Extraction metallurgical process using molten salt eutectics

Abstract

This invention relates to a method for extracting metals from metal ores, the method comprising the steps of: (i) leaching the ore to provide a metal salt, (ii) forming a eutectic system containing the metal salt, and (iii) recovering the metal from the eutectic system by electrolytic deposition, preferably electrodeposition. The method of this invention is particularly applicable to iron ores, especially for separating iron from hematite ore; however, the invention can be used to extract multiple metals from various other metal ores.

Description

Technical Field

[0001] This invention relates to the field of ore processing.

[0002] In one form, the present invention relates to processing metal ores to separate the metals.

[0003] In one particular aspect, the present invention is applicable to the separation of iron from iron ore.

[0004] For convenience, the invention will be described below in conjunction with iron ore, particularly the separation of iron from hematite ore; however, it should be understood that the invention is not limited thereto, but is applicable to a variety of metal ores and a variety of metals. Background Technology

[0005] It should be understood that any discussion of documents, devices, operations, or knowledge in this specification is for the purpose of explaining the background of the invention. Furthermore, the discussions throughout this specification stem from the inventor's knowledge and / or understanding of certain related technical problems. In addition, any discussion of materials (such as documents, devices, operations, or knowledge) in this specification is included and is based on the inventor's knowledge and experience to explain the background of the invention; therefore, any such discussion should not be construed as an admission that any material constituted part of the prior art or common general knowledge in the relevant field in Australia or elsewhere on or before the priority date of this invention and the claims.

[0006] Iron ore is a metallic ore that typically contains iron oxides, primarily in the forms of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), and limonite (FeO(OH)·). n H2O or siderite (FeCO3). Almost all (98%) of iron ore is used for steelmaking.

[0007] Iron is typically recovered from iron ore using pyrometallurgical methods or extractive metallurgy. Extractive metallurgical techniques are generally classified into three categories: hydrometallurgy, pyrometallurgy, and electrometallurgy (including electrolytic refining and electrolytic deposition). Many of these methods utilize high operating temperatures and are inefficient.

[0008] The term "leaching" originates from the Old English word leccan, meaning "to water," and is a common method in metallurgy for extracting metals. It involves treating metal ores with water and reagents to convert the metals in the ore into soluble salts, while insoluble impurities remain in the ore. The soluble salts are then washed out and processed to provide pure metals; the remaining portion is called "tailings."

[0009] For example, some industrial extraction methods extract iron from iron ore by applying hot acid to the ore. Iron oxides generally have low solubility in water but good solubility in acids. The leaching efficiency of common acids decreases in the following order: hydrofluoric acid > hydrochloric acid > sulfuric acid > perchloric acid. For a given acid, the main factors affecting iron dissolution are temperature, pH, acid concentration, specific surface area, chemical composition, and crystallization properties.

[0010] In industrial processes, acids can be used at high temperatures. For example, hydrochloric acid is typically used with iron ore at temperatures above 750°C.

[0011] United Steel Companies Limited's U.S. Patent Application No. 2,723,912 describes a method for leaching iron in the form of ferric chloride using hot hydrochloric acid gas. The ferric chloride can then be treated with a reducing agent (such as hydrogen) to produce metallic iron and fresh hydrochloric acid gas, which can be used to distill more ferric chloride from the fresh ore according to the following chemical equation:

[0012] Fe2O3+ HCl → 2FeCl3+ 3H2O…Formula (1)

[0013] 2FeCl3 + 3H2 → 2Fe + 6HCl … Equation (2)

[0014] However, as described in U.S. Patent Application No. 2,723,912, such methods have several drawbacks, such as the formation of water vapor during the chlorination reaction, which leads to the formation of an aqueous hydrochloric acid solution and a moist, viscous ferric chloride hydrate. Under certain conditions, unwanted ferrous chloride (FeCl2) and ferric chloride oxychloride (FeOCl) may be formed. Furthermore, both reactions are reversible, resulting in an equilibrium mixture in the gas phase and tending to prevent either reaction from completing completely.

[0015] Other drawbacks associated with the prior art include high operating temperatures and the adverse effects of side reactions present in aqueous electrolytic deposition systems. Summary of the Invention

[0016] One object of the present invention is to provide a more commercially convenient method for extracting metals from metal ores, particularly iron from iron ore.

[0017] Another object of the present invention is to mitigate at least one disadvantage associated with related technologies.

[0018] One objective of the embodiments described herein is to overcome or mitigate at least one of the aforementioned disadvantages of the relevant technical system, or at least to provide a useful alternative to the relevant technical system.

[0019] In a first aspect of the embodiments described herein, a method for extracting metals from metal ores is provided, comprising the following steps:

[0020] (i) Leaching the ore to provide metal salts,

[0021] (ii) Formation of a eutectic system containing metal salts, and

[0022] (iii) Recover metals from eutectic systems by means of electrolytic deposition and preferred electrodeposition.

[0023] Preferably, the method for extracting metal from metal ore includes the following steps:

[0024] (i) Leaching the ore to provide metal halide salts,

[0025] (ii) Forming a eutectic system comprising a metal halide salt and one or more alkali metal halides or alkaline earth metal halides, and

[0026] (iii) Recover metals from eutectic systems by means of electrolytic deposition and preferred electrodeposition.

