Füüsiksorptsiooni

Füüsiksorptsioon, often referred to as physisorption, is a type of adsorption where the forces holding adsorbate molecules to the adsorbent surface are van der Waals forces. These forces are relatively weak, arising from temporary fluctuations in electron distribution within molecules, leading to transient dipoles. Unlike chemisorption, physisorption does not involve the formation of chemical bonds or the transfer of electrons between the adsorbate and adsorbent.

The process of physisorption is typically reversible. When the temperature is increased or the pressure of the adsorbate is decreased, the adsorbate molecules readily desorb from the surface. This reversibility makes physisorption useful for applications such as gas separation and purification, where the adsorbed substance needs to be recovered. The enthalpy of physisorption is generally low, comparable to the heat of liquefaction of the adsorbate.

Physisorption is a non-specific process, meaning that the adsorbent material is not as critical as in chemisorption. Any surface can exhibit physisorption. The extent of physisorption is highly dependent on temperature and pressure. At low temperatures and high pressures, physisorption is favored as the kinetic energy of the adsorbate molecules is reduced, and there are more molecules available to interact with the surface. Common examples include the adsorption of gases like nitrogen or argon onto solid surfaces at low temperatures, often used to determine the surface area and pore size distribution of materials through techniques like BET analysis.