C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 1 - METALLURGICAL EXTRACTION FIELD OF THE INVENTION The invention relates generally to metallurgical extraction processes, and more specifically to a process to extract one or more metals from an alloy. BACKGROUND OF THE INVENTION Conventional techniques for extracting metals from a metal source such as an alloy involve hydro- and pyro-metallurgical procedures. Those procedures are conducted under extreme physical and chemical conditions, such as leaching in harsh acidic environments and high temperature melting. Those processes are therefore energy intensive and present significant environmental pollution risks. Due to tremendous technological advances in applications requiring extensive use of alloys, such as electronics and batteries, alloys constitute a significant fraction of e-waste and spent batteries. There are therefore large fast-growing volumes of alloy waste, which today present as a viable secondary resource of metals. While a fraction of alloy waste can be repurposed, the majority ends up in landfills. The lack of effective closed-loop circular economy models for metals separation from alloys increases the environmental burden of this waste as it contains toxic metals (e.g. lead, lithium and cadmium). These metals, if dumped incorrectly, may seep into the groundwater posing a threat to human health and the environment. There is a growing demand for metals in various industries, while conventional methods for extracting and refining metals from alloys waste are prohibitively expensive and inefficient. There remains therefore an opportunity to address or ameliorate the shortcomings of existing extraction techniques.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 2 - SUMMARY OF THE INVENTION The present invention provides a process to extract one or more solute metals from a ternary or higher liquid alloy, the process comprising the steps of: a) providing a binary or higher alloy, b) dissolving said binary or higher alloy in a post-transition metal to obtain a ternary or higher liquid alloy, said ternary or higher liquid alloy comprising at least two solute metals dissolved in the post-transition metal, and c) extracting at least one of the solute metals from the ternary or higher liquid alloy by electro-capillary. The dissolution of the alloy of step a) in a post-transition metal in step b) allows to obtain a ternary or higher liquid alloy which can be processed in liquid form at significantly lower temperatures than the melting temperature of the starting alloy. This makes the resulting liquid alloys ideal candidates for highly controlled electro-capillary extraction of each discrete solute metal from the liquid alloy. The proposed process therefore provides a metallurgical extraction procedure by which starting alloys can be liquefied and their pure constituent metals extracted individually at operative temperatures that are significantly lower than the melting temperature of the starting alloy. This approach can therefore dramatically reduce the energy demand for a given metal extraction relative to conventional extraction procedures. The invention therefore presents an alternative extractive metallurgical pathway to retrieve metals from alloy waste and secondary alloy resources, potentially mitigating future metal supply shortages. In some embodiments, the extraction by electro-capillary comprises a) immersing the ternary or higher liquid alloy into an electrolyte, and b) applying a negative half-cell potential to the immersed ternary or higher liquid alloy to expel at least one of the solute metals from the ternary or higher liquid alloy into the electrolyte.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 3 - By tailoring some of the operative parameters of the electro-capillary procedure to expel a single target metal, it is advantageously possible to achieve preferential extraction of one target metal over the others present in the liquid alloy. For example, at least one of the solute metals can be selectively expelled from the liquid alloy by controlling at least one of (i) the applied voltage, (ii) pH of the electrolyte, and (iii) composition of the electrolyte. The invention therefore offers an alternative, simple, sustainable, and low-temperature approach for metal extraction from an alloy that can eliminate and/or reduce the environmental burden of conventional metal extraction processes. Alloy waste, such as e- waste and spent batteries, represents a valuable secondary resource that is often underutilized. The proposed extraction process therefore provides an effective circular economy roadmap for such secondary resources and offers a sustainable means of extracting valuable metals from them. BRIEF DESCRITION OF THE DRAWINGS Embodiments of the invention will be now described with reference to the following non- limiting drawings, in which: Figure 1 shows a schematic diagram an example metal expulsion unit performing an embodiment of the extraction process of the invention, Figure 2 shows a schematic representation of a metal expulsion cell used for metal extraction in an example procedure described in Examples 2 and 3, Figure 3 shows an example process flow diagram (PFD) of an embodiment process with an integrated metal expulsion unit for recovering post-transition metals from waste streams, Figure 4 shows characterisation of metal expelled from a gallium-tin-bismuth liquid alloy in accordance with an embodiment of the invention, in which (a) and (b) show Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) analysis of the expelled
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 4 - product using 0.50 M Na2SO4 at -1.5 V vs RHE and 50°C, (c) and (d) show EDS and XRD analysis of product expelled using 0.50 M Na2SO4 electrolyte at -2.2 V vs RHE at 50°C, (e) and (f) show EDS and XRD analysis of product expelled using in DMF containing 0.2 M NBu4PF6 at -5.0 V vs SCE, and Figure 5 shows (a) an electrocapillary assessment of liquid metals using pendant drop tensiometry, and (b) measured surface tensions of Ga and Ga96Sn3Bi1 liquid alloy used in the procedure described in Example 2 at different potentials at 50°C. DETAILED DESCRIPTION OF THE INVENTION The present invention provides relates to a process to extract one or more solute metals from a ternary or higher liquid alloy. The process of the invention is essentially a metallurgical extraction process. By the expression "metallurgical extraction" is meant herein a procedure that affords individual extraction of discrete metals from a multiple-metal source. As such, a metallurgical extraction can ultimately afford complete sequential separation of all metals from the starting metal source. As a skilled person would appreciate, this is not the same as metallurgical "refining", which does not strictly achieve isolation of each solute metal but the fine tuning of the formulation of a given alloy. The expression "liquid alloy" used herein refers to an alloy that contains at least one post- transition metal and has a melting temperature below 150°C. For example, liquid alloys suitable for use in the invention include alloys presenting a melting temperature at or below room temperature. As used herein, "room temperature" refers to ambient temperatures which may be, for example, between 10ºC to 40ºC, and more typically between 15ºC to 30ºC. For example, room temperature may be a temperature between 20ºC and 25ºC.