Durable and eco-friendly peroxymonosulfate activation over cobalt/tin oxides-based heterostructures for antibiotics...

Potential leaching of Co ions could decrease the catalytic activity and cause secondary pollution of water, thereby threatening ecological safety and human health. In response, the in-situ generation of well-dispersed Co₂SnO₄ and SnO₂ with fine interfacial feature was constructed for PMS activation toward efficient tetracycline degradation and lower cobalt ion leaching feature. The synergistic effect of Co₂SnO₄ and SnO₂ endowed Co₂SnO₄-SnO₂ an outstanding catalytic performance for tetracycline degradation in alkaline condition. Meanwhile, the catalysts can effectively degrade the quinolones, dyes and mixture pollutant solution. The excellent performance can attributed to the in-situ introduction of SnO₂, which stabilizes the microstructure and provides an effective electronic pathway to enhance the activity of Co₂SnO₄ in the Co₂SnO₄-SnO₂. In optimized condition, the tetracycline degradation efficiency was enhanced to 94.9% within 20 min and maintained the stability at least four cycles. The degradation rate constant of Co₂SnO₄-SnO₂ was 0.149 min^-1, which was about 1.93, 2.98, 11.5 times higher than of Co₂SnO₄, Co₃O₄ and SnO₂, respectively. Notably, the leaching performance of Co₂SnO₄-SnO₂ was greatly suppressed to be 7.45 ug/L, which was lower than that of Co₂SnO₄ (6.41 mg/L) and Co₃O₄ (1.12 mg/L). Radical quenching and EPR experiments showed that singlet oxygen (¹O₂), rather than hydroxyl active species and sulfate radicals, played a predominating role for PMS activation in the Co₂SnO₄-SnO₂/PMS system. The intermediates and degradation routes for tetracycline degradation were characterized by liquid chromatograph-tandem mass spectrometry. This study expected to provide a novel strategy to construct heterostructural catalysts with lower cobalt ion leaching for the activation of PMS.