Dye-effect in TiO_2 catalyzed contaminant photo-degradation: Sensitization vs. charge-transfer formalism

摘要

Anatase TiO_2 surfaces have been treated with 2,4,6-triphenylpyrilium hydrogen sulfate (TPPHS) dye to yield the modified TiO_2/TPPKS surface. The modified TiO_2/TPPHS surface was then supported onto activated carbon (AC) surfaces to yield a new class of catalytic system AC/TiO_2/TPPHS. The catalytic activities of naked TiO_2, TPPHS solution, TiO_2/TPPHS and AC/TiO_2/TPPHS systems were examined in photo-degradation of phenol and benzoic acid in water, using both UV and visible regions. All studied systems showed low catalytic activiy when used in the visible region. In UV, the AC/TiC_2/TPPHS showed highest activity, whereas the naked TiO_2 and TPPHS solutions were the least active systems. The dye role, in enhancing activity of modified surfaces in UV degradation of contaminants, is understandable by a charge-transfer catalytic effect rather than a sensitizing effect. AC role is explainable by its ability to adsorb contaminant molecules and bringing them closer to catalytic sites.