Electrochemical ion exchange with textured membranes and cartridge
View Patent ↗An electrochemical cell 102 comprises an ion exchange membrane 10 having anion and cation exchange materials. The membrane 10 can have separate anion and cation exchange layers 12, 14 that define a heterogeneous water-splitting interface therebetween. In one version, the membrane 10 has a textured surface having a pattern of texture features 26 comprising spaced apart peaks 28 and valleys 30 . The membranes 10 can also have an integral spacer 80 . A cartridge 100 can be fabricated with a plurality of the membranes 10 for insertion in a housing 129 of the electrochemical cell 102 . The housing 129 can also have a detachable lid 96 that fits on the cartridge 100 . The electrochemical cell 102 can be part of an ion controlling apparatus 120.
1. An electrochemical cell comprising:
(a) a housing comprising a vessel having a solution inlet and a solution outlet, and a detachable lid;
(b) a cartridge in the vessel, the cartridge comprising a plurality of textured bipolar ion exchange membranes abutting one another, each membrane having:
(i) an anion exchange layer abutting a cation exchange layer to form a heterogeneous water-splitting interface therebetween, the heterogeneous water-splitting interface comprising continuous contact between the anion exchange layer and the cation exchange layer; and
(ii) an exposed textured surface having a pattern of texture features comprising spaced apart peaks and valleys; and
(c) first and second electrodes about the cartridge.
2. An electrochemical cell according to claim 1 wherein either:
(i) the peaks are ridges and the valleys comprise furrows between adjacent ridges, the ridges and furrows being generally parallel to a direction that solution travels across the membrane during use of the membrane; or
(ii) the peaks comprise conical protrusions or mesas, and the peaks extend out from a substantially flat surface region which defines the valleys.
3. An electrochemical cell according to claim 2 wherein each ridge on the anion exchange layer of the membrane lies generally opposite a furrow on the cation exchange layer.
4. An electrochemical cell according to claim 1 wherein the peaks and valleys comprise at least one of:
(i) a dimension that is 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; or
(vi) an aspect ratio d pv /d pp of at least about 1.
5. An electrochemical cell according to claim 1 comprising an integral spacer on the textured membranes, the integral spacer characterized by at least one of:
(i) filaments on the textured surface;
(ii) a coating on the peaks of the texture features;
(iii) a thickness of less than about 1000 microns; or
(iii) a thickness of less than about 500 microns.
6. An electrochemical cell according to claim 1 wherein the membranes are spirally wound around a core tube.
7. An electrochemical cell according to claim 6 wherein the cartridge comprises end caps and at least one end cap has a hole through which an electrode may pass.
8. An electrochemical cell according to claim 7 wherein both end caps have O-ring seals.
9. An electrochemical cell according to claim 1 wherein the membranes are spirally wound.
10. An electrochemical cell according to claim 1 wherein the membranes are 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.
11. An electrochemical cell according to claim 1 wherein the ends of the membranes are attached to one another.
12. An electrochemical ion exchange system comprising the electrochemical cell of claim 1 and further comprising:
(a) a power supply for supplying a voltage to the first and second electrodes; and
(b) a pump for flowing a solution stream through the electrochemical cell.
13. An electrochemical cell according to claim 1 wherein the ends of the membranes are offset from one another in the same direction.
14. An electrochemical cell according to claim 1 comprising at least one of the following:
(i) at least one of the first or second electrodes comprises a wire;
(ii) a dielectric between the first and second electrodes; or
(iii) the first and second electrodes comprise titanium or niobium, and an outer coating of a noble metal.
15. An electrochemical cell according to claim 1 wherein the cartridge comprises a core tube which slides into a through-hole in the housing to form the solution outlet.
16. An electrochemical cell according to claim 1 wherein the vessel comprises a sidewall and the detachable lid comprises a plate that is removably attached to the sidewall, the plate comprising a keyhole.
17. An electrochemical cell according to claim 16 wherein the cartridge comprises top and bottom end caps, and the top end cap comprises an end-cap extension which protrudes out and is capable of extending into the keyhole of the plate, the end-cap extension comprising a distal end having an outwardly extending flange.
18. An electrochemical cell according to claim 1 wherein the vessel comprises a sidewall having a recessed groove, and the plate of the detachable lid comprises a side surface having at least a pair of outwardly projecting pins that slide into the recessed groove.
19. An electrochemical cell according to claim 18 wherein the recessed groove comprises a sloped portion with a step-down locking channel so that the detachable lid can be pushed down and rotated into the step-down locking channel to lock the lid into the vessel.
