Solar light-driven photocatalytic destruction of cyanobacteria by F-Ce-TiO2/expanded perlite floating composites

A series of efficient solar light-driven F-Ce-TiO2/expanded perlite (EP) floating photocatalysts were successfully synthesized using a facile sol-gel method and applied as algaecides in eutrophic waters. The as-synthesized photocatalysts were characterized by means of XRD, FESEM/EDX, TEM, N2 adsorption/desorption, XPS, UV–vis DRS and PL spectrum. The results show that F-Ce-TiO2/EP has a honeycomb-like structure with F-Ce co-doped TiO2 particles distributed on EP surface. Calcination temperature can greatly affect the doping status, specific surface area and photoelectric properties of F-Ce-TiO2/EP. Among the synthesized photocatalysts, those calcined at 450°C (i.e., F-Ce-TiO2/EP450) exhibited the highest photocatalytic activity. The photocatalytic destruction process could be described by the modified Chick–Watson kinetic model and Hom kinetic model. F-Ce-TiO2/EP450 can achieve the algal cells removal rate of 98.1% within 9h. The algal cell walls obviously damaged in this process. Following the damages, the electron transfer in water-water cycle was also inhibited, thereby accelerating the death of algal cells with the accumulation of the reactive oxygen species (ROS). In addition, microcystin-LR (MC-LR) and metabolic products proved to be effectively removed by photocatalytic oxidation during the algal destruction process. After three consecutive cycles, the removal rate of algal cells can still achieve 88.7% by F-Ce-TiO2/EP450, indicating the F-Ce-TiO2/EP photocatalyst has good reusability and stability.