H2O2/VisUV process for photo-oxidation of waterborne hazardous substances — C1---C6 chlorinated hydrocarbons

This paper presents results from the first phase development of the H2O2/VisUV process for photo-oxidation of waterborne hazardous substances. The technology is generally applicable to numerous situations requiring removal of hazardous substances from: (a) groundwater; (b) drinking water; (c) chemical process water; (d) leakage contamination; and (e) wastewater. However, the first phase research focused attention on drinking water contaminants. The compounds investigated, C1---C6, were: tetrachloromethane, tetrachloroethene, dichloroethane, dichloroethene, trichloroethane, trichloroethene and benzene. Dark (no VisUV) oxidation rates and photo-oxidation rates were determined; the latter rate constants were 104–105 greater than dark reaction values. The VisUV photons produce oxidizing free radicals from H2O2 and H2O, and excited state species or free radicals from the reactant compound. The experimental work was conducted in a photochemical batch stirred tank reactor, with 100 W and 450 W mercury vapor lamps, covering the VisUV range, 578.0-222.4 nm. A mathematical model was used to analyze the results and obtain the rate constants. Also, the rate constants were successfully correlated by a molecular composition structure (MCS) model, which permits estimation of rate constants for other C1---C6 chlorinated hydrocarbon compounds.