EXTRACTION AND RECOVERY OF METALS UNDER AMBIENT CONDITIONS

Abstract

Methods for extracting a target metal from a mixed metal input are described. The method includes milling the mixed metal input with ammonium bicarbonate to form a milled solid product, aging the milled solid product, and leaching the target metal from the aged solid product.

Claims

1. A method of extracting a target metal from a mixed metal input, comprising: milling the mixed metal input with ammonium bicarbonate to form a milled solid product; aging the milled solid product to form an aged solid product; and leaching the target metal from the aged solid product.

2. The method of claim 1, wherein target metal is one or more of nickel, cobalt, and copper.

3. The method of claim 1, wherein aging includes aging for up to 1 year.

4. The method of claim 1, wherein milling includes low energy milling for 1 hour up to 5 hours.

5. The method of claim 1, wherein leaching includes contacting the aged solid product with an aqueous leaching solution at a temperature less than 45 C.

6. The method of claim 1, further comprising chelating ferric iron from the aged solid product with an anionic chelator to release nickel ions.

7. A method of extracting a target metal from a mixed metal input, comprising: mechanochemically reacting the mixed metal input with ammonium bicarbonate to form a milled solid product; waiting an aging duration to form an aged solid product from the milled solid product; contacting the aged solid product with an aqueous leaching solution; and isolating the target metal from the aqueous leaching solution.

8. The method of claim 7, wherein the aging duration is at least one week.

9. The method of claim 7, wherein contacting the aged solid product with the aqueous leaching solution includes moving the aqueous leaching solution or agitating the aged solid product in the aqueous leaching solution.

10. The method of claim 7, further comprising separating the aqueous leaching solution from the aged solid product and adding ion exchange resin to the aqueous leaching solution.

11. The method of claim 7, wherein isolating the target metal from the aqueous leaching solution includes one or more of electrowinning, cementation, ion exchange resin, crystallization, and solvent extraction.

12. The method of claim 7, wherein a pH of the aqueous leaching solution is in a range of 7.0 to 9.9.

13. The method of claim 7, wherein leaching the aged solid product leaches more target metal than leaching the milled solid product.

14. A method of extracting nickel from a mixed metal input, comprising: low energy milling the mixed metal input with ammonium bicarbonate and milling media to react the nickel with the ammonium bicarbonate and form a milled solid product; aging the milled solid product to form an aged solid product from the milled solid product, wherein the aged solid product is chemically different from the milled solid product; and leaching the nickel from the aged solid product with an aqueous leaching solution comprising one or more of ammonium bicarbonate, a carboxyl metal extractant, and an amine metal extractant.

15. The method of claim 14, wherein low energy milling includes jar milling.

16. The method of claim 14, wherein one or more of the carboxyl metal extractant and amine metal extractant is included in the aqueous leaching solution in molar excess of the nickel in the aged solid product.

17. The method of claim 14, wherein aging the milled solid product includes aging in relative humidity in a range of 40% to 85%.

18. The method of claim 14, wherein the ammonium bicarbonate is added to the mixed metal input in a ratio of 0.5:1 up to 2:1.

19. The method of claim 14, wherein leaching leaches greater than or equal to 90% of the nickel from the aged solid product to the aqueous leaching solution.

20. The method of claim 14, wherein low energy milling includes dry low energy milling.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0006] FIG. 1 shows a process flow for extracting a target metal from a mixed metal input.

[0007] FIG. 2 shows an X-ray diffraction spectrum of an example of a mixed metal input compared to identified reference spectra.

[0008] FIG. 3 shows a flowchart of an example of a method for extracting the target metal.

[0009] FIG. 4 shows an X-ray diffraction spectrum of ammonium bicarbonate compared with an X-ray diffraction spectrum of a milled solid product.

[0010] FIG. 5 shows a flowchart of an example of a method for leaching the target metal from an aged solid product.

[0011] FIG. 6 shows a flowchart of an example of a method for chelating the target metal from the aged solid product.

[0012] FIG. 7 shows X-ray diffraction spectra of a mixed metal input, an aqueous leached aged solid product, and an aqueous leached and anionic metal chelator rinsed aged solid product.

DETAILED DESCRIPTION

[0013] The following description relates to methods for extracting a target metal from a mixed metal input. An overview of the extraction method is shown in the process flow diagram of FIG. 1. Herein, a mixed metal input may be a primarily inorganic material comprising the target metal in addition to other non-target metals. Herein, the target metal may include nickel, copper, and/or cobalt. Further, the target metal may not be iron. Additionally, herein the target metal is a transition metal that is selectively leached from the mixed metal input. An X-ray diffraction (XRD) spectrum of an exemplary embodiment of a mixed metal input is shown in FIG. 2. FIG. 2 also shows reference spectra for the phases comprising the mixed metal input. A flowchart of an example of the method for extracting the target metal from the mixed metal input is shown in FIG. 3. The method includes mechanochemically reacting the mixed metal input with ammonium bicarbonate. FIG. 4 compares an XRD spectrum of the ammonium bicarbonate reagent with an XRD spectrum of the result of the mechanochemical reaction of the ammonium bicarbonate with the mixed metal input. The XRD spectrum of the resulting product includes peaks that are not associated with ammonium bicarbonate or the mixed metal input, shown in FIG. 2. After the mechanochemical reaction and aging, the target metal is leachable at room temperature using an aqueous solution. A flowchart of an example of a method for leaching the target metal is shown in FIG. 5. In some examples, an anionic chelator rinse may further extract the target metal from the aged solid product. A flowchart of an example of a method for an anionic chelator rinse is shown in FIG. 6. The results of successive aqueous leaching and chelator rinsing are showed in XRD spectra in FIG. 7.

[0014] Turning now to FIG. 1, a process diagram 100 for extracting the target metal from a mixed metal input is shown. For example, the mixed metal input may be an unprocessed ore, an intermediate product of ore processing, or an already processed material for recycling. For example, the mixed metal input may be battery black mass obtained from shredding of depleted lithium ion batteries. As a further example, the mixed metal input may be a laterite ore, a sulfidic orc, a mixed hydroxide precipitate, or a hybrid ore including a plurality of different phases. The target metal may be a metal having a high value. For example, the metal may be used extensively in synthesis of cathode/anode electroactive materials for secondary batteries. For example, the target metal may be one or more of nickel, cobalt, and/or copper.

