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Adsorption Isotherms Applications - Explain, FAQs

Adsorption Isotherms Applications - Explain, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 05:05 PM IST

You are about to head out on an extended dive down into the deep ocean as a scuba diver. The tanks you are about to use are not filled just with compressed air but have special filters in them to absorb harmful gases so that you will be able to breathe safely while submerged. An important process whereby gases are attached to the surface of a material is adsorption in action. Not only in scuba tanks, but adsorption is employed in many applications: water purification systems, like air conditioners, and even some medical treatments using activated charcoal to adsorb toxins. These applications, related to real life, shall underline the necessity to understand the adsorption isotherms defining how the molecules will distribute at equilibrium between the liquid phase and the solid surface.

Detailed Explanation and Article Outline

Adsorption isotherms provide basic theory for a huge area of industrial applications and scientific research. They set a mathematical basis according to which adsorbates interact with surfaces. This paper is aimed at presenting the Landsberg optical constants, which shall help delve into the very basics of adsorption isotherms: types, underlying principles, and practical implications. The paper shall start with a definition of the main concepts and terminology. In the next section, various types of adsorption isotherms, such as Langmuir, Freundlich, and BET isotherms, are considered. Afterward, we will turn to the meaning and applications of adsorption isotherms in practical cases and academia. It goes from environmental engineering to pharmaceuticals.

Also read -

Adsorption Isotherms: Understanding and Implications

Adsorption isotherms are graphic representations of the interaction of adsorbate-adsorbent at constant temperature. It plots the amount of adsorbate on the adsorbent versus its fluid-phase concentration to project a view of the adsorption process. Keywords:

  • Adsorbate: It means the adsorbed substance.
  • Adsorbent: It refers to the material on which adsorption will take place.
  • Isotherm: It is the curve showing the variation of adsorbate concentration under constant temperature with its adsorption extent.
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The characteristic studies of adsorption isotherms would make it possible to understand the surface properties and capacities of different adsorbents so an effective adsorption system could be designed.

Types of Adsorption Isotherms

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There are different types of adsorption isotherm models, all with their own characteristics. These include:

  1. Langmuir Isotherm: Assumption of monolayer adsorption onto a surface comprising a finite number of adsorption sites. It is characterized by the equation:

The Langmuir adsorption isotherm equation is given by:

$$
\theta = \frac{bP}{1 + bP}
$$

where:
$\theta$ is the fraction of the surface covered by the adsorbate.
$P$ is the pressure of the adsorbate.
$b$ is the Langmuir constant.

  1. Freundlich Isotherm: Applied for heterogeneous surfaces, it can commonly be expressed as:

The Freundlich adsorption isotherm equation is given by:

$$
x/m = kP^{1/n}
$$

where:
$x/m$ is the amount of adsorbate per unit mass of adsorbent.
$P$ is the pressure of the adsorbate.
$k$ and $n$ are empirical constants specific to the system.

3. BET Isotherm: Generalization of the Langmuir model for multilayer adsorption usually applied for porous materials.

Each model offers insights into different dimensions of the interaction of adsorbate with the surface, hence providing clues to choosing relevant models depending on the application.

Relevance and Applications

Adsorption isotherms find application in the following industrial and research sectors:

  • Environmental Engineering: Adsorption isotherms turn out to be useful during water and air treatments in the selection and design of adsorbents for removing contaminants.
  • Pharmaceuticals: The principles of adsorption are utilized in drug delivery systems by controlling the release of active ingredients.
  • Chemical Engineering: Understanding adsorption isotherms helps in the design of catalysts and reactors.
  • Agriculture: In soil science, adsorption isotherms are applied to the study of nutrient uptake and pesticide behavior.

The applicability of adsorption isotherms in academic research falls under very significant application. Characterization of novel materials and understanding their surface properties are fundamentally important in the materials field. They provide insights into the adsorption mechanisms critical in developing innovative solutions in the domain of science.

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Recommended topic video on(adsorption isotherms)

Some Solved Examples

Example 1

Question:
The curve showing the variation of adsorption with pressure at constant temperature is called?

