Stable lead dioxide anode and method of use

Abstract

An aspect disclosed herein is a method of stabilizing a lead anode, the method comprising operating an electrochemical cell comprising conducting electrochemical reduction at a first cathode and electrochemical oxidation at the first anode, the electrochemical cell comprising a first anolyte chamber in contact with the first anode, a first catholyte chamber in contact with the first cathode, and a first separator separating the first anolyte from the first catholyte, the first anode being a lead electrode, the first anolyte and the first catholyte each independently comprising aqueous iron cations and aqueous anions, the first anolyte comprising aqueous iron cations at a concentration selected from the range of 0.01M to 0.5M.

Description

Detailed Description of the Invention

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 410,092, filed September 26, 2022, which is incorporated herein by reference in its entirety for all purposes unless inconsistent herewith.

[0002] [Background of the invention]

[0002] Lead electrodes are useful as oxygen evolution anodes for the oxygen evolution reaction (OER) in a variety of electrochemical systems. However, ongoing problems have complicated the use of lead electrodes in many such processes. Two major problems are: (1) mechanical delamination of lead oxide and lead sulfate materials from the electrode, causing dimensional instability, loss of catalytic material, and loss of electrode conductivity, ultimately limiting electrode life; and (2) manganese oxide deposits collect on and around the electrode, requiring regular cleaning to prevent blockage of PbO catalytic sites and uneven current distribution. For example, manganese metal is typically included in zinc electrowinning anolyte to minimize lead dissolution and incorporation into the plated zinc. Manganese can also be present as an impurity in the initial process feedstock, such as ore.

[0003]

[0003] When OER at the anode is required, a typical solution in the art to avoid the above problems is to not use inexpensive lead anodes and instead utilize more expensive OER anodes, such as iridium-based anode materials. In addition to being expensive, iridium-based anode materials have their own set of challenges, such as limited international supply.

[0004]

[0004] To utilize inexpensive lead anodes for OER, the above-mentioned challenges and others are addressed by the methods, systems, and related aspects disclosed herein.

[0005] [Summary of the Invention] Aspects disclosed herein include a method of stabilizing a lead anode, the method comprising operating an electrochemical cell comprising performing electrochemical reduction at a first cathode and electrochemical oxidation at a first anode; The electrochemical cell includes a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte, the first anode being a lead electrode, the first anolyte and the first catholyte each independently comprising aqueous iron cations and aqueous anions, and the first anolyte comprising aqueous iron cations at a concentration of at least 0.01M.

[0006] Aspects disclosed herein include a method of stabilizing a lead anode, the method comprising operating an electrochemical cell comprising performing electrochemical reduction at a first cathode and electrochemical oxidation at the first anode, and recycling a second electrolyte from a metal electroplating cell to a first anolyte, the second electrolyte having aqueous iron cations, the electrochemical cell comprising a first anode chamber having the first anolyte in contact with the first anode, a second anode chamber having the first anolyte in contact with the first cathode, and a third anode chamber having the first anolyte in contact with the first cathode. The present invention also includes a method for producing an electrolyte electrolyte membrane comprising: a first cathode chamber having an anolyte; and a first separator separating the first anolyte from the first catholyte, wherein the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; and the first anolyte comprises aqueous iron cations at a concentration of at least 0.01 M and no more than 0.5 M, optionally no more than 0.45 M, optionally no more than 0.445 M, optionally no more than 0.44 M, and optionally no more than 0.4 M. Optionally, in aspects herein, the first anolyte comprises aqueous iron cations at a concentration of at least 0.01 M and no more than 0.4 M (in some embodiments, no more than 0.44 M, and in some embodiments, no more than 0.445 M). Optionally, in aspects herein, the first anolyte comprises aqueous iron cations at a concentration of at least 0.02 M and no more than 0.4 M. Optionally in embodiments herein, the first anolyte comprises aqueous iron cations at a concentration of at least 0.03 M and not more than 0.4 M. Optionally in embodiments herein, the first anolyte comprises aqueous iron cations at a concentration of at least 0.04 M and not more than 0.4 M. Optionally in embodiments herein, the first anolyte comprises aqueous iron cations at a concentration of at least 0.05 M and not more than 0.4 M. Optionally in embodiments herein, the first anolyte comprises aqueous iron cations at a concentration of at least 0.1 M and not more than 0.4 M.

[0007] Aspects disclosed herein include a method for stabilizing a lead anode, the method comprising operating an electrochemical cell comprising conducting an electrochemical reduction at a first cathode and an oxygen evolution reaction (OER) at the first anode, the electrochemical cell comprising a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first anolyte in contact with the first cathode, and a first separator separating the first anolyte from the first anolyte, the first anode being a lead electrode, the first anolyte and the first anolyte each independently comprising aqueous iron cations and aqueous anions, and the first anolyte comprising aqueous iron sulfate at a concentration of at least 0.01M.

[0008]

[0008] Anion exchange membranes (AEMs) can "leak" cations transported toward the negative electrode by diffusion and electric fields. Therefore, maintaining the iron sulfate concentration within a target range (also referred to herein as a stable concentration range for iron cations) requires the addition of aqueous iron cations to replace the aqueous iron lost through the leakage. Optionally, for example, in some embodiments, replenishing or maintaining the stable or target concentration range for iron cations in the anolyte can be achieved by flowing the anolyte, or a portion thereof, through one or more solid iron salts, such as ferrous sulfate and / or ferric sulfate, ferric oxide and / or ferrous oxide, metallic iron, magnetite, or any combination thereof. Optionally, for example, in some embodiments, replenishing or maintaining the stable or target concentration range for iron cations in the anolyte can be achieved by adding the anolyte to or dosing the anolyte into an aqueous solution having aqueous iron cations (also referred to herein as an aqueous dosing solution or liquid iron source). Optionally, for example, in some embodiments, metallic iron may be provided in the catholyte, or the catholyte may be exposed to metallic iron to consume protons (acid) that leak from the anolyte into the AEM.

[0009] Aspects disclosed herein include a method comprising operating an electrochemical cell, including performing electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, wherein the electrochemical cell comprises a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first anolyte in contact with the first cathode, and a first separator separating the first anolyte from the first anolyte, wherein the first anode is a lead electrode, and each of the first anolyte and the first anolyte independently comprises aqueous iron cations and aqueous anions, and the method further comprises dissolving solid manganese oxide in the first anolyte in the presence of aqueous ferrous ions.

[0010]

[0010] Aspects disclosed herein include a method comprising the step of operating an electrochemical cell, which comprises performing electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, wherein the electrochemical cell comprises a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first anolyte in contact with the first cathode, and a first separator separating the first anolyte from the first anolyte, wherein the first anode is a lead electrode, and the first anolyte and the first anolyte each independently comprise aqueous iron cations and aqueous anions, and the method further comprises the step of applying a reverse bias to the first anode for a finite time, which comprises electrochemically reducing aqueous ferric ions to aqueous ferrous ions in the presence of the first anolyte at the first anode.

[0011]

[0011] Aspects disclosed herein include a method comprising operating an electrochemical cell comprising performing electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, wherein the electrochemical cell comprises a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first anolyte in contact with the first cathode, and a first separator separating the first anolyte from the first anolyte, wherein each of the first anode and the first cathode is independently a lead electrode, and each of the first anolyte and the first anolyte independently comprises aqueous iron cations and aqueous anions.

[0012]

[0012] While not wishing to be bound by any particular theory, a discussion of underlying principles or understandings related to the devices and methods disclosed herein may be made herein. It is recognized that regardless of the ultimate accuracy of any mechanistic explanation or hypothesis, embodiments of the invention may nevertheless be functional and useful. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating a cross-section of a three-dimensional porous substrate with a layer of lead on one or both sides. [Figure 2] FIG. 1 is a schematic diagram illustrating a cross-sectional view of a bipolar electrode structure. [Figure 3] FIG. 1 is a schematic diagram illustrating a cross-sectional view of a bipolar stack including a series of bipolar electrodes between end plates. [Figure 4] FIG. 1 is a schematic diagram illustrating a cross-sectional view of a bipolar electrode structure, showing some example reactions that may optionally be catalyzed by each electrode according to some embodiments. [Figure 5] FIG. 1 is a schematic diagram illustrating an acid generating ferric iron reduction cell optionally containing an oxygen evolving anode containing lead. [Figure 6] FIG. 1 is a schematic diagram illustrating an iron electroplating cell optionally equipped with an oxygen evolving anode comprising lead. [Figure 7]FIG. 1 is a schematic illustrating a two-stage iron conversion system having various subsystems including an oxygen evolution reaction at a first anode according to various embodiments herein. [Figure 8] FIG. 1 is a schematic diagram illustrating a two-stage iron conversion system having various subsystems including an oxygen evolution reaction at the anode of the acid regeneration subsystem (first anode) and an oxygen evolution reaction at the anode of the plating cell (second anode), according to various embodiments herein. [Figure 9] FIG. 1 is a schematic illustrating a two-stage iron conversion system with various subsystems including an oxygen evolution reaction at the anode (first anode) of the acid regeneration subsystem and further illustrating possible fluid flow between the subsystems. [Figure 10] FIG. 1 is a schematic illustrating a two-stage iron conversion system with various subsystems, including an oxygen evolution reaction at the anode of the acid regeneration subsystem (first anode) and an oxygen evolution reaction at the anode of the plating cell (second anode), and further illustrating possible fluid flow between the subsystems. [Figure 11] FIG. 1 is a schematic diagram illustrating an ore dissolution subsystem including an acid regeneration cell. [Figure 12A] Scanning electron microscope (SEM) images of the electrode surface (FIG. 12A) before electrochemical cycling in acid. The lead electrode exposed to acid and without aqueous iron cations has a surface with large PbSO crystals, making the lead electrode dimensionally unstable. The lead electrode exposed to acid with aqueous iron cations has much smaller PbSO crystals, corresponding to a dimensionally more stable lead electrode. [Figure 12B] Scanning electron microscope (SEM) image of an equivalent electrode surface, but after electrochemical cycling in sulfuric acid without dissolved iron (FIG. 12B). [Figure 12C] Scanning electron microscope (SEM) images of equivalent electrode surfaces but after electrochemical cycling in the presence of aqueous iron sulfate or sulfuric acid with dissolved iron ions (FIG. 12C). [Figure 13]1A-1C are a series of schematic diagrams illustrating potential mechanisms, according to some embodiments, that occur when a lead electrode is exposed to sulfuric acid without aqueous cations (left image) compared to when the lead electrode is exposed to sulfuric acid with aqueous iron cations, or ferric and / or ferrous sulfate (right image). Generally, in the absence of iron sulfate, large surface destabilized PbSO4 crystals form, and the destabilizing effect is enhanced when oxygen bubbles emanate from the surface. In contrast, generally, according to some embodiments, the presence of iron sulfate prevents, or significantly impedes, or slows the formation of large PbSO4 crystals, including when oxygen bubbles emanate from the surface, resulting in a stable, robust surface. In some embodiments, the presence of iron sulfate can result in the formation of a protective layer, optionally including an Fe—Pb—SO4 composition (e.g., Fe—Pb—SO4), on the lead electrode surface. [Figure 14] As named, this is a series of SEM images of Pb and PbO2 surfaces after 12 hours of immersion in H2SO4, PbSO4, or Pb2(SO4)3, followed by air drying (no liquid wash). In particular, it is clear that the PbO2 exposed to sulfuric acid in the absence of iron sulfate has a significantly rougher surface with large crystals of PbSO4 compared to the other surfaces shown. [Figure 15] 1 is a series of SEM images of Pb surfaces exposed to 1 M ferric sulfate (top image) or 0.1 M sulfuric acid (bottom image) for 1 day at a 50% duty cycle at about 30 mA / cm or about 50 mA / cm.

[0014] Compound and nomenclature descriptions

[0028] Generally, the terms and phrases used herein have their art-recognized meanings, which can be found by reference to standard textbooks, periodical references, and contexts known to those of ordinary skill in the art. The following definitions are provided to clarify their specific use in the context of this disclosure.

[0015]

[0029] As used herein, the term "electrolyte" refers to an aqueous solution containing one or more dissolved ionic species. The electrolyte may be acidic, basic, or neutral in pH, although examples herein are described in terms of acidic electrolytes.

[0016]

[0030] As used herein, the term "anolyte" refers to the electrolyte in contact with the "anode" electrode. Similarly, the term "catholyte" refers to the electrolyte in contact with the "cathode" electrode. In some examples and embodiments, the anolyte and catholyte may be maintained as distinct, unmixed solutions, typically separated from each other by a separator membrane within the electrochemical cell and by separate fluid conduits outside the cell. However, in some cases, the terms "anolyte" and "catholyte" may refer to a single electrolyte, such as in an undivided electrochemical cell.

[0017]

[0031] In the art of electrochemical cells, such as with respect to electrolytic cells, an anode refers to the electrode where electrochemical oxidation occurs, and a cathode refers to the electrode where electrochemical reduction occurs. As used herein, reverse-biasing an anode refers to applying a voltage such that electrochemical reduction occurs at the anode. As used herein, when an anode is reverse-biased, reduction occurs at the anode during reverse biasing, but the name of the anode is not changed, but rather characterized as reverse-biased for purposes of consistent electrode identification. Optionally, but not necessarily, an anode may be reverse-biased by applying a negative potential to the anode, or by applying a potential that is more or less negative than the potential on the respective counter electrode (e.g., cathode), such that electrons may flow from the electrical circuit to the reverse-biased anode in the presence of an electrolyte, facilitating electrochemical reduction at the reverse-biased anode. Optionally, but not necessarily, reverse-biasing an anode specifically refers to a potential on the anode such that ferric ions are reduced to ferrous ions at the anode.

[0018]

[0032] The term "lead electrode" refers to an electrode having lead and / or lead oxide exposed to an electrolyte, e.g., anolyte. A lead electrode optionally comprises, or optionally is formed essentially of, bulk lead. Optionally, the lead electrode may comprise one or more layers of lead and / or lead oxide on a different material that serves as a mechanical and electrical support and / or substrate, such that the lead and / or lead oxide is exposed to the electrolyte. As the oxygen evolution reaction (OER) proceeds, the lead metal surface of the lead electrode is converted into lead oxide (PbO x ), or in some embodiments first to lead sulfate (PbSO4) in the presence of sulfate ions, and then to lead oxide (PbO x ) oxidizes to PbSO4. Thus, some lead electrodes may also contain PbSO4. Lead electrodes may contain intentional dopants and / or alloying species to modify their electrochemical or other properties. As used herein, the formula PbO x includes lead dioxide (PbO2), and further includes non-stoichiometric oxygen-deficient modifications of lead (di)oxide, e.g., x is 1 to 2. As used herein, the formula PbO2 is a shorthand expression for lead dioxide, and compounds represented by the formula PbO2 are PbO x It is intended to include non-stoichiometric oxygen deficient variants thereof to include those represented by

[0019]

[0033] The terms "aqueous iron cation" and "aqueous iron ion" as used herein, including the claims, refer to all aqueous iron cations in any oxidation state, such as at least aqueous ferrous iron (Fe 2+ (aq) ) ions and aqueous ferric (Fe 3+ (aq) ) ions.

[0020]

[0034] The term "solid manganese oxide" refers to any solid manganese oxide or undissolved precipitate of manganese oxide. 2-δ ”, “Solid MnO x The terms "solid MnO2" and "solid MnO2" are used interchangeably. xwhere x is greater than or equal to 1 and less than or equal to 2. The term "manganese oxide" refers to manganese dioxide (MnO2) and has the formula MnO 2-δ and / or formula MnO x where δ is greater than or equal to 0 and less than or equal to 1, and x is greater than or equal to 1 and greater than or equal to 2. Optionally, the term "manganese oxide" may refer to, but is not limited to, manganese(II) oxide (MnO), manganese(II, III) oxide (Mn3O4), manganese(III) oxide (Mn2O3), manganese(VI) oxide (MnO3), manganese(VII) oxide (Mn2O7), Mn5O8, Mn7O 12 and MnO 13 As used herein, the formula MnO2 is a shorthand expression for manganese dioxide, and the compound represented by the formula MnO2 is MnO. x where x is 1 to 2, inclusive.

[0021]

[0035] The term "manganese sulfate" refers to MnSO. Optionally, the term "manganese sulfate" refers to MnSO and further other manganese sulfate species.

[0022]

[0036] The term "depleted" electrolyte is intended to be consistent with the terminology used in Applicant's International Application PCT / US2022 / 021732, entitled "Two-Stage Iron Conversion System," published on September 29, 2022, as PCT International Publication No. 2022204394 (hereinafter referred to as "PCT '732," which is incorporated herein by reference and also included as Appendix A to U.S. Provisional Patent Application No. 63 / 410,092, filed September 26, 2022 (hereinafter referred to as "Provis '092")), the benefit of and priority to which is claimed herein and which is incorporated herein by reference in its entirety. Generally, depleted electrolyte, which may be depleted catholyte and / or depleted anolyte, is an electrolyte that has been used in electrochemical reduction and / or electrochemical oxidation in an electrochemical cell and is then removed from its respective electrochemical cell. For example, a depleted catholyte (or anolyte) is a part of an electrochemical reduction (or oxidation) reaction in an electrochemical cell that is subsequently removed from the electrochemical cell. During each electrochemical reaction (reduction or oxidation) that occurs in the presence of an electrolyte (catholyte or anolyte), one or more reagents (e.g., iron ions) may be depleted and / or one or more products may be deposited in the electrolyte. Thus, a depleted electrolyte may optionally be characterized as an electrolyte in which one or more reagents have been depleted and / or one or more products have been deposited during the respective electrochemical reaction in amounts that are technically and / or commercially undesirable or undesirable for the same respective electrochemical reaction, and therefore the depleted electrolyte is removed from its respective electrochemical cell. For example, the catholyte in an iron electroplating cell, e.g., a second catholyte in a second electrochemical cell according to embodiments of PCT '732 and Provis '092, may be depleted of ferrous ions during iron electroplating to the extent that it is preferable to remove the (depleted) catholyte from the electroplating cell. The removed (depleted) catholyte, which has ferrous ions at a concentration too low for electroplating, may then optionally be recycled, directly or indirectly, to the first anolyte of an electrochemical cell according to embodiments disclosed herein. The removal and recycling of the depleted electrolyte may be carried out as part of a batch or continuous process.

