WO2025118033A1

WO2025118033A1 - Extractive metallurgical process using molten salt eutectics

Info

Publication number: WO2025118033A1
Application number: PCT/AU2024/051320
Authority: WO
Inventors: Bjorn Winther-Jensen; Bartlomiej KOLODZIEJCZYK
Original assignee: Element Zero Pty Ltd
Current assignee: Element Zero Pty Ltd
Priority date: 2023-12-08
Filing date: 2024-12-06
Publication date: 2025-06-12
Anticipated expiration: 2026-06-08

Abstract

The invention relates to a method for the extraction of metal from metallic ores, the method including the steps of; (i) leaching the ore to provide a metal salt, (ii) forming a eutectic system comprising the metal salt, and (iii) recovering the metal from the eutectic system using electrowinning, preferably electrodeposition. The method of the present invention has particular application in respect of iron ore, particularly the isolation or iron from haematite ore, however the invention may be applied to extraction of a wide range of metal metals from a corresponding wide range of metal ores.

Description

Extractive Metallurgical Process Using Molten Salt Eutectics

FIELD OF INVENTION

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

[0002] In one form, the invention relates to processing metal ores to isolate metal.

[0003] In one particular aspect the present invention is suitable for isolation of iron from iron ore.

[0004] It will be convenient to hereinafter describe the invention in relation to iron ore, particularly the isolation or iron from haematite ore, however it should be appreciated that the present invention is not so limited but extends to a wide range of metal ores and a wide range of metals.

BACKGROUND ART

[0005] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor’s knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

[0006] Iron ore is a metal ore that typically comprises iron oxides, the primary forms of which are magnetite (FesC ) and haematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH)-/?H2O) or siderite (FeCOa). Almost all (98%) of iron ore is used in steelmaking. [0007] Iron is typically recovered from iron ore using a pyrometallurgical process or extractive metallurgy. Extractive metallurgy techniques are commonly grouped into three categories: hydrometallurgy, pyrometallurgy and electrometallurgy including electrorefining and electrowinning. Many of these processes use high operating temperatures and have high inefficiencies.

[0008] The term “leaching”, which originates from the Old English word leccan meaning ‘to water’, is a commonly used method in extractive metallurgy and comprises treating metal ore with water and reagents to convert the metal in the ore into soluble salts, while insoluble impurities remain in the ore. The soluble salts are then washed out and processed to provide the pure metal, the remainder being referred to as ‘tailings’.

[0009] For example, some extractive industrial processes mobilise iron from iron ore by applying hot acid to the ore. Iron oxides, in general, have low solubility in water and good solubility in acid, with the acid leaching efficiency of common acids decreasing in the following order: hydrofluoric acid > hydrochloric acid > sulfuric acid > perchloric acid. The main properties that influence iron dissolution for a given acid are temperature, pH, acid concentration, specific surface area, chemical composition, and crystalline habit.

[0010] In industrial processes the acid may be applied at high temperatures. For example, hydrochloric acid is typically applied to iron ore at temperatures greater than 750°C.

[0011] United States patent no. 2,723,912 to The United Steel Companies Limited describes one such process for leaching iron in the form of ferric chloride using hot hydrochloric acid gas. The ferric chloride may subsequently be treated with a reductant such as hydrogen gas to produce metallic iron and fresh hydrochloric gas, which can be used to distil more ferric chloride from fresh ore according to the following equations:

Fe20a + HCI — 2FeCh + 3H2O ... equation (1 ) 2FeCh + 3H2 — 2Fe + 6HCI ... equation (2)

[0012] However, as noted in United States patent no. 2,723,912, these types of processes have numerous drawbacks such as the formation of water vapour in the chlorination reaction, which can lead to the formation of aqueous hydrochloric acid and damp, sticky hydrates of ferric chloride. Under certain conditions, unwanted ferrous chloride (FeCh) and ferric oxychloride (FeOCI) may form. Furthermore, both reactions are reversible, which leads to the production of equilibrium mixtures in the gaseous phase and tends to prevent either reaction moving fully to completion.

[0013] Other disadvantages associated with the prior art include high operating temperature and the adverse effects of parasitic reactions present in aqueous electrowinning systems.

SUMMARY OF INVENTION

[0014] An object of the present invention is to provide a more commercially convenient method for extracting metals from metal ores, particularly extracting iron from iron ore.

[0015] A further object of the present invention is to alleviate at least one disadvantage associated with the related art.

