WO2016183427A1

WO2016183427A1 - Systems and methods for recovery of sulfate from lead acid batteries

Info

Publication number: WO2016183427A1
Application number: PCT/US2016/032330
Authority: WO
Inventors: Richard Clarke; Robert Lewis Clarke; Brian Dougherty
Original assignee: Aqua Metals Inc.
Priority date: 2015-05-13
Filing date: 2016-05-13
Publication date: 2016-11-17

Abstract

Sulfate produced in lead acid battery processing can be recovered as sulfuric acid. A lead paste from a lead acid battery is collected and contacted with a base to produce a two-phase reaction product. The two-phase reaction product comprises a supernatant having a soluble sulfate salt and a precipitate having an insoluble lead salt. The supernatant is treated in an electrochemical flow cell to thereby produce sulfuric acid and a regenerated base.

Description

SYSTEMS AND METHODS FOR RECOVERY OF SULFATE FROM LEAD ACID

BATTERIES

[0001] This application claims priority to U.S. Provisional Application Ser. No. 62/160,842, filed May 13, 2015. All extrinsic materials identified herein are incorporated by reference in their entirety.

Field of the Invention

[0002] The field of the invention is recycling of lead acid batteries, especially as it relates to systems and methods that recover sulfate from lead paste of a lead acid battery.

Background [0003] The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0004] Lead acid batteries (LABs) are the single largest class of batteries used today. They are widely used in applications ranging from providing power for starter motors used with internal combustion engines, providing emergency back-up power for data centers, storage of power generated by off-grid photovoltaic systems, and powering industrial and recreational vehicles such as fork lift trucks and golf carts. Fortunately, almost all LABs are recycled. LAB production is, however, increasing at an average rate of about 5% per year globally. Not surprisingly, new and more efficient methods for recycling of LAB components, such as lead, are urgently needed.

[0005] Unfortunately, all or almost all of the current lead recycling from LABs remains based on lead smelting technology, originally developed over 2000 years ago to produce lead from lead-bearing ores. Lead smelting is a pyro-metallurgical process in which lead, lead oxides, and other lead compounds are heated to about 1600 °F and then mixed with various reducing agents to remove oxides, sulfates, and other non-lead materials.

[0006] Unfortunately, lead smelting is a highly polluting process, generating significant airborne waste (e.g., toxic lead dust, CO2, arsenic, SO2), solid waste (lead containing slag), and liquid waste (e.g. , sulfuric acid, arsenic salts). The resulting pollution issues have forced the closure of many recycling facilities in the US and other Western countries. Migration and expansion of smelters to countries with less restrictive environmental regulations has resulted in large scale pollution and high levels of human lead contamination.

[0007] Efforts have been made to move away from smelting operations and to use more environmentally friendly solutions to recover components of a spent lead acid battery. For example, United States Patent No. 4,927,510 to Olper teaches recovering lead in pure metal form from desulfurized battery sludge. All publications identified herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. Unfortunately, Olper requires use of a fluorine containing electrolyte (e.g. , fluoboric or fluosilic acid), which is also highly problematic.

[0008] Others have contemplated processing of lead acid batteries without use of a fluorine containing electrolyte. For example, United States Patent No. 4,107,007 to Gaumann discloses a process for recovering of lead from scrapped lead batteries using an alkaline solution to convert lead oxide and sulfate to a solution having dissolved lead compounds. Pure lead is recovered by electrolyzing the solution. However, the presence of sulfate in the electrolytic solution can be problematic in reuse of the electrolytic solution. [0009] Desulfurized lead active materials have been dissolved in methane sulfonic acid as described in United States Patent No. 5,262,020 to Masante and United States Patent No. 5,520,794 to Gemon. However, since lead sulfate is poorly soluble in methane sulfonic acid, upstream pre-desulfurization is still necessary and residual insoluble materials typically reduce the overall yield. To improve at least some of the aspects associated with lead sulfate, oxygen and/or ferric methane sulfonate can be added as described in International Patent Application Publication No. WO 2014/076544 to Fassbender, or mixed oxides can be produced as taught in International Patent Application Publication No. WO 2014/076547 to Fassbender. However, despite the improved yield, several disadvantages nevertheless remain. Among other things, solvent reuse in these processes often requires additional effort, and potentially useful sulfates are still lost as waste product. Moreover, if the process is halted midstream (e.g. , due to a power outage, which is not uncommon in electrolytic processing), the plated metallic lead will dissolve back into the electrolyte unless the cathode was removed and the lead peeled off, rendering batch operation at best problematic.

[0010] Recently, as described in our copending International Patent Publication No. WO 2015/077227, it has been found that the inclusion of chelating agents (e.g. , EDTA) with solvents such as MSA at acidic pH improves the solubility of lead oxides and lead sulfate salts, permitting recovery of lead by electrodeposition from such solvent systems. However, the breakdown of EDTA during electrodeposition and accumulation of sulfates in the solvent system limits the ability to reuse such solvents without further modifications.

[0011] Although the above references relate to recovery of lead, some have contemplated recovery of other components in lead acid battery processing. For example, United States Patent No. 5, 106,466 to Olper discloses a process for recovering components of spent lead acid batteries. A sodium sulfate solution is formed in a desulfurization stage of lead acid battery recovery process. The sodium sulfate solution is subject to electrolysis whereby soda is formed at the cathode and sulfuric acid is formed at the anode. The soda and sulfuric acid are concentrated by evaporation prior to recycling the soda to the desulfurization stage and reusing the sulfuric acid for a new battery. Unfortunately, a step of evaporation to concentrate the soda and sulfuric acid before reuse increases the energy requirements of the Olper process.

[0012] In another example, United States Patent No. 5,429,661 to Khodov discloses treating a sodium sulfate solution produced when recovering lead from spent lead acid batteries. The sodium sulfate solution is subject to electrochemical treatment to produce an alkaline solution and sulfuric acid. The alkaline solution is used to treat a lead-containing polymer material to produce sodium sulfate and sodium plumbate. However, the formation of plumbate in the Khodov process can be undesirable. Additionally, any residual sodium sulfate from the electrochemical treatment can create a problematic accumulation of sodium sulfate in recycle streams.

[0013] Thus, even though numerous methods for lead acid battery processing are known in the art, all or almost all of them, suffer from one or more disadvantages in regards to recovery and reuse of sulfate materials. Most notably, residual sulfate in regenerated NaOH and high energy demand of electrolysis along with possible generation of byproducts have prevented commercially relevant recycling systems. Therefore, there is still a need for improved devices and method for processing of lead acid batteries.

Summary of the Invention

[0014] The present invention provides apparatus, systems, and methods of lead acid battery processing in which sulfate is recovered as sulfuric acid using an electrochemical flow cell that advantageously reduces residual sulfate, significantly reduces energy demand, and does not produce significant quantities of side products. A lead paste from a lead acid battery is collected and treated with a base. The resulting product is a mixed phase that includes a solid precipitate fraction (which includes Pb(OH)₂ and PbO) and a liquid supernatant fraction (which includes a soluble metal sulfate compound). The supernatant is collected and treated in an electrochemical flow cell to recover the sulfate as sulfuric acid (H₂SO₄), which can be used in the production of new lead acid batteries or other industrial processes. Additionally, the base is regenerated in the electrochemical flow cell, which can be reused in the sulfate recovery process, and recyclable water is produced that can be reused in the electrochemical flow cell or used for other processes. Thus, sulfate is recovered in a useful form while providing a solid, sulfate-free source of lead salts that can be further processed to recover lead.

