desorpce

Desorption is the process by which a substance detaches from a surface and enters a surrounding phase. It is the reverse of adsorption and is a common phenomenon in natural and engineered systems. The term desorpce is sometimes encountered as a misspelling or alternate spelling of desorption.

Desorption occurs when adsorbed species are released into air, water, or another solvent, driven by changes in conditions such as temperature, pH, ionic strength, or solvent composition. It is observed in soils and sediments, activated carbons, catalysts, and other porous materials, and plays a major role in contaminant transport and remediation.

Mechanisms can be divided into physical and chemical desorption. Physical desorption involves weaker, noncovalent interactions and can be driven by diffusion, dilution, or heating. Chemical desorption involves bond cleavage or changes in chemical state at the interface, such as redox reactions or chelation, which reduce the surface affinity of the adsorbate. Desorption can occur rapidly or be time-delayed, depending on the system and conditions. Temperature-programmed desorption is a common analytical technique in catalysis and surface science.

Desorption is often described using kinetic and equilibrium concepts. Desorption kinetics may follow pseudo-first-order or pseudo-second-order behavior, depending on the system. Desorption isotherms, frequently analyzed with Langmuir or Freundlich models, characterize how the remaining adsorbate distributes between surface and bulk at equilibrium. Hysteresis between adsorption and desorption is common in porous materials, reflecting irreversible or slowly reversible interactions.

Applications and significance: in environmental science, desorption governs contaminant mobility, bioavailability, and remediation strategies. In chromatography and sensor technologies, it describes analyte elution. In heterogeneous catalysis, desorption is a critical step that can limit overall reaction rates.