TecKnow of the day
The most common means for removing water hardness rely on ion-exchange resin or reverse osmosis. Other approaches include precipitation methods and sequestration by the addition of chelating agents.Conventional water-softening appliances intended for household use depend on an ion-exchange resin in which “hardness ions” – mainly Ca2+ and Mg2+ – are exchanged for sodium ions. As described by NSF/ANSI Standard 44, ion-exchange devices reduce the hardness by replacing magnesium and calcium (Mg2+ and Ca2+) with sodium or potassium ions (Na+ and K+).”An ion-exchange resin or ion-exchange polymer is a resin or polymer that acts as a medium for ion exchange. It is an insoluble matrix (or support structure) normally in the form of small (0.5–1 mm diameter) microbeads, usually white or yellowish, fabricated from an organic polymer substrate. The beads are typically porous, providing a large surface area on and inside them. The trapping of ions occurs along with the accompanying release of other ions, and thus the process is called ion exchange. There are multiple types of ion-exchange resin. Most commercial resins are made of polystyrene sulfonate.