[0015] In one embodiment, a method of recovering sulfate as sulfuric acid from a lead acid battery is contemplated. The method comprises collecting a first portion of lead paste comprising lead sulfate from the lead acid battery. The first portion of lead paste is contacted with a base to thereby generate a supernatant comprising a soluble sulfate salt and a precipitate comprising an insoluble lead salt. The supernatant is separated from the precipitate and is fed through a channel of an electrochemical flow cell comprising a segmented anode and a segmented cathode. A flow of current at the segmented anode and the segmented cathode can be controlled as a function of a concentration of the soluble sulfate salt to optimize electrochemical processes at each segment thereby reducing energy demands and reducing side reactions. It should be appreciated that in some embodiments the sulfuric acid and regenerated base can be used without any further processing (e.g., evaporation to concentrate sulfuric acid and the regenerated base). [0016] The electrochemical flow cell typically comprises a cation exchange membrane, an anion exchange membrane, or an electrodialysis membrane. As used herein, the term "cation exchange membrane" means a membrane that allows passage of cations while blocking passage of anions, the term "anion exchange membrane" means a membrane that allows passage of anions while blocking passage of cations, and the term "electrodialysis membrane" means a membrane that allows passage of cations and anions at respective transfer locations.

[0017] In some embodiments, the electrochemical flow cell comprises a cation exchange membrane disposed in the channel to create an anode compartment and a cathode compartment, and the supernatant is fed through the anode compartment. In other embodiments, the electrochemical flow cell comprises an anion exchange membrane disposed in the channel to create an anode compartment and a cathode compartment, and the supernatant is fed through the cathode compartment. In yet another embodiment, the electrochemical flow cell comprises an electrodialysis membrane or a cation exchange membrane and an anion exchange membrane disposed in the channel to create an anode compartment, a soluble sulfate salt compartment, and a cathode compartment, and the supernatant is fed through the soluble sulfate salt compartment.

[0018] The base can comprise at least one of an alkali or alkaline earth metal hydroxide and a carbonate, and the insoluble lead salt can comprise at least one of a lead oxide, a lead hydroxide, and a lead carbonate. For example, the soluble sulfate salt can comprise sodium sulfate, the base can comprise sodium hydroxide, and the insoluble lead salt can comprise lead hydroxide. Thus, sodium sulfate can be fed into an anode compartment when the electrochemical flow cell comprises a cation exchange membrane whereby sodium ions can pass through the cation exchange membrane to the cathode compartment in exchange for protons (H⁺) to generate a regenerated sodium hydroxide, sodium sulfate can be fed into a cathode compartment when the electrochemical flow cell comprises an anion exchange membrane whereby sulfate ions can pass through the anion exchange membrane to the anode compartment in exchange for hydroxyl ions to generate sulfuric acid, and the sodium sulfate can be fed to a soluble sulfate compartment when the electrochemical flow cell comprises an electrodialysis membrane or a cation exchange membrane and an anion exchange membrane whereby sodium ions can pass through the cation exchange membrane or an area of the electrodialysis membrane that selectively allows passage of cations into the cathode compartment to generate sodium hydroxide and sulfate ions can pass through the anion exchange membrane or an area of the electrodialysis membrane that selectively allows passage of anions into the anode compartment to generate sulfuric acid.

[0019] The segmented anode can comprise a first anode segment and a second anode segment, and the segmented cathode can comprise a first cathode segment and a second cathode segment. In some embodiments, the first cathode segment and first anode segment are positioned upstream of the second cathode segment and second anode segment with respect to flow direction of the supernatant. It is contemplated that current at each of the first cathode segment, the first anode segment, the second cathode segment, and the second anode segment can be individually controlled. For example, current at the second cathode segment and the second anode segment can be higher than current at the first cathode segment and the first anode segment, or vice versa. In another example, a first current at the first cathode segment and the first anode segment can be adjusted to a second current that is higher than the first current as the concentration of the soluble sulfate salt decreases at at least one of the first cathode segment and the first anode segment. Thus, current can be individually manipulated at each of the cathode and anode segments to have a complete, or substantially complete, conversion of the soluble sulfate salt to produce sulfuric acid and a regenerated base without side reactions or accumulation of residual soluble sulfate salt in a recycle stream.

[0020] As discussed above, a sulfate-free, or substantially sulfate-free, source of lead salts is produced as a precipitate. The supernatant can be separated from the precipitate by at least one of settling, centrifugation, and filtration. The insoluble lead salt in the precipitate can be contacted with an electrochemically stable solvent to generate solvated lead ions in the electrochemically stable solvent. The electrochemically stable solvent containing the solvated lead ions can be treated in an electrochemical cell to recover lead. In contemplated embodiments, the recovery of lead from the electrochemically stable solvent is a continuous process using a rotating cathode whereby lead is removed from one part of the cathode while lead ions are reduced on another part of the cathode.

[0021] Another embodiment of the inventive concept is a system for recovering sulfate as sulfuric acid from a lead paste of a lead acid battery. The system comprises a separation unit configured to separate a two-phase reaction product of the lead paste into a supernatant having a soluble sulfate salt and a precipitate having an insoluble lead salt. An

electrochemical flow cell is fluidly coupled to the separation unit and configured to receive the supernatant to electrolytically generate sulfuric acid and a base from the supernatant. Also, as used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously.

[0022] The electrochemical flow cell comprises a plurality of anode segments, a plurality of cathode segments, and a separator disposed between the plurality of anode segments and the plurality of cathode segments. In some embodiments, the separator comprises a cation exchange membrane, an anion exchange membrane, or an electrodialysis membrane. A controller is electronically coupled to the electrochemical flow cell to control current at the plurality of anode segments and the plurality of cathode segments as a function of a concentration of the soluble sulfate salt. Most typically, the controller is configured to individually control current at each of the plurality of anode segments and each of the plurality of cathode segments as a function of a concentration of the soluble sulfate salt.

