Applying the FastIAS algorithm to the Redlich-Peterson isotherm

Abstract The Redlich-Peterson isotherm is widely used in liquid phase adsorption studies but the combination with the Ideal Adsorbed Solution Theory is hampered by the fact that an analytical expression for the reduced grand potential does not exist in the range of low pressures or concentrations. In this contribution we demonstrate an efficient approach to approximate the reduced grand potential using a Padé approximant allowing to perform the calculations with the Fast-IAS algorithm leading to execution times that are slightly slower but comparable to a dual site Langmuir/Fast-IAS combination. While the non-autonomous initial value approach remains a simpler method for this isotherm, the proposed method is recommended when execution times have to be minimized.