Visible-Light-Driven Photocatalytic Degradation of Dyes and Ciprofloxacin Using Coral-like β-Bi₂O₃

Contamination of water bodies caused by increasing human and industrial activities poses a serious threat to human health and environmental sustainability, highlighting the need for green and efficient remediation strategies. In this study, a facile hydrothermal synthesis followed by controlled calcination was developed to fabricate phase-pure α- and β-Bi₂O₃ with a unique coral-like hierarchical morphology as visible-light-active photocatalysts. Phase selectivity was achieved by tuning the calcination temperature, yielding pure β-Bi₂O₃ while preserving the hierarchical structure. Optical characterization revealed a narrower bandgap for β-Bi₂O₃ (2.24 eV) compared to α-Bi₂O₃ (2.75 eV), favoring visible-light absorption. Photocatalytic performance was evaluated using Rhodamine B as a model pollutant, where β-Bi₂O₃ achieved complete degradation within 240 min, significantly outperforming α-Bi₂O₃. The degradation followed pseudo-first-order kinetics, and the catalyst exhibited excellent robustness and reusability. To further demonstrate applicability toward persistent contaminants, Methyl Orange (MO) and the antibiotic ciprofloxacin (CIP) were employed as additional model pollutants. The coral-like β-Bi₂O₃ showed high visible-light activity toward MO, including complete removal under acidic conditions. Moreover, efficient degradation of CIP was achieved at neutral pH, with 90% removal within 150 min and complete degradation after 240 min. Overall, these results highlight coral-like β-Bi₂O₃ as an efficient standalone photocatalyst for visible-light-driven degradation of dye and pharmaceutical pollutants.