Ion exchange resins

Ion exchange resins are used to replace the magnesium and calcium ions found in hard water with sodium ions. When the resin is fresh, it contains sodium ions at its active sites. When in contact with a solution containing magnesium and calcium ions (but a low concentration of sodium ions), the magnesium and calcium ions preferentially migrate out of solution to the active sites on the resin, being replaced in solution by sodium ions. The most important application of resins is in water softening. Tehran Zist is a supplier of ion exchange resins and exclusive agent of Hydrolite.