1) An innovative
2) Adsorption isotherm
3) Adsorption isobar
4) All are incorrect

Solution:
The correct answer is option (2), Adsorption isotherm. An adsorption isotherm represents the relationship between the amount of gas adsorbed by an adsorbent and the pressure of the gas at a constant temperature.

Example 2

Question:
How is the extent of adsorption represented?

1) $(\frac{m}{x})$
2) $(m \times x)$
3) $(\frac{x}{m})$
4) All are incorrect

Solution:
The correct representation of the extent of adsorption is (frac{x}{m}), where (x) is the mass of gas adsorbed and (m) is the mass of the adsorbent. This ratio gives a measure of the adsorption capacity relative to the mass of the adsorbent.

Example 3

Question:
If adsorption of a gas follows Freundlich adsorption isotherm, and (x) is the mass of gas absorbed on mass (m) of the adsorbent, what is the correct plot of (frac{x}{m}) vs (P)?

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Solution:
According to the Freundlich adsorption isotherm, the plot of (frac{x}{m}) vs (P) is not linear but follows a specific empirical equation. However, for the purposes of this question, Option (4) would typically show a non-linear curve representing the Freundlich isotherm relationship.

These examples illustrate the application of adsorption isotherms and the representation of adsorption extent in various contexts.

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Related Topics Link,

Summary

Adsorption isotherms are among the preferred methods of understanding substance–surface interactions. They guide practical applications in such wide fields as environmental engineering, pharmaceuticals, and even chemical engineering. Knowing the basics of adsorption isotherms, their types, and applications will help us achieve an all-rounded understanding of this key process. The adsorption isotherms can not only help design a viable adsorption system but also enhance our capabilities towards pollution control, advanced material development, and many more.

Also check-

NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What is isotherm?

Isotherm is a change in a system where the temperature remains constant and it is known as an isothermal process. Here, ΔT = 0. Isotherm, is line drawn on a map or chart joining points with the same temperature. Isotherms are commonly used on a chart indicating constant level.

2. What is the meaning of Desorption?

The release of an adsorbed substance from a surface is referred to as desorption. This is the reversal of the sorption process. Desorption happens when the bulk phase and the adsorbing surface are in a condition of sorption equilibrium. As a result, lowering the bulk phase concentration causes some of the desorbed substance to revert to the bulk state. Desorption process helps the mobility of the mobile phase in chromatography.

3. Write about chemical adsorption?

The process is unique in that it will only occur if a chemical bond is formed between the adsorbent and the adsorbate. In nature, the process is irreversible. It's an exothermic reaction, which means the temperature rises as a result of the reaction. In chemical adsorption the rate of adsorption is slow when the temperature is low, but as the pressure rises, it happens faster. Chemisorption, like physisorption, is directly proportional to surface area and so increases as surface area grows. The enthalpy is high because the process requires chemical bond formation. It necessitates a specific amount of activation energy.

4. What is an absorption isotherm?

Adsorption isotherm; Adsorption isotherms have played a critical role in studies of environmental protection and adsorption strategies. The Freundlich and Langmuir isotherms are the two most used approaches for predicting a material's adsorption capacity. At a constant temperature, the Freundlich adsorption isotherm graph is a graph that depicts the fluctuation in the amount of adsorbate(x) adsorbed on the surface of the adsorbent as a function of pressure. The direction of equilibrium in a reaction varies in the direction that stress is relieved, as we know from Le Chatelier's principle. As a result, we can see that when the system is subjected to excessive pressure, the equilibrium moves in the direction of fewer molecules, lowering the pressure in the system.

5. Write any two applications of Adsorption?

Removal of colour: To obtain a clear liquid solution, the juice collected from cane is treated with animal charcoal to remove the colouring ingredient.

As Catalysts: Appropriate materials are used as catalysts so that reactants attach to their surface, allowing the reaction to occur more quickly and increasing the rate of reaction.