[0016] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

[0017] In a first aspect of embodiments described herein there is provided a method for the extraction of metal from metallic ores including the steps of;

(i) leaching the ore to provide a metal salt,

(ii) forming a eutectic system comprising the metal salt, and

(iii) recovering the metal from the eutectic system using electrowinning, preferably electrodeposition. [0018] Preferably, the method for the extraction of metal from metallic ores including the steps of;

(i) leaching the ore to provide a metal halide salt,

(ii) forming a eutectic system comprising the metal halide salt and one or more alkali metal halides or alkaline earth metal halides, and

(iii) recovering the metal from the eutectic system using electrowinning, preferably electrodeposition.

Metal ores

[0019] It will be apparent to the person skilled in the art that a very wide range of ores can be processed according to the present invention. Preferably, ore for use in the present invention is chosen from the group comprising one or more of the following: iron ore including hematite, goethite, magnetite, titanomagnetite and pisolitic ironstone; aluminium containing ores including bauxite, cryolite and corundum; gold ores including gold-polysulfide, gold-quartz, gold-telluride, gold-tetradymite, gold-antimony, gold-bismuth-sulfosalt, gold-pyrrhotite, and gold-fahlore; manganese containing ores such as romanechite, manganite hausmannite and rhodochrosite; lead ores including galena, cerussite and anglesite; zinc ores including calamine and smithsonite; cobalt containing ores; uranium containing ores; copper containing ores including copper pyrite, malachite, cuprite and copper glance; nickel containing ores such as laterites and magmatic sulphide deposits; titanium containing ores; tungsten containing ores; silicon containing ores; rare earth containing ores; chromium containing ores; silver containing ores such as argentite; tin containing ores such as cassiterite, tinstone, stannite or cylindrite; heavy sands and quartz.

[0020] In a preferred embodiment the ore is iron ore, particularly in the form of magnetite (FesC ), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH)-/?H2O) or siderite (FeCOa).

[0021] Preferably a single metal is extracted using the process of the present invention, however extraction of more than one metal at the same time is also contemplated as being within the scope of the present invention. Leaching

[0022] Preferably the metal is leached by a highly oxidative reagent such as an acid or halide gas. For example, the leaching agent may be chosen from HF, HCI, HBr, HI, F2. Br2 or CI2 in liquid or gaseous form.

[0023] The presence of a halide acid or halide gas, such as CI2 or HCI, is particularly preferred. Concomitantly, the metal salt extracted by the leaching process is preferably a metal halide.

[0024] When the metal is iron, preferably the metal halide leached form the ore is an iron halide such as iron(lll) fluoride or iron(lll) chloride. Iron(lll) fluoride is extremely stable and has a melting point of >1000°C, however iron(lll) chloride is more economically viable to synthesis and to use in downstream processing. Iron(lll) chloride is also considerably more stable than the equivalent bromide salt, reflecting the greater oxidizing power of chlorine. Above 200°C, FeBra decomposes to ferrous bromide according to:

2FeBra - 2FeBr2 + Br2 equation (3)

[0025] Iron(lll) bromide is more stable than iron(lll) iodide because iron(lll) tends to oxidize iodide ions.

Eutectic

[0026] A eutectic system is a homogeneous mixture that has a melting point lower than the melting points of the components. In addition to the metal salt, the eutectic system of the present invention comprises salts, such as halide salts.

[0027] For example, in addition to the metal salt extracted by the leaching process, the eutectic system may include one or more salts chosen from NaCI, KCI, LiCI, CaCh, MgCh, MnCh or other alkali metal halides and alkaline earth metal halides.

[0028] The optimal composition of the eutectic system will depend on the composition at or near the eutectic system point and the person skilled in the art can identify a suitable eutectic system from the phase diagram for the eutectic system mixture.

[0029] An important consideration when selecting components of the eutectic system is their reduction voltage. Carrier salts; that is salts that form eutectic systems with metal halide feedstock but are not meant to be reduced; must have higher reduction voltage compared to metal halide feedstock that act as a source for electrodeposited metal. Failure to comply with this requirement will lead to parasitic reactions, consumption of carrier salts, and product contamination.

[0030] When the metal is iron, preferably the eutectic system comprises an iron halide, such as iron(lll) chloride, and an alkali metal chloride or alkaline earth metal chloride. Eutectic systems comprising iron(lll) chloride and common alkali metal chlorides such as NaCI, KCI or LiCI are particularly preferred because they have a relatively low melting temperature, typically 150 to 200°C. Eutectic systems formed from iron(lll) chloride with calcium(ll) chloride are particularly advantageous because they melt at ambient temperature and exhibit a low moisture uptake.

