Adsorption vs Absorption
People often get confused with the terms adsorption and absorption. These words are two of the most common terms that are encountered by students in their Science classes. The most obvious reason why these words are confused with each other is that they are spelled almost the same (differs only with just one letter) and that they sound almost the same too.
There are topics more often discussed in chemistry and biology and they are included under the umbrella of sorption processes. These reactions can either be absorption and adsorption. In the more technical explanation, absorption is the phenomenon when some molecules, atoms, ions and the like enter something quite bulky in nature, let’s say a solid object, a liquid and or a gas medium. This can best be exemplified when a piece of dry sponge absorbs liquid.
In another phenomenon known as wave propagation, attenuation (the process of absorbing light) happens. The light being absorbed is in the form of photons that are taken by another kind of atom. This process can actually destroy the photons, which will be re-emitted into a form of radiant energy like heat. This is a second situation where absorption occurs.
On the contrary, adsorption is different from absorption in the sense that it focuses not on the volume but on the surface. If fluids and gases settle on the surface of another material (liquids or solids) rather than be diffused into the said material, then this forms a solution. The said process is an adsorption.
To use another explanation, adsorption is the process when an outside contaminant (atoms) gets attracted to the outside surface of a piece of material while absorption involves the uptake of the contaminant into the literal structure of the material. Similarly, absorption occurs when the outside contaminant has merged or has become part of the other material. A similar analogy occurs when you drink water. In drinking such, you are therefore absorbing fluid making it a part of you. Adsorption occurs when you accidentally spill water on your shirt. The water did not actually become part of you but just fell on you. It just bonded physically with a certain surface (your shirt).
Overall, although both absorption and adsorption are sorption processes they still differ in the following areas:
1. Absorption happens when atoms pass through or enter a bulky material like sponges.
2. Adsorption happens when the atoms settle or accumulate on the surface of a material rather than literally entering or diffusing into that same material.
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The sponge reference here is innaccurate, because something can go into a sponge and still be adsorbed to the surface of it. In other words, the holes in a sponge just increase the surface area and just because water is in a hole doesn’t mean that it is part of the sponge. In fact, if you squeeze the sponge the water will come out. Otherwise, the article was helpful as a reminder from chemistry class. The drinking water example is better because you can’t squeeze someone and get the water they drank back out…it is part of them.
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