An investigation of TiO2 photocatalysis for the treatment of water contaminated with metals and organic chemicals

Results are reported from laboratory experiments on the removal of dissolved metals and various organic compounds from water by semiconductor photocatalysis, using UV-illuminated titanium dioxide, with particular reference to the kinetic interactions between reduction and oxidation processes. Only metals with half-reaction standard reduction potentials more positive than 0.3 V (against normal hydrogen electrode) could be removed using titanium dioxide as catalyst. The process was efficient only if both the oxidation and reduction half-reactions occurred rapidly. Photo-efficiencies close to 85 per cent were obtained for conversion of hexavalent chromium to the trivalent form when citric acid was used as reductant, but photo-efficiency was only 4 per cent for oxidation of salicylic acid using oxygen as the oxidant. There are 49 references.