[0015] Turning briefly to FIG. 2, an XRD spectrum 200 of an exemplary embodiment of a mixed metal input is shown. XRD spectrum 200 may be compared to reference spectra 202, used to identify and quantify a plurality of mineral phases comprising the mixed metal input. Reference spectra 202 which comprise the mixed metal input XRD spectrum 200 include pyrite (FeS.sub.2) 204, talc (Mg.sub.3Si.sub.4O.sub.10(OH.sub.2) 206, pentlandite ((Fc.sub.2Ni).sub.9S.sub.8) 208, lizardite (Mg.sub.3(Si.sub.2O.sub.5) (OH).sub.4) 210, berethicrine ((Fe.sup.2+, Fe.sup.3+, Al,Mg,Mn).sub.2(Si,Al).sub.2O.sub.5 (OH).sub.4) 212, and quartz (SiO.sub.2) 214. Further, XRD spectrum 200 indicates that the exemplary mixed metal input includes 22.1 wt. % pyrite, 15.9 wt. % talc, 49.9 wt. % pentlandite, 2.8 wt. % lizardite, 8.0 wt. % berthierine, and 1.3 wt. % quartz. The target metal of the exemplary mixed metal input may be nickel. Based on the composition described above, an exemplary mixed metal input may be partly comprised of a phase including the target metal (e.g., pentlandite). In this way, the target metal (e.g., Ni) may comprise a small amount (e.g., less than 50% by weight) of the mixed metal input. The target metal may comprise a minority of the mixed metal input by weight.

[0016] Returning now to FIG. 1, the mixed metal input and the ammonium bicarbonate may be input to the milling process 102 (e.g., milling). During milling 102, the mixed metal input mechanochemically reacts with the ammonium bicarbonate, driven by the energy input by collisions experienced by the reagents (e.g., ammonium bicarbonate and mixed metal input) with the container walls and milling media during milling. Parameters of the milling process are discussed further below with respect to the flowchart of FIG. 3.

[0017] The contents of the mill may then be passed through sieving 104. Sieving 104 may separate the milling media from the milled solid product produced from the reaction of the mixed metal material/ammonium bicarbonate mixture. The milled solid product may then be subject to aging 106. Parameters of the aging process are described further below with respect to the flowchart of FIG. 3. After aging, the aged solid product undergoes leaching 108. Leaching may pull the target metal ions from the solid phase into the liquid phase. Optionally, the leachate may then be contacted with a target metal ion exchange (IEX) resin 110. The target metal IEX resin may adsorb the target metal from the leachate and an acid may be used to extract the target metal ion from the target metal ion exchange resin. Adsorbing the target metal ion from the leachate may regenerate the leach solution and it may be reused for leaching 108. Leaching, with and without the target metal IEX resin is discussed further below with respect to FIG. 5.

[0018] After contacting the target metal IEX resin the remaining liquid phase may include excess ammonium bicarbonate from the leaching process. The remaining liquid phase may be returned to milling 102. The excess ammonium bicarbonate may then be repurposed for the reaction occurring during milling. The added liquid phase may be enough to hydrate the mixed metal input without forming a slurry.

[0019] After leaching, the solid product may be subject to a chelator rinsing 114. The chelator of chelator rinse 114 may be an anionic chelator selected to chelate ferric iron. The chelator rinse may be used to further extract nickel that has been entrapped by ferric iron compounds. Without being bound by theory, the nickel extraction may be limited if the mixed metal input includes high oxidation state ferric iron compounds (such as but not limited to iron hydroxide, iron oxy hydroxide, iron oxide, iron hydroxyl sulfate, berthierine, and combinations thereof), the nickel may be entrapped or passivated by the high oxidation ferric iron compound. Chemically dissolving the ferric ions may release the nickel ions, resulting in their eventual recovery in solution. The anionic chelator may partition the ferric ions into solution, thereby causing the release of nickel ions. In some examples, leaching 108 and chelator rinsing 114 may be combined into a single step in which the anionic chelator is added to the leaching solution. Chelator rinse 114 may lower the chemical cost for nickel extraction and may help increase the extraction efficiency to over 96%. Further, chelator rinse 114 may decrease an amount of ammonium bicarbonate demanded for the overall target metal extraction process.

[0020] The anionic chelator may include, but is not limited to, chlorides, bromides, iodides, perchlorates, sulfates, nitrates, phosphates, oxalates, acetates, citrates, carbonates, and organic acids. Organic acids may include, but are not limited to acetic acid, citric acid, lactic acid, formic acid, malic acid, malonic acid, salicylic acid, adipic acid, oxalic acid, tartaric acid, butyric acid, glyceric acid, propionic acid, succinic acid, benzoic acid, fumaric acid, trifluoroacetic acid, acrylic acid, gallic acid, glycolic acid, uric acid, adipic acid, barbituric acid, ascorbic acid, trichloroacetic acid.

[0021] The liquid phase resulting from the chelator rinse may include both ferric ions and nickel ions and/or other target metal ions. The liquid phase may be optionally directed to an iron IEX resin 112. The iron IEX resin 112 may adsorb the ferric ions, leaving behind the nickel ions and/or other target metal ions to be recovered. Chelator rinse 114 is discussed further below with respect to FIG. 6. Other methods of separating iron from nickel and other target metal ions, such as precipitation, are also considered within a scope of the application.

[0022] The process shown in FIG. 1 may take a mixed metal input and extract a target metal ion using low energy inputs, benign reagents, and may produce little waste. An example of a method 300 for extracting a target metal according to the process outlined in FIG. 1 is shown in FIG. 3.

[0023] At 302, method 300 includes adding the mixed metal input, ammonium bicarbonate and milling media to a mill. As one example the milling media may be stainless-steel, although other milling media are also considered within the scope of the disclosure. As one example a ratio (by weight) of ammonium bicarbonate to mixed metal input added to the mill may be in a range of 0.5:1 up to 2:1. In some examples, increasing an amount of ammonium bicarbonate relative to the mixed metal input may decrease a demanded aging time to leach the target metal at a high yield. Further, a weight ratio of milling media to solids (e.g., the ammonium bicarbonate and mixed metal input) added to the mill may be in range of 3:1 up to 5:1. In some examples, decreasing the ratio of milling media to solids may increase a yield of the target metal during the leaching step.

