Ion Exchange

Sometimes, water that is fine for drinking isn’t nearly good enough for other purposes. The dissolved minerals present in all natural water supplies may make the water undesirable for other domestic uses and unacceptable for some industrial applications. The solution is to remove these minerals, and the most widely used method is ion exchange, employing synthetic zeolite resins.

The most commonly offensive minerals in water are the so-called “hardness” ions, principally calcium and magnesium. These ions are responsible for soap scum in a bathtub, scale in a water heater or an industrial boiler, and contamination of chemical product solutions.

To remove them, we pass the water through a tank containing a bed of zeolite resin beads which have been charged with acceptable ions, usually sodium. The sodium ions leave their resin sites and “change places” with the hardness ions, which are held by the resin. The hard water is now made “soft”. When the resin has chemisorbed all the hardness it can handle, it is regenerated with a strong solution of sodium chloride, ordinary salt. It is then ready for another cycle.

Fort Bend Services’ engineers are experienced in the design, construction, and maintenance of units capable of softening a few hundred gallons per day, as in a home, up to units which can process several hundred thousand gallons per cycle, as needed for industrial processes or boiler feedwater.

In some applications, no mineral ions at all can be tolerated. Removal of both the cations like calcium, magnesium, etc., and the anions, like chloride, carbonate, etc., is called deionization. This set of processes uses an extension of softening technology, and requires at least two different zeolite resins. In one resin bed, cations are exchanged for hydrogen ions supplied by an acid. In another, anions are exchanged for hydroxyl ions supplied by an alkali. The end result is replacement of the mineral ions by a bit more water! Variations of these basic processes are capable of producing water of very high quality – the closest thing to totally pure water there is.

Fort Bend Services’ experience includes design, installation, and maintenance of deionizers from laboratory water supply size to power generating boiler feed size. Wherever the need is for pure water, we can help.