[0027] Metal ores

[0028] It will be apparent to those skilled in the art that various ores can be processed according to the present invention. Preferably, the ores used in the present invention are selected from one or more of the following: iron ores, including hematite, goethite, magnetite, titanomagnetite, and pisiform iron ore; aluminum-bearing ores, including bauxite, cryolite, and corundum; gold ores, including gold polysulfides, gold quartz, gold tellurides, gold-tetradymite, gold antimony, gold bismuth sulfide minerals, gold-pyrrhotite, and gold-tetradymite; and manganese-bearing ores, such as barite, manganese bauxite, and malachite. Rhodochrosite; lead ore, including galena, cerussite, and lead sulfate; zinc ore, including calamine and smithsonite; cobalt-bearing ore; uranium-bearing ore; copper-bearing ore, including chalcopyrite, malachite, cuprite, and chalcocite; nickel-bearing ore, such as laterite deposits and magmatic sulfide deposits; titanium-bearing ore; tungsten-bearing ore; silicon-bearing ore; rare earth-bearing ore; chromium-bearing ore; silver-bearing ore, such as argentite; tin-bearing ore, such as cassiterite, tinstone, stannite, or cylindrical cassiterite; heavy sands and quartz.

[0029] In a preferred embodiment, the ore is iron ore, particularly magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), and limonite (FeO(OH)· n Iron ore in the form of H2O or siderite (FeCO3).

[0030] It is preferred to use the method of the present invention to extract a single metal; however, the simultaneous extraction of more than one metal is also considered to be within the scope of the present invention.

[0031] Leaching

[0032] Preferably, the metal is leached by a strong oxidizing agent (such as an acid or a halide gas). For example, the leaching agent may be selected from liquid or gaseous forms of HF, HCl, HBr, HI, F2, Br2, or Cl2.

[0033] The presence of halogenated acids or halide gases, such as Cl2 or HCl, is particularly preferred. Furthermore, the metal salts extracted by leaching are preferably metal halides.

[0034] When the metal is iron, the preferred metal halide leached from the ore is an iron halide, such as iron(III) fluoride or iron(III) chloride. Iron(III) fluoride is extremely stable with a melting point greater than 1000°C, but iron(III) chloride is more economically feasible in synthesis and for downstream processing. Iron(III) chloride is also much more stable than its equivalent bromide salts, reflecting the stronger oxidizing power of chlorine. Above 200°C, FeBr3 decomposes into ferrous bromide according to the following formula:

[0035] 2FeBr3→ 2FeBr2+ Br2 (Formula 3)

[0036] Ferric bromide (III) is more stable than ferric iodide (III) because iron (III) tends to oxidize iodide ions.

[0037] Eutectic

[0038] A eutectic system is a homogeneous mixture with a melting point lower than that of its components. In addition to metal salts, the eutectic systems of this invention contain salts, such as halide salts.

[0039] For example, in addition to metal salts extracted by leaching, the eutectic system may contain one or more salts selected from the following: NaCl, KCl, LiCl, CaCl2, MgCl2, MnCl2 or other alkali metal halides and alkaline earth metal halides.

[0040] The optimal composition of a eutectic system will depend on the composition at or near the eutectic point, and those skilled in the art can determine a suitable eutectic system from the phase diagram of the eutectic mixture.

[0041] When selecting components for a eutectic system, an important consideration is their reduction voltage. The support salt (i.e., the salt that forms a eutectic system with the metal halide feedstock but is not reduced itself) must have a higher reduction voltage than the metal halide feedstock used as the electrodeposition metal source. Failure to meet this requirement will lead to side reactions, consumption of the support salt, and product contamination.

[0042] When the metal is iron, the preferred eutectic system comprises ferric halides (such as ferric chloride (III)) and alkali metal chlorides or alkaline earth metal chlorides. Eutectic systems comprising ferric chloride (III) and common alkali metal chlorides (such as NaCl, KCl, or LiCl) are particularly preferred because they have relatively low melting temperatures, typically between 150°C and 200°C. Eutectic systems formed from ferric chloride (III) and calcium chloride (II) are particularly advantageous because they melt at ambient temperature and exhibit low hygroscopicity.

[0043] In a eutectic system comprising FeCl3 and NaCl, based on the relevant phase diagram, the eutectic system preferably comprises 40% to 60% (molar) NaCl, more preferably about 50% NaCl. Alternatively, for CaCl2 and FeCl3, based on the relevant phase diagram, the eutectic system preferably comprises 30% to 60% (molar) CaCl2, more preferably about 50% CaCl2.

[0044] In all cases, the presence of the second salt prevents the undesirable formation of gaseous FeCl3, which sublimates at high temperatures. Compared to FeCl3, some other salts in the NaFeCl4 and eutectic mixtures have moderate hygroscopicity and are therefore preferred because of the lower risk of water absorption during electrolytic deposition, which could potentially lead to the formation of hydrogen and oxygen.

[0045] Combinations of ferric chloride (III) with divalent metal chlorides (such as MnCl2, NiCl2, MgCl2) are not preferred because they only exhibit moderate or no eutectic system characteristics.

