desorbs

Desorb, and desorption, refer to the release of a substance from a surface or phase after adsorption. Adsorption is the accumulation of a substance on a solid or liquid interface; desorption is its counter-process, often governed by temperature, pressure, solvent, or illumination.

Physical desorption occurs when weak van der Waals or electrostatic interactions are overcome, typically reversibly with changes in temperature or pressure, or with contact of a desorbent solvent. Chemical desorption involves breaking chemisorption bonds, usually requiring greater energy. Methods include thermal desorption (heating the material to release adsorbates), temperature-programmed desorption, solvent desorption, and photodesorption.

In catalysis and surface chemistry, desorption is a step in the catalytic cycle: adsorption of reactants, surface reaction to form products, then desorption to free sites for further reaction. Desorption rates can be described by kinetics, often Arrhenius-type: k_des = A exp(-E_des/RT). Equilibrium with adsorption is described by isotherms (e.g., Langmuir).

Applications include activated-carbon regeneration and environmental remediation (desorbing contaminants from soils or sorbents), gas sensing and storage, chromatography and solid-phase extraction (desorption of analytes by a suitable solvent), and analytical techniques such as thermal desorption spectroscopy. Desorption concepts are central to understanding how surfaces interact with molecules in fields ranging from environmental engineering to materials science and analytical chemistry.