A Kinetic Model of the Hydrogen Peroxide/UV Process for the Treatment of Hazardous Waste Chemicals

Abstract

The effectiveness of the H2O2/UV process has been investigated using trichloroethylene (TCE), tetrachloroethylene (PCE), benzene, and toluene as model compounds. The UV source used in this study was the low pressure mercury vapor lamp using mainly 254 nm of radiation. For irradiation of aromatic compounds such as benzene and toluene at high concentration, by-products formed by the irradiation process were found to reduce the oxidation rate; these by-products also acted as UV absorbers in competition with the parent compounds. A kinetic model for the rate of direct photolysis of organics has been developed illustrating a method of measuring quantum yields of photolysis in the presence of by-products. It was also found that the addition of peroxide enhanced the oxidation rate. The enhancement rate of TCE was greater than that of benzene even though kbenzene,OH is greater than kTCE,OH. The overall rate of the H2O2/UV system was found to depend on the relative importance of the OH radical pathway, the direct photolysis reaction rate, and the absorptivity of by-products at 254 nm.