A new approach to adsorption isotherms

Abstract A new isotherm Θ = 1/[1 + 1/ b φ 1/(m+ϵ/ RT ) ] is derived from a chemical potential of adsorption which includes temperature-dependent and temperature-independent parts from statistical and potential models. Most experimental gas-phase adsorption data are not of a pure statistical or potential type; however, the mixed form proposed is able to describe the data over a wide range of pressure and temperature even for very different binding forces. A knowledge of the chemical potential provides equations for the enthalpy, entropy and spreading pressure and the influence from the heat expansion of the adsorbed layers. Comparison with experimental data shows the improvement of the new method.