Influence of parameters on the photocatalytic bromate removal by F-graphene-TiO₂

Batch experiments of photocatalytic bromate removal by F-Graphene-TiO₂ (FGT) were conducted under different reaction conditions. The dosage of FGT, initial bromate concentration, pH, water temperature, and the coexisting substances including common halogen anions, oxyacid ion and humic acid factors affecting the efficiencies of bromate reduction were systematically discussed. Increasing the temperature or the dosage of FGT increased the bromate removal efficiency. The efficiency of bromate reduction was significantly increased by decreasing the pH from 6 to 5, because the isoelectric point of FGT samples was found at a pH of approximately 6.0. The coexisting anions, such as chloride ion, bromide ion, nitrate, chlorate and sulfate, had modest inhibitory effects on bromate removal under the experimental conditions, and the inhibitory effect from fluoride ion was relatively larger. These observations indicate that bromate reduction by FGT is a surface-mediated process, the competitive consumption of photogenerated electrons and the competitive adsorption by coexisting anions on FGT samples probably lead to the decreasing of bromate reduction efficiency. And the increase of appropriate dosage can partly eliminate the influence of coexisting ions. Over 90% of 100 μg/L bromate could be removed with a 0.05 g/L dosage of F_1.0G_0.1T in 15 min under UV irradiation at intensity of 26 μW/cm² and pH of 5.2. Moreover, the specific roles of photogenerated electron-hole pairs and the mechanism of photocatalytic bromate reduction were also discussed. These findings suggest that photocatalytic bromate removal by FGT/UV can be a promising method for bromate from water.