Physisorption (Physical adsorption) | Chemisorption (Chemical adsorption) |
Weak van der Waals forces are present between the adsorbate molecules and the adsorbent. | Strong chemical forces similar to chemical bonds are present between the adsorbate molecules and the adsorbent. |
The enthalpy of adsorption is low (20 to 40 kJ/mol). | The enthalpy of adsorption is high (40 to 400 kJ/mol). |
Occurs at low temperature and decreases with an increase in temperature. | Occurs at high temperature and increases with increase in temperature. |
It is reversible. | It is irreversible. |
No significant activation energy is required. | Usually, high activation energy is required. |
It forms multimolecular layers. | It forms unimolecular layers. |