[Influencing Factors and Transformation Mechanism of Venlafaxine Degradation by UV]

As a member of antidepressants, venlafaxine degradation by UV was investigated in this study. The influence of initial concentration of venlafaxine, pH 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 pH 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).