Question

Define the following:

1. Permutit process
2. Calgon's process
3. Ion exchange process

Answer 1

(a) Permutit process:

• The process in which hard water containing ${\mathrm{Ca}}^{++}$ is filtered through sand named zeolite is called the Permutit process.
• Permutit is a zeolite of an artificial source.
• It is an orthosilicate of sodium aluminium compound with the chemical formula ${\mathrm{Na}}_2{\mathrm{Al}}_2{\mathrm{Si}}_2{\mathrm{O}}_8{\mathrm{xH}}_2\mathrm{O}$.
• Chemically, it is hydrated sodium aluminium orthosilicate.
• In this method, sodium aluminium ortho silicate known as permutit or zeolite is used to remove the permanent hardness of the water.

Chemical reaction:

${\mathrm{Na}}_2{\mathrm{Al}}_2{\mathrm{Si}}_2{\mathrm{O}}_8.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{aq}\right)+{\mathrm{Ca}}^{++}\left(\mathrm{aq}\right)\to 2{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{CaAl}}_2{\mathrm{Si}}_2{\mathrm{O}}_8.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{aq}\right)$

(b) Calgon process:

• This method is used for softening the hard water.
• Calgon is a complex salt with the formula ${\left({\mathrm{NaPO}}_3\right)}_6$.
• In this method when Calgon is added to hard water, calcium and magnesium ions of hard water displace sodium ions of the Calgon.
• This results in the removal of hardness from water and sodium ion from Calgon is released into the water.

Chemical reaction:

${\left({\mathrm{NaPO}}_3\right)}_6\left(\mathrm{aq}\right)\to 2{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Na}}_4{\mathrm{P}}_6{{\mathrm{O}}_{18}^{}}^{2-}\left(\mathrm{aq}\right)$

${\mathrm{Ca}}^{++}\left(\mathrm{aq}\right)+{\mathrm{Na}}_4{\mathrm{P}}_6{{\mathrm{O}}_{18}}^{2-}\left(\mathrm{aq}\right)\to \mathrm{Ca}{\mathrm{Na}}_4{\mathrm{P}}_6{\mathrm{O}}_{18}\left(\mathrm{aq}\right)$

(c) Ion exchange:

• Both cations and anions have a tendency to get adsorbed on the surfaces of the cell walls and exchange with ions present in the soil solution.
• This process of exchange between the adsorbed ions and ions in the solution is known as ion exchange.