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 5 - By being ternary or higher, the liquid alloy is made of three or more alloying elements, at least one of which being a post-transition metal. The expression "post-transition metals" is used herein to refer to a group of elements in the periodic table located between the transition metals and metalloids. Examples of post- transition metals in that regard include gallium, indium, tin, lead, bismuth, mercury, rubidium, cesium, and francium. Post-transition elements possess electrons distributed in spatially separated orbitals, leading to an incomplete screening effect of each subsequent increase in nuclear charge, hence their nuclear charges can dominate and atomic radii contract. Therefore, in comparison to other metals, post-transition metals have fewer electrons available for metallic bonding, resulting in them exhibiting both metallic and non-metallic properties simultaneously. In terms of macroscopic characteristics, post-transition metals are highly fusible metals that can be used to form low-melting-point alloys, which can maintain a liquid state at low temperature, for example at near room temperature. Those alloys can be referred to as "liquid alloys". A post-transition metal can effectively act as a solvent metal. That is, post-transition metals can dissolve one or more other metal elements to form liquid metal solutions. Those solutions comprise the post-transition metal as solvent metal, and said one or more other metal elements as metal solutes. Accordingly, the invention may also be said to provide a metallurgical extraction process to separate one or more solute metals from a ternary or higher liquid alloy, the process comprising the steps of a) providing a binary or higher alloy, b) adding a solvent metal to said binary or higher alloy to obtain a ternary or higher liquid alloy, said ternary or higher liquid alloy comprising at least two solute metals dissolved in the solvent metal, and c) extracting at least one of the solute metals from the ternary or higher liquid alloy by electro- capillary. The invention may also be said to provide a metallurgical extraction process to separate one or more solute metals from a ternary or higher liquid alloy, the process comprising the steps of a) providing a secondary or higher alloy, b) adding a solvent metal
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 6 - to said secondary or higher alloy to obtain a ternary or higher liquid alloy, said ternary or higher liquid alloy comprising at least two solute metals dissolved in the solvent metal, and c) extracting at least one of the solute metals from the ternary or higher liquid alloy by electro-capillary. Example of suitable post-transition metals for use in the method of the invention include at least one of gallium, indium, tin, lead, bismuth, mercury, rubidium, cesium, and francium. In some embodiments, the post-transition metal is at least one of gallium, indium, lead, and tin. In some embodiment, the post-transition metal is gallium. In those instances, the resulting ternary or higher alloy is a gallium-based ternary or higher alloy. Examples in that regard include Galinstan (68% Ga, 22% In, 10% Sn; melting temperature, Tm, is ~ -19˚C), Field's Metal (32.5% Bi, 51% In, 16.5% Sn, Tm is ~62˚C), Wood's Metal (50% Bi, 26.7% Pb, 13.3% Sn, 10% Cd, Tm is ~70˚C), Rose's Metal (50% Bi, 28% Pb, 22% Sn, Tm is ~94˚C), Cerrosafe (42.5% Bi, 37.7% Pb, 11.3% Sn, 8.5% Cd, Tm is ~70˚C), and Newton’s Metal (50% Bi, 31.2% Pb, 18.8% Sn, Tm is ~97˚C). All percentages above are wt%. The use of gallium as the post-transition metal is particularly advantageous to obtain the required liquid alloy due to its good metal-solvating characteristics. The process of the invention comprises a step a) of providing a binary or higher alloy. The alloy for use in step a) may be any alloy that (i) has two or more alloying elements, and (ii) can be dissolved in a post-transition metal to form a liquid alloy. The binary or higher alloy may also be referred herein interchangeably as secondary or higher alloy. Accordingly, the present invention may alternatively be said to provide a process to extract one or more solute metals from a ternary or higher liquid alloy, the process comprising the steps of: a) providing a secondary or higher alloy, b) dissolving said secondary or higher alloy in a post-transition metal to obtain a ternary or higher liquid alloy, said ternary or higher liquid alloy comprising at least two solute metals dissolved in the post-
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 7 - transition metal, and c) extracting at least one of the solute metals from the ternary or higher liquid alloy by electro-capillary. In some embodiments, the alloy in step a) is selected from alloys of bismuth with tin, lead or cadmium. In other words, in some embodiments the binary or higher alloy is selected from alloys of bismuth with tin, lead or cadmium. In other words, in some embodiments the secondary or higher alloy is selected from alloys of bismuth with tin, lead or cadmium. These alloys may find application in fire detectors and extinguishers. In addition, several “hard-to- process” waste, metallurgical reject streams and/or intermediate products such as e-waste solder alloys, crude gallium, crude tin, crude bismuth, lead dross, lead bullion, Betts anode slimes, and copper dross that includes post-transition metals may also be used. In some embodiments, the alloy in step a) comprises two or more alloying elements selected from indium, tin, bismuth, lead, antimony, zinc, germanium, and aluminum. In other words, in some embodiments the binary or higher alloy comprises two or more alloying elements selected from indium, tin, bismuth, lead, antimony, zinc, germanium, and aluminum. In other words, in some embodiments the secondary or higher alloy comprises two or more alloying elements selected from indium, tin, bismuth, lead, antimony, zinc, germanium, and aluminum. In some embodiments, the alloy in step a) is a solder alloy. For example, the alloy in step a) may be a solder alloy derived from electronic waste. In other words, in some embodiments the binary or higher alloy is a solder alloy. For example, the binary or higher alloy may be a solder alloy derived from electronic waste. In other words, in some embodiments the secondary or higher alloy is a solder alloy. For example, the secondary or higher alloy may be a solder alloy derived from electronic waste. Typically, a solder alloy for use in the invention would be an alloy containing any two or more elements selected from lead, tin, silver, bismuth, antimony, indium, and cadmium.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 8 - Solder alloy suitable for use in the invention may be categorized based on their dominant metal. In the Sn dominant group, alloys such as Sn89Zn8Bi3, Sn83.6Zn7.6In8.8, and Sn95Sb5 showcase variations of tin with other elements. Bismuth dominant alloys include Bi57Sn42Ag1, Bi58Sn42, and Bi56Sn30In14. The Pb dominant category comprises diverse compositions like Pb90Sn10, Pb80Sn20, and Sn50Pb50. Additionally, alloys with complex compositions involving multiple elements such as Bi, Pb, Sn, Ag, Cu, Zn, and Cr, can be designed materials for various applications, such as Sn90.7Ag3.6Cu0.7Cr5. Examples of suitable solder alloys for use in the process of the invention include Sn75Bi25, Sn70Pb30, Sn67Pb37, Sn60Pb40, Sn50Pb50, Sn40Pb60, Sn30Pb70, Sn25Pb75, Sn10Pb90, Sn5Pb95, Sn62Pb36Ag2, Sn10Pb88Ag2, Sn5Pb90Ag5, Sn96.5Ag3.5, Sn95Sb5, Sn42Bi58, and Sn95.5Ag4Cu0.5. In some embodiments, the alloy used in step a) is selected from In-Sn alloy, In-Sn-Zn alloy, Bi-Sn alloy, Bi-Pb alloy, Bi-Pb-Sn alloy, Bi-Sn-Pb alloy, Bi-Sn-Ag alloy, Bi-Sn-In alloy, Bi-Sn-Cd alloy, Bi-Sn-Zn alloy, Bi-Pb-Sn-Cd-In alloy, Sn-Pb alloy, Sn-Sb alloy, Sn-Pb-Ag alloy, Sn-Ag-Cu alloy, and Sn-Zn-In alloy. In other words, in some embodiments the binary or higher alloy is selected from In-Sn alloy, In-Sn-Zn alloy, Bi-Sn alloy, Bi-Pb alloy, Bi-Pb- Sn alloy, Bi-Sn-Pb alloy, Bi-Sn-Ag alloy, Bi-Sn-In alloy, Bi-Sn-Cd alloy, Bi-Sn-Zn alloy, Bi-Pb-Sn-Cd-In alloy, Sn-Pb alloy, Sn-Sb alloy, Sn-Pb-Ag alloy, Sn-Ag-Cu alloy, and Sn- Zn-In alloy. In other words, in some embodiments the secondary or higher alloy is selected from In-Sn alloy, In-Sn-Zn alloy, Bi-Sn alloy, Bi-Pb alloy, Bi-Pb-Sn alloy, Bi-Sn-Pb alloy, Bi-Sn-Ag alloy, Bi-Sn-In alloy, Bi-Sn-Cd alloy, Bi-Sn-Zn alloy, Bi-Pb-Sn-Cd-In alloy, Sn- Pb alloy, Sn-Sb alloy, Sn-Pb-Ag alloy, Sn-Ag-Cu alloy, and Sn-Zn-In alloy. In some embodiments, the alloy used in step a) is selected from Sn89Zn8Bi3, Sn83.6Zn7.6In8.8, Sn95Sb5, Sn97Sb3, Sn99Sb1, Bi57Sn42Ag1, Bi58Sn42, Bi58Pb42, Bi50Pb28Sn22, Bi56Sn30In14, Bi48Pb25.4Sn12.8Cd9.6In4, Bi49Pb18Sn15In18, Bi47.5Pb25.4Sn12.6Cd9.5In5, Bi49Pb18Sn12In21, Bi50.5Pb27.8Sn12.4Cd9.3, Bi50Pb26.7Sn13.3Cd10, Bi44.7Pb22.6In19.1Cd5.3Sn8.3, Sn50Zn49Cu1, Sn90Zn7Cu3, Sn95.5Cu4Ag0.5, Pb90Sn10, Pb88Sn12, Pb85Sn15, Pb80Sn20, Pb75Sn25, Pb70Sn30, Pb68Sn32, Pb67Sn33, Pb65Sn35, Pb60Sn40, Pb55Sn45, Sn50Pb50, Sn62Pb38, Sn63Pb37, Sn60Pb38Cu2, Sn60Pb39Cu1, Sn62Pb37Cu1, Sn50Pb48.5Cu1.5, Pb80Sb15Sn5, Pb68Sn30Sb2, Sn30Pb50Zn20,