[0023] In another aspect, a method of processing sulfate in a lead acid battery recycling process is contemplated. The method comprises obtaining lead paste from a lead acid battery that comprises lead sulfate. A first portion of the lead paste is contacted with a base to thereby generate a supernatant comprising a soluble sulfate salt and a precipitate comprising an insoluble lead salt. The supernatant is separated from the precipitate and is fed through a channel of the electrochemical flow cell. The channel comprises a first cathode and anode segment upstream of a second cathode and anode segment with respect to flow direction of the supernatant. A first current is applied at the first cathode and anode segment as a function of a first concentration of the soluble sulfate salt at the first cathode and anode segment, and a second current is applied at the second cathode and anode segment as a function of a second concentration of the soluble sulfate salt at the second cathode and anode segment to collectively form sulfuric acid and a regenerated base. In some embodiments, the electrochemical flow cell can comprise a cation exchange membrane, an anion exchange membrane, or an electrodialysis membrane. [0024] In another aspect, a method of recycling sulfate as sulfuric acid from a lead acid battery is contemplated. The method comprises disassembling the lead acid battery and collecting a first portion of a lead paste from the lead acid battery having lead sulfate. The first portion of the lead paste can be contacted with a base to thereby generate a supernatant comprising a soluble sulfate salt, and a precipitate comprising an insoluble lead salt. The supernatant can be separated from the precipitate and pumped through at least one of a cathode compartment, a soluble sulfate salt compartment, and an anode compartment disposed between a plurality of anode segments and a plurality of cathode segments of an electrochemical flow cell to generate sulfuric acid and a regenerated base. In some embodiments, current at each of the plurality of cathode segments and the plurality of anode segments is individually controlled. The electrochemical flow cell typically comprises at least one of a cation exchange membrane, an anion exchange membrane, and an

electrodialysis membrane to form the at least one cathode compartment, soluble sulfate salt compartment, and anode compartment. The sulfuric acid can be collected for manufacturing a new lead acid battery. Additionally, or alternatively, a second portion of the lead paste can be contacted with at least a portion of the regenerated base to thereby form a second supernatant comprising soluble sulfate salt, and a second precipitate comprising insoluble lead salt.

[0025] It should be appreciated that the precipitate comprising the insoluble lead salt is substantially free, or completely free, of sulfate. In typical embodiments, the insoluble lead salt comprises between 0.01-0.1% w/w sulfate, 0.1-1% w/w sulfate, or 1 -5% w/w sulfate. The insoluble lead salt can be contacted with an electrochemically stable solvent to generate solvated lead ions in the electrochemically stable solvent. The electrochemically stable solvent containing the solvated lead ions can be treated in an electrochemical cell to recover lead. The recovered lead can be utilized in the manufacture of the new lead acid battery.

[0026] In another aspect, use of a plurality of anode and cathode segments in an

electrochemical flow cell to generate sulfuric acid and a regenerated base from a sodium sulfate solution produced in lead acid battery recycling is contemplated. At least one of an electrodialysis membrane, a cation exchange membrane and an anion exchange membrane is disposed within the electrochemical flow cell to separate the sulfuric acid from the regenerated base. In preferred embodiments, current at each of the plurality of anode and cathode segments is individually controlled. In some embodiments, a controller can be coupled to the plurality of anode and cathode segments to control current to the plurality of anode and cathode segments as a function of a concentration of a soluble sulfate salt in the electrochemical flow cell. [0027] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components. Brief Description of the Drawing

[0028] Figure 1 is a schematic of an embodiment of lead acid battery processing according to the inventive subject matter.

[0029] Figure 2 is an exemplary configuration of an embodiment of an electrochemical flow cell comprising a segmented electrode and an anion exchange membrane. [0030] Figure 3 is an exemplary configuration of another embodiment of an electrochemical flow cell comprising a segmented electrode and a cation exchange membrane.

[0031] Figure 4 is an exemplary configuration of an embodiment of an electrochemical flow cell comprising a segmented electrode and an electrodialysis membrane or an anion exchange membrane and a cation exchange membrane. [0032] Figure 5 is an exemplary schematic of an embodiment of an electrochemical cell comprising a rotating cathode.

Detailed Description

[0033] The following discussion provides example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0034] The inventors have now discovered that sulfate from a lead acid battery can be recovered in a conceptually simple, yet effective manner where the sulfate is extracted from a lead paste (which includes lead oxide and lead sulfate) using a base to form a soluble sulfate solution, and the soluble sulfate solution is treated in an electrochemical flow cell to thereby generate sulfuric acid, a regenerated base, and water. In preferred embodiments, the electrochemical flow cell comprises a segmented anode and a segmented cathode that are individually controlled. As the sodium sulfate solution flows through the electrochemical flow cell, it is contemplated that current to each of the segments in the segmented anode and cathode can be controlled to substantially, or completely, convert the sodium sulfate to a regenerated base and sulfuric acid. Additionally, water used in the electrochemical flow cell can be advantageously recycled or reused in the electrochemical flow cell thereby reducing, or eliminating, the need for an external source of water for the electrochemical flow cell. Thus, current can be locally controlled throughout the electrochemical flow cell to account for the change in concentration of sodium sulfate as it flows through the electrochemical cell. [0035] One should appreciate that the disclosed techniques provide many advantageous technical effects including generating appropriate quantities of ions of water (H⁺ and OH^") on demand and in a localized area of the electrochemical flow cell to interact with the soluble sulfate salt to produce sulfuric acid and a base. In other words, use of the electrochemical flow cell is not for reduction of the cations of the soluble sulfate salt (e.g., sodium ions of sodium sulfate) or oxidation of sulfate ions of the soluble sulfate salt, but rather to generate ions of water (H⁺ and OH^") that react with ions of the soluble sulfate salt to form the corresponding base and sulfuric acid. Advantageously, localized treatment of soluble sulfate salt within the electrochemical flow cell is possible through use of the segmented anode and cathode, such that current can be modified at different points on the segmented anode and cathode to account for varying concentrations of soluble sulfate salt as it flows through the electrochemical flow cell improving energy efficiency and control of side reactions otherwise occurring at decreasing concentrations of the soluble sulfate salt. Viewed from another perspective, the disclosed techniques allow for deep removal of residual soluble sulfate salt from the supernatant to prevent buildup when recycling regenerated base, and also to provide recyclable water that can be used in the process.

[0036] It is contemplated that the soluble sulfate salt can be substantially (i.e. , less than 85%), or completely (i.e. , less than 95%), converted to sulfuric acid and a base in an energy efficient manner without side reactions. For example, it is contemplated that more than 85% of soluble sulfate salt in the supernatant is converted to sulfuric acid and a base, more than 90% of soluble sulfate salt is converted to sulfuric acid and a base, more than 95% of soluble sulfate salt is converted to sulfuric acid and a base, and even more than 99% of soluble sulfate salt is converted to sulfuric acid and a base. Thus, substantially, or completely, converting the soluble sulfate salt reduces, or eliminates, the need to remove accumulated soluble sulfate in recycle streams caused by residual soluble sulfate salt from incomplete reactions in conventional electrochemical cells. It should also be appreciated that the disclosed techniques yields a solid, lead-containing product that is essentially sulfur free (e.g., less than 0.1% w/w sulfate) that is highly suitable for subsequent processing.

