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 _x 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 ²⁺ ), 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 ^-1 ) and Sulfadiazine (SDZ) (90.73% and 0.047 min ^-1 ) within 10 min and 30 min, respectively. Three sites of generation of ¹ O ₂ , 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 ³⁺ /Co ²⁺ 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.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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