Cu-doped CoOOH activates peroxymonosulfate to generate high-valent cobalt-oxo species to degrade organic pollutants in saline environments

A Cu doped CoOOH-activated peroxymonosulfate (CoCu10/PMS) process was developed to enable the generation of Co(IV)=O for efficient oxidation of pollutants in saline water. The formation of Co(IV)=O was demonstrated through phenylmethyl sulfoxide (PMSO) probe and 18O-isotope-labeling tests. CoCu10 was synthesized using a simple and scalable co-precipitation method, enabling efficient synthesis at laboratory scale for large quantities (gram level). Cu doping increased the surface hydroxyl density of CoOOH, thereby improving its activation performance. Coordinating with PMS through surface hydroxyls, CoCu10 formed catalyst-PMS complexes, then donated electrons to induce heterolytic cleavage of O–O bonds in complexes, resulting in the formation of Co(IV)=O. At a concentration of 0.2 g/L catalyst and 0.2 mM PMS, 97.7% of tetracycline was degraded within 10 min. CoCu10 maintained stable performance over eight cycles. Thanks to Co(IV)=O, the CoCu10/PMS system efficiently operates under different concentrations of Cl−, HCO3−, NO3−, SO42−, H2PO4− and mixed salt.