An in-situ electrogenerated persulfate and its activation by functionalized sludge biochar for efficient degradation of sulfamethoxazole

A novel oxidation system of in-situ electrogenerated persulfate (EO-PS) derived from sulphate in water and its activation by Fe/Mn bimetal co-functionalized sludge biochar (Fe/Mn-SBC) was built in this study to degrade sulfamethoxazole (SMX). The result showed that 98.8% of SMX was degraded within 60 min in EO/Fe/Mn-SBC/ Na2SO4 system. The abundant defect structures, oxygen-containing functional groups, Mn(II)/Mn(III) and magnetic Fe3O4 on Fe/Mn-SBC surface guaranteed its outstanding activation performance for EO-PS. The quenching and electron paramagnetic resonance (EPR) experiments confirmed that non-radicals of( 1)O(2) and surface-bound radicals were the dominant contributors for SMX elimination. The pathway I and III were proposed to be the main pathways of SMX degradation in EO/Fe/Mn-SBC/Na2SO4 system based on its transformed products (TPs) identification and density functional theory (DFT) calculation. Overall, the TPs of SMX generated in EO/Fe/Mn-SBC/Na2SO4 system were less toxic to aquatic organisms compared to that of SMX. Also, EO/Fe/ Mn-SBC/Na2SO4 system displayed favorable degradation performance for SMX in real waters (98.5%, 91.1%, 84.8%, 81.2% and 77.4% in pure water, tap water, river water, lake water and sewage effluent, respectively). Additionally, Fe/Mn-SBC exhibited the easy magnetic separation, excellent reusability and environmental safety. This study developed a promising technology of in-situ EO-PS and its activation by carbon-based material for SMX elimination without addition of exogenous PS, in addition to that the resource utilization of sewage sludge and wastewater sulphate were simultaneously achieved.