Cartridge having textured membrane

1. A cartridge for an ion exchange electrochemical cell, the cartridge comprising

at least one spiral wound, textured, bipolar ion exchange membrane having:

(i) an anion exchange layer abutting a cation exchange layer to form an interface at which there is continuous contact between the anion exchange layer and the cation exchange layer; and

(ii) an exposed textured surface having a pattern of texture features.

2. A cartridge according to claim 1 wherein the anion exchange layer and the cation exchange layer are arranged to provide a heterogeneous water-splitting interface.

3. A cartridge according to claim 1 wherein the texture features comprise spaced apart peaks and valleys characterized in that:

the peaks are ridges and the valleys comprise furrows between adjacent ridges; or (ii) the peaks comprise conical protrusions or mesas.

4. A cartridge according to claim 1 wherein the texture features comprise peaks and valleys, and the texture features comprise at least one of:

(i) a dimension greater than the thickness of a stagnant layer formed at the membrane surface by a solution traveling across the membrane surface;

(ii) a dimension of at least about 2 microns;

(iii) a peak to peak distance d pp of at least about 10 microns;

(iv) a peak to valley distance d pv of at least about 10 microns;

(v) an aspect ratio d pv /d pp of at least about 0.1; and

(vi) an aspect ratio d pv /d pp of at least about 1.

5. A cartridge according to claim 1 wherein the membrane is spirally wound around a core tube.

6. A cartridge according to claim 1 comprising end caps, at least one end cap comprising a hole through which an electrode may pass.

7. A cartridge according to claim 1 comprising a plurality of membranes offset from one another by a distance d o =3.14*d c /n, where d c is the outer diameter of a core tube on which the membranes are wrapped.

8. A cartridge according to claim 1 comprising a plurality of membranes having their ends attached to one another.

9. A cartridge according to claim 1 comprising a pair of end caps that each have an O-rings seal.

10. An electrochemical cell comprising:

(1) a housing comprising a vessel;

(2) the cartridge of claim 1 in the vessel;

(3) first and second electrodes about the cartridge; and

(4) a power supply for supplying a voltage to the first and second electrodes.

11. A method of manufacturing a cartridge for an ion exchange electrochemical cell, the method comprising:

(a) forming at least one bipolar ion exchange membrane having anion and cation ion exchange materials arranged to have at least one interface at which the anion exchange material and the cation exchange material contact one another, and an exposed textured surface having a pattern of texture features; and

(b) winding the textured, bipolar ion exchange membrane into a spiral wound membrane.

12. A method according to claim 11 wherein (b) comprises positioning the bottom surface of an offset membrane stack on a core tube and winding the offset membrane stack around the core tube while maintaining a tension on the offset membrane stack.

13. A method according to claim 12 wherein (b) comprises offsetting a plurality of the membranes during winding to form an offset membrane stack.

14. A method according to claim 11 wherein (b) comprises winding a plurality of the membranes around a core tube to form a cartridge roll.

15. A method according to claim 14 comprising attaching top and bottom end caps to the cartridge roll.

16. A method of forming a cartridge, the method comprising providing a electrochemical cell housing having a solution inlet and a solution outlet, and positioning a spiral wound membrane according to claim 14 within the housing such that the core tube is fluidly connected to the solution outlet.

17. A method according to claim 12 wherein (b) comprises winding a plurality of the membranes on top of one another so that the top ends of the membranes are offset from one another in the same direction.

18. A method according to claim 17 wherein (b) comprises winding the membranes on a core tube such that the top ends of the membranes are offset by a distance d o =3.14*d c /n, where d c is the outer diameter of a core tube.

19. A method according to claim 11 comprising attaching an outer sleeve over the spiral wound membrane.

20. A method according to claim 12 wherein (a) comprises forming the membrane with texture features comprising peaks and valleys, and with the texture features having at least one of:

(i) a dimension greater than the thickness of a stagnant layer formed at the membrane surface by a solution traveling across the membrane surface;

(ii) a dimension of at least about 2 microns;

(iii) a peak to peak distance d pp of at least about 10 microns;

(iv) a peak to valley distance d pv of at least about 10 microns;

(v) an aspect ratio d pv /d pp of at least about 0.1; and

(vi) an aspect ratio d pv /d pp of at least about 1.

21. A cartridge for an ion exchange electrochemical cell, the cartridge comprising

at least one spiral wound membrane comprising:

(i) an anion exchange material and a cation exchange material arranged to have at least one interface at which the anion and cation exchange materials contact one another; and

(ii) an exposed textured surface having a pattern of texture features.

22. A cartridge according to claim 21 wherein the anion and cation exchange materials are arranged to provide at least one heterogeneous water-splitting interface.

23. A cartridge according to claim 21 wherein the texture features comprise peaks and valleys, and the texture features comprise at least one of:

(i) a dimension greater than the thickness of a stagnant layer formed at the membrane surface by a solution traveling across the membrane surface;

(ii) a dimension of at least about 2 microns;

(iii) a peak to peak distance d pp of at least about 10 microns;

(iv) a peak to valley distance d pv of at least about 10 microns;

(v) an aspect ratio d pv /d pp of at least about 0.1; and

(vi) an aspect ratio d pv /d pp of at least about 1.

24. A cartridge according to claim 21 wherein the membrane is spirally wound around a core tube.

25. An electrochemical cell comprising:

(1) a housing comprising a vessel;

(2) the cartridge of claim 21 in the vessel;

(3) first and second electrodes about the cartridge; and

(4) a power supply for supplying a voltage to the first and second electrodes.