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 9 - Sn33Pb40Zn28, Pb96Sn2Ag2, Sn61Pb36Ag3, Sn56Pb39Ag5, and Sn90.7Ag3.6Cu0.7Cr5. In other words, in some embodiments the binary or higher alloy is selected from Sn89Zn8Bi3, Sn83.6Zn7.6In8.8, Sn95Sb5, Sn97Sb3, Sn99Sb1, Bi57Sn42Ag1, Bi58Sn42, Bi58Pb42, Bi50Pb28Sn22, Bi56Sn30In14, Bi48Pb25.4Sn12.8Cd9.6In4, Bi49Pb18Sn15In18, Bi47.5Pb25.4Sn12.6Cd9.5In5, Bi49Pb18Sn12In21, Bi50.5Pb27.8Sn12.4Cd9.3, Bi50Pb26.7Sn13.3Cd10, Bi44.7Pb22.6In19.1Cd5.3Sn8.3, Sn50Zn49Cu1, Sn90Zn7Cu3, Sn95.5Cu4Ag0.5, Pb90Sn10, Pb88Sn12, Pb85Sn15, Pb80Sn20, Pb75Sn25, Pb70Sn30, Pb68Sn32, Pb67Sn33, Pb65Sn35, Pb60Sn40, Pb55Sn45, Sn50Pb50, Sn62Pb38, Sn63Pb37, Sn60Pb38Cu2, Sn60Pb39Cu1, Sn62Pb37Cu1, Sn50Pb48.5Cu1.5, Pb80Sb15Sn5, Pb68Sn30Sb2, Sn30Pb50Zn20, Sn33Pb40Zn28, Pb96Sn2Ag2, Sn61Pb36Ag3, Sn56Pb39Ag5, and Sn90.7Ag3.6Cu0.7Cr5. In other words, in some embodiments the secondary or higher alloy is selected from Sn89Zn8Bi3, Sn83.6Zn7.6In8.8, Sn95Sb5, Sn97Sb3, Sn99Sb1, Bi57Sn42Ag1, Bi58Sn42, Bi58Pb42, Bi50Pb28Sn22, Bi56Sn30In14, Bi48Pb25.4Sn12.8Cd9.6In4, Bi49Pb18Sn15In18, Bi47.5Pb25.4Sn12.6Cd9.5In5, Bi49Pb18Sn12In21, Bi50.5Pb27.8Sn12.4Cd9.3, Bi50Pb26.7Sn13.3Cd10, Bi44.7Pb22.6In19.1Cd5.3Sn8.3, Sn50Zn49Cu1, Sn90Zn7Cu3, Sn95.5Cu4Ag0.5, Pb90Sn10, Pb88Sn12, Pb85Sn15, Pb80Sn20, Pb75Sn25, Pb70Sn30, Pb68Sn32, Pb67Sn33, Pb65Sn35, Pb60Sn40, Pb55Sn45, Sn50Pb50, Sn62Pb38, Sn63Pb37, Sn60Pb38Cu2, Sn60Pb39Cu1, Sn62Pb37Cu1, Sn50Pb48.5Cu1.5, Pb80Sb15Sn5, Pb68Sn30Sb2, Sn30Pb50Zn20, Sn33Pb40Zn28, Pb96Sn2Ag2, Sn61Pb36Ag3, Sn56Pb39Ag5, and Sn90.7Ag3.6Cu0.7Cr5. In some embodiments, the alloy used in step a) is Sn75Bi25. In some embodiments, the alloy used in step a) is high-melting alloy. For example, the alloy used in step a) may be an alloy with melting point of 150°C or above. In some embodiments, the alloy used in step a) has melting temperature of at least 350°C. The process of the invention comprises a step of dissolving the alloy provided in step a) in a post-transition metal of the kind described herein. As explained herein, the dissolution of the binary or higher liquid alloy into post-transition metals (solvent metals) results in the formation of low-melting-point ternary or higher alloys that are liquid at low temperatures. Dissolution of said alloy in a post-transition metal may be effected in accordance to any means known to the skilled person.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 10 - For example, a post-transition metal is first provided in liquid form, and the binary or higher alloy added to it. Due it its metal-solvating characteristics, the post-transition metal can dissolve the added alloy, resulting in a formulation of the required liquid alloy. Advantageously, the resulting liquid alloy would be typically characterised by a melting point that is significantly lower than that of the starting binary or higher alloy. Dissolution of the alloy provided in step a) into the post-transition metal can be performed according to conditions of temperature and formulation such that the resulting ternary or higher liquid presents in liquid form at a required temperature. Those conditions may be derived by any means known to the skilled person, for example from the phase diagram specific to the combination of alloy elements and the post-transition metal. For instance, based on the relevant phase diagram, a skilled person can tailor the amount of post-transition metal to the specific formulation of the starting alloy such that the resulting ternary or higher liquid presents in liquid form at the required temperature. By way of example, based on their phase diagram, the amount of secondary solder alloy Sn43Bi14 to be dissolved in gallium may be selected to be 8% (by mass), such that the resulting ternary alloy presents in a liquid state at near room temperatures. When a ternary phase diagram is not readily available, a practical approach may involve examining both binary phase diagrams, such as Ga-Sn and Ga-Bi. By assessing these diagrams, one can identify the critical element for achieving the liquid form. For example, in the Ga-Sn system, you can dissolve up to 30% of Sn in gallium, resulting in a liquid alloy at around 50°C. Conversely, with Bi, the alloy solidifies if the Bi content exceeds 4% in Ga. In this case, bismuth emerges as the critical element, and attention should be directed to its phase diagram with Ga to maintain its content in the alloy and achieve the liquid form at near room temperature. In step b) of the proposed process, dissolving the alloy provided in step a) in the post- transition metal results in formation of a ternary or higher liquid alloy. By being a "ternary or higher" liquid alloy, the alloy will include at least the post-transition metal and the two
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 11 - (or more) alloying elements of the starting binary or higher alloy. Given the solvation role played by the post-transition metal, said two or more alloying elements of the starting binary or higher alloy may also be referred to as "solute metals". Accordingly, the ternary or higher liquid alloy comprises at least two solute metals dissolved in the post-transition metal. In some embodiments, the ternary or higher liquid alloy is a eutectic ternary alloy. By the expression "eutectic alloy" is meant herein a homogeneous mixture of metals that will melt or solidify at a temperature lower than the melting point of any of its constituents. The composition and melting temperatures of common reference eutectic alloys are shown in the Table 1 below. These alloys do not require additional energy input and can maintain a molten state at low temperatures. Tab
