(719g) Esiex-Electrical Swing Ion Exchange:a Process Coupling Ion Exchange, Carbonic Acid Elution and Electroregeneration by Electrodialysis

Consider an electrodialysis cell with ion exchange resin between the membranes (this is typically EDI : electrodeionization). The process is in three steps.

In the first step, the mixture to be separated is percolated on the ion exchange bed. Conditions must be chosen in order that only one specie is fixed on the resin. For example, the dipeptide GLYGLY in water is fixed on an anion exchange resin in carbonate initial form.

The second step is elution of GLYGLY with a carbonic acid solution. This solution allows to recover pure GLYGLY in water, contrary to other classical methods in ion exchange where the desorption occurs in a buffer or in a salt solution. During this step, the resin converts to bicarbonate form. The carbonic acid solution was obtained thanks to the third step of the previous cycle.

The third step is to return the resin to the carbonate form. This is done by passing an electrical current trough the cell. An anion exchange membrane is chosen so that hydroxiles anions move toward the resin bed. Half of the bicarbonate anions move trough the opposite anion exchange membrane of the cell toward a compartment where they dissolve in water. In this compartment, protons are produced by a bipolar membrane : thus the elution solution for the second step is regenerated. The second half of bicarbonate anions transform on the resin to carbonate anions. Thus the initial state is recovered.