Efficient degradation of tetracycline over vacancy-modified Cu-doped Bi2O2S via peroxymonosulfate activation and photocatalysis

Herein, Cu-doped Bi2O2S catalysts with abundant oxygen vacancies (abbreviated Cu/BOS-OV) were prepared by calcining one-step hydrothermally synthesized Cu-doped Bi2O2S in a tube furnace. The photodegradation efficiency of tetracycline (TC, 15 mg L-1) over Cu/BOS-OV reached 79% under visible light owing to the introduction of impurity bands by Cu doping and oxygen vacancies, improving the separation efficiency of photogenerated carriers. However, the Cu/BOS-OV catalyst achieved an efficiency of 90.4% for 30 mg L-1 TC degradation within 30 min due to peroxymonosulfate (PMS) activation by oxygen vacancies and copper ions. The intermediates of TC degradation were analyzed by LC-MS, and the possible decomposition process of TC was proposed. The free radical trapping and ESR experiments showed that center dot O-2(-), O-1(2), and center dot OH/SO4 center dot- participated in the degradation of TC. Furthermore, the free energy diagram of HSO5- dissociation and center dot OH/SO4 center dot- desorption processes indicated that the enhanced PMS activation efficiency toward TC degradation was contributed by the decreased adsorption energy and increased O-O bond length of HSO5- on Cu/BOS-OV. This study provides good application prospects for removing organic contaminants based on photocatalysis and PMS activation technology.