Rationally designed Co3O4-SnO2 activated peroxymonosulfate for the elimination of chloramphenicol

In this study, the Co3O4-SnO2 composite derived from bimetallic oxalates was rationally fabricated and utilized as a catalyst for peroxymonosulfate (PMS) activation towards the destruction of chloramphenicol (CAP). The physicochemical properties of the Co3O4-SnO2 were systematically characterized to discover the relationship between its structure and catalytic performance. SnO2 as a cocatalyst with high conductivity and stability immensely improved the activity of Co3O4 in the Co3O4-SnO2 composite. Approximately 98% of CAP (10 mg/L) was eliminated by the Co3O4-SnO2 (0.1 g/L) activated PMS (1.0 mmol/L) at initial pH 7 within 20 min. The rationally designed Co3O4-SnO2 composite exhibited higher catalytic activity than Co3O4, SnO2, and other cobalt-based bimetallic oxides (such as Co-Fe, Co-Mn, and Co-Cu) in the PMS activation for the CAP degradation. The synergistic effect of Co3O4 and SnO2 endowed the Co3O4-SnO2 composite with higher conductivity and more electron transfer, which was proved by the electrochemical tests. The presence of SO4•−, •OH, O2•−, and 1O2 during the CAP degradation was testified by both quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. In addition, the catalytic mechanism and degradation pathways were further proposed via the characterization of X-ray photoelectron spectroscopy (XPS) and the identification of transformation products, respectively. This work provides a new insight into the preparation of novel catalysts and their application in wastewater treatment.