[0046] When the metal is aluminum, the preferred eutectic system includes aluminum halides (such as aluminum chloride (III)) and alkali metal chlorides or alkaline earth metal chlorides.

[0047] In another aspect of the embodiments described herein, a metal recovered using the method of the present invention is provided.

[0048] Other aspects and preferred forms disclosed in the specification and / or defined in the appended claims form part of this specification.

[0049] Essentially, the embodiments of this invention stem from the understanding that combining known processes for dissolving / converting metals in metal ores with electrolytic deposition from molten salt eutectic systems can greatly enhance these processes. In particular, the dissolution / conversion process for iron oxides to salts (such as FeCl3) can be significantly enhanced by combining it with electrolytic deposition from molten chloride salt solutions. It is noteworthy that while prior art utilizes HCl to dissolve iron ore and hydrogen to reduce FeCl3 to Fe, this invention utilizes an electrochemical method.

[0050] The advantages provided by this invention include:

[0051] This method allows for an integrated anhydrous system (loop), thereby eliminating the risk of generating byproducts hydrogen and oxygen at the cathode and anode, respectively.

[0052] • Metal eutectic systems allow for a high percentage of the target metal ion species to participate in the electrodeposition process. This is fundamentally different from aqueous systems (e.g., copper production), where the molar concentration of the electrolytic deposition solution is typically limited to the millimolecular range due to the risk of deposition. It also differs from most molten salt electrolytic deposition methods, where only a small amount of the target metal species is added to the non-depositional salt (e.g., aluminum electrolytic deposition) (eutectic system). Therefore, this eliminates diffusion limitations and provides a basis for very high current densities;

[0053] Electrolytic reduction in eutectic systems can significantly reduce the temperature, especially compared to traditional pyrometallurgical methods, which typically require temperatures exceeding 1000°C.

[0054] Chlorination is a well-established method that has been successfully tested on a variety of iron-bearing ores. Therefore, this method provides a general approach applicable to variations in ore composition (mineralogy) and ore quality (iron content).

[0055] • During the electrodeposition process, chlorine gas released at the anode can be captured and recovered to produce more metal chloride salts; and

[0056] Chlorination is selective for metals, so silica impurities will not consume chlorine and will not become impurities in the harvested metal (as in the case of blast furnace methods or direct reduction of iron (DRI) methods).

[0057] The further applicability of the embodiments of the present invention will become apparent from the detailed description given below. However, it should be understood that while the detailed description and specific examples indicate preferred embodiments of the invention, they are given by way of illustration only, as various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art based on this detailed description. Attached Figure Description

[0058] Those skilled in the art can better understand the preferred embodiments and other embodiments of this application, as well as their further disclosures, purposes, advantages, and aspects, by referring to the following description of the embodiments in conjunction with the accompanying drawings. The drawings are for illustrative purposes only and therefore do not constitute a limitation on the disclosure herein.

[0059] · Figure 1 A schematic diagram illustrating the electrochemical method for producing iron according to the present invention;

[0060] Figure 2 shows FeCl3-NaC-Cl2 ( Figure 2A ), FeCl3-KCl-Cl2 ( Figure 2B ) and FeCl3-LiCl-Cl2 ( Figure 2C Phase diagrams of eutectic systems are provided for reference.

[0061] Figure 3 shows CaCl2-FeCl3-Cl2 ( Figure 3A ), FeCl3-MgCl2-Cl2 ( Figure 3B ) and FeCl3-MnCl2-Cl2 ( Figure 3C Phase diagrams of eutectic systems are provided for reference.

[0062] · Figure 4 Cyclic voltammetry was performed at 250 °C in a 1:1 (molar) FeCl3-NaCl eutectic system with a steel cathode and a graphite rod anode. The scan rate used in this measurement was 100 mV / s.

[0063] · Figure 5 Cyclic voltammetry was performed at 200 °C in a 1:1:1 (molar) FeCl3-NaCl-CaCl2 eutectic system with a steel cathode and a graphite rod anode. The scan rate used in this measurement was 100 mV / s.

[0064] · Figure 6 This is a flowchart illustrating the extraction of two different metals from the same ore using chlorine leaching and electrolytic deposition from two different molten salts;

[0065] · Figure 7 To illustrate a flowchart of an embodiment of the present invention, a process is provided for producing iron from iron ore using molten NaFeCl4 as the electrolyte for electrolytic deposition.

[0066] · Figure 8 The phase diagram of the CaCl2-NaCl eutectic system is shown for reference;

[0067] Figure 9 shows the equilibrium phase diagram between water and alkali metal chlorides or alkaline earth metal chlorides for reference. Figure 9A The phase diagram between water and NaCl; Figure 9B A phase diagram between water and potassium salt (KCl in its natural mineral form); Figure 9C A phase diagram of water and CaCl2; Figure 9D The phase diagram between water and MgCl2; and

[0068] · Figure 10 The theoretical reduction voltage versus temperature relationship is shown for various alkali metal chlorides and alkaline earth metal chlorides, as well as ferric chloride, aluminum chloride, alumina, hematite, magnetite, and water.

