Fenton degradation of tetrachloroethene and hexachloroethane in Fe(II) catalyzed systems

The degradation of tetrachlorothene (PCE) and hexachloroethane (HCA) using Fe(II) and Fe(II)-citrate at different H2O2 concentrations was studied to clarify the role of oxidation and reduction pathways in Fenton chemistry. The interactions between oxidative and reductive radicals, and the cyclic nature of the Fe(II)-Fe(III) ions make for a complex system that displays a suppression or enhancement of PCE or HCA degradation as the experimental conditions are varied. PCE degradation decreased, while HCA degradation increased, for larger H2O2 concentration. The degradations of PCE and HCA were lower in vials where they were individually present compared to vials with the PCE-HCA mixture. Using Fe(II)-citrate instead of Fe(II) resulted in slower PCE and insignificant HCA degradation. These observations indicate that degradation efficiency losses arise from interactions between the oxidant and reductant radical moieties, and that the production of reduction radicals is only significant when the hydroxyl radical (OH center dot) production is rapid. (C) 2010 Elsevier B.V. All rights reserved.