Anion permselective membrane

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Abstract
Experimental composite membranes were synthesized on a lab scale consisting of a thin layer of anion permselective resin supported by and bonded to a porous physically strong and conductive substrate film. These showed good selectivity and also substantially lower electrical resistivities than the homogenous candidate membrenes optimized in the previous contract. A wide range of resin porosities were examined for three candidate membrane systems, CD1L, CP4L, and A3L to identify the formulation giving the best overall redox cell performance. The objective was to obtain the optimum membrane porosity giving an acceptable selectivity and long range resistance stability in redox cell operation. Candidate anion membranes showed large increases in resistivity after a short time of immersion in concentrated FeCl/sub 3//HC1 solution. The resistance rise was attributed to exchange site fouling by the complex ions FeCl/sub 4//sup -1/ and FeCl/sub 6//sup -3/ and was found to be reversible by HCl washing. Limited quantities of two candidate membranes CD1L and CP4L (in the 10'' x 10'' size) were made up using several fabrics and various N.P. contents from 25 to 33%. Largely on the basis of resistance stability the CD1L formulation was selected as prime candidate and about thirty-five membranes (one foot square)more » were produced for experimental static and dynamic evaluation. A better appreciation of the significance of the various processing parameters was gained during this study. This improved understanding permitted us to increase the batch size and therefore the number of membranes per batch, while making substantial improvements in both uniformity and reliability. « less

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