Iron recovery with wüstite intermediate

Abstract

Various processes, apparatus, systems, and methods for improved extraction of metallic iron from iron ore sources are disclosed. Thermal reduction pre-treatment is used to reduce a starting iron-containing feedstock material, for example, hematite, to a thermally reduced material having a net iron oxidation of approximately +2. For example, disclosed is a method for producing metallic iron from a starting iron-containing feedstock material, the method comprising: processing the starting iron-containing feedstock material to form a pre-leach material, wherein the starting iron-containing feedstock material comprises one or more iron ores; wherein the step of processing comprises thermally reducing the starting iron-containing feedstock in the presence of a reducing atmosphere to form a thermally-reduced material; wherein the thermally reduced material is characterized by a lower net iron oxidation state than that of the starting iron-containing feedstock material; and wherein the pre-leach material comprises at least a portion of the thermally-reduced material.

Description

Iron Recovery With Wiistite IntermediateCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. US 63 / 566,564, filed March 18, 2024, to U.S. Provisional Patent Application Serial No. 63 / 672,599, filed July 17, 2024, and to U.S. Provisional Patent Application Serial No. 63 / 704,204, filed October 7, 2024, each of which is incorporated herein by reference in its entirety for all purposes.BACKGROUND

[0002] This application relates generally to the field of metallurgy, and more particularly to systems and methods for extracting metallic iron from iron ore using hydrometallurgy and electrowinning. Metallic iron may be electroplated from an acidic solution having iron ions dissolved therein. There are advantages in electrowinning metallic iron from an acidic solution with iron ions being predominantly in the ferrous state. To obtain a ferrous-rich acidic solution, iron ore needs to be first dissolved, or leached. The leaching of some iron ores, such as hematite, in an acidic solution can be difficult to make economical, however, due to slow kinetics, in some cases, and formation of aqueous ferric ions. Various embodiments and aspects are disclosed herein to address these and other challenges to ultimately extract metallic iron from iron ores.SUMMARY

[0003] As described in Applicant’s prior patent application, now granted as US Patent 11 ,767,604 (the ‘604 patent, which is incorporated herein by reference in its entirety to the extent not inconsistent with the disclosure herein), extraction of metallic iron from iron oxide ores may be advantageously promoted in some cases by thermally reducing ores containing hematite (Fe2Os) and / or goethite (FeOOH) to magnetite (FesCM). When dissolved in aqueous solution, hematite predominantly forms “ferric” (Fe3+) ions, while magnetite forms both ferric and “ferrous” (Fe2+) ions in an approximately 2:1 ratio. As further described in the ‘604 patent, reducing the aqueous ferric ions to a ferrous state advantageously facilitates further ore dissolution and also simplifies removal of deleterious impurities through a precipitation process optionally driven by a pH shift. Reducing aqueous ferric to ferrous is advantageous in impurity removal because ferrous iron compounds will tend to precipitate at higher pH ranges than the main impurities, whereas ferric compounds would tend to precipitate at pH ranges overlapping theranges at which the targeted impurities will tend to precipitate. Once problematic impurities are removed, metallic iron may then be extracted from the aqueous ferrous solution by electrowinning (also known as electrolytic reduction, electroplating, electrodeposition, etc.) or other methods.

[0004] Various embodiments and aspects of processes, apparatus, systems, and methods for extracting metallic iron from iron ore sources are described herein. Some iron ores (and ore components) dissolve in sulfuric acid more easily than others. Applicants have shown that dissolution kinetics of sulfuric acid leaching at low temperatures (e.g., approximately 50 °C to approximately 90 °C and atmospheric pressure) for some iron ores can be substantially increased by performing, prior to the leaching, a thermal reduction pre-treatment (for example, using one or more gaseous reducing agents such as hydrogen gas) sufficient to reduce at least some, most, or all hematite (Fe2Os) ore components to predominantly magnetite (FesCM) or to a mixture comprising predominantly magnetite with the balance being predominantly iron metal. The thermal reduction pre-treatment may be used to chemically reduce one or more constituents of a feedstock material comprising iron oxide predominantly or substantially in the form of hematite, to a material mixture comprising magnetite, wustite, and metallic iron metal.

[0005] In various embodiments and aspects herein, a feedstock comprising iron oxide in forms including hematite and / or goethite may be thermally reduced to predominantly convert the iron oxides to ferrous oxide (wustite) or to a mixture containing predominantly wustite with some iron metal and optionally including some magnetite. Such thermal reduction may be performed at temperatures greater than 570 °C, for example, in the presence of one or more reductants such as hydrogen gas (whether produced by water electrolysis, by reforming hydrocarbons, or by other methods), forming gas (e.g., mixtures of hydrocarbon gas and hydrogen gas), natural gas, reformed natural gas, carbon monoxide, methane, any other natural or reformed hydrocarbon gas, hydrogen sulfide gas, sulfur dioxide gas, or mixtures of any of these or other reducing gases or solid precursors capable of producing these or other reducing gases at or below the thermal reduction temperature.

[0006] In some embodiments and aspects, an iron feedstock material comprising, consisting of, or consisting essentially of iron carbonate or siderite (FeCOs) may be used as an iron feedstock material. In such embodiments, a thermal reduction step may be unnecessary as the iron is present in a 2+ oxidation state. However, in suchembodiments, a thermal roasting step may be performed in order to release CO2 from the material, leaving predominantly, substantially, or entirely FeO. In such embodiments, the thermal roasting may be performed at a temperature sufficient to release the CO2 and may be performed in an inert atmosphere (e.g., nitrogen, vacuum, or other nonoxidizing atmosphere). In some embodiments, a passivation step according to any of the embodiments described herein may also be employed prior to or during cooling of the reduced material to an ambient temperature to prevent air oxidation of the FeO.

[0007] With reference to the attached figures, the description herein provides various embodiments and examples of process flows, process steps, apparatus, systems, and methods that take advantage of the reduction of a feedstock material to a reduced iron- containing material mixture having a net iron oxidation state (as defined herein) selected from the range of approximately +1 .5 to approximately +2.3, and in some aspects of approximately +1.5 to approximately +2.0. In various embodiments and examples, the reduced iron-containing mixture may be predominantly wustite (alternatively referred to as “ferrous oxide” or “FeO”).BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 A is a schematic illustration of one embodiment of an iron electrowinning process that benefits from a ferrous oxide input material.

[0009] FIG. 1B is a schematic illustration of one embodiment of an iron electrowinning process that benefits from a ferrous oxide input material.

[0010] FIG. 2 is a schematic illustration of another embodiment of an iron electrowinning process that benefits from a ferrous oxide input material.

[0011] FIG. 3 is a schematic illustration of a leaching subsystem, according to aspects herein.

[0012] FIG. 4 is a schematic illustration of an exemplary thermal reduction subsystem and thermal reduction process 400, according to various aspects herein.

[0013] FIG. 5 is a schematic illustration of an exemplary iron electrowinning process, according to various aspects herein, optionally being free of an acid regenerator cell.STATEMENTS REGARDING CHEMICAL COMPOUNDS AND NOMENCLATURE

[0014] In general, the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references andcontexts known to those skilled in the art. The following definitions are provided to clarify their specific use in the context of this disclosure.

[0015] As used herein, the term “iron ore” is intended to be consistent with the term as it is known in the art of iron or steel manufacturing and includes any naturally- occurring material (whether or not processed, refined, or beneficiated) that contains one or more forms of iron oxide including any of the iron ores or other iron feedstock materials described in the ‘604 patent, and / or other materials containing substantial quantities (such as but not limited to at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, at least 35 wt.%, at least 40 wt.%, at least 45 wt.%, at least 50 wt.%, at least 55 wt.%, at least 60 wt.%, at least 65 wt.%, at least 70 wt.%, at least 75 wt.%, at least 80 wt.%, at least 85 wt.%, at least 90 wt.%, or at least 95 wt.%) of iron compounds (iron oxides, iron carbonates, iron silicates, etc).

[0016] 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 more pure than an iron source material, and contains an acceptably low quantity of one or more impurities. In some aspects, pure iron is at least 98 at.% Fe, at least 98.5 at.% Fe, at least 99.0 at.% Fe, at least 99.5 at% Fe, at least 99.9 at.% Fe, at least 99.95 at.% Fe, at least 99.99 at.% Fe, at least 99.995 at.% Fe, or at least 99.999 at.% Fe.

[0017] As used herein, the terms “iron source material,” “iron feedstock” or simply “feedstock” are used to refer to iron-containing materials that may be used as inputs into the various systems and methods described herein. “Iron source materials” and “feedstocks” may include iron in any form, such as iron oxides, iron hydroxides, iron oxyhydroxides, iron carbonates, iron sulfides, iron silicates, and / or other iron-containing compounds, ores, rocks or minerals, including any mixtures thereof, in naturally- occurring states or beneficiated or purified states. The term “iron-containing ore” or simply “iron ore” may include materials recognized, known, or referred to in the art as iron ore(s), rock(s), natural rock(s), sediment(s), natural sediment(s), mineral, and / or natural mineral(s), whether in naturally-occurring states or in beneficiated or otherwise purified or modified states. Some embodiments of processes and systems described herein may be particularly useful for iron feedstocks comprising, consisting of, or consisting essentially of one or more iron ores (or blends of iron ores) including hematite, goethite, magnetite, limonite, siderite (FeCOs), ankerite, turgite, bauxite, pyrite, fayalite, or any combination thereof.

[0018] In various embodiments of systems and methods described herein, suitable feedstock materials may have a net iron oxidation state of greater than +2.0, optionally greater than +2 and less than or equal to approximately +3.2, wherein any value and any range therebetween is explicitly contemplated and disclosed herein.

[0019] As used herein, the term “impurity” refers to an element or compound other than a desired final product material (e.g., iron). In various embodiments, depending on the intended end-use of a product material, a given element or compound may or may not be considered an “impurity.” In some cases, one or more elements or compounds that may be impurities to one process or sub-process may be isolated or purified, collected, and sold as a secondary product material (also referred to as “co-products” or “by-products”).

[0020] The term “iron-based metal” refers to a metal or metallic material containing iron in a metallic, Fe°, state, including iron metals or iron-containing alloys, such as steels, pig iron, ferroalloys, or others, with more than a de-minimus quantity of iron (e.g., greater than about 5 atomic %). Iron-based metals include, but are not limited to, metallic iron or iron metal, steel materials, silicon steel, silicon iron, electrical steel, electrical iron, cast iron, gray iron, white iron, ductile iron, malleable iron, wrought iron, any iron-carbon alloy, and any combinations.

[0021] As used herein, the terms “steel” and “steel material” are inclusive of any material known in the art as “steel”, such as, but not limited to, stainless steels, carbon steels, tool steels, crucible steels, spring steels, alloy steels, maraging steels, highspeed steels, weathering steels, and any variations and grades thereof.

[0022] As used herein, the term “oxidation state” carries its normal meaning in the context of chemistry and refers to a number assigned to an element which represents the number of electrons lost (if the number is positive) or gained (if negative) by an atom of that element in a chemical compound or aqueous ionic state. The oxidation number is generally denoted as a superscript such as the “2+” in Fe2+(ferrous iron), but may also be denoted by parenthetical roman numerals such as Fe(ll).

[0023] As used herein, the term “wustite” refers to a predominantly ferrous oxide compound and includes materials with non-stoichiometric ratios of iron and oxygen, including 0% ferric iron up to approximately 30% ferric iron, and consequentially includes materials with a higher oxygen-to-iron ratio than 1 :1.

[0024] As used herein the term “net iron oxidation state” refers to a molar average of the oxidation states of individual iron atoms in a material. For example, a material with a mixture of FeO (ferrous oxide or wustite), of which the iron atoms have an oxidation state of +2, and iron metal (Fe°), such as iron powder, of which the iron atoms have an oxidation state of 0, will have a net iron oxidation state somewhere between 0 and 2 depending on the ratio of moles of FeO to the moles of Fe°.

[0025] The net iron oxidation state may be determined by determining the relative amounts of different phases or species of elements or compounds in the material (also referred to as the “phase composition” of the material). Phase composition of a material may be determined by any suitable method, such as X-ray diffraction (XRD) optionally employing a reference intensity ratio (RIR) analysis, thermogravimetric analysis (TGA), wet chemical methods such as an aqueous copper sulfate reaction, or a combination of these or other methods, and then assigning an oxidation state for each detected phase. The net iron oxidation state may then be calculated based on the oxidation state defined by each detected phase and the relative quantities of each phase detected in the material. Another method of determining a net iron oxidation state of a material is to digest the material in a non-oxidizing acid while measuring hydrogen gas evolved and then determining a quantity of ferrous (Fe2+) and ferric (Fe3+) iron ions in solution. The quantity (or ratio) of ferrous and ferric ions in the solution may be measured via electrochemical techniques known in the art (e.g., coulometric titration, oxidationreduction potential measurements, or others), via chemical titration, and / or other useful techniques known in the art. In some cases, a combination of these or other methods may be used to determine the net iron oxidation state of a material. For example, leaching tests may be used to measure reduction of ferric in the resulting leachate solution, the final ferrous / ferric ratio in solution, total Fe recovery, and leaching kinetics and quantitation of absolute iron ion concentration in solution may be determined coulometric titration.

[0026] 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., ferrous iron solutions, ferric iron solutions, or plated metallic iron) may have a chemical purity of 90% (e.g., by molarity of ionic concentrations or by weight) or more. For various applications, a material may be “pure” if it has a chemical purity of 95%, 99%, 99.9%, 99.99%, or 99.999% pure.

[0027] Reference made herein to a “tank” is intended to include any vessel suitable for containing liquids, such as highly acidic or caustic aqueous solutions if needed. In some embodiments, such a vessel may include additional features or components to assist or improve mixing of solid and / or liquid contents of the vessel. For example, a dissolution tank may include passive or actively operated structures or features for agitating a solution or solid / liquid mixture, such as baffles, stirrers, etc. A dissolution tank or other tank useful in the systems and methods herein may also include features to allow for sparging a gas into or through solid and / or liquid contents of the tank to increase gas contact with solid and / or liquid materials within the tank. Various tanks may also include baskets, sieves, pans, filters, or other structures to collect and separate solids from liquids. In some embodiments, a tank may be configured to direct liquid or gas flow through the tank in such a way as to agitate the mixture therein (e.g., flowdirecting structures, pumps, impellers, baffles, impellers, stir-bars, stir blades, vibrators, cyclonic flow channels, etc.).

