Visible light induced photodegradation of organic pollutants on dye adsorbed TiO2 surface

Visible light assisted degradation of aromatics, viz phenol, chlorophenol, 1,2-dichloroethane, trichloroethylene and surfactants, viz cetyl pyridinium chloride (CPC; cationic), sodium dodecylbenzene sulfonate (DBS; anionic) and neutral Triton-X 100 in air-equilibrated aqueous mixtures has been achieved on the surface of TiO2 semiconductor modified with methylene blue (MB) and rhodamine B (RB). Under 5 h of irradiation with a 150 W xenon lamp, over 40-75% degradation of pollutants has been observed. The failure of pollutants to degrade on non-conducting Al2O3 surface essentially suggests the role of semiconducting TiO2 photocatalyst in the photochemical process. A working mechanism involving excitation of surface adsorbed dye, followed by charge injection into the TiO2 conduction band and formation of reactive .O-2(-) /.HO2 radicals is proposed for the degradation of organics to carbon dioxide. (C) 2002 Elsevier Science B.V All rights reserved.