Removal of Sulfonamide Antibiotics by Non-free Radical Dominated Peroxymonosulfate Oxidation Catalyzed by Cobalt-doped Sulfur-containing Biochar from Sludge

The reuse of activated sludge as a solid waste is severely underutilized due to the limitations of traditional treatment and disposal methods. Given that, the sulfur-containing activated sludge catalyst doped with cobalt (SK-Co(1.0)) was successfully prepared by one-step pyrolysis and calcinated at 850 ℃. The generation of CoS was successfully characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), indicating that the sulfur inside the sludge was the anchoring site for the externally doped cobalt. Cobalt (Ⅱ) (Co), as the main adsorption site for peroxymonosulfate(PMS), formed a complex (SK-Co(1.0)-PMS* ) and created the conditions for the generation of surface radicals. The SK-Co(1.0)/PMS system showed high degradation efficiency and apparent rate constants for Sulfamethoxazole (SMX) (91.56% and 0.187 min) and Sulfadiazine (SDZ) (90.73% and 0.047 min) within 10 min and 30 min, respectively. Three sites of generation of O, which played a dominant role in the degradation of SMX and SDZ in the SK-Co(1.0)/PMS system, were summarized as：sulfur vacancies (SVs), the Co/Co cycles promoted by sulfur(S) species, oxygen-containing functional groups (C-O). The degradation mechanisms and pathways had been thoroughly investigated using DFT calculations. In view of this, a new idea for the resource utilization of activated sludge solid waste was provided and a new strategy for wastewater remediation was proposed.