[0028] The term “iron electroplating” (or “iron plating” as used synonymously herein) refers to a process by which dissolved iron is electrochemically reduced to metallic iron on a cathodic surface. Equivalent terms “electrodeposition,” “electroforming,” and “electrowinning” are also used herein synonymously 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, electroplated iron may take any shape or form and may be deposited on any suitable cathodic surface as described in various embodiments herein. Examples of possible physical forms of “electroplated” iron include chips, flakes, coins, crowns, powder, strips, or other shapes. In some embodiments, a cathodic surface material may be selected for a degree to which deposited iron adheres to the cathodic surface. For example, if a desired electroplated product is a powder, a cathodic surface with a low iron adhesion may be desired. Examples of materials with high and low iron adhesion properties are described herein, and additional examples will be clear to those skilled in the art. In various embodiments, some regions of a cathode may be masked prior to electroplating for producing electroplated material in a desired shape or formfactor, for example as described in US Patent 4,139,430.

[0029] As used herein, any reference to a “PEM” or “proton exchange membrane” may be interpreted as also including a “CEM” or “cation exchange membrane”, both terms may include any available membrane material that selectively allows passing positively charged cations and / or protons. The abbreviation “AEM” is used to refer toanion exchange membranes selectively allowing passage of negatively-charged aqueous ions and includes any available anion-selective membrane.

[0030] As used herein, aqueous protons and electrochemically generated protons are intended to be inclusive of aqueous protons and aqueous hydronium ions.

[0031] As used herein, unless otherwise specified, the terms “ferric iron solution” or “ferric solution” may refer to an aqueous solution that contains dissolved iron that is at least predominantly (i.e., between 50 mol.% and 100 mol.%) in the Fe3+(i.e., “ferric”) ionic state with the balance of dissolved iron being in the “ferrous” Fe2+state. Similarly the term “ferric ion” refers to one or more ions in the ferric (Fe3+) state. Either “ferric solutions” or “ferrous solutions” may also contain other dissolved ions or colloidal or particulate materials, including impurities.

[0032] As used herein, the term “thermally reducing” refers to a thermal treatment at an elevated temperature in the presence of a reductant. Thermal reduction is also referred to in the art as reduction roasting. In various embodiments, thermal reduction may be performed at a temperatures selected from the range of approximately 400 °C to approximately 1000 °C in the presence of a gaseous reductant or precursors (e.g., solids or liquids) capable of producing one or more gaseous reductants at the process temperature.

[0033] As used herein, the term “reducing gas” (or “gaseous reductant”) includes one or more gaseous species useful as a reagent for chemically reducing a material, i.e., decreasing an oxidation state of the material, under some conditions. The term “reducing gas” includes but is not limited to hydrogen gas, forming gas, natural gas, reformed natural gas, carbon monoxide, methane, one or more other natural or reformed hydrocarbon gas, hydrogen sulfide gas, sulfur dioxide, one or more other gases known in the art as reducing gas(es), or any combination of these and / or others.

[0034] As used herein, the term “air roasting” refers to a thermal treatment performed at an elevated temperature in the presence of air or other oxygen-containing atmosphere. Air roasting of ore, such as iron-containing ore, can break down or decrease average particle size of an ore. Optionally, air roasting is performed at temperature selected from the range 300° C. and 500° C.

[0035] In various embodiments, any acid or mix of acids can be used for dissolution of iron ores (and / or other feedstock materials), including but not limited to hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, oxalic acid, citric acid, boricacid, perboric acid, carbonic acid, methanesulfonic acid, or any mixture or combination of these or other acids. In various embodiments, “iron ore” can include any iron oxide such as, but not limited to, hematite (Fe2O3), maghemite, ferrihydrite, magnetite (FesCM), or hydroxides such as geothite (FeOOH), akaganite, lepidocrocite, ferrihydrite, limonite, or any combinations of these or other iron-containing ores.

[0036] As used herein, the terms “acid regenerator” and “acid regeneration cell” are used interchangeably. In aspects herein, an acid regeneration cell may incorporate or by characterized by one or more aspects thereof in the ‘604 patent. In various aspects herein, an acid regeneration cell is generally consistent with aspects thereof and use of the term in the ‘604 patent.

[0037] As used herein, the term “material” is inclusive of pure materials and mixtures of a plurality of different materials or species.

[0038] As used herein, the term “wt.%” or “wt%” refers to a weight percent, or a mass fraction represented as a percentage by mass. The term “at.%” or “at%” refers to an atomic percent, or an atomic ratio represented as a percentage of a type of atom with respect to total atoms in a given matter, such as a molecule, compound, material, nanoparticle, polymer, dispersion, etc. The term “mol.%” refers to molar percent or percent by moles. The term “vol.%” refers to volume percent.

[0039] As used herein, the term “and / or” is used herein, in the description and in the claims, to refer to a single element alone or any combination of elements from the list in which the term and / or appears. In other words, a listing of two or more elements having the term “and / or” is intended to cover embodiments having any of the individual elements alone or having any combination of the listed elements. For example, the phrase “element A and / or element B” is intended to cover embodiments having element A alone, having element B alone, or having both elements A and B taken together. For example, the phrase “element A, element B, and / or element C” is intended to cover embodiments having element A alone, having element B alone, having element C alone, having elements A and B taken together, having elements A and C taken together, having elements B and C taken together, or having elements A, B, and C taken together.

[0040] As used herein, the term “±” refers to an inclusive range of values, such that “X±Y,” wherein each of X and Y is independently a number, refers to an inclusive range of values selected from the range of X-Y to X+Y. In the cases of “X±Y” wherein Y is apercentage (e.g., 1 ,0±20%), the inclusive range of values is selected from the range of X-Z to X+Z, wherein Z is equal to X*(Y / 100). For example, 1 ,0±20% refers to the inclusive range of values selected from the range of 0.8 to 1 .2.

[0041] The term “predominantly” is used herein to refer to a property, condition, or value being greater than 50%. In specific instances, the term “predominantly” may indicate a property, condition, or value being greater than 60%, greater than 70%, greater than 80%, greater than 90%, greater than 95%, greater than 98%, greater than 99%, greater than 99.5%. For example, a material mixture characterized as “predominantly wustite” is more than 50 mol.% wustite, or in other instances at least 60 mol.% wustite, at least 70 mol.% wustite, at least 80 mol.% wustite, at least 90 mol.% wustite, at least 95 mol.% wustite, at least 98 mol.% wustite, at least 99 mol.% wustite, at least 99.5 mol.% wustite, with the balance being other compositions, such as but not limited to hematite, magnetite, iron metal, and / or impurities.

[0042] The terms “substantially” and “approximately” are used interchangeably and refer to a property, condition, or value that is equivalent to or is within a reasonable variance from a stated property, condition, or value. For example, a property, condition, or value described as “substantially” or “approximately” X (X being a number for purpose of this paragraph), may include properties, conditions, or values that are within 20%, within 10%, within 5%, within 1 %, or within 0.1 % of said X. Examples of such uses include phrases such as “substantially equal”, “substantially equivalent”, “substantially unchanged”, “approximately”, and “approximately equal to.”DETAILED DESCRIPTION

[0043] In the following description, numerous specific details of devices, device components and methods are set forth to provide a thorough explanation of the precise nature of the various inventions described herein. It will be apparent, however, to those of skill in the art that the various inventions can be practiced without these specific details. Without wishing to be bound by any particular theory, there may be discussion herein of beliefs or understandings of underlying principles relating to the devices and methods disclosed herein. It is recognized that regardless of the ultimate correctness of any mechanistic explanation or hypothesis, an embodiment of devices and methods may nonetheless be operative and useful.

[0044] Aspects discussed herein include thermal reduction of a feedstock material prior to performing leaching thereof. Among other advantages of thermally reducing afeedstock material according to various examples and embodiments described herein, doing so decreases some operating costs and burdens in subsequent processes. For example, via aspects of thermal reduction disclosed herein, it is possible to achieve a ferrous-rich leachate solution, having a high post-leach ferrous-to-ferric concentration ratio (e.g., greater than or equal to 100:1 ), as a result of the composition of the thermally-reduced material and without necessarily requiring a post-leach and preelectroplating chemical or electrochemical process to achieve such ferrous-to-ferric concentration ratio. In various aspects and configurations disclosed herein, an ferric reduction reactor may be employed after electroplating to convert at least a portion of ferric ions generated during electroplating to ferrous ions.

[0045] Each of FIG. 1A, FIG. 1B, and FIG. 2 independently illustrates a process 100, 150, and 200, respectively, according to aspects herein, for producing metallic iron from an iron-containing feedstock material, preferably having one or more iron oxides and / or iron ores. Each of blocks 102 and 202, independently, receives an iron-containing feedstock material and thermally reduces the received iron-containing feedstock material, respectively, to a thermally-reduced material, also referred to herein as a thermally-reduced feedstock material or a pre-leach material. Each of blocks 102 and 202, independently, is an exemplary ore preparation subsystem according to various aspects herein.

[0046] In some embodiments, the iron-containing feedstock material is preconditioned or prepared prior being thermally reduced (i.e. , pre-conditioning may be performed within or prior to blocks 102 and 202), where the pre-conditioning may include one or more processes, such as but not limited to milling, grinding or other comminution to reduce the feedstock particle size and / or make the particle size more uniform or less polydisperse. Pre-conditioning may also include other mineral treatment or beneficiation steps or processes, including rejection of gangue, magnetic separation, flotation, classification, gravimetric separation, or others.

[0047] Following the thermal reduction and / or other preconditioning steps at blocks 102, 202, the prepared material may be leached at block 104, 204 to obtain a solution containing dissolved metallic species leached from the prepared feedstock. The preparation steps of blocks 102 & 202 may beneficially be operated so as to produce a leach solution (or “lixiviant”) containing iron predominantly (or substantially entirely) in a “ferrous” (Fe2+) state. Following the leaching step, the leach solution may be treated at blocks 106 and 206 to remove at least some impurities from the solution. The purifiedsolution may then be directed to an electrowinning cell 110, 111 , or 210 in which dissolved iron is electroplated from the solution. Spent plating electrolytes exiting the plating cell may be directed to subsequent process steps for recycling or re-conditioning for future leaching operations.

[0048] In various embodiments, the feedstock material may include an iron source material in which at least some of the iron is in an oxidized state. For example, the feedstock material may comprise one or more iron ores, one or more iron oxides, one or more iron carbonates, one or more iron-based metals, one or more other iron metal or iron-containing materials that are products or products of ironmaking or steelmaking processes (e.g., slags, dusts, off-fall, scrap, pickling liquors, etc), or any combinations or mixtures of any of these in naturally-occurring states, man-made states, and / or beneficiated and / or purified states. For example, the feedstock material may be predominantly an iron ore with a net oxidation state of greater than 2.0, or greater than 2.0 and less than or equal to approximately 3.0. For example, some iron feedstock materials are predominantly an iron ore including one or more of goethite, hematite, magnetite, or a combination of these. For example, in some embodiments the iron feedstock material is predominantly hematite, which may correspond to a net iron oxidation state of about 3. As an illustrative example, a feedstock may comprise 50 mol.% FeTiOs and 50 mol.% magnetite, which may correspond to a net iron oxidation state of about 2.33. In a pure magnetite material, approximately 2 / 3 of the iron is in the Fe(lll) state and approximately 1 / 3 of the iron is in the Fe(ll) state, corresponding to a net oxidation state of about 2.67.

[0049] In various aspects described herein, the feedstock material may be thermally- reduced sufficiently to achieve a net iron oxidation state less than about 2.0 in the thermally-reduced material (pre-leach material). In various aspects, the target net oxidation state may be greater than or equal to approximately 1 .6 but less than 2.0. In some aspects, the thermally-reduced material is predominantly wustite (FeO), optionally with the balance being predominantly a combination of an iron metal (Fe°) and magnetite. In some aspects, the thermally-reduced material is predominantly a combination of wustite (FeO) and iron metal (Fe°) with little or no magnetite. In some aspects, the thermally-reduced material is predominantly a combination of wustite (FeO), iron metal (Fe°), and magnetite. In some aspects, the thermally-reduced material is predominantly a combination of magnetite and iron metal (Fe°). In some aspects, the thermally-reduced material is characterized by a composition having a quantity of Fe°selected from the range of greater than 0 mol.% Fe° to less than or equal to approximately 50 mol.% Fe°, wherein any value and any range therebetween is explicitly contemplated and disclosed herein. In some aspects, a target thermally- reduced material composition may have a quantity of FeO approximately equivalent to a quantity of Fe(lll) in the material. For example, a thermally-reduced material containing magnetite may also contain a target quantity of Fe° approximately equal to 2 / 3 the quantity of magnetite.

[0050] Thermal reduction, at each of blocks 102 and 202, independently, is performed at a thermal-reduction temperature in the presence of a reducing atmosphere for a thermal-reduction time. The thermal reduction may be performed using one or more techniques or processes and any suitable furnaces or other apparatus known in the art. Thermal reduction may include a dehydration zone or chamber in a furnace to improve uniformity of the reduction. Thermal reduction may performed using a counterflow configuration. Thermal reduction may performed using a fluidized bed configuration. Thermal reduction may performed using direct fired and / or indirect fired kiln or screw (e.g., rotary kiln, cooling screw, etc.) configuration(s) Thermal reduction may be performed using shaft furnaces, including cupola configurations.

