Electrochemical Metallurgical Slag Recycling

Abstract

Described herein are various embodiments of systems and methods for extracting and isolating reusable materials from metallurgical slags, such as iron slag, steel slag, blast furnace slag, BOF slag, and / or EAF slag, using aqueous acid and base solutions. In some embodiments, the acid and base solutions or materials can be generated electrochemically in a salt cracking acid-base generation (ABG) cell or cell stack.

Description

Detailed Description of the Invention

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 407,998, filed September 19, 2022, and U.S. Provisional Patent Application No. 63 / 408,034, filed September 19, 2022, each of which is incorporated by reference in its entirety into this specification.

[0002] [Background technology] This application relates generally to the field of metallurgy, and more particularly to systems and methods for recycling industrial by-products, such as metallurgical slag, into reusable materials.

[0003]

[0002] Currently, steel is traditionally made by one of two processes: the "integrated" process and the "electric arc furnace" or EAF process. In the integrated process, iron ore is refined into pig iron in a "blast furnace," and the (typically still molten) pig iron is then transferred to a "basic oxygen furnace" (BOF) where it is converted into steel by the removal of excess carbon and the addition of alloying elements. In the EAF process, scrap steel, scrap iron, pig iron, reduced iron, and / or other iron-containing materials are melted by an electric arc between graphite electrodes. In both the BOF and EAF processes, impurities are removed by the formation of a "slag" material composed of molten impurities. The slag floats on top of the molten iron, allowing the iron and slag to be separated from each other, thus allowing a pure steel product to be formed from the molten iron.

[0004]

[0003] Slag is formed in part by the addition of "flux" materials, typically composed primarily of carbonates and / or oxides of calcium and / or magnesium. The flux materials melt and combine with impurities (e.g., silica, alumina, phosphorus, and metal oxides) to form less dense compounds. The flux materials can also provide a protective layer to the furnace's refractory materials to minimize or prevent damage to the refractory.

[0005] In various applications, naturally occurring limestone (CaCO3) and / or dolomite (CaMg(CO3)2) minerals are frequently used as fluxes in steelmaking. In other cases, mixtures of lime (CaO), magnesia (MgO), magnesite (MgCO3), brucite (Mg(OH)2), or one or more calcium and / or magnesium carbonates and / or calcium and / or magnesium oxides (including hydroxides) may be used as fluxes in steelmaking. In some cases, the flux material may also contain other elements or compounds as impurities, such as silica, iron oxides, sulfur compounds, or phosphorus oxides.

[0006]

[0005] Iron and steel slag can be broadly classified into "blast furnace slag", which is produced when iron ore (a naturally occurring rock containing substantial amounts of iron oxide) is melted in a blast furnace and chemically reduced to remove the oxides, "steelmaking slag", which is produced during the steelmaking process and is used to adjust the composition of the iron, and "ladle slag", which is produced to aid in the final purification of molten steel just prior to casting.

[0007]

[0006] Blast furnace slag is a combination of silica and other non-ferrous components of iron ore, ash from coke used as a reducible material, and limestone adjuncts. Because its specific gravity is less than that of pig iron, during the heating process, the molten slag rises above the pig iron and can be easily separated and recovered.

[0008]

[0007] Steelmaking slag is generated during the conversion of pig iron from a blast furnace into strong, highly workable steel. Converter furnace slag (or BOF slag) is an oxidized material generated when lime and other auxiliary materials are added and oxygen is blown through the pig iron to remove carbon, phosphorus, sulfur, and other elements from the pig iron and refine it to produce strong steel. Another type of steelmaking slag, "electric arc furnace slag," is generated when scrap iron and metallic iron, typically as ore-based metals (OBM), such as pig iron, reduced iron (DRI), hot briquetted iron (HBI), and / or other OBM, or other materials containing primarily metallic iron, are melted and refined in an EAF.

[0009]

[0008] The specific composition of steel slag material (i.e., the presence, amount, and crystalline state of elements and compounds) tends to vary based on the type of furnace used, the composition of the source iron material being melted in the furnace, the type and grade of steel being produced, and even the materials and operating practices of the individual furnace. Nevertheless, steel slags are generally composed of, among other possible compounds, CaO, MgO, SiO2, FeO, Fe2O3, Fe3O4, Al2O3, MnO, PO 5、 It may contain compounds such as TiO2 and sulfur compounds such as CaS. Much of the material is often in the form of calcium silicates, calcium alumino-ferrites, and fused oxides of calcium, iron, magnesium, and manganese.

[0010]

[0009] The global steel industry produces nearly 300 million tons of steel slag annually, with approximately 0.3 tons of slag produced for every ton of steel. Some jurisdictions are discussing classifying some slag materials as hazardous waste, which would dramatically increase their transportation and disposal costs. While some steel slag is used as aggregate in cement production or as roadbed material, the industry as a whole is having difficulty finding sufficient demand for the large quantities of slag produced. Therefore, there is a need for methods to more effectively reuse steel and iron slag.

[0011] [overview]

[0010] Various aspects of systems and methods are described herein for extracting and isolating reusable materials from metallurgical slags, such as iron slag, steel slag, blast furnace slag, BOF slag, and / or EAF slag, using aqueous acid and base solutions. In some aspects, the acid and base solutions or materials can be generated electrochemically in a salt cracking acid-base generation (ABG) cell or cell stack.

[0012]

[0011] Aspects disclosed herein include a method of recycling a first slag (and a system for carrying out the method), comprising the steps of: dissolving the first slag with a first acid to form a starting leach solution, the starting leach solution comprising at least dissolved (aqueous) aluminum ions, dissolved iron ions, dissolved (aqueous) magnesium ions, and dissolved (aqueous) manganese ions; first precipitating one or more first precipitate products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first pre-plating leachate fraction, the one or more first precipitate products comprising one or more precipitated aluminum-containing products, and the first pre-plating leachate fraction comprising dissolved (aqueous) iron ions, magnesium ions, and manganese ions; and extracting metallic iron from the first pre-plating leachate fraction using a first electrochemical cell. to form electroplated metallic iron and a first post-plating leachate fraction, the first post-plating leachate fraction having a reduced concentration of iron ions compared to the first pre-plating leachate fraction; second precipitating one or more second precipitated products from the first post-plating leachate fraction by combining a second base with the first post-plating leachate fraction to increase its pH, thereby forming a second leachate fraction, the one or more second precipitated products comprising one or more precipitated manganese-containing products; and third precipitating one or more third precipitated products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction, the one or more third precipitated products comprising one or more precipitated magnesium-containing products. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic block diagram illustrating a method for recycling metallurgical slag to extract reusable materials using electrochemically generated acid and base solutions. [Figure 2]FIG. 1 is a schematic block diagram illustrating a process for recycling metallurgical slag including an electroplating cell configured to electroplate iron from a leach solution containing ions of Mg, Ca, Mn, and / or other ions. [Figure 3] FIG. 1 is a schematic block diagram illustrating the recycling of slag from a steel mill into reusable components in the steel mill. [Figure 4] FIG. 1 is a schematic diagram of an exemplary electrochemical acid-base generating cell. [Figure 5] FIG. 1 is a schematic diagram of an iron electroplating cell for electroplating metallic iron from an aqueous solution containing ferrous iron (Fe ions). [Figure 6] FIG. 1 is a schematic diagram illustrating another configuration of an electrochemical acid-base generation system. [Figure 7] FIG. 1 is a schematic diagram illustrating another configuration of an electrochemical acid-base generation system. [Figure 8] FIG. 1 is a schematic diagram illustrating an exemplary electrodialysis cell for producing acids and bases using bipolar membranes.

[0014] [Description of chemical compounds and nomenclature]

[0020] Generally, the terms and phrases used herein have their art-recognized meanings, which can be found by reference to standard textbooks, journals, and contexts known to those skilled in the art. The following definitions are provided to clarify their specific use in the context of this disclosure.

[0015]

[0021] In various aspects, the present disclosure provides processes, systems, and methods for recycling steel slag into value-added materials using electrochemically generated acid and base solutions, creating a circular economy for steel production. In various aspects described herein, components of steel slag can be isolated and formulated for use as CO2 capture materials, steelmaking flux materials, or other applications.

[0016]

[0022] In various aspects, the present disclosure provides processes, systems, and methods for enabling an efficient, low-temperature hydrometallurgical process for producing pure iron from a variety of iron source materials, including relatively low-purity iron source materials. Broadly speaking, the iron source material is dissolved in an acidic aqueous solution, and metallic iron is electrolytically plated and removed as a solid. In various aspects, the iron source material or aqueous iron may be converted from one form to another during one or more process steps.

[0017]

[0023] As used herein, the terms "pure iron" and "high purity iron" are used in a relative sense to refer to a metallic iron material that is purer than the iron source material and contains an acceptably small amount of one or more impurities.

[0018]

[0024] As used herein, the terms "iron source material" and "iron feedstock" are used interchangeably to refer to iron-containing materials that may be used as inputs to the various systems and methods described herein. "Iron source material" and "iron feedstock" can include any form of iron, such as iron oxide, iron hydroxide, iron oxyhydroxide, iron carbonate, or other iron-containing compounds, ores, rocks, or minerals (including any mixtures thereof), whether naturally occurring or beneficiated or otherwise purified or modified. The terms "iron-containing ore" or simply "iron ore" can include materials recognized, known, or referred to in the art as iron ore(s), rock(s), natural rock(s), deposit(s), natural deposit(s), mineral, and / or natural mineral(s), whether naturally occurring or beneficiated or otherwise purified or modified. Some aspects of the processes and systems described herein may be particularly useful for iron ores that include hematite, goethite, magnetite, limonite, siderite, ankerite, hydrohematite, bauxite, or any combination thereof.

[0019]

[0025] Optionally, the ferrous source material or raw ferrous material may include ferrous metal materials such as, but not limited to, iron dust (e.g., fine particles produced as a by-product of the iron or steel making process in a blast furnace, oxygen furnace, electric arc furnace, etc.), iron powder, scrap steel, and / or scrap cast iron. "Iron source material" and "ferrous raw material" may also contain various other non-ferrous materials commonly referred to as "impurities."

[0020]

[0026] As used herein, the term "impurity" refers to elements or compounds other than the desired end product material (e.g., iron). In various embodiments, a given element or compound may or may not be considered an "impurity" depending on the intended end use of the product material. In some cases, one or more elements or compounds that may be impurities to a process or sub-process may be isolated or purified, collected, and sold as a secondary product material.

[0021]

[0027] In various embodiments herein, various compositions, compounds, or solutions may be substantially "isolated" or "purified" to a degree sufficient for the purposes described herein. In various embodiments, a substantially purified composition, compound, or formulation (e.g., a ferrous solution, a ferric solution, or plated metallic iron) may have a chemical purity that is 90% (e.g., by molarity of ionic concentration or by weight), optionally in some applications 95%, optionally in some applications 99%, optionally in some applications 99.9%, optionally in some applications 99.99%, and optionally in some applications 99.999% pure.

[0022]

[0028] References herein to a "tank" are intended to include any vessel suitable for containing a liquid, such as a highly acidic or caustic aqueous solution, as appropriate. In some embodiments, such vessels may include additional features or components to aid or improve mixing of the solid and / or liquid contents of the vessel. For example, a dissolving tank may include structures or features that operate passively or actively to agitate the solution or solid / liquid mixture. Dissolving tanks or other tanks useful in the systems and methods herein may also include features that allow for sparging gas into or through the solid and / or liquid contents of the tank to increase gas contact with the solid and / or liquid materials within the tank. Various tanks may also include baskets, sieves, pans, filters, or other structures for collecting and separating solids from liquids. In some embodiments, the tank may be configured to direct liquid or gas flow through the tank in a manner that agitates the mixture therein (e.g., flow-directing structures, pumps, impellers, baffles, impellers, stirrers, stirring blades, vibrators, cyclonic flow channels, etc.).

[0023]

[0029] In some embodiments described herein, a system for converting iron ore to iron metal (i.e., an "iron conversion system") may include two or more subsystems. Some embodiments include a "dissolving subsystem" in which components of an iron-containing feedstock are dissolved in an aqueous solution. Some embodiments further include an "iron plating subsystem" in which the molten iron is electrochemically reduced to iron metal in an "electroplating" (or simply "plating") process. The iron metal can then be removed from the iron plating subsystem.

[0024]

[0030] In some embodiments, the iron-containing aqueous solution may be transferred to and processed in a "transition subsystem" after exiting the dissolution subsystem and before being delivered to the plating subsystem. Processing within the transition subsystem may include pH adjustment, impurity removal, filtration, or other processes. In some embodiments, any of the above subsystems may be fluidly coupled to one another by "inter-subsystem fluid connections," which may include any combination of fluid-carrying conduits (pipes, channels, grooves, etc.) and any number of flow control devices, including valves, pumps, expansion chambers, gas-liquid separators, solid-liquid separators, filters, or other similar devices.

[0025]

[0031] The term "iron electroplating" (or "iron plating" used synonymously herein) refers to a process in which molten iron is electrochemically reduced to metallic iron at a cathode surface. The equivalent terms "electrodeposition," "electroforming," and "electrowinning" are also used synonymously herein with "iron electroplating." The shape or form factor of the electroplated iron need not be a "plate" by any definition of this term. For example, the electroplated iron can take any shape or form and can be deposited on any suitable cathode surface described in various aspects herein.

[0026]

[0032] The term "dissolution step" refers to the processes occurring within the dissolution subsystem, including but not limited to dissolution of iron oxide materials, and the "acid regeneration cell" where Fe 3+ ions to Fe 2+ The dissolution step process may also include, for example, oxidizing water or hydrogen gas in a first electrochemical cell to generate protons, which may allow for the regeneration of the acid (in the form of protons) used to facilitate the dissolution of the iron-containing feedstock.

[0027]

[0033] The term "iron plating step" refers to the process of plating Fe in a "plating cell," also referred to herein as a "plating cell."2+ The iron plating process also includes the process(es) occurring within the iron plating subsystem, including, but not limited to, the electrochemical process(es) occurring within or through the claimed "plating cell," including, but not limited to, the electrochemical reduction of Fe ions to Fe metal. 2+ Oxidize the second part of the ions to Fe 3+ In some embodiments, such Fe ions may be formed. 2+ The ions may be provided from the first electrochemical cell or from another part of the system.

[0028]

[0034] As used herein, unless otherwise specified, the term "ferrous iron solution" or "ferrous solution" refers to a solution containing at least a majority (i.e., 50% to 100%) of Fe. 2+ (i.e., "ferrous") ionic state, with the remainder of the dissolved iron being "ferric" Fe 3+ Similarly, the term "ferrous ion" can refer to an aqueous solution of ferrous iron (Fe 2+ ) state.

[0029]

[0035] As used herein, unless otherwise specified, the term "ferric iron solution" or "ferric solution" refers to a solution containing at least a majority (i.e., 50% to 100%) of Fe. 3+ (i.e., "ferric") ionic state, with the remainder of the dissolved iron being "ferrous" Fe 2+ Similarly, the term "ferric ion" can refer to an aqueous solution of ferric iron (Fe 3+ ) state. Either a "ferric solution" or a "ferrous solution" may also contain other dissolved ions or colloidal or particulate materials, including impurities.

[0030]

[0036] As used herein, references to "PEM" or "proton exchange membrane" may be construed to also include "CEM" or "cation exchange membrane," both of which terms may include any available membrane material that selectively allows positively charged cations and / or protons to pass through. The abbreviation "AEM" is used to refer to anion exchange membranes that are selective for negatively charged aqueous ions, and includes any available anion-selective membrane.

[0031]

[0037] As used herein, aqueous protons and electrochemically generated protons are intended to include aqueous protons and aqueous hydronium ions.

[0032]

[0038] As used herein, the term "raw ore" refers to iron-bearing ore that has not been thermally reduced or air roasted in accordance with embodiments disclosed herein. The raw ore is optionally an iron-bearing raw ore.

[0033]

[0039] As used herein, electrochemically generated ions, such as electrochemically generated protons and electrochemically generated iron ions (e.g., Fe 2+ , Fe 3+ ) refers to ions generated or produced in an electrochemical reaction. For example, the electrochemical oxidation of water at an anode can electrochemically generate protons and can electrochemically generate oxygen.

[0034]

[0040] As used herein, the term "thermal reduction" refers to heat treatment at high temperatures in the presence of a reducing agent. Thermal reduction is also referred to in the art as reduction roasting. Optionally, the thermal reduction is carried out at a temperature selected from the range of 200°C to 600°C. Optionally, the reducing agent is a gas comprising hydrogen (H2) gas. Additional descriptions and potentially useful aspects of thermal reduction can be found in the following reference, which is incorporated herein in its entirety: "Hydrogen reduction of hamatite ore fines to magnetite ore fines at low temperatures," Hindawi, Journal of Chemistry, Volume 2017, Article ID 1919720.

[0035]

[0041] As used herein, the term "parasitic hydrogen" or "hydrogen (H) from the parasitic hydrogen generation reaction of the iron electroplating process" refers to hydrogen (H) generated in the same electrochemical cell as the iron electroplating reaction (e.g., Fe 2+ to Fe, or Fe 3+ From Fe 2+ Parasitic hydrogen generation refers to hydrogen (H2) gas that is electrochemically generated by a side reaction simultaneously with the electrochemical generation of parasitic hydrogen (via Fe to Fe). Additional discussion and potentially useful aspects of parasitic hydrogen generation can be found in the following reference, which is incorporated herein in its entirety: "An investigation into factors affecting the iron plating reaction for an all-iron flow battery," Journal of the Electrochemical Society 162 (2015) A108.

[0036]

[0042] As used herein, the term "air roasting" refers to a heat treatment carried out at an elevated temperature in the presence of air. Air roasting of ores, such as iron-bearing ores, can crush the ore or reduce its average particle size. Optionally, air roasting is carried out at a temperature selected from the range of 300°C to 500°C. Additional descriptions and potentially useful aspects of air roasting can be found in the following reference, which is incorporated herein in its entirety: "Study of the calcination process of two limonitic iron ores between 250°C and 950°C," Revista de la Facultad de Ingeneria, p. 33 (2017).

[0037]

[0043] As used herein, the term "redox pair" refers to two chemical species, such as ions and / or molecules, that correspond to the reduced and oxidized species of an electrochemical reaction or half-cell reaction. For example, Fe 3+ ions to Fe 2+ In the electrochemical reduction to ions, the corresponding redox couple is Fe 3+ / Fe 2+ and Fe 3+ is an oxidized species, and Fe 2+ is the reducing species. As used herein, the order in which redox pairs are listed (e.g., Fe 3+ / Fe 2+ vs. Fe 2+ / Fe 3+ ) is not intended to indicate which species is the reduced species and which is the oxidized species. Additional explanations of redox couples and potentially useful aspects can be found in the following references, which are incorporated herein in their entirety: "Redox - Principles and Advanced Applications": Book by Mohammed Khalid, Chapter 5: Redox Flow Battery Fundamental and Applications.

[0038]

[0044] As used herein, the terms "steady state" and "steady-state" generally refer to a condition or set of conditions that characterize a process, method step, reaction(s), solution, (sub)system, etc., that are true for a longer period of time than they are not true during operation or performance of the process, method step, reaction(s), solution, (sub)system, etc. For example, the dissolution of an ore or feedstock may be characterized by steady-state conditions that are true for at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90%, and optionally at least 95% of the time that dissolution is occurring. For example, steady-state conditions may exclude conditions that characterize transient start and end stages of a process, such as the dissolution of a feedstock.

[0039]

[0045] The term "cathode chamber" refers to an area, compartment, tank, etc. that contains a cathode or at least a portion or surface thereof and a catholyte. The term "anode chamber" refers to an area, compartment, tank, etc. that contains an anode or at least a portion or surface thereof and an anolyte.

