Cobalt-Doped Carbon Nitride for Efficient Removal of Microcystis aeruginosa via Peroxymonosulfate Activation

Heterogeneous persulfate activation is an advanced technology for treating harmful algae in drinking water sources, while it remains a significant hurdle in the efficient management of cyanobacterial blooms. In this study, super-dispersed cobalt-doped carbon nitride (2CoCN) was prepared to activate peroxymonosulfate (PMS) for simultaneous Microcystis aeruginosa inhibition and microcystin (MC-LR) degradation. When the initial PMS and 2CoCN concentrations were 0.3 g/L and 0.4 g/L, respectively, the efficiency of algal cell removal reached 97% in 15 min, and the degradation of MC-LR reached 96%. Analyses by SEM, TEM, and EEM spectra revealed that the reaction led to changes in algal cell morphology, damage to the cell membrane and cell wall, and the diffusion of thylakoid membranes and liposomes. The activities of antioxidant enzymes (superoxide dismutase and catalase) and antioxidants (glutathione) in algal cells generally increased, and the content of malondialdehyde increased, indicating severe damage to the cell membrane. Radical capture experiments confirmed that singlet oxygen (¹O₂) was the key species destroying algal cells in the 2CoCN/PMS system. The 2CoCN/PMS system was effective in removing M. aeruginosa within a wide pH range (3-9), and 2CoCN had good reusability. Additionally, three degradation products of MC-LR were identified by LC-MS/MS analysis, and a possible mechanism for the inactivation of M. aeruginosa and the degradation of MC-LR was proposed. In conclusion, this study pioneered the 2CoCN/PMS system for inhibiting M. aeruginosa and degrading microcystin, aiming to advance water purification and algae removal technology.