Flower-like C/CoO/Co3O4 heterostructures with abundant oxygen vacancies for effective peroxymonosulfate activation and tetracycline degradation

The sulfate radical-mediated advanced oxidation processes are emerging as an effective technology for water purification. Herein, flower-like C/CoO/Co 3 O 4 heterojunctions with abundant oxygen vacancies (OVs) were fabricated by a facile method and employed as excellent activators for peroxymonosulfate activation towards tetracycline (TC) degradation. The emerging OVs in C/CoO/Co 3 O 4 not only facilitate electron transfer for accelerating the redox cycle of Co 3+ /Co 2+ but promote the generation of non-radical 1 O 2 involved in TC elimination. Consequently, 99 % of TC (20 mg/L) could be removed by the C/Co-2/PMS system within a period of 80 s, more superior to that of commercial CoO (33 % in 80 s) and Co 3 O 4 (28 % in 80 s), respectively. In addition, the C/Co-2/PMS system displayed excellent activities for different pollutant degradation, such as rhodamine B (99 % in 80 s), congo red (99 % in 80 s), and ciprofloxacin (78 % in 80 s). The quenching experiment together with EPR characterization indicated that the produced SO 4 •- / • OH/ 1 O 2 species participated in TC removal with the sequence of SO 4 •- > 1 O 2  >  • OH. Besides, the effects of catalyst dosage, TC concentration, PMS concentration, inorganic anions and organic matter on TC degradation were studied. The cyclic experiment demonstrated the robust stability of the as-prepared sample. After 7 cycles, the C/Co-2/PMS system can still remain a TC degradation rate of 88 % with low Co (0.05 mg/L) ions leakage. Finally, the possible reaction mechanism of the current catalytic system was explored and discussed in detail.