[0037] An embodiment of the inventive concept is depicted schematically in Figure 1. A system 100 comprises a disassembly unit 101 that receives a lead acid battery 103 for recycling. Disassembly unit 101 can be ordered, for example by splitting or cutting along edges and/or seams of a lead acid battery case. Alternatively, disassembly can be carried out by crushing, grinding, fragmenting, and/or shredding. Liquid and solid (e.g. , plastic, metallic lead, lead paste) components produced in disassembly unit 101 can be separated by decantation and/or density separation. Plastic components, sulfuric acid solution, and metallic lead (Pb(0)) in the form of grids 105 can be recovered directly in a form that is substantially ready for reuse and sent to a new battery assembly unit 107. Insoluble lead paste 109 containing active material lead species (e.g. , PbSC>4, PbO, and PbC^) is collected for further treatment in a treatment unit 111.

[0038] While the sulfate component in insoluble lead paste 109 may in known processes complicate downstream recovery of lead, the processes contemplated herein render it a valuable source of useful sulfate. Insoluble lead paste 109 is mixed with a base 113 to thereby generate a two-phase reaction product 115 that includes a supernatant and a precipitate. Suitable bases include, but are not limited to, an alkali or alkaline earth metal hydroxide (M_x(OH)_y) for which the corresponding metal sulfate (M_a(S04)_b) is soluble. For example, Group I metal hydroxides LiOH, NaOH, and KOH are contemplated as base 113. In another example, lead paste 109 is mixed with NaOH to thereby generate a supernatant comprising sodium sulfate and a precipitate comprising an insoluble lead salt (insoluble lead oxides and lead hydroxide (Pb(OH)₂) that is essentially free of sulfate. Other suitable bases that provide soluble sulfate salts (i.e. soluble at greater than or equal to 10, 25, 50, 75, 100, 200, 400, 600, or 800 or more g/L) and relatively insoluble (i.e. insoluble at 10, 3, 1, 0.3, 0.1, 0.03, 0.01 or less g/L) lead salts on reaction with Pb(S0₄), for example carbonates (such as Na₂(C0₃) and K₂(C0₃)), are also suitable. In typical embodiments, base is added (e.g. , 1-3N NaOH ) to insoluble lead paste 109 in sufficient quantities as to form a precipitate comprising an insoluble lead salt without formation of plumbate (i.e., less than 0.1 mol% of the incoming lead species in insoluble lead paste 109).

[0039] A separation unit 117 is configured to separate two-phase reaction product 115 into a supernatant 119 having a soluble sulfate salt and a precipitate 121 having an insoluble lead salt. Separation of supernatant 119 from precipitate 121 can be performed by any suitable method. For example, supernatant 119 can be separated from precipitate 121 by settling via a settler, centrifugal separation (for example in a hydrocy clone) via a centrifuge, and/or filtration via a filtration unit. Suitable filters include filtration membranes and meshes, bed filters, press filters, and belt filters. Preferred separation methods are selected to efficiently separate precipitate 121 from supernatant 119 while facilitating recovery of precipitate 121 for subsequent processing. It should thus be particularly appreciated that lead sulfate is split into two value components, precipitate 121 comprising substantially sulfate free lead, and supernatant 119 comprising a substantially lead free sulfate solution.

[0040] Following separation from precipitate 121, it should further be recognized that supernatant 119 can be electrolytically processed to generate sulfuric acid, recyclable water, and regenerate the base used in the treatment of insoluble lead paste 109 recovered from the recycled battery. This can be accomplished through the use of an electrochemical flow cell 123. It should be appreciated that the recyclable water can be reused in electrochemical flow cell 123 to thereby reduce, or eliminate, the need for an external source of water for electrochemical flow cell 123.

[0041] As shown in Fig. 1, electrochemical flow cell 123 is fluidly coupled to separation unit 117 and configured to receive supernatant 119 and electrolytically generate sulfuric acid 125 and a base 127 from supernatant 119. It should be appreciated that such a process advantageously reuses sulfur from lead sulfate of insoluble lead paste 109 as sulfuric acid 125, which is an essential component of LABs, while also generating a base 127 that can be utilized in the recovery process (e.g., in treatment unit 111 to generate two-phase reaction product 115). For example, when NaOH is used as base 113, sodium atoms react with hydroxyl ions from water at the cathode of electrochemical flow cell 123 to form regenerated NaOH. This regenerated base 127 can be recovered and returned to the treatment unit 111 for extraction of insoluble lead paste 109 as part of a closed loop system. It is contemplated that regenerated base 127 can be delivered in quantities that substantially reduce, or eliminate, base 113. Similarly, H2SO4 can be recovered from the anode of electrochemical flow cell 123, and subsequently used in any number of industrial processes. In a preferred embodiment, the recovered sulfuric acid 125 is utilized in the manufacture of lead acid batteries via new battery assembly unit 107. Additionally, as discussed above, water is generated that can be recycled or reused in electrochemical flow cell 123. [0042] Electrochemical flow cell 123 preferably comprises a plurality of anode segments, a plurality of cathode segments, and a separator or disposed between the plurality of anode segments and the plurality of cathode segments as will be shown in more detail below. Suitable separators for electrochemical flow cell 123 comprise a cation exchange membrane, an anion exchange membrane, or an electrodialysis membrane. It is contemplated that a controller is electronically coupled to electrochemical flow cell 123 to control current at the plurality of anode segments and the plurality of cathode segments as a function of a concentration of the soluble sulfate salt. Thus, single-pass processing through

electrochemical flow cell 123 is at high efficiency to substantially, or completely, convert the soluble sulfate salt in supernatant 119 to sulfuric acid 125 and regenerated base 127. An exemplary contemplated electrochemical cell having a segmented electrode is described in United States Patent No. 8,580,414. However, it should be noted that such cell was used as a redox flow battery or a redox reactor for complete consumption of reactants in a redox reaction. On a finer note, it should be noted that use of electrochemical flow cell 123 is to provide appropriate quantities of ions from water (H⁺ and OH^") to react with ions of the soluble sulfate salt rather than completely consuming reactants in a redox reaction. Viewed from another perspective, electrochemical flow cell 123 is used to split water and to generate regenerated base 127 and sulfuric acid 125 from the soluble sulfate solution.

[0043] In some embodiments, supernatant 1 19 can be pumped through a channel of electrochemical flow cell 123. It is contemplated that the controller can also control the flow rate of supernatant 1 19 a suitable flow rate to allow sufficient time for the soluble sulfate salt to convert to sulfuric acid 125 and base 127.

[0044] Precipitate 121 recovered from treatment unit 1 11 can be treated to recover lead. Advantageously, precipitate 121 having an insoluble lead salt is sulfate-free or has essentially no sulfate content, which greatly simplifies the recovery of lead. For example, it is contemplated that precipitate 121 comprises between 0.01 -0.1 % w/w sulfate, 0.1 -1% w/w sulfate, or 1 -5% w/w sulfate. In a preferred embodiment, precipitate 121 is contacted with an electrochemically stable solvent 131 in a second treatment unit 129 to thereby generate solvated lead ions in the electrochemically stable solvent 133. It is contemplated that a suitable electrochemically stable solvent 131 comprises an alkane sulfonic acid (e.g. , methanesulfonic acid or MSA).

