Question

Define the following: a) Permutit process b) Calgon’s process c) Ion exchange process.

Answer 1

Hint: Water when contains large amounts of minerals, it is known as hard water. In hard water, mainly the salts of calcium and magnesium are present. Hardness of water can be removed through different processes such as Permutit process, Calgon’s process, Ion exchange process. So, we will now discuss all these processes in detail.

Complete answer:
When water has a very high content of minerals, it is known as hard water. It mainly contains salts of calcium and magnesium such as calcium bicarbonate, calcium chloride, calcium sulphate, calcium carbonate, magnesium carbonate, magnesium chloride, magnesium bicarbonate and magnesium sulphate.
We know that there are many disadvantages of using hard water such as, it is unfit for washing because scum may be formed in the reaction with soap, it can block water pipes by depositing layers of carbonates of calcium and magnesium. Hence, the hardness of water should be removed.

So, the processes to remove the hardness of water are:-
a) Permutit process- Permutit is a zeolite with an artificial source.It is hydrated sodium aluminium orthosilicate with the chemical formula $N{a_2}A{l_2}S{i_2}{O_8}.x{H_2}O$ . In this process, the hard water containing $C{a^{2 + }}$ is filtered through a sand called zeolite.
In this method, hard water is passed through permutit taken in a cylinder. The calcium and magnesium ions get trapped in zeolite whereas sodium ions are passed in water and hence, the water becomes soft.
Chemical reaction:-
$N{a_2}X + (C{a^{2 + }}orM{g^{2 + }}){\text{ }} \to CaXorMgX + 2N{a^ + }$
Where, X is $N{a_2}A{l_2}S{i_2}{O_8}.x{H_2}O$ .

b) Calgon’s process- Calgon is a complex salt with formula $${\left( {NaP{O_3}} \right)_6}$$ . In this method when calgon is added to hard water, calcium and magnesium ions of hard water displace sodium ions from anion of the calgon.
Chemical reactions involved:-
${(NaP{O_3})_6} \to 2N{a^ + } + N{a_4}{P_6}O_{18}^{2 - }$
$2C{a^ + } + N{a_4}{P_6}O_{18}^{2 - } \to CaN{a_4}{P_6}{O_{18}}$
c) Ion exchange process- In this method, when hard water is passed through man- made ion exchange resin containing sodium ions, the calcium and magnesium ions in hard water get exchanged with sodium ions of resin.

Note:
There are two types of hardness present in water, one is temporary and second is permanent. Temporary hardness in water is caused by the bicarbonates of calcium and magnesium while the permanent hardness in water is caused by sulphate and chloride compounds of calcium and magnesium.