IX Resin Testing: How Do I Understand What Has Been Reported?
By Don Downey
Resin capacity, moisture content, bead size, metals fouling, and other items. What does this list mean? At last count, there were more than 25 separate ion-exchange (IX) resin tests (analyses) that were available to endusers. Standard testing procedures identify the resin properties, but more specific procedures can be used to identify problems with equipment operation.
Then, there is the cost to consider; simple cation resin testing (moisture content, total capacity and bead integrity) is in the $200/sample range. However, add to this Chatillon, HIAC particle size, metals, % regeneration test procedures, and the lab work can increase costs to more than $1,000/sample.
In this article, the author will explain the “must-do” test procedures and why they are important and the key to understanding optional testing and how the results can help with on-site equipment troubleshooting.
Introduction to Polymer Chemistry
IX resins are synthetic with a chemical structure based on a cross-linked three-dimensional polymer molecule into which functional groups such as sulfonic acid and quaternary ammonium are introduced. Most of the polymer bases used for IX resins are copolymers of styrene and divinylbenzene (DVB), generally consisting of spherical particles of 300 to 1,200 microns. The cross-linked copolymer is synthesized by mixing styrene (which has one vinyl group) with DVB (which has two vinyl groups) and carrying out a suspension polymerization in water.
The IX resin is then manufactured by introducing functional groups into this copolymer matrix by means of chemical reactions. The IX groups introduced are chemically bonded to the polymer, and as they cannot move freely, they are known as fixed ions. Mobile ions of the opposite sign to the IX are known as counter ions.
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