Cu^2+强化UV活化过氧乙酸降解水中的双氯芬酸

Degradation of diclofenac in water by Cu^2+enhanced UV activation of peracetic acid

研究了Cu^2+强化UV活化过氧乙酸(Cu^2+/UV/PAA)对水中双氯芬酸(DCF)的降解,考察了pH值、PAA投加量、Cu^2+投加量、无机阴离子(Cl^-、SO4^2-、NO3^-和CO3^2-)和溶解有机物(DOM)对DCF去除的影响;探讨了DCF在该体系中的降解产物和转化机理.结果表明:UV和Cu^2+都能活化PAA产生活性自由基促进DCF降解.DCF在Cu^2+/UV/PAA中的降解遵循准一级动力学,其降解可能归因于直接光解、HO·氧化和CH3COO·、CH3COOO·等其它自由基氧化.在pH=3~11范围内,DCF降解的最佳pH=8.5.DCF的降解效率随着PAA投加量的增大而逐渐增高,过量的PAA能与DCF竞争HO·.Cu^2+用量的提高也能促进DCF的去除,但是过量的Cu^2+可生成Cu(OH)2导致其催化能力下降.由于NO3-在UV照射下可以产生HO·,其对DCF降解有促进作用,且NO3-浓度越高,促进作用越明显.不同浓度的Cl^-、SO4^2-、CO3^2-和DOM对DCF降解影响较小.在Cu^2+/UV/PAA降解DCF的过程中,共检测出13种降解产物.根据这些降解产物,提出了DCF可能的转化机理,包括8种不同的反应路径.

The degradation of diclofenac(DCF)by Cu^2+enhanced UV activation of peracetic acid(Cu^2+/UV/PAA)was investigated.The effects of pH,PAA dose,Cu^2+dose,inorganic anions(such as Cl^-,SO4^2-,NO3^-and CO3^2-)and dissolved organic matter(DOM)on DCF removal by Cu^2+/UV/PAA were also evaluated.The degradation products and transformation mechanism of DCF by Cu^2+/UV/PAA were studied.Both UV and Cu^2+could activate PAA to produce active radicals,which could promote DCF removal.The degradation of DCF by Cu^2+/UV/PAA followed the pseudo first-order kinetics and its degradation was probably attributed to direct photolysis,HO·oxidation and other radicals oxidation such as CH3COO·and CH3COOO·.In the pH range of 3-11,DCF had the best degradation efficiency at pH 8.5.When PAA dose increased,the degradation efficiency of DCF was enhanced gradually,but excessive PAA could compete with DCF for HO·.The increase of Cu^2+dose could also promote DCF removal,while excessive Cu^2+could form Cu(OH)2,which might lead to the reduction of its catalytic ability.Since NO3^-can generate HO·under UV irradiation,its existence promoted the degradation of DCF,and the enhancement effect increased with the increase in its concentration.The presence of Cl^-,SO4^2-,CO3^2-and DOM in different concentrations had little effect on DCF removal.Thirteen degradation products were detected in the degradation of DCF by Cu^2+/UV/PAA.According to these degradation products,the probable transformation mechanism of DCF was proposed exhibiting eight reaction pathways.