Why is zeolite used in the purification of water?

Zeolite is used in the purification (more correctly softening) of water. Water in some localities contains salts of Calcium, Magnesium and Iron present in the earth. Such water finds it ‘hard’ or difficult to lather with ordinary washing soaps. This is because these salts react with the sodium compounds in soap causing wastage.

Further when such hard water is used in boilers these salts form a coating on the wells. This could be seen even in household vessels in which we use to boil water. Zeolite is the common name for a complex compound Sodium Aluminum Silicate. When hard water is passed through filters containing Zeolite, the salts of Calcium and Magnesium get absorbed and Sodium salts are released in exchange. Special kinds of Zeolite based on Manganese salts could remove salts of iron also if present in water.

 When the softening power of Zeolite gets weakened by constant use, it could be revived by pouring solutions of common salt and Potassium permanganate.