Chemistry ADSORPTION FROM SOLUTION

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ADSORPTION FROM SOLUTION

Adsorption from Solutions :

Some solids are capable of adsorbing certain solutes from the solution. This property is made use of in adsorbing colouring matter from solutions of organic substances. Raw cane juice is decolourised by activated charcoal. Similarly, charcoal adsorbs oxalic and acetic acid dyes from their aqueous solutions. Freundlich adsorption isotherm is also applicable to solutions by replacing the pressure term by the concentration (`C`) of adsorbates in solutions. The relationship is modified as follows

`x/m = kC^(1/n)`

Taking logarithm, it becomes

`log(x/m) = logk + (1/n) logC`

A graph between `log(x/m)` and `log C` is a straight line for small ranges of concentrations.

Applications of Adsorption :

Some of the applications of adsorption are as follows:

(i) Activated charcoal is used in gas masks to remove poisonous gases such as carbon monoxide, methane etc. Animal charcoal is used to remove colouring matter from cane sugar juice in the manufacture of sugar.

(ii) ion exchange resin is used to remove hardness of water.

(iii) Several organic compounds are purified by chromatographic adsorption.

(iv) Silica gel is used for removing and controlling humidity.

(v) The catalytic effect of a number of catalysts like spongy iron (in the manufacture of ammonia) and nickel, platinum or palladium (used in the reduction of unsaturated hydrocarbons) is based on the principle of adsorption.