The influence of spatially nonuniform electric fields on the transport of ions through ion-selective membranes is investigated both experimentally and theoretically. The flux of ions is determined indirectly by following the change of pH with time. The uniformity of the field is varied with a Pt wire electrode configuration by changing the relative positions of the anode and cathode. Higher fluxes are found for the nonuniform configuration than for the uniform configuration. These results were previously predicted in a theoretical investigation which revealed the importance of nonlinearity in the transport laws. The experimental observations are found to be consistent with theoretical calculations based on the Goldman flux equation.

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030ChemInform Abstract It is demonstrated experimentally that transport of ions through ion-exchange membranes via the application of electric field can be enhanced by 10% if the field is spatially nonuniform. This can be explained in terms of the influence of nonuniformity in a transport system which obeys nonlinear transport laws. A model based on the Goldman flux equation is in qualitative agreement with theexperiment, as are previous calculations by another group. The use of nonuniform fields in devices such as electrodialysis units, fuel cells, batteries, and the like may lead to more efficient transport of ions and, therefore, less energy consumption.

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