Adsorptionsentfeuchtung

Adsorption is a surface phenomenon in which atoms, ions, or molecules from a gas, liquid, or dissolved phase adhere to the surface of a solid or liquid (the adsorbent). It differs from absorption, where particles diffuse into the bulk material, whereas adsorption confines the adhered species to an interfacial layer.

Two main types are recognized: physisorption (weak van der Waals forces; usually reversible) and chemisorption (strong chemical bonds; often slower and more selective).

Isotherms describe the relation between amount adsorbed and pressure or concentration at constant temperature. Langmuir models monolayer adsorption on a homogeneous surface; Freundlich handles heterogeneous surfaces; BET extends Langmuir to multilayer adsorption and is widely used to measure surface areas.

Factors influencing adsorption include the surface area and porosity of the adsorbent, temperature, pressure, and the properties of the adsorbate. In many cases, adsorption is exothermic and favored at lower temperatures, with desorption promoted by heating or increased temperature.

Applications span environmental and industrial areas, including water and air purification, catalysis, chromatography, and gas storage or capture. Activated carbons, zeolites, and porous materials such as metal–organic frameworks are commonly used adsorbents.

Characterization and reuse are aided by adsorption measurements, including isotherms and BET surface area analysis, as well as desorption studies. Regeneration methods such as thermal treatment, pressure swings, or solvent washing enable adsorbents to be reused in multiple cycles.