UV-enhanced Fe2+/PDS system for degradation of acid orange 7: Kinetics, degradation mechanism and toxicity assessment
Yingzi Lin, Mengshi Wang, Junjie Chen, Siwen Li, Yuanyuan Zhang, Liangliang Wei, Ningning Sun, Chengyu Liu, Junjie Zhao
Abstract
Based on the deficiency of the Fe 2+ catalyzed persulfate (PDS) process, ultraviolet (UV) synergistic Fe 2+ activated PDS system was introduced in this study for the degradation of acid orange 7 (AO7) dye. The effects of different initial pH, PDS dosage, Fe 2+ dosage, and different UV intensities on the degradation rate of AO7 were investigated, and a kinetic model for the apparent reaction rate was determined. The results showed that the UV/Fe 2+ /PDS system was effective in degrading AO7 in a wide pH range. Under optimal conditions, 96 % removal of AO7 was achieved in 10 min. The effects of different inorganic anions on AO7 were discussed; Cl − had little effect on the degradation effect, and SO 4 2− , NO 3 − and HCO 3 − inhibited the degradation of AO7 by the system to varying degrees. The presence of reactive radicals (SO 4 ·− and·OH) in the reaction was determined by quenching experiments and EPR capture and their degradation contribution was further investigated. Nine intermediates of AO7 were detected by LC-MS/MS, and the degradation pathway of AO7 was inferred by combining with UV-Vis spectra. Finally, the ecotoxicity and tritogenic effects of AO7 intermediates were assessed by Toxtree and T.E.S.T toxicity prediction models, which showed that the final degradation product toxicity was non-mutagenic, non-teratogenic, and devoid of hereditary and non-hereditary carcinogenicity.