exchange capacity
Thread Content
We have an aminophosphonic acid-type chelating resin from Rohm and Haas, and it indicates that its total exchange capacity is 1.75 eq/L (Na type). What does this mean when it is used to adsorb calcium ions? What is its corresponding full switching capacity? Assume that the working switching capacity is its full switching capacity. Thank you for your advice!
This post was last edited by kylin08 on 2009-8-21 at 16:22. Definition of resin exchange capacity: The number of grams (or gram-equivalents) of anions and cations that can be exchanged by the exchange groups per unit volume or weight of resin; it is a measure of the resin’s exchange capability. It can also be divided into the working exchange capacity of the resin, the saturated working exchange capacity of the resin, and the total exchange capacity of the resin, among others. Definition of total exchange capacity: The total number of active groups present in an ion exchange resin, expressed in milliequivalents per gram (dry). When the ion is monovalent, the number of milliequivalents is equal to the number of millimoles (for divalent or polyvalent ions, the former is the latter multiplied by the valence of the ion)
Calculation: 1.75×20/23=1.52 eq/l. The equivalent weight of Na is 23/1=23 g, while that of Ca is 40/2=20 g. Hence, the above relationship holds. The working switching capacity is not the same as the total switching capacity! Their relationship is as follows: the normal regeneration exchange capacity is 50–90% of the total exchange capacity, while the operating exchange capacity is 30–90% of the regeneration exchange capacity (for regenerated resins); this latter ratio is also referred to as the utilization rate of the resin.