Synthesis of novel Co3O4 hierarchical porous nanosheets via corn stem and MOF-Co templates for efficient oxytetracycline degradation by peroxymonosulfate activation

To further enhance the peroxymonosulfate (PMS) activation performance, novel Co3O4 hierarchical porous nanosheets composed of 5–10-nm ultrafine nanoparticles (Co3O4-MC) are successfully fabricated by calcining corn straw (CS) biotemplates coated with a metal–organic framework (MOF)–Co precursor. In view of the combined advantages that MOF-Co derivation and biotemplates afford, the resulting Co3O4-MC catalysts have a large specific surface area (64.42 m2/g) with the cobalt active sites distributed over entire catalysts nanosheets. These catalysts exhibited excellent PMS activation activity toward oxytetracycline (OTC) degradation with a 100% removal rate in 12 min. Additionally, Co3O4-MC is found to be highly stable with a minor Co leaching of 11 μg/L. Quenching tests and electron paramagnetic resonance (EPR) measurements indicated that radical and nonradical PMS activation mechanisms coexisted in the Co3O4-MC/PMS system. The pathway of OTC degradation is investigated based on the OTC intermediates whose presence is confirmed by gas chromatography-mass spectroscopy (GC–MS). It is also found that the toxicity of the degraded OTC toward zebrafish is lower than that of the initial OTC. This study provides a prospective strategy for developing highly effective metal oxide toward PMS activation for the rapid removal of stubborn organic pollutants in water.