Visible-light-driven photoelectrocatalytic degradation of diclofenac by N, S–TiO2/TiO2 NTs photoelectrode: performance and mechanism study

作者：Xiuwen Cheng; Pu Wang; Huiling Liu

来源：Journal of Environmental Chemical Engineering, 2015, 3(3): 1713-1719.

DOI：10.1016/j.jece.2015.06.015

• Diclofenac
• Photoelectrocatalysis
• Mechanism
• Kinetics
• Reactive species

Diclofenac is a common non-steroidal anti-inflammatory drug, which has been widely used in clinic that leads to the frequently detection in the freshwater bodies. In the present study, we explored the visible-light-driven photoelectrocatalytic (PEC) degradation of diclofenac solution by the as-fabricated N, S–TiO2/TiO2 NTs photoelectrode. Meanwhile, the PEC degradation performance and kinetics were also investigated. It was found that 73.3% of diclofenac could be degraded within 12 h visible light irradiation with the help of external potential (+0.4 V vs SCE). Additionally, the PEC processes followed the pseudo-first-order kinetics according to the Langmuir–Hinshelwood (L–H) model, in which the highest apparent rate constant of 0.101 h−1 could be achieved. Moreover, the further study of reactive species indicated that both H2O2 and OH radicals were responsible for the major degradation of diclofenac molecule. Besides, five degradation intermediates were elucidated by HPLC–MS/MS analysis. Based on these results, three tentative pathways for the PEC degradation of diclofenac solution were proposed, for example hydroxylation addition to parent pharmaceuticals, C–N cleavage of side chain from the diclofenac attacked by photogenerated holes and directly decarboxylation, subsequently dechlorination and oxidation processes. This study provides an effective strategy for the removal of pharmaceuticals from wastewater or freshwater bodies.