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What do you mean by adsorption isotherm? Describe Freundlich adsorption isotherm.?
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What do you mean by adsorption isotherm? Describe Freundlich adsorptio...
Adsorption isotherms have been of immense importance to researches dealing with environmental protection and adsorption techniques. The two primary methods used for predicting the adsorption capacity of a given material are known as the Freundlich and Langmuir isotherms.
An adsorption isotherm is a graph that represents the variation in the amount of adsorbate(x) adsorbed on the surface of the adsorbent with the change in pressure at a constant temperature.

Adsorption Isotherm
As we know from Le Chatelier’s principle, the direction of equilibrium in a reaction shifts in the direction in which stress is relieved. So, here we can see that upon application of excess pressure on the system, the equilibrium shifts in thedirection where the number of molecules decreases so that the pressure in the system decreases. Different adsorption isotherms have been proposed by different scientists namely,
Langmuir isotherm
Freundlich isotherm
BET theory
Freundlich adsorption gives the variation in the quantity of gas adsorbed by a unit mass of solid adsorbent with the change in pressure of the system for a given temperature.
The Freundlich adsorption isotherm is followed by another two isotherms, Langmuir adsorption isotherms and BET theory. The Langmuir adsorption isotherms predict linear adsorption at low adsorption densities and a maximum surface coverage at higher solute metal concentrations
The theory of multilayer adsorption proposed by Brunauer, Emmett and Teller in 1938 (BET Theory) assumes that physisorption results in the formation of multilayer adsorption. The theory also assumes that the solid surface has uniform sites of adsorption and that adsorption at one site does not affect adsorption at neighbouring sites.
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What do you mean by adsorption isotherm? Describe Freundlich adsorptio...
Adsorption Isotherm

Adsorption isotherm is a mathematical relationship that describes the distribution of adsorbate molecules between the solid adsorbent and the liquid or gas phase at equilibrium. It provides quantitative information about the adsorption process and helps in understanding the interaction between the adsorbent and adsorbate.

Freundlich Adsorption Isotherm

The Freundlich adsorption isotherm is one of the most commonly used empirical equations that describes the adsorption process. It was developed by Herbert Freundlich in 1906. The equation is expressed as:

Q = K * C^(1/n)

Where:
- Q is the amount of adsorbate adsorbed per unit mass of adsorbent (adsorption capacity),
- K is the Freundlich constant related to the adsorption capacity,
- C is the equilibrium concentration of the adsorbate in the liquid or gas phase,
- n is the Freundlich exponent related to the intensity of adsorption.

The Freundlich adsorption isotherm assumes that the adsorption occurs on a heterogeneous surface with different adsorption sites of varying energies. The equation suggests that the adsorption process is multilayered and that the adsorption capacity increases with increasing adsorbate concentration.

Explanation of Freundlich Adsorption Isotherm

1. Adsorption Capacity: The Freundlich equation indicates that the amount of adsorbate adsorbed increases with increasing concentration. As the concentration of the adsorbate increases, more adsorbate molecules are attracted to the available adsorption sites on the adsorbent surface.

2. Freundlich Constant: The Freundlich constant (K) represents the adsorption capacity of the adsorbent. It depends on the nature of the adsorbate and adsorbent and is determined experimentally. A higher value of K indicates a higher adsorption capacity.

3. Freundlich Exponent: The Freundlich exponent (n) is a measure of the intensity of adsorption. It signifies the degree of nonlinearity in the adsorption isotherm. If the value of n is less than 1, the adsorption is favorable. If n is greater than 1, the adsorption is less favorable.

4. Limitations: The Freundlich adsorption isotherm assumes that the adsorption process is reversible, non-specific, and occurs on a heterogeneous surface. It does not consider factors such as the presence of multiple layers of adsorption or the effect of temperature on adsorption.

In conclusion, the Freundlich adsorption isotherm provides valuable insights into the adsorption process. It helps in understanding the interaction between the adsorbate and adsorbent and provides a mathematical model for predicting the adsorption capacity at different equilibrium concentrations.
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What do you mean by adsorption isotherm? Describe Freundlich adsorption isotherm.?
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