[0031] In a eutectic system comprising FeCh and NaCI, preferably the eutectic system comprises 40% to 60% NaCI (molar), more preferably -50% NaCI based on the relevant phase diagram. Alternatively, for CaCh and FeCh, based on the relevant phase diagram the eutectic system preferably comprises 30% to 60% CaCh (molar), more preferably -50% CaCh.

[0032] In all cases the presence of a second salt can prevent the unwanted formation of gaseous FeCh which undergoes sublimation at elevated temperatures. NaFeCk and some other salts of eutectic system mixtures are moderately hydroscopic compared to FeCh and are therefore preferred due to lower risk of water uptake and thereby the possibility of hydrogen and oxygen formation during the electrowinning process. [0033] Combinations of iron(lll) chloride with divalent metal chlorides such as (MnCh, NiCh, MgCh etc.) are not preferred because they show only moderate, or no eutectic system characteristics.

[0034] When the metal is aluminium, preferably the eutectic system comprises an aluminium halide, such as aluminium(lll) chloride, and an alkali metal chloride or alkaline earth metal chloride.

[0035] In another aspect of embodiments described herein there is provided a metal recovered using the method of the present invention.

[0036] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0037] In essence, embodiments of the present invention stem from the realization that the known process of dissolution/conversion of metal from metal ores can be greatly enhanced by combination with electrowinning from a molten salt eutectic system. In particular, the process of dissolution/conversion of iron oxides by conversion to a salt such as FeCh can be greatly enhanced by combination with electrowinning from a molten chloride salt solution. Notably, the prior art uses HCI for dissolving iron ore and hydrogen gas for the reduction of FeCh to Fe, whereas the present invention uses electrochemical means.

[0038] Advantages provided by the present invention comprise the following:

• the process allows an integrated water-free system (loop) thereby eliminating the risk of parasitic hydrogen and oxygen production at the cathode, and anode, respectively;

• the metal containing eutectic system has a high percentage of target metal ions species that can participate in the electrodeposition process. This is substantially different from aqueous systems (e.g., copper production) where the molarity of the electrowinning solution is often limited to the millimolar range due to risk of sedimentation. It is also different from most molten salt electrowinning processes where the target metal species are only added in small amount to (a eutectic system of) non-depositing salts (e.g., aluminium electrowinning). As such this removes diffusion limitations and provides the foundation for very high current densities;

• the electroreduction in eutectic systems allow for significant temperature reduction, in particular, when compared to traditional pyrometallurgical processes which often require temperatures in excess of 1000°C;

• chlorination is a well-established process and has been tested successfully on various iron-containing ores. It thereby provides a general approach, suitable for comping with variations in ore composition (mineralogy) and ore quality (iron content);

• chlorine gas evolved at the anode during electrodeposition process can be captured and recycled to produce more metal chloride salts; and

• the chlorination is selective for metals hence silica impurities will not consume chlorine and will not be an impurity in the metals harvested (as is the case with a blast furnace process or with the direct reduction of iron (DRI) process).

[0039] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which: • Fig. 1 is a diagram illustrating in general terms, the process of the present invention for the electrochemical production of iron;

• Fig. 2 illustrates, for reference, the phase diagrams for the eutectic systems of FeCh-NaC-Ch (Fig. 2A), FeCh-KCl-Ch (Fig. 2B) and FeCh-LiCI-Ch (Fig. 2C);

• Fig. 3 illustrates, for reference, the phase diagrams for the eutectic systems of CaCl2-FeCI₃-Cl2 (Fig. 3A), FeCh-MgCh-Ch (Fig. 3B) and FeCh-MnCh- Cl₂ (Fig. 3C);

• Fig. 4 is a cyclic voltammogram performed in 1 :1 molar eutectic system of FeCh-NaCI at 250°C with steel cathode and graphite rod anode. Scan rate used in this measurement was 100 mV/s;

• Fig. 5 is a cyclic voltammogram performed in 1 :1 :1 molar eutectic system of FeCh-NaCI-CaCh at 200°C with steel cathode and graphite rod anode. Scan rate used in this measurement was 100 mV/s.

• Fig. 6 is a flow diagram depicting the extraction of two different metals from the same ore using chlorine gas leaching and electrowinning from two different molten salts;

• Fig. 7 is a flow diagram depicting the production of iron from iron ore according to one embodiment of the present invention using molten NaFeCk as the electrolyte for the electrowinning;

• Fig. 8 illustrates, for reference, the phase diagram for the eutectic system of CaCI₂-NaCI;

• Fig. 9 depicts for reference, equilibrium phase diagrams between water and alkali metal chlorides or alkaline earth metal chlorides. Fig. 9A is between water and NaCI; Fig. 9B is between water and sylvite (KCI in natural mineral form); Fig. 9C is between water and CaCh; and Fig. 9D is between water and MgCh; and

Fig. 10 presents theoretical reduction voltages versus temperature for various alkali metal chlorides and alkaline earth metal chlorides as well as iron chloride, aluminium chloride, alumina, hematite, magnetite, water. [0041] Figs. 2, 3, and 8 are reproduced from FactSage™ thermochemical software and databases.