[0045] With respect to the alkane sulfonic acid, it should be appreciated that numerous alkane sulfonic acids are deemed suitable for use herein. However, MSA is especially preferred as this compound is environmentally friendly and stable under electrolytic conditions used. Other suitable alkane sulfonic acids include ethyl sulfonate, proplyene sulfonate, trifluro methyl sulfonate (triflic acid), sulfamic acid, etc. In most circumstances, the MSA or other alkane sulfonic acid will be present in a significant concentration, typically at least 1-5 wt%, more typically 5-15 wt%, even more typically 25-50 wt%, and most typically between 10 and 35 wt% of electrochemically stable solvent 133. Thus, suitable concentrations will typically be between 5 and 50 wt%, or between 20 and 30 wt% of electrochemically stable solvent 133. The pH of electrochemically stable solvent 133 is most preferably acidic, and most typically between pH 5-7, or between pH 1-3, or between pH 3-5. Viewed form a different perspective, the pH of electrochemically stable solvent 133 will be less than 7, or equal or less than 5, or equal or less than 3.

[0046] It should be appreciated that, with the removal of sulfate from insoluble lead paste 109, a chelator (e.g. , ethylenediaminetetraacetic acid or EDTA) is not required.

Electrochemically stable solvent containing solvated lead ions 133 is treated in an electrochemical cell 135. Depletion of lead ions from electrochemically stable solvent 133 effectively produces a regenerated electrochemically stable solvent 137, permitting its reuse in solvating precipitate 121.

[0047] Lead 139 can be collected by electrodeposition from a cathode of electrochemical cell 135 (for example, by scraping) and utilized in any number of industrial processes. As shown in Figure 1, the materials recovered from an old lead acid battery can be utilized in the construction of a new lead acid battery 141 with no or essentially no net consumption of either a base for treating insoluble lead paste 109 or an electrochemically stable solvent for solvating lead ions from precipitate 121, providing a closed loop system for recycling of such batteries that does not utilize a smelting step. [0048] As described above, a system for recovering sulfate as sulfuric acid from a lead paste of a lead acid battery is contemplated. It is contemplated that an electrochemical flow cell is used to generate sulfuric acid, recyclable water and a regenerated base from a supernatant comprising a soluble sulfate salt. One embodiment of an electrochemical flow cell 223 is shown in Figure 2. Electrochemical flow cell 223 has a channel 243 that comprises a segmented anode 245 and a segmented cathode 247. Channel 243 is sized and dimensioned to receive a supernatant 219 that comprises a soluble sulfate salt (e.g. , sodium sulfate).

[0049] It is contemplated that electrochemical flow cell 223 comprises an anion exchange membrane 246 disposed in the channel to create an anode compartment 248 and a cathode compartment 249. In such embodiment, supernatant 219 is fed through cathode compartment 249. As shown in Fig. 2, anion exchange membrane 246 allows passage of anions from cathode compartment 249 to anode compartment 248, and vice versa. Typically, sulfate ions of the soluble sulfate salt in supernatant 219 pass from cathode compartment 249 to anode compartment 248 to react with a proton (H⁺) from water to generate sulfuric acid 225.

Furthermore, the cations of soluble sulfate salt in supernatant 219 (e.g. , sodium ion when sodium sulfate) react with a hydroxyl ion from water to generate a base 227 (e.g. , NaOH) in cathode compartment 249. It should be appreciated that the cations of soluble sulfate salt in supernatant 219 can also react with hydroxyl ions that pass through anion exchange membrane 246 from anode compartment 248 to generate base 227. Recyclable water is also generated, which can be reused in electrochemical flow cell 223 to create ions for additional portions of supernatant 219 comprising a soluble sulfate salt (e.g., sodium sulfate). [0050] Segmented anode 245 can comprise a first anode segment 251 and a second anode segment 253, and segmented cathode 247 can comprise a first cathode segment 255 and a second cathode segment 257. As shown in Fig. 2, first cathode segment 255 and first anode segment 251 are positioned upstream of second cathode segment 257 and second anode segment 253 with respect to flow direction of supernatant 219. In preferred embodiments, it is contemplated that a controller 259 can control current at at least one anode segment of segmented anode 245 and at least one cathode of segmented cathode 247. For example, controller 259 can individually control current at each of first cathode segment 255, the first anode segment 251, the second cathode segment 257, and the second anode segment 253. Thus, current at second cathode segment 257 and second anode segment 253 can be higher than current at first cathode segment 255 and first anode segment 251 to accommodate a decreased concentration of soluble sulfate salt in supernatant 219 near second cathode segment 257 and second anode segment 253. Additionally, or alternatively, a first current at first cathode segment 255 and first anode segment 251 can be adjusted to a second current that is higher than the first current as the concentration of the soluble sulfate salt decreases at at least one of first cathode segment 255 and first anode segment 251.

[0051] It should be appreciated that individually controlling current at segmented anode 245 and segmented cathode 247 allows for current adjustments at localized areas within electrochemical flow cell 223 to address the decreasing concentration of soluble sulfate salt as it is converted to sulfuric acid 225 and base 227. In other words, as the concentration of soluble sulfate decreases, increasing current can be applied at specific segments of segmented anode 245 and segmented cathode 247 to drive the reaction of soluble sulfate to sulfuric acid 225 and base 227 to completion or substantial completion. For example, a first current can be applied at first cathode segment 255 and first anode segment 251 as a function of a first concentration of the soluble sulfate salt at first cathode segment 255 and first anode segment 251, and a second current can be applied at second cathode segment 257 and second anode segment as a function of a second concentration of the soluble sulfate salt at the second cathode segment 257 and second anode segment 253 to collectively form sulfuric acid 225 and base 227. Thus, accumulation of soluble sulfate salt in recycle streams is substantially, or completely, eliminated.

[0052] In another embodiment as shown in Figure 3, it is also contemplated that an electrochemical flow cell 323 can comprise a cation exchange membrane 361.

Electrochemical flow cell 323 comprises a channel 343 having a segmented anode 345 and a segmented cathode 347. Cation exchange membrane 361 is disposed in channel 343 to create an anode compartment 348 and a cathode compartment 349. In such embodiment, it is contemplated that supernatant 319 is fed through anode compartment 348.

[0053] Cation exchange membrane 361 allows passage of cations from anode compartment 348 to cathode compartment 349, and vice versa. Typically, cations of the soluble sulfate salt (e.g. , sodium ion when sodium sulfate) in supernatant 319 pass through cation exchange membrane 361 from anode compartment 348 to cathode compartment 349 to react with hydroxyl ions from water to generate a base 327 (e.g. , NaOH). Furthermore, sulfate ions of the soluble sulfate salt in supernatant 319 remain in anode compartment 348 and react with protons (H⁺) from water to generate sulfuric acid 325. It should be appreciated that sulfate ions from the soluble sulfate salt in supernatant 319 can also react with protons (H⁺) that pass through cation exchange membrane 361 from cathode compartment 349 to anode compartment 348 to further generate sulfuric acid 325. Recyclable water is also generated, which can be reused in electrochemical flow cell 323 to create ions for additional portions of supernatant 319 comprising a soluble sulfate salt (e.g. , sodium sulfate).

