Simplified mathematical description and hydrodynamic characterization to the ionic transport through selective membranes in bi-ionic systems

This paper is aimed to the characterization of a bi-ionic membrane system by means of the study of transport rate in a rotating diffusion cell. A simplified mathematical description was developed, allowing the hydrodynamic characterization of a system by determinations of the diffusion coefficients of counter ion in the membrane and boundary layers, as well as the thickness of these layers. The effect of temperature and rotating frequency on these parameters were studied. An Ionics CR61AZL cation exchange membrane and aqueous electrolyte solutions were used in experiments with the system: HCl(aq) feed solution/membrane/MClz(aq) receiving solution, where Mz+ is a metallic ion (Ca2+ in our case). The membrane separating feed and receiving aqueous solutions was mounted in the bottom of a hollow rotating cylinder containing an aqueous solution of HCl. This cylinder rotated at different constant frequencies over the range 5.0-10.0 Hz and was partially submerged in the other aqueous solution contained in a fixed jacketed vessel. The transport was studied over a temperature range from 20 to 50 degrees C. The Mz+ transport rates, obtained by pH measurements in the outer solution, were recorded as a function of time and temperature. (c) 2012 Elsevier B.V. All rights reserved.