Heterogeneous activation of peroxymonosulfate using ordered mesoporous Co 3 O 4 for the degradation of chloramphenicol at neutral pH

Abstract

Ordered mesoporous Co3O4 was fabricated using nanocasting route with SBA-15 or KIT-6 as the hard template and innovatively studied as the potential alternative to conventional Co3O4 nanoparticles for peroxymonosulfate activation. The formation of spinel Co3O4 was confirmed by wide-angle X-ray diffraction, fourier transform infrared, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy, meanwhile the replication of ordered mesoporous structure was evidenced by low-angle X-ray diffraction, N2 adsorption/desorption and transmission electron microscopy images. Among three different Co3O4 catalysts tested, Co3O4-KIT6 displayed the best catalytic activity in PMS solution, achieving almost complete removal of 30 μM chloramphenicol within 60 min at the reaction conditions of 0.1 g L−1 catalyst and 1.0 mM peroxymonosulfate. The superior catalytic performance of Co3O4-KIT6 was ascribed to the combination of multiple unique characteristics, including the large specific surface area, high pore volume, high Co2+ content and high density of surface active sites. Several factors played important roles in controlling the degradation of chloramphenicol. Higher catalyst dosage, higher PMS concentration, neutral pH and higher reaction temperature favored the removal. The balance among Co2+/Co3+, O2−/O2 and PMS decomposed in solution ensured the continuous generation of hydroxyl and sulfate radicals, and the latter made the predominant contribution for the CAP degradation. Considering its outstanding catalytic activity, excellent reusability and long-term stability, ordered mesoporous Co3O4 should be an ideal catalyst for environmental application.