A water softener operates on the principle of

A water softener operates on the principle of

• A. Filtration
• B. Ion exchange
• C. Reverse osmosis
• D. Adsorption

Answer: (B)

Water softeners work through ion exchange. In a softening bed, resin beads are loaded with sodium ions. As hard water flows through, calcium and magnesium ions—responsible for hardness—prefer to stick to the resin. They exchange places with the sodium ions, so calcium and magnesium are retained on the resin and sodium ions are released into the water. The water leaving the bed becomes softened because the dissolved hardness minerals have been swapped out for sodium. Over time the resin becomes saturated with hardness ions and must be regenerated with a salt solution, which replenishes the sodium on the resin and flushes the calcium and magnesium away to waste. This is different from filtration (which removes particles), reverse osmosis (which uses a membrane to remove many dissolved ions but is a different technology and energy requirement), and adsorption (which binds contaminants to a surface without true ion replacement).

Water softeners work through ion exchange. In a softening bed, resin beads are loaded with sodium ions. As hard water flows through, calcium and magnesium ions—responsible for hardness—prefer to stick to the resin. They exchange places with the sodium ions, so calcium and magnesium are retained on the resin and sodium ions are released into the water. The water leaving the bed becomes softened because the dissolved hardness minerals have been swapped out for sodium. Over time the resin becomes saturated with hardness ions and must be regenerated with a salt solution, which replenishes the sodium on the resin and flushes the calcium and magnesium away to waste. This is different from filtration (which removes particles), reverse osmosis (which uses a membrane to remove many dissolved ions but is a different technology and energy requirement), and adsorption (which binds contaminants to a surface without true ion replacement).