[0024] In some examples the mill may be a low energy mill. A low energy mill may be a materials processing equipment configured to rotate and/or vibrate materials with or without the use of milling medial. The low energy mill may include one or more of, but is not limited to, a jar rolling mill, a vibratory mill, a rock tumbler, a tumbler polishers, and a trammel. In alternate examples, the mill may be a high energy mill such as a high energy ball mill. In some examples, a milling time and an aging duration (as described further below) may be shorter when milling using a high energy mill as compared to a low energy mill. A low energy milling process may demand less energy input than a high energy milling process, and may be preferred to keep overall operating costs of the process to a minimum. Additionally, a low energy milling process may be less likely to contaminate the mixed metal input with the material of the mill and/or milling media than a high energy milling process. During milling, the ammonium bicarbonate may react with the nickel or other target metal of the mixed metal input to form a water-soluble compound. Without being bound by theory, the ammonium bicarbonate may be reactive under low energy milling conditions due to a relatively low (e.g., <30 C.) decomposition temperature as compared to ammonium carbonate. For example, milling may form amine nickel carbonate (Ni(NH.sub.3).sub.n.sup.2+)(CO.sub.3) or (Ni(NH.sub.3).sub.n.sup.2+)(SO.sub.4) from in-situ oxidation of sulfur.

[0025] At 303, method 300 optionally includes adding one or more of a calcium base, oxidant, and/or chloride salt to the mill. For example, a calcium base may include calcium carbonate and/or calcium hydroxide (e.g., lime). The calcium base may be added if the target metal is copper in addition to cobalt.

[0026] Adding chloride salt may increase a selectivity of nickel and cobalt as the target metal over copper. In this way, the purity of the resulting leachate may be high enough to convert to a mixed hydroxide precipitate or sulfate product (e.g., for battery cathode production). Additionally, chloride may result in the aging process being performed at a wider range of temperature and humidity storage conditions without decreasing the extraction efficiency. Chloride salt may include salts of one or more of ammonium, sodium, magnesium, calcium, or mixtures thereof. A concentration of the chloride salt may be in a range of 0.1 M to 2 M. An amount of chloride included may be greater than or equal to the stoichiometric chloride compound formed with the total molar amount of iron, nickel, and cobalt in the mixed metal input. For example, nickel reacts with chlorides to make NiCl.sub.2, thus if 1 g of nickel metal was left in the solid then 1/58.69 (the atomic weight of nickel)=0.017 moles of nickel and since 1 mole of nickel metal in NiCl.sub.2 has 2 corresponding chlorides ions, then a stoichiometric amount is 0.0172+0.034 moles of chloride ions, and since chlorine's mass is 35.45 grams/mole, we have 0.034 moles35.45 grams/mole which yields 1.208 grams of chloride for 1 gram of residual nickel. The same calculation can be used for iron and cobalt to determine the stoichiometric amount of chloride for 1 g each of those metals, and then adding up the chloride for all three metals is the minimum chloride to leach said metals. In some examples, the mole ratio of total chloride ions to total metal ions may be in a range of 1:1 to 10:1.

[0027] Adding an oxidant may increase the leaching process (e.g., leaching 108) occurring down stream of milling. The oxidant may be in a solid, solution, or gaseous form. The oxidant may be one or more of hydrogen peroxide, 2KHSO.sub.5.Math.KHSO.sub.4.Math.K.sub.2SO.sub.4 (e.g., Oxone), persulfate salts, ferric salts, ozone, oxygen, air gas, and mixtures thereof. If in a solution, a concentration of the oxidant added may be in a range of 0.1 M to 2 M. The oxidant may be an added in an amount relative to the mass of mixed metal input added at 302. For example, oxidant: ore mass ratio may be in a range of 0.1:1 to 2:1.

[0028] At 304, method 300 includes milling the ammonium bicarbonate and mixed metal input in addition to the optional calcium base and/or anionic chelator with milling media for a duration to form a milled solid product. As one example, milling may include dry low energy milling and a solvent may not be added to the mill. Further, milling may occur at a low speed. For example, milling may include milling at a rate of 100 rpm up to 500 rpm. The duration may be at most 5 hours. In some examples the duration may be in a range of 1 hour up to 5 hours. In some examples, increasing a milling time may increase a yield of the target metal but may also decrease a selectivity of the leaching towards the target metal.

[0029] In examples where the low energy mill is used the loading percent of mixed metal input and ammonium bicarbonate may be in a range of 25%-65% solids. The loading percent may be equivalent to a percentage of the volume of the mill filled with solids. Solids may include all of milling media, mixed metal input, and other solid additives. Conventionally, solids loading of jar mills is in a range 24% to 40%. Surprisingly, accessing solids loading percentages above 40% when milling to produce the milled solid product has advantages of allowing for lower rotational speeds during the milling process without negatively impacting other factors such as total milling time and target metal extraction efficiency. Lower rotational speeds may result in less wear on the mill and a lower energy demand for the milling process. Lower rolling speeds include rolling at a speed between 1 rpm and 200 rpm. As a further example, the low rolling speed may be in a range of 10 rpm-50 rpm. As a further example, the low rolling speed may be in a range of 15 rpm to 30 rpm.

[0030] Turning briefly to FIG. 4, an XRD spectrum 400 of the ammonium bicarbonate starting material is shown and may be compared to an XRD spectrum 402 of a product obtained from jar rolling the mixed metal input characterized in FIG. 2 with ammonium bicarbonate for ten hours. A peak 404 at 10.5 degrees and a peak 406 at 12.5 degrees are present in the XRD spectrum 402 and are not present in the XRD spectrum 400 of the ammonium bicarbonate or the XRD spectrum 200 of the mixed metal input. The appearance of new XRD peaks indicate a chemical reaction occurred during jar rolling to form a new material phase. Additionally, decrease in intensity of XRD peaks associated with the ammonium bicarbonate and of XRD peaks associated with the nickel containing pentlandite phase indicate the chemical reaction is between the ammonium bicarbonate and the pentlandite phase. In this way, the ammonium bicarbonate acts as a metal chelator with the target metal during the milling process and is functioning as more than just a pH controlling agent in the milling process.

[0031] In one example, as described above, milling may be a low energy milling process. A low energy milling process may mechanochemically react the mixed metal input and ammonium bicarbonate without significantly changing (e.g., by less than 15% or by less than 20%) a size of the mixed metal input particles. An example of ore particle sizes before (control) and after jar milling (Jar roll) is shown in Table 1 below. Based on the merely small change in particle size, it is further shown that the efficient target metal leaching occurs due to a mechanochemical reaction and not due to an increase in surface area.

