs in water and in MgCl 2 -rich brine were rapid using a LDH concentration of 10 g/L. Equilibrium, indicated by stable p

Influence of organic fertilization on the sorption mechanisms of 241 Am in tropical soils

International Nuclear Information System (INIS)

Pereira, Tatiane Rocha

2009-01-01

In this work the mechanisms involved in the sorption of 241 Am were investigated depending on the physicochemical properties of some Brazilian soils and on alterations promoted by organic amendment. This experimental study was conducted in a controlled area, where pots containing different kinds of soils (histisol, ferralsol and nitisol), with different organic amendment doses (without amendment; 2 kg m -2 and 4 kg m -2 ) were artificially contaminated by radioactive solution water, which contained 241 Am. Migration studies, distribution (or partition) coefficient (KJ), bioavailability and organic matter were carried out in these soils, with ar without organic amendment. In order to evaluate the effective bioavailability of radionuclides, radish (Raphanus sativus L.) was cultivated in these pots, and later the concentration of 241 Am in radish's roots was measured. The main results show that 241 Am tends to be strongly attached to organic matter and that organic amendment in tropical soils minimizes the radionuclide studied desorption. Also, distribution (or partition) coefficient values for 241 Am were generated and these values are smaller than those ones determined for soils from temperate zones. Physical and chemical fractioning of organic matter were carried out. (author)

Simulation of radionuclide retardation at Yucca Mountain using a stochastic mineralogical/geochemical model

International Nuclear Information System (INIS)

Birdsell, K.H.; Campbell, K.; Eggert, K.; Travis, B.J.

1990-01-01

This paper presents preliminary transport calculations for radionuclide movement at Yucca Mountain. Several different realizations of spatially distributed sorption coefficients are used to study the sensitivity of radionuclide migration. These sorption coefficients are assumed to be functions of the mineralogic assemblages of the underlying rock. The simulations were run with TRACRN 1 , a finite-difference porous flow and radionuclide transport code developed for the Yucca Mountain Project. Approximately 30,000 nodes are used to represent the unsaturated and saturated zones underlying the repository in three dimensions. Transport calculations for a representative radionuclide cation, 135 Cs, and anion, 99 Tc, are presented. Calculations such as these will be used to study the effectiveness of the site's geochemical barriers at a mechanistic level and to help guide the geochemical site characterization program. The preliminary calculations should be viewed as a demonstration of the modeling methodology rather than as a study of the effectiveness of the geochemical barriers. The model provides a method for examining the integration of flow scenarios with transport and retardation processes as currently understood for the site. The effects on transport of many of the processes thought to be active at Yucca Mountain may be examined using this approach. 11 refs., 14 figs., 1 tab

Radionuclides retention: from macroscopic to microscopic

International Nuclear Information System (INIS)

Simoni, E.

2002-01-01

In order to determine the radionuclides' sorption constants on solid natural minerals, both thermodynamic and structural investigations, using spectroscopic techniques, are presented. The natural clays, that could be used as engineering barriers in the nuclear waste geological repository, are rather complex minerals. Therefore, in order to understand how these natural materials retain the radionuclides, it is necessary first to perform these studies on simple substrates such as single crystal, oxides and silicates, and then extrapolate the obtained results on the natural minerals. We examine in this paper the sorption processes of the hexavalent uranium on zircon (ZrSiO 4 ) and the trivalent curium on a natural clay (bentonite). The corresponding sorption curves are simulated using the results obtained with the following spectroscopic techniques: laser induced spectro-fluorimetry, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (EXAFS), diffuse reflectance infrared Fourier transform (DRIFT). (authors)

Simulation of the distribution of radionuclides in the reservoir bed for deep-well injection disposal of acid liquid radioactive waste

International Nuclear Information System (INIS)

Noskov, M.D.; Istomin, A.D.; Kesler, A.G.; Zubkov, A.A.; Zakharova, E.V.; Egorov, G.F.

2007-01-01

A mathematical model was developed for describing the changes in the state of the reservoir bed for dee-well injection disposal of acid liquid radioactive waste. The model considers the multicomponent filtration of the solution in the heterogeneous bed, sorption-desorption of radionuclides, taking into account the dependence of the distribution coefficient on the temperature and pH, as well as radioactive decay, interaction of acids with minerals, radiation-chemical and thermochemical decomposition of the acids, and dynamics of the temperature field, taking into account the convective heat transfer, thermal conductivity, and radiogenic heat release. The results of the simulation of the migration of radionuclides were reported, as well as of the distribution of the acids and the dynamics of the temperature field in the vicinity of the injection well of the site for deep-well injection disposal of the waste from Siberian Chemical Combine. A man-caused barrier is formed in the vicinity of the injection well, hindering the spread of radionuclides in the reservoir bed [ru

Preliminary report on retardation factors and radionuclide migration

International Nuclear Information System (INIS)

Isherwood, D.

1977-01-01

Available data on distribution coefficients for the biologically important radionuclides present in high-level waste were used to estimate retardation factors (K/sub f/) for a mass transport hydrologic model. The radionuclides were divided into 3 groups: fission products with no sorption (K/sub f/ = 1), fission products with sorption (K/sub f/ = 10 2 ), and the actinides and their daughter products (K/sub f/ = 10 4 ). Minimum and maximum values were assigned the latter two groups. Uncertainties as a function of time were estimated at +- an order of magnitude. 39 references, 5 tables

Conditions and processes affecting radionuclide transport

Science.gov (United States)

Simmons, Ardyth M.; Neymark, Leonid A.

2012-01-01

Characteristics of host rocks, secondary minerals, and fluids would affect the transport of radionuclides from a previously proposed repository at Yucca Mountain, Nevada. Minerals in the Yucca Mountain tuffs that are important for retarding radionuclides include clinoptilolite and mordenite (zeolites), clay minerals, and iron and manganese oxides and hydroxides. Water compositions along flow paths beneath Yucca Mountain are controlled by dissolution reactions, silica and calcite precipitation, and ion-exchange reactions. Radionuclide concentrations along flow paths from a repository could be limited by (1) low waste-form dissolution rates, (2) low radionuclide solubility, and (3) radionuclide sorption onto geological media.

Retardation characteristics of radionuclides in geologic media through batch and packed column experiments

International Nuclear Information System (INIS)

Park, Hun Hwee; Han, Kyung Won; Han, Pil Soo; Lee, Jae Owan; Park, Chung Kyun; Yang, Ho Yeon

1988-03-01

Batch and packed column experiments are performed to investigate the retardation characteristics of radionuclide,i.e, Cs-137 in geologic media. In batch experiment, the effects of important parameters on the sorption of radionuclide in geologic media, such as nuclide concentration, pH, and particle size are examined. The Kd value obtained from breakthrough curve was compared with that from the batch sorption experiment to investigate the applicability of the Kd value from batch experiment to prediction of radionuclide migration in dynamic flow through porous media. The proposed model of radionuclide migration in porous media is also verified using the experimental results. (Author)

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

Science.gov (United States)

Cáceres, Tanya; Venkateswarlu, Kadiyala

2018-02-02

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

Periodic Sorption of Tungstate Ions on Anionite AV-17-8

Directory of Open Access Journals (Sweden)

D’yachenko Aleksandr

2017-01-01

Full Text Available The multiple sorption of sodium tungstate resulting from the autoclave-soda digestion of a tungsten-bearing concentrate was studied using anion-exchange resin AV-17-8. The choice of ion exchange resin was carried out under static conditions using highly basic anionites. The sorption and desorption plots for tungstate and carbonate ions were demonstrated under dynamic conditions. The total dynamic capacity of the resin was estimated for each species of the ions in three sorption cycles. The applicability of the AV-17-8 resin as a sorbent in the autoclave-soda process flowsheet was determined.

Containment of uranium in the proposed Egyptian geologic repository for radioactive waste using hydroxyapatite

International Nuclear Information System (INIS)

Moore, Robert Charles; Hasan, Ahmed Ali Mohamed; Headley, Thomas Jeffrey; Sanchez, Charles Anthony; Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A.; Holt, Kathleen Caroline

2003-01-01

Currently, the Egyptian Atomic Energy Authority is designing a shallow-land disposal facility for low-level radioactive waste. To insure containment and prevent migration of radionuclides from the site, the use of a reactive backfill material is being considered. One material under consideration is hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 , which has a high affinity for the sorption of many radionuclides. Hydroxyapatite has many properties that make it an ideal material for use as a backfill including low water solubility (K sp > 10 -40 ), high stability under reducing and oxidizing conditions over a wide temperature range, availability, and low cost. However, there is often considerable variation in the properties of apatites depending on source and method of preparation. In this work, we characterized and compared a synthetic hydroxyapatite with hydroxyapatites prepared from cattle bone calcined at 500 C, 700 C, 900 C and 1100 C. The analysis indicated the synthetic hydroxyapatite was similar in morphology to 500 C prepared cattle hydroxyapatite. With increasing calcination temperature the crystallinity and crystal size of the hydroxyapatites increased and the BET surface area and carbonate concentration decreased. Batch sorption experiments were performed to determine the effectiveness of each material to sorb uranium. Sorption of U was strong regardless of apatite type indicating all apatite materials evaluated. Sixty day desorption experiments indicated desorption of uranium for each hydroxyapatite was negligible.

Containment of uranium in the proposed Egyptian geologic repository for radioactive waste using hydroxyapatite

International Nuclear Information System (INIS)

Moore, Robert Charles; Hasan, Ahmed Ali Mohamed; Headley, Thomas Jeffrey; Sanchez, Charles Anthony; Zhao, Hongting; Salas, Fred Manuel; Hasan, Mahmoud A.; Holt, Kathleen Caroline

2004-01-01

Currently, the Egyptian Atomic Energy Authority is designing a shallow-land disposal facility for low-level radioactive waste. To insure containment and prevent migration of radionuclides from the site, the use of a reactive backfill material is being considered. One material under consideration is hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 , which has a high affinity for the sorption of many radionuclides. Hydroxyapatite has many properties that make it an ideal material for use as a backfill including low water solubility (K sp >10 -40 ), high stability under reducing and oxidizing conditions over a wide temperature range, availability, and low cost. However, there is often considerable variation in the properties of apatites depending on source and method of preparation. In this work, we characterized and compared a synthetic hydroxyapatite with hydroxyapatites prepared from cattle bone calcined at 500 C, 700 C, 900 C and 1100 C. The analysis indicated the synthetic hydroxyapatite was similar in morphology to 500 C prepared cattle hydroxyapatite. With increasing calcination temperature the crystallinity and crystal size of the hydroxyapatites increased and the BET surface area and carbonate concentration decreased. Batch sorption experiments were performed to determine the effectiveness of each material to sorb uranium. Sorption of U was strong regardless of apatite type indicating all apatite materials evaluated. Sixty day desorption experiments indicated desorption of uranium for each hydroxyapatite was negligible

Fluoride ions sorption of the water using natural and modified hematite with aluminium hydroxide

International Nuclear Information System (INIS)

Teutli S, E. A.

2011-01-01

Fluorine is a mineral known for its dental benefits, but fluoride ions can cause fluoro sis in excessive quantities. There are many epidemiological studies on possible adverse effects resulting from prolonged ingestion of fluoride through drinking water. These studies demonstrate that fluoride mainly affects the bone tissue (bones and teeth), may produce an adverse effect on tooth enamel and can cause mild dental fluoro sis at concentrations from 0.9 to 1.2 mg/L in drinking water. In several states of Mexico, water contaminated with fluoride ions can be found, such as Aguascalientes, Chihuahua, Coahuila, Durango, Guanajuato, Sonora, Zacatecas, San Luis Potosi and Jalisco, where the fluoride ions levels are higher than 1.5 mg/L, established by the Mexican Official Standard (NOM-127-Ssa-2000) which sets the permissible limits of water for human use and consumption. Currently, several technologies have been proposed to remove fluoride ions from water such as precipitation methods which are based on the addition of chemicals to water and sorption methods to removed fluoride ions by sorption or ion exchange reactions by some suitable substrate capable of regenerate and reuse. In this work, the sorption of fluoride ions using unmodified and modified hematite with aluminum hydroxide to remove fluoride ions from water by bath experiments was studied. The hematite was modified by treating it with aluminum hydroxide, NaOH and Al 2 (SO 4 ) 3 solutions. The characterization of hematite before and after modification with aluminum hydroxide was studied by X-ray diffraction, scanning electron microscopy, EDS and Bet. The effect of ph, contact time, concentration of fluoride ions, and the dose of sorbent on the sorption of fluoride ions by the modified hematite were studied. Equilibrium was reached within 48 hours of contact time and the maximum sorption of fluoride ions were in the range pH eq between 2.3 and 6.2. Sorption capacities of fluoride ions as a function of dose of

Sorption of streptococcus faecium to glass

International Nuclear Information System (INIS)

Oerstavik, D.