[0040]

[0046] As used herein, the term "iron-rich solution" may also be referred to as "ferrous iron-rich solution" or "ferrous product solution," which corresponds to the solution rich in iron ions in the ore dissolution subsystem.

[0041]

[0047] As used herein, the term "ore dissolution subsystem" may also be referred to as "dissolution subsystem," "first subsystem," and "step 1." The "dissolution subsystem" includes the "acid regenerator" described herein.

[0042]

[0048] As used herein, the term "iron plating subsystem" may also be referred to as "second subsystem" and "step 2."

[0043]

[0049] As used herein, the term "precipitation pH" refers to the pH at which one or more referenced ions or salts are or are predicted to precipitate from a host aqueous solution in a thermodynamically favorable manner. In general, the solubility of ions and salts dissolved in an aqueous solution may depend on the pH of the aqueous solution. As the pH increases in the acidic region, many metal ions form metal hydroxides, which tend to precipitate from the host solution due to reduced solubility. The precipitation pH is defined herein as the pH corresponding to the point at which the solubility of a given ion or salt is below a concentration threshold. The precipitation pH may be the upper boundary above which the solubility of a given ion or salt is less than 1 mM, optionally less than 0.1 mM.

[0044]

[0050] As used herein, the term "metallic iron" refers to materials containing metallic iron, such as, but not limited to, scrap iron, electroplated iron, iron powder, and the like.

[0045]

[0051] As used herein, the terms "supporting salt" and "supporting ion" refer to salts and ions that correspond to or function as a supporting electrolyte when dissolved to increase the conductivity of a host solution, or salts and ions that at least partially form the supporting electrolyte. In some embodiments, for example, in both the dissolution subsystem and the plating subsystem, the electrolyte and solution may contain dissolved iron species, acid, and an additional inert salt that functions as a supporting electrolyte to improve electrolyte conductivity (which may be particularly beneficial at low ferrous concentrations), and the inert salt that functions as a supporting electrolyte to improve conductivity may be referred to as a supporting salt. Supporting salts may include any electrochemically inert salt or combination of salts, such as sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, sodium chloride, potassium chloride, ammonium chloride, or others. The concentration of the supporting salt in the solution, if used, may range, for example, from about 0.1 to about 1 M.

[0046]

[0052] As used herein, "wt.%" or "wt%" refers to weight percent or mass fraction expressed as a mass percentage. The term "at.%" or "at%" refers to the atomic percent of a type of atom relative to all atoms in a given entity, such as a molecule, compound, material, nanoparticle, polymer, dispersion, etc., or the atomic ratio expressed as a percentage. The term "mol.%" refers to mole percent or percent by number of moles. The term "vol.%" refers to volume percent.

[0047]

[0053] The terms "substantially" and "approximately" are used interchangeably and refer to a property, condition, or value that is within 20%, 10%, 5%, 1%, optionally within 0.1%, or equivalent of a reference property, condition, or value. In some embodiments, the terms "substantially" and "approximately" are used interchangeably and refer to a property, condition, or value that is within 20% of a reference property, condition, or value. The terms "substantially equal," "substantially equivalent," "substantially unchanged," "approximately," and "approximately equal," when used in conjunction with a reference value that describes a property or condition, refer to a value that is within 20%, 10%, optionally within 5%, optionally within 1%, optionally within 0.1%, or optionally equivalent to the stated reference value. For example, if the diameter value is within 20%, optionally within 10%, optionally within 5%, optionally within 1%, optionally within 0.1%, or optionally equal to 100 nm, then the diameter is approximately equal to 100 nm (or "is approximately 100 nm"). The term "substantially greater than," when used in conjunction with a reference value describing a property or condition, refers to a value that is at least 1%, optionally at least 5%, optionally at least 10%, or optionally at least 20% greater than the stated reference value. The term "substantially smaller than," when used in conjunction with a reference value describing a property or condition, refers to a value that is at least 1%, optionally at least 5%, optionally at least 10%, or optionally at least 20% less than the stated reference value. As used herein, the term "about" refers to a range of values ​​that includes the specified value that one of ordinary skill in the art would consider reasonably similar to the specified value. In certain aspects, about and approximately mean within a standard deviation using measurements generally accepted in the art. In some aspects, about refers to a range that extends to + / - 10% of the specified value. In certain embodiments, about refers to the specified value. In certain aspects, the terms "about," "approximately," and "substantially" are interchangeable and have the same meaning. For example, a particle having a size of about 1 μm may have a size within 20%, optionally within 10%, optionally within 5%, optionally within 1%, optionally within 0.1%, or optionally equal to 1 μm.

[0048]

[0054] As used herein, the term "and / or" is used in the specification, description, and claims to refer to only a single element or any combination of elements from a list in which the term and / or appears. For example, a list of two or more elements with the term "and / or" is intended to cover embodiments having only any of the individual elements or any combination of the listed elements. For example, the phrase "element A and / or element B" is intended to cover embodiments having only element A, only element B, or both elements A and B together. For example, the phrase "element A, element B, and / or element C" is intended to cover embodiments having only element A, only element B, only element C, elements A and B together, elements A and C together, elements B and C together, or elements A, B, and C together.

[0049]

[0055] As used herein, the term "±" refers to an inclusive range of values, thus "X±Y" (where each of X and Y is independently a number) refers to an inclusive range of values ​​selected from the range XY to X+Y. In the case of "X±Y" where Y is a percentage (e.g., 1.0±20%), the inclusive range of values ​​is selected from the range XZ to X+Z, where Z is equal to X(Y / 100). For example, 1.0±20% refers to an inclusive range of values ​​selected from the range 0.8 to 1.2.

[0050]

[0056] As used in this description, the term "consisting essentially of" is used to describe a product that consists largely of the specified material(s) with minor amounts of other materials that may or may not be specified. For example, in some embodiments, a product "consisting essentially of" a specified compound (e.g., Fe(OH)2) may describe a product in which the specified compound accounts for at least 90% of the product mass, with the remainder consisting of other specified or unspecified materials. In other embodiments, the specified compound may account for 95%, 98%, 99%, 99.9%, or more of the mass of the specified product. Any use of the phrase "consisting essentially of" in this description is intended to include all of these embodiments, unless otherwise specified.

[0051]

[0057] Sequence terms such as "first," "second," and "third" are used in various examples and embodiments herein. It should be understood that these terms are used merely for convenience in the description herein and are not intended to exclude other steps or products before, between, or after any step or product referenced in the sequence name.

[0052] [Detailed explanation]

[0058] In the following description, numerous specific details of devices, device components, and methods are set forth in order to fully explain the precise nature of the various inventions described herein. However, it will be apparent to those skilled in the art that the various inventions may be practiced without being limited to these specific details. While not wishing to be bound by any particular theory, an idea or understanding of the basic principles related to the devices and methods disclosed herein may be discussed herein. It is recognized that aspects of the devices and methods may be effective and useful regardless of the ultimate accuracy of any mechanistic explanation or hypothesis.

[0053] Metallurgical slag refining and recycling

[0059] Various aspects of systems and methods for extracting and isolating reusable materials and compounds from metallurgical slag and other input materials are described herein. While some examples are described with reference to steel slag, other slags and materials may also be used, including blast furnace slag, BOF slag, ladle slag, EAF slag, etc. For example, various aspects described herein may also be used with inputs including slag, clay, kaolin, metakaolin, pumice, pozzolana, mafic and / or ultramafic rock, olivine, pyroxene, amphibole, serpentine, wollastonite, peridotite, talc, biotite, basalt, hematite, magnetite, goethite, taconite, bauxite, diabase, gabbro, limestone, dolomite, calcium silicate, wollastonite, coal ash, fly ash, bottom ash, settler ash, incineration ash, economizer ash, or any combination of these or other materials.

[0054]

[0060] In various embodiments, slag or other input material(s) may be dissolved / leached in aqueous acid to produce a slag leach solution, from which various components may be extracted by selective precipitation following a pH shift induced by adding aqueous base and / or solid soluble base materials to the slag leach solution. Alternatively, components may be selectively removed from the leach solution by other processes, such as electrowinning (also referred to herein as electroplating), recrystallization, cementation, or other methods.

[0055] Acid and base formation

[0061] In several embodiments and examples described herein, the "acid" and "base" used in leaching and / or pH shifting are described as being generated in an electrochemical acid-base generating cell (or cell stack). However, any of the processes, embodiments, or examples described herein may alternatively be practiced using acid or base materials or solutions obtained from other sources, including the process itself. For example, in various embodiments, processes are described herein for obtaining solid hydroxide materials (base materials), such as Ca(OH), Mg(OH), Fe(OH), Fe(OH), Al(OH), Mn(OH), MnO, or others. Any of these materials may be reused as solid base materials for subsequent processing of slag or other feedstock materials as described herein. Similarly, any strong or weak acid (HCl, alkali bisulfate, ammonium bisulfate, sulfuric acid, carbonic acid, or any other acid), whether generated by an electrochemical acid-base generating system or otherwise, may be used in connection with various embodiments herein. In some embodiments, commercially purchased, recycled, or otherwise obtained acid or base materials may be used in combination with the acid and / or base materials generated by the electrochemical acid-base generating system.

[0056]

[0062] Steel slag (from the EAF, BOF, or otherwise) is in a molten state when it leaves the steelmaking operation and is typically cooled for storage, transportation, or subsequent use. Depending on the chemical composition of the slag and how rapidly it is cooled, the crystalline morphology of the final cooled solid slag can range from highly crystalline (e.g., very slowly cooled) to highly amorphous (e.g., after rapid cooling or quenching in water). In some cases, the rate and / or extent of slag dissolution in the acid can be a function of the acid(s) used and the degree of crystallinity or amorphousness of the slag (or other input materials). Thus, in some embodiments, it may be desirable to select or selectively produce amorphous or crystalline slag materials for use in one or more of the embodiments herein and / or adjust the slag production process (e.g., cooling rate or quench) to achieve a desired degree of crystallinity or amorphousness.

[0057]

[0063] In some embodiments, some materials extracted and isolated from the slag leach solution, including calcium hydroxide and / or magnesium hydroxide, may be used to capture carbon dioxide from point sources (e.g., EAF or BOF steel mills, blast furnaces, CO2-emitting direct reduced iron (DRI) plants, CO2-emitting power plants) or directly from the air. Alternatively, or additionally, some materials, such as calcium oxide, calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide, and / or magnesium carbonate, may be used again as fluxes in new steelmaking operations. In some embodiments, iron oxide, iron hydroxide, iron sulfate, iron chloride, or other iron compounds may be extracted from the slag leach solution and reduced or otherwise converted to metallic iron for steelmaking or other purposes. In some embodiments, metallic iron may be extracted directly from the slag leach solution. In some embodiments, one or more oxides or hydroxides of manganese (e.g., MnO, Mn(OH), MnO, or other oxides, hydroxides, or salts of Mn) may be extracted and used or sold for other products or processes. Other extracted materials such as aluminum oxide, aluminum hydroxide, or aluminum phosphate may also be extracted and used or sold.

[0058]

[0064] In some embodiments, acid and base solutions may be generated electrochemically in a salt-splitting acid-base generating (ABG) cell or cell stack, some examples of which are shown and described in Applicant's PCT International Patent Application PCT / US2022 / 020796, entitled "Carbon Capture Using Electrochemically-Produced Acid and Base," published as WO 2022 / 197954, which is incorporated herein by reference in its entirety unless inconsistent therewith. Other exemplary acid-base generating cells are described in U.S. Pat. Nos. 4,561,945, 5,595,641, and 5,200,046, which are incorporated herein by reference in their entireties unless inconsistent therewith. Any of the electrochemical acid-base generating cells shown and described in any of the above-referenced documents may be used to generate acid and base solutions for use in connection with any of the various embodiments described herein. Alternatively, a conventional electrochemical chlor-alkali plant may be used to generate aqueous alkali and chlorine gas. Chlorine gas can be combined with water at high temperatures (e.g., about 250° C.) to produce aqueous HCl. Using electrochemical methods, acids and bases can be produced economically and with zero carbon emissions by one or more electrochemical systems powered by zero carbon electrical energy sources, such as wind, solar, geothermal, hydroelectric, tidal / wave, nuclear, or other power sources that are substantially free of carbon dioxide (CO) or other greenhouse gas emissions.

[0059]

[0065] 4 illustrates an exemplary electrolytic acid-base generation ("ABG") cell 400. The cell 400 of FIG. 4 contains an aqueous "catholyte" (or "catholyte") and / or a base concentration (i.e., OH - The cell 400 includes a basification chamber 404 (alternatively referred to as a "cathode chamber") that contains an aqueous "salt solution" in which ions (or hydroxide ions) are enriched during operation of the cell 400.

[0060]

[0066] The cell 400 also contains an aqueous "acidifying solution" or "acid solution," and / or an aqueous acid concentration (i.e., H + The cell comprises an acidification chamber 402 (alternatively referred to as the "middle" or "intermediate" chamber) containing an aqueous "salt solution" whose concentration (or hydronium ion concentration) increases during operation of the cell. The basification chamber 404 is separated from the acidification chamber 402 by an anion exchange membrane (AEM).

[0061]

[0067] The cell 400 also comprises an anode chamber 406 containing an anode electrode 410 (optionally a gas diffusion anode) separated from the acidification chamber 402 by a proton exchange membrane or a cation exchange membrane (collectively referred to as a PEM).

[0062]

[0068] In operation, while an electrical current is supplied to the anode 410 and cathode 408 electrodes, water is reduced (or "split") to form hydroxide ions (OH - ) and hydrogen gas (H2). The hydrogen gas is separated from the aqueous catholyte and transported to the anode chamber 406 via conduit 412. At the anode electrode 410, the hydrogen gas is converted into H + (or hydronium) ions, which are transported through the PEM separator membrane into the central acidification chamber 402.

[0063]

[0069] Anions from a basified salt solution (sulfate ions SO4 in the illustrated example) - ) migrate from the negative basification chamber 404 through the AEM separator membrane to the central acidification chamber 402 where they can combine with the "free" protons (from the anode) to form a strong or weak acid.

[0064]

[0070] In various embodiments, the solution delivered into the central chamber 402 may be a substantially salt-free aqueous solution or may be a salt solution, which may be the same salt solution or a different salt solution as that provided to the basification chamber 404.

[0065]

[0071] The electrochemical potential between the H evolution reaction under alkaline conditions at the cathode and the H oxidation reaction under acidic conditions at the anode results in a theoretical cell potential of just 0.83 V. In the illustrated example (assuming sodium sulfate salt), the theoretical energy requirement is 0.5 MWh per ton of NaOH produced, which is one-third the energy required to produce both the base and acid solutions via the chlor-alkali process. While Figure 4 and the above description are shown in relation to sodium sulfate salt, the illustrated cell can be similarly operated with any other salt to produce other acid and base combinations.

[0066]

[0072] In commercial-scale practice, electrochemical acid-base generating systems typically include multiple electrochemical cells integrated into a common system. In some cases, the cells may be integrated into a single "bipolar stack," where many cells are assembled into a single breadloaf stack, with the individual cells separated from one another by electrically conductive "bipolar plates." The cells in a bipolar stack are electrically connected to one another in series. Electrolyte typically flows through the cells in the bipolar stack in fluid parallel, in a flow-through configuration. However, a series-flow configuration is also possible. In various configurations, multiple bipolar stacks may be connected to one another both electrically and fluidly in parallel or series (or a combination thereof). In an alternative configuration, "monopolar" cells may be electrically and fluidly connected to one another in parallel. The relative advantages of bipolar versus monopolar configurations are well understood by those skilled in the art, and any such configuration approach may be applied to the embodiments of the electrochemical acid-base generating system described herein.

[0067]

[0073] Whether the ABG is configured in a bipolar or monopolar format, the acid and base solutions may each be circulated between the electrochemical reactor and a respective storage tank (e.g., one or more storage tanks may be provided for each of the acid and base solutions). In some embodiments, the acid and / or base solutions may be directed to a chemical reactor, such as a leachate tank or ion exchange reactor, to remove (or consume) the acid and / or base from the solution(s) in order to limit the concentration of the acid or base in the electrolyte(s) returned to the electrochemical reactor.

[0068]

[0074] For example, in some embodiments, acid can be recirculated between the acid-base generation reactor and the acid storage tank so that the acid concentration of the acidified electrolyte increases during each pass through the reactor. Such recirculation can continue until a target acid concentration (or pH) is reached, at which point the acid solution can be used as described herein. The same can be done for the basifying solution. Alternatively, or additionally, the acid solution can be recirculated between the acid-base generation reactor and the dissolution or leaching reactor, where a portion of the acid is consumed in a dissolution or leaching reaction after each cycle (or every two cycles, or every three cycles, etc.) through the ABG reactor. For example, the acid can be consumed in any of the dissolution or leaching reactions described herein before returning all or a portion of the acidified solution to the acidification chamber of the ABG reactor. Alternatively, the acid may be consumed in a base neutralization reaction, in a precipitation reaction, or by reaction with an ion exchange resin. Examples of acid-consuming reactions herein include dissolving slag or other raw materials, dissolving gypsum materials, dissolving precipitated iron products or other precipitation products. Similarly, the same can be done for basified solutions to consume some of the base in an acid neutralization reaction, in a high pH leaching reaction, in a precipitation reaction, or by reaction with an ion exchange resin.

[0069]

[0075] In various embodiments, one or both of the acid solution and the base solution may comprise an aqueous solution containing one or more dissolved salts. Some examples are described herein in connection with an electrolyte containing dissolved sodium chloride salt, which generates sodium cations and chloride anions. Other salts may also be used, alone or in combination. For example, in various embodiments, the acid solution and / or the base solution may contain any one salt or combination of salts, such as sodium chloride (NaCl), sodium sulfate (NaSO), sodium carbonate (NaCO), sodium nitrate (NaNO), sodium acetate (CHCOONa), sodium citrate (NaCHO), sodium maleate (CHONa), sodium oxalate (NaCO), potassium chloride (KCl), potassium sulfate (KSO), potassium carbonate, etc. (K2CO3), potassium nitrate (KNO3), potassium acetate (CH3COOK), potassium citrate (K3C6H5O7), potassium maleate (C4H3O4K), potassium oxalate (K2C2O4), lithium chloride (LiCl), lithium sulfate (Li2SO4), lithium nitrate (LiNO3), lithium acetate (C2H3LiO2), lithium oxalate (C2Li2O4), one or more sodium, potassium, or lithium phosphates ([Na, K, or Li] X H Y PO4(H2O) z ) (including hydrated and anhydrous forms of any di- or polyphosphate salt), or any other organic or inorganic salt or combination of salts. In some embodiments, the amount of salt used can be selected based on the desired acid and / or base concentrations to be produced.

[0070] [Table 1]

[0071]

[0076] In some embodiments, an electrolytic or electrodialytic acid-base generator can be configured to produce aqueous bisulfate (HSO) compounds by decomposing sulfate salts, such as sodium sulfate, potassium sulfate, lithium sulfate, ammonium sulfate, and / or others, without proceeding to form sulfuric acid (HSO). The produced sodium bisulfate and / or ammonium bisulfate can be used to dissolve (or "leach") slag or other feedstock materials as described in various embodiments herein.

[0072]

[0077] In some embodiments, the acid-base generator provides an initial cation (e.g., Na ) equal to the target or intended bisulfate concentration in the central (acidification) chamber of a cell such as that shown in FIG. + , K. + , Li + , NH4 + etc.) to produce a primarily bisulfite solution in the acidification chamber rather than sulfuric acid.