[0023]

[0037] As used herein, the terms "pure iron" and "high purity iron" are used in a relative sense to refer to a metallic iron material that is purer than the iron source material and contains an acceptably low amount of one or more impurities.

[0024]

[0038] As used herein, the terms "iron source material" and "iron raw material" are used interchangeably to refer to iron-containing materials that may be used as input to the various systems and methods described herein. "Iron source material," "iron raw material," and "solid iron-containing material" can include iron in any form, such as iron oxide (e.g., iron(II) sulfate, iron(III) sulfate, iron(II) chloride, iron(III) chloride, iron oxide, iron hydroxide, iron oxyhydroxide, iron carbonate, or other iron-containing compounds, ores, rocks, or minerals (including any mixtures thereof) in their natural state or in a beneficiated or otherwise refined or modified state. The terms "iron-containing ore" or simply "iron ore" refer to iron-containing ore in its natural state or in a beneficiated or otherwise refined or modified state. Regardless of the type, iron ore may include materials recognized, known, or referred to in the art as iron ore(s), rock(s), natural stone(s), precipitate(s), natural precipitate(s), minerals, and / or natural mineral(s). Some embodiments of the processes and systems described herein may be particularly useful for iron ores including hematite, goethite, magnetite, limonite, siderite, ankerite, tergite, bauxite, or any combination thereof.

[0025]

[0039] Optionally, the ferrous source material or raw ferrous material may include ferrous metal materials such as, but not limited to, iron dust (e.g., fine particles produced as a by-product of the iron or steel making process in a blast furnace, oxygen furnace, electric arc furnace, etc.), iron powder, scrap steel, and / or scrap cast iron. "Iron source material" and "ferrous raw material" may also contain various other non-ferrous materials, commonly referred to as "impurities."

[0026]

[0040] As used herein, the term "impurity" refers to elements or compounds other than the desired end product material (e.g., iron). In various embodiments, a given element or compound may or may not be considered an "impurity" depending on the intended end use of the product material. In some cases, one or more elements or compounds that may be impurities to one process or subprocess may be isolated or purified, collected, and sold as a secondary product material.

[0027]

[0041] In various embodiments herein, various compositions, compounds, or solutions may be substantially "isolated" or "purified" to a degree sufficient for the purposes described herein. In various embodiments, a substantially purified composition, compound, or formulation (e.g., a ferrous solution, a ferric solution, or plated metallic iron) may have a chemical purity of 90%, optionally in some applications 95%, optionally in some applications 99%, optionally in some applications 99.9%, optionally in some applications 99.99%, and optionally in some applications 99.999% pure (e.g., by molarity of ion concentration or by weight).

[0028]

[0042] References herein to a "tank" are intended to include any vessel suitable for containing a liquid, such as a highly acidic or caustic aqueous solution, as appropriate. In some embodiments, such vessels may include additional features or components to aid or improve mixing of the solid and / or liquid contents of the vessel. For example, a dissolving tank may include passively or actively operating structures or features for agitating the solution or solid / liquid mixture. Dissolving tanks or other tanks useful in the systems and methods herein may also include features to allow for sparging of gas into or through the solid and / or liquid contents of the tank to increase contact of the gas with the solid and / or liquid materials within the tank. Various tanks may also include baskets, sieves, pans, filters, or other structures for collecting and separating solids from liquids. In some embodiments, the tank may be configured to direct the flow of liquid or gas through the tank in a manner to agitate the mixture therein (e.g., flow-directing structures, pumps, impellers, baffles, impellers, stirrer rods, stirring blades, vibrators, cyclone channels, etc.).

[0029]

[0043] In some embodiments described herein, a system for converting iron ore to iron metal (i.e., an "iron conversion system") may comprise two or more subsystems. Some embodiments include a "dissolution subsystem" in which components of an iron-containing feedstock are dissolved in an aqueous solution. Some embodiments further include an "iron plating subsystem" in which the dissolved iron is electrochemically reduced to iron metal in an "electroplating" (or simply "plating") process. The iron metal may then be removed from the iron plating subsystem.

[0030]

[0044] The term "iron electroplating" (or "iron plating" used synonymously herein) refers to a process in which dissolved iron is electrochemically reduced to metallic iron on a cathode surface. The equivalent terms "electrodeposition," "electroforming," and "electrowinning" are also used synonymously herein with "iron electroplating." The shape or form factor of the electroplated iron need not be a "plate" by any definition of that term. For example, the electroplated iron can take any shape or form and can be deposited on any suitable cathode surface as described in various aspects herein.

[0031]

[0045] The term "dissolution step" refers to the processes occurring in the dissolution subsystem, including, but not limited to, dissolution of iron oxide materials, and the regeneration of Fe in the acid regeneration cell. 3+ ions to Fe 2+ The dissolution step process may also include oxidizing water or hydrogen gas in the first electrochemical cell to produce, for example, protons, which may allow for the regeneration of acid (in the form of protons) used to facilitate dissolution of the iron-containing feedstock.

[0032]

[0046] The terms "acid regenerator" and "acid regeneration cell" refer to an electrochemical cell according to any one of the embodiments and aspects herein, such as those described in any one of Aspects 1-56 below. Optionally, the "acid regenerator" and "acid regeneration cell" may correspond to and / or further include any of the embodiments or aspects disclosed in PCT '732 and Provis '092, which are incorporated herein as part of this disclosure.

[0033]

[0047] The term "iron plating step" refers to the process of plating Fe in a "plating cell," also referred to herein as a "plating cell." 2+The iron plating process also includes the process(es) occurring within the iron plating subsystem, including, but not limited to, the electrochemical process(es) occurring within or through the claimed "plating cell," including, but not limited to, the step of "electrochemically reducing" Fe ions to Fe metal. 2+ Oxidize the second part of the ions to Fe 3+ In some embodiments, such Fe ions may be formed. 2+ The ions may be supplied from the first electrochemical cell or from another part of the system.

[0034]

[0048] As used herein, unless otherwise specified, a "ferrous iron solution" or "ferrous solution" refers to a solution containing at least a majority (i.e., 50% to 100%) of Fe. 2+ (i.e., "ferrous") ions, and the remainder of the dissolved iron is "ferric" Fe 3+ Similarly, the term "ferrous ion" can refer to an aqueous solution containing dissolved iron, which is in the form of ferrous iron (Fe 2+ ) state.

[0035]

[0049] As used herein, unless otherwise specified, a "ferric iron solution" or "ferric solution" refers to a solution containing at least a majority (i.e., 50% to 100%) of Fe. 3+ (i.e. "ferric") ionic state, and the remainder of the dissolved iron is "ferrous" Fe 2+ Similarly, the term "ferric ion" can refer to an aqueous solution containing dissolved iron (Fe 3+ ) state. Either a "ferric solution" or a "ferrous solution" may also contain other dissolved ions or colloidal or particulate material, including impurities.

[0036]

[0050] As used herein, any reference to "PEM" or "proton exchange membrane" may be construed as also including "CEM" or "cation exchange membrane," both of which terms may include any available membrane material that selectively allows positively charged cations and / or protons to pass through. The abbreviation "AEM" is used to refer to anion exchange membranes that are selective for negatively charged aqueous ions, and includes any available anion-selective membranes.

[0037]

[0051] As used herein, aqueous protons and electrochemically generated protons are intended to include aqueous protons and aqueous hydronium ions.

[0038]

[0052] As used herein, the term "raw ore" refers to iron-bearing ore that has not been thermally reduced or air roasted according to embodiments disclosed herein. The raw ore is optionally an iron-bearing raw ore.

[0039]

[0053] As used herein, electrochemically generated ions, such as electrochemically generated protons and electrochemically generated iron ions (e.g., Fe 2+ , Fe 3+ ) refers to ions produced or produced in an electrochemical reaction. For example, the electrochemical oxidation of water at the anode may result in electrochemically generated protons and electrochemically generated oxygen.

[0040]

[0054] As used herein, the term "air roasting" refers to a heat treatment carried out at an elevated temperature in the presence of air. Air roasting of ores, such as iron-bearing ores, can reduce the average particle size of the ore or the ore. Optionally, air roasting is carried out at a temperature selected from the range of 300°C to 500°C. Additional description and potentially useful aspects of air roasting can be found in the following reference, which is incorporated herein in its entirety: "Study of the calcination process of two limonitic iron ores between 250°C and 950°C," Revista de la Facultad de Ingeneria, p. 33 (2017).

[0041]

[0055] As used herein, the term "redox pair" refers to two chemical species, such as ions and / or molecules, that correspond to the reduced and oxidized species of an electrochemical reaction or half-cell reaction. For example, Fe 3+ ions to Fe 2+ In the electrochemical reduction of Fe ions, the corresponding redox couple is Fe 3+ / Fe 2+ and Fe 3+ is an oxidized species, and Fe 2+ is the reduced species. As used herein, the order in which redox pairs are listed (e.g., Fe 3+ / Fe 2+ vs. Fe 2+ / Fe 3+ ) is not intended to indicate which species is the reduced species and which is the oxidized species. Additional explanations and potentially useful aspects of redox couples can be found in the following reference, which is incorporated herein in its entirety: "Redox - Principles and Advanced Applications": Book by Mohammed Khalid, Chapter 5: Redox Flow Battery Fundamental and Applications.

[0042]

[0056] As used herein, the terms "steady state" and "steady-state" generally refer to a condition or set of conditions characterizing a process, method step, reaction(s), solution, (sub-)system, etc. that are true longer than they are not true during operation or performance of the process, method step, reaction(s), solution, (sub-)system, etc. For example, the dissolution of an ore or feedstock may be characterized by steady-state conditions that are true for at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90%, optionally at least 95% of the time that dissolution is occurring. For example, steady-state conditions may exclude conditions that characterize transient start-up and shutdown phases of a process, such as the dissolution of a feedstock.

[0043]

[0057] The term "cathode chamber" refers to the area, compartment, reservoir, etc. containing the cathode, or at least a portion of its surface, and the catholyte. The term "anode chamber" refers to the area, compartment, reservoir, etc. containing the anode, or at least a portion of its surface, and the anolyte.

[0044]

[0058] As used herein, the term "iron-rich solution" may also be referred to as "ferrous iron-rich solution" or "ferrous product solution," which corresponds to the solution rich in iron ions formed in the ore dissolution subsystem.

[0045]

[0059] As used herein, the term "precipitation pH" refers to the pH at which one or more referenced ions or salts are thermodynamically favorable to precipitate or are predicted to precipitate from a host aqueous solution. Generally, the solubility of ions and salts dissolved in an aqueous solution may depend on the pH of the aqueous solution. As the pH increases, many metal ions form metal hydroxides, which tend to precipitate from the host solution due to their decreased solubility. Herein, the precipitation pH is defined as the pH corresponding to the point at which the solubility of a given ion or salt falls below a concentration threshold. The precipitation pH may be an upper limit above which the solubility of a given ion or salt is less than 1 mM, optionally less than 0.1 mM.

[0046]

[0060] As used herein, the term "metallic iron" refers to materials containing metallic iron, such as, but not limited to, scrap iron, electroplated iron, iron powder, and the like.

[0047]

[0061] As used herein, the terms "supporting salt" and "supporting ion" refer to salts and ions that correspond to or function as, or at least partially form, a supporting electrolyte upon dissolution to increase the conductivity of the host solution, respectively. In some embodiments, for example, the electrolytes and solutions of both the dissolution subsystem and the plating subsystem may contain dissolved iron species, an acid, and additionally an inert salt that functions as a supporting electrolyte to improve the electrolyte's conductivity. This can be particularly beneficial at low ferrous concentrations, and the inert salt that functions as a supporting electrolyte to improve conductivity may be referred to as a supporting salt. The supporting salt may include any electrochemically inert salt, such as sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, sodium chloride, potassium chloride, ammonium chloride, etc., or a combination of salts. The concentration of the supporting salt in the solution, if used, may range, for example, from about 0.1 to about 1 M.

[0048]

[0062] As used herein, the terms "dissolved iron," "dissolved iron ions," "aqueous iron," and "aqueous iron ions" are used interchangeably to refer to aqueous or dissolved iron ions, including ferrous ions, ferric ions, and combinations thereof, present in solution.

[0049]

[0063] As used herein, the term "wt.%" or "wt%" refers to weight percent, or mass fraction expressed as a percentage by mass. The term "at.%" or "at%" refers to atomic percent, or the atomic ratio expressed as a percentage of atoms of a certain type relative to all atoms in a given substance, such as a molecule, compound, material, nanoparticle, polymer, dispersion, etc. The term "mol.%" refers to mole percent, or percent by mole. The term "vol.%" refers to volume percent.

[0050]

[0064] The terms "substantially" and "about" interchangeably refer to a property, condition, or value that is within 20%, 10%, 5%, 1%, optionally within 0.1%, or equivalent to a reference property, condition, or value. The terms "substantially equal," "substantially equivalent," or "substantially unchanged," when used in conjunction with a reference value describing a property or condition, refer to a value that is within 20%, 10%, optionally within 5%, optionally within 1%, optionally within 0.1%, or optionally equivalent to the described reference value. For example, a diameter is substantially equal to or about equal to 100 nm (or "is substantially 100 nm" or "is about 100 nm") if the diameter value is within 20%, optionally within 10%, optionally within 5%, optionally within 1%, 0.1%, or optionally equal to 100 nm. The term "substantially greater than," when used in conjunction with a reference value describing a property or condition, refers to a value that is at least 1%, optionally at least 5%, optionally at least 10%, or optionally at least 20% greater than the reference value described. The term "substantially smaller than," when used in conjunction with a reference value describing a property or condition, refers to a value that is at least 1%, optionally at least 5%, optionally at least 10%, or optionally at least 20% less than the reference value described. As used herein, the term "about" refers to a range of values ​​that includes the specified value that one of ordinary skill in the art would consider to be reasonably close to the specified value. In embodiments, about means within a standard deviation using measurements generally accepted in the art. In embodiments, about means a range that extends to + / - 10% of the specified value. In embodiments, about means the specified value. In embodiments, the terms "about," "approximately," and "substantially" are interchangeable and have the same meaning. For example, particles having a size of about 1 μm may have a size within 20%, optionally within 10%, optionally within 5%, optionally within 1%, optionally within 0.1%, or optionally equal to 1 μm of 1 μm.

[0051]

[0065] As used herein, the term "and / or" is used herein to refer to only a single element or any combination of elements from a list in which the term and / or appears in the description and claims. In other words, a list of two or more elements with the term "and / or" is intended to include embodiments having only any individual element of the listed elements, or any combination thereof. For example, the phrase "element A and / or element B" is intended to include embodiments having only element A, only element B, or both elements A and B together. For example, the phrase "element A, element B, and / or element C" is intended to include embodiments having only element A, only element B, only element C, elements A and B together, elements A and C together, elements B and C together, or elements A, B, and C together.

[0052]

[0066] As used herein, the term "±" refers to an inclusive range of values, such as "X±Y" (where X and Y are each independently a number) refers to an inclusive range of values ​​selected from the range XY to X+Y. For "X±Y" (where Y is a percentage (e.g., 1.0±20%)), the inclusive range of values ​​is selected from the range XZ to X+Z (where Z is equal to X×(Y / 100)). For example, 1.0±20% refers to an inclusive range of values ​​selected from the range 0.8 to 1.2.

[0053] [Detailed Description of the Invention]

[0067] In the following description, numerous specific details of the devices, device components and methods of the present invention are set forth in order to fully explain the precise nature of the invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0054]

[0068] In aspects, the present disclosure provides processes, systems, and methods for stabilizing lead anodes against shedding, dissolution, and / or other decomposition processes, such as in the context of lead anodes used in oxygen evolution reactions (OER). In various aspects, the present disclosure provides processes, systems, and methods for reducing or eliminating solid manganese oxide sludge or contamination, which may deleteriously deposit in the anode chamber or anolyte, or which may foul or coat the anode, such as by dissolving manganese oxide in the anolyte. In various aspects, the present disclosure further includes processes, systems, and methods for enabling an efficient, low-temperature aqueous hydrometallurgical process for producing pure iron from a variety of iron source materials, including relatively low-purity iron feedstocks.

[0055]

[0069] Various additional useful aspects, embodiments and definitions of the present systems and methods are further described and exemplified in PCT '732 and Provis '092.

[0056]

[0070] Electrodes containing lead and / or lead oxide (typically lead dioxide) have been used as oxygen evolution anodes in various electrochemical systems for many years. However, persistent problems have complicated the use of lead electrodes in many processes. Two major problems include shedding and sludge formation.

[0057]

[0071] The "shedding" or mechanical spalling of lead oxide material, and in some embodiments lead sulfate, from the electrode causes dimensional instability, loss of catalytic material, and loss of electrode conductivity, ultimately resulting in limited electrode life. As a precursor to lead shedding, large crystals of PbSO4 typically form (see, e.g., the top right SEM image in Figure 14, labeled "PbO2 in H2SO4"), which promotes mechanical spalling, particularly by (re)starting OER.

[0058]

[0072] Manganese oxide deposits, or "sludge," collect on and around the electrodes and require periodic cleaning to prevent (a) PbO2 blockage, (b) permanganate formation, and (c) uneven current distribution, which can interfere with cell operation. For example, manganese ions are typically included in zinc electrowinning anolyte to minimize lead dissolution and incorporation into the plated zinc. Manganese can also be present because it is an impurity in the original process feedstock, e.g., iron ore.

[0059]

[0073] The unexpected discovery disclosed and contemplated herein includes that the operation of lead dioxide anodes in the presence of finite concentrations of dissolved iron facilitates the use of lead as a viable electrode material in iron electrowinning systems and / or other electrowinning systems. Furthermore, several system configurations, electrode structures, and methods of operation are contemplated that may advantageously utilize the discovered operation.

