Electrodialysis is a process for the separation of ions in saline solutions and is therefore suited to converting these into their corresponding acids and bases. The necessary separation of ions is effected by an electric field applied via an anode and a cathode as well as by consecutive ion exchange membranes.

In many types of industrial production it is necessary to add acids and bases to aqueous processes. However, this increases the salt concentration and/or the conductivity, which is why the recovery rate of the water in the cycle is limited as a result of the accumulation or the increase. Additionally, the acids and bases are themselves lost for the process. On the one hand, these can now be recovered by means of the electrodialysis and on the other the water, freed of the salt load, can also be recirculated.

Operation principle of a bipolar membrane stack applied in electrodialysis processes

The membrane stack consists of cation exchange, anion exchange and bipolar membranes. Here the sodium cations and sulfate anions of the salt are transferred by the electric field to base or acid chambers, where they form caustic soda and sulfuric acid with hydroxide ions (OH) or protons (H+) formed heterolytically on bipolar membranes. Thus the acid and base concentrations increase during the process, whereas those of the saline solution decrease.

R&D focus and applications

The focus of the present research is on the reduction of the energy consumption of this process, in order to make it attractive for industrial scale use as well. Other possible applications for electrodialysis are in the food industry (pH modification, demineralization) and in the production of organic acids.


Reference projects


Valorization of condensate streams from the torrefaction of biomass


In the VALORKON project, a fermentation-free biorefinery concept is being developed based on the drying and torrefaction process with superheated steam established at IGB. A new process chain is used to selectively separate valuable substances such as formic acetic acid, furfurals and phenols, which are released in the volatile phase during torrefaction.


Duration: March 2019 – February 2022

NovEED –

A novel energy efficient electrodialysis cell to recycle Acids and Bases from industrial process water based on new types of electrodes to enable internal energy recovery


In the NovEED project, a novel energy-efficient electrodialysis cell is being developed for internal energy recovery, based on a new type of electrode. The electrodialysis cell is to be used for the recycling of acids and bases from industrial process waters.


Duration: November 2013 – October 2015



ECO-efficient management of WAter in the MAnufacturing industry


The effluents from the metal and plastic surface processing industry, particularly from galvanization, are rich in organic loading, salts, and heavy but valuable metals like nickel, copper and zinc. Led by the Fraunhofer IGB, the ECOWAMA project (“ECO-efficient management of WAter in the MAnufacturing industry”) seeks to develop an efficient and cost-effective method for electrochemical treatment of the effluents of the project partners from France, Spain, the Netherlands and Germany.


Duration: October 2012 – September 2016