In water treatment, which process is defined as the exchange of ions where one ion is displaced by another?

In water treatment, which process is defined as the exchange of ions where one ion is displaced by another?

• A. Ion Exchange
• B. Adsorption
• C. Filtration
• D. Precipitation

Answer: (A)

In ion exchange, ions in water are swapped with ions attached to a solid. In water treatment this happens when a resin bearing certain ions (such as sodium) encounters water containing ions like calcium and magnesium. The calcium and magnesium ions are displaced from the water and replaced on the resin by sodium ions, softening the water. This swapping process is what defines ion exchange. Other processes don’t involve a true ion-for-ion swap: adsorption is about particles sticking to a surface, filtration removes particles by size or structure, and precipitation forms solid particles from dissolved ions.

In ion exchange, ions in water are swapped with ions attached to a solid. In water treatment this happens when a resin bearing certain ions (such as sodium) encounters water containing ions like calcium and magnesium. The calcium and magnesium ions are displaced from the water and replaced on the resin by sodium ions, softening the water. This swapping process is what defines ion exchange. Other processes don’t involve a true ion-for-ion swap: adsorption is about particles sticking to a surface, filtration removes particles by size or structure, and precipitation forms solid particles from dissolved ions.