WO2024081721A1 - Methods of extracting metals by electrochemical processing of a sulfoarsenide compound - Google Patents

Abstract

A method of extracting a metal of interest comprises dissolving an oxidizable metal compound in an electrolyte contained in an electrochemical cell; dissolving a sulfoarsenide compound comprising the metal of interest in the electrolyte; applying a current between an anode and a cathode of the electrochemical cell to produce an electrochemical product solution comprising soluble metal ions of the oxidizable metal compound, soluble metal ions of the metal of interest, and a soluble arsenic acid; reacting the soluble arsenic acid with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound; and separating the soluble metal ions of the metal of interest from the insoluble arsenate compound. Also disclosed is a method of extracting a metal of interest from a metal containing feed stream, and a method of isolating cobalt from a metal containing feed stream.

Description

METHODS OF BY ELECTROCHEMICAL PROCESSING OF A COMPOUND PRIORITY CLAIM This application claims priority to the United States Provisional Patent Application Serial No.63/379,119, filed October 11, 2022, the disclosure of which is hereby incorporated herein in its entirety by this reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Contract Number DE- AC07-05ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention. TECHNICAL FIELD The disclosure relates generally to methods of extracting a metal of interest by electrochemical processing. More specifically, the disclosure relates to methods of extracting a metal of interest that involves an electrochemical reaction between an oxidizable metal compound and a sulfoarsenide compound comprising the metal of interest. BACKGROUND The U.S. is highly dependent on foreign sources of cobalt (Co), with domestic supplies provided primarily from recycling. Domestic primary production is limited, with only the Eagle Mine in Michigan currently producing Co concentrates (and slated to close by 2025). Nearly all Co is produced as a byproduct of Cu and Ni mining. This situation, together with geographic concentration and geopolitical instability, cause unpredictable trends in Co prices. However, steep increases in demand for Co to be used in magnet and battery applications from 2025 to 2045 are predicted with expected increases in electric vehicle production. Arsenic handling and immobilization is a critical issue in the mining of sulfoarsenide minerals, due to arsenic’s toxicity to the environment. A significant amount of arsenic is present in Cu-, Zn-, Ni-, and Co-containing minerals. Cobaltite (CoAsS), for example, is one sulfoarsenide compound from which Co can be mined as the primary mineral. However, extraction of Co from CoAsS generates an equivalent mass of arsenic per extract of cobalt. Variability in Co price and the presence of metalloid arsenic are obstacles to obtaining the Co, leading to handling and disposition challenges. Hydrometallurgical and pyrometallurgical processes are known for immobilizing (e.g., removing) the arsenic. These processes use co-oxidants, such as oxygen gas (O₂) or hydrogen peroxide (H₂O₂), or microorganisms to immobilize the As. Some of these processes use high pressure, high temperature, and low amounts of chemicals. Some other processes use low pressure, low temperature, and high amounts of chemicals. An electrochemical process that forms scorodite from arsenic oxides through the electrochemical generation of H₂O₂ is also known. DISCLOSURE In the first aspect of the disclosure, a method of extracting a metal of interest from a metal containing feed stream is disclosed. The method comprises contacting the metal containing feed stream with an aqueous solution comprising a leaching agent to produce a leaching product solution comprising an aqueous leaching component and an insoluble solid, wherein the aqueous leaching component comprises a sulfoarsenide compound. The aqueous leaching component comprising the sulfoarsenide compound is separated from the insoluble solid. The method further comprises electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising an oxidizable metal compound to produce an aqueous product solution comprising soluble metal ions of the metal of interest, soluble metal ions of the oxidizable metal compound, and arsenic acid. The generated arsenic acid reacts with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound. The insoluble arsenate compound is separated from an aqueous electrochemical composition comprising the soluble metal ions of the metal of interest and the soluble metal ions of the oxidizable metal compound. The metal of interest is recovered from the aqueous electrochemical composition. In the second aspect of the disclosure, a method of extracting a metal of interest is disclosed. The method comprises dissolving an oxidizable metal compound in an electrolyte contained in an electrochemical cell and dissolving a sulfoarsenide compound comprising the metal of interest in the electrolyte. Upon applying a current between an anode and a cathode of the electrochemical cell, an electrochemical product solution comprising soluble metal ions of the oxidizable metal compound, soluble metal ions of the metal of interest, and a soluble arsenic acid is produced. The soluble arsenic acid reacts with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound. The soluble ions of the metal of interest are separated from the insoluble arsenate compound. In the third aspect of the disclosure, a method of isolating cobalt from a metal containing feed stream is disclosed. The method comprises electrochemically reacting the metal containing feed stream with an aqueous solution comprising a leaching agent to obtain a sulfoarsenide compound comprising cobaltite. Upon electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound, an aqueous product solution is produced that comprises soluble oxidized metal ions of the metal of interest, soluble and oxidizable metal ions of the oxidizable metal compound, and arsenic acid. The arsenic acid in the aqueous product solution reacts with oxidized metal ions of the oxidizable metal compound to form an insoluble arsenate of the metal of the oxidizable metal compound. The insoluble arsenate is separated from the aqueous product solution to produce an aqueous composition comprising the oxidized metal ions of the metal of interest. Then, the metal of interest is recovered from the aqueous composition comprising the oxidized metal ions of the metal of interest. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a simplified flow diagram of a method of extracting metal by electrochemical processing of a sulfoarsenide compound, in accordance with embodiments of the disclosure; FIGS.2A to 2C are simplified schematics of an electrochemical cell for an electrochemical As (arsenic) immobilization process, in accordance with embodiments of the disclosure; FIG.3 is a simplified schematic of the electrochemical reactions in an electrochemical cell during an electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.4 is a graph of potentiodynamic polarization results for the cobaltite anolyte (CoAsS, FeSO₄), plotting current as a function of electric potential difference, during the electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.5 is a graph of potentiodynamic polarization results for the surrogate anolyte (As₂O₅, FeSO₄, CoSO₄), plotting current as a function of electric potential difference, during the electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.6 is a scanning electron (SEM) image of the solid component isolated from the product solution of an electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.7 is the XRD spectroscopy result of the solid component isolated from the product solution of an electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.8 is the Raman spectroscopy result of the solid component isolated from the product solution of an electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.9 is the Raman spectroscopy result of scorodite; FIG.10 is a plot of the scorodite yield from the surrogate solution and the charge consumption as a function of current during an electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.11 is a plot of Faraday efficiency as a function of electric potential difference during an electrochemical As immobilization process, in accordance with embodiments of the disclosure; FIG.12 shows the XRD spectroscopy result of a product solution of the electrochemical leaching process performed at a cell potential of 2V for 72 hours at a temperature of 70°C; FIG.13 shows the XRD spectroscopy result of a product solution of the electrochemical leaching process performed at a cell potential of 9.5 V for 72 hours at a temperature of 70°C; FIG.14 is a graph showing the amounts of arsenic present (in %weight) in an aqueous component and a solid component of the product solution obtained from an electrochemical leaching process at different cell potentials; FIG.15 shows the amounts of cobalt present (in %weight) in an aqueous component and a solid component of the product solution obtained from an electrochemical leaching process at different cell potentials; FIG.16 shows the XRD spectroscopy result of the cobalt concentrate obtained from the Idaho Cobalt Operations, Central Idaho, USA; FIG.17 shows the chronopotentiometry profile of the electrochemical As immobilization process that was performed using 1.5 M of H2SO4 anolyte at the current of 350 mA and the Fe/As molar ratio of 3.25; FIG.18 is a normal plot of the effects, response to Co extraction efficiency in (a) full quadratic model and (b) reduced model, a=0.05; FIG.19 shows a standardized residual of fitted value in (a) full quadratic model and (b) reduced model; FIG.20 shows the histogram of frequency with standardized residual in (a) full quadratic model and (b) reduced model; FIG.21 shows a standardized residual of observation order in (a) full quadratic model and (b) reduced model; FIG.22 (A) and (B) represent a pareto chart and a normal plot, respectively; FIG.23 shows the XRD spectroscopy result of cobaltite; FIG.24 shows the XRD spectroscopy result of cobalt mine tailings; FIG.25 shows the XRD spectroscopy result of cobalt concentrate obtained from Jervois Mining Ltd.; FIG.26 is a simplified schematic of a system and an electrochemical cell for an electrochemical leaching process of cobalt mine tailings, in accordance with embodiments of the disclosure; and FIG.27 shows the XRD spectroscopy result of scorodite obtained from the electrochemical As immobilization process at a cell potential of 9.5 V for 72 hours at a temperature of 70°C. MODE(S) FOR CARRYING OUT THE INVENTION Increases in demand for cobalt (Co) and other metals of interest, such as nickel (Ni), copper (Cu) or zinc (Zn), have led to development of alternative processes of obtaining the metal of interest. A sulfoarsenide compound is composed of arsenic, sulfur, and metal of interest. Isolation of the metal of interest from the sulfoarsenide compound poses health and environmental concerns due to the toxicity of arsenic (As), which is most hazardous when mobile. An electrochemical process that effectively and efficiently immobilizes arsenic from a sulfoarsenide compound is disclosed. The terms “comprise(s),” “comprising,” “include(s),” “including,” “having,” “has,” “contain(s),” “containing,” and variants thereof, as used herein, are open-ended transitional phrases that are meant to encompass the elements listed thereafter and equivalents thereof as well as additional items. