Self-doped biochar by in-situ copper adsorption as an efficient peroxymonosulfate activator for antibiotics degradation: non-covalent bond driving direct electron transfer and surface-bound radicals mechanisms

This study developed a novel low-valent copper (Cu) self-doped biochar (Cu 0 @RBC), in which Cu was integrated into the carbon skeleton via in-situ pyrolytic reduction following its adsorption on biomass, using rice straw as the precursor to activate peroxymonosulfate (PMS) for degrading sulfonamides. PMS/Cu 0 @RBC system achieved 96.6% degradation rate of sulfadiazine (SDZ) within 60 min, with an impressive mineralization rate of 70.4%. The excellent PMS activation performance was attributed to the abundant oxygen-containing functional groups in the Cu self-doped biochar and its stable low-valent copper grafting performance. Mechanistic investigations confirmed that non-covalent bond driving direct electron transfer and surface-bound radicals played pivotal roles in SDZ degradation. This system demonstrated desirable tolerance to pH fluctuations and background interference through its non-radical dominated mechanisms, ensuring effective sulfonamides removal in various actual waters. DFT calculations and products analysis pinpointed reactive sites for SDZ degradation and three possible degradation pathways. The detoxification efficacy of this system was validated through ECOSAR analysis and biological toxicology experiments. To assess practical applicability, a device for the dynamic removal of sulfonamides was also designed to confirm its high degradation rate and sustainable removal ability. Overall, this work provided a novel technology for elimination of sulfonamides, characterized by high degradation/mineralization rates, exceptional detoxification performance, robust tolerance to environmental conditions, and sustainable utilization of rice straw as resources.