[0073]

[0078] In various embodiments, aqueous bisulfate solution can be generated in an electrochemical acid-base generating cell 400, such as that shown in FIG. 4. As protons produced by the oxidation of hydrogen gas traverse into the central chamber 402, they convert into sulfate anions (SO 2- ) and pair with salt cations in the acidified salt solution, tending to form bisulfate salts (e.g., NaHSO4) with the metal cations. Once all of the salt cations have paired with protons and sulfate anions in the absence of additional metal cations, further addition of protons and sulfate anions to the acidification chamber tends to form sulfuric acid (H2SO4).

[0074]

[0079] Thus, in a batch process, to stop acid production with bisulfate before proceeding to sulfuric acid production, the current delivered to cell 400 should be stopped when the total charge (or coulombs = current x time) delivered to the cell equals a stoichiometric amount equivalent to the total molar amount of metal cations present in the salt solution delivered to the central chamber. In some embodiments, the concentration of salt delivered to the acidification chamber can be measured at the beginning of the batch process to determine the current and / or duration of the next batch of bisulfate production.

[0075]

[0080] In a continuous bisulfate generation process, the acidification chamber is configured to ensure that the salt solution delivered into the acidification chamber (which may contain a concentration of bisulfate from a previous cycle) contains at least a minimum concentration of a selected cation (e.g., Na + or NH4 + ), bisulfate can continue to be produced as long as it contains

[0076]

[0081] In some embodiments, acid and base generation by an electrolytic acid-base generator can be further improved by generating weak acids rather than strong acids. Weak acids are defined as acids that do not completely ionize when dissolved in water. Because weak acids bind protons more tightly (i.e., they are "weak" in that they are less likely to donate protons), those protons bound to the weak acid are less likely to migrate through any separator membrane into the chamber containing hydroxyl ions, resulting in inefficiency by recombining to form water.

[0077]

[0082] In various embodiments, any of the acid-base generator cell configurations described herein can be used to generate weak acids by selecting a salt that has a tendency to generate a weak acid upon decomposition into its component acids and bases. Examples of common salts that yield weak acids include Na2CO3 or NaHCO3 (e.g., to make carbonic acid), NaH2PO4 (e.g., to make phosphoric acid), CH3CO2Na (e.g., to make acetic acid), salts of oxalic acid (C2H2O4), salts of citric acid (C6H8O7), salts of maleic acid (C4H4O4), and salts of boric acid (H3BO3).

[0078]

[0083] Other salts that decompose to produce weak acids, including some organic acids, may be used in acid-base generators to produce weak acids rather than strong acids, thereby improving the coulombic efficiency of the acid-base generator. In some embodiments, any combination of salts may be used, including combinations of salts in this paragraph, or combinations of one or more salts in this paragraph with any other salt(s) disclosed elsewhere herein.

[0079]

[0084] In various embodiments, the acid and / or base solutions can have a salt concentration (i.e., the concentration of anions and cations corresponding to the dissolved salt) of about 0.1 M to about 5 M, or in some embodiments, up to the saturation limit for a given salt (e.g., NaCl has a room temperature solubility limit of about 6.2 M). In other embodiments, the salt concentration of the acid and / or base solutions can be selected based on a concentration ratio sufficient to promote the transport of preferred ions (cations or anions) across the separator in favor of more ionically mobile ions as described in the above-referenced International Application PCT / US22 / 20796.

[0080]

[0085] In various embodiments described below, the salt(s) decomposed in the electrochemical acid regeneration cell may be recovered and recycled after extraction of reusable materials from the slag to form new acid and base solutions. Thus, the systems described herein may be configured to consume substantially only electricity and water (a portion of which may be recovered as described herein) and to minimize consumption or loss of any chemical reactants.

[0081] Metallurgical slag refining and recycling

[0086] In various embodiments, examples of which are described below with reference to Figures 1 and 2, slag and / or other input material(s) may be dissolved / leached in aqueous acid to produce a slag leach solution, from which various components may be extracted by selective precipitation following a pH shift induced by adding aqueous base and / or solid soluble base materials to the slag leach solution. Alternatively, components may be selectively removed from the leach solution by other processes, such as electrowinning (also referred to herein as electroplating), recrystallization, cementation, and / or other methods.

[0082]

[0087] 1 and 2 may be operated using acid, base, and / or leach solutions at elevated temperatures relative to ambient temperature. For example, in some embodiments, at least the leaching and precipitation steps (including the solid / liquid separation step to recover the product) may be carried out using aqueous solutions at temperatures of about 50° C. to about 90° C., in some more particular embodiments, about 60° C. to about 80° C., and in some particular embodiments, about 60° C. + / - 5° C., about 70° C. + / - 5° C., or about 80° C. + / - 5° C. In some embodiments, different steps may be carried out at different temperatures relative to other steps, some examples of which are described below.

[0083]

[0088] Some embodiments of a process for extracting reusable materials from metallurgical slag will now be described with reference to the schematic block diagram of Figure 1. In some embodiments, a process 100 for extracting components of metallurgical slag may include utilizing an electrochemical acid-base generator (ABG) 120 to generate an acid solution, which may be stored in one or more acid storage tanks 122, and a base solution, which may be stored in one or more base storage tanks 124. By storing the acid and base in respective storage tanks, the generation of the solutions may be decoupled in time from their use in subsequent processing. This allows the generation of the acid and base to proceed at different times and at different rates compared to the material dissolution and precipitation processes.

[0084]

[0089] At block 102, the slag material may be crushed into smaller particles, if desired. Crushing may include ball milling, grinding, crushing, pulverizing, or any similar process or equipment for converting rock-sized pieces into smaller particles suitable for acid leaching. In various embodiments, the slag may be crushed to particles less than about 10 mm in average or maximum size.

[0085]

[0090] In some embodiments, an optional magnetic separation step may be performed after comminution. The slag may contain some magnetic material(s), but this tends to be primarily iron-containing oxides such as magnetite (FeO) and iron metal. The separated magnetic material may be removed and processed into iron or steel. For example, the separated magnetic material may be thermally reduced to metallic iron in a direct reduction of iron (DRI) or blast furnace process, or the magnetic material may be dissolved in a separate acid and electrodeposited as metallic iron.

[0086]

[0091] In some embodiments, the slag material may be treated to convert any non-magnetic iron to a magnetic form of iron prior to magnetic separation. For example, the slag (before or after grinding) may be heated under a reducing atmosphere (e.g., hydrogen gas, carbon monoxide, syngas, etc.) to reduce non-magnetic iron oxide (e.g., FeO) to a magnetic form such as magnetite (FeO) or even metallic iron. In such cases, substantially all of the iron present in the slag may be separated and removed from the slag by magnetic separation; i.e., steps 106 and / or 112 of FIG. 1 may be omitted.

[0087]

[0092] In some embodiments, it may be advantageous to concentrate the acid produced by the acid-base generator before using it to leach slag or other raw materials. In some cases, the acid exiting the acid storage tank 122 may be concentrated by removing water via a distillation or evaporation process, such as multiple-effect evaporation, mechanical vapor recompression, steam distillation, vacuum distillation, membrane distillation, reverse osmosis, or a combination of these and / or other processes. In various embodiments, any heat required for these or other distillation methods may be provided by waste heat generated by other parts of the process or by an adjacent steel mill or other plant. In other embodiments, the acid solution may be concentrated using an electrodialysis cell, such as the one shown and described in FIG. 8, or electrodialysis cells of different configurations utilizing bipolar membranes.

[0088]

[0093] In block 104, the ground slag material may be mixed with a portion of the acid solution from the acid storage tank(s) 122 to dissolve the components of the slag, thereby producing an aqueous leachate solution containing the dissolved components of the slag. Any components of the slag that do not dissolve in the acid solution may be separated and removed in block 130 by filtration, agglomeration, centrifugation, sedimentation, or any other suitable solid / liquid separation technique or combination of techniques. The undissolved solids 130 may be discarded as waste or may be subjected to further processing to extract components for subsequent sale or use. In some embodiments, the undissolved solids 130 may be separated in the form of an acidic slurry, which may be washed with a portion of the base solution to neutralize any residual acid.

[0089]

[0094] Optional blocks 160 and 162 are shown to illustrate optional or alternative steps useful when the acid solution contains sulfate anions. In such cases, any calcium in the feedstock material (e.g., slag) tends to precipitate immediately as calcium sulfate (CaSO) almost as soon as it dissolves because CaSO has a low water solubility limit. Therefore, in embodiments where sulfate salts are used, the CaSO may be collected with other “undissolved” solids at 130. The CaSO may then be separated from the other undissolved solids (primarily silica) by any suitable solid / solid separation technique (160), such as density separation, high-shear mixing, centrifugation, flotation, etc. The separated CaSO may then be converted to hydroxide compounds at 162 using a portion of the base solution from 161 (and / or a separate base solution), from which calcium hydroxide (Ca(OH)) can be precipitated by adding sufficient base to reach a pH at which calcium hydroxide (Ca(OH)) precipitates (e.g., a pH of about 12). The remaining solution, which tends to be a salt solution containing sulfate and base cations, can be sent back to the ABG 120 via 164 for subsequent decomposition into fresh acid and base solutions. Optionally, the remaining solution after Ca(OH) precipitation can be treated with an ion exchange resin at 116 to remove any remaining dissolved calcium or magnesium.

[0090]

[0095] In various embodiments, the leaching / dissolution step 104 can be carried out in a dissolution tank or tank (e.g., a continuous stirred tank reactor) or other vessel. Alternatively, the leaching / dissolution step 104 can be carried out in a heap leaching operation, in which acid is sprayed onto a pile (or heap) of slag and the leachate is collected from the bottom.

[0091]

[0096] In various embodiments, the choice of acid (and therefore salt) used in slag dissolution can be made based on which components of the slag are desired, as some components may dissolve more readily or completely depending on each component's thermodynamic solubility limit and its dissolution kinetics in a given acid.

[0092]

[0097] After or during the acid leaching 104, the leach solution may be enriched with any ferric ions (Fe ) for the purpose of facilitating subsequent separation of iron independently of other major slag components (described in more detail below). 3+ ) to ferrous ions (Fe 2+ In various embodiments, the reduction of ferric ions to ferrous ions may be carried out electrochemically in one or more electrochemical cells or chemically in a suitable reactor. For example, Fe 3+ The ions may be chemically reduced to ferrous ions by sparging or bubbling a reducing gas (e.g., carbon monoxide or hydrogen gas) through the aqueous solution, optionally at elevated temperatures and optionally in the presence of a catalyst. In another exemplary embodiment, Fe 3+ The Fe ions are obtained by dissolving metallic iron in the leach solution. 2+ Metallic iron can be reduced to Fe ions. 3+ reacts with Fe ions 2+Any source of metallic iron may be used, including scrap iron, scrap steel, bushing steel, electrolytic iron, iron or steel dust (i.e., typical waste materials produced in iron or steel making processes), or others. Alternatively, the ferric iron reduction step of step 106 may be omitted entirely, and any ferric iron may be precipitated separately from the ferrous iron (as described below).

[0093]

[0098] In some embodiments, acid leaching 104 and Fe 3+ (ferric iron) to Fe 2+ The conversion of iron to ferrous iron may be coupled to one another via an "acid regeneration cell," such as that described in applicant's PCT International Patent Application PCT / US2022 / 021729, entitled "Ore Dissolution and Iron Conversion System," published as WO 2022 / 204391, which is incorporated herein by reference in its entirety except where inconsistent herein (hereinafter referred to as the "Iron Conversion" patent). As described in the Iron Conversion patent, an electrochemical acid regeneration cell may be configured with an anode separated from a cathode by a cation exchange membrane (also known as a proton exchange membrane or PEM). When the acid solution is primarily sulfuric acid (H2SO4), such an acid regeneration cell oxidizes water at the anode to generate oxygen from the anode electrolyte, while generating dissolved ferric iron (Fe) in the cathode electrolyte solution. 3+ ) ions to ferrous (Fe 2+ ) at the cathode. The regenerator anode. Thus, in some embodiments, it may be preferable to use pure water (e.g., deionized water) or a different acid (e.g., sulfuric acid, acetic acid, etc.) as the anode electrolyte in the acid regeneration cell. Alternatively, if an economical hydrogen gas source is available, the acid generator anode may be configured to oxidize hydrogen gas at the anode.

[0094]

[0099] The anode water splitting reaction (or chlorine gas evolution or hydrogen gas oxidation) also releases protons, which tend to cross the cation exchange membrane and enter the cathode electrolyte, thereby increasing the acidity (lowering the pH) of the cathode electrolyte. Acid regeneration cell By recirculating the cathode electrolyte between the cathode and the tank where leaching / dissolution takes place, the acid (H) consumed during dissolution can be replenished. + Some of the slag may be regenerated in an electrochemical acid regeneration cell, thereby allowing for faster or more complete dissolution of the slag material.

[0095]

[0100] After leaching 104 and ferric iron reduction 106 (if performed) are complete, the leach solution may be transferred to a first precipitation step 108, during which base from a base storage tank 124 (or other liquid or solid source) may be mixed with the leach solution in a precipitation vessel (e.g., a settling tank or other suitable solid / liquid separation vessel).

[0096]

[0101] In various embodiments, the base used to raise the pH in any of the precipitation steps may be (or may be replenished with) a solid base material produced in a previous cycle of this process or in another process. Such solid base materials may include Ca(OH), Mg(OH), Al(OH), Fe(OH), Fe(OH), or others.

[0097]

[0102] In various embodiments, removal of products after some or each precipitation step may be aided by additional solid / liquid separation techniques. For example, any combination of techniques may be used to aid in the separation of one or more products from the leach solution or from other products. Such techniques may include, but are not limited to, filtration, shear mixing, gravity separation, sedimentation, centrifugation, settling, cementation, agglomeration, crystallization, or evaporation.

[0098]

[0103] Base may be added during the first precipitation step 108 to raise the leach solution pH to a level at which the first product begins to precipitate, for example, a pH of about 3-4. The addition of base may continue (optionally at a slow rate or in discrete amounts) until the first product has completely precipitated. In some embodiments, the base added during the first precipitation step may be an aqueous base solution from an acid-base generating system.

[0099]

[0104] In some embodiments, the first product collected from the first precipitation step 108 may comprise, consist of, or consist essentially of aluminum hydroxide (Al(OH)). In other embodiments, the first product may also be present in the leaching solution if the leaching solution contains a measurable amount of Fe. 3+ ions (e.g., if the ferric reduction step 106 is omitted, if less than 100% of the ferric ions in the solution are reduced, and / or if some ferrous ions are oxidized to ferric), it may contain some ferric hydroxide (Fe(OH)).

[0100]

[0105] In some embodiments, the products of first precipitation 108 can include minerals containing aluminum, among other elements, such as alumite (potassium aluminum sulfate, e.g., KAl(SO)(OH)) and / or natrium (sodium aluminum sulfate, e.g., NaAl(SO)(OH)). In such embodiments, the alumite and / or natrium can be physically separated from the other precipitation materials and redissolved in an aqueous acid or base solution (e.g., a base solution produced by an ABG), and then products such as Al(OH) and / or Fe(OH) can be precipitated from the second solution.

[0101]

[0106] The inventors have found that when a sulfate acid (sulfuric acid or bisulfate) is used, filtration of the first product can be improved by using calcium hydroxide (Ca(OH)2) as the base to drive the pH shift for the first precipitation 108. This is due in part to the immediate formation of gypsum (calcium sulfate, CaSO4) as a fine particle that acts as a filtration medium through which the first product can be filtered. After the first precipitation, the first product can be separated from the gypsum filter cake by gravity separation, flotation, density separation, or other suitable separation techniques.

[0102]

[0107] In some embodiments, the first product may also contain silica, which may be agglomerated by the first precipitation product. Thus, in some embodiments, some amount of ferric iron (Fe 3+ ) can be left in solution and the ferric hydroxide can be precipitated at a pH of about 2-3 before precipitation of the separate aluminum hydroxide product.

[0103]

[0108] Other materials present in the slag that precipitate at a pH greater than about 3 can optionally be included with the first product. For example, titanium hydroxide (Ti(OH)4) precipitates at a pH of about 2 to 3 and therefore can be included with the first product or precipitated as a separate product. Similarly, any other materials present in the slag that tend to precipitate at a pH of about 3 to about pH 8 can be precipitated and included with the product of first precipitation 108 or the product of second precipitation 112.

[0104]

[0109] In some embodiments, the second precipitation step 112 may be performed in a separate precipitation tank or in the same precipitation tank as the first precipitation 108. In various embodiments, the product collected from the second precipitation step 112 may include, consist of, or consist essentially of ferrous hydroxide (Fe(OH)), which tends to precipitate at a pH of about 7-8. Optionally, the second product may also include manganese hydroxide (Mn(OH)) or other materials, as described elsewhere herein.

[0105]

[0110] In some embodiments, the iron-containing product may alternatively be produced by recrystallization. For example, in some embodiments, before or after the first precipitation step 108, the solution containing dissolved iron may be heated to an elevated temperature (e.g., during the initial dissolution or at a later point), and additional ferrous iron may be added to the solution to supersaturate it with ferrous iron. The elevated temperature may be from about 50°C to about 80°C, or in some embodiments, about 60°C. The solution may then be cooled to below ambient temperature, allowing the iron salt (e.g., ferrous sulfate, ferrous chloride, etc., depending on the acid used) to recrystallize into a solid. The ferrous salt crystals may then be separated from the solution.

[0106]

[0111] In some embodiments, any iron-containing products precipitated from the leach solution may be sent to an optional electroplating plant 149 as shown in Figure 1. For example, the precipitated ferrous hydroxide may be redissolved at 151 to form Fe 2+ An aqueous solution rich in iron may be formed from which, optionally, metallic iron may be electroplated in electroplating cell 150. Electroplating cell 150 may be a plating cell such as that described in the above-referenced Iron Conversion application, or a cell such as that described below with reference to FIGS.

[0107]

[0112] In some embodiments, the first and / or second products may comprise, consist of, or consist essentially of magnetite (Fe3O4). Magnetite is a metal ion that reacts with the Fe3O4 in the aqueous leachate solution. 3+ and Fe 2+ The appropriate ratio of Fe:Fe is 2:1. 3+ vs. Fe 2+ In a solution with a pH of about 3 (e.g., just before or just after the first precipitation step 108), some of the ferric iron present in the solution can be preferentially precipitated by ensuring a ratio of Fe 3+The ferric iron may be oxidized to ferric iron by adding a liquid oxidizer such as hydrogen peroxide or by contacting the leach solution with a gaseous oxidizer such as air, ozone, or others until ferric iron is produced. In embodiments where magnetite is precipitated, the optional reduction step 106 may be omitted. In various embodiments, magnetite precipitation may be carried out at a temperature of about 50°C to about 80°C, and in some embodiments, about 60°C.

[0108]

[0113] Once the desired ratio of ferric to ferrous ions is achieved, base can be added to the solution (in some embodiments, slowly over a period of several to 24 hours) to raise the pH to about 8 until the magnetite product precipitates.

[0109]

[0114] Once the magnetite has precipitated, it may be separated from the leach solution (e.g., by filtration). The magnetite (which is magnetic) may be magnetically separated from any other constituents of the second precipitation product, such as manganese-containing products or compounds such as Mn(OH)2 and / or Mn3O4. The magnetite and / or Mn-containing products may then optionally be separated, collected, optionally calcined, and sold or used directly. In some embodiments, the separated product consisting essentially of magnetite may be transferred to a two-step iron conversion system, such as that described in the above-referenced Iron Conversion application, for electroplating of metallic iron products.

[0110]

[0115] In yet other embodiments, as described below with reference to FIG. 2, all or a substantial portion of the molten iron may be removed (e.g., by electroplating or recrystallization as described above) prior to second precipitation 108, leaving substantially only manganese compounds, such as Mn(OH) and / or MnO, which are removed as products of the second precipitation.