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Where the term “comprising” is used, the disclosure also contemplates other “comprising,” “consisting of,” or “consisting essentially of” elements presented herein, whether explicitly set forth or not. The phrase “consist(s) essentially of” or “consisting essentially of,” as used herein, is meant to encompass the elements listed thereafter and equivalents thereof, and to lack any elements that materially affects the basic and novel characteristics of the disclosed methods or compositions. The phrase “consist(s) of” or “consisting of,” as used herein, is a close-ended transitional phrase that is meant to encompass the elements listed thereafter and equivalents thereof, and to exclude any unlisted element. Any numerical range recited herein includes all values from the lower value to the upper value. For example, if a concentration range is stated as 1% to 50%, it is intended those values such as 2% to 40%, 10% to 30%, or 1% to 3%, etc., are expressly enumerated in this specification. These are only examples of what is specifically intended, and all possible combinations of numerical values between and including the lowest value and the highest value enumerated are to be considered to be expressly stated in this disclosure. The term “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity). The term “about” refers to plus or minus 10% of the indicated number. For example, “about 10%” indicates a range of 9% to 11 %, and “about 1%” means a range of 0.9% to 1.1%. Other meanings of “about” may be apparent from the context, such as rounding off, so, for example, “about 1” means from 0.5 to 1.4. It is desirable to increase the production of Co, Cu, Ni, and/or Zn to improve supply chain stability. The sulfoarsenide compound is electrochemically oxidized in an electrochemical cell to release the metal of interest, which is then recovered. The As is removed from a solution (e.g., an electrolyte) initially containing the sulfoarsenide compound by reacting the sulfoarsenide compound with an oxidizable metal compound to form an insoluble As compound. The insoluble As compound is removed from the electrolyte while the metal of interest remains in solution. By separating the insoluble As compound from the solution containing the metal of interest, the metal of interest may be recovered as a solution (e.g., a leachate). The metal of interest and the insoluble As compound are separated based on a difference in respective solubilities in the electrolyte. The sulfoarsenide compound the metal of interest may be present in an ore obtained from a mining process or other extraction process. The ore may, for example, be obtained from the Idaho Cobalt Belt (ICB). The ore may contain a sufficient amount of the metal of interest, in the form of one or more sulfoarsenide compounds (e.g., one or more compounds of the metal of interest, sulfur, and arsenic), to be recoverable. The metal of interest may be Co, Ni, Cu, Zn, or any combination thereof. The sulfoarsenide compound may include, but is not limited to, cobaltite (CoAsS), gersdorffite (NiAsS), copper sulfoarsenide (CuAsS), arsenopyrite (FeAsS), proustite (Ag₃AsS₃), tennantite (Cu₁₂As₄S₁₃), enargite (Cu3AsS4), gratonite (Pb9As4S15), seligmannite (PbCuAsS3), geocronite (Pb₁₄(Sb,As)₆S₂₃), or a combination thereof. In some embodiments, the sulfoarsenide compound includes CoAsS. In addition to Co, the ore may also include other valuable metals, such as Cu, Ag, Au, and rare earth elements, which may be co-produced with Co. A hydroelectrometallurgical process is disclosed for isolation of the metal of interest (e.g., cobalt) from a metal containing feed stream. The term “a metal containing feed stream,” as used herein, includes a metal containing primary resource, a metal containing secondary resource, or both. Non-limiting examples of the metal containing primary resources are ore, concentrate. Non-limiting examples of the metal containing secondary resources are tailings, slag. Leaching of the metal containing feed stream is performed by contacting the metal containing feed stream with an aqueous solution comprising a leaching agent to dissolve the metal of interest in the metal containing feed stream into an aqueous phase. In some embodiments, the metal containing feed stream is contacted with an aqueous solution comprising an acidic leaching agent. In some embodiments, the metal containing feed stream is contacted with an aqueous solution comprising a basic leaching agent. In some embodiments, the metal containing feed stream is pretreated with an aqueous solution comprising an acidic leaching agent, and thereafter contacted with an aqueous solution comprising a basic leaching agent. Any known acidic leaching agents or basic leaching agents may be used. Non-limiting examples of acidic leaching agents are sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, carbonic acid, citric acid, acetic acid, oxalic acid, formic acid, or a combination thereof. Non-limiting examples of basic leaching agents are ammonia, urea, thiourea, thiosulphate or a combination thereof. In some embodiments, the leaching agent also includes a reducing agent or an oxidizing agent. Non-limiting examples of suitable reducing agents are sulfate, sulfur dioxide, magnesium oxide, manganese dioxide, or a combination thereof. Non-limiting examples of suitable oxidizing agents are oxygen, hydrogen peroxide, calcium peroxide, or a combination thereof. In some embodiments, leaching of the metal containing feed stream is performed by electrochemically leaching the metal containing feed stream with ferrous sulfate in an aqueous sulfuric acid solution. FIG.1 is a simplified flow diagram showing embodiments of the disclosed method of extracting a metal of interest from a metal containing feed stream. In an electrochemical leaching process (I), the metal containing feed stream 1 is added along with a leaching agent 2 (e.g., FeSO₄) to an electrolyte 3 (e.g., H₂SO₄) contained in an electrochemical cell. Upon applying a current between an anode and a cathode of the electrochemical cell, the electrochemical leaching process proceeds to produce a leaching product solution. The leaching product solution is composed of an aqueous leaching component 4 comprising a sulfoarsenide compound (e.g., one or more sulfoarsenide compounds), and an insoluble solid 5 that is depleted of the sulfoarsenide compound. The sulfoarsenide compound may include the metal of interest. In the separation of electrochemical leaching product solution (II), the insoluble solid 5 may be removed from the aqueous leaching component 4 by any known techniques suitable for separating solid from liquid. Non-limiting examples of such separation techniques are filtration, sedimentation, decantation, crystallization, evaporation, or the like. The aqueous leaching component 4, obtained from the separation process (II), comprises the sulfoarsenide compound (i.e., one or more sulfoarsenide compounds). Non- limiting examples of sulfoarsenide compounds are cobaltite (CoAsS), gersdorffite (NiAsS), copper sulfoarsenide (CuAsS), arsenopyrite (FeAsS), proustite (Ag3AsS3), tennantite (Cu₁₂As₄S₁₃), enargite (Cu₃AsS₄), gratonite (Pb₉As₄S₁₅), seligmannite (PbCuAsS₃), geocronite (Pb14(Sb,As)6S23), or a combination thereof. The sulfoarsenide compound comprises the metal of interest such as cobalt, nickel, zinc, copper, or the like. Optionally, the disclosed method comprises a pH adjustment process (III), wherein the pH of the aqueous leaching component 4 is adjusted to be in a range of from about 1 to about 2. A conventional acidic or basic pH adjusting agent may be used in the pH adjustment process. As a non-limiting example, the aqueous leaching component 4 has a pH of less than about 1. The aqueous leaching component 4 is added with an effective amount of a basic pH adjusting agent to increase the pH of the aqueous leaching component 4 to be in the range of from about 1 to about 2, resulting in an composition 6 that comprises the sulfoarsenide compound. In the electrochemical As immobilization process (IV), the metal of interest and the arsenic in the sulfoarsenide compound is released from the sulfoarsenide compound. The arsenic is then immobilized as an insoluble solid (e.g., an insoluble arsenate compound), while the metal of interest is dissolved in an aqueous component. As shown in FIG.1, in the electrochemical As immobilization process (IV), the aqueous composition 6 comprising the sulfoarsenide compound is added along with an oxidizable metal compound 7 to an electrolyte 8 contained in an electrochemical cell. Upon applying a current between an anode and a cathode of the electrochemical cell, the electrochemical As immobilization proceeds to produce a product solution that comprises an insoluble As component 9 (e.g., arsenate compound) and an aqueous component 10 comprising the metal of interest. In the separation of electrochemical As immobilization product solution (V), the insoluble As component 9 may be removed from the aqueous component 10 comprising the metal of interest by any known techniques suitable for separating solid from liquid. Non-limiting examples of such separation techniques are filtration, sedimentation, decantation, crystallization, evaporation, or the like. The oxidizable metal compound 7 may be a chemical compound that is readily commercially available and relatively inexpensive. By way of example only, the oxidizable metal compound may be a metal salt, such as a metal halide or a metal sulfate. The oxidizable metal compound 7 may include a metal that reacts with arsenic from the sulfoarsenide compound under conditions of the electrochemical process to form the insoluble As compound. An anion of the metal salt may be the same as an anion of an acid used as the electrolyte or may be a different anion. The metal of the oxidizable metal compound may form an ion having an ionic charge of +3 under conditions of the electrochemical process. Non-limiting examples of such metals of the oxidizable metal compounds include iron (Fe), chromium (Cr) and cerium (Ce). The metal of the oxidizable metal compound may also be relatively non-toxic, so that the insoluble As compound is relatively easily disposed of. The sulfoarsenide compound and the oxidizable metal compound 7 are dissolved in the electrolyte 8, which is contained in the electrochemical cell. The ratio of metal of the oxidizable metal compound to As of the sulfoarsenide compound may be in a range of from about 1:1 to about 5:1. The electrolyte 8 used in the cell provides conditions in the electrochemical cell under which ions of