Methods of recovering metal, methods of creating multiple PH zones, and electrochemical apparatus

Abstract

A method of recovering a metal includes positioning a solution having a plurality of metal cations in at least a first compartment that is in fluid communication with other compartments through one or more membranes at interfaces between the compartments. Applying a potential difference between a pair of electrodes positioned in opposite compartments drives at least a first metal cation from the solution through a membrane into an adjacent compartment. Afterwards, the metal can be recovered as a precipitate of the first metal cation. An electrochemical apparatus includes one or more membranes positioned at corresponding interfaces between compartments arranged in series to provide fluid communication between adjacent compartments. The electrochemical apparatus further includes a pair of electrodes positioned opposite compartments and configured to apply a potential difference through a liquid positioned in at least one compartment such that ions in the liquid migrate in response to the potential difference.

Description

Attorney Reference No.: SP24-256METHODS OF RECOVERING METAL, METHODS OF CREATING MULTIPLE PH ZONES, AND ELECTROCHEMICAL APPARATUSCROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63 / 698838 filed on September 25, 2024, the content of which is relied upon and incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to an electrochemical apparatus, methods of recovering method using the same, and methods of creating multiple pH zones using the same, and more particularly, to an electrochemical apparatus having multiple compartments separated by corresponding membranes, methods of recovering method using the same, and methods of creating multiple pH zones using the same.BACKGROUND

[0003] Display devices include liquid crystal displays (LCDs), electrophoretic displays (EPD), organic light-emitting diode displays (OLEDs), plasma display panels (PDPs), or the like. Display devices can be part of a portable electronic device, for example, a consumer electronic product, a smartphone, a tablet, a wearable device, or a laptop. It is known to provide a glass article as part of a display device.

[0004] During the manufacturing of glass articles from a glass web, portions of the glass web can be separated or otherwise discarded. There is a desire to reuse the discarded portions to form more glass. Likewise, there is a desire to recover critical minerals including lithium from batteries. However, there are problems associated with recovering metals from such materials, even when the product can be converted into a solution of its constituent compounds. Consequently, there is a need to provide a new method of recovering metal from a solution as well as apparatus that can be used in such methods.SUMMARY

[0005] The present disclosure provides an electrochemical apparatus as well as methods of recovering metal from a solution and methods of creating multiple pH zones, which can make use of the electrochemical apparatus. The electrochemical apparatus comprises a pair of electrodes configured to apply a potential difference across as liquid (e.g., solution including metal cations).Attorney Reference No.: SP24-256The potential difference can selectively drive ions based on the charge to mass (q / m) ratio of the cations (e.g., metal cations) and / or anions. Further, the electrochemical apparatus comprises one or more membranes positioned at interfaces between adjacent compartments, where the one or more membranes can allow ions to pass through pores therein. The one or more membranes can facilitate the formation (and separation) of different properties (e.g., pH, metal cation concentration) in each of the plurality of compartments. Further, it is believed that the relatively limited surface area presented by of pores of each membrane effectively constricts the flow of ions through the membrane relative to the corresponding movement within a corresponding compartment. Consequently, different pHs and / or metal cation concentrations can be obtained even in adjacent pairs of compartments, as demonstrated by the Examples herein.

[0006] Methods of the present disclosure can create multiple pH zones in a corresponding plurality of compartments through the application of the potential difference with the one or more membranes positioned at the interface between adjacent compartments of the plurality of compartments. Without wishing to be bound by theory, it is believed that the diffusivity of hydroxide ions are much slower (e.g., by about a factor of 2) than the diffusivity of hydronium ions. This difference in diffusivity can generate different pHs in each compartment of the plurality of compartments. Further, it is believed that the relatively limited surface area presented by of pores of each membrane effectively constricts the flow of ions through the membrane relative to the corresponding movement within a corresponding compartment. As demonstrated by the Examples herein, the pHs obtained can be adjusted by controlling the median pore size of the one or more membranes, controlling a concentration of ions in (or ionic strength of) the liquid, membrane material, applied potential difference, and / or time that potential difference is applied. The results in Table 3 demonstrate that (1) smaller median pore sizes allow for larger pH differences between the middle compartments (which can be extended to the situation with more than 4 compartments), (2) increasing solution concentration (e.g., ionic strength) increases the charge density, and (3) differences in membrane material are more pronounced at lower solution concentrations. The plurality of pH zones can be created on-demand for processing of pH sensitive materials

[0007] Methods of the present disclosure can comprise concentrating metal cations and / or recovering metal from a solution. Applying the potential difference selectively drives the metal cations in the solution through a membrane towards one of the electrodes. This can generate aAttorney Reference No.: SP24-256 concentrated solution that is enriched in one or more of the metal cations. Also, the time that the potential difference is applied can be adjusted to control a relative proportion of the cations in a particular compartment. The concentrated solution can be recovered and / or further processed (e.g., further concentrated, subjected to liquid-liquid extraction), which can lead the precipitation of the metal (from the metal cation in the concentrated solution). As such, the electrical chemical apparatus can be used to recover lithium from a mixed metal solution. For example, the electrical chemical apparatus can recover lithium from a mixed metal solution. Such mixed metal solutions can be produced as part of lithium recycling from waste (e.g., cullet, broken) lithium-containing glass.

[0008] Some example aspects of the disclosure are described below with the understanding that any of the features of the various aspects may be used alone or in combination with one another.

[0009] Aspect 1. A method of recovering a metal comprising: positioning a solution comprising a plurality of metal cations in at least a first compartment of a plurality of compartments, the plurality of compartments are in fluid communication with one another through a corresponding membrane of one or more membranes at an interface between an adjacent pair of compartments of the plurality of compartments, wherein the first compartment is in fluid communication with an adjacent compartment of the plurality of compartments by a first membrane of the plurality of compartments; applying a potential difference between a pair of electrodes positioned in opposite compartments of the plurality of compartments, wherein the potential difference drives at least a first metal cation of the plurality of metal cations through the first membrane into the adjacent compartment; and recovering the metal as a precipitate of the first metal cation after the applying the potential difference.

[0010] Aspect 2. The method of aspect 1, wherein the first metal cation is lithium.

[0011] Aspect 3. The method of aspect 2, wherein the precipitate is lithium carbonate.

[0012] Aspect 4. The method of any one of aspects 1-3, wherein the plurality of metal cations includes alkali metal cations and alkali earth metal cations.

[0013] Aspect 5. The method of any one of aspects 1-4, wherein the first membrane is a non-specific, porous membrane.Attorney Reference No.: SP24-256

[0014] Aspect 6. The method of any one of aspects 1-5, wherein the potential difference is from 0.1 Volts to 5 Volts.

[0015] Aspect 7. The method of any one of aspects 1-6, wherein a gradient of the potential difference is from 0.01 V / cm to 5.0 V / cm.

[0016] Aspect 8. The method of any one of aspects 1-7, wherein the plurality of compartments includes 4 or more compartments.

[0017] Aspect 9. The method of any one of aspects 1-8, wherein a path between the pair of electrodes extends entirely through liquid in the plurality of compartments including the solution.

[0018] Aspect 10. The method of any one of aspects 1-9, further comprising, recovering the metal as a precipitate of the first metal cation after the applying the potential difference, wherein a second pH of the second compartment is higher than a first pH of the first compartment.

[0019] Aspect 11. The method of any one of aspects 1-9, further comprising, after the concentrating, precipitating the precipitate of the first metal cation in the second compartment.

[0020] Aspect 12. The method of any one of aspects 1-9, further comprising: precipitating a second metal cation of the plurality of metal cations different from the first metal cation in the second compartment; and removing a concentrated solution including the first metal cation from the second compartment after the precipitating the second metal cation.

[0021] Aspect 13. The method of aspect 12, wherein the second metal cation is an alkali earth metal cation.

[0022] Aspect 14. The method of any one of aspects 12-13, further comprising: positioning the concentrated solution in at least another first compartment of a plurality of another compartments, wherein the another first compartment is in fluid communication with another adjacent compartment of the plurality of compartments by another first membrane of the plurality of compartments; and applying another potential difference between another pair of electrodes positioned in opposite another compartments of the plurality of another compartments, wherein the another potential difference drives at least the first metal of the plurality of metal cations through the another first membrane into the adjacent compartment.Attorney Reference No.: SP24-256

[0023] Aspect 15. The method of aspect 14, further comprising, after the applying another potential difference, precipitating the precipitate of the first metal cation in another second compartment, wherein the another second compartment is positioned in another region between and including the another adjacent compartment and another compartment having another first electrode of the plurality of another electrodes.

