Patent Application
20220307148
Cobalt is commonly used to produce samarium cobalt permanent magnets, lithium-ion battery cathodes, catalysts, and high-grade metal alloys. These important strategic uses for cobalt combined with its limited domestic production have led the U.S. Department of the Interior to list it as a critical material. Furthermore, approximately 70% of the world's supply of mined cobalt comes from the Democratic Republic of the Congo where concerns over environmental degradation and child labor have led some large cobalt consumers to selectively purchase cobalt from suppliers who meet certain standards, providing an economic incentive to develop alternate cobalt sources. Recycling has already been shown to be a viable cobalt source with an estimated 29% of cobalt consumption in the United States coming from recycled scrap. One source for recycled cobalt is from samarium cobalt (SmCo) magnets, which are commonly used as high-strength permanent magnets in applications where thermal stability and corrosion resistance is required. These magnets have been produced with two nominal formulas: SmCo5 and Sm2Co17 with the second generation Sm2Co17 formulation being more common and representing the bulk of the market. In practice, Sm2Co17 magnets contain additional transition metals including iron, copper, and zirconium which makes their recovery and reuse challenging and expensive. However, as these magnets typically contain about 50% cobalt by weight, they are a desirable secondary source for cobalt.
Several processes have been developed for the recovery of cobalt from secondary sources. One such process was developed by the U.S. Bureau of Mines using a double-membrane electrolytic cell to electro-refine alloy scrap into high-purity cobalt. This process uses an electrolytic dissolution step, multiple purification steps including cementation and multiple solvent extraction steps to produce a purified cobalt solution prior to electrodeposition of the cobalt. This process can produce high purity cobalt but requires many processing steps that increase the overall cost if additional valuable metals are not also purified and recovered, e.g., nickel in this approach.
Direct recycling of samarium cobalt magnets is possible through a process termed hydrogen disproportionation desorption recombination (HDDR). First, magnet scrap is converted into a powder through reaction with hydrogen at high pressure or temperature causing dissociation of the material to elemental forms or hydrides. Next, the hydrogen is desorbed by heating in vacuum leading to recombination of the material, which can then be sintered or plastic bonded to form a new magnet. However, this process requires high-pressure or high-temperature conditions to fully dissociate the material and, as magnet manufacturing is not the major use of cobalt, is limited to the production of additional samarium cobalt magnets.
Alternate approaches include acidic digestion and solvent extraction using various surfactants and complexing ligands. However, these approaches all suffer from various drawbacks. Acidic digestion solutions are not recyclable and require significant consumption of base to neutralize the acid, generating a significant amount of waste in the process. Solvent extraction often requires many stages to achieve sufficient purity resulting in complex and costly systems.
Systems and methods herein provide for recovering cobalt (and/or other metals) from a permanent magnet material having variable composition, such as samarium cobalt magnets. In one embodiment, a method includes converting the permanent magnet material to a higher surface area form, such as a powder. The method also includes treating the converted permanent magnet material with an aqueous solution of ammonium carbonate to form a mixture (e.g., a slurry) that includes dissolved cobalt. In some embodiments, the method includes exposing the mixture to an oxidant to oxidize metallic constituents and form soluble species. The method also includes filtering the mixture to yield a filtrate, and electroplating the cobalt and/or other metals, such as copper or nickel, onto a cathode from the filtrate.
For example, in some embodiments, filtering the slurry may remove precipitated compounds and form a filtrate. From there, the filtrate may be placed in an electrochemical reactor which selectively reduces elements by applying a potential across two electrodes to plate other metal contaminants or coproducts (e.g. copper). Then, the electrode and plated metal (e.g., on the cathode) from solution can be removed. This process may be repeated at increasing electric potential to sequentially plate additional metals, to remove the plated cobalt metal from the electrode, and to rinse the cobalt metal product. The extraction solution, depleted of cobalt and any coproducts, can be directly reused to extract more cobalt or coproducts from additional cobalt-containing material.
