Electrochemically driven inactivation of harmful cyanobacteria assisted with the visible light photocatalyst of CeO2-Fe3O4-CQDs

Abstract

The application of photoelectrocatalysis in the inactivation of algae is attracting growing attention. In this study, CeO₂-Fe₃O₄-carbon quantum dots (CQDs) were prepared as particle electrodes to assess their effectiveness in inactivating cyanobacteria within a three-dimensional (3D) electrochemical system under visible light. The results showed that both algal cells and extracellular organic matter (EOM) could be efficiently removed. The incorporation of 10 mg/mL CQDs significantly boosts the efficiency of photoelectrocatalysis under the optimal conditions, where the CeO₂-Fe₃O₄-CQDs concentration is 0.20 g/L, j = 21 mA/cm², under a neutral pH. Notably, the CeO₂-Fe₃O₄-CQDs exhibit favorable electrochemical catalytic performance, outstanding photocurrent responsiveness, and efficient magnetic separation (for recyclability). The coexistence of Ce³⁺ and Ce⁴⁺ species gives rise to the formation of a redox couple (Ce³⁺/Ce⁴⁺) at the interface of CeO₂, thereby demonstrating favorable performance in terms of oxygen release and storage capabilities. The activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) confirm the apoptosis of algal cells. Hydroxyl radicals (•OH) and singlet oxygen (¹O₂) are participated in the algae inactivation process, with ¹O₂ playing a more prominent role. Our research clarifies the complex mechanisms of algal apoptosis and promotes practical algae inactivation from wastewater.