[0051] The thermal-reduction temperature is optionally greater than 570 °C up to about 1 ,000 °C to facilitate the reduction of iron oxide and ore materials to a desired combination of wustite, magnetite, and / or iron metal phases. The thermal-reduction temperature, thermal reduction time, composition of the reducing atmosphere (including but not limited water vapor concentration), pressure, material particle size, and / or material porosity may be selected based upon a variety of parameters, such as a particular composition and / or net iron oxidation state of the starting feedstock material and parameters and conditions of the downstream processes and compositions. Optionally, the thermal-reduction temperature is selected based on a target net iron oxidation stated desired for the thermally-reduced material, for example where a high temperature may favor producing wustite and a lower temperature (e.g., approx. < 600 °C) may favor producing a combination of magnetite (FesO4) and Fe°.

[0052] In some aspects, the thermal-reduction temperature may be defined as the approximate steady state elevated temperature or the approximate elevated temperature maintained the longest during the entirety of the thermal-reduction process. In other aspects, the thermal-reduction temperature is defined as an averagetemperature of the material being reduced while heat is applied to the material or the reducing atmosphere.

[0053] In other aspects, the thermal-reduction temperature is defined as an average temperature of the material being reduced over the time that the material is in a heated kiln. In example aspects, the thermal-reduction temperature is an 80th, 85th, 90th, 95th, or 99thpercentile temperature (where 100thpercentile is the maximum reached temperature) of the material being reduced over the time that the material is in a heated kiln. For example, in a fluidized bed configuration, the temperature may be measured within the fluidized bed or the mixture of fluid and particulates (e.g., via a temperature probe exposed to the fluidized bed) and / or the temperature may be measured of the fluid after or exiting (e.g., at or adjacent to an outlet of) the fluidized bed.

[0054] In other aspects, the thermal-reduction temperature is defined as an average temperature of the reducing atmosphere in the presence of the material being reduced while heat is applied. The thermal-reduction temperature generally does not refer to transient heat-up or cool-down conditions, such as, but not limited to, when a kiln is heated up to a setpoint or cooled to a setpoint. The thermal-reduction temperature is selected from the range of approximately 570 °C to approximately 1000 °C, wherein any value and any range therebetween is explicitly contemplated and disclosed herein.

[0055] The reduction atmosphere comprises a reducing gas such as hydrogen gas, carbon monoxide (among others described herein), or a combination thereof. In various aspects, the reducing atmosphere is partially, predominantly, or substantially entirely the reducing gas. For example, in some aspects the reducing atmosphere is at least 50 mol.% the reducing gas with the balance being an inert gas or a mixture of inert gases, water vapor or other constituents. In some aspects, the reduction atmosphere may be greater than 50 mol. % an inert or non-oxidizing atmosphere with a minority portion being one or more reducing gases. Optionally, in aspects herein, the reduction atmosphere may include a minority portion (i.e. , less than approximately 50 mol.%) made up of oxidizing gaseous species, such as O2, H2O, CO2, or any combination thereof. In other aspects, the oxidizing species may be less than 25 mol. %, less than 10 mol. %, or less than 1 mol. %.

[0056] The thermal reduction process optionally includes a “passivation” step or stage for avoiding or minimizing re-oxidation of the thermally-reduced material. While not wishing to be bound by any mechanistic theory, it is believed that the thermallyreduced material may be passivated by forming a protective surface-layer of one or more oxides on the surface of the reduced particles. In some aspects, the passivation step / stage includes exposing the thermally-reduced material to an oxidizing atmosphere, such as air or an atmosphere comprising oxygen gas, for a time and at a temperature sufficient to form a thin oxide shell / layer on any atmosphere-exposed surface of the thermally-reduced material (optionally, surface of each or at least a majority of discreet particles of the thermally-reduced material). In some aspects, the passivation step / stage includes exposing the thermally-reduced material to an oxidizing atmosphere, such as air or an atmosphere comprising oxygen gas, at a lower temperature than the thermal-reduction temperature for a time sufficient to form a thin oxide shell / layer. In some aspects, the thin oxide shell / layer has a thickness selected from the range of approximately 20 nm to approximately 10 pm, wherein any value and range therebetween is explicitly contemplated and disclosed herein, such as approximately 50 nm to approximately 1 pm. In some aspects, the passivation stage includes decreasing the temperature of the thermally-reduced material or gas temperature to which it is exposed from the thermal-reduction temperature while maintaining a passivation atmosphere. In some aspects, the passivation atmosphere may comprise less than approximately 50 mol.% (optionally less than approximately 40 mol.%, optionally less than approximately 30 mol.%, optionally less than approximately 25 mol.%, optionally less than approximately 20 mol.%, optionally less than approximately 15 mol.%, optionally less than approximately 10 mol.%, optionally less than approximately 5 mol.%, or optionally less than approximately 1 mol.%) of oxidizing gas(es) including but not limited to oxygen. In some aspects, the passivation atmosphere is an inert atmosphere or a reducing atmosphere. In some aspects, the passivation step / stage includes maintaining the thermally-reduced material at a passivation temperature or a range thereof, such as between approximately 20 °C and approximately 400 °C (optionally between approximately 20 °C and approximately 200 °C, between approximately 20 °C and approximately 100 °C, between approximately 50 °C and approximately 100 °C) under an inert atmosphere (e.g., N2 gas) and slowly introducing an oxidizing gas, such as air or oxygen gas, in some aspects thereby resulting in the formation of the thin oxide shell / layer described in this paragraph. In some aspects, the passivation step / stage includes quenching or exposing the thermally- reduced material with liquid water.

[0057] In various aspects, the passivation atmosphere may be maintained, during the cooling / passivation step, until one or more passivation-done conditions is met. In some aspects, a passivation-done condition is defined as the thermally-reduced material being characterized by an average temperature of less than or equal to an end-of-passivation temperature. An end-of-passivation temperature is defined as a temperature at which wustite is unlikely to spontaneously convert to hematite and the metallic iron is unlikely to be oxidized. In various aspects, the end-of-passivation temperature may be approximately 400 °C or less.

[0058] In some aspects, a passivation-done condition is when the thermally-reduced or passivated material will / would not heat up (e.g., as result of spontaneous exothermic oxidation) to 200 °C, or more, upon to exposure to approximately 0.5 atm to approximately 1 atm of air (or other gas mixture with a proportion of oxygen similar to air), optionally within a period of 5 hours or less. In some aspects, a passivation-done condition is when the thermally-reduced or passivated material will / would increase in temperature (e.g., as result of spontaneous exothermic oxidation) by less than 10 °C, optionally 5°C, optionally 3 °C, upon exposure to approximately 0.5 atm to approximately 1 atm of air or oxygen, optionally within a period of 5 hours or less. Generally, rapid cooling is advantageous for minimizing re-oxidation. Passivation may be performed, optionally using water and / or a controlled atmosphere.

[0059] Thermal reduction may also be performed using one or more conditions described in Spreitzer, et al. (Spreitzer, D. and Schenk, J. (2019), Reduction of Iron Oxides with Hydrogen — A Review, steel research int. , 90: 1900108. DOI: 1O.1OO2 / srin.2O19OO1O8).

[0060] FIG. 4 illustrates an exemplary thermal reduction subsystem and thermal reduction process 400, according to various aspects herein. A feedstock material is provided to thermal reduction subsystem 400 as feed stream 401 . The feedstock material is thermally reduced in the presence of a reduction atmosphere at thermal reduction stage 402, according to any aspect(s) described herein. Optionally, the thermally reduced material formed at 402 is provided to passivation stage 404 as stream 403. In some embodiments, stage 402 and stage 403 are performed in the same vessel, system, or apparatus (e.g., in a batch-mode process), in which case line 403 represents a change of process but not necessarily a movement of material. For example, thermal reduction may be performed using a fluidized bed configuration, and passivation may be performed in the same fluidized bed, wherein process controls are adjusted (e.g., theheating is decreased and / or turned off) to switch from thermal reduction to passivation. Alternatively, stage 402 and stage 403 may be performed in separate vessels, systems, or apparatuses (e.g., in a more continuous process). After passivation, according to any aspect(s) above, the passivated thermally reduced material is output as stream 405. In implementations, a supporting system will optionally also include additional hardware such as Bag houses, cyclones, scrubbers, and other hardware for conveying and cleaning gases, liquids, and solids.

[0061] Each of blocks 104 in FIG. 1A and FIG. 1 B and 204 in FIG. 2 is independently performing dissolution or leaching of an input material, referred to herein as a pre-leach material, in an aqueous acidic solution to produce an aqueous ferrous-rich leachate. Each of blocks 104 and 204, independently, is an exemplary leaching subsystem according to various aspects herein. The pre-leach material comprises the thermally- reduced material, but is not necessarily limited to the thermally-reduced material. The acid in the aqueous acidic solution is optionally predominantly sulfuric acid (H2SO4), but may also include any other acid suitable for leaching the input material as described herein.

[0062] In some aspects, the target predominant iron ion species in the ferrous-rich leachate is Fe2+. Optionally, in aspects herein, the ferrous-rich leachate is characterized by a ratio of concentrations of Fe3+ions to Fe2+ions being less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.009, optionally less than or equal to approximately 0.0075, optionally less than or equal to approximately 0.005, optionally less than or equal to approximately 0.0025, optionally less than or equal to approximately 0.001 , or optionally the ratio can be greater than or equal to 0.0075, 0.005, 0.0025, or 0.001 and such values can be combined in any manner to form a range, such as 0.001 to 0.01.

[0063] To produce the ferrous-rich leachate having primarily Fe2+ions, parameters such as pH of the acidic solution, temperature of the acidic solution, and composition of the thermally-reduced material may be adjusted or selected accordingly. Wustite, or ferrous oxide (FeO), from the thermally-reduced material may generally dissolve to produce predominantly ferrous (Fe2+) ions and some ferric (Fe3+) ions in the aqueous acidic solution, depending on the sub-stoichiometry of the wustite. Magnetite from the thermally-reduced material will generally dissolve to produce a combination of ferrous and ferric (Fe3+) ions in the aqueous acidic solution, and Fe°, in the form of one or more iron metal and / or iron-based metal materials, will generally react with and reduceaqueous ferric ions to ferrous ions in the aqueous acidic solution. Therefore, selecting particular ratios of these constituents in combination with other leaching parameters can achieve a range of desired ferrous / ferric ratios in a resulting leach solution.

[0064] In various aspects, the leaching process is optionally performed at an elevated temperature. For example, the leaching temperature may be less than or equal to 100 °C, such as a temperature selected from the range of 50 °C to 80 °C. The resulting ferrous-rich leachate may have a target concentration of ferrous ions, or for example ferrous sulfate, selected from the range of approximately 0.1 mol / L to approximately 2 mol / L (including all discrete values within that range), although any other ferrous ion concentrations are contemplated within this disclosure.

[0065] The pre-leach material, in addition to comprising the thermally-reduced material, may optionally further comprise one or more other iron-containing materials, such as, but not limited to, one or more iron-based metal materials in one or more forms (such as, but not limited to: iron dust, iron powder, one or more steel materials or steelmaking byproducts (including but not limited to: iron dust, steel slag, iron powder, stainless steel, carbon steel, tool steel, crucible steel, spring steel, alloy steel, maraging steel, high-speed steel, weathering steel, and any variations and grades thereof), mill scale, cast iron, gray iron, white iron, ductile iron, malleable iron, wrought iron, one or more iron-carbon alloys or steel materials, one or more other iron metal or iron-based materials, an iron ore, such as but not limited to naturally-occurring wustite, or ferrous carbonates or ferrous silicates. For example, the FeO in the pre-leach material may be a combination of FeO from the thermally-reduced material and FeO sourced otherwise, such as by including a steelmaking slag, which contains significant amount of FeO, in the pre-leach material. The pre-leach material optionally also comprises Fe° from sources other than the thermally-reduced material, such as scrap steel, scrap iron, direct reduced iron, or a combination thereof.

[0066] A leaching or dissolution subsystem, such as but not limited to each of block 104 and block 204, may be configured as a countercurrent leaching process. FIG. 3 shows an exemplary leaching configuration, according to some aspects herein, comprising two concurrent leaching tanks (also referred to as “dissolution tanks”): primary leach tank 321 and secondary leach tank 323. It will be appreciated by one skilled in the art that the configuration of FIG. 3 is illustrative and representative whereas a practical implementation may incorporate any number of leaching or leach tanks (e.g.,stages in a cascade) and / or solid-liquid separation stages as needed. For example, it is contemplated that a sequence of more than two leaching tanks may be used.

[0067] Pre-leach material, optionally comprising a thermally-reduced material as described herein, may be provided as stream 301 to primary leach tank 321. Therefore, pre-leach material is initially dissolved in primary leach tank 321. The dissolution in primary leach tank 321 may comprise a suspension or mixture of solid particulates and an aqueous acidic iron-rich solution, also referred to herein as the primary acidic iron- rich solution, which has iron ions dissolved therein and is preferably ferrous-rich. The solid particulates in primary tank 321 may include yet-undissolved iron compounds such as, but not limited to, wustite, magnetite, and / or hematite. The solid particulates are transferred as stream 305 to secondary leach tank 323 for further leaching. Secondary leach tank 323 is fed a highly acidic, low pH, ferrous-rich solution, optionally comprising a catholyte, from an acid regenerator cell (for example as described herein and / or in the ‘604 patent), such as cell 116 or cell 216, as stream 309.

[0068] Some of the aqueous acidic solution, having iron ions dissolved therein, exiting the secondary leach tank 323 (referred to herein as secondary acidic iron-rich solution) may be transferred to the primary leach tank 321 to consume remaining acid in the secondary acidic iron-rich solution. Optionally, the transferred secondary acidic iron- rich solution is substantially free of undissolved solids or other solid particulates. Optionally, therefore, the acidic solution in secondary leach tank 323 has a lower pH compared to that of primary leach tank 321 to facilitate the further dissolution of iron- containing material undissolved in primary leach tank 321. The pre-leach material may intentionally comprise Fe°, such as in the form of iron-based metal material, which facilitates conversion of ferric ions to ferrous ions. As such, under steady state or continuous operation of leach subsystem 300, the primary acidic iron-rich solution may be ferrous-rich. Some of the primary acidic iron-rich solution is removed from primary leach tank 321 , as stream 303, which may become the acidic ferrous-rich leachate leaving the dissolution subsystem (e.g., 104 or 204).

