UV降解水溶液中文拉法辛的影响因素及机制

Influencing Factors and Transformation Mechanism of Venlafaxine Degradation by UV

采用UV工艺处理水体中的抗抑郁药物文拉法辛,分别考察了初始浓度、pH值、水质等因素对文拉法辛降解的影响.结果表明,文拉法辛的降解过程符合伪一级动力学模型,其降解速率常数随着药物浓度的降低而增加. pH为10时,文拉法辛降解速率最快.其降解过程包括直接光解、·OH和~1O_2参与的自敏化反应,其中直接光解贡献较大.水体中常见无机阴离子Br^-、Cl^-、NO_3^-和NO_2^-均抑制文拉法辛降解,其中NO_2^-的抑制作用最强.天然有机物腐殖酸和富里酸也会影响文拉法辛的降解.相比超纯水,文拉法辛在二级出水中的降解速率明显降低.经超高效液相色谱质谱联用仪(UPLC-MS/MS)对文拉法辛降解产物的全扫描分析,推测出5种主要的转化途径:①芳香环的顺序羟基化;②去甲基化;③去胺基化;④环己烷的断链;⑤小分子有机酸的转化.此外,文拉法辛中87%的N元素转化成无机离子(NH_4^+和NO_3^-).

As a member of antidepressants,venlafaxine degradation by UV was investigated in this study.The influence of initial concentration of venlafaxine,p H value,and water quality on venlafaxine removal were studied.The results showed that venlafaxine degradation fitted the pseudo-first-order kinetics model.The reaction rate increased with the decrease of venlafaxine concentration.It was found that the highest removal rate of venlafaxine occurred at p H 10.The degradation of venlafaxine involves direct photolysis and self-sensitized photolysis caused by hydroxyl radical(·OH)and singlet oxygen(1O2).Moreover,the direct photolysis played a dominant role in the venlafaxine removal.Water matrix also affected venlafaxine degradation.The results indicated that the degradation rate of venlafaxine in the secondary effluent was lower than that in the ultrapure water.Inorganic anions(Br-,Cl-,NO3-,and NO2-)impacted venlafaxine removal,and the inhibition of NO2-was stronger than others’.Both humic acid and fulvic acid also inhibited venlafaxine decomposition.UPLC-MS/MS was used to perform full scan to identify intermediates of venlafaxine degradation.Five degradation pathways were proposed:①demethylation;②deamination;③sequential hydroxylation of aromatic rings;④ring opening of cyclohexane;⑤low-molecular-weight acid transformation.In addition,87%of the N element in the molecules were transformed into inorganic ions(ammonium ions and nitrate ions).