Decreased peak tailing during transport of solutes in porous media with alternate adsorption properties

In adsorption based separation techniques or in environmental applications where adsorption on a porous matrix is involved, the broadening of migrating bands of solutes varies with the characteristics of the adsorption isotherms and is generally overwhelming at solute concentrations deep in the non-linear region. We introduce here a novel concept to minimize concentration overloading dispersion: We show theoretically that a spatial alternation of Langmuir (L) and Anti-Langmuir (AL) zones along the displacement direction induces an accordion effect, i.e. an alternation of sharpening and dilution of the solute zones, reducing in the end the final broadening of the peak. We quantify in the parameter space of the problem the reduction in concentration overloading related band widening of the L-AL system compared to the pure L or AL cases. A numerical analysis of the solute transport reveals a dependence of solute spreading on the ratio of sample to stationary phase zone widths and on the intensity of the adsorption parameter. The initial position of the sample solvent in its surrounding liquid i.e. whether the displacement starts in a L or AL zone is also shown to have an influence on the dispersive behavior. An analysis is performed to highlight the optimal alternance geometry to minimize solute spreading. (C) 2019 Elsevier Ltd. All rights reserved.