[0069] Undissolved solids remaining in the secondary leach tank 323 may include undissolved material such as silica or other materials that substantially do not dissolve in the acid. It is also contemplated that a composition of the pre-leach material, which may be at least partially determined by the thermal-reduction conditions, influences the pH of the resulting acidic iron-rich solution exiting the leaching process. In furtherembodiments, a countercurrent cascade leach system such as that shown in FIG. 3 may include 3, 4, 5, or more leaching stages in addition to the two shown in FIG. 3.

[0070] Some components of the pre-leach material or the thermally-reduced material, such as silica and quartz, may not dissolve in the aqueous acidic solution and may instead be removed as undissolved solids or precipitates. Impurities that do dissolve may be removed from the ferrous-rich leachate at 106 or 206 to produce a purified ferrous-rich leachate such as by a precipitation and filtration process driven by a pH shift as described in the ‘604 patent. For example, one or more bases, such as but not limited to NaOH, KOH, and NH4OH, can be added to the leachate to increase the pH, such as to greater than 3, to precipitate impurities such as aluminum and phosphorus compounds. Alternatively or in addition, metallic iron may be used increase the solution pH. Alternatively, other impurity removal methods such as solvent extraction, cementation, or other methods may be used at block 106 and 206 which are representative of any impurity removal subsystem according to aspects herein.

[0071] The purified ferrous-rich leachate may then be directed to an iron- electroplating cell 110, 111 , or 210. In the electroplating cell 110 of FIG. 1A and 210 of FIG. 2, the leachate may be divided into a catholyte volume to be reacted in the cathode half-cell 114 and 214 and a separate anolyte volume to be reacted in the anode half-cell112 and 212. In some embodiments, catholyte and anolyte may be stored in tanks, and the catholyte and anolyte may be circulated between the respective electroplating halfcell and tank until the reactants (Fe2+) are depleted.

[0072] In some embodiments, represented by the example in FIG. 1 B, the purified leach solution exiting the impurity removal stage at 106 may be directed into only the cathode chamber 114 of the plating cell 111. In such embodiments, the purified leach solution acting as electrolyte will first be reacted at the cathode as catholyte in the cathode chamber 114, after which the electrolyte is directed into the anode chamber113 where it may serve as reactant at the anode. In some configurations, a porous flow- through diaphragm may be used to separate the cathode chamber from the anode chamber while allowing electrolyte to flow through the diaphragm from the catholyte chamber into the anolyte chamber. In other configurations, a less porous separator may be used, and electrolyte may be transferred from the cathode chamber into the anode chamber by flowing over a dam or through one or more conduits. Iron may be electrodeposited at the cathode while ferrous ions are oxidized to ferric ions as electrolyte reaches the anode. In some embodiments, the anode may also beconfigured and / or operated to promote an oxygen evolution reaction (OER) or a chlorine evolution reaction if chloride is present in the electrolyte. Spent anolyte (which may also be referred to as spent electrolyte in this example) may then be directed to the ferric reduction reactor in which ferric ions produced at the plating cell anode may be reduced to ferrous ions.

[0073] In various aspects, the electroplating cell 110, 111 , and 210 is configured to electroplate metallic iron from the Fe2+ions at the cathode(s), for example in the form of a plated Fe metal sheet. In some aspects, the electroplating cell 110, 111 , and 210 is configured to electrochemically generate iron powder at the cathode(s). Whether iron metal is produced as a plated shape (plates, coins, crowns, sheet, etc.) on the cathode or as a powder may be controlled via, for example, the operating current density, where higher current densities, such as greater than or equal to approximately 0.2 A / cm2(such as optionally selected from the range of 0.2 A / cm2to 0.5 A / cm2or higher) will prefer to form Fe metal powder, whereas lower current densities result in a preference for denser Fe metal plates (or other shapes) on the cathode. Regardless of the form factor, the resulting electrochemically generated Fe metal is highly pure, in various aspects being at least 99 wt.% Fe.

[0074] In some aspects wherein Fe metal is electroplated onto the cathode in the form of a plate, sheet, crowns, coins, or other plated shapes, it may be desirable for the cathode material, or a surface material thereof, to have sufficient adhesion with the electroplated iron to avoid premature delamination of the deposited iron while potentially allowing for mechanical removal of the iron. Cathodic materials with surfaces having such adhesion properties may include iron, mild steel, stainless steel (e.g., stainless 304, stainless 316, or other grades of stainless steel), or other metals (e.g., zinc or copper if a multi-layered structure is desired). In various embodiments, a re-usable cathode may be treated prior to electroplating iron and after removal of deposited iron.

[0075] When it is desired that iron powder is produced at the cathode in an iron electroplating cell, cathodic surface materials or mechanical properties may be selected to promote and or facilitate powder generation at the cathode and / or removal of powder from the cathode. For example, in some aspects, a vibrating belt cathode may be used to facilitate the separation of the Fe powder from the cathode and subsequent removal from the iron plating cell. In some aspects, the cathode surface material may be selected for low iron adhesion to facilitate the iron powder separation and subsequent removal. Some example low iron adhesion cathode surface materials may includealuminum, graphite, lead, nickel, conductive polymer(s), graphene, titanium, or a combination of these or other materials with a tendency for low adhesion of electrodeposited iron.

[0076] Alternatively or in addition to selecting a low-adhesion cathode surface, the plating catholyte may be circulated intensely through a cathodic region of a plating cell to help loosen electrodeposited powder, thereby further facilitating removal of electrochemical generated iron powder.

[0077] Optionally, electrochemically generated iron powder is harvested with the aid of one or more hydrocyclone(s) in series and / or using permanent magnets or electromagnets installed at the underflow of the hydrocyclone(s). Optionally, the electrochemically generated iron powder is rinsed with slightly acidic water to remove traces of catholyte, and optionally further passivated with nitric acid and dried in an inert (e.g., nitrogen gas) atmosphere. Additional details of various systems and methods for electrolytically producing iron powder are provided in the art, including: U.S. Patent Publication 2011 / 0089045 (Cardarelli); U.S. Patent 3,969,207 (Kerti, et al.); and UK Patent Publication GB899028A (Montan Union Handelsges M B H).

[0078] Some iron electroplating cells disclosed herein, such as electroplating cells 110, 111 , and 210 may be configured to oxidize ferrous ions to ferric ions at the anodes. In some aspects herein, an iron electroplating cell disclosed herein, such as electroplating cell 110, is optionally configured to perform an oxygen evolution reaction (OER). Such OER anodes may include lead, platinum group metals, mixed-metal oxides, or other materials known to catalyze OER reactions from an acidic electrolyte. Ferrous-to-ferric oxidation reactions may be performed using a wider range of materials including carbon, graphite, lead, or others.

[0079] In various other aspects, the iron electroplating cell may be configured as an electrolyte flow-through cell. In an electrolyte flow-through cell, electrolyte flow from a cathodic chamber / section / bath, through a separator, to an anodic chamber / section / bath. Electrolyte may be provided to the cathodic chamber / section / bath and electrolyte (anolyte) may be removed from the anodic chamber / section / bath, thereby facilitating the flow from cathode(s) to anode(s). The separator may be a diaphragm or porous material that facilitates electrolyte flow from cathode(s) to anode(s) with minimal or no electrolyte flow in the opposite direction. This directional control facilitates extraction of whatever species are generated at the anode, such as the directional control facilitating extractionof ferric ions generated at the anode and minimizing or avoiding flow of those anodically generated ferric ions back to the catholyte or cathodic chamber / section / bath. In some aspects, a plating cell configured as an electrolyte flow-through cell useful herein has a separator, such as a diaphragm, surrounding each anode of the plating cell. Such a configuration may be referred to in the art as a bagged anode. A ferrous-rich aqueous solution, such as an impurity-treated ferrous-rich solution described herein, is provided to the catholyte or catholyte bath / chamber. The electrolyte (catholyte) flows through the separator (at which point it is an anolyte). In various aspects, the anodic reaction is aqueous dissolved ferrous ion oxidation to aqueous dissolved ferric ion. The anolyte is then removed. The flow of electrolyte from catholyte to anolyte and use of the separator avoids or minimizes mixing of anodically-generated ferric ions in the catholyte while allowing for the anodically-generated ferric ions to be removed, with the anolyte, for subsequent re-reduction elsewhere in the system, such as in a reductive leach reactor. Various aspects and embodiments useful herein with respect to electrolyte flow-through cells is found in the following U.S. Patents, all of which are incorporated herein in their entirety: US9,932,683 (Barker, et al.), US4,087,339 (Elliott, et al.), and US4,201 ,653 (O’Neill, et al.). In aspects described throughout herein comprising an iron electroplating / electrodeposition cell with an anodic reaction of aqueous dissolved ferrous ion oxidation to aqueous dissolved ferric ion, the respective cell may optionally be configured as an electrolyte flow-through cell. With an electrolyte flow-through cell, the used / spent electrolyte is the removed anolyte, such as anolyte removed from the volume formed around the bagged anode. Non-limiting examples of anode compositions useful for flow-through cells herein include one or more allotropes of carbon, such as graphite, lead, and mixed metal oxide(s).

[0080] Once the plating anolyte and / or catholyte are depleted of reactants (as described in various examples in the ‘604 patent), one or both of the spent electrolytes may be returned to a ferric reduction reactor (FRR) 116, 216. In some embodiments, a ferric reduction reactor may comprise an electrochemical acid regeneration cell. As described in the ‘604 patent, an acid regeneration cell may be configured to oxidize water (and evolve oxygen) at its anode while reducing ferric ions to ferrous ions at its cathode. Protons liberated by the anodic water splitting reaction may then cross the PEM separator of the acid regeneration cell and enter the acid regeneration cell’s catholyte, thereby acidifying the acid regeneration cell catholyte.

[0081] In alternative configurations, a ferric reduction reactor may comprise one or more chemical reactors configured to reduce ferric ions to ferrous ions through predominantly chemical reactions, optionally in the presence of a catalyst. In some embodiments, a ferric reduction reactor may comprise one or more consumable reducing agents such as one or more organometallic compounds, sulfite (e.g., as described in LIS3109732, which is incorporated by reference herein), metallic iron (e.g., in powder, plate, or other forms), gaseous reductants such as hydrogen gas, sulfur dioxide, hydrogen sulfide, or others.

[0082] In some implementations, spent plating catholyte may become substantially depleted of ferrous ions over the course of electroplating and may contain predominantly water and acid salt (e.g., sulfate, chloride, and / or others), such as when approaching shut down conditions. In other implementations, electroplating may be operated as a continuous process such that the plating catholyte is fed or replenished, as needed and / or continuously, with a purified ferrous-rich leachate solution, such that the catholyte does not necessarily become substantially depleted of ferrous ions during steady state continuous operation of the electroplating cell. Optionally, the plating catholyte is bled or a portion thereof is removed periodically or continuously to manage catholyte volume and mitigate accumulation of concentrations of salts and / or impurities whose impact may become deleterious at higher concentrations. Optionally, at least a portion of the bled or removed plating catholyte or spent catholyte is processed to remove water, such as using an evaporator. Optionally, the removed or evaporated water from the plating catholyte is provided to the ferric reduction reactor or an acid regeneration cell, such as to the acid regenerator’s anolyte to replenish the water thereof. Optionally, salt extracted or separated from the bled or removed plating catholyte, may be provided to the acid regeneration cell’s catholyte or the leach tank(s). Alternatively or in addition, recovered water may be directed to and re-used in other process equipment, such as the water electrolyzer 218 described below with reference to FIG. 2. Optionally in some aspects, acid salt from the spent plating catholyte may be re-acidified by acid produced in an acid regeneration cell or other acid-producing ferric reduction reactors 116.

[0083] Optionally in some aspects, dissolved iron in the spent plating anolyte may be substantially converted to ferric ions over the course of electroplating such as when approaching shut down condition. Optionally in some aspects, electroplating is a continuous process such that the plating anolyte is fed or replenished, continuouslyand / or as needed, with a purified ferrous-rich leachate solution, such that the plating anolyte does not necessarily become substantially ferric ions during steady state continuous operation of the electroplating cell. Optionally, the plating anolyte is bled or a portion thereof is removed periodically or continuously to manage anolyte volume and / or concentrations of ferric ions, optionally to also mitigate accumulation of other salts or impurities. At least a portion of the bled or periodically or continuously removed plating anolyte plating anolyte is provided to the leach process (e.g., a dissolution tank) and / or to the acid regenerator cell (e.g., it’s catholyte) where the ferric ions having been formed in the plating anolyte may be reduced to ferrous ions.

[0084] In some aspects, a portion of the returning spent plating anolyte may be directed to the leach tank. Metallic iron reacts with acid to rapidly produce hydrogen gas. Therefore, if the thermal reduction 102, 202 produces substantial quantities of metallic iron in addition to FeO, then it may be desirable to consume the metallic iron with ferric ions prior to introducing large quantities of acid, thereby minimizing hydrogen production in the leaching vessel(s). The quantity and timing of delivery of a ferric solution to the leach tank may be determined empirically or based on a measurable parameter such as pH of the solution in the leach tank (the reaction of metallic iron with ferric ions will tend to increase the pH of the solution).

[0085] In some aspects herein, at least a first portion of the plating anolyte is recycled to the catholyte of the acid regeneration cell (also referred to herein as regen catholyte), as described with reference to FIG. 1A and FIG. 2. In such aspects, the recycled first portion of the plating anolyte contains at least a portion of the ferric ions electrochemically-generated in the plating cell. In such aspects, at least a portion of the electrochemically generated ferric ions is reduced to ferrous ions (also referred to herein as regenerated ferrous ions) in the regen catholyte. As also described herein, at least a second portion of the plating anolyte may be recycled to the aqueous acid solution of the leaching step (e.g., to one or more of the leaching or dissolution tanks), the recycled second portion of the plating anolyte having at least a portion of the electrochemically- generated ferric ions.

