Development of a More Efficient Transition Metal-based Chemical Oxidant Than the Fenton's Reagent for the Degradation of Chloroaromatics in Water

The Fenton's Reagent (Fe(II)/H2O2) and the Fenton-like Advanced Oxidation Technologies (Fe(III)/H2O2, Fe(II)/H2O2/UV, Fe(III)/H2O2/UV) have been widely applied for the treatment of industrial wastewater and drinking water polluted with recalcitrant organic compounds such as chlorinated phenols, BTEX (benzene, toluene, ethyl benzene, xylene) and dyes. Nevertheless, Fenton's Reagent still faces several and important limitations. The major constraints lie upon its limited efficiency in a narrow range of pH values (2-6) and its requirement for large amounts of iron (stoichiometric, with respect to hydrogen peroxide). The latter suggests that iron is not acting as a catalyst of the system. Motivated by the need to overcome those limitations, this study introduces an alternative transition metal-catalyzed oxidizing system that demonstrates higher efficiencies than the Fenton's Reagent at all the conditions tested for the degradation of a model chloroaromatic contaminant such as 2,4-dichlorophenol (2,4-DCP). The proposed new oxidant system includes the use of peroxymonosulfate (HSO5-, PMS), instead of H2O2, as the oxidant that provides the radicals that are needed for the destruction of the organic contaminants. Cobalt(II) plays the role of the catalyst that respectively iron(II) plays in the Fenton's Reagent.