Bromate ion removal by electrochemical reduction using an activated carbon felt electrode.

The electrochemical removal of bromate ion (BrO3-) was investigated using a two-compartment electrolytic flow cell with activated carbon felt electrodes. Bromate ion removal and corresponding Br- increase was observed during electrochemical treatment whereas the activated carbon felt used possessed no catalytic effect on BrO3- reduction. The BrO3-reduction rate was accelerated at lower pH, which also improved current efficiency. Transition of chemical equilibrium of the BrO3- reductive reaction was theorized as the reason for pH dependency of the BrO3- reduction.The electrochemicaltreatment of BrO3- -contaminated tap water resulted in a rapid decrease in BrO3- concentration from 100 to 48 microg/L with a contact time of 9.2 s. Thus, electrochemical treatment allowed the rapid removal of BrO3-. However, competitive hydrogen evolution at the cathodes reduced current efficiency of BrO3- reduction. Standard potentials of corresponding anodic and cathodic reactions suggested that electrolysis at a terminal voltage less than 1.229 V would promote BrO3- reduction without hydrogen evolution. However, the activated carbon felt electrode did not function well at a terminal voltage of 1.0 V. Accordingly, the development of an electrode material with high catalytic activity will be required to improve current efficiency.