Molybdate-loaded magnetic biochar activates persulfate for efficient degradation of sulfamethazine

Abstract

Molybdate-doped magnetic biochar (MoMBC) was synthesized using sawdust as the raw material through impregnation and pyrolysis. MoMBC was utilized to activate persulfate (PS) for the degradation of sulfamethazine (SMT). The results demonstrated that at a MoMBC dosage of 0.1 g/L and PS concentration of 2 mM, the MoMBC/PS system exhibited a stabilization of SMT degradation efficiency at a level exceeding 98.1 % within 120 min. This was accompanied by a reaction rate constant was 31 times greater than observed in the MBC/PS system. Characterization analysis of MoMBC revealed that molybdate loading facilitated the redox cycling of Fe³⁺/Fe²⁺ and Mo⁶⁺/Mo⁴⁺, thereby enhancing the activation efficiency of PS and accelerating SMT degradation. Through free radical quenching experiments and electron paramagnetic resonance analysis, it was found that the contribution rates of superoxide radicals and hydroxyl radicals were 44.47 % and 33.09 %, respectively, which were the main free radicals promoting the degradation of SMT. Under the coexistence of natural organic matter and anions, the influence of MoMBC/PS system is insignificant. Its powerful broad-spectrum features make it appropriate for the degradation of diverse antibiotics, with a mineralisation rate of 59.9 %. The degradation of SMT undergoes processes such as oxidation, hydroxylation, and removal of SO₂. This study provides new technical support for the practical implementation of magnetic biochar in the remediation of water pollution.