TY - JOUR
T1 - Molecular dynamics simulations of cesium adsorption on illite nanoparticles
AU - Lammers, Laura N.
AU - Bourg, Ian Charles
AU - Okumura, Masahiko
AU - Kolluri, Kedarnath
AU - Sposito, Garrison
AU - Machida, Masahiko
N1 - Funding Information:
The authors gratefully acknowledge support for this research from the Japan Atomic Energy Agency (JAEA)- LBNL Collaboration on Repository Geoscience and PA Technology Development. IB was partly supported by the Office of Science, Office of Basic Energy Sciences of the US Department of Energy under Contract DE-AC02-05CH11231 . The MD and TI simulations reported in this paper were carried out using resources of the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the US Department of Energy under Contract DE-AC02-05CH11231 . The DFT simulations were carried out using the SGI ICE X supercomputer at the Japan Atomic Energy Agency. GS was supported by funds allocated through his appointment as Chancellor’s Professor, Emeritus, University of California, Berkeley.
Publisher Copyright:
© 2016 Elsevier Inc.
PY - 2017/3/15
Y1 - 2017/3/15
N2 - The charged surfaces of micaceous minerals, especially illite, regulate the mobility of the major radioisotopes of Cs (134Cs, 135Cs, 137Cs) in the geosphere. Despite the long history of Cs adsorption studies, the nature of the illite surface sites remains incompletely understood. To address this problem, we present atomistic simulations of Cs competition with Na for three candidate illite adsorption sites – edge, basal plane, and interlayer. Our simulation results are broadly consistent with affinities and selectivities that have been inferred from surface complexation models. Cation exchange on the basal planes is thermodynamically ideal, but exchange on edge surfaces and within interlayers shows complex, thermodynamically non-ideal behavior. The basal planes are weakly Cs-selective, while edges and interlayers have much higher affinity for Cs. The dynamics of Na[sbnd]Cs exchange are rapid for both cations on the basal planes, but considerably slower for Cs localized on edge surfaces. In addition to new insights into Cs adsorption and exchange with Na on illite, we report the development of a methodology capable of simulating fully-flexible clay mineral nanoparticles with stable edge surfaces using a well-tested interatomic potential model.
AB - The charged surfaces of micaceous minerals, especially illite, regulate the mobility of the major radioisotopes of Cs (134Cs, 135Cs, 137Cs) in the geosphere. Despite the long history of Cs adsorption studies, the nature of the illite surface sites remains incompletely understood. To address this problem, we present atomistic simulations of Cs competition with Na for three candidate illite adsorption sites – edge, basal plane, and interlayer. Our simulation results are broadly consistent with affinities and selectivities that have been inferred from surface complexation models. Cation exchange on the basal planes is thermodynamically ideal, but exchange on edge surfaces and within interlayers shows complex, thermodynamically non-ideal behavior. The basal planes are weakly Cs-selective, while edges and interlayers have much higher affinity for Cs. The dynamics of Na[sbnd]Cs exchange are rapid for both cations on the basal planes, but considerably slower for Cs localized on edge surfaces. In addition to new insights into Cs adsorption and exchange with Na on illite, we report the development of a methodology capable of simulating fully-flexible clay mineral nanoparticles with stable edge surfaces using a well-tested interatomic potential model.
KW - Geochemistry
KW - Molecular dynamics simulations
KW - Radiocesium
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U2 - 10.1016/j.jcis.2016.11.084
DO - 10.1016/j.jcis.2016.11.084
M3 - Article
C2 - 27930922
AN - SCOPUS:85001022738
SN - 0021-9797
VL - 490
SP - 608
EP - 620
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
ER -