Transformation of chlorinated aliphatic compounds by ferruginous smectite

A series of chlorinated aliphatic compounds (RCl, including carbon tetrachl oride (PCM), 1,1,1 -trichloroethane (TCA), 1,1,2,2-tetrachloroethane (TeCA) , pentachloroethane (PCA), hexachloroethane (HCA), trichloroethene (TCE), t etrachloroethene (PCE), trichloronitromethane (chloropicrin, CP), and trich loroacetonitrile (TCAN)) was reacted with ferruginuous smectite (sample SWa -1 from The Source Clays Repository), SWa, in aqueous suspension under anox ic conditions. Compounds highly polarizable or sharing substituents that fa cilitate charge delocalization adsorbed faster by reduced (SWa-R) than by u naltered (SWa-U) clay, indicating stronger dipole-dipole interactions betwe en the substituents and the clay surface and/or hydrating water molecules. The reduction of the clay accelerated RCl adsorption up to 100-fold. Incuba tions with SWa-R promoted RCl reduction (CP, TCAN) or dehydrochlorination ( TeCA and PCA). The reduction of structural Fe catalyzes the transformation of RCl via Bronsted grid Lewis-basic promoted pathways. This study indicate s that oxidation state of the structural Fe in SWa greatly alters surface c hemistry and has a large impact on clay-organic interactions.