adsorption
n.n. the process where a substance sticks to the surface of another material. It is like when a sponge soaks up water, but it happens at a very small level you cannot see.
n. the process by which molecules of a gas or liquid are held on the surface of a solid or liquid. This is distinct from absorption, where the substance is taken into the bulk of the material.
The filter uses adsorption to remove impurities from the water.
In environmental science, the adsorption of heavy metals onto activated carbon is a common method for water purification.
The efficiency of the catalytic converter depends on the adsorption of exhaust gases onto the surface of the platinum catalyst, which facilitates the chemical reaction necessary for emission control.
Borrowed from German Adsorption, from ad- + (Ab)sorption.