In some embodiments, the ternary or higher liquid alloy is selected from Ga-Sn-Bi, Ga-Sn- Bi-Pb, Ga-In-Sn, Ga-In-Sn-Zn, In-Sn-Zn, Bi-Pb-Sn, Bi-Sn-Pb, Bi-Sn-Ag, Bi-Sn-In, Bi-Sn- Cd, Bi-Sn-Zn, Bi-Pb-Sn-Cd-In, Sn-Pb, Sn-Sb, Sn-Pb-Ag, Sn-Ag-Cu, and Sn-Zn-In. The method of the invention comprises a step of extracting at least one of the solute metals from the ternary or higher liquid alloy by electro-capillary (also known as electro- capillarity). As skilled person would know, electro-capillary is a physical phenomenon related to changes in the surface free energy (or interfacial tension) of charged fluid interfaces.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 12 - From a practical standpoint, it was observed that when immersed in an electrolyte, liquid alloys can establish a dynamic liquid-liquid interface (liquid metal-electrolyte). The application of an electric potential across said interface can modulate the liquid-liquid interfacial tension and induce interfacial diffusion of metals. In particular, when a negative voltage is applied to the liquid alloy immersed in an electrolyte, target solute metals from the liquid alloy can be selectively an individually expelled through the liquid-liquid interface into the electrolyte. This phenomenon is referred to herein also as "metal expulsion". Accordingly, in the context of the present invention the term "electro-capillary" indicates a procedure to modulate the surface tension of the liquid alloy by immersing the liquid alloy in an electrolyte and applying an external electric potential across the resulting liquid-liquid interface. Accordingly, in some embodiments the extraction by electro-capillary comprises a) immersing the ternary or higher liquid alloy into an electrolyte, and b) applying a negative voltage to the immersed ternary or higher liquid alloy to expel at least one of the solute metals from the ternary or higher liquid alloy into the electrolyte. Without wanting to be limited by theory, it is postulated that applying an electric potential across the liquid alloy-electrolyte interface can modulate the surface tension (or surface energy) of the liquid alloy (i.e. to induce an electro-capillary effect), resulting in surface segregation between the alloy and its constituent metals. The application of a cathodic electric potential to the liquid−liquid interfaces of the liquid alloy immersed in an electrolyte can trigger a phase separation and liberation of solute metal atom clusters from the alloy. The electric field is believed to enhance the diffusion of solute elements in the liquid alloy matrix to the interface. This may be followed by interfacial clustering of metals and complete release of the clusters due to the interfacial tension modulation via the electro-capillary effect. Variations in the surface energy of each solute metal in the liquid alloy may therefore be used to discriminate between solute metals and provide practical electro-capillary conditions for the preferential expulsion of a target metal from the liquid alloy over the other metals in the alloy.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 13 - By way of example, gallium may be used as the post-transition metal to obtain a ternary or higher liquid alloy starting from a binary or higher alloy containing two or more of In, Sn, Pb and Bi. When the liquid alloy is immersed in an electrolyte to establish a liquid alloy- electrolyte interface, the application of a negative potential to the liquid alloy leads to surface enrichment and surface segregation of the metal solutes. This results in the substantial accumulation of In, Sn, Pb and Bi metals in the outermost layer of the liquid alloy. A potential explanation for this phenomenon is attributed to minimization of surface energy levels of each metal constituent. As shown in Table 2, bismuth has the lowest surface tension energy (383 mJ m-2), while gallium has the largest. Bismuth would therefore segregate from the liquid alloy as a single concentrated layer atop of the bulk liquid alloy. Similarly, Sn would tend to segregate into both the outermost and the second layers of the liquid-liquid interface. If it becomes feasible to induce phase separation within liquid metals while simultaneously disrupting surface tension, there exists the potential to achieve the selective expulsion of discrete solute metals from the liquid alloy. Table 2 - The calculated a of liquid at their melting points
Once expelled, solute metals characterized by higher melting points compared to the post- transition metal solidify and precipitate away from the interface, while the alloy phase containing the post-transition metal retains its liquid state. The electrolyte for use in the method of the invention may be any liquid medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 14 - Examples of suitable electrolytes for use in the method of the invention include liquid solutions of one or more electrolyte salts. Accordingly, in some embodiments the electrolyte is a liquid solution of one or more salts selected from sodium sulphate, potassium sulphate, potassium chloride, sodium chloride, sodium hydroxide, potassium hydroxide, tetrabutylammonium hexafluorophosphate/dimethylformamide, potassium nitrate, sodium nitrate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, trisodium phosphate, buffer solutions that offer a pH control, and ionic liquids such as 1- methylimidazole, tetrafluoroborate, hexafluorophosphate. Molten salts, ionic liquids or eutectic slags maybe used as electrolytes to expel metal components from molten alloys in pyrometallurgical applications. The electrolyte may contain any amount of electrolyte salt that is conducive to the intended extraction. In some embodiments, the salt is present in the electrolyte solution in a concentration of from 0.01 M to 1 M. In some embodiments, the salt is present in the electrolyte solution in a concentration of 0.5 M. Surfactants such as ethylene glycol, dodecyl Sulfate, cetyltrimethylammonium bromide, or polyvinylpyrrolidone maybe added to the electrolyte to control the particle size and shape of expelled metals. For a given set of electro-capillary conditions and a given target metal to be extracted, a skilled person may elect a suitable electrolyte formulation based on principles outlined herein. From a practical standpoint, selective extraction of a target solute metal in its pure form can be achieved by acting on a number of operational parameters of the electro-capillary procedure. In that regard, it was observed it is particularly advantageous to perform selective extraction of a given solute metal by acting on at least one of the applied voltage, the pH of the electrolyte, and the composition of the electrolyte. In that regard, each solute metal may
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 15 - have a set of specific conditions at which it can be selectively precipitated from the liquid alloy-electrolyte interface. Accordingly, in some embodiments the at least one of the solute metals is selectively extracted by controlling at least one of (i) the negative voltage, (ii) pH of the electrolyte, and (iii) composition of the electrolyte. Voltage selection Once the liquid-liquid interface between the ternary or higher liquid alloy and a given electrolyte is formed, working voltages can be determined with respect to the minimum required voltage input to trigger the expulsion of a given metal and the amount of that metal collected in the electrolyte within a certain expulsion time. In the process of the invention, the voltage between the liquid alloy and the relevant counter- electrode is such that the alloy functions as the cathode. As a general principle, the expulsion of a given metal from the liquid alloy is observed to occur when applying a cathodic voltage to the liquid alloy that is more negative than the reduction potential of that metal, i.e. to avoid any metal redox reactions, for example to prevent the corrosion or oxidation of the metal. In a typical configuration, electro-capillary is performed in a three-electrode cell configuration. The liquid alloy is electrically connected to function as a working electrode against a given counter electrode. A saturated calomel reference electrode (SCE) is also employed to control the potential of the working electrode. In some embodiments, the negative voltage applied to the liquid alloy is -1.5V (vs RHE) or higher. By "higher" potential relative to a negative value is meant a negative potential with higher absolute value (i.e. -2V would be understood to be a higher potential than -1V). For example, the negative voltage applied to the liquid alloy is at least -1.5 V (vs RHE), at least -2.2V (vs RHE), at least -2.5V (vs RHE), at least -2.75V (vs RHE), at least -3V (vs RHE), at least -3.5V (vs RHE), or at least -4V (vs RHE).
