Inactivation of Microcystis aeruginosa by peroxydisulfate activated with single-atomic iron catalysis: Efficiency and mechanisms

Harmful algal blooms caused by cyanobacteria in drinking water have posed serious threats to destroy aquatic ecosystems, and the toxins they produce are harmful to human and animal health. Herein, the feasibility of removing Microcystis aeruginosa (M. aeruginos) and microcystin-LR (MC-LR) by free radicals produced by simple-atomic iron-doped g-C3N4 (Fe-g-C3N4)-activated peroxydisulfate (PDS) was studied. Pristine g-C3N4 and three kinds of Fe-g-C3N4 with different compositions were successfully synthesized and characterized. When the initial algae density was 2.5 x 10(6) cells.mL(-1), approximately 96.25 % of M. aeruginosa cells were inactivated with 2.0 g.L-1 Fe-g-C3N4 and 4.0 mM PDS under the conditions of pH 7.0, and MC-LR could also be effectively degraded. The activated system can effectively remove M. aeruginosa, and MC-LR was evaluated for its morphological characteristics, cell membrane integrity and microcystin degradation. In addition to the widely recognized reaction species (SO4 center dot- and center dot OH), singlet oxygen (O-1(2)) was another predominant radical for destroying the cell structure and removing MC-LR. The materials can be well recycled, and a possible removal mechanism was proposed. This work shows that the Fe-g-C3N4-activated PDS system is an environmentally friendly and efficient technology for algae removal and algal toxin reduction.