1977-01-01

A method has been developed by which to study the sorption of Streptococcus faecium to soda-lime cover glasses. Conditions were chosen to minimize the influence on sorption of bacterial polymer production, passive sorption being studied rather than attachment mediated by metabolic activities. Sorption of S. faecium increased with increasing temperature (to 50degC), time, and cell concentration, but equilibrium apparently was not reached even after incubation for 8 hours or at a cell concentration of 3 x 10 10 per ml. Sorption increased with solute molarity up to 0.1 M concentration of NaCl and KCl, indicating an effect of the electrical double layers on the apposition of cells to the glass surface. Desorption of bacteria could be obtained after multiple washings of the glasses in buffer or by the action of Tween 80, but not if sorbed bacteria were left in distilled water, various salt solutions, urea, or in suspensions of unlabelled bacteria. It was concluded that sorption occurred as a result of chemical interactions between the glass and the cell surface. Tween 80 at a concentration of 1 per cent inhibited sorption to 26 per cent of buffer controls, 2 M urea was less effective, and 1 M NaCl was without effect. It is suggested that hydrophobic interactions may be of importance in the binding of S. faecium to glass. (author)

Sorption separation of Eu and As from single-component systems by Fe-modified biochar. Kinetic and equilibrium study

International Nuclear Information System (INIS)

Fristak, Vladimir; Soja, Gerhard; Michalekova-Richveisova, Barbora; Pipiska, Martin; Viglasova, Eva; Galambos, Michal; Duriska, Libor; Moreno-Jimenez, Eduardo

2017-01-01

The utilization of carbonaceous materials in separation processes of radionuclides, heavy metals and metalloids represents a burning issue in environmental and waste management. The main objective of this study was to characterize the effect of chemical modification of corncob-derived biochar by Fe-impregnations on sorption efficiency of Eu and As as a model compounds of cationic lanthanides and anionic metalloids. The biochar sample produced in slow pyrolysis process at 500 C before (BC) and after (IBC) impregnation process was characterized by elemental, FTIR, SEM-EDX analysis to confirm the effectiveness of Fe-impregnation process. The basic physico-chemical properties showed differences in surface area and pH values of BC- and IBC-derived sorbents. Sorption processes of Eu and As by BC and IBC were characterized as a time- and initial concentration of sorbate-dependent processes. The sorption equilibrium was reached for both sorbates in 24 h of contact time. Batch equilibrium experiments revealed the increased maximum sorption capacities (Q max ) of IBC for As about more than 20 times (Q max BC 0.11 and Q max IBC 2.26 mg g -1 ). Our study confirmed negligible effect of Fe-impregnation on sorption capacity of biochar for Eu (Q max BC 0.89 and Q max IBC 0.98 mg g -1 ). The iron-impregnation of biochar-derived sorbents can be utilized as a valuable treatment method to produce stable and more effective sorption materials for various xenobiotics separation from liquid wastes and aqueous solutions.

Results and discussion

International Nuclear Information System (INIS)

1998-01-01

The author deals with the experimental study of sorption, desorption and vertical migration of radionuclides in Sr-85 and Cs-137 in selected soil samples from around of NPP Bohunice and NPP Mochovce and other localities of the Slovakia. The influence of different materials [concurrent ions (K + , Ca 2+ , NH 4 + , pH), organic matter (peat) and zeolite, humidity] on kinetic of sorption and desorption of strontium and cesium as well as distribution coefficient (K D ) and transfer coefficients in followed samples of soils were followed. Obtained adsorption isotherm are presented and discussed. Using the Tessiere's sequential extraction analysis a gross variability in binding of radionuclides on soils was found. The obtained results were processed with the correlation analysis and the compartment model

Recent developments in nanostructured inorganic materials for sorption of cesium and strontium: Synthesis and shaping, sorption capacity, mechanisms, and selectivity-A review.

Science.gov (United States)

Alby, Delhia; Charnay, Clarence; Heran, Marc; Prelot, Bénédicte; Zajac, Jerzy

2018-02-15

Liquid wastes containing non-ferrous heavy metal ions and some radionuclides, 137 Cs and 90 Sr in particular, represent one of the most dangerous sources of environmental contamination. The remediation of wastewater containing such pollutants continue to be among the biggest challenges of Sustainable Development and Environmental Safety. Sorption-based technologies have proven their efficiency also in reducing the radionuclide content in aqueous streams to low-level residual activity, with the concomitant decrease in the amount of ultimate solid waste generated. Although sorption of cesium and strontium by resins, clays, and zeolites has been investigated intensively and even used in real applications, there is still considerable scope for improvement in terms of retention capacity and selectivity. Recent progress in design and preparation of nanostructured inorganic materials has attracted growing interest based on the potential for improving the retention performance when coupling such functionalities as ion exchange capacity, structural flexibility that may result in steric retention effects, as well as the propensity to interact specifically with the target metal cations. Titanate, vanadate, and tungsten based materials, manganese oxides, hexacyanoferrates, metal sulfides, ammonium molybdophosphates, or hydroxyapatite, characterized by various structures and morphologies, are reviewed with the emphasis being put on synthesis and shaping of such materials, their structure in relationship with the capacity and selectivity of trapping cesium and strontium from either single or multi-component aqueous solutions, as well as the possible retention mechanism. The potential candidates for remediation uses are selected with regard to their sorption capacity and distribution coefficient towards target cations, and also the pH window for an optimum cation capture. Copyright © 2017 Elsevier B.V. All rights reserved.

Performance of LiCl Impregnated Mesoporous Material Coating over Corrugated Heat Exchangers in a Solid Sorption Chiller

Directory of Open Access Journals (Sweden)

Hongzhi Liu

2018-06-01

Full Text Available The composite material made by impregnating 40 wt. % lithium chloride (LiCl into the mesopores of a kind of natural porous rock (Wakkanai Siliceous Shale: WSS micropowders (short for “WSS + 40 wt. % LiCl” had been developed previously, and can be regenerated below 100 °C with a cooling coefficient of performance (COP of approximately 0.3 when adopted as a sorbent in a sorption cooler. In this study, experiments have been carried out on an intermittent solid sorption chiller with the WSS + 40 wt. % LiCl coating over two aluminum corrugated heat exchangers. Based on the experimental condition (regeneration temperature of 80 °C, condensation temperature of 30 °C in the desorption process; sorption temperature of 30 °C and evaporation temperature of 12 °C in the sorption process, the water sorption amount changes from 20 wt. % to 70 wt. % in one sorption cooling cycle. Moreover, a specific cooling power (SCP of 86 W/kg, a volumetric specific cooling power (VSCP of 42 W/dm3, and a specific sorption power of 170 W/kg can be achieved with a total sorption and desorption time of 20 min. The obtained cooling COP is approximately 0.16.

Fabrication of hierarchical core-shell polydopamine@MgAl-LDHs composites for the efficient enrichment of radionuclides

Energy Technology Data Exchange (ETDEWEB)

Zhu, Kairuo [Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy Sciences, P.O. Box 1126, Hefei, 230031 (China); Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou, 215123 (China); Lu, Songhua; Gao, Yang; Zhang, Rui; Tan, Xiaoli [Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy Sciences, P.O. Box 1126, Hefei, 230031 (China); Chen, Changlun, E-mail: clchen@ipp.ac.cn [Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy Sciences, P.O. Box 1126, Hefei, 230031 (China); Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou, 215123 (China); AAM Research Group, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

2017-02-28

Highlights: • Novel hierarchical core/shell structured PDA@MgAl-LDHs were prepared. • PDA@MgAl-LDHs exhibited higher sorption ability for U(VI) and Eu(III). • PDA@MgAl-LDHs were promising materials for the enrichment of radionuclides. - Abstract: Novel hierarchical core/shell structured polydopamine@MgAl-layered double hydroxides (PDA@MgAl-LDHs) composites involving MgAl-layered double hydroxide shells and PDA cores were fabricated thought one-pot coprecipitation assembly and methodically characterized by X-ray diffraction, Fourier transformed infrared spectroscopy, scanning/transmission electron microscopy, selected area electron diffraction, elemental mapping, thermogravimetric analysis and X-ray photoelectron spectroscopy technologies. U(VI) and Eu(III) sorption experiments showed that the PDA@MgAl-LDHs exhibited higher sorption ability with a maximum sorption capacity of 142.86 and 76.02 mg/g at 298 K and pH 4.5, respectively. More importantly, according to XPS analyses, U(VI) and Eu(III) were sorbed on PDA@MgAl-LDHs via oxygen-containing functional groups, and the chemical affinity of U(VI) by oxygen-containing functional groups is higher than that of Eu(III). These observations show great expectations in the enrichment of radionuclides from aquatic environments by PDA@MgAl-LDHs.

Clay as a barrier to radionuclide migration: a review

International Nuclear Information System (INIS)

Higgo, J.J.W.

1986-05-01

Because of their low permeability, high sorption capacity and plasticity, clay bodies are potentially suitable repositories for radioactive waste. The paper discusses the factors that influence radionuclide mobility in natural clay materials. Methods for determining radionuclide migration rates are described and compared. Data requirements necessary to establish whether or not a particular site is suitable for waste disposal are discussed. Suggestions are made as to the most important generic research that needs to be carried out. In the appendix, some of the most relevant, published, sorption and diffusion data are summarised and compared. (author)

Geochemical effects on the behavior of LLW radionuclides in soil/groundwater environments

Energy Technology Data Exchange (ETDEWEB)

Krupka, K.M.; Sterne, R.J. [Pacific Northwest Lab., Richland, WA (United States)

1995-12-31

Assessing the migration potential of radionuclides leached from low-level radioactive waste (LLW) and decommissioning sites necessitates information on the effects of sorption and precipitation on the concentrations of dissolved radionuclides. Such an assessment requires that the geochemical processes of aqueous speciation, complexation, oxidation/reduction, and ion exchange be taken into account. The Pacific Northwest National Laboratory (PNNL) is providing technical support to the U.S. Nuclear Regulatory Commission (NRC) for defining the solubility and sorption behavior of radionuclides in soil/ground-water environments associated with engineered cementitious LLW disposal systems and decommissioning sites. Geochemical modeling is being used to predict solubility limits for radionuclides under geochemical conditions associated with these environments. The solubility limits are being used as maximum concentration limits in performance assessment calculations describing the release of contaminants from waste sources. Available data were compiled regarding the sorption potential of radionuclides onto {open_quotes}fresh{close_quotes} cement/concrete where the expected pH of the cement pore waters will equal to or exceed 10. Based on information gleaned from the literature, a list of preferred minimum distribution coefficients (Kd`s) was developed for these radionuclides. The K{sub d} values are specific to the chemical environments associated with the evolution of the compositions of cement/concrete pore waters.

Sorption and desorption of arsenate and arsenite on calcite

DEFF Research Database (Denmark)

Sø, Helle Ugilt; Postma, Diederik Jan; Jakobsen, Rasmus

2008-01-01

The adsorption and desorption of arsenate (As(V)) and arsenite (As(111)) oil calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic...