[0024] Aspect 16. A method of creating multiple pH zones: positioning a liquid in at least a first compartment of a plurality of compartments, the plurality of compartments are in fluid communication with one another through a corresponding membrane of a one or more membranes at an interface between an adjacent pair of compartments of the plurality of compartments, wherein the first compartment is in fluid communication with an adjacent compartment of the plurality of compartments by a first membrane of the plurality of compartments; and applying a potential difference between a pair of electrodes positioned in opposite compartments of the plurality of compartments, wherein the potential difference drives cations through the first membrane into the adjacent compartment, the cations are driven towards a first electrode of the pair of electrodes, anions are driven towards a second electrode of the pair of electrodes, where the applying the potential difference generates a pH difference between the first compartment and the adjacent compartment.

[0025] Aspect 17. The method of aspect 16, wherein the applying the potential difference generates a different pH in each compartment of the plurality of compartments.

[0026] Aspect 18. The method of any one of aspects 16-17, wherein the anions include hydroxide ions.

[0027] Aspect 19. The method of any one of aspects 16-18, wherein the liquid comprises an ionic strength from 0.001 molar to 5.0 molar.

[0028] Aspect 20. The method of any one of aspects 16-19, wherein the potential difference is from 0.1 Volts to 5 Volts.

[0029] Aspect 21. The method of any one of aspects 16-20, wherein a gradient of the potential difference is from 0.01 V / cm to 5.0 V / cm.

[0030] Aspect 22. The method of any one of aspects 16-21, wherein the first membrane is a non-specific, porous membrane.Attorney Reference No.: SP24-256

[0031] Aspect 23. The method of any one of aspects 16-22, wherein the plurality of compartments includes 4 or more compartments.

[0032] Aspect 24. An electrochemical apparatus comprising: one or more membranes; a plurality of compartments arranged in series and in fluid communication with one another through a corresponding membrane of the one or more membranes at an interface between an adjacent pair of compartments of the plurality of compartments, wherein each compartment of the plurality of compartments are configured to contain a liquid, and a pair of electrodes positioned in opposite compartments of the plurality of compartments, wherein the pair of electrodes are configured such that a potential difference can be applied across the pair of electrodes through the liquid to migrate ions of the liquid through the corresponding membrane of the one or more membranes into an adjacent compartment of the plurality of compartments.

[0033] Aspect 25. The electrochemical apparatus of aspect 24, wherein the plurality of compartments includes 4 or more compartments.

[0034] Aspect 26. The electrochemical apparatus of any one of aspects 24-25, wherein a membrane at the interface of the interface between the adjacent pair of compartments is a nonspecific, porous membrane.

[0035] Aspect 27. The electrochemical apparatus of any one of aspects 24-25, wherein a membrane at the interface of the interface between the adjacent pair of compartments is an ionexchange membrane.

[0036] Aspect 28. The electrochemical apparatus of any one of aspects 26-27, wherein a thickness of the membrane is from 50 micrometers to 1 millimeter.

[0037] Aspect 29. The electrochemical apparatus of any one of aspects 26-28, wherein a median pore size of the membrane is from 3 nanometers to 3 millimeters.

[0038] Aspect 30. The electrochemical apparatus of aspect 29, wherein the median pore size of the membrane is from 0.05 micrometers to 1 micrometer.

[0039] Aspect 31. The electrochemical apparatus of any one of aspects 24-30, further comprising a first aperture configured to selectively permit fluid to flow through the first aperture into or out of a first compartment of the plurality of compartments.

[0040] Aspect 32. The electrochemical apparatus of aspect 31, further comprising:Attorney Reference No.: SP24-256 a second aperture configured to selectively permit fluid to flow through the second aperture into a second compartment of the plurality of compartments different from the first compartment; a third aperture configured to selectively permit fluid to flow through the third aperture out of the second compartment; and wherein the first aperture is configured to selectively permit fluid to flow through the aperture into the first compartment.BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and other features and advantages of aspects of the present disclosure are better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0042] FIG. 1 is a schematic cross-sectional view of an electrochemical apparatus having two compartments in accordance with aspects of the present disclosure;

[0043] FIG. 2 is a schematic cross-sectional view of an electrochemical apparatus having a plurality of compartments and a plurality of membranes positioned therebetween in accordance with aspects of the present disclosure;

[0044] FIG. 3 is a schematic cross-sectional view of an electrochemical apparatus having a plurality of compartments (e.g., four) and a plurality of membranes (e.g., there positioned therebetween, where fluid can be selectively permitted to enter and / or exit a e electrochemical apparatus; and

[0045] FIG. 4 is a flowchart of a method to recover a metal in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0046] FIGS. 1-3 illustrate cross-sectional views of electrochemical apparatus 101, 201, and / or 301 having a plurality of compartments 111 and a pair of electrodes 105 and 107 positioned in opposite compartments of the plurality of compartments 111. As discussed herein, the electrochemical apparatus can be used to recover metal from a solution (e.g., containing a plurality of metal ions). For example, the electrical chemical apparatus can recover lithium from a mixed metal solution. Such mixed metal solutions can be produced as part of lithium recycling from waste (e.g., cullet, broken) lithium-containing glass. Also, as discussed herein, the electrical chemical apparatus can be used to generate a plurality of pH zones, which can be created on-demand for processing of pH sensitive materials. Unless otherwise noted, a discussion of features of aspectsAttorney Reference No.: SP24-256 of one electrochemical apparatus, method of recovering a metal, and / or method of producing a plurality of pH zones can apply equally to corresponding features of any aspects of the disclosure. For example, identical part numbers throughout the disclosure can indicate that, in some aspects, the identified features are identical to one another and that the discussion of the identified feature of one aspect, unless otherwise noted, can apply equally to the identified feature of any of the other aspects of the disclosure.

[0047] As shown in FIGS. 1-3, the electrochemical apparatus 101, 201, and / or 301 can comprise a container 103 or 303. In aspects, the container 103 or 303 can be resistant and / or impervious to fluid (e.g., configured to contain a solution in the one or more compartments). In further aspects, as shown in FIG. 3, the container 303 can completely surround the plurality of compartments 111, although the container 103 may not be present on all sides as shown in FIGS. 1-2. In further aspects, fluid (e.g., liquid, gas) can be selectively added or removed into the container 103 or 303 (e.g., electrochemical apparatus 101, 201, or 301, one or more compartments of the plurality of compartments 111), for example, through one or more apertures (e.g., valves 341, 343, 345, 351, and / or 353 shown in FIG. 3) (likewise for optional valve 161 shown in FIG. 1).

[0048] In aspects, as shown, the electrochemical apparatus 101, 201, or 301 comprises a plurality of compartments 111 arranged in series. For example, the plurality of compartments is arranged such that each compartment is adjacent to at most two other compartments (with the compartments on the ends being adjacent to only one compartment). With reference to FIG. 3, the plurality of compartments 111 comprises four compartments 312, 314, 316, and 318 arranged in series, where the central compartments (e.g., compartment 314 or 316) are adjacent to two other compartments 312 and 316 or 314 and 318, respectively, while the compartments 312 or 318 at the ends are only adjacent to one compartment 314 or 316, respectively. In further aspects, as shown in FIG. 2-3, the plurality of compartments 111 can comprise three or more compartments, although two compartments can be provided as shown in FIG. 2. In even further aspects, as shown in FIG. 3, the plurality of compartments 111 comprises four or more compartments. In an exemplary aspect, as shown in FIG. 3, the plurality of compartments 111 can comprise four compartments 312, 314, 316, and 318. In further aspects, one or more of the plurality of compartments 111 (e.g., all of the compartments) can be configured to contain a liquid (e.g., comprising a plurality of metal ions).Attorney Reference No.: SP24-256

[0049] As shown in FIGS. 1-3, the electrochemical apparatus 101, 201, or 301 comprises one or more membranes 121 positioned at an interface between adjacent compartments (of the plurality of compartments 111). For example, as shown in FIG. 3, there are three membranes 321, 323, and 325 of the one or more membranes 121 positioned at corresponding interfaces of adjacent compartments (e.g., membrane 321 is positioned between adjacent compartments 312 and 314, membrane 323 is positioned between adjacent compartments 314 and 316, compartments 325 is positioned between adjacent compartments 316 and 318). The corresponding membrane (of the one or more membranes 121) positioned at the interface between adjacent compartments can allow fluid communication (e.g., of one or more components, or all components of a fluid) between the adjacent compartments. In aspects, the number of the one or more membranes can be one less than the number of the plurality of compartments. For example, the electrochemical apparatus 301 shown in FIG. 3 contains three membranes 321, 323, and 325 of the one or more membranes 121 and four compartments 312, 314, 316, and 318 of the plurality of compartments 111, where the number membranes (3) is one less than the number of compartments (4).

