Degradation of diclofenac by UV-activated persulfate process: Kinetic studies, degradation pathways and toxicity assessments.
Diclofenac (DCF) is the frequently detected non-steroidal pharmaceuticals in the aquatic environment. In this study, the degradation of DCF was evaluated by UV-254nm activated persulfate (UV/PS). The degradation of DCF followed the pseudo first-order kinetics pattern. The degradation rate constant (kobs) was accelerated by UV/PS compared to UV alone and PS alone. Increasing the initial PS dosage or solution pH significantly enhanced the degradation efficiency. Presence of various natural water constituents had different effects on DCF degradation, with an enhancement or inhibition in the presence of inorganic anions (HCO3-or Cl-) and a significant inhibition in the presence of NOM. In addition, preliminary degradation mechanisms and major products were elucidated using LC-MS/MS. Hydroxylation, decarbonylation, ring-opening and cyclation reaction involving the attack of SO4•-or other substances, were the main degradation mechanism. TOC analyzer and Microtox bioassay were employed to evaluate the mineralization and cytotoxicity of solutions treated by UV/PS at different times, respectively. Limited elimination of TOC (32%) was observed during the mineralization of DCF. More toxic degradation products and their related intermediate species were formed, and the UV/PS process was suitable for removing the toxicity. Of note, longer degradation time may be considered for the final toxicity removal.
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China.
Xian
X
Lu
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China; China Academy of Urban Planning & Design, Beijing, China. Electronic address: lucaspp@163.com.
Yisheng
Y
Shao
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China.
Naiyun
N
Gao
College of Architecture and Civil Engineering, Xinjiang University, Urumqi, China.
Juxiang
J
Chen
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China.
Yansen
Y
Zhang
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China.
Huiming
H
Xiang
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China.
Youluo
Y
Guo
D002853:Chromatography, Liquid; D004008:Diclofenac / Q000032:analysis* / Q000737:chemistry / Q000633:toxicity; D007700:Kinetics; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry* / Q000528:radiation effects; D053719:Tandem Mass Spectrometry; D014466:Ultraviolet Rays; D014733:Vibrio / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000633:toxicity; D018508:Water Purification / Q000379:methods*
D013431:Sulfates; D014874:Water Pollutants, Chemical; D004008:Diclofenac
Degradation mechanism; Diclofenac; Kinetic studies; Toxicity assessments; UV activated persulfate