Morphology-transport relationships for silica monoliths: from physical reconstruction to pore-scale simulations

This work describes individual steps of an approach toward quantitative correlations between morphological and mass transport properties of capillary silica monoliths. The macropore space morphology of the central core region of the capillary monolith is visualized by a fast, nondestructive, and quantitative method using three-dimensional reconstruction from confocal laser scanning microscopy images. The reconstructed 60 μm×60 μm×12 μm monolith domain consisted of 1.6×10(9) cubic voxels with 30 nm edge length. The received morphological data were chord length distributions for the bulk macropore space and skeleton of the monolith, which we characterized by k-gamma distributions. This analysis provides parameters that can be correlated with the mass transport properties obtained by macropore-scale simulations of flow and transport in the reconstructed monolith. These simulations were realized on a supercomputing platform and comprised the lattice-Boltzmann method for fluid flow and a random-walk particle-tracking method for advective-diffusive mass transport. The characteristic length scales of eddy dispersion correlate with the statistical measures of the chord length distributions. Simulated plate height curves demonstrate that the bulk monolith is very homogeneous, and that the intraskeleton transport properties and a stochastic variation of macropore space characteristics can be neglected compared with the importance of reducing column radial heterogeneity in chromatographic practice.