The adsorption of a gas on a solid surface is an example of physical adsorption. It is influenced by the following factors :
(i) Nature of the adsorbate
(ii) Nature of the adsorbent
(iii) Surface area of the adsorbent
(iv) Activation of the adsorbent
(v) Effect of pressure
(vi) Effect of temperature.
Factors affecting adsorption of a gas on solids are :
Nature of the adsorbate: The same gas is adsorbed to different extents by different solids at the same temperature. Also, greater the surface area of the adsorbent, more is the gas adsorbed.
Nature of the adsorbent: Different gases are adsorbed to different extents by different solids at the same temperature. Higher the critical temperature of the gas, greater is its amount adsorbed.
Surface area of the adsorbent: Surface area available for adsorption per gram of the adsorbent increases the extent of adsorption. Greater the surface area, higher would be the adsorption therefore, porous or powdered adsorbents are used.
Activation of adsorbent: It means increasing the adsorbing power of an adsorbent by increasing its surface area. It is done by :
- making the adsorbent’s surface rough
- removing gases already adsorbed
- subdividing the adsorbent into smaller pieces.
Pressure: At constant temperature, the adsorption of gas increases with pressure.
Temperature: Since adsorption is an exothermic process, applying Le Chatelier’s principle, we can find out that adsorption decreases with an increase in temperature.
