Non-radical mediated reduced graphene oxide/polypyrrole catalytic ceramic membrane-PDS system for source control of SMX

The activation of persulfate by a novel heterogeneous metal-free catalyst is of great significance in the efficient degradation of antibiotics. In this study, a novel reduced graphene oxide/polypyrrole ceramic membrane (rGO/PPy CM) integrated with in-situ peroxydisulfate (PDS) activation was operated for sulfamethoxazole (SMX) removal. Membrane confinement effect was used to enhance the interaction among SMX, PDS and catalytic membrane, whose removal rate of SMX reached 95 % after filtration for 10 min. Five-cycle filtration of SMX showed superior stability and reusability with all removal efficiencies above 90 %. Quenching experiments and in-situ open circuit potential testing established that this system maximized the induction of non-radical pathways for SMX degradation. rGO/PPy played a dual role as a PDS activator to form singlet oxygen and as an electron transfer medium. Density functional theory calculations illustrated that the combination of rGO and PPy enhanced the binding force with PDS, promoting non-radical oxidation. The possible degradation pathways of SMX by rGO/PPy CM-PDS system were proposed, including S-N bond cleavage, oxidation, aniline ring cleavage and hydroxylation. In general, this system enhanced the efficiency of PDS activation and SMX removal through membrane confinement and non-radical oxidation, which showed the promise of rGO/PPy CM in water purification.