Electrochemical oxidation of the pesticide nitenpyram using a Gd‐PbO2 anode: operation parameter optimization and degradation mechanism

Abstract

AbstractBACKGROUNDNitenpyram is a neonicotinoid insecticide widely used in agriculture and horticulture, which is stable and builds up in wastewater, causing serious environmental concerns. In this work, the process of advanced electrochemical oxidation for degrading nitenpyram was investigated in detail. The influences of operation parameters (including applied current density, initial nitenpyram concentration, Na2SO4 concentration and pH value) on the electrochemical removal of nitenpyram and its relative degradation mechanism were studied by a gadolinium‐doped lead dioxide (Gd‐PbO2) anode.RESULTSThe results demonstrated that the electrochemical oxidation of nitenpyram follows pseudo‐first‐order reaction kinetics under different operation conditions. After that, 95.44% of nitenpyram and 79.22% of COD could be eliminated from 0.15 mol L−1 Na2SO4 solution dissolving 75 mg L−1 nitenpyram under 70 mA cm−2 at pH = 5.0. Ultimately, high‐performance liquid chromatography (HPLC) and HPLC/mass spectroscopy (MS) were adopted to discover the degradation by‐products during the nitenpyram oxidization process, and up to 14 by‐products were successfully identified. Then a typical nitenpyram degradation pathway was proposed based on these by‐products, comprising two divided parallel sub‐routes. Indirect electrochemical oxidation was responsible for nitenpyram degradation by Gd‐PbO2 anode, and hydroxyl radicals were the main reactive oxygen species.CONCLUSIONThe Gd‐PbO2 electrode presented remarkable performance in nitenpyram degradation. Therefore, the electrochemical oxidation method by Gd‐PbO2 anode is considered to be a very promising and practical mode of herbicide wastewater treatment. © 2020 Society of Chemical Industry