Durable and eco-friendly peroxymonosulfate activation over cobalt/tin oxides-based heterostructures for antibiotics removal: Insight to mechanism, degradation pathway.

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 CoSnO and SnO with fine interfacial feature was constructed for PMS activation toward efficient tetracycline degradation and lower cobalt ion leaching feature. The synergistic effect of CoSnO and SnO endowed CoSnO-SnO 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 SnO, which stabilizes the microstructure and provides an effective electronic pathway to enhance the activity of CoSnO in the CoSnO-SnO. 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 CoSnO-SnO was 0.149 min, which was about 1.93, 2.98, 11.5 times higher than of CoSnO, CoO and SnO, respectively. Notably, the leaching performance of CoSnO-SnO was greatly suppressed to be 7.45 ug/L, which was lower than that of CoSnO (6.41 mg/L) and CoO (1.12 mg/L). Radical quenching and EPR experiments showed that singlet oxygen (O), rather than hydroxyl active species and sulfate radicals, played a predominating role for PMS activation in the CoSnO-SnO/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.