Question

What are cation and anion exchangers?

Answer 1

Ion-exchange resins are insoluble, cross-linked, long chained organic polymer with a microporous structure. The functional group attached to the chains are responsible for the ionexchange properties. Resins containing acidic functional groups like -COOH, -S0₃ H etc. are capable of exchanging their H+ ions with other cations which come into their contact. Those containing basic functional groups like -NH₂ =NH as hydrochloride etc are capable of exchanging their anions with other anions which come into their contact. The ion exchange resins are classified as follows:

1. Cation exchange resins
These are mainly styrene divinyl benzene copolymer which on sulphonation or carboxylation become capable of exchanging their hydrogen ions with the cations in the water.

2. Anion exchange resins.
These are styrene divinyl benzene or amine formaldehyde copolymer which contain amino or Quaternary ammonium or quaternary phosphonium or tertiary sulphonium groups as an integral part of the resins matrix. These after treatment with dil. NaOH solution , become capable of exchanging their OH- anions with anions in water.