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Title: Cesium sorption reversibility and kinetics on illite, montmorillonite, and kaolinite

Abstract

Understanding sorption and desorption processes is essential to predicting the mobility of radionuclides in the environment. We investigate adsorption/desorption of cesium in both binary (Cs + one mineral) and ternary (Cs + two minerals) experiments to study component additivity and sorption reversibility over long time periods (500 days). Binary Cs sorption experiments were performed with illite, montmorillonite, and kaolinite in a 5 mM NaCl/0.7 mM NaHCO3 solution (pH 8) and Cs concentration range of 10–3 to 10–11 M. The binary sorption experiments were followed by batch desorption experiments. The sorption behavior was modeled with the FIT4FD code and the results used to predict desorption behavior. Sorption to montmorillonite and kaolinite was linear over the entire concentration range but sorption to illite was non-linear, indicating the presence of multiple sorption sites. Based on the 14 day batch desorption data, cesium sorption appeared irreversible at high surface loadings in the case of illite but reversible at all concentrations for montmorillonite and kaolinite. A novel experimental approach, using a dialysis membrane, was adopted in the ternary experiments, allowing investigation of the effect of a second mineral on Cs desorption from the original mineral. Cs was first sorbed to illite, montmorillonite or kaolinite, thenmore » a 3.5–5 kDalton Float-A-Lyzer® dialysis bag with 0.3 g of illite was introduced to each experiment inducing desorption. Nearly complete Cs desorption from kaolinite and montmorillonite was observed over the experiment, consistent with our equilibrium model, indicating complete Cs desorption from these minerals. Results from the long-term ternary experiments show significantly greater Cs desorption compared to the binary desorption experiments. Approximately ~ 45% of Cs desorbed from illite. However, our equilibrium model predicted ~ 65% desorption. Importantly, the data imply that in some cases, slow desorption kinetics rather than permanent fixation may play an important role in apparent irreversible Cs sorption.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1409965
Report Number(s):
LLNL-JRNL-733377
Journal ID: ISSN 0048-9697
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Science of the Total Environment
Additional Journal Information:
Journal Volume: 610-611; Journal Issue: C; Journal ID: ISSN 0048-9697
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY

Citation Formats

Durrant, Chad B., Begg, James D., Kersting, Annie B., and Zavarin, Mavrik. Cesium sorption reversibility and kinetics on illite, montmorillonite, and kaolinite. United States: N. p., 2018. Web. doi:10.1016/j.scitotenv.2017.08.122.
Durrant, Chad B., Begg, James D., Kersting, Annie B., & Zavarin, Mavrik. Cesium sorption reversibility and kinetics on illite, montmorillonite, and kaolinite. United States. doi:10.1016/j.scitotenv.2017.08.122.
Durrant, Chad B., Begg, James D., Kersting, Annie B., and Zavarin, Mavrik. 2018. "Cesium sorption reversibility and kinetics on illite, montmorillonite, and kaolinite". United States. doi:10.1016/j.scitotenv.2017.08.122. https://www.osti.gov/servlets/purl/1409965.
@article{osti_1409965,
title = {Cesium sorption reversibility and kinetics on illite, montmorillonite, and kaolinite},
author = {Durrant, Chad B. and Begg, James D. and Kersting, Annie B. and Zavarin, Mavrik},
abstractNote = {Understanding sorption and desorption processes is essential to predicting the mobility of radionuclides in the environment. We investigate adsorption/desorption of cesium in both binary (Cs + one mineral) and ternary (Cs + two minerals) experiments to study component additivity and sorption reversibility over long time periods (500 days). Binary Cs sorption experiments were performed with illite, montmorillonite, and kaolinite in a 5 mM NaCl/0.7 mM NaHCO3 solution (pH 8) and Cs concentration range of 10–3 to 10–11 M. The binary sorption experiments were followed by batch desorption experiments. The sorption behavior was modeled with the FIT4FD code and the results used to predict desorption behavior. Sorption to montmorillonite and kaolinite was linear over the entire concentration range but sorption to illite was non-linear, indicating the presence of multiple sorption sites. Based on the 14 day batch desorption data, cesium sorption appeared irreversible at high surface loadings in the case of illite but reversible at all concentrations for montmorillonite and kaolinite. A novel experimental approach, using a dialysis membrane, was adopted in the ternary experiments, allowing investigation of the effect of a second mineral on Cs desorption from the original mineral. Cs was first sorbed to illite, montmorillonite or kaolinite, then a 3.5–5 kDalton Float-A-Lyzer® dialysis bag with 0.3 g of illite was introduced to each experiment inducing desorption. Nearly complete Cs desorption from kaolinite and montmorillonite was observed over the experiment, consistent with our equilibrium model, indicating complete Cs desorption from these minerals. Results from the long-term ternary experiments show significantly greater Cs desorption compared to the binary desorption experiments. Approximately ~ 45% of Cs desorbed from illite. However, our equilibrium model predicted ~ 65% desorption. Importantly, the data imply that in some cases, slow desorption kinetics rather than permanent fixation may play an important role in apparent irreversible Cs sorption.},
doi = {10.1016/j.scitotenv.2017.08.122},
journal = {Science of the Total Environment},
number = C,
volume = 610-611,
place = {United States},
year = 2018,
month = 1
}

