Explain the inorganic cation exchange method to remove the permanent hardness with the help of reaction
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Permanent hardness can be a removed by the following ways:
(a) By the use of soda:
Soda removes both temporary and permanent hardness. It is also inexpensive and easy to use. This makes it the ideal substance for softening water in the home.
(b) Other softening agents in the home:
It is difficult for the housewife to be very precise in the use of soda and the water softened by soda may often contain an excess of it, which even if it is slight, may damage certain fabrics. Hence, other softening agents could be used. They are:
(i) Soap:
Soap is used as a softening agent. However, the use of soap as a softening agent is extravagant on account of its high cost compared with soda.
(ii) Caustic soda:
t removes temporary hardness but reduces permanent hardness only when the lather is very slight.
(iii) Solution of Ammonia:
It may be used for softening water, when the fabrics to be treated would be harmed by soda. If used in excess, ammonia may destroy the Iustre of rayon's, discolour and injure animal fabrics and loosen the dyes of coloured articles. Since, it is not possible to be very certain of the quantity to be used; this is not practicable for softening water.
(iv) Borax:
It is useful for softening water containing over 20% of hardness. Borax is usually used to reduce the alkalinity of soap solution rather than to soften water.
(c) Removal of Permanent Hardness by the Base-Exchange Process:
Base exchange process' is a chemical method by which, softening of permanent hardness in water can be done on a large scale or for household purposes. It is the most popular and effective means of softening hard water. It was discovered by Dr. Robert Gans, who found out the natural minerals called 'Zeolites', which is very effective in softening water