Photo-oxidation of organic material in aqueous suspensions of titanium dioxide

Twenty-one organic compounds, known to be possible contaminants of water, have been treated with u.v.-illuminated titanium dioxide powder in aqueous suspension. In each case the organic material was converted to carbon dioxide. The rate of carbon dioxide formation did not vary greatly from one compound to another; even nitrobenzene was converted at 40% of the maximum rate observed with 2,4 dichlorophenol. Chlorobenzene, benzoic acid and 4-chlorophenol were selected for more detailed studies of the effect of solute concentration, pH and products other than CO2. Results were compared using illumination by a 100 W medium pressure mercury lamp, an 0.25 m2 parabolic trough solar collector and by solar illumination of a flat bed. The CO2 production rate from 300 ml of 10−3 M 4-chlorophenol in contact with 0.15 g TiO2 solar illuminated with the 0.25 m2 collector was 20 μM min−1 which corresponds to the oxidizing radicals generated in water by a 60Co gamma ray dose rate of not less than 8.3 krad min−1. The possible use of solar-illuminated TiO2 for the disinfection of water is suggested.

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