Which one of the following methods can be used to remove permanent hardness of water ?
[amp_mcq option1=”Boiling” option2=”Ion-exchange” option3=”Lime treatment” option4=”Bubbling sulphur dioxide gas” correct=”option2″]
This question was previously asked in
UPSC CAPF – 2020
The Ion-exchange method can be used to remove permanent hardness of water.
Permanent hardness in water is caused by dissolved sulfates and chlorides of calcium and magnesium, which do not precipitate out upon boiling. The ion-exchange method, using materials like zeolite or synthetic resin, replaces the hard ions (Ca2+, Mg2+) with soft ions (usually Na+). This process is effective in removing both temporary and permanent hardness.