Sorption of Cs, Eu and U(VI) onto rock samples from Nizhnekansky massive

Energy Technology Data Exchange (ETDEWEB)

Petrov, V.; Vlasova, I.; Kalmykov, S. [Lomonosov Moscow State University (Russian Federation); Kuzmenkova, N. [Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Science (Russian Federation); Petrov, V.; Poluektov, V. [Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences - IGEM RAS (Russian Federation)

2014-07-01

The accepted in Russia concept for high level wastes (HLW) and spent nuclear fuel (SNF) disposal is based on their isolation into the deep underground crystalline rock formations. The 'Eniseysky' area (Nizhnekansky massive) is supposed as the most perspective location for the future HLW and SNF repository. Core materials from different areas of Nizhnekasnsky massive have been studied in terms of petrographic and mineralogical characterization; definition of filtration, elastic, petro-physical and strength properties; estimation of hydrothermal-metasomatic transformation of rocks. We used both undisturbed sliced cores and crushed material for the sorption experiments. Preliminary results of uranium sorption show some significant differences between used rock samples from different depth in sorption rate and pH-dependence. In all cases maximum sorption (more than 90%) is reached in 2-3 weeks. The pH-dependence of sorbed uranium fraction has typical hump-shape: increase of sorption percentage with increasing pH values to 6, plateau (90-98 % of uranium sorbed), decrease of sorption percentage with increasing pH values from 8 due to U(VI) hydrolysis. In the case of cesium the sorption maximum is reached within 10-12 days and in the case of europium - about 5 days. All radionuclides sorbed preferentially onto dark minerals. Local distribution and preferential sorption of cesium, europium and uranium (VI) onto different minerals within the sample were studied by radiography, SEM-EDX, etc. These data accompanying with rock sample composition will allow the development of quantitative model for Cs, Eu and U(VI) sorption onto investigated rocks. Document available in abstract form only. (authors)

Experimental Studies to Evaluate the Role of Colloids on the Radionuclide Migration in a Crystalline Medium

International Nuclear Information System (INIS)

Albarran, Nairoby; Missana, Tiziana; Alonso, Ursula; Garcia-Gutierrez, Miguel; Mingarro, Manuel; Lopez, Trinidad

2008-01-01

In a deep geological repository (DGR) of high level radioactive waste, all the possible phenomena affecting radionuclide migration have to be studied to assess its security over time. Colloids can play an important role for contaminant transport if the following conditions are fulfilled: colloids exist in a non negligible concentration, they are mobile and stable in the environment of interest, and they are able to adsorb radionuclides irreversibly. In this study, different transport experiments where performed to improve the knowledge on the main mechanisms affecting the radionuclide migration in the presence of colloids in a crystalline medium. Firstly, colloid stability was analysed and then transport experiments in an artificial granite longitudinal fracture were carried out. Synthetic colloids of different size and bentonite clay colloids were used to evaluate the effects of colloid size, charge, and water flow rate on their mobility. Results showed that both major importance of the water flow rate on the mobility of colloids and their recovery and a higher interaction of smaller particles with the surface. Finally, the migration behaviour of Sr, and Sr adsorbed onto bentonite colloids was compared. The elution curves of Sr adsorbed onto colloid were significantly different from the ones of Sr alone, pointing out that sorption/desorption mechanisms must be taken into account to understand the radionuclide migration in the fracture in the presence of colloids. (authors)

Retention and radionuclide migration mechanisms in the environment of a radioactive waste repository in granitic formation

International Nuclear Information System (INIS)

Rancon, D.; Miara, P; Vinson, J.M.; Petronin, J.C.; Dozol, J.F.

1986-01-01

A laboratory pre-determination of retention mechanisms of radionuclides migrating outside the primary waste containers in repository surroundings was started up. Backfillings materials (clay and sand) as well as granite and its weathering products are concerned here. A method allowing the evaluation of the sorption and desorption of radionuclides of the surfaces of fractures by measuring surface retention coefficients, had initially been started up as well as a laboratory device developed for experiments in a reducing environment. The experiments have consisted of studying the sorbing properties of granite minerals of Auriat and its weathering products and of determining the retention of Np, Pu, AM, CS and Sr on the surface fractures of this granite. The influence of a reducing environment on the behaviour of activities has been studied. Complementary percolation tests have also been carried out on clays, at raised temperature and under irradiation. These experiments have enabled a deeper knowledge of retention mechanisms, the taking of parametric sensitivity measurements and the preparation of elaborating more performing experimental devices which included the parameters needed for a realistic simulation of transfer phenomena

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

International Nuclear Information System (INIS)

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

2011-03-01

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

A fully coupled diffusion-reaction scheme for moisture sorption-desorption in an anhydride-cured epoxy resin

KAUST Repository

El Yagoubi, Jalal; Lubineau, Gilles; Roger, Frederic; Verdu, Jacques

2012-01-01

Thermoset materials frequently display non-classical moisture sorption behaviors. In this paper, we investigated this issue from an experimental point of view as well as in terms of modeling the water transport. We used the gravimetric technique to monitor water uptake by epoxy samples, with several thicknesses exposed to different levels of humidity during absorption and desorption tests. Our results revealed that the polymer displays a two-stage behavior with a residual amount of water that is desorbed progressively. We proposed a phenomenological reaction-diffusion scheme to describe this behavior. The model describes water transport as a competition between diffusion and the reaction, during which the local diffusivity and solubility depend on the local advancement of the reaction. We then implemented our model using COMSOL Multiphysics and identified it using a MATLAB-COMSOL optimization tool and the experimental data. We discussed the relation between the hydrophilicity of the product of the reaction and the diffusion behavior. We examined the reaction-induced modification of the water concentration field. It is worth noting that part of the phenomenology can be explained by the presence of hydrolyzable groups. © 2012 Elsevier Ltd. All rights reserved.

A fully coupled diffusion-reaction scheme for moisture sorption-desorption in an anhydride-cured epoxy resin

KAUST Repository

El Yagoubi, Jalal

2012-11-01

Thermoset materials frequently display non-classical moisture sorption behaviors. In this paper, we investigated this issue from an experimental point of view as well as in terms of modeling the water transport. We used the gravimetric technique to monitor water uptake by epoxy samples, with several thicknesses exposed to different levels of humidity during absorption and desorption tests. Our results revealed that the polymer displays a two-stage behavior with a residual amount of water that is desorbed progressively. We proposed a phenomenological reaction-diffusion scheme to describe this behavior. The model describes water transport as a competition between diffusion and the reaction, during which the local diffusivity and solubility depend on the local advancement of the reaction. We then implemented our model using COMSOL Multiphysics and identified it using a MATLAB-COMSOL optimization tool and the experimental data. We discussed the relation between the hydrophilicity of the product of the reaction and the diffusion behavior. We examined the reaction-induced modification of the water concentration field. It is worth noting that part of the phenomenology can be explained by the presence of hydrolyzable groups. © 2012 Elsevier Ltd. All rights reserved.

Polymer Microstructures: Modification and Characterization by Fluid Sorption

Science.gov (United States)

Boyer, S. A. E.; Baba, M.; Nedelec, J.-M.; Grolier, Jean-Pierre E.

2008-12-01

Polymer micro-organization can be modified by a combination of three constraints, thermal, hydrostatic, and fluid sorption. In selecting the fluid’s nature, chemically active or inert, and its physical state, liquid or supercritical, new “materials” can be generated. In addition, the interplay of temperature and pressure allows tailoring the obtained material structure for specific applications. Several complementary techniques have been developed to modify, analyze, and characterize the end products: scanning transitiometry, vibrating-wire (VW)-PVT coupling, thermoporosimetry, and temperature-modulated DSC (TMDSC). The great variety of possible applications in materials science is illustrated with different polymers which can produce materials from soft gel to rigid foams when submitted to fluid sorption, typical fluids being methane or a simple gas (CO2 or N2). Absorption of an appropriate fluid in a cross-linked polymer leads to a swelling phenomenon. Thermoporosimetry is a calorimetric technique developed to measure the shift by confinement of thermal-transition temperatures of the swelling fluids, which can be currently used solvents or mercury. Application of thermoporosimetry to a swollen cross-linked polymer allows calculation of the mesh size distribution and evaluation of the degree of reticulation of the polymer. The same technique can be applied to characterize the pore size distribution in a foamed polymer.

Experimental methodology to study radionuclide sorption and migration in geological formations and engineered barriers of waste repositories; Metodologia experimental para estudios de sorcion y migracion de radionucleidos en formaciones geologicas y barreras de almacenamientos de residuos

Energy Technology Data Exchange (ETDEWEB)

Rojo Sanz, H.

2010-07-01

In Spain, the waste management options include either the possibility of a final storage in a deep geological repository (DGR) or the centralized temporal surface disposal (CTS). DGRs are based in a multi-barrier concept with the geological barrier and including the vitrified waste, the metal containers and engineered barriers such as compacted bentonite and cement-based materials. On the other hand, CTS mainly considers concrete and cement to confine the metal canisters containing the waste. Radionuclide migration will mainly take place by the existence of chemical concentration gradients being thus diffusion the main transport mechanism or by the existence of hydraulic gradients due to the existence of water-conductive fractures. Radionuclide sorption/retention on the materials composing the natural and engineered barriers is the fundamental process controlling contaminant migration. The evaluation of sorption parameters and the understanding of the different mechanisms leading to radionuclide retention are very important issues. The study of diffusion processes is very relevant as well. This paper describes the main experimental methodologies applied to analyse radionuclide transport in the different barriers of radioactive repositories. Particularly we focused on obtaining of retention parameters as distribution coefficients, kd, or retardation factors, Rf, and diffusion coefficients of radionuclides. (Author) 6 refs.

Sorption-reagent treatment of brines produced by reverse osmosis unit for liquid radioactive waste management

International Nuclear Information System (INIS)

Avramenko, V. A.; Zheleznov, V. V.; Sergienko, V. I.; Chizhevsky, I. Yu

2003-01-01

The results of the pilot plant tests (2002-2003) of the sorption-reagent decontamination of high salinity radioactive waste (brines) remaining after the low-salinity liquid radioactive waste (LRW) treatment in the reverse-osmosis unit from long-lived radionuclides are presented. The sorption-reagent materials used in this work were developed in the Institute of Chemistry FEDRAS. They enable one to decontaminate brines with total salt content up to 50 g/l from long-lived radionuclides of Cs, Sr and Co. At joint application of the reverse-osmosis and sorption-reagent technologies total volume of solid radioactive waste (SRW) decreases up to 100-fold as compared to the technology of cementation of reverse osmosis brines. In this case total cost of LRW treatment and SRW disposal decreases more than 10-fold. Brines decontaminated from radionuclides are then diluted down to the ecologically safe total salts content in water to be disposed of. Tests were performed to compare the efficiency of technologies including evaporation of brines remaining after reverse osmosis process and their decontamination by means of the sorption-reagent method. It was shown that, as compared to evaporation, the sorption-reagent technology provides substantial advantages as in regard to radioactive waste total volume reduction as in view of total cost of the waste management

Sorption of 241Am onto montmorillonite, illite and hematite colloids

International Nuclear Information System (INIS)

Degueldre, C.; Ulrich, H.J.; Silby, H.

1994-01-01

Actinide sorption on colloids may be described as a competition between the formation of complexes in solution and the build up of surface complexes. The role of particle and of carbonate concentrations on the sorption/desorption of 241 Am on montmorillonite, illite and hematite colloids is investigated. Since the partition coefficient (K p ) values are virtually independent of the colloid concentrations, within the range 1 to 300 ppm, no significant aggregation takes place in the sorption/desorption experiment. At pH 8, a slight decrease of K p is observed if the concentration of total carbonate exceeds 10 -2 M. The formation of the carbonato- (and hydroxo-carbonato-) complexes in the solution competes with the formation of surface complexes on the colloids. A relationship between the sorption coefficient and the complexation of 241 Am in the solution has been found. This leads to the conclusion that, besides free americium cation, the hydroxo-, and carbonato- as well as the mixed hydroxo-carbonato-complexes are sorbed. Only when the tricarbonatocomplex [Am(CO 3 ) 3 ] 3- prevails (total carbonate concentration > 10 -2 M), a significant decrease of the distribution coefficient is observed. At pH 10 this decrease disappears because under these conditions the strong hydroxo-complexes dominate. A pragmatic and relatively simple application of surface complexation model describes the observed features. (orig.)

