For continuous concentration of ions, electrodialysis is one of the commonly used technques in chemical industry. In this technique, an electrolyte solution is introduced to a chamber which is parted with ion exchange membranes. An electric field is applied to the chamber, and then charged ions migrate towards one of the electrodes. The role of the membrane is to define the direction of ion migration, and to prevent treated solutions from mixing. One of the drawback of the electrodialysis is the need to renew the membrane regularly, and thus the operatinal cost can be high.

This study was devoted to explore the possibility of microchannel electrophoresis for continuous ion enrichment. There are already many reports on realizing electrophoresis in microchannels. In these studies, the electrodes are installed at the inlet and outlet of the microchannel, and thus the direction of the electric field was parallel to the fluid flow. Such microdevices can be operated batchwise only, and thus not suited for continuous separation. In our approach, the electrodes are installed on the channel walls, and thus the electric field was normal to the flow direction. The charged ions are attracted to either one of the electrodes, and carried over to the downstream. By separating the fluid flow into two parts in a simple branch, an enriched solution can be easily obtained.

The validity of the proposed approach was examined in an experimental study. As an example, a sodium chloride solution was used as the feed stock, and the degree of ion enrichment was measured for various operating conditions. The results showed that the proposed technique can be used to enrich sodium ions.