Electrochemically assisted ion exchange

An electrochemical cell capable of removing ions from a solution stream, the cell comprising:

• (a) a housing having first and second electrodes;
• (b) at least one water-splitting ion exchange membrane positioned between the electrodes, the water-splitting membrane comprising (i) a cation exchange surface facing the first electrode, and (ii) an anion exchange surface facing the second electrode;
• and
• (c) a unitary and contiguous solution channel that allows an influent solution stream to flow past (i) the electrodes, and (ii) both the cation and anion exchange surfaces of the water-splitting membrane.

An assembly of electrochemical cells for selectively removing multivalent ions from a solution, the assembly comprising:

• (a) a first electrochemical cell including:
• (1) two electrodes,
• (2) at least one water-splitting ion exchange membrane between the electrodes, each water-splitting membrane comprising a cation exchange surface facing the first electrode, and an anion exchange surface facing the second electrode, and
• (3) a first solution stream pathway having (i) an inlet for influent solution stream, (ii) at least one channel that allows influent solution stream to flow past at least one surface of the water-splitting membrane to form one or more treated solution streams, and (iii) a single outlet that combines the treated solution streams to form a first effluent solution;
• (b) at least one second electrochemical cell comprising
• (1) two electrodes,
• (2) at least one water-splitting ion exchange membrane between the electrodes, each water-splitting membrane comprising a cation exchange surface facing the first electrode, and an anion exchange surface facing the second electrode, and
• (3) a second solution stream pathway having (i) an inlet for influent solution stream, (ii) at least one channel that allows influent solution stream to flow past at least one surface of the water-splitting membrane to form one or more treated solution streams, and (iii) a single outlet that combines the treated solution streams to form a second effluent solution;
• (c) means for supplying a voltage to the electrodes of the first and second cells;
• and
• (d) a flow controller for apportioning a flow of a solution stream into the first and second cells so that the solution stream flows into the first cell at a first flow rate and into the second cell at a second flow rate, the first and second flow rates being selected to provide a desired concentration of multivalent ions in the combined first and second effluent solutions.

A method of replacing ions in an ion exchange material by applying a voltage to an electrochemical cell comprising:

• (a) first and second electrodes;
• (b) at least one water-splitting membrane between the electrodes, each water-splitting membrane comprising ion exchange layers A and B, one a cation exchange layer facing the first electrode and the other an anion exchange layer facing the second electrode, which layers contain ions I.sub.1A and I.sub.1B respectively;
• wherein a unitary and contiguous solution channel is defined by the cation and anion exchange layer surfaces of the membranes, the solution channel abutting both electrodes and extending continuously from the inlet to the outlet of the housing;
• (c) an ion-containing solution electrically connecting the electrodes and the water-splitting membranes;
• in which cell ions I.sub.1A and I.sub.1B are replaced by ions I.sub.2A and I.sub.2B, respectively.

A method for removing multivalent ions from a solution, which method comprises applying a voltage to an assembly comprising first and second electrochemical cells:

• (a) the first electrochemical cell comprising:
• (i) first and second electrodes;
• (ii) at least one water-splitting membrane between the electrodes, each water-splitting membrane comprising a cation exchange layer A and an anion exchange layer B, which layers comprise ions I.sub.4A and I.sub.4B, respectively, ions I.sub.4A and I.sub.4B comprising substantially H.sup.+ and OH.sup.-, respectively, wherein the cation exchange layers face the first electrode and the anion exchange layers face the second electrode, in which cell there is a unitary and contiguous solution channel, and
• (iii) a solution containing ions I.sub.2A and I.sub.2B which electrically connects the electrodes and water-splitting membrane, in which cell ions I.sub.4A and I.sub.4B are replaced by ions I.sub.2A and I.sub.2B ;
• (b) a second electrochemical cell, comprising:
• (i) first and second electrodes;
• (ii) at least one water-splitting membrane arranged between the electrodes, each water-splitting membrane comprising a cation exchange layer A and an anion exchange layer B, which layers comprise ions I.sub.5A and I.sub.5B, respectively, ions I.sub.5A and I.sub.1B comprising monovalent ions other than H.sup.+ and OH.sup.-, respectively, wherein the cation exchange layers face the first electrode and the anion exchange layers face the second electrode, in which cell there is a unitary and contiguous solution channel, and
• (iii) a solution containing ions I.sub.2A and I.sub.2B which electrically connects the electrodes and water-splitting membrane,
• in which cell ions I.sub.5A and I.sub.5B are replaced by ions I.sub.2A and I.sub.2B, respectively.