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%) for tetracycline (TC, 20 mg L-1) due to the generation of 1O2, Fe(IV)=O and •OH. The introduction of sulfur was found to be beneficial for improving the electronic structure and electron transfer efficiency of S-Fe@G, enhancing the Fe reaction site activity, increasing the multivalent distribution of Fe, lowering the reaction energy barrier for the dissociation of PMS and accelerating the Fe(II)/Fe(III) cycle, leading to the rapid degradation of pollutants and stable operation of the catalytic system over a long period. 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.

Keywords: PMS activation, Tetracycline degradation, Two-dimensional catalytic membrane, Reduced sulfur species, water treatment