Sorption of organophosphate and triazine agrochemicals on biochars and soils

Science.gov (United States)

Biochars are known to strongly sorb polar and nonpolar organic compounds, and biochar soil amendment can have counteracting impacts on the efficacy of, and runoff contamination by agrochemicals. This study investigated the sorption-desorption isotherms and kinetics of triazine (deisopropylatrazine)...

Laboratory studies of radionuclide migration in tuff

International Nuclear Information System (INIS)

Rundberg, R.S.; Mitchell, A.J.; Ott, M.A.; Thompson, J.L.; Triay, I.R.

1989-01-01

The movement of selected radionuclides has been observed in crushed tuff, intact tuff, and fractured tuff columns. Retardation factors and dispersivities were determined from the elution profiles. Retardation factors have been compared with those predicted on the basis of batch sorption studies. This comparison forms a basis for either validating distribution coefficients or providing evidence of speciation, including colloid formation. Dispersivities measured as a function of velocity provide a means of determining the effect of sorption kinetics or mass transfer on radionuclide migration. Dispersion is also being studied in the context of scaling symmetry to develop a basis for extrapolating from the laboratory scale to the field. 21 refs., 6 figs., 2 tabs

Sorption behaviour of cobalt-60 on Suez Canal bottom sediments

International Nuclear Information System (INIS)

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

1981-01-01

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

Sorption separation of Eu and As from single-component systems by Fe-modified biochar. Kinetic and equilibrium study

Energy Technology Data Exchange (ETDEWEB)

Fristak, Vladimir; Soja, Gerhard [Austrian Institute of Technology GmbH, Tulln (Austria). Energy Dept. Environmental Resources and Technologies; Michalekova-Richveisova, Barbora; Pipiska, Martin [Trnava Univ. (Slovakia). Dept. of Chemistry; Viglasova, Eva; Galambos, Michal [Comenius Univ., Bratislava (Slovakia). Dept. of Inorganic Chemistry; Duriska, Libor [Slovak Univ. of Technology in Bratislava, Trnava (Slovakia). Faculty of Materials Science and Technology; Moreno-Jimenez, Eduardo [Univ. Autonoma de Madrid (Spain). Dept. de Quimica Agricola y Bromatologia

2017-03-15

The utilization of carbonaceous materials in separation processes of radionuclides, heavy metals and metalloids represents a burning issue in environmental and waste management. The main objective of this study was to characterize the effect of chemical modification of corncob-derived biochar by Fe-impregnations on sorption efficiency of Eu and As as a model compounds of cationic lanthanides and anionic metalloids. The biochar sample produced in slow pyrolysis process at 500 C before (BC) and after (IBC) impregnation process was characterized by elemental, FTIR, SEM-EDX analysis to confirm the effectiveness of Fe-impregnation process. The basic physico-chemical properties showed differences in surface area and pH values of BC- and IBC-derived sorbents. Sorption processes of Eu and As by BC and IBC were characterized as a time- and initial concentration of sorbate-dependent processes. The sorption equilibrium was reached for both sorbates in 24 h of contact time. Batch equilibrium experiments revealed the increased maximum sorption capacities (Q{sub max}) of IBC for As about more than 20 times (Q{sub max} BC 0.11 and Q{sub max} IBC 2.26 mg g{sup -1}). Our study confirmed negligible effect of Fe-impregnation on sorption capacity of biochar for Eu (Q{sub max} BC 0.89 and Q{sub max} IBC 0.98 mg g{sup -1}). The iron-impregnation of biochar-derived sorbents can be utilized as a valuable treatment method to produce stable and more effective sorption materials for various xenobiotics separation from liquid wastes and aqueous solutions.

Investigation of strontium sorption on Kula volcanites treated with HCl

International Nuclear Information System (INIS)

Kuetahyali, C.; Cetinkaya, B.; Acar, M. B.; Isik, N. O.; Cireli, I.

2009-01-01

In planning the disposal of radioactive waste in a deep geologic repository, consideration must be given to the ways in which radionuclides might leave the repository and migrate through the geosphere. In performance assessment studies the uptake of the radioactive elements by rock formations play an important role in retarding their aqueous phase migration. Sorption studies of radionuclides have been conducted to obtain data on the distribution coefficient (K d ) that is as an input parameter in the performance assessment of the geological disposal of radioactive wastes. In many studies, the sorption experiments employed natural soils and rocks as sorbents. Adsorption experiments were studied in a batch adsorption system using Sr(NO 3 ) 2 (Merck) solution. Strontium sorption on Kula Volcanites treated with HCl was investigated. Central Composite Design Method was used in the experiments. Sr adsorption was studied as a function of pH, contact time, concentration of adsorbate, and temperature.

Sorção e dessorção do imazaquin em solos com diferentes características granulométricas, químicas e mineralógicas Imazaquin sorption and desorption in soils with different mineralogical, physical and chemical characteristics

Directory of Open Access Journals (Sweden)

Robson Rolland Monticelli Barizon

2005-10-01

cinética indica que mecanismos de difusão podem estar envolvidos neste processo.The aim of this study was to evaluate the sorption and desorption of imazaquin in soils with different granulometric, chemical and mineralogical characteristics. Isotherms and kinetics studies were carried out to quantify the hysteresis between sorption and desorption processes. The soils were classified as Rhodic Hapludox (LVdf, Typic Hapludox (LVA and Typic Quartzipsamment (RQ. The soils were air-dried and passed through a 2 mm mesh sieve, and the chemical, physical and mineralogical properties characterized. The radiolabeled molecule (14C was imazaquin, an herbicide of the imidazolinone group. Radioactivity was quantified by liquid scintillation spectrometry. The trials were carried out under controlled temperature conditions (25 ± 2 °C. Five imazaquin concentrations were used (0.67; 1.34; 2.68; 5.36; and 10.72 µmol L-1 for the sorption isotherms. The experimental data were fitted to the Freundlich equation so that sorption parameters were obtained. Subsequently, four extractions were performed with a 0.005 mol L-1CaCl2 solution in order to determine desorption parameters in a similar way for sorption. For sorption kinetics, the sorbed imazaquin amount (2.99 µmol L-1 was determined after different time intervals (0; 0.5; 1; 3; 6; 12; 24, and 48 h after imazaquin application, and the results adjusted to the Elovich equation. Imazaquin generally presented low sorption to the three soils, with higher sorption coefficients in the soils with higher clay and organic carbon content. The desorption coefficients were higher than those of sorption, evidencing the occurrence of hysteresis. Sorption kinetics showed that imazaquin is sorbed in two phases - a rapid one that presented the largest sorbed fraction, and another slower one. The application of Fick´s Law to the kinetic data showed that diffusion mechanisms might be involved in this process.

Behavior of Cs and Co in marine sediments of Enseada de Piraquara de Fora, Angra dos Reis, RJ, Brazil; Comportamento Cs e Co em sedimentos marinhos da Enseada de Piraquara de Fora - Angra dos Reis

Energy Technology Data Exchange (ETDEWEB)

Ferreira, I. M.; Carvalho, F. M.; Lauria, D.C., E-mail: dejanira@ird.gov.br [Instituto de Radioproteção e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro - RJ (Brazil)

2017-07-01

The release of {sup 137}Cs and {sup 60}Co in the liquid effluents from the Angra dos Reis power plants could radiologically impact the Saco de Piraquara de Fora (SPF) inlet. The mobility and trend of the radionuclides in the water-sediment compartment were investigated by studies of thermodynamic and sorption-desorption. The values of distribution coefficients (Kd) were around 500 L. kg{sup -1} for {sup 60}Co and 400 L. kg{sup -1} for {sup 137}Cs that are lower than the literature values. The predominance of kaolinite in the clay fraction may have played a major role in the low observed Kd values. For both radionuclides, the sorption was higher for the sediment with higher cation exchange capacity, and the equilibrium conditions were reached only after the third day. Despite the relatively low Kd values and low sorption rates, both can considerably be accumulated in sediments, and the sorption reactions are partially irreversible. {sup 60}Co and {sup 137}Cs accumulate in orders of magnitude of 1010 and 109 Bq g{sup -1} sediment, respectively, which shows the ability of the sediments to remove and retain much of the {sup 137}Cs and {sup 60}Co released by the power plants. Considering the range of temperature of the SPF water, both sorption and desorption of the two metals increase with temperature. However, in general, the retention rates of the radionuclides in sediments remain constant. The sorption sites are heterogeneous since the sorption data can be adjusted by the Langmuir and Freündlich isotherms. The sorption of Co and Cs are endothermic processes, which are spontaneous at low temperature. (author)

Characterization of Tar Deposits, Extraction and Sorption Properties

Directory of Open Access Journals (Sweden)

Pryszcz Adrian

2016-06-01

Full Text Available The main goal of this paper was to characterize and find a useful solution for the decomposition of tar deposits. For the experimental part, tar deposits, formed by polymerization and condensation reactions, were chosen from a storage tank for tars. At first the initial analyses of tar deposits (elemental, thermogravimetric, and calorimetric analyses were performed. After the characterization, the tar deposits were extracted in the Soxhlet extractor by acetone, toluene, and quinolone and activated with potassium hydroxide. As the final step of this work, the sorption characterization on the 3Flex Surface Characterization Analyzer (Micromeritics was performed. The specific surface area of the samples was evaluated using two methods - a single point measurement at p/p0=0.2 and BET method. Micropore and external surface areas were calculated based on a t-plot analysis (carbon black model.

Radionuclide sorption on low-exchange capacity Hanford site soils

International Nuclear Information System (INIS)

Routson, R.C.; Barney, G.S.; Smith, R.M.

1984-01-01

Trace Distribution Coefficients (Kd values) for 134 Cs, 85 Sr, and 60 Co sorption were found to be a function of sediment type (soil type) and of the solution concentration of macroions including NA + , K + , and Ca +2 over wide macroion concentration ranges. These Kd value functions are required as input sorption parameters to a mass transport model. Four methods were evaluated for measuring the Kd value macroion functional relationships for each sediment type. Precision, bias, and cost effectiveness were compared for choosing a preferred method. The prefered method, an empirical-statistical method (Box-Behnken method), was found to be as precise and unbiased as the other methods and the most cost effective. 12 references, 7 figures, 10 tables

Fundamental approach to the analysis of radionuclide transport resulting from fluid flow through jointed media

International Nuclear Information System (INIS)

Erickson, K.L.

1981-02-01

A theoretical and experimental basis is being developed for analysis of radionuclide transport in jointed geologic media. Batch equilibration and rate experiments involving samples of Eleana argillite and Tertiary silicic tuffs in contact with solutions containing Cs, Sr or Pm indicated that most radionuclide sorption is associated with the surfaces of very small intergranular regions and that the rate of sorption is controlled by diffusion of the nuclides into such regions. Based on these experimental results, the continuity equations for radionuclides in the mobile and immobile phases were reduced to a model analogous to Rosen's equations for packed beds and were solved similarly to Rosen's solutions. Using the model and experimental data, limited radionuclide transport analyses were made which indicated that important parameters controlling transport include the intergranular porosity and nuclide penetration depth, fracture plate spacing and length, fluid velocity, and sorption distribution coefficient

Influence of microbial activity on the migration behaviour of redox-sensitive radionuclides (technetium and selenium) in loose rock

International Nuclear Information System (INIS)

Stroetmann, I.

