Resin Technical Terms

Find and learn technical terms related to ion exchange resins here.

Ion-exchange capacity (IEC)

IEC is a measure of the total amount of exchangeable ions that a particular ion-exchange resin can adsorb or exchange at a given pH and temperature. The IEC is expressed in terms of milliequivalents per gram (meq/g) of dry resin or in terms of milligrams of equivalent per gram (mg-eq/g) of dry resin. Higher IEC's equate to greater exchange capacity and higher removal efficiency.

Regeneration Capacity

The regeneration capacity of ion resins refers to the ability of the ion exchange resin to be restored to its functional state after it has been exhausted or saturated with ions. This is achieved by flushing the resin with a regeneration solution, which displaces the ions that are attached to the functional groups on the resin and replaces them with a new set of ions. The regeneration capacity of ion resins depends on the composition, size, and charge of the resin beads, as well as the nature of the ions that are being exchanged.

Bed Depth Gradient (BDG)

It is a measure of the variation in resin concentration or activity with respect to the depth of an ion exchange bed. It is commonly used to evaluate the performance of ion exchange resins. The BDG can be expressed as the percentage change in resin concentration or activity over the bed depth. It is calculated by dividing the difference in resin concentration or activity between the inlet and outlet of the bed by the bed depth and multiplying by 100.


The selectivity of ion exchange resins refers to their ability to selectively remove certain ions from a solution while leaving others behind. The selectivity depends on their chemical composition, pore size, and physical structure.

Functional Groups

Typical ion exchange resin functional groups include sulfonic acid groups (-SO3H), carboxylic acid groups (-COOH), quaternary ammonium groups (-NR3+), tertiary amine groups (-NR2H+), imidazole groups (-C3H3N2H), phosphonic acid groups (-PO3H2), and chelating groups (-COCH2NH2), etc.


It refers to the ability of ion exchange resins to selectively adsorb and exchange certain ions based on their chemical and physical properties.


Diffusion in ion exchange resin refers to the movement of ions through the material of the ion exchange resin. This diffusion occurs when an ion from the solution to be treated moves into the resin bead or granule, displacing the ion of the same charge that was previously attached to the resin.

Diffusion Rate

The diffusion rate in ion exchange resin refers to the speed or rate at which ions diffuse or move through the resin. This rate depends on several factors, such as the type of resin, the size of the resin particles, the type of ions being exchanged, the concentration of ions in the solution, and the temperature and pressure of the system.


It is a column of ion exchange resin beads commonly used in water softening and purification processes.

Bed Expansion

It refers to the increase in the volume of the resin bed due to the flow of liquid through it. This occurs when the flow rate of liquid is high enough to cause the resin particles to move and separate from each other, creating larger gaps between them.

Other Common Technical Terms

Technical TermsDescriptionTechnical TermsDescription
AcidityAn expression of the concentration of hydrogen ions present in a solution.Brine DecalcificationA process used to soften hard water by removing the calcium and magnesium ions that cause water hardness.
AdsorbentA synthetic resin possessing the ability to attract and to hold charged particles.Cross-linkingIt involves the formation of chemical bonds, either covalent or ionic, between the polymer chains that make up the resin matrix.
AdsorptionThe attachment of charged particles to the chemically active groups on the surface and in the pores of an ion exchanger.CycleA complete course of ion exchange operation, which include Backwash, Regeneration, Rinse, and Service.

Related Ion Exchange Resins

Discover series of ion exchange resins that may be of interest to you here

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