Effects of structural and kinetic parameters on the performance of chromatographic columns packed with perfusive and purely diffusive adsorbent particles

A mathematical model describing dynamic adsorption in columns with spherical bidisperse perfusive or spherical bidisperse purely diffusive adsorbent particles is used to study the effects of the structural parameters of the adsorbent particles and of the parameters of the adsorption mechanism on the performance of chromatographic systems involving the adsorption of bovine serum albumin onto anion-exchange porous adsorbent particles. Four structural parameters are studied: the particle diameter, d(p), the macropore void fraction, epsilon(p), the microparticle diameter, d(m), and the parameter phi, which affects the value of the permeability of the adsorbent particle. Two parameters of the adsorption mechanism are studied: the maximum equilibrium concentration of adsorbate in the adsorbed phase of the adsorbent particle, C-T and the rate constant k(l), which characterizes the adsorption step of the interaction mechanism between the adsorbate molecules and the active sites on the surface of the pores of the adsorbent particles. The performance of columns packed with purely diffusive particles improves when the value of d(p) is decreased, when the value of epsilon(p) is increased and when the value of d(m) is decreased; the effect of d(m) is much smaller than the effects of d(p) and epsilon(p). Intraparticle flow in perfusive particles can improve column performance if it is of sufficient magnitude; intraparticle flow increases when the value of d(m) is decreased, when the value of epsilon(p) is increased, when the value of d(m) is increased and when the value of epsilon is decreased. The difference between the performance of a column packed with perfusive particles and that of a column packed with purely diffusive particles will depend upon the particular combination of the parameters d(p), epsilon(p) d(m) and phi. When the value of k(l) is small, an increase in k(l) improves column performance. However, when the value of k(l) becomes sufficiently large, further increases have no effect on column performance. Increasing the value of C-T has a large effect on column performance by increasing the breakthrough time and the mass of adsorbate in the adsorbed phase at breakthrough. The performance of chromatographic systems with purely diffusive particles can be better than the performance of chromatographic systems with perfusive particles, if purely diffusive particles carl be made that have higher values of C-T than otherwise comparable perfusive particles.