ION-EXCHANGE RESIN

"A polymeric resin that contains electrically charged fragments (""fixed ions"") permanently attached to the polymer backbone, electrical neutrality is achieved by attached mobile ""counterions"" in the solution phase the resin is immersed into. A practical use of such resin is the removal of unwanted ions from a solution by replacing them with other ions. E.g., a cation exchange resin containing fixed negative charges with attached mobile sodium ions can be used to remove ""hardness"" from water if the calcium and magnesium ions are more strongly attracted to the resin and therefore will replace the sodium ions. Eventually all the sodium ions will go into solution and the ion-exchange process terminates. The resin can be regenerated by soaking in a high concentration sodium salt solution. Such process can also be used to remove unwanted ions from polluted water streams. "