紫外高级还原技术还原降解水中N-亚硝基二甲胺

Reductive Degradation of N⁃Nitrosodimethylamine in Water by Ultraviolet Advanced Reduction Processes

采用2种高级还原技术(UV/Na_(2)SO_(3)和UV/Na_(2)S_(2)O_(4))还原降解N-亚硝基二甲胺(NDMA),考察pH值、光照强度、还原剂质量浓度和溶解氧等因素对NDMA还原降解效果的影响,计算还原降解反应过程中的表观反应动力学常数,推断NDMA的还原降解机理。研究结果表明,弱酸性条件下有利于2种高级还原技术对NDMA的还原降解。增加光照强度会显著促进高级还原技术对NDMA的还原降解效果,而增加还原剂质量浓度对NDMA去除效果的影响较小。当pH=6.76,光照强度为8.7×10^(-11) E/s,Na_(2)SO_(3)质量浓度为10 mg/L时,经过60 min的反应后,NDMA去除率达到了94.4%。溶解氧会与还原性自由基发生反应,从而抑制了高级还原技术对NDMA的还原降解效果。高级还原技术与NDMA的还原降解反应主要存在3种可能的反应途径:光致水解、光致消去和光氧化。

Two ultraviolet advanced reduction processes(UV/Na_(2)SO_(3) and UV/Na_(2)S_(2)O_(4))were used to reductively degrade N-nitrosodimethylamine(NDMA)in water and the effects of pH,light intensity,reductant dosage and dissolved oxygen on the removal efficiency of NDMA were investigated in this study.Moreover,the apparent kinetic constants under different reaction conditions were calculated and the reductive degradation mechanisms of NDMA by advanced reduction processes were inferred.The results show that the weak acid condition is favorable for the reductive degradation of NDMA by both UV/Na_(2)SO_(3) and UV/Na_(2)S_(2)O_(4) advanced reduction processes.Increasing the light intensity can significantly promote the reductive degradation of NDMA by both advanced reduction processes,while increasing the reductant dosage has little influence on the reductive degradation of NDMA.The removal efficiency of NDMA reaches 94.4%after 60 minutes of reaction when the light intensity is 8.7×10^(-11) E/s,pH=6.76,and the Na_(2)SO_(3) dosage is 10 mg/L.Dissolved oxygen can react with free reducing radicals,thus inhibit the reductive degradation of NDMA by advanced reduction processes.There are three possible reaction pathways for the reductive degradation of NDMA by advanced reduction processes:photohydrolysis,photolimination and photooxidation.