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Regeneration of Cation Exchanger

September 5, 2008

There was a discussion the other day that a Cation Exchanger can be regenerated with Sodium Chloride Solution. As far as my knowledge is concerned the regeneration of Cation Exchanger is done by either HCi or sulfuric Acid, please provide me with the information is there has been developed any cationic resin that could be regenerated using Sodium Chloride.

Moreover I have no idea that what should be the concentration of the acid that is to be used to regenerate a Cationic Resin, please guide me.

Thanks to one & All,

Bharati Salgaonkar
Student - Hyderabad, A. P., India

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Hi, Bharati. I'd be open to hearing how that can be done but it is not in accord with my understanding.

My understanding is that the cation exchanger replaces any cations with H+, while the anion exchanger replaces any anions with OH-. I don't see where the H+ could come from if you were to regenerate the cation exchanger with Na+ instead of H+.

Now, if you were only talking about softening water, rather than deionizing it, you could use NaCl -- leaving the Na+ in the water and replacing carbonates and other ingredients of hardness with Cl-

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 5, 2008

You are correct Ted as far as Deionization is concerned. Water softening however is actually the removal of Mg and Ca from water. Some Mn and Fe may also be removed but to a much lesser degree. NaCl is used regenerate the ion exchange resins but it is the Na that is of interest and not the Cl. Therefore a water softener is a cation exchange tank using Na. This however would be useless in a deionized water system. DI water requires both a cation and an anion exchanger. One is regenerated with acid and the other with caustic. Then you exchange the metals for H and OH which gives you H2O.

Kurt Sammons
- Inman, South Carolina
September 8, 2008

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Hi, Kurt. You're certainly right; I can't imagine what I was thinking -- it must have been very late, on my second bourbon of the night :-)

You prevent scale such as calcium carbonate by replacing the calcium with sodium, not by replacing the carbonate with chloride.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 8, 2008