Aqueous Bromate Reduction by UV Activation of Sulfite: Fid-Bau Portal

Aqueous Bromate Reduction by UV Activation of Sulfite

Liu, Xiaowei / Zhang, Tuqiao / Shao, Yu

Photoactivation of SO₃²⁻ with UV (254 nm) irradiation was adopted to generate the hydrated electron‐based advanced reduction process, which was used to degrade BrO₃⁻ in water. The second‐order reaction rate constant of BrO₃⁻ with hydrated electron was determined, and the effects of operational parameters (dosage of SO₃²⁻, solution pH, HCO₃⁻, humic acids (HA), and dissolved oxygen (DO)) were evaluated. The transformation intermediates of BrO₃⁻ and SO₃²⁻ were identified and mass balances of bromine and sulfur were checked. Results showed a positive correlation between the removal efficiency of BrO₃⁻ and dosage of SO₃²⁻ (0.5–2.0 mM). Increasing the solution pH from 5 to 9 promoted elimination of BrO₃⁻ because of the pH‐dependent effect of SO₃²⁻ photoactivity, whereas further increasing the pH from 9 to 10 caused no further enhancement. In addition, 1–4 mM HCO₃⁻ exerted about 5% inhibition on BrO₃⁻ destruction, indicating that HCO₃⁻ is a weak inhibitor. The presence of 1.5–4.0 mg L⁻¹ HA deteriorated BrO₃⁻ degradation, while depletion of DO by N₂ bubbling benefitted BrO₃⁻ removal. The balances of bromine and sulfur denoted that the final transformation products of BrO₃⁻ and SO₃²⁻ were harmless SO₄²⁻, bromide, and minor dithionate.