Abstract

In this study, we investigate the generation of hydroxyl radicals mediated by a composite containing TiO₂ and 1.6% m/m of zinc phthalocyanine (TiO₂/ZnPc) in aqueous suspensions containing methanol as oxidisable substrate. The composite features a specific surface 20% less than the value estimated for TiO₂ P25, probably due to the covering of the surface of the oxide by ZnPc and the pH of the isoelectric point of this composite equal of 5.5, about two units of pH lower than the value estimated for TiO₂ P25, are probably related to the difference in photocatalytic activity found for these materials. To assess the influence of different spectral bands of electromagnetic radiation on the production of hydroxyl radicals, we used different sources of radiation in experiments conducted to estimate the quantum efficiency of hydroxyl radical formation (HO•), via photocatalytic oxidation of methanol. The association between zinc phthalocyanine and TiO₂ has allowed the formation of a light absorber material with absorption spectral range extended to the visible region. Our results suggest that, despite the higher values of F_HO• for TiO₂ P25, the combination of visible and ultraviolet radiation furnished by a high pressure mercury lamp without the protective bulb, or solar radiation, causes the composite to present good values for the same parameter.

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