[0050] In aspects, a thickness 129, 329a, 329b, or 329c (e.g., total thickness, see FIGS. 1 and 3) of a membrane (or stack of membranes - of the one or more membranes) between an adjacent pair of compartments can be 50 pm or more, 80 pm or more, 100 pm or more, 120 pm or more, 150 pm or more, 200 pm or more, 250 pm or more, 300 pm or more, 400 pm or more, 500 pm or more, 600 pm or more, 750 pm or more, 1 millimeter (mm) or less, 800 pm or less, 600 pm or less, 400 pm or less, 300 pm or less, 250 pm or less, 200 pm or less, 150 pm or less, 100 pm or less, or 80 pm or less. In aspects, a thickness 129, 329a, 329b, or 329c (e.g., total thickness) of a membrane (or stack of membranes - of the one or more membranes) between an adjacent pair of compartments can be from 50 pm to 1 mm, from 80 pm to 800 pm, from 100 pm to 600 pm, from 120 pm to 400 pm, from 150 pm to 300 pm, from 200 pm to 250 pm, or any range or subrange therebetween. In aspects, a thickness 129, 329a, 329b, or 329c (e.g., total thickness) of a membrane (or stack of membranes - of the one or more membranes) between an adjacent pair of compartments can be less than 500 pm, for example, from 50 pm to 400 pm, from 50 pm to 300 pm, from 80 pm to 250 pm, from 80 pm to 200 pm, from 100 pm to 150 pm, from 120 pm to 150 pm, or any range or subrange therebetween.

[0051] In aspects, a membrane of the one or more membranes can comprise a non-specific, porous membrane. As used herein, a “non-specific” membrane refers to a membrane that permitsAttorney Reference No.: SP24-256 molecules (e.g., ions) to pass through based on their ability to pass through the pores of the membrane. The “non-specific” membrane is not configured to selectively permit (or reject) molecules (e.g., ions) based on their charge. The “non-specific” membrane is in contrast to an “ion-exchange” membrane. As used herein, an “ion-exchange” membrane is a semi-permeable membrane that transports certain ions while blocking other ions or neutral molecules. For example, an ion-exchange membrane can be a cation-exchange membrane with anions fixed on the surface such that cations in solution are electrostatically attracted to and allowed to pass through the membrane while anions are electrostatically repelled from the membrane. In further aspects, all of the membranes of the one or more membranes can be non-specific, porous membranes. For example, as shown in FIG 3, membrane 329a, 329b, or 329c can allow cations, anions, and even neutral molecules to flow therethrough, although due to the application of a potential difference (discussed below) the predominant flow is expected to be cations through the membrane in one direction (e.g., arrow 322, 324b, or 326b) and anions in the other direction (e.g., arrow 324a, 326a, or 328). Likewise, as shown in FIG 2, any or all of the membranes 223a-223n can allow cations, anions, and even neutral molecules to flow therethrough, although due to the application of a potential difference (discussed below) the predominant flow is expected to be cations through the membrane in one direction (e.g., arrow 222 or 226) and anions in the other direction (e.g., arrow 224 or 288). Exemplary aspects of materials for the non-specific porous membrane include polyamides (e.g., nylon6-6), cellulose acetate, fluorinated polymers (e.g., poly vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE)), and polyolefins (e.g., polyethylene (PE)), dialysis tubing, or glass (e.g., having through-glass vias). Alternatively or additionally, in aspects, a membrane of the one or more of the membranes comprises an ion-exchange membrane. In further aspects, all of the membranes of the one or more membranes can be an ion-exchange membrane. In further aspects, a membrane (e.g., all of the membranes) of the one or more membranes can be a cation-exchange membrane. Exemplary aspects of ion-exchange membranes (e.g., cationexchange membranes) include sulfonated polymers (e.g., sulfonated fluorinated polymers including sulfonated PTFE such as NAFION, polyether sulfone (PES)). Without wishing to be bound by theory, the application of a potential difference across the electrodes (discussed below) preferentially drives anions and cations in opposite directions, which naturally separates these species. Consequently, it is believed that the electrochemical apparatus and associated methods discussed herein can operate perfectly fine with a non-specific, porous membrane (e.g., without anAttorney Reference No.: SP24-256 ion-exchange membrane). Also, as discussed below, the difference in diffusivity of hydronium ions (H+or H3O ) and hydroxide ions (OH ) can form a pH gradient when the potential difference is applied across the electrodes (discussed below).

[0052] As used herein, “median pore size” of a membrane is calculated in accordance with ASTM 1245-03. In aspects, a median pore size a membrane of the one or more membranes can be 3 nanometers (nm) or more, 5 nm or more, 8 nm or more, 10 nm or more, 15 nm or more, 25 nm or more, 50 nm or more, 100 nm or more, 200 nm or more, 400 nm or more, 1 pm or more, 2 pm or more, 3 pm or more, 5 pm or more, 8 pm or more, 10 pm or more, 15 pm or more, 25 pm or more, 50 pm or more, 100 pm or more, 3 millimeter (mm) or less, 2 mm or less, 1 mm or less, 600 pm or less, 400 pm or less, 250 pm or less, 150 pm or less, 100 pm or less, 50 pm or less, 30 pm or less, 10 pm or less, 5 pm or less, 3 pm or less, 1 pm or less, 600 nm or less, 400 nm or less, 100 nm or less, 60 nm or less, 40 nm or less, or 25 nm or less. In aspects, a median pore size of a membrane of the one or more membranes can be from 3 nm to 3 mm, from 5 nm to 2 mm, from 8 nm to 1 mm, from 10 nm to 600 pm, from 15 nm to 400 pm, from 25 nm to 250 pm, from 50 nm to 150 pm, from 100 nm to 100 pm, from 200 nm to 50 pm, from 400 nm to 30 pm, from 1 pm to 10 pm, from 2 pm to 5 pm, or any range or subrange therebetween.

[0053] As shown in FIGS. 1-3, the electrochemical apparatus 101, 201, and 301 comprise a pair of electrodes 105 and 107. The electrodes 105 and 107 are positioned in opposite compartments of the plurality of compartments 111. When the compartments are arranged in series (as discussed above), opposite compartments are those that are at the ends of the series. Generally, opposite compartments, are separated by as many compartments as possible. For example, in FIG. 3, compartment 312 is opposite compartment 318 since these compartments are at opposite ends of the series of compartments 312, 314, 316, and 318 of the plurality of compartments 111, which also positions the most additional compartments 314 and 316 between compartment 312 and the opposite compartment 318. In aspects, one or more of the electrodes can comprise one or more of activated carbon, copper, titanium, and / or stainless steel. An exemplary aspect of the pair of electrodes is a pair of activated carbon electrodes. For example, an activated carbon electrode can have a relatively high surface area for a given weight of the electrode, which can increase an effective capacitance in the electrochemical apparatus. Although not shown, it is to be understood that a reference electrode can be positioned in any (or one or more) compartment(s) of the plurality of compartments to monitor changes in voltage drop while the potential difference is applied.Attorney Reference No.: SP24-256

[0054] Also, the electrochemical apparatus comprises a voltage source 141, which is attached to the pair of electrodes 105 and 107 by corresponding wires 142 and 143, respectively. In the configuration shown in FIGS. 1-3, the voltage source 141 is configured to apply a potential difference across the electrochemical apparatus 101, 201, or 301 (e.g., between the pair of electrodes 105 and 107 - across the plurality of compartments). In aspects, as shown in FIGS. 1- 3, each of the plurality of compartments can comprise enough liquid to allow a path (e.g., electrical path) between the pair of electrodes to extend through (e.g., entire through) the liquid in the plurality of compartments (including liquid positioned in the one or more membranes). In aspects, applying the potential difference (e.g., voltage source 141 electrically connected to the pair of electrodes 105 and 107) can be configured to drive at least a cation in the liquid in a compartment (e.g., compartment 112, 216, or 316) towards one of the electrodes (e.g., electrode 107), including driving the cation from the compartment through a membrane (e.g., membrane 123, 223n, or 325) into an adjacent compartment (e.g., compartment 118, 218, or 318 - as indicated by arrow 122, 226, or 326b) closer to the electrode (e.g., electrode 107). In further aspects, the cation can be a metal cation, including an alkali metal cation (e.g., Li+, Na+, K+) and / or an alkaline earth metal cation (e.g., Mg2+, Ca2+, Sr2+, Ba2+). Alternatively or additionally, in further aspects, the cation can be a hydronium ion (e.g., H+or H3O ). At the same time, the potential difference can also drive anions in the opposite direction as the cations. For example, applying the potential difference (e.g., voltage source 141 electrically connected to the pair of electrodes 105 and 107) can be configured to drive at least an anion in the liquid in a compartment (e.g., compartment 118, 214, or 314) towards the other electrodes (e.g., electrode 105), including driving the anion from the compartment through a membrane (e.g., membrane 123, 223a, or 321) into an adjacent compartment (e.g., compartment 112, 212, or 312 - as indicated by arrow 128, 224, or 324a) closer to the other electrode (e.g., electrode 105). In further aspects, the anion can include a hydroxide anion (OFT), although other anions (e.g., nitrates, sulfates, chlorides) can be provided in other aspects.

