Dye degradation in aqueous solution by dithionite/UV-C advanced reduction process (ARP): Kinetic study, dechlorination, degradation pathway and mechanism

Abstract

In this study, the first attempt was carried out for the degradation of dye by an advanced reduction process (ARP). UV/dithionite process was used to explore the degradation of acid yellow 17 (AY17). The effects of operational parameters were investigated on AY17 removal. More than 90 % of AY17 was eliminated at only 5 min reaction time under conditions of 1.5 mM dithionite and pH = 9.0. The results of scavenging experiments confirmed that the hydrated electron (e−aq) was the dominant agent for the degradation of AY17. Although decolorization was fast by the UV/dithionite process, mineralization was not effective enough. Several intermediates were identified by LC/MS based on which the degradation pathways were proposed for AY17 for the first time. Electrical energy consumption was also considered which was significantly decreased with increase of dithionite concentration. Quantum yield was calculated for UV and UV/dithionite processes. Using dithionite, the quantum yield was increased by 75 times as compared to the UV process. This study showed that ARPs can be effective for the degradation of pollutants with large molecular structures. However, low mineralization of organic pollutants is still a limitation for the application of ARPs.