[0111]

[0116] In some embodiments, a third precipitation step 114 can be performed in the same or a different precipitation tank. In the third precipitation step, base can be added until the third product is completely precipitated. As shown in FIG. 1, the third product can comprise, consist of, or consist essentially of calcium hydroxide and / or magnesium hydroxide (Ca(OH) and / or Mg(OH)), or other compounds comprising, consisting of, or consisting essentially of magnesium and / or calcium. For example, if sulfate chemistry is used, very small amounts of calcium may remain in solution before the third precipitation step 114; therefore, in such cases, the third product can consist essentially of magnesium compounds, with very small amounts of calcium (if any). If a different acid salt is used (e.g., HCl), the third precipitation can include two parts: a first part that produces Mg(OH) at a pH of about 10 to about 12, and a second part that produces Ca(OH) at a pH above 12. In another embodiment, the product may comprise, consist of, or consist essentially of both magnesium and calcium compounds. In some embodiments, shear mixing may be used to aid in the separation of the Mg(OH)2 product.

[0112]

[0117] After the third precipitation 114, the solution tends to contain essentially only the salt(s) from the mixture of the acid and base solutions. However, some non-precipitated ions may remain. Therefore, in some embodiments, the leach solution exiting the third precipitation 114 may be optionally treated with an ion exchange resin to remove any residual ions that may interfere with the operation of the electrochemical acid-base generator. For example, any residual calcium or magnesium may be harmful to the separator membrane in the ABG cell and therefore should be removed before returning the salt solution to the electrochemical acid-base generator via conduit 118. If necessary, additional base may be added to the remaining leach solution after the final precipitation step to neutralize the pH and homogenize the salt solution. If necessary, any of the precipitation products may be washed with water or a portion of the base solution to dilute or neutralize any residual acid.

[0113]

[0118] In some embodiments, each of the major components described above may be precipitated separately. Thus, although only three precipitation "steps" are shown in FIG. 1, in various embodiments, any number of precipitation steps may be used to separate various products, including a mixture of products. For example, using sulfuric acid, ferric hydroxide (Fe(OH)) may be first precipitated at a pH of 2±0.5 to 3±0.5, followed by aluminum hydroxide (Al(OH)) at a pH of 3±0.5 to 5±0.5, then ferrous hydroxide (Fe(OH)) at a pH of 7±0.5 to 8±0.5, then magnesium hydroxide (Mg(OH)) at a pH of 8±0.5 to 10±0.5, and then calcium hydroxide (Ca(OH)) at a pH of 10±0.5 to 12±0.5. Similarly, any other dissolved components may be precipitated separately or together with another component. In various embodiments, some components may have slight overlap or very close solubility limits (pH ranges) at which precipitation occurs, so any one precipitation product may contain materials of two or more components. Furthermore, the need to separate different products may also depend on the intended use(s) and desired purity of the product materials. For example, in some applications, it may not be necessary to separate Ca from Mg, and thus the two hydroxide compounds may be precipitated together in a single step.

[0114]

[0119] In some embodiments, the slag recycling system may include two or more electrochemical acid-base generation systems configured to decompose different salts or salt mixtures to produce different acid and base solutions to enable more effective extraction of components with different solubility limits in different acid or base solutions.

[0115]

[0120] As will be appreciated by those skilled in the art, metal hydroxides are generally hydrated forms of the corresponding metal oxides. Thus, in various embodiments, any of the hydroxides described above can be dehydrated to remove excess water and convert the material to its corresponding oxide. Dehydration can typically be carried out by heating the hydroxide material and releasing the water as water vapor. In some embodiments, the water vapor can be captured and returned to the ABG for reuse. For example, calcium hydroxide (Ca(OH)2) can be dehydrated to form CaO according to the following: 2Ca(OH)2 → 2CaO + H2O

[0116]

[0121] Similarly, magnesium hydroxide, iron hydroxide, and aluminum hydroxide can be converted to the corresponding oxides before reuse, sale, or other disposal. In some embodiments, waste heat from high temperature plants (e.g., steel mills, power plants, iron foundries, or others) can be used to dehydrate one or more of the hydroxides.

[0117]

[0122] In some embodiments, the precipitated iron product may be redissolved in a separate aqueous solution at 151 and electrochemically reduced to metallic iron in an iron electroplating cell 150 such as that shown in FIG. 1 (and / or using an electroplating cell configured as shown and described with reference to FIG. 2 or FIG. 5). The precipitated ferrous hydroxide (Fe(OH)) and / or ferrous oxide (FeO) may be dissolved in an aqueous solution and introduced into the cathode chamber 152 of the plating cell 150 (in some embodiments, by flowing the plating catholyte through a bed of solid Fe(OH)). The metallic iron may then be electroplated onto the cathode electrode, and the metallic iron may be removed for use as described herein. In some embodiments, the reaction in the anode chamber 154 of the plating cell 150 may include the evolution of oxygen 156 or chlorine (not shown). In some embodiments, the anode electrode of the plating cell may be separated from the cathode electrode of the plating cell by an anion exchange membrane (AEM). Alternatively, the anode electrode of the plating cell may be separated from the cathode electrode of the plating cell by a proton exchange membrane (PEM).

[0118]

[0123] Figure 2 shows an alternative embodiment of the process described above with reference to Figure 1. Steps and structures common to both embodiments are numbered consistently with the above description of Figure 1. The embodiment of Figure 2 introduces an alternative method of recovering iron by electroplating it directly from the leach solution.

[0119]

[0124] 2, the dissolved iron in the leach solution can be removed by electroplating metallic iron onto a cathode electrode in a plating cell 250 (also referred to as electrowinning, electrodeposition, electroplating, electrolytic deposition, or similar terms). In some embodiments, after first precipitation 108, all or a portion of the leach solution can be directed via 248 to the cathode chamber 252 of the electroplating cell 250, where iron can be electroplated from the leach solution. In the context of an electroplating cell, the leach solution can be referred to as the plating cell cathode electrolyte or "plating catholyte."

[0120]

[0125] In some embodiments, the plating catholyte may be recirculated between the electroplating cell and a plating catholyte storage tank (not shown) in a manner similar to that shown and described with reference to the "plating cell" in the above-referenced Iron Conversion Application and in Figure 5 below. In some embodiments, once the concentration of dissolved iron in the plating catholyte is depleted to a desired lower iron concentration limit, it may be referred to as "spent" plating catholyte.

[0121]

[0126] In some embodiments, the spent plating catholyte may be concentrated by removing water, for example, via one or more distillation or evaporation techniques, such as those described herein. In various embodiments, the lower iron concentration limit that defines a "spent" plating catholyte may be between about 0.2M and 1M.

[0122]

[0127] The spent plating catholyte may be concentrated by removing water via a distillation or evaporation process, such as multiple-effect evaporation, mechanical vapor recompression, steam distillation, vacuum distillation, membrane distillation, reverse osmosis, or a combination of these and / or other processes. In various embodiments, any heat required for these or other distillation processes may be provided by waste heat generated by other parts of the process or by an adjacent steel mill or other plant.

[0123]

[0128] In other embodiments, the iron remaining in the "spent" plating catholyte may be removed by recrystallization as described herein above.

[0124]

[0129] In various embodiments, electroplating in plating cell 250 can occur while other non-ferrous ions are present in the leach solution (plating catholyte). Such non-ferrous ions can include ions of calcium, magnesium, manganese, and / or other elements or compounds. For example, in various embodiments, during electroplating of iron, the leach solution (plating catholyte) can contain any combination of Mg and Mn ions at a concentration of about 0.01 M to about 1 M. If a non-sulfate acid is used, the plating catholyte can also contain Ca ions at about 0.01 M to 1 M.

[0125]

[0130] In some embodiments, the anode chamber 254 of the electroplating cell 250 can contain a plating cell anolyte electrolyte or "plating anolyte," which can include an aqueous electrolyte such as sulfuric acid, deionized water, ferrous sulfate, or other aqueous solutions. In some embodiments, the anodic reaction of the plating cell 250 can be oxygen evolution 256 by the decomposition of water in the aqueous anolyte. The water-splitting reaction also produces protons, which acidify the plating anolyte.

[0126]

[0131] Alternatively, if a chloride salt is used, the anodic reaction may include chlorine gas evolution. In such an embodiment, chloride is trapped and dissolved in water to form an acid (H + or hydronium ions).

[0127]

[0132] In some embodiments, a quantity of ferrous hydroxide (Fe(OH)2) dissolves in the plating catholyte to dissolve any acid (H2O3) that can cross the separator membrane (e.g., AEM or PEM) from the anode to the cathode. + Any such protons or acid reaching the plating cell cathode can cause a parasitic hydrogen evolution reaction, resulting in inefficiency as current is wasted on producing hydrogen instead of metallic iron.

[0128]

[0133] In some embodiments, all or a portion of the spent plating catholyte may be directed to the anode chamber 254 of the electroplating cell 250. Under the oxidizing conditions of the anode electrode, any Mn ions in the leach solution may tend to be oxidized to MnO, which may tend to precipitate within the anode chamber 254. Such precipitated MnO may be collected as a manganese-containing product.

[0129]

[0134] In various embodiments, once electroplating is deemed complete, the remaining electrolyte, which may contain ions such as Ca, Mn, Mg, etc., may be returned to precipitation reactors 112 and / or 114 for precipitation and removal of the remaining constituents as described herein. For example, Mn compounds may be removed as Mn(OH) by adding a base (e.g., a base from an acid-base generator or a different base such as Mg(OH) or Ca(OH). Alternatively, Mn compounds may be removed as Mn(OH) by contacting with a liquid or gaseous oxidizer in a 2:1 ratio, as described herein for the precipitation of magnetite (FeO). 3+ vs. Mn 2+ By generating Mn, some of the dissolved Mn is converted to Mn 3+ By oxidation to the ionic state, it can be removed as Mn3O4 by precipitation at a pH of about 8. In some embodiments, magnesium hydroxide (Mg(OH)2) can be used as a base to shift the solution pH into a range where the Mn compound(s) will precipitate. Such Mg(OH)2 can be collected from a previous cycle of the process or can come from an external source.

[0130]

[0135] 5 illustrates an exemplary iron electroplating system (also referred to as a "plating cell" or "electrodeposition cell"). As shown, an aqueous anolyte, such as water or other aqueous solution (e.g., sulfuric acid, ferric sulfate, or the like), can be recirculated between an anolyte storage tank 502 and an anode chamber 508 of the electroplating cell 500. The anodic reaction in the anode half-cell can be oxygen evolution according to the following: H2O→H + +1 / 2O2+e - (Formula 1)

[0131]

[0136] The cathodic reaction in the cathode half-cell may be the reduction of ferrous iron to metallic iron according to the following: Fe 2+ +2e - →Fe (Formula 2)

[0132]

[0137] The anode chamber 508 is separated from the cathode chamber 506 by an anion exchange membrane (although in some alternative embodiments a PEM or porous separator may be used).

[0133]

[0138] As water is consumed in the anodic reaction of Equation 1, make-up water can be supplied to anolyte storage tank 502 or directly to the anodic chamber 508 of plating cell 500 to replenish it.

[0134]

[0139] The metallic iron may be removed from the cathode chamber as a plate, powder, or other form factor by any method, such as those described in the Iron Conversion application referenced herein above.

[0135]

[0140] The anode material of an iron electroplating cell, such as the plating cell of Figure 5, optionally has a composition including a carbon material, a graphite material, a mixed metal oxide, or any combination thereof. The cathode material of an iron electroplating cell, such as the plating cell of Figure 5, optionally has a composition including steel, low carbon steel, stainless steel, copper, a copper alloy, or any combination thereof. Additional components typical of an electrochemical cell or stack can include current collectors, bipolar plates, flow channels, end plates, etc., depending on the plating cell configuration selected.

[0136]

[0141] H produced by the anodic reaction of Eq. + Ions tend to gradually acidify the anolyte solution. As the concentration of acid increases in the anolyte, the likelihood of protons (or hydronium ions) crossing the separator into the catholyte increases. Increasing the acid concentration in the catholyte can reduce the efficiency of the electroplating reaction by causing parasitic hydrogen generation at the cathode and / or by redissolving the plated iron.

[0137]

[0142] Therefore, it is desirable to consume excess acid present in the plating catholyte. In some embodiments, this can be accomplished by contacting the plating catholyte with a quantity of ferrous hydroxide (Fe(OH)) in reactor 512. Reactor 512 can be any suitable reactor or vessel for contacting an electrolyte with ferrous hydroxide, such as a fluidized bed reactor or others. While reactor 512 is shown between catholyte tank 504 and cell 500, reactor 512 can alternatively be located between cell 500 and catholyte tank 504, within cathode chamber 506 itself, or at any other point in the catholyte flow path. In various embodiments, the ferrous hydroxide in reactor 512 can be obtained from a process such as those described herein or from another source.

[0138]

[0143] The molten iron is electroplated at the cathode (indicated by the "-" sign), so the Fe in the catholyte 2+The concentration of ions decreases, ultimately causing the reactant electroplating reaction to cease, thereby increasing the occurrence of parasitic side reactions such as hydrogen evolution. Therefore, it is desirable to maintain the concentration of ferrous ions in the catholyte. In some embodiments, this can be achieved by removing water from the catholyte in the concentration reactor 510.

[0139]

[0144] In some embodiments, water may be removed via a concentration reactor during each cycle of the catholyte through the cathode chamber 506. In other embodiments, water may be removed via a concentration reactor every second, third, or more cycles of the catholyte through the cathode chamber 506. In still other embodiments, water may be removed from the storage tank 504 or directly from the cathode chamber 506.

[0140]

[0145] Alternatively or additionally, supplemental amounts of Fe 2+ may be provided to the catholyte stream as an aqueous solution or as a solid (which can be dissolved in the catholyte). In various embodiments, supplemental Fe 2+ The materials may be added to the storage tank 504 or directly to the cathode chamber 506 .

[0141]

[0146] In some embodiments, if the plating catholyte or replenisher solution also contains additional elements, such as Mg or Mn, as described in various embodiments herein, reconcentration of the plating catholyte will also concentrate the other element(s). If proceeding through sufficient cycles, the concentrations of the other materials may approach their solubility limits, risking precipitation of compounds of those materials in the cathode chamber 506, which may be detrimental to plating quality.

[0142]

[0147] In such cases, a "bleed stream" (as known to those skilled in the art of electrowinning) may be withdrawn from the catholyte. The bleed stream removes a portion of the electrolyte from the catholyte flow stream. In some embodiments, the bleed stream may be replaced by water or other supporting solution. The bleed stream may be treated to remove dissolved constituents such as Mn, Mg, and Fe, for example, by removing water (as described herein), by pH shift-driven precipitation (as described herein), or by a recrystallization process (as described herein).

[0143]

[0148] In some embodiments, Fe can be removed from the bleed stream by precipitation as Fe(OH), which can provide a source of Fe(OH) for reactor 512. Alternatively, Fe can be removed from the bleed stream by recrystallization as (for example) FeSO, which can provide a source of Fe 2+ The ions may be returned to the tank 504 as a replenishment source.

[0144]

[0149] Similarly, other constituents (eg, Mn and Mg) may be removed by any of the methods described herein and as any of the products described herein.

[0145] Reuse of materials recovered from slag in steelmaking.

[0150] FIG. 3 illustrates a process 300 for reusing materials extracted from steelmaking slag in a steelmaking plant. As described in various embodiments above, an ABG plant 320 can be used to extract materials from steelmaking slag 312. The steelmaking slag in FIG. 3 can be any slag from any steelmaking plant (i.e., the same steelmaking plant or a different steelmaking plant from the one to which it is recycled), including steel slag, iron slag, blast furnace slag, basic oxygen furnace slag, EAF slag, ladle slag, etc. As also described above, the products extracted from the slag can include iron(III) hydroxide, iron(II) hydroxide 322, calcium hydroxide and / or magnesium hydroxide 326, or their respective oxides (e.g., CaO, MgO, and FeOx, where x reflects the different possible oxidation states of iron, such as x=1 for Fe(II), x=1.5 for Fe(III), or intermediate values ​​between 12 and 1.5).

[0146]

[0151] 3, the iron hydroxide or iron oxide extracted from the slag 312 may be reduced to metallic iron in a steel mill 324. The steel mill may include any suitable technique or method for removing oxygen (i.e., reducing the oxide) to form metallic iron. Such methods may include blast furnace, natural gas direct reduction, hydrogen direct reduction, melting and electrolytic deposition, etc. The metallic iron may then be sent back to the steel mill 310 to make steel.

[0147]

[0152] In some embodiments, some or all of the calcium and magnesium hydroxide 326 (or dehydrated CaO and / or MgO) may be sent directly back to the steel mill 310 for use as a flux to help protect the refractory materials and / or to aid in the creation of slag in new steelmaking operations.

[0148]

[0153] Alternatively, or additionally, all or a portion of the calcium hydroxide and / or magnesium hydroxide 326 can be used to capture CO 328 from the steel mill 310 or from another CO emitting plant, such as a power plant (not shown) or steel mill 324. Calcium hydroxide and magnesium hydroxide readily form carbonates when exposed to carbon dioxide-containing gases, especially at elevated temperatures. Thus, by contacting solid calcium hydroxide and / or magnesium hydroxide 326 with elevated temperatures (e.g., 200-600°C) CO -containing flue gases 328 from the steel mill 310 or other plant, the hydroxides 326 can be converted to calcium carbonate and / or magnesium carbonate, which can also be used as fluxes in steelmaking operations. For example, in some embodiments, carbon dioxide-containing gases (at ambient temperature or elevated temperatures of 200°C-500°C or higher) can be flowed through columns containing solid calcium hydroxide and / or magnesium hydroxide to form the respective carbonates. In other embodiments, a gas or gas mixture containing carbon dioxide may be bubbled through an aqueous slurry of water and solid calcium and / or magnesium hydroxide. In some embodiments, the calcium and / or magnesium carbonate so produced may be pelletized prior to use as a flux.

[0149]

[0154] Alternatively, or additionally, all or a portion of the calcium hydroxide 326 may be used to make cement / clinker without CO2 emissions.

[0150]

[0155] In various embodiments, the extracted silica and / or titania 342, and aluminum hydroxide (or dehydrated aluminum oxide, AlO) and / or aluminum phosphate 340, and any other extracted products, can be sold, used, or otherwise disposed of.

[0151] Ladle slag recycling and bauxite processing

[0156] The term "ladle slag" refers to the intentionally formed slag material used during the steel refining process in a ladle refining furnace. Ladle slag forms a molten layer over the molten steel, assisting in the removal of impurities from the steel, protecting the steel from reoxidation, and protecting the molten steel from premature cooling. Ladle slag is typically removed from the ladle just prior to casting. Ladle slag typically contains substantially the same constituents as other iron and steel slags (as described herein above), but in significantly different proportions.

[0152]

[0157] Due to the common use of calcium aluminate as the primary slag component, waste ladle slag tends to contain large amounts of alumina (Al2O3, typically on the order of 30% to 50% by weight) and calcium oxide (typically on the order of about 40% to 60%). Ladle slag also tends to contain very small amounts of iron oxide (typically less than 1%) and larger amounts of silica and magnesium oxide (both typically on the order of 5% to 10%). By comparison, bauxite ore, which is mined for its aluminum content, typically contains about 30% to 60% alumina, about 3% to 20% silica, and about 20% to about 33% iron oxide. Thus, in terms of elemental composition, ladle slag is similar to bauxite ore, which has a very low iron content.

[0153]

[0158] Thus, in some embodiments, ladle slag can be ground and processed by the Bayer process instead of bauxite to produce alumina while producing dramatically less red mud waste. Using the Bayer process, ladle slag can be ground, crushed, or otherwise comminuted into small particles, then leached with sodium hydroxide (or other base) and filtered to remove undissolved solids (primarily iron oxide, which gives red mud its red color). The filtered alumina-containing solution is then cooled to precipitate / crystallize aluminum hydroxide, which is then dehydrated to produce aluminum oxide of sufficient purity to be refined into aluminum metal.

