How Does Ion Exchange Resin Work, and How Long Does It Last?

How Does Ion Exchange Resin Work, and How Long Does It Last?

November 5, 2019

If you’re investigating various types of water treatment strategies, you might consider the use of ion exchange resin.

Ion exchange is a chemical reaction process in which dissolved ions get removed from a solution and then get replaced with other ions that have a similar (or the exact same) electrical charge. The ion exchange resin, then, is the medium used to facilitate that ion exchange reaction. This resin is made out of polymers that create a system of hydrocarbons. As a general rule, you can expect an ion exchange resin to last about 10 to 15 years in water treatment (as opposed to four to eight years for anion exchange resins).

How does the process of ion exchange work?

As mentioned above, ion exchange is a process in which there is a (reversible) exchange of like-charged ions. The process begins when the ions found in an ion exchange resin swap spots with ions of the same or similar charge found in the solution that passes through. For our purposes, that “solution” is the water that flows through the ion exchange “filtration” system.

The functional groups of ion exchange resins make this happen. These groups are fixed ions that are bound together within the resin’s polymer matrix. The charged ions are then able to bond with ions that have an opposing charge, which get delivered through the use of a counterion solution. The counterions, then, continue bonding with the functional groups until the entire solution reaches a state of equilibrium.

During the process of ion exchange, the solution being treated runs into the ion exchange resin bed and is allowed to freely flow through the ion exchange beads. As the solution passes through the resin, the resin’s functional groups attract the counterions that are present in the solution. It is at this point that the ions in the solution dislodge the existing ions in the resin to take their place, resulting in a bond with the functional groups through electrostatic attraction. The larger the ion or the greater its valency, the greater an affinity the ion will have with oppositely charged ions.

In a water softening system that uses ion exchange processes, the softening mechanism in question is a cation exchange resin, in which sulfonate anion functional groups are attached to the ion exchange resin matrix. A counterion solution that features sodium cations gets applied to the resin. The sodium cations are then held to the sulfonate anions through electrostatic attraction, which results in there being a balanced, neutral charge in the resin. The sulfonate functional groups have a greater affinity for hardness cations than sodium cations, which means the hardness ions will displace those sodium cations, which then come out of the ion exchange unit.

This is a fairly technical overview of ion exchange, but it should give you a general idea of how the process works. To learn more about the use of ion exchange resin and how often you need to replace it, contact the team at M.L. Ball Company, Inc. today.

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