Physicochemical Properties of Profiled Heterogeneous Ion-Exchange Membranes

Abstract

Optimum values of parameters of hot pressing of heterogeneous ion-exchange membranes pressure, exposure duration) with the aim of creating geometrical profiles on their surfaces are determined. A method of optical visualization of membrane profiles and a diffusion technique of diagnostics of through pores in the membranes are developed and substantiated. Most important physicochemical and physicomechanical characteristics of profiled membranes are investigated. It is shown that the major obstacle in the production of profiled cation-exchange heterogeneous membranes is encapsulation of grains of the ion-exchange resin by an inert polyethylene film, which leads to an increase in the surface resistance of the membranes and to a decrease in the fraction of their active surface areas. The profiling of heterogeneous anionexchange membranes is accompanied by an increase in their microscopic porosity and diffusion penetrability.

Characterization of Ion Exchange Membranes with Special Surface Structure

“…One of the promising ways of this intensification is the creation of microscopic relief on the surface of an ion exchange membrane (IEM) [1]. The first successful application of structured membranes in reverse electrodialysis (RED) was achieved by Vermaas et al [2].…”

“…Structured membranes can be produced by many different techniques, such as calendaring (roll-pressing) thermoplastic ion exchange film between rollers with a geometrical structure at an elevated temperature [6,9,10], hot pressing (hot embossing) of ion exchange film [1,2,7,9,11] and casting a solution of ion exchange material followed by evaporation of the solvent [5,12,13,14].…”

“…The most typical problems are ruptures or deformation of the microstructures which occur during the release of the membrane film from the melt [16]. Moreover, electrochemical properties (permselectivity and electrochemical resistance) are usually changed during hot pressing [1,2].…”

“…The optimum values of parameters (temperature 20 -140 °C, pressure 10 -13 MPa, exposure duration 10 -600 s) of hot pressing of heterogeneous IEMs are discussed by Zabolotskii et al [1]. The optimum values of parameters of hot pressing of heterogeneous ion-exchange membranes with the aim of creating geometrical profiles on their surfaces are determined.…”

“…The optimum values of parameters of hot pressing of heterogeneous ion-exchange membranes with the aim of creating geometrical profiles on their surfaces are determined. It is shown that the major problem in the production of structured heterogeneous membranes is encapsulation of particles of the ion exchange resin in an inert polyethylene film, which leads to an increase in the surface resistance [1].…”