the oxidizable metal compound, arsenic ions, and ions of the metal of interest are produced. The sulfoarsenide compound comprising the metal of interest, as well as the oxidizable metal compound, may be substantially soluble in the electrolyte 8. The electrolyte 8 may be an acidic solution, such as an aqueous acidic solution. The electrolyte may, for example, be an aqueous solution of sulfuric acid. However, other acids may be used. The concentration of acid in the electrolyte may be sufficient to substantially completely dissolve the metal of interest and the oxidizable metal compound in the electrolyte. The concentration of acid in the electrolyte may be in a range of from about 0.05 M to about 3 M, such as from about 0.05 M to about 2.0 M, from about 0.05 M to about 1.0 M, from about 0.5 M to about 2.5 M, from about 0.5 M to about 2.0 M, from about 0.5 M to about 1.5 M, from about 1.5 M to about 3.0 M, from about 1.5 M to about 2.5 M, from about 1.0 M to about 2.5 M, from about 1.5 M to about 2.0 M, or from about 1.0 M to about 2.0 M. The electrolyte may exhibit a pH of greater than 0 and less than about 1.0. However, the pH may be greater in order to achieve substantially complete solubility of the metal of interest and the oxidizable metal compound in the electrolyte. In some embodiments, the electrolyte is an aqueous solution of sulfuric acid, and the concentration of sulfuric acid is about 2.0 M. The disclosed electrochemical As immobilization process (IV) may be conducted in an electrochemical cell, such as in a two-compartment electrochemical cell as shown in FIGS.2A, 2B and 2C. In FIG.2A, the electrochemical cell 100 includes a first compartment on a first side of the electrochemical cell and a second compartment on a second side of the electrochemical cell 100. The first compartment and the second compartment are separated (e.g., isolated) from each other by a membrane 103, such as an anion exchange membrane or a bipolar membrane. The anion exchange membrane or the bipolar membrane may be formulated to distribute hydroxide ions and protons between the first compartment and the second compartment. The electrochemical cell 100 also includes a cathode 101, an anode 102, the membrane 103 positioned between the cathode 101 and the anode 102, and an electrolyte. FIG.2B shows the electrochemical cell 100 that further includes an optional heating element 104 to facilitate the electrochemical reaction at an elevated temperature. FIG.2C shows the electrochemical cell 100 that further includes a reference electrode 105 to provide a constant and defined potential in the electrochemical cell. The cathode 101 and the anode to a power supply (not shown) configured to apply a current between the cathode 101 and the anode 102. The cathode 101, the anode 102, and the reference electrode 105 may be formed of and include conventional materials, which are selected depending on the electrolyte being used and the metal of interest to be recovered. Energy from the power supply may be obtained from carbon free energy sources. By using clean energy, efficient operation of the electrochemical process according to embodiments of the disclosure may be achieved. The electrochemical cell may be operated at a current density range of from about 5 mA/cm² to about 200 A/cm², such as from about 5 mA/cm² to about 50 mA/cm², from about 50 mA/cm² to about 100 mA/cm², or from about 100 mA/cm² to about 200 mA/cm². In some embodiments, the current density range is from about 100 mA/cm² to about 200 mA/cm². However, a higher or lower current density may be used. In some embodiments, the oxidizable metal compound 7 comprises ferrous sulfate (FeSO₄). The electrochemical As immobilization product solution comprises an insoluble scorodite (ferric arsenate, FeAsO4) compound 9 and an aqueous component 10 comprising the metal of interest. Scorodite has low water solubility and may be readily separated from the aqueous component 10 comprising the metal of interest by any known techniques suitable for separating a solid component from a liquid component. The As immobilization process of the disclosure provides a solid arsenic-based compound that is separated from an aqueous component comprising the metal of interest by any known techniques suitable for separating a liquid component from a solid component. Furthermore, the disclosed As immobilization process provides a solid arsenic-based compound (e.g., scorodite or other arsenate compounds) that may be in a stable form for long- term storage. The disclosed electrochemical As immobilization process may be conducted at a wide range of temperatures and pressures. The electrochemical As immobilization process may be operated at a temperature range from a freezing point of the electrolyte to a boiling point of the electrolyte (each of which may depend on, for example, the molarity of the acid in the electrolyte). In some embodiments, the electrochemical As immobilization process is performed at a temperature range of from about ambient temperature to about a boiling point of the electrolyte. By way of example only, the electrochemical As immobilization process may be conducted at ambient temperature (e.g., from about 20°C to about 25°C, such as about 22°C) and at ambient pressure. However, higher temperatures and pressures may be used. The electrochemical As may be performed at a temperature range of from about 20°C to about 100°C, such as from about 50°C to about 100°C, from about 60°C to about 100°C, from about 65°C to about 100°C, from about 50°C to about 90°C, from about 50°C to about 85°C, from about 50°C to about 80°C, from about 50°C to about 75°C, from about 60°C to about 80°C, from about 65°C to about 80°C, from about 65°C to about 75°C, or from about 70°C to about 80°C. In some embodiments, the temperature is about 70°C. In some embodiments, the electrochemical As immobilization process is performed at a temperature range of from about an ambient temperature to about 70°C. In some embodiments, the electrochemical As immobilization process is performed at a temperature of about 70°C. In some embodiments, the electrochemical As immobilization process is performed at a temperature of about 80°C. Therefore, the disclosed electrochemical As immobilization process may be readily operated at an atmospheric pressure, enabling the use of conventional materials of construction in the electrochemical cell and avoiding the high expense and excessive maintenance problems associated with costly materials of construction and a high-pressure operation. The disclosed electrochemical As immobilization process may be conducted at a low pressure and at a low temperature. Furthermore, the disclosed electrochemical As immobilization process may be conducted without consuming large amounts of chemicals. The electrochemical process according to embodiments of the disclosure enables the metal of interest and the As immobilization to be achieved in a single process. In contrast, conventional hydrothermal processes require high energy inputs, the use of autoclaves for high pressure operations, excessive addition of Fe (Fe:As molar ratios higher than four), and/or the addition of external oxidants, such as hydrogen peroxide (H₂O₂), to achieve successful scorodite formation. Conventional chemical processes for the ambient pressure scorodite formation use hydrogen peroxide. However, there are costs, risks, and environmental impacts associated with the synthesis, storage/transportation, and handling of hydrogen peroxide. In the metal recovery process (VI), the metal of interest 11 may be recovered from the aqueous component 10 obtained from the electrochemical As immobilization process, and then purified by any known process suitable for the selected metal of interest. Examples of the metal recovery processes include, but are not limited to, solvent extraction, precipitation, sorption, among others. The recovered metal may be greater than or equal to about 80% pure. For example, the purity of the recovered be in a range of from about 80% to about 100% pure. In some embodiments, the metal containing feed stream is cobalt arsenic sulfide (CoAsS, cobaltite) ores or concentrates. Over 100 kilotons of Co (ten times the total Co imports for 2020) are present in the U.S. in the region known as the Idaho Cobalt Belt (ICB). This region hosts primary deposits of Co, mostly composed of the mineral cobaltite. The cobaltite may be present in ore obtained from a mining process or other extraction process. The ore may also contain one or more compounds of Cu, Ag, Au, or rare earth elements, which may be co-extracted with the Co. The disclosed method is suitable for separating and recovering cobalt from a cobalt arsenic sulfide concentrate, tailings, or ore. In the metal recovery process (VI), cobalt may be separated from the aqueous component 10 obtained from the electrochemical As immobilization process by conventional procedures, such as extraction using a highly selective cobalt to iron ion exchange solvent or resin such as Amberlite DPL, or by selective precipitation methods. Then, the isolated cobalt may be purified by, e.g., hydrogen reduction or electrowinning. FIG.3 shows a schematic drawing of one non-limiting exemplary electrochemical As immobilization process of the disclosure, wherein cobalt is the metal of interest to be isolated from cobaltite. Without being bound by any theory, it is believed that the hydroelectrometallurgical process breaks Co-As bonds in the cobaltite and immobilizes the arsenic as scorodite (FeAsO₄.2H₂O) that has a high arsenic content with low solubility in the electrolyte. As shown in FIG.3, an electrochemical cell 300 comprises a cathode 301, an anode 302, and a membrane 303 positioned between the cathode 301 and the anode 302. In some embodiments, the electrochemical cell 300 may optionally comprise a heating element 304, to conduct the electrochemical As immobilization process at an elevated temperature. An aqueous composition 305 comprising cobalt sulfoarsenide (CoAsS) is introduced, along with an oxidizable metal compound 306 (ferrous sulfate, FeSO₄), to an electrolyte 307 in the first compartment of the electrochemical cell 300. The ratio of Fe in the oxidizable metal compound 306 (FeSO₄) to As in the cobalt sulfoarsenide may be in a range of from about 1:1 to about 5:1. The electrolyte 307 may be an aqueous solution of sulfuric acid. A concentration of the sulfuric acid may be sufficient to substantially completely solubilize the ferrous sulfate and the CoAsS. The concentration may be from about 0.5 M to about 2.0 M sulfuric acid, such as from about 0.5 M to about 1.0 M or from about 1.0 M to about 2.0 M sulfuric acid. The electrolyte may exhibit a pH of greater than 0 and less than about 1.0. Electrical current is applied to the electrochemical cell 300 to polarize the anode 302 and generate the oxidation of metal ions of the oxidizable metal compound. By way of example only, if the oxidizable metal compound 306 is ferrous sulfate (FeSO4), the Fe²⁺ metal ion of FeSO₄ may be oxidized to Fe³⁺ metal ion according to the reaction shown below. The generated Fe³⁺ metal

