Photocatalytic degradation of dye sulforhodamine B: a comparative study ofphotocatalysis with photosensitization

The direct photocatalytic degradation of dye pollutant sulforhodamine B (SR B) in aqueous TiO2 dispersions has been examined and compared to the photos ensitization process. The mineralization extent of SRB degradation, the for mation of intermediates and final products were monitored to assess the deg radation pathways caused by direct photocatalysis. In the initial stage of the direct photocatalysis, SRB is mainly oxidized by a positive hole upon b and-gap excitation of TiO2 by UV light (330 nm < lambda < 380 nm) and subse quently undergoes the similar degradation pathways as occur in the photosen sitization under visible irradiation (lambda > 420 nm). Diethylamine, N,N-d iethylacetamide, N-ethylformamide, N,N-diethylformamide, formic acid and ac etic acid were identified as intermediate species; SO42-, NH4+, CO2 and H2O are final mineralized products produced in the direct photocatalytic proce ss.