adsorption

Noun B2 – Upper-Intermediate

The process by which molecules of a gas or liquid stick to the surface of a solid, rather than being absorbed into it.

"Activated charcoal filters work through adsorption, trapping impurities on the huge surface area of the carbon."

'Adsorption' is often confused with 'absorption': adsorption sticks particles onto a surface, while absorption draws them into the whole volume of a material.