First, I have to qualify the answer by indicating that you did not provide any additional information about the liquid in which the Bromium ion was dissolved, other than it was water.

Bromium can, depending upon pH, be stripped from water by aeration. That is the easiest and cheapest method. Depending upon the amount of Bromium in the air used for stripping, you can probably get the Bromium concentrations down to well under 0.1 mg/l, and possibly down to non-detect levels.

If you need to get the Bromium out with high assurance, try using silver or Mercury salts at the collection agent. The precipitation reaction with Silver is very good. (Ksp Hg2Br = 6 × 10^-23, sand the solubility with Silver is also very good: AgBr    0.000014 g/100 gm of water. (0.14 mg/l if I have correctly placed the decimal.)

If that's too expensive, consider hydroxyl ion exchange. That should replace the Bromium with OH ions and it will raise the pH.  It can be a part of a full deionization of the water, or just a part of an anion exchange column.  The advantage of an hydroxyl exchange resin is that you back wash it with Sodium hydroxide and get a fluid of NaBr out.