MICROSCOPIC ANALYSIS OF THE SURFACE OF HETEROGENEOUS MEMBRANES WITH A DIFFERENT DEGREE OF ION EXCHANGER DISPERSITY AFTER TEMPERATURE INFLUENCE

Abstract

At present, one of the areas for the improvement of electromembrane methods of substance separation and isolation is the development of new membranes with optimized surface morphology that in particular can be achieved by the influence of elevated temperatures on ion-exchange materials. The purpose of this work is to evaluate the effect of temperature influence on the surface properties of experimental samples of heterogeneous sulfocation exchange membranes.

Experimental samples of heterogeneous cation-exchange membranes with varying dispersion degrees were chosen as the objects for investigation. The dispersion degree of sulfocation exchanger was varied by the use of different duration of their milling. The experimental studies of surface morphology of membranes were conducted using the scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. Microphase fractions and sizes were estimated by means of an original software system.

The differences in the microstructure of the experimental samples of the sulfocation exchange membranes with different ion exchanger milling time were visualized by SEM and AFM methods. From the analysis of micrographs of membrane samples, it was found that the proportion of ion exchange for heterogeneous membranes CM Pes is 15-17%. The increase in the duration of the milling of ion-exchange particles is accompanied by a change in their dispersion degree. With an increase in the dispersion degree of the ion exchanger, the decrease in the distances between inhomogeneity zones, in the linear dimensions of the ion-exchange particles and pores, and the less developed surface microrelief were revealed. A comparative analysis of the structural properties of the membrane surface showed that as a result of prolonged effect of elevated temperatures, a significant increase in macroporosity and the appearance of structural defects and a decrease in the fraction of the ion exchange phase occur. The established changes in the microstructure of sulfocation exchange membranes are due to the partial destruction of ion-conducting and inert polymers.

ACKNOWLEDGMENTS

Microphotographs of the membranes surface were obtained with equipment of Voronezh State University Centre for Collective Use of Scientific Equipment

This work was financially supported by RFBR grants (projects Nos. 15-08-05031 and 16-38-00572 mol_a).