TABLE-US-00001 TABLE 1 Particle characterization before and after jar rolling Particle Characterization Control Jar Roll Mean Diameter Volume 33.670 30.868 Vol 10% Dia. m Volume 14.278 11.370 Vol 50% Dia. m Volume 31.890 28.788 Vol 90% Dia. m Volume 55.189 53.122 Circularity 0.908 0.912 Mean Diameter Numbers 8.556 7.413 Vol 10% Dia. m Numbers 2.965 2.719 Vol 50% Dia. m Numbers 5.701 5.158 Vol 90% Dia. m Numbers 18.113 16.737

[0032] Returning to FIG. 3, at 306, method 300 includes separating the milled solid product from the milling media. As one example, the milled solid product may be separated from the milling media by sieving. The milled solid product may be chemically different from the mixture of the mixed metal input and ammonium bicarbonate as shown by the XRD spectra discussed above with respect to FIG. 4. Further, in some examples, the mixed metal input may be hydrophobic whereas the milled solid product may be hydrophilic. Without being bound by theory, the change from hydrophobic to hydrophilic may be due to oxidization of sulfur and/or the target metal complexing with neutral ammonia molecules or carbonate ligands, which are water soluble. The milled solid product may be the product resulting from the reaction of ammonium bicarbonate with the mixed metal sample.

[0033] At 308, method 300 includes aging the milled solid product. In some examples, aging may be a passive process. For example, aging may include resting the milled solid product (e.g., ammonium bicarbonate reacted with the mixed metal input) by waiting for an aging duration. The aging duration may be up to 12 weeks. In further examples, the aging duration may be up to 8 weeks. In some examples the aging duration may be at least 1 week. In further examples, the aging duration may be in a range of 1 week up to 8 weeks. In further examples, the aging duration may be in a range of 1 week up to 12 weeks. In some examples, the aging duration may be up to 6 months. In some examples, the aging duration may be up to 1 year. In further examples, the aging duration may be in a range of 1 week up to 1 year. In some examples, the aging duration may be in a range of 1 week up to 6 months. In further examples, the aging duration may be in a range of 6 months up to 1 year. A longer aging duration may increase a yield of the target metal in the subsequent leaching steps. Over-oxidation during the aging process may be accounted for in the leaching process which is not dependent on an oxidation state of the milled solid product. In some examples, aging may be a passive process wherein the milled solid product is left undisturbed in an ambient environment for a duration.

[0034] In some examples, the aging may be an active process for all or part of the aging duration. For example, during the aging duration, the milled solid product may be agitated periodically. In some examples, the milled solid product may be under atmospheric pressure for the aging duration. In alternate examples, during all or part of the aging duration, the milled solid product may be placed in a pressurized chamber and exposed to greater than atmospheric pressure. In some examples, an atmosphere surrounding the milled solid product during aging may be a humid atmosphere. For example, a relative humidity of the atmosphere may be in a range of 40% up to and including 85%. In further examples, the relative humidity of the atmosphere may be in a range of 40% up to and including 60%. In further examples, the atmosphere may be comprised of air. In alternate examples, a composition of the atmosphere may be adjusted to be different from air for all or part of the aging duration. For example, the atmosphere may be a nitrogen rich atmosphere, hydrogen enriched atmosphere, argon atmosphere, or the like.

[0035] At 310, method 300 includes leaching/chelating to isolate the target metal from the aged solid product. The aged solid product may be chemically different from the milled solid product. For example, the milled solid product may change colors during the aging duration, indicative of a chemical reaction. Leaching may include mixing the aged solid product with an aqueous leaching solution to selectively solvate the target metal ion. Leaching the aged solid product may leach more target metal into the leach solution than leaching the milled solid product without any aging. In some examples, the mixed metal input may include nickel in addition to cobalt and/or copper. In such an example, leaching may be controlled to leach zero up to 100% of the cobalt in addition to the nickel. Leaching of cobalt in addition to nickel may be controlled by adding an oxidant to the leaching solution as described further below. Additionally or alternatively leaching may be controlled to leach from zero up to 100% of copper along with the nickel. Controlled leaching of copper may include adding a calcium base during to the mill as described above and/or the calcium base may be added to the leaching solution as described further below. The leaching process is described further below with respect to FIG. 5 and chelating is further described below with respect to FIG. 6.

[0036] FIG. 5 shows a flowchart of an example of a method for leaching the target metal from the aged solid product. At 502, method 500 includes preparing the aqueous leaching solution. In some examples, the aqueous leaching solution may be comprised of substantially (e.g., greater than or equal to 95%) pure water. In some examples, preparing the aqueous leaching solution includes at 504 adding ammonium bicarbonate to the water. The ammonium bicarbonate added may be in addition to any ammonium bicarbonate included in the aged solid product resulting from the jar milling process. For example, ammonium bicarbonate may be added to the aqueous leaching solution in a range of 1 g/L up to saturation (e.g., 360 g/L at 40 C.). In alternate examples ammonia bicarbonate may be added to the leach solution in a range of 100 g/L up to 160 g/L.

[0037] In some examples, preparing the aqueous leaching solution may include at 503 adding chloride ion. The chloride may increase a selectivity for leaching nickel and cobalt over copper. Target metals including nickel and cobalt without copper may be desired for conversion to a high purity mixed hydroxide precipitate or sulfide product. The chloride ion may be a chloride salt of one or more of ammonium, potassium, sodium, magnesium, calcium, or mixtures thereof. A concentration of chloride salt in a range of 0.1 M to 2 M.

[0038] Additionally or alternatively, preparing the aqueous leaching solution may include adding carboxyl metal extractant and/or amine metal extractant 505. As one example the carboxyl metal extractant and/or amine metal extractant may be an amino acid. Amino acids may act as metal chelators and may increase a yield of the target metal during extraction. Amino acids may include one or more of, but not limited to, histidine, serine, arginine, and combinations thereof. Adding the carboxyl metal extractant and/or amine metal extractant may be in molar excess to the amount of target metal to be leached from the aged solid product. As one example, the mole ratio of metal extractant and/or ammonium bicarbonate to target metal ion may be at least 4:1. In further examples, the mole ratio may be in a range of 4:1 up to 8:1. As one example, a pH of the aqueous leaching solution may be less than 10.0. In further examples, a pH of the aqueous leaching solution may be in a range of 7.0-9.9.

[0039] In some examples, an oxidant may be added to the leaching solution at 506. An oxidant may be added based on a desired amount of cobalt leaching in addition to nickel. For example, if no cobalt leaching is desired, the aqueous leaching solution may not include the oxidant and an amount of cobalt leaching may be increased by increasing an amount of oxidant added at 506. The oxidant may be added as a solid, liquid, or a gas dissolved in the aqueous leaching solution. For example, the oxidant may be one or more of bleach, hydrogen peroxide, ozone, oxygen, or air. As further examples, the oxidant may additionally or alternatively include one or more of 2KHSO.sub.5.Math.KHSO.sub.4.Math.K.sub.2SO.sub.4, persulfate salts, and ferric salts. A concentration of the oxidant in the leaching solution may be in a range of 0.1 M to 2 M.

