Abstract: Electrodeionization apparatus having a novel polarity reversal protocol designed to provide continuous, high-quality product fluid is described. The protocol involves substitution of a recirculating fluid stream established in an ion-concentrating compartment by a fluid stream having a lower ionic concentration, while maintaining fluid flow through an adjacent ion-depleting compartment. A method and protocol for modifying the ionic makeup of compartment ion exchange material and fluids are also provided. A flow reversal protocol is also provided, during which high-quality fluid product is recovered from the inventive apparatus. The polarity reversal protocol and flow reversal protocol may each be effected separately, or the flow reversal may be introduced into the sequence of the polarity reversal protocol.

Abstract: An ultra-thin composite membrane is provided which includes a base material and an ion exchange resin. The base material is a membrane which is defined by a thickness of less than 1 mil (0.025 mm) and a microstructure characterized by nodes interconnected by fibrils, or a microstructure characterized by fibrils with no nodes present. The ion exchange resin substantially impregnates the membrane such that the membrane is essentially air impermeable.

Abstract: The invention is a demineralization apparatus comprising an anode chamber disposed at one end of a vessel having an anode at the inside of the anode chamber. A cathode chamber is disposed at the other end of the vessel, having a cathode at the inside of the cathode chamber. At lease one diluting chamber and at least one concentrating chamber are located alternately between the anode chamber and the cathode chamber. The diluting chamber has an anion exchange membrane on the anode chamber side and a cation exchange membrane on the cathode chamber side. The diluting chamber has an inlet for water to be treated and an outlet for demineralized water. The concentrating chamber has an inlet for water and an outlet for ion-concentrated water. The diluting chamber contains a cloth comprising a mixture of strongly acidic cation exchange fibers, strongly basic anion exchange fibers and ionically inactive synthetic fibers. Preferably, the mixture contains from 20 to 70% by weight ionically inactive synthetic fibers.

Abstract: Electrodialysis ("ED") stacks are disclosed having components selected from the group:a) cation exchange ("CX") membranes and/or CX granules having in at least a surface a predominant amount of sulfonate exchange groups and a minor amount of weakly ionized exchange groups;b) anion exchange ("AX") membranes and/or AX granules having in at least a surface substantially only quaternary ammonium and/or phosphonium exchange groups which upon decomposition leave almost no amine or phosphine groups bound to the membranes or granules;c) AX and/or CX granules which are selective to monovalent ions at currents which are fractions of the limiting current of such granules;d) AX and/or CX membranes and granules, such membranes and granules selective to monovalent ions at currents which are fractions of the limiting current of such membranes and granules;e) ion exchange ("IX") granules in which the concentration of IX groups in the inner regions is a fraction (including zero) of the concentration in the outer regions;f) AX