A. Zeolites
B. Sulphonides
C. Lime
D. Nitrates
¨ Temporary hardness and permanent hardness in water are removed by different methods.
¨ Temporary hardness is caused by the presence of dissolved calcium and magnesium bicarbonates in water, which can be removed by boiling the water or by using ion exchange resins or zeolites. Boiling the water causes the bicarbonates to decompose into insoluble calcium and magnesium carbonates, which can be removed by filtration. Ion exchange resins or zeolites exchange the calcium and magnesium ions for sodium ions, effectively removing the hardness from the water.
¨ Permanent hardness, on the other hand, is caused by the presence of calcium and magnesium sulphates or chlorides, which cannot be removed by boiling the water. Permanent hardness can be removed by chemical methods such as lime-soda ash softening or ion exchange. In lime-soda ash softening, lime is added to the water to convert the sulphates or chlorides into insoluble calcium or magnesium compounds, which can then be removed by filtration. In ion exchange, a special resin is used to exchange the calcium and magnesium ions for sodium or hydrogen ions, effectively removing the hardness from the water.
Submitted by :- Jamil Ahmed