Adsorption Kinetics of Pentachloroethane by Iron-Bearing Smectites

Javiera Cervini-Silva, Jun Wu, Joseph W. Stucki and Richard A. Larson
Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois 61801 USA
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Abstract: The oxidation state of structural Fe greatly alters surface chemistry, which may have a large influence on clay-organic interactions. The effect of structural-iron oxidation state on chlorinated hydrocarbons at the clay-water interface was examined. Pentachloroethane (5CA) was reacted with oxidized, reduced, and reoxidized forms of three different smectites: montmorillonite, ferruginous smectite, and nontronite in aqueous suspension under controlled-atmosphere conditions. Pentachloroethane was found to adsorb at different rates for the three smectites. A series of 5CA-adsorption rate constants in the presence of these clays showed a strong correlation with the Fe(II) content of the clay (r2 = 0.98). The clay surface behaves as a Brønsted base and promotes 5CA dehydrochlorination. The adsorption kinetics at the clay-water interface were described by the formation of a precursor complex prior to 5CA dehydrochlorination.

Key Words: CMS Clay SWa-1 • CMS Clay NG-1 • Dehydrochlorination • Iron(II) • Iron(III) • Montmorillonite • Nontronite • Oxidation • Pentachloroethane • Reduction Reactions • Tetrachloroethene

Clays and Clay Minerals; February 2000 v. 48; no. 1; p. 132-138; DOI: 10.1346/CCMN.2000.0480116
© 2000, The Clay Minerals Society
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