紫外增强NaOCl氧化泛影酸钠的效果及产物毒性变化

UV-enhanced NaOCl oxidizing sodium diatrizoate and the variation for its intermidates toxicity

研究紫外(UV)增强NaOCl氧化泛影酸钠(Sodium Diatrizoate,DTZ)的效果,考察了NaOCl浓度和初始溶液pH对该过程的影响,分析主要活性物种及其贡献,并探讨DTZ的氧化路径和氧化产物毒性的变化.结果表明,UV/NaOCl能够显著提高DTZ的氧化效果,初始pH=6.5,40 min,DTZ的降解率达到100%.氧化过程遵循准一级反应动力学,k为4.999×10^(-2) min^(-1),分别是NaOCl氧化(k=7.517×10^(-3)min^(-1))和UV(k=1.451×10^(-2) min^(-1))的6.65倍和3.45倍.自由基抑制实验表明,与HO·和Cl·相比,二级氯自由基ClO·和Cl_(2)^(-)·是UV/NaOCl氧化DTZ的主要活性物种.NaOCl浓度在50~150μmol·L^(-1)范围升高,DTZ的降解率增加;初始pH对DTZ降解的影响较为显著,pH=6.50降解效果最好,ClO·和Cl_(2)^(-)·的贡献率最高(50.37%).采用液相色谱串联二级质谱(HPLC/MS/MS)共检测出6种产物,UV/NaOCl氧化DTZ的路径包括脱碘、脱羧、亲电反应和分子内环化.IO_(3)-的生成量随DTZ降解率升高而增加.基因毒理组学表明,DTZ的毒性随反应进行逐渐降低.本研究表明UV/NaOCl是一种有效、安全去除水中含碘有机污染物的方法.

Enhancement of ultraviolet irradiation on chlorinating sodium diatrizoate(DTZ)was studied.The effects of experimental parameters,NaOCl concentration and initial pH on DTZ degradion in UV/NaOCl system were investigated.In addition,the main reactive species and their respective contribution to DTZ oxidation in UV/NaOCl system were analyzed.DTZ degradation pathways and the toxicity change of intermediates were discussed.The results showed that compared with single UV and NaOCl system,the combined UV/NaOCl system improved DTZ oxidation effectively,with complete degradation of DTZ in 40 min at initial pH 6.5.The oxidation process followed the pseudo-first-order reaction kinetics with the rate constant k of 4.999×10^(-2) min^(-1),which was 6.65 and 3.45 times higher than those of single NaOCl(k=7.517×10^(-3) min^(-1))and UV radiation(k=1.451×10^(-2) min^(-1))processes,respectively.The radical inhibition results revealed that the secondary chlorine radicals,such as ClO·and Cl_(2)^(-)·were the major contributors to DTZ oxidation in UV/NaOCl system.DTZ removal rate increased with NaOCl concentration in range of 50~150μmol·L^(-1).Initial pH of solution affected DTZ removal obviously.Under the optimum pH 6.5,the total contribution of ClO·and Cl_(2)^(-)·reached the highest value of 50.37%.Six intermediates were detected by HPLC/MS/MS analysis,and DTZ oxidization was through deiodination,decarboxylation,electrophilic reaction,and intramolecular cyclization pathways.Moreover,the production of iodate ion increased with DTZ removal amount.Meanwhile,the genotoxicomic results showed that after oxidation,DTZ toxicity declined gradually.Finally,this study may suggest that the UV/NaOCl system can be used to eliminate iodine-containing micropollutants in water effectively and safely.