Visible-light induced water detoxification catalyzed by PtII dye sensitized titania

A new dye sensitization system incorporating Pt(dcbpy)Cl-2 on Degussa P-25 TiO2 for the photomineralization of aqueous organic pollutants under visible light irradiation is described. The representative wastewater pollutant, 4-chlorophenol (4-CP), is readily oxidized (ultimately to CO2) when the Pt-II dye sensitized TiO2 is exposed to visible light in the presence of dissolved 02, and the reaction is accelerated when the solution is purged with O-2 gas at 1 atm. The sensitizer is regenerated during the photocatalysis; therefore, 4-CP effectively reduces the oxidized form of the surface bound dye. The experimental data are consistent with parallel oxidative decomposition pathways for 4-CP, one which operates using conduction band electrons to produce hydroxyl radicals and another where the oxidized sensitizer irreversibly oxidizes 4-CP.