Photocatalytic inactivation of algae using floating visible-light-responsive photocatalyst Ag₂CrO₄-g-C₃N₄-TiO₂/modified expanded perlite

Based on Al₂O₃ modified expanded perlite (mEP), floating visible-light responsive photocatalysts Ag₂CrO₄-g-C₃N₄-TiO₂/mEP were prepared via a sol-gel-impregnation deposition method. The synthesized photocatalysts were characterized using XRD, N₂ adsorption/desorption, FESEM-EDS, XPS and UV-vis DRS. The results show that the concentration of Ag₂CrO₄ has influence on the crystal structure and specific surface area of the photocatalysts. High concentration of Ag₂CrO₄ could form agglomerated particles on the surface of the photocatalyst which are not conductive to the adsorption and photocatalytic inactivation of algae. When the theoretical molar ratio of Ag₂CrO₄/TiO₂ is 0.05 and the initial algal cell concentration of Microcystis aeruginosa is 2.75×10⁶ cells/mL, the removal rate of algal after adsorption for 8 h was 10.3%. Under the synergistic effect of adsorption and photocatalysis, the removal rate of algal could reach 81.88%. The inactivation of algae cell mainly ascribed to the attack by the photo-generated holes (h⁺). The removal rate of algae could reach to 72.19% after three successive cycles which indicated the stability of the photocatalst.