[0086] Optionally, the recycled portions of the plating anolyte may be slightly, substantially, or nearly entirely depleted of ferrous ions relative to the purified ferrous- rich leachate entering the plating cell. Optionally, the first and / or the second recycled portion of the plating anolyte has a concentration of ferrous ions being at least approximately 50% (optionally at least approximately 60%, optionally at leastapproximately 70%, optionally at least approximately 80%, optionally at least approximately 90%) of the concentration of ferrous ions in the purified ferrous-rich solution. Optionally, the first and / or the second recycled portion of the plating anolyte has a concentration of ferrous ions being less than approximately 50% (optionally less than approximately 40%, optionally less than approximately 30%, optionally less than approximately 20%, optionally less than approximately 10%, optionally less than approximately 5%, optionally less than approximately 1 %) of the concentration of ferrous ions in the purified ferrous-rich solution.

[0087] In the example of FIG. 1 , the ferric reduction reactor comprises an acid regeneration cell 116, which is shown as having an oxygen evolution anode as described in various embodiments in the ‘604 patent. In alternative embodiments, represented for example in FIG. 2, an acid regeneration cell may have a hydrogen oxidation anode fed by hydrogen produced in a separate water electrolyzer (or provided from another process such as SMR or from another source such as storage or geologic hydrogen). The water electrolyzer 218 may be configured to produce hydrogen in advance which may be stored until use. Alternatively, the electrolyzer 218 may be configured to produce hydrogen on-demand based on a control signal from a controller controlling or monitoring operation of the acid regeneration cell.

[0088] FIG. 2 illustrates an alternative process for producing metallic iron from iron ore. The primary difference between the FIG. 1 process and the FIG. 2 process is that the FIG. 2 acid regeneration cell is configured as a hydrogen oxidizing acid regeneration fuel cell 216. Hydrogen gas may be supplied to the acid regeneration fuel cell 216 from a water electrolyzer 218 or other hydrogen production process or hydrogen source.

[0089] In alternative embodiments, a portion of or the entirety of the FeO feedstock material introduced into the leach tank may come from a source other than a thermal reduction process. For example, steelmaking slag contains substantial quantities of FeO and could be used as an FeO feedstock in addition to or in place of a thermally reduced ore material. Mill scale or other iron source materials may also be included as feedstock materials.

[0090] As with the examples above, some components of the reduced ore, such as silica and quartz, will not dissolve and may be removed from the leaching step 204 as undissolved solids. Impurities that do dissolve may be removed from the leachate at 206 such as by a precipitation and filtration process driven by a pH shift as described in the‘604 patent. Alternatively, other impurity removal methods such as solvent extraction, cementation, or other methods may be used.

[0091] The purified leachate may then be directed to the electroplating cell 210. As with the examples above, the leachate may be divided into plating anolyte and plating catholyte portions, and electroplating may proceed at the plating anode 212 and plating cathode 214 as described elsewhere herein and in the ‘604 patent. Alternatively, the system of FIG. 2 may be configured as described above with reference to FIG. 1 B in which the electrolyte flows from the cathode chamber into the anode chamber.

[0092] Once the plating anolyte and / or catholyte are depleted of reactants (as described in various examples above and in the ‘604 patent), one or both spent electrolytes may be returned to a ferric reduction reactor 216. In the configuration of FIG. 2, an acid regeneration cell will take the form of an acid regeneration fuel cell 216 which produces energy. This is because the oxidation of hydrogen at the anode of an acid regeneration cell is an energy-producing reaction when coupled with ferric-to- ferrous reduction. The energy produced may be used to power the plating cell or other components of the system.

[0093] In some embodiments, a portion of the spent plating anolyte may be directed to the leach tank. Metallic iron reacts with acid to rapidly produce hydrogen gas. Therefore, if the thermal reduction 202 produces substantial quantities of metallic iron in addition to FeO, then it may be desirable to consume the metallic iron with ferric ions prior to introducing large quantities of acid, thereby minimizing hydrogen production. The quantity and timing of delivery of a ferric solution to the leach tank may be determined empirically or based on a measurable parameter such as pH of the solution in the leach tank (the reaction of metallic iron with ferric ions will tend to increase the pH of the solution).

[0094] Non-limiting Examples:

[0095] The following examples include some specific but non-limiting examples and embodiments intended for illustration of some aspects. The methods, techniques, parameters, system configurations, apparatuses, and results provided in these examples do not limit the scope of any aspects, embodiments, or claims herein. As would be recognized by one of skill in the art, one or more parameters, techniques, configurations, or apparatuses may be tuned, adjusted, or optimized to produce a desired result, where the combination provided in these examples may be useful asstarting points for experimentation, where such variations or tuning or experimentation is within the scope of Aspects and claims herein.

[0096] For the purpose of these non-limiting examples, leaching tests are used to determine reduction of ferric in the lixiviant (e.g., a “leach solution” or “electrolyte” as described herein), the final ferrous / ferric ratio in solution, total Fe recovery, and leaching kinetics. Quantitation of iron concentrations in solution are carried out by coulometric titration. Residues are analyzed by XRD with reference intensity ratio (RIR) analysis, wherein 8 calculations are averaged with selecting 3 of 6 signals, is used to quantify the phase composition of the reduction products and validated with leaching data and mass loss measurements. SEM analysis is used evaluate sintering or dense superficial iron formations. The following thermal reduction experiments are performed on a static powder in a tube furnace. The reducing atmosphere is H2 gas with varied concentrations of water vapor.

[0097] As noted above, variations of conditions or parameters in these examples are contemplated and within the scope disclosed herein. For example, it is contemplated herein that while the thermal reduction experiments were performed on a static powder in a tube furnace, resulting parameters can be tuned by performing a thermal reduction in different configurations, such by perturbing (e.g., mixing, shaking, etc.) the powder during thermal reduction and in a tube furnace versus a rotary kiln or fluidized bed configuration.

[0098] Example 1 :

[0099] The variation of thermal reduction temperature, duration at temperature, and humidity of the reducing atmosphere affects resulting composition and oxidation state of the thermally reduced material. Some exemplary, non-limiting, combinations of conditions and results are provided in Table 1 :Table 1 : Controlling the final phase mixture by varying temperature, residence time, and H2O %:

[0100] In some aspects, a humid atmosphere may slow kinetics forming both FeO and Fe°, but formation of Fe° may be more significantly impacted. In some aspects, selectivity for FeO may be increased at the cost of kinetics. In some aspects, having approximately 10% of H2O can yield FeO free of Fe° but the net oxidation state of the resulting reduced material is typically still greater than 2, depending on temperature, for example. In some aspects, Fe° can be yielded in the presence of 10% water vapor at 600°C, but at the trade-off of a longer thermal reduction duration. In some aspects, reduction at 600°C for 3 hours in the presence of 20-30% water vapor may result in magnetite as the only iron phase observed. In some aspects, at a reduction temperature of 700°C in the presence of 10% water vapor, iron metal (Fe°) formation may occur at rates similar to but slower than in a dry atmosphere at 600°C, while also having low FesCM concentration and high FeO concentration. In some aspects, reduction in presence of 10% H2O shows increasing FeO as temperature increased.

[0101] Example 2:

[0102] It is contemplated that, depending on handling, the thermally-reduced material can spontaneously oxidize in the presence of air and the exothermic oxidation reaction may self-perpetuate, thereby causing deviation from the net oxidation state conditions achieved during thermal reduction. To address this issue, a passivation is performed in various aspects herein. One exemplary passivation approach is to provide the thermally- reduced material to an inert atmosphere, such as N2, and slowly introduce air while maintaining a passivation temperature, such as between 60 °C and 400 °C, optionally between 60 °C and 200 °C, optionally less than 100 °C. An alternative exemplary passivation approach is to expose the thermally-reduced material to liquid water. In some aspects, the thermally-reduced material may be processed to reduce surface area exposed to air, such as by compacting the thermally-reduced material, which is optionally performed in addition to a passivation step according to aspects herein.

[0103] Example 3:

[0104] The net oxidation state of the thermally-reduced material, according to aspects herein, may affect the rate of leaching or dissolution of the material and the ferrous-to-ferric ion concentration ratio in the resulting leachate.

[0105] Non-limiting exemplary leaching parameters are provided in Table 2 and Table 3.Table 2: Average net oxidation state of the thermally-reduced material and exemplary resulting leachate parameters.Table 3: Average net oxidation state of the thermally-reduced material and exemplary resulting leachate parameters.

[0106] Oxidation measure via leach is calculated using:which is solved for Avg Oxidation, which is the oxidation state of the ore.

[0107] High Purity Iron Applications:

[0108] Aspects disclosed herein include processes and systems for electroplating iron for use in applications requiring high purity iron, such as but not limited to batteries, including lithium iron phosphate batteries, all-iron flow batteries, iron-chromium flow batteries, iron-air batteries, or others. In some such aspects, an acid regeneration cell is omitted. For some battery industries, the ferric ions produced in the plating anolyte may not need to be reduced to regenerate ferrous ions, and as such the plating anolyte may be a waste or co-product, for example, optionally without a subsequent electrochemical process to reduce the ferric ions. Some aspects, therefore, include processing a feedstock material to form a pre-leach material, leaching the pre-leach material to produce a ferrous-rich leachate, optionally removing impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution, providing at least a portion of theferrous-rich leachate or of the purified ferrous-rich solution to a plating catholyte of an iron electroplating cell, electroplating metallic iron from the plating catholyte at a plating cathode, and subsequently utilizing the electroplated metallic iron, directly or indirectly, in a battery or an electrochemical energy storage device, optionally without an electrochemical step of electrochemically reducing ferric ions from the plating anolyte to ferrous ions. In such aspects, optionally the anodic reaction in the iron electroplating cell is either an Fe2+to Fe3+oxidation or an oxygen evolution reaction (OER). Optionally, the electroplated iron is generated and collected in the form of iron metal powder, iron plates, iron coins, iron chips, or other formats.

[0109] Aspects and Embodiments:

[0110] Various aspects are contemplated and disclosed herein, a plurality of which is set forth in the paragraphs below. It is explicitly contemplated and disclosed that any aspect or portion thereof can be combined to form an aspect. In addition, it is explicitly contemplated and disclosed that: any reference to Aspect 1 includes reference to Aspects 1 a, 1 b, 1c, ... 11, and any combination thereof; any reference to Aspect 8 includes reference to Aspects 8a, 8b, 8c, and 8d; and so on (any reference to an aspect includes reference to that aspect’s lettered versions). Moreover, the terms “any preceding aspect” and “any one of the preceding aspects” means any aspect that appears prior to the aspect that contains such phrase (for example, the sentence “Aspect 36: The method or system of any one of the preceding Aspects...” means that any aspect prior to aspect 36 is referenced, including letter versions, including aspects 1 a through 35). For example, it is contemplated and disclosed that, optionally, any method, any step, any system, any subsystem, any composition, etc., according to any of the below aspects may be useful with or combined with any other aspect(s) provided below. Further, for example, it is also contemplated and disclosed that any embodiment or aspect described above may, optionally, be combined with any of the below listed aspects.

[0111] In aspects, the thermal reduction pre-treatment is used to reduce a feedstock material, optionally being predominantly hematite, to a thermally reduced material having a net iron oxidation state of +2, approximately +2, optionally less than 2.0, optionally selected from the range of +1 .5 to +2.3, wherein any value and any range therebetween is explicitly contemplated and disclosed herein, such as optionally selected from the range of +1 .6 to +2.2, optionally selected from the range of +1 .6 to +2.1 , optionally selected from the range of +1 .7 to +2.1 , optionally selected from therange of +1 .8 to +2.1 , optionally selected from the range of +1 .9 to +2.1 , optionally selected from the range of +1 .6 to +2.0, optionally selected from the range of +1 .7 to +2.0, optionally selected from the range of +1 .8 to +2.0, optionally selected from the range of +1 .9 to +2.0, optionally selected from the range of +1 .5 to +1.9, optionally selected from the range of +1 .6 to +1 .9, optionally selected from the range of +1 .7 to +1 .9, optionally selected from the range of +1 .8 to +1 .9, optionally selected from the range of +1 .5 to +1 .8, optionally selected from the range of +1 .5 to +1 .7. For example, a net oxidation state of less than +2, such as +1.8, may be obtained via reducing the feedstock to a mixture of majority wustite (+2 oxidation state) and minority iron metal (0 oxidation state), while optionally also containing magnetite.

[0112] Aspect 1a: A method for producing metallic iron from a feedstock material, the method comprising: processing the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; leaching the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0;(optionally) removing impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution; providing a first portion of the purified ferrous-rich solution to a plating catholyte of an iron-electroplating cell;providing a second portion of the purified ferrous-rich solution to a plating anolyte of the iron-electroplating cell; wherein the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at a cathode; and wherein the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically- generated ferric ions at an anode; and electroplating metallic iron in the iron-electroplating cell.

[0113] Aspect 1 b: A method for producing metallic iron from a feedstock material, the method comprising: processing the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; leaching the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0; providing a first portion of the ferrous-rich solution (optionally, a purified ferrous- rich solution) to a plating catholyte of an iron-electroplating cell; providing a second portion of the purified ferrous-rich solution to a plating anolyte of the iron-electroplating cell;wherein the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at a cathode; and wherein the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically- generated ferric ions at an anode; and electroplating metallic iron in the iron-electroplating cell.

[0114] Aspect 1c: A method for producing metallic iron from a feedstock material, the method comprising: processing the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; leaching the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0;(optionally) removing impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution; providing a first portion of the purified ferrous-rich solution to a plating catholyte of an iron-electroplating cell;(optionally) providing a second portion of the purified ferrous-rich solution to a plating anolyte of the iron-electroplating cell;wherein the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at a cathode; and(optionally) wherein the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically-generated ferric ions at an anode; and electroplating metallic iron in the iron-electroplating cell.

[0115] Aspect 1d: A method for producing metallic iron from a feedstock material, the method comprising: processing the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; leaching the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0; providing a first portion of the ferrous-rich solution (optionally, the purified ferrous- rich solution (see Aspect 1e)) to a plating catholyte of an iron-electroplating cell; wherein the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at a cathode; and electroplating metallic iron in the iron-electroplating cell.

