Question

Which separation technique will you apply for the separation of the following mixture?

Fine mud particles floating in water

Answer 1

The separation technique applied for the separation of fine mud particles floating in water is coagulation followed by sedimentation.

• The reason why sedimentation (the process where particles with high density settle down under gravity) alone cannot be used is that the fine particles are very light in weight and fine-sized that they cannot settle under the influence of gravity.
• The reason why filtration (separating insoluble solid by using a filter paper) alone cannot be used is that fine mud particles cannot be separated effectively as they might even pass through the pores of filter paper.

So it is important that the fine mud particles are converted to rather larger particles. This can be done by the addition of alum to water.

• Alum (phitkari) coagulates the fine particles of mud into a mass of large-sized particles called floc which is high in density and settles down at the bottom of the container under the influence of gravity i.e., sedimentation occurs.

The water on the top or supernatant is transferred to another beaker leaving behind the mud particles.