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 16 - A given cathodic voltage may be applied to the liquid alloy for a duration of time conducive to extraction of the desired amount of the target metal. Expulsion of a target metal from the liquid alloy can be advantageously fast. In some embodiments, the cathodic voltage is applied to the liquid alloy for at least 5 minutes, at least 10 minutes, at least 25 minutes, or at least 50 minutes. pH selection The electrolyte may have any pH that is conducive to the selective extraction of a target solute metal. In selecting an appropriate pH for the electrolyte, a skilled person would have regard to electing a pH at which metal species are expelled from the liquid alloy into the electrolyte in metal form and do not form metal oxide or dissolve in the electrolyte in their corresponding ionic form. As a general guidance, the pH of the electrolyte can be selected for a target metal based on its corresponding Pourbaix diagram. Pourbaix Diagrams plot electrochemical stability for different redox states of an element as a function of pH. Accordingly, a Pourbaix diagram for a given metal solute would depict the most stable species or phase of that metal element, typically in aqueous solution, as a function of potential (y-axis) and pH (x-axis). One would therefore have to ensure that for a given system potential, the pH of the electrolyte is such that the metal solute is stable in its pure metal form. In certain instances, metal nanoparticles released from the liquid metal might be susceptible to oxidation in aqueous electrolytes. To mitigate this, oxidation inhibitors like organic acids (e.g., ascorbic acid), are employed.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 17 - In some embodiments, the pH of the electrolyte is 3 or higher. In some embodiments, the pH of the electrolyte is between 3 and 11. In some embodiments, the electrolyte has a pH of from 7 to 8. These pH ranges are particularly advantageous for the efficient and effective extraction of target metals in their pure form from the ternary or higher alloy. Electrolyte composition Also, the nature and formulation of the electrolyte can be selected and tuned to control the metal expulsion process. For example, and without wanting to be limited by theory, it is postulated that the electrolyte formulation can determine whether the solute metals are expelled selectively in their pure form, impure or as alloys (for example binary or higher solid solutions). It is postulated that selectivity in the surface separation process achieved by the alteration of the electrolyte is due to the interplay between electrodynamic interactions and the electro-capillary effect. In practical terms, the formulation of the electrolyte may be devised such that the ionic strength of the resulting electrolyte is tuned based on the surface energy of target metal solute in the liquid alloy. In that regard, a skilled person would appreciate that for a given ionic strength of the electrolyte, a metal solute with lowest surface energy tends to preferentially segregate from the surface of the liquid alloy. Accordingly, the ionic strength of the electrolyte may be selected to be the minimum at which the metal solute with lowest surface energy can segregate from the liquid alloy-electrolyte interface, from which it can be expelled first. In other words, the ionic strength of the electrolyte is small enough to promote the segregation of only the metal solute with lowest surface energy. Once that first metal solute is expelled, the ionic strength of the electrolyte may be increased to trigger the segregation of the metal solute with the second lowest surface energy, and so on. The extraction via electro-capillary may be performed at any temperature at which (i) the ternary or higher liquid alloy presents in liquid form and (ii) the solute metal expelled from the ternary or higher liquid alloy into the electrolyte presents in its pure metal form.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 18 - Advantageously, the provision of a ternary or higher liquid alloy affords metal solute extraction at temperatures that can be significantly lower than those required in conventional hydro- and pyro-metallurgical extraction procedures. For example, the extraction may be performed at room temperature. Practically, this may be achieved by maintaining the ternary liquid alloy at room temperature, for example by immersing the liquid alloy in an electrolyte that is kept at room temperature. In some embodiments, the extraction is performed at a temperature of 150°C or less. For example, the extraction may be performed at a temperature ranging from 0°C to 150°C. The extraction may also be performed at higher temperature when, for example, molten salts or eutectic slags are used as electrolytes. In some embodiments, the extraction may be performed at a temperature ranging from 10°C to 150°C, from 10°C to 100°C, from 0°C to 75°C, or from 0°C to 50°C. These temperatures ranges are particularly effective to expel the target solute metal from the ternary or higher liquid alloy into the electrolyte in its pure metal form. By affording extraction of at least one of the solute metals from the ternary or higher liquid alloy by electro-capillary, the process can advantageously be performed to expel all said solute metals selectively as pure metals from the ternary or higher liquid alloy by electro- capillary. Accordingly, in some embodiments the process comprises a step c) of expelling all said solute metals selectively as pure metals from the ternary or higher liquid alloy by electro-capillary. From a practical standpoint, electro-capillary extraction of metal solutes from the ternary or higher liquid alloy may be performed by any system known to the skilled person. The electrocapillary-driven metal expulsion of a solute metal from the ternary or higher liquid alloy can be conducted in an H-cell. The H-cell may employ a cation or anion exchange membrane to separate the anolyte and catholyte, preventing the mixing of water splitting byproducts, hydrogen and oxygen. The catholyte may feature a conical-shaped
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 19 - bottom to contain the liquid metal cathode. The liquid metal pool may be electrically connected to conductor (e.g. tinned copper, gold or silver) wire, linked to the negative terminal, effectively serving as the cathode. The anode may be made of platinum foil or spiral wire. A saturated calomel reference electrode (SCE) may be employed in the catholyte to control the half-cell potential of the liquid metal cathode. To initiate the metal expulsion from alloys via electro-capillary, the electric potential can be applied via a potentiostat using a chrono-amperometry protocol. Metal expulsion may be conducted under potentials that are more negative than the oxidation-reduction potentials of the constituent metals of the alloys. This approach is taken to prevent corrosion or oxidative dissolution of the metals involved. The H-cell can be filled with various electrolytic solutions, including but not limited to sodium sulphate, potassium sulphate, potassium chloride, sodium chloride, sodium hydroxide, potassium hydroxide, tetraethylammonium hexafluorophosphate / dimethylformamide, among others. By applying a negative half-cell potential, typically exceeding -1.5 V vs RHE or -2.0 V (vs SCE), to the liquid metal, solute metals are separated from the interface between the liquid metal and the electrolyte. These expelled metals become dispersed within the electrolyte. As shown in the schematic of Figure 1, a pump may be employed to extract the electrolyte and pass it through an in-line filter or another solid-liquid separation device. The filtrate can subsequently be reintroduced into the cell. Figure 1 shows a schematic diagram of an embodiment of a process and an apparatus for extraction of metal constituents from an alloy, for example a solder alloy. Solder alloy waste can be liquefied using, for example, gallium as the post-transition metal. The example system consists of five main sections: (a) alloying liquation, where feed metals are introduced into an alloying chamber (f), (b) power source (e.g. Electrical Power Supply), (c) electrocapillary separation, (d) solid-liquid separation, and (e) gas collection/conversion system, in the form of a fuel cell. Solute metals diffuse from the alloying chamber (f) to the
