The quality of ion-exchange resins is characterized by the number of physical and chemical properties that determine effectiveness and cost-efficiency of the ion exchange methods. The main physical properties include: grain-size distribution, bulk mass, mechanical strength, and osmotic stability, resin structure and swelling index in the aqueous solutions.

The chemical properties include first of all chemical stability, acid value (for cation-exchange resins) or alkalinity (for anion-exchange resins), exchange capacity, specific consumption of reagents and wash water at the set degree of removal of adsorbed ions from water.

Usually the filtration process in the ion-exchange filters is stopped at the moment when concentration of adsorbed ions in the processed solution reaches the set quite low value that is reliably determined by analytical method. In this case the ion-exchange resin capacity is defined as the "working exchange capacity". If the filtration process is stopped at the moment of ion breakthrough and when the concentration of this ion is slightly different from the average concentration per the filter run, then such ion-exchange resin capacity is called "before-the-breakthrough capacity". In practice the value of working and before-the-breakthrough ion exchange resin capacities are quite close that's why these values could be assumed as equal to each other.

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* The text is taken from:
A.S. Kopylov, V.M. Lavygin, V.F. Ochkov, "Water-treatment in power energetics"
(M. MEI Publishing House, 2003)

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