Chemical adsorption orChemisorption or Activated adsorption
1. It is very slow
2. It is very specific depends on nature of adsorbent and adsorbate.
3. chemical adsorption is fast with increase pressure, it can not alter the amount.
4. When temperature is raised chemisorption first increases and then decreases.
5. Chemisorption involves transfer of electrons between the adsorbent and adsorbate,
Heat of adsorption is high i.e., from 40 – 400kJ/mole.
6. Monolayer of the adsorbate is formed.
7. Adsorption occurs at fixed sites called active centres. It depends on surface area .
8. Chemisorption involves the formation of activated complex with appreciable activation energy.
9. Physical adsorption or van der waals adsorption or Physisorptlon
10. It is irreversible
Physical adsorption or van der waals adsorption or physisorption.
1. It is instantaneous
2. It is non-specific
3. In Physisorption. when pressure increases the amount of adsorption increases.
4. Physisorption decreases with increase in temperature.
5. No transfer of electrons
6. Heat of adsorption is low in the order of 4OkJ/mole.
7. Multilayer of the adsorbate is formed on the adsorbent.
8. It occurs on all sides.
9. Activation energy is insignificant.
10. It is reversible.
