Catalytic ozonation performance and mechanism of nanostructured Ag3PO4/NiAl layered double hydroxide composites for efficient inactivation of Microcystis aeruginosa

Compared to traditional treatment methods, the catalytic ozonation process based on an advanced and reliable ozone generator and highly efficient catalysts has shed new light on treating algal blooms in water bodies. In this study, Ag 3 PO 4 /NiAl-LDH nanocomposites were synthesized by a two-step co-precipitation method, characterized, and applied as ozonation catalysts for the inactivation of Microcystis aeruginosa . Under controlled conditions, the nanocomposite (ANA-10) with an Ag 3 PO 4 : NiAl-LDH weight ratio of 1:10 exhibited excellent catalytic ozonation performance and reusability, effectively achieving a nearly complete algae removal within 60 min. The rate constant of ANA-10 reached approximately 0.0958 min −1 , being 6.4-, 2.8-, and 2.1-fold higher than that of individual O 3 , Ag 3 PO 4 , and NiAl-LDH, respectively. The variations in the physiological properties of the algal cells reflect severe damage and destruction of their cellular morphology, membrane permeability, intracellular and extracellular organics, proteins, and antioxidant system during the ANA-10 catalyzed ozonation process. Electron spin resonance (ESR) and quenching experiments indicated that algae inactivation can be attributed to the formed reactive oxygen species (ROS), such as OH, O 2 − and 1 O 2 . In addition, the mechanism of ROS formation over ANA-10 was clarified and involved Ag 3 PO 4 -assisted enhancement of the redox of Ni 2+ /Ni 3+ and accelerated surface hydroxylation. Overall, this study offers useful insights into the control of harmful cyanobacterial blooms.