Removal of methamphetamine by UV-activated persulfate: Kinetics and mechanisms

Abstract In this study, removal of methamphetamine (METH) was investigated by UV activated persulfate (PS), and the influence of key factors was evaluated. Results suggested that METH degradation followed pseudo-first order reaction kinetics. The combination of UV and persulfate (UV/PS) could completely degrade 100 μg/L of METH in 30 min with a PS dosage of 200 μM at pH 7. Both hydroxyl radical ( OH) and sulfate radical (SO 4 − ) were confirmed to contribute to the degradation of METH. The bimolecular reaction rate constants of METH with OH and SO 4 − were 7.91 × 10 9 and 3.29 × 10 9 M − 1 s −1 , respectively. The degradation rate constant of METH was proportional to the PS dosage (0–800 μM) and was high at neutral pH condition. The presence of inorganic anions significantly reduced METH degradation to different degrees, with the inhibitory effect order of Cl − > NO 3 − > HCO 3 − . The degradation efficiency of METH was suppressed by the presence of humic acid due to the effect of UV absorption and free radical quenching. The degradation intermediates and products were identified by UPLC-MS/MS and possible transformation pathways were proposed. Results suggested that the combination of UV/PS is a promising treatment technique for the removal of METH in the water environment.