A mathematical analysis for the pulse responses of a liquid chromatographic column packed with crystal powders having a particle size distribution and a nonlinear adsorption isotherm is presented. The mathematical model is solved numerically by the orthogonal collocation method. Based on the parametric analysis of the model, the effects of a symmetrical and moderately asymmetric PSD on the LC responses are shown to be negligible in comparison with the effects of other parameters, such as isotherm nonlinearity, whose effects are much more profound. The simulated responses are compared with the experimental response data for an LC column packed with silicalite crystals, and a good agreement is found between the theoretical and experimental results. Using the nonlinear LC model, the simultaneous determination of nonlinear adsorption isotherms and intraparticle diffusivities from LC pulse responses is demonstrated for liquids in porous adsorbents.
Y. S. Lin
Y. H. Ma
Chemical Engineering DepartmentWorcester Polytechnic Institute Worcester, MA 01609
IntroductionWith extensive applications of chromatographic techniques in bulk separations, purifications and physico-chemical parameter determinations (Conder and Young, 1979;Ruthven, 1984;Wankat, 1986), many mathematical models have been developed and solved for the mass transfer in chromatographic columns packed with porous particles. These studies include: the analytical solutions for the problems of chromatography with simpler mathematical models which neglect either axial dispersion or intraparticle diffusion (e.g., Rosen, 1952;Masamune and Smith, 1964); the modeling and analytical solutions for chromatography with the consideration of both intraparticle diffusion and axial dispersion (Deisler and Wilhem, 1953; Rasmuson and Nerenieks, 1980;Rasmuson, 1981); and the development of many more complex models for chromatography such as the macro-micropore diffusion models for the chromatographic columns packed with bidisperse structured adsorbents (Ma and Mancel, 1973;Hashimoto and Smith, 1973; Haynes and Sarma, 1973). Most of these models, however, were developed for gas chromatographic columns under the assumption of a linear adsorption isotherm.Nonlinear adsorption isotherms are more frequently encountered in liquid chromatographic systems. The mathematical