Bromide removal from chloride solutions by combined electrolysis and anion exchange processes

Abstract

Selective bromide removal from chloride solution was carried out by combined electrolysis and anion exchange processes. First the bromide was oxidized to bromine in an electrolysis cell. Then Br2 was combined with Br– and or Cl– to form complex anions (Brx Cly– ) mainly as Br3–, Br2Cl– or BrCl2– that have high selectivity to anion exchange resins. The results showed that the separation factor of Br increased from 2.5 when Br– was not oxidized to about 30–50 when oxidation was applied. Moreover, the total Br capacity increased from about 3 to more than 9 meq. Br/g. The Br capacity of the resin depends on chloride and bromide concentrations in solution, probably because they influence the transition of Br3– to Br2Cl– and to BrCl2–. Regeneration occurred after reducing the bromine with NaHSO3 to bromide. The concentration of bromide in the column regeneration solution was about hundred times higher than in the feed solution.