The Effect of the Cation-Exchange Membranes MK-40 Modification by Perfluorinated Sulfopolymer and Ceria on Their Transport Properties
Composite materials based on heterogeneous membranes MK-40 modified by a thin layer of homogeneous cation-exchange perfluorinated sulfo membrane MF-4SK doped with 2 and 5% ceria are prepared. The transport characteristics of these membranes in different ionic forms are studied. It is shown that the conductivity of ionic forms of membranes increases in the sequence Li+ < Na+ < К+ < H+. In all these forms except for the lithium form, the membrane containing 2% ceria has the highest conductivity. Modification leads to a considerable increase in selectivity of membranes which manifests itself as a decrease in transport numbers of anions (from 0.006 for the original membrane to 0.002 for the membrane with 5% ceria). The higher selectivity with respect to the transfer of nitrate ions as compared with chloride ions is observed.