Efficient activation of peroxymonosulfate by sulfur-coordinated iron-based two-dimensional composite membrane (S–Fe@G) via sulfur doping and nanoconfined catalysis

Abstract

The combination of nanoconfined catalysis, sulfate radicals based-advanced oxidation processes (SR-AOPs) and membrane filtration processes, can remove organic pollutants efficiently while eliminating the need for secondary recovery of heterogeneous catalysts. In this study, sulfur-doped iron-based carbonaceous two-dimensional composite nanoconfined catalytic membranes (S–Fe@G membranes) were prepared to rapidly activate peroxymonosulfate (PMS) for efficient water purification. The best performing 2S–20Fe@G catalytic membrane/PMS system achieved an ultra-rapid (158.7 ms retention time) removal (94.9 %) and high mineralization (>66.7 %) of tetracycline (TC, 20 mg/L) due to the generation of ¹O₂, Fe(IV)=O and •OH. The introduction of sulfur was found to significantly improve the electronic structure and electron transfer efficiency of S–Fe@G. This enhancement promoted the activity of Fe reaction sites and increased the multivalent distribution of Fe. Additionally, sulfur incorporation lowered the reaction energy barrier for PMS dissociation and accelerated the Fe(II)/Fe(III) cycle. These combined effects resulted in the rapid degradation of pollutants and ensured the stable operation of the catalytic system over extended periods. In addition, the nanoconfined space composed of the two-dimensional carbonaceous structure was conducive to the accumulation of pollutants and the rapid activation of PMS. The 2S–20Fe@G catalytic membrane achieved a high selective removal of TC (>94.5 %) and substantial mineralization of pollutants (>52.1 %) in both simulated (Humic acid + TC) and real (Lake water + TC) waters, demonstrating its potential for practical applications.