Permutit process

Removal of Permanent Hardness of water

It is not easy to remove permanent hardness of water as temporary hardness. It is quit difficult to remove permanent hardness of water. There are various ways to remove it. Here, we discuss below is the best method to remove it.
 Permanent hardness can be removed by following methods:

a) Treatment with washing soda: 

 

Washing powder

Washing powder

Soluble salts of calcium and magnesium turn into insoluble salts when washing soda (sodium carbonate) is mixed with it as shown below in examples.

CaCl2 + Na2CO3 = CaCO3 + 2NaCl
MgSO4 + Na2CO3 = MgCO3 + Na2SO4


b) Permutit process: 

 

       

Permutit process

Permutit process

Permutit is the trade name for an artificially prepared sodium zeolite or sodium aluminium orthosilicate obtained by fusing together sodium carbonate, silica and alumina. Its composition corresponds to Na2Al2Si2O8 or Na2Z where Z stands for zeolite = Al2Si2O8. It possesses remarkable property of reacting with calcium and magnesium ions forming insoluble calcium or magnesium zeolite. By passing hard water through a cylinder packed with permutit all the ions responsible for the hardness of water are drawn and replaced by sodium ions.

Ca-salt + Na-permutit = Ca-permutit + Na-salt

Mg-salt + Na-permutit  = Mg-permutit + Na-salt

In due course, however, the permutit is exhausted by having given up all its sodium ions. This can be regenerated by soaking in a 10% solution of common salt when the reverse change take place and calcium and magnesium ions pass into solution and sodium zeolite is formed again.

CaZ + 2NaCl = Na2Z + CaCl2

MgZ + 2Nacl = Mg2Z + MgCl2

The resulting calcium and magnesium chlorides are washed out and the regenerated permutit used over again.

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