Exploring adsorption vs. absorption in Sorption Science

Overview

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• Source: Microbioz India


• Date: 11 Oct,2023

Adsorption and absorption are two essential processes in the study of the interaction of chemicals with solid materials, which is known as sorption science. These processes differ in that they involve molecules adhering to the surface of materials or penetrating the material itself.

Let’s explore the key differences between adsorption and absorption:

Adsorption:

Surface Interaction:

Molecules that attach to the surface of a solid or liquid medium are said to be adsorbing. This can happen in pores or fissures, as well as on a material’s exterior surface.

Attachment Mechanism:

Van der Waals forces, electrostatic forces, or chemical bonds that draw and hold molecules to the surface of the substance are the main causes of adsorption.

Reversible Process:

When circumstances, such temperature or pressure, change during an adsorption process, molecules may desorb (detach) from the surface.

Common Examples:

Adsorption is frequently observed in a variety of events, including the adsorption of gases on solid catalysts in chemical reactions, the adsorption of gases on activated carbon in the presence of gases, and the adsorption of ions on the surface of electrodes in electrochemistry.

Typical Applications:

Applications for adsorption include wastewater treatment, catalysis, and gas separation.

Absorption:

Internal Penetration:

Molecules must enter a material’s bulk in order to be absorbed. Within the structure of the substance, these molecules diffuse and are distributed.

Attachment Mechanism:

Absorption often entails interactions with the interior of the material, such as diffusion into a porous structure or dissolution.

Not Necessarily Reversible:

Depending on the substance and the makeup of the molecules being absorbed, absorption can be a reversible or irreversible process.

Common Examples:

The processes of water absorbing into a sponge, a gas absorbing into a liquid (for example, carbon dioxide absorbing into water), and solutes absorbing into solvents are examples of absorption.

Typical Applications:

Numerous uses of absorption exist, such as gas-liquid absorption processes in chemical engineering, the use of scrubbers to remove pollutants from the air or water, and the absorption of gases in biological systems. In conclusion, absorption includes the penetration and dispersion of molecules within a substance, whereas adsorption involves the adhesion of molecules to the surface of a material. Both processes are essential in several scientific and industrial applications, and building efficient sorption systems requires an understanding of how they vary from one another.