[0060]

[0074] First, it is discovered that, for example, in the presence of ferric sulfate, the surface of a lead dioxide electrode appears to behave very differently compared to an electrode in acid without ferric sulfate. When a lead electrode is cycled between OER and open-circuit rest in the presence of substantial ferric sulfate concentrations, the electrode surface remains denser and does not exhibit the highly crystalline, fractured, and broken surface seen on electrodes similarly cycled in sulfuric acid without ferric ions. In the absence of iron ions (e.g., ferric ions), the surface of a lead electrode can self-discharge to form PbSO4 in the presence of sulfate ions in the anolyte under transient or rest conditions, such as when the lead anode is at open-circuit voltage (OCV), a potential too low for OER, and / or if the potential on the anode decreases too rapidly. Without wishing to be bound by any particular theory, it is believed that iron-lead compounds (e.g., Fe ions) protect the lead electrode surface from the formation of large lead sulfate (PbSO4) crystals in the presence of iron ions (e.g., ferric ions) and sulfate ions in the anolyte. x Pb ySO4) can be formed, which is thought to be prone to shedding commonly seen with lead electrodes. Lead / lead dioxide electrodes operating in an electrolyte containing ferrous sulfate are found to be much more mechanically stable with less shedding than similar electrodes operating in an electrolyte without ferrous sulfate. Iron-lead compounds can also be smooth, which may promote the stability of the lead electrode surface.

[0061]

[0075] For example, Figure 14 shows a series of SEM images of Pb and PbO surfaces, as named, after 12 hours of immersion in H2SO4, PbSO4, or Pb2(SO4)3, followed by air drying (no liquid wash). It is clear that PbO2 exposed to sulfuric acid in the absence of iron sulfate has a significantly rougher surface with large agglomerates or crystals of PbSO4 compared to the other surfaces shown, even without current-voltage cycling. Figures 12B-12C show similar results after a lead oxide surface was electrochemically cycled, where electrochemical cycling in the presence of sulfuric acid without dissolved iron ions (Figure 12A) results in the formation of large PbSO4 crystals, while the presence of dissolved iron ions in sulfuric acid (Figure 12B) suppresses PbSO4 formation, so that any PbSO4 crystals present are much smaller and less destabilizing. FIG. 15 similarly shows images of lead electrode surfaces exposed to ferric sulfate or sulfuric acid, demonstrating that the surface of a lead electrode exposed to sulfuric acid without ferric sulfate becomes rougher, corresponding to poorer dimensional stability, compared to a lead electrode exposed to ferrous sulfate. Without being bound by any particular theory, FIG. 13 explains that, according to some embodiments, the presence of ferrous sulfate protects the PbO electrode surface from the formation of large, unstable PbSO crystals, or at least slows their formation. When oxygen bubbles emerge from the PbO electrode, they can aggressively destroy the surface roughness features and composition that are weakly attached to the surface, thereby causing Pb to slough off from the PbO electrode exposed to sulfuric acid. The reduction, delay, or prevention of PbSO crystal formation is achieved by the presence of ferrous sulfate in the electrolyte, thus stabilizing the PbO electrode.

[0062]

[0076] Accordingly, it is believed that lead may be advantageously used in a variety of electrochemical cells, including electrowinning cells (e.g., iron electrowinning cells with OER anodes), as an oxygen evolving anode in contact with an electrolyte (e.g., acidic, alkaline, or neutral pH) containing at least 0.01 M total dissolved iron (optionally at least 0.05 M), acid regeneration cells (e.g., cells with OER anodes and ferric reducing cathodes), and water electrolysis cells (e.g., PEM electrolyzers for hydrogen production). It is further believed that lead may be used as the anode and / or cathode in iron electroplating cells, such as those defined as an "iron plating subsystem" or its "second electrochemical cell" as described in PCT '732 and Provis '092, where ferrous iron is oxidized at the anode. As described in PCT '732 and Provis '092, it is further contemplated that in a two-stage (or "separated") iron electrowinning system, e.g., the "iron plating subsystem" as described in PCT '732 and Provis '092, at least a portion of the "expended" plating anolyte or catholyte may be directed as anolyte to the oxygen-evolving anode of an acid regeneration cell, e.g., the "dissolution subsystem" or "first electrochemical cell thereof" as described in PCT '732 and Provis '092.

[0063]

[0077] The use of a lead anode in an iron electrowinning cell can result in the incorporation of some amount of lead into the plated iron. It has been found that a ferrous sulfate plating electrolyte saturated with lead ions (optionally having ∼30-40 micromoles or about 5-10 ppm lead ions) can result in plated iron containing Pb amounts of 0.014 wt% to 0.022 wt%. Thus, plated iron containing a measurable amount of lead (e.g., greater than about 3 ppm) can be indicative of an iron electrowinning process using a lead anode.

[0064]

[0078] Another challenge traditionally encountered when using lead dioxide electrodes as OER anodes in standard electrowinning processes is the formation of manganese dioxide (MnO) in the anolyte during oxygen evolution if dissolved manganese is present in the electrolyte. This MnO does not tend to adhere to the lead dioxide anode, but instead deposits as a solid sludge in the electrolyte and on the electrode surface. While Zn electrowinning processes frequently use Mn impurities in the ore to "protect" PbO from the shedding problem, these processes require very frequent cleaning schedules to remove excess MnO sludge from the anolyte. Cu electrowinning processes tend to strive to minimize the Mn concentration present in the electrolyte to avoid the need for expensive or destructive MnO removal methods. In embodiments herein, for example, if a salt solution produced by ore dissolution, e.g., in the "dissolution subsystem" described in PCT '732 and Provis '092, is used to provide dissolved iron to the anolyte ("first anolyte") as described above, the electrolyte may contain a concentration of dissolved Mn, which may concentrate over time.

[0065]

[0079] Because ferrous sulfate reacts very rapidly with and dissolves any solid MnO to form aqueous MnSO as a product by electrochemical reduction, it has been discovered that ferrous sulfate can be used in situ in electrochemical cells to reduce or remove solid MnO without degrading cell performance. For example, if / when MnO is formed in an OER anolyte, then it is contemplated that a maintenance procedure may be performed by introducing or producing an appropriate amount of ferrous sulfate to dissolve the MnO.

[0066]

[0080] For example, the (first) anolyte or (first) anode chamber can be flushed or rinsed with a solution having an aqueous ferrous salt, e.g., aqueous ferrous sulfate, to dissolve any solid manganese oxide. As another example, a volume of a solution having an aqueous ferrous salt, e.g., aqueous ferrous sulfate, can be added to the (first) anolyte. For example, ferrous sulfate can be introduced into the anolyte (first anolyte) by deriving a volume of ferrous-containing solution from a separate electrowinning system, e.g., the "iron plating subsystem" described in PCT '732 and Provis '092, or an electrochemical cell according to embodiments disclosed herein, into the anode chamber (first anode chamber) of the acid regenerator. For example, the ferrous-containing solution can include electrolyte, optionally depleted electrolyte, from the acid regenerator catholyte and a "depleted" plating cell anolyte or catholyte, e.g., the "iron plating subsystem" described in PCT '732 and Provis '092. For example, ferrous sulfate can be introduced periodically or occasionally in the (first) chamber using a ferrous sulfate solution stored in a separate tank for the sole purpose of washing manganese sludge from the anode chamber. In such an approach, manganese compounds are not returned in the main electrolyte circuit, thereby allowing natural separation of manganese impurities from the main circuit.

[0067]

[0081] Alternatively, or in addition, ferrous sulfate can be produced in situ in the acid regenerator anode chamber (first anode chamber) by self-discharging the cell for a short period of time or by applying a reverse polarity current to the cell or stack to reduce ferric ions in the anolyte to ferrous iron. Such production can be done with or without flowing the anolyte and / or catholyte through the acid regeneration cell / stack.

[0068]

[0082] Lead electrodes can be fabricated and structured in a variety of ways. In some embodiments, the lead electrode may comprise a substantially solid or porous bulk lead structure. The reduced shedding caused by operating the lead electrode in a ferrous (and / or ferric) sulfate electrolyte allows for the use of lead anode structures not usable in other systems. For example, in some embodiments, the lead electrode may comprise a lead-free substrate supporting one or more layers of lead, including thin and porous layers. The lead may provide a protective layer over the substrate material that may otherwise be susceptible to chemical attack by the liquid electrolyte.

[0069]

[0083] Referring to FIG. 1 , lead electrode 100 may include a porous substrate 102 coated with a single layer of lead on one surface 104, a lead coating on both surfaces 104 and 106, or a coating covering the interior surfaces of the three-dimensional substrate. Such lead coatings may be applied to the substrate surface(s) by electroplating, spray pyrolysis (e.g., spraying a liquid containing dissolved lead onto the substrate and heating the substrate to evaporate and / or burn the liquid and / or binder material, leaving the lead attached to the substrate surface), dipping the substrate in molten lead and cooling, spraying, or painting the molten lead on one or both substrate surfaces, or other processes. Alternatively, or additionally, lead may be applied to a solid substrate in a form selected to impart a microstructured and / or nanostructured surface. For example, lead may be applied by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), sol-gel deposition, or any other method. In some cases, the method of applying the lead coating layer may be selected based on the applied layer thickness. For example, techniques such as electroplating, spray pyrolysis, PVD, CVD, and ALD may be useful for applying relatively thin layers, while techniques involving dipping a substrate in molten lead, painting a substrate with molten lead, or spraying molten lead onto a substrate may be useful for thicker layers. In other embodiments, thin layer techniques may be used to apply multiple layers to build up a thicker overall lead coating.

[0070]

[0084] The porous substrate 102 may be composed of a conductive material such as titanium, graphite, carbon, stainless steel, nickel, or other conductive material suitable for use in the electrolyte of choice (e.g., acidic, alkaline, or neutral). In various embodiments, the porous substrate may comprise a foam, a woven mesh, a nonwoven mesh, expanded metal (e.g., "EXMET"), a felt, a perforated sheet, or other two- or three-dimensional structure composed of metal, carbon, graphite, other materials, or combinations of materials. In some embodiments, the substrate may beneficially possess sufficient mechanical strength to resist bending, warping, compression, and the like. For example, the substrate material may have a compressive yield strength of about 10 to about 200 MPa and / or a Young's modulus of about 600 to about 1,500 MPa.

[0071]

[0085] The lead layer can have a thickness of about 50 microns to about 5 millimeters or less. In some specific embodiments, the lead layer on the porous or three-dimensional substrate can have an average or minimum thickness of about 50 microns, about 100 microns, about 500 microns, about 1 mm, about 1.5 mm, about 2 mm, about 2.5 mm, about 3 mm, about 3.5 mm, about 4 mm, about 4.5 mm, or about 5 mm.

[0072]

[0086] Referring to Figure 2, a bipolar lead electrode 200 may be fabricated by coating a solid (non-porous, electrolyte-impermeable) substrate with layers of lead 204, 206 on each side of the substrate. The use of a lead protective layer may allow for the use of lower-cost materials that may be more susceptible to chemical attack from the electrolyte. Optionally, the edge surfaces of the substrate are also coated with lead, thereby completely encapsulating the substrate in lead. The lead layers 204, 206 are preferably thick and dense enough that liquid electrolyte and dissolved ions cannot reach the substrate 202.

[0073]

[0087] The bipolar electrode 200 may further include a carbon cathode layer 208 on one side and a lead anode layer 210 on the opposite side.

[0074]

[0088] In some embodiments, each side of the porous or non-porous substrate 102 or 202 may be coated with a lead layer of equal or different thickness. For example, one side 204 may have a thinner or thicker lead layer than the opposing side 206. In some embodiments, the lead layers 204, 206 may have a thickness of from about 0.1 mm to about 2 mm.

[0075]

[0089] In some embodiments, the protective layer 204 underlying the carbon cathode 208 may comprise a material other than lead, such as graphite, a conductive polymer, a conductive graphitized polymer, carbon nanotubes, carbon glue, carbon adhesive, or a polymer impregnated with other carbon-based materials of sufficient thickness and density to protect the substrate 202 while providing through-plane and in-plane conductivity.

[0076]

[0090] The carbon cathode layer 208 may comprise a high surface area structure of carbon, graphite, graphene, or other conductive carbon material. The cathode layer may be provided in the form of felt, foam, paper, machined or cast graphite sheet, or other structure with a high surface area surface.

[0077]

[0091] The carbon cathode layer 208 may be conductively attached to the protective layer 204 (whether lead or other material(s)) by any suitable method that maintains electrical conductivity between the cathode layer 208, the protective layer 204, and the substrate 202. Such techniques may include conductive adhesives, welding, soldering, mechanical compression, or a combination of these or other techniques.

[0078]

[0092] In some embodiments, the lead anode layer 210 may be part of the lead layer 206 or may be an additional layer on the lead layer 206. For example, the lead layer 206 may have a very low surface area to form a high-density protective layer. Such a high-density, low-surface buildup may provide insufficient electrochemical surface area to catalyze an efficient electrochemical oxidation reaction (e.g., oxygen evolution). Thus, the lead anode layer 210 may be fabricated with a higher surface area than the underlying protective lead layer 206. In various embodiments, a high-surface area lead anode layer may be fabricated by fabricating porous or "spongy" lead on the protective layer 206. In some embodiments, such porous or spongy lead may be fabricated directly on the protective layer 206 or may be formed separately and attached to the protective lead layer 206 by welding, adhesives, soldering, mechanical compression, or a combination of these or other techniques. US Pat. No. 778,894 (issued in 1905) describes a process for making spongy lead that can be used to form a high surface area lead anode layer 210 .

[0079]

[0093] In other embodiments, the high surface area lead anode layer 210 may be fabricated by laminating a lead electrode 100 of the type described in Figure 1 onto a protective lead layer 206. Such lamination may be performed by heating the protective lead layer to sufficiently soften it, and then mechanically pressing the lead electrode 100 onto the protective lead layer. Alternatively, conductive adhesives, welding, or other techniques may be used to attach the lead electrode 100 to the protective lead layer while maintaining electrical conductivity between the lead layer 206 and the lead electrode 100.

[0080]

[0094] The solid substrate 202 may comprise a solid single sheet, plate, or laminated structure configured to provide electrical conductivity and mechanical support while also providing mechanical strength for the lead layers 204, 206 when the bipolar electrodes are compressed in a cell stack. Alternatively, in some embodiments, the solid substrate may comprise a solid lead sheet or plate. As used herein, the term "solid" refers to a non-porous material or a material that is impermeable to the anolyte, catholyte, or both.

[0081]

[0095] In various embodiments, the material composition and properties of the substrate 202, the lead deposition technique, and the thickness of the lead layer may include those described above for use with porous substrates. The solid substrate 202 may be composed of a conductive material such as titanium, graphite, carbon, stainless steel, nickel, or other conductive material suitable for use in the electrolyte of choice (e.g., acidic, alkaline, or neutral). In some embodiments, the substrate may beneficially have sufficient mechanical strength to resist bending, warping, compression, and the like. For example, the substrate material may have a compressive yield strength of about 10 to about 200 MPa and / or a Young's modulus of about 600 to about 1,500 MPa.

[0082]

[0096] 3, in some embodiments, a series of bipolar electrodes 200 may be combined electrically in series into a bipolar cell stack 300. As shown, an impermeable, non-porous conductive substrate (e.g., 202 in FIG. 2) may form a bipolar plate 302 when stacked in a bipolar cell. The bipolar plate 302 is so named because it has different or opposite polarity charges on opposing surfaces, e.g., a positive charge on its anode-adjacent surface and a negative charge on its cathode-adjacent surface.

[0083]

[0097] In Figure 3, each bipolar plate 302 may be a substrate 202 of the type described with reference to Figure 2. Similarly, each bipolar plate 302 may be coated with a cathode-side protective layer 304 and an anode-side protective layer 306. Furthermore, each cathode-side protective layer 304 may be covered by a cathode layer 308, and each anode-side protective layer may be covered by an anode layer 310.

[0084]

[0098] Each anode layer 310 is separated from the adjacent cathode layer 308 by a separator membrane 316 (which may be a PEM, AEM, or microporous separator). In the bipolar stack 300, end plates 320 and 321 may be provided for applying mechanical compression and electrical conductivity. The anode end plate 320 may be covered (coated or simply mechanically covered) with a protective layer 326 (e.g., lead) and may be covered by an end anode 326. The cathode end plate 321 may be covered (coated or simply mechanically covered) with a protective layer 324 (e.g., lead or other material as described above) and may be covered (coated or simply mechanically covered) with an end cathode layer 308.

[0085]

[0099] In some embodiments, the bipolar stack 300 may also include conductive spacer layers or flow field layers (not shown in FIG. 3 ) through which fluids may flow. Such fluids may include liquid electrolyte, gaseous reactants, gaseous electrolysis products, etc. Alternatively, flow fields, spacers, or other fluid flow channels may be provided as features of the anode layer 310 and cathode layer 308 themselves. The anolyte and catholyte (and other reactants) may be flowed through each electrode chamber in a common direction, or in opposite (or orthogonal) directions, as desired.

[0086]

[0100] In some embodiments, a bipolar stack 300, such as that shown in FIG. 3, may be configured as an acid regeneration cell as described in PCT '732 and Provis '092. In such embodiments, an iron sulfate anolyte solution may be flowed through the anode chamber. The anolyte, which contains primarily ferric sulfate and may have some ferrous ions present, tends to oxidize to the ferric state. As described in PCT '732 and Provis '092, the catholyte may contain a mixture of ferric and ferrous sulfates depending on the stage of dissolution and reduction.

[0087]

[0101] FIG. 4 is a schematic diagram illustrating a cross-sectional view of an exemplary bipolar electrode structure incorporating a lead structure according to some embodiments herein. As shown in FIG. 4, the substrate (e.g., 202) may be formed from stainless steel. Protective lead sheets (e.g., examples of layers 204 and 206) may be used on each of the anode-facing and cathode-facing sides of the substrate. A cathode, e.g., a carbon electrode, may be deposited on the lead sheet on the cathode-facing side of the substrate. A lead anode may be deposited on the lead sheet on the anode-facing side of the substrate. When used as an "acid regenerator" cell, ferric-ferrous reduction may occur on the carbon cathode and hydroxide oxidation may occur on the lead anode. In other embodiments, different reactions may occur at the anode and / or cathode.

