Synergistic charge separation and magnetic recovery in a noble-metal-free Fe3O4/TiO2/Bi photocatalyst for bromate reduction

Bromate (BrO 3 − ), a carcinogenic and regulated disinfection by-product, poses a persistent challenge to drinking water safety due to its high solubility and chemical stability. In this work, a noble-metal-free Fe 3 O 4 /TiO 2 /Bi photocatalyst was successfully prepared and subsequently applied for BrO 3 − reduction under ultraviolet light. The ternary composite design enables cooperative functionality among the components, where Fe 3 O 4 facilitates charge transfer and magnetic separability, Bi 0 acts as a hole scavenger, and TiO 2 serves as the primary photoactive material. Characterization results confirmed the successful formation of the heterostructure with enhanced charge separation properties. The composite containing 5 wt% Bi exhibited the highest activity, achieving 99 % BrO 3 − removal within 25 min at pH 7.0, with a pseudo-first-order rate constant of 0.185 min −1 , which is 11.8 times that of pure TiO 2 . The enhanced photocatalytic performance is ascribed to the synergistic effect between Bi, Fe 3 O 4 and TiO 2 . Bi 0 nanoparticles functioned as hole acceptors to suppress recombination, while Fe 3 O 4 facilitated electron transport and provided magnetic separability. The photocatalyst retained high activity over five consecutive cycles with negligible metal leaching and performance loss. In addition, its effectiveness was verified in tap water containing typical inorganic ions and dissolved organic matter, demonstrating moderate inhibition but maintaining BrO 3 − reduction capability. This study provides a cost-effective, magnetically recoverable, and noble-metal-free photocatalyst with improved charge separation efficiency and recovery feasibility, offering practical potential for BrO 3 − mitigation in drinking water treatment.