Selective production of singlet oxygen for harmful cyanobacteria inactivation and cyanotoxins degradation: Efficiency and mechanisms

Abstract

Knowledge about the impact of singlet oxygen (¹O₂) on the characteristics and inactivation of harmful cyanobacterial organic matter is limited. In this study, the feasibility of using an improved single-iron doped graphite-like phase carbon nitride catalyst (FeCN) to activate peroxymonosulfate (PMS) catalytic production of ¹O₂ to inactivate four harmful cyanobacteria was investigated. The inactivation efficiencies at 30 min were 92.77%, 66.84%, 91.06%, and 93.45% for Microcystis aeruginosa (M. aeruginosa), Nodularia harveyana, Oscillatoria sp., and Nostoc sp., respectively. This was associated with adjusting experimental parameters, such as the FeCN and PMS doses and initial pH, to obtain the maximum ¹O₂ yield. The quenching experiment results and electron paramagnetic resonance spectra showed that ¹O₂ generated via the non-radical pathway might play a dominant role in inactivating harmful cyanobacteria and degrading harmful algal toxins (Microcystin-LR and Nodularin). In addition, the FeCN-PMS system not only effectively destroyed the integrity of harmful cyanobacterial cells but also effectively degraded cyanobacterial toxins, thereby preventing severe secondary contamination by cell rupture. A possible removal mechanism was proposed. This reveals the potential of ¹O₂ to simultaneously inactivate harmful cyanobacteria and degrade harmful cyanobacterial toxins.

Keywords: Cyanobacterial toxins; Degradation pathway; Microcystis aeruginosa; Peroxymonosulfate; Singlet oxygen.