Why is zeolite used in the purification of water?
R. Venkataramani, Mysore ANSWER: Before we look into zeolite, we should first know that water which does not lather easily with soap is called hardwater. Hardness in water is due to the presence of carbonates and biocarbonates of Calcium or Magnesium (when it is temporary hardness) or sulphates and chlorides of Calcium and Magnesium (when it is permanent hardness). Temporary hardness of water can be removed easily by boiling water or by adding washing soda (Sodium Carbonate-hydrated). Permanent hardness cannot be removed by merely boiling or adding washing soda. A complex salt called sodium aluminium silicate (zeolite) is used to remove permanent hardness in water. Nowadays this material is made synthetically. Permotit or zeolite is packed into a column and the hard water is allowed to flow through it. Double decomposition occurs and calcium aluminium silicate is formed. Eventually the permotit is completely converted into its calcium salt. It can be made fit for use again by pouring a
