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How does a hydroxyl-loaded anion-exchange resin neutralize acids during deionization?
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ion-exchange reaction
Figure 1: Chemical structure of cation exchanger. The exchangeable ions are marked +. The whole structure is permeated by solvent molecules, usually water (not shown).
During the process of deionization, water is typically passed through two separate resin beds. The first bed, containing a cation-exchange resin, converts dissolved salts into their corresponding free acids.1
The second bed contains an anion-exchange resin loaded with hydroxyl ions. As the acidic water flows through this resin, the hydroxyl ions facilitate the neutralization of the acids by holding back their anions. This process effectively removes the ionic components from the water, leaving behind only nonionic impurities.1