The ammonium carbonate process is a recyclable solution that eliminates waste generated from neutralizing acids, and avoids the complexity and cost of the many stages used in traditional solvent extraction methods. For example, reagents such as ammonium carbonate, oxygen, and water can be recycled in a process that uses moderate temperatures, pressures, and environmentally benign chemicals.
In some embodiments, the permanent magnet material comprises samarium cobalt magnets (e.g., either partially or completely oxidized samarium cobalt magnets). In some embodiments, the method includes deriving the permanent magnet material from magnet manufacturing wastes.
In some embodiments, electroplating the cobalt includes recovering at least one of copper or nickel from the electroplating as a co-product. In some embodiments, converting the permanent magnet material to a higher surface area form includes at least one of grinding or milling the permanent magnet material.
In some embodiments, the method also includes heating the mixture in at least one of air, an inert atmosphere, or hydrogen to temperatures up to 1500° C. The method may also include demagnetizing the mixture using an externally applied magnetic field or a mechanical shock treatment. The method may also include adjusting an oxidation state of the mixture prior to extraction with a chemical oxidant, a reductant, or an electrochemical method that employs an electric current to transfer electrons between materials.
In some embodiments, the aqueous solution of ammonium carbonate comprises ammonium carbonate and ammonia, and the method also includes recycling the aqueous solution of ammonium carbonate after use. For example, the aqueous solution of ammonium carbonate may be thermally treated after use to convert the used ammonium carbonate solution into ammonia and carbon dioxide.
In some embodiments, treating the converted permanent magnet material with an aqueous solution of ammonium carbonate includes adding at least one of oxygen gas, air, hydrogen peroxide, a chemical oxidant, hydrogen gas, or a chemical reductant. In some embodiments, the method also includes applying an electrical potential to a slurry containing alkaline carbonates and the permanent magnet material to increase a dissolution rate. In some embodiments, the method also includes heating the aqueous solution of ammonium carbonate to a temperature between 0° C. and 100° C. at a pressure above 1 bar.
In some embodiments, one or more of said converting, treating the converted permanent magnet material, filtering, and treating the filtrate are performed in a container constructed of at least one of stainless steel, glass, polytetrafluoroethylene, fiberglass-reinforced plastic, corrosion resistant alloy, or a corrosion barrier. In some embodiments, the method also includes adding reagents to the mixture to slow hydrogen evolution at the cathode or to increase a rate of oxygen evolution at an anode.
In some embodiments, additives may improve the quality of the electroplating. An electroplating reactor may include at least one of a single chamber or multiple chambers separated by an ionically conductive membrane. Two or more electrodes may be used in the electroplating (e.g., for reduction, oxidation, and/or reference). And, solids obtained by filtration may be recovered as a byproduct for additional processing or recycled use.
The figures and the following description illustrate specific exemplary embodiments of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within the scope of the invention. Furthermore, any examples described herein are intended to aid in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the invention is not limited to the specific embodiments or examples described below.
Exemplary Cobalt Extraction and Recycling from Permanent Magnets (CERPM) processes are disclosed herein and are operable to recover cobalt and other valuable metal elements from samarium cobalt magnets.
The leaching vessel 14 is generally a sealed container in which (NH4)2CO3 and air (and/or O2) is combined with the samarium cobalt magnet powder to selectively dissolve the materials of the samarium cobalt magnet powder. For example, the samarium cobalt magnet may comprise materials other than samarium cobalt, including iron, copper, nickel, etc. The leaching vessel 14 dissolves these materials with the (NH4)2CO3 and air/O2 and transfers the solution to a filter 16. Iron and/or samarium are removed from the solution and come out as solids. The filtrate from filter 16 is transferred to an electrowinning cell 18 comprising a cathode and an anode (not shown).
The electrowinning cell 18 performs an electrowinning (also called an electroextraction) on the filtrate from the filter 16, which results in the electrodeposition of metals, such as cobalt, copper, nickel, and the like, from the filtrate on the cathode. In some embodiments, this electrodeposition may be a selective/repetitive process. For example, the anode may initiate with a relatively low voltage such that copper from the filtrate may be deposited on the cathode. Then, the anode and the cathode may be removed such that the copper may be recovered. The anode and the cathode may then operate on the filtrate by applying a higher voltage on the anode to extract cobalt from the filtrate on the cathode. This process may repeat until all of the desired metals had been recovered from the filtrate.
