Why anion resin is exhausted before anion resin in ion exchange process in water treatment?
Sridhar Balakrishnan, Bharat Oman Refineries Limited , email@example.com
Anion resins are small plastic beads that are composed of organic polymer chains that have charged functional groups built into the resin bead. Anion resin has a positive functional group ( also known as active sites) and therefor attracts negatively charged ions. When these active sites of resins gets saturated , it has to be regenerated with suitable reagent . It is regenerated with chemical that is passed through the resin, and trapped negative ions are flushed out, renewing the resin exchange to its fullest capacity. 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 . 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 can only be regenerated with strong bases. Caustic soda (NaOH) is almost always used as an SBA regenerant for demineralization. For WBA regeneration, though weaker alkalis can also be used, such as Ammonia (NH3), Sodium carbonate (Na2CO3), or lime suspensions.