[0055] Without wishing to be bound by theory, applying the potential difference can separate cations from anions in a compartment by driving the cations toward one electrode while driving the anions toward the other electrode (while still maintaining net charge neutrality). Providing the one or more membranes allows the cations to be detectably separated from the anions by the one or more membranes. Further, the diffusivity of hydroxide ions is much slower (e.g., byAttorney Reference No.: SP24-256 about a factor of 2) than the diffusivity of hydronium ions. This difference in diffusivity can generate different pHs in each compartment of the plurality of compartments.

[0056] Also, applying the potential difference can selectively drive cations based on the charge-to-mass (q / m) ratio of the cations. For example, a first cation (e.g., lithium, Li+having a q / m of 1 / 6.94 ~ 0.144) can move quicker towards the electrode than a second cation (e.g., calcium, Ca2+having a q / m of 1 / 40.08 ~ 0.025; or sodium, Na2+having a q / m of 1 / 22.99 ~ 0.043) having a lower q / m ratio - based on the force being proportional to the ion’s charge and the acceleration being proportional to the inverse of the mass. This can be used to concentrate and / or separate cations from a liquid having a mixture of cations (e.g., metal cations).

[0057] In aspects, the electrochemical apparatus can be configured to apply a potential difference (e.g., between the pair of electrodes) of 0.01 Volts (V) or more, 0.05 V or more, 0.10 V or more, 0.25 V or more, 0.4 V or more, 0.6 V or more, 1.0 V or more, 1.5 V or more, 2.0 V or more, 2.5 V or more, 3.0 V or more, 3.5 V or more, 5.0 V or less, 4.5 V or less, 4.0 V or less, 3.5V or less, 3.0 V or less, 2.5 V or less, 2.0 V or less, 1.5 V or less, 1.0 V or less, 0.7 V or less, 0.5V or less, or 0.3 V or less. In aspects, the electrochemical apparatus can be configured to apply a potential difference (e.g., between the pair of electrodes) in a range from 0.01 V to 5.0 V, from 0.05 V to 4.0 V, from 0.10 V to 3.5 V, from 0.25 V to 3.0 V, from 0.4 V to 2.5 V, from 0.6 V to 2.0 V, from 1.0 V to 1.5 V or any range or subrange therebetween. In aspects, the potential difference can be 2.0 V or more, for example, in a range from 2.0 V to 5.0 V, from 2.5 V to 4.5 V, from 3.0 V to 4.0 V, from 3.0 V to 3.5 V, or any range or subrange therebetween. In aspects, a gradient of the potential difference (e.g., between the pair of electrodes) can be 0.01 Volts per centimeter (V / cm) or more, 0.05 V / cm or more, 0.10 V / cm or more, 0.25 V / cm or more, 0.40 V / cm or more, 0.60 V / cm or more, 0.75 V / cm or more, 1.0 V / cm or more, 1.5 V / cm or more, 2.0 V / cm or more, 2.5 V / cm or more, 5.0 V / cm or less, 4.0 V / cm or less, 3.5 V / cm or less, 3.0 V / cm or less, 2.5 V / cm or less, 2.0 V / cm or less, 1.5 V / cm or less, 1.0 V / cm or less, 0.75 V / cm or less, 0.5 V / cm or less, 0.25 V / cm or less, or 0.10 V / cm or less. In aspects, a gradient of the potential difference (e.g., between the pair of electrodes) can be in a range from 0.01 V / cm to 5.0 V / cm, from 0.05 V / cm to 4.0 V / cm, from 0.10 V / cm to 3.5 V / cm, from 0.25 V / cm to 3.0 V / cm, from 0.40 V / cm to 2.5 V / cm, from 0.60 V / cm to 2.0 V / cm, from 0.75 V / cm to 1.5 V / cm, from 1.0 V / cm to 1.5 V / cm, or any range or subrange therebetween.Attorney Reference No.: SP24-256

[0058] Methods in accordance with the present disclosure (that can use the electrochemical apparatus described above and / or shown in FIGS. 1-3) will now be discussed with reference to the flow chart shown in FIG. 3. First, methods of recovering a metal will now be discussed (while methods of creating multiple pH zones will be discussed further below). In aspects, the metal to be recovered can be an alkali metal, although the metal can be an alkaline earth. An exemplary alkali metal is lithium (e.g., separating lithium cations from a solution as a lithium-containing precipitate such as U2CO3). An exemplary alkaline earth metal is calcium (e.g., separating calcium cations from a solution as a calcium-containing precipitate such as Ca(OH)2).

[0059] Methods of recovering a metal can start at step 401. In step 401, a solution containing a mixture of alkali metal ions (i.e., cations) and alkaline earth metal ions (i.e., cations) can be provided. In aspects, the solution can be formed by dissolving waste material. For example, glass cullet (e.g., scrap lithium-containing glass) can be turned into the solution by treatment with one or more acids that can leach the alkali metal ions and / or alkaline earth metal ions from the glass and / or disrupt (e.g., dissolve) a glass-forming network (e.g., aluminosilicates). Alternatively, the solution can be obtained by purchase, although other processes can be used to generate or otherwise obtain the solution. Methods can recover a metal from the solution (e.g., present as a metal cation in the solution). In further aspects, the cation can be a metal cation, including an alkali metal cation (e.g., Li+, Na+, K+) and / or an alkaline earth metal cation (e.g., Mg2+, Ca2+, Sr2+, Ba2+).

[0060] After step 401, methods can proceed to step 403 comprising disposing the solution in one or more of the plurality of compartments 111. In further aspects, enough of the solution can be disposed in each of the compartments to allow an electrical path to travel entirely through the solution from one electrode to the other electrode (as discussed above). Alternatively, in other aspects, water or a solution of ions (that do not negatively affect the recovery process but can increase electrical conductivity) can be placed in one or more compartment(s) of the plurality of compartments. For example, the solution with the metal ions can be placed in one compartment while the water or solution of ions (that do not negatively affect the recovery process but can increase electrical conductivity) can be placed in the other compartments of the plurality of compartments. Also, as shown in FIG. 1, the solution can be disposed in the compartment 112 from a container 131 (e.g., pipette, conduit), as indicated by droplet 133.

[0061] After step 403, methods can proceed to step 405 comprising applying a potential difference between the pair of electrodes 105 and 109. In aspects, as discussed above, the pair ofAttorney Reference No.: SP24-256 electrodes 105 and 109 can be positioned in opposite compartments of the plurality of compartments. In aspects, the potential difference can be within one or more of the corresponding ranges discussed above (e.g., from 0.1 V to 5 V, from 1.0 V to 4 V, from 2.0 V to 3.0 V). In aspects, a gradient of the potential difference can be within one or more of the corresponding ranges discussed above (e.g., from 0.01 V / cm to 5 V / cm, from 0.1 V / cm to 3.0 V / cm, from 0.25 V / cm to 1.0 V / cm). The applied potential difference can drive at least a first metal cation (e.g., Li+) in the solution through a first membrane into an adjacent compartment. For example, with reference to FIG. 3, a first metal cation in the liquid in a first compartment 316 can be driven towards a first electrode 107 through a membrane 325 and into an adjacent compartment 318 (as indicated by arrow 326b) closer to the electrode 107 than the first compartment 316. In further aspects, the membrane can be a non-specific, porous membrane (e.g., within one or more of the corresponding aspects discussed above). Alternatively, in further aspects, the membrane can be an ion-exchange membrane (e.g., cation-exchange membrane). In further aspects, applying the potential difference can concentrate at least the first metal cation (e.g., Li+) in the adjacent compartment (e.g., compartment 318). Additionally, in further aspects, the applying the potential difference can decrease the pH of the adjacent compartment (e.g., compartment 318) relative to the first compartment 316. Additionally or alternatively, step 403 (or following arrow 402 as discussed below) can include forming a precipitate 151 of a second metal (i.e., from a second metal cation different from the first metal cation) in the adjacent compartment 318. For example, a calcium precipitate (e.g., Ca(OH)2 or Ca3(PO4)2) can be formed (e.g., near the electrode 105 - shown as precipitate 151 in FIGS. 1-3) through the application of a sufficient potential difference. Alternatively, a precipitate can be formed through the addition of a fluid (e.g., liquid or gas), for example, carbon dioxide (e.g., forming CaCCh). Although not shown, it is to be understood that a reference electrode can be positioned in any (or one or more) compartment(s) of the plurality of compartments to monitor changes in voltage drop while the potential difference is applied. For example, changes in the voltage difference between a reference electrode and one of the electrodes (in the pair of electrodes) can be monitored to determine how long the potential difference is to be applied and / or if the magnitude of the potential difference needs to be adjusted.