[0069] Figures 2 and 3 Figure 8 Copied from FactSage™ thermochemistry software and database. Detailed Implementation

[0070] The specific apparatuses and methods shown in the accompanying drawings and described in the following specification are merely exemplary embodiments of the inventive concept defined in the appended claims. Therefore, specific dimensions and other physical features associated with the embodiments disclosed herein should not be considered limiting unless expressly stated otherwise in the claims.

[0071] This invention provides a method for extracting metals (such as iron) from metal ores, the method comprising the following steps:

[0072] (i) The ore is usually leached with acid (such as HCl) or halide gas (such as Cl2) to form metal salts (such as ferric chloride (III)).

[0073] (ii) Forming a eutectic system comprising a metal salt, preferably combined with a common alkali metal chloride (such as sodium chloride), and

[0074] (iii) Recover metals from eutectic systems by electrodeposition.

[0075] Reference to extracting iron from ores containing Fe2O3, in Figure 1 The reaction of the present invention is illustrated in the figure. In this case, chlorine gas at a temperature greater than 400°C is applied to the ore to extract iron in the form of ferric chloride (III), which combines with NaCl to form a eutectic system. The eutectic system undergoes electrolytic deposition, causing Fe to be deposited from the molten eutectic system onto the cathode. Chlorine gas is formed at the anode and can be returned to the extraction step.

[0076] In a particularly preferred embodiment, iron ore is leached with HF to form ferric fluoride (III), or with HCl or Cl2 to form ferric chloride (III), both of which readily form eutectic systems with a variety of alkali metal chlorides or alkaline earth metal chlorides.

[0077] Eutectic systems containing ferric chloride (III) and common alkali metal halides (such as NaCl, KCl, or LiCl) are particularly preferred because they have relatively low melting temperatures, typically 150°C to 200°C. Figure 2 shows the phase diagram of the FeCl3-NaCl-Cl2 eutectic system. Figure 2A The eutectic system of FeCl3-KCl-Cl2 ( Figure 2B The phase diagram is provided for reference.

[0078] The eutectic system formed by ferric chloride (III) and calcium chloride (II) is particularly advantageous because they melt at ambient temperature.

[0079] In all cases, the presence of the second salt prevents the formation of gaseous FeCl3 that sublimates at high temperatures. Figure 3 shows the phase diagram of the CaCl2-FeCl3-Cl2 eutectic system. Figure 3A Phase diagram of the eutectic system of FeCl3-MgCl2-Cl2 ( Figure 3B (This is for reference only.)

[0080] Combinations of ferric chloride (III) with divalent metal chlorides (such as MnCl2, NiCl2, MgCl2) are not preferred because they only exhibit moderate or no eutectic system characteristics.

[0081] Regarding the leaching step, chlorination extraction can be used not only for iron ore but also for a wider range of other metallic ores. This includes oxides and ores of aluminum, copper, tin, zinc, cobalt, and nickel, where chlorination typically occurs in the range of 700°C to 1000°C.

[0082] However, extracting chlorine from other metal-bearing ores may differ from extracting chlorine from iron ore. Several practical problems and biases with significant implications exist.

[0083] First, due to the different melting points of different chloride salts (listed below), an important difference arises:

[0084] - Aluminum chloride, at a pressure of 2 bar, sublimes at approximately 180°C and melts at 192°C;

[0085] -St chloride 245℃;

[0086] - Zinc chloride 290℃;

[0087] - Ferric chloride 307℃;

[0088] - Copper chloride at 620℃;

[0089] - Cobalt chloride 735℃; and

[0090] - Nickel chloride 1001℃.

[0091] The low melting temperature of some chlorides facilitates gaseous separation from the ore during leaching at moderate temperatures.

[0092] Secondly, it is possible to form deep eutectic systems with other chlorides, especially FeCl3 and AlCl3. Cobalt chloride and copper chloride both form eutectic systems with NaCl, and the melting temperature of this eutectic system is 375°C.

[0093] Third, most commercial ores of aluminum, tin, copper, nickel, and cobalt contain significantly more iron than the target metal. David John Milne (Newcastle University) successfully electrodeposited aluminum from pure molten aluminum chloride in the 1970s, but bauxite beneficiation (removal of iron species) prior to electrolytic deposition did not make the method commercially successful because iron deposition was not achieved at that time. The presence of iron in the ore is a common problem and further complicates the method because ferric chloride forms as an impurity during leaching. Therefore, utilizing high-value metal concentrates (such as cobalt / nickel ore) may help minimize the problem and further provide a pathway for separating cobalt and nickel.

[0094] Therefore, the melting point differences of various metal chlorides can be utilized to facilitate the separation of various metal chloride gases in a multi-step separator, or the various metal chlorides can be evaporated one by one by gradually increasing the temperature in a batch chlorination leaching step. In other words, two or more different metal chlorides can be extracted and electrolytically deposited separately to recover two different metals. Figure 6 This is an illustration of one such example. In this example, bauxite (containing iron and aluminum) is used as the feed to the chlorinator, and both iron and aluminum are produced by electrolytic deposition from separate electrolytic cells. In this example, both electrolytic deposition electrolytic cells utilize sodium chloride to form a eutectic system, thus limiting the possible formation of gaseous metal chlorides. However, as mentioned above, it is possible to electrodeposit aluminum metal from pure molten AlCl3 when moderate pressure is applied to the system.

