Difference Between Adsorption and Absorption (With Table)

Adsorption and Absorption are the two vital process that occurs regularly in our day-to-day life. Both are natural phenomena that we witness occurring around us. It is seen in both living and non-living objects. The application might differ from balancing internal stability to intaking nutrients.

The name is quite similar to each other. However, they are two completely different processes. The chemical changes or reaction occurring in the two is quite the opposite.

Adsorption vs Absorption

The main difference between Adsorption and Absorption is how the fluid is dissolved by a solid or a liquid. In the case of Adsorption, the molecules get concentrated on the surface of the given adsorbent. Whereas Absorption, pass through large material and has an even concentration.

Adsorption is a surface phenomenon. It is the phenomenon of adhesion of the molecules of a substance that are present on the surface of a given solid or liquid. The substance which is linked to it and gets adsorbed is known as the absorbate. The substance which adsorbs adsorbate is known as adsorbent.

On the other hand, Absorption is a bulk phenomenon. It is the phenomenon where a given substance enters a volume of another substance. The given substance which gets absorbed is known as absorbate. The substance which absorbs it is known as absorbent.

Comparison Table Between Adsorption and Absorption

Parameters of ComparisonAdsorptionAbsorption
DefinitionIt is the process of the accumulation of molecules at the bottom.It is the process of assimilation of the molecular system throughout the state of solid or liquid.
ProcessIt is an exothermic process.It is an endothermic process.
ConcentrationIts concentration varies. The concentration at the bottom differs from that at the top.It has an even concentration throughout.
TemperatureIt is mainly influenced by low temperatures.The temperature does not influence it.
Reaction RateIt occurs at a uniform rate.It keeps increasing until it reaches a state of equilibrium.

What is Adsorption?

It is always an exothermic process and there is interesting scientific reasoning behind it. This is because in this process the particles are concentrated at the surface for the reaction to take place. Hence, the residual forces on the surface of the adsorbent decrease. This eventually results in decreased surface energy. The energy henceforth appears in the form of heat.

The principle of Adsorption is applicable for various industrial purposes. For example, activated charcoal, heterogeneous catalyst, etc. Furthermore, it includes water purification and increasing storage capacity. Just like the phenomenon of surface tension, Adsorption is a consequence of surface energy.

Adsorption is of two types – Physisorption and Chemisorption. Physical Adsorption is referred to as Physisorption. It takes place when the gas molecules are held together by a sum of attractive or repulsive force. The force acts between the molecules and electrostatic force. It is a reversible process. It can be brought back to its original state by decreasing the pressure.

Chemical Adsorption is referred to as Chemisorption. It takes place when the gas molecules are bound together with the surface by a strong chemical bond. It occurs in specific locations known as active sites. This process results in an increasing rate of reaction or catalyst presence. It requires high pressure and is irreversible in nature.

What is Absorption?

In brief, Absorption means the process in which any substance collects energy and then transforms it. It is a phenomenon where a certain substance accepts or takes in another substance. The absorbent then distributes the collected substance throughout the whole container or medium.

Absorption is of two types – Physical Absorption and Chemical Absorption. In Physical Absorption, the electronic configuration of the molecule or atom barely takes part. It is a complete non-reactive process. For instance, when oxygen is present in the air the dissolves in water, Physical Absorption takes place.

Chemical Absorption is also known as reactive Absorption. It sometimes combines with the physical Absorption and is referred to as the chemical reaction that takes place between the absorbate and the absorbing substance.

There are a few common applications of the absorption cycle for industrial purposes, absorption chillers being the most common. It is required for ice production, inlet cooling, and cold storage. Environment-friendly refrigerators are based on the principle of the absorption cycle. Few types of machinery comprise moving parts that require high maintenance. For such cases, the process of absorption is a great choice.

Main Differences Between Adsorption and Absorption

  1. The main difference between Adsorption and Absorption is the type of phenomenon. Adsorption is a surface phenomenon and is an exothermic process. Whereas, Absorption is a bulk phenomenon and is endothermic. . 
  2. The next distinct difference is the process. Adsorption refers to the process of accumulation of molecules at the bottom. Absorption refers to the process of assimilation of the molecular system throughout the state of solid or liquid.
  3. In Adsorption, the reaction takes place at a uniform rate. In Absorption, it keeps increasing until it reaches a state of equilibrium.
  4.  In Adsorption, concentration varies. The concentration at the bottom differs from that at the top. However, in the case of Absorption, it has an even concentration throughout.
  5. Low temperatures influences adsorption. On the other hand, the temperature does not influence absorption.

Conclusion

Both Adsorption and Absorption are termed sorption processes. Absorption mainly occurs when the molecules enter a bulky material. This results in uneven concentration. The particles completely dissolve in the absorbent to form a solution. Once this action is completed, the particle and absorbent can not be extracted separately by any means.

The process of Adsorption is caused due to electrostatic force of attraction. In this condition, the molecules are present on the surface of the absorbent. It is held very loosely hence can easily be removed. The inside forces are balanced, whereas the surface forces are unbalanced. This, in turn, tends to attract the absorbate.

References

  1. https://gcms.cz/labrulez-bucket-strapi-h3hsga3/application::paper.paper/7943.pdf
  2. https://www.sciencedirect.com/science/article/pii/S1381514803001664
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