1995-01-01

In closed cycle column tests under sterile conditions there was no or hardly any sorption of the two radionuclides. In closed cycle column tests with unsterile soils, however, the two radionuclides were extremely immobilised (80 % of the output activity of Tc-95m and 40 % of the output activity of Se-75). By inoculation of the sterile columns with mixed soil cultures an increase in sorption of 40 % of the output activity was achieved which is attributed to the microbial activity. The adsorbed radionuclides in unsterile columns could be remobilized by adding a bactericide. In columns with saline water the sorption of radionuclides was slightly lower. Soils with a 5 % organic carbon content showed extremely increased sorption of the two radionuclides. In comparison with closed cycle columns shake tests were carried out. During turbulent intermixing of water and solid, no sorption of technetium was observed in unsterile tests either, while Se-75 added as selenite was strongly adsorbed to the solid. When adding acetate as a C-source, the microbially conditioned reduction of the redox potential to -100 mV and, subsequently, a strong increase of sorption could be observed. A reduction of the pH value in the soils to pH 4, and simultaneous adding of acetate significally reduced the microbial activity and the sorption of technetium, while selenite sorption remained strong as before. Sorption tests with bacteria-pure and mixed cultures showed no sorption of the pertechnetate anion in the oxidation stage (VII). However, when reducing the pertechnetate by means of SnCl2, up to 40 % of the feed activity of killed and living biomass was immobilized. Between 20-30 % of the adsorbed technetium quantity was outside at the membrane, and 40% inside the cells. After a three-day incubation period in a technetium-containing solution, a factor of 15,5 was achieved as the maximum intracellular concentration factor for the isolate 143 (Xanthomas sp.). (orig./MG) [de

Sorption data bases for generic Swiss argillaceous rock systems

International Nuclear Information System (INIS)

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

2010-09-01

In Switzerland the site selection procedure for both high level waste (HLW) and low and intermediate level waste (L/ILW) repositories is specified by the Swiss Federal Office of Energy in the Sectoral Plan for Deep Geological Repositories. In the forthcoming stage 2 of this plan, potential sites will be identified within regions previously selected based on the presence of suitable host rocks, namely Opalinus Clay, 'Brauner Dogger', Effingen Member and Helvetic Marl. Preliminary safety analyses are an integral part of this procedure, and require, amongst other information, the radionuclide sorption properties of the host rock. This report describes a methodology to develop a Generic Rock Sorption Data Base (GR-SDB) for argillaceous rocks. The method will be used to compile specific SDBs for the above mentioned host rocks. Arguments are presented that the main factor influencing sorption on argillaceous rocks is the phyllosilicate mineral content. These minerals are particularly effective at binding metals to their surfaces by cation exchange and surface complexation. Generally, the magnitude of sorption is directly correlated with the phyllosilicate content (2:1 type clays: illite/smectite/illitesmectite mixed layers), and this parameter best reflects the sorption potential of a given mineral assembly. Consequently, sorption measurements on illite were preferably used as source data for the GR-SDB. The second component influencing radionuclide sorption is the porewater chemistry. In the present report, generic water compositions were extracted from the analytical ranges of deep ground waters in various sedimentary formations in Switzerland. In order to cover the range of ionic strength (I) and pH values of Swiss ground waters in argillaceous rocks, five types of generic water compositions were defined, combining low, intermediate and high values of ionic strength and pH. The GR-SDB for in situ conditions was derived using conversion factors (CF). As the name

Quantitative Assessment of the Potential Significance of Colloids to the KBS-3 Disposal Concept

International Nuclear Information System (INIS)

Klos, R.A.; White, M.J.; Wickham, S.M.; Bennett, D.G.; Hicks, T.W.

2002-06-01

Colloids are minute particles in the size range 1 nm to 1 μm that can remain suspended in water, and may influence radionuclide transport in radioactive waste disposal systems. Galson Sciences Ltd (GSL) has undertaken a quantitative assessment of the impact that colloid-facilitated radionuclide transport may have on the performance of the Swedish KBS-3 concept for disposal of high-level radioactive waste and spent fuel. This assessment has involved the evaluation and application of SKI's colloid transport model, COLLAGE II, modelling of km-scale Pu transport at the Nevada Test Site (NTS), USA, and identification of circumstances under which colloid-facilitated transport could be important for a KBS-3-type environment. Colloids bearing traces of plutonium from the BENHAM underground nuclear test have been detected in samples obtained from Nevada Test Site (NTS) groundwater wells 1.3 km from the detonation point. Plutonium is generally fairly immobile in groundwater systems, and it has been suggested that colloids may have caused the plutonium from the BENHAM test to be transported 1.3 km in only 30 years. This hypothesis has been tested by modelling plutonium transport in a fracture with similar characteristics to those present in the vicinity of the BENHAM test. SKI's colloid transport code, COLLAGE II, considers radionuclide transport in a one-dimensional planar fracture and represents radionuclide-colloid sorption and desorption assuming first-order, linear kinetics. Recently published data from both the ongoing NTS site investigation and from the associated Yucca Mountain Project have been used to define a COLLAGE II dataset. The kinetics of radionuclide-colloid sorption and desorption have been found to be crucial in explaining the transport of plutonium associated with colloids, as inferred at the NTS. Specifically, it has been found that for plutonium to have been transported by colloids over the full 1.3 km transport path, it is likely that the plutonium

Radionuclide sorption to a mixture of anaerobic bacteria in the repository environment

International Nuclear Information System (INIS)

Sasaki, Takayuki; Kubota, Takumi; Kudo, Akira

2002-01-01

The sorption of the radionuclides, Pu, Np, Pa, Sr and Cs, to a mixture of anaerobic bacteria activated under specific conditions of temperature, pH and depleted nutrients after a long dormant period has been investigated. For Pu, after 4 hours at neutral pH, the distribution coefficient (K d ) between bacteria and aqueous phase at 308 and 278K was around 10 3-4 (ml g -1 ). Over 5 days, however, the K d at 308K increased to over 10 5 . Sterilized (dead) and dormant anaerobic bacteria adsorbed Pu to the same extent. K d for Np at 308K after 5 days had a low value around 10 2 . After 10 days, however, K d was >100-fold higher. On the other hand, K d for Np at 278K remained low, without any significant increase over time. The interaction between Pa and bacteria was found to be stronger than that for Np, with K d for Pa about 100 times higher. For Sr and Ca, significant K d change was not seen through 120 d. The value for Sr is a few times larger than that for Cs due to the different electrostatic interaction with the bacteria based on the charge of ion. (author)

Colloid-facilitated radionuclide transport: a regulatory perspective

Science.gov (United States)

Dam, W. L.; Pickett, D. A.; Codell, R. B.; Nicholson, T. J.

2001-12-01

What hydrogeologic-geochemical-microbial conditions and processes affect migration of radionuclides sorbed onto microparticles or native colloid-sized radionuclide particles? The U.S. Nuclear Regulatory Commission (NRC) is responsible for protecting public health, safety, and the environment at numerous nuclear facilities including a potential high-level nuclear waste disposal site. To fulfill these obligations, NRC needs to understand the mechanisms controlling radionuclide release and transport and their importance to performance. The current focus of NRC staff reviews and technical interactions dealing with colloid-facilitated transport relates to the potential nuclear-waste repository at Yucca Mountain, Nevada. NRC staff performed bounding calculations to quantify radionuclide releases available for ground-water transport to potential receptors from a Yucca Mountain repository. Preliminary analyses suggest insignificant doses of plutonium and americium colloids could be derived from spent nuclear fuel. Using surface complexation models, NRC staff found that colloids can potentially lower actinide retardation factors by up to several orders of magnitude. Performance assessment calculations, in which colloidal transport of plutonium and americium was simulated by assuming no sorption or matrix diffusion, indicated no effect of colloids on human dose within the 10,000 year compliance period due largely to long waste-package lifetimes. NRC staff have identified information gaps and developed technical agreements with the U.S. Department of Energy (DOE) to ensure sufficient information will be presented in any potential future Yucca Mountain license application. DOE has agreed to identify which radionuclides could be transported via colloids, incorporate uncertainties in colloid formation, release and transport parameters, and conceptual models, and address the applicability of field data using synthetic microspheres as colloid analogs. NRC is currently

Experimental study on an innovative multifunction heat pipe type heat recovery two-stage sorption refrigeration system

International Nuclear Information System (INIS)

Li, T.X.; Wang, R.Z.; Wang, L.W.; Lu, Z.S.

2008-01-01

An innovative multifunction heat pipe type sorption refrigeration system is designed, in which a two-stage sorption thermodynamic cycle based on two heat recovery processes was employed to reduce the driving heat source temperature, and the composite sorbent of CaCl 2 and activated carbon was used to improve the mass and heat transfer performances. For this test unit, the heating, cooling and heat recovery processes between two reactive beds are performed by multifunction heat pipes. The aim of this paper is to investigate the cycled characteristics of two-stage sorption refrigeration system with heat recovery processes. The two sub-cycles of a two-stage cycle have different sorption platforms though the adsorption and desorption temperatures are equivalent. The experimental results showed that the pressure evolutions of two beds are nearly equivalent during the first stage, and desorption pressure during the second stage is large higher than that in the first stage while the desorption temperatures are same during the two operation stages. In comparison with conventional two-stage cycle, the two-stage cycle with heat recovery processes can reduce the heating load for desorber and cooling load for adsorber, the coefficient of performance (COP) has been improved more than 23% when both cycles have the same regeneration temperature of 103 deg. C and the cooling water temperature of 30 deg. C. The advanced two-stage cycle provides an effective method for application of sorption refrigeration technology under the condition of low-grade temperature heat source or utilization of renewable energy

Tracer sorption and macroscopic transport in clay nano-pores: a lattice-Boltzmann study

International Nuclear Information System (INIS)

Levesque, Maximilien; Rotenberg, Benjamin; Duvail, Magali; Benichou, Olivier; Voituriez, Raphael; Pagonabarraga, Ignacio; Frenkel, Daan

2012-01-01

Document available in extended abstract form only. The Agence Nationale pour la gestion des Dechets Radioactifs (ANDRA) has been entrusted to find a safe solution for disposing of existing and future nuclear wastes. A prototype site has been considered for the waste disposal in a deep underground sedimentary geological formation. It is composed of clay minerals chosen, among other reasons, for their remarkable ability to limit radionuclide transport. Clay minerals are complex charged porous media characterized by heterogeneities at several length scales. They naturally occur as an assembly of few nano-meter-sized particles connected to form 10 to 100 nm interparticle pores containing water and ions. This intrinsically multi-scale structure, that gives the material its remarkable properties, makes the description of sorption and transport phenomena of transported ions particularly challenging. Experimental studies of water and ion transport through clays mostly consist in evaluating macroscopic effective transport coefficients like permeability or conductivity. They showed that the main transport mechanism is an effective diffusion that not only depends on particle charge but also on its chemical nature, or specificity. The goal of assessing the performance of clays as confinement barriers, particularly in the context of the geological disposal of nuclear waste, requires not only quantitative prediction of the retention and transport of species but also an understanding of the microscopic mechanisms underlying them. A successful approach has been to use numerical simulations via the Lattice-Boltzmann method (LB). It consists in making evolve populations describing the fluid at a level which is consistent with time and length-scales involved in transport properties, while still including a microscopic description of the phenomena. The transport of charged ions at the pore scale has recently been included in LB. In this method, the evolution of a tracer population is

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

International Nuclear Information System (INIS)

Sugiyama, D.; Fujita, T.