[0054] Similar to electrochemical flow cell 223 in Fig. 2, electrochemical flow cell 323 can comprise a controller 359 to control current at at least one segment of segmented anode 345 and at least one segment of segmented cathode 347. In some embodiments, controller 352 can individually control current at each of a first cathode segment 355, a first anode segment 351, a second cathode segment 357, and a second anode segment 353. Thus, current at second cathode segment 357 and second anode segment 353 can be higher than current at first cathode segment 355 and first anode segment 351 to accommodate a decreased concentration of soluble sulfate salt in supernatant 319. Additionally, or alternatively, a first current at first cathode segment 355 and first anode segment 351 can be adjusted to a second current that is higher than the first current as the concentration of the soluble sulfate salt decreases at at least one of first cathode segment 355 and first anode segment 351. [0055] In yet another embodiment of an electrochemical flow cell, it is contemplated that an electrochemical flow cell 423 can comprise an electrodialysis membrane 463 as shown in Figure 4. Electrochemical flow cell 423 comprises a channel 443 having a segmented anode 445 and a segmented cathode 447. Electrodialysis membrane 463 can be disposed in channel 443 to thereby create an anode compartment 448, a soluble sulfate salt compartment 465, and a cathode compartment 449. In such embodiment, supernatant 419 is fed through soluble sulfate salt compartment 465 formed by electrodialysis membrane 463.

[0056] Electrodialysis membrane 463 can be a membrane having a first area that allows passage of cations and prevents passage of anions, and a second area that allows passage of anions and prevents passage of cations. In preferred embodiments, the first area is disposed near segmented cathode 447 and the second area is disposed near segmented anode 445. Alternatively, it is contemplated that electrodialysis membrane 463 comprises two separate walls whereby a first wall is disposed near segmented cathode 447 to selectively allow passage of cations, and a second wall is disposed near segmented anode 445 to selectively allow passage of anions. In other embodiments, electrochemical flow cell 423 can comprises an anion exchange membrane and a cation exchange membrane that form anode compartment 448, soluble sulfate salt compartment 465, and cathode compartment 449. [0057] As shown in Fig. 4, supernatant 419 comprising soluble sulfate salt is fed to soluble sulfate salt compartment 465. Cations of the soluble sulfate salt (e.g., sodium ions when sodium sulfate) in supernatant 419 pass through a first area of electrodialysis membrane 463 to cathode compartment 449. In cathode compartment 449, cations of the soluble sulfate salt in supernatant 419 react with hydroxyl ions from water to thereby produce a base 427.

Sulfate ions of the soluble sulfate salt in supernatant 419 pass through a second area of electrodialysis membrane 463 to anode compartment 448. In anode compartment 448, hydroxyl ions of the soluble sulfate salt in supernatant 419 react with protons (H⁺) of water to thereby create sulfuric acid 425. Recyclable water is also generated, which can be reused in electrochemical flow cell 423 to create ions for additional portions of supernatant 419 comprising a soluble sulfate salt (e.g., sodium sulfate).

[0058] Similar to the electrochemical flow cells of Figs. 2-3, it is contemplated that a controller 459 can be used to control current at segmented anode 445 and segmented cathode 447. For example, it is contemplated that controller 459 can individually control current at each of a first cathode segment 455, a first anode segment 451, a second cathode segment

457, and a second anode segment 453. Thus, current can be modified at each of the segments in segmented anode 445 and segmented cathode 447 to account for concentrations of soluble sulfate salt and thereby substantially, or completely, convert with soluble sulfate salt to base 427 and sulfuric acid 425. [0059] As described above, it is contemplated that lead can be recovered from precipitate produced when treating an insoluble lead paste from a lead acid battery with an alkaline earth metal hydroxide and a carbonate. The precipitate is contacted with an electrochemically stable solvent to solvate lead ions and lead is recovered using an electrochemical cell. One contemplated electrochemical cell 535 is shown in Figure 5. Electrochemical cell 535 contains an electrochemically stable solvent containing solvated lead ions 533. An anode 567 and a rotating disk-shaped cathode 569 are at least partially disposed in electrochemical cell 535 to contact electrochemically stable solvent containing solvated lead ions 533, and to promote formation of lead 539 that is taken up by lead harvester 571 (typically a plastic wiper or otherwise proximally positioned surface). In some embodiments anode 567 is made from titanium and is coated with ruthenium oxide and cathode 569 is aluminum.

[0060] Of course, it should be appreciated that the inventive subject matter is not limited to use of a disk-shaped electrode, but that in fact all electrodes are deemed suitable that allow active (e.g. , using a wiping blade or surface) or passive removal (e.g. , via bubbles, solvent jetting, or flotation) of high-purity lead from the cathode. Thus, suitable electrodes may be configured as simple plates that may be static relative to the solvent or moved in a reciprocal manner, or electrodes that can be continuously moved and that are configured to allow reduction of lead ions on one portion and lead removal on another portion. For example, suitable electrode configurations include conductive disks, cylinders, spheres, belts, etc. Likewise, it should be recognized that the number of cathodes may vary considerably, and that most typically multiple cathodes are operated in parallel (or serially, especially where the cathodes are static relative to the solvent. [0061] A solvent conditioning unit 573 for removal of sulfate can be coupled to

electrochemical cell 535 to receive spent solvent and provide back conditioned solvent in embodiments where removal of accumulated sulfate as well as other impurities (e.g. , Sn²⁺, Ca²⁺, particulates, etc.) from the electroprocessing solvent is needed. Solvent processing can be performed in numerous manners and may be continuous or batch-wise. Most typically, processing the solvent includes a step of filtering to remove at least some of the particulates, a step of sulfate removal (e.g., via lime precipitation, reverse osmosis, ion exchange, electro- osmosis, salt splitting, liquid chromatography, liquid/liquid extraction etc.,), and/or a step of non-lead metal ion removal (e.g., ion exchange). Where the process is operated in a batch mode, collection of multiple streams of solvent is especially preferred, and a surge or holding tank may therefore be added to the system. On the other hand, where the system is continuously operated, multiple streams may be combined and then processed to reduce redundancy and plot space.

[0062] Surprisingly, the inventors discovered that the lead was recovered from processes of the inventive concept in the form of a micro- or nanoporous mixed matrix in which the lead formed micro- or nanometer sized structures (typically needles/wires) that trapped some of the electrochemically stable solvent and a substantial quantity of molecular hydrogen (e.g. , H₂). Most notably, such a matrix had a black appearance and a remarkably low bulk density. Indeed, in most of the experimental test runs the matrix was observed to float on the solvent and had a density of less than 1 g/cm³. Upon pressing the matrix or application of other force, the density increased (e.g., 1-3 g/cm³, or 3-5 g/cm³, or higher) and a metallic silvery sheen appeared. [0063] Additionally, it was unexpectedly observed that the reduced lead ions did not form a tightly bonded film on the cathode, but could be readily removed from the cathode by simply wiping the cathode with a material to which the lead could adhere (e.g. , plastic, lead-film, etc.). Therefore, lead recovery can be performed in a continuous manner. Particularly where a rotating or reciprocating electrode was employed, lead ions could be reduced one part of an electrode or electrode assembly, while metallic lead can be removed from another part of the electrode or electrode assembly.

