Electrochemical removal of metribuzin in aqueous solution by a novel PbO2/WO3 composite anode: Characterization, influencing parameters and degradation pathways

摘要

In this work, we fabricated PbO2/WO3 composite electrode through composite electrodeposition method and employed it in electrocatalytic degradation of metribuzin. The effects of WO3 particles on surface morphology, structure and electrochemical characters of PbO2 electrodes were investigated. Different from PbO2 electrodes, the PbO2/WO3 composite electrodes owned higher oxygen evolution overpotential, longer service life and higher hydroxyl radicals generation performance. The effect of key operating parameters, for instance, current density, initial metribuzin concentration, initial pH values, and supporting electrolyte concentration, upon electrochemical removal process of metribuzin were studied. The current density and initial metribuzin concentration exerted prominent effects on electrochemical degradation of metribuzin. Kinetic analysis indicated that the electrochemical decomposition of metribuzin was a pseudo-first-order reaction. The byproducts during metribuzin degradation process were identified, several aromatic products and inorganic ions were generated along with the reaction time. Finally, the electrochemical pathways of metribuzin degradation at the PbO2/WO3 composite electrode were proposed based on the identified reaction byproducts, which were separated into three parallel sub pathways according to the different degradation reactions by hydroxyl radicals, and quantities of hydroxylation, oxidation, demethylation, deamination, and addition reactions' products were generated. All the byproducts were finally decomposed into inorganic H2O, CO2, NO3-, and NH4+. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.