2005-01-01

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

Study of {sup 137}Cs e {sup 60}Co sorption in sediments from Saco de Piraquara de Fora, Angra dos Reis and its application for environmental monitoring; Estudo da sorcao de {sup 137}Cs e {sup 60}Co em sedimentos do Saco de Piraquara de Fora em Angra dos Reis e sua aplicacao para o monitoramento ambiental

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Ingryd Marques

2016-08-01

Both the suspended solid particles and the bed sediments sorb radionuclides, released in water systems. Sorption is usually represented mathematically by the distribution coefficient that is based in equilibrium between phases. Here the adsorption/desorption kinetics of {sup 60}Co and {sup 137}Cs in sea water were simulated by batch equilibrium experiments with sediments in two points (PT - 01, PT - 02) from Saco de Piraquara de Fora inlet (SPF). For both radionuclides, partition coefficient values (Kd) for the sampling point PT - 02 (509 and 385 L/kg for {sup 60}Co and {sup 137}Cs, respectively) were higher than the values determined for PT - 01 one (426 and 182 L/kg for {sup 137}Cs and {sup 60}Co, respectively). The higher values of Kd of PT-02 reflects the higher CEC (71,4 cmolc.dm{sup 3}) and content of mud < 63 μm (87%) when compared to PT-01 (CEC of 39,5 cmol{sub c}.dm{sup 3}) and mud (55%). In comparison with the values reported in the literature, the found Kd values are low, which may be related to the predominance of kaolinite, which is a clay of low sorption capacity. The Kd values with an increase in temperature of 23 deg C to 27 deg C were similar ({sup 60}Co in PT-02 and {sup 137}Cs in both sediment) or 27 ° C values were higher ({sup 60}Co the PT-01). With increasing temperature to 31 °C Kd values for the two radionuclides showed a decrease. However, increasing temperature increases the desorption of the two radionuclides for both sediments The sorption process is spontaneous and favorable for both sediments and the model of sorption can be fitted by both Freundlich and Langmuir sorption isotherms. The maximum amount of {sup 60}Co that can be sorbed on sediments were 1,64 10{sup -5} moles/g (4,12 10{sup 10} Bq/g) and 2,79 10{sup -5} moles/g (7,03 10{sup 10} Bq/g) to PT-01 and PT-02, respectively, and of {sup 137}Cs 1,99 10{sup -6} moles/g (9,70 10{sup 8} Bq/g) and 6,60 10{sup -6} mol/g (2,87 10{sup 9} Bq/g ) to PT-01 and PT-02. Two areas in SPF can

Sorption of phenanthrene and benzene on differently structural kerogen: important role of micropore-filling.

Science.gov (United States)

Zhang, Yulong; Ma, Xiaoxuan; Ran, Yong

2014-02-01

Shale was thermally treated to obtain a series of kerogen with varied maturation. Their chemical, structural and porous properties were related to the sorption and/or desorption behaviors of phenanthrene and benzene. As the treatment temperature increases, aliphatic and carbonyl carbon of the kerogen samples decrease, while their aromaticity and maturation increase. Meanwhile, the isothermal nonlinearity of phenanthrene and benzene increases whereas the sorption capacity and micropore adsorption volumes (Vo,d) initially increase and then decrease. The Vo,d of benzene is significantly correlated with, but higher than that of phenanthrene, suggesting similar micropore filling mechanism and molecular sieve effect. The benzene desorption exhibits hysteresis, which is related to the pore deformation of the kerogen and the entrapment of solute in the kerogen matrix. The Vo,d of phenanthrene and benzene on the kerogen samples accounts for 23-46% and 36-65% of the maximum sorption volumes, respectively, displaying the importance of the micropore filling. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sorption of phenanthrene and benzene on differently structural kerogen: Important role of micropore-filling

International Nuclear Information System (INIS)

Zhang, Yulong; Ma, Xiaoxuan; Ran, Yong

2014-01-01

Shale was thermally treated to obtain a series of kerogen with varied maturation. Their chemical, structural and porous properties were related to the sorption and/or desorption behaviors of phenanthrene and benzene. As the treatment temperature increases, aliphatic and carbonyl carbon of the kerogen samples decrease, while their aromaticity and maturation increase. Meanwhile, the isothermal nonlinearity of phenanthrene and benzene increases whereas the sorption capacity and micropore adsorption volumes (V o,d ) initially increase and then decrease. The V o,d of benzene is significantly correlated with, but higher than that of phenanthrene, suggesting similar micropore filling mechanism and molecular sieve effect. The benzene desorption exhibits hysteresis, which is related to the pore deformation of the kerogen and the entrapment of solute in the kerogen matrix. The V o,d of phenanthrene and benzene on the kerogen samples accounts for 23–46% and 36–65% of the maximum sorption volumes, respectively, displaying the importance of the micropore filling. -- Highlights: • The microporosity estimated by benzene vapor differs greatly from that by N 2 . • The micropore volume changes with kerogen maturation. • The phenanthrene or benzene sorption is related to the microporosity of kerogen. • Higher adsorption volume for benzene than for phenanthrene suggests molecular sieve effect. • The pore-filling plays an important role in the sorption of phenanthrene and benzene. -- The sorption behaviors of benzene and phenanthrene are related to the microporosity of the differently matured kerogen, indicating the importance of pore-filling

Inclusion of radionuclides absorption by sediments in the RIVLAK program

International Nuclear Information System (INIS)

Rodrigues Junior, O.; Moreira, J.M.L.

1992-01-01

The RIVLAK code solves the one-dimensional transport equation for radionuclide concentrations within a water body for routine and accidental releases of liquid effluents. The principal phenomena considered in the RIVLAK code are advection by the water body flow, longitudinal and transversal diffusion, and radioactive decay. This work incorporates the interaction between radionuclides and suspended or bed sediments to the RIVLAK code. An approximate equation for the radionuclide concentration in an effective sediment is included in the code with explicit terms for adsorption and desorption from the water to the effective sediment. The modified RIVLAK code is utilized for estimating the radionuclide concentration from release experiments in the Clinch river. The original code overestimates the Cs concentration downstream by approximately two orders of magnitude. The modified version predicts the Cs concentration with few percents, and underestimates its longitudinal dispersion by about 35%. The special care needed with parameters such as the radionuclide diffusion coefficient in the water, and the adsorption and desorption coefficients are discussed. (author)

Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

Energy Technology Data Exchange (ETDEWEB)

Schroefl, Christof, E-mail: christof.schroefl@tu-dresden.de [Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden (Germany); Mechtcherine, Viktor [Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden (Germany); Vontobel, Peter; Hovind, Jan; Lehmann, Eberhard [Paul Scherrer Institut, Laboratory for Neutron Scattering and Imaging, CH-5232 Villigen/AG (Switzerland)

2015-09-15

Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1.

Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

International Nuclear Information System (INIS)

Schroefl, Christof; Mechtcherine, Viktor; Vontobel, Peter; Hovind, Jan; Lehmann, Eberhard

2015-01-01

Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1

Desorption behaviors of BDE-28 and BDE-47 from natural soils with different organic carbon contents

International Nuclear Information System (INIS)

Liu Wenxin; Cheng Fangfang; Li Weibo; Xing Baoshan; Tao Shu

2012-01-01

Desorption kinetic and isothermal characteristics of BDE-28 and BDE-47 were investigated using natural soils with different organic carbon fractions. The results indicated that a two-compartment first-order model with dominant contribution of slow desorption could adequately describe the released kinetics of studied PBDEs. Desorption isotherms of different samples could be fitted well by linear distribution model or nonlinear Freundlich model. Moreover, most desorption procedures roughly exhibited hysteresis with respect to preceding sorption ones. At the statistically significant level of 0.05 or 0.1, total organic carbon content (f OC ) exhibited significant correlations with the fitted parameters by the isothermal models. The correlations of f OC and SOM fractions (e.g., fulvic acid and humin) with the single point desorption coefficients at lower aqueous concentrations of studied PBDEs were significant; while at higher aqueous concentrations, the relationships were less significant or insignificant. Our findings may facilitate a comprehensive understanding on behaviors of PBDEs in soil systems. - Highlights: ► A two-compartment first-order kinetic model for the PBDEs studied was established. ► Isotherm was fitted well by a linear distribution or a nonlinear Freundlich model. ► Desorption commonly exhibited somewhat hysteresis relative to sorption. ► Soil organic carbon fractions showed close correlations with the model parameters. - Two-compartment first-order model, and linear distribution model or nonlinear Freundlich model could well elucidate desorption kinetics and isotherms of PBDEs in natural soils, respectively.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-06-01

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

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

International Nuclear Information System (INIS)

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

1988-05-01

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

Gas sorption properties of microporous metal organic frameworks

International Nuclear Information System (INIS)

Lee, JeongYong; Li Jing; Jagiello, Jacek

2005-01-01

A low-temperature gas sorption study has been carried out on four three-dimensional microporous metal organic framework (MMOF) structures and two two-dimensional layered structures. The pore characteristics are analyzed based on the argon adsorption-desorption isotherms at 87 K. The results from hydrogen sorption experiments conducted at 77 and 87 K show that all MMOFs have a relatively high hydrogen uptake, with adsorbed hydrogen densities falling in the range of liquid hydrogen. Isosteric heats of hydrogen adsorption data calculated based on the Clausius-Clapeyron equation are consistent with these observations, indicating strong sorbent-sorbate interactions. - Graphical abstract: Hydrogen adsorption isotherms measured at 77 and 87 K

Functionalization of Magnetic Chitosan Particles for the Sorption of U(VI, Cu(II and Zn(II—Hydrazide Derivative of Glycine-Grafted Chitosan

Directory of Open Access Journals (Sweden)

Mohammed F. Hamza

2017-05-01

Full Text Available A new magnetic functionalized derivative of chitosan is synthesized and characterized for the sorption of metal ions (environmental applications and metal valorization. The chemical modification of the glycine derivative of chitosan consists of: activation of the magnetic support with epichlorohydrin, followed by reaction with either glycine to produce the reference material (i.e., Gly sorbent or glycine ester hydrochloride, followed by hydrazinolysis to synthesize the hydrazide functionalized sorbent (i.e., HGly sorbent. The materials are characterized by titration, elemental analysis, FTIR analysis (Fourrier-transform infrared spectrometry, TGA analysis (thermogravimetric analysis and with SEM-EDX (scanning electron microscopy coupled to energy dispersive X-ray analysis. The sorption performances for U(VI, Cu(II, and Zn(II are tested in batch systems. The sorption performances are compared for Gly and HGly taking into account the effect of pH, the uptake kinetics (fitted by the pseudo-second order rate equation, and the sorption isotherms (described by the Langmuir and the Sips equations. The sorption capacities of the modified sorbent reach up to 1.14 mmol U g−1, 1.69 mmol Cu g−1, and 0.85 mmol Zn g−1. In multi-metal solutions of equimolar concentration, the chemical modification changes the preferences for given metal ions. Metal ions are desorbed using 0.2 M HCl solutions and the sorbents are re-used for five cycles of sorption/desorption without significant loss in performances.

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

International Nuclear Information System (INIS)

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

2002-01-01

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

Using fluorescent dyes as proxies to study herbicide removal by sorption in buffer zones.

Science.gov (United States)

Dollinger, Jeanne; Dagès, Cécile; Voltz, Marc

2017-04-01

The performance of buffer zones for removing pesticides from runoff water varies greatly according to landscape settings, hydraulic regime, and system design. Evaluating the performance of buffers for a range of pesticides and environmental conditions can be very expensive. Recent studies suggested that the fluorescent dyes uranine and sulforhodamine B could be used as cost-effective surrogates of herbicides to evaluate buffer performance. However, while transformation mechanisms in buffers have been extensively documented, sorption processes of both dyes have rarely been investigated. In this study, we measured the adsorption, desorption, and kinetic sorption coefficients of uranine and sulforhodamine B for a diverse range of buffer zone materials (soils, litters, plants) and compared the adsorption coefficients (Kd) to those of selected herbicides. We also compared the global sorption capacity of 6 ditches, characterized by varying proportions of the aforementioned materials, between both dyes and a set of four herbicides using the sorption-induced pesticide retention indicator (SPRI). We found that both the individual Kd of uranine for the diverse buffer materials and the global sorption capacity of the ditches are equivalent to those of the herbicides diuron, isoproturon, and metolachlor. The Kd of sulforhodamine B on plants and soils are equivalent to those of glyphosate, and the global sorption capacities of the ditches are equivalent for both molecules. Hence, we demonstrate for the first time that uranine can be used as a proxy of moderately hydrophobic herbicides to evaluate the performance of buffer systems, whereas sulforhodamine B can serve as a proxy for more strongly sorbing herbicides.

As(III) and As(V) sorption on iron-modified non-pyrolyzed and pyrolyzed biomass from Petroselinum crispum (parsley).