DETAILED DESCRIPTION

[0042] The specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

[0043] The present invention provides a method for the extraction of metal such as iron from metallic ores, the method including the steps of;

(i) leaching the ore, typically with an acid, such as HCI, or a halide gas, such as CI2, to form a metal salt such as iron(lll) chloride,

(ii) forming a eutectic system comprising the metal salt, preferably in combination with a common alkali chloride such as sodium chloride, and

(iii) recovering the metal from the eutectic system using electrodeposition.

[0044] The reaction according to the present invention is depicted diagrammatically in Fig. 1 with reference to the extraction of iron from an ore comprising Fe20a. In this case, chlorine gas at >400°C is applied to the ore, to extract the iron as iron(lll) chloride, which is combined with NaCI to form a eutectic system. The eutectic system is subjected to electrowinning, such that Fe is deposited from the molten eutectic system on to a cathode. Chlorine gas is formed at the anode and can be fed back into the extraction step.

[0045] In a particularly preferred embodiment, iron ore is leached with HF, to form iron(lll) fluoride, or leached with HCI, or CI2 to iron(lll) chloride, both of which readily form eutectic systems with many alkali metal chlorides or alkaline earth metal chlorides. [0046] Eutectic systems comprising iron(lll) chloride and common alkali metal halides, such as NaCI, KCI or LiCI, are particularly preferred because they have relatively low melting temperatures, typically 150 to 200°C. Fig. 2 illustrates for reference, the phase diagrams for the eutectic systems of FeCh-NaCI-Ch (Fig. 2A) and for the eutectic systems of FeCh-KCl-Ch (Fig. 2B).

[0047] Eutectic systems formed from iron(lll) chloride with calcium(ll) chloride are particularly advantageous because they melt at ambient temperature.

[0048] In all cases the presence of a second salt can prevent the formation of gaseous FeCh which undergoes sublimation at elevated temperatures. Fig. 3 illustrates for reference, the phase diagrams for the eutectic systems of CaCh-FeCh- CI2 (Fig. 3A) and for the eutectic systems of FeCh-MgCh-Ch (Fig. 3B).

[0049] Combinations of iron(lll) chloride with divalent metal chlorides such as (MnCh, NiCh, MgCh, etc.) are not preferred because they show only moderate, or no eutectic system characteristics.

[0050] With respect to the leaching step, chlorine extraction is possible not only with iron ores, but with a much larger range of other metal containing ores. This includes aluminium, copper, tin, zinc, cobalt and nickel oxides and ores where chlorination generally occurs in the 700°C to 1000°C range.

[0051] However, chlorine extraction from the other metal containing ores may differ from chlorine extraction from iron ores. There are a few practical issues and deviations which may be significant.

[0052] Firstly, one important difference arises due to the disparate melting points of the different chloride salts, listed below:

- aluminium chloride, which sublimes at about 180°C and melts at 192°C under 2 bar pressure;

- tin chloride 245°C; - zinc chloride 290°C;

- iron chloride 307°C;

- copper chloride 620°C;

- cobalt chloride 735°C; and

- nickel chloride 1001 °C.

[0053] The low melting temperature of some chlorides facilitates the gaseous separation from the ore during leaching at moderate temperatures.

[0054] Secondly, the formation of deep eutectic systems with other chlorides is possible, in particular with FeCh and AlCh. Cobalt chloride and copper chloride both form a eutectic system with NaCI, the eutectic systems having melting temperatures in the 375°C range.

[0055] Thirdly, most commercial ores of aluminium, tin, copper, nickel and cobalt contain significantly more iron than the target metal. Electrodeposition of aluminium from neat molten aluminium chloride was successfully pursued in the 1970’s by David John Milne (University of Newcastle), but beneficiation of bauxite (removal of iron species) prior to the electrowinning did not allow the method to gain commercial success as deposition of iron was not pursued at that stage. The presence of iron in the ores is a general issue and can further complicate the process because iron chloride will be formed as an impurity during leaching. Thus, it can be an advantage to use concentrates of high value metal - such as cobalt/nickel - ores to minimize the issue and further provide a route for separating cobalt and nickel.