[0154]

[0159] In further embodiments of the invention described herein, ladle slag or bauxite ore may be processed using electrochemically generated acids and bases as described in various embodiments herein to precipitate a separate aluminum hydroxide product, which may then be refined in a smelting cell using, for example, the Hall-Heroult process or other suitable aluminum smelting process to produce aluminum metal. The process for extracting alumina from ladle slag or bauxite ore may proceed substantially as illustrated and described herein with reference to Figure 1, except that in some embodiments, Fe 3+ The reduction step may be omitted due to the small amount of iron present. As with embodiments described elsewhere herein, the calcium and / or magnesium hydroxide may be dehydrated, pelletized, and used as a flux in a new steelmaking process.

[0155]

[0160] In further embodiments, the product obtained by any of the embodiments herein can be used in cement making. Cement is generally made by calcining calcium carbonate (limestone) in a kiln in the presence of silicon, aluminum, iron, and other ingredients to produce calcium oxide. In some embodiments, calcium hydroxide (or calcium oxide) can be used in place of limestone in standard cement making processes, eliminating the generation of CO gas from the calcination process. Thus, calcium hydroxide (or calcium oxide) can be heated with iron, aluminum, silicon, and other materials (derived from processes described herein or other sources) to produce clinker. Alternatively, calcium hydroxide may be used directly as Portland cement.

[0156]

[0161] In a further embodiment, calcium hydroxide (and / or calcium oxide) and aluminum hydroxide (and / or aluminum oxide) can be heated to a temperature of about 1,400° C. to produce a calcium aluminate product, which may be used as a flux in new steelmaking operations.

[0157] Further examples of acid-base generating systems

[0162] Any other electrochemical acid-base generating system (or combination of systems) may be used in place of or in combination with the electrochemical acid-base generating system of Figure 4 described above to generate the acids and bases used in any of the processes or systems, and embodiments thereof, described herein. Some exemplary embodiments of acid-base generating systems are described in PCT Application WO 2022 / 197954, entitled "Carbon Capture Using Electrochemically-Produced Acid And Base" (hereinafter the "'954 Application"), which is incorporated herein by reference in its entirety to the extent not inconsistent herewith. Any of the acid-base generating systems described in the '954 Application may be used in any of the processes or systems, and embodiments thereof, described herein.

[0158]

[0163] 6 shows a schematic of an electrolytic acid-base generation system 600 that can be configured to operate with either an AEM or PEM separator membrane that separates the cell into two chambers. In either case, the system can be configured to circulate an "acidified solution" liquid and a "basified solution" liquid through an electrolytic reactor, where constituents of the liquids are treated to convert a portion of the acidified solution liquid to an acid and a portion of the basified solution liquid to a base.

[0159]

[0164] The system 600 generally comprises at least one electrolysis cell 601, which may include a separator membrane 602 separating the cell 601 into a cathode chamber 604 and an anode chamber 606. The cathode chamber 604 may include a cathode electrode 608 and a current collector 610 connected to a negative terminal 612, and the anode chamber 606 may include an anode electrode 618 and a current collector 620 connected to a positive terminal 622. The cathode chamber 604 may further include a fluid inlet through which a "basifying solution" solution may enter and a fluid outlet through which the basifying solution may exit after processing in the cathode chamber 604. The basifying solution may be stored in a basifying solution reservoir 605, which may have a volume many times larger than the cell 601 (or collection of cells).

[0160]

[0165] Similarly, the anode chamber 606 may include a fluid inlet through which an "acidifying solution" solution may enter and a fluid outlet through which the acidifying solution may exit after processing in the cathode chamber 606. The acidifying solution may be stored in an acidifying solution reservoir 615, which may have a volume many times larger than the cell 601 (or collection of cells). The acidifying and basifying solutions may enter the cell via respective inlet conduits 636, 634 and, after exiting the cell 601, may be returned to the respective reservoirs 615, 605 via return conduits 632, 638. In some embodiments, the basifying and acidifying solutions may be circulated by respective pumps and / or other flow control devices. In various embodiments, the acidifying and basifying solutions may be configured to flow in the same direction (co-current) or in opposite directions (counter-current) within the cell through an acid-base generator (of any type or configuration described herein).

[0161]

[0166] As the acidified and basified solutions (and in some cases gaseous reactants such as hydrogen) flow through the cell, current applied to the electrodes typically results in an electrolytic reaction that reforms ions in the liquid, increasing the concentration of the basified solution product (i.e., the base solution) and correspondingly increasing the concentration of the acidified solution product (i.e., the acid solution). As explained further below, the acidified solution exiting the anode chamber 606 typically contains an increased concentration of acidic anodic products in addition to a reduced concentration of unreacted components of the supplied acidified solution. Similarly, the basified solution exiting the cathode chamber 604 typically contains an increased concentration of basic anodic products in addition to a reduced concentration of unreacted components of the supplied basified solution.

[0162]

[0167] According to some embodiments, the intended electrochemical reaction at the cathode involves water decomposition to produce hydrogen gas and hydroxyl ions according to the following equation: Cathode: H2O+e- → 1 / 2H2+OH- (Equation 3)

[0163]

[0168] The system may include a hydrogen gas circulation conduit 621 that may collect hydrogen gas produced in the cathode chamber 604 and direct the collected hydrogen gas, along with optional supplemental hydrogen gas from a hydrogen source 640, into the anode chamber 606 of the cell 601. While FIG. 6 schematically illustrates the introduction or injection of hydrogen gas directly into the anode chamber of the cell, hydrogen gas may be introduced or injected into the acidifying solution at any point between the acidifying solution tank and the anode chamber(s) of the cell or cell stack. For example, in some embodiments, hydrogen gas may be injected into the acidifying solution conduit upstream of the cell or cell stack. In various embodiments, hydrogen gas may be mixed into the acidifying solution by a sparger and / or other gas-liquid mixing device. Such hydrogen injection and / or mixing methods and systems may be used in combination with any of the embodiments described herein.

[0164]

[0169] In embodiments configured to consume hydrogen gas at the anode, the intended electrochemical reaction at the anode may include hydrogen oxidation, in which hydrogen gas is oxidized to form protons according to the following equation: Anode: H2 → 2H + +2e - (Formula 4)

[0165]

[0170] Either or both of the acidifying and basifying solutions may comprise an aqueous solution having anions and cations from one or more dissolved salts. Depending on the ion selectivity of the separator membrane, either the salt anions or the salt cations may pass through the separator membrane to interact with species in the opposite chamber.

[0166]

[0171] FIG. 7 shows an electrolytic acid-base generator configured to operate with a three-chamber cell 700 (or stack or other bundle of such cells) similar to the configuration described above with reference to FIG. 4. In such embodiments, the intermediate chamber 702 is separated from the anode chamber 704 by a first separator membrane 710 and from the cathode chamber 706 by a second separator membrane 712. The anode electrode 718 and the cathode electrode 716 may be in contact with respective current collectors 714, 720. In some embodiments, the anode chamber may contain substantially only hydrogen gas, a first salt solution may be forced to flow through the intermediate chamber, and a second salt solution (which may contain the same salt(s) as the first salt solution or different salts) or water may be forced to flow through the cathode chamber.

[0167]

[0172] In some embodiments, the first separator membrane 710 may be a PEM separator, and the second separator membrane 712 may be an AEM separator. In such embodiments, protons produced by oxidation of hydrogen gas at the anode may cross the PEM (first) separator 710 and enter the intermediate chamber 702, where a salt solution may be introduced. At the same time, salt anions (e.g., Cl in the above example) may be introduced from the cathode chamber 706. -) can cross the AEM (second) separator 712 and enter the intermediate chamber 702. Protons (H + ) and salt anions (e.g., Cl - ) can combine to form an acid (e.g., HCl). At the same time, hydroxyl anions (OH - ) and salt cations (e.g., Na + ) can combine to form a base.

[0168]

[0173] In some embodiments, the intermediate chamber 702 may be configured as narrow as possible to provide the smallest possible distance between the anode and cathode electrodes. For example, in some embodiments, the intermediate chamber may be limited to a thickness on the order of about 0.1 mm or less to about 2 centimeters. In some embodiments, the intermediate chamber may have a width of about 0.2 mm to about 10 mm (1 cm). Larger anode-cathode spacing results in increased ohmic resistance within the cell (particularly in bipolar cell stacks). Therefore, while spacings greater than 1 cm or 2 cm are possible, smaller spacings may provide more energy-efficient operation. For example, in some embodiments, the intermediate chamber 702 comprises a porous flow-through material (preferably electrically non-conductive) that can be compressed between the anode-side separator and the cathode-side separator. In various embodiments, the flow-through material within the intermediate chamber 702 may comprise a mesh, felt, corrugations, ribs, vanes, or other structures suitable for maintaining a flow channel while minimizing the electrode-separator interface distance, or any combination thereof.

[0169]

[0174] As mentioned above, the hydroxyl anions (OH - ) can compete with salt anions to cross the AEM separator. Any of the various methods described elsewhere herein for increasing the probability of salt anions crossing the AEM instead of hydroxyl anions can be used in a three-chamber system as well.

[0170]

[0175] In other embodiments, both the first separator membrane 710 and the second separator membrane 712 may be PEM separators. In such embodiments, protons produced by oxidation of hydrogen gas at the anode may traverse the first PEM separator 710 and enter the intermediate chamber 702. The protons (H + ) and salt anions (e.g., Cl - ) can combine in the intermediate chamber 702 to form an acid (e.g., HCl). At the same time, salt cations (e.g., Na in the example above) can be extracted from the intermediate chamber 702. + ) can cross the second PEM separator 712 and enter the cathode chamber 706. The salt cations (e.g., Na + ) is the hydroxyl (OH) produced by the reduction of water at the anode. - ) to form a salt (e.g., NaOH).

[0171]

[0176] In various embodiments, acids and bases may be generated in an electrodialysis bipolar membrane-based system. Such a system for acid-base generation (i.e., an electrodialysis acid-base generator) typically includes a CEM (or PEM), an AEM, and a bipolar membrane, as shown in FIG.

[0172]

[0177] The process of electrodialysis using bipolar membranes combines electrodialysis for salt splitting with electrodialysis water splitting to convert salts into their corresponding acids and bases. The bipolar membrane facilitates the splitting of water into protons and hydroxide ions. Bipolar membranes are a special type of layered ion exchange membrane, comprising an AEM, which is selectively permeable to anions, and a cation exchange membrane (CEM) or proton exchange membrane (PEM), which is selectively permeable to protons and / or other cations.

[0173]

[0178] A bipolar electrodialysis cell refers to an electrodialysis cell containing at least one bipolar membrane. The bipolar membrane dissociates water into hydronium ions and hydroxyl ions upon application of an electric field. These generated ions combine with cations and anions from a salt-containing process stream, which are separated by one or more ion exchange membranes within the electrodialysis cell. The combination of the hydronium ions with the anions and the hydroxyl ions with the cations results in a product stream having an acid and a base.

[0174]

[0179] Bipolar electrodialysis cells can be two-compartment or three-compartment cells. Two-compartment cells contain a cation or anion exchange membrane between two bipolar membranes. The choice of using a cation or anion exchange membrane depends on which salts are being treated. Cation exchange membranes can be used to treat solutions containing salts of weak acids and strong bases, such as sodium salts of organic acids and amino acids. Anion exchange membranes are used to treat solutions containing weak bases and salts of strong or weak acids, such as ammonium salts of chlorides, sulfates, or lactates.

[0175]

[0180] A three-compartment cell, as shown in FIG. 8, includes an anion exchange membrane and a cation exchange membrane between two bipolar membranes, thereby forming three compartments. The first compartment 802 is an acidic solution-producing compartment 802 between the first bipolar membrane (left side of FIG. 8) and the anion exchange membrane (AEM). The second compartment 804 is a basic solution-producing compartment 804 between the second bipolar membrane (right side of FIG. 8) and the cation exchange membrane (CEM). The third compartment 806 is between the cation exchange membrane and the anion exchange membrane, producing a salt-reduced solution as anions exit the third compartment 806 and are propelled into the first compartment 802 for acidification, and cations exit the third compartment 806 and are propelled into the second compartment 804 for basification. Three-compartment electrodialysis cells are well suited for recovering inorganic acids and bases from their corresponding salts. In the example shown in FIG. 8, sodium chloride (NaCl) salt is decomposed into hydrochloric acid (HCl) and sodium hydroxide (NaOH).

[0176]

[0181] In some embodiments, an electrodialysis system may be used to concentrate the acid produced by an electrolytic acid-base generator such as those described herein.

[0177]

[0182] Additionally, any electrodialytic acid-base generator may be used in a recirculation configuration with acid and base storage tanks to concentrate the acid and base products in the tanks to reach desired concentrations as described herein with reference to the electrolytic acid-base generator, further enabling decoupling of the production and use of the acid and base solutions.

[0178]

[0183] Other electrodialysis acid-base generating systems are shown and described in U.S. Patent No. 8,778,156, U.S. Patent Application Publication No. 2021 / 0069645, U.S. Patent No. 9,586,181, U.S. Patent No. 9,862,643, and U.S. Patent No. 9,873,650, which are incorporated herein by reference for all purposes.

[0179] Certain exemplary aspects and embodiments:

[0184] Various embodiments are contemplated and disclosed herein, some of which are described in the following paragraphs. It is expressly contemplated and disclosed that any embodiment, or portions thereof, may be combined to form an embodiment. Furthermore, it is expressly contemplated and disclosed that any reference to Embodiment 1 includes a reference to Embodiments 1a, 1b, and / or 1c, and any combination thereof (i.e., any reference to an embodiment includes a reference to lettered versions of that embodiment). Furthermore, the terms "any preceding embodiment" and "any one of the preceding embodiments" refer to any embodiment that appears before the embodiment containing such phrase (e.g., the phrase "Embodiment 15:...a material, device, electrolyte, or method of any preceding embodiment" means that any embodiment before Embodiment 15, including lettered versions, is referred to). For example, it is contemplated and disclosed that, optionally, any composition, method, or formulation of any of the following embodiments may be useful in combination with any other embodiment provided below. Furthermore, it is contemplated and disclosed that, for example, any of the embodiments or aspects described above may optionally be combined with any of the aspects listed below or any portion(s) thereof.

[0180]

[0185] Aspect 1a: A method for recycling first slag, comprising: dissolving the first slag with a first acid to form a starting leach solution; the starting leach solution comprises at least dissolved (aqueous) aluminum ions, dissolved iron ions, dissolved (aqueous) magnesium ions, and dissolved (aqueous) manganese ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first pre-plating leachate fraction; the one or more first precipitation products comprise one or more precipitated aluminum-containing products; a first pre-plating leachate fraction containing dissolved (aqueous) iron ions, magnesium ions, and manganese ions; first electroplating metallic iron from the first pre-plating leachate fraction using a first electrochemical cell to form electroplated metallic iron and a first post-plating leachate fraction; the first post-plating leachate fraction having a reduced concentration of said iron ions compared to the first pre-plating leachate fraction; second precipitating one or more second precipitation products from the first post-plating leachate fraction by combining a second base with the first post-plating leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated manganese-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products comprising one or more precipitated magnesium-containing products; A method comprising:

[0181]

[0186] Aspect 1b: A system for carrying out the method of aspect 1a.

[0182]

[0187] Aspect 1c: A system having components, parts, systems, subsystems, devices, features, etc. according to Aspect 1a, such as but not limited to electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or any combination of components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of Aspect 1a, such as but not limited to electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0183]

[0188] Aspect 2: The method or system of aspect 1, wherein the first electrochemical cell comprises a first electroplating catholyte, the first electroplating catholyte comprising a first pre-plating leachate fraction such that the first electroplating catholyte comprises dissolved (aqueous) iron ions, magnesium ions, and manganese ions.

[0184]

[0189] Aspect 3: A method or system according to aspect 2, comprising separately dosing iron hydroxide into the first electroplating catholyte. Optionally, the dosing is performed as one or more separate steps during the first electroplating step. Optionally, the dosing is performed continuously during at least a portion of the electroplating step. Dosing iron hydroxide into the catholyte serves to consume acid that may leak through the anion exchange membrane into the catholyte. Thus, optionally, the amount and / or rate of iron hydroxide dosing is within 50% (optionally within 40%, optionally within 30%, optionally within 20%, optionally within 10%, optionally within 5%) of the amount and / or rate of acid leaking from the respective anolyte through the respective membrane or separator into the catholyte.

[0185]

[0190] Aspect 4: The first electroplating catholyte comprises: 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, Optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, optionally 0.46M) to 1.3M (optionally 1.29M, optionally 1.28M, optionally Optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, optionally 0.98M, optionally 0.96M, optionally 0.95M, optionally 0.94M , optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.and optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M) (any ranges and values ​​therebetween are expressly contemplated and disclosed herein). 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, Optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, optionally 0.46M) to 1.3M (optionally 1.29M, optionally 1.28M, optionally Optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, optionally 0.98M, optionally 0.96M, optionally 0.95M, optionally 0.94M , optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.and / or dissolved (aqueous) manganese ions having a concentration selected from the range of (any range and value therebetween is expressly contemplated and disclosed herein) optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M). 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, Optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, optionally 0.46M) to 1.3M (optionally 1.29M, optionally 1.28M, optionally Optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, optionally 0.98M, optionally 0.96M, optionally 0.95M, optionally 0.94M , optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.and optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M) (any ranges and values ​​therebetween are expressly contemplated and disclosed herein). 4. The method or system according to aspect 2 or 3, comprising:

[0186]

[0191] Aspect 5: The method or system of any of the preceding aspects, wherein the step of first electroplating metallic iron is performed against an electrochemical oxygen evolution reaction at a first anode.

[0187]

[0192] Aspect 6: A first electrochemical cell comprising: a first anode in the presence of a first anolyte; a first cathode in the presence of a first electroplating catholyte; and an anion exchange membrane separating the first electroplating catholyte from the first anolyte; 6. The method or system of embodiment 5, wherein the first electroplating catholyte comprises the first pre-plating leachate fraction, and metallic iron is electroplated at the first cathode.

[0188]

[0193] Aspect 7: The method further comprises generating a product acid and a product base with an electrochemical acid-base generator; the first acid comprises the product acid;

[0023] Aspect 10. The method or system of any of the preceding aspects, wherein the first base, the second base, and the third base each comprise a portion of a product base.

[0189]

[0194] Aspect 8: Returning the neutralized salt solution to the electrochemical acid-base generator; regenerating the product acid and product base from the neutralized salt solution via an electrochemical acid-base generator; 8. The method or system according to embodiment 7, comprising:

[0190]

[0195] Aspect 9: The method or system of any preceding aspect, further comprising first providing at least a portion of the first, second, and / or third precipitation products to a steelmaking furnace, with or without further processing.

[0191]

[0196] Aspect 10: The method or system of aspect 9, wherein the providing step includes converting at least a portion of the provided first, second, and / or third precipitation products to a respective metal product and / or metal oxide product, and then providing the converted respective metal product and / or metal oxide product to the steelmaking furnace.

[0192]

[0197] Aspect 11: The method or system of any of the preceding aspects, wherein the third precipitation product comprises magnesium hydroxide and / or calcium hydroxide, and the method comprises converting the magnesium hydroxide and / or calcium hydroxide to magnesium oxide and / or calcium oxide, respectively, and providing the magnesium oxide and / or calcium oxide as a flux to a steelmaking furnace.

[0193]

[0198] Aspect 12: Collecting fresh steel slag from a steelmaking furnace; Repeating the method using a new steel slug. 12. The method or system according to any one of aspects 9 to 11, comprising:

[0194]

[0199] Aspect 13: The method or system of aspect 12, comprising dissolving fresh steel slag in the first or second acid to form a fresh starting leach solution.

