Investigation of bromide removal and bromate minimization of membrane capacitive deionization for drinking water treatment.

The ubiquitous bromide (Br-) poses a challenge to current drinking water treatment schemes due to the formation of brominated disinfection by-products, especially bromate (BrO3-). A cost-effective and energy-efficient technology to remove Br- before disinfection is highly desired. In this work, the application of membrane capacitive deionization (MCDI) for the removal of Br- and BrO3- minimization for drinking water treatment was systematically investigated. Results showed that the removal of Br- by MCDI followed the pseudo-second-order kinetics, in which kinetics was faster at lower Br- concentration. Additionally, Br- displayed a preferential electrosorption over Cl- in MCDI despite the relatively smaller amounts. Due to high removal performance of Br-, 99.49% of BrO3- minimization can be achieved. Moreover, the presence of humic acid (HA) had a negative effect on the removal of Br- and BrO3- minimization. However, Br- could be more preferentially removed than Cl- in the presence of HA due to the weak interaction with HA. Finally, by treating an actual surface water sample, it was found that the removal rate of Br- was 91.80%, and 83.97% of BrO3- minimization can be achieved. BrO3- concentration of effluent meets the control standard. Overall, these results prove the feasibility of MCDI for practical drinking water treatment.