Trace-Cu(II)/CaO₂ pre-oxidation coupled with coagulation for algal elimination: A triple-mechanism cascade involving...

Harmful algal blooms release microcystins and other metabolites that threaten aquatic ecosystems and human health. Conventional removal methods often induce cell lysis and are affected by matrix interference in natural waters, limiting their practical applicability. A sequential process coupling trace-Cu(II)/CaO₂ pre-oxidation with PAC coagulation was developed for efficient algal removal. The system removed 98.5% of M. aeruginosa from lake water. During the 10-min pre-oxidation stage, trace-Cu(II)/CaO₂ effectively degraded extracellular microcystin-LR (MC-LR) and the dissolved organic matter (DOM) surrounding algal cells, thereby weakening electrostatic repulsion and enhancing coagulation efficiency. The coupled process generated Cu(III), •OH, •O₂^-, and ¹O₂ within the cells, which led to functional cell death without severe membrane rupture. Conventional molecular dynamics (MD) simulations confirmed the stability of a representative pentameric cation-channel model, and steered molecular dynamics (SMD) further showed that Cu²⁺ and H₂O₂ could be guided through its pore under an applied axial bias, supporting the physical plausibility of channel-mediated intracellular access. Mechanistically, OH^- generated during CaO₂ hydrolysis promoted the Cu(II)/Cu(I)/Cu(III) catalytic cycle and sustained reactive species production, with Cu(III) as the dominant contributor to functional inactivation (68.5%). These findings establish an innovative and practical strategy for the safe and effective removal of algae from contaminated natural waters.