Adsorbeerunud

Adsorbeerunud is the Estonian term used to describe atoms, ions, or molecules that have become attached to a surface by adsorption rather than being absorbed into the bulk of a material. The resulting interfacial layer forms on solid interfaces such as mineral surfaces, activated carbon, metals, oxides, or membranes. Adsorbed species are distinguished from those that have diffused into the interior of a substance.

Adsorption can occur via two main mechanisms. Physisorption involves weak van der Waals forces and tends to be reversible and influenced by temperature and pressure. Chemisorption involves the formation of stronger chemical bonds between the adsorbate and the surface and can be more specific and often less readily reversible. In many systems, both processes may occur to some extent depending on conditions. The arrangement of adsorbed molecules can range from monolayers to multilayers, depending on the surface and the adsorbate.

Adsorption is often described by isotherm models such as Langmuir (monolayer, homogeneous surface), Freundlich (heterogeneous surfaces), and BET (multilayer adsorption). Key factors include the surface area and pore structure of the adsorbent, the nature and concentration of the adsorbate, temperature, and pressure. Competing species and the presence of solvents can also influence adsorption equilibria.

Applications of adsorption are widespread. In environmental engineering, activated carbon removes organic pollutants from water and air. In industry, adsorption is used in catalysis, gas capture, sensing, and chromatography. Examples include CO2 on zeolites or activated carbon, dyes on clay, and various organic molecules on porous materials.