Fiziszorpció

Fiziszorpció, often shortened to physisorption, is a type of adsorption where the adsorbate molecules are held to the surface of the adsorbent by weak van der Waals forces. Unlike chemisorption, which involves the formation of chemical bonds, physisorption is a reversible process characterized by low enthalpies of adsorption. The strength of the van der Waals interactions is generally comparable to the latent heat of condensation of the adsorbate.

This phenomenon occurs when the adsorbate molecules are attracted to the adsorbent surface due to temporary fluctuations in electron distribution, leading to induced dipole moments. These forces are non-specific and act between all atoms and molecules. Physisorption is typically observed at low temperatures, as higher temperatures provide sufficient kinetic energy for the adsorbate molecules to overcome the weak attractive forces and desorb from the surface.

The rate of physisorption is generally fast, and it can occur on any solid surface. The number of adsorbed layers is not limited to a monolayer; multilayer adsorption is possible as the forces are long-range. The process is often described by the Brunauer-Emmett-Teller (BET) theory, which models multilayer adsorption.

Applications of physisorption include gas storage, separation processes, and catalysis where it can play a role in the initial interaction of reactants with a catalyst surface before potential chemisorption occurs. The reversibility of physisorption makes it useful in applications where adsorbates need to be readily released.