[0088]

[0102] In various aspects, the lead coatings, layers, or bulk structures described in the various examples above may also include additives or dopants, or alloying elements such as silver, tin, calcium, cobalt, cadmium, antimony, copper, strontium, barium, titanium, or other metals, or non-metallic elements or compounds.

[0089]

[0103] In some embodiments, a lead anode in contact with an anolyte solution containing iron sulfate may be configured as a monopolar cell stack.

[0090]

[0104] In various embodiments, a lead anode in contact with an anolyte solution containing iron sulfate may be used in an iron electroplating cell such as those described in PCT '732 and Provis '092, with reference to Figures 1A, 1B, 3, 4, etc., herein.

[0091]

[0105] In various embodiments, the first anode (lead anode) is a high surface area lead anode. The high surface area lead anode may be microstructured and / or nanostructured. The high surface area lead anode, or its lead microstructures and / or nanostructures, may be electroplated. For example, electroplating the high surface area lead anode involves applying a high current density (e.g., about 50 mA / cm in some embodiments) of lead onto a lead protective layer or other substrate. 2 This may include electroplating (larger) and reducing or eliminating any leveler additives present in the electroplating electrolyte used to electroplate onto the high surface area lead anode. Microstructures and / or nanostructures may be introduced onto the lead surface (e.g., onto the lead protective layer or onto the additional lead anode layer) by roughening and / or grooving, such as electrochemical cycling, mechanical techniques such as sandblasting, laser etching, chemical etching, etc. In some embodiments, the lead anode may be or include a catalyst coated membrane (CCM) comprising a lead catalyst layer coated on the membrane surface.

[0092]

[0106] In various embodiments, the bipolar stack may comprise a zero-gap bipolar stack. For example, in at least some of the electrochemical cells, the first anode and the first cathode may be in direct contact with a separator membrane having a thickness of less than 2 mm, less than 1 mm, less than 0.5 mm, less than 0.3 mm, or less than 0.2 mm.

[0093]

[0107] In another embodiment, a lead anode in contact with an anolyte solution containing iron sulfate may be used in a copper electrowinning cell in which oxygen is evolved at the anode and copper metal is plated at the cathode. Some copper electrowinning cells use a single electrolyte without a separator between the anode and cathode. Thus, in such cases, the "anolyte" and "catholyte" are the same solution.

[0094]

[0108] An explicitly contemplated embodiment includes an electrochemical cell with a lead oxide electrode in contact with an electrolyte having an iron (ferric or ferrous or total Fe) salt, such as iron sulfate or iron chloride, at a concentration of at least 0.01 mol / l or at least 0.05 mol / l, the lead electrode operating as follows: (1) As a negative electrode for OER; (2) Iron 2+ -Fe 3+ as an anode to carry out oxidation (e.g., in an acid regenerator); and / or (3) Iron 3+ -Fe 2+ As a cathode to carry out reduction (e.g. in an acid regenerator).

[0095]

[0109] An explicitly contemplated embodiment involves operating an electrochemical cell with an oxygen-evolving lead (or lead dioxide) anode in contact with an anolyte solution containing at least 0.01 mol / L total dissolved iron, then reversing the polarity of the cell before shutting it down, and removing the Fe 3+ At least a part of 2+ This includes converting it into

[0096]

[0110] An explicitly contemplated embodiment involves directing depleted electrolyte (e.g., plating anolyte and / or plating catholyte) from a metal electroplating cell to the anode chamber (first anode chamber) of an acid regenerator in a two-stage iron conversion system, such as those described in PCT '732 and Provis '092, and operating the acid regenerator (an electrochemical cell according to embodiments and aspects herein) to generate O in the anode.

[0097]

[0111] A specifically contemplated embodiment includes periodically introducing a solution containing at least 0.01 mol / L of ferrous iron into an OER anode chamber (first anode chamber) containing solid MnO sludge to dissolve the MnO . For example, preferably for some applications, the molar ratio of aqueous ferrous ions in the anolyte (first anolyte) to the MnO 2 in the anode chamber or exposed to the anolyte (first anolyte) is 1:1 or greater. For example, preferably for some applications, the molar ratio of aqueous ferrous ions in the anolyte (first anolyte) to the MnO 2 in the anode chamber or exposed to the anolyte (first anolyte) is 2:1 or greater. For example, preferably for some applications, the molar ratio of aqueous ferrous ions in the anolyte (first anolyte) to the MnO 2 in the anode chamber or exposed to the anolyte (first anolyte) is 3:1 or greater.

[0098]

[0112] An explicitly contemplated embodiment involves generating ferrous iron in an OER anode chamber (first anode chamber) containing a quantity of solid MnO sludge by electrochemically reducing a quantity of dissolved ferric ions.

[0099] Stable lead anodes for acid regeneration.

[0113] 5 is a schematic diagram illustrating an exemplary system 500 according to embodiments herein, having an electrochemical cell 580. Cell 580 may be substantially similar to the "acid-regenerated" cell described in more detail in PCT '732 and elsewhere herein. The cathode of cell 580 is a cathode containing Fe in the catholyte. 3+ ionic Fe 2+ The anode of cell 580 performs the electrochemical oxidation of water to oxygen, also referred to as the oxygen evolution reaction (OER). A proton exchange membrane (PEM), according to some embodiments, separates the catholyte and anolyte compartments.

[0100]

[0114] The catholyte is shown fluidly connected to a catholyte circulation tank 570 and contains dissolved ferric iron (Fe 3+) and ferrous iron (Fe 2+ In various embodiments and aspects, the ferric and ferrous ions may be provided to the catholyte as an aqueous solution or as a soluble solid contacted by the catholyte to dissolve the iron-containing material in the solution as described in various examples in PCT '732 and herein.

[0101]

[0115] The anolyte (or anolyte electrolyte) is shown fluidly connected to the anolyte circulation tank 560. In some embodiments, the anolyte may be an aqueous acid solution containing iron cations at a concentration within the ranges described herein.

[0102]

[0116] In various embodiments or aspects, the electrolyte may be recirculated between each half-cell and a reservoir tank. In some embodiments, reactants (e.g., dissolved or dissolvable iron and water) may be added to the electrolyte stream via a tank or directly to each half-cell compartment.

[0103]

[0117] In some circumstances, iron cations (ferric or ferrous) from the anolyte may cross over or become trapped in the separator membrane that separates the anolyte from the catholyte and reduces the availability of iron cations for the lead anode stabilization function as described herein. As a result, the concentration of iron in the anolyte may be too low to provide the stabilization function as described herein. In various embodiments and aspects, iron cations lost from the anolyte may be replenished by periodically or continuously "dosing" additional iron to the anolyte by one or more mechanisms.

[0104]

[0118] Optionally, the anolyte may be dosed with iron cations to replenish, maintain, or establish a target or PbO2 electrode stabilization concentration of iron cations, or in the form of ferric and / or ferrous sulfate. Inputs 501, 502, 503 and solid iron source 505 represent any source or method for dosing iron cations to the catholyte. In some embodiments, for example, optionally, an aqueous dosing solution and / or one or more solid iron-containing materials may be provided via input 503. For example, optionally, in some embodiments, the anolyte may be dosed by providing anolyte from an iron electroplating cell via input 501. For example, optionally, in some embodiments, the anolyte may be dosed by providing catholyte from an iron electroplating cell via input 502. For example, optionally, in some embodiments, the anolyte may be dosed by rapidly or slowly providing a solid iron source 505 that may dissolve in the anolyte, as may be appropriate for the application.

[0105]

[0119] System 500 optionally includes a tap 510 for supplying liquids and / or solids to the anolyte and / or for extracting the anolyte. Optionally, for example, inputs 501, 502, and 503 may be supplied to / via tap 510 rather than directly to tank 560. System 500 includes an "iron extraction" mechanism. Optionally, the iron extraction mechanism may include extracting a ferrous-containing solution and supplying the ferrous-containing solution to an iron electroplating cell to extract metallic iron. Optionally, the iron extraction mechanism may include extracting a ferrous-containing solution and precipitating an iron-containing material, such as an iron-containing salt, from the extraction solution, thereby extracting iron from system 500.

[0106]

[0120] In some embodiments and aspects, iron may be extracted from the catholyte as a solid. In some aspects, iron may be extracted from the catholyte by precipitating or crystallizing iron salts, iron oxides, or iron hydroxides from solution. Alternatively, the iron of the ferrous-rich catholyte may be directed to an electroplating cell where the iron can be electroplated from solution.

[0107] Single-stage iron conversion using lead anodes.

[0121] 6 is a schematic diagram illustrating an exemplary system 600 for electroplating iron metal from an aqueous solution containing dissolved iron. According to embodiments herein, system 600 includes an electrochemical cell 680. A cathode 634 of cell 680 is connected to an iron electroplating reaction, or the aqueous Fe in the catholyte. 2+ ions and / or Fe 3+ Metallic iron (Fe 0 Cathode 634 may be comprised of any conductive material suitable to serve as a substrate or support onto which metallic iron can be electroplated.

[0108]

[0122] In some embodiments, any Fe present in the catholyte solution 3+ "Ferric" ions are added to the Fe 2+ The aqueous ferric ions may be advantageously reduced to the "ferrous" oxidation state. In some embodiments, the ferric ions may be reduced to ferrous ions using an acid regeneration cell as described above with reference to Figure 5. In other embodiments or aspects, the aqueous ferric ions may be reduced to aqueous ferrous ions by contacting the solution with a reducing gas such as hydrogen sulfide or sulfur dioxide. In yet other embodiments, the ferric ions may be reduced by contacting the solution with metallic iron.

[0109]

[0123] The anode 636 of the cell 680 undergoes electrochemical oxidation of water to produce oxygen and acid in the anode electrolyte (anolyte). The anode 363 may be a lead dioxide anode for catalyzing the oxygen evolution reaction (OER). The anolyte may be an acidic aqueous solution containing dissolved iron cations at a concentration described herein appropriate for stabilizing the lead dioxide electrode. The anolyte is shown fluidly connected to the anolyte tank 660, and the catholyte is shown fluidly connected to the catholyte tank 670.

[0110]

[0124] In various embodiments, the acid produced in the anolyte may be removed, depleted, such as by a dissolution reaction to convert the iron-containing feedstock into an aqueous iron-containing solution.

[0111]

[0125] According to some aspects, an anion exchange membrane (AEM) may separate the catholyte and anolyte. Some anion exchange membranes tend to "leak" cations, such as aqueous iron cations, from the anolyte into the catholyte, which can cause a decrease in the concentration of iron in the anolyte over time. As a result, the concentration of iron in the anolyte may become too low to provide the stabilizing function described herein. In various embodiments and aspects, iron ions lost from the anolyte may be replenished by periodically or continuously "dosing" additional iron into the anolyte by one or more mechanisms.

[0112]

[0126] Optionally, the anolyte may be dosed with iron cations to replenish, maintain, or establish a target or PbO2 electrode stabilization concentration of iron cations, or in the form of ferric and / or ferrous sulfate. Input 604 and solid iron source 605 represent any source or method for dosing iron cations to the catholyte. In some embodiments, for example, optionally, an aqueous dosing solution and / or one or more solid iron-containing materials may be provided via input 604. For example, optionally, in some embodiments, the anolyte may be dosed by rapidly or slowly providing a solid iron source 605 that can dissolve in the anolyte, as may be appropriate for the application. System 500 optionally includes tap 610 for providing liquids and / or solids to the anolyte and / or for extracting the anolyte. Optionally, for example, input 604 may be provided to / via tap 610 rather than directly to tank 660. Tap 612 is optional and may also be used to supply liquids and / or solids to the catholyte and / or to extract the catholyte.

[0113] Two-stage iron conversion using lead anodes.

[0127] 7-11 , in some embodiments, the iron conversion system 700, 800, 900, 1000, or 1100 may be separated into two main subsystems: a melting subsystem 102 and a plating subsystem 130. The melting subsystem 102 may be generally configured to efficiently melt the iron source material 152 at a low temperature and relatively quickly to form the molten iron solution 122. The melting subsystem 102 may also be configured to remove ferric iron (Fe ) from the molten iron solution 122 before the molten iron solution 122 is transferred to the plating cell 132 in the plating subsystem 130. 3+ ) ions in the "acid regeneration" cell 104. 2+ ) ions. The plating subsystem 130 is generally configured to electrolytically plate the dissolved ferrous iron at 148 into a solid form that can be removed and sold as relatively pure iron, preparing the plating subsystem 130 for further plating. Once the dissolved iron solution 122 has been sufficiently depleted of ferrous iron by the plating cell 132, it may be returned to the dissolving subsystem 102 for use in subsequent dissolving operations in conjunction with the acid regeneration cell 104.

[0114]

[0128] As shown, the acid regeneration cell 104 may be configured to reduce ferric ions (produced during dissolution of feedstock 120) to ferrous ions in the cathode chamber 106 (first cathode chamber) while oxidizing a depleted reactant provided from a reactant source 116 at the anode 112 (first anode). In some embodiments, the anode reactant may be water, and the anode 112 (first anode) may generate oxygen 111 from the anode chamber 110 (first chamber). In some embodiments, water 154 is added to the anode chamber 110 to replenish water depleted by the OER.

[0115]

[0129] In various embodiments, one or more processing steps 124, 126, 128, and 127 may be performed to condition the dissolved iron solution 122 to remove materials or to increase or decrease the concentration of one or more components of the solution. For example, processing step 124 may include directing the dissolved iron solution 122 exiting the dissolving tank 118 through a processing vessel configured to remove solid particulates and / or colloidal dispersions of materials released during dissolution. In some cases, silica from the iron source may enter the dissolved iron solution 122 as a gel-like mass in a colloidal dispersion, which could interfere with operation within the acid regeneration cell 104. Processing step 124 may include contacting the solution with a flocculant, such as polyethylene glycol, polyethylene oxide, or other flocculant known to be effective in removing colloidal silica from the solution. Processing step 124 may also include any other solid-liquid separation techniques, devices, or additives as needed to remove materials that may be detrimental to operation in the acid regeneration cell 104.

[0116]

[0130] The plating subsystem 130 may include a plating cell 132 including a cathode electrode 136 (second cathode) in a cathode chamber 134 (second chamber) fluidly connected to a catholyte tank 142 (second catholyte tank) and an anode electrode 140 (second anode) in an anode chamber 138 (second anode chamber) fluidly connected to an anolyte tank 144 (second anolyte tank). Ferrous ions may be reduced to plated metallic iron in the cathode chamber 134 (second chamber) of the plating cell 132. An oxidation reaction, such as OER or ferrous ions to ferric ions, occurs in the anode chamber 138 (second anode chamber) of the plating cell 132.

[0117]

[0131] In some embodiments, the plating reaction is 2+ -Fe 3+The oxidation reaction may be carried out, for example, as shown in systems 700 and 900 of Figures 7 and 9, respectively. In such embodiments, for example, systems 700 or 900, the dissolved iron solution 122 may be divided into a plating anolyte and a plating catholyte. The plating anolyte may be recirculated between a plating anolyte tank 144 and the anode chamber 138 of the plating cell 132, where species in the plating anolyte are oxidized at the anode electrode 140. The plating catholyte may be recirculated between the plating catholyte tank 142 and the cathode chamber 134 of the plating cell 132, and iron may be electroplated onto the cathode electrode 108. Iron may be removed from the plating cell 132 at 148 by various methods, examples of which are described below. In some cases, hydrogen gas may be evolved 146 from the plating cell cathode chamber 134. Such hydrogen gas may be captured and stored for use in other subprocesses described herein.

[0118]

[0132] In some embodiments, the plating reaction is carried out in an oxygen evolution reaction (OER) as shown in systems 800 and 1000 of Figures 8 and 10, respectively.

[0119]

[0133] In some embodiments, the anolyte (first anolyte) of the acid regeneration cell of the dissolution subsystem contains a concentration of aqueous iron cations. In some embodiments, the electrochemical oxidation reaction that takes place in the anolyte (second anolyte) of the plating cell of the plating subsystem is an oxygen evolution reaction, as shown in Figures 8 (system 800) and 10 (system 1000), and the second anolyte contains a concentration of aqueous iron cations. In some embodiments, aqueous iron cations may be depleted from the first anolyte over time through one or more processes, including, but not limited to, leakage of aqueous iron cations through a membrane into the respective catholyte; uptake of aqueous iron cations through chemical and / or physical mechanisms in or at components of the cell, such as in a membrane or in the pores of a porous lead electrode, thereby optionally losing iron cations when the porous electrode or anode chamber is flushed or rinsed; side or parasitic reactions, etc. Thus, in embodiments, the concentration of aqueous iron cations in the first anolyte, the second anolyte (e.g., in systems 800 and 1000), or both the first anolyte and the second anolyte (e.g., in systems 800 and 1000) may be maintained within a stabilization concentration range during one or more interim operation periods of the acid-regenerated cell, whereby operation refers to operation of the cell under an operating voltage such that a desired electrochemical reduction occurs at the cathode and a desired electrochemical oxidation, e.g., OER, occurs at the cathode. Generally, in embodiments, a cell under an open-circuit voltage is not in operation. In embodiments, the concentration of aqueous iron cations in the first anolyte, the second anolyte (e.g., in systems 800 and 1000), or both the first anolyte and the second anolyte (e.g., in systems 800 and 1000) may be maintained within a stabilization concentration range throughout, or at least most of, the operation of the acid-regenerated cell.

[0120]

[0134] Establishing and / or maintaining the aqueous iron cation concentration within the stabilization concentration in the first anolyte and / or the second anolyte may include dosing a bulk iron source and / or a solid iron source to the first anolyte and / or the second anolyte. Dosing may occur continuously and / or via one or more discrete events. Dosing may occur directly, e.g., by supplying the liquid and / or solid iron source directly to the anode chamber or its anolyte, and / or indirectly, e.g., by supplying the liquid and / or solid iron source to a circulation tank fluidly connected to the anode chamber or its anolyte. In some embodiments, the liquid iron source is an aqueous solution containing aqueous iron cations (also referred to herein as a dosing solution). The dosing solution may comprise depleted or used electrolytes from different cells and / or leachates from metal and / or ore processing systems, an aqueous solution formed by dissolving one or more iron-containing materials, e.g., dissolving iron-containing salts or oxides in the solution and / or flowing the solution over an iron-containing substrate, or any combination thereof, as described throughout this specification.

