Tayssir Hamieh
The Brunauer–Emmett–Teller (BET) method is widely employed for specific surface area (SSA) determination from gas adsorption isotherms, despite its implicit assumption of an ideal, non-interacting adsorbed monolayer. In this work, a unified thermodynamic reassessment of SSA determination is developed by explicitly incorporating lateral interactions and thermal agitation within the first adsorbed layer. The classical BET first-layer equilibrium is replaced by an interaction-aware activity formulation while preserving the BET multilayer closure.A hierarchy of adsorption models is examined, including phenomenological interaction models (Temkin, Frumkin, Fowler–Guggenheim), virial expansions, and equation-of-state-based descriptions (two-dimensional van der Waals, Hard-Disk + Mean-Field (HD+MF)), alongside a two-dimensional Redlich–Kwong (2D-RK) equation of state constructed to ensure thermodynamic consistency. The framework is applied to diverse material families comprising several solid materials.Systematic deviations in SSA relative to BET span from negligible values to more than 50%, depending on the strength of adsorbate–adsorbate interactions and surface characteristics. The 2D-RK formulation consistently provides the most thermodynamically coherent descriptors offering an accurate and computationally efficient approximation. These results demonstrate that BET represents a low-interaction asymptotic limit rather than a universally valid description, and that reliable SSA determination requires explicit consideration of lateral interactions within the adsorbed monolayer.