[Study on the degradation of AO7 by UV/K2S2O8, system: kinetics and pathways].

The UV photolysis of S2O82-is a novel advanced oxidation technologies (AOTs),which leads to the formation of strong oxidizing radicals,sulfate radicals (SO·4-).The effect of oxidant K2 S2 O8 concentration,the initial pH of solution and various inorganic anions (H2 PO 4-,HCO 3-,NO 3-and Cl-) were investigated using AO7,a kind of azo dye,as a model pollutant.The degradation kinetics of AO7 followed pseudo first-order kinetics and reaction rates related to PMS concentrations.When the initial concentration of AO7 was 0.14 mmol /L,the optimal molar ratio of oxidant K2 S2 O8 to pollutants AO7 was 20.The effect of initial pH had great effect on the AO7 degradation rate during UV /K2 S2 O8 system.Increasing system pH results in the formation of·OH from SO·4-.The effects of four inorganic anions (H2 PO 4-,HCO 3-,NO 3-and Cl-) all had some negative effect on the degradation of AO7.Based on the results of GC /MS,three main intermediates (2-naphthalenol,coumarin and 1,2-benzenedicarboxylic acid) were identified,thus the degradation pathway for SO·4-induced by UV /K2 S2 O8 was proposed accordingly.