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Encapsulating MnFe LDH in Biochar Tunes Persulfate Activation from Radical to Nonradical Pathway: Significant Role of Electron Transfer
journal contributionposted on 2023-09-19, 06:13 authored by Hongqing Zhu, Hui Ma, Jingyang Yu, Zhiliang Zhao, Lanxin Xu, Xinyi Li, Yongfang Rao, Bo Lai, Shengyan Pu
Nonradical peroxydisulfate (PDS) oxidation has attracted great interest due to its mild oxidant dosage and little environmental impact. In this study, biochar-supported flower-like MnFe layered double hydroxide (BC-LDH) was prepared, and the PDS activation mechanisms were probed with ciprofloxacin (CIP) as representative contaminant. Compared to biochar (BC), MnFe LDH, and physical mixed BC/LDH, PDS activation was tuned to an electron-transfer-dominated nonradical pathway with coprecipitated BC-LDH. Electrochemical techniques including electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), Tafel, and two-chamber experiments confirmed that the synergistic effect between BC and LDH remarkably facilitated electron transfer from CIP to PDS. Degradation efficiency ranging from 92 to 94% was achieved with a PDS dosage ranging from 0.2 to 4 mM, and degradation rate constant was inversely proportional to the electron transfer resistance of PDS activators. Three degradation pathways for CIP were proposed based on the intermediates analyzed by ultra-performance liquid chromatography-mass spectrometry/MS (UPLC-MS/MS), and the toxicity of CIP was significantly decreased. This study proposed a novel strategy for enhancing electron-transfer-dominated nonradical PDS activation pathway with biochar/transition-metal oxide composites for the remediation of contaminants.
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