[0116] Aspect 1e: The method of any one of Aspects 1 d-1 j comprising removing impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution.

[0117] Aspect 1f: The method of Aspect 1d or 1e comprising providing a second portion of the purified ferrous-rich solution to a plating anolyte of the iron-electroplating cell.

[0118] Aspect 1g: The method of any one of Aspects 1 d-1 f, wherein the iron- electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically-generated ferric ions at an anode.

[0119] Aspect 1 h: The method of any one of Aspects 1 d-1 f, wherein the iron- electroplating cell is configured to perform an oxygen evolution reaction (OER) in the plating anolyte at an anode.

[0120] Aspect 1 i: The method of any one of Aspects 1 d-1 h being free of a step of electrochemically reducing at least a portion of the electrochemically-generated ferric ions to regenerated ferrous ions in an acid regeneration cell.

[0121] Aspect 1j: The method of any one of Aspects 1d-1 i being free of an acid regeneration cell.

[0122] Aspect 1 k: The method of any one of Aspects 1 d-1 j comprising using the electroplated metallic iron in a battery and / or providing the electroplated metallic iron to a battery manufacturing process or wherein said method is part of a battery manufacturing process.

[0123] Aspect 11: A system for producing metallic iron from a feedstock material, the system comprising: an ore preparation subsystem configured to process the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; a leaching subsystem configured to leach the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionallygreater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0;(optionally) an impurity removal subsystem configured to remove impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution; and an iron-electroplating cell comprising a plating catholyte in the presence of a plating cathode and a plating anolyte in the presence of a plating anode; wherein: the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at the cathode; the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically-generated ferric ions at the anode; a first portion of the purified ferrous-rich solution is provided to the plating catholyte; and a second portion of the purified ferrous-rich solution is provided to the plating anolyte.

[0124] Aspect 1 m: A system for producing metallic iron from a feedstock material, the system comprising: an ore preparation subsystem configured to process the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; a leaching subsystem configured to leach the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0; and an iron-electroplating cell comprising a plating catholyte in the presence of a plating cathode and a plating anolyte in the presence of a plating anode; wherein: the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at the cathode; a first portion of the ferrous-rich solution (optionally, the purified ferrous-rich solution (see Aspect 1 n)) is provided to the plating catholyte; and

[0125] Aspect 1 n: The system of Aspect 1 m comprising an impurity removal subsystem configured to remove impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution.

[0126] Aspect 1 o: The system of Aspect 1 m or 1 n, a second portion of the ferrous- rich solution (optionally, the purified ferrous-rich solution (see Aspect 1 n)) is provided to the plating anolyte.

[0127] Aspect 1 p: The system of any one of Aspects 1 m-1 o, wherein the iron- electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically-generated ferric ions at an anode.

[0128] Aspect 1 q: The system of any one of Aspects 1 m-1 o, wherein the iron- electroplating cell is configured to perform an oxygen evolution reaction (OER) in the plating anolyte at an anode.

[0129] Aspect 1 r: The system of any one of Aspects 1 m-1 q being free of a step of electrochemically reducing at least a portion of the electrochemically-generated ferric ions to regenerated ferrous ions in an acid regeneration cell.

[0130] Aspect 1 s: The system of any one of Aspects 1 m-1 r being free of an acid regeneration cell.

[0131] Aspect 1t: The system of any one of Aspects 1 m-1s wherein the electroplated metallic iron is used in a battery or is provided to a battery manufacturing process or wherein said system is part of a battery manufacturing system.

[0132] Aspect 2a: The method or system of Aspect 1 , wherein processing comprises thermally reducing the feedstock in the presence of a reducing atmosphere to form a thermally-reduced material; wherein the thermally reduced material is characterized by a lower net iron oxidation state than that of the feedstock material; and wherein the preleach material comprises at least a portion of the thermally-reduced material.

[0133] Aspect 3a: The method or system of Aspect 2, wherein the thermally-reduced material is characterized by a net iron oxidation state selected from the range of 1 .0 to less than 2.0, wherein any range and value therebetween is explicitly contemplated and disclosed herein. Aspect 3b: The method or system of Aspect 2, wherein the thermally- reduced material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1.5).

[0134] Aspect 4a: The method or system of Aspect 2 or 3, wherein each of the thermally-reduced material and the pre-leach material is characterized by a net iron oxidation state selected from the range of 1.5 to less than 2.0. Aspect 4b: Aspect 4a: The method or system of Aspect 2 or 3, wherein each of the thermally-reduced material and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1 .0, optionally greater than 1 .0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1 .8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1.5), such as optionally greaterthan 1 .0 and less than 2.0. Aspect 4c: The method or system of Aspect 2 or 3, wherein the thermally-reduced material is characterized by a net iron oxidation state selected from the range of approximately 1 .5 to less than 2.0, wherein any range and value therebetween is explicitly contemplated and disclosed herein. Aspect 4d: The method or system of Aspect 2 or 3, wherein the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 1 .5 to less than 2.0, wherein any range and value therebetween is explicitly contemplated and disclosed herein.

[0135] Aspect 5a: The method or system of any one of Aspects 2-4, wherein each of the thermally-reduced material and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 1 .5 to less than or equal to approximately 1.9, wherein any range and value therebetween is explicitly contemplated and disclosed herein. Aspect 5b: The method or system of any one of Aspects 2-4, wherein the thermally-reduced material is characterized by a net iron oxidation state selected from the range of approximately 1 .5 to less than or equal to approximately 1 .9, wherein any range and value therebetween is explicitly contemplated and disclosed herein. Aspect 5c: The method or system of any one of Aspects 2-4, wherein the preleach material is characterized by a net iron oxidation state selected from the range of approximately 1 .5 to less than or equal to approximately 1 .9, wherein any range and value therebetween is explicitly contemplated and disclosed herein.

[0136] Aspect 6a: The method or system of any one of Aspects 2-5, wherein the preleach material is at least 50 mol.% the thermally-reduced material. Aspect 6b: The method or system of any one of Aspects 2-5, wherein the pre-leach material is at least 51 mol.% (optionally at least 55 mol.%, optionally at least 60 mol.%, optionally at least65 mol.%, optionally at least 70 mol.%, optionally at least 75 mol.%, optionally at least80 mol.%, optionally at least 85 mol.%, optionally at least 90 mol.%, optionally at least95 mol.%, optionally at least 98 mol.%, optionally at least 99 mol.%) the thermally- reduced material. Aspect 6b: The method or system of any one of Aspects 2-5, wherein the pre-leach material is at least 50 wt.% (optionally at least 55 wt.%, optionally at least wt mol.%, optionally at least 65 wt.%, optionally at least 70 wt.%, optionally at least 75 wt.%, optionally at least 80 wt.%, optionally at least 85 wt.%, optionally at least 90 wt.%, optionally at least 95 wt.%, optionally at least 98 wt.%, optionally at least 99 wt.%) the thermally-reduced material.

[0137] Aspect 7: The method or system of any one of Aspects 2-6, wherein the preleach material is at least 75 mol.% the thermally-reduced material.

[0138] Aspect 8a: The method or system of any one of Aspects 1-7, wherein the feedstock material is characterized by a net iron oxidation state greater of than 2.0. Aspect 8b: The method or system of any one of Aspects 1-7, wherein the feedstock material is characterized by a net iron oxidation state greater of than approximately 2.0. Aspect 8c: The method or system of any one of Aspects 1-7, wherein the feedstock material is characterized by a net iron oxidation state greater of than 2.0 and less than approximately 3.0, wherein any range and value therebetween is explicitly contemplated and disclosed. Aspect 8d: The method or system of any one of Aspects 1-7, wherein the feedstock material is characterized by a net iron oxidation state greater of than 2.0 and less than approximately 3.2, wherein any range and value therebetween is explicitly contemplated and disclosed, such as optionally selected from the range of approximately +2.1 to approximately +3.1 , optionally selected from the range of approximately +2.1 to approximately +3.0, optionally selected from the range of approximately +2.2 to approximately +3.0, optionally selected from the range of approximately +2.3 to approximately +3.0, optionally selected from the range of approximately +2.4 to approximately +3.0, optionally selected from the range of approximately +2.5 to approximately +3.0, optionally selected from the range of approximately +2.6 to approximately +3.0, optionally selected from the range of approximately +2.7 to approximately +3.0, optionally selected from the range of approximately +2.8 to approximately +3.0, optionally selected from the range of approximately +2.9 to approximately +3.0.

[0139] Aspect 9a: The method or system of any one of Aspects 1 -8, wherein the preleach material comprises predominantly wustite. Aspect 9b: The method or system of any one of Aspects 1-8, wherein the pre-leach material is more than approximately 50 mol.% wustite, optionally at least approximately 60 mol.% wustite, optionally at least approximately 70 mol.% wustite, optionally at least approximately 80 mol.% wustite, optionally at least approximately 85 mol.% wustite, optionally at least approximately 90 mol.% wustite, optionally at least approximately 91 mol.% wustite, optionally at least approximately 92 mol.% wustite, optionally at least approximately 93 mol.% wustite, optionally at least approximately 94 mol.% wustite, optionally at least approximately 95 mol.% wustite, optionally at least approximately 96 mol.% wustite, optionally at least approximately 97 mol.% wustite, optionally at least approximately 98 mol.% wustite, optionally at least approximately 99 mol.% wustite, optionally at least 99.5 mol.% wustite.

[0140] Aspect 10a: The method or system of any one of Aspects 1 -8, wherein the pre-leach material comprises predominantly a combination of wustite and one or more materials having Fe°, such as one or more iron-based metals, such as optionally metal iron. Aspect 10b: The method or system of any one of Aspects 1-8, wherein the preleach material is more than approximately 50 mol.%, optionally at least approximately 55 mol.%, optionally at least approximately 60 mol.%, optionally at least approximately65 mol.%, optionally at least approximately 70 mol.%, optionally at least approximately75 mol.%, optionally at least approximately 80 mol.%, optionally at least approximately85 mol.%, optionally at least approximately 90 mol.%, optionally at least approximately95 mol.%, optionally at least approximately 98 mol.%, optionally at least approximately99 mol.%, optionally at least 99.5 mol.% a combination of wustite and one or more materials having Fe°, such as one or more iron-based metals, such as optionally metal iron.

[0141] Aspect 11a: The method or system of any one of Aspects 1-8, wherein the pre-leach material comprises predominantly a combination of wustite, one or more materials having Fe°, and magnetite. Aspect 11 b: The method or system of any one of Aspects 1-8, wherein the pre-leach material is more than approximately 50 mol.%, optionally at least approximately 55 mol.%, optionally at least approximately 60 mol.%, optionally at least approximately 65 mol.%, optionally at least approximately 70 mol.%, optionally at least approximately 75 mol.%, optionally at least approximately 80 mol.%, optionally at least approximately 85 mol.%, optionally at least approximately 90 mol.%, optionally at least approximately 95 mol.%, optionally at least approximately 98 mol.%, optionally at least approximately 99 mol.%, optionally at least 99.5 mol.% a combination of a combination of wustite, magnetite, and one or more materials having Fe°, such as one or more iron-based metals, such as optionally metal iron.

[0142] Aspect 12a: The method or system of any one of Aspects 1-8, wherein the pre-leach material comprises predominantly a combination of magnetite and one or more materials having Fe°. Aspect 12b: The method or system of any one of Aspects 1- 8, wherein the pre-leach material is more than approximately 50 mol.%, optionally at least approximately 55 mol.%, optionally at least approximately 60 mol.%, optionally at least approximately 65 mol.%, optionally at least approximately 70 mol.%, optionally at least approximately 75 mol.%, optionally at least approximately 80 mol.%, optionally at least approximately 85 mol.%, optionally at least approximately 90 mol.%, optionally at least approximately 95 mol.%, optionally at least approximately 98 mol.%, optionally atleast approximately 99 mol.%, optionally at least 99.5 mol.% a combination of a combination of magnetite and one or more materials having Fe°, such as one or more iron-based metals, such as optionally metal iron.

[0143] Aspect 13a: The method or system of any one of Aspects 1-12, wherein the pre-leach material is characterized by a composition having more than 0 mol.% and less than or equal to 50 mol.% of Fe° or one or more iron-based metals, wherein any value and any range therebetween is explicitly contemplated and disclosed herein. Aspect 13a: The method or system of any one of Aspects 1-12, wherein the pre-leach material is characterized by a composition comprising Fe° or one or more iron-based metals selected from the range of greater than 0 mol.% to less than or equal to approximately 45 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 40 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 35 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 30 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 25 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 20 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 15 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 10 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 9 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 8 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 7 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 6 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 5 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 4 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 3 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 10 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 9 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 8 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 7 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal toapproximately 6 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 5 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 4 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 3 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 10 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 9 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 8 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 7 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 6 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 5 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 4 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 3 mol.%, optionally selected from the range of approximately 1 mol.% to approximately 25 mol.%, optionally selected from the range of approximately 2 mol.% to approximately 25 mol.%, optionally selected from the range of approximately 5 mol.% to approximately 25 mol.%. Aspect 13c: The method or system of any one of Aspects 2-12, wherein the thermally reduced material is characterized by a composition having more than 0 mol.% and less than or equal to 50 mol.% of Fe° or one or more iron-based metals, wherein any value and any range therebetween is explicitly contemplated and disclosed herein. Aspect 13d: The method or system of any one of Aspects 2-12, wherein the thermally reduced material is characterized by a composition comprising Fe° or one or more iron-based metals selected from the range of greater than 0 mol.% to less than or equal to approximately 45 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 40 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 35 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 30 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 25 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 20 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 15 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 10 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 9mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 8 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 7 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 6 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 5 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 4 mol.%, optionally selected from the range of greater than 0 mol.% to less than or equal to approximately 3 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 10 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 9 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 8 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 7 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 6 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 5 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 4 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 3 mol.%, optionally selected from the range of approximately 0.5 mol.% to less than or equal to approximately 10 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 9 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 8 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 7 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 6 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 5 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 4 mol.%, optionally selected from the range of approximately 1 mol.% to less than or equal to approximately 3 mol.%, optionally selected from the range of approximately 1 mol.% to approximately 25 mol.%, optionally selected from the range of approximately 2 mol.% to approximately 25 mol.%, optionally selected from the range of approximately 5 mol.% to approximately 25 mol.%.

