Activation of Peroxymonosulfate by Boron Carbide Modified Biochar Catalyst Derived from Waste Sludge for the Removal of Organic Pollutants

The synthesis of functional materials from sludge is considered an innovative and sustainable approach for the resource utilization of sewage sludge. In this study, sludge biochar modified with boron carbide (B-SBC) possessing different B contents and pyrolysis temperatures was prepared and applied in the activation of peroxymonosulfate (PMS) for the selective decomposition of various organic pollutants. The pseudo-first-orde rate constant of rhodamine B degradation in the system mediated by B-SBC prepared under optimal conditions was 9.8 and 3.9 times higher than those in PMS and SBC/PMS systems, respectively. Electron spin resonance (ESR), quenching experiments, and electrochemical analysis revealed that nonradical pathways including 1O2 generation (74.6 %) and direct electron transfer (22.0 %) were the main routes for RhB oxidation in the B-SBC/PMS system. The B-SBC mediated systems exhibited significant selectivity toward organic pollutant decomposition. Spectroscopic analysis identified that - BCO2 was the main active site for PMS activation, which exhibited positive linear correlations between its contents and rate constants of rhodamine B decomposition. Density functional theory calculations showed that, the doped B atoms improved the reactive ability of SBC by serving as adsorption sites of PMS and electron transfer channels, and act as an electron-deficient center to change the electron density of surrounding atoms, thereby accelerating electron transfer. This study provides insights into the mechanism of carbocatalysis for selective oxidation of pollutants in non-radical pathways, and develops an innovative technology for sludge utilization and wastewater remediation.