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Uniform Particle Size Ion Exchange Resins

We received notice today that Purolite Ion Exchange Company will no longer be selling the anion resins, A-300 and A-400. These resins will be replaced by Purofine PFA-300 and PFA-400. The Purofine line of resins is uniform particle size (UPS). Dow did this a number of years ago when they introduced the Marathon grade of Dowex Ion Exchange Resins. The Marathon line of Ion Exchange resins pretty much replaced the entire line of standard Gaussian resins.

In general there are many advantages to using UPS resins.

Higher Regeneration Efficiency:
According to Dow regeneration is the least efficient step in the ion exchange process. Large beads regenerate more slowly than small beads. The typical Gaussian mesh range is 16-50 whereas UPS resins are 30-40 mesh, a much tighter specification. The UPS resins have a smaller average particle diameter and will regenerate more quickly resulting in more efficient use of regenerant chemicals. So you use less and get a higher operating capacity.

Greater Operating Capacity:
The kinetics of the UPS resins is more favorable than that of Gaussian. "This leads to an increase in usage of the entire resin capacity from the top to the bottom of the bed...the net effect of the more efficient higher throughput."

Better Rinse Efficiency:
Excess regenerant chemicals diffuse more quickly from within the beads, thus decreasing the time required to reach the specified endpoint. Faster rinse times trim water and wastewater disposal costs.

Reduced Leakage:
The result of these increased efficiencies is an increase in production of pure water for a longer time since the leakage endpoint is extended

Better Separations for Mixed Beds:
For many years now Res-Kem has been advising customers to use UPS resins in their mixed bed units. In fact, our sister company, General Water Services, uses UPS resins to service their high-purity customers. One reason for doing so is better separation prior to regeneration. With Gaussian resins, the smaller cation beads are easily trapped with the larger anion beads. With better separation you get lower leakages, a better regeneration and greater throughput.

Operating Considerations:
Backwash Rates are lower when using UPS resins. Consult the engineering graphs, Dow Marathon, Purolite Anion or Purolite Cation, prior to installation or contact a qualified equipment manufacturer to determine the changes required when upgrading to Uniform Particle Size resins.

Posted on September 15, 2008 by Tom Dupnik

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