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

Tuqiao Zhang,Dingyun Yan,Jiajie Wang,Xiaowei Liu,Lili Wang

doi:10.3390/catal8120652

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.

Highlights

Bromate (BrO3− ) is considered as a carcinogen, and is produced during bromide-containing water treatment processes including chlorination, ozonation, and advanced oxidation [1]
Direct UV photolysis and sulfite/I− reduction showed a slow degradation rate, which can be attributed to the weak absorbance at 254 nm for BrO3− [10] and low reduction potential of sulfite/I− (E(I2 /I− ) = 0.535 V, and E(S(VI)/S(IV)) = −0.94 V [19])
This study examined the potential of an iodide-assisted UV/sulfite process (UV/Sulfite/I− )

Summary

Introduction

Bromate (BrO3− ) is considered as a carcinogen, and is produced during bromide-containing water treatment processes including chlorination, ozonation, and advanced oxidation [1]. One solution is to install household water purifiers to remove BrO3−. The small site occupancy for household water purifiers means that the technologies adopted must remove BrO3− within a short contact time and at high operational cost. The methods of degrading BrO3− from drinking water include activated carbon or resin adsorption [2], electron beam irradiation [3], membrane separation [4], biological reduction [5], zero-valent iron (ZVI) reduction [6], photo [7] or photocatalytic reduction [8], layered double hydroxide reduction [9], advanced reduction

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