[0121]

[0135] Optionally, the first anolyte may be dosed with the aqueous dosing solution and / or the solid iron source directly and / or indirectly via inputs 703, 803, 903, 1003, or 1103. Optionally, in embodiments where OER is performed in a second anolyte, the second anolyte may be dosed with the aqueous dosing solution and / or the solid iron source directly and / or indirectly via inputs 804 or 1004. For example, optionally, a solid iron containing substance, e.g., an iron salt or oxide, may be provided via inputs 703, 803, 903, 1003, 804, or 1004. For example, optionally, an aqueous dosing solution may be provided via inputs 703, 803, 903, 1003, 804, or 1004. In some embodiments, direct dosing corresponds to providing a liquid and / or solid iron source directly to the anode chamber or its anolyte. In some embodiments, indirect administration corresponds to providing a liquid and / or solid iron source to a circulation tank fluidly connected to the anode chamber or its anolyte.

[0122]

[0136] Optionally, the first anolyte may be administered by including a solid iron source 705, 805, 905, or 1005 in contact with the first anolyte. Optionally, the conditions of the first anolyte (such as but not limited to temperature) and the conditions of the solid iron source 705, 805, 905, 1005, or 1105 (such as but not limited to composition) are selected or controlled such that the solid iron source dissolves slowly or at a selected rate during cell operation to maintain a stabilized concentration of aqueous iron cations. The solid iron source 705, 805, 905, or 1005 may be provided in the first anolyte chamber, in a circulation tank fluidly connected to the first anolyte chamber or the first anolyte, or both.

[0123]

[0137] Optionally, in embodiments where OER is performed in a second anolyte, the second anolyte may be administered by including a solid iron source 805 or 1005 in contact with the second anolyte. Optionally, the conditions of the second anolyte (such as but not limited to temperature) and the conditions of the solid iron source 805 or 1005 (such as but not limited to its composition) are selected or controlled so that the solid iron source dissolves slowly or at a selected rate during cell operation to maintain a stabilized concentration of aqueous iron cations. The solid iron source 805 or 1005 may be provided in the second anolyte chamber, in a circulation tank 810 or 1010 fluidly connected to the second anolyte chamber or its first anolyte, or both.

[0124]

[0138] Optionally, iron cation oxidation (Fe 2+ -Fe 3+ In embodiments where the iron reduction / plating reaction is performed relative to the anolyte reaction, the first anolyte may be dosed, for example, via input 701 or 901, with an aqueous dosing solution containing spent or depleted anolyte (second anolyte) from the plating cell shown in FIGS. 7 and 9.

[0125]

[0139] Optionally, the first anolyte may be an aqueous dosing solution containing used or depleted catholyte (second catholyte) from a plating cell, such as those shown in Figures 7-10, dispensed via inputs 702, 802, 902, 1002, or 1102.

[0126]

[0140] Optionally, in some embodiments, metallic iron may be provided in the first catholyte, or the first catholyte may be exposed to metallic iron to deplete protons (acid) leaking from the first anolyte through the AEM. Optionally, in some embodiments, metallic iron may be provided in the second catholyte, or the second catholyte may be exposed to metallic iron to deplete protons (acid) leaking from the second anolyte through the separator.

[0127] Various further aspects:

[0141] Various aspects are contemplated herein, some of which are described in the following paragraphs. It is expressly contemplated that any aspect or portion thereof may be combined to form an aspect. Furthermore, any reference to aspect 1 is expressly contemplated to include aspects 1a, 1b, 1c, and / or 1d, any reference to aspect 5 is expressly contemplated to include aspects 5a and 5b, etc. (any reference to an aspect includes a reference to an aspect followed by a version letter). Furthermore, the terms "any of the aforementioned aspects" and "any one of the aforementioned aspects" refer to any aspect that appears before the aspect containing such a phrase (in other words, the phrase "Aspect 32: a method or system according to any of the aforementioned aspects" refers to any aspect prior to aspect 32, including aspects 1a-31). For example, it is contemplated that any system or method of any of the following aspects may optionally be useful or combined with any other aspect provided below. Furthermore, for example, it is contemplated that any of the above aspects may optionally be combined with any of the aspects described below.

[0128]

[0142] Aspect 1a: A method of stabilizing a lead anode, the method comprising: operating an electrochemical cell comprising electrochemical reduction at a first cathode and electrochemical oxidation at a first anode; an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The first anolyte contains aqueous iron cations at a concentration of at least about 0.01M or from about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about 0.1M). optionally about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), for example, optionally at a concentration selected from the range of about 0.01M to about 0.45M, optionally at a concentration selected from the range of about 0.01M to about 0.4M, optionally at a concentration selected from the range of about 0.01M to about 0.44M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, or optionally at a concentration selected from the range of about 0.02M to about 0.08M.

[0129]

[0143] Aspect 1b: A system for stabilizing a lead anode, comprising: the system comprising an electrochemical cell; an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The first anolyte contains aqueous iron cations at a concentration of at least about 0.01M or from about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about 0.1M). The system includes a soluble soluble cellulose at a concentration selected from the range of about 0.01M to about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), for example, optionally at a concentration selected from the range of about 0.01M to about 0.45M, optionally at a concentration selected from the range of about 0.01M to about 0.4M, optionally at a concentration selected from the range of about 0.01M to about 0.44M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, optionally at a concentration selected from the range of about 0.02M to about 0.08M.

[0130]

[0144] Aspect 1c: A method of stabilizing a lead anode, comprising: operating the electrochemical cell, including electrochemical reduction at a first cathode and electrochemical oxidation at a first anode; and recycling the second electrolyte from the metal electroplating cell to the first anolyte; the second electrolyte having aqueous iron cations; an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The first anolyte contains aqueous iron cations at a concentration of at least about 0.01M or from about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0. 0.43M, optionally about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), for example, optionally at a concentration selected from the range of about 0.01M to about 0.45M, optionally at a concentration selected from the range of about 0.01M to about 0.4M, optionally at a concentration selected from the range of about 0.01M to about 0.44M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, or optionally at a concentration selected from the range of about 0.02M to about 0.08M.

[0131]

[0145] Aspect 1d: A system for stabilizing a lead anode, comprising: The system, an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; a metal electroplating cell; and an electrolyte recycling subsystem for recycling electrolyte from the metal electroplating cell to the first anolyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The first anolyte contains aqueous iron cations at a concentration of at least about 0.01M or from about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about The system comprises a soluble soluble cellulose at a concentration selected from the range of about 0.01M to about 0.44M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, optionally at a concentration selected from the range of about 0.02M to about 0.08M), for example, optionally at a concentration selected from the range of about 0.01M to about 0.45M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, optionally at a concentration selected from the range of about 0.02M to about 0.08M.

[0132]

[0146] Aspect 1e: The method or system of Aspect 1, e.g., any one of Aspects 1a-1d, wherein the concentration of aqueous iron cations in the first anolyte is selected from the range of about 0.01 M to about 0.1 M, any value and range therebetween being expressly contemplated and disclosed herein, e.g., optionally about 0.02 M to about 0.09 M, or optionally about 0.03 M to about 0.08 M, or optionally about 0.04 M to about 0.07 M, or optionally about 0.03 M to about 0.08 M, or optionally about 0.05 M.

[0133]

[0147]

[0014] Aspect 2a: The method or system of aspect 1, wherein the second electrolyte comprises catholyte and / or anolyte from an iron electroplating cell, and the second electrolyte comprises aqueous iron ions. Aspect 2b: The method or system of aspect 1 or 2a, wherein the second electrolyte comprises depleted catholyte and / or depleted anolyte from an iron electroplating cell.

[0134]

[0148] Aspect 3: The method or system of any one of claims 1-2b, wherein conducting electrochemical oxidation comprises an oxygen evolution reaction (OER) at the first anode.

[0135]

[0149] Aspect 4: The method or system of any one of Aspects 1-3, wherein the first anolyte comprises aqueous sulfate anions.

[0136]

[0150] Aspect 5a: A method of stabilizing a lead anode, the method comprising: operating an electrochemical cell comprising conducting an electrochemical reduction at a first cathode and an oxygen evolution reaction (OER) at a first anode; an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The first anolyte contains aqueous iron cations at a concentration of at least about 0.01M or from about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about 0.1M). optionally about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), for example, optionally at a concentration selected from the range of about 0.01M to about 0.45M, optionally at a concentration selected from the range of about 0.01M to about 0.4M, optionally at a concentration selected from the range of about 0.01M to about 0.44M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, or optionally at a concentration selected from the range of about 0.02M to about 0.08M.

[0137]

[0151] Aspect 5b: A system for stabilizing a lead anode, comprising: the system comprising an electrochemical cell; The electrochemical cell a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; The oxygen evolution reaction (OER) occurs at the first anode; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The first anolyte comprises aqueous iron sulfate at a concentration of at least about 0.01M or from about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about The system comprises a soluble soluble cellulose at a concentration selected from the range of about 0.01M to about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), for example, optionally at a concentration selected from the range of about 0.01M to about 0.45M, optionally at a concentration selected from the range of about 0.01M to about 0.4M, optionally at a concentration selected from the range of about 0.01M to about 0.44M, optionally at a concentration selected from the range of about 0.01M to about 0.445M, optionally at a concentration selected from the range of about 0.01M to about 0.440M, or optionally at a concentration selected from the range of about 0.02M to about 0.08M.

[0138]

[0152] Aspect 6a: The method or system of any one of Aspects 1-5b, wherein the concentration of aqueous iron cations in the first anolyte is at least about 0.05 M or is selected from the range of about 0.05 M to about 0.5 M.

[0139]

[0153] Aspect 7a: The method or system of any one of Aspects 1-6a, wherein the concentration of aqueous iron cations in the first anolyte is less than the concentration of aqueous iron cations in the first catholyte. Aspect 7b: The method or system of any one of Aspects 1-7a, wherein the concentration of aqueous iron cations in the first anolyte is equal to, greater than, or less than the concentration of aqueous iron cations in the first catholyte. Aspect 7c: The method or system of any one of Aspects 1-7b, wherein the concentration of aqueous iron cations in the first anolyte is greater than the concentration of aqueous iron cations in the first catholyte. Aspect 7d: The method or system of any one of Aspects 1-7c, wherein the concentration of aqueous iron cations in the first anolyte is equal to the concentration of aqueous iron cations in the first catholyte.

[0140]

[0154] Aspect 8a: The steady-state concentration of aqueous iron cations in the first anolyte is at least about 0.01 M or about 0.01 M (optionally about 0.02 M, optionally about 0.03 M, optionally about 0.04 M, optionally about 0.05 M, optionally about 0.06 M, optionally about 0.07 M, optionally about 0.08 M, optionally about 0.09 M, optionally about 0.095 M, optionally about 0.099 M, optionally about 0.1 M) to about 0.5 M (optionally about 0.49 M, optionally about 0.48 M, optionally about 0.47 M, optionally about 0.46 M, optionally about 0.45 M, optionally about 0.44 M, optionally about 0.43 M, optionally about 0.42 M). The method or system of any one of Aspects 1 to 7d, wherein the α-glutamic acid is at a concentration selected from the range of about 0.01M to about 0.45M, optionally about 0.01M to about 0.4M, optionally about 0.01M to about 0.44M, optionally about 0.01M to about 0.445M, optionally about 0.01M to about 0.440M, or optionally about 0.02M to about 0.08M.Aspect b8: The steady-state concentration of aqueous iron cations in the first anolyte is at least about 0.01 M [or about 0.01 M (optionally about 0.02 M, optionally about 0.03 M, optionally about 0.04 M, optionally about 0.05 M, optionally about 0.06 M, optionally about 0.07 M, optionally about 0.08 M, optionally about 0.09 M, optionally about 0.095 M, optionally about 0.099 M, optionally about 0.1 M) to about 0.5 M (optionally about 0.49 M, optionally about 0.48 M, optionally about 0.47 M, optionally about 0.46 M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), for example, optionally a concentration selected from the range of about 0.01M to about 0.5M, or optionally a concentration selected from the range of about 0.01M to about 0.45M, or optionally a concentration selected from the range of about 0.01M to about 0.4M], and the steady-state concentration of aqueous iron cations in the first anolyte is at least about 0.01M [or about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to about 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about 0.42M, optionally about

[0039] The method or system of any one of Aspects 1 to 8a, wherein the concentration is selected from the range of about 0.01M to about 0.5M, or optionally about 0.01M to about 0.45M, or optionally about 0.01M to about 0.445M, or optionally about 0.01M to about 0.44M, or optionally about 0.01M to about 0.4M.

[0141]

[0155] Aspect 9a: The method or system of any one of Aspects 1 through 8b, wherein the steady-state concentration of aqueous iron cations in the first anolyte is at least about 0.05 M or selected from the range of about 0.05 M to 0.5 M. Aspect 9b: The method or system of any one of Aspects 1 through 9a, wherein the steady-state concentration of aqueous iron cations in the first anolyte is at least about 0.05 M or selected from the range of about 0.05 M to 0.5 M, and the steady-state concentration of aqueous sulfate anions in the first anolyte is at least about 0.05 M or selected from the range of about 0.05 M to 0.5 M.

[0142]

[0156] Aspect 10a: The method or system of any one of Aspects 1 through 9b, wherein the steady-state concentration of aqueous iron cations in the first anolyte is less than the steady-state concentration of aqueous iron cations in the first catholyte. Aspect 10b: The method or system of any one of Aspects 1 through 10a, wherein the steady-state concentration of aqueous iron cations in the first anolyte is greater than, equal to, or less than the steady-state concentration of aqueous iron cations in the first catholyte. Aspect 10c: The method or system of any one of Aspects 1 through 10b, wherein the steady-state concentration of aqueous iron cations in the first anolyte is greater than the steady-state concentration of aqueous iron cations in the first catholyte. Aspect 10d: The method or system of any one of Aspects 1 through 10c, wherein the steady-state concentration of aqueous iron cations in the first anolyte is equal to the steady-state concentration of aqueous iron cations in the first catholyte.

[0143]

[0157] Embodiment 11: The method or system of any one of Embodiments 1 through 10d, wherein the aqueous iron cations in the first anolyte comprise aqueous ferric ions.

[0144]

[0158] Aspect 12a: A method comprising operating an electrochemical cell comprising performing electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method further comprises: 1. A method comprising dissolving solid manganese oxide in a first anolyte in the presence of aqueous ferrous ions.

[0145]

[0159] Embodiment 12b: A system comprising an electrochemical cell, The electrochemical cell a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The system wherein the first anolyte comprises aqueous ferrous ions that promote dissolution of solid manganese oxide present in the first anode chamber in the first anolyte.

[0146]

[0160] Aspect 13: The method or system of aspect 12, wherein the dissolving step comprises converting the solid manganese oxide to one or more aqueous manganese salts in the presence of aqueous ferrous ions.

[0147]

[0161] Embodiment 14: The method or system of embodiment 13, wherein the converting comprises (i) reacting the solid manganese oxide with aqueous ferrous ions, and / or (ii) electrochemically reducing the solid manganese oxide to one or more aqueous manganese salts in the presence of aqueous ferrous ions.

[0148]

[0162] Aspect 15: The method or system of aspect 13 or 14, wherein a ratio of moles of aqueous ferrous ions in the first anolyte to moles of solid manganese oxide in the first anode chamber is at least 0.9 (optionally at least 0.95, optionally at least 0.99, optionally at least 1, optionally at least 1.2, optionally at least 1.5, optionally at least 1.7, optionally at least 2, optionally at least 2.2, optionally at least 2.5, optionally at least 2.7, optionally at least 3) during at least a portion of the dissolving step (optionally during the entire dissolving step, and optionally at the start of the dissolving step).

[0149]

[0163] Aspect 16: The method or system of aspect 15, wherein a ratio of moles of aqueous ferrous ions in the first anolyte to moles of solid manganese oxide in the first anode chamber is at least 2 during at least a portion of the dissolving step.

[0150]

[0164] Aspect 17a: The method of any one of claims 12-16, wherein the first anolyte comprises at least 5 mM aqueous ferrous ions during at least a portion of the dissolving step (optionally during the entire dissolving step and optionally at the start of the dissolving step). Aspect 17b: The method of any one of claims 12-16, wherein the first anolyte comprises at least 5 mM aqueous iron cations during at least a portion of the dissolving step (optionally during the entire dissolving step and optionally at the start of the dissolving step). Aspect 17c: The method of any one of claims 12-16, wherein the first anolyte comprises at least 10 mM aqueous ferrous ions during at least a portion of the dissolving step (optionally during the entire dissolving step and optionally at the start of the dissolving step). Aspect 17d: The method of any one of claims 12-16, wherein the first anolyte comprises at least 10 mM aqueous iron cations during at least a portion of the dissolving step (optionally during the entire dissolving step and optionally at the start of the dissolving step).

[0151]

[0165] Aspect 18: The method or system of aspects 12-17, comprising providing aqueous ferrous ions to the first anolyte prior to and / or during the dissolving step.

[0152]

[0166] Aspect 19a: The method or system of aspect 18, wherein the providing step comprises flushing the first anode chamber with a solution comprising aqueous ferrous ions. Aspect 19b: The method or system of aspect 18, wherein the providing step comprises adding a solution comprising aqueous ferrous ions to the first anode chamber.

[0153]

[0167] Aspect 20: The method or system of aspect 18 or 19, wherein the providing step includes directly or indirectly recycling the iron-containing electrolyte from the electroplating cell to the first anolyte.

[0154]

[0168] Aspect 21: The method or system of any one of aspects 18-20, wherein the providing step comprises electrochemically generating aqueous ferrous ions in the first anolyte.