[0095] It should be understood that some chloride salts (such as NiCl2 and CuCl2) that may be formed during the extraction step are not suitable as precursors for electrolytic deposition from molten chlorides. However, these salts may be valuable as commercial products or may be suitable metal salts for conventional aqueous electrolytic deposition methods.

[0096] Ferric chloride eutectic system

[0097] The practical range of iron-containing eutectic salt compositions is limited by the emission of gaseous FeCl3 (FeCl3 is known to readily sublimate). Preferably, the eutectic system forms in the portion of the relevant phase diagram that is richer in FeCl3 salts, where more precipitates will form.

[0098] For example, refer to Figure 2A The eutectic system of NaCl and FeCl3 preferably contains 40% to 60% (molar) NaCl, more preferably about 50% NaCl.

[0099] In another example, refer to Figure 3A The eutectic system of CaCl2 and FeCl3 preferably contains 30% to 60% (molar) of CaCl2, more preferably about 50% of CaCl2.

[0100] The temperature range is primarily limited at one end by the solidification temperature of the eutectic system, and at the other end by the temperature at which a large amount of FeCl3 gas may be generated. It should also be noted that ternary eutectic systems (such as NaCl, KCl, and FeCl3) can further lower the melting temperature.

[0101] Aluminum chloride eutectic system

[0102] Aluminum(III) chloride and NaCl (or KCl and LiCl) form a eutectic system similar to ferric chloride, but with a lower melting temperature of about 50 °C. The melting point of the eutectic system MCl-AlCl3 (M = Li+Na+K, M:Al = 1.31) has been reported to be only about 75 °C [Q.Pang, Nature 608, 704–711 (2022)].

[0103] In the case of a eutectic system containing AlCl3, there is a high chance of gaseous AlCl3 forming. Therefore, it is necessary to seek eutectic systems with very low melting temperatures and to operate electrolytic deposition electrolyzers with excess AlCl3.

[0104] Example

[0105] Example 1A: Electrolytic deposition of a eutectic system containing FeCl3-NaCl

[0106] Anhydrous FeCl3 was mixed with pre-dried NaCl (120°C) at a molar ratio of 1:1 and immediately heated to 250°C in a Teflon beaker to form a liquid eutectic system.

[0107] Electrolytic deposition of the eutectic system was performed using a low-carbon steel cathode and a glassy carbon anode at 250°C and 200°C.

[0108] At 250°C, iron electrodeposition begins when a voltage >2.8 V is applied, while at 200°C, a voltage greater than 3.0 V is required. These voltages represent significant overpotentials compared to the expected thermodynamic values. Existing literature indicates that high-density graphite is the most suitable anolyte for the chlorine precipitation reaction in molten chloride salts, which is expected to reduce the required potential to approximately -2.0 V.

[0109] Chlorine gas was detected above the anode, and the deposited iron was analyzed to have a purity of 94%.

[0110] Example 1B: Electrolytic deposition of a FeCl3-NaCl eutectic system

[0111] Anhydrous FeCl3 was mixed with pre-dried NaCl (200°C) at a molar ratio of 1:1 and immediately heated to 250°C in a glass beaker to form a molten eutectic system. The eutectic formation takes approximately 40 minutes without stirring.

[0112] Electrolytic deposition of the eutectic system was performed at 250°C using a low-carbon steel cathode and a graphite rod anode.

[0113] At 250°C, iron electrodeposition begins when a voltage exceeding 2.2 V is applied. These voltages represent a significant overpotential compared to the expected thermodynamic values. As previously mentioned, graphite is a suitable anolyte for the chlorine precipitation reaction in molten chloride salts, allowing for a reduced overpotential and reduction at -2.0 V to -2.2 V while achieving 25 mA / cm². 2 Up to 30 mA / cm 2 The current density range, such as Figure 4 As shown.

[0114] Chlorine gas was detected above the anode, and the deposited iron was analyzed to have a purity of 94%.

[0115] Example 1C: Electrolytic deposition of a FeCl3-CaCl2 eutectic system

[0116] In a separate experiment, anhydrous FeCl3 powder and anhydrous CaCl2 powder were mixed at a molar ratio of 2:1 and immediately heated to 100°C in a sealed Teflon container.

[0117] An hour later, a eutectic mixture was formed, and the temperature dropped to 70°C, where an attempt was made to use a low-carbon steel cathode and a graphite anode for electrodeposition.

[0118] Surprisingly, electrodeposition only occurs at very high overpotentials, from an applied electrolytic cell voltage of 4 V and below 5 mA / cm². 2The current begins to rise. This behavior is attributed to the high ion aggregation in the eutectic system, which effectively limits the number of free ions, thereby reducing the diffusion coefficient. The temperature is gradually increased to overcome these problems. At 200 °C, the current reaches 60 mA / cm². 2 Electrodeposition was performed at an electrolytic cell voltage of 2.1 V. However, significant evaporation of FeCl3 was observed under these conditions, which impaired the usefulness of the temperature rise.

