Electro-controlled membrane coupling heterogeneous electro-Fenton (EM-HEF) in treating acetaminophen: performance, mechanism, DFT calculation, and application

Abstract

The utilization of hybrid electro-Fenton (EF) processes has gained considerable attention, which can combine the advantages of two or more treatment methods resulting in efficient removal of refractory pollutants from water. Here, an electro-controlled membrane coupling heterogeneous EF (EM-HEF) system was constructed for the degradation of acetaminophen (APAP) in water. In the EM-HEF system, a bifunctional ACF/CC-FeOCl-Cu cathode material was synthesized to enhance the HEF reaction, while a tubular Ti microfiltration membrane was used as both cathode and membrane. Degradation experiments indicated the EM-HEF system exhibited remarkable removal efficiency (97.0 %) towards APAP within 30 min under the conditions of flow rate at 60 mL min−1, initial pH at 7.1, and current density at 3 mA cm−2. Notably, the cathode materials showed low metal leaching rate and high APAP removal rate in the 10 cyclic experiments. The common inorganic anions (Cl−, HCO3−, HPO42−, and NO3−) did not inhibit the removal of APAP significantly, whereas humic acid exhibited a more pronounced inhibitory effect only at concentrations exceeding 10 mg L−1. Quenching experiments and electron spin resonance (ESR) tests confirmed the pivotal role of hydroxyl radicals in the decomposition of APAP. Combining density functional theory (DFT) and LC-MS results, three pathways were proposed. The overall toxicity of intermediates was relieved during EM-HEF degradation of APAP. Furthermore, it also achieved good performance in the treatment of landfill leachate, with increasing BOD5/COD ratio from 0.11 to 0.34. This work provides an efficient strategy for the removal of refractory pollutants in water.