How to Remove Permanent Hardness of Water?
Permanent hardness of water occurs because of the presence of CaCl2, MgCl2, CaSO4, MgSO4 compounds. To permanently remove the hardness of water we will use certain chemical methods. These methods are discussed below:
By Using of Washing Soda
In this method we add washing soda i.e., Na2CO3 ·10H2O to hard water. The washing soda converts soluble chlorides and sulfates of calcium and magnesium into insoluble salts. The reactions are:
CaCl2 + Na2CO3 → CaCO3 + 2NaCl
MgCl2 + Na2CO3 → MgCO3 + 2NaCl
CaSO4 + Na2CO3 → CaCO3 + Na2SO4
MgSO4 + Na2CO3 → MgCO3 + Na2SO4
These CaCO3 and MgCO3 can be removed from the water by filtration. After filtration we get Ca+2 and Mg+2 ions free water which is the soft water.
Calgon’s Method
In this method we add Calgon i.e., Sodium Hexametaphosphate (Na6P6O18) to water. In this reaction, Ca+2 and Mg+2 ions of hard water displace two Na+ ions of Calgon, resulting in the removal of calcium and magnesium minerals from water and addition of sodium ion from Calgon into the water. After this reaction the water becomes soft. The chemical reactions are:
Na6P6O18 → 2Na+ + Na4P6O18 2-
Mg2+ + Na4P6O18 2- → Mg Na4P6O18
Gan’s Permutit Method
In this method we use Zeolite or Sodium Aluminum Ortho Silicate i.e., Na2Al2Si2O8 ·KH2O to remove hardness from water permanently. The reaction is:
Na2Al2Si2O8·KH2O + Ca+2 → 2Na+2 + CaAl2Si2O8·KH2O
Ion-Exchange Resins Method
To remove permanent hardness of water we also use ion-exchange method. In this method we add synthetic ion-exchange resins (RNa+) or Zeolite i.e., Sodium Aluminum Silicate to the water, which is insoluble in water. In this reaction the ion-exchange process occurs between it and the Ca2+ or Mg2+ ions of the hard water. By this process the water becomes free from Ca+2 and Mg+2 ions and no longer remains hard.
Methods to Remove Permanent Hardness of Water
Water is a crucial part of our lives. It is enriched with minerals that are important for our good health. Permanent Hardness of water is not only a theory but also a real-life problem we deal with every day in our lives. Knowledge of this concept helps the students relate the chemistry concepts to real-life problems and is also important for many exams like JEE and NEET. While temporary hardness is easy to eliminate by boiling, permanent hardness is not, so we have to use some chemical methods in this case. In this article, we will discuss in detail the methods of removing the permanent hardness of water, along with a few topics related to it.