Based on the foregoing, the system 10 is any device, system, software, or combination thereof operable to convert a samarium cobalt permanent magnet into a higher surface area form such that cobalt and/or other metals may be extracted for reuse. Other exemplary embodiments are shown and described below.
While this embodiment illustrates one exemplary process for extracting cobalt from a permanent magnet material feed, the embodiments may also be operable to extract other metals, such as iron, copper, nickel, etc. from the permanent magnet material feed. In some embodiments, the system 10 may be operable to extract cobalt from various forms of ore materials that have been mined and/or are a result of manufacturing waste. Additionally, the processing and extraction of the materials described herein are not intended to be limited to materials mined or manufactured on earth. Rather, the materials described herein may be extracted from ore material mined from various planets, moons, asteroids, and the like.
Experimental
Although the following exemplary experimental procedures are described in detail, they are illustrative and non-limiting. Two different starting magnet materials were used for the research. Samarium cobalt disc magnets (⅜″ diameter×⅛″ thick, SMCO-D5) were used and crushed in a hydraulic press prior to use. This resulted in a collection of magnetic particles which were used without further preparation. Alternate preparation methods and demagnetization were investigated and will be described where appropriate. Samarium cobalt cutting swarf submerged in an impure aqueous fluid was received as a smooth powder/paste from a manufacturer. 110.0 g of the wet swarf was filtered, washed with distilled water (400 mL), and allowed to dry in a Buchner funnel under vacuum filtration. The mass of solid remaining was 82.6 g or 75.1%. This partially dried sample was then placed in a ceramic dish and heated to 120° C. in a furnace for 2 hours. After cooling to room temperature, the final mass was 70.8 g. This material was used in leaching experiments without further processing. In some experiments, oxidized magnet material was used instead of the alloys. In this case, the material was heated to 850° C. in a muffle furnace for 8 hours (ramp rate: 10° C./min) prior to use. The sintered material was then lightly ground using a glass mortar and pestle to further break up any agglomerated particles. X-ray fluorescence (XRF) analysis was performed at Pioneer Astronautics using a Rigaku NEX-DE Energy-Dispersive XRF spectrometer with a silicon photodetector and a 60 kV sealed-tube source. A fundamental parameters measurement method was used for all samples. As this measurement is sensitive to elements from Na—U, all XRF results are given as mass % of a specific element out of the total mass of all detectable elements. So, even if the metals were most likely present as oxides, the analytical results will give relative amounts of one metal to another. Powder samples were placed in polypropylene sample cups or microsample cups and tamped by hand to create a packed powder. Liquid samples were analyzed by adding 4 g to a sample cup and running a manufacturer-installed method.
1 gram (2.5 g/L) of crushed magnets was added to a 500 mL round-bottom flask along with a magnetic stir bar and 400 mL of 1.6 molar (NH4)2CO3. Some of the magnet powder was attracted to the stir bar, but while stirring vigorously, the liquid became cloudy and it was clear that a suspension was obtained. The suspension was stirred for 3 days at room temperature and left open to ambient air during which it turned a dark purple hue. Upon filtering the suspension, a purple solution and a brown solid fraction were obtained with the solid fraction composed primarily of iron and samarium. The purple solution was heated at 120° C. to evaporate water and decompose ammonium carbonate into ammonia, carbon dioxide, and water which then were evolved as gasses. The remaining solids were composed of 83% cobalt and yielded a mass of cobalt equivalent to 100% of the initial cobalt in the magnets.
1 gram of crushed magnets was leached as outlined in Experiment 1, but the process was performed in a nitrogen atmosphere instead of being open to air. The solids collected at the end of the experiment were composed of 87% cobalt and yielded a mass of cobalt equivalent to 18% of the initial cobalt in the magnets.
