Rapid activation of PMS driven by bimetallic redox on transition metal selenides for sulfamethoxazole degradation: mechanism, degradation pathway and intermediates toxicity

BACKGROUND

The increasing presence of antibiotics in aquatic environments poses significant ecological risks, with sulfamethoxazole (SMX) being a prominent example due to its persistence and widespread use in medical and veterinary practices. Advanced oxidation processes, particularly those based on peroxymonosulfate (PMS), have shown promise in degrading such contaminants. This work explored the efficacy of a bimetallic selenide catalyst, FeSe₂/MoSe₂ (FM), synthesized via a hydrothermal method, for the rapid activation of PMS and subsequent degradation of SMX.

RESULTS

Over 95% SMX degradation was achieved with a 0.25 g/L catalyst dosage and 1.5 g/L PMS dosage, demonstrating that FM was an effective PMS activator capable of efficiently oxidizing SMX. The EPR tests and quenching experiments confirmed the presence of ¹O₂, SO₄^•– and ^•OH in the degradation system, with SO₄^•- predominating. The redox cycling of Mo with Fe was involved in the activation of PMS. Moreover, the DFT calculations of the SMX molecule revealed that the vulnerable sites were mainly in the vicinity of the sulfonamide group and the oxygen-containing group. The toxicity assessment disclosed that most of the primary degradation intermediates of SMX were toxic, while the further small molecule products were non-toxic.

CONCLUSION

This work underscores the potential of the FM/PMS system as an efficient and sustainable solution for degrading antibiotic contaminants like SMX in water. The low toxicity of the final degradation products further supports the environmental safety of this approach, making it a promising candidate for real-world water treatment applications. © 2024 Society of Chemical Industry (SCI).