Multiple-pathway degradation of acetochlor by UV-LED coupled electrochemical process: A promising solution for rural household water treatment.

The extensive use of amide pesticides in rural areas, coupled with their recalcitrance to conventional treatment processes and poor environmental compatibility, has posed potential threats to ecosystems and human health. In response, the newly revised chinese standard for drinking water quality (GB 5749-2022) mandated a maximum contaminant level for acetochlor (ACE). This study introduced a UV-LED coupled electrochemical process (UV-LED/ECCl2), employing one inert anode (BDD) and two active anodes (RuO2-IrO2 and IrO2), to achieve sustained and efficient removal of ACE in water without external sodium hypochlorite addition. The UV-LED/BDD-Cl2 system achieved 92.2% removal within 30 min, 1.16 and 1.13 times higher than those of the UV-LED/RuO2-IrO2Cl2 and UV-LED/IrO2Cl2 systems, respectively. This enhancement was attributed to UV-LED photolysis (41%), non-selective HO• oxidation (10%), the action of reactive chlorine species generated from Cl⁻ conversion (13.7%), and other contribution (11%). HO• and RCS synergistically initiate ACE degradation via hydrogen abstraction from the chloroacetyl side chain and N-ethoxymethyl group, followed by aromatic ring oxidation and ring-opening, ultimately converting ACE into small-molecule organic compounds and mineralization products. UV-LED/ECCl2 system exhibited superior electrical energy per order performance while reducing resource consumption associated with the high-energy ECCl2 system. Under amended groundwater condition, the ACE removal efficiency decreased by only 2.92%, and was even unaffected by the complex water matrix, indicating the potential application of UV-LED/ECCl2 system for effectively addressing water purification challenges in rural areas.