Difference between absorption and adsorption

What is the difference between adsorption and absorption is a concept often misunderstood by science students.

When dealing with materials science and chemistry, it can be hard to understand what the difference is between absorption and adsorption. Many teachers try to explain it, but it is hard to understand. This blog will explore the difference between absorption and adsorption and how to apply them in your own life.

Absorption and adsorption are two different methods that can be used to separate a liquid from a solid. The most common example of absorption is a carbonated drink. The drink is basically distilled water with an added sugar. The sugar can be extracted by boiling the water until the sugar has dissolved into the water. The sugar becomes one with the water.

The main difference – absorption and adsorption

Difference between absorption and adsorption

Both absorption and adsorption are physicochemical processes in which one species in a relatively small amount invades/adheres to another in relatively high quantities. The way the materials are taken into each other clearly distinguishes the two processes.

When a small amount of one material completely creeps into the entire volume of other materials and spreads, the so-called “absorption.” 

In contrast, if a small amount of one material adheres only to the outer surface of the other material, it is “adsorption” hence the main difference between absorption and adsorptionand the absorption is the distribution of a particular substance over the entire volume of the other substrate. Adsorption is the adhesion of one substance to the surface of another substrate.

What is absorption?

What is absorption?
What is absorption?

As mentioned above, if we say that one substance is absorbed by another, it means that the first material, depending on the concentration, completely enters the second material over the entire space occupied by its volume. 

Thus, theoretically, atoms, molecules, and ions can enter the bulk phase of another gas, liquid or solid phase. Based on the absorption rate of different substances by absorption (substances that absorb foreign substances), various separation mechanisms have been born. One example is liquid-liquid extraction of chemical substances.

In this case, a substance absorbed by one liquid is brought into contact with another liquid, which has a higher affinity for that substance, and therefore it is distributed into a second liquid, thereby being able to extract it.

Similarly, another example would be the absorbance of oxygen into the water, such that the entire amount of gas is dissolved and evenly distributed throughout the volume of water. Here, the gas dissolves after first contact with the surface. And the amount that moves ultimately depends on the properties of both the liquid and the gas.

This type of absorption is called “physical absorption”. Absorption can be broadly classified as follows: In the latter case, it will be due to a chemical reaction rather than a bulk transfer, depending on the properties of the material involved.

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What is adsorption?

What is adsorption?
What is adsorption?

Adsorption is a “surface phenomenon” and is not strictly different from absorption, which involves the total volume of the material. Therefore, in the case of adsorption, as a result of various types of interactions, a relatively small amount of one substance adheres to the surface of the bulk substrate. 

The substance to be absorbed is called ‘adsorption’ can be broadly divided into two categories: physical adsorption and chemisorption. In the case of physical adsorption, that is, the type of interaction between the adsorbent and the adsorbent is a physical force, such as the van der Waals interaction. However, in the case of chemisorption, it is the chemical bond that binds the chemisorptor to the adsorbent.

The reason for adsorption is similar to surface tension. The molecules in the adsorbent are surrounded by other adsorbent molecules, and their energies on the surface are neutralized. However, this is not the case, since the outer surface layer of the adsorbent is not surrounded by other molecules.

Therefore, the surface of the adsorbent gives extra energy to the inner layer. Therefore, it absorbs other molecules into their surface to minimize surface energy. However, if the surface area of the adsorbent is significantly large, the difference between adsorption and absorption will be almost eliminated on a micromolecular scale.

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Difference between absorption and adsorption


Absorption is the distribution of a substance in the volume of another substrate.

Adsorption is the adherence of a particular substance to the surface of another substrate.

Isolation Process

Absorbed materials can be separated between different phases due to their chemical properties.

The technique of adsorption can be used to separate certain substances by adsorbing them to one surface while flowing another substance that had previously absorbed that substance.


The material acquires absorbed through the availability of space and also to other materials due to the properties of each material.

The vacant surface of the adsorbent has extra energy on it that stimulates the adhesion of foreign molecules.


The resulting material is absorbed and remains in the space of the absorber without completely compromising the chemical relationship as it is when it is free. It may convey only weak physical interactions.

In adsorption, adsorbent most commonly binds to the surface of the adsorbent via van der Waals interaction or covalent bonding.

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