Absorb and Adsorb. Two similar words, two very different processes. Most of us understand what the word ‘absorb’ means, but the use of the similarly spelt word ‘adsorb’ can cause confusion. These words do not mean the same thing.
The meaning of absorb (absorption)
Absorption is a process whereby one material (a gas or a liquid) is taken into another. This happens at an atomic and molecular level when the atoms and molecules of the two materials combine. When something is absorbed it either diffuses or dissolves. An example of absorption would be the purification of natural gas. In order to remove the unwanted hydrogen sulphide (H2S) and carbon dioxide (CO2), the natural gas is passed through a water-based solution of ethanolamine (a viscous liquid). The ethanolamine removes these two acidic gasses by making them more soluble and dissolving them. Wikipedia defines absorption here.
The meaning of adsorb (adsorption)
Adsorption is an entirely different process. Instead of two materials combining their atoms or molecules, one material will gather on the surface of another. The atoms or molecules of the two materials do not combine. When something is adsorbed it adheres instead of diffusing or dissolving. An example of adsorption would be in paint manufacture. Paint needs to adhere or stick well to the surface it has been designed to cover. Specific paint is designed for specific surfaces so that the adsorption is strong enough to maintain over time a bond between the paint and the surface. For a lot more details and equations, check out Wikipedia.
A comparison between absorption and adsorption:
Absorb is when two materials chemically combine.
Adsorb is when one material sticks to the surface of another.
In absorption one material is taken internally into another.
In adsorption one material coats the surface of another.
Absorption is related to volume.
Adsorption is related to surface area.
Absorption involves a process of dissolution or diffusion.
Adsorption involves a process of adhesion.
An example of absorption would be table salt dissolving into water.
An example of adsorption would be mist on a window.
Does activated charcoal use absorption or adsorption?
Activated charcoal (also called active carbon) is so effective at filtering because it works through the process of adsorption. In other words, a wide range of impurities can chemically adhere to its surface. The additional advantage of active charcoal is that it has a huge surface area and can adsorb a large number of molecules and atoms. Active charcoal is used in a wide variety of filtering and odor-eliminating products, including Innofresh’s wide range of odor eliminating products.