Applications of Adsorption

• Many applications are based on the phenomenon of adsorption. Some important applications of adsorption are as follows:

A) Applications of the Adsorption of Gases on Solids

i) For creating partial vacuum

• The phenomenon of adsorption of gases on solids has been used for creating partial vacuum particularly at low temperature.
• The vessel that has to be evacuated is connected to a narrow container containing activated animal charcoal which is dipped into liquid nitrogen.
• At low temperature, the extent of adsorption of gases on solids is very high.
• So, by the use of animal charcoal, the gases present in the vessel are adsorbed, and partial vacuum is created.

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ii) In gas masks

• The inhalation of poisonous gases can be prevented using Gas masks.
• The common form of gas masks contains a layer of activated charcoal.
• The air that is inhaled must pass through this layer of activated charcoal.
• The poisonous gases present in the air, such as chlorine, oxides of sulphur, carbon monoxide, etc., get adsorbed on the activated charcoal.
• Thus, the inhaled air is freed from such toxic/poisonous gases.

iii) In heterogeneous catalysis

• Most heterogeneous catalytic reactions initiate through the adsorption of gaseous reactants on solid catalyst. For example:

1. Use of finely powdered nickel for the hydrogenation of oils.
2. Use of finely divided vanadium pentoxide (V₂O₅) in the Contact Process for the manufacture of sulphuric acid.
3. Use of Pt, Pd in many industrial processes as catalyst.

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iv) For desiccation or dehumidification

• There are certain substances that have a strong tendency to adsorb water.
• These substances can be used to reduce or remove water vapours present in the air.
• Silica gel is used for dehumidification in electronic equipment.

B) Applications of Adsorption From Solutions

• The phenomenon of adsorption from solutions has been used for many industrial or domestic applications. Some main applications are mentioned here below:

i) In dyeing

• Many dyes get adsorbed on the cloth either directly or by the use of mordant.

ii) In removing colouring and odouring matter

• The principle of adsorption is used in removing the undesirable colouring and odouring matter from the solutions or liquids.
• From solutions of sugar and other organic liquids such as oils, etc., colouring matter is removed using activated charcoal.
• Undesirable colouring/odouring matter from solutions or liquids can also be removed using Fuller’s earth.

iii) For recovery from industrial wastes/ mixtures

• Components of mixture may be separated making use of the differences in the adsorption power of the various components of any mixture.
• Adsorption provides an efficient method in concentrating the substances present in very dilute solutions.
• The principle of adsorption is employed in several valuable recoveries made from the industrial wastes.

iv) For softening of water

• Hard water can be softened by the use of ion exchange resins.
• The use of these ion exchange resins is based on the selective adsorption from solutions.

v) Chromatographic analysis

• The chromatographic technique depends on the principle of adsorption.
• This technique is used for the identification/separation of various components of a mixture or solutions.

vi) Use of adsorption indicators

• Many dyes can be used as adsorption indicator such as, fluorescein, in silver nitrate precipitation titrations.
• At the completion of the titration, the ions produced by the dye in the solution get adsorbed onto the precipitates of silver halide, and undergo a colour change.

References:

i) https://classnotes.org.in/class12/chemistry12/surface-chemistry/application-adsorption/

ii) http://soft-matter.seas.harvard.edu/index.php/Gas_adsorption_applications

iii) https://sciencing.com/examples-adsorption-18540.html

Applications of Adsorption