[0056] As such, the difference in melting points of the various metal chlorides can be utilised to facilitate the separation of various metal chloride gases in a multi-step separator or by gradually increasing the temperature in a batch based chlorination leaching step to allow various metal-chlorides to evaporate one-by-one. In other words, two or more different metal chlorides can be extracted and separately subjected to electrowinning to recover two different metals. Fig. 6 is an illustration of one such example. In this example, bauxite ore (comprising both iron and aluminium) is used as feed into a chlorinator and both iron and aluminium are produced by electrowinning from separate cells. In this example both electrowinning cells use sodium chloride to form eutectic systems and thereby limit the possible formation of gaseous metal chlorides. However, as mentioned above, electrodeposition of aluminium metal from neat molten AlCh is possible when a moderate pressure is applied to the system.

[0057] It should be appreciated that some chlorine salts, that may be formed during the extraction step, are not suitable as precursors for electrowinning from molten chlorides (e.g. NiCh and CuCh). However, they may be valuable as a commercial product in their own right or may be suitable metal salts for use in conventional aqueous electrowinning processes.

Iron chloride eutectic systems

[0058] The practical range of iron containing eutectic system salt compositions is limited by the emission of gaseous FeCh. (FeCh is known to readily sublime). Preferably the eutectic system is formed in the more FeCh salt rich part of the relevant phase diagram, where more precipitate will form.

[0059] For example, with reference to Fig. 2A, a eutectic system of NaCI and FeCh will preferably comprise 40% to 60% NaCI (molar), and more preferably about 50% NaCI.

[0060] In another example, with reference to Fig. 3A, a eutectic system of CaCh and FeCh will preferably comprise 30% to 60% CaCh (molar), and more preferably -50% CaCh.

[0061] The temperature ranges are mainly limited at one end by the temperature at which the eutectic system solidifies, and at the other end by the temperature at which there is a significant chance of producing FeCh gas. It should also be noted that tertiary eutectic systems (e.g., NaCI, KCI, FeCh) may lower the melting temperatures further.

Aluminium chloride eutectic systems

[0062] Aluminium(lll) chloride and NaCI (or KCI and LiCI) form eutectic systems similar to those for iron chloride but with a melting temperature that is approximately 50°C lower. A eutectic system of formula MCl-AICh (M = Li+Na+K, M:AI = 1.31 ) has been reported with a melting point of only ~75°C [Q.Pang, Nature 608, 704-711 (2022)].

[0063] In the case of eutectic systems comprising AlCh the chance of gaseous AlCh formation is significant so pursuing eutectic systems with very low melting temperatures and running the electrowinning cell with excess of AlCh is essential.

EXAMPLES

EXAMPLE 1 A: Electrowinninq from FeCh-NaCI containing eutectic systems

[0064] Anhydrous FeCh was mixed with pre-dried NaCI (120°C) in a 1 :1 molar ratio and immediately heated to 250°C in a Teflon beaker to form a liquid eutectic system.

[0065] The eutectic system was subjected to electrowinning at 250°C and 200°C using a mild steel cathode and a glassy carbon anode.

[0066] At a temperature of 250°C the electrodeposition of iron commenced when a voltage of >2.8 V was applied whereas at 200°C more than 3.0 V was required. These voltages represent significant overpotentials compared to the expected thermodynamic values. Existing literature suggests that high density graphite is the most suitable anode material for the chlorine evolution reaction in molten chloride salts and it is expected that this will decrease the requisite potential to about -2.0 V.

[0067] Chlorine gas was detected over the anode and the iron deposited was analysed to be of 94% purity.

EXAMPLE 1 B: Electrowinninq from FeCh-NaCI containing eutectic systems

[0068] Anhydrous FeCh was mixed with pre-dried NaCI (200°C) in a 1 :1 molar ratio and immediately heated to 250°C in a glass beaker to form a molten eutectic system. Eutectic formation took about 40 minutes without stirring. [0069] The eutectic system was subjected to electrowinning at 250°C using a mild steel cathode and a graphite rod anode.

[0070] At a temperature of 250°C the electrodeposition of iron commenced when a voltage in excess of 2.2 V was applied. These voltages represent significant overpotentials compared to the expected thermodynamic values. As suggested before graphite is a suitable anode material for the chlorine evolution reaction in molten chloride salts, allowing to decrease the overpotential and perform the reduction at -2.0 V to -2.2 V, while reaching the current density range between 25 mA/cm² to 30 mA/cm², as seen in Fig. 4.

[0071] Chlorine gas was detected over the anode and the iron deposited was analysed to be of 94% purity.

EXAMPLE 1 C: Electrowinninq from FeCh-CaCh containing eutectic systems

[0072] In a separate experiment, anhydrous FeCh powder was mixed with anhydrous CaCh powder in a 2:1 molar ratio and immediately heated to 100°C in a closed Teflon container.

