Effects on the dynamic utilization of the adsorptive capacity of chromatographic columns induced by non-uniform...

The dynamic behavior of the breakthrough curves of a single adsorbate obtained from columns employing adsorbent media which differ from one another only on the spatial distribution of the immobilized ligands in the porous particles is examined. The spatial distributions of the immobilized ligands considered in this study are uniform and non-uniform, but the total number of immobilized ligands in the particles has the same value whether the spatial distribution is uniform or non-uniform. The results clearly show that the columns employing adsorbent particles in which the spatial distribution of the immobilized ligands is non-uniform and such that the concentration of the immobilized ligands increases monotonically from the center of the particle to the outer particle surface, exhibit (i) larger breakthrough times, (ii) steeper breakthrough curves, and (iii) higher dynamic utilization of the adsorptive capacity of the column as the superficial velocity of the flowing fluid stream in the column increases (throughput increase) than the columns using adsorbent particles in which the spatial distribution of the immobilized ligands is uniform. The importance of employing in the columns adsorbent media whose spatial ligand density distributions satisfy the mathematical property of monotonically increasing ligand concentration with increasing from the particle center radial position, will be significantly enhanced when (i) the size of the particle radius is increased, and (ii) continuous counter-current and periodic counter-current (simulated moving beds) operations are employed.