Efficient degradation of sulfamethazine sodium via hydrogen peroxide activation in the presence of calcite: Synergistic effect of Co(II) and Cu(II)

Abstract

The bimetallic synergistic effect plays a significant role in enhancing the efficiency of antibiotics degradation via hydrogen peroxide (H₂O₂) activation. In this study, the degradation of sulfamethazine sodium (SMT) by H₂O₂ was comprehensively explored in a system where Cu(II) and Co(II) ions synergistically activate H₂O₂ in the presence of calcite. The Cu(II)/Co(II)/calcite/H₂O₂ system using only 1.0 mg/L of Cu(II), exhibits excellent oxidation capacity, enabling complete removal of SMT within 1 h (0.085 min⁻¹). This rate is 4.5 and 23.5 times higher than those observed in the Cu(II)/calcite/H₂O₂ (0.019 min⁻¹) and Co(II)/calcite/H₂O₂ systems (0.0036 min⁻¹), respectively. According to scavenger experiments, ESR captures test, and chemical probe experiments, it is determined that Cu(III) primarily contributes to SMT degradation, rather than hydroxyl radicals (·OH), singlet oxygen (¹O₂), and high valent cobalt-oxo species [e.g. Co(IV)]. The introduction of Co(II) promotes the formation of Cu(III) by accelerating the oxidation of Cu(II). Furthermore, the degradation pathways for SMT are elucidated through UPLC-ESI-MS/MS analysis, and variations in toxicity are rigorously assessed using the ECOSAR program. In summary, this study reveals the highly effective synergistic activation of H₂O₂ by Cu(II) and Co(II) in the presence of calcite, offering new insights into the comprehensive utilization of calcite in environmental catalysis, particularly for addressing the pollution caused by coexisting heavy metals and antibiotics.