[0073] After one hour the eutectic system mixture had formed and the temperature was lowered to 70°C where electrodeposition was attempted using a mild steel cathode and a graphite anode.

[0074] Surprisingly, the electrodeposition only occurred at a very high overpotential starting at an applied cell voltage of 4 V and current below 5 mA/cm². This behaviour was ascribed to a large degree of ion clustering in the eutectic system, effectively limiting the number of free ions and thereby decreasing the diffusion coefficient. The temperature was gradually raised to overcome these issues. At 200°C, electrodeposition was performed at 2.1 V cell voltage at 60 mA/cm². However, under these conditions a significant evaporation of FeCh was observed, compromising the usefulness of the temperature increase. [0075] A second mixture of FeCh and CaCh powder was made with a 1 :1 molar ratio and heated to 200°C. A liquid phase formed atop a slurry of calcium rich solid particles, thereby reflecting the prediction of the phase diagram.

[0076] Electrodeposition was again performed at 200°C with similar outcome as for the 2:1 ratio however without any detectable evaporation of FeCh. The deposited iron was washed trice in water at pH 12 to prevent corrosion of the deposited iron then dried at 120°C.

[0077] Analysis confirmed the deposit to be 93% iron with impurities of oxygen (2.5%), calcium (2.5%) and chlorine (2%). Scanning electron microscopy revealed calcium and chlorine rich particles which suggest that the washing procedure used in the test was insufficient.

EXAMPLE 1 D: Electrowinninq from FeCh-NaCI-CaCh tertiary eutectic system

[0078] In another experiment, a pre-dried at 200°C mixture of NaCI and CaCh in a 1 :1 molar ratio was mixed with anhydrous FeCh powder forming 1 :1 :1 molar ratio of FeCh-NaCI-CaCh. The FeCh was at room temperature when added to a glass beaker to form a molten eutectic system. Eutectic formation took about 30 minutes without stirring.

[0079] As seen in Fig. 8, mixture of NaCI-CaCh in a molar ration of 1 :1 remains solid at 200°C. Only addition of FeCh allows to form eutectic system mixture at given temperature.

[0080] Visible advantage of this tertiary system was significantly lower viscosity and faster eutectic system formation, likely due to significantly broader eutectic system range as shown in Fig. 2A, Fig. 3A, and Fig. 8 and lower tendency of ion clustering in the eutectic system melt.

[0081] Electrodeposition was performed at 200°C by applying constant cell voltage of 2.0 V. The corresponding current density was measured to be about 60 mA/cm². Electrodeposition was performed in glass beaker using a mild steel cathode and a graphite rod anode. Cyclic voltammogram is presented in Fig. 5.

[0082] The deposited iron was washed trice in water at pH 12 to prevent product corrosion and subsequently dried in oven at 120°C.

[0083] Analysis confirmed the deposit to be 96% iron with impurities of oxygen (1.7%), calcium (0.7%), sodium (0.3%) and chlorine (1.3%).

EXAMPLE 2: Closed loop process

[0084] The present invention may be carried out in a “closed loop” set up as depicted diagrammatically in Fig. 7, wherein the chlorine/chloride is cycled between the chlorine leaching process and the electrowinning process.

[0085] Iron ore in the form of hematite was reacted in a chlorinator with chlorine gas at elevated temperature (>700°C) to produce gaseous iron(lll) chloride and oxygen according to the following equation:

Fe2O3 + 3CI2 — 2FeCh + 1 .502

[0086] In the process chlorine was reduced to chloride whereas the oxygen in the ore was oxidized to di-oxygen gas. Silica impurities from the iron ore were not converted and were removed as solids from the bottom of the chlorinator. Alumina impurities were chlorinated in the process to form AlCh and joined the FeCh stream exiting the separator.

[0087] To avoid this a two-step separator can be employed, taking advantage of the vapour pressure of AlCh being approximately -106 times that of FeCh at 100°C. Furthermore, the reduction potential of aluminium is significantly larger than the reduction potential of iron and aluminium could thus be avoided in the iron product by controlling the applied voltage in the electrowinning cell. [0088] At the separator, the gaseous stream from the chlorinator cooled, and solid iron(lll) chloride was removed from the gaseous oxygen. For alumina rich iron ores, a further step may be added to separate AlCh from FeCh.

[0089] In an electrowinning cell, a eutectic system was formed by adding molten NaFeCk (>160°C) to the FeCh. The eutectic system was used as the electrolyte in the electrowinning cell. At the anode chlorine gas was produced (according to the equation, 2CI- - CI2 + 2e^_) and metallic iron was deposited on the cathode (according to the equation Fe³⁺ + 3e^_ - Fe°).

