Fast removal of sulfamethoxazole by MIL-101(Fe)–NH2/perylene diimide activated persulfate under visible light

Abstract

Photocatalytically induced persulfate (PS) activation is considered a viable approach to counter the threat of resistance genes caused by the continuous accumulation of sulfamethoxazole (SMX) in the aqueous environment. In this study, the electrostatic interaction between MIL-101(Fe)–NH₂ and perylene diimide (PDI) was exploited to fabricate composite catalysts (MNP_x) with Z-scheme heterojunctions, which were applied to active peroxydisulfate (PDS) for SMX degradation under visible light. The most efficient MNP_x/PDS/vis system recorded a 99.2 % reduction in SMX concentration, with an associated reaction rate of 0.8873 min⁻¹. This performance was superior to the PDI/PDS/vis and MIL-101(Fe)–NH₂/PDS/vis systems, being 106.9-fold and 15.2-fold more effective, respectively. The Z-scheme heterojunction of the photocatalyst accelerated electron transport, inhibited electron-hole recombination, and improved the efficiency of PDS activation; meanwhile, the substantial surface area of the MIL-101(Fe)–NH₂ provided additional reaction sites, these features synergize to enable the rapid removal of SMX. The MNP_x/PDS/vis system degraded SMX at a higher rate under acidic and neutral conditions. Besides, degradation pathways for SMX have been proposed, and the biotoxicity of SMX as well as the by-products gradually decreased as the degree of degradation deepens. This study presented a simple strategy for the Z-scheme heterojunction photocatalyst preparation and a reference for the disposal of sulfamethoxazole-containing wastewater.