[0062] In aspects, after step 405, methods can proceed to step 407 comprising extracting the concentrated solution from a compartment of the plurality of compartments. In further aspects, as shown in FIGS. 1 and 3, the concentrated solution in compartment 118, 316, or 318 can beAttorney Reference No.: SP24-256 extracted through valve 161, 351, or 353, respectively. In aspects, as discussed below, after step 407, methods can be complete upon reaching step 409. Alternatively, in aspects, methods can proceed along arrow 406 to repeat at least steps 403 and 405 to further concentrate the concentrated solution, which can eventually be treated to precipitate out a predetermined metal (e.g., alkali metal) therefrom.

[0063] Alternatively, after step 405, methods can follow arrow 402 to step 411 comprising precipitating a metal cation from the concentrated solution to form precipitate 151 (see FIGS. 1- 3). In aspects, as discussed above, a metal cation can be an alkaline earth metal cation precipitated through the application of the potential difference (e.g., forming Ca(OH)2 from Ca2+) and / or through the addition of fluid (e.g., forming CaCCF from Ca2+). Alternatively or additionally, in aspects, the metal cation can be an alkali metal cation (e.g., Li+). In further aspects, the alkali metal cation can be precipitated through the addition of fluid (e.g., a solution of sodium carbonate or potassium carbonate, or the addition of carbon dioxide gas) to form a precipitate of the corresponding alkali metal (e.g., I^CCh). For example, as shown in FIG. 3, a fluid can be selectively added through valve 345 into compartment 318 to form precipitate 151. In aspects, as discussed below, after step 407, methods can be complete upon reaching step 409, for example, when the predetermined metal (e.g., alkali metal, lithium) is recovered as a metal precipitate. Alternatively, in aspects, methods can proceed along arrow 408 to step 407, where the concentrated solution (without the precipitant) can be extracted from the compartment (as discussed above). In further aspects, methods can proceed along arrow 406 to repeat at least steps 403 and 405 to further concentrate the concentrated solution, which can eventually be treated to precipitate out a predetermined metal (e.g., alkali metal) therefrom. For example, one or more alkaline metal cations (e.g., Ca2+) can be precipitated from the concentrated solution (e.g., through the application of the potential difference; the (remaining) concentrated solution can extracted and then further concentrated through the application of another potential difference (repeating steps 403 and 405); and eventually the predetermined metal (e.g., alkali metal, lithium) is precipitated from the further concentrated solution to recover the predetermined metal as a metal precipitate, for example through the addition of a fluid, although additional metals can be sequentially precipitated out and the remaining solution further concentrated until the predetermined metal is to be extracted by precipitating the corresponding metal cation.Attorney Reference No.: SP24-256

[0064] After step 405, 407, or 411, methods can be complete upon reaching step 409. In aspects, methods can proceed sequentially along steps 401, 403, 405, 407, and 409 (as discussed above), for example, to form a concentrated solution of the predetermined metal cation. Alternatively, in aspects, methods can follow arrow 402 to step 411 to precipitate a metal cation from the solution. For example, as discussed above, the precipitant can be of the predetermined metal to be recovered. Additionally, in further aspects, methods can follow arrow 408 from step 411 to step 407 to extract the (remaining) concentrated solution, for example, where a metal cation other than the predetermined metal (cation) is precipitated in step 411 and the (remaining) concentrated solution can be further processed (e.g., along arrow 406), although methods can be complete by proceeding to step 409. Alternatively, in aspects, methods can follow arrow 404 from step 405 to step 409, for example, when methods are complete at the end of step 405. In aspects, methods can follow arrow 406 from step 407 to step 401, for example, if the concentrated solution is to be further processed through the application of another potential difference to form at least a further concentrated solution. Then, the method can proceed along any of the aspects discussed above. Any of the above options may be combined in accordance with aspects of the present disclosure. Consequently, the method can recover the metal cation in a concentrated solution or as a metal precipitate.

[0065] Now, methods of creating multiple pH zones in accordance with the aspects of the present disclosure will now be discussed with reference to the flow chart shown in FIG. 4 and (that can use the electrochemical apparatus described above and / or shown in FIGS. 1-3). As used herein, a pH of the treatment solution is measured in accordance with ASTM E70-90 at 25°C.

[0066] Methods of creating multiple pH zones can start at step 401. In step 401, a liquid can be provided. In aspects, the liquid can be a protic liquid (e.g., aqueous solution and / or water - deionized water, filtered water). In further aspects, the protic liquid can be a solution having a predetermined ionic strength, which can enhance an electrical conductivity of the liquid to facilitate the formation of the multiple pH zones. As used herein, ionic strength Z is defined as half of the sum of products between a molar concentration of an ion (z;) and the charge of the ion (z;) squared for all of the ions in solution: Z = ’ / 2Si CiZi2. In further aspects, the predetermined ionic strength can be 0.001 molar (M) or more, 0.005 M or more, 0.01 M or more, 0.03 M or more, 0.05 M or more, 0.1 M or more, 0.3 M or more, 0.5 M or more, 1.0 M or more, 5.0 M or less, 3.0 M or less, 1.0 M or less, 0.6 M or less, 0.4 M or less, 0.2 M or less, 0.1 M or less, 0.06 M or less, 0.03Attorney Reference No.: SP24-256M or less, or 0.01 M or less. In further aspects, the predetermined ionic strength can be from 0.001 M to 5.0 M, from 0.005 M to 3.0 M, from 0.01 M to 1.0 M, from 0.03 M to 0.6 M, from 0.05 M to 0.3 M, from 0.1 M to 0.2 M, or any range or subrange therebetween. In exemplary aspects, the liquid can comprise an aqueous solution of an alkali metal nitrate (e.g., KNO3). The liquid can be obtained by purchase, although the liquid can be obtained by mixing an ionic additive to a solvent in other aspects.

[0067] After step 401, methods can proceed to step 403 comprising disposing the liquid in one or more of the plurality of compartments 111. In further aspects, enough of the liquid can be disposed in each of the compartments to allow an electrical path to travel entirely through the solution from one electrode to the other electrode (as discussed above). Alternatively, in other aspects, water or another solution of ions can be placed one or more compartment(s) of the plurality of compartments. Also, as shown in FIG. 1, the liquid can be disposed in the compartment 112 from a container 131 (e.g., pipette, conduit), as indicated by droplet 133.

[0068] After step 403, methods can proceed to step 405 comprising applying a potential difference between the pair of electrodes 105 and 109. In aspects, as discussed above, the pair of electrodes 105 and 109 can be positioned in opposite compartments of the plurality of compartments. In aspects, the potential difference can be within one or more of the corresponding ranges discussed above (e.g., from 0.1 V to 5 V, from 1.0 V to 4 V, from 2.0 V to 3.0 V). In aspects, a gradient of the potential difference can be within one or more of the corresponding ranges discussed above (e.g., from 0.01 V / cm to 5 V / cm, from 0.1 V / cm to 3.0 V / cm, from 0.25 V / cm to 1.0 V / cm).

[0069] The applied potential difference can drive at least a cation (e.g., H+, H3O ) in the liquid through a first membrane into an adjacent compartment. For example, with reference to FIG. 3, a cation in the liquid in a first compartment 316 can be driven towards a first electrode 107 through a membrane 325 and into an adjacent compartment 318 (as indicated by arrow 326b) closer to the electrode 107 than the first compartment 316. In further aspects, the membrane can be a non-specific, porous membrane (e.g., within one or more of the corresponding aspects discussed above). Alternatively, in further aspects, the membrane can be an ion-exchange membrane (e.g., cation-exchange membrane). In further aspects, applying the potential difference can concentrate at least the cation (e.g. , H+, H3O ) in the adjacent compartment (e.g., compartment 318), resulting in a decrease in the pH of the adjacent compartment. Additionally, in furtherAttorney Reference No.: SP24-256 aspects, the applying the potential difference can drive an anion (e.g., OH') in the liquid through a second membrane into another adjacent compartment (e.g., opposite the first membrane discussed above with reference to the cation). For example, with reference to FIG. 3, an anion in the liquid in a first compartment 316 can be driven towards a second electrode 105 through a membrane 323 and into an adjacent compartment 314 (as indicated by arrow 326a) closer to the electrode 105 than the first compartment 316. Although not shown, it is to be understood that a reference electrode can be positioned in any (or one or more) compartment(s) of the plurality of compartments to monitor changes in voltage drop while the potential difference is applied. For example, changes in the voltage difference between a reference electrode and one of the electrodes (in the pair of electrodes) can be monitored to determine how long the potential difference is to be applied and / or if the magnitude of the potential difference needs to be adjusted.

[0070] Without wishing to be bound by theory, it is believed that the diffusivity of hydroxide ions are much slower (e.g., by about a factor of 2) than the diffusivity of hydronium ions. This difference in diffusivity can generate different pHs in each compartment of the plurality of compartments. For example, the diffusivity of hydronium ions can be about 9.3 x 10'5cm2 / s while the diffusivity of hydroxide ions can be about 5.3 x 10'5cm2 / s. Further, it is believed that the relatively limited surface area presented by of pores of each membrane effectively constricts the flow of ions through the membrane relative to the corresponding movement within a corresponding compartment. Consequently, different pHs can be obtained even in adjacent pairs of compartments, as demonstrated by the Examples herein. In further aspects, as demonstrated by the Examples herein, each compartment of the plurality of compartments can develop a different pH. At the end of step 405, a plurality of pHs may be created in the plurality of compartments.