[0144] Aspect 14: The method or system of any one of Aspects 10-13, wherein the one or more materials having Fe° are one or more iron-based metals.

[0145] Aspect 15: The method or system of any one of Aspects 2-14, wherein the step of thermally reducing is performed at a temperature greater than 570 °C.

[0146] Aspect 16a: The method or system of any one of Aspects 2-15, wherein the step of thermally reducing is performed at a temperature selected from the range of approximately 570 °C to approximately 1000 °C, wherein any value and any range therebetween is explicitly contemplated and disclosed herein. Aspect 16b: The method or system of any one of Aspects 2-15, wherein the step of thermally reducing is performed at a temperature selected from the range of approximately 600 °C to approximately 1000°C, optionally selected from the range of approximately 700 °C to approximately 1000°C, optionally selected from the range of approximately 800 °C to approximately 1000°C, optionally selected from the range of approximately 600 °C to approximately 900°C, optionally selected from the range of approximately 600 °C to approximately 800°C, optionally selected from the range of approximately 700 °C to approximately 950°C, optionally selected from the range of approximately 700 °C to approximately 900°C, optionally selected from the range of approximately 750 °C to approximately 900 °C, optionally selected from the range of approximately 700 °C to approximately 850°C, optionally selected from the range of approximately 700 °C to approximately 800°C.

[0147] Aspect 17: The method or system of any one of Aspects 2-16, wherein the reducing atmosphere is at least 50 mol.%, optionally at least 60 mol.%, optionally at least 70 mol.%, optionally at least 80 mol.%, optionally at least 80 mol.%, optionally at least 90 mol.%, optionally at least 95 mol.%, optionally at least 98 mol.%, optionally at least 99 mol.% a reducing gas.

[0148] Aspect 18: The method or system of any one of Aspects 2-17, wherein the reducing atmosphere comprises a reducing gas selected from the group consisting of hydrogen gas, forming gas, natural gas, reformed natural gas, carbon monoxide, methane, one or more other natural and / or reformed hydrocarbon gas, hydrogen sulfide gas, sulfur dioxide, and any combination thereof.

[0149] Aspect 19: The method or system of any one of the preceding Aspects, wherein the step of processing further comprises passivating the thermally reduced material in the presence of a passivation atmosphere; wherein the step of passivating comprises cooling the thermally reduced material from a thermal-reduction temperature to an end-of-passivation temperature; and wherein the passivation atmosphere is atleast 50 mol.% (optionally at least 55 mol.%, optionally at least 60 mol.%, optionally at least 65 mol.%, optionally at least 70 mol.%, optionally at least 75 mol.%, optionally at least 80 mol.%, optionally at least 85 mol.%, optionally at least 90 mol.%, optionally at least 95 mol.%, optionally at least 98 mol.%, optionally at least 99 mol.%, optionally at least 99.5 mol.%) the reducing atmosphere, an inert atmosphere, or any combination thereof.

[0150] Aspect 20a: The method or system of Aspect 19, wherein the passivation atmosphere is less than approximately 50 mol.%, optionally less than or equal to approximately 45 mol.%, optionally less than or equal to approximately 40 mol.%, optionally less than or equal to approximately 35 mol.%, optionally less than or equal to approximately 30 mol.%, optionally less than or equal to approximately 25 mol.%, optionally less than or equal to approximately 20 mol.%, optionally less than or equal to approximately 15 mol.%, optionally less than or equal to approximately 10 mol.%, optionally less than or equal to approximately 5 mol.%, optionally between approximately 0 mol.% and approximately 50 mol.%, optionally between approximately 5 mol.% and approximately 30 mol.%, of oxidizing gaseous species, such as O2, CO2, or any combination thereof. Aspect 20b: The method or system of Aspect 19, wherein the passivation atmosphere comprises less than 20 mol.%, optionally less than or equal to 18 mol.%, optionally less than or equal to 15 mol.%, optionally less than or equal to 12 mol.%, optionally less than or equal to 10 mol.%, optionally less than or equal to 8 mol.%, optionally less than or equal to 6 mol.%, optionally less than or equal to 5 mol.%, optionally less than or equal to 3 mol.%, optionally less than or equal to 2 mol.%, optionally less than or equal to 1 mol.%, optionally less than or equal to 0.8 mol.%, optionally less than or equal to 0.5 mol.% of oxygen gas.

[0151] Aspect 21 : The method or system of Aspect 19 or 20, wherein the passivation atmosphere is maintained until an average temperature of the thermally reduced material is the end-of-passivation temperature being less than approximately 200 °C, optionally less than or equal to approximately 250 °C, optionally less than or equal to approximately 100 °C, optionally less than or equal to approximately 90 °C, optionally less than or equal to approximately 80°C, optionally less than or equal to approximately 70 °C, optionally less than or equal to approximately 60 °C.

[0152] Aspect 22: The method or system of any one of the preceding Aspects comprising electrochemically reducing at least a portion of the electrochemical ly-generated ferric ions to regenerated ferrous ions in an acid regeneration cell to form a regenerated ferrous-rich solution.

[0153] Aspect 23: The method or system of Aspect 22 comprising recycling at least a first portion of the plating anolyte to a regen catholyte of the acid regeneration cell, the recycled first portion of the plating anolyte having at least a portion of the electrochemically-generated ferric ions.

[0154] Aspect 24: The method or system of Aspect 22 or 23, comprising recycling at least a second portion of the plating anolyte to the aqueous acid solution of the leaching step, the recycled second portion of the plating anolyte having at least a portion of the electrochemically-generated ferric ions.

[0155] Aspect 25a: The method or system of Aspect 23 or 24, wherein the recycled plating anolyte is a spent plating anolyte; wherein the spent plating anolyte has a concentration of ferric ions being less than a ferric ion concentration in the purified ferrous-rich solution. Aspect 25b: The method or system of Aspect 23 or 24, wherein the recycled plating anolyte is a spent plating anolyte; wherein the spent plating anolyte has a concentration of ferric ions being less than or equal to 98%, optionally less than or equal to approximately 95%, optionally less than or equal to approximately 92%, optionally less than or equal to approximately 90%, optionally less than or equal to approximately 88%, optionally less than or equal to approximately 85%, optionally less than or equal to approximately 83%, optionally less than or equal to approximately 80%, optionally less than or equal to approximately 75%, optionally less than or equal to approximately 70%, optionally less than or equal to approximately 65%, optionally less than or equal to approximately 60%, optionally less than or equal to approximately 55%, optionally less than or equal to approximately 50%, optionally less than or equal to approximately 45%, optionally less than or equal to approximately 40%, optionally less than or equal to approximately 35%, optionally less than or equal to approximately 30%, optionally less than or equal to approximately 25%, optionally less than or equal to approximately 20%, optionally less than or equal to approximately 15%, of a ferric ion concentration in the purified ferrous-rich solution.

[0156] Aspect 26: The method or system of any one of Aspects 22-25 comprising providing the regenerated ferrous-rich solution to the aqueous acid solution of the leaching step.

[0157] Aspect 27: The method or system of any one of Aspects 22-26, wherein a leach solution from the leaching step is not provided to the acid regeneration cell.

[0158] Aspect 28: The method or system of any one of Aspects 22-27 comprising providing at least a portion of the plating catholyte to a regen anolyte of the acid generation cell.

[0159] Aspect 29: The method or system of any one of Aspects 22-27 comprising performing electrochemical oxygen gas evolution at an anode of the acid regeneration cell.

[0160] Aspect 30: The method or system of any one of Aspects 22-29 comprising performing electrochemical hydrogen gas evolution at an anode of the acid regeneration cell.

[0161] Aspect 31 : The method or system of Aspect 30, wherein the hydrogen gas is produced on-demand in a water electrolyzer.

[0162] Aspect 32: The method or system of any one of the preceding Aspects, wherein the step of leaching is performed using a countercurrent configuration (optionally continuous countercurrent configuration) having at least a primary dissolution tank and a secondary dissolution tank.

[0163] Aspect 33: The method or system of Aspect 32, wherein: the pre-leach material is provided to the primary dissolution tank; undissolved solids from the primary dissolution tank are provided to at least the secondary dissolution tank for further dissolution; at least a portion of a regen catholyte or a regenerated ferrous-rich solution is provided from the acid regeneration cell to at least the secondary dissolution tank; a secondary aqueous solution from at least the secondary dissolution tank is provided to the primary dissolution tank; the primary dissolution tank comprises a primary aqueous solution; and the ferrous-rich leachate comprises the primary aqueous solution.

[0164] Aspect 34a: The method or system of any one of the preceding Aspects, wherein the ferrous-rich leachate and / or the purified ferrous-rich solution comprises a ratio of concentrations of Fe3+ions to Fe2+ions being less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.0075, optionally less than or equal to approximately0.005, optionally less than or equal to approximately 0.0025, optionally less than or equal to approximately 0.001 , optionally wherein the ratio can be greater than or equal to approximately 0.0075, approximately 0.005, approximately 0.0025, or approximately 0.001 and such values can be combined in any manner to form a range, such as approximately 0.001 to approximately 0.01 . Aspect 34b: The method or system of any one of the preceding Aspects, wherein the ferrous-rich leachate comprises a ratio of concentrations of Fe3+ions to Fe2+ions being less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.0075, optionally less than or equal to approximately 0.005, optionally less than or equal to approximately 0.0025, optionally less than or equal to approximately 0.001 , optionally wherein the ratio can be greater than or equal to approximately 0.0075, approximately 0.005, approximately 0.0025, or approximately 0.001 and such values can be combined in any manner to form a range, such as approximately 0.001 to approximately 0.01 . Aspect 34b: The method or system of any one of the preceding Aspects, wherein the purified ferrous-rich solution comprises a ratio of concentrations of Fe3+ions to Fe2+ions being less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.01 , optionally less than or equal to approximately 0.0075, optionally less than or equal to approximately 0.005, optionally less than or equal to approximately 0.0025, optionally less than or equal to approximately 0.001 , optionally wherein the ratio can be greater than or equal to approximately 0.0075, approximately 0.005, approximately 0.0025, or approximately 0.001 and such values can be combined in any manner to form a range, such as approximately 0.001 to approximately 0.01 .

[0165] Aspect 35a: The method or system of any one of the preceding Aspects, wherein the purified ferrous-rich solution is characterized by a pH selected from the range of 1 .8 to 3.5. Aspect 35b: The method or system of any one of the preceding Aspects, wherein the purified ferrous-rich solution is characterized by a pH greater than 0.5 (e.g., greater than: 0.5, 0.6, 0.7, 0.8, 1 , 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6, optionally wherein the pH is less than: 0.6, 0.7, 0.8, 1 , 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 and such pHs can be combined in any manner to form a range, such as 0.5-6).

[0166] Aspect 36: The method or system of any one of the preceding Aspects, wherein the step of removing impurities comprises precipitating one or more aluminum- containing salts and one or more phosphate-containing salts.

[0167] Aspect 37: The method or system of any of Aspects 1 -21 being free of a step of electrochemically reducing at least a portion of the electrochemically-generated ferric ions to regenerated ferrous ions in an acid regeneration cell.

[0168] Aspect 38: The method or system of any of Aspects 1 -21 being free of an acid regeneration cell.

[0169] Aspect 39: The method or system of any one of the preceding Aspects comprising using the electroplated metallic iron in a battery and / or providing the electroplated metallic iron to a battery manufacturing process or wherein said method is part of a battery manufacturing process.

[0170] Aspect 40a: A system for producing metallic iron from a feedstock material, the system comprising: an ore preparation subsystem configured to process the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron ores; a leaching subsystem configured to leach the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material comprises one or more iron oxide materials and the pre-leach material is characterized by a net iron oxidation state selected from the range of approximately 0.5 (optionally approximately 0.6, optionally approximately 0.7, optionally approximately 0.8, optionally approximately 0.9, optionally approximately 1.0, optionally greater than 1.0, optionally approximately 1.1 , optionally approximately 1.2, optionally approximately 1.3, optionally approximately 1.4, optionally approximately 1.5, optionally approximately 1.6, optionally approximately 1.7, optionally approximately 1.8, optionally approximately 1 .9) to less than 2.0 (optionally approximately 2.0, optionally approximately 1.9, optionally approximately 1.8, optionally approximately 1.7, optionally approximately 1.6, optionally approximately 1 .5), such as optionally greater than 1 .0 and less than 2.0; an impurity removal subsystem configured to remove impurities from the ferrous- rich leachate to produce a purified ferrous-rich solution; andan iron-electroplating cell comprising a plating catholyte in the presence of a plating cathode and a plating anolyte in the presence of a plating anode; wherein: the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at the cathode; the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically-generated ferric ions at the anode; a first portion of the purified ferrous-rich solution to the plating catholyte; and a second portion of the purified ferrous-rich solution is provided to the plating anolyte.

[0171] Aspect 41 : The method or system of any preceding Aspect, wherein the electroplated metallic iron is in the form of a plate or sheet.

[0172] Aspect 42: The method or system of any preceding Aspect, wherein the electroplated metallic iron is in the form of metallic iron powder.STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS

[0173] All references throughout this application, for example patent documents including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source material; are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference).

[0174] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of any particular claimed invention. Thus, it should be understood that although inventions have been specifically disclosed by preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of inventions as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the inventions and it will be apparent to one skilledin the art that the inventions may be carried out using a large number of variations of the devices, device components, methods steps set forth in the present description. As will be obvious to one of skill in the art, methods and devices useful for the present methods can include a large number of optional composition and processing elements and steps.

[0175] As used herein and in the appended claims, the singular forms "a", "an", and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art. As well, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. It is also to be noted that the terms "comprising", "including", and "having" can be used interchangeably. The expression “of any of claims XX-YY” (wherein XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form, and in some embodiments is interchangeable with the expression “as in any one of claims XX-YY.”

