A ________ is a highly efficient ion-exchange process in which resin is regenerated with sulfuric acid in the first vessel and caustic soda in the second vessel

A ________ is a highly efficient ion-exchange process in which resin is regenerated with sulfuric acid in the first vessel and caustic soda in the second vessel

• A. softener
• B. distiller
• C. adsorber
• D. demineralizer

Answer: (D)

This question tests understanding of a two-bed ion-exchange setup used to produce highly mineral-free water, known as a demineralizer. In this arrangement, water passes through a cation resin first, which removes hardness ions like calcium and magnesium and forms the resin in a form that is regenerated with a strong acid, typically sulfuric acid. After the cation bed is exhausted, it is regenerated with the acid to restore its ability to exchange ions. The water then flows to an anion resin, which removes remaining anions and is regenerated with a strong base, such as caustic soda (sodium hydroxide). When both beds are in service, the overall effect is that the exchanged ions are replaced in such a way that the finished water is essentially devoid of mineral ions, because the resin cycles are reset with acid and base to their original forms.

This setup is characteristic of a demineralizer. A softener, by contrast, uses a salt brine for regeneration and mainly targets hardness with limited removal of other ions. A distiller separates water by phase change, not ion exchange. An adsorber is a broad term for various adsorption processes and does not specify the acid/base regeneration scheme described. The combination of a cation bed regenerated with sulfuric acid and an anion bed regenerated with caustic soda points to a demineralizer.