[0155]

[0169] Embodiment 22: The method or system of any one of embodiments 12-21, wherein the first anolyte comprises aqueous Mn ions.

[0156]

[0170] Aspect 23a: A method comprising operating an electrochemical cell comprising performing an electrochemical reduction at a first cathode and an electrochemical oxidation at a first anode, an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method further comprises: 1. A method comprising: reverse biasing a first anode for a finite time, the method comprising electrochemically reducing aqueous ferric ions to aqueous ferrous ions at the first anode in the presence of a first anolyte.

[0157]

[0171] Aspect 23b: A system comprising an electrochemical cell, an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The system includes an electrochemical cell configured to reverse bias a first anode for a finite period of time to electrochemically reduce aqueous ferric ions to aqueous ferrous ions at the first anode in the presence of a first anolyte.

[0158]

[0172] Aspect 24a: A method comprising operating an electrochemical cell comprising performing an electrochemical reduction at a first cathode and an electrochemical oxidation at a first anode, an electrochemical cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; the first anode and the first cathode each comprise lead; The method, wherein the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions.

[0159]

[0173] In embodiments and aspects herein, a lead-containing electrode may include a lead layer as an underlayer or support layer. For example, a lead-containing cathode may include a lead layer as an underlayer or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily include lead, and as a result, a lead-containing cathode does not necessarily have lead in contact with the catholyte, as lead is optionally part of the cathode only as a support or underlayer. For example, a lead-containing cathode may be a carbon electrode on a lead support or underlayer.

[0160]

[0174] Aspect 25a: A method or system according to any one of Aspects 1-24a, comprising operating two or more electrochemical cells, wherein adjacent electrochemical cells share a bipolar plate therebetween, each bipolar plate comprising a first lead electrode that is a first anode of the electrochemical cell and a second electrode comprising lead that is a first cathode of the adjacent electrochemical cell. In embodiments and aspects herein, the lead-containing electrode may comprise a lead layer as an underlayer or support layer. For example, a lead-containing cathode may comprise a lead layer as an underlayer or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily comprise lead. As a result, the lead-containing cathode does not necessarily have lead in contact with the catholyte, since lead is optionally only part of the cathode as a support or underlayer. For example, the lead-containing cathode may be a carbon electrode on a lead support or underlayer. Aspect 25b: A method or system according to any of aspects 1-25a, comprising operating two or more of the electrochemical cells, wherein adjacent electrochemical cells share a bipolar plate therebetween, the bipolar plate each comprising a first electrode that is a first anode of the electrochemical cell and a second electrode that is a first cathode of the adjacent electrochemical cell.

[0161]

[0175] Aspect 26: A method or system according to any one of aspects 1 to 25b, comprising operating a bipolar stack of electrochemical cells, each electrochemical cell of the stack being independently an electrochemical cell according to any one of claims 1 to 25.

[0162]

[0176] Aspect 27a: A bipolar stack comprising one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; The method or system of aspect 26, wherein the bipolar plates each include a first lead electrode that is a first anode of an electrochemical cell and a second electrode that includes lead that is a first cathode of an adjacent electrochemical cell. In embodiments and aspects herein, the lead-containing electrode may include a lead layer as an underlayer or support layer. For example, a lead-containing cathode may include a lead layer as an underlayer or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily include lead. As a result, the lead-containing cathode does not necessarily have lead in contact with the catholyte, as lead is optionally only part of the cathode as a support or underlayer. For example, the lead-containing cathode may be a carbon electrode on a lead support or underlayer.

[0163]

[0177] Aspect 27b: A bipolar stack comprising one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; 27. The method or system of embodiment 26, wherein the bipolar plates each comprise a first electrode that is a first anode of an electrochemical cell and a second electrode that is a first cathode of an adjacent electrochemical cell.

[0164]

[0178] Aspect 28a: A method of manufacturing a semiconductor device comprising: operating two or more electrochemical cells comprising electrochemical reduction at a first cathode and electrochemical oxidation at a first anode; Each electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; adjacent electrochemical cells share a bipolar plate therebetween; The method includes a bipolar plate, each comprising a first lead electrode that is a first anode of an electrochemical cell and a second electrode that includes lead that is a first cathode of an adjacent electrochemical cell. In embodiments and aspects herein, the lead-containing electrode may include a lead layer as a bottom or support layer. For example, a lead-containing cathode may include a lead layer as a bottom or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily include lead. As a result, the lead-containing cathode does not necessarily have lead in contact with the catholyte, since lead is optionally only part of the cathode as a support or bottom layer. For example, the lead-containing cathode may be a carbon electrode on a lead support or bottom layer.

[0165]

[0179] Aspect 28b: A method comprising operating two or more electrochemical cells comprising performing an electrochemical reduction at a first cathode and an electrochemical oxidation at a first anode, Each electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; adjacent electrochemical cells share a bipolar plate therebetween; The method, wherein the bipolar plates each comprise a first lead electrode that is a first anode of an electrochemical cell and a second electrode that is a first cathode of an adjacent electrochemical cell.

[0166]

[0180] Aspect 28c: A method comprising operating a bipolar stack of electrochemical cells, each electrochemical cell of the stack having an independent first cathode for electrochemical reduction and a first anode for electrochemical oxidation; each electrochemical cell comprising a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the bipolar stack comprises one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; The method includes a bipolar plate, each comprising a first lead electrode that is a first anode of an electrochemical cell and a second electrode that includes lead that is a first cathode of an adjacent electrochemical cell. In embodiments and aspects herein, the lead-containing electrode may include a lead layer as a bottom or support layer. For example, a lead-containing cathode may include a lead layer as a bottom or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily include lead. As a result, the lead-containing cathode does not necessarily have lead in contact with the catholyte, since lead is optionally only part of the cathode as a support or bottom layer. For example, the lead-containing cathode may be a carbon electrode on a lead support or bottom layer.

[0167]

[0181] Aspect 28d: A method comprising operating a bipolar stack of electrochemical cells, each electrochemical cell of the stack having an independent first cathode for electrochemical reduction and a first anode for electrochemical oxidation; each electrochemical cell comprising a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the bipolar stack comprises one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; The method, wherein the bipolar plates each comprise a first lead electrode that is a first anode of an electrochemical cell and a second electrode that is a first cathode of an adjacent electrochemical cell.

[0168]

[0182] Embodiment 28e: A system comprising two or more electrochemical cells, each cell comprising: a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first catholyte in contact with the first cathode, and a first separator separating the first anolyte from the first catholyte; providing a bipolar plate between two adjacent electrochemical cells such that the adjacent electrochemical cells share a bipolar plate therebetween; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; A system in which each bipolar plate comprises a first lead electrode that is a first anode of an electrochemical cell and a second electrode that includes lead that is a first cathode of an adjacent electrochemical cell. In embodiments and aspects herein, the lead-containing electrode may include a lead layer as a bottom or support layer. For example, a lead-containing cathode may include a lead layer as a bottom or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily include lead. As a result, the lead-containing cathode does not necessarily have lead in contact with the catholyte, as the lead is optionally only part of the cathode as a support or bottom layer. For example, a lead-containing cathode may be a carbon electrode on a lead support or bottom layer.

[0169]

[0183] Embodiment 28f: A system comprising two or more electrochemical cells, each cell comprising: a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first catholyte in contact with the first cathode, and a first separator separating the first anolyte from the first catholyte; providing a bipolar plate between two adjacent electrochemical cells such that the adjacent electrochemical cells share a bipolar plate therebetween; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; A system in which the bipolar plates each include a first lead electrode that is a first anode of an electrochemical cell and a second electrode that is a first cathode of an adjacent electrochemical cell.

[0170]

[0184] Embodiment 28g: A system comprising a bipolar stack of two or more electrochemical cells, each cell comprising: a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the bipolar stack comprises one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; A system in which each bipolar plate comprises a first lead electrode that is a first anode of an electrochemical cell and a second electrode that includes lead that is a first cathode of an adjacent electrochemical cell. In embodiments and aspects herein, the lead-containing electrode may include a lead layer as a bottom or support layer. For example, a lead-containing cathode may include a lead layer as a bottom or support layer, but the surface or electrocatalytic material exposed to the catholyte does not necessarily include lead. As a result, the lead-containing cathode does not necessarily have lead in contact with the catholyte, as the lead is optionally only part of the cathode as a support or bottom layer. For example, a lead-containing cathode may be a carbon electrode on a lead support or bottom layer.

[0171]

[0185] Aspect 25h: A system comprising a bipolar stack of two or more electrochemical cells, each cell comprising: a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the bipolar stack comprises one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; A system in which the bipolar plates each include a first lead electrode that is a first anode of an electrochemical cell and a second electrode that is a first cathode of an adjacent electrochemical cell.

[0172]

[0186] Embodiment 29: The method or system of any one of embodiments 25-28, wherein the bipolar plates each comprise a conductive substrate, an anode-facing side, and a cathode-facing side.

[0173]

[0187]

[0041] Aspect 30: The method or system of aspect 29, wherein the conductive substrate is porous or permeable to the electrolyte and dissolved ions.

[0174]

[0188] Aspect 31: The method or system of aspect 30, wherein the bipolar plates each comprise a lead coating on at least a portion of the interior or pore surface of the porous substrate.

[0175]

[0189] Aspect 32: The method or system of aspect 31, wherein the coating has a thickness selected from the range of 50 μm to 5 mm.

[0176]

[0190] Embodiment 33: The method or system of embodiment 29, wherein the conductive substrate is non-porous or non-permeable to the electrolyte and dissolved ions.

[0177]

[0191] Aspect 34: A method or system described in any one of aspects 29 to 33, wherein the bipolar plates each have a first layer of lead on the side facing the anode, a second layer of lead on the side facing the cathode, or separate layers of lead on each of the anode-facing side and the cathode-facing side.

[0178]

[0192] Aspect 35: The method or system described in aspect 34, wherein each layer of lead is a layer on a substrate.

[0179]

[0193] Aspect 36: A method or system according to aspect 34 or 35, wherein the lead layer is non-porous or non-permeable to the electrolyte and dissolved ions, respectively.

[0180]

[0194] Aspect 37: A method or system according to any one of aspects 34 to 36, wherein each lead layer protects the substrate from exposure to the nearest electrolyte.

[0181]

[0195] Aspect 38: A method or system according to any one of aspects 34 to 37, wherein the lead layers each independently have a thickness selected from the range of 50 μm to 5 mm.

[0182]

[0196] Aspect 39: A method or system described in any one of aspects 29 to 38, wherein the conductive substrate is characterized by a compressive yield strength selected from the range of 10 MPa to 200 MPa and / or a Young's modulus selected from the range of 600 MPa to 1500 MPa.

[0183]

[0197] Embodiment 40: The method or system of any one of embodiments 25-39, wherein the first cathode of each of the bipolar plates is a carbon cathode or a carbon-containing cathode.

[0184]

[0198] Aspect 41: A method or system described in any one of aspects 34 to 40, wherein each bipolar plate has a first layer of lead on a side facing the anode, the first layer of lead being the first anode of each bipolar plate.

[0185]

[0199] Aspect 42: A method or system described in any one of aspects 34 to 40, wherein the bipolar plates each comprise a layer of lead on a side facing the anode, and the bipolar plates each further comprise a first anode on, bonded to, coated on, or otherwise adjacent to the first layer of lead.

[0186]

[0200] Aspect 43: A method or system according to any one of aspects 28 to 42, wherein the bipolar stack comprises a conductive spacer layer or a flow field layer through which a fluid can flow.

[0187]

[0201] Embodiment 44a: The method or system of any one of embodiments 1-43, wherein the first anode is a lead electrode including a microstructured and / or nanostructured lead-containing surface in contact with the anolyte.Embodiment 44b: The method or system of any one of embodiments 1-44a, wherein the lead electrode is porous and at least partially permeable to the first anolyte.Embodiment 44c: The method or system of any one of embodiments 1-44b, wherein the lead electrode is lead-containing and / or lead-coated wool or foam.

[0188]

[0202] Aspect 45: The method or system of any one of aspects 1 to 44c, wherein the first anode is free of lead shedding or the rate of lead shedding is less than an equivalent electrochemical cell under equivalent conditions where the first anolyte is free of aqueous iron cations.

[0189]

[0203] Embodiment 46: The method or system of any one of embodiments 1 to 45, wherein the aqueous anions include aqueous sulfur-containing anions, aqueous chloride anions, or both.

[0190]

[0204]

[00137] Aspect 47a: The method or system of aspect 46, wherein the aqueous sulfur-containing anions comprise aqueous sulfate ions. Aspect 47b: The method or system of aspect 46, wherein the aqueous sulfur-containing anions are aqueous sulfate ions. Aspect 47c: The method or system of aspect 46, wherein the aqueous sulfur-containing anions are aqueous sulfate ions having a stoichiometric concentration relative to the concentration of aqueous iron cations in the respective electrolytes. Aspect 47d: The method or system of aspect 46, wherein the aqueous sulfur-containing anions comprise aqueous sulfate ions, and the first anolyte does not comprise aqueous chloride anions.

[0191]

[0205]

[0037] Aspect 48a: The method or system of any one of Aspects 1 to 47d, wherein the first anolyte comprises aqueous lead ions having a concentration of at least 5 ppm.

[0038] Aspect 48b: The method or system of any one of Aspects 1 to 48a, wherein the first anolyte comprises aqueous lead ions having a concentration of at least 10 PPM, or selected from the range of 10 ppm to 0.5 M.

[0192]

[0206] Aspect 49: The method or system of any one of Aspects 1 to 48b, wherein the first anolyte comprises aqueous lead ions having a concentration greater than 10 ppm and less than or equal to the lead ion saturation concentration in the first anolyte at that temperature (e.g., the lead ion saturation concentration in H2SO4 and / or HCl at ∼50°C to 80°C).

[0193]

[0207] Embodiment 50: The method or system of any one of embodiments 1 to 49, wherein the electrochemical cell further includes a secondary or sacrificial source of lead ions (other than the first anode itself) in contact with the first anolyte to slow or prevent dissolution of Pb from the first anode into the first anolyte.

[0194]

[0208] Aspect 51: Operating the electrochemical cell comprises discharging a first Fe 3+ ions are electrochemically reduced to form Fe in the first catholyte. 2+ The method or system according to any one of embodiments 1 to 50, wherein ions are formed.

[0195]

[0209] Aspect 52: The step of operating the electrochemical cell further comprises:

[0039] The method or system of any one of embodiments 1 to 51, comprising electrochemically oxidizing water at a first anode to produce O2 and aqueous protons in the first anolyte.

[0196]

[0210] Aspect 53a: The operating step includes a first anode characterized by a steady-state anode potential selected from the range of 1.2 to 3.0 V vs. NHE, and / or the operating step includes a first anode characterized by a steady-state anode potential selected from the range of 5 to 200 mA / cm 2 (Optionally select approximately 30 to 100mA / cm 2 ) and / or operating each electrochemical cell characterized by a current density selected from the range of 5 to 50 mA / cm 2Aspect 53b: The method or system of any one of aspects 1 through 53a, wherein the operating step includes a first anode characterized by a steady-state anode potential of at least 1 V relative to the NHE (optionally at least 1.1, optionally at least 1.2, optionally at least 1.3 V, optionally at least 1.4 V, optionally at least 1.5 V, optionally at least 1.6 V relative to the NHE), and optionally no more than 2.5 V relative to the NHE (optionally 2.7 V, optionally 2.9 V, optionally 3.0 V, optionally 3.2 V, optionally 3.5 V relative to the NHE). Aspect 53c: The method or system of any one of aspects 1 through 53a, wherein the operating step includes a first anode characterized by a steady-state anode potential of at least 1 V relative to the NHE (optionally at least 1.1, optionally at least 1.2, optionally at least 1.3 V, optionally at least 1.4 V, optionally at least 1.5 V, optionally at least 1.6 V relative to the NHE). Aspect 53d: The method or system of any one of aspects 1 through 53a, wherein the operating step includes a first anode characterized by a steady-state anode potential of at least 1 V relative to the NHE (optionally at least 1.1, optionally at least 1.2, optionally at least 1.3 V, optionally at least 1.4 V, optionally at least 1.5 V, optionally at least 1.6 V relative to the NHE). 2 (Optionally select approximately 30 to 100mA / cm 2 ) and / or operating each electrochemical cell characterized by a current density selected from the range of 5 to 50 mA / cm 2 The method or system of any one of embodiments 1 through 53b, comprising: each electrochemical cell characterized by a bias current density of

[0197]

[0211] Aspect 54a: Electrochemical cell having a current of 1 to 500 mA / cm 2 The method or system of any one of embodiments 1 through 53c, wherein the electrochemical cell is characterized by a steady-state current density selected from the range of at least 1 mA / cm. 2 (Optionally at least 5mA / cm 2 , optionally at least 10mA / cm 2 , optionally at least 20mA / cm 2 , optionally at least 50mA / cm 2 , optionally at least 75mA / cm 2 , optionally at least 100mA / cm 2 ) and optionally 2A / cm 2 or less (optionally 1.5 A / cm 2 , optionally 1A / cm 2 , optionally 900mA / cm 2, optionally 800mA / cm 2 , optionally 700mA / cm 2 , optionally 600mA / cm 2 , optionally 500mA / cm 2 , optionally 400mA / cm 2 The method or system of any one of embodiments 1 through 54a, characterized by a steady-state current density of

[0198]

[0212] Embodiment 55a: The method or system of any one of embodiments 1-54b, comprising adding a dosing solution having aqueous iron cations to the first anode chamber and / or the first anolyte.Embodiment 55b: The method or system of any one of embodiments 1-55a, comprising rinsing or flushing the anode chamber with a solution having aqueous iron cations.

[0199]

[0213] Aspect 56a: The method or system of aspect 55, wherein the dosing solution comprises aqueous ferrous iron. Aspect 56b: The method or system of aspect 55, wherein the aqueous iron cations in the solution are predominantly or substantially aqueous ferrous ions.

[0200]

[0214] Embodiment 57: The method or system of embodiment 55 or 56, wherein the dosing solution is an electrolyte from a different electrochemical cell or system.