of redox reactions at the anode 302 of the electrochemical cell 300 according to the reactions shown below:

a soluble Co²⁺ metal ion, along with elemental arsenic (Ar) and elemental sulfur (S). The generated arsenic is then oxidized by Fe³⁺ metal ion to produce a soluble arsenous acid (H₃AsO₃) containing As³⁺ metal ions. The As³⁺ metal ions in the arsenous acid (H₃AsO₃) are further oxidized to As⁵⁺ metal ions either by the electrochemically generated Fe³⁺ metal ion of the oxidizable metal compound as shown in the equations above, or through direct electrochemical oxidation. During the electrochemical process as shown above, the oxidized metal ions (Fe³⁺ ions) of the oxidizable metal compound (FeSO4) are reduced back to the reduced metal ions (Fe²⁺ ions) of the oxidizable metal compound (FeSO₄), followed by subsequent regeneration of the oxidized metal ions (Fe³⁺ ions) of the oxidizable metal compound at the anode 302. The resulting arsenic acid with the ferric (Fe³⁺) metal ion to produce an insoluble scorodite (FeAsO4) compound as shown below: H₃AsO₄ + Fe³⁺ + 2H₂O → FeAsO₄.2H₂O + 3H⁺ As shown in the chemical equations above, the elemental sulfur (S) may be oxidized ^{by the Fe3+ metal ions to produce sulfite (SO} ₃ ^{–) ions. Therefore, a total of eleven cycles of} electrochemical reactions is used to generate one mole of Co²⁺ metal ion. At the cathode 301 of the electrochemical cell 300, hydrogen (H⁺) ions of water (H2O) are reduced to produce hydrogen (H₂) gas and hydroxide (OH-) ions as shown below: 11H2O + 11e^– → ^^{^^ –} ଶ ^H2 + 11OH Thus, the of cobaltite (CoAsS) produces a

product solution comprising an scorodite (FeAsO4) compound 309. Upon separation of the soluble Co²⁺ ions from the insoluble scorodite compound 309 (e.g., through filtration), a filtrate is obtained comprising Co²⁺ metal ions (cobalt-rich filtrate, 308). Cobalt metal is then isolated from the cobalt-rich filtrate 308 and purified. Alternatively or simultaneously, the generated Fe³⁺ metal ions may be involved in a series of redox reactions at the anode 302 of the electrochemical cell 300 according to the reactions shown below:

