Efficient Reduction of Bromate by Iodide-Assisted UV/Sulfite Process

Abstract

Bromate ( BrO 3 − ) residue in drinking water poses a great health risk. Ultra-fast reduction of BrO 3 − , under aerobic conditions, was realized using an ultraviolet (UV)/sulfite process in the presence of iodide (UV/sulfite/iodide). The UV/sulfite/iodide process produced BrO 3 − removal efficiency of 100% at about 5 min with complete conversion to bromide, while UV/sulfite induced 13.1% BrO 3 − reduction under the same conditions. Hydrated electrons, generated from the photolysis of sulfite and iodide, was confirmed as the main contributor to BrO 3 − degradation (77.4% of the total contribution). As the concentration of iodide was kept constant, its presence remarkably enhancing the generation of hydrated electrons led to its consideration as a homogeneous catalyst in the UV/sulfite/iodide system. Sulfite played a role not only as a hydrated electron precursor, but also as a reactive iodine species shielding agent and a regenerant of iodide. Results surrounding the effects on common water quality parameters (pH, bicarbonate, nitrate, natural organic matter, and solution temperature) indicated that preferred degradation of BrO 3 − occurred in an environment of alkaline pH, low-content natural organic matter/bicarbonate/nitrate, and high natural temperature.