[0040] Additionally or alternatively a calcium base 507 may be added to the aqueous leaching solution at 507. The calcium base may be added based on a desired amount of copper leaching in addition to nickel. The calcium base may be added in addition to or instead of adding calcium base to the mill at step 303 of method 300 as discussed above. An amount of calcium base added at either the milling step or leaching step may be used to adjust an amount of copper leached from the mixed metal input. Increasing an amount of calcium base added may increase a yield (up to 100%) of copper leached from the mixed metal input.

[0041] At 508, method 500 includes contacting the aged solid product with the prepared aqueous leaching solution. In some examples, the aqueous leaching solution may be less than 45 C. when contacting the aged solid product. In further examples, the aqueous leaching solution may be in a range of 15 C. up to 45 C.

[0042] In some examples, contacting the aged solid product with the aqueous leaching solution may include moving the aqueous leaching solution 510. For example, the aged solid product may be held in place in a perforated receptacle, such as a Buchner funnel and the aqueous leaching solution may be moved by vacuum pumps or other liquid pumps over the aged solid product. The leaching process is fast enough that even the brief contact made while flowing the aqueous leaching solution past the aged solid product solution leaches some of the target metal from the aged solid product. Additionally or alternatively, contacting the aged solid product with aqueous leaching solution includes agitating the aged solid product in the aqueous leaching solution at 512. For example, the aged solid product may be placed into an open receptacle such as a beaker or tank along with the aqueous leaching solution and the two may be agitated by stirring, such as by an overhead impeller, magnetic mixer, or the like. Additionally or alternatively, agitation may include agitation by acoustic waves via a sonicator. Additionally or alternatively, agitation may include agitation by a circulation pump, circulating the aqueous leaching solution and aged solid product together, for example, from the bottom of a tank to the top of a tank.

[0043] At 513, method 500 includes separating the aqueous leaching solution from the leached aged solid product (e.g., leached solid product) and directing the leached solid product to an anionic chelator as described further below with respect to FIG. 6. At this point, at least a portion of the target metal from the aged solid product may be leached into the aqueous leaching solution. Additional target metal may be further recovered with the anionic chelator. At 514, method 500 optionally includes adding target metal ion exchange (IEX) resin to the aqueous leaching solution. The target metal IEX resin may be selected to adsorb the target metal ions from the aqueous leaching solution. For example, the target metal IEX resin may be an iminodiacetic acid resin, such as but not limited to, Purloite S930 Plus and/or Lewatit Monoplus 207. In some examples, the IEX resin may be an iminodiacetic acid based resin. In an alternate example, the target metal IEX may be the same as the iron IEX if a pH of the aqueous leaching solution is adjusted to a basic level before adding the IEX. For example, the pH of the aqueous leaching solution may be adjusted to above 7 or above 8 and Puromet MTS9570 may be added. In this way, the target metal ion is drawn out of solution thereby regenerating the aqueous leaching solution for subsequent leaching steps.

[0044] At 516, method 500 determines if the target metal leaching is plateaued. Target metal leaching may be plateaued when additional steps of contacting the aged solid product with the aqueous solution does not remove substantially more of the target metal from the aged solid product. In some examples, the leaching may plateau when 90% or more of the target metal is leached from the aged solid product. In this way a leaching efficiency may be greater than or equal to 90%. If method 500 determines that the target metal leaching is not plateaued, method 500 returns to 508 and continues to contact the aged solid product with the aqueous leaching solution. In some examples, the aqueous leaching solution may be fresh aqueous leaching solution that has not yet contacted the aged solid product. In further examples, the aqueous leaching solution may have already leached some amount of target metal. Additionally or alternatively, the aqueous leaching solution may be recovered aqueous leaching solution where the target metal has been removed by ion exchange resin.

[0045] If method 500 determines that the target metal leaching is plateaued, method 500 proceeds to 518 and includes isolating the target metal from the aqueous leachate and/or the ion exchange resin. As one example a strong acid, such as sulfuric acid may be used to extract the target metal from the target metal ion exchange resin into an aqueous solution. The target metal may be further recovered from aqueous solution and/or the aqueous leaching solution by one or more of electrowinning, cementation, ion exchange resins, crystallization, and solvent extraction. In some examples, the method of isolation may depend on a desired form of the target metal. For example, if the metal is desired as a specific water insoluble salt, cementation may be used and if the metal is desired in a reduced form, electrowinning may be used.

[0046] Additional target metal may be recovered from the aged solid product by contact with an anionic chelator rinse. An example of a method 600 for using an anionic chelator rinse is shown in FIG. 6. Method 600 may be performed after leaching as described above with respect FIG. 5. Additionally, or alternatively, method 600 may be performed at the same time as leaching, in which case the steps of method 600 are performed simultaneously with method 500. For example, an anionic chelating solution may be combined with the leaching solution.

[0047] At 602, method 600 include preparing an anionic chelating solution. Preparing the anionic chelating solution may include mixing an anionic chelator with water to form a homogeneous solution. In some examples, the water may also include components of the aqueous leaching solution in examples where leaching and chelating are done at the same time. The anionic chelator may include anionic compounds with an affinity for ferric iron as described above with respect to FIG. 1. An amount of anionic chelator included in the anionic chelating solution may depend on an amount of iron determined to be present in the mixed metal input. The amount of anionic chelator added may be at a level to chelate all ferric ions contained in the mixed metal input. For example, the ratio of anionic chelator to total iron present may be in a range of 1:1 to 10:1. Total iron includes metallic, ferrous, and ferric iron combined. The molar ratio may further be based on the valence of the anionic chelator. For example, a ratio may be 3:1 for a monovalent chelator, 1:1 for a trivalent chelator, and 1.5:1 for a divalent chelator.

[0048] Optionally, preparing the anionic chelating solution may include adding an oxidant at 604. Adding an oxidant may include mixing the oxidant into the anionic chelating solution until a homogenous solution is formed. The oxidant may be one or more of peroxide, oxygen, ozone, nanobubbles of oxygen and ozone and air, 2KHSO.sub.5.Math.KHSO.sub.4.Math.K.sub.2SO.sub.4, persulfates, ferric salts, and combinations thereof.

[0049] At 606, method 600 includes contacting the solid product with the anionic chelating solution. The solid product may be the leached solid product recovered after leaching the aged solid product at step 513 of FIG. 5. Additionally, or alternatively, the solid product may be the aged solid product in examples where leaching and chelating are done at the same time. Contacting may include the same steps as contacting the aged solid product with the leaching solution at step 508 of FIG. 5. For example, contacting may include moving the anionic chelating solution by moving the anionic chelating solution and/or agitating the solid product in the anionic chelating solution.

