紫外/亚硫酸盐高级还原工艺加速降解水中难降解含碘造影剂

紫外/亚硫酸盐（UV/SO₃^2-）是一种基于紫外活化SO₃^2-离子依靠生成还原性自由基——水合电子降解目标污染物的高级还原工艺.本文研究了UV/SO₃^2-加速降解含碘造影剂泛影酸钠（DTZ）的效能、机制与影响因素以及UV/SO₃^2-降解DTZ的路径.结果表明，UV/SO₃^2-降解DTZ符合一级动力学模型，降解速率快于单独UV和紫外/过氧化氢工艺，且降解速率随SO₃^2-浓度的增加而升高.弱碱性或碱性水质可强化UV/SO₃^2-降解效率，背景有机物对降解DTZ有一定抑制作用.DTZ降解机制包括直接光解和还原性自由基攻击，其中自由基攻击占主要部分.DTZ在UV/SO₃^2-的降解路径包括取代、脱羧基羟基化和酰胺键断裂等.

Accelerated Degradation of Aqueous Recalcitrant Iodinated Contrasting Media Using a UV/SO32- Advanced Reduction Process

Based on the formation of free radical-hydrated electrons by the activation of sulfite (SO₃^2-), the UV/SO₃^2- process is an advanced reduction process that can reduce pollutants. This study investigated the degradation kinetics, mechanism, influencing factors, and degradation pathways of sodium diatrizoate (DTZ), an iodinated contrasting media, during the UV/SO₃^2- process. The degradation kinetics of DTZ were well fitted by the pseudo-first-order model, the degradation rate of which was higher than that of UV only and UV/H₂ O₂. The degradation rate of DTZ during the UV/SO₃^2- process was positively correlated with the initial SO₃^2- concentration. Weakly alkaline and alkaline conditions promoted the degradation of DTZ, while organic matter inhibited degradation during the UV/SO₃^2- process. The degradation mechanism included direct photolysis and free radical attack, whereby free radical attack played a more important role than direct photolysis. Sulfite radicals dominated DTZ degradation efficiency, and hydrated electrons controlled the deiodination efficiency. The degradation pathways of DTZ during the UV/SO₃^2- process included substitution, decarboxylation-hydroxylation, and amide bond cleavage.