Write the principle behind the following:

A. Vapour phase refining

B. Chromatography

C. Froth floatation process

Option (A)

Principle:

Purification of crystal solids by converting it into its volatile compound and separating it from the ore is vapour phase refining. The separated vapour is then decomposed to obtain the pure metal.

Now this method requires two operations to be carried out

(i) To convert metal into volatile compound

(ii) To recover the pure metal by decomposition

For this process to work, the metal should first form a volatile component and hence, the volatile component should be easily recoverable or decomposable.

For e.g.:

Refining nickel (Mond process)

Nickel forms carbonyl coordination compound Nickel tetracarbonyl which is volatile in nature. This can be decomposed at higher temperature to obtain pure Ni metal.

Rxn:

The complex can be decomposed at temperature of 450 – 480 K

Option (B)

Principle:

In a mixture, Different components have different adsorptivity on a specific adsorbent. The liquid to be separated is made to pass through a column when the different traveling velocity of the components of the mixture varies with each other and separation takes place.

Following types of chromatography exists:

(i) Column chromatography

(ii) Paper chromatography

(iii) Thin –layer chromatography

(iv) Gas chromatography

(v) Liquid chromatography

(vi) Ion exchange chromatography and so on.

Option (C)

Principle:

Separation of materials on the basis of their affinity to water i.e. based on its hydrophobic nature is called froth floatation. The metal to be separated is reduced to smaller particles to facilitate separation. A surfactant is used in order to increase the hydrophobicity difference between the valuable compound or metal to be separated from the gangue.

Generally waste water treatment process use this separation technique where the fats, oil, grease and other suspended solids is removed from waste water. Another example is paper recycling.