Demineralized water purity

[dpugliesi]

What is the typical purity of water demineralized by anionic and cationic resins? In particular, how much ppm or ppb of salt it typically contains? Thanks.

 

[bimr]

In general, you should expect anywhere from 1 - 10 mg/L sodium leakage from a dual bed demineralizer. The amount of sodium is dependent on the raw water quality (higher salt content in raw water results in higher leakage) and regenerant dosage (higher regenerant dosage results in lower leakage).

Sodium leakage occurs because sodium and hydrogen have a very similar attraction to the cation resin bead and sometimes the sodium ion does not exchange itself for a hydrogen ion. If sodium "leaks" past the cation exchange tank, then it combines with hydroxyl ion to form sodium hydroxide, which has conductivity.

 

[dpugliesi]

Thank you. Do you know which other substances are found in demineralized water and in which percentage?

 

[bimr]

The ions will be essentially sodium hydroxide. You may also have silica depending on the water supply.

 

[dpugliesi]

Thank you very much. Please let me know if you have a source (e.g. a book) where I can have more information at this regard.

 

[bimr]

Demineralization by Ion Exchange Applebaum

 

[dpugliesi]

Thank you again.