Activated carbon is a carbonaceous product with a porous structure (pore volume > 0.2 cm³/g) and a large internal surface area (> 400 m²/g) with pore diameters between 0.3 nm and several thousand nanometers, to whose surface molecules can attach. The surface of activated carbon is essentially nonpolar and thus hydrophobic and organophilic, which is why the less water-soluble a substance is, the better it is adsorbed from aqueous phase. The activated carbon surface has an affinity for organic adsorptives such as fatty acids, alcohols and esters.
Due to the hydrophobic nature of the surface, adsorption of water vapor is very low at low concentrations. Only at higher concentrations (higher humidity) does the water loading increase steeply. For this reason, activated carbon is suitable for the treatment of humid gases or air. They are used, among other things, in aeration dryers for hydraulics, in fume hoods or even in respiratory masks.