Electrocatalytic reduction of bromate ion using a polyaniline-modified electrode: An efficient and green technology for the removal of BrO3− in aqueous solutions

The electrocatalytic reduction of bromate ion (BrO3−) was investigated in a three-electrode system using polyaniline (PANI) as the electrode material. Bromate ion reduction and Br− removal were observed during electrochemical treatment because of the catalytic and doping capabilities of the PANI film. BrO3− removal efficiency in the 0.10 mol L−1 Na2SO4 supporting electrolyte achieved 99% at pH 7 in 25 min, with no bromide ion detected in the solution. Optimal removal was found in pH range 6–7, and the pH of the solution had a significant impact on bromate reduction. A reduction mechanism was also discussed by analyzing the cyclic voltammograms of the reduction process and X-ray photoelectron spectra of the main elements (N 1s and Br 3d) on the PANI surface. We propose that during the electrocatalytic reduction process, bromate is reduced to bromide because of the loss of electrons from the nitrogen atoms on the PANI chains. The doping of the resultant Br− ions in the PANI film has an important role in avoiding further oxidation of Br− to BrO3−. The used PANI film can be regenerated by de-doping the Br− ions with a 0.5 mol L−1 H2SO4 solution. Thus the process can be considered efficient and green.