Question

Describe the permutit process for softening of hard water.

Answer 1

Permutit is a modern technique used to soften the hard water. “Hydrated sodium aluminium silicate” is called “permutit”. These “complex salts” are also known as “zeolites”.

The water softening process is carried out in a high cylindrical vessel packed with gravel sand and permutit. Durable water is introduced via an inlet. Water reaches the bottom of the vessel. The separation of impurities is done by the gravel layer.  It then comes in contact with permutit that replaces $C{ a }^{ 2+ }$and $M{ g }^{ 2+ }$ ions with $N{ a }^{ + }$ ions in tank water.

Therefore, free $C{ a }^{ 2+ }$and$M{ g }^{ 2+ }$ ions water are collected from outlet.

The chemical reactions are as follows.

$\begin{matrix} N{ a }_{ 2 }Z \\ Sodium\quad zeolite \end{matrix}\quad +\quad$$\begin{matrix} C{ a }^{ 2+} \\ \quad\end{matrix}\quad \rightarrow \quad \begin{matrix} CaZ \\ Calcium\quad zeolite \end{matrix}\quad +\quad \begin{matrix} 2{ Na }^{ + } \\ \quad\end{matrix}$

$\begin{matrix} N{ a }_{ 2 }Z \\ Sodium\quad zeolite \end{matrix}\quad +\quad \begin{matrix} Mg^{ 2+} \\ \quad  \end{matrix}\quad \rightarrow \quad \begin{matrix} MgZ \\ Magnesium\quad zeolite\end{matrix}\quad +\quad \begin{matrix} 2{ Na }^{ + } \\ \quad\end{matrix}$

Where,$\quad Z\quad =\quad { A }l_{ 2 }{ Si }_{ 2 }{ O }_{ 8 }.x{ H }_{ 2 }O$

Answer 2

Permanent hardness present in the water can be removed by treating it with soda water and using permutit process. Soluble salts of calcium and magnesium change into insoluble salts due to the treatment with sodium carbonate (washing soda).