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 20 - next conditioning chamber (g) where the temperature is adjusted. From there, the solute atoms diffuse to the electrocapillary section (c) where they are selectively and sequentially liberated from the alloy. This diffusion is driven primarily by the concentration gradient caused by the separation and depletion of solute metals in the expulsion process. In section (d), the electrolyte (h1) is circulated through a pump and filtered or centrifuged to recover the metals in the form of pure nano-metals (l), and the electrolyte filtrate (h2) is circulated back to the electrocapillary section (c). During expulsion, H2 and O2 are generated simultaneously. These gases may be either sold directly or converted back into electricity to power the system through fuel cell (e). Once powered up, the liquid alloy (i) operates as the cathode against anode (j) in the electrolyte side of the cell. Any insolubles (k) remain floating on the liquid alloy in chambers (f) and (g). As shown in Figure 1, applying a cathodic potential to the liquid alloy can trigger the separation of each metal at near room temperature. Hydrogen and oxygen are simultaneously generated as by-products, which can be harnessed to sustain the expulsion process. Upon separation and drying, the products can be utilised for advanced electrochemical application such as electro-catalysts for CO2 electrochemical conversion. Another significant product generated during the process of metal expulsion in the schematic is hydrogen produced from the cathode. Hydrogen gas can be collected then transferred to a fuel cell which convert hydrogen to electricity. This process can serve as a clean fuel for the cells, providing a continuous energy source for the metal expulsion process and enabling the cyclic utilization of energy. The invention can make it possible to selectively extract specific metals from liquid alloys at near room temperature using electricity. For instance, bismuth, lead and tin can be successfully extracted from their liquid alloy with gallium using electricity in different electrolytic systems. This capability to selectively precipitate solute metals from liquid alloys not only presents a low-energy metallurgical approach for extracting elemental components from alloys but also promises to revolutionize commercial applications by harnessing renewable energy sources, ultimately enabling the production and supply of zero emissions metal feedstocks.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 21 - This approach is particularly useful for recovering pure metals from electronic waste (e- waste) since it allows for the sustainable extraction of their elemental components at lower temperatures. Enabling this innovative circular economy roadmap for managing this substantial, and sometimes hazardous, waste stream holds the promise of substantial socio- economic and environmental advantages. It unlocks the value within these waste streams, reduces the dependence on virgin resources, and effectively mitigates the risk of environmental pollution. The metal expulsion procedure described herein has a great potential for extractive metallurgical applications since alloy metals can be selectively expelled from the interface in their pure form. For example, Ga is a highly fusible metal that can be used as a liquefying medium to dissolve alloys of high melting temperature. The ability to access the liquid form of these alloys at near room temperature can enable low energy metallurgical solutions for processing alloys and extracting metals from them through metal expulsion. For instance, the metal expulsion presents an alternative to the less efficient Betts electrolytic process, which relies on toxic and expensive reagents. A potential metal expulsion unit is similar in principle to what is shown in the schematic of Figure 2. The unit is a three-electrode configuration cell consisting of a tinned copper wire (1) immersed in liquid alloy (2) through a glass sleeve (5) and functioning as the working electrode (WE), a platinum plate electrode (3) functioning as the counter electrode (CE), and a saturated calomel reference electrode (4), SCE. A glass custom conical H-cell (30 mm diameter) containing 25 ml of electrolyte solution (6) in each cell was used as the electrochemical cell. The tinned-copper wire electrode (1) was inserted through the bottom of the cathode compartment of the H cell and brought into contact with the liquid metal (2) in the cell. The H cell includes a Nafion proton-exchange membrane (7) made of PEM (30 mm diameter and 183 um thickness) to separate the anolyte and catholyte and prevent the mixing of water splitting products, hydrogen and oxygen. The catholyte has a conical-shaped bottom to contain the liquid alloy (2), acting as liquid metal cathode. Voltage to the cell is applied by potentiostat (8).
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 22 - The proposed method allows to envisage how several 'hard-to-process' waste, metallurgical reject streams and/or intermediate products such as e-waste solder alloys, crude gallium, crude tin, crude bismuth, lead dross, lead bullion, Betts anode slimes, and copper dross that includes post-transition metals. There streams can be processed using metal expulsion process, as shown for example in the process flow schematic of Figure 3. The process flow diagram (Figure 3) includes two main steps: thermal treatment of waste PCBs and metal expulsion. The initial step involves a thermal treatment of PCBs at 350°C in a rotary kiln to selectively melt and recover the solder alloy from PCBs. In the second step, the solder melt is added to Ga and processed in a metal expulsion plant to recover Sn, Bi, Pb, and Sb. To our knowledge, this is the first report demonstrating selectivity in the metal expulsion phenomenon. This breakthrough holds immense promise for low-energy metallurgical processes, enabling the extraction and purification of solder alloys from e-waste into their constituent metals. This work represents a significant advancement in the field of metallurgy, offering a sustainable and energy-efficient solution to metal extraction and alloy refinement. Certain embodiments of the present invention will now be described with reference to the following non-limiting Examples. EXAMPLES EXAMPLE 1 Design A prototype or experimental setup of the H-cell has been created. This includes the design and assembly of the H-cell apparatus, incorporating components such as the cathode (gallium-solder alloy liquid), anode (Platinum foil, mesh, spiral wire or Graphite electrode, or lead alloy electrode, or Nickel electrode), cation or anion exchange membrane, catholyte
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 23 - container with a conical-shaped bottom, and the necessary electrical connections. The reference electrode, when used, is also part of this prototype. The gallium-solder liquid alloy serves as the cathode material within the H-cell setup. This material is crucial for selectively expelling solute metals (bismuth, lead and tin). Various electrolytic solutions, such as sodium sulfate, potassium sulfate, sodium hydroxide, or potassium chloride, etc. can be used as part of the experimental setup. These solutions are essential materials for the metal expulsion within the H-cell. The invention proposes to utilise hydrogen and oxygen byproducts generated during the metal expulsion process. While not materials in the traditional sense, the protocols and systems for collecting and utilizing these gases sustainably are integral to the invention. The primary claimed advantage is the ability to selectively expel different metals as pure solid nanostructures from liquid alloys at near room temperature. This is supported by the characterization data in Figure 4. The first expulsion in 0.50 M Na2SO4 at -1.5 V vs RHE at 50°C resulted in nano-sized bismuth particles with a popcorn-like morphology. The EDS and XRD analyses confirm that this expulsion product contained only bismuth and was free of gallium and tin (Figure 4a and b). In the electrolyte containing 0.50 M Na2SO4, the expulsion product was found to be pure bismuth. This demonstrates that the metal expulsion process can be tuned or controlled to achieve the desired selectivity (Figure 4a and b). Voltage higher than -1.5 V vs RHE will yield bismuth first and then tin in 0.50 M Na2SO4 electrolyte. Voltages around -1.5 V vs RHE will yield only bismuth. After expelling Bi, the electrolyte can be centrifuged to separate bismuth product and used again in the cell to continue expelling Sn. After applying voltage of -2.2 V vs RHE, tin was successfully expelled. The EDS and XRD results confirm that the expulsion product in this case is tin (Figure 4a and b).
