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

A new dye sensitization system incorporating Pt(dcbpy)Cl2 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 PtII dye sensitized TiO2 is exposed to visible light in the presence of dissolved O2, and the reaction is accelerated when the solution is purged with O2 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.