Donnan dialysis and electrodialysis as viable options for removing bromates from natural water

Dorman dialysis with an anion-exchange membrane and electrodialysis were used for removing bromate ions from natural water. Donnan dialysis with the Selemion AMV membrane provided total bromate removal from water containing 50 mu g BrO3-/L at a salt concentration in the receiver of 100 mM NaCl. The exchange of bromates for chloride ions was concomitant with the exchange of associated anions: sulfates (93% efficiency) and bicarbonates (73% efficiency). Donnan dialysis with the Neosepta ACS membrane (which is characterized by a compact surface structure) also provided total removal of bromates, but the efficiency with which SO42- and HCO3- were exchanged for chloride ions was far below that achieved with Selemion AMV (3% and 47%, respectively). Electrodialysis with standard ion-exchange membranes, Neosepta AMX/CMX, was less efficient at removing bromates (83%), but was able to reduce their concentrations in the treated water (8.8 mu g/L) to a level lower than the maximum admissible value for potable water (10 mu g/L). The efficiency of bromate removal by electrodialysis can be enhanced using the mono-anion-selective membrane Neosepta ACS, which augments the extent of removal to 94%, the concentrations of bromates in the treated water being as low as 3.3 mu g/L. (C) 2011 Elsevier B.V. All rights reserved.