6Zeolite holds sodium ions loosely and can be simply represented as Na2Z where Z = the insoluble radical frame work. When hard water is passed through a bed of active granular Na2Z. The following cation exchange reactions take place.
It is seen that sodium zeolite is converted to calcium and magnesium zeolites. In the process, the water becomes free from Ca2+and Mg2+, the main hardness producing cations, but gets more concentrated with respect to sodium salts. Eventually, the bed loses its sodium exchange capacity and the zeolite is said to be "exhausted".
