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Define absorption and adsorption/difference between them

What is absorption

when we say that a certain material is absorbed by another material, this means that the first material enters and completely spreads into the second material throughout the entire volume, occupying space depending on the concentration.Therefore , theoretically, atoms, molecules and ions can enter into another gaseous, liquid or solid bulk phase. Based on the rate of absorption of various substances, absorbates(material that absorbs foreign material), various separation mechanisms have emerged. For example, liquid-liquid extraction for chemicals. In this case, a certain substance that has been absorbed by one liquid is brought into contact with another liquid that has a higher affinity for the substance, and therefore, it is distributed into the second liquid, whereby it can be recovered. Define absorption and adsorption

Likewise, another example would be the absorption of oxygen by water, when the entire amount of gas is dissolved and evenly distributed throughout the volume of water. Here, the gas initially dissolves after initial contact with the surface. And the amount that is ultimately translated depends on the characteristics of both the liquid and the gas. This type of takeover is called “physical takeover”. Absorption can be broadly divided into physical absorption and chemical absorption, where in the latter case it will be associated with a chemical reaction and not with volumetric transfer, depending on the characteristics of the materials used.

What is adsorption

Adsorption is a “surface phenomenon” and strictly deviates from absorption, which encompasses the entire volume of the material. Therefore, in the case of adsorption, a relatively small amount of a single substance will attach to the surface of a bulk substrate as a result of various types of interactions . The substance that is absorbed is called an ‘ adsorbate ‘, and the bulk that absorbs the incoming material is called an “absorbent”. Adsorption can be broadly divided into two categories: physical sorption and chemisorption. In the case of physisorption, the type of interaction between adsorbate and adsorbent is physical forces such as van der Waals interactions. However, in the case of chemisorptionThese are the chemical bonds that bind the adsorbates to the adsorbent. Define absorption and adsorption

The reasons for adsorption are similar to surface tension. The molecules inside the adsorbent are surrounded by other adsorbent molecules and their energy on the surfaces is neutralized. But this does not apply to the outer surface layer of the adsorbent, since it is not surrounded by other molecules. Consequently, the surface of the adsorbent has additional energy for the inner layers. Hence, it absorbs other molecules on its surface to minimize surface energy. However, the distinction between adsorption and absorption almost disappears on the micromolecular scale when the surface area of ​​the adsorbent is significantly large.

The main difference is absorption versus adsorption

Both absorption and adsorption are physicochemical processes in which a relatively small amount of one species enters / binds to another species of a relatively higher amount. The way the materials are incorporated into each other clearly distinguishes between the two processes. When a small amount of one material completely enters and spreads through the entire volume of another material , it is called ” absorption. ” In contrast, when a small amount of one material is attached only to the outer surface of the other material, it is called ” adsorption .” Therefore, the main difference between absorption and adsorption, absorption is the distribution of a certain substance over the entire volume of another substrate.while adsorption is the attachment of a certain substance to the surface of another substrate. Define absorption and adsorption

Difference between absorption and adsorption


absorption is the distribution of a particular substance throughout the volume of another substrate.

adsorption is the attachment of a certain substance to the surface of another substrate.

Separation processes

absorbed Materials can be separated between different phases due to their chemical characteristics.

The adsorption technique can be used to separate a specific material by adsorbing them on one surface, while a stream of another material that previously absorbed the substance. Define absorption and adsorption


Materials get absorbed into another material due to the availability of space and also due to the properties of each material.

The free surface of the adsorbent has additional energy, which stimulates the attachment of foreign molecules to it.


The materials that get absorbed remain in the absorbent space, without chemical bonds, being completely intact, as when it is free. It can only carry weak physical interactions.

In adsorption, adsorbates are bound on the surface of the adsorbent most often through van der Waals interactions or through covalent bonds. Define absorption and adsorption

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