What is the difference between absorption and adsorption?

It is the difference between a substance passing into a material or a substance attaching to the surface of the material.

Both absorption and adsorption are considered to be sorption processes, which refer to the attachment of one substance to another. The primary distinction between the two processes is that absorption involves the transfer of particles from one material to another, while adsorption involves the adhesion of particles to the surface of a material.

ABSORPTION is the process in which atoms, ions, or molecules pass into a bulky material.

The particles diffuse or dissolve into another substance (which absorbs them), forming a solution. Once dissolved, the molecules cannot be easily separated from the absorbent.

A common example of absorption can be observed when a paper towel is used to absorb water, as the water gradually permeates the paper towel and becomes evenly dispersed within it. The degree of absorption can be influenced by various factors, including the concentration levels of the substance, the surface area exposed, and the applied pressure.

ADSORPTION is the process in which atoms, ions, or molecules from a substance adhere to a surface.

This is classified as an exothermic process because energy is released when the adsorbed substance sticks to the surface of the adsorbent substance. The rate of the process depends mainly on the surface area and temperature: lower temperatures promote adsorption.

Find out more about the two sorption processes here.