What is the difference between Freundlich and Langmuir isotherm?
The key difference between Freundlich and Langmuir adsorption isotherms is that Freundlich adsorption isotherm is empirical, whereas Langmuir adsorption isotherm is theoretical. The adsorption isotherm is a primary method that we can use to predict the adsorption capacity of a particular substance.
Which is better Langmuir or Freundlich?
It was observed that the Freundlich isotherm model described the adsorption process with high coefficient of determination R2, better than the Langmuir isotherm model and for low initial concentration of heavy metal.
What are the main points of the Langmuir theory of adsorption?
All adsorption sites on the surface of the adsorbent are identical. The surface of the adsorbent is covered with a monolayer of adsorbed molecules. There is no interaction between the adsorbed molecules on the adsorbent surface.
In what respect Langmuir isotherm is superior to Freundlich adsorption isotherm?
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. The Freundlich isotherm does not have this restriction.
What is the significance of the Langmuir constants A & B?
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.
What is Langmuir Freundlich isotherm?
The Langmuir isotherm models the adsorption of gas molecules on the surface of a solid sorbent at constant temperature on a fixed absorption bed. It simulates the surface coverage of a monolayer without intermediate forces between gas molecules already adsorbed on the surface of sorbent.
Under what conditions Freundlich adsorption isotherm fails?
Freundlich isotherm fails at high pressure. If the plot of log x/m on the y-axis and log P on the x-axis is a straight line, then Freundlich isotherm is valid.
Is Freundlich an isotherm monolayer?
Langmuir and Freundlich isotherms to discriminate between chemisorption and physisorption. Langmuir model is associated with monolayer adsorption, while Freundlich one is related to multilayer adsorption.
What are the Freundlich and Langmuir adsorption isotherms?
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.
When did Anderson and Hingston use Langmuir isotherm?
Anderson et al. (1976) used the Langmuir isotherm to fit arsenate adsorption at different pH values. Hingston et al. (1971) used a modified Langmuir isotherm to model competitive adsorption of arsenate in presence of phosphate at different pH values.
How is the Langmuir-Freundlich isotherm model used in marine algae?
Yu and Kaewsarn (1999) used a modified Langmuir isotherm to describe pH dependent bio-sorption of heavy metals on marine algae. However, these studies have simply regressed various forms of Langmuir isotherm expressions by fitting the values of the affinity constant and adsorption capacity to pH-dependent sorption datasets.
What is the Langmuir isotherm model Eq.( 1 )?
The Langmuir isotherm model Eq. (1) was originally developed to describe and quantify sorption on a set of distinct localized adsorption sites and has been used to describe both physical and chemical adsorption. This model is based upon the following main assumptions ( Langmuir, 1916 ):