40 mL of the filtrate obtained from Experiment 1 were added to a 50 mL beaker and a nickel plate anode and a carbon plate cathode were placed in the solution and separated by a distance of one inch. A controlled potential of 2.5 V was applied across the electrodes while the solution was magnetically stirred for two hours. Afterward, the cathode was removed and found to have plated a copper-colored solid with a mass of 23 mg and was found to be composed of 80% copper, 18.4% cobalt, and 0.6% iron via XRF analysis. A new, identical cathode was placed in the solution, electrically connected as before, and a controlled current of 300 mA was passed while the voltage was allowed to float. After 40 minutes, the cathode was removed, rinsed with distilled water, and allowed to dry. The cathode was found to have a dark coating with a mass of 82 mg and was found to be composed of 93.3% cobalt, 4.3% nickel, 1.1% iron, and 0.8% copper. The remaining solution was found to have a pH of 9.4, largely unchanged from the starting value of 9.2.
2 g (5 g/L) of samarium cobalt magnet swarf was added to a 500 mL round-bottom flask along with a magnetic stir bar and 400 mL of 1.6 molar (NH4)2CO3. Some of the magnet powder was attracted to the stir bar, but while stirring vigorously, the liquid became cloudy, and it was clear that a suspension was obtained. The suspension was stirred for 48 hours at room temperature and left open to ambient air during which it turned a dark purple hue. Upon filtering the suspension, a purple solution and a brown solid fraction were obtained. The solids were found to be composed of 48.0% iron, 41.1% samarium, 8.8% cobalt, and 1.4% zirconium, likely as either oxides or carbonates. The purple solution was analyzed and found to contain dissolved metals as 85% cobalt, 8% copper, 3% zirconium, 2% iron, and 2% samarium.
A hydrothermal experiment was conducted in a 50 mL autoclave reactor with a PTFE liner and a pressure limit of 870 psia. 15 mL of distilled water, 10 mL of 34% hydrogen peroxide solution, and 5 g of ammonium carbonate were added to the autoclave reactor along with 1 g of crushed samarium cobalt magnets. The sealed reactor was then placed into a muffle furnace and heated to 130° C. at a rate of 10° C./min and held at that temperature for 16 hours, resulting in an estimated pressure inside the vessel of greater than 300 psia. The reactor was then allowed to cool to room temperature prior to opening the reactor. Upon opening, the reactor contents were filtered, and the filtrate was completely evaporated at 120° C. to isolate the dissolved solids as a residue. This residue was calcined at 850° C. for eight hours and washed with distilled water to remove soluble salts prior to analysis using Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDS) by a commercial analytical lab. 13 percent of the initial cobalt was recovered in the final product which was 81% cobalt. The concentration of dissolved solids was estimated as 13 g/L, far in excess of what was obtained in the alternate approaches described above.
Any of the above embodiments herein may be rearranged and/or combined with other embodiments. Accordingly, the concepts herein are not to be limited to any particular embodiment disclosed herein. Additionally, the embodiments can take the form of entirely hardware or comprising both hardware and software elements. Portions of the embodiments may be implemented in software, which includes but is not limited to firmware, resident software, microcode, etc. For example, software may be used to control various reactions, processes, and hardware (e.g., pumps, reactors, condensers, etc.) presented herein.
Furthermore, the embodiments can take the form of a computer program product accessible from the computer readable medium 506 providing program code for use by or in connection with a computer or any instruction execution system. For the purposes of this description, the computer readable medium 506 can be any apparatus that can tangibly store the program for use by or in connection with the instruction execution system, apparatus, or device, including the computer system 500.
The medium 506 can be any tangible electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system (or apparatus or device). Examples of a computer readable medium 506 include a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), NAND flash memory, a read-only memory (ROM), a rigid magnetic disk and an optical disk. Some examples of optical disks include compact disk—read only memory (CD-ROM), compact disk—read/write (CD-R/W) and digital versatile disc (DVD).
The computing system 500, suitable for storing and/or executing program code, can include one or more processors 502 coupled directly or indirectly to memory 508 through a system bus 510. The memory 508 can include local memory employed during actual execution of the program code, bulk storage, and cache memories which provide temporary storage of at least some program code in order to reduce the number of times code is retrieved from bulk storage during execution. Input/output or I/O devices 504 (including but not limited to keyboards, displays, pointing devices, etc.) can be coupled to the system either directly or through intervening I/O controllers. Network adapters may also be coupled to the system to enable the computing system 500 to become coupled to other data processing systems, such as through host systems interfaces 512, or remote printers or storage devices through intervening private or public networks. Modems, cable modem and Ethernet cards are just a few of the currently available types of network adapters.
