Determination of Adsorption Equilibrium Constants from Experimental Chromatograms for Liquid Adsorption

Equilibrium and kinetic parameters are very important factors for the design of absorbers. Determination techniques of intraparticle diffusivities and fluid-to-solid mass transfer coefficients from experimental result(s) are already proposed for liquid adsorption. Some of them require very small amount of sample mixture.

For determination of equilibrium parameters, on the other hands, “Batch Bottle Technique” is usually employed. This technique is very simple but some amount of fluid volume is required. The other environment-friendly determination procedure of the parameters employs chromatogram technique. The procedures are roughly divided into tow determination methods. First, chromatograms are estimated numerically under conditions of various equilibrium constants and the curves are compared with the experimentally obtained chromatograms. Then, the optimal equilibrium parameters are determined from the comparison results. Second, derivatives of the isotherm are evaluated from chromatograms experimentally obtained by stepwise technique with the aide of moment analysis and amounts adsorbed are estimated by use of numerical integration. Then, the equilibrium parameters are determined from equilibrium relationships between amounts adsorbed and fluid concentrations by use of traditional technique. The former technique requires calculation time and the constants obtained by the latter technique might have larger experimental error.

In the presentation, new simple determination technique of the isotherm constants directly from the derivatives of the isotherm without any integration procedures will be shown.