Absorption or Adsorption?
Did you hear it wrong, or did he really say adsorption? Well, yes, it is not a mistake. Adsorption and absorption are phenomena that allow molecules to adhere to or integrate another molecule.

What is absorption?

Absorption is defined as the passage of a substance into or through the mass of a media.


The phenomenon of absorption is very well known and widespread in everyday life. To put it into perspective, imagine that you spill a glass of water on the counter while reading this article. Immediately, you grab your paper towels and clean up the mess by absorbing the water with the paper towels.


Absorption is characterized by relatively high stability. Your paper towel filled with water holds the water and to remove the water you have to twist it. The principle remains the same when the absorption is in a liquid. Shaking the liquid will not separate the substances.



What is adsorption

Adsorption is characterized by the adhesion of molecules to free surfaces. Here, the prefix "ad" is the key.


Although the phenomenon of adsorption is just as widespread as that of absorption, it is generally less well understood. Again, to put things in perspective, let's go back to the puddle on your countertop. After searching everywhere for your paper towels, you decide to use a sheet of paper to collect the water. As you lay the sheet down, you notice that the water is sticking brittle to the sides of the sheet: the water is adsorbed onto the sheet.


Unlike absorption, adsorption is relatively unstable. This is why you will quickly notice that the water adsorbed on your sheet of paper runs off quickly. This is the same principle for liquid adsorption. For example, if activated carbon is added to dyed water, the carbon will adsorb the dye. By shaking the solution, the dye molecules adhering to the surface of the charcoal will be released and the water will become coloured again.


What do the notations PPM/PPB/PPT mean?
The notations PPM, PPB and PPT are acronyms used to express low concentrations of parameter present in a liquid or solid like water or earth.