EFFECTS OF CONCENTRATION AND UV RADIATION WAVELENGHTS ON PHOTOLYTIC AND PHOTOCATALYTIC DEGRADATION OF AZO DYES AQUEOUS SOLUTIONS BY SOL-GEL TiO2 FILMS

摘要

The photocatalytic and photolytic degradation of anionic azo dyes Methyl Orange and Congo Red dye aqueous solutions was investigated in glass reactors with/without TiO2 films that were irradiated with UV light. Two nanostructured sol-gel TiO2 films were prepared by means of the dip-coating technique with and without of polyethylene glycol (PEG) as a structure-directing agent. Experiments were carried out by varying the concentration of dyes, TiO2 films and sources of UV radiation. The concentrations of dyes were 0.0125 mmol L-1, 0.025 mmol L-1 and 0.05 mmol L-1; the wavelengths of the incident ultraviolet light were predominantly 254 (UV-C) and 365 nm (UV-A). In the presence of TiO2 film UV-C radiation showed higher degradation efficiency for both dyes than UV-A radiation. Also, UV-C radiation without TiO2 photocatalyst was capable of degrading both dyes, while UV-A radiation alone did not show a potential for dyes degradation. Higher photoactivity showed TiO2 film with addition of PEG.