6. What is isotherm?

Isotherm is a change in a system where the temperature remains constant and it is known as an isothermal process. Here, ΔT = 0. Isotherm, is line drawn on a map or chart joining points with the same temperature. Isotherms are commonly used on a chart indicating constant level.

7. What is the meaning of Desorption?

The release of an adsorbed substance from a surface is referred to as desorption. This is the reversal of the sorption process. Desorption happens when the bulk phase and the adsorbing surface are in a condition of sorption equilibrium. As a result, lowering the bulk phase concentration causes some of the desorbed substance to revert to the bulk state. Desorption process helps the mobility of the mobile phase in chromatography.

8. Write about chemical adsorption?

The process is unique in that it will only occur if a chemical bond is formed between the adsorbent and the adsorbate. In nature, the process is irreversible. It's an exothermic reaction, which means the temperature rises as a result of the reaction. In chemical adsorption the rate of adsorption is slow when the temperature is low, but as the pressure rises, it happens faster. Chemisorption, like physisorption, is directly proportional to surface area and so increases as surface area grows. The enthalpy is high because the process requires chemical bond formation. It necessitates a specific amount of activation energy.

9. What is an absorption isotherm?

Adsorption isotherm; Adsorption isotherms have played a critical role in studies of environmental protection and adsorption strategies. The Freundlich and Langmuir isotherms are the two most used approaches for predicting a material's adsorption capacity. At a constant temperature, the Freundlich adsorption isotherm graph is a graph that depicts the fluctuation in the amount of adsorbate(x) adsorbed on the surface of the adsorbent as a function of pressure. The direction of equilibrium in a reaction varies in the direction that stress is relieved, as we know from Le Chatelier's principle. As a result, we can see that when the system is subjected to excessive pressure, the equilibrium moves in the direction of fewer molecules, lowering the pressure in the system.

10. Write any two applications of Adsorption?

Removal of colour: To obtain a clear liquid solution, the juice collected from cane is treated with animal charcoal to remove the colouring ingredient.

As Catalysts: Appropriate materials are used as catalysts so that reactants attach to their surface, allowing the reaction to occur more quickly and increasing the rate of reaction.

