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Multicomponent space‐charge transport model for ion‐exchange membranes
Author(s) -
Yang Yahan,
Pintauro Peter N.
Publication year - 2000
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690460610
Subject(s) - membrane , chemistry , ion , aqueous solution , ion transporter , charge density , ion exchange , radius , donnan potential , dipole , electric field , analytical chemistry (journal) , surface charge , alkali metal , chemical physics , electrolyte , inorganic chemistry , chromatography , electrode , organic chemistry , biochemistry , physics , computer security , quantum mechanics , computer science
A multicomponent space‐charge transport model for ion‐exchange membranes was developed, where the membrane structure was modeled as an array of cylindrical pores with a uniform distribution of fixed‐charge sites on the pore walls. Ion/fixed‐charge site electrostatic interactions, electric‐field‐induced water dipole orientation, ion‐hydration free‐energy changes during ion partitioning, and concentration‐dependent transport parameters were considered in the analysis. The model predicted experimental concentration vs. time data accurately for Donnan dialysis separations with a DuPont Nafion 117 cation‐exchange membrane, where the membrane separated a dilute H 2 SO 4 solution from an aqueous mixture of either Cs 2 SO 4 + Li 2 SO 4 or Cs 2 SO 4 + Na 2 SO 4 . Both computer predictions and experimental measurements showed that the alkali metal cation with the larger hard‐sphere radius (lower surface charge density) was selectively absorbed in and transported across the membrane during a multicomponent separation. The cation/cation transport permselectivity was less than the selectivity for equilibrium uptake due to slow ion transport near the pore wall, where discrimination between like‐charge cations was greatest.