20. An electrochemical cell according to claim 1 wherein the surfaces of each of the anion and cation exchange layers at their interface are textured, and the boundary between the anion and cation exchange layers at their water-splitting interface follows the contour of the textured surfaces.
21. An electrochemical cell according to claim 1 wherein the membranes undulate to form corrugated membranes.
22. An electrochemical cell according to claim 1 wherein the plurality of membranes are arranged to provide a solution passageway that forms a unitary and contiguous solution channel that flows past both the anion exchange layer and the cation exchange layer of each membrane.
23. An electrochemical cell according to claim 22 wherein the unitary channel is connected throughout in an unbroken sequence extending continuously from the solution inlet to the solution outlet.
24. A method of manufacturing a cartridge for an ion exchange electrochemical cell, the method comprising:
(a) forming a plurality of textured bipolar ion exchange membranes, each membrane having (i) anion and cation ion exchange materials arranged to form a heterogeneous water-splitting interface comprising continuous contact between the anion exchange material and the cation exchange material, and (ii) an exposed textured surface having a pattern of texture features comprising peaks and valleys which are spaced apart from one another;
(b) forming an offset membrane stack of the textured bipolar membranes which are offset from one another;
(c) providing a core tube and winding the offset membrane stack around the core tube to form a cartridge roll; and
(d) attaching top and bottom end caps to the cartridge roll.
25. A method according to claim 24 comprising forming membranes with 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; or
(vi) an aspect ratio d pv /d pp of at least about 1.
26. A method according to claim 24 wherein (b) comprises laying the membranes on top of one another so that the top ends of the membranes are offset from one another in the same direction.
27. A method according to claim 26 comprising offsetting the top ends of the membranes by a distance d o =3.14*d c /n, where d c is the outer diameter of the core tube on which the membranes are wrapped.
28. A method of forming an electrochemical cell, the method comprising providing a electrochemical cell housing having a solution inlet and a solution outlet, and positioning the cartridge roll formed according to claim 27 within the housing such that the core tube is fluidly connected to the solution outlet.
29. A method according to claim 26 comprising attaching the top ends of the membranes to one another by clips, glue, heat staking, rivets, sewing, staples, ultrasonic bonding or welding.
30. A method according to claim 24 wherein (c) comprises positioning the bottom surface of the offset membrane stack on the core tube and winding the membrane stack around the core tube while maintaining a tension on the membrane stack by pulling the membrane stack or applying a radial force.
31. A method according to claim 24 wherein (b) comprises forming one or more sub-assembly stacks of membranes.
32. A method according to claim 24 wherein (c) further comprises attaching an outer sleeve over the cartridge roll.
33. A method according to claim 32 comprising attaching the outer sleeve to the membranes prior to winding, and attaching the outer sleeve to itself with glue, a weld, or a fiber.
34. A method of manufacturing a cartridge for an ion exchange electrochemical cell, the method comprising:
(a) forming a plurality of textured bipolar ion exchange membranes, each membrane having (i) anion and cation ion exchange materials arranged to form a heterogeneous water-splitting interface comprising continuous contact between the anion exchange material and the cation exchange material, and (ii) an exposed textured surface having a pattern of texture features comprising peaks and valleys which are spaced apart from one another;
(b) forming an offset membrane stack of the textured membranes by laying the membranes on top of one another so that the top ends of the membranes are offset from one another in the same direction, and attaching the top ends of the offset membranes to one another;
(c) providing a core tube and winding the offset membrane stack around the core tube to form a cartridge roll;
(d) wrapping an outer sleeve around the cartridge roll to overlap itself; and
(e) applying top and bottom end caps on the cartridge roll.
35. A method of manufacturing a cartridge according to claim 34 comprising forming the membranes such that either:
(i) the peaks are ridges and the valleys comprise furrows between adjacent ridges, the ridges and furrows being generally parallel to a direction that solution travels across the membranes during use of the membranes; or
(ii) the peaks comprise conical protrusions or mesas, and the peaks extend out from a substantially flat surface region which defines the valleys.
36. A method of manufacturing a cartridge according to claim 34 comprising forming the membranes such that the peaks and valleys comprise at least one of:
(i) a dimension that is greater than the thickness of a stagnant layer formed at a 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; or
(vi) an aspect ratio d pv /d pp of at least about 1.
37. A method of manufacturing a cartridge according to claim 34 comprising winding the membranes in a spiral around the core tube.