[0119] A second mixture of FeCl3 and CaCl2 powders was prepared in a 1:1 molar ratio and heated to 200°C. A liquid phase formed above the calcium-rich solid particles in the slurry, thus reflecting the prediction of the phase diagram.

[0120] Electrodeposition was performed again at 200°C, yielding similar results to the 2:1 ratio, but no FeCl3 evaporation was detected. The deposited iron was washed three times in water at pH 12 to prevent corrosion, and then dried at 120°C.

[0121] Analysis confirmed that the sediment consisted of 93% iron, along with impurities of oxygen (2.5%), calcium (2.5%), and chlorine (2%). Scanning electron microscopy revealed particles rich in calcium and chlorine, indicating that the washing procedure used in the experiment was inadequate.

[0122] Example 1D: Electrolytic deposition of a FeCl3-NaCl-CaCl2 ternary eutectic system

[0123] In another experiment, a 1:1 molar ratio mixture of NaCl and CaCl2, pre-dried at 200°C, was mixed with anhydrous FeCl3 powder to form a 1:1:1 FeCl3-NaCl-CaCl2 molar ratio. The FeCl3 was at room temperature when it was added to a glass beaker to form a molten eutectic system. Without stirring, the eutectic formation took approximately 30 minutes.

[0124] like Figure 8 As shown, a NaCl-CaCl2 mixture with a molar ratio of 1:1 remains solid at 200°C. Adding only FeCl3 allows for the formation of a eutectic mixture at a given temperature.

[0125] The significant advantage of this ternary system is its significantly lower viscosity and faster formation of the eutectic system, which may be due to factors such as... Figure 2A , Figure 3A and Figure 8 The range of the eutectic system shown is significantly wider, and the tendency of ions to aggregate in the eutectic melt is lower.

[0126] Electrodeposition was performed at 200°C with a constant electrolytic cell voltage of 2.0 V applied. The corresponding current density was measured to be approximately 60 mA / cm². 2Electrodeposition was performed in a glass beaker using a low-carbon steel cathode and a graphite rod anode. The cyclic voltammetry is shown below. Figure 5 As shown.

[0127] The deposited iron was washed three times in water at pH 12 to prevent product corrosion, and then dried in an oven at 120°C.

[0128] Analysis confirmed that the sediment contained 96% iron and impurities of oxygen (1.7%), calcium (0.7%), sodium (0.3%), and chlorine (1.3%).

[0129] Example 2: Closed-loop method

[0130] This invention can be used in, for example Figure 7 The process is carried out in a “closed-loop” apparatus, wherein chlorine / chloride is circulated between chlorine leaching and electrolytic deposition methods.

[0131] At high temperatures (>700°C), iron ore in the form of hematite reacts with chlorine gas in a chlorinator to produce gaseous ferric chloride (III) and oxygen, as shown in the following reaction formula:

[0132] Fe₂O₃ + 3Cl₂ → 2FeCl₃ + 1.5O₂

[0133] In this method, chlorine is reduced to chloride, while oxygen in the ore is oxidized to dioxide. Silica impurities in the iron ore are not converted but are removed as solids from the bottom of the chlorinator. Alumina impurities are chlorinated in this method to form AlCl3, which then merges with the FeCl3 stream leaving the separator.

[0134] To avoid this, a two-step separator can be used, taking advantage of the fact that the vapor pressure of AlCl3 at 100°C is approximately 106 times that of FeCl3. Furthermore, the reduction potential of aluminum is significantly greater than that of iron; therefore, aluminum can be avoided in iron products by controlling the voltage applied in the electrolytic deposition cell.

[0135] In the separator, the gas stream from the chlorinator is cooled, and solid ferric chloride (III) is removed from the gaseous oxygen. For alumina-rich iron ore, further steps can be added to separate AlCl3 from FeCl3.

[0136] In an electrolytic deposition cell, a eutectic system is formed by adding molten NaFeCl4 (>160℃) to FeCl3. This eutectic system is used as the electrolyte in the electrolytic deposition cell. Chlorine gas is generated at the anode (according to formula 2Cl...). - →Cl2+2e - And metallic iron (according to formula, Fe) is deposited on the cathode. 3+ + 3e - →Fe0 ).

[0137] The FeCl3 from the separator is transferred to the electrolytic deposition cell to compensate for the generated metallic iron and chlorine gas. The generated chlorine gas is then reheated and recycled back to the chlorinator.

[0138] A similar closed-loop method can also be constructed using FeCl3 eutectic systems derived from other chloride salts.

[0139] Hydrophilic properties of eutectic systems

[0140] When selecting a eutectic system, an important consideration is the hydrophilicity of alkali metal halides, alkaline earth metal halides, and the electroreduced metal halides. The presence of water in a eutectic system leads to water decomposition side reactions, resulting in the production of hydrogen and oxygen, as well as the consumption of electrons. This undesirable side reaction significantly reduces the efficiency of metal electroreduction.

