In this work, an electrochemical (EC) method was studied for oxidation of bromide (Br-) in simulated coal-fired power plant wastewater. Bromide is often elevated in such waste waters and can become an environmental problem if released in high concentrations as a precursor to toxic brominated organic compounds. Br- can be oxidized into removable elemental bromine (BrE) and/or recalcitrant and carcinogenic bromate (BrO3-). The results suggested that lower pH was favorable for BrE generation while higher pH was favorable for BrO3- generation, due to proton inhibition of both BrO3- generation and anodic water oxidation. The ratios between first-order kinetic coefficients for BrO3- (kBromate) and BrE (kBromine) generation were 5.6�10-4 and 2.2�10-3 at pH 1 and pH 3, respectively, with EC current at 350 mA and initial chloride (Cl-) of 62.75 mg/L. Cl- contributed to the generation of both BrE and BrO3- through electrochemically generated free chlorine; however, such contribution to BrE generation may be compromised by insufficient proton inhibition of anodic water oxidation at higher pH. At pH 1 and 350 mA, the kBromate/kBromine values decreased from 5.6�10-4 to 4.7�10-4 when initial Cl- increased from 62.75 to 125.5 mg/L. In comparison, at pH 3, the kBromate/kBromine values increased from 2.2�10-4 to 3.1�10-4 when other conditions were constant.  Generation of BrO3- at both pH 1 and 3 increased with EC current. BrE generation increased with EC current (from 100 to 350 mA) significantly at pH 1 (2.4�10-2 to 7.2�10-2 1/min), and slightly at pH 3 (1.1�10-2 to 1.2�10-2 1/min), due to insufficient proton inhibition of anodic water oxidation. It has also been demonstrated that lower pH and current were favorable to enhance the efficiency for bromate free BrE generation. This work establishes an approach for controllable oxidation and effective removal of Br- and, potentially, other halogen anions.

Kinetic study of bromide removal through controllable electrochemical oxidation

247th National Meeting (2014)

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