Co(CO₃)_0.5(OH)?0.11H₂O as superior peroxymonosulfate activator for ciprofloxacin degradation via co-acting mechanism of low & high-valent cobalt and oxygen vacancy

In this study, oxygen vacancies-rich (OVs-rich) Co(CO3)(0.5)(OH)center dot 0.11H(2)O catalyst was prepared by a hydrothermal process, which was used to activate peroxymonosulfate (PMS) and degrade ciprofloxacin (CIP). Although its specific surface area was only 46.2 m(2) g(-1), the Co(CO3)(0.5)(OH)center dot 0.11H(2)O catalyst exhibited high performance. Under its natural pH, 91.0% of CIP (50 ppm) was degraded and chemical oxygen demand removal reached 70% in 10 min. The rapid degradation reaction followed Behnajady-Modirshahla-Ghnbery kinetic model. The research on catalytic mechanism indicated that three coexisting catalytic pathways resulted in the efficient degradation of CIP. (1) The low-valent Co2+ in Co(CO3)(0.5)(OH)center dot 0.11H(2)O activate PMS to generate four kinds reactive oxygen species such as SO4 center dot-, (OH)-O-center dot, O-2(center dot-) and O-1(2). (2) The dissolved oxygen was adsorbed on Co (CO3)(0.5)(OH)center dot 0.11H(2)O surface and the abundant localized electrons of OVs made them easily endow electrons to O-2, reducing O-2 to O-2(center dot-) and then to O-1(2). (3) The reaction between the Co2+ and PMS resulted in the high-valent Co4+(O) species, which possessed outstanding oxidation ability for CIP degradation.