Photocatalytic degradation of phthalic acid on TiO2 nanoparticles Original Research Article

The photocatalytic oxidation of phthalic acid was studied in aerated sols of TiO2 nanoparticles under monochromatic irradiation at pH=4.25. We report initial quantum efficiencies for phthalate degradation, ΦPHT0, as a function of phthalate concentration and quantitative yields of the primary products. Formation rates of the hydroxyl radical adduct (DMPO-OH) from the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were determined at various initial concentrations of phthalate. Kinetic analysis of the spin-trapping experiments indicates that phthalate is oxidized by a dual hole-radical mechanism. The effect of added phosphate on phthalate photocatalytic degradation is examined in detail. Dark-adsorption of phthalate on TiO2 particles is significantly inhibited by the presence of phosphate, however, ΦPHT0 is almost independent of phosphate concentration.