CuOx-coated titanium hollow fiber electrocatalytic membrane for efficient sulfamethoxazole removal: Preparation, performance and degradation mechanism

In this work, novel CuO_x-coated titanium hollow fiber membrane (CTHM) was developed by depositing copper oxide catalyst onto the titanium hollow fiber membrane (THM) through a facile and controllable electrodeposition-thermal treatment. The CTHM samples obtained at different treatment temperatures exhibited varying catalyst morphologies, distinct crystal structures, and oxygen vacancy (O_V) concentrations, which resulted in different electrochemical activities. Specifically, at a thermal treatment temperature of 450 °C, a cauliflower-like CuO catalyst was formed on the surface of CTHM-450, exhibiting superior electrochemical activity compared to CTHM samples prepared under other conditions. Consequently, CTHM-450 demonstrated optimal electrocatalytic filtration treatment performance, achieving a removal rate of 96.83% for sulfamethoxazole (SMX) and 50.48% for total organic carbon (TOC). Electron paramagnetic resonance (EPR) tests and quenching experiments indicated that the efficient removal of SMX by CTHM-450 was mainly due to the electrocatalytic oxidation process, which was dominated by hydroxyl radicals (·OH), singlet oxygen (¹O₂), and sulfate radicals (SO₄^∙-). The possible degradation pathways of SMX during the treatment were analyzed based on the intermediate products detected in the permeate and computational results obtained from density functional theory (DFT). Moreover, the toxicity of the detected degradation products was analyzed, confirming that the electrocatalytic filtration using CTHM efficiently removes SMX without elevating the toxicity of the aqueous solution.