Science.gov (United States)

Jiménez-Cedillo, M J; Olguín, M T; Fall, C; Colin-Cruz, A

2013-03-15

The sorption of As(III) and As(V) from aqueous solutions onto iron-modified Petroselinum crispum (PCFe) and iron-modified carbonaceous material from the pyrolysis of P. crispum (PCTTFe) was investigated. The modified sorbents were characterized with scanning electron microscopy. The sorbent elemental composition was determined with energy-dispersive X-ray spectroscopy (EDS). The principal functional groups from the sorbents were determined with FT-IR. The specific surfaces and points of zero charge (pzc) of the materials were also determined. As(III) and As(V) sorption onto the modified sorbents were performed in a batch system. After the sorption process, the As content in the liquid and solid phases was determined with atomic absorption and neutron activation analyses, respectively. After the arsenic sorption processes, the desorption of Fe from PCFe and PCTTFe was verified with atomic absorption spectrometry. The morphology of PC changed after iron modification. The specific area and pzc differed significantly between the iron-modified non-pyrolyzed and pyrolyzed P. crispum. The kinetics of the arsenite and arsenate sorption processes were described with a pseudo-second-order model. The Langmuir-Freundlich model provided the isotherms with the best fit. Less than 0.02% of the Fe was desorbed from the PCFe and PCTTFe after the As(III) and As(V) sorption processes. Copyright © 2013 Elsevier Ltd. All rights reserved.

Influence of the redox state on the neptunium sorption under alkaline conditions. Batch sorption studies on titanium dioxide and calcium silicate hydrates

International Nuclear Information System (INIS)

Tits, Jan; Laube, Andreas; Wieland, Erich; Gaona, Xavier

2014-01-01

Wet chemistry experiments were carried out to investigate the effect of the redox state and aqueous speciation on the uptake of neptunium by titanium dioxide (TiO 2 ) and by calcium silicate hydrates (C-S-H) under alkaline conditions. TiO 2 was chosen as a reference sorbent to determine the surface complexation behaviour of neptunium under alkaline conditions. C-S-H phases are important constituents of cement and concrete. They may contribute significantly to radionuclide retention due to their high recrystallization rates making incorporation the dominating sorption mechanism for many radionuclides (e.g. the actinides) on these materials. The sorption of neptunium on both solids was found to depend strongly on the degree of hydrolysis. On TiO 2 R d values for Np(IV), Np(V) and Np(VI) are identical at pH = 10 and decrease with progressing hydrolysis in case of Np(V) and Np(VI). On C-S-H phases, R d values for the three redox states are also identical at pH = 10. While the R d values for Np(VI) sorption on C-S-H phases decrease with progressing hydrolysis, the R d values for Np(IV) and Np(V) sorption are not affected by the pH. In addition to the effect of hydrolysis, the presence of Ca is found to promote Np(V) and Np(VI) sorption on TiO 2 whereas on C-S-H phases, the present wet chemistry data do not give unambiguous evidence. Thus, the aqueous speciation appears to have a similar influence on the sorption of the actinides on both types of solids despite the different sorption mechanism. The similar R d values for Np(IV,V,VI) sorption at pH = 10 can be explained qualitatively by invoking inter-ligand electrostatic repulsion between OH groups in the coordination sphere of Np(V) and Np(VI). This mechanism was proposed earlier in the literature for the prediction of actinide complexation constants with inorganic ligands. A limiting coordination number for each Np redox state, resulting from the inter-ligand electrostatic repulsion, allows the weaker sorption of the

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

International Nuclear Information System (INIS)

Tachi, Yukio; Suyama, Tadahiro; Ochs, Michael

2014-01-01

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

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

International Nuclear Information System (INIS)

Choi, Hyeok; Al-Abed, Souhail R.

2009-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2009-06-15

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

Behaviour and fate radionuclides in soils. Mathematical modelling and experimental investigations

International Nuclear Information System (INIS)

Rovdan, E.N.

2003-01-01

The uncontrolled release of radionuclides as result of Chernobyl accident has led to contamination of 23% of territory of Republic of Belarus. Soil has high capacity to adsorb radionuclides and their intensive sorption provides the creation of a long-lived radionuclide source in a terrestrial environment. In the management of the contaminated areas and application of a countermeasure strategy it is extremely important to know the environmental mechanisms governing the behaviour of radionuclides in soils. Basic attention in the work is paid to the study of 137 Cs and 90 Sr because they are the main radionuclides from the view point of radioactive danger in polluted areas. The main features and processes that control radionuclide behaviour in soil have been analysed. On the basis of natural researches, lab test and mathematical modelling the impact of physical-chemical factors and the soil component composition changes upon the radionuclides migration and sorption in natural dispersed systems (peat, sand, bentonite, kaolin, sapropel) has been investigated. The investigations done allowed to substantiate the mathematical models of the radionuclides migration in the regions of positive and negative temperatures, to develop methods of experimental identification of main transfer characteristics and to compile a data base for these models. (orig.)

The radionuclide migration experiment - overview of investigations 1985 - 1990

International Nuclear Information System (INIS)

Frick, U.; McKinley, I.G.; Baeyens, B.; Bradbury, M.H.; Eikenberg, J.; Heer, W.; Hoehn, E.; Smith, P.A.; Alexander, W.R.; Bossart, P.; Buehler, C.; Fierz, T.

1992-03-01

This paper provides an overview of the investigations conducted from 1985 to 1990 as a part of the radionuclide migration experiment which is currently in progress in the Nagra underground research laboratory at the Grimsel pass in the Central Swiss Alps. The major aims of the project are (1) to test the extrapolation of laboratory sorption data to field conditions, (2) to analyse retardation processes in a fractured rock, (3) to improve and develop the necessary methodologies for site characterization and (4) to test existing geochemical, hydrodynamic, and solute transport models or their associated data bases. Field and modeling work are complemented by an extensive laboratory support programme. The Grimsel migration experiment demonstrates conclusively how the combined efforts of modeling, laboratory and field investigations can substantially widen the understanding of radionuclide transport in a geological environment. (author) figs., tabs., refs

Sorption of Cu(II) Ions on Chitosan-Zeolite X Composites: Impact of Gelling and Drying Conditions.

Science.gov (United States)

Djelad, Amal; Morsli, Amine; Robitzer, Mike; Bengueddach, Abdelkader; di Renzo, Francesco; Quignard, Françoise

2016-01-19

Chitosan-zeolite Na-X composite beads with open porosity and different zeolite contents were prepared by an encapsulation method. Preparation conditions had to be optimised in order to stabilize the zeolite network during the polysaccharide gelling process. Composites and pure reference components were characterized using X-ray diffraction (XRD); scanning electron microscopy (SEM); N₂ adsorption-desorption; and thermogravimetric analysis (TG). Cu(II) sorption was investigated at pH 6. The choice of drying method used for the storage of the adsorbent severely affects the textural properties of the composite and the copper sorption effectiveness. The copper sorption capacity of chitosan hydrogel is about 190 mg·g(-1). More than 70% of this capacity is retained when the polysaccharide is stored as an aerogel after supercrititcal CO₂ drying, but nearly 90% of the capacity is lost after evaporative drying to a xerogel. Textural data and Cu(II) sorption data indicate that the properties of the zeolite-polysaccharide composites are not just the sum of the properties of the individual components. Whereas a chitosan coating impairs the accessibility of the microporosity of the zeolite; the presence of the zeolite improves the stability of the dispersion of chitosan upon supercritical drying and increases the affinity of the composites for Cu(II) cations. Chitosan-zeolite aerogels present Cu(II) sorption properties.

The function of alginic acid on the radioactive contamination of some marine invertebrates deposite-feeders

International Nuclear Information System (INIS)

Amiard-Triquet, C.

1975-01-01

The contamination of invertebrates by radionuclides in a sedimentary environment is a function of the mobility of radioactive ions and especially of the mode of sorption of the radionuclides on the sediment and the ion retention by the algines. Since the enzymatic system of species feeding on the sediment includes little or no alginase, there occurs no desorption of the radionuclides during the passage of the algines along the digestive tract [fr

Sorption, Diffusion and Solubility Databases for Performance Assessment

International Nuclear Information System (INIS)

Garcia Gutierrez, M.

2000-01-01

This report presents a deterministic and probabilistic databases for application in Performance Assessment of a high-level radioactive waste disposal. This work includes a theoretical description of sorption, diffusion and solubility phenomena of radionuclides in geological media. The report presents and compares the databases of different nuclear wastes management agencies, describes the materials in the Spanish reference system, and the results of sorption diffusion and solubility in this system, with both the deterministic and probabilistic approximation. The probabilistic approximation is presented in the form of probability density functions (pdf). (Author) 52 refs

Isothermal titration calorimetry of sorption processes. A promising approach

Energy Technology Data Exchange (ETDEWEB)

Jordan, Norbert; Foerstendorf, Harald [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Drobot, B. [Technische Univ. Dresden (Germany); Fahmy, Karim [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biophysics; Reder, Christian

2017-06-01

As a consequence of nuclear waste disintegration heat, elevated temperatures in the near field may influence radionuclide retention significantly. However, there is a nearly complete lack of spectroscopic investigations of sorption processes at elevated temperatures. In addition, experimental data on free Gibbs energy (Δ{sub R}G), enthalpy (Δ{sub R}H) and entropy (Δ{sub R}S) of reactions of most radionuclides including fission products such as {sup 79}Se are sparse. Using the Se(IV)/hematite system, we show that microcalorimetry can provide these thermodynamic parameters with high accuracy and in a manner that allows studying various radionuclides.

Sorption of hydrophobic organic compounds to plastics in marine environments: Equilibrium

NARCIS (Netherlands)

Endo, S.; Koelmans, A.A.

2016-01-01

Marine plastics have shown to contain various environmental chemicals. For evaluating the potential of plastics to influence regional and global dynamics of these chemicals and to serve as a vector to marine biota, understanding of sorption and desorption of chemicals by plastics is important. In

Radionuclide chain migration in fissured rock

International Nuclear Information System (INIS)

Rasmuson, A.; Neretnieks, I.

1982-04-01

Diffusion into the rock matrix has a large impact on the migration of radionuclides in the geosphere. The aim of the present study is to investigate the effect of this mechanism on radionuclide chain migration. For this purpose a previously used numerical code TRUMP is extended to incorporate chain decay. The algorithm is also changed to directly include the decay terms. The extended version was given the acronym TRUCHN. Numerical solutions from TRUCHN are compared with the analytical solutions developed by Lester et al. A good agreement is obtained. To illustrate the impact of matrix diffusion on the arrival times to the biosphere of the members of a radionuclide chain a number of numerical calculations were done for the two chains U-238 to Th-230 to Ra-226 and Pu-239 to U-235 to Pa-231. The resulting curves are compared with the results for surface sorption (penetration depth 10 - 4 m) and volume sorption (complete penetration) obtained with the computer program GETOUT. The difference in first arrival times are very large. The arrival times in the surface and volume sorption cases, differ with as much as four orders of magnitude. The corresponding times for instationary diffusion are located between these extreme values. A daughter nuclide which is strongly sorbed may be heavily retarded if it is produced far inside the rock matrix and has a long way to diffuse before it reaches the flowing water. This effect is investigated, by considering diffusion only of a radionuclide chain, with analytical and numerical (TRUCHN) methods. Finally, in connection with the reconcentration effect, some means of describing the outflow of a daughter nuclide in terms of the outflow of its parent nuclide are proposed. (Authors)

Iodine sorption by microwave irradiated hydrotalcites

Energy Technology Data Exchange (ETDEWEB)

Paredes, S.P. [Universidad Autonoma de Puebla, Facultad de Ciencias Quimicas, C.P. 72570, Puebla, Pue (Mexico); Instituto Politecnico Nacional, ESIQIE, C.P. 07738, Mexico, D.F. (Mexico); Fetter, G. [Universidad Autonoma de Puebla, Facultad de Ciencias Quimicas, C.P. 72570, Puebla, Pue (Mexico)]. E-mail: geolarfetter@yahoo.com.mx; Bosch, P. [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, C.P. 04510, Mexico, D.F. (Mexico); Bulbulian, S. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, C.P. 11801, Mexico, D.F. (Mexico)

2006-12-15

Mg-Al hydrotalcite-like compounds (HT) were prepared by the microwave method on the one hand with ethoxide-acetylacetonate and on the other with acetylacetonate as precursors. They presented a maximum sorption capacity of 2.179 and 1.517 meq of {sup 131}I{sup -}/g of hydrotalcite respectively. When the hydrotalcites were calcined and rehydrated in a {sup 131}I{sup -} solution, iodine sorption decreased in both samples to 1.515 and 1.446, respectively. The corresponding value for nitrated hydrotalcite which was prepared by the conventional method for comparison purposes, was 0.570. The radionuclide content in hydrotalcites was determined by {gamma}-spectrometry. {sup 131}I{sup -} sorption is dependent on two main parameters: one is the type of the interlayer organic material and the second the surface area. It was found that hydrotalcites prepared with ethoxide-acetylacetonate were better sorbents for {sup 131}I{sup -} than those with acetylacetonate. Still, if the specific surface area increased, {sup 131}I{sup -}sorption increased as well; nitrated HT resulted in low specific surface area and a low sorption capacity. It is, therefore, concluded that organic residues present in the samples prepared by the microwave method favor the sorption of radioactive anions, in particular {sup 131}I{sup -} if compared with nitrated and/or carbonate interlayered hydrotalcites.

