Enhanced Photocatalytic Reduction of Carcinogenic Bromate in Water Using Self-Assembled Integration of Titanium Dioxide and Alpha-Sulfur

Bromate (BrO₃⁻), a carcinogenic disinfection by-product, presents significant health risks, requiring its effective removal from drinking water. Photocatalysis offers a promising method for reducing bromate to bromide (Br⁻). In this study, we developed a novel composite material, aS/TiO₂ (aSTO), integrating TiO₂ nanoparticles onto the surface of alpha-sulfur (aS) to enhance reduction under UV irradiation. The aSTO composite, with a bandgap energy of 2.69 eV, addresses the limitations of pure TiO₂, such as limited UV absorption and agglomeration, which reduce its photocatalytic efficiency. We conducted photocatalytic experiments to compare the performance of aSTO, TiO₂, and aS in bromate reduction. The experiments were conducted under varying conditions, including different temperatures, pH levels, and the presence of co-existing anions such as nitrate and phosphate. Recyclability tests were performed to assess the material’s reusability. The aSTO composite outperformed both TiO₂ and aS, achieving up to 20 μmol/g of bromate removal at a dosage of 1500 mg/L over 120 min, with significantly higher bromate removal compared to TiO₂ (~ 15 μmol/g) and aS (~ 5 μmol/g). The reduction of bromate was accompanied by the stoichiometric formation of bromide, confirming the efficient conversion process. Its efficiency improved under acidic conditions and elevated temperatures. Although co-existing anions slightly inhibited the process, aSTO remained highly effective. Recyclability tests confirmed that aSTO retained its catalytic performance and structural integrity over multiple cycles. Overall, aSTO shows great potential as a reusable photocatalyst for sustainable bromate removal in real-world water treatment applications.