Stepwise biofabrication of CuMnS from electroplating wastewater: bimetal-sulfur synergy for enhanced...

Microbial upcycling of heavy metal wastewater into catalysts offers a sustainable solution for antibiotic degradation, yet traditional synthesis is hindered by severe metal toxicity and complexation issues. To address these challenges, a stepwise biosynthesis strategy was developed using Shewanella oneidensis MR-1 to fabricate copper-manganese bimetallic sulfide (bio-CuMnSs) from heavy metal-laden wastewater. Unlike the one-step method, this strategy maintained high cell viability, enabling the efficient production of uniform nanoparticles. The bio-CuMnS (Cu/Mn molar ratio of 2:1) significantly outperformed its chemically synthesized counterpart, achieving 96 % degradation of tetracycline hydrochloride (TCH, 20 mg/L) within 60 min via peroxymonosulfate (PMS) activation. Mechanistic investigations revealed that the degradation was predominantly driven by surface-bound radicals (HO^•/SO₄^•-) confined by biogenic functional groups, with supplementary contributions from singlet oxygen (¹O₂). A distinct bimetal-sulfur synergy was confirmed, where intermediate-valence sulfur species (S₂^2-, S_n^2-, and S⁰) served as internal electron donors to drive the cooperative regeneration of Cu(I) and Mn(II) active sites, thereby sustaining PMS activation. The bio-CuMnS/PMS system maintained high efficiency over a broad pH range (5-11), in complex water matrices, and for different tetracycline antibiotics. Furthermore, the catalyst derived from real electroplating wastewater exhibited performance comparable to that from laboratory precursors, confirming the feasibility of simultaneous heavy metal valorization and antibiotic wastewater treatment.