[0071] In aspects, after step 405, methods can proceed to step 407 comprising extracting the liquid from a compartment of the plurality of compartments. In further aspects, as shown in FIGS. 1 and 3, the liquid in compartment 118, 316, or 318 can be extracted through valve 161, 351, or 353, respectively. Once the liquid is removed from the compartment, the pH of the liquid can be maintained (since there is no longer exchange with the fluid in other compartments). Likewise, fluids from other compartments (having different pH values) can be extracted for future use. For example, the extracted fluid can then be used for pH sensitive reactions, including the selective precipitation of metal cations (e.g., alkali metal cations), which can be used in methods of recovering a metal from a solution (discussed above).Attorney Reference No.: SP24-256

[0072] Alternatively, after step 405 methods can proceed to step 411 comprising using the liquid in a compartment (e.g., without needed to extract the liquid from the compartment). For example, the liquid can be used for pH sensitive reactions, including the selective precipitation of metal cations (e.g., alkali metal cations) from a solution by adding the solution to the liquid.

[0073] After step 405, 407, or 411, methods can be complete upon reaching step 409. In aspects, methods can proceed sequentially along steps 401, 403, 405, 407, and 409 (as discussed above), for example, to create a plurality of pHs and extract the corresponding liquid from one or more of the plurality of compartments. Alternatively, in aspects, methods can follow arrow 402 to step 411 to use the liquid while it is still in a compartment. Alternatively, in aspects, methods can follow arrow 404 from step 405 to step 409, for example, when methods are complete at the end of step 405. Any of the above options may be combined in accordance with aspects of the present disclosure. Consequently, the method can recover the metal cation in a concentrated solution or as a metal precipitate.EXAMPLES

[0074] Various aspects will be further clarified by the following examples. These examples make use of one or more of the membranes have the properties presented in Table 1. As shown, Membranes A-C comprise Nylon6,6 with different pore sizes, including 0.1 pm, 0.2 pm, and 0.45 pm. Membranes D-F comprise different materials, but all comprise the same median pore size (0.2 pm) as Membrane B. Membrane G has the smallest median pore size (0.02 pm) while Membrane H has the largest median pore size (100 pm). Unless specified otherwise (as a total thickness), the membrane at the interface between adjacent compartments was formed by using 2 of the stated membrane (e.g., 240 pm for Membranes A-C).Table 1 : Properties of MembranesAttorney Reference No.: SP24-256

[0075] Tables 2-7 demonstrate the ability of the electrochemical apparatus to generate a plurality of pH zones and how changing various parameters (e.g., potential difference, treatment time, median pore size of the membrane, membrane thickness, solution concentration and / or ionic strength) on the achieved pH zones. For Tables 2-7, different pHs were established using solutions potassium nitrate (KNO3), ranging from 0.01 M to 1.0 M. Unless otherwise indicated, the width of each compartment (e.g., between a membrane at one interface of the compartment and a membrane at the other interface) is 9 mm (with a volume of 5.5 mb), and both electrodes comprised activated carbon. The charge density (q) presented in Tables 2-7 is calculated by integrating the current passed between the electrodes over the time the potential difference was applied, and then the value of that integral is divided by the surface area (geometric area) of the electrode. The potential gradient is calculated as the applied potential difference divided by the distance between the pair of electrodes. Unless otherwise indicated, pH was measured using a glass pH probe (Model 59001-65, Oakton) connected to a pH meter (Orion 3-Star Benchtop pH Meter, Thermo Scientific), where the liquid in each compartment was extracted at the end of the applied potential difference and then the pH was measured for the extracted liquid. Also, the compartments are arranged in series (see FIGS. 2-3).Table 2: Conditions and pH using Membrane B with 1.5 V Potential Difference for 15 minutesAttorney Reference No.: SP24-256

[0076] Table 2 presents the conditions and pH for electrochemical apparatus, where a potential difference of 1.5 V was applied between the pair of electrodes for 15 minutes, and Membrane B (doubled for a thickness of 240 pm) was positioned between adjacent compartments. Conditions 1 and 5 have 1 compartment (no membrane between the pair of electrodes). Conditions 2 and 6 have 2 compartments (one electrode in each compartment), Conditions 3 and 7 have 3 compartments (one compartment between the compartments having each electrode), and Conditions 4 and 8 have 4 compartments (two compartments between the compartments having the electrodes). Conditions 1-4 have a KNO3 concentration of 0.01 M while Condition 5-8 have a KNO3 concentration of 1.0 M. Before the potential difference was applied, the 0.01 M KNO3 solution had an initial pH of 7.0 (essentially neutral) while the 1.0 MKNO3 solution had an initial pH of 6.2 (slightly acidic). Generally, the pHs for Conditions 6-10 are more acidic than Conditions 1-5, which is consistent with the difference in initial pH. Also, the charge density generally decreases as the number of compartments (and consequently membranes) increases (with the notable exception of Condition 8). Additionally, since the distance between the electrodes increases in this particular configuration as the number of compartments increases, the potential gradient decreases as the number of compartments increases, which also helps justify the decrease in charge density with an increase in the number of compartments.

[0077] As shown in Table 2, applying the potential difference increases the pH of the single compartment in Conditions 1 and 4. Adding the membrane in Conditions 2 and 5 creates an acidic compartment (pH < 4.0) and a basic compartment (pH > 9.0), which demonstrates that the addition of the membrane allows different pH values to be obtained in different compartments of the electrochemical apparatus. Further, the three compartments in Conditions 3 and 7 produce an acidic compartment (pH < 4.0), a roughly neutral pH (6.0 < pH < 8.0), and a basic compartment (pH > 9). Interestingly, adding another compartment (4 compartments in Conditions 4 and 8) produces two acidic to slightly acidic compartments with an average pH (or each compartment’s pH) that is lower than the pH of middle compartment in the 3 compartment version (Conditions 3 and 7).Attorney Reference No.: SP24-256

[0078] Table 3 presents the conditions and pH for electrochemical apparatus, where a potential difference of 1.5 V was applied between the pair of electrodes for 15 minutes. Conditions 9-13 have a KNO3 concentration of 0.01 M while Condition 14-19 have a KNO3 concentration of 1.0 M. In Table 3, the median pore size of the membranes was the same (0.2 pm) in Conditions 9- 12 and 14-17, although the membrane material was different. The end compartments (having the electrodes) was at the pH extremes (pH < 4.0 or pH > 10.0) with each Condition having the same concentration solution having roughly the same pH in these compartments (excluding Condition 10, where Membrane H has a much larger mean pore size than the other membranes). For the lower concentration solution, Membrane D (Condition 10) produces a greater difference in pH between the middle compartments than Membrane B (Condition 9). Also (for the lower concentration), the middle compartments have a more acidic pH with Membrane B (Condition 9) than Membranes D-F (Conditions 10-12) - for Membrane D, the higher pH of the middle compartments can be attributed to the ion-exchange nature of Membrane D and consequently the higher charge density whereas the other membranes are non-specific. For the higher concentration solution, the differences in the pH of the middle compartments (in Conditions 14-17) is less pronounced than for the lower concentration solution (Conditions 9-12). The lower median pore size in Membrane G (Conditions 13 and 18) generates a larger charge density and a lower pH in Compartment 2 while the pH of the other compartments is largely unchanged. The higher median pore size in Membrane H (Condition 19) has the opposite effect (of Membrane G) by decreasing the charge density and decreasing the pH difference between the middle compartments. Consequently, the results in Table 3 demonstrate that (1) smaller median pore sizes allow for larger pH differences between the middle compartments (which can be extended to the situation with more than 4 compartments), (2) increasing solution concentration (e.g., ionic strength) increases the charge density, and (3) differences in membrane material are more pronounced at lower solution concentrations.Table 3: Conditions and pH using Various Membranes forming Four Compartments with1.5 V Potential Difference for 15 minutesAttorney Reference No.: SP24-256Table 4: Effect of Pore Size on pH using Membranes A-C with 1 M KNO3 liquid with 1.5 V Potential Difference for 15 minutes

[0079] Table 4 presents the effect on pH for Membranes A-C comprising the same material but with different median pore sizes, where the solution was 1 MKNO3 with a potential difference of 1.5 V applied for 15 minutes. At this higher KNO3 concentration, the differences on pH are less pronounced than would be expected at lower concentrations. Conditions 20-21 have similar pH profiles. However, Condition 22 (having the larger pore size) has a higher difference in pH between the central compartments (mainly an increase in Compartment 3). This indicates that noticeable pH differences between the middle compartments can still be obtained when the median pore size is 0.45 pm (although 100 pm is likely too large at this ionic strength and applied voltage as indicated by Condition 19).

