Heterogeneous electro–Fenton using three–dimension NZVI–BC electrodes for degradation of neonicotinoid wastewater

Abstract

Neonicotinoids (NEOs), as the most widely used pesticides, pose a serious threat to water ecosystems, especially clothianidin (CLO). However, the degradation behavior of CLO, as a new type of persistent organic pollutant, is rarely studied in wastewater treatment. To bridge this gap, heterogeneous electro-Fenton system using three-dimension electrodes made of biochar-supported zero-valent iron nanoparticle hybrid material (NZVI–BC), abbreviated as 3D–ICE–EF system, is invented and initially applied in CLO wastewater degradation, without the addition of Fenton reagent. NZVI–BC in 3D–ICE–EF system can concentrate CLO on electrodes by excellent adsorption and effectively eliminate it to achieve self-cleaning effect. In addition, the deposition of iron mud (Fe(OH)3) and the circular utilization of Fe in Fenton system is effectively improved by the addition of hydroquinone (HQ) in 3D–ICE–EF system. The pH applicable scope of Fenton system is extended to alkaline condition by the applications of NZVI–BC electrodes. The increase in the acidity of electrolyte is considered the primary reason of the high degradation efficiency of CLO in 3D–ICE–EF system at an initial pH of 9.0. The degradation performance of 3D–ICE–EF system tends to be promoted by the increase of current intensity and air flow rate. Seven plausible mechanisms of CLO degradation were identified in 3D–ICE–EF system. The ecotoxicity evaluation of degradation products indicated that CLO degradation in 3D–ICE–EF system exhibits a remarkable tendency to reduce toxicity levels.