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 24 - Figure 4(c) and 4(d) show EDS and XRD analysis of product expelled using 0.50 M Na2SO4 electrolyte at -2.2 V vs RHE at 50°C. After expelling Bi and Sn, we switched to the non-aqueous electrolyte 0.20 M NBu4PF6/DMF to further expel Pb from the remaining Ga-Pb liquid system using -5.0 V vs SCE. The EDS result shows the expelled product is Pb as shown in Figure 4e. XRD result (Figure 4f) shows the presence of both Pb and Pb(SO₄). The Pb(SO₄) is originated from the sulfur impurity in the Pb raw material. These results collectively demonstrate the advantage of being able to selectively expel specific metals from a solution and provide concrete evidence of the effectiveness of the process. The capability to selectively precipitate solute metals from these liquid alloys offers a low-energy metallurgical approach to refining alloys into their individual constituent metals, eliminating the need for high-temperature processes. Additionally, this innovative process is anticipated to find commercial applications that leverage established renewable energy sources. EXAMPLE 2 Ga-Sn-Bi Ternary Alloy This Example relates to the separation of metals from ternary Ga-Sn-Bi liquid system. In the procedure, electrocapillary was applied to a Ga-Sn-Bi liquid alloy, resulting in selective expulsion of Bi or Sn from the alloy surface as pure metals. The metals are expelled sequentially from the alloy with Bi first, followed by Sn. First-principal calculations suggest that the sequence of expulsion is primarily determined by the surface energy of solute metals. Materials: Tin (Sn, popcorn flakes, 99.9%), bismuth (Bi, ingots, 99.9%) were purchased from Rotometals, USA. Gallium (Ga, beads, 99.9%) was obtained from Indium Corporation, USA. Sodium sulfate (Na2SO4, analytical grade) was purchased from Chem-supply.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 25 - Preparation of Gallium-Tin-Bismuth Alloy: We formulated in-house model compound of real solder alloy waste (Sn0.75Bi0.25). Around 8 wt.% of the alloy was liquefied by adding it to gallium and heating the mixture on a hotplate at 350°C for 15 min. To ensure a homogeneous fusion, the molten metals were stirred with a glass rod. The melting point of the resulting gallium-bismuth alloy is slightly above room temperature. Electrochemical Cell Configuration: Since the metal expulsion requires cell potentials higher than the electrolysis potential of water, hydrogen and oxygen are generated as by- products. To separate and collect these by-products, the metal expulsion was demonstrated utilising a two-compartment H-type electrochemical cell (Figure 2). The unit is a three- electrode configuration cell consisting of a tinned copper wire (1) immersed in liquid alloy (2) through a glass sleeve (5) and functioning as the working electrode (WE), a platinum plate electrode (3) functioning as the counter electrode (CE), and a saturated calomel reference electrode (4), SCE. A glass custom conical H-cell (30 mm diameter) containing 25 ml of electrolyte solution (6) in each cell was used as the electrochemical cell. The tinned- copper wire electrode (1) was inserted through the bottom of the cathode compartment of the H cell and brought into contact with the liquid metal (2) in the cell. The H cell includes a Nafion proton-exchange membrane (7) made of PEM (30 mm diameter and 183 um thickness) to separate the anolyte and catholyte and prevent the mixing of water splitting products, hydrogen and oxygen. The catholyte has a conical-shaped bottom to contain the liquid alloy (2), acting as liquid metal cathode. Voltage to the cell is applied by potentiostat (8). Electric potential was applied at the optimized potential for each alloy. The optimal voltages were determined with respect to the minimum required voltage input to trigger the expulsion of nanostructure entities and the amount of products collected within a certain expulsion time. Metal Expulsion from Ga-Sn-Bi Ternary Alloy The metal expulsion from liquid alloys was triggered by applying electric potential to the liquid alloy. The gallium-tin-bismuth liquid alloy served as the working electrode in a three- electrode cell, as described in the previous section. The voltage was applied via a
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 26 - chronoamperometry protocol using a sample interval of 0.10 s and a sensitivity of 0.10 A V−1. For expelling bismuth, the experiment was carried out in 0.50 M Na2SO4 at -1.5 V (vs RHE) under 50°C, until no more bismuth was generated. To expel the remaining tin, the electrolyte was removed, and the remaining liquid alloy was cleaned using Milli-Q water. The cell was refilled with 0.50 M Na2SO4 as electrolyte and the experiment was resumed but using an applied half-cell potential of -2.2 V (vs RHE) and 50°C. The expelled products were removed from the cell using a dropper and transferred into a centrifuge tube for centrifugation. The obtained precipitate was washed with Milli-Q water, followed by centrifugation. This washing process was repeated three times. After removing all the liquid, the precipitate was dried in air, then weighed and characterized. The recovery was estimated by weighing the precipitate from the metal expulsion and comparing that to the alloyed amount of bismuth in the liquid alloy droplet. The metal recovery is expressed as: ^^^^^ ^^^^^^^^^%^ = ^^^^ℎ^ ^^ ^^^^^^^^ ^^^^^ × 100 ^^^^^^^ ^^^^^^ ^^^^^ ^^^^ℎ^ ^^ ^^^^^^ ^^^^^ EXAMPLE 3 Ga-Sn-Bi-Pb Quaternary Alloy This Example relates to the separation of metals from solder alloys derived from e-waste. In the procedure, electrocapillary was applied to a Ga-Sn-Bi-Pb liquid alloy, resulting in selective expulsion of Bi, Sn or Pb from the alloy surface as pure metals. The metals are expelled sequentially from the alloy with Bi first, followed by Sn, and then Pb. First- principal calculations suggest that the sequence of expulsion is primarily determined by the surface energy of solute metals. Materials Tin (Sn, popcorn flakes, 99.9%), bismuth (Bi, ingots, 99.9%) and lead (Pb, sheet, 99+%) were purchased from Rotometals, USA. Gallium (Ga, beads, 99.9%) was obtained from
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 27 - Indium Corporation, USA. Sodium sulfate (Na2SO4, analytical grade) was supplied by Sigma-Aldrich. Milli-Q water (18.2 MΩ cm at 25 °C) was used in all experiments. Tetrabutylammonium hexafluorophosphate (NBu4PF6, ≥99.0%) was obtained from Sigma- Aldrich. Dimethylformamide (DMF, analytical grade), was purchased from Chem-Supply Pty Ltd., Australia. Non-aqueous electrolytes (0.20 M NBu4PF6/DMF) were prepared by dissolving NBu4PF6 in DMF. Liquid Alloys Preparation An in-house model compound (Sn-Bi) was formulated according to an actual ratio of solder alloy waste (75 at.% Sn and 25 at.% Bi). Ga-Sn-Bi alloys were prepared by liquefying Sn3Bi1 (8 wt.%) in Ga (92 wt.%) by heating the mixture on a hotplate at 350 °C for 15 min. Similarly, quaternary liquid alloy Ga95.8Sn2.6Bi1.3Pb0.4 was prepared by mixing Bi, Sn, and Pb metals with Ga at 350 °C for 15 minutes. To ensure a uniform fusion, the molten alloys were gently stirred with a glass rod. The prepared liquid alloys were stored in an oven at 60 °C. Electrochemical Cell Configuration As described in Example 2. Metal Expulsion from Ga-Sn-Bi-Pb Quaternary Alloy Selective separation of Bi, Sn, and Pb is achieved by adjusting expulsion conditions, including applied potential and electrolyte type. The quaternary Ga95.8Sn2.6Bi1.3Pb0.4 liquid alloy was prepared by dissolving Sn, Bi, and Pb in Ga at 350°C, as detailed in the previous section. First, Bi was separated from the Ga95.8Sn2.6Bi1.3Pb0.4 liquid alloy using an applied potential of -1.5 V vs. RHE in 0.50 M Na₂SO₄ solution at 50°C. The expelled product was
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 28 - collected, centrifuged, and washed multiple times with Milli-Q water. Bi expulsion leaves behind a Ga97Sn2.6Pb0.4 ternary liquid alloy. Next, Sn was selectively expelled from the Ga97Sn2.6Pb0.4 liquid alloy in 0.5 M Na2SO4 solution using a potential of -2.0 V vs. RHE at 50°C. The expelled product was collected, centrifuged, and washed several times with Milli-Q water. Sn expulsion leaves behind a Ga96Pb4 liquid alloy. In the final step, Pb was removed from the Ga96Pb4 alloy in a non-aqueous electrolyte (0.20 M NBu4PF6/DMF) using an applied potential of -5.0 V vs SCE at 50°C. We note that Pb expulsion was not possible using the aqueous solution 0.50 M Na₂SO₄; and therefore, 0.20 M NBu4PF6/DMF was used. The expelled product was collected, centrifuged, and washed several times with DMF. EXAMPLE 4 In ternary or higher liquid alloy systems, it is possible to predict the solute atoms that enrich the alloy surface, and hence we can determine the metal that can be preferentially surface segregated from the alloy. In the Ga-Sn-Bi alloy such as that of Example 2, Bi has the lowest surface energy, and therefore it populates the liquid alloy surface to reduce its surface tension. The phase separation in liquid alloys can be also predicted from the excess Gibbs free energy (#$^. The #$ values for liquid alloys involving Ga, Sn or Bi suggest that the Ga-Bi and Ga- Sn-Bi alloys exhibit the highest #$. This indicates that systems involving Ga and Bi have the highest tendency to undergo phase separation. This also suggests that if controlled phase separation occurs in a ternary Ga-Sn-Bi liquid alloy, Bi is likely to segregate prior to Sn. Increasing Bi content in the alloy yields higher #$ , and hence lower solution stability. Therefore, establishing means through electrocapillary to enrich solute atoms in the alloy surface can lead to unstable thermodynamic phases that crystallize and segregate from the alloy.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 29 - To evaluate the effectiveness of electrocapillary in inducing phase separation, it is essential to establish a correlation between surface tension and the surface atom concentrations of the alloy. To derive theoretical models that can describe this relationship, it can be proposed that the surface phase and the bulk phase of a multi-component solution is regarded as two separate phases: surface phase S and bulk phase B. Assuming that the components in the surface phase of the solution are in thermodynamic equilibrium with those in the bulk phase B, a relationship between surface concentration and surface tension can be established (see correlation (1) below).
