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

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

紫外/亚硫酸盐(UV/SO_(3)^(2)-)是一种基于紫外活化SO_(3)^(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/SO_(3)^(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/SO_(3)^(2)-降解DTZ的路径.结果表明,UV/SO_(3)^(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SO_(3)^(2)-浓度的增加而升高.弱碱性或碱性水质可强化UV/SO_(3)^(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/SO_(3)^(2)-的降解路径包括取代、脱羧基羟基化和酰胺键断裂等.

Based on the formation of free radical-hydrated electrons by the activation of sulfite (SO_(3)^(2)-),the UV/SO_(3)^(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/SO_(3)^(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/H2O2.The degradation rate of DTZ during the UV/SO_(3)^(2)-process was positively correlated with the initial SO_(3)^(2)-concentration.Weakly alkaline and alkaline conditions promoted the degradation of DTZ,while organic matter inhibited degradation during the UV/SO_(3)^(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/SO_(3)^(2)-process included substitution,decarboxylation-hydroxylation,and amide bond cleavage.