New generation of advanced membranes

The development of a new generation of membranes based on conducting polymers has been the subject of a recent line of research in the Department of New Materials at CIDETEC, in association with the LEIA Technological Centre.

This involves a field of work wherein the excellent advantages presented by electro-dialysis conventional membranes (continuous separation, low energy consumption, ease of combination with other separation processes, absence of additives) are combined with other, highly promising, properties shown by conducting polymer membranes, with special reference to the possibility of manipulation of the pore size by means of the application of potential differences. These developments target the increasingly specific demands from industrial sectors: surface coating/treatment sector (automobile, printing, locksmiths, machine-tools, etc.), chemicals, agricultural feeds, pharmaceuticals and textiles, etc.

The interest provoked by conducting polymers for their application in membrane technologies is explained when we look at the fundamental specification which an ion interchange membrane has to have: great selectivity, low electric resistance to minimise specific energy consumption and low electro-osmotic flow in order to obtain the maximum possible concentration of salts in the concentration compartment.

One of the drawbacks that these membranes have is that they cannot be considered “adaptable”. Effectively, once manufactured (for example, with a determined pore size, a determined ionic selectivity, etc), it is not possible to modify their properties through an external stimulus to “adapt” them to new process conditions, new effluents, etc. This is why membranes based on conducting polymers have been developed. In this sense, conducting polymers show themselves to be ideal candidates for use as membranes, given the special made-to measure characteristics they have for this application, such as: electrical conductivity, reversible electroactive properties and the possibility of controlling the chemical structure and the free volume of the conducting polymers in order to achieve a specific selectivity.