UV/Chlorine process for dye degradation in aqueous solution: Mechanism, affecting factors and toxicity evaluation for textile wastewater

In this study, UV/chlorine was used for the degradation of a food dye (Brilliant Blue FCF, BBF). The effect of pH, chlorine dosage and reaction time was studied on BBF degradation. More than 95 % of BBF was eliminated during 30 min reaction time at optimized conditions of pH = 3 and chlorine dosage = 0.6 mM. The scavenging assay showed that hydroxyl radicals had the highest contribution (66.9 %) while chlorine radicals (17 %) and dichlorine radicals (10.4 %) had minor role in degradation of the dye. Pseudo-first order model was well fitted for UV/chlorine process with the rate constant of 0.088 min(-1). The effect of sulfate, chloride, nitrate and bicarbonate anions were studied in a way that bicarbonate ions showed high inhibitory effect on BBF degradation. The presence of iron and copper enhanced the degradation rate of BBF in UV/chlorine process. The application of solar irradiation instead of UV lamp was also tested. The results exhibited that solar irradiation can be considered for decolorization of BBF especially in the presence of transition metals. Mineralization of different processes were considered, the highest value obtained was around 37 % for UV/chlorine. The UV/chlorine was performed on a real wastewater. UV/chlorine process showed a high efficient process in terms of decolorization while the removal of organic compounds and detoxification (acute toxicity) was relatively poor. Finally, EE/O was calculated for BBF and COD removals from synthetic solution and real wastewater respectively.