Cobaltite (CoAsS) is oxidized by the generated Fe³⁺ metal ion to produce a soluble Co²⁺ metal ion, along with elemental arsenic (Ar) and elemental sulfur (S). The generated arsenic is then oxidized by Fe³⁺ metal ions to produce a soluble arsenous acid (H₃AsO₃) containing As³⁺ metal ions. The arsenous acid (H ³⁺ 3AsO₃) is further oxidized by Fe metal ions to produce a soluble arsenic acid (H ⁵⁺ 3AsO₄) containing As metal ions. The resulting arsenic acid (H AsO ) reacts with the ferric metal ions ( ³⁺ 3 ₄ Fe ) to provide an insoluble scorodite (FeAsO4) compound as shown below: H₃AsO₄ + Fe³⁺ + 2H₂O → FeAsO₄.2H₂O + 3H⁺ As shown in the chemical sulfur (S) is oxidized by Fe³⁺ metal ion to ^{produce sulfate (SO} ₄ ^{2–) ions. A total of thirteen cycles of electrochemical reactions are used} to generate one mole of Co²⁺ metal ion. At the cathode 301 of the second electrochemical cell 300, hydrogen (H⁺) ions of water (H₂O) are reduced to produce hydrogen (H₂) gas and hydroxide (OH-) ions as shown below: 13H2O + 12e^– → ^^{^ଷ –} ଶ ^H2 + 13OH While embodiments of the disclosure, as shown in FIG.3, are described as separating and recovering Co from CoAsS, a similar process may be used to separate one or more of Ni, Cu, or Zn from other insoluble As compounds by using a difference in solubility in the electrolyte between the metal of interest and the insoluble As compound. In addition, while embodiments of the disclosure are described as using ferrous sulfate (FeSO4) as the oxidizable metal compound, other iron salts may be used or metal salts of one or more of Ni, Cu, Ce, or Zn may be used. The recovered Co or other metal of interest may be used in batteries for electrical vehicles or other electronic devices, super alloys, industrial metals, industrial chemicals. The following examples serve to explain embodiments of the disclosure in more detail. These examples are not to be construed as being exhaustive or exclusive as to the scope of this disclosure. EXAMPLES Example 1: Electrochemical As Immobilization Process An electrochemical cell, as generally illustrated in FIGS.2A to 2C, included an anode, a cathode, a membrane, and an electrolyte. A surrogate anolyte was 20 g/L As, Fe : As : Co = 5 : 1 : 1 (molar ratio), and 0.26 M As⁵⁺ (As2O5), 0.26 M Co²⁺ (CoSO4), 1.33 M Fe²⁺ (FeSO4). A cobaltite anolyte was 20 g/L As, Fe : As : Co = 5 : 1 : 1 (molar ratio) and 0.26 M CoAsS, 1.33 M Fe²⁺ (FeSO₄). Catholyte was 1M H2SO4. The electrochemical process was performed at a temperature of about 70°C and a pressure of 1 bar for 18 hours, with 25 mL of anolyte and 25 mL of catholyte. Potentiodynamic polarization results for the cobaltite anolyte (CoAsS, FeSO4) and for the surrogate anolyte (As2O5, FeSO4, CoSO4) are shown in FIGS.4 and 5, respectively. The plots showed current as a function of electric potential difference. An electrochemical product solution was obtained that was composed component and a solid component. Filtration was performed to separate the solid component from the product solution. The isolated solid component was analyzed by X-ray powder diffraction (XRD) spectroscopy, scanning electron micrograph (SEM) spectroscopy, and Raman spectroscopy. FIG.6 is the scanning electron micrograph (SEM) image of the isolated solid component. FIG.7 is the XRD spectroscopy result of the isolated solid component, showing the presence of scorodite in the isolated solid component. FIG.8 is the Raman spectroscopy result of the isolated solid component, while FIG.9 is the Raman spectroscopy result of a known sample of scorodite. Comparison between the Raman spectroscopy results of FIGS.8 and 9 showed that the electrochemical reaction produced scorodite. The presence of scorodite precipitate from the surrogate anolyte (as shown by the SEM, XRD and Raman spectroscopies) confirmed the electrochemical As immobilization. FIG.10 is a plot of the scorodite yield from the surrogate solution and the charge consumption as a function of current. No cobalt was observed in the precipitate. FIG.11 is a plot of Faraday efficiency as a function of electric potential difference. Example 2: Electrochemical Leaching Process of Metal containing feed stream A metal containing feed stream comprising cobaltite was subjected to an electrochemical leaching process. The electrochemical leaching process of the metal containing feed stream was performed in the presence of ferrous sulfate (FeSO₄) and aqueous sulfuric acid as an electrolyte. During the electrochemical leaching process, the metals contained in the metal containing feed stream were reduced by the ferrous (Fe²⁺) from ferrous sulfate (FeSO4) and dissolved in the electrolyte, providing an aqueous leaching component. The product solution of the electrochemical leaching process comprised the aqueous leaching component containing the metals of interest, such as in a form of sulfoarsenide, and the solid component that was depleted of the metal of interest. FIG.12 shows the XRD spectroscopy result of the products from the electrochemical leaching process performed at a cell potential of 2V for 72 hours at a temperature of 70°C. The XRD spectroscopy result of FIG.12 indicated that scorodite (FeAsO4.2H2O), cobaltite (CoAsS), skutterudite (CoAs₃), and arsenious oxide (As₄O₆) were present in the product solution of the electrochemical leaching process. FIG.13 shows the XRD spectroscopy result of the products from the electrochemical leaching process performed at a cell potential of 9.5V for 72 hours at a temperature of 70°C. The XRD spectroscopy result of FIG.13 indicated that jarosite (KFe3(SO4)2(OH)6) and cobaltite (CoAsS) were present in the of the electrochemical leaching process. The electrochemical leaching process was performed on the metal containing feed stream at different cell potentials. At the end of each process, a product solution was obtained that comprised an aqueous leaching component containing the metals of interest (e.g., in the form of a sulfoarsenide compound) and the solid component that was depleted of the metal of interest. The product solution was filtered to separate the aqueous leaching component from the solid component. Each of the isolated components was analyzed to determine the amounts of arsenic and cobalt therein. FIG.14 shows the amount of arsenic present (in % by weight) in the aqueous component and the solid component when the electrochemical leaching process was performed at different cell potentials. FIG.15 shows the amount of cobalt present (in % by weight) in the aqueous component and the solid component when the electrochemical leaching process was performed at different cell potentials. Example 3: Isolation Of Cobalt From Cobalt Concentrate Cobalt concentrate was obtained from the Idaho Cobalt Operations in central Idaho, U.S. To characterize the chemical composition of the material, a digested solution of the cobalt concentrate was prepared in aqua regia. Analytical characterization using an inductively-coupled plasma optical emission spectroscopy (ICP-OES) revealed that the cobalt concentrate contained 15.11 wt% of As, 12.29% of Fe, 9.22% of Co, and 1.74% of Cu, among other metals as shown in TABLE 1 below. Furthermore, the solid state of the cobalt concentrate was structurally characterized using a powder X-ray diffraction (XRD). FIG.16 shows the XRD spectroscopy result of the cobalt concentrate, indicating that the cobalt concentrate consisted of various sulfides (FeS, CoAsS, and AsS), and oxides (As₂O₃ and SiO2). Notably, the presence of SiO2 was typically expected in the material because quartz is very commonly detected in mining concentrates. The cobalt concentrate was subjected to an electrochemical leaching process as described in Example 2. At the end of the electrochemical leaching process, the generated aqueous leaching component was separated from the solid component. The aqueous leaching component was then analyzed for the amounts of metals contained therein. TABLE 1 summarizes the amounts of metals contained in the cobalt concentrate (reported as % by weight based on the total weight of the cobalt concentrate), the amounts of metals present in the aqueous leaching component generated from the electrochemical leaching process (reported in ppm unit), and the levels of metals recovered in the aqueous leaching component (reported as % metal recovery based on of metals present in the cobalt concentrate) TABLE 1 Cu Al Mn Fe Co Ni Pb As Am nt f th 174% 119% 002% 1229% 922% 004% 000% 1511% 2

The electrochemical As immobilization process was performed as described in Example 1. The electrochemical cell used in the study included an anodic compartment and a cathode compartment, each with a maximum occupiable volume of 175 mL. The anodic and cathodic compartments were separated with an anion exchange membrane (FORBLUE™ SELEMION™ ion exchange membrane commercially available from AGC Chemical Americas). A titanium mesh with iridium oxide coating with an immerse area of 10 cm² was used as the anode. The anode compartment contained an anolyte composed of 80 mL aqueous sulfuric acid (H₂SO₄), ferrous sulfate, and cobalt concentrate. The anolyte acidity was determined by the molarity of H2SO4, and the Fe/As molar ratio was determined by the amount of ferrous sulfate in the anolyte. A platinum mesh with an immersed area of 15 cm² was used as the cathode. The cathode compartment contained 100mL of 1M H2SO4 solution. To simplify the data processing, all the reported current values were shown in absolutes terms. The current densities (mA/cm²) were calculated by dividing the reported current values by the area of the electrode. The anolyte was heated at a temperature of about 70°C using a heating mantle tape, while continuously being a mechanical stirrer at a speed of 700 rpm for 24 hours. The electrochemical As immobilization process was monitored via chronopotentiometry (changes in cell potential with time at constant current) using a Biologic potentiostat and EC-lab software. FIG.17 shows the chronopotentiometry profile of the electrochemical As immobilization process that was performed using 1.5 M of H₂SO₄ anolyte at the current of 350 mA and the Fe/As molar ratio of 3.25. Based on the chronopotentiometry result, the amount of charge passed (in coulomb) was determined and was used to evaluate the electrical energy consumed (kWh). Following the electrochemical As immobilization process in each experimental set, the anolyte was filtered with double P8 filter papers (20 μm-pore size) to separate an aqueous component and a solid component. The anolyte compartment, anode, and stirrer were rinsed during the filtration process. The isolated solid component was dried at a temperature of about 75°C in an oven for a minimum of 5 hours, and then weighed for gravimetric measurement. Approximately 125 mg of the dry solid component in 20 mL aqua regia solution was digested for 12 hours at room temperature to determine the residual Co and As contents. The aqueous component comprising Co, As, and other metals isolated from the anolyte was measured in volume and analyzed for the Co and As contents. The catholyte was measured in volume after the electrochemical As immobilization process and analyzed for the Co and As contents. Each of the aqueous component isolated from the anolyte, the digested solution of the solid component isolated from the anolyte, and the catholyte was analyzed by atomic absorption spectroscopy (AAS, Agilent 240FS) for Co, Fe, and other metals concentration measurements and by ICP-OES for As concentration measurement. Notably, due to some cationic migration through the anion exchange membrane from the anolyte to the catholyte, some cobalt was also detected in the catholyte. This was due to the large concentration gradient of cations between the two compartments of the electrochemical cell. Hence, the total extraction efficiency (%) for each of the metals was determined by considering the sum of metal mass in both anolyte and catholyte, as shown below. ^ ^{^^^^^^^^^% = ^ ^^^^௬௧^ ^+^^^^௧^^^௬௧^} All the