[0080] Table 5 presents the effect of changing membrane thickness on the pH profile. The membrane was Membrane B, where the number of this membrane used at the interface (to formAttorney Reference No.: SP24-256 an effective membrane with a larger thickness) was varied to isolate the effect of membrane thickness from the material of the membrane and the median pore size. Conditions 9-13 have a KNO3 concentration of 0.01 M while Condition 14-19 have a KNO3 concentration of 1.0 M. Membrane thickness appears to have substantially no impact on charge density. However, increasing membrane thickness is associated with decreased pH (and generally decreases in differences in pH) between the middle compartments.Table 5: Effect of Membrane Thickness on pH using Membrane B with1.5 V Potential Difference for 15 minutesTable 6: Effect of Applied Potential Difference on pH using Membrane BAttorney Reference No.: SP24-256

[0081] Table 6 presents the effect of the applied potential difference on the resulting pH profile, using Membrane B and the potential difference is applied for 15 minutes. Conditions 29- 43 have a KNO3 concentration of 1.0 M, Condition 44-57 have a KNO3 concentration of 0.10 M, and Condition 48-51 have a KNO3 concentration of 0.01 M. The initial pH of the 0.1 M KNO3 solution was 6.6. For Conditions 29-43, the potential difference was varied from 0.50 V to 4.00 V, which is also associated with increasing potential gradient (going from Condition 29 to Condition 43) since the dimensions are the same. As shown, the charge density increased as the applied potential difference increased. Also, the pH of the end compartments became more extreme as the applied potential difference increased. For these conditions, the middle compartments had roughly the same pH when the applied potential difference was below 0.75 V (up to at least 0.60 V). For higher applied potential difference, the difference in pH between the middle compartments generally increased, although there is noticeable variability especially in the trend for compartment 3 (see Conditions 32-33 versus Conditions 34-35). For the Conditions with the 0.1 M concentration, similar trends are observed for charge density and the end compartments (as for the Conditions with the 1.0 M concentration). The pH difference of the middle compartments increased as the applied potential difference increased. Interestingly, the pH of compartment 3 isAttorney Reference No.: SP24-256 fairly consistent until 1.5 V, where there is a jump in pH between 1.5 V and 2.0 V. For the Conditions with the 0.01 M concentration, similar trends are observed as for the Conditions with the 0.1 M concentration; however, the middle compartments have difference pHs by 1.5 V (rather than above 1.5 V for 0.1 M).

[0082] Table 7 presents the effect of time on the pH profile. Conditions 52-60 have Membrane B and a 1.0 M KNO3 solution with an applied potential difference of 4.0 V The time ranged from 1 minute to 240 minutes. The charge density increased as the time increased. Due to the relatively high applied potential difference, the pHs were different for each compartment even after 1 minute. The pH of the end compartments became more extreme as the time increased. Also, the difference in pH between the middle compartments increased as the time increased.Table 7: Effect of Time on pH using Membrane B and 1.0 M KNO3 with 4.0 V Potential Difference

[0083] Tables 8-12 demonstrate the effect of treating a solution with a potential difference in the electrochemical apparatus to concentrate a predetermined metal (e.g., in a method of recovering a corresponding metal). For these examples, the solution placed in each compartment comprised a mixture of alkali metal cations (i.e., -3600 parts per million (ppm) Li+, 6600 ppm Na+) and alkali earth metal cations (i.e., 2570 ppm Ca2+) along with corresponding anions (e.g., 35000 ppm Cl" and 1080 ppm NO3 ), which mimics the composition expected for recycling culletAttorney Reference No.: SP24-256 of an alkali-containing glass. This solution had an initial pH of 4.6. Unless otherwise indicated for Tables 8-12, the membrane comprised Membrane B (doubled for an effective thickness of 240 pm) at the interface between adjacent compartments. For Tables 8-12, the potential difference was applied for 2.43 hours (146 minutes) after which the liquid in each compartment was extracted, isolated, and analyzed.

[0084] Table 8 presents the results of applying a potential difference of 3.5 V to an electrochemical apparatus with two compartments. The charge density was 73 C / cm2The applied potential difference causes the pH of Compartment 2 to increase dramatically. Also, in all of the examples in Tables 8-12, applied potential difference caused the formation of a white precipitate in the compartment having the cathode (Compartment 2: rightmost column in Tables 8-12). This white precipitate was identified as calcium hydroxide (Ca(OH)2). This is further confirmed by the drop in calcium concentration (in solution) in this compartment. Otherwise, the calcium concentration (in solution) would be expected to be larger in Compartment 2 than in Compartment 1. This also explains why the voltage drop is much larger for Compartment 2 than for Compartment 1. Without wishing to be bound by theory, it is believed that calcium salted out of the solution as the concentration of the metal cations increased in this compartment. For the other cations, the concentration is higher in Compartment 2 than in Compartment 1. Similarly, the concentration of the anions is higher in Compartment 1 than in Compartment 2. The increase in lithium (along with the other cations), demonstrates the ability of methods of the present disclosure (e.g., using the electrochemical apparatus described herein) to concentrate metal cations in one compartment.Table 8: Concentration for Two Compartments with 3.5 V Potential DifferenceAttorney Reference No.: SP24-256Table 9: Concentration for Three Compartments with 3.5 V Potential Difference

[0085] Table 9 presents the results of applying a potential difference of 3.5 V to an electrochemical apparatus with three compartments. The charge density was 57 C / cm2The applied potential difference causes the pH of Compartments 2 and 3 to increase dramatically. As noted above, the calcium concentration (in solution) in the right-most compartment is low due to its precipitation in that compartment. For the other cations, the concentration is greatest in compartment 3 and the lowest in compartment 1. Similarly, the concentration of the anions is highest in Compartment 1 and the lowest in Compartment 3. Notably, the concentration of cations is higher in Compartment 3 (Table 9) than in Compartment 2 (Table 8) even though the compartments are the same size. This demonstrates that additional compartments can produce further concentrated solutions (even when the charge density is lower).

[0086] Table 10 presents the results of applying a potential difference of 3.5 V to an electrochemical apparatus with four compartments. The charge density was 48 C / cm2. The applied potential difference causes the pH of Compartments 3 and 4 to increase dramatically while the pH in Compartments 1 and 2 decreased. As noted above, the calcium concentration (in solution) in the right-most compartment is low due to its precipitation in that compartment. For the other cations, the concentration is greatest in compartment 4 and the lowest in compartment 1. Similarly, the concentration of the anions is highest in Compartment 1 and the lowest in Compartment 4. However, the concentration of cations is higher in Compartment 3 (Table 9) than in CompartmentAttorney Reference No.: SP24-2564 (Table 10) even though the compartments are the same size. This likely indicates that the distance between the electrodes is too far for the applied potential difference.Table 10: Concentration for Four Compartments with 3.5 V Potential Difference

[0087] Tables 11-12 relate to an applied potential difference of 4.0 V (rather than 3.5 V in Tables 8-10). Table 11 presents the results of applying a potential difference of 4.0 V to an electrochemical apparatus with three compartments. The charge density was 90 C / cm2As in Table 9, the applied potential difference causes the pH of Compartments 2 and 3 to increase dramatically while the pH in Compartment 1 decreased. As noted above, the calcium concentration (in solution) in the right-most compartment is low due to its precipitation in that compartment. For the other cations, the concentration is greatest in compartment 3 and the lowest in compartment 1. Similarly, the concentration of the anions is highest in Compartment 1 and the lowest in Compartment 3. Compared to Compartment 3 of Table 9 (3.5 V), the lithium concentration (and other cations - excluding calcium) is roughly the same (perhaps slightly less) in Compartment 3 of Table 10 (4.0 V). While the precipitate here was not analyzed for the presence of metals other than calcium, it is possible that the potential difference here was sufficient to start precipitating these metal cations.Table 11 : Concentration for Three Compartments with 4.0 V Potential DifferenceAttorney Reference No.: SP24-256Table 12: Concentration for Four Compartments with 4.0 V Potential Difference

[0088] Table 12 presents the results of applying a potential difference of 4.0 V to an electrochemical apparatus with three compartments. The charge density was 70 C / cm2As in Table 10, the applied potential difference causes the pH of Compartments 3 and 4 to increase dramatically while the pH in Compartments 1 and 2 decreased. As noted above, the calcium concentration (in solution) in the right-most compartment is low due to its precipitation in that compartment. For the other cations, the concentration is greatest in compartment 4 and the lowest in compartment 1. Similarly, the concentration of the anions is highest in Compartment 1 and the lowest in Compartment 4. Compared to Compartment 4 of Table 10 (3.5 V), the lithium concentration is slightly increased in Compartment 4 of Table 11 (4.0 V) while the concentration of other cations (sodium) is more noticeably increased. This suggests that the treatment time may have been sufficient for the lithium cations to re-equilibrate (due to their higher charge-to-mass ratio than other cations) under the applied potential difference of 3.5 V while other cations required an increased potential difference (4.0 V) (or additional time) to re-equilibrate.Attorney Reference No.: SP24-256

[0089] In any case, the (concentrated) solution from the rightmost compartment is concentrated in metal cations (e.g., alkali cations) than the original solution. In aspects, the concentrated solution can be treated again (e.g., as in any of Tables 8-12). However, in further aspects, the time that a potential difference is applied might be less since the lithium ions will more quickly re-equilibrate to the applied potential difference. Alternatively or additionally, in further aspects, instead of filling each compartment with the solution, the compartment having the cathode (i.e., rightmost compartment in Tables 8-12) could be water (or a less concentrated solution) such that there is less (or none) of the other metal cations already in the compartment that the lithium ions will migrate towards when the potential difference is applied. Alternatively, in further aspects, lithium cations and metal cations can be separated by liquid-liquid extraction; lithium cations and metal cations can be separated using an ion-exchange membrane (e.g., instead of a non-specific membrane); and / or one or more of the cations can be precipitated through the addition of a carbonate (e.g., through the addition carbon dioxide gas to form carbonic acid or the addition of potassium carbonate).