[0050] At 608, method 600 includes separating the leached chelated solid product from the anionic chelating solution. Separating may include isolating the leached chelated solid product (e.g., solid phase) from the anionic chelating solution (e.g., liquid phase). Separating may include processes such as, but not limited to, gravity filtration, vacuum filtration, decanting, and centrifugation.

[0051] At 610, method 600 includes isolating the target metal from the anionic chelating solution. Isolating may include separating the target metal or metals (e.g., nickel, cobalt, and/or copper) from the iron ions that were also brought into solution by the anionic chelator.

[0052] Isolating may include, at 612, contacting an iron IEX resin to the anionic chelating solution. Contacting may include adding the iron IEX resin directly to the anionic chelating solution and may optionally include agitation to increase contact between the iron IEX resin and the anionic chelating solution. The anionic chelating solution may include both target metal ions and ferric ions. The iron IEX resin may include functional groups to selectively adsorb iron while not adsorbing target metals, such as nickel. For example, the iron IEX resin may include phosphonic/sulfonic acid functional groups. The iron IEX resin may include, but is not limited to Puromet MTS9570. With the ferric ions adsorbed to the iron IEX resin, the remaining solution may include the target metal ions and may not include iron ions. After separating the solid iron IEX resin from the liquid phase, the target metal may remain behind, isolate in the liquid phase.

[0053] Isolating may additionally, or alternatively include at 614 adding a base to the chelating solution, the base may be a strong base, such a sodium hydroxide. The base may be added in amount to increase a pH of the anionic chelating solution to level causing the iron ions to precipitate from solution and low enough for the target metal ions to remain in solution. Solid/liquid separation may be used to separate the iron precipitate from the liquid phase including the target metal. The isolated target metal solution may then be direct to step 518 to further isolate the target metals from the solutions as describe above. Method 600 ends.

[0054] Processes are provided below as examples of aging, leaching and optionally chelating milled solid product. The processes are intended as non-limiting examples. The milled solid product is obtained by milling as described above with respect to FIG. 3.

[0055] In a first example, a 15 g sample, aged 6 weeks in an environment of relative humidity >40% and temperature >40 F., was washed with 150 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes (M(NH.sub.3).sub.4.sup.2+), where M=Ni, Co, Cu) and the residual solid was brown due to the presence of ferric ions. No follow-up rinse was used. The brown solid weighed 8.37 g compared to the 5 g or raw ore present in the mixture prior to the water leach (e.g., leaching solution), representing a 68% mass increase due to the formation of ferric oxy/hydroxide.

[0056] In a second example, a 15 g sample aged in the same manner as in the first example was washed with 150 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes and the residual solid was brown due to the presence of ferric ions. The residual solid was left in the vacuum funnel and a 75 g dilute hydrochloric acid solution (1M) (e.g., anionic chelating solution) was poured over the solid. The liquid pass through the solid in seconds and yielded a bright yellow filtrate and the solid turned from brown to light grey and weighed 1.57 g. The final pH of the filtrate was 1.3.

[0057] FIG. 7 shows a first XRD spectrum 700 of the mixed metal input used in the first example and second example. FIG. 7 also shows a second XRD spectrum 702 of the brown solid obtained after leaching in the first example is shown. FIG. 7 also shows a third XRD spectrum 704 of the grey solid obtained in the second example after leaching and containing the anionic chelating solution. A key 706 provides symbols which identify peaks of the XRD spectra with the composition of the sample.

[0058] Comparing first XRD spectrum 700 to second XRD spectrum 702 it is shown that peaks associated with pentlandite (filled circles) decrease in number and intensity, indicating a decrease in content of the nickel-containing phase in the leached brown solid. For example, peak 708 in first XRD spectrum 700 is associated pentlandite and does not appear in the second XRD spectrum 702. Additionally, peaks associate with iron oxy hydroxide (FeOOH, open triangles) are observed in the second XRD spectrum 702 which are not in the first XRD spectrum 700. For example, peak 710 is present in second XRD spectrum 702 and not in first XRD spectrum 700.

[0059] In contrast, third XRD spectrum 704 shows almost not peaks associated with pentlandite and no peaks associated with the iron oxy hydroxide phase. Lack of the iron oxy hydroxide phase shows that the anionic chelating rinse in the second example dissolved the ferric ions and released the residual nickel ions into solution.

[0060] Table 2 below compares semi-quantitative analysis of the composition of the XRD spectra shown in FIG. 7.

TABLE-US-00002 TABLE 2 Semi-quantitative analysis of XRD Material % Pentlandite Balance Composition Mixed Metal Input 36 Pyrite, talc, quartz 1.sup.st Example Residue 14 Pyrite, talc, quartz 2.sup.nd Example Residue Not detectable
As the nickel contain phase, decrease in the percentage of pentlandite is indicate of leaching of nickel from the solid milled product into the leaching solution and anionic chelating solution respectively.

[0061] Quantitative analysis of the first and second examples was also performed via X-ray fluorescence (XRF) and the results are shown in Table 3 below. XRF is used to analyze both the solid residue and the resulting leaching solution (leachate) and anionic chelating solution (chelate).

TABLE-US-00003 TABLE 3 Quantitative XRF analysis Material Ni Zn Cu Co Fe Si S Mixed Metal Input 22.6% 0.01% 2.9% 0.62% 39.2% 8.5% 24.2% 1.sup.st Residue 16.5% 0.09% 2.6% 1.4% 62% 10.6% 6.8% Example Leachate 43.4% n/a 6.88% 0.92% n/a n/a n/a 2.sup.nd Residue 2.02% 0 2.37% 0.79% 54.24% 20.56% 19.1% Example Chelate 17.64% n/a 3.24% 1.47% 44.7% n/a n/a

[0062] From the XRF analysis of the residue shown in Table 2, a nickel extraction efficiency can be semi-quantitatively assessed by comparing a ratio of iron to nickel (Fe:Ni ratio) in the input and in the residues. As nickel is removed, the percentage iron solid increases. Thus, a larger increase in the Fe:Ni ratio suggests more nickel extraction. From the results shown in Table 2, the Fe:Ni ratio of the input material 1.73 and increases to 3.74 in the residue of the first example using the water leaching solution and further increases to 27 in the second example, using the anionic chelator rinse. Additionally, an actual nickel extraction efficiency is calculated by dividing a final nickel mass in the leach/chelate solutions by the initial mass of nickel added to the mill as the mixed metal input. By such analysis, it is shown that the nickel extraction efficiency of the second example is 97%.

