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Degradation of sodium diatrizoate by thermally activated persulfate oxidation process

摘要：利用热活化过硫酸盐氧化降解水体中的泛影酸钠，主要研究了体系反应温度、氧化剂浓度、溶液初始pH、底物浓度及自然水体组分对降解效果的影响.结果表明，热活化过硫酸盐降解泛影酸钠符合准一级反应动力学模型及遵循阿伦尼乌斯模型，计算得到反应活化能为105.57 kJ·mol^-1.增加过硫酸盐初始浓度或提高反应温度及降低泛影酸钠初始浓度可以增大泛影酸钠的降解速率常数k（k=0.0062×[K₂S₂O₈]₀，R²=0.98，[K₂S₂O₈]₀=2~8 mmol·L^-1；lnk=-12698×1/T+34.91，R²=0.98，T=325~345 K；k=-1.54×[泛影酸钠]₀+0.064，R²=0.98）.泛影酸钠的降解速率常数k受溶液初始pH影响较小.溶液中Cl^-、HCO₃^-和HA的存在均会抑制泛影酸钠的降解.较低的TOC去除率和产物的检测表明，泛影酸钠降解过程中仅发生苯环侧链的破坏.泛影酸钠的降解途径主要有酰胺键断裂、氨基氧化和脱羧基羟基化.

Abstract：Thermally activated persulfate oxidation process was applied to degrade sodium diatrizoate in the aqueous solution. The impact factors, such as temperature, the initial concentrations of K₂S₂O₈ and substrate, the initial solution pH and water matrix were investigated. The results show that diatrizoate degradation by thermally activated persulfate oxidation was fitted well with pseudo-first-order mode and Arrhenius equation. The apparent activation energy for this reaction was estimated as 105.57 kJ·mol^-1. Increasing initial persulfate concentration or temperature and reducing initial substrate concentration significantly increased the apparent rate constant (k) of diatrizoate degradation (k=0.0062×[K₂S₂O₈]₀, R²=0.98,[K₂S₂O₈]₀=2~8 mmol·L^-1; lnk=-12698×1/T+34.91, R²=0.98, T=325~345 K; k=-1.54×[diatrizoate]₀+ 0.064, R²=0.98), while k was less affected by the initial pH of the solution. The presence of Cl^-, HCO₃^- and HA in the solution inhibited the degradation of diatrizoate. The low TOC removal rate and formation of organic by-products indicate that the degradation of diatrizoate was incomplete and only its side chain was destructed. The transformation pathways of diatrizoate in the heat-activated persulfate system mainly included amide bond cleavage, amino oxidation and decarboxylation-hydroxylation.