[0195]

[0200] Aspect 14: The method of any of the preceding aspects, comprising providing at least a portion of the electroplated metallic iron to a steelmaking furnace.

[0196]

[0201] Aspect 15: The method or system of any one of the preceding aspects, comprising generating at least a portion of each of the first acid, the second acid, the first base, the second base, and the third base using an electrochemical acid-base generator.

[0197]

[0202] Aspect 16: The method or system of any one of the preceding aspects, comprising: first collecting at least a portion of the spent catholyte from the first electroplating step; and concentrating the collected spent catholyte.

[0198]

[0203] Aspect 17: The spent catholyte is, prior to the concentrating step, 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, optionally 0.46M) ~1.3M (optionally 1.29M, optionally 1.28M, optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, optionally 0.98M, Optionally 0.96M, optionally 0.95M, optionally 0.94M, optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.17. The method or system of embodiment 16, wherein the dissolved (aqueous) iron ion concentration is selected from the range of (any range and value therebetween is expressly contemplated and disclosed herein), for example, optionally selected from the range of 0.2 M to 1 M.

[0199]

[0204] Aspect 18. The method or system of aspect 16 or 17, comprising, after the concentrating step, Mn-precipitating one or more precipitated manganese-containing products from the concentrated spent catholyte.

[0200]

[0205] Aspect 19: The method or system of aspect 18, wherein the second precipitating step comprises a Mn precipitating step, and the Mn precipitating step comprises combining the concentrated spent catholyte with the first post-plating leachate fraction and a base.

[0201]

[0206] Aspect 20: The method or system of any of the preceding aspects, comprising removing a bleed stream from the first electroplating catholyte.

[0202]

[0207] Aspect 21: Concentrating the removed bleed stream by reducing its water content; fourth precipitating one or more fourth precipitation products from the concentrated bleed stream by adding a fourth base; wherein the one or more fourth precipitation products comprise magnesium.

[0203]

[0208] Aspect 22: The concentration of dissolved (aqueous) magnesium ions in the first pre-plating leachate fraction is 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, Optionally 0.46M) ~ 1.3M (optionally 1.29M, optionally 1.28M, optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, Optionally 0.98M, optionally 0.96M, optionally 0.95M, optionally 0.94M, optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M) (any ranges and values ​​therebetween are expressly contemplated and disclosed herein).

[0204]

[0209] Aspect 23: The concentration of dissolved (aqueous) manganese ions in the first pre-plating leachate fraction is 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0. 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, 0.46M) to 1.3M (optionally 1.29M, optionally 1.28M, optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, Optionally 0.98M, optionally 0.96M, optionally 0.95M, optionally 0.94M, optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M) (any ranges and values ​​therebetween are expressly contemplated and disclosed herein).

[0205]

[0210] Aspect 24a: A method of recycling first slag, comprising: dissolving the first slag with a first acid to form a starting leach solution; the starting leach solution comprises at least one or more dissolved (aqueous) aluminum ions, dissolved (aqueous) iron ions, and one or more dissolved (aqueous) calcium ions and / or (aqueous) magnesium ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first leachate fraction; the one or more first precipitation products include one or more precipitated aluminum-containing products; second precipitating one or more second precipitation products from the first leachate fraction by combining a second base with the first leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated iron-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products include one or more precipitated calcium-containing products and / or one or more precipitated magnesium-containing products; Including, generating a product acid and a product base in an electrochemical acid-base generator; further comprising the first acid comprises a product acid; The method, wherein the first base, the second base, and the third base each comprise a portion of a product base.

[0206]

[0211] Embodiment 24b: A system for performing the method of embodiment 24a.

[0207]

[0212] Aspect 24c: A system having components, parts, systems, subsystems, devices, features, etc. according to aspect 24a, such as, but not limited to, electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or any combination of components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of aspect 24a, such as, but not limited to, electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0208]

[0213] Aspect 25: Returning the neutralized salt solution to the electrochemical acid-base generator; regenerating the product acid and product base from the neutralized salt solution via an electrochemical acid-base generator; 25. The method or system of embodiment 24, further comprising:

[0209]

[0214] Aspect 26a: A method of recycling first slag, comprising: dissolving the first slag with a first acid to form a starting leach solution; the starting leach solution comprises at least one or more dissolved aluminum ions, dissolved iron ions, and one or more dissolved calcium and / or magnesium containing products; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first leachate fraction; the one or more first precipitation products include one or more precipitated aluminum-containing products; second precipitating one or more second precipitation products from the first leachate fraction by combining a second base with the first leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated iron-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products include one or more precipitated calcium-containing products and / or one or more precipitated magnesium-containing products. and providing at least a portion of the one or more third precipitation products to a steelmaking furnace as a flux, and / or reducing at least a portion of the precipitated iron-containing products to metallic iron and using the metallic iron in the steelmaking furnace; collecting fresh steel slag from a steelmaking furnace; Repeating the method using a new steel slug. The method further comprises:

[0210]

[0215] Embodiment 26b: A system for performing the method of embodiment 26a.

[0211]

[0216] Aspect 26c: A system having components, parts, systems, subsystems, devices, features, etc. according to aspect 26a, such as, but not limited to, electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or any combination of components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of aspect 26a, such as, but not limited to, electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0212]

[0217] Aspect 27: The method or system of aspect 26, comprising providing at least a portion of the one or more third precipitation products to a steelmaking furnace as a flux.

[0213]

[0218] Aspect 28: The method or system of aspect 26 or 27, wherein the third precipitation product comprises magnesium hydroxide and / or calcium hydroxide; the method comprises converting the magnesium hydroxide and / or calcium hydroxide to magnesium oxide and / or calcium oxide, respectively; and the providing step comprises providing the magnesium oxide and / or calcium oxide to a steelmaking furnace as a flux.

[0214]

[0219] Aspect 29: The method or system of any one of Aspects 26-28, comprising reducing at least a portion of the precipitated iron-containing product to metallic iron and using the metallic iron in a steelmaking furnace.

[0215]

[0220] Aspect 30: The method or system of any one of aspects 26-29, comprising dissolving fresh steel slag in the first acid or the second acid to form a fresh starting leach solution.

[0216]

[0221] Aspect 31: The method or system of any one of aspects 26-30, comprising using an electrochemical acid-base generator to generate at least a portion of each of the first acid, the second acid, the first base, the second base, and the third base.

[0217]

[0222] Aspect 32: The method or system of any preceding aspect, wherein the dissolving step comprises separating undissolved solids from the starting leach solution; and the undissolved solids comprise silica, titania, and / or calcium sulfate.

[0218]

[0223] Aspect 33: The method or system of aspect 32, wherein the undissolved solids comprise calcium sulfate; and the method further comprises the steps of physically separating the calcium sulfate from other undissolved solids and redissolving the separated calcium sulfate (optionally in a base, optionally in a hydroxide base) to form solid precipitated calcium hydroxide and aqueous dissolved sulfate.

[0219]

[0224] Aspect 34: The method or system of aspect 33, comprising returning the aqueous dissolved sulfate to the electrochemical acid-base generator.

[0220]

[0225] Aspect 35: A method or system according to any of the preceding aspects, comprising a step of milling the first slag to reduce its particle size prior to the step of melting the first slag.

[0221]

[0226] Aspect 36: A method or system described in aspect 34, comprising a step of magnetically separating and removing magnetic components from the pulverized slag prior to the step of melting the first slag.

[0222]

[0227] Embodiment 37: The method or system of any of the preceding embodiments, wherein the first acid comprises one or more weak acids.

[0223]

[0228] Embodiment 38: The method or system of any of the preceding embodiments, wherein the first acid comprises an aqueous bisulfate acid.

[0224]

[0229] Aspect 39: The method or system of aspect 38, wherein the aqueous bisulfate acid comprises alkali bisulfate, ammonium bisulfate, or a combination thereof.

[0225]

[0230] Embodiment 40: The method or system of embodiment 38 or 39, wherein the aqueous bisulfate acid is generated using an electrochemical acid-base generator.

[0226]

[0231] Embodiment 41: The method or system of any of the preceding embodiments, wherein the first acid comprises sulfuric acid.

[0227]

[0232] Aspect 42: The method or system of any of the preceding aspects, wherein the first acid comprises hydrochloric acid.

[0228]

[0233] Aspect 43: The method or system of any of the preceding aspects, comprising reducing ferric ions to ferrous ions in the starting leach solution prior to the first precipitating step.

[0229]

[0234] Aspect 44: The method or system of aspect 43, wherein the step of reducing ferric ions to ferrous ions is performed electrochemically.

[0230]

[0235] Embodiment 45: The method or system of embodiment 43 or 44, wherein the step of reducing ferric ions to ferrous ions is performed chemically by providing ferric ions in the presence of a reducing agent.

[0231]

[0236] Aspect 46: The method or system of aspect 45, wherein the reducing agent is metallic iron, steel, or another iron-containing metal.

[0232]

[0237] Aspect 47: The method or system of any one of aspects 43-46, wherein the step of reducing the ferric ions to ferrous ions comprises recirculating the leach solution between the dissolution tank and a cathode chamber of an electrochemical acid regeneration cell configured to reduce the ferric ions to ferrous ions at the cathode while generating oxygen gas at the anode to release protons that are transported to the leach solution in the cathode chamber.

[0233]

[0238] Embodiment 48: The method or system of any preceding embodiment, wherein the first base, the second base, the third base, or any combination thereof comprises calcium hydroxide, ferric hydroxide, ferrous hydroxide, metallic iron, and / or magnesium hydroxide.

[0234]

[0239] Aspect 49: A method or system according to any of the preceding aspects, wherein each step of the first precipitating step, the second precipitating step, the third precipitating step, or any combination thereof, is conducted at a liquid temperature (the temperature of the aqueous solution from which the solid precipitates) selected from a range of about 50°C (optionally about 55°C, optionally about 60°C, optionally about 65°C, optionally about 70°C, optionally about 75°C) to about 90°C (optionally about 85°C, optionally about 80°C), e.g., optionally about 60°C±5°C, optionally about 70°C±5°C, optionally about 80°C±5°C.

[0235]

[0240] Aspect 50: The one or more precipitated aluminum-containing products comprise aluminum hydroxide; the one or more precipitated iron-containing products include iron(II) hydroxide (ferrous hydroxide); the one or more precipitated calcium-containing products comprise calcium hydroxide;

[0023] Aspect 11. The method or system of any preceding aspect, wherein the one or more precipitated magnesium-containing products comprise magnesium hydroxide.

[0236]

[0241] Embodiment 51: The method or system of any preceding embodiment, wherein the one or more first precipitation products also include one or more precipitated chromium-containing products.

[0237]

[0242] Embodiment 52: The method or system of any preceding embodiment, wherein the one or more first precipitation products also include one or more precipitated phosphorus-containing products or one or more precipitated phosphate-containing products.

[0238]

[0243] Embodiment 53: The method or system of any preceding embodiment, wherein the one or more second precipitation products also comprise one or more precipitated manganese-containing products.

[0239]

[0244] Aspect 54: A method or system according to any of the preceding aspects, wherein the starting leaching solution has a pH of about 2.5 or less, optionally about 2.3 or less, optionally about 2.2 or less, optionally about 2.1 or less, optionally about 2.0 or less, optionally about 1.9 or less, optionally about 1.8 or less, optionally about 1.7 or less, optionally about 1.6 or less, optionally about 1.4 or less, optionally about 1.2 or less, optionally about 1.1 or less, optionally about 1.0 or less, optionally about 0.9 or less, optionally about 0.8 or less, optionally about 0.7 or less, optionally about 0.5 or less.

[0240]

[0245] Embodiment 55: A method or system according to any of the preceding embodiments, wherein the first leachate fraction has a pH selected from the range of about 2.5 (optionally about 2.6, optionally about 2.7, optionally about 2.8, optionally about 2.9, optionally about 3.0, optionally about 3.1) to about 5.7 (optionally about 5.6, optionally about 5.5, optionally about 5.4, optionally about 5.3, optionally about 5.2, optionally about 5.1, optionally about 5.0, optionally about 4.9, optionally about 4.8, optionally about 4.6, optionally about 4.5, optionally about 4.4, optionally about 4.3, optionally about 4.2, optionally about 4.1, optionally about 4.0, optionally about 3.9, optionally about 3.8).

[0241]

[0246] Embodiment 56a: The method or system of any of the preceding embodiments, wherein the second leachate fraction has a pH selected from the range of about 6.4 (optionally about 6.5, optionally about 6.6, optionally about 6.7, optionally about 6.8, optionally about 6.9, optionally about 7.0, optionally about 7.1, optionally about 7.2, optionally about 7.3, optionally about 7.4, optionally about 7.5, optionally about 7.6, optionally about 7.7, optionally about 7.8) to about 9.2 (optionally about 9.1, optionally about 9.0, optionally about 8.9, optionally about 8.8, optionally about 8.7, optionally about 8.6, optionally about 8.5, optionally about 8.4, optionally about 8.3, optionally about 8.2). Embodiment 56b: The second leachate fraction is from about 6.4 (optionally about 6.5, optionally about 6.6, optionally about 6.7, optionally about 6.8, optionally about 6.9, optionally about 7.0, optionally about 7.1, optionally about 7.2, optionally about 7.3, optionally about 7.4, optionally about 7.5, optionally about 7.6, optionally about 7.7, optionally about 7.8) to about 10 (optionally about 9.9, optionally about 9.8, optionally about 9.7, optionally about 9.6, optionally about 9.5, optionally about 9.4, optionally about 9.3, optionally about 9.2, optionally about 9.1, optionally about 9.0, optionally about 8.9, optionally about 8.8, optionally about 8.7, optionally about 8.6, optionally about 8.5, optionally about 8.4, optionally about 8.3, optionally about 8.2.

[0242]

[0247] Aspect 57: The third leachate fraction is between about 9.5 (optionally about 9.6, optionally about 9.7, optionally about 9.8, optionally about 9.9, optionally about 10.0, optionally about 10.1, optionally about 10.2, optionally about 10.4, optionally about 10.5, optionally about 10.6, optionally about 10.7, optionally about 10.8, optionally about 10.9, optionally about 11.0) and about 13 (optionally about 12.9, optionally about 13.9). 12.8, optionally about 12.7, optionally about 12.6, optionally about 12.5, optionally about 12.4, optionally about 12.3, optionally about 12.2, optionally about 12.1, optionally about 12.0, optionally about 11.9, optionally about 11.8, optionally about 11.7, optionally about 11.6, optionally about 11.5.

[0243]

[0248] Aspect 58: The one or more first, second, and / or third precipitation products comprise a metal hydroxide product; and the method comprises:

[0023] A method or system according to any of the preceding aspects, further comprising dehydrating at least a portion of the metal hydroxides (optionally at least a portion of the metal hydroxides obtained from the third precipitation product) to form respective metal oxide products.

[0244]

[0249] Aspect 59: The method or system of aspect 58, comprising using at least a portion of the formed metal oxide product as at least a portion of a flux in a steelmaking furnace.

[0245]

[0250] Aspect 60a: The method or system of aspect 59, wherein the metal oxide product formed comprises magnesium oxide, calcium oxide, and / or aluminum oxide. Aspect 60b: The method or system of aspect 59, wherein the metal oxide product formed consists essentially of magnesium oxide, calcium oxide, and / or aluminum oxide. Aspect 60c: The method or system of aspect 59, wherein the metal oxide product formed consists essentially of magnesium oxide and / or calcium oxide.

[0246]

[0251] Aspect 61: The method or system of any one of aspects 58 to 60, wherein the first precipitation product comprises magnesium hydroxide, and the method comprises the steps of dehydrating the magnesium hydroxide to form magnesium oxide, and using the formed magnesium oxide in a steelmaking furnace as at least part of a flux.

[0247]

[0252] Aspect 62: The method or system of any one of aspects 57 to 59, wherein the third precipitation product comprises calcium hydroxide, and the method includes the steps of dehydrating the calcium hydroxide to form calcium oxide, and using the formed calcium oxide in a steelmaking furnace as at least part of a flux.

[0248]

[0253] Aspect 63: The method or system of any one of aspects 58-62, wherein the second precipitation product comprises iron hydroxide, and the method comprises the steps of dehydrating the iron hydroxide to form iron oxide, reducing the iron oxide to metallic iron, and using the formed metallic iron in a steelmaking furnace.

[0249]

[0254] Aspect 64: The method or system of any of the preceding aspects, wherein the one or more precipitated aluminum-containing products comprise aluminum hydroxide; and the method further comprises dehydrating the precipitated aluminum hydroxide to form alumina (Al2O3) and purifying the alumina to aluminum metal in an aluminum smelting process.

[0250]

[0255] Aspect 65: The method or system of any of aspects 58 to 64, wherein the dehydrating step is performed using waste heat from a steel mill or a power plant.

[0251]

[0256] Aspect 66: The method or system of any of the preceding aspects, wherein the one or more magnesium-containing products comprise Mg(OH) and the one or more calcium-containing products comprise Ca(OH); and the method comprises contacting the precipitated Mg(OH) and / or Ca(OH) with a CO-containing gas to form MgCO and / or CaCO, respectively.

[0252]

[0257] Aspect 67: The method or system of aspect 66, wherein the CO2-containing gas is at a temperature of at least about 200°C during the contacting step.

[0253]

[0258] Aspect 68: The method or system of aspect 66 or 67, wherein the CO2-containing gas is exhaust or flue gas from a steelmaking furnace.

[0254]

[0259] Aspect 69: The method or system of any one of aspects 66-68, further comprising using MgCO and / or CaCO as a flux in the steelmaking furnace.

[0255]

[0260] Aspect 70: The method or system of any of the preceding aspects, wherein the steelmaking furnace is an electric arc furnace.

[0256]

[0261] Aspect 71: The method or system of any of the preceding aspects, wherein the first slag is a steel slag or an iron slag.

[0257]

[0262] Aspect 72: The method or system of any of the preceding aspects, wherein the first slag is ladle slag.

[0258]

[0263] Aspect 73: The method or system of any of the preceding aspects, wherein the one or more precipitated calcium-containing products comprise Ca(OH); and the method comprises combining the Ca(OH) with silica, alumina, and iron in a kiln and heating to produce a clinker.

[0259]

[0264] Embodiment 74: The method or system of any one of embodiments 24 to 73, wherein the one or more second precipitation products comprise magnetite (Fe3O4).

[0260]

[0265] Aspect 75: The method or system of aspect 74, comprising reducing precipitated magnetite to iron and providing the reduced iron to a steelmaking process or furnace.

[0261]

[0266] Embodiment 76: The method or system of any one of embodiments 24 to 75, comprising redissolving at least a portion of the one or more metal salts to create a redissolved iron salt solution; and further comprising first electroplating metallic iron from the redissolved iron salt solution.

[0262]

[0267] Aspect 77: A method or system described in aspect 76, comprising first collecting at least a portion of the spent electrolyte from the first electroplating step, and first re-precipitating Fe-containing and / or Mn-containing salts from the collected spent electrolyte.

[0263]

[0268] Aspect 78: The method or system of aspect 76 or 77, comprising the steps of first collecting at least a portion of the used electrolyte from the first electroplating step, concentrating the collected used electrolyte to reduce its water content, second electroplating metallic iron from the concentrated used electrolyte, second collecting at least a portion of the used electrolyte from the second electroplating step, and first re-precipitating Fe-containing and / or Mn-containing salts from the second collected used electrolyte.

[0264]

[0269] Embodiment 79: The method or system of any one of embodiments 24 to 78, wherein the one or more precipitated iron-containing products comprise Fe(OH).

[0265]

[0270] Example 80: The method or system of example 79, comprising heating Fe(OH) to make FeO.

