Photocatalytic degradation of DNOC in aqueous TiO2 dispersions: Investigation of the initial reaction steps

The photocatalytic transformation of the pesticide 4,6-dinitro-o-cresol (DNOC) over irradiated TiO2 suspensions was investigated in aerated aqueous solutions. Complete and relatively fast substrate degradation was achieved after irradiation with simulated solar light, being the reaction rate dependent on the initial pH. The slower evolution of the mineralization process, which can be accomplished after longer irradiation times, was evidenced by monitoring the dissolved organic carbon decrease and the formation of nitrogen inorganic products. he analysis of the reaction end-products and the HPLC–MS characterization of the organic intermediates are consistent with a reaction mechanism where the hydroxylation of the aromatic ring and the oxidation of the methyl group can play a major role as initial reaction steps and occur at comparable rates. The direct reduction of nitro groups at the semiconductor surface to form ammonium ion, inferred from the MS analysis of minor aromatic intermediates, appears to be another viable reaction path. arly quantitative mineralization of the pesticide has been observed after long term (3 h) irradiation, time after which no aromatic products were detected.