[0201]

[0215] Embodiment 58: The method or system of any one of embodiments 55 to 57, wherein the dosing solution comprises an electrolyte from a metal electroplating cell or system.

[0202]

[0216] Embodiment 59: A method or system according to any one of embodiments 55 to 58, wherein the administration solution is supplied from a separate solution reservoir tank.

[0203]

[0217] Aspect 60: The method or system of any one of aspects 1 to 59, comprising recycling the second electrolyte from the metal electroplating cell to the first anolyte, the second electrolyte having aqueous iron cations.

[0204]

[0218] Aspect 61a: The second electrolyte has an aqueous iron cation concentration of at least about 0.01M, or about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, optionally about 0.099M, optionally about 0.1M) to 0.5M (optionally about 0.49M, optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M) , optionally about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M), e.g., optionally at a concentration selected from the range of about 0.01M to 0.5M, or optionally at a concentration selected from the range of about 0.01M to 0.45M, or optionally at a concentration selected from the range of about 0.01M to 0.445M, or optionally at a concentration selected from the range of about 0.01M to 0.44M, or optionally at a concentration selected from the range of about 0.01M to 0.4M, or optionally at a concentration selected from the range of about 0.05M to 0.5M. Embodiment 61b: The method or system of embodiment 60, wherein the second electrolyte comprises a concentration of aqueous ferrous or ferric cations in the range of at least about 0.01 M or selected from the range of about 0.01 M to about 0.5 M, and optionally selected from the range of about 0.05 M to about 0.5 M.

[0205]

[0219] Embodiment 62: The method or system of embodiment 60 or 61, wherein the second electrolyte comprises catholyte and / or anolyte from an iron electroplating cell.

[0206]

[0220] Aspect 63: The method or system of aspect 62, wherein the catholyte and / or anolyte from the iron electroplating cell is depleted catholyte and / or depleted anolyte, respectively.

[0207]

[0221] Aspect 64: Further, dissolving an iron-bearing ore in an acid to form an acidic iron salt solution; and 64. The method or system of any one of aspects 1-63, comprising providing an acidic iron salt solution to a cathode chamber of an electrochemical cell.

[0208]

[0222] Aspect 65: Further, Fe at the second cathode in the presence of the second catholyte 2+ performing a second electrochemical reduction of the ions to Fe metal; 65. The method or system of any one of aspects 1-64, wherein the iron electroplating cell comprises a second cathode and a second catholyte.

[0209]

[0223] Aspect 66: A method or system according to any one of aspects 1 to 65, comprising switching the first electrochemical cell to a first temporary intermediate condition, the first temporary intermediate condition being characterized by an open circuit voltage where the first anode is in contact with the first anolyte.

[0210]

[0224] Aspect 67: The method or system of aspect 66, wherein the surface of the first anode does not contain lead sulfate during the electrochemically oxidizing and / or switching steps.

[0211]

[0225] Aspect 68: The method or system of aspect 67, wherein the surface of the first anode is free of lead sulfate while in contact with the first anolyte and is characterized by an open circuit voltage.

[0212]

[0226] Embodiment 69: A method or system described in any one of embodiments 66 to 68, wherein the first temporary intermediate condition further includes that the surface of the first anode has a lead-iron alloy containing Pb, Fe, S, and O.

[0213]

[0227] Aspect 70: The lead-iron alloy has the formula FX1:Fe x Pb 2-x 70. The method or system of embodiment 69, wherein SO4, x is greater than 0 and less than 2.

[0214]

[0228] Aspect 71: The method or system described in aspect 69 or 70, wherein the surface of the first anode does not contain a lead-iron alloy during steady-state operation of the electrochemically oxidizing step.

[0215]

[0229] Aspect 72: A method or system described in any one of aspects 69 to 71, comprising a step of forming a lead-iron alloy during the switching step or when the surface of the first anode contacts the first anolyte and is characterized by an open-circuit voltage.

[0216]

[0230] Aspect 73: The method or system of aspect 72, wherein the lead-iron alloy is produced in the presence of aqueous iron sulfate in the first anolyte.

[0217]

[0231] Aspect 74: The method or system of any one of Aspects 1-73, wherein the electrochemical cell is according to any embodiment or aspect of the “first electrochemical cell” disclosed in PCT '732 and Provis '092 and / or further comprises any embodiment or aspect of the “first electrochemical cell” disclosed in PCT '732 and Provis '092, each of which is incorporated herein in its entirety.

[0218]

[0232] Aspect 75: The method or system of any one of aspects 1 to 74, wherein the metal electroplating cell or iron electroplating cell is according to any embodiment or aspect of the “second electrochemical cell” disclosed in PCT '732 and Provis '092.

[0219]

[0233] Aspect 76: A method or system according to any one of aspects 1 to 75, further comprising any feature, step, embodiment or aspect disclosed in PCT '732 and Provis '092.

[0220]

[0234] Aspect 77: The method or system of any one of aspects 1 to 76, wherein the first separator is a first separator described in any embodiment or aspect described in PCT '732 and Provis '092.

[0221]

[0235] Embodiment 78: The method or system of any one of embodiments 1 to 77, wherein the first cathode includes lead as an underlayer or support layer.

[0222]

[0236] Embodiment 79: The method or system of any one of embodiments 1 to 78, wherein the first cathode does not include lead in contact with the first catholyte.

[0223]

[0237] Embodiment 80: The method or system of any one of embodiments 1 to 79, wherein the first cathode comprises a carbon electrode in contact with the first catholyte.

[0224]

[0238] Aspect 81: A method of making one or more electrochemical cells according to any one and / or any embodiment of Aspects 1-80 disclosed herein, such as any embodiment, feature, aspect, process, technique, and step described in paragraphs

[0064] -

[0093] and illustrated in Figures 1-4.

[0225]

[0239] Aspect 82: A method of making a bipolar stack described in any one and / or any embodiment of Aspects 1 to 81 disclosed herein, such as any embodiment, feature, aspect, process, technique, and step described in paragraphs

[0064] to

[0093] and illustrated in Figures 1 to 4.

[0226]

[0240] Aspect 83a: The operating step includes one or more of establishing and / or maintaining a concentration of aqueous iron cations in the first anolyte within a stability concentration range, the stability concentration range being about 0.01M (optionally about 0.02M, optionally about 0.03M, optionally about 0.04M, optionally about 0.05M, optionally about 0.06M, optionally about 0.07M, optionally about 0.08M, optionally about 0.09M, optionally about 0.095M, 83. The method or system of any one of aspects 1-82, wherein the ATP concentration is selected from the range of about 0.099M, optionally about 0.1M) to optionally about 0.5M (optionally about 0.49M), optionally about 0.48M, optionally about 0.47M, optionally about 0.46M, optionally about 0.45M, optionally about 0.44M, optionally about 0.43M, optionally about 0.42M, optionally about 0.41M, optionally about 0.40M, optionally about 0.39M, optionally about 0.38M). Optionally, in any aspect herein, the stable concentration range is selected from the range of about 0.01 M to about 0.1 M, with any value and range therebetween being expressly contemplated and disclosed herein, e.g., optionally about 0.02 M to about 0.09 M, or optionally about 0.03 M to about 0.08 M, or optionally about 0.04 M to about 0.07 M, or optionally about 0.03 M to about 0.08 M, or optionally about 0.05 M. Aspect 83b: The method or system of any one of aspects 1-83a, wherein the operating step comprises establishing the one or more. Aspect 83c: The method or system of any one of aspects 1-83b, wherein the operating step comprises maintaining.

[0227]

[0241] Embodiment 84: The method or system described in embodiment 83, wherein the establishing each temporarily provides a stable concentration range.

[0228]

[0242] Aspect 85: The method or system of aspect 83 or 84, wherein establishing occurs prior to starting up the electrochemical cell and / or shutting down the electrochemical cell. Optionally, starting up the cell includes transitioning a cell voltage, e.g., a voltage between a first anode and a first cathode, from an open circuit voltage (OCV) to an operating voltage, where the operating voltage corresponds to a voltage corresponding to the electrochemical reduction at the first cathode and the electrochemical oxidation at the first anode, such as an oxygen evolution reaction. Optionally, shutting down the cell includes transitioning a cell voltage, e.g., a voltage between a first anode and a first cathode, from an operating voltage, where the operating voltage corresponds to a voltage corresponding to the electrochemical reduction at the first cathode and the electrochemical oxidation at the first anode, such as an oxygen evolution reaction. The electrochemical reduction at the first cathode and the electrochemical oxidation at the first anode do not or cannot occur when the cell is in OCV.

[0229]

[0243] Embodiment 86a: The method or system of any one of embodiments 83-85, wherein establishing and maintaining each comprise administering the aqueous iron cations to a first anolyte, if present.Embodiment 86b: The method or system of any one of embodiments 83-85, wherein establishing each comprises administering the aqueous iron cations to a first anolyte.Embodiment 86c: The method or system of any one of embodiments 83-85, wherein maintaining comprises administering the aqueous iron cations to a first anolyte.Embodiment 86d: The method or system of any one of embodiments 83-85, wherein establishing and maintaining each comprise administering the aqueous iron cations to a first anolyte.

[0230]

[0244] Aspect 87: The method or system of aspect 86, wherein the administering occurs as one or more separate events during the step of operating the cell.

[0231]

[0245] Embodiment 88: The method or system of embodiment 86, wherein the administering is performed continuously during the step of operating the cell.

[0232]

[0246] Embodiment 89: The method or system of any one of embodiments 86 to 88, wherein the administering comprises providing a liquid iron source, and the liquid iron source is an aqueous solution comprising a dosage concentration of aqueous iron cations.

[0233]

[0247] Aspect 90: The method or system of aspect 89, wherein the liquid iron source comprises depleted or used anolyte from a metal electroplating cell or system.

[0234]

[0248] Embodiment 91: The method or system of embodiment 89 or 90, wherein the liquid iron source comprises depleted or used catholyte from a metal electroplating cell or system.

[0235]

[0249] Aspect 92: The method or system of any one of aspects 89-91, wherein the liquid iron source is supplied directly to the first anolyte or to the first anode chamber having the first anolyte.

[0236]

[0250] Aspect 93: The method or system of any one of aspects 89 to 92, wherein the liquid iron source is indirectly supplied to the first anolyte or to the first anode chamber having the first anolyte.

[0237]

[0251] Aspect 94: A method or system described in any one of aspects 89 to 93, wherein a liquid iron source is provided to a first anolyte circulation tank in fluid communication with a first anode chamber having a first anolyte, in a fluid line entering the first anode chamber and / or in a fluid line exiting the first anode chamber.

[0238]

[0252] Embodiment 95: The method or system of any one of embodiments 89 to 94, wherein the liquid iron source comprises aqueous ferrous ions.

[0239]

[0253] Aspect 96: The method or system of any one of aspects 89 to 95, wherein the liquid iron source is an iron-bearing slag and / or an iron-bearing leachate from a metal and / or ore processing system.

[0240]

[0254] Embodiment 97: The method or system of any one of embodiments 89 to 96, wherein the dosage concentration of aqueous iron cations in the liquid iron source is greater than 0M and less than 0.5M.

[0241]

[0255] Embodiment 98: The method or system of any one of embodiments 83 to 97, wherein the administering comprises providing a solid iron source in the presence of the first anolyte, wherein the solid iron source is capable of being at least partially dissolved by the first anolyte.

[0242]

[0256] Aspect 99: The method or system of aspect 98, wherein the solid iron source is raw ore and / or processed ore.

[0243]

[0257] Aspect 100: The method or system of aspect 98 or 99, wherein the solid iron source is heat-treated ore.

[0244]

[0258] Embodiment 101: The method or system of any one of embodiments 98-100, wherein the solid iron source comprises solid ferrous ion.

[0245]

[0259] Embodiment 102: The method or system of any one of embodiments 86-101, wherein each of the administering is performed in response to a trigger event, the trigger event comprising a concentration of aqueous iron cations in the first anolyte being below a stable concentration range and / or a current density of the electrochemical cell being below a normal operational current density.

[0246]

[0260] Aspect 103: The method or system of any one of aspects 1 to 102, wherein the electrochemical reduction at the first cathode is an iron electroplating reaction and the electrochemical oxidation reaction is an oxygen evolution reaction (OER) at the first anode.

[0247]

[0261] Embodiment 104: The method or system of embodiment 103, wherein the separator is an anion exchange membrane.

[0248]

[0262] Embodiment 105: The method or system of any one of embodiments 1 to 104, wherein the first anode does not comprise a mixed metal oxide (MMO) material.

[0249]

[0263] Embodiment 106: The method or system of any one of embodiments 1 to 105, wherein the first anode does not include Ir, Ru, or Pt.

[0250]

[0264] Embodiment 107: The method or system of any one of embodiments 1 to 106, wherein the first anode is an undoped or unalloyed lead electrode.

[0251] Incorporation-by-Reference and Modification Statement

[0265] All references throughout this application (e.g., patent documents, published patent applications, and non-patent documents or other materials, including issued or granted patents or equivalents) are incorporated herein by reference in their entirety, to the extent that each reference is at least partially inconsistent with the disclosure in this application, as if each were separately incorporated by reference (e.g., a partially inconsistent reference is incorporated by reference except for the partially inconsistent portion of the reference).

[0252]

[0266] The terms and expressions used herein are used for purposes of description and not limitation, and there is no intention in the use of such terms and expressions to exclude any equivalents of the shown and described features or portions thereof, recognizing that various modifications are possible within the scope of any particular claimed invention. Thus, while the present invention has been specifically disclosed by preferred embodiments, exemplary embodiments, and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be made by those skilled in the art, and that such modifications and variations are considered to be within the scope of the present invention as defined by the appended claims. The specific embodiments described herein are examples of useful embodiments of the present invention, and it will be apparent to those skilled in the art that the present invention can be practiced using numerous variations of the devices, device components, and method steps described herein. As will be apparent to those skilled in the art, the methods and devices useful for the methods may include numerous optional composition and processing elements and steps.

[0253]

[0267] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to a "cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art. Similarly, the terms "a" (or "an"), "one or more," and "at least one" can be used interchangeably herein. It should also be noted that the terms "comprise," "include," and "have" can also be used interchangeably. The phrase "as defined in any of claims XX-YY" (XX and YY refer to the claim number) is intended to indicate multiple dependent claims in the alternative and, in some embodiments, is interchangeable with the phrase "as defined in any one of claims XX-YY."

[0254]

[0268] When a group of substituents is disclosed herein, it is understood that all individual members and all subgroups of that group are separately disclosed, including structural and compositional polymorphs of the iron oxide ore material or members of that group. When Markush groups or other groupings are used herein, it is intended that all individual members of the group and all possible combinations and subcombinations of the group are individually included in the disclosure. When a compound is described herein, e.g., in a formula or chemical name, without specifying a specific isomer, enantiomer, or diastereomer of the compound, the description is intended to include each isomer and enantiomer of the described compound, individually or in any combination. Furthermore, unless otherwise specified, all isotopic variations of the compounds disclosed herein are intended to be encompassed by the disclosure. For example, it will be understood that any one or more hydrogens in a disclosed molecule can be replaced with deuterium or tritium. Isotopic variations of molecules are generally useful as standards in assays of molecules and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variations are known in the art. The specific names of the compounds are intended as examples, as it is known that one of skill in the art can refer to the same compound by different names.

[0255]

[0269] With respect to salts of the compounds herein, one skilled in the art can select from a wide variety of available counterions appropriate for preparing the salts of the invention for a given application. In a particular application, the selection of a given anion or cation for preparing a salt may result in an increase or decrease in the solubility of that salt.

[0256]

[0270] All devices, systems, subsystems, methods, processes, components, and / or combinations of components described or illustrated herein can be used to practice any claimed invention(s), unless otherwise stated.

[0257]

[0271] When a range is given herein, such as a temperature range, a time range, or a composition or concentration range, it is intended that the disclosure include all intermediate ranges and subranges, as well as all individual values ​​included in the given range. It will be understood that any subrange or individual value included in a range or subrange included in the description herein can be excluded from the claims herein.

[0258]

[0272] All patents and publications mentioned in the specification are indicative of the level of skill of those skilled in the art to which the disclosed devices, systems, methods, and processes pertain. It is intended that the references cited herein are incorporated by reference in their entirety to represent the state of the art as of their publication or filing date, and that this information can be used, if necessary, to exclude certain embodiments that fall within the prior art. For example, if a composition of matter is claimed, it should be understood that compounds that were known and available in the art prior to Applicant's invention, including compounds whose enabling disclosures are described in the references cited herein, are not intended to be included in the composition of matter claims herein.

[0259]

[0273] As used herein, "comprising" is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended, not excluding additional, unrecited elements or method steps. As used herein, "consisting of" does not exclude any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of" does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein, any of the terms "comprising," "consisting essentially of," and "consisting of" are interchangeable with either of the other two terms. The claimed invention(s) illustratively described herein may be suitably practiced in the absence of any element(s), limitation(s) not specifically disclosed herein.

[0260]

[0274] Those skilled in the art will understand that starting materials, reagents, synthetic, purification, analytical, and assay methods other than those specifically exemplified can be used in the practice of the claimed invention without undue experimentation. All art-known functional equivalents of such materials and methods are intended to be encompassed by these inventions.

Claims

1. 1. A method for stabilizing a lead anode, comprising: the method comprising operating an electrochemical cell comprising electrochemical reduction at a first cathode and electrochemical oxidation at a first anode; the electrochemical cell comprises a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first catholyte in contact with the first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method of claim 1, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of 0.01M to 0.5M.

2. 1. A method for stabilizing a lead anode, comprising: operating an electrochemical cell, the method including electrochemical reduction at a first cathode and electrochemical oxidation at a first anode; and recycling a second electrolyte from a metal electroplating cell to the first anolyte; the second electrolyte having aqueous iron cations; the electrochemical cell comprises a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first catholyte in contact with the first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method of claim 1, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of 0.01M to 0.5M.

3. 3. The method of claim 2, wherein the second electrolyte comprises depleted catholyte and / or depleted anolyte from an iron electroplating cell.

