Question

55. Explain the role of alum in purification of water.

Answer 1

1. The chemical formula of potash alum KAl(SO₄)₂·12H₂O.
2. With the help of coagulation process the water is purified at water treatment plants.
3. When alum is added to the impure water, suspended particles that are insoluble in the water get coagulated due to the presence of Al³⁺ ions from alum, as they are negatively charged.
4. Then these coagulated impurities are removed with the help of filtration process.