Influence of metallic species on TiO2 for the photocatalytic degradation of dyes and dye intermediates

The present work is focused on the influence of metal salts on the photocatalytic efficiency of TiO2 for the elimination of two azo dyes: acid orange-7 (AO-7), tartrazine and a dye intermediate: 3-nitrobenzenesulfonic acid (3-NBSA). A beneficial effect of the presence of metallic species was observed only with samples containing silver. In contrast when compared with Ag+, Cu2+ and specifically VO3- showed an inhibiting effect on the kinetics of degradation for the three substrates studied. No significant decrease in the initial concentration of the substrates was observed for direct phototransformation in sunlight during the same time. (C) 2003 Elsevier Science B.V. All rights reserved.