In one embodiment, a Cobalt Extraction and Recycling from Permanent Magnets (CERPM) process recovers cobalt and other valuable metal elements from samarium cobalt magnets.
In one embodiment, the CERPM process recovers cobalt and other valuable metal elements from partially or fully oxidized samarium cobalt magnets.
In one embodiment, the CERPM process recovers copper as a co-product.
In one embodiment, the CERPM process recovers nickel as a co-product.
In one embodiment the CERPM process recovers cobalt, copper, or nickel from manufacturing wastes such as cutting swarf in which oxidation of the alloy may have occurred.
In one embodiment the CERPM process recovers cobalt and other valuable metal elements as high-quality feed stock to support manufacture of new high-performance magnets. The product metals may be combined with fresh material in any proportion to alter or enhance the magnetic properties.
In one embodiment, the cobalt metal product may be used as a high-quality feed stock for battery production.
In one embodiment, the cobalt metal product may be sold as a commodity to manufacturers or end-users.
In one embodiment of the process, a mechanical crushing pre-treatment is used to increase the surface area and partially demagnetize the starting material.
In one embodiment of the process, a hydraulic press is used to crush the starting material.
In another embodiment, pretreatment may include further grinding or milling of the brittle magnet material to open additional surface area.
In other embodiments, additional pretreatment may be applied to adjust the oxidation state prior to extraction using chemical, electrical, or other oxidation or reduction methods.
In one embodiment of the process, pretreatment of magnet powders by exposure to air at temperatures up to 1500° C. to oxidize magnet powder prior to extraction.
In one embodiment of the process, pretreatment of magnet powders heating in an oxygen-free atmosphere above the Curie temperature to demagnetize magnet powder prior to extraction. This may be up to 1500° C. for typical applications, or higher for specific feeds.
In one embodiment of the process, pretreatment of magnet powders by exposure to hydrogen at temperatures up to 1500° C. to reduce cobalt and other oxides to metal prior to extraction.
In one embodiment of the process, pretreatment of magnets by exposure to hydrogen at high temperature or pressure to decompose the phases to elemental or hydride forms.
In one embodiment of the process, pretreatment may include demagnetization of the magnetic starting material using an externally applied magnetic field or a shock treatment.
In one embodiment, a recoverable aqueous ammonium carbonate leach solution is used to decompose permanent magnet alloy compositions at low temperature and pressure into insoluble precipitates and soluble metal complexes.
In one embodiment, the leach solution is composed of 1.6 molar ammonium carbonate.
In other embodiments, the leach solution is composed of ammonia and ammonium carbonate in any proportion from 0.1 molar to saturated.
In one embodiment, after selective recovery of constituents from the mixture, the extraction solution is directly recycled.
In another embodiment, the extraction solution is heated to release ammonia and carbon dioxide, which are recovered and then recycled to the process.
In one embodiment, oxygen gas is used as an oxidant in the leaching step.
In one embodiment, air is used as an oxidant in the leaching step.
In one embodiment, a chemical oxidant such as hydrogen peroxide is used as an oxidant in the leaching step.
In one embodiment, an inert atmosphere is used in the leaching step.
In one embodiment, hydrogen gas or another chemical reductant is used in the leaching step.
In one embodiment, the extraction process is typically carried out at ambient temperature.
In one embodiment, the extraction process is typically carried out at temperatures between ambient and 60° C.
In one embodiment, the extraction process is typically carried out at temperatures above 60° C. and at pressure greater than 1 atmosphere.
In one embodiment, the extraction process is typically carried out at temperatures above 100° C. and at pressure greater than 1 atmosphere.
In one embodiment, the extraction process is typically carried out in vessels constructed of stainless-steel without any lining.
In one embodiment, the extraction process is typically carried out in vessels composed of or lined with glass.
