An Investigation into the Chemistry of the UV-Ozone Purification Process

摘要

The synergistic effect of ozone and UV light in the decomposition of organic compounds in water is studied. The nature and quantities of oxidation products by ozonation, UV-ozonation, and hydroxyl radical oxidation were assessed to understand the UV-ozonation mechanism. Nitrobenzene was selected as the primary model compound due to its relative resistance to UV-ozonation. This model compound followed an identical sequence of reactions in both O3 and UV/O3 oxidation via mono-, di-, and trihydroxylation of the benzene ring; the major stable intermediates were oxalic acid, formic acid, and glyocal. The ratios of O-, M-, and p-R-phenols produced by ozonation and UV-ozonation of nitrobenzene and chlorobenzene (a secondary model compound) were almost identical and very different from the isomeric phenol ratios given by Fenton's reagent and H2O2/UV systems. Various mono-, di-, tri-, and tetra-substituted benzene derivatives were studied using the oxidation regimes; the kinetics were determined to be pseudo-first order. A hypothesis was advanced that ozone can act also as a nucleophilic reagent towards benzene derivatives with electron withdrawing substituents. The initial work of the pH study has been completed, namely, the effect of very high and very low pH values on the rates of UV-ozonation and ozonation of selected model compounds.