Ion-exchange membrane processes for Br ~- and BrO3 ion removal from water and for recovery of salt from waste solution

摘要

The applicability of Donnan dialysis with an anion-exchange membrane for bromide and bromate ion removal was studied. The rate of bromide, bromates and associated ion (HCO_3~- SO_4~(2-)) removal with the use of Selemion AMV and Neosepta ACS membranes at different salt concentrations in the receiver was analyzed. The process of anion exchange through the Neosepta ACS membrane allows effective bromides removal (90%), at a relatively low salt concentration in the receiving solution (100 mM NaCl). In order to achieve a similar effect of bromide removal by using the Selemion AMV membrane (91%) three times higher salt concentration in the receiver is required. Moreover, the potential of electrodialysis to recover NaCl from waste receiving solution after the Donnan dialysis and the usefulness of recovered solution to remove bromides and bromates was examinated. The best results of the process, i.e. required salt concentration in the concentrate (100 mM NaCl), and possible minimum contamination of the ballast ions (Br~- or BrO_3~- and HCO_3~- and SO_4~(2-)) were obtained at a current density of 50 A/m~2. Depending on a modification method of the recovered salt solution, it was obtained from 61 to 78% removal of bromides and from 79 to 86% removal of bromates.