desorbeerumise

Desorbeerumise is the process by which species that are adsorbed on a solid surface or within a porous material leave the surface and enter a surrounding phase, such as a gas or a liquid. It is the reverse operation of adsorption and a central concept in surface science, catalysis, and environmental engineering.

Desorption can occur through thermal energy (thermal desorption), changes in pressure or gas composition (pressure- or vacuum-desorption), or chemical or solvent interactions that destabilize the adsorbate. The mechanism is broadly categorized as physical desorption, where weak van der Waals forces hold the adsorbate, and chemical desorption (chemisorption), where bonds with the surface must be broken.

Thermodynamically, desorption is generally endothermic, requiring energy input to overcome binding between the surface and the adsorbate. The balance between adsorption and desorption is described by adsorption isotherms and depends on temperature, pressure, and surface properties. Common models include Langmuir, Freundlich, and Temkin frameworks.

Kinetically, desorption rates are described by models such as the Polanyi–Wigner equation: rate = ν Θ^n exp(-E_des/(RT)), with E_des the desorption energy, Θ the surface coverage, ν a pre-exponential factor, and n the order. In simple cases, first-order desorption is assumed. Temperature-programmed desorption (TPD) is a key experimental method to study desorption kinetics.

Applications of desorbeerumise include regeneration of adsorbents (for example, heating activated carbon), gas purification and storage, environmental remediation, catalysis, solid-phase extraction, chromatography, and sensor technology. Understanding desorption helps optimize separation processes and catalyst lifetimes.

See also: adsorption, adsorption isotherm, Langmuir isotherm, desorption kinetics.