Discarded mask-derived carbon boosting peroxymonosulfate activation for efficient photothermal synergistic degradation of sulfamethoxazole: Catalytic performance and mechanism study

Abstract

Efficient decomposition of organic pollutants in treating wastewater through persulfate system is vital but challenging. Herein, a novel disposable medical masks-derived carbon material (MDC) fabricated by via sulfonation, carbonation, and graft modification was prepared for photothermal effect synergistic persulfate (PDS) activation, manifesting satisfactory degradation efficiency of sulfamethoxazole (SMX) of 100 % within 15 min when MDC was 1.0 g/L and persulfate was 0.2 g/L. Inspired by the excellent photothermal properties of MDC, Light/MDC-900/PDS/PT system exhibited a remarkably fast degradation rate, showcasing a reaction rate constant of 0.2461 min⁻¹, which was 2.21 times higher than that without the photothermal effect. Electron paramagnetic resonance (EPR) and quenching trials unveiled singlet oxygen (¹O₂) was the primary reactive oxygen species for driving the eradication of SMX molecules. Additionally, experimental analyses combined with Density functional theory (DFT) identified the interface C-OH functional groups as the dominant active site, which played a significant role in accelerating PDS molecule adsorption and O-O bond activation. Furthermore, SMX underwent ring opening and oxygen hydrogenation yielding low-toxicity products. Overall, this work enhances the understanding of the mechanisms underlying the photothermal synergistic activation of PDS by carbon-based materials, particularly highlighting the often-overlooked thermal effects, and significantly broadens the application of photothermal technology in pollutant degradation.