2 shows the amounts of cobalt and arsenic extracted from the cobalt concentrate and the energy consumptions required for the electrochemical As process, according to different sets of experiments. TABLE 2 S_et ^{Extracted Co mass} Extracted As mass Energy consumption (_g) (g) (kWh)

t ree- actor and t ree-eve ox- e n en expermenta desgn was ut zed to understand the statistical significance and impacts of three process parameters in the electrochemical As immobilization process on the cobalt extraction efficiency. The three investigated processing parameters were the current level (A), the Fe/As molar ratio (B), and anolyte H2SO4 concentration (C). The levels of the three process parameters was investigated as shown in TABLE 3. TABLE 3 Experimental Value P i P 1

TABLE 4 shows the Box-Behnken Experimental Design for the electrochemical As immobilization process for 15 experimental sets having three different levels of each investigated processing parameter (the current level, the Fe/As molar ratio, and anolyte H₂SO₄ concentration). TABLE 4 also shows the efficiencies of Co and As for each experimental set. TABLE 4 Set Level of the Processing Parameters Extraction Efficiency (%)

ion efficiency values (15-18%) for both Co and As; while the experimental set 4 provided the highest extraction efficiency values (57-62%) for both Co and As. This suggested that both Co and As metal extraction efficiencies attained the highest values at the highest levels (+1) of both current level (A) and the Fe/As molar ratio (B). FIG.18 is a normal plot of the standardized effects, response to Co extraction efficiency in (a) full quadratic model and (b) reduced model, a=0.05. FIG.19 shows a standardized residual of fitted value in (a) full quadratic model and (b) reduced model. FIG.20 shows the histogram of frequency with standardized residual in (a) full quadratic model and (b) reduced model. FIG.21 shows a standardized residual of observation order in (a) full quadratic model and (b) reduced model. Experimental data analysis was carried out with Minitab. Response surface regression methodology (RSM) was employed to find the most optimal operational condition (with combined contributions from three different processing parameters) that may offer the maximum Co extraction efficiency. Notably, RSM utilizes statistical and mathematical approaches to develop multivariable on an experimental design for the optimization of one or more response variables. Analysis of variance (ANOVA) was used to delineate the statistical significance of the individual processing parameters (A, B and C) and their quadratic (AA, BB and CC), as well as 2-way interaction (AB, AC and BC) terms with the response variable, i.e., Co extraction efficiency. Accordingly, a full second-order model was developed to account for the variability of the response surface with changes of the factors with about 95% confidence level (P-value <0.05). While this full model offered good correlation coefficients, for example, R² = 94.23% and R² (Adj) = 83.84%, it yielded relatively poor correlation coefficient for the predicted optimal response variable, for example, R² (Pred) = 53.27%. To eliminate this setback and achieve a more accurate model, it was recognized that excluding some of the quadratic (AA and BB) and 2-way interaction (AC and BC) terms from this second-order model could simplify and significantly improve the quality of the model. Accordingly, by modifying the full model, a reduced second-order model was developed to yield a more impactful predicted correlation coefficient, for example, R² (Pred) = 70.43%. The equations below showed uncoded regression equations of the full quadratic and the reduced second-order models. ^^^^^^^^^^^^^^^^^^^^^^^^ = 1.435 + 0.00123^ − 0.1885^^ − 1.671^ − 0.000001^^ + 0.01354^^ + 0.543^^ + 0.000277^^ − 0.000198^^ + 0.0317^^ ^^^^^^^^^^^^^^^^^^^^^^^^ = 1.415 − 0.000059^ − 0.0528^^ − 1.629^ + 0.540^^ + 0.000277^^ TABLE 5 shows the coded coefficients for the full quadratic model, and TABLE 6 shows the full quadratic model summary. TABLE 5 T^erm _Coefficient ^SE 95% CI T- P- VIF Coefficient Value Value 1 1

Anolyte H₂SO₄ molarity (C) -0.000033 (-0.000050, -4.72 0.005 1.01 *Anolyte H₂SO₄ molarity -0.000015) (C)

S R-sq R-sq(adj) PRESS R-sq(pred) AICc BIC 07

, 8 shows the reduced model summary. TABLE 7 Term Coefficient SE 95% CI T- P- VIF Coefficient Value Value

TABLE 8 S R-sq R-sq(adj) PRESS R-sq(pred) AICc BIC 9

TABLE 9 provides the details of ANOVA of a full quadratic model and a reduced second-order model obtained from RSM. TABLE 9 shows the statistical significance of different processing parameters on the of co-extraction efficiency as the response variable. TABLE 9 Model^Type^ Full^Second-Order^Model^ Reduced^Second-Order^Model^ Source^ DF^ Contribution F-Value^ P-Value^ DF^ Contribution^ F- P- l ^ lue^ 01 ^ 05^ 6 02^ 02^ 37^ 37^ 24^

As shown in TABLE 9 above, the reduced model provided the P value < 0.05. This indicated that the processing parameters and their quadratic, as well as their interaction terms were statistically significant in modulating the response variable within the desired confidence level; while those with p-value > 0.05 only had inconsequential statistical effects. In other words, the lower the p-value is, the higher will be the statistical importance of the term. FIG.22(A) and (B) represent a pareto chart and a normal plot, respectively. FIG.22 shows the relative standardized effects and hence, the statistical significance of the different processing parameters and their quadratic, as well as 2-way interaction terms on Co extraction efficiency. The Co extraction efficiency was most impacted by the individual influence of the current level (A), while it was least impacted by the individual influence of the anolyte H₂SO₄ concentration (C). The sequence in which the terms statistically influence the response variable followed the order: A > CC > B > AB >>> C (and within the excluded terms, the order: BB > AA > BC > AC >C). The overall RSM analysis showed of all the processing parameters and their quadratic and interaction terms, the current level (A) had the most significant influence on the response variable, i.e., Co extraction efficiency. This could be rationalized based on the fact that the electrochemical As immobilization process is driven by electrochemistry. In other words, increasing current allows for faster redox reactions in the anolyte and hence faster kinetics for the release of cobalt from the cobalt concentrate in the non-homogeneous anolyte system. Higher current drives forward the chemical equilibrium of the overall process by increasing the polarization of the electrodes, facilitating, thereby: 1) faster electrochemical regeneration of the oxidizing agent, Fe³⁺, in the reaction medium, 2) faster transport rates of the sulfate/bisulfate anions across the anion-exchange membrane from the anolyte to the catholyte, and 3) faster hydrogen evolution reaction kinetics in the catholyte. The Fe/As molar ratio (B) was another influential factor in increasing Co extraction efficiency. This could be explained based on the fact that in the presence of higher concentration of the oxidizing agent, Fe³⁺, the equilibrium of the redox reactions in the anolyte proceeds faster due to the overall equilibrium being driven forward based on Le Chatelier’s principle. The significance of the two factors, A and B, on Co extraction efficiency could also be observed from the statistical importance of their 2-way interaction term AB as mentioned earlier. The anolyte H2SO4 concentration (C) had the least impact on Co extraction efficiency. Example 4: Isolation Of Cobalt From Cobalt Mine Tailing FIGS.23 to 25 show the XRD spectroscopy results of different metal containing feed streams. FIG.23 shows the XRD spectroscopy result of cobaltite; FIG.24 shows the XRD spectroscopy result of cobalt mine tailings; and FIG.25 shows the XRD spectroscopy result of cobalt concentrate obtained from Jervois Mining Ltd. An inductively-coupled plasma optical emission spectroscopy (ICP-OES) was utilized to analytically characterize the chemical composition of each different metal containing feed stream (the cobaltite, the cobalt mine tailings, and the cobalt concentrate. The analytical results are summarized in TABLE 10. ^{i %} N _{– 7} ^{% 4.} _{4 0} ^0. ₀ o _{% C} ⁰ ₀ ^{% %} . _{0 2} 9 ⁶ 2 ^. ₁ ^2. ₉ s _{% A} ⁰ ₀ ^% _{% . 5} ^{1 7 7} 3 ^. _{1. 6} ⁵ _{1 % %}

