Mechanistic insights into activation of periodate by sludge biogas residue biochar loaded with manganese for efficient sulfadiazine degradation in aqueous solutions

The sewage sludge anaerobic digestion process produces a large amount of biogas residue. This study proposes a new path for the resource utilization of sludge biogas residue. Biogas residue biochar (BRBC) showed efficient periodate (PI) activation capability after hydrothermal loading of Mn. Under neutral conditions, the optimal removal rate of sulfadiazine (SDZ) could reach 100% within 5 min, and the pseudo-first-order kinetic reaction constant of the Mn-modified biogas residue biochar (Mn-BRBC) activating the PI system was 0.6942 min −1 , which was 8.97 times that of the BRBC/PI system. It was confirmed that 1 O 2 plays a dominant role in the degradation process of SDZ. Characterization results showed that the hydrothermal process changes the vacancy structure of the BRBC surface, and the rearrangement of surface biomass during the process produces abundant oxygen-containing functional groups. Electrochemical experiments demonstrated that the ability of BRBC-mediated electron transfer was significantly enhanced after Mn loading. The biotoxicity of the sulfadiazine degradation products was greatly reduced compared with that of the parent pollutant. Moreover, the system achieved sulfadiazine degradation rates of 88.4% and 83.35% in tap water and lake water, respectively. This study offers a highly promising method for the resource utilization of sludge digestate.