Investigation of solution chemistry effects on sorption behavior of radionuclide 64Cu(II) on illite

International Nuclear Information System (INIS)

Shitong Yang; Guodong Sheng; Zhiqiang Guo; Yubing Sun; Donglin Zhao

2011-01-01

In this work, a series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, coexisting electrolyte ions, humic substances and temperature on the sorption behavior of illite towards 64 Cu(II). The results indicated that 64 Cu(II) sorption on illite achieved equilibrium quickly. The pH- and ionic strength-dependent sorption suggested that 64 Cu(II) sorption on illite was dominated by ion exchange or outer-sphere surface complexation at pH 7. A positive effect of humic substances on 64 Cu(II) sorption was found at pH 6.5. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 64 Cu(II) at three different temperatures of 293, 313, and 333 K. The thermodynamic parameters (ΔH 0 , ΔS 0 , and ΔG 0 ) of 64 Cu(II) sorption on illite were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption of 64 Cu(II) on illite was endothermic and spontaneous. From the experimental results, it is possible to conclude that illite has good potentialities for cost-effective treatments of 64 Cu(II)-contaminated wastewaters. (author)

Research into the behaviour and transport of radionuclides in waters. Methods of testing sorption properties of materials present in aquatic environment and evaluation of results. Part of a coordinated programme on radiological and environmental studies in the Danube river catchment area

International Nuclear Information System (INIS)

Mansfeld, A.

1981-12-01

The presented study gives some basic information about the behaviour of selected radionuclides ( 226 Ra, U, 51 Cr, 60 Co, 0 879.Sr, 131 I, and 137 Cs) in aqueous environment. It proves the great significance of bottom sediments in the investigation of radionuclide sorption and migration and for obtaining data for the predicition of their behaviour in aqueous environment

Dosimeter-Type NOx Sensing Properties of KMnO4 and Its Electrical Conductivity during Temperature Programmed Desorption

Directory of Open Access Journals (Sweden)

Ralf Moos

2013-04-01

Full Text Available An impedimetric NOx dosimeter based on the NOx sorption material KMnO4 is proposed. In addition to its application as a low level NOx dosimeter, KMnO4 shows potential as a precious metal free lean NOx trap material (LNT for NOx storage catalysts (NSC enabling electrical in-situ diagnostics. With this dosimeter, low levels of NO and NO2 exposure can be detected electrically as instantaneous values at 380 °C by progressive NOx accumulation in the KMnO4 based sensitive layer. The linear NOx sensing characteristics are recovered periodically by heating to 650 °C or switching to rich atmospheres. Further insight into the NOx sorption-dependent conductivity of the KMnO4-based material is obtained by the novel eTPD method that combines electrical characterization with classical temperature programmed desorption (TPD. The NOx loading amount increases proportionally to the NOx exposure time at sorption temperature. The cumulated NOx exposure, as well as the corresponding NOx loading state, can be detected linearly by electrical means in two modes: (1 time-continuously during the sorption interval including NOx concentration information from the signal derivative or (2 during the short-term thermal NOx release.

Extrapolation studies on desorption of thorium and uranium at different solution compositions on contaminated soil sediments (Malaysia)

International Nuclear Information System (INIS)

Syed Hakimi Sakuma

2000-01-01

By means of batch desorption experiments, the thorium and uranium desorption properties of contaminated soil sediments are investigated as a function of the effect of cations present in the groundwater. A phenomenological correlation between the desorption coefficient and the concentration of Ca and Mg in the water is determined. Kd Thorium -0.15849 ± 0.03237 log (Ca + Mg) + 5.06715 ± 0.09106; Kd Uranium = -0.11984 ± 0.03237 log (Ca + Mg) + 2.99909 ± 0.09105. By these models the sorption/desorption behaviour of soils can be predicted phenomenologically as function of the groundwater composition. (author)

Radionuclide getters in the near-field chemistry of repositories

International Nuclear Information System (INIS)

Holland, T.R.; Lee, D.J.

1991-06-01

The solubility of many radionuclides in a radwaste repository will be limited by the high pH of the cement based system. However, the inclusion of specific sorbing media, within the cement backfill, offers the ability to improve the retention of the more mobile radionuclides, such as caesium and iodine; thereby further reducing their environmental impact. This programme of work is intended to assess the radionuclide sorption efficiency of selected inorganic getters incorporated in cement. (author)

Plutonium sorption to nanocast mesoporous carbon

Energy Technology Data Exchange (ETDEWEB)

Parsons-Moss, Tashi; Wang, Deborah; Jones, Stephen; Olive, Daniel; Nitsche, Heino [California Univ., Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Nuclear Science Div.; Tueysuez, Harun [Lawrence Berkeley National Laboratory, Berkeley, CA (United States). Nuclear Science Div.; Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

2014-09-01

Nanocast ordered mesoporous carbons are attractive as sorbents because of their extremely high surface areas and large pore volumes. This paper compares Pu uptake, added as Pu(VI), to both untreated and chemically oxidized CMK-(carbon molecular sieves from KAIST) type mesoporous carbon with that to a commercial amorphous activated carbon. The CMK was synthesized via nanocasting by using cubic ordered mesoporous silica KIT-6 as a hard template, and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption. A portion of the CMK was oxidized by treatment with nitric acid, and will be called OX CMK. The three carbon powders have similar particle morphology, and high BET surface areas. The activated carbon is disordered, while the CMK materials show large domains of ordered cubic mesostructure. The CMK material seems to have more oxygen-containing functional groups than the activated carbon, and the oxidation of the CMK increased the density of these groups, especially - COOH, thus lowering the point of zero charge (PZC) of the material. Batch studies of all 3 materials with plutonium solutions, in a 0.1 M NaClO{sub 4} matrix were performed to investigate pH dependence, sorption kinetics, Pu uptake capacities, competition with ethylenediaminetetraacetic acid (EDTA) in solution, and Pu desorption. Both CMK materials demonstrated high Pu sorption from solutions of pH 3 or greater, and the oxidized CMK also showed high sorption from pH 2 solutions. The activated carbon bound less Pu, and at a much slower rate than CMK. All other batch experiments were carried out in pH 4 solutions. The Pu uptake from low-concentration solutions was faster for the oxidized CMK than for untreated CMK, but in more concentrated samples (∝ 250 μM Pu), the Pu uptake kinetics and apparent capacity were the same for oxidized and untreated CMK. The 23-h Pu uptake capacity of the CMK

Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides.

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, Mark Andrew; Bencoe, Denise Nora; Brinker, C. Jeffrey; Murphy, Andrew Wilson; Holt, Kathleen Caroline; Turnham, Rigney; Kruichak, Jessica Nicole; Tellez, Hernesto; Miller, Andy; Xiong, Yongliang; Pohl, Phillip Isabio; Ockwig, Nathan W.; Wang, Yifeng; Gao, Huizhen

2010-09-01

The United States is now re-assessing its nuclear waste disposal policy and re-evaluating the option of moving away from the current once-through open fuel cycle to a closed fuel cycle. In a closed fuel cycle, used fuels will be reprocessed and useful components such as uranium or transuranics will be recovered for reuse. During this process, a variety of waste streams will be generated. Immobilizing these waste streams into appropriate waste forms for either interim storage or long-term disposal is technically challenging. Highly volatile or soluble radionuclides such as iodine ({sup 129}I) and technetium ({sup 99}Tc) are particularly problematic, because both have long half-lives and can exist as gaseous or anionic species that are highly soluble and poorly sorbed by natural materials. Under the support of Sandia National Laboratories (SNL) Laboratory-Directed Research & Development (LDRD), we have developed a suite of inorganic nanocomposite materials (SNL-NCP) that can effectively entrap various radionuclides, especially for {sup 129}I and {sup 99}Tc. In particular, these materials have high sorption capabilities for iodine gas. After the sorption of radionuclides, these materials can be directly converted into nanostructured waste forms. This new generation of waste forms incorporates radionuclides as nano-scale inclusions in a host matrix and thus effectively relaxes the constraint of crystal structure on waste loadings. Therefore, the new waste forms have an unprecedented flexibility to accommodate a wide range of radionuclides with high waste loadings and low leaching rates. Specifically, we have developed a general route for synthesizing nanoporous metal oxides from inexpensive inorganic precursors. More than 300 materials have been synthesized and characterized with x-ray diffraction (XRD), BET surface area measurements, and transmission electron microscope (TEM). The sorption capabilities of the synthesized materials have been quantified by using stable

Development of a new generation of waste form for entrapment and immobilization of highly volatile and soluble radionuclides

International Nuclear Information System (INIS)

Rodriguez, Mark Andrew; Bencoe, Denise Nora; Brinker, C. Jeffrey; Murphy, Andrew Wilson; Holt, Kathleen Caroline; Turnham, Rigney; Kruichak, Jessica Nicole; Tellez, Hernesto; Miller, Andy; Xiong, Yongliang; Pohl, Phillip Isabio; Ockwig, Nathan W.; Wang, Yifeng; Gao, Huizhen

2010-01-01

The United States is now re-assessing its nuclear waste disposal policy and re-evaluating the option of moving away from the current once-through open fuel cycle to a closed fuel cycle. In a closed fuel cycle, used fuels will be reprocessed and useful components such as uranium or transuranics will be recovered for reuse. During this process, a variety of waste streams will be generated. Immobilizing these waste streams into appropriate waste forms for either interim storage or long-term disposal is technically challenging. Highly volatile or soluble radionuclides such as iodine ( 129 I) and technetium ( 99 Tc) are particularly problematic, because both have long half-lives and can exist as gaseous or anionic species that are highly soluble and poorly sorbed by natural materials. Under the support of Sandia National Laboratories (SNL) Laboratory-Directed Research and Development (LDRD), we have developed a suite of inorganic nanocomposite materials (SNL-NCP) that can effectively entrap various radionuclides, especially for 129 I and 99 Tc. In particular, these materials have high sorption capabilities for iodine gas. After the sorption of radionuclides, these materials can be directly converted into nanostructured waste forms. This new generation of waste forms incorporates radionuclides as nano-scale inclusions in a host matrix and thus effectively relaxes the constraint of crystal structure on waste loadings. Therefore, the new waste forms have an unprecedented flexibility to accommodate a wide range of radionuclides with high waste loadings and low leaching rates. Specifically, we have developed a general route for synthesizing nanoporous metal oxides from inexpensive inorganic precursors. More than 300 materials have been synthesized and characterized with x-ray diffraction (XRD), BET surface area measurements, and transmission electron microscope (TEM). The sorption capabilities of the synthesized materials have been quantified by using stable isotopes I and

Monitoring and characterization of radionuclide transport in the hydrogeologic system