Modeling of dispersion in a polymeric chromatographic monolith

Abstract

Dispersion in a commercial polymeric monolith was simulated on a sample geometry obtained by direct imaging using high-resolution electron microscopy. A parallelized random walk algorithm, implemented using a velocity field obtained previously by the lattice-Boltzmann method, was used to model mass transfer. Both point particles and probes of finite size were studied. Dispersion simulations with point particles using periodic boundaries resulted in plate heights that varied almost linearly with flow rate, at odds with the weaker dependence suggested by the experimental observations and predicted by theory. This discrepancy resulted from the combined effect of the artificial symmetry in the velocity field and the periodic boundaries implemented to emulate macroscopic column lengths. Eliminating periodicity and simulating a single block length instead resulted in a functional dependence of plate heights on flow rate more in accord with experimental trends and theoretical predictions for random media. The lower values of the simulated plate heights than experimental ones are attributed in part to the presence of walls in real systems, an effect not modeled by the algorithm. On the other hand, analysis of transient dispersion coefficients and comparison of lateral particle positions at the entry and exit hinted at non-asymptotic behavior and a strong degree of correlation that was presumably a consequence of preferential high-velocity pathways in the raw sample block. Simulations with finite-sized probes resulted in particle trajectories that frequently terminated at narrow constrictions of the geometry. The amount of entrapment was predicted to increase monotonically with flow rate, evidently due to the relative contributions to transport of convection that carries particles to choke-points and diffusion that dislodges these entrapped particles. The overall effect is very similar to a flow-dependent entrapment phenomenon previously observed experimentally for adenovirus.

Sol‐Gel and Porous Glass‐Based Silica Monoliths with Hierarchical Pore Structure for Solid‐Liquid Catalysis

“…9), even though this monolith shares the macroporosity of silica monoliths (e ext = 0.69). Narrow constrictions in the macropore space of organic polymer monoliths can cause entrapment of larger molecules, which has been seen in simulations and also revealed by experiments [65]. Intraskeleton mass transfer resistance and intense backmixing are serious issues for organic polymer monoliths [19 -23].…”

Predictive model of solute transport with reversible adsorption in spatially periodic hierarchical porous media

“…1 can be described by the macroscopic advection-diffusion equation as Eq. (18). The zone retention factor describes the interaction between the solute and the pore surface.…”

“…Most theoretical and experimental works addressing solute transport in porous media have focused on porous media comprising impermeable particles, pillars or monoliths [4,[13][14][15][16][17][18][19][20]. Perhaps due to their complex pore geometry, experimental and theoretical predictions of solute transport in hierarchical porous media are few.…”

Computational investigation of longitudinal diffusion, eddy dispersion, and trans-particle mass transfer in bulk, random packings of core–shell particles with varied shell thickness and shell diffusion coefficient

“…Finally, the transport of point-like tracers in the interparticle void space and porous shells of the packing particles was modeled by a random-walk particle-tracking (RWPT) technique. A similar simulation approach was previously applied to study the effect of packing porosity, morphology, and particle size distribution on effective diffusivity and eddy dispersion in packed beds [25,[27][28][29][30][31]; to analyze the impact of the packing confinement on eddy dispersion [32,33]; to study hydrodynamic dispersion in silica and polymeric chromatographic monoliths [34][35][36][37][38]; and to investigate the influence of analyte retention and adsorption kinetics on mass transport in open channels and packed beds [39][40][41]. In this study, we mainly focus on the analysis of the influence of two core-shell particle characteristics -the shell thickness and the value of the effective diffusion coefficient in the shell -on the plate height.…”