Effects of pH on the Photocatalytic Activity and Degradation Mechanism of Rhodamine B over Fusiform Bi Photocatalysts under Visible Light

In this study, fusiform bismuth (Bi) was synthesized, and its photocatalytic performance, degradation mechanism, and pathways for removing rhodamine B (RhB) at different pH levels were investigated. Additionally, the morphologies, structural characteristics, surface electronic states, optical properties, active species, and potential degradation pathways of RhB over the fusiform Bi were analyzed. The comparison of the results before and after RhB degradation using the fusiform Bi revealed the formation of a Bi/BiOCl heterojunction photocatalyst. At pH 2.0, 3.0, 5.0, 7.0, and 9.0, the heterojunction exhibited excellent photocatalytic activity, with RhB removal efficiencies of ~97%, 96.7%, 72.6%, 53.5%, and 27.6%, respectively. Moreover, total organic carbon and chemical oxygen demand analyses were performed to evaluate the mineralization rates of RhB with the fusiform Bi at pH 3.0 and 7.0. Furthermore, the effects of catalyst content, initial RhB concentration, light source distance, inorganic anions, and reactant temperature on the photocatalytic performance of the fusiform Bi were investigated. Additionally, the types of active species and potential photocatalytic mechanisms for RhB degradation over the fusiform Bi at different pH levels (3.0 and 7.0) were elucidated. The appropriate degradation pathways were identified via liquid chromatography–mass spectrometry at pH 3.0 and 7.0.