Fe/N-doped porous carbon spheres enable ^•OH-to-¹O₂ mechanism shift for selective sulfonamide degradation in high-salinity wastewater via low-temperature plasma

Abstract

The degradation of sulfonamide pollutants in high-salinity wastewater is hindered by chloride radicals scavenging hydroxyl radicals. This study aims to achieve efficient degradation of sulfonamides in high-salinity wastewater by enabling a mechanistic switch from hydroxyl radicals (^•OH) to singlet oxygen (¹O₂). To this end, we fabricated MMFeP-800 °C porous carbon spheres via in-situ growth of MIL-100(Fe) on a MET 6/PVDF/PVP substrate followed by carbonization. In the low-temperature plasma system, we selected nine different types of target pollutants and found that the catalyst was particularly effective toward sulfonamide pollutants. This is attributed to (i) the Fe/N-doped catalyst inducing the generation of ¹O₂, which enhances the efficient removal of sulfonamide pollutants; (ii) the in-situ growth strategy ensuring full exposure of active components and accelerating interfacial reactions; and (iii) the high-salinity background itself, under plasma action, also promoting the ^•OH→¹O₂ conversion, producing a synergistic benefit. Quenching experiments, LC–MS, and DFT calculations elucidated degradation pathways. Cycling tests and biotoxicity assays demonstrated good stability and reduced toxicity, confirming the catalyst's practical potential. This work provides a promising strategy for treating high-salinity wastewater containing sulfonamides.

Graphical abstract

Keywords

High-salinity wastewater / Porous microspheres / in-situ growth / Low temperature plasma / Ssinglet oxygen

Highlight

	● Fe/N-doped carbon catalysts induce 1O2 for selective sulfonamide removal.
	● High salinity alone promotes •OH to 1O2 conversion.
	● In-situ MIL-100(Fe) growth on microspheres enhances degradation.
	● Porous carbon spheres facilitate recovery and real-world use.

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