[0063] Further examples described below compare results of using different composition of the anionic chelating solutions. In a third example, the anionic chelator is a chloride ion in the form of a dilute hydrochloric acid solution. A 15 g jar rolled sample aged for four weeks was washed with 200 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes and the residual solid was brown due to the presence of ferric ions. The residual solid was left in the vacuum funnel and a 150 g dilute hydrochloric acid solution (1M) was poured over the solid. The liquid pass through the solid in seconds and yielded a bright yellow filtrate and the solid turned from brown to light grey and yielded a final mass of 2.75 g compared to the 5 g raw ore present in the mixture prior to leaching. The final pH of the filtrate was 1.3.

[0064] In a fourth example, an oxidant and chloride ion are included in the anionic chelating solution. The oxidant included is hydrogen peroxide. A 6 g jar rolled sample aged for three weeks was washed with 70 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes and the residual solid was brown due to the presence of ferric ions. The residual solid was left in the vacuum funnel and a 50 g dilute hydrochloric acid/hydrogen peroxide solution (1M/0.2M)) was poured over the solid. The liquid pass through the solid in seconds and yielded a bright yellow filtrate and the solid turned from brown to light grey and yielded a final mass of 1.27 g compared to the 2 g raw ore present in the mixture prior to leaching. The final pH of the filtrate was 1.3.

[0065] In a fifth example, citrate, in the form of citric acid, is included as the anionic chelator along with the hydrogen peroxide oxidant. A 6 g jar rolled sample aged for three weeks was washed with 70 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes and the residual solid was brown due to the presence of ferric ions. The residual solid was left in the vacuum funnel and a 50 g dilute citric acid/hydrogen peroxide solution (1M/0.2M)) was poured over the solid. The liquid pass through the solid in seconds and yielded a bright yellow filtrate and the solid turned from brown to light grey and yielded a final mass of 1.44 g compared to the 2 g raw ore present in the mixture prior to leaching. The final pH of the filtrate was 2.3.

[0066] In a sixth example, sulfate, in the form of sulfuric acid, is included as the anionic chelator along with the hydrogen peroxide oxidant. A 6 g jar rolled sample aged for three weeks was washed with 70 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes and the residual solid was brown due to the presence of ferric ions. The residual solid was left in the vacuum funnel and a 50 g dilute sulfuric acid/hydrogen peroxide solution (1M/0.2M)) was poured over the solid. The liquid pass through the solid in seconds and yielded a bright yellow filtrate and the solid turned from brown to light grey and yielded a final mass of 1.3 g compared to the 2 g raw ore present in the mixture prior to leaching. The final pH of the filtrate was 0.74.

[0067] In a seventh example, a non-acidic chloride, in the form of potassium chloride, is included as the anionic chelator along with hydrogen peroxide as the oxidant. A 6 g jar rolled sample aged for three weeks was washed with 70 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was deep blue due to the solubility of nickel, cobalt, and copper amine complexes and the residual solid was brown due to the presence of ferric ions. The residual solid was left in the vacuum funnel and a 50 g dilute potassium chloride/hydrogen peroxide solution (1M/0.2M)) was poured over the solid. The liquid pass through the solid in seconds and yielded a champagne color filtrate and the solid turned from brown to red and yielded a final mass of 2.5 g compared to the 2 g raw ore present in the mixture prior to leaching. The final pH of the filtrate was 8.4.

[0068] Table 4 shows results of XRF analysis of the third through seventh examples described above including different anionic chelators (AC) and oxidant (Ox.). The Fe:Ni ratio determined from the XRF analysis as well as the nickel extraction efficiency (EE), determined as described above is also provided.

TABLE-US-00004 TABLE 4 XRF analysis of residues. Ex. AC Ox. Ni % Zn % Cu % Co % Fe % Si % S % Fe:Ni EE % 3.sup.rd HCl n/a 3.49 0.8 0.82 0.56 51.64 29.4 10.9 14.8 88 4.sup.th HCl H.sub.2O.sub.2 1.3 3.14 0.39 0.0 41.48 30.9 20.51 32 96 5.sup.th CA H.sub.2O.sub.2 2.67 1.27 0.85 0.49 52.3 29.5 11.72 19.6 91.3 6.sup.th SA H.sub.2O.sub.2 1.98 3.04 0.72 0.65 34.91 45.97 0 17.6 94.1 7.sup.th KCl H.sub.2O.sub.2 15 n/a n/a n/a 61 n/a 3 4 15 CA = citric acid, SA = sulfuric acid
As shown in table 3, there is a complex interplay between the oxidant and aniconic chelator in the anionic chelating solution and the resulting extraction efficiency. Further, it is observed that the presence of an oxidant causes zinc to precipitate out of the anionic chelating solution. Such precipitation may help purify the nickel saturated anionic chelating solution in-situ.

[0069] A further example is provided of nickel recovery from a nickel saturated anionic chelating solution. Seventy-five milliliters of the yellow anionic chelator filtrate were exposed to 20 g of an ion exchange resin, specifically Puromet MTS 9570 at room temperature for several minutes and the resulting filtrate was green. The XRF analysis of the resultant liquid showed only nickel, cobalt and copper remaining and no iron, proving that the resin is selective for trivalent ferric ions over divalent metal ions in slightly acidic medium.

[0070] The resin was then washed with 2M sulfuric acid and the blue/green resin beads turned cream color instantly, the same color as the virgin resin, suggesting that the ferric ions were stripped and resin regenerated, yielding a ferric sulfate solution which can be used as an oxidant for future processing.

[0071] As an alternative, precipitation may be used to isolate cobalt and nickel from the anionic chelating solution. For example, a separate seventy-five milliliters of the yellow anionic chelator filtrate were pH adjusted to 3.4 with 1 M sodium hydroxide and resulted in the formation of a red solid. The slurry was filtered, and the red filter cake was analyzed using XRF and showed only iron, sulfur and zinc and copper, and no nickel or cobalt (17% Ni, 0% Co, 1.97% Co, and 0% Fc). The resulting filtrate was pale green, indicative of the presence of mainly nickel and cobalt which the XRF confirmed (88.5% Fe, 8.5% S, 1.9% Zn, no nickel detected).

[0072] In further examples, a concentration of ammonium bicarbonate in the aqueous leaching solution may be increased by decreasing liquid to solid (L:S) ratio of the aqueous leaching solution to the solid product, as described in the examples below. In an eighth example, a 24 g jar rolled sample aged for four weeks was washed with 50 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The filtrate was opaque blue, almost black looking due to the higher concentration of metals present due to the lower L:S ratio employed. The leach solution was determined by XRF to include Co, Cu, and Ni (52.9% Ni, 12.4% Cu, 1.03% Co, 23.3% S).