[0090] The FeCh from the separator was transferred to the electrowinning cell to compensate for the metallic iron and chlorine gas produced. The chlorine gas produced was reheated and cycled back to the chlorinator.

[0091] Similar closed-loop processes using FeCh eutectic systems from other chlorine salts can also be constructed.

Water affinity characteristics of the eutectic system

[0092] An important consideration when selecting the eutectic system is the water affinity of alkali metal halides, alkaline earth metal halides and metal halides which are being electroreduced. Presence of water in the eutectic system can lead to parasitic reactions of water splitting, which result in hydrogen and oxygen generation and consumption of electrons. This undesired secondary reaction effectively reduces the efficiency of metal electroreduction.

[0093] Figs. 9, 10, 11 and 12 depict an equilibrium phase diagram between water and alkali metal chlorides or alkaline earth metal chlorides. While these phase diagrams are limited to four instances, a clear trend emerges. Alkali metal chlorides, in particular NaCI and KCI, require lower temperatures to fully dry and remove any residual water, compared to alkaline earth metal chlorides. In addition, not only alkaline earth metal chlorides (particularly CaCh and MgCh) require higher temperature to dehydrate, but the dehydration is incomplete at temperatures in excess of 200°C. NaCI and KCI become anhydrous at temperatures of 108.7°C and 108.6°C, respectively. However, in the case of CaCh it becomes a monohydrate (CaCl2-H2O) at 178°C, and MgCh become a dihydrate (MgCl2-2H2O) at 192°C. Further dehydration requires substantial increase in temperature, which could jeopardize the low electrowinning temperature claims. As previously mentioned, having monohydrate or dihydrate species in the eutectic system can lead to parasitic hydrogen and oxygen formation.

[0094] Based on the above observations, alkali metal halides, in particular NaCI and KCI, seem to be much better candidates for deep eutectic systems used for metal electrodeposition.

Reduction voltage characteristics of characteristics of the eutectic system

[0095] An important consideration when selecting components of the eutectic system is their reduction voltage. Carrier salts; that is salts that form eutectic systems with metal halide feedstock, but are not meant to be reduced; must have higher reduction voltage compared to metal halide feedstock that act as a source for electrodeposited metal. Failure to comply with this requirement will lead to parasitic reactions, consumption of carrier salts, and product contamination.

[0096] Theoretical reduction voltages as function of operating temperature are shown in Fig. 10. It is important to mention that these voltages shift due to change in pressure, pH, electrode material selection, and other factors. In particular, the effect of overpotential was already explored to some extent in the examples provided. While the theoretical voltage required to reduce iron(lll) chloride is about -1 .0 V at 200°C to 250°C, in practice voltage in excess of -2.0 V was required to facilitate the reduction of iron (111) chloride. The reason behind this fairly large potential is yet to be better explored and understood. However, without wishing to be bound by theory, it is believed that high viscosity might be a limiting factor.

[0097] The scenarios presented in Fig .10 assume melting and boiling temperatures for pure compounds presented in this figure. However, formation of eutectic systems allows to reduce melting and boiling points of these species, this also positively impacts the reduction voltage enabling a slight decrease of required reduction voltage. [0098] When it comes to a closed loop system presented in Example 2, and Figs. 6 and 7, the reduction voltage for aluminium(lll) chloride is considerably higher than reduction voltage for iron(lll) chloride. As such, electroreduction of iron(lll) chloride feedstocks contaminated with aluminium(lll) chloride should not result in parasitic reactions or iron product contamination if applied voltage is reasonable and below reduction voltage of aluminium(lll) chloride. However, the aluminium reduction loop presented in Example 2, and Figs. 6 and 7, will likely experience parasitic reactions, and aluminium product contamination with iron if aluminium(lll) chloride feedstock is contaminated with iron(lll) chloride. This is purely due to lower reduction voltage for iron (111) chloride which makes this iron (111) chloride more thermodynamically favourable reaction.

[0099] For the same reason, certain carrier salts may not be compatible with metal salts which serve as feedstock. For example, Fig. 10 shows that reduction voltages for aluminium(lll) chloride and manganese(ll) chloride are not compatible due to similar reduction voltages, which could result in parasitic reaction of manganese reduction and contamination of aluminium product with manganese. In addition, aluminium(lll) chloride and manganese(ll) chloride form eutectic systems with very narrow temperature window of liquid phase (this phase diagram is not included in this document). This raises a further question with respect to their compatibility for formation of suitable electroreduction environment.

