Patent ID: 7666288

Claim:
An electrodeionization apparatus comprising: an anolyte compartment having an anode; a catholyte compartment having a cathode; concentrating compartments and desalting compartments wherein the concentrating compartments and the desalting compartments are formed between the anolyte compartment and the catholyte compartment by arranging alternately at least one anion-exchange membrane and at least one cation-exchange membrane; ion-exchanger with which the desalting compartments are filled; at least one of ion-exchanger, activated carbon, and electric conductor which fills the concentrating compartments; a device for introducing electrode water into the anolyte compartment and the catholyte compartment, respectively; a concentrated water introducing device for introducing concentrated water into the concentrating compartments; a device for feeding raw water into the desalting compartments to produce deionized water; and outlets formed at the desalting compartments for taking out the deionized water; wherein the outlets of the desalting compartments are connected to the concentrated water introducing device to introduce a part of the deionized water containing at least one of silica and boron at a lower concentration than the raw water and obtained from the desalting compartments into the concentrating compartments at a side near the outlets for the deionized water of the desalting compartments; the concentrated water introducing device makes the concentrated water flow out of the concentrating compartment at a side near an inlet for the raw water of the desalting compartment; at least a part of the concentrated water flows out of the concentrating compartments out of a circulatory system; the desalting compartments are filled with an anion exchanger and a cation exchanger in such a manner that anion exchanger/cation exchanger volume ratio becomes 8/2 to 5/5; and at least one part of the anion exchanger in the desalting compartment is made of a II type anion exchanger.