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

Abstract

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.