(640e) A Multi-Scale Modeling Study of Protein Adsorption in Porous Polymeric Adsorbent Particles

Recent molecular dynamics modeling and simulation studies have shown that the density distribution of the immobilized charged ligands in polymeric ion-exchange porous adsorbent particles is most likely non-uniform and local nonelectroneutrality can result from the porous structure and the non-uniform ligand distribution. In this work, various non-uniform distributions of the density of the immobilized ligands, including those determined by molecular dynamics studies, were employed in a macroscopic continuum model that describes the transport and adsorption of a charged protein in different ion-exchange adsorbent media. Supporting electrolyte was considered to be in sufficient excess so that the effects of the electrical phenomena on the mass transfer and adsorption mechanisms were suppressed. The results of this work clearly show that inner radial humps in the concentration profiles of the adsorbed protein can occur when the density distribution of the immobilized charged ligands in the porous adsorbent particles is non-uniform and has local maxima or minima along the radial direction in the particles. They also indicate that the rate for an adsorption system to reach equilibrium depends significantly on the functional form of the density distribution of the immobilized charged ligands. When adsorption equilibrium has been reached, the concentration profile of the adsorbed protein coincides with the density distribution of the immobilized charged ligands in the porous adsorbent particles and this suggests that by measuring the concentration profile of adsorbed protein at equilibrium, the technique of confocal scanning laser microscopy could be used to provide the density distribution of the immobilized ligands in the porous adsorbent particles and a means for quality control of the adsorbent medium. The results in this work not only provide engineering science insight with respect to modeling and quality control of adsorbent media for adsorption separation systems but also have implications in the modeling and quality control of other systems involving biocatalysis, multi-valent adsorption interactions, and a range of values of pH and ionic strength.