38. A method of manufacturing a cartridge according to claim 34 comprising offsetting the membranes from one another by a distance d o =3.14*d c /n, where d c is the outer diameter of the core tube on which the membranes are wrapped.
39. A method of manufacturing a cartridge according to claim 34 comprising forming the offset membrane stack such that the plurality of membranes are arranged to provide a solution passageway that forms a unitary and contiguous solution channel that flows past both the anion exchange material and the cation exchange material of each membrane.
40. A method of forming an electrochemical cell, the method comprising:
(a) providing a housing having a solution inlet and a solution outlet;
(b) forming a cartridge by:
(1) forming a membrane stack by laying textured bipolar ion exchange membranes on top of one another so that the top ends of the membranes are offset from one another in the same direction, and attaching the top ends of the offset membranes to one another, each textured bipolar ion exchange membrane having an anion exchange layer abutting a cation exchange layer to form (i) a heterogeneous water-splitting interface comprising continuous contact between the anion exchange layer and the cation exchange layer, and (ii) an exposed textured surface;
(2) providing a core tube and winding the offset membrane stack around the core tube to form a cartridge roll; and
(3) applying top and bottom end caps on the ends of the cartridge roll; and
(c) positioning the cartridge roll within the housing so that the core tube is fluidly connected to the solution outlet of the housing.
41. A method of forming an electrochemical cell according to claim 40 comprising forming the membranes such that each membrane has an exposed textured surface having a pattern of texture features comprising peaks and valleys which are spaced apart from one another and either:
(i) the peaks are ridges and the valleys comprise furrows between adjacent ridges, the ridges and furrows being generally parallel to a direction that solution travels across the membranes during use of the membranes; or
(ii) the peaks comprise conical protrusions or mesas, and the peaks extend out from a substantially flat surface region which defines the valleys.
42. A method of forming an electrochemical cell according to claim 40 comprising forming membranes such that each membrane has an exposed textured surface having a pattern of texture features comprising peaks and valleys which are spaced apart from one another, the peaks and valleys comprising at least one of:
(i) a dimension that is 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; or
(vi) an aspect ratio d pv /d pp of at least about 1.
43. A method of forming an electrochemical cell according to claim 40 comprising winding membranes in a spiral around the core tube.
44. A method of forming an electrochemical cell according to claim 40 comprising offsetting the membranes from one another by a distance d o =3.14*d c /n, where d c is the outer diameter of the core tube on which the membranes are wrapped.
45. A method of forming an electrochemical cell according to claim 40 comprising forming the membrane stack such that the plurality of membranes are arranged to provide a solution passageway that forms a unitary and contiguous solution channel that flows past both the anion exchange layer and the cation exchange layer of each membrane.
46. A housing for an electrochemical ion exchange cell comprising a cartridge having an end-cap extension with a flange, the housing comprising:
(a) a vessel having a sidewall connected to a bottom wall, a solution inlet, and a solution outlet; and
(b) a detachable lid that can be removably attached to the sidewall of the vessel, the detachable lid comprising a plate having a keyhole that extends therethrough, the keyhole comprising a first hole having a dimension larger than the end-cap extension, and a second hole which opens into the first hole, the second hole having a dimension smaller than the flange of the end-cap extension.
47. A housing according to claim 46 wherein the keyhole comprises a first hole that is circular and a second hole that is an elongated aperture with a semicircular end.
48. A housing according to claim 46 wherein the plate comprises a side surface having a thread for screwing into a receiving thread in the sidewall of the vessel.
49. A housing according to claim 46 wherein the plate comprises a handle which assists an operator in screwing the lid.
50. An electrochemical cell comprising the housing of claim 46 , and further comprising a cartridge having a plurality of spiral wrapped membranes, the membranes having a textured surface, and electrodes about the membranes.
51. A housing for an electrochemical ion exchange cell comprising a cartridge having an end-cap extension, the housing comprising:
(a) a vessel having a sidewall connected to a bottom wall, a solution inlet, and a solution outlet; and
(b) a detachable lid that can be removably attached to the sidewall of the vessel, the detachable lid comprising a plate with a hollow post extending outwardly therefrom, the hollow post sized to slide into or over the end-cap extension of the cartridge of the electrochemical cell.
52. A housing according to claim 51 further comprising a groove about the base of the hollow post and an O-ring in the groove.
53. A housing according to claim 51 wherein the plate comprises a side surface having a plurality of pins extending outwardly therefrom, the pins sized to fit into a recessed groove in the sidewall of the vessel.