BETállandót

The BET constant, often denoted as $B$, is a fundamental parameter in the Brunauer-Emmett-Teller (BET) theory of gas adsorption. This theory is widely used to determine the surface area of porous materials. The BET constant is dimensionless and is related to the energy of adsorption of the adsorbate molecules onto the solid surface.

Specifically, the BET constant is derived from the ratio of the adsorption energy of the first layer to the condensation energy of the bulk adsorbate. A higher BET constant suggests stronger interactions between the adsorbate and the adsorbent surface, or weaker interactions of the adsorbate with itself in the condensed phase. Conversely, a lower BET constant indicates weaker adsorption forces or stronger adsorbate-adsorbate interactions.

The value of the BET constant is crucial for the accurate calculation of the monolayer capacity ($V_m$) from the BET equation. The BET equation relates the amount of gas adsorbed at a given relative pressure and temperature to the surface area. The BET constant, along with the monolayer capacity, is determined by fitting the experimental adsorption data to the BET equation, typically over a specific range of relative pressures. Its value can provide insights into the nature of the adsorbent-adsorbate interactions, such as van der Waals forces or specific chemical interactions. The BET constant is temperature-dependent, although this dependence is often simplified in practical applications.