When the concentration of salt increases, the following things happen for anion and cation exchange resins:
(a) For an anion exchange resin:
- As the concentration of salt increases, more anions from the salt will bind to the positively charged sites on the resin, displacing the original anions that were bound.
- This means that the resin will release more of the original anions that it was removing from the solution.
- In effect, an anion exchange resin works less efficiently at removing anions from the solution as the salt concentration increases.
(b) For a cation exchange resin:
- As the concentration of salt increases, more cations from the salt will bind to the negatively charged sites on the resin, displacing the original cations that were bound.
- This means that the resin will release more of the original cations that it was removing from the solution.
- In effect, a cation exchange resin works less efficiently at removing cations from the solution as the salt concentration increases.
So in summary, for both anion and cation exchange resins, as the salt concentration increases, the resin releases more of the ions that it was originally meant to remove, making it work less efficiently. The increased concentration of ions in the salt compete for the binding sites on the resin.