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
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.