[00100] Water splitting reaction to liberate hydrogen and oxygen was presented in Fig. 10 to illustrate how close the water splitting voltage is in relation to various iron species. This also supports previous claims made above regarding water contamination and parasitic reactions involving water.

[00101] An additional advantage that is clearly demonstrated in Fig. 10 is that metal halides have lower reduction voltage compared to their oxide counterparts. At least in the case of iron, iron(lll) chloride has reduced reduction voltage by about 0.2 V compared to hematite (Fe2Oa) and magnetite (FeaC ). When it comes to aluminium the benefit is even greater. Depending on temperature, the difference between reduction voltage of alumina and aluminium(lll) chloride can be greater than 0.6 V. [00102] Finally, salts such as lithium chloride (LiCI), sodium chloride (NaCI), potassium chloride (KCI) and calcium chloride (CaCh) benefit from a very broad electrochemical window. This makes them suitable carrier salt candidates for eutectic systems for a large variety of metal halides.

[00103] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[00104] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed 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 as illustrative only and not restrictive.

[00105] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

[00106] When a Markush group or other grouping is used herein, all individual members of the group and all combinations and sub-combinations possible of the group members are intended to be individually included in the disclosure. Every combination of components described or exemplified herein can be used to practice the invention, unless otherwise stated. [00107] Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition or concentration range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein.

[00108] As used herein, "comprising" is synonymous with "including," "containing," or "characterized by," and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, "consisting of excludes any element, step, or ingredient not specified in the claim element. As used herein, "consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. The broad term "comprising" is intended to encompass the narrower "consisting essentially of and the even narrower "consisting of." Thus, in any recitation herein of a phrase "comprising one or more claim element" (e.g., "comprising A), the phrase is intended to encompass the narrower, for example, "consisting essentially of A" and "consisting of A". Thus, the broader word "comprising" is intended to provide specific support in each use herein for either "consisting essentially of or "consisting of". The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

[00109] One of ordinary skill in the art will appreciate that materials and methods, other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in this invention. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by examples, preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

[00110] Each reference cited herein is incorporated by reference herein in their entirety. Such references may provide sources of materials; alternative materials, details of methods, as well as additional uses of the invention.

Claims

1 . A method for the extraction of a metal from metallic ores including the steps of;

(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 salt or alkaline earth metal salt, and

(iii) recovering the metal from the eutectic system using electrowinning.

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

3. The method of 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 claim 2, wherein the metallic ore is chosen from the group comprising: iron ore; aluminium containing ores; gold ores; manganese containing ores; lead ores; zinc ores; cobalt containing ores; uranium containing ores; copper containing ores; nickel containing ores; titanium containing ores; tungsten containing ores; silicon containing ores; rare earth containing ores; chromium containing ores; silver containing ores; tin containing ores; heavy sands and quartz.

5. The method according to claim 1 or claim 2, wherein the metallic ore is an iron ore chosen from the group comprising magnetite (FesC ), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH)-/?H2O) and siderite (FeCOa).

6. The method according to claim 1 or claim 2, wherein the metallic ore is leached by a leaching agent in liquid or gaseous form chosen from the group comprising HF, HCI, HBr, HI, F₂, Br₂ or Cl₂.

7. The method according to claim 1 or claim 2, wherein the eutectic system includes one or more salts chosen from NaCI, KCI, LiCI, CaCh, MgCh or MnCh.

8. The method according to claim 1 or claim 2, wherein

(i) the ore is leached by a leaching agent to provide iron(lll) halide,

(ii) a eutectic system is formed comprising the iron(lll) halide and one or more of alkali metal halide or alkaline earth metal halide salt, and

(iii) the iron is recovered from the eutectic system using electrowinning.

9. The method of claim 1 or claim 2, wherein additional non-halide salts are included in the eutectic system.

10. The method of claim 1 or claim 2, wherein recovery of metal from the eutectic system takes place between room temperature and 500°C.

1 1 . The method of claim 1 or claim 2, wherein the eutectic system comprises alkali metal chlorides and recovery of metal from the eutectic system takes place between 110°C and 250°C.

12. The method of claim 1 or claim 2, wherein the eutectic system comprises alkaline earth metal chlorides, and recovery of metal from the eutectic system takes place between 200°C and less than 300°C.

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

14. The method of claim 1 or claim 2, wherein water in the eutectic system is minimised to avoid parasitic reactions during electrowinning.

15. The method of claim 1 or claim 2, wherein the eutectic system is chosen from the group comprising FeC -NaCI, FeCh-CaCh, and FeCh-NaCI-CaCh.

16. A metal recovered using a method according to any one of the preceding claims.