₂ e _{% F –} ⁸ _{% 6.} ^{9 0} _{2. 1} ² ₁ n ^% M _{– 3} ^{% 0.} _{2 0} ^0. ₀ l A _– ^% ₁ ^{% 3.} _{9 0} ^1. ₁ u ^% ₈ ^% C _– ^8. _{4 1} ^7. ₁ r ^{% %} C _{– 1} ^0. _{2 0} ^0. ₀ a ^{% %} C _{– 6} ^0. _{3 1} ^2. ₀ cⁱ _n ^{e e} _{s n et r e i} ^{s Ad} t ⁱ _g ^t _l ^a _{rt l fl} ^M _t ^{ni a} _b ⁿ _e a_b ^u _l ^a _li ^{a o c} _n o _{S b} ^o _{T C} ^o C _{C C} Cobalt mine tailing was subjected electrochemical leaching process. FIG.26 is a simplified schematic of the system and the electrochemical cell for an electrochemical leaching process of cobalt mine tailings. As shown in FIG.26, an electrochemical cell 400 was composed of an anode 410, a cathode 420, and an electrolyte 430 of aqueous sulfuric acid. Cobalt mining tailings 500 was added along with ferrous sulfate to the electrolyte 430 contained in the electrochemical cell 400. The electrochemical leaching process was performed for 36 hours at an ambient pressure and an ambient temperature. At the anode 410, the ferrous (Fe²⁺) ion from the ferrous sulfate (FeSO4) was oxidized to the ferric (Fe³⁺) ion according to the reaction below: Fe²⁺ → Fe³⁺ + e^– At the cathode 420, the metal (M²⁺) ion in the cobalt mine tailings was reduced to metal according to the reaction below. Some of these metal ions were Cu²⁺, Co²⁺, Ni²⁺, and As³⁺. M²⁺ + e^– → M At the end of the electrochemical leaching process, a product solution was obtained that comprised copper arsenide (Cu3As) 600 deposited on the cathode 420, a leachate solution 700, and a leachate precipitate 800. Separation was conducted to isolate each component of the product solution. The leachate solution 700 was analyzed for the contents of cobalt (Co) and arsenic (As). About 23,713 ppm of Co and about 18,139 ppm of As were found in the leachate solution 700. Furthermore, the amount of metal present in each component of the product solution was determined, and a mass percentage of the extracted metal was calculated. TABLE 11 shows the amount and % extracted mass of metals (Cu, Fe, Co and As) in each component of the product solution. TABLE 11 Metal

The leachate solution 700 compounds including cobaltite (CoAsS) was subjected to the electrochemical As immobilization process as described in Example 1. The electrochemical As immobilization process was performed at a cell potential of 8V for 24 hours at a temperature of about 70°C and an ambient pressure. FIG.27 is the XRD spectroscopy result of the electrochemical As immobilization process and confirmed that scorodite was produced from the electrochemical As immobilization process of the cobalt mine tailings. About 81% of arsenic was recovered in the form of scorodite from the electrochemical As immobilization process. Additional non-limiting example embodiments of the disclosure are described below. Embodiment 1: A method of extracting a metal of interest from a metal containing feed stream, comprising: contacting the metal containing feed stream with an aqueous solution comprising a leaching agent to produce a leaching product solution comprising an aqueous leaching component and an insoluble solid, the aqueous leaching component comprising a sulfoarsenide compound; separating the aqueous leaching component comprising the sulfoarsenide compound from the insoluble solid; electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising an oxidizable metal compound to produce an aqueous product solution comprising soluble metal ions of the metal of interest, soluble metal ions of the oxidizable metal compound, and arsenic acid; reacting the arsenic acid with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound separating the insoluble arsenate compound from an aqueous electrochemical composition comprising the soluble metal ions of the metal of interest and the soluble metal ions of the oxidizable metal compound; and recovering the metal of interest from the aqueous electrochemical composition. Embodiment 2: The method of Embodiment 1, wherein contacting the metal containing feed stream comprises electrochemically leaching the metal containing feed stream with ferrous sulfate in an aqueous sulfuric acid solution. Embodiment 3: The method of Embodiment 1, wherein contacting the metal containing feed stream comprises leaching the metal containing feed stream with one or more of an acidic leaching agent and a basic leaching agent. Embodiment 4: The method of any one of Embodiments 1 to 3, wherein separating the aqueous leaching component comprising the sulfoarsenide compound from the insoluble solid comprises obtaining an aqueous solution comprising cobaltite, gersdorffite, proustite, tennantite, enargite, gratonite, geocronite, seligmannite, or a combination thereof. Embodiment 5: The method of of Embodiments 1 to 4, further comprising adjusting a pH of the aqueous leaching component comprising a sulfoarsenide compound to a pH range of from about 1 to about 2. Embodiment 6: The method of any one of Embodiments 1 to 5, wherein electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising an oxidizable metal compound comprises electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising ferrous sulfate and sulfuric acid. Embodiment 7: The method of Embodiment 6, wherein electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising ferrous sulfate and sulfuric acid comprises producing an aqueous product solution comprising soluble metal ions of the metal of interest, ferrous ions, ferric ions, and arsenic acid. Embodiment 8: The method of Embodiment 6, wherein reacting the arsenic acid with the metal ions of the oxidizable metal compound comprises forming an insoluble arsenate compound comprising scorodite. Embodiment 9: The method of any one of Embodiments 1 to 8, wherein isolating the metal of interest from the aqueous electrochemical composition comprises isolating a metal comprising cobalt, nickel, zinc, copper, or any combination thereof. Embodiment 10: A method of extracting a metal of interest, comprising: dissolving an oxidizable metal compound in an electrolyte, the electrolyte contained in an electrochemical cell; dissolving a sulfoarsenide compound in the electrolyte, the sulfoarsenide compound comprising the metal of interest; applying a current between an anode and a cathode of the electrochemical cell to produce an electrochemical product solution comprising soluble metal ions of the oxidizable metal compound, soluble metal ions of the metal of interest, and a soluble arsenic acid; reacting the soluble arsenic acid with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound; and separating the soluble metal ions of the metal of interest from the insoluble arsenate compound. Embodiment 11: The method of Embodiment 10, wherein dissolving an oxidizable metal compound in an electrolyte comprises dissolving the oxidizable metal compound in a sulfuric acid solution. Embodiment 12: The method of Embodiment 10, wherein dissolving an oxidizable metal compound in an electrolyte comprises dissolving ferrous sulfate in a sulfuric acid solution. Embodiment 13: The method of of Embodiments 10 to 12, wherein dissolving a sulfoarsenide compound in the electrolyte comprises dissolving a sulfoarsenide compound comprising cobalt, nickel, zinc, copper, or a combination thereof in the electrolyte. Embodiment 14: The method of any one of Embodiments 10 to 13, wherein dissolving a sulfoarsenide compound in the electrolyte comprises dissolving cobaltite in the electrolyte. Embodiment 15: The method of any one of Embodiments 10 to 14, wherein: dissolving an oxidizable metal compound in an electrolyte comprises dissolving ferrous sulfate in a sulfuric acid solution, and reacting the arsenic acid with the metal ion of the oxidizable metal compound to form an insoluble arsenate of the metal of the oxidizable compound comprises forming an insoluble scorodite. Embodiment 16: A method of isolating cobalt from a metal containing feed stream, comprising: electrochemically reacting the metal containing feed stream with an aqueous solution comprising a leaching agent to obtain a sulfoarsenide compound comprising cobaltite; electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound to produce an aqueous product solution comprising soluble oxidized metal ions of the metal of interest, soluble and oxidizable metal ions of the oxidizable metal compound, and arsenic acid; reacting the arsenic acid in the aqueous product solution with oxidized metal ions of the oxidizable metal compound to form an insoluble arsenate of the metal of the oxidizable metal compound; separating the insoluble arsenate from the aqueous product solution to produce an aqueous composition comprising the oxidized metal ions of the metal of interest; and recovering the metal of interest from the aqueous composition comprising the oxidized metal ions of the metal of interest. Embodiment 17: The method of Embodiment 16, wherein electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound comprises: electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising ferrous sulfate and sulfuric acid to produce an aqueous product solution comprising soluble metal ions of the metal of interest, soluble ferrous ions, soluble ferric ions, and arsenic acid, wherein the soluble metal ions of the metal of interest comprise cobalt ions. Embodiment 18: The method of Embodiment 16 or 17, wherein reacting the arsenic acid in the aqueous product solution with an oxidized metal ions of the oxidizable metal compound comprises: reacting the arsenic the aqueous product solution with ferric ions to form an insoluble scorodite. Embodiment 19: The method of any one of Embodiments 16 to 18, wherein separating the insoluble arsenate from the aqueous product solution to produce an aqueous composition comprising the oxidized metal ions of the metal of interest comprises: filtering the aqueous product solution to remove the insoluble arsenate comprising scorodite and to provide an aqueous composition comprising cobalt (II) ions. Embodiment 20: The method of any one of Embodiments 16 to 19, wherein electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound comprises performing the electrochemically reacting at a temperature range of from about room temperature to about 70℃. While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the disclosure is not limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the following appended claims and their legal equivalent. For example, elements and features disclosed in relation to one embodiment may be combined with elements and features disclosed in relation to other embodiments of the disclosure.

