Patent ID: 8241478

Claim:
An electrodeionization apparatus comprising: an ion-concentrating compartment partially bounded by a first ion permeable membrane and also partially bounded by a separator element, wherein the first ion permeable membrane is one of an anion permeable membrane and a cation permeable membrane; wherein the separator element is a second ion permeable membrane, and the second ion permeable membrane is the other one of the one of the anion permeable membrane and the cation permeable membrane, and the at least a portion of the ion-concentrating compartment side surface of the first ion permeable membrane defines an operative side surface fraction; wherein the operative side surface fraction defines an operative side surface area fraction of the ion-concentrating compartment side surface of the first ion permeable membrane which is at least 10% of the ion-concentrating compartment side surface area of the first ion permeable membrane; a first ion exchange material domain disposed within the ion-concentrating compartment, wherein the first ion exchange material domain is contiguous with at least a portion of an ion-concentrating compartment side surface of the first ion permeable membrane, wherein the at least a portion of the ion-concentrating compartment side surface of the first ion permeable membrane defines an operative side surface fraction of the ion-concentrating compartment side surface of the first ion permeable membrane; a second ion exchange material domain disposed within the ion-concentrating compartment, wherein the disposition of the first ion exchange material domain relative to the separator element defines a first space between the first ion exchange material domain and the separator element, and wherein at least a portion of the second ion exchange material domain is disposed within the first space; such that, where the first ion permeable membrane, having the at least a portion of the ion-concentrating compartment side surface with which the first ion exchange material domain is contiguous, is an anion permeable membrane, the first ion exchange material domain is an anion exchange material predominant domain and the second ion exchange material domain is a non-anion exchange material predominant domain; and where the first ion permeable membrane, having the at least a portion of the ion-concentrating compartment side surface with which the first ion exchange material domain is contiguous, is a cation permeable membrane, the first ion exchange material domain is a cation exchange material predominant domain and the second ion exchange material domain is a non-cation exchange material predominant domain.