[0090] The above observations can be combined to provide an electrochemical apparatus as well as methods of recovering metal from a solution and methods of creating multiple pH zones, which can make use of the electrochemical apparatus. The electrochemical apparatus comprises a pair of electrodes configured to apply a potential difference across as liquid (e.g., solution including metal cations). The potential difference can selectively drive ions based on the charge to mass (q / m) ratio of the cations (e.g., metal cations) and / or anions. Further, the electrochemical apparatus comprises one or more membranes positioned at interfaces between adjacent compartments, where the one or more membranes can allow ions to pass through pores therein. The one or more membranes can facilitate the formation (and separation) of different properties (e.g., pH, metal cation concentration) in each of the plurality of compartments. Further, it is believed that the relatively limited surface area presented by of pores of each membrane effectively constricts the flow of ions through the membrane relative to the corresponding movement within a corresponding compartment. Consequently, different pHs and / or metal cation concentrations can be obtained even in adjacent pairs of compartments, as demonstrated by the Examples herein.

[0091] Methods of the present disclosure can create multiple pH zones in a corresponding plurality of compartments through the application of the potential difference with the one or more membranes positioned at the interface between adjacent compartments of the plurality ofAttorney Reference No.: SP24-256 compartments. Without wishing to be bound by theory, it is believed that the diffusivity of hydroxide ions are much slower (e.g., by about a factor of 2) than the diffusivity of hydronium ions. This difference in diffusivity can generate different pHs in each compartment of the plurality of compartments. Further, it is believed that the relatively limited surface area presented by of pores of each membrane effectively constricts the flow of ions through the membrane relative to the corresponding movement within a corresponding compartment. As demonstrated by the Examples herein, the pHs obtained can be adjusted by controlling the median pore size of the one or more membranes, controlling a concentration of ions in (or ionic strength of) the liquid, membrane material, applied potential difference, and / or time that potential difference is applied. The results in Table 3 demonstrate that (1) smaller median pore sizes allow for larger pH differences between the middle compartments (which can be extended to the situation with more than 4 compartments), (2) increasing solution concentration (e.g., ionic strength) increases the charge density, and (3) differences in membrane material are more pronounced at lower solution concentrations. The plurality of pH zones can be created on-demand for processing of pH sensitive materials

[0092] Methods of the present disclosure can comprise concentrating metal cations and / or recovering metal from a solution. Applying the potential difference selectively drives the metal cations in the solution through a membrane towards one of the electrodes. This can generate a concentrated solution that is enriched in one or more of the metal cations. Also, the time that the potential difference is applied can be adjusted to control a relative proportion of the cations in a particular compartment. The concentrated solution can be recovered and / or further processed (e.g., further concentrated, subjected to liquid-liquid extraction), which can lead the precipitation of the metal (from the metal cation in the concentrated solution). As such, the electrical chemical apparatus can be used to recover lithium from a mixed metal solution. For example, the electrical chemical apparatus can recover lithium from a mixed metal solution. Such mixed metal solutions can be produced as part of lithium recycling from waste (e.g., cullet, broken) lithium-containing glass.

Claims

1. Attorney Reference No.: SP24-256CLAIMSWhat is claimed is:

1. A method of recovering a metal comprising: positioning a solution comprising a plurality of metal cations in at least a first compartment of a plurality of compartments, the plurality of compartments are in fluid communication with one another through a corresponding membrane of one or more membranes at an interface between an adjacent pair of compartments of the plurality of compartments, wherein the first compartment is in fluid communication with an adjacent compartment of the plurality of compartments by a first membrane of the plurality of compartments; applying a potential difference between a pair of electrodes positioned in opposite compartments of the plurality of compartments, wherein the potential difference drives at least a first metal cation of the plurality of metal cations through the first membrane into the adjacent compartment; and concentrating the first metal cation in a second compartment, the second compartment is positioned in a region between and including the adjacent compartment and a compartment having a first electrode of the pair of electrodes.

2. The method of claim 1 , wherein the first metal cation is lithium.

3. The method of any one of claims 1-2, wherein the plurality of metal cations includes alkali metal cations and alkali earth metal cations.

4. The method of any one of claims 1 -3, wherein the first membrane is a non-specific, porous membrane.

5. The method of any one of claims 1-4, wherein a gradient of the potential difference is from 0.01 V / cm to 5.0 V / cm.

6. The method of any one of claims 1-5, wherein the plurality of compartments includes 4 or more compartments.Attorney Reference No.: SP24-2567. The method of any one of claims 1 -6, wherein a path between the pair of electrodes extends entirely through liquid in the plurality of compartments including the solution.

8. The method of any one of claims 1-7, further comprising, recovering the metal as a precipitate of the first metal cation after the applying the potential difference, wherein a second pH of the second compartment is higher than a first pH of the first compartment.

9. The method of any one of claims 1-7, further comprising, after the concentrating, precipitating the precipitate of the first metal cation in the second compartment.

10. The method of any one of claims 1-7, further comprising: precipitating a second metal cation of the plurality of metal cations different from the first metal cation in the second compartment; and removing a concentrated solution including the first metal cation from the second compartment after the precipitating the second metal cation.

11. The method of claim 10, further comprising: positioning the concentrated solution in at least another first compartment of a plurality of another compartments, wherein the another first compartment is in fluid communication with another adjacent compartment of the plurality of compartments by another first membrane of the plurality of compartments; and applying another potential difference between another pair of electrodes positioned in opposite another compartments of the plurality of another compartments, wherein the another potential difference drives at least the first metal of the plurality of metal cations through the another first membrane into the adjacent compartment.

12. The method of claim 11 , further comprising, after the applying another potential difference, precipitating the precipitate of the first metal cation in another second compartment, wherein the another second compartment is positioned in another region between and including the anotherAttorney Reference No.: SP24-256 adjacent compartment and another compartment having another first electrode of the plurality of another electrodes.

13. An electrochemical apparatus comprising: one or more membranes; a plurality of compartments arranged in series and in fluid communication with one another through a corresponding membrane of the one or more membranes at an interface between an adjacent pair of compartments of the plurality of compartments, wherein each compartment of the plurality of compartments are configured to contain a liquid, and a pair of electrodes positioned in opposite compartments of the plurality of compartments, wherein the pair of electrodes are configured such that a potential difference can be applied across the pair of electrodes through the liquid to migrate ions of the liquid through the corresponding membrane of the one or more membranes into an adjacent compartment of the plurality of compartments.

14. The electrochemical apparatus of claim 13, wherein the plurality of compartments includes 4 or more compartments.

15. The electrochemical apparatus of any one of claims 13-14, wherein a membrane at the interface of the interface between the adjacent pair of compartments is a non-specific, porous membrane.

16. The electrochemical apparatus of any one of claims 13-15, wherein a membrane at the interface of the interface between the adjacent pair of compartments is an ion-exchange membrane.

17. The electrochemical apparatus of any one of claims 15-16, wherein a thickness of the membrane is from 50 micrometers to 1 millimeter.

18. The electrochemical apparatus of any one of claims 15-17, wherein a median pore size of the membrane is from 3 nanometers to 3 millimeters.Attorney Reference No.: SP24-25619. The electrochemical apparatus of any one of claims 13-18, further comprising a first aperture configured to selectively permit fluid to flow through the first aperture into or out of a first compartment of the plurality of compartments.

20. The electrochemical apparatus of claim 19, further comprising: a second aperture configured to selectively permit fluid to flow through the second aperture into a second compartment of the plurality of compartments different from the first compartment; a third aperture configured to selectively permit fluid to flow through the third aperture out of the second compartment; and wherein the first aperture is configured to selectively permit fluid to flow through the aperture into the first compartment.

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