Nonradicals-dominated peroxymonosulfate activation of g-C3N4/CeO2 floating beads for enhanced inactivation of M. aeruginosa: Performance studies and mechanistic insights

Abstract

Microcystis aeruginosa (M. aeruginosa) is a typical harmful algal associated with eutrophication, making the study of its inactivation critical for water restoration. In this research, g-C₃N₄/CeO₂ composites with S-scheme heterojunctions were synthesized and incorporated into sodium alginate (SA) to successfully prepare photocatalytic gel beads with floating capabilities. A photocatalytic persulfate (g-C₃N₄/CeO₂/SA/Vis/PMS) system was developed to systematically investigate the algal inactivation efficacy of floating catalysts. The g-C₃N₄/CeO₂ S-scheme heterojunctions significantly enhanced algal inactivation efficiency, achieving up to 96.65 % inactivation within 80 min. The alterations in algal cell properties during the inactivation process were examined. A decrease in the content of algal bile proteins indicated a disruption of the photosynthetic system within the algal cells, while an increase in the concentrations of K⁺, Ca²⁺, and Mg²⁺ suggested further disruption of algal cell membranes and walls. Additionally, three-dimensional fluorescence spectroscopy (EEM) results indicated that the extracellular organic matter produced during the rupture of algal cells was degraded into humic acid-like substances. The energy bands and electronic structure of g-C₃N₄/CeO₂ were calculated using density functional theory (DFT) to analyze the electron transfer mechanism involved in this process, which is consistent with the S-scheme electron transfer pathway. The effective inactivation of M. aeruginosa was successfully achieved through the combined action of the non-radical ¹O₂,·O₂^–, and h⁺ generated during the photogenerated carrier transfer process. This approach offers a promising strategy for the management of algal blooms in eutrophic waters.