Adsorb is defined as the process by which atoms, ions or molecules are attracted and held on the surface of a material without entering its interior. This differs from absorption, which involves substances penetrating the full volume of another material. The term was introduced in 1881 by German physicist Heinrich Kayser, who combined the Latin prefix ad- meaning toward with sorbere meaning to suck in, to distinguish surface attachment from absorption. Pronunciation places emphasis on the second syllable as ad-SORB. Adsorption appears in many fields including chemistry and environmental science. Activated carbon filters use it to remove impurities from water and air. Silica gel packets adsorb moisture to protect packaged goods. Industrial catalysts rely on the process to speed reactions by holding reactant molecules on their surfaces. Additional applications include gas masks, chromatography, gold extraction, and medical treatments that clear toxins from blood.
