How does Ion Exchange softening function?

Ion exchange softening functions by a process where sodium ions are exchanged for calcium and magnesium ions, which are primarily responsible for water hardness. In typical water softening systems, a resin bed contains sodium ions. When hard water passes through this resin, the higher affinity of calcium and magnesium ions for the resin causes them to displace sodium ions. The result is that the water becomes softer, having had the hardness-causing calcium and magnesium ions removed.

This method is effective because it does not simply filter out the hardness minerals but actively replaces them with sodium, which does not cause the same hardness problems in plumbing and appliances. The exchange resin can be regenerated periodically by passing a concentrated salt solution through it, restoring its sodium content and allowing the process to continue. This is a key mechanism in water treatment facilities and home water softeners.

The other options describe processes that do not directly relate to the ion exchange process. Introducing chlorine treats water for microbial control but does not address hardness. Filtering out particulates involves physical removal of solid particles rather than chemical changes to ion content. Boiling water can effectively precipitate some hardness, but it doesn't remove it in the same targeted and efficient manner as ion exchange softening.