Organo-macromolecular transport relationships for argillaceous membranes at ultra-high hydraulic gradients

Abstract

Empirically derived parameters and analytical solutions were used to determine possible mechanistic processes of organo-macromolecular fate in dead-end hyperfiltration at abnormal hydraulic pressure settings. Ideally the concentration polarization is assumed to have an ideal geometry but this may not be so since preferential flow paths in an experimental setup limits this. Most analytical solutions also tend to support this idealized geometry. A regular perturbation theory can be employed to characterize the permselective properties of compacted Na-montmorillonite membranes. Membrane efficiency and osmotic pressure at specific hydraulic pressures were periodically determined and averaged over several hydraulic pulse phases. These phases corresponded to gradual increment of applied differential pressure over a specific time period till the onset of steady state. Pore plugging at ultra-high hydraulic gradients shows non-uniformity contributing to anomalous effluent concentration variations at invariant membrane selectivity rates. This phenomenon can arise due to non-uniform distribution of surface charges and high charge density areas, preferential surficial retention compared to basal absorption amongst other factors. Osmotic pressure suppression due to high hydraulic differential pressures results in convergence of solute flux and mass transfer coefficient values close to and at steady state.