Peroxydisulfate degradation of diclofenac sodium activated by nZVI@MoS2: Key roles of superoxide radicals in the free radical pathway and electron transfer in the nonradical pathway

• Published in: Journal of water process engineering Vol. 61; p. 105309
• Main Authors: Lei, Haoxin, Lin, Qintie, Zheng, Junli, Liu, Yuxin, Sun, Jian, Chen, Tingxi, Luo, Hao, Huang, Haofeng, Zhao, Zirui
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2024
• Subjects: Electron transfer; Iron cycle; nZVI@MoS2; Peroxydisulfate activation; Superoxide radicals; Electron transfer; Peroxydisulfate activation; Superoxide radicals; nZVI@MoS2; Iron cycle
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2024.105309

Diclofenac sodium (DCF) has potential biological toxicity and is difficult to degrade through conventional methods; therefore, there is a pressing imperative to develop an approach to address this environmental predicament. In this work, nZVI@MoS2 was synthesized via liquid-phase reduction to activate peroxydisulfate (PDS) for the degradation of DCF. The results demonstrated efficient degradation of DCF within 30 min with the nZVI@MoS2/PDS system. Quenching experiments, electron paramagnetic resonance (EPR) spectroscopy, steady-state concentration calculations, and electrochemical experiments demonstrated that DCF predominantly underwent degradation through an O2−-dominated free radical pathway and an electron transfer-dominated nonradical pathway. The nZVI@MoS2 composite promoted the Fe2+/Fe3+ cycle, generated O2− and showed exceptional electrochemical performance in enhancing electron transfer. The paths for DCF degradation were revealed via HPLC–MS analyses. Toxicological assessment software revealed reduced toxicity of DCF. This study presents a novel approach for the degradation of wastewater containing pharmaceuticals and personal care products (PPCPs). [Display omitted] •Superoxide radical (O2•−) was identified as the dominant active substance in the free radical pathway.•In the nZVI@MoS2 composite material, MoS2 can promote the cycling of Fe2+ and Fe3+, producing more active substances.•The incorporation of nZVI onto MoS2 can enhance the electrochemical performance, promoting electron transfer.•The nZVI@MoS2/PDS system can effectively mineralize DCF and reduce the toxicity of the reaction intermediates.•The nZVI@MoS2/PDS system is applicable to various pollutants.