The Basics of Ion Exchange
So how does Ion Exchange work?
Ion exchange resins are used to produce deionized (demineralized or “DI”) water. These resins are small plastic beads that are composed of organic polymer chains that have charged functional groups built into the resin bead. Each functional group has either a fixed positive or negative charge.
Cation resin has a negative functional group and therefore attracts positively charged ions. There are two types of cation resins, weak acid cation (WAC) and strong acid cation (SAC). Weak acid cation resin is used mainly in dealkalization and other unique applications. For this reason we will focus on explaining the role of strong acid cation resins used for producing deionized water.
Anion resin has a positive functional group and therefore attracts negatively charged ions. There are two types of anion resins; weak base anion (WBA) and strong base anion (SBA). Both types of anion resins are used to produce deionized water, however, they have different characteristics listed below:
WBA resins do not remove silica, C02 or have the ability to neutralize weak acids and has a lower than neutral pH when used in a dual separate bed system.
SBA resins remove all anions in the above table, including C02, and has a higher than neutral pH when used in a dual separate bed system due to sodium leakage.
Mixed Bed resins use SAC and SBA resins combined together.