| |
A relation between the amount of adsorbate adsorbed on a given surface at constant temperature and the equilibrium concentration of the substrate in contact with the adsorbent is known as Adsorption Isotherm. Two types of typical adsorption isotherms are shown in the following Figures A & B. Figure A shows adsorption with monolayer formation at saturation point. Figure B shows a situation when several layers of adsorbate molecules are formed on the surface of the adsorbent (multilayer adsorption).
|
| |
Fig 36.1 Monolayer vs multilayer adsorption. |
| |
Xm is the amount of the substrate required to make a monolayer where as Po is the saturation equilibrium concentration of the substrate. |
| |
Arrangement of adsorbed molecules on the surface of the adsorbent could normally be monolayer in nature. Normally, chemisorption leads to monolayer adsorption whereas multilayer arrangement of substrate molecules is observed due to physisorption only. Multilayer formation is also possible due to chemisorption followed by physisorption. |
