Transformation of chlorinated aliphatic compounds by ferruginous smectite.
A series of chlorinated aliphatic compounds (RCI, including carbon tetrachloride (PCM), 1,1,1-trichloroethane (TCA), 1,1,2,2-tetrachloroethane (TeCA), pentachloroethane (PCA), hexachloroethane (HCA), trichloroethene (TCE), tetrachloroethene (PCE), trichloronitromethane (chloropicrin, CP), and trichloroacetonitrile (TCAN)) was reacted with ferruginuous smectite (sample SWa-1 from The Source Clays Repository), SWa, in aqueous suspension under anoxic conditions. Compounds highly polarizable or sharing substituents that facilitate charge delocalization adsorbed faster by reduced (SWa-R) than by unaltered (SWa-U) clay, indicating stronger dipole--dipole interactions between the substituents and the clay surface and/or hydrating water molecules. The reduction of the clay accelerated RCI adsorption up to 100-fold. Incubations with SWa-R promoted RCI reduction (CP, TCAN) or dehydrochlorination (TeCA and PCA). The reduction of structural Fe catalyzes the transformation of RCI via Brønsted and Lewis-basic promoted pathways. This study indicates that oxidation state of the structural Fe in SWa greatly alters surface chemistry and has a large impact on clay-organic interactions.
Cervini-Silva
J
J
Department of Environmental Science, Policy, and Management, University of California, 151 Hilgard Hall #3110, Berkeley, California 94720-3110, USA. jcervini@nature.berkeley.edu
Larson
R A
RA
Wu
J
J
Stucki
J W
JW
D000538:Aluminum Silicates; D000077215:Clay; D005765:Gastrointestinal Agents / Q000737:chemistry*; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D007501:Iron; D010084:Oxidation-Reduction; D017640:Silicates; D012989:Soil Pollutants
D000538:Aluminum Silicates; D005765:Gastrointestinal Agents; D006843:Hydrocarbons, Chlorinated; D017640:Silicates; D012989:Soil Pollutants; C033214:Smectite; D007501:Iron; C100187:chloropicrin; D000077215:Clay