[0141] Figure 9 Figure 10 Figures 11 and 12 show equilibrium phase diagrams between water and alkali metal chlorides or alkaline earth metal chlorides. Although these phase diagrams are limited to four cases, a clear trend emerges. Alkali metal chlorides, particularly NaCl and KCl, require lower temperatures to completely dry and remove any residual water compared to alkaline earth metal chlorides. Furthermore, not only do alkaline earth metal chlorides (especially CaCl2 and MgCl2) require higher temperatures for dehydration, but dehydration is incomplete at temperatures exceeding 200°C. NaCl and KCl become anhydrous at temperatures of 108.7°C and 108.6°C, respectively. However, calcium chloride becomes a monohydrate (CaCl2·H2O) at 178°C, and magnesium chloride becomes a dihydrate (MgCl2·2H2O) at 192°C. Further dehydration requires significantly higher temperatures, which may affect the requirements for low electrolytic deposition temperatures. As previously mentioned, the presence of monohydrate or dihydrate species in the eutectic system leads to the formation of byproducts hydrogen and oxygen.

[0142] Based on the above observations, alkali metal halides, especially NaCl and KCl, appear to be better candidates for deep eutectic systems used in metal electrodeposition.

[0143] Reduction voltage characteristics of eutectic systems

[0144] When selecting components for a eutectic system, an important consideration is their reduction voltage. The carrier salt (i.e., the salt that forms a eutectic system with the metal halide feedstock, but is not necessarily reduced) must have a higher reduction voltage than the metal halide feedstock that serves as the source of the electrodeposition metal. Failure to meet this requirement will result in side reactions, consumption of the carrier salt, and product contamination.

[0145] Figure 10The variation of the theoretical reduction voltage with operating temperature is shown. It should be noted that these voltages will deviate due to variations in pressure, pH, electrode material selection, and other factors. In particular, the effect of overpotential has been explored to some extent in the provided examples. While the theoretical voltage required for the reduction of ferric chloride (III) at 200°C to 250°C is approximately -1.0 V, a voltage exceeding -2.0 V is actually required to facilitate the reduction of ferric chloride (III). The reasons behind this large potential difference require further exploration and understanding. However, to avoid being bound by theory, high viscosity is considered a possible limiting factor.

[0146] Figure 10 The scheme shown assumes the melting and boiling temperatures of the pure compounds illustrated in the figure. However, the formation of a eutectic system can lower the melting and boiling points of these substances, which also positively affects the reduction voltage, resulting in a slight decrease in the required reduction voltage.

[0147] For Example 2, Figure 6 and Figure 7 In the closed-loop system shown, the reduction voltage of aluminum(III) chloride is significantly higher than that of ferric(III) chloride. Therefore, if the applied voltage is reasonable and lower than the reduction voltage of aluminum(III) chloride, the electroreduction of ferric(III) chloride feedstock contaminated with aluminum(III) chloride should not lead to side reactions or iron product contamination. However, if the aluminum(III) chloride feedstock is contaminated with ferric(III) chloride, then Example 2, Figure 6 and Figure 7 The aluminum reduction circuit shown may result in side reactions and iron contamination of the aluminum product. This is purely due to the low reduction voltage of ferric chloride (III), which makes the reaction thermodynamically more favorable for ferric chloride (III).

[0148] For the same reason, some carrier salts may be incompatible with the metal salts used as raw materials. For example, Figure 10 The reduction voltages of aluminum chloride (III) and manganese chloride (II) are shown to be incompatible due to their similar reduction voltages, which could lead to manganese reduction side reactions and manganese contamination of aluminum products. Furthermore, aluminum chloride (III) and manganese chloride (II) form a eutectic system with a very narrow liquidus temperature window (this phase diagram is not included in this paper). This further questions whether they can co-form a suitable electroreduction environment.

[0149] Figure 10 The water splitting reaction, which releases hydrogen and oxygen, is shown to illustrate how closely the water splitting voltage correlates with various iron compounds. This also supports the claims made earlier in this paper regarding water pollution and water-related side reactions.

[0150] Figure 10Another clearly demonstrated advantage is the lower reduction voltage of metal halides compared to their oxide counterparts. At least in the case of iron, the reduction voltage of ferric chloride (III) is reduced by approximately 0.2 V compared to hematite (Fe₂O₃) and magnetite (Fe₃O₄). The benefit is even greater for aluminum. Depending on temperature, the reduction voltage difference between alumina (III) and aluminum chloride (III) can exceed 0.6 V.

[0151] Finally, salts such as lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), and calcium chloride (CaCl2) benefit from very wide electrochemical windows. This makes them suitable candidates as support salts for various metal halide eutectic systems.

[0152] Although the invention has been described in conjunction with its specific embodiments, it should be understood that further modifications are possible. This application is intended to cover any variations, uses, or modifications of the invention that generally follow the principles of the invention and include portions of the invention that are known or conventional in the field to which it pertains that deviate from its scope, as well as the essential features that may be applied as set forth above.

[0153] The invention can be embodied in various forms without departing from its essential spirit and characteristics. It should be understood that, unless otherwise specified, the above embodiments do not limit the invention, but should be interpreted broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects merely illustrative and not restrictive.

[0154] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of this invention and the appended claims. Therefore, the specific embodiments should be understood as illustrating many ways in which the principles of the invention can be practiced. In the following claims, the clauses for "means plus function" are intended to cover structures that perform the defined function, including not only structural equivalents but also equivalent structures.

