Two-phase electro-electrodialysis for recovery and concentration of citric acid

In order to overcome the disadvantages of electro-electrodialysis (EED), a coupled technique of two-phase electrophoresis and EED named two-phase electro-electrodialysis (TPEED) has been developed for recovering and concentrating citric acid solution in this work. In this new technique, an organic phase of n-butanol was used to replace the aqueous phase as anolyte and AM-203 anion-exchange membrane as separation medium. Citric acid was transferred from catholyte (aqueous phase) to anolyte (organic phase) under the action of an electric field. The characteristics of the new technique have been investigated. The electric current efficiency, recovery ratio, concentrated ratio, and volume change of the anolyte were studied. Our experimental results show that the new technique has two major advantages. One is that TPEED has the ability to overcome the electro-osmosis and osmosis of water, which causes the volume of the anolyte to increase. The other is that back diffusion caused by concentration difference can be well controlled by liquid-liquid interface. (C) 2004 Elsevier B.V. All rights reserved.