[0266]

[0271] Embodiment 81: The method or system of any one of embodiments 24 to 80, wherein the one or more iron-containing products comprise iron hydroxide; and the method comprises thermally reducing the iron hydroxide to iron metal.

[0267]

[0272] Aspect 82: The method or system of aspect 81, comprising using ferrous metal to produce steel in a steelmaking furnace.

[0268]

[0273] Aspect 83a: A method for electrochemically producing metallic iron in the presence of dissolved magnesium and dissolved manganese, comprising: first electroplating metallic iron from the first catholyte at a first cathode for an oxygen evolution reaction at a first anode in the presence of the first anolyte; the first catholyte comprising dissolved iron ions, dissolved magnesium ions, and dissolved manganese ions; the first catholyte and the first anolyte are separated by an anion exchange membrane; The method, wherein the first electrochemical cell comprises a first cathode, a first catholyte, a first anode, and a first anolyte.

[0269]

[0274] Aspect 83b: A system for performing the method of aspect 83a.

[0270]

[0275] Aspect 83c: A system having components, parts, systems, subsystems, devices, features, etc. according to aspect 83a, such as, but not limited to, electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or any combination of components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of aspect 83a, such as, but not limited to, electrochemical cell(s), tank(s), bath(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0271]

[0276] Aspect 84: The concentration of dissolved magnesium ions in the first catholyte is 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, Optionally 0.20M, optionally 0.21M, optionally 0.22M, optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, optionally 0.46 M) to 1.3M (optionally 1.29M, optionally 1.28M, optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, optionally 0.98M , optionally 0.96M, optionally 0.95M, optionally 0.94M, optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.84. The method or system of embodiment 83, wherein the ionic strength is selected from the range of (any range and value therebetween) 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M).

[0272]

[0277] Aspect 85: The concentration of dissolved manganese ions in the first catholyte is 0.009M (optionally 0.01M, optionally 0.02M, optionally 0.03M, optionally 0.04M, optionally 0.05M, optionally 0.06M, optionally 0.07M, optionally 0.08M, optionally 0.09M, optionally 0.10M, optionally 0.11M, optionally 0.12M, optionally 0.13M, optionally 0.14M, optionally 0.15M, optionally 0.16M, optionally 0.17M, optionally 0.18M, ​​optionally 0.19M, optionally 0.20M, optionally 0.21M, optionally 0.22M, optionally 0.23M, optionally 0.24M, optionally 0.25M, optionally 0.26M, optionally 0.27M, optionally 0.28M, optionally 0.29M, optionally 0.30M, optionally 0.31M, optionally 0.32M, optionally 0.33M, optionally 0.34M, optionally 0.35M, optionally 0.36M, optionally 0.39M, optionally 0.40M, optionally 0.41M, optionally 0.44M, optionally 0.45M, optionally 0.46M ) ~ 1.3M (optionally 1.29M, optionally 1.28M, optionally 1.26M, optionally 1.25M, optionally 1.24M, optionally 1.23M, optionally 1.21M, optionally 1.20M, optionally 1.19M, optionally 1.16M, optionally 1.15M, optionally 1.14M, optionally 1.11M, optionally 1.10M, optionally 1.09M, optionally 1.06M, optionally 1.05M, optionally 1.04M, optionally 1.01M, optionally 1.00M, optionally 0.99M, optionally 0.98M, Optionally 0.96M, optionally 0.95M, optionally 0.94M, optionally 0.91M, optionally 0.90M, optionally 0.89M, optionally 0.86M, optionally 0.85M, optionally 0.84M, optionally 0.81M, optionally 0.80M, optionally 0.79M, optionally 0.76M, optionally 0.75M, optionally 0.74M, optionally 0.71M, optionally 0.70M, optionally 0.69M, optionally 0.66M, optionally 0.65M, optionally 0.64M, optionally 0.61M, optionally 0.85. The method or system of aspect 83 or 84, wherein the ionic strength is selected from the range of (any range and value therebetween is expressly contemplated and disclosed herein), optionally 0.60M, optionally 0.59M, optionally 0.56M, optionally 0.55M, optionally 0.54M, optionally 0.51M, optionally 0.50M, optionally 0.49M.

[0273]

[0278] Aspect 86a: A method of electrochemically producing metallic iron, comprising: first electroplating metallic iron from the first catholyte at a first cathode for an oxygen evolution reaction at a first anode in the presence of the first anolyte; During the first electroplating step, adding iron hydroxide to the first catholyte; Including, the first catholyte comprises dissolved iron ions; the first catholyte and the first anolyte are separated by an anion exchange membrane; The method, wherein the first electrochemical cell comprises a first cathode, a first catholyte, a first anode, and a first anolyte.

[0274]

[0279] Aspect 86b: A system for performing the method of aspect 86a.

[0275]

[0280] Aspect 86c: A system having components, parts, systems, subsystems, devices, features, etc. according to aspect 86a, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or any combination of components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of aspect 86a, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0276]

[0281] Aspect 87a: A method of producing a bisulfate solution, comprising: propelling a first sulfate salt solution into an acidification chamber of an electrochemical acid-base generating cell, the first sulfate salt solution having a known concentration of cations that are counterions to sulfate anions in the first sulfate salt solution; propelling the second sulfate solution into a basification chamber of an electrochemical acid-base generating cell, the basification chamber including a cathode electrode; applying a current across the cathode and anode of the cell at an applied magnitude, the current propelling protons into the acidification chamber at a rate directly proportional to the applied magnitude of the current; wherein the amount of current applied propels protons into the acidification chamber at a rate that does not exceed the rate of cations entering the acidification chamber; A method whereby a bisulfate solution is formed in the acidification chamber.

[0277]

[0282] Aspect 87b: A system for performing the method of aspect 87a.

[0278]

[0283] Aspect 87c: A system having components, parts, systems, subsystems, devices, features, etc. according to aspect 26a, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or any combination of components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of aspect 87a, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0279]

[0284] Aspect 88: The method or system of aspect 87, wherein 0.001 M or less sulfuric acid is formed in the acidification chamber.

[0280]

[0285] Aspect 89: The cation is a sodium cation (Na + ), lithium cation (Li + ), or potassium cation (K + 89. The method or system of embodiment 87 or 88, wherein

[0281]

[0286] Embodiment 90: The cation is an ammonium cation (NH + 89. The method or system of embodiment 87 or 88, wherein

[0282]

[0287] Embodiment 91: A method or system according to any one of embodiments 87 to 90, wherein the basic solution is generated in the basification chamber.

[0283]

[0288] Aspect 92: The method or system of any one of aspects 87-91, further comprising contacting a bisulfate solution with metallurgical slag material and leaching metal constituents of the metallurgical slag material in the bisulfate solution.

[0284]

[0289] Aspect 93: A method or system described in any one of aspects 87 to 92, wherein the step of applying an electric current to the anode and cathode of the electrochemical acid-base generating cell produces hydrogen gas at the cathode; extracts hydrogen gas from the hydrogen gas by directing it to the anode; and oxidizes the hydrogen gas to protons at the anode.

[0285]

[0290] Aspect 94: The method or system of aspect 93, wherein the anode is a gas diffusion anode.

[0286]

[0291] Embodiment 95: The method or system of any one of embodiments 87 to 94, wherein the electrochemical acid-base generating cell has three chambers: an acidification chamber, a basification chamber, and a hydrogen oxidation chamber comprising a hydrogen oxidation anode.

[0287]

[0292] Embodiment 96: The method or system of any one of embodiments 87 to 94, wherein the electrochemical acid-base generating cell is a two-chamber electrolytic cell.

[0288]

[0293] Aspect 97a: A method of extracting alumina from bauxite ore, comprising: dissolving the bauxite ore with a first acid to form a starting leach solution; the starting leach solution comprises at least one or more of dissolved aluminum ions, dissolved iron ions, and one or both of calcium ions and magnesium ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first leachate fraction; the one or more first precipitation products comprise precipitated aluminum hydroxide; second precipitating one or more second precipitation products from the first leachate fraction by combining a second base with the first leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated iron-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products comprise one or more precipitated calcium-containing products and / or one or more precipitated magnesium-containing products; dehydrating the precipitated aluminum hydroxide to form alumina (Al2O3); A method comprising:

[0289]

[0294] Aspect 97b: A system for performing the method of aspect 97a.

[0290]

[0295] Aspect 97c: A system having any combination of components, parts, systems, subsystems, devices, features, etc. according to aspect 97a, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or components, parts, subsystems, devices, features, etc. for facilitating or carrying out the processes and steps of aspect 97a, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0291]

[0296] Aspect 98: The method further comprising generating a product acid and a product base with an electrochemical acid-base generator; the first acid comprises a product acid; 98. The method or system of embodiment 97, wherein each of the first base, the second base, and the third base comprises a portion of a product base.

[0292]

[0297] Aspect 99: The method or system of aspect 97 or 98, comprising reducing ferric ions to ferrous ions in the starting leach solution prior to the first precipitating step.

[0293]

[0298] Aspect 100: The method or system of any one of aspects 97 to 99, comprising the step of crushing the bauxite ore to reduce its particle size prior to the step of dissolving the bauxite ore.

[0294]

[0299] Aspect 101: A method or system according to any one of aspects 97 to 100, comprising returning the third leachate fraction to the electrochemical acid-base generator and generating new acid and base from recovered salts in the third leachate fraction.

[0295]

[0300] Aspect 102: The method or system of any one of aspects 97 to 101, wherein the dehydrating step is performed using waste heat from a steel mill, a power plant, or an aluminum smelter.

[0296]

[0301] Embodiment 103: The method or system of any one of embodiments 97-102, further comprising refining the precipitated alumina to aluminum metal in an aluminum smelting process.

[0297]

[0302] Embodiment 104: The method or system of any one of embodiments 97 to 103, further comprising the steps of heating the at least one precipitated hydroxide to dehydrate the at least one precipitated hydroxide, collecting water released during the dehydration, and returning the collected water to the electrochemical acid-base generator, wherein the heating step is optionally performed using waste heat from a steel mill, a power plant, or an aluminum smelter.

[0298]

[0303] Aspect 105: The method or system of any one of aspects 97 to 104, wherein the returned residual leachate solution is neutralized before being returned.

[0299]

[0304] Aspect 106: A method or system described in any one of aspects 97 to 105, wherein the dehydrating step further includes condensing water vapor produced by the dehydration and recycling the condensed water to the electrochemical acid-base generator.

[0300]

[0305] Embodiment 107: A method or system according to any preceding embodiment, wherein at least 50%, optionally at least 75%, optionally at least 85%, optionally at least 90%, optionally at least 95%, optionally at least 99% of the dissolved iron ions are ferrous ions.

[0301]

[0306] Aspect 108: A component, part, system, subsystem, device, feature, etc. according to any preceding aspect or any combination of the preceding aspects, such as but not limited to electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or a system having any combination of components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) of any preceding aspect or any combination of the preceding aspects, such as but not limited to electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0302]

[0307] Aspect 109: A component, part, system, subsystem, device, feature, etc. according to any preceding aspect or any combination of the preceding aspects, such as but not limited to electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or a system having any combination of components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) of any preceding aspect or any combination of the preceding aspects, such as but not limited to electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0303]

[0308] Aspect 110: A system having any combination of components, parts, systems, subsystems, devices, features, etc. described herein and / or shown in any one or combination of Figures 1-8, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) described herein and / or shown in any one or combination of Figures 1-8, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0304]

[0309] Aspect 111: A system having any combination of components, parts, systems, subsystems, devices, features, etc. shown in FIG. 1 , such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) shown in FIG. 1 , such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0305]

[0310] Aspect 112: A system having any combination of components, parts, systems, subsystems, devices, features, etc. shown in FIG. 2 , such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) shown in FIG. 2 , such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0306]

[0311] Aspect 113: A system having any combination of components, parts, systems, subsystems, devices, features, etc. shown in FIG. 3 , such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) shown in FIG. 3 , such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0307]

[0312] Aspect 114: A system having any combination of components, parts, systems, subsystems, devices, features, etc. shown in FIG. 4, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc., and / or components, parts, subsystems, devices, features, etc. for facilitating or performing the process(es) and / or step(s) shown in FIG. 4, such as, but not limited to, electrochemical cell(s), tank(s), vessel(s), chamber(s), fluid connection(s), dryer(s), heater(s), mixer(s), reactor(s), etc.

[0308]

[0313] Embodiment 115: A system or method according to any preceding embodiment, wherein the electrochemical acid-base generator, if present, is according to FIG. 4 or any combination of its embodiments.

[0309]

[0314] Embodiment 116: The system or method according to any preceding embodiment, wherein the first electrochemical cell, if present, is according to FIG. 5 or any combination of its embodiments.

[0310]

[0315] Embodiment 117: A system or method according to any preceding embodiment, wherein the electrochemical acid-base generator, if present, is according to FIG. 6 or any combination of its embodiments.

[0311]

[0316] Embodiment 118: A system or method according to any preceding embodiment, wherein the electrochemical acid-base generator, if present, is according to FIG. 7 or any combination of its embodiments.

[0312]

[0317] Embodiment 119: A system or method according to any preceding embodiment, optionally comprising the cell of FIG. 8 or any combination of its embodiments.

[0313] INCORPORATION-BY-REFERENCE AND MODIFICATION STATEMENT

[0318] All references throughout this application, such as patent documents, published patent applications, including issued or granted patents or equivalents, and non-patent documents or other materials, are incorporated by reference in their entirety, to the extent that each reference is at least partially inconsistent with the disclosure in this application, as if each were individually incorporated by reference (e.g., a partially inconsistent reference is incorporated by reference except for the partially inconsistent portion of the reference).

[0314]

[0319] The terms and expressions used herein are used for purposes of description and not limitation, and there is no intention in the use of such terms and expressions to exclude any equivalents of the shown and described features or portions thereof, recognizing that various modifications are possible within the scope of any particular claimed invention. Thus, while the present invention has been specifically disclosed by preferred embodiments, exemplary embodiments, and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be made by those skilled in the art, and that such modifications and variations are considered to be within the scope of the present invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the invention, and it will be apparent to one skilled in the art that the invention can be practiced using numerous variations of the devices, device components, and method steps described herein. As will be apparent to one skilled in the art, the methods and devices useful in the methods of the present invention may include numerous optional compositions and process elements and steps.

[0315]

[0320] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to a "cell" includes a plurality of such cells and equivalents thereof known to those skilled in the art. Similarly, "a" (or "an"), "one or more," and "at least one" can be used interchangeably herein. It should also be noted that the terms "comprise," "include," and "have" can also be used interchangeably. The phrase "as defined in any of claims XX-YY" (where XX and YY refer to claim numbers) is intended to provide multiple alternative dependent claims and, in some embodiments, can be interchanged with the phrase "as defined in any one of claims XX-YY."

[0316]

[0321] When a group of substituted components is disclosed herein, it is understood that all individual members of that group and all subgroups, including ore iron oxide materials, or structural and compositional polymorphs of the group members, are separately disclosed. When a Markush group or other grouping is used herein, it is intended that all individual members of that group, and all possible combinations and subcombinations of that group, are individually included in the disclosure. When a compound is described herein, e.g., in a formula or chemical name, such that a specific isomer, enantiomer, or diastereomer of the compound is not specified, the description is intended to include each isomer and enantiomer of the described compound, individually or in any combination. Furthermore, unless otherwise specified, all isotopic variations of the compounds disclosed herein are intended to be encompassed by the disclosure. For example, it is understood that any one or more hydrogens in a disclosed molecule may 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. The particular names of the compounds are intended as examples, as it is known that one of skill in the art can refer to the same compound by different names.

[0317]

[0322] With respect to salts of the compounds herein, one skilled in the art can select from a wide variety of available counterions appropriate for preparing the salts of the invention for a given application. In a particular application, the selection of a given anion or cation for preparing a salt may result in an increase or decrease in the solubility of the salt.

[0318]

[0323] All devices, systems, subsystems, methods, processes, components, and / or combinations of components described or illustrated herein can be used to practice any claimed invention(s), unless stated otherwise.

[0319]

[0324] When a range is given herein, such as a temperature range, a time range, or a composition or concentration range, all intermediate and subranges, as well as all individual values ​​included in the given range, are intended to be included in the disclosure. It is understood that any subrange or individual value included in a range or subrange described herein can be excluded from the claims herein.

[0320]

[0325] All patents and publications mentioned in the specification are indicative of the level of skill of those skilled in the art to which the disclosed devices, systems, methods, and processes pertain. It is intended that the references cited herein are incorporated by reference in their entirety to represent the state of the art as of their publication or filing date, and that this information can be used, if necessary, to exclude certain embodiments that fall within the prior art. For example, if a composition of matter is claimed, it should be understood that compounds that were known and available in the art prior to Applicant's invention, including compounds for which enabling disclosures are provided in the references cited herein, are not intended to be included within the scope of the composition of matter claims herein.

[0321]

[0326] As used herein, "comprising" is synonymous with "including," "containing," or "featuring," and is inclusive or open-ended, not excluding additional, unrecited elements or method steps. As used herein, "consisting of" excludes any element, step, or ingredient not specified in the claimed 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 all instances herein, "comprising," "consisting essentially of," and "consisting of" are interchangeable with either of the other two terms. The claimed invention(s) illustratively described herein can be suitably practiced in the absence of element(s), limitation(s) not specifically disclosed herein.

[0322]

[0327] Those skilled in the art will understand that starting materials, reagents, synthetic, purification, analytical and assay methods, other than those specifically exemplified, can be used in the practice of the claimed invention without undue experimentation. All art-known functional equivalents of any such materials and methods are intended to be included in this invention.

Claims

1. 1. A method for recycling a first slag, comprising: dissolving the first slag with a first acid to form a starting leach solution; the starting leach solution comprising at least dissolved aluminum ions, dissolved iron ions, dissolved magnesium ions, and dissolved manganese ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first pre-plating leachate fraction; the one or more first precipitation products comprise one or more precipitated aluminum-containing products; the first pre-plating leachate fraction comprising dissolved iron ions, magnesium ions and manganese ions; first electroplating metallic iron from the first pre-plating leachate fraction using a first electrochemical cell to form electroplated metallic iron and a first post-plating leachate fraction; the first post-plating leachate fraction having a reduced concentration of the iron ions compared to the first pre-plating leachate fraction; second precipitating one or more second precipitation products from the first post-plating leachate fraction by combining a second base with the first post-plating leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated manganese-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products comprising one or more precipitated magnesium-containing products; A method comprising:

2. 10. The method of claim 1, wherein the first electrochemical cell comprises a first electroplating catholyte, the first electroplating catholyte including the first pre-plating leachate fraction such that the first electroplating catholyte includes the dissolved iron ions, magnesium ions, and manganese ions.

3. 3. The method of claim 2, including the step of separately doping iron hydroxide into the first electroplating catholyte.

4. the first electroplating catholyte comprising: Dissolved magnesium ions having a concentration selected from the range of 0.01 M to 1.2 M; Dissolved manganese ions having a concentration selected from the range of 0.01 M to 1.2 M, and / or Dissolved calcium ions having a concentration selected from the range of 0.01M to 1.2M The method of claim 2 or 3, comprising:

5. 5. The method of any one of claims 1 to 4, wherein the step of first electroplating metallic iron is carried out in response to an electrochemical oxygen evolution reaction at a first anode.

6. a first electrochemical cell comprising: a first anode in the presence of a first anolyte; a first cathode in the presence of a first electroplating catholyte; and an anion exchange membrane separating the first electroplating catholyte from the first anolyte; 6. The method of claim 5, wherein the first electroplating catholyte comprises the first pre-plating leachate fraction and the metallic iron is electroplated at the first cathode.

7. further comprising generating a product acid and a product base in an electrochemical acid-base generator; the first acid comprises the product acid; The method according to any one of claims 1 to 6, wherein each of the first base, the second base, and the third base comprises a portion of the product base.