[0073] The residual solid was left in the vacuum funnel and a solution containing 8 g sulfuric acid plus 42 g water (anionic chelating solution) was poured over the solid. The liquid passed through the solid in seconds and yielded a bright orange filtrate and the solid turned from brown to light grey and yielded a final mass of 5.3 g compared to the 8 g raw ore present in the mixture prior to leaching. XRF of the collected anionic chelating solution filtrate indicates the presence of both nickel and iron (14.9% Ni, 0.6% Cu, 0.9% Co, 45.1% Fe, 33% S). XRF analysis of the light grey residue indicated a Fe:Ni ratio of 19.8 and a nickel extraction efficiency of 92% (2.65% Ni, 4.7% Cu, 1.2% Co, 52.6% Fe, 17.2% Si, 20% S). In this way, it is shown the lower L:S ratio in the leaching step yields a higher metal extraction while the overall nickel and cobalt extraction may be similar to a higher L:S leach followed by a chelator rinse.

[0074] About 40 mL of the anionic chelating solution filtrate of the above example was exposed to 25 g of Puromet MTS9570 resin at room temperature. After only several minutes, >92% of the dissolved ferric ions were extracted onto the resin and the resulting filtrate was green due to the lack of ferric ions and dominance of nickel ions as confirmed by XRF of the anionic chelating solution after resin exposure (39% Ni, 1.92% Cu, 0% Co, 0.5% Fc).

[0075] The ferric ions may be removed from the iron IEX resin (e.g., Puromet MTS9570) by using either dilute sulfuric acid or hydrochloric acid in the resin regeneration process. The iron laden iron IEX resin was analyzed by XRF and showed an iron to nickel selectivity of about 77:1 with substantially no nickel or cobalt adsorption relative to iron. In this way, is shown that slightly acidic pH values, the iron IEX resin can selectively remove ferric ions leaving mainly copper and nickel ions in solution.

[0076] In a further example, nickel extraction was tested using the Puromet MTS9570 resin in a slightly basic aqueous leaching solution. A 6 g jar rolled sample aged for four weeks was washed with 75 mL water for 10 minutes at room temperature and the filtered using vacuum filtration. The recovered aqueous leaching solution was analyzed by XRF and showed extraction of nickel, copper, and cobalt (Ni 42.9%, Cu 10.4%, Co 1.27%)

[0077] The blue aqueous filtrate, pH 8.95, was exposed to 20 g of Puromet MTS9570 at room temperature. After five minutes, >96% of the nickel ions were extracted onto the resin and the resulting filtrate was colorless as a result almost quantitative removal of nickel. The nickel ions can be removed from the resin using dilute sulfuric acid and the resin regenerated in the process. These results show that the same ion exchange resin can be used to generate relatively pure nickel sulfate streams from the water leach and anionic chelator rinse steps.

[0078] The technical effect of methods 300 and 500 and 600 are to selectively recover a target metal from a mixed metal input. The methods may demand a low energy input and may use safe, non-caustic chemical reagents. Further the method results in a highly selective recovery, whereby the valuable target metal, such as nickel, copper and/or cobalt, is recovered without lower value contaminants, such as iron. Further the method results in a high yield of the target metal ion in the leaching solution. The target metals may be isolate with a high enough purity that further costly refinement steps, such as solvent extraction are not demanded, thereby lowering the cost of a mixed hydroxide precipitate product.

[0079] The disclosure also provides support for a method of extracting a target metal from a mixed metal input, comprising: milling the mixed metal input with ammonium bicarbonate to form a milled solid product, aging the milled solid product, and leaching the target metal from the aged solid product. In a first example of the method, target metal is one or more of nickel, cobalt and copper. In a second example of the method, optionally including the first example, aging includes aging for up to 1 year. In a third example of the method, optionally including one or both of the first and second examples, milling includes low energy milling for 1 hour up to 5 hours. In a fourth example of the method, optionally including one or more or each of the first through third examples, leaching includes contacting the aged solid product with an aqueous leaching solution at a temperature less than 45 C. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, chelating ferric iron from the aged solid product with an anionic chelator to release nickel ions.

[0080] The disclosure also provides support for a method of extracting a target metal from a mixed metal input, comprising, mechanochemically reacting the mixed metal input with ammonium bicarbonate to form a milled solid product, waiting an aging duration to form an aged solid product from the milled solid product, contacting the aged solid product with an aqueous leaching solution, and isolating the target metal from the aqueous leaching solution. In a first example of the method, the aging duration is at least one week. In a second example of the method, optionally including the first example contacting the aged solid product with the aqueous leaching solution includes moving the aqueous leaching solution or agitating the aged solid product in the aqueous leaching solution. In a third example of the method, optionally including one or both of the first and second examples, the method further comprises: separating the aqueous leaching solution from the aged solid product and adding ion exchange resin to the aqueous leaching solution. In a fourth example of the method, optionally including one or more or each of the first through third examples, isolating the target metal from the aqueous leaching solution includes one or more of electrowinning, cementation, ion exchange resin, crystallization, and solvent extraction. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, a pH of the aqueous leaching solution is in a range of 7.0 to 9.9. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, leaching the aged solid product leaches more target metal than leaching the milled solid product.

[0081] The disclosure also provides support for a method of extracting nickel from a mixed metal input, comprising, low energy milling of the mixed metal input with ammonium bicarbonate and milling media to react the nickel with the ammonium bicarbonate and form a milled solid product, aging the milled solid product to form an aged solid product from the milled solid product, wherein the aged solid product is chemically different from the milled solid product, and leaching the nickel from the aged solid product with an aqueous leaching solution comprising one or more of ammonium bicarbonate and a carboxyl and/or amine metal extractant. In a first example of the method, low energy milling includes jar milling. In a second example of the method, optionally including the first example, the carboxyl and/or amine metal extractant is included in the aqueous leaching solution in molar excess of the nickel in the aged solid product. In a third example of the method, optionally including one or both of the first and second examples, aging the milled solid product includes aging in relative humidity in range of 40% to 85%. In a fourth example of the method, optionally including one or more or each of the first through third examples, the ammonium bicarbonate is added to the mixed metal input in a ratio of 0.5:1 up to 2:1. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, leaching leaches greater than or equal to 90% of the nickel from the aged solid product to the aqueous leaching solution. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, low energy milling includes dry low energy milling.

[0082] The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to an element or a first element or the equivalent thereof. Such claims may be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.