= , − , . & 3^ ^ ^ ^ = … ) . & 345,6,… & 3 345,6,… & ,& )& ^1^ where ^ is the gas constant; ( is the absolute temperature (in Kelvin, K); %& is the surface tension of the pure liquid ^; )& is the molar partial surface area in a monolayer of pure liquid ^. ,- and ,& . are the mole fractions
a surface phase and a bulk respectively. #0,-^(, , - 0,. . ^345,6,… ^ ^ and #& ^(, ,3^
excess Gibbs free energies of ^ in function of ( and ,3 - ^ ^ and that of ^ in the bulk
345,6,… phase as a function of ( and ,3 . ^345,6,… ^ . According to Equation (1) above, the surface atomic configuration of liquid alloys is primarily influenced by their bulk composition, surface tension, and temperature. By controlling these parameters, it is possible to manipulate surface enrichment to form crystalline surface
in liquid alloys. There is an inverse relationship between the Bi surface concentration (,.- & ) and surface tension (σ). While this relationship is based on liquid alloys in a vacuum, during electrocapillary in electrolytic systems surface tension is influenced by both interfacial ions and the surface concentration of solute atoms. As the surface tension of liquid alloy decreases through electrocapillary, the concentration of Bi at the surface increases, partially contributing to the reduction in surface tension. This process continues until ,.- & reaches a threshold where a thermodynamically unstable phase of Bi is formed, leading to its separation from the alloy.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 30 - To assess the contribution of surface enrichment to electrocapillary, the electrocapillary behaviour of Ga-Sn-Bi alloy and pure Ga liquid were measured and compared. After applying voltage, the surface tension of Ga-Sn-Bi drops from 561 mN/m at -0.40 V to 414 mN/m at -0.60 V (Figure 5a and b). Pure Ga metal droplet shows similar trend (Figure 5b), but at -0.60 V vs RHE, the surface tension of the Ga-Sn-Bi alloy drops more steeply (relative to Ga) to around 414 mN/m. The slightly stronger electrocapillary response for the Ga-Sn- Bi alloy indicates that lowering surface tension via electrocapillary forces more Bi to the interface. The phase separation caused by electrocapillary performed in Example 6 is characterised by the rapid crystallisation and liberation of solute metals from the liquid alloy surface, hence it is referred to here as ‘metal expulsion’. Since the metal expulsion requires potentials higher than the electrolysis potential of water, hydrogen and oxygen are generated as by-products. To separate and collect these by-products, the metal expulsion was demonstrated utilising a two-compartment H-type electrochemical cell (Figure 2). By examining the underlying mechanisms of metal expulsion, the process can be selective in terms of the composition of metal products. Experimental results have been consistent with this conclusion. We found that applying a potential between -1.45 to -1.60 V (vs RHE) expels Bi from the alloy, while potentials higher than -1.60 V expel Bi followed by Sn after Bi expulsion is completed. EXAMPLE 5 The metal expulsion process of the procedure described in Examples 2 and 3 was further evaluated through electrochemical diagnosis and detailed analysis of the expelled products. The linear sweep voltammogram (LSV) of Ga96Sn3Bi1 liquid alloy in 0.50 M Na2SO4 shows that the expulsion and hydrogen evolution reaction (HER) are triggered at around the same potential at -1.45 V vs RHE. The expulsion of Bi (from 1.56 g of alloy with 1.97 cm2 electrochemical surface area at -1.5 V vs RHE) was completed within 18 min, achieving a recovery of around 92%. The scanning electron microscopy (SEM) image of Bi product (not shown) reveals dendritic structures that clump together to form a porous network with diameters ranging from 0.1 to 1 µm. The metals are initially expelled as particles smaller
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 31 - than 10 nm, as evidenced by TEM analysis (not shown). The particle size increases from less than 10 nm up to 0.36 µm after centrifugation, washing and drying, suggesting that the expelled Bi undergo Ostwald ripening where small particles dissolve into each other to form larger particles. The energy-dispersive X-ray spectroscopy (EDS) analysis confirmed that the elemental composition of the sample is pure Bi. The XRD pattern confirms that the product is Bi. The XPS and depth profiling analyses of Bi product reveal a ~10 nm passive oxide layer (Bi2O3) due to exposure to air or aqueous solutions, as indicated by Bi4f and O1s core-level spectra. Following Bi expulsion from Ga96Sn3Bi1, LSV was carried out on the remaining liquid alloy in 0.50 M Na2SO4 electrolyte. The LSV shows that the metal expulsion and HER are triggered at around the same potential at -1.6 V. The expulsion of Sn (from 2.2 g of alloy with 2.54 cm2 electrochemical surface area at -2.2 V vs RHE) was completed within 36 min, achieving a recovery of around 92%. The SEM and TEM analyses of the product from the second expulsion reveal clumped particles of ~20 nm size. The EDS and XRD analyses confirm that the expelled product is pure Sn, with no other phases or metal impurities detected. XPS and depth profiling analyses reveal a surface oxide layer of SnO₂ (~50 nm thick) on the expelled Sn, formed due to interactions with air or aqueous solutions. These results confirm that the expulsion product selectivity can be achieved to produce pure Sn and Bi nano-sized metals. We have also tested the metal expulsion in more complicated quaternary alloy system of Ga- Sn-Bi-Pb, and were able to expel each metal selectively adopting a separation procedure in line with what described for the corresponding ternary alloy system. As used herein, the term “about”, in the context of numerical values, typically means +/−5% of the stated value, more typically +/−4% of the stated value, more typically +/−3% of the stated value, more typically, +/−2% of the stated value, even more typically +/−1% of the stated value, and even more typically +/−0.5% of the stated value.
C:\Users\ANH\AppData\Roaming\iManage\Work\Recent\35630143PCT Metallurgical Extraction\35630143 - PCT Specification(26887063.1).docx-10/04/2025 - 32 - Throughout this specification and the claims which follow, unless the context requires otherwise, the word ‘comprise’, and variations such as ‘comprises’ and ‘comprising’, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.