Semiconductor-mediated photocatalytic degradation of an azo dye, chrysoidine Y in aqueous suspensions

The photocatalytic degradation of an azo dye derivative, chrysoidine Y (1), was investigated in aqueous suspensions of titanium dioxide and zinc oxide by monitoring the change in substrate concentration employing UV spectroscopic analysis and decrease in total organic carbon content as a function of irradiation time under a variety of conditions. The degradation of the dye was studied under different conditions such as pH, catalyst concentration, substrate concentration and in the presence of electron acceptors such as hydrogen peroxide (H2O2) and potassium bromate (KBrO3) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with zinc oxide.

TiO2 (Degussa P25) and ZnO can efficiently catalyze the photomineralization of a textile dye derivative 1 in the presence of light and oxygen. The dye was found to degrade more efficiently in the presence of TiO2 as compared to ZnO. The efficiency for the degradation of the dye in the presence of both photocatalysts was found to be dependent on several parameters. The observations of these investigations clearly demonstrate the importance of choosing the optimum degradation parameters to obtain a high degradation rate, which is essential for any practical application of photocatalytic oxidation processes. The investigations were conducted at laboratory scale in order to determine the optimal degradation condition and further studies are required for the practical effluent treatment.