The idea of ion exchange is not new. Scientists have been aware of the principle for a long time. One area in which it has been highly effective is in the treatment of water for removal of hardness minerals. Equipment using the ion exchange principle contains a bed of permanent bead-like or granular softening material through which water flows. As the water travels through the bed of ion exchange material, the hardness minerals are removed, leaving the water soft.
Hard water contaminated with calcium and magnesium ions enters the exchange column or bed.
As it flows through it, the magnesium and calcium cations in the water are drawn to the anions of the ion exchanger. The ion exchanger has a greater affinity for the calcium and magnesium ions than for the sodium ions. Therefore, the calcium and magnesium ions are absorbed, and a chemically equivalent number of sodium ions is released into the water. Thus, water containing the ions of calcium bicarbonate when it enters, contains the ions of sodium bicarbonate as it leaves the ion exchanger bed. In brief, harmless sodium ions have replaced the troublesome hardness ions.