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  • Adsorption, desorption, and isotopic exchange have been used to investigate the kinetics and reversibility of cesium sorption on illite. Trace concentrations of cesium were used and experimental conditions were kept close to those to those of many freshwater environments. Initials adsorptions of cesium on illite was rapid but was followed by slower uptake process with time scales of weeks to months. The uptake proceeded faster and reached much higher K{sub d} values in a Ca{sup 2+} environment than in a K{sup +} environment. The apparent reversibility of sorption was affected by both the slow sorption processes and the nature ofmore » the competing cation. The desorption equilibration patterns indicate that cesium is released from rapidly accessible sorption sites but that the slow forward reaction continues. On time scales relevant for modeling its transport and retention in aquatic systems, cesium shows partially irreversible behavior. A mechanistic interpretation for the observed sorption and isotopic exchange behavior is proposed whereby cesium migrates slowly to energetically favorable interlayer sites from which it is not easily released.« less
  • The behavior of anthropogenic cesium isotopes in the aquatic environment is controlled by sorption on solid particles, especially illitic clays. The authors reviewed data previously published and present new results which show that cesium sorption on potassium- and calcium-saturated illite is kinetically controlled. Two kinetic models incorporating Freundlich isotherms and an irreversible process are used to describe sorption data spanning a range of cesium concentrations. Although empirical in nature and origin, the models are consistent with mechanistic hypotheses proposed by earlier workers. The models predict that effectively instantaneous and reversible kinetic processes control cesium sorption over time scales of amore » few days and less. Irreversible or apparently irreversible sorption is more significant over longer times. The implications of these findings for radiocesium remobilization in anoxic sediments and transport in the water column are discussed.« less
  • Selectivity coefficients for Pb/sup 2 +/, Cd/sup 2 +/, and Ca/sup 2 +/ exchange adsorption with montmorillonite, illite, and kaolinite clays were determined over a wide range of clay surface concentration and found constant. The average selectivity coefficients describing the ion distributions for montmorillonite, illite, and kaolinite, respectively, were 0.60, 0.44, 0.34 for Pb-Ca exchange, 1.04, 1.01, 0.89 for Cd-Ca exchange, and 0.58, 0.56, 0.31 for Pb-Cd exchange. Whereas Cd/sup 2 +/ may compete more or less on an even basis with Ca/sup 2 +/ for clay adsorption sites, the adsorption of Pb/sup 2 +/ would be favored by amore » factor of 2 or 3 over Ca/sup 2 +/. 21 references.« less
  • This paper investigates the decomposition of three clayey structures (kaolinite, illite and montmorillonite) when thermally treated at 600 {sup o}C and 800 {sup o}C and the effect of this treatment on their pozzolanic activity in cementitious materials. Raw and calcined clay minerals were characterized by the XRF, XRD, {sup 27}Al NMR, DTG and BET techniques. Cement pastes and mortars were produced with a 30% substitution by calcined clay minerals. The pozzolanic activity and the degree of hydration of the clinker component were monitored on pastes using DTG and BSE-IA, respectively. Compressive strength and sorptivity properties were assessed on standard mortars.more » It was shown that kaolinite, due to the amount and location of OH groups in its structure, has a different decomposition process than illite or montmorillonite, which results in an important loss of crystallinity. This explains its enhanced pozzolanic activity compared to other calcined clay-cement blends.« less
  • {sup 133}Cs MAS NMR of Cs-exchanged illite, kaolinite, boehmite, and silica gel is shown to be a powerful tool to investigate the adsorption sites and atomic dynamics of Cs on mineral surfaces. Cesium is adsorbed on these mineral surfaces in primarily two ways: at sites relatively tightly bonded to the surface (Stern layer, Cs1) and at more loosely bonded sites in the diffuse (Gouy) layer (Cs2). For illite, both edge sites and crystallite basal surfaces are important adsorption sites. For kaolinite, edge sites, expandable layers, and probably crystallite basal surfaces are important. The {sup 133}Cs NMR chemical shifts of Cs2more » do not vary systematically with solid composition due to the larger distance sites from the surface and weaker electrostatic attraction to the surface compared to Cs1. Rather, the Cs2 chemical shifts are significantly influenced by relative humidity (R.H.) and Cs population (Cs/H{sub 2}O ratio) on the surface. The Cs1 chemical shifts vary less with these parameters. Cs2 is removed by washing with 1-5 mL of deionized water due to its weak attraction to the surface. The Cs1 chemical shifts become less shielded after washing and with decreasing solution concentration due to a decrease in the Cs surface density. At 100% R.H., Cs in the two sites undergoes motional averaging at frequencies > 100 kHz. With decreasing R.H., peaks for Cs on the two sites are resolved due to decreasing exchange frequencies related to a decreasing number of adsorbed water layers. Motional averaging at 100% R.H. is verified by low temperature experiments with illite. 69 refs., 9 figs., 2 tabs.« less