Electrodeionization process
AssigneeMillipore Corporation
InventorsGastón De Los Reyes, Linda M. Denoncourt, Bienvenido Garcia
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Abstract
An electrodeionization-based process for purifying water to remove ionic species is disclosed. Ionic removal is accomplished by supplying an electrical current between an anode and a cathode of an electrodeionization module in the range of about 1.5 to 15 times a “theoretical minimum current”. The current is supplied by a power source capable of automatically increasing or decreasing voltage in response to a change in the electrical impedance of the electrodeionization module to maintain constant current. Conduct of the process on pretreated water yields deionized water of good quality, while maintaining conditions that promote the longevity of the electrodeionization module.
Claims6
A water purification process comprising the following steps:
- (a) providing an electrodeionization module comprising, between a cathode and an anode, at least one ion depletion compartment interposed adjacently between a pair of ion concentration compartments, each compartment containing an ion-exchange medium;
- (b) passing water through said ion depletion compartment contemporaneously with passing water through said ion concentration compartments;
- (c) supplying a current between the anode and the cathode in the range of about 1.5×I* and about 15×I*,
- (i) wherein I*=(Q×C×F)/(3600×N), I* being a theoretical minimum current measured in amps, Q being the total water flow rate passing through all ion depletion compartments in said electrodeionization module measured in liters/hour, C being total ion concentration measured in equivalents/liter, F being Faraday's Constant of 96,500 coulombs/equivalent, and N being total number of ion depletion compartments, and
- (ii) wherein said current is supplied by a power source capable of automatically increasing or decreasing voltage in response to a change in the electrical impedance of the electrodeionization module to maintain constant said current;
- and
- (d) recovering water from said ion depletion compartment.
Dependencies are inferred from the claim text.