In one embodiment, the extraction process is typically carried out in vessels composed of or lined with polytetrafluoroethylene (PTFE).
In other embodiments, the extraction process is typically carried out in vessels composed of or lined with a corrosion barrier that does not react with the mixture.
In one embodiment of the process, CO2 is added to the filtrate to precipitate some of the dissolved compounds prior to further processing.
In one embodiment of the process, addition of a base to the filtrate causes precipitation of dissolved cobalt.
In one embodiment of the process, addition of an acid to the filtrate causes precipitation of dissolved cobalt.
In one embodiment of the process, addition of either an acid or a base to the filtrate causes precipitation of dissolved iron or another base metal.
In one embodiment of the process, CO2, air, oxygen, hydrogen peroxide, etc. is used to change the Eh of the filtrate and cause precipitation of the cobalt or dissolved iron.
In one embodiment of the process, heat, steam, or evaporation is employed to cause precipitation of dissolved compounds from the filtrate.
In one embodiment of the process, a reagent such as a sulfur compound is added to the filtrate to form an insoluble cobalt species.
In one embodiment, the electrochemical reactor consists of two electrodes in a single chamber.
In another embodiment, the electrochemical reactor consists of two electrodes in two separate chambers.
In another embodiment, the electrochemical reactor consists of two electrodes separated by a membrane which allows some but not all components to pass through.
In another embodiment, a third or fourth electrode is used as a reference electrode.
In one embodiment, the potential is held constant throughout the electrowinning step.
In another embodiment, the current passed is held constant throughout the electrowinning step.
In another embodiment, the potential or current are varied or swept following a programmed pattern throughout the electrowinning step.
In one embodiment, the anode is composed of nickel and the cathode is composed of carbon.
In other embodiments, the anode or cathode may be composed of any conductive material.
In another embodiment, the anode or cathode may be prepared or structured to increase the surface area, increase the rate of the desired reaction, or limit the rate of undesired reactions.
In another embodiment, additional chemicals may be added to the solution to improve the quality of the plating.
In another embodiment, additional chemicals may be added to improve the reaction kinetics of oxygen evolution at the anode.
In another embodiment, additional chemicals are added to slow the hydrogen evolution reaction at the cathode.
In one embodiment, copper metal or another coproduct is plated prior to plating cobalt.
In another embodiment, copper, cobalt, and/or other dissolved metal compounds are co-plated on an electrode.
In one embodiment of the process, direct recycle of ammonium carbonate and/or ammonia is done after precipitation of solids.
In one embodiment of the process, multiple extraction stages are employed to further separate cobalt from iron or other contaminants.
In one embodiment of the process, additives for leaching or precipitation are recovered and reused.
In one embodiment, the solution is heated after electrowinning cobalt to evolve ammonia and carbon dioxide for capture and reuse.
In one embodiment of the process, the process feed is obtained from an asteroid, the moon, Mars, or other extraterrestrial resources.
In situ resource utilization (ISRU) may be generally defined as the collection, processing, storing and use of materials encountered in the course of human or robotic terrestrial or space exploration that replace materials that would otherwise be brought from a remote location such as another geographic location or another planet or location in space.
In some embodiments, the process employs ISRU leveraging resources found or manufactured on other astronomical objects (the Moon, Mars, asteroids, etc.) to fulfill or enhance the requirements and capabilities of a space or terrestrial mission.
In other embodiments, the process is useful in recovering cobalt, rare-earth, and/or precious metals from an asteroid and other extra-terrestrial site such as planet Mars or the moon.
In one embodiment, the process is used in asteroid mining to recover valuable cobalt, rare-earth metals, and precious metals.
This patent application claims the benefit of U.S. Provisional Patent Application No. 63/165,467 (entitled “Cobalt Extraction and Recycling from Permanent Magnets” and filed on Mar. 24, 2021), the contents of which are hereby incorporated by reference.
This invention was made with government support under U.S. Department of Energy contract no. DE-SC0020853. The government has certain rights in this invention.
| Number | Date | Country | |
|---|---|---|---|
| 63165467 | Mar 2021 | US |
