UV/K_2S_2O_8降解偶氮染料AO7的研究:动力学及反应途径

Study on the Degradation of AO7 by UV /K_2S_2O_8 System:Kinetics and Pathways

紫外光分解过硫酸盐(S2O28-)是一种新型的高级氧化技术,可以产生强氧化性的硫酸根自由基(SO·4-).以偶氮染料AO7为目标污染物,重点研究了反应体系氧化剂K2S2O8浓度、溶液初始pH值和无机阴离子(H2PO4-、HCO3-、NO3-和Cl-)对反应体系的影响.结果表明,AO7的降解遵循准一级动力学,当AO7初始浓度为0.14mmol/L时,最佳的氧化剂K2S2O8与污染物AO7的摩尔比为20.pH值对UV/K2S2O8体系降解AO7的反应速率影响较大,增大pH有利于SO·4-转化为·OH.溶液中的无机离子对反应体系有一定的抑制作用.采用GC/MS分析了UV/K2S2O8体系降解AO7的主要中间产物(萘酚、1,2-苯并吡喃酮、邻苯二甲酸),并根据中间产物的分析推测了降解途径.

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.