[0064] It should be appreciated that the described processes can be performed in a batch manner, in which a single bolus of lead paste is processed to produce a discrete batch of sulfuric acid and a discrete batch of precipitate. Using suitable separation methods, however, processes of the inventive concept can be performed in a continuous fashion, with a stream of lead paste being processed to produce streams of sulfuric acid and essentially sulfate-free lead containing precipitate. In some embodiments processes of the inventive concept can be performed in a semi-continuous manner, for example by providing discrete boluses of lead paste in succession.

[0065] It should also be appreciated that methods and reagents of the inventive concept, while described above in terms of recycling of lead acid batteries, can also be applied to the recovery of sulfate from other sources. Suitable alternative sources include sulfate- containing salts with corresponding insoluble hydroxides or, alternatively, unstable hydroxides that form insoluble oxides. Examples of sulfate-containing materials from which sulfate can be extracted include materials that include sulfate salts of Group II elements, transition metals, and aluminum.

[0066] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0067] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about." Moreover, and unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

[0068] It should be apparent, however, to those skilled in the art that many more

modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the disclosure. Moreover, in interpreting the disclosure all terms should be interpreted in the broadest possible manner consistent with the context. In particular the terms "comprises" and "comprising" should be interpreted as referring to the elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps can be present, or utilized, or combined with other elements, components, or steps that are not expressly reference

Claims

CLAIMS What is claimed is:

1. A method of recovering sulfate as sulfuric acid from a lead acid battery, comprising: collecting a first portion of lead paste from the lead acid battery, wherein the lead paste comprises lead sulfate;

contacting the first portion of the lead paste with a base to thereby generate a

supernatant comprising a soluble sulfate salt and a precipitate comprising an insoluble lead salt;

separating the supernatant from the precipitate;

feeding the supernatant through a channel of an electrochemical flow cell, wherein the channel comprises a segmented anode and a segmented cathode; and controlling a flow of current at the segmented anode and the segmented cathode as a function of a concentration of the soluble sulfate salt to thereby generate the sulfuric acid and a regenerated base.

2. The method of claim 1 , wherein the electrochemical flow cell comprises a cation exchange membrane, an anion exchange membrane, or an electrodialysis membrane.

3. The method of claim 2, wherein the electrochemical flow cell comprises the cation exchange membrane, and the cation exchange membrane is disposed in the channel to create an anode compartment and a cathode compartment, and wherein the feeding the supernatant through the channel comprises feeding the supernatant through the anode compartment.

4. The method of claim 2, wherein the electrochemical flow cell comprises the anion exchange membrane, and the anion exchange membrane is disposed in the channel to create an anode compartment and a cathode compartment, and wherein the feeding the supernatant through the channel comprises feeding the supernatant through the cathode compartment.

5. The method of claim 2, wherein the electrochemical flow cell comprises the

electrodialysis membrane or the cation exchange membrane and the anion exchange membrane, and wherein the electrodialysis membrane or the cation exchange membrane and the anion exchange membrane are disposed in the channel to create an anode compartment, a soluble sulfate salt compartment, and a cathode compartment, and wherein the feeding the supernatant through the channel comprises feeding the supernatant through the soluble sulfate salt compartment.

6. The method of any of claims 1-5, further comprising contacting a second portion of the lead paste with at least a portion of the regenerated base.

7. The method of any of claims 1-6, further comprising separating a sulfuric acid solution, metallic lead, and a plastic component from the lead acid battery to thereby provide the lead paste.

8. The method of any of claims 1-7, wherein the base comprises at least one of an alkali or alkaline earth metal hydroxide and a carbonate, and the insoluble lead salt comprises at least one of a lead oxide, a lead hydroxide, and a lead carbonate.

9. The method of any of claims 1-8, wherein the soluble sulfate salt comprises sodium sulfate, the base comprises sodium hydroxide, and the insoluble lead salt comprises lead hydroxide.

10. The method of any of claims 1-9, wherein the separating the supernatant from the precipitate is performed by at least one of settling, centrifugation, and filtration.

11. The method of any of claims 1-10, wherein the segmented anode comprises a first anode segment and a second anode segment, and the segmented cathode comprises a first cathode segment and a second cathode segment, and the first cathode segment and first anode segment are positioned upstream of the second cathode segment and second anode segment with respect to flow direction of the supernatant.

12. The method of claim 11, further comprising individually controlling current at each of the first cathode segment, the first anode segment, the second cathode segment, and the second anode segment.

13. The method of any of claims 11-12, wherein current at the second cathode segment and the second anode segment is higher than current at the first cathode segment and the first anode segment.

14. The method of claim 11, further comprising adjusting a first current at the first cathode segment and the first anode segment to a second current that is higher than the first current as the concentration of the soluble sulfate salt decreases at at least one of the first cathode segment and the first anode segment.

15. The method of any of claim 1-14, further comprising contacting the insoluble lead salt with an electrochemically stable solvent to generate solvated lead ions in the

electrochemically stable solvent.

16. The method of claim 15, further comprising treating the electrochemically stable solvent containing the solvated lead ions in an electrochemical cell to recover lead.

17. The method of any of claims 1-16, wherein the precipitate is substantially free of sulfate.

18. The method of claim 1, further comprising contacting a second portion of the lead paste with at least a portion of the regenerated base.

19. The method of claim 1, further comprising separating a sulfuric acid solution, metallic lead, and a plastic component from the lead acid battery to thereby provide the lead paste.

20. The method of claim 1, wherein the base comprises at least one of an alkali or alkaline earth metal hydroxide and a carbonate, and the insoluble lead salt comprises at least one of a lead oxide, a lead hydroxide, and a lead carbonate.

21. The method of claim 1, wherein the soluble sulfate salt comprises sodium sulfate, the base comprises sodium hydroxide, and the insoluble lead salt comprises lead hydroxide.

22. The method of claim 1, wherein the separating the supernatant from the precipitate is performed by at least one of settling, centrifugation, and filtration.

23. The method of claim 1, wherein the segmented anode comprises a first anode segment and a second anode segment, and the segmented cathode comprises a first cathode segment and a second cathode segment, and the first cathode segment and first anode segment are positioned upstream of the second cathode segment and second anode segment with respect to flow direction of the supernatant.

24. The method of claim 23, further comprising individually controlling current at each of the first cathode segment, the first anode segment, the second cathode segment, and the second anode segment.

25. The method of any of claims 23-24, wherein current at the second cathode segment and the second anode segment is higher than current at the first cathode segment and the first anode segment.

26. The method of claim 23, further comprising adjusting a first current at the first cathode segment and the first anode segment to a second current that is higher than the first current as the concentration of the soluble sulfate salt decreases at at least one of the first cathode segment and the first anode segment.

27. The method of claim 1, further comprising contacting the insoluble lead salt with an electrochemically stable solvent to generate solvated lead ions in the electrochemically stable solvent.

