Natural Pyrite as a Sustainable Mineral Reagent for Rapid Removal and Detoxification of Microcystis aeruginosa Blooms: Aggregation by Iron Oxyhydroxides and Oxidation with In Situ Fenton-Like • OH

Microcystis aeruginosa (M. aeruginosa) , a prevalent cyanobacterial species in eutrophic waters, threatens aquatic ecosystems and public health through bloom formation and toxin release. This study investigates the use of natural pyrite for controlling M. aeruginosa , examining both removal efficiency and underlying mechanisms. Within 240 min of pyrite treatment, turbidity, cell density, and chlorophyll a (Chl-a) decreased significantly to 0.94 ± 0.06 NTU, 0.08 ± 0.01 × 10 6 cells / mL , and 8.2 ± 0.6 μ g / L , corresponding to removal rates of 93.8%, 97.9%, and 98.2%, respectively, effectively ending eutrophic conditions. Mechanistic analyses indicated that FeOOH and Fe 2 O 3 , formed during pyrite oxidation, serve as binding sites that promote M. aeruginosa aggregation and sedimentation. Meanwhile, hydroxyl radicals ( • OH) generated via Fenton-like reactions disrupted cellular integrity and facilitated the degradation of dissolved extracellular organic matters and microcystin-LR (MC-LR). By Day 7, the MC-LR concentration was reduced to 0.37 ± 0.02 μ g / L , below the regulatory limit, thus avoiding secondary pollution. This study demonstrates the potential of pyrite as a sustainable, mineral-based strategy for mitigating M. aeruginosa blooms, offering both theoretical and practical insights for environmentally friendly water remediation.