Application Of Adsorption
Category : JEE Main & Advanced
The phenomenon of adsorption finds a number of applications. Important applications are given as follows.
(1) Production of high vacuum
(2) In Gas masks : This apparatus is used to adsorb poisonous gases (e.g. \[C{{l}_{2}},\,CO,\,\]oxide of sulphur etc.) and thus purify the air for breathing.
(3) For desiccation or dehumidification : These substances can be used to reduce/remove water vapours or moisture present in the air. Silica gel and alumina are used for dehumidification in electronic equipment.
(4) Removel of colouring matter from solution : (i) Animal charcoal removes colours of solutions by adsorbing coloured impurities. (ii) Animal charcoal is used as decolouriser in the manufacture of cane sugar.
(5) Heterogeneous catalysis : Mostly heterogeneous catalytic reactions proceed through the adsorption of gaseous reactants on solid catalyst. For example,
(i) Finely powdered nickel is used for the hydrogenation of oils.
(ii) Finely divided vanadium pentaoxide \[({{V}_{2}}{{O}_{5}})\] is used in the contact process for the manufacture of sulphuric acid.
(6) Separation of inert gases : Due to the difference in degree of adsorption of gases by charcoal, a mixture of inert gases can be separated by adsorption on coconut charcoal at different low temperatures.
(7) Softening of hard water
(i) The hard water is made to pass through a column packed with zeolite (sodium aluminium silicate)
(ii) Ca++, Mg++ ions which are responsible for hardness, get adsorbed on zeolite, exchanging sodium ions.
\[N{{a}_{2}}A{{l}_{2}}S{{i}_{2}}{{O}_{8}}+CaC{{l}_{2}}\xrightarrow{{}}CaA{{l}_{2}}S{{i}_{2}}{{O}_{8}}+2NaCl\]
(iii) The exhausted zeolite is regenerated with 10% of sodium chloride solution.
\[CaA{{l}_{2}}S{{i}_{2}}{{O}_{8}}+2NaCl\xrightarrow{{}}N{{a}_{2}}A{{l}_{2}}S{{i}_{2}}{{O}_{8}}+CaC{{l}_{2}}\]
(8) De-ionisation of water
(i) Water can be de-ionised by removing all dissolved salts with the help of cation and anion-exchanger resin.
(ii) Cation-exchanger is an organic synthetic resin such as polystyrene-containing a macroanion \[(R-SO_{3}^{-}\,\text{etc}.)\]which has adsorbed H+ ions.
(iii) A resin containing a basic group \[({{R}_{3}}N_{{}}^{+}\,\text{etc}\text{.})\] which has adsorbed \[O{{H}^{-}}\] ions acts as anion exchanger.
(9) In curing diseases : A number of drugs are adsorbed on the germs and kill them or these are adsorbed on the tissues and heat them.
(10) Cleaning agents : Soap and detergents get adsorbed on the interface and thus reduce the surface tension between dirt and cloth, subsequently the dirt is removed from the cloth.
(11) Froth floatation process
A low grade sulphide ore is concentrated by separating it from silica and other earthy matter by this method.
(12) In adsorption indicators
Surface of certain precipitates such as silver halide, have the property of adsorbing some dyes like eosin, fluorescein etc.
(13) Chromatographic analysis
The phenomenon of adsorption has given an excellent technique of analysis known as chromatographic analysis.
(14) In dyeing : Many dyes get adsorbed on the cloth either directly or by the use of mordants.
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