8. returning the neutralized salt solution to the electrochemical acid-base generator; regenerating the product acid and the product base from the neutralized salt solution via the electrochemical acid-base generator; The method of claim 7, comprising:

9. 9. The method of any one of claims 1 to 8, further comprising the step of first providing at least a portion of the first, second, and / or third precipitation products to a steelmaking furnace, with or without further processing.

10. 10. The method of claim 9, wherein the providing step comprises converting the at least a portion of the provided first, second, and / or third precipitation products to a respective metal product and / or metal oxide product, and then providing the converted respective metal product and / or metal oxide product to the steelmaking furnace.

11. 11. The method of any one of claims 1 to 10, wherein the third precipitation product comprises magnesium hydroxide and / or calcium hydroxide, and the method comprises converting the magnesium hydroxide and / or calcium hydroxide to magnesium oxide and / or calcium oxide, respectively, and providing the magnesium oxide and / or calcium oxide as a flux to a steelmaking furnace.

12. collecting fresh steel slag from the steelmaking furnace; repeating the method using the new steel slug; The method according to any one of claims 9 to 11, comprising:

13. 13. The method of claim 12, including dissolving the new steel slag in the first or second acid to form a new starting leach solution.

14. The method of any one of claims 1 to 13, including providing at least a portion of the electroplated metallic iron to a steelmaking furnace.

15. 15. The method of any one of claims 1 to 14, comprising generating at least a portion of each of the first acid, the second acid, the first base, the second base, and the third base using an electrochemical acid-base generator.

16. 16. The method of any one of claims 1 to 15, comprising first collecting at least a portion of spent catholyte from the first electroplating step; and concentrating the collected spent catholyte.

17. 17. The method of claim 16, wherein the spent catholyte has a dissolved iron ion concentration selected from the range of 0.2M to 1M prior to the concentrating step.

18. 18. The method of claim 16 or 17, comprising, after the step of concentrating, Mn-precipitating one or more precipitated manganese-containing products from the concentrated spent catholyte.

19. 20. The method of claim 18, wherein the second precipitating step comprises the step of precipitating Mn, and wherein the step of precipitating Mn comprises combining the concentrated spent catholyte with the first post-plating leachate fraction and the base.

20. removing a bleed stream from the first electroplating catholyte; The method of any one of claims 1 to 19, comprising:

21. concentrating the removed bleed stream by reducing its water content; fourth precipitating one or more fourth precipitation products from the concentrated bleed stream by adding a fourth base; and wherein the one or more fourth precipitation products comprise magnesium.

22. 22. The method according to any one of the preceding claims, wherein the concentration of dissolved magnesium ions in the first pre-plating leachate fraction is selected from the range of 0.01M to 1M.

23. 23. The method of any one of claims 1 to 22, wherein the concentration of the dissolved manganese ions in the first pre-plating leachate fraction is selected from the range of 0.01M to 1M.

24. 1. A method for recycling a first slag, comprising: dissolving the first slag with a first acid to form a starting leach solution; the starting leach solution comprises at least one or more of dissolved aluminum ions, dissolved iron ions, and dissolved calcium and / or magnesium ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first leachate fraction; the one or more first precipitation products comprise one or more precipitated aluminum-containing products; second precipitating one or more second precipitation products from the first leachate fraction by combining a second base with the first leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated iron-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products comprising one or more precipitated calcium-containing products and / or one or more precipitated magnesium-containing products; Including, generating a product acid and a product base in an electrochemical acid-base generator; further comprising the first acid comprises the product acid; The method, wherein the first base, the second base, and the third base each comprise a portion of the product base.

25. returning the neutralized salt solution to the electrochemical acid-base generator; regenerating the product acid and the product base from the neutralized salt solution via the electrochemical acid-base generator; 25. The method of claim 24, further comprising:

26. 1. A method for recycling a first slag, comprising: dissolving the first slag with a first acid to form a starting leach solution; the starting leach solution comprises at least one or more dissolved aluminum ions, dissolved iron ions, and one or more dissolved calcium ions and / or magnesium ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first leachate fraction; the one or more first precipitation products comprise one or more precipitated aluminum-containing products; second precipitating one or more second precipitation products from the first leachate fraction by combining a second base with the first leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated iron-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products comprising one or more precipitated calcium-containing products and / or one or more precipitated magnesium-containing products; Including, providing at least a portion of the one or more third precipitation products to a steelmaking furnace as a flux, and / or reducing at least a portion of the precipitated iron-containing products to metallic iron and using the metallic iron in the steelmaking furnace; collecting fresh steel slag from the steelmaking furnace; repeating the method using the new steel slug; The method further comprises:

27. 27. The method of claim 26, comprising providing at least a portion of the one or more third precipitation products as a flux to a steelmaking furnace.

28. 28. The method of claim 26 or 27, wherein the third precipitation product comprises magnesium hydroxide and / or calcium hydroxide; the method comprises converting the magnesium hydroxide and / or calcium hydroxide to magnesium oxide and / or calcium oxide, respectively; and the providing step comprises providing the magnesium oxide and / or calcium oxide to the steelmaking furnace as the flux.

29. 29. The method of any one of claims 26 to 28, comprising reducing at least a portion of the precipitated iron-containing product to metallic iron and using the metallic iron in the steelmaking furnace.

30. 30. A method according to any one of claims 26 to 29, comprising dissolving the fresh steel slag in the first acid or the second acid to form a fresh starting leach solution.

31. 31. The method of any one of claims 26-30, comprising generating at least a portion of each of the first acid, the second acid, the first base, the second base, and the third base using an electrochemical acid-base generator.

32. 32. The method of any one of claims 1 to 31, wherein the dissolving step comprises separating undissolved solids from the starting leach solution; and the undissolved solids comprise silica, titania, and / or calcium sulfate.

33. 33. The method of claim 32, wherein the undissolved solids comprise calcium sulfate; and the method further comprises physically separating the calcium sulfate from other undissolved solids and re-dissolving the separated calcium sulfate to form solid precipitated calcium hydroxide and aqueous dissolved sulfate.

34. 34. The method of claim 33, comprising returning the aqueous dissolved sulfate to an electrochemical acid-base generator.

35. 35. The method of any one of claims 1 to 34, comprising, prior to said step of melting said first slag, a step of grinding said first slag to reduce its particle size.

36. 35. The method of claim 34, including magnetically separating and removing magnetic components from the pulverized slag prior to the step of melting the first slag.

37. 37. The method of any one of claims 1 to 36, wherein the first acid comprises one or more weak acids.

38. 38. The method of any one of claims 1 to 37, wherein the first acid comprises an aqueous bisulfate acid.

39. 39. The method of claim 38, wherein the aqueous bisulfate acid comprises alkali bisulfate, ammonium bisulfate, or a combination thereof.

40. 40. The method of claim 38 or 39, wherein the aqueous bisulfate acid is generated using an electrochemical acid-base generator.

41. 41. The method of any one of claims 1 to 40, wherein the first acid comprises sulfuric acid.

42. 42. The method of any one of claims 1 to 41, wherein the first acid comprises hydrochloric acid.

43. 43. The method of any one of claims 1 to 42, comprising reducing ferric ions to ferrous ions in the starting leach solution prior to the first precipitation step.

44. 44. The method of claim 43, wherein the step of reducing ferric ions to ferrous ions is performed electrochemically.

45. 45. The method of claim 43 or 44, wherein the step of reducing ferric ions to ferrous ions is carried out chemically by providing the ferric ions in the presence of a reducing agent.

46. 46. ​​The method of claim 45, wherein the reducing agent is metallic iron, steel, or another iron-containing metal.

47. 47. The method of any one of claims 43 to 46, wherein the step of reducing ferric ions to ferrous ions comprises recirculating the leach solution between a dissolution vessel and a cathode chamber of an electrochemical acid regeneration cell configured to reduce the ferric ions to ferrous ions at a cathode while generating oxygen gas at an anode to release protons which are transported to the leach solution in the cathode chamber.

48. 48. The method of any one of claims 1 to 47, wherein the first base, the second base, the third base, or any combination thereof comprises calcium hydroxide, ferric hydroxide, ferrous hydroxide, metallic iron, and / or magnesium hydroxide.

49. 49. The method of any one of claims 1 to 48, wherein each of the first precipitating step, the second precipitating step, the third precipitating step, or any combination thereof, is conducted at a liquid temperature selected from the range of 50°C to 90°C.

50. the one or more precipitated aluminum-containing products comprise aluminum hydroxide; the one or more precipitated iron-containing products comprise iron(II) hydroxide (ferrous hydroxide); the one or more precipitated calcium-containing products comprise calcium hydroxide; 50. The method of any one of claims 1 to 49, wherein the one or more precipitated magnesium-containing products comprise magnesium hydroxide.

51. 51. The method of any one of the preceding claims, wherein the one or more first precipitation products also comprise one or more precipitated chromium-containing products.

52. 52. The method of any one of claims 1 to 51, wherein the one or more first precipitation products also comprise one or more precipitated phosphorus-containing products or one or more precipitated phosphate-containing products.

53. 53. The method of any one of claims 1 to 52, wherein the one or more second precipitation products also comprise one or more precipitated manganese-containing products.

54. 54. The method of any one of the preceding claims, wherein the starting leach solution has a pH of less than 2.

5.

55. 55. The method of any one of claims 1 to 54, wherein the first leachate fraction has a pH selected from the range of 2.5 to 4.

5.

56. 56. The method of any one of claims 1 to 55, wherein the second leachate fraction has a pH selected from the range of 6.5 to 9.

57. 57. The method of any one of claims 1 to 56, wherein the third leachate fraction has a pH selected from the range of 9.5 to 13.

58. the one or more first, second, and / or third precipitation products comprise a metal hydroxide product; the method further comprising: dehydrating at least a portion of said metal hydroxide to form respective metal oxide products.

58. The method of any one of claims 1 to 57, further comprising:

59. 60. The method of claim 58, including using at least a portion of the formed metal oxide product as at least a portion of a flux in the steelmaking furnace.

60. 60. The method of claim 59, wherein the formed metal oxide product comprises magnesium oxide, calcium oxide, and / or aluminum oxide.

61. 61. The method of any one of claims 58 to 60, wherein the first precipitation product comprises magnesium hydroxide, and the method comprises dehydrating the magnesium hydroxide to form magnesium oxide, and using the formed magnesium oxide as at least part of the flux in the steelmaking furnace.

62. 60. The method of any one of claims 57 to 59, wherein the third precipitation product comprises calcium hydroxide, the method comprising dehydrating the calcium hydroxide to form calcium oxide, and using the formed calcium oxide as at least part of the flux in the steelmaking furnace.

63. 63. The method of any one of claims 58 to 62, wherein the second precipitation product comprises iron hydroxide, and the method comprises dehydrating the iron hydroxide to form iron oxide, reducing the iron oxide to metallic iron, and using the formed metallic iron in the steelmaking furnace.

64. The one or more precipitated aluminum-containing products comprise aluminum hydroxide; the method further comprises dehydrating the precipitated aluminum hydroxide to produce alumina (Al ２ O ３ 64. The method of any one of claims 1 to 63, further comprising forming alumina from aluminium smelting process.

65. 65. A method according to any one of claims 58 to 64, wherein the dewatering step is carried out using waste heat from a steel mill or a power plant.

66. The one or more magnesium-containing products may be Mg(OH) ２ wherein the one or more calcium-containing products are Ca(OH) ２ wherein the method comprises: ２ and / or Ca(OH) ２ CO ２ and MgCO ３ and / or CaCO ３ 66. The method of any one of claims 1 to 65, comprising forming

67. The CO ２ 67. The method of claim 66, wherein the containing gas is at a temperature of at least 200°C during said contacting step.

68. The CO ２ 68. The method of claim 66 or 67, wherein the contained gas is exhaust or flue gas from the steelmaking furnace.

69. MgCO ３ and / or CaCO ３ 69. The method of any one of claims 66 to 68, further comprising using as a flux in the steelmaking furnace.

70. 70. The method of any one of claims 1 to 69, wherein the steelmaking furnace is an electric arc furnace.

71. 71. The method of any one of claims 1 to 70, wherein the first slag is a steel slag or an iron slag.

72. 72. The method of any one of the preceding claims, wherein the first slag is ladle slag.

73. The one or more precipitated calcium-containing products are Ca(OH) ２ wherein the process comprises: ２ with silica, alumina, and iron; and heating to form a clinker.

74. The one or more second precipitation products are magnetite (Fe ３ O ４ 74. The method of any one of claims 24 to 73, comprising:

75. 75. The method of claim 74, comprising reducing the precipitated magnetite to iron and providing the reduced iron to a steelmaking furnace.

76. 76. The method of any one of claims 24 to 75, comprising redissolving at least a portion of the one or more metal salts to create a redissolved iron salt solution; and further comprising first electroplating metallic iron from the redissolved iron salt solution.

77. 77. The method of claim 76, comprising first collecting at least a portion of spent electrolyte from said first electroplating step, and first re-precipitating Fe-containing and / or Mn-containing salts from said collected spent electrolyte.

78. 78. The method of claim 76 or 77, comprising the steps of first collecting at least a portion of the spent electrolyte from the first electroplating step; concentrating the collected spent electrolyte to reduce its water content; second electroplating metallic iron from the concentrated spent electrolyte; second collecting at least a portion of the spent electrolyte from the second electroplating step; and first re-precipitating Fe-containing and / or Mn-containing salts from the second collected spent electrolyte.

79. The one or more precipitated iron-containing products are Fe(OH) ２ 79. The method of any one of claims 24 to 78, comprising:

80. Fe(OH) ２ to produce FeO.

81. 81. The method of any one of claims 24 to 80, wherein the one or more iron-containing products comprise iron hydroxide; and the method comprises the step of thermally reducing the iron hydroxide to iron metal.

82. 82. The method of claim 81, comprising using the ferrous metal to make steel in a steelmaking furnace.

83. 1. A method for electrochemically producing metallic iron in the presence of dissolved magnesium and dissolved manganese, comprising: first electroplating metallic iron from the first catholyte at a first cathode for an oxygen evolution reaction at a first anode in the presence of the first anolyte; the first catholyte comprising dissolved iron ions, dissolved magnesium ions, and dissolved manganese ions; the first catholyte and the first anolyte are separated by an anion exchange membrane; A first electrochemical cell comprises the first cathode, the first catholyte, the first anode, and the first anolyte.

84. 84. The method of claim 83, wherein the concentration of dissolved magnesium ions in the first catholyte is selected from the range of 0.01 M to 1 M.

85. 85. The method of claim 83 or 84, wherein the concentration of the dissolved manganese ions in the first catholyte is selected from the range of 0.01M to 1M.

86. 1. A method for electrochemically producing metallic iron, comprising: first electroplating metallic iron from the first catholyte at a first cathode for an oxygen evolution reaction at a first anode in the presence of the first anolyte; during the step of first electroplating, adding iron hydroxide to the first catholyte; Including, the first catholyte comprises dissolved iron ions; the first catholyte and the first anolyte are separated by an anion exchange membrane; A first electrochemical cell comprises the first cathode, the first catholyte, the first anode, and the first anolyte.

87. 1. A method for producing a bisulfate solution, comprising: propelling a first sulfate solution into an acidification chamber of an electrochemical acid-base generating cell, the first sulfate solution having a known concentration of cations that are counterions to sulfate anions in the first sulfate solution; propelling the second sulfate solution into a basification chamber of an electrochemical acid-base generating cell, the basification chamber including a cathode electrode; applying an electric current at an applied magnitude across the cathode and anode of the cell, the electric current propelling protons into the acidification chamber at a rate directly proportional to the applied magnitude of the electric current; Including, the amount of current applied propels protons into the acidification chamber at a rate that does not exceed the rate at which the cations enter the acidification chamber; A method whereby a bisulfate solution is formed in said acidification chamber.

88. 88. The method of claim 87, wherein no more than 0.001 M sulfuric acid is formed in the acidification chamber.

89. The cation is a sodium cation (Na ＋ ), lithium cation (Li ＋ ), or potassium cation (K ＋ 89. The method of claim 87 or 88, wherein

90. The cation is an ammonium cation (NH ４ ＋ 89. The method of claim 87 or 88, wherein

91. 91. The method of any one of claims 87 to 90, wherein a basic solution is generated in the basification chamber.

92. 92. The method of any one of claims 87 to 91, further comprising contacting the bisulfate solution with metallurgical slag material and leaching metal constituents of the metallurgical slag material into the bisulfate solution.

93. 93. The method of any one of claims 87 to 92, wherein the step of applying a current to the anode and cathode of the electrochemical acid-base generating cell produces hydrogen gas at the cathode; removes the hydrogen gas from the anode by directing the hydrogen gas to the anode; and oxidizes the hydrogen gas to the protons at the anode.

94. 94. The method of claim 93, wherein the anode is a gas diffusion anode.

95. 95. The method of any one of claims 87 to 94, wherein the electrochemical acid-base generating cell has three chambers: the acidification chamber, the basification chamber, and a hydrogen oxidation chamber comprising a hydrogen oxidation anode.

96. The method of any one of claims 87 to 94, wherein the electrochemical acid-base generating cell is a two-chamber electrolysis cell.

97. 1. A method for extracting alumina from bauxite ore, comprising: dissolving the bauxite ore with a first acid to form a starting leach solution; the starting leach solution comprising at least one or more of dissolved aluminum ions, dissolved iron ions, and one or both of calcium ions and magnesium ions; first precipitating one or more first precipitation products from the starting leach solution by combining a first base with the starting leach solution to increase its pH, thereby forming a first leachate fraction; the one or more first precipitation products comprise precipitated aluminum hydroxide; second precipitating one or more second precipitation products from the first leachate fraction by combining a second base with the first leachate fraction to increase its pH, thereby forming a second leachate fraction; the one or more second precipitation products comprise one or more precipitated iron-containing products; third precipitating one or more third precipitation products from the second leachate fraction by combining a third base with the second leachate fraction to increase its pH, thereby forming a third leachate fraction; the one or more third precipitated products comprising one or more precipitated calcium-containing products and / or one or more precipitated magnesium-containing products; The precipitated aluminum hydroxide is dehydrated to obtain alumina (Al ２ O ３ forming a A method comprising:

98. generating a product acid and a product base in an electrochemical acid-base generator; the first acid comprises the product acid; 98. The method of claim 97, wherein each of the first base, the second base, and the third base comprises a portion of the product base.

99. 99. The method of claim 97 or 98, comprising reducing ferric ions to ferrous ions in the starting leach solution prior to the first precipitating step.

100. 100. A method according to any one of claims 97 to 99, comprising crushing the bauxite ore to reduce its particle size prior to said step of smelting the bauxite ore.

101. 101. The method of any one of claims 97-100, comprising returning the third leachate fraction to the electrochemical acid-base generator and generating new acids and bases from recovered salts in the third leachate fraction.

102. 102. The method of any one of claims 97 to 101, wherein the dehydrating step is performed using waste heat from a steel mill, a power plant, or an aluminium smelter.

103. 103. The method of any one of claims 97 to 102, further comprising refining the precipitated alumina to aluminium metal in an aluminium refining process.

104. 104. The method of any one of claims 97-103, further comprising heating at least one precipitated hydroxide to dehydrate said at least one precipitated hydroxide, collecting water released during dehydration, and returning said collected water to said electrochemical acid-base generator, wherein said heating is optionally performed using waste heat from a steel mill, a power plant, or an aluminum smelter.

105. 105. The method of any one of claims 97 to 104, wherein the returned residual leach solution is neutralized before being returned.

106. 106. The method of any one of claims 97-105, wherein the dehydrating step further comprises condensing water vapor produced by the dehydration and recycling the condensed water to the electrochemical acid-base generator.

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