Anti-scale electrochemical apparatus with water-splitting ion exchange membrane

1. An ion exchange cell comprising:

(a) a housing having a plurality of openings to receive and release a water stream;

(b) inner and outer electrodes in the housing;

(c) a water-splitting membrane between the inner and outer electrodes to treat an influent water stream to form an effluent water stream; and

(d) a controlled-release scale-inhibitor composite in the housing, the controlled-release scale-inhibitor composite comprising a concentration ratio of a scale-inhibitor agent to a thermoplastic polymer that is sufficiently high to provide an average concentration of at least about 0.5 ppm of the scale-inhibitor agent in a regenerant water stream that is generated during cell regeneration over treatment of the entire volume of water that can be processed by the water-splitting membrane before the water-splitting membrane needs to be replaced.

2. A cell according to claim 1 wherein the controlled-release scale-inhibitor composite comprises a concentration ratio of scale-inhibitor agent to thermoplastic polymer that is sufficiently high to dissolve at least about 25% of the scale-inhibitor agent over treatment of the entire volume of water that can be processed by the water-splitting membrane before the water-splitting membrane needs to be replaced.

3. A cell according to claim 1 wherein the controlled-release scale-inhibitor composite comprises a concentration ratio of the scale-inhibitor agent to the thermoplastic polymer of from about 20% by volume to about 60% by volume.

4. A cell according to claim 1 wherein the scale-inhibitor agent comprises sodium polyphosphate.

5. A cell according to claim 1 wherein the controlled-release scale-inhibitor composite is shaped as a disc, net, rod, band or granule.

6. A cell according to claim 1 wherein the water-splitting membrane is spiral wound to form a cartridge, and the controlled-release scale-inhibitor composite is attached to the cartridge.

7. A cell according to claim 1 wherein the controlled-release scale-inhibitor composite is located adjacent to the outer electrode.

8. A cell according to claim 1 wherein the controlled-release scale-inhibitor composite comprises a surface barrier.

9. An anti-scale electrochemical apparatus comprising:

(a) a plurality of ion exchange cells according to claim 1 , the ion exchange cells connected to one another to allow regeneration of one ion exchange cell while another ion exchange cell is used to treat water;

(b) a power supply to apply a current to the inner and outer electrodes of each ion exchange cell; and

(c) a valve system to control a flow of water between the ion exchange cells for water treatment or regeneration.

10. A method of fabricating an anti-scale electrochemical apparatus, the apparatus comprising an ion exchange cell having a housing enclosing a water-splitting membrane between inner and outer electrodes, the method comprising:

(a) forming a controlled-release scale-inhibitor composite comprising a scale-inhibitor agent and a thermoplastic polymer such that a concentration ratio of the scale-inhibitor agent to the thermoplastic polymer is sufficiently high to provide an average concentration of at least about 0.5 ppm of the scale-inhibitor agent in a regenerant water stream that is generated during cell regeneration over treatment of the entire volume of water that can be processed by the water-splitting membrane before the water-splitting membrane needs to be replaced;

(b) providing the ion exchange cell comprising the housing enclosing the water-splitting membrane between the inner and outer electrodes, the cell having a water flow pathway; and

(c) providing the controlled-release scale-inhibitor composite in the water flow pathway of the ion exchange cell.

11. A method according to claim 10 comprising shaping the controlled-release scale-inhibitor composite by pressure forming.

12. A method according to claim 10 comprising positioning the controlled-release scale-inhibitor composite adjacent to the outer electrode in the housing.

13. An anti-scale water-splitting membrane comprises a water-splitting interface formed by contact of (i) an anion exchange layer and ii) a cation exchange layer, wherein either the anion exchange layer or the cation exchange layer comprises a scale-inhibitor agent in a concentration that is sufficiently high to provide an average concentration of at least about 0.5 ppm of the scale-inhibitor agent in a regenerant water stream that is generated during cell regeneration over treatment of the entire volume of water that can be processed by the anti-scale water-splitting membrane before the anti-scale water-splitting membrane needs to be replaced.

14. A membrane according to claim 13 wherein the anion exchange layer comprises the scale-inhibitor agent.

15. A membrane according to claim 13 wherein the scale-inhibitor agent comprises sodium polyphosphate, and wherein the anion exchange layer further comprises a thermoplastic polymer.

16. An ion exchange cell comprising:

(a) a housing having a plurality of openings to receive and release a water stream;

(b) inner and outer electrodes in the housing; and

(c) an anti-scale water-splitting membrane according to claim 13 .

17. An apparatus according to claim 1 wherein the water-splitting membrane is replaced before the membrane exhibits water channeling.

18. An apparatus according to claim 1 wherein the water-splitting membrane is replaced before the membrane exhibits at least one of (i) a reduction in deionization performance of at least 10%, or (ii) a decrease in flow rate through the membrane of at least 30%.

19. An apparatus according to claim 1 wherein the thermoplastic polymer comprises a polyolefin.

20. An anti-scale electrochemical apparatus comprising:

(a) a plurality of ion exchange cells, each ion exchange cell comprising:

(i) a housing having a plurality of openings to receive and release a water stream;

(ii) inner and outer electrodes in the housing;

(iii) a water-splitting membrane between the inner and outer electrodes to treat an influent water stream to form an effluent water stream; and

(b) a power supply to apply a current to the inner and outer electrodes of each ion exchange cell;

(c) a valve system to control a flow of water between the ion exchange cells for water treatment or regeneration; and

(d) a canister in a water flow pathway of the ion exchange cells or valve system, the canister comprising a controlled-release scale-inhibitor composite, the controlled-release scale-inhibitor composite comprising a concentration ratio of a scale-inhibitor agent to a thermoplastic polymer that is sufficiently high to provide an average concentration of at least about 0.5 ppm of the scale-inhibitor agent in a regenerant water stream that is generated during cell regeneration over treatment of the entire volume of water that can be processed by the water-splitting membrane before the water-splitting membrane needs to be replaced.

21. An apparatus according to claim 20 wherein the controlled-release scale-inhibitor composite comprises a concentration ratio of the scale-inhibitor agent to the thermoplastic polymer of from about 20% by volume to about 60% by volume.

22. An apparatus according to claim 20 wherein the controlled-release scale-inhibitor composite comprises a thermoplastic polymer comprising a polyolefin.

23. An apparatus according to claim 20 wherein the water-splitting membrane is replaced before the membrane exhibits water channeling.

24. A membrane according to claim 13 comprising a concentration ratio of the scale-inhibitor agent to a thermoplastic polymer of from about 20% by volume to about 60% by volume.

25. A membrane according to claim 24 wherein the thermoplastic polymer comprises a polyolefin.

26. A membrane according to claim 13 wherein the anti-scale water-splitting membrane is replaced before the membrane exhibits water channeling.

27. A cartridge comprising an anti-scale water-splitting membrane according to claim 13 , the membrane being spiral wound.