THE ION EXCHANGE PRINCIPLE

The idea of ion exchange is not new. Scientists have been aware of the principle for a long time. However, it has only been since the start of the present century that the principle has been put to practical use. One area in which it has been highly effective has been in the treatment of water for removal of hardness minerals and certain other contaminants.

THE ION EXCHANGE COLUMN

HARD WATER ENTERING SOFTENER

All recognized household water softening equipment now on the market makes use of the ion exchange principle. Equipment using this principle contains a bed of permanent bead-like or granular softening material through which the water flows. As the water travels through the bed of ion exchange material, the hardness minerals are removed, leaving the water soft and more satisfactory for household use.

Bed. The granules or particles of ion exchange material in a softener are referred to as the bed.

The ion exchange material (usually resin beads or granules) consists of permanent insoluble anions, kept electrically neutral by replaceable sodium cations. 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, a 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 trouble­producing hardness ions.

Ion exchange occurs literally billions of times between the material in the exchange column and the minerals in the water as softening proceeds.