Photocatalytic degradation of rhodamin B and diclofenac sodium on hollow hierarchical microspheres of BiOBr modified with sepiolite and polyvinyl pyrrolidone (PVP)

A novel hollow PVP/AS/BiOBr hierarchical microsphere was successfully fabricated with surface modifications of acidized sepiolite (AS) and polyvinyl pyrrolidone (PVP). The structure, morphology and optical properties of the PVP/AS/BiOBr were systematically characterized. The degradation of rhodamine B (RhB) and diclofenac sodium aqueous solution were studied using this composite photocatalyst to determine the optimal blending rate of AS (6%). The result also indicated that the photocatalytic activity of PVP/AS/BiOBr photocatalysts were superior to that of AS/BiOBr. The enhanced activities of PVP/AS/BiOBr could be attributed to the hollow structure, the improved visible light absorption, the effective separation of photogenerated electron-hole pairs and narrowing band-gap. In addition, the possible photocatalytic degradation pathways of PVP/AS/BiOBr were also analyzed through tracking the degradation by-products. After consecutive degradation experiments, the degradation performance and the catalyst structure both remained unchanged, highlighting the excellent stability and reusability of this novel catalyst.