Development of attapulgite based catalytic membrane for activation of peroxymonosulfate: A singlet oxygen-dominated catalytic oxidation process for sulfamethoxazole degradation

Abstract

Antibiotic contamination of aquatic ecosystems has attracted growing concern over the past few years. As a novel and low-cost catalytic membrane, attapulgite-based ceramic membrane (ATPCM) impregnated with Co3O4 (Co-ATPCM) was successfully prepared for the degradation of sulfamethoxazole (SMX) under peroxymonosulfate (PMS) activation. The physical and chemical properties of ATPCM and Co-ATPCM were characterized by SEM-EDS, XRD, XPS, zeta potential, contact angle and the three-point bending test. Co was stably anchored on ATPCM via X-O-Co (X denotes Al, Si or Mg) bonds during the catalytic process, avoiding Co leaching. Approximately 70 % SMX could be removed by the optimized Co-ATPCM in batch experiments over a wide pH range from 4.0 to 10.0. Furthermore, 58 % SMX degradation was observed during filtration experiments with a high water flux of up to 774 L m−2h−1 (LMH). According to the quenching experiment and electron paramagnetic resonance (EPR) spectroscopy, SO4−, OH and 1O2 were involved in the SMX degradation process, while 1O2 played a dominant role. Density functional theory (DFT) calculation successfully predicted that the sits on SMX molecules with high Fukui index were more susceptible to attacks by free radicals, confirmed by liquid chromatography-Quadrupole-time of flight mass spectrometer (LC-MS). Consequently, a possible pathway for the catalytic oxidation process was proposed based on the results of DFT and LC-MS. This study provided a promising strategy using natural magnesium aluminum silicate clay minerals to prepare cost-effective, efficient, and eco-friendly catalytic membranes for wastewater treatment.