Recently a new deionization technology, the continuous electro-deionization has been developed, which is a combination of electro-dialysis and ion exchange. It is obtained by a process, which deionized water while the resins are continuously regenerated by means of the electric current inside the unit. This electrochemical regeneration replaces the traditional chemical regeneration of ion exchange systems.
The electro-deionization module must be supplied with pre-treated water with reverse osmosis: By combining these two techniques is obtained ultrapure water (0.1-0.2 mS / cm), starting from the drinking water.
The electro-deionization module for continuously is formed by a number of cells placed between two electrodes, each of which is formed by a polypropylene frame on which are placed on one side of a membrane permeable to cations, and on the other a membrane permeable to the anions . The interior space of the cell, between the two ion-selective membranes, is filled by a layer of resin ion exchange.
The cells are divided from each other by separators screens; the feed water which enters the module is divided into three parts: a small part touches the electrodes, the 65-75% of the power passes through the resin bed within the cells and the remainder flows along the separator screens between cells.
The ion exchange resin to capture the ions present in the feed, in the upper part of the cell, and the electric current applied pushes them through the ion selective membrane towards the electrodes. The cations are pushed through the membrane permeable to cations towards the cathode and anions through the anion selective membrane towards the anode. On the other hand, these ions can not reach to the electrodes, as rejected by the membrane with the same charge of the adjacent cell.
The ions are then to focus in the space between cells, called channel of the "concentrate," are continuously removed from the washing flow and discharged. The format of the two ion-selective membrane channel containing resins is called channel of the "diluted" .Mano hand that water passes into the channel is progressively ionised.
In the terminal part of this channel, where the water is free of ions, it has inside the electric field the dell'H20 cleavage, and H + ions and OH- formed regenerate the resins. The module will then work as a unit to ion exchange with continuous regeneration.