[0155] When the Markush group or other groupings are used herein, all individual members of that group and all combinations and possible sub-combinations of those members are intended to be included individually in this invention. Unless otherwise stated, every combination of the components described or illustrated herein may be used to practice this invention.

[0156] Whenever a range is given in the specification, such as a temperature range, time range, or composition or concentration range, all intermediate ranges and sub-ranges, as well as all individual values ​​included within the given ranges, are intended to be included in the scope of this invention. It should be understood that any sub-range or individual value included in any range or sub-range in the specification may be excluded from the claims.

[0157] As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized in,” and is inclusive or open-ended, not excluding additional, unlisted elements or method steps. As used herein, “consisting of” excludes any element, step, or component not specified in the claim elements. As used herein, “substantially constitutes” does not exclude materials or steps that do not substantially affect the essential elements and novel features of the claim. The broad term “comprising” is intended to cover both the narrower “substantially constitutes” and the even narrower “consisting of.” Thus, in any recitation herein of the phrase “comprising one or more claim elements” (e.g., “comprising A”), the phrase is intended to cover the narrower, e.g., “substantially constitutes A” and “consisting of A.” Therefore, the broader term “comprising” is intended to provide specific support for “substantially constitutes” or “consisting of” in every use herein. The invention described illustratively herein may suitably be practiced without any elements or limitations not specifically disclosed herein.

[0158] Those skilled in the art will understand that, in addition to the materials and methods specifically illustrated, other materials and methods may be used in the practice of this invention without excessive experimentation. This invention is intended to include all known functional equivalents of any such materials and methods. The terms and expressions used are descriptive rather than restrictive, and their use is not intended to exclude any equivalents of the features shown and described or portions thereof, but rather to recognize that various modifications are possible within the scope of the invention as claimed. Therefore, it should be understood that although the invention has been specifically disclosed through embodiments, preferred embodiments, and optional features, modifications and variations of the concepts disclosed herein can be made by those skilled in the art, and such modifications and variations are considered to be within the scope of the invention as defined by the appended claims.

[0159] Each reference cited herein is incorporated herein by reference in its entirety. These references may provide sources of material, alternative materials, methodological details, and other uses of the invention.

Claims

1. A method for extracting metal from metal ore, comprising the following steps: (i) Leaching the metal ore to provide a metal salt, (ii) Forming a eutectic system comprising the metal salt and one or more alkali metal salts or alkaline earth metal salts, as well as (iii) Recovering metals from the eutectic system by electrolytic deposition.

2. The method of claim 1, wherein the metal is recovered from the eutectic system by electrodeposition.

3. The method according to claim 1, wherein the metal salt is a metal halide salt, the alkali metal salt is an alkali metal halide, and the alkaline earth metal salt is an alkaline earth metal halide.

4. The method according to claim 1 or 2, wherein the metal ore is selected from: iron ore, aluminum ore, gold ore, manganese ore, lead ore, zinc ore, cobalt ore, uranium ore, copper ore, nickel ore, titanium ore, tungsten ore, silicon ore, rare earth ore, chromium ore, silver ore, tin ore, heavy sand, and quartz.

5. The method according to claim 1 or 2, wherein the metal ore is an iron ore selected from the following: magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH)· n H2O and siderite (FeCO3).

6. The method according to claim 1 or 2, wherein the metal ore is leached by a leaching agent selected from HF, HCl, HBr, HI, F2, Br2 or Cl2 in liquid or gaseous form.

7. The method according to claim 1 or 2, wherein the eutectic system comprises one or more salts selected from the group consisting of NaCl, KCl, LiCl, CaCl2, MgCl2 or MnCl2.

8. The method according to claim 1 or 2, wherein (i) Leach the ore with a leaching agent to provide iron halide (III). (ii) Forming a eutectic system comprising the said iron halide (III) and one or more alkali metal halide or alkaline earth metal halide salts, and (iii) Iron is recovered from the eutectic system by electrolytic deposition.

9. The method according to claim 1 or 2, wherein the eutectic system contains an additional non-halide salt.

10. The method according to claim 1 or 2, wherein the recovery of metal from the eutectic system occurs at room temperature to 500°C.

11. The method according to claim 1 or 2, wherein the eutectic system comprises an alkali metal chloride, and the metal recovery from the eutectic system occurs at 110°C to 250°C.

12. The method according to claim 1 or 2, wherein the eutectic system comprises an alkaline earth metal chloride, and the metal recovery from the eutectic system occurs at 200°C to below 300°C.

13. The method according to claim 1 or 2, wherein one or more alkali metal halides or alkaline earth metal halides forming the eutectic system have a higher reduction voltage than metal halide salts.

14. The method according to claim 1 or 2, wherein water in the eutectic system is minimized to avoid side reactions during the electrolytic deposition process.

15. The method according to claim 1 or 2, wherein the eutectic system is selected from: FeCl3-NaCl, FeCl3-CaCl2, and FeCl3-NaCl-CaCl2.

16. A metal recovered using the method described in any one of the preceding claims.

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