Effect of electron acceptors on photocatalytic decolorization of organic dyes in water

Color in textile effluents has become a potentially serious environmental problem. Photocatalytic process with TiO2 as photocatalyst has been considered as an effective alternative for removing color from wastewater. In this study, the decoloring efficiency of organic reactive dyes including RB21, RY145, and RR195 with a concentration of 10 mg/L in water was examined. In addition, the effect of the additional use of an electron acceptor such as hydrogen peroxide or peroxodisulfate for promoting decoloring rate and efficiency was investigated. Results showed that the higher the concentration of electron acceptor dosing, the better the decoloring efficiency of dye solutions was. The decoloring efficiency of dye solutions were more than 90% within 1 h of treatment with an addition of 240 mg/L of H2O2 or Na2S2O8, while the decoloring efficiency of RB21, RY145 and RR195 could only reach 52.8%, 26.4%, and 44.7%, respectively for a simply UV/TiO2 film system. This phenomenon could be attributed to the additional use of an electron acceptor for promoting competition for electrons and then avoid recombination of e-/h+ pairs, leading more radicals involved in the decoloring reaction. Moreover, it was found that peroxodisulfate was more effective for promoting decoloring rate than hydrogen peroxide. This was probably due to S2O8(2-) (lambda(max): 230 nm) was also decomposed to *SO4- radicals under UV irradiation in addition to play a role of electron acceptor *SO4- radicals have been shown to be a strong oxidant to oxidize organic pollutants in water. Accordingly, an immobilized TiO2 photocatalytic process along with the aid of an adequate electron acceptor such as peroxodisufate could be a potential alternative for the decolorization of wastewater.