Metal finishing Q&As since 1989

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Separate bed regeneration resin

July 21, 2010

We have regenerated a cation and anion resin. It has reached quality (above 50K) at the manufacturing facility with a conductivity of 60 - 80 microSiemens/cm. When it is being shipped out to a customer site with a conductivity of 200 - 500 microsiemens/cm, it does not meet quality (below 50K). Besides the difference in feed water conductivity, what other possible causes for the difference in quality readings?

Sue Nair
employee - East Rutherford, New Jersey

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July 26, 2010

You appear to be confused regarding water quality specifications. A resistivity of > 50K-Ohms is equivalent to a conductivity below 20 microsiemens.

Properly regenerated, it should be possible to achieve water with a conductivity of < 5 microsiemens, (>200K-Ohms resistivity).

That being said, DI water always increases in conductivity due to dissolved gases from the air (typically carbon dioxide) and from contamination. You didn't mention what type of container is being used for shipping, but it is likely the cause of the increase in conductivity. An increase of 200 microsiemens corresponds to a Total Dissolved Solids concentration of about 125 mg/L for water with a neutral pH, which seems unlikely.

Check the pH of the water to see if there is any acid or caustic contamination.

Any acid or caustic contamination will cause a large increase in conductivity at a much lower concentration. For example, a 200 microsiemen increase in conductivity corresponds to a concentration of only 41 mg/L of sodium hydroxide.

Lyle Kirman
consultant - Cleveland Heights, Ohio