Development of composite films of bismuthates immobilized in alginate biopolymers for application in photocatalysis under visible light

The immobilization of photocatalysts in films represents an alternative for mitigating the drawbacks associated with suspensions, such as deactivated catalyst separation from the reaction medium. The present study sought to help prevent immobilization from harming the environment through the use of biodegradable alginate films as a matrix. Furthermore, the study employed bismuth-based photocatalysts active in the visible spectrum, making greater use of solar energy. Employing the sol-gel method, the photocatalysts NaBiO3, BiOI, Bi2MoO6, and Bi2WO6 were immobilized to form films, characterized using X-ray diffraction, surface morphology, point of zero charge (pHPZC), and thermogravimetric analysis. The photocatalytic activity of the films was measured by batch assay, using methylene blue and phenol as model molecules. The alginate and NaBiO3 films showed high efficacy for degrading organic pollutants, while BiOI exhibited the highest adsorption rate. The Bi2MoO6 and Bi2WO6 films offered superior stability and efficiency for up to three reuses. The results demonstrated that, by immobilizing photocatalysts in alginate films, photocatalytic activity can be preserved and particle carryover prevented, representing an advancement in sustainable technologies for treating organic pollutants in aqueous environments.