4. The method of any one of claims 1 to 3, wherein performing electrochemical oxidation comprises an oxygen evolution reaction (OER) at the first anode.

5. The method of any one of claims 1 to 4, wherein the first anolyte comprises aqueous sulfate anions.

6. 1. A method for stabilizing a lead anode, comprising: the method comprising operating an electrochemical cell comprising conducting an electrochemical reduction at a first cathode and an oxygen evolution reaction (OER) at a first anode; the electrochemical cell comprises a first anode chamber having a first anolyte in contact with the first anode, a first cathode chamber having a first catholyte in contact with the first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method of claim 1, wherein the first anolyte comprises aqueous iron sulfate at a concentration selected from the range of 0.01M to 0.5M.

7. 7. The method of any one of claims 1 to 6, wherein the concentration of the aqueous iron cations in the first anolyte is selected from the range of 0.05M to 0.5M.

8. 8. The method of any one of claims 1 to 7, wherein the concentration of the aqueous iron cations in the first anolyte is less than the concentration of the aqueous iron cations in the first catholyte.

9. 9. The method of any one of claims 1 to 8, wherein the steady-state concentration of the aqueous iron cations in the first anolyte is selected from the range of 0.01M to 0.5M.

10. 10. The method of any one of claims 1 to 9, wherein the steady-state concentration of the aqueous iron cations in the first anolyte is selected from the range of 0.05M to 0.5M.

11. 11. The method of any one of claims 1 to 10, wherein the steady-state concentration of the aqueous iron cations in the first anolyte is less than the steady-state concentration of the aqueous iron cations in the first catholyte.

12. 12. The method of any one of claims 1 to 11, wherein the aqueous iron cations in the first anolyte comprise aqueous ferric ions.

13. 1. A method comprising: operating an electrochemical cell comprising electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, the electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method further comprises: a step of dissolving solid manganese oxide in said first anolyte in the presence of aqueous ferrous ions.

14. 14. The method of claim 13, wherein the dissolving step comprises converting the solid manganese oxide into one or more aqueous manganese salts in the presence of the aqueous ferrous ions.

15. 15. The method of claim 14, wherein said converting comprises (i) reacting said solid manganese oxide with said aqueous ferrous ions, and / or (ii) electrochemically reducing said solid manganese oxide to one or more aqueous manganese salts in the presence of said aqueous ferrous ions.

16. 16. The method of any one of claims 13 to 15, wherein the ratio of moles of aqueous ferrous ions in the first anolyte to moles of solid manganese oxide in the first anolyte chamber is at least 0.9 during at least a portion of the dissolving step.

17. 17. The method of claim 16, wherein the ratio of moles of aqueous ferrous ions in the first anolyte to moles of solid manganese oxide in the first anode chamber is at least 2 during at least a portion of the dissolving step.

18. 18. The method of any one of claims 13 to 17, wherein the first anolyte comprises at least 5 mM aqueous ferrous ions during at least a portion of the dissolving step.

19. 19. The method of any one of claims 13 to 18, comprising the step of providing aqueous ferrous ions to the first anolyte prior to and / or during the dissolving step.

20. 20. The method of claim 19, wherein the providing step comprises flushing the first anode chamber with an aqueous ferrous ion-containing solution.

21. 21. The method of claim 19 or 20, wherein the providing step comprises directly or indirectly recycling ferrous iron-containing electrolyte from an electroplating cell to the first anolyte.

22. 22. The method of any one of claims 19 to 21, wherein the providing step comprises electrochemically producing aqueous ferrous ions in the first anolyte.

23. The method of any one of claims 13 to 22, wherein the first anolyte comprises aqueous Mn ions.

24. 1. A method comprising: operating an electrochemical cell comprising electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, the electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The method further comprises: applying a reverse bias to said first anode for a finite time, said method comprising electrochemically reducing aqueous ferric ions to aqueous ferrous ions at said first anode in the presence of said first anolyte.

25. 25. A method according to any one of claims 1 to 24, comprising operating a bipolar stack of electrochemical cells, each electrochemical cell of the stack being independently an electrochemical cell according to any one of claims 1 to 24.

26. the bipolar stack comprising one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; 26. The method of claim 25, wherein each bipolar plate comprises a first lead electrode that is the first anode of an electrochemical cell and a second electrode comprising lead that is the first cathode of an adjacent electrochemical cell.

27. 1. A method comprising operating two or more electrochemical cells comprising electrochemical reduction at a first cathode and electrochemical oxidation at a first anode, Each electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; adjacent electrochemical cells share a bipolar plate therebetween; The method, wherein each bipolar plate comprises a first lead electrode that is the first anode of an electrochemical cell and a second electrode comprising lead that is the first cathode of an adjacent electrochemical cell.

28. 1. A method comprising operating a bipolar stack of electrochemical cells, comprising: each electrochemical cell of the stack having an independent first cathode for electrochemical reduction and a first anode for electrochemical oxidation; Each electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the bipolar stack comprising one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; The method, wherein each bipolar plate comprises a first lead electrode that is the first anode of an electrochemical cell and a second electrode comprising lead that is the first cathode of an adjacent electrochemical cell.

29. The method of any one of claims 25 to 28, wherein the bipolar plates each comprise a conductive substrate, an anode-facing side and a cathode-facing side.

30. 30. The method of claim 29, wherein the conductive substrate is porous or permeable to electrolytes and dissolved ions.

31. 31. The method of claim 30, wherein each bipolar plate comprises a coating of lead on at least a portion of the interior or pore surfaces of the porous substrate.

32. 32. The method of claim 31, wherein the coating has a thickness selected from the range of 50 μm to 5 mm.

33. 30. The method of claim 29, wherein the conductive substrate is non-porous or non-permeable to electrolytes and dissolved ions.

34. 34. The method of any one of claims 29 to 33, wherein each bipolar plate comprises a first layer of lead on the anode-facing side, a second layer of lead on the cathode-facing side, or separate layers of lead on each of the anode-facing side and the cathode-facing side.

35. 35. The method of claim 34, wherein each layer of lead is a layer on the substrate.

36. 36. The method of claim 34 or 35, wherein the lead layer is non-porous or non-permeable to the electrolyte and dissolved ions, respectively.

37. A method according to any one of claims 34 to 36, wherein each layer of lead protects the substrate from exposure to the nearest electrolyte.

38. 38. A method according to any one of claims 34 to 37, wherein the layers of lead each independently have a thickness selected from the range of 50 μm to 5 mm.

39. 39. The method according to any one of claims 29 to 38, wherein the conductive substrate is characterized by a compressive yield strength selected from the range of 10 MPa to 200 MPa and / or a Young's modulus selected from the range of 600 MPa to 1500 MPa.

40. 40. The method of any one of claims 25 to 39, wherein the first cathode of each bipolar plate is a carbon cathode or a carbon-containing cathode.

41. 41. The method of any one of claims 34 to 40, wherein each bipolar plate comprises a first layer of lead on a side facing the anode, the first layer of lead being the first anode of the respective bipolar plate.

42. 41. The method of any one of claims 34 to 40, wherein each bipolar plate comprises a layer of lead on a side facing the anode, and each bipolar plate further comprises the first anode on, bonded to, coated on, or otherwise adjacent to the first layer of lead.

43. A method according to any one of claims 28 to 42, wherein the bipolar stack comprises a conductive spacer layer or a flow field layer through which a fluid can flow.

44. 44. The method of any one of claims 1 to 43, wherein the first anode is a lead electrode comprising a microstructured and / or nanostructured lead-containing surface in contact with the anolyte.

45. 45. The method of any one of claims 1 to 44, wherein the lead electrode is porous or at least partially permeable to the first anolyte.

46. 46. ​​A method according to any one of the preceding claims, wherein the lead electrode is a lead-containing and / or lead-coated wool or foam.

47. 47. The method of any one of claims 1 to 46, wherein the first anode is free of lead shedding or the rate of lead shedding is less than an equivalent electrochemical cell under equivalent conditions where the first anolyte is free of aqueous iron cations.

48. 48. The method of any one of claims 1 to 47, wherein the aqueous anions comprise aqueous sulfur-containing anions, aqueous chloride anions, or both.

49. 49. The method of claim 48, wherein the aqueous sulfur-containing anions comprise aqueous sulfate ions.

50. 50. The method of any one of claims 1 to 49, wherein the first anolyte comprises aqueous lead ions having a concentration of at least 10 ppm.

51. 51. The method of any one of claims 1 to 50, wherein the first anolyte comprises aqueous lead ions having a concentration of 10 ppm or more and up to a saturation concentration of lead ions in the first anolyte.

52. 52. The method of any one of claims 1 to 51, wherein the electrochemical cell further comprises a secondary or sacrificial source of lead ions in contact with the first anolyte to slow or prevent dissolution of Pb from the first anode.

53. the step of operating the electrochemical cell further comprising: The first cathode is a first Fe ３＋ ions are electrochemically reduced to form Fe in the first catholyte. ２＋ 53. The method of any one of claims 1 to 52, wherein ions are formed.

54. The step of operating the electrochemical cell further comprises: Water is electrochemically oxidized at the first anode to produce O in the first anolyte. ２ and generating aqueous protons.

55. the operating step includes a first anode characterized by a steady-state anode potential selected from the range of 1.2 to 3.0 V; The step of operating is 5 to 200 mA / cm ２ and / or each electrochemical cell characterized by a current density selected from the range The step of operating is 5 to 50 mA / cm ２ 55. The method of any one of claims 1 to 54, comprising each electrochemical cell characterized by a bias current density of

56. The electrochemical cell has a current density of 1 to 500 mA / cm ２ 56. The method according to any one of claims 1 to 55, characterized by a steady state current density selected from the range

57. 57. The method of any one of claims 1 to 56, comprising adding a dosing solution having aqueous iron cations to the first anodic chamber and / or the first anolyte.

58. 58. The method of claim 57, wherein the dosing solution comprises aqueous ferrous iron.

59. 59. The method of claim 57 or 58, wherein the dosing solution is an electrolyte from a different electrochemical cell or system.

60. 60. The method of any one of claims 57 to 59, wherein the dosing solution comprises electrolyte from a metal electroplating cell or system.

61. 61. The method of any one of claims 57 to 60, wherein the dosing solution is supplied from a separate solution reservoir.

62. 62. The method of any one of claims 1-61, comprising recycling a second electrolyte from a metal electroplating cell to the first anolyte, the second electrolyte having aqueous iron cations.

63. 63. The method of claim 62, wherein the second electrolyte comprises a concentration of aqueous iron cations selected from the range of 0.01 M to 0.5 M.

64. 64. The method of claim 62 or 63, wherein the second electrolyte comprises catholyte and / or anolyte from an iron electroplating cell.

65. 65. The method of claim 64, wherein the catholyte and / or anolyte from the iron electroplating cell is depleted catholyte and / or depleted anolyte, respectively.

66. further comprising dissolving the iron-containing ore in an acid to form an acidic iron salt solution; and 66. The method of any one of claims 1 to 65, comprising providing the acidic iron salt solution to the cathode chamber of the electrochemical cell.

67. Furthermore, in the presence of the second catholyte, Fe ２＋ performing a second electrochemical reduction of the ions to Fe metal; 67. The method of any one of claims 1 to 66, wherein an iron electroplating cell comprises the second cathode and the second catholyte.

68. 68. The method of any one of claims 1 to 67, wherein the operating step comprises one or more establishing and / or maintaining a concentration of the aqueous iron cations in the first anolyte within a stable concentration range, the stable concentration range being selected from the range of 0.01 M to 0.5 M.

69. 69. The method of claim 68, wherein each of said establishing provides said stable concentration range temporarily.

70. 70. The method of claim 68 or 69, wherein said establishing occurs prior to starting up the electrochemical cell and / or prior to shutting down the electrochemical cell.

71. 71. The method of any one of claims 68-70, wherein each of establishing and maintaining comprises administering the aqueous iron cations, if present, to the first anolyte.

72. 72. The method of claim 71, wherein said administering occurs as one or more separate events during said step of operating said cell.

73. 72. The method of claim 71, wherein said administering is performed continuously during said step of operating said cell.

74. 75. The method of any one of claims 71 to 74, wherein the administering comprises providing a liquid iron source, the liquid iron source being an aqueous solution comprising the dosage concentration of aqueous iron cations.

75. 75. The method of claim 74, wherein the source of liquid iron comprises depleted or used anolyte from a metal electroplating cell or system.

76. 76. The method of claim 74 or 75, wherein the source of liquid iron comprises depleted or used catholyte from a metal electroplating cell or system.

77. 77. The method of any one of claims 74 to 76, wherein the liquid iron source is supplied directly to the first anolyte or to a first anode chamber containing the first anolyte.

78. 78. The method of any one of claims 74 to 77, wherein the liquid iron source is indirectly supplied to the first anolyte or to a first anode chamber having the first anolyte.

79. 79. The method of any one of claims 74 to 78, wherein the source of liquid iron is supplied to a first anolyte circulation tank in fluid communication with the first anode chamber having the first anolyte, to a fluid line entering the first anode chamber, and / or to a fluid line exiting the first anode chamber.

80. 80. The method of any one of claims 74 to 79, wherein the liquid iron source comprises aqueous ferrous ions.

81. 81. A method according to any one of claims 74 to 80, wherein the source of liquid iron is an iron-bearing slag and / or an iron-bearing leachate from a metal and / or ore processing system.

82. 82. The method of any one of claims 74 to 81, wherein the dosage concentration of the aqueous iron cations in the liquid iron source is greater than 0M and less than 0.5M.

83. 83. The method of any one of claims 71 to 82, wherein the administering comprises providing a solid iron source in the presence of the first anolyte, the solid iron source being capable of being at least partially dissolved by the first anolyte.

84. 84. The method of claim 83, wherein the solid iron source is raw ore and / or processed ore.

85. 85. The method of claim 83 or 84, wherein the solid iron source is heat-treated ore.

86. 86. The method of any one of claims 84-85, wherein the solid iron source comprises solid ferrous ions.

87. Each of said administering is in response to a trigger event, said trigger event being: a concentration of the aqueous iron cations in the first anolyte that is less than the stability concentration range; and / or A method according to any one of claims 71 to 86, comprising: a current density of the electrochemical cell below a normal operational current density.

88. 88. The method of any one of claims 1 to 87, wherein the electrochemical reduction at the first cathode is an iron electroplating reaction and the electrochemical oxidation reaction at the first anode is an oxygen evolution reaction (OER).

89. 89. The method of claim 88, wherein the separator is an anion exchange membrane.

90. 90. The method of any one of claims 1 to 89, wherein the first anode does not comprise a mixed metal oxide (MMO) material.

91. The method of any one of claims 1 to 90, wherein the first anode is free of Ir, Ru and Pt.

92. 92. The method of any one of claims 1 to 91, wherein the first anode is an undoped or unalloyed lead electrode.

93. 1. A system for stabilizing a lead anode, comprising: the system comprises an electrochemical cell; the electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of 0.01M to 0.5M.

94. 1. A system for stabilizing a lead anode, comprising: the system comprises an electrochemical cell; The electrochemical cell comprises: an electroplating cell comprising: a first anode chamber having a first anolyte in contact with a first anode; a first cathode chamber having a first catholyte in contact with a first cathode; and a first separator separating the first anolyte from the first catholyte; a metal electroplating cell; and an electrolyte recycling subsystem for recycling electrolyte from the metal electroplating cells to the first anolyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The system wherein the first anolyte comprises aqueous iron cations at a concentration selected from the range of 0.01M to 0.5M.

95. 1. A system for stabilizing a lead anode, comprising: the system comprises an electrochemical cell; The electrochemical cell comprises: a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; an oxygen evolution reaction (OER) occurs at the first anode; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; The system wherein the first anolyte comprises aqueous iron sulfate at a concentration selected from the range of 0.01M to 0.5M.

96. 1. A system comprising an electrochemical cell, The electrochemical cell comprises: a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the first anolyte comprises aqueous ferrous ions that promote dissolution of solid manganese oxide present in the first anolyte chamber in the first anolyte.

97. 1. A system comprising an electrochemical cell, the electrochemical cell comprises a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the electrochemical cell is configured to electrochemically reduce aqueous ferric ions to aqueous ferrous ions at the first anode in the presence of the first anolyte by applying a reverse bias to the first anode for a finite period of time.

98. two or more electrochemical cells, each cell including a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; and providing a bipolar plate between two adjacent electrochemical cells such that the adjacent electrochemical cells share a bipolar plate therebetween; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; A system in which each bipolar plate comprises a first lead electrode that is a first anode of the electrochemical cell and a second electrode comprising lead that is a first cathode of the adjacent electrochemical cell.

99. 1. A system comprising a bipolar stack of two or more electrochemical cells, each cell comprising a first anode chamber having a first anolyte in contact with a first anode, a first cathode chamber having a first catholyte in contact with a first cathode, and a first separator separating the first anolyte from the first catholyte; the first anode is a lead electrode; the first anolyte and the first catholyte each independently comprise aqueous iron cations and aqueous anions; the bipolar stack comprising one or more bipolar plates; adjacent electrochemical cells share a bipolar plate therebetween; A system in which each bipolar plate comprises a first lead electrode that is a first anode of the electrochemical cell and a second electrode comprising lead that is a first cathode of the adjacent electrochemical cell.

100. 100. The system of claim 98 or 99, wherein the first cathode comprises lead as an underlayer or support layer.

101. 101. The system of claim 100, wherein the first cathode is free of lead in contact with the first catholyte.

102. 102. The system of claim 100 or 101, wherein the first cathode comprises a carbon electrode in contact with the first catholyte.

103. 2. The method of claim 1, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of at least 0.01M to 0.44M.

104. 3. The method of claim 2, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of at least 0.01M to 0.44M.

105. 4. The method of claim 3, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of at least 0.01M to 0.44M.

106. 94. The system of claim 93, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of at least 0.01M to 0.44M.

107. 95. The system of claim 94, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of at least 0.01M to 0.44M.

108. 96. The system of claim 95, wherein the first anolyte comprises the aqueous iron cations at a concentration selected from the range of at least 0.01M to 0.44M.

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