28. The method of claim 27, further comprising treating the electrochemically stable solvent containing the solvated lead ions in an electrochemical cell to recover lead.

29. The method of claim 1, wherein the precipitate is substantially free of sulfate.

30. A system for recovering sulfate as sulfuric acid from a lead paste of a lead acid battery, comprising:

a separation unit configured to separate a two-phase reaction product of the lead paste into a supernatant having a soluble sulfate salt and a precipitate having an insoluble lead salt;

an electrochemical flow cell fluidly coupled to the separation unit and configured to receive the supernatant and electrolytically generate sulfuric acid and a base from the supernatant;

wherein the electrochemical flow cell comprises a plurality of anode segments, a plurality of cathode segments, and a separator disposed between the plurality of anode segments and the plurality of cathode segments; and a controller electronically coupled to the electrochemical flow cell and configured to control current at the plurality of anode segments and the plurality of cathode segments as a function of a concentration of the soluble sulfate salt.

31. The system of claim 30, wherein the separator comprises a cation exchange membrane, an anion exchange membrane, or an electrodialysis membrane.

32. The system of claim 31, wherein the separator comprises the cation exchange membrane.

33. The system of claim 31, wherein the separator comprises the anion exchange membrane.

34. The system of claim 30, wherein the separator comprises an electrodialysis membrane or the cation exchange membrane and the anion exchange membrane, and wherein the separator is configured to create a soluble sulfate salt compartment disposed between an anode compartment and a cathode compartment.

35. The system of claim 34, wherein the separator comprises the cation exchange membrane and the anion exchange membrane.

36. The system of claim 34, wherein the separator comprises the electrodialysis membrane.

37. The system of claim 30, wherein the separation unit comprises at least one of a settler, a centrifuge, and a filtration unit.

38. The system of claim 30, wherein the controller is configured to individually control current at each of the plurality of anode segments and the plurality of cathode segments as a function of a concentration of the soluble sulfate salt.

39. A method of processing sulfate in a lead acid battery recycling process, comprising: obtaining lead paste from a lead acid battery that comprises lead sulfate;

contacting a first portion of the lead paste with a base to thereby generate a

separating the supernatant from the precipitate;

feeding the supernatant through a channel of the electrochemical flow cell, wherein the channel comprises a first cathode and anode segment upstream of a second cathode and anode segment with respect to flow direction of the supernatant; applying a first current at the first cathode and anode segment as a function of a first concentration of the soluble sulfate salt at the first cathode and anode segment, and applying a second current at the second cathode and anode segment as a function of a second concentration of the soluble sulfate salt at the second cathode and anode segment to collectively form sulfuric acid and a regenerated base.

40. The method of claim 39, wherein the electrochemical flow cell comprises a cation exchange membrane that is disposed in the channel to form an anode compartment and a cathode compartment, and wherein feeding the supernatant through the channel comprises feeding the supernatant through the anode compartment.

41. The method of claim 39, wherein the electrochemical flow cell comprises an anion exchange membrane that is disposed in the channel to create an anode compartment and a cathode compartment, and wherein the feeding the supernatant through the channel comprises feeding the supernatant through the cathode compartment.

42. The method of claim 39, wherein the electrochemical flow cell comprises an

electrodialysis membrane or a cation exchange membrane and an anion exchange membrane disposed in the channel to create a soluble sulfate salt compartment between an anode compartment and a cathode compartment, and wherein the feeding the supernatant through the channel comprises feeding the supernatant through the soluble sulfate salt compartment.

43. The method of claim 39, wherein the separating the supernatant from the precipitate is performed by at least one of settling, centrifugation, and filtration.

44. The method of claim 39, further comprising contacting a second portion of the lead paste with at least a portion of the regenerated base.

45. The method of claim 39, wherein the base comprises at least one of a metal hydroxide and a carbonate, and the insoluble lead salt comprises at least one of a lead oxide, a lead hydroxide, and a lead carbonate.

46. The method of any of claims 39-45, wherein the soluble sulfate salt comprises sodium sulfate, the base comprises sodium hydroxide, and the insoluble lead salt comprises lead hydroxide.

47. A method of recycling sulfate as sulfuric acid from a lead acid battery, comprising:

disassembling the lead acid battery and collecting a first portion of a lead paste from the lead acid battery, wherein the lead paste comprises lead sulfate;

separating the supernatant from the precipitate; pumping the supernatant through at least one of a cathode compartment, a soluble sulfate salt compartment, and an anode compartment disposed between a plurality of anode segments and a plurality of cathode segments of an electrochemical flow cell to generate sulfuric acid and a regenerated base; wherein the electrochemical flow cell comprises at least one of a cation exchange membrane, an anion exchange membrane, and an electrodialysis membrane to form the at least one cathode compartment, soluble sulfate salt compartment, and anode compartment;

collecting the sulfuric acid for manufacturing a new lead acid battery; and contacting a second portion of the lead paste with at least a portion of the regenerated base.

48. The method of claim 47, further comprising individually controlling current at each of the plurality of cathode segments and the plurality of anode segments.

49. The method of any one of claims 47-48, further comprising contacting the insoluble lead salt with an electrochemically stable solvent to generate solvated lead ions in the

electrochemically stable solvent, and treating the electrochemically stable solvent containing the solvated lead ions in a electrochemical cell to recover lead.

50. The method of claim 49, further comprising utilizing the lead in the manufacture of the new lead acid battery.

51. The method of claim 47, wherein the pumping the supernatant further comprises pumping the supernatant through the cathode compartment when the electrochemical flow cell comprising the anion exchange membrane, pumping the supernatant through the anode compartment when the electrochemical flow cell comprising the cation exchange membrane, or pumping the supernatant through the soluble sulfate salt compartment when the electrochemical flow cell comprises the electrodialysis membrane.

52. Use of a plurality of anode and cathode segments in an electrochemical flow cell to generate sulfuric acid and a regenerated base from a sodium sulfate solution produced in lead acid battery recycling, wherein at least one of an electrodialysis membrane, a cation exchange membrane and an anion exchange membrane are disposed within the electrochemical flow cell to separate the sulfuric acid from the regenerated base, and wherein current at each of the plurality of anode and cathode segments is individually controlled.

53. The use of claim 52, wherein the plurality of anode and cathode segments comprises a first anode and cathode segment positioned upstream of a second anode and cathode segment with respect to a flow direction of the sodium sulfate solution.

54. The use of any of claims 52-53, further comprising a controller coupled to the plurality of anode and cathode segments configured to control current to the plurality of anode and cathode segments as a function of a concentration of a soluble sulfate salt in the

electrochemical flow cell.

55. The use of claim 52, wherein the electrochemical flow cell comprises the cation exchange membrane, and wherein the cation exchange membrane forms a cathode compartment and an anode compartment.

56. The use of claim 52, wherein the electrochemical flow cell comprises the anion exchange membrane, and wherein the anion exchange membrane forms a cathode compartment and an anode compartment.

57. The use of claim 52, wherein the electrochemical flow cell comprises the electrodialysis membrane or the anion exchange membrane and the cation exchange membrane.