The electrical conductivity and electro-osmotic permeability of a cation-exchange resin

Abstract

Various anomalies in the thermodynamic and kinetic properties of ion-exchange resins are attributed to a non-uniform distribution of the gegen-ions. It is suggested that some information on this distribution should be derivable from the correlation of a number of electro-kinetic properties of the resin. Electrical conductance and electro-osmosis have been studied using a highly swollen cation-exchanger and the results combined with previous determinations of ionic self-diffusion coefficients and transport numbers.At one temperature and concentration a fairly detailed application of the irreversible thermodynamic theory of membrane phenomena has been possible and this is tentatively extended to other concentrations. It appears that for resins containing little or no sorbed electrolyte the interaction between the gegen-ions and the matrix is important and also has the effect of concentrating the gegen-ions into regions of relatively high solution viscosity. In the presence of sorbed electrolyte these effects, per mole of cations, become less significant.The electro-osmotic permeability of the resin decreases by about 25 % as the external solution concentration is increased from 0.01 to 1-00 M. This suggests that the interaction between gegen-ions and matrix does not take the form of specific ion-pairing, association or incomplete dissociation, but that it is due to electrostatic interactions controlling the distributions of the ions in the pore solution. An analysis is given in terms of a general distribution of the gegen-ions which shows that these conclusions are consistent with the experimental data and electrostatic theory.The implications of these results with regard to the convection contribution to electrical conduction are considered in the light of the conductance and diffusion coefficient data. The difficulties in computing the convection current from the electro-osmotic permeability are pointed out and an attempt made to estimate the diffusion coefficient of H+ ions from the conductance of the H+-form resin.

Electroosmotic Transport through a Cation-Exchange Membrane: Effect of the Stirring on the Dependence of the Electroosmotic Permeability on the Temperature

“…The passing of an electric current through the system Anode/Solution ͑c͒/Membrane/Solution ͑c͒/Cathode [1] gives rise to a water flux associated to the transport of the ions (electroosmosis).…”

“…Although this phenomenon has been widely studied in the literature (1)(2)(3)(4)(5)(6), little attention has been devoted to the influence of the temperature on the value of the electroosmotic permeability, the manner of this dependence being not very clear in most of the scarce references found (7)(8)(9)(10).…”

Suitability of the Nernst‐Planck equations for describing electrokinetic phenomena

“…This is because of the large amount of information required for such a description: n ( n -1)/2 diffusivities and associated activity data for a system of n diffusing species.' The most complete available treatments appear to be those of Spiegler (13) and Mackay and Meares (11).…”

On the correction for unstirred solution films in ion-exchange membrane cells

“…where co is a constant for the particular membrane -4-solution system and is relatively insensitive to the external concentration and nature of the cations [11]. For such similar external solutions the cationic activity coefficient gradients will also be negligible so that [1] may be rewritten…”