A mechanistic study of amorphous CoSx cages as advanced oxidation catalysts for excellent peroxymonosulfate activation towards antibiotics degradation

A catalyst with multivalent of elements and a hollow structure is very promising for peroxymonosulfate (PMS) activation. In this work, a novel, hollow, and amorphous CoSx hexagonal cage was prepared by an aqueous solution assisted solvothermal method for effective PMS activation towards antibiotics degradation via an advanced oxidation process. The detailed structure of CoSx was characterized by X-ray diffraction patterns, transmission electron microscopy and X-ray photoelectron spectroscopy. As expected, the as-prepared hollow, amorphous CoSx cages presented excellent tetracycline (TC) decomposing ability by PMS activation, which was much better than those of classic Co3O4 and Fe3O4 as well as the conventional Fenton reaction of Co3O4. In addition, the effect of parameters (PMS dosage, pH, reaction temperature, TC concentration, and catalyst content) on catalytic activity was studied in detail. Meanwhile, the influence of co-existing anions (Cl-, NO3- and HCO3-) in aqueous solution on TC degradation was also investigated. A possible mechanism for PMS activation was proposed based on a quenching experiment and an electron paramagnetic resonance (EPR) test. The results confirmed that the superior catalytic performance of CoSx by PMS activation could be contributed to the hollow structure and the effective recycling of Co3+/Co2+ and S2-/S-2(2-). The as-prepared hollow amorphous CoSx cages could provide an effective catalyst for PMS activation towards wastewater/water treatment.