Difference Between Freundlich and Langmuir Adsorption Isotherms

There is a fundamental difference between both models. Langmuir's model was a theoretical construct, while the Freundlich isotherm is empirical. In the Langmuir model, it is assumed that at maximum coverage, there is only a monomolecular layer on the surface. This means that there is no stacking of adsorbed molecules.

1. What are Freundlich adsorption isotherms?
2. What is Freundlich and Langmuir constant?
3. What are the three assumptions of the Langmuir isotherm?
4. What do you understand by adsorption isotherm discuss briefly Freundlich adsorption isotherm?
5. What is the drawback of Freundlich adsorption isotherm?
6. Which is Freundlich's equation?
7. How is Langmuir constant calculated?
8. What is Langmuir constant?
9. Which is Freundlich adsorption isotherm equation?
10. What is Langmuir surface area?
11. What is the physical significance of Langmuir adsorption isotherm?
12. Why do the desorption and adsorption isotherms not lying in the same line?

What are Freundlich adsorption isotherms?

The Freundlich equation or Freundlich adsorption isotherm, an adsorption isotherm, is an empirical relationship between the quantity of a gas adsorbed into a solid surface and the gas pressure. ... This equation is known as Freundlich adsorption isotherm or Freundlich adsorption equation.

What is Freundlich and Langmuir constant?

In adsorption process the adsorbate is adhered to the surface of adsorbent. ... K and b are constants indicating adsorption affinity and capacity and is dependent on the nature of the adsorbent and adsorbate and on temperature.

What are the three assumptions of the Langmuir isotherm?

Basic hypotheses of the model

• The surface containing the adsorbing sites is a perfectly flat plane with no corrugations (assume the surface is homogeneous). ...
• The adsorbing gas adsorbs into an immobile state.
• All sites are energetically equivalent and the energy of adsorption is equal for all sites.

What do you understand by adsorption isotherm discuss briefly Freundlich adsorption isotherm?

Freundlich adsorption isotherm gives an empirical relationship between the quantity of gas adsorbed by the unit mass of solid adsorbent and pressure at a specific temperature. From the given plot it is clear that at pressure PS,(x/m) reaches the maximum valve. Ps is called the saturation pressure.

What is the drawback of Freundlich adsorption isotherm?

Limitations of Freundlich Isotherm

Freundlich isotherm only approximately explains the behaviour of adsorption. The value of 1/n can be between 0 and 1, therefore the equation holds good only over a limited range of pressure.

Which is Freundlich's equation?

mx​=exp−(−Kp)

How is Langmuir constant calculated?

For langmuir isotherm: Using the formula qe=(Ci−Cf)Vmass of adsorbent, and then plot the graph 1qe versus 1Cf. It would be easier by using excel. From the graph, we can calculate the slope.

What is Langmuir constant?

The Langmuir constant (K) indicates the extent of interaction between adsorbate and the surface. If the value of K is relatively larger it indicates that there is a strong interaction between adsorbate and adsorbent while smaller value implies a weak interaction.

Which is Freundlich adsorption isotherm equation?

A gas undergoes physical adsorption on a surface and follows the given Freundlich adsorption isotherm equation: mx​=kp0.

What is Langmuir surface area?

Brunauer–Emmett–Teller (BET) surface area is measured by specific surface area of the adsorbent. ... Langmuir surface area depends on adsorption capacity of the adsorbent.

What is the physical significance of Langmuir adsorption isotherm?

The Langumuir adsorption isotherm describes the fraction of the surface that is covered by adsorbate molecules for a particular temperature and pressure of adsorbate. This constant is analogous to the K values used to describe the equilibrium of components distributing between gas/liquid phases.

Why do the desorption and adsorption isotherms not lying in the same line?

As partial pressure in sample cell is increased gas is adsorbed initially and gets condensed over the surface. N2 isotherms are usually a straight line below 0.3 partial pressure. ... Above 0.3, usually BET isotherm is not a straight line. This occurs due to multilayer adsorption process.