UV-Fenton degradation of diclofenac, sulpiride, sulfamethoxazole and sulfisomidine: Degradation mechanisms, transformation products, toxicity evolution and effect of real water matrix.

Four common refractory pharmaceuticals, diclofenac (DF), sulpiride (SP), sulfamethoxazole (SMX) and sulfisomidine (SIM) were detected in the Disc Tubular Reverse Osmosis (DTRO) concentrates with higher concentrations ranging from 0.85 to 11.57 μg/L from the local landfill. The effect of complex matrix of DTRO concentrates on the UV-Fenton degradation kinetics of DF, SP, SMX and SIM and their transformation products (TPs) were studied. All the four pharmaceuticals could be degraded more efficiently in the ultrapure water than that in the DTRO-concentrate matrix, which also had a significant negative effect on the kinetic constants of the degradation. Twenty-two out of forty-nine TPs were newly identified by HPLC-QTOF-MS and their peak-area evolution was presented. The main degradation pathways for four pharmaceuticals were identified. When assessing cytotoxicity by using HepG2 cells, there appeared to be an obvious toxicity-increase region for each of SP, SMX and SIM. Eleven TPs were identified as the potential toxicity-increase causing TPs by combination of the QSAR prediction, HepG2 cytotoxicity assessment and peak-area evolution of TPs. Therefore, UV-Fenton process was a promising method for the refractory pharmaceutical degradation even in the complex water matrix and choosing appropriate reaction parameters for the UV-Fenton could eliminate the cytotoxicity of the TPs.