[0176] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, including iron oxide materials of an ore or structural and compositional polymorphs of the group members, are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and sub-combinations possible of the group are intended to be individually included in the disclosure. When a compound is described herein such that a particular isomer, enantiomer or diastereomer of the compound is not specified, for example, in a formula or in a chemical name, that description is intended to include each isomers and enantiomer of the compound described individual or in any combination. Additionally, unless otherwise specified, all isotopic variants of 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 molecule disclosed can be replaced with deuterium or tritium. Isotopic variants of a molecule are generally useful as standards in assays for the molecule and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variants are known in the art. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently.

[0177] With regard to salts of the compounds herein, one of ordinary skill in the art can select from among a wide variety of available counterions those that are appropriate for preparation of salts of this invention for a given application. In specific applications,the selection of a given anion or cation for preparation of a salt may result in increased or decreased solubility of that salt.

[0178] Every device, system, subsystem, method, process, component, and / or combination of components, described or exemplified herein can be used to practice any claimed invention(s), unless otherwise stated.

[0179] Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein.

[0180] All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the disclosed devices, systems, methods, and processes pertain. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information can be employed herein, if needed, to exclude specific embodiments that are in the prior art. For example, when composition of matter are claimed, it should be understood that compounds known and available in the art prior to Applicant's inventions, including compounds for which an enabling disclosure is provided in the references cited herein, are not intended to be included in the composition of matter claims herein.

[0181] As used herein, “comprising” is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of" excludes 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" may be replaced with either of the other two terms. The claimed inventions illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[0182] One of ordinary skill in the art will appreciate that starting materials, reagents, synthetic methods, purification methods, analytical methods, and assay methods otherthan those specifically exemplified can be employed in the practice of the claimed inventions without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in these inventions.

[0183] The term “and / or” is used herein, in the description and in the claims, to refer to a single element alone or any combination of elements from the list in which the term and / or appears. In other words, a listing of two or more elements having the term “and / or” is intended to cover embodiments having any of the individual elements alone or having any combination of the listed elements. For example, the phrase “element A and / or element B” is intended to cover embodiments having element A alone, having element B alone, or having both elements A and B taken together. For example, the phrase “element A, element B, and / or element C” is intended to cover embodiments having element A alone, having element B alone, having element C alone, having elements A and B taken together, having elements A and C taken together, having elements B and C taken together, or having elements A, B, and C taken together.

Claims

We claim:1 . A method for producing metallic iron from a feedstock material, the method comprising: processing the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron oxides; leaching the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material is characterized by a net iron oxidation state less than 2.0 and greater than 1.0; electroplating metallic iron from the ferrous-rich leachate in an iron-electroplating cell.

2. The method of claim 1 , further comprising: removing impurities from the ferrous-rich leachate to produce a purified ferrous- rich solution prior to electroplating, and electroplating metallic iron from the purified ferrous-rich solution in the iron-electroplating cell.

3. The method of claim 2, further comprising: providing a first portion of the purified ferrous-rich solution to a plating catholyte of the iron-electroplating cell; providing a second portion of the purified ferrous-rich solution to a plating anolyte of the iron-electroplating cell; wherein the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at a cathode; and wherein the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically-generated ferric ions at an anode.

4. The method of claim 1 , further comprising: providing a first portion of the purified ferrous-rich solution to a plating catholyte of the iron-electroplating cell; providing a second portion of the purified ferrous-rich solution to a plating anolyte of the iron-electroplating cell;wherein the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at a cathode; and wherein the iron-electroplating cell is configured to electrochemically evolve oxygen at an anode.

5. The method of any of claims 1-4, wherein the step of processing comprises thermally reducing the feedstock in the presence of a reducing atmosphere to form a thermally-reduced material; wherein the thermally reduced material is characterized by a lower net iron oxidation state than that of the feedstock material; and wherein the pre-leach material comprises at least a portion of the thermally-reduced material.

6. The method of claim 5, wherein the thermally-reduced material is characterized by a net iron oxidation state less than 2.0 and greater than 1 .0.

7. The method of claim 5, wherein each of the thermally-reduced material and the preleach material is characterized by a net iron oxidation state less than 2.0 and greater than 1.0.

8. The method of claim 5, wherein each of the thermally-reduced material and the preleach material is characterized by a net iron oxidation state greater than 1 .5 and less than or equal to 1.9.

9. The method of any one of claims 5-8, wherein the pre-leach material is at least 50 mol.% the thermally-reduced material.

10. The method of any one of claims 5-9, wherein the pre-leach material is at least 75 mol.% the thermally-reduced material.11 . The method of any one of claims 1 -10, wherein the feedstock material is characterized by a net iron oxidation state greater than 2.0.

12. The method of any one of claims 1-11 , wherein the pre-leach material comprises predominantly wustite.

13. The method of any one of claims 1-11 , wherein the pre-leach material comprises predominantly a combination of wustite and one or more materials having Fe°.

14. The method of any one of claims 1-11 , wherein the pre-leach material comprises predominantly a combination of wustite, one or more materials having Fe°, and magnetite.

15. The method of any one of claims 1-11 , wherein the pre-leach material comprises predominantly a combination of magnetite and one or more materials having Fe°.

16. The method of any one of claims 1-15, wherein the pre-leach material is characterized by a composition having more than 0 mol.% and less than or equal to 50 mol.% of Fe° or one or more iron-based metals.

17. The method of any one of claims 10-16, wherein the one or more materials having Fe° are one or more iron-based metals.

18. The method of any one of claims 5-17, wherein the step of thermally reducing is performed at a temperature greater than 570 °C.

19. The method of any one of claims 5-18, wherein the step of thermally reducing is performed at a temperature selected from the range of 570 °C to 1000 °C.

20. The method of any one of claims 5-19, wherein the reducing atmosphere is at least 50 mol.% a reducing gas.21 .The method of any one of claims 5-20, wherein the reducing atmosphere comprises a reducing gas selected from the group consisting of hydrogen gas, forming gas, natural gas, reformed natural gas, carbon monoxide, methane, one or more other natural and / or reformed hydrocarbon gas, hydrogen sulfide gas, sulfur dioxide, and any combination thereof.

22. The method of any of claims 5-21 , wherein the step of processing further comprises passivating the thermally reduced material in the presence of a passivation atmosphere; wherein the step of passivating comprises cooling the thermally reduced material from a thermal-reduction temperature to an end-of-passivation temperature; and wherein the passivation atmosphere is at least 50% the reducing atmosphere, an inert atmosphere, or a combination thereof.

23. The method of claim 22, wherein the passivation atmosphere is less than 30 mol.% oxygen gas.

24. The method of claim 22 or 23, wherein the passivation atmosphere is maintained until the thermally reduced material is characterized by the end-of-passivation temperature being less than or equal to approximately 100 °C.

25. The method of any of claims 3-24, comprising electrochemically reducing at least a portion of the electrochemically-generated ferric ions to regenerated ferrous ions in a ferric reduction reactor to form a regenerated ferrous-rich solution.

26. The method of claim 25, wherein the ferric reduction reactor comprises a chemical reactor; and the method further comprises contacting at least a first portion of the plating anolyte with a chemical reductant in the chemical reactor, thereby reducing at least a portion of the electrochemically-generated ferric ions to form a regenerated ferrous-rich solution.

27. The method of claim 25, wherein the ferric reduction reactor comprises an electrochemical acid regeneration cell, and comprising recycling at least a first portion of the plating anolyte to a regen catholyte of the acid regeneration cell, the recycled first portion of the plating anolyte having at least a portion of the electrochemically-generated ferric ions.

28. The method of claim 26, comprising recycling at least a second portion of the plating anolyte to the aqueous acid solution of the leaching step, the recycled second portion of the plating anolyte having at least a portion of the electrochemically- generated ferric ions.

29. The method of claim 26 or 27, wherein the recycled plating anolyte is a spent plating anolyte; wherein the spent plating anolyte has a concentration of ferric ions being greater than a ferric ion concentration in the purified ferrous-rich solution.

30. The method of any one of claims 25-28 comprising providing the regenerated ferrous-rich solution to the aqueous acid solution of the leaching step.31 .The method of any one of claims 26-30 comprising providing at least a portion of the plating catholyte to a regen anolyte of the acid generation cell.

32. The method of any one of claims 26-30 comprising performing electrochemical oxygen gas evolution at an anode of the acid regeneration cell.

33. The method of any one of claims 26-32 comprising performing electrochemical hydrogen gas evolution at an anode of the acid regeneration cell.

34. The method of claim 33, wherein the hydrogen gas is produced on-demand in a water electrolyzer.

35. The method of any one of the preceding claims, wherein the step of leaching is performed using a countercurrent configuration having at least a primary dissolution tank and a secondary dissolution tank.

36. The method of claim 35, wherein: the pre-leach material is provided to the primary dissolution tank;undissolved solids from the primary dissolution tank are provided to at least the secondary dissolution tank for further dissolution; at least a portion of a regen catholyte or a regenerated ferrous-rich solution is provided from the acid regeneration cell to at least the secondary dissolution tank; a secondary aqueous solution from at least the secondary dissolution tank is provided to the primary dissolution tank; the primary dissolution tank comprises a primary aqueous solution; and the ferrous-rich leachate comprises the primary aqueous solution.

37. The method of any one of the preceding claims, wherein the ferrous-rich leachate and / or the purified ferrous-rich solution comprises a ratio of concentrations of Fe3+ions to Fe2+ions being less than or equal to 0.01.

38. The method of any one of the preceding claims, wherein the purified ferrous-rich solution is characterized by a pH selected from the range of 1 .8 to 3.5.

39. The method of any of the preceding claims comprising using the electroplated metallic iron in a battery and / or providing the electroplated metallic iron to a battery manufacturing process or wherein said method is part of a battery manufacturing process.

40. A system for producing metallic iron from a feedstock material, the system comprising: an ore preparation subsystem configured to process the feedstock material to form a pre-leach material, wherein the feedstock material comprises one or more iron oxides; a leaching subsystem configured to leach the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate; wherein the pre-leach material is characterized by a net iron oxidation state less than 2.0 and greater than 1.0; an iron-electroplating cell comprising a plating catholyte in the presence of a plating cathode and a plating anolyte in the presence of a plating anode; wherein: the iron-electroplating cell is configured to electrochemically reduce ferrous ions in the plating catholyte to electroplate metallic iron at the cathode; anda first portion of the purified ferrous-rich solution is provided to the plating catholyte41 . The system of claim 40, wherein a second portion of the purified ferrous-rich solution is provided to the plating anolyte, and the iron-electroplating cell is configured to electrochemically oxidize ferrous ions in the plating anolyte to electrochemically- generated ferric ions at the anode.

42. The system of claim 40 or 41 , wherein the iron-electroplating cell comprises an oxygen evolution anode, and wherein the iron-electroplating cell is configured to perform an oxygen evolution reaction (OER), to evolve oxygen from the plating anolyte.

43. The system of any of claims 40-42, further comprising an impurity removal subsystem configured to remove impurities from the ferrous-rich leachate to produce a purified ferrous-rich solution prior to electroplating.

44. The system of claim 41 , further comprising a ferric reduction reactor configured to chemically and / or electrochemically reduce the electrochemically-generated ferric ions to generated ferrous ions to produce a regenerated ferrous solution; and wherein the system is configured to deliver the regenerated ferrous solution from the ferric reduction reactor to the leaching subsystem.

45. The system of claim 44, wherein the ferric reduction reactor comprises an electrochemical acid regenerator configured to reduce the electrochemically- generated ferric ions to regenerated ferrous ions by consuming electrical energy.

46. The system of claim 44, wherein the ferric reduction reactor comprises a chemical ferric reduction reactor configured to reduce the electrochemically-generated ferric ions to regenerated ferrous ions by contacting a portion of spent plating anolyte with a reductant.

47. The system of claim 40 being free of an acid regeneration cell.

48. The system of any of claims 40-42, wherein the electroplated metallic iron is used in a battery and / or is provided to a battery manufacturing process.

49. The system of any one of claims 40-48, wherein the electroplated metallic iron is in the form of a plate, sheet, coins, or crowns on the cathode.

50. The system of any one of claims 40-48, wherein the electroplated metallic iron is in the form of metallic iron powder.

51. The method of any claims 44-49 comprising using the electroplated metallic iron in a battery and / or providing the electroplated metallic iron to a battery manufacturing process or wherein said method is part of a battery manufacturing process.

52. The method of any one of claims 1 -39 or 44-50, wherein the electroplated metallic iron is in the form of a plate, sheet, coins, or crowns on the cathode.

53. The method of any one of claims 1 -39 or 44-50, wherein the electroplated metallic iron is in the form of metallic iron powder.

54. A method for producing metallic iron from a feedstock material comprising one or more iron oxides, the method comprising: thermally reducing oxides in the feedstock material to form a pre-leach material, wherein thermally reducing comprises heating the feedstock to a temperature greater than 570 °C in the presence of a reductant to produce a pre-leach material having a net iron oxidation state greater than 1 .0 and less than 2.0; leaching the pre-leach material with an aqueous acid solution to produce a ferrous-rich leachate solution; electroplating metallic iron from the ferrous-rich leachate solution in an iron- electroplating cell.

55. The method of claim 54, wherein the reductant comprises one or more gaseous reductants selected from the group consisting of: hydrogen gas, forming gas, natural gas, reformed natural gas, carbon monoxide, methane, hydrogen sulfide gas, sulfur dioxide gas.

56. The method of claim 51 , wherein electroplating metallic iron comprises producing electrochemically-generated ferric ions in the ferrous-rich leachate solution.

57. The method of claim 56, further comprising: reducing the electrochemically- generated ferric ions in a ferric reduction reactor.

58. The method of claim 56, wherein reducing the electrochemically-generated ferric ions comprises electrochemically reducing the electrochemically-generated ferric ions in an electrochemical acid regeneration cell.

59. The method of claim 56, wherein reducing the electrochemically-generated ferric ions comprises contacting the ferrous-rich leachate solution containingelectrochemically-generated ferric ions with a gaseous reductant, a solid reductant, or an aqueous reductant.

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