11. What is an adsorption isotherm?
An adsorption isotherm is a graph that shows the relationship between the amount of gas adsorbed on a solid surface and the pressure or concentration of the gas at a constant temperature. It helps us understand how molecules interact with surfaces and is crucial in various applications of surface chemistry.
12. How are adsorption isotherms used to determine the surface area of materials?
Adsorption isotherms, particularly those analyzed using the BET theory, are used to determine the surface area of materials by measuring the amount of gas (usually nitrogen) adsorbed at different pressures. The data is then used to calculate the monolayer capacity, which, combined with the known size of the gas molecule, allows for the estimation of the material's specific surface area.
13. What is the Henry's law region in adsorption isotherms?
The Henry's law region is the initial, linear portion of an adsorption isotherm at very low pressures or concentrations. In this region, the amount of gas adsorbed is directly proportional to its pressure or concentration in the bulk phase. This relationship is described by Henry's law and is useful for understanding adsorption behavior at low surface coverages.
14. How do adsorption isotherms help in understanding gas storage mechanisms?
Adsorption isotherms help in understanding gas storage mechanisms by:
15. What is the Freundlich adsorption isotherm, and when is it applicable?
The Freundlich adsorption isotherm is an empirical model that describes adsorption on heterogeneous surfaces. It is applicable when:
16. How do adsorption isotherms help in understanding the behavior of porous materials?
Adsorption isotherms help in understanding porous materials by:
17. What is the difference between linear and nonlinear adsorption isotherms?
Linear and nonlinear adsorption isotherms differ in several ways:
18. Why are adsorption isotherms important in surface chemistry?
Adsorption isotherms are important because they provide valuable information about the adsorption process, surface properties of adsorbents, and the nature of adsorbate-adsorbent interactions. This information is essential for designing and optimizing various industrial processes, environmental remediation techniques, and materials science applications.
19. How do adsorption isotherms help in designing gas masks and air purifiers?
Adsorption isotherms help in designing gas masks and air purifiers by providing information on:
20. What role do adsorption isotherms play in catalysis?
Adsorption isotherms play a crucial role in catalysis by:
21. How are adsorption isotherms used in the field of environmental remediation?
In environmental remediation, adsorption isotherms are used to:
22. How are adsorption isotherms used in the design of desiccants and dehumidifiers?
Adsorption isotherms are used in the design of desiccants and dehumidifiers by:
23. What are the main types of adsorption isotherms?
The main types of adsorption isotherms are:
24. How does the Langmuir adsorption isotherm differ from other types?
The Langmuir adsorption isotherm (Type I) assumes monolayer adsorption on a homogeneous surface with no interactions between adsorbed molecules. It reaches a plateau at high pressures, indicating complete surface coverage. Other isotherms, like Types II-VI, account for multilayer adsorption, heterogeneous surfaces, or different adsorbate-adsorbent interactions.
25. What is the difference between physisorption and chemisorption, and how do their isotherms differ?
Physisorption involves weak van der Waals forces between the adsorbate and adsorbent, while chemisorption involves the formation of chemical bonds. Physisorption isotherms (e.g., Types II, III, V) typically show multilayer adsorption and are reversible. Chemisorption isotherms (e.g., Type I) often show monolayer adsorption, have higher adsorption enthalpies, and may be irreversible or only partially reversible.
26. What is the BET (Brunauer-Emmett-Teller) theory, and how does it relate to adsorption isotherms?
The BET theory extends the Langmuir model to account for multilayer adsorption. It assumes that molecules can adsorb on top of already adsorbed molecules, forming multiple layers. The BET theory is widely used to analyze Type II and Type IV isotherms and is particularly useful for determining the specific surface area of porous materials.
27. How do temperature changes affect adsorption isotherms?
Temperature changes can significantly affect adsorption isotherms:
28. What is the significance of hysteresis in adsorption isotherms?
Hysteresis in adsorption isotherms occurs when the adsorption and desorption curves do not coincide. It is typically observed in mesoporous materials (Type IV isotherms) and provides information about the pore structure, size distribution, and shape. Hysteresis is significant because it helps in characterizing porous materials and understanding capillary condensation phenomena.
29. How are adsorption isotherms used in the design of pressure swing adsorption (PSA) systems?
Adsorption isotherms are crucial in designing pressure swing adsorption (PSA) systems by:
30. What is the significance of the inflection point in Type V adsorption isotherms?
The inflection point in Type V adsorption isotherms is significant because:
31. How are adsorption isotherms used in the pharmaceutical industry?
In the pharmaceutical industry, adsorption isotherms are used for:
32. What is the Dubinin-Radushkevich isotherm, and what information does it provide?
The Dubinin-Radushkevich isotherm is a model used to describe adsorption on microporous materials. It provides information about:
33. How do adsorption isotherms help in the design of chromatographic separations?
Adsorption isotherms help in the design of chromatographic separations by:
34. What is the Temkin adsorption isotherm, and how does it differ from other models?
The Temkin adsorption isotherm is a model that assumes the heat of adsorption decreases linearly with increasing surface coverage due to adsorbate-adsorbent interactions. It differs from other models by:
35. How are adsorption isotherms used in the food industry?
In the food industry, adsorption isotherms are used for:
36. What is the significance of the C constant in the BET equation?
The C constant in the BET equation is significant because:
37. How do adsorption isotherms help in understanding the behavior of surfactants?
Adsorption isotherms help in understanding surfactant behavior by:
38. What is the difference between excess adsorption and absolute adsorption?
Excess adsorption and absolute adsorption are two ways of quantifying the amount of gas adsorbed:
39. What is the Sips isotherm, and when is it useful?
The Sips isotherm, also known as the Langmuir-Freundlich isotherm, is a combination of the Langmuir and Freundlich models. It is useful when:
40. How are adsorption isotherms used in the field of ion exchange?
In ion exchange, adsorption isotherms are used to:

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