Claims

We claim: 1. A method of extracting a metal of interest from a metal containing feed stream, comprising: contacting the metal containing feed stream with an aqueous solution comprising a leaching agent to produce a leaching product solution comprising an aqueous leaching component and an insoluble solid, the aqueous leaching component comprising a sulfoarsenide compound; separating the aqueous leaching component comprising the sulfoarsenide compound from the insoluble solid; electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising an oxidizable metal compound to produce an aqueous product solution comprising soluble metal ions of the metal of interest, soluble metal ions of the oxidizable metal compound, and arsenic acid; reacting the arsenic acid with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound; separating the insoluble arsenate compound from an aqueous electrochemical composition comprising the soluble metal ions of the metal of interest and the soluble metal ions of the oxidizable metal compound; and recovering the metal of interest from the aqueous electrochemical composition. 2. The method of claim 1, wherein contacting the metal containing feed stream comprises electrochemically leaching the metal containing feed stream with ferrous sulfate in an aqueous sulfuric acid solution. 3. The method of claim 1, wherein leaching the metal containing feed stream comprises leaching the metal containing feed stream with one or more of an acidic leaching agent and a basic leaching agent. 4. The method of any one of 1 to 3, wherein separating the aqueous leaching component comprising the sulfoarsenide compound from the insoluble solid comprises obtaining an aqueous solution comprising cobaltite, gersdorffite, proustite, tennantite, enargite, gratonite, geocronite, seligmannite, or a combination thereof. 5. The method of any one of claims 1 to 4, further comprising adjusting a pH of the aqueous leaching component comprising a sulfoarsenide compound to a pH range of from about 1 to about 2. 6. The method of any one of claims 1 to 5, wherein electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising an oxidizable metal compound comprises: electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising ferrous sulfate and sulfuric acid. 7. The method of claim 6, wherein electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising ferrous sulfate and sulfuric acid comprises producing an aqueous product solution comprising soluble metal ions of the metal of interest, ferrous ions, ferric ions, and arsenic acid. 8. The method of claim 6, wherein reacting the arsenic acid with the metal ions of the oxidizable metal compound comprises forming an insoluble arsenate compound comprising scorodite. 9. The method of any one of claims 1 to 8, wherein isolating the metal of interest from the aqueous electrochemical composition comprises isolating a metal comprising cobalt, nickel, zinc, copper, or any combination thereof. 10. A method of extracting a of interest, comprising: dissolving an oxidizable metal compound in an electrolyte, the electrolyte contained in an electrochemical cell; dissolving a sulfoarsenide compound in the electrolyte, the sulfoarsenide compound comprising the metal of interest; applying a current between an anode and a cathode of the electrochemical cell to produce an electrochemical product solution comprising soluble metal ions of the oxidizable metal compound, soluble metal ions of the metal of interest, and a soluble arsenic acid; reacting the soluble arsenic acid with the metal ions of the oxidizable metal compound to form an insoluble arsenate compound comprising the metal of the oxidizable metal compound; and separating the soluble metal ions of the metal of interest from the insoluble arsenate compound. 11. The method of claim 10, wherein dissolving an oxidizable metal compound in an electrolyte comprises dissolving the oxidizable metal compound in a sulfuric acid solution. 12. The method of claim 10, wherein dissolving an oxidizable metal compound in an electrolyte comprises dissolving ferrous sulfate in a sulfuric acid solution. 13. The method of any one of claims 10 to 12, wherein dissolving a sulfoarsenide compound in the electrolyte comprises dissolving a sulfoarsenide compound comprising cobalt, nickel, zinc, copper, or a combination thereof in the electrolyte. 14. The method of any one of claims 10 to 13, wherein dissolving a sulfoarsenide compound in the electrolyte comprises dissolving cobaltite in the electrolyte. 15. The method of any one of 10 to 14, wherein: dissolving an oxidizable metal compound in an electrolyte comprises dissolving ferrous sulfate in a sulfuric acid solution, and reacting the arsenic acid with the metal ion of the oxidizable metal compound to form an insoluble arsenate of the metal of the oxidizable compound comprises forming an insoluble scorodite. 16. A method of isolating cobalt from a metal containing feed stream, comprising: electrochemically reacting the metal containing feed stream with an aqueous solution comprising a leaching agent to obtain a sulfoarsenide compound comprising cobaltite; electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound to produce an aqueous product solution comprising soluble oxidized metal ions of the metal of interest, soluble and oxidizable metal ions of the oxidizable metal compound, and arsenic acid; reacting the arsenic acid in the aqueous product solution with oxidized metal ions of the oxidizable metal compound to form an insoluble arsenate of the metal of the oxidizable metal compound; separating the insoluble arsenate from the aqueous product solution to produce an aqueous composition comprising the oxidized metal ions of the metal of interest; and recovering the metal of interest from the aqueous composition comprising the oxidized metal ions of the metal of interest. 17. The method of claim 16, wherein electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound comprises: electrochemically reacting the sulfoarsenide compound with an aqueous solution comprising ferrous sulfate and sulfuric acid to produce an aqueous product solution comprising soluble metal ions of the metal of interest, soluble ferrous ions, soluble ferric ions, and arsenic acid, wherein the soluble metal ions of the metal of interest comprise cobalt ions. 18. The method of claim 16 or reacting the arsenic acid in the aqueous product solution with an oxidized metal ions of the oxidizable metal compound comprises: reacting the arsenic acid in the aqueous product solution with ferric ions to form an insoluble scorodite. 19. The method of any one of claims 16 to 18, wherein separating the insoluble arsenate from the aqueous product solution to produce an aqueous composition comprising the oxidized metal ions of the metal of interest comprises: filtering the aqueous product solution to remove the insoluble arsenate comprising scorodite and to provide an aqueous composition comprising cobalt (II) ions. 20. The method of any one of claims 16 to 19, wherein electrochemically reacting the sulfoarsenide compound comprising cobaltite with an aqueous solution comprising an oxidizable metal compound comprises performing the electrochemically reacting at a temperature range of from about room temperature to about 70℃.