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.

How do you calculate Langmuir model?

How can I plot the Langmuir adsorption isotherm? ce/qe = 1/qm KL + ce/qm , where ce is the equilibrium concentration of the adsorbate and qe is the adsorption capacity adsorbed at equilibrium, qm is maximum adsorption capacity and KL is the Langmuir adsorption constant.

What is Langmuir and Freundlich?

Langmuir-type adsorption is considered to be a monolayer process. Freundlich-type adsorption is considered to be a multi-layer process in which the amount of adsorbed solute per unit adsorbent mass increases gradually. Freundlich parameters were also used to characterize the adsorption process.

What are the three assumptions of the Langmuir isotherm?

The Langmuir adsorption isotherm was derived by the US chemist Irving Langmuir (1881–1957), using the kinetic theory of gases and making the assumptions that: (1) the adsorption consists entirely of a monolayer at the surface; (2) there is no interaction between molecules on different sites and each site can hold only …

What are the limitations of Langmuir adsorption isotherm?

(i) One of the drawbacks of Freundlich adsorption isotherm is that it fails at high pressure of the gas. Irving Langmuir in 1916 derived a simple adsorption isotherm, on theoretical considerations based on kinetic theory of gases. This is named as Langmuir adsorption isotherm.

What is the value of Langmuir constant?

The average values of the empirical constant and adsorption constant (saturation coefficient) for the Langmuir equation were a = 0.022 mg/g and b = 1.46 l/mg, respectively. The average values of the Freundlich adsorption constant and empirical coefficient were Kf = 0.010 mg/g and n = 1.58 l/mg, respectively.

Which is better Langmuir or Freundlich?

The adsorption data were analyzed by the Langmuir and Freundlich isotherm model. 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 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.

Is Langmuir an isotherm Physisorption?

Langmuir model is associated with monolayer adsorption, while Freundlich one is related to multilayer adsorption. I have seen in some papers that, according with the previous info, Langmuir isotherm seems to reveal chemisorption, while Freundlich equation seems inform about physisorption.

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.

What is KF in Freundlich?

The units of KF from Freundlich isotherm are (mg/g)*(L/mg)^1/n and not unitless or L/g or mg/g as expressed in many manuscripts. there is only one case that gives you the sorption capacity (not the maximum adsorption capacity) which is when the solution concetration is 1 mg/L.

Why is Langmuir isotherm used in protein adsorption studies?

Because isotherm data from protein adsorption studies often appear to be fit well by the Langmuir isotherm model, estimates of protein binding affinity have often been made from its use despite that fact that none of the conditions required for a Langmuir adsorption process may be satisfied for this type of application.

What are the assumptions of the Langmuir adsorption model?

In 1932, the Langmuir adsorption model was proposed by Irving Langmuir [16] and the main assumptions of this isotherm model are the following: Adsorption occurs at specific binding sites that are localized on the surface of the adsorbent. All adsorption sites on the surface of the adsorbent are identical.

Which is the correct approach for hydroxylation of Langmuir?

Both approaches account for hydroxylation and retrieve the electrostatic contributions from some electrical double layer (EDL) model. If compared to 1-pK models, the 2-pK approach is widely used particularly for metal (hydrous) oxides.

What does Langmuir assume about fractional surface coverage?

Langmuir further assumes that the fractional surface coverage θ is in direct proportion to the rate of desorption from the surface, and the adsorption and desorption rates are equal at equilibrium. ka is the respective rate constant for adsorption kd is the respective rate constant for desorption.