Enhanced degradation of tetracycline hydrochloride using photocatalysis and sulfate radical-based oxidation processes by Co/BiVO4 composites

The Co/BiVO4 composites were prepared by wet impregnation method and used to combine photocatalysis and sulfate radical-based oxidation processes for degradation of tetracycline hydrochloride. The effect factors including the mass percentage of cobalt and peroxymonosulfate (PMS) concentration were investigated in detail. The tetracycline hydrochloride solution with an initial concentration of 40 mg/L could be completely degraded within only 25 min in Co/BiVO4 + Vis + PMS system. By cyclic degradation experiment, as-prepared Co/BiVO4 composites had good reusability and stability. Free radicals quenching experiment indicated that SO4-center dot and (OH)-O-center dot played an important role for degradation of tetracycline hydrochloride. We confirmed the redox cycle of Co2+/Co3+ during the PMS activation process by X-ray photoelectron spectroscopy. Based on the above results, a possible enhanced reaction mechanism was proposed.