Methods and systems for recovery of rare earth elements from magnets

Abstract

A method and system for the recovery of rare earth elements, cobalt, and electrolytic iron from magnets. The system can include an electrochemical cell assembly configured to dissolve the magnets in an acid solution. The system can also include a filtration unit operatively connected to the electrochemical cell assembly for removing impurities from the dissolved magnet solution. The system can also include a precipitation unit operatively connected to the filtration unit. The system can also include an electrowinning cell operatively connected to the precipitation unit. The system can also include a recycling unit for regenerating sulfuric acid from the process effluent, operatively connected to the electrowinning cell.

Description

TITLE: METHODS AND SYSTEMS FOR RECOVERY OF RARE EARTH ELEMENTS FROM MAGNETSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit ofU.S. Provisional Application No. 63 / 619,024, titled “METHODS AND SYSTEMS FOR RECOVERY OF RARE EARTH ELEMENTS FROM MAGNETS” filed January 9, 2024, the content of which is incorporated herein by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure is situated in the field of materials science and environmental sustainability, particularly focusing on the recycling of rare earth elements and iron from permanent magnets, such as for example neodymium-iron-boron (NdFeB) permanent magnets. In particular, the present disclosure combines principles of electrochemistry, hydrometallurgy, and environmental engineering for an efficient and environmentally friendly electrochemical process.STATEMENT OF FEDERALLY FUNDED RESEARCH

[0003] None.BACKGROUND

[0004] The landscape of modern technology is increasingly reliant on critical minerals, essential for the well-being of economies and the advancement of various high-tech applications. Among these, rare earth elements, a sub-group encompassing seventeen minerals and fifteen lanthanide elements, have emerged as vital resources. Their significant use in permanent magnet manufacturing, which accounted for 29-35% of these materials in 2020, highlights their importance. Permanent magnets, incorporating valuable rare earth elements like neodymium,dysprosium, and terbium, are central to a myriad of advanced technologies, ranging from electronics to defense applications. The global distribution of rare earth element production, heavily skewed towards a few countries, poses both economic burdens and national security risks due to geopolitical issues and trade policies.

[0005] The quest for efficient recycling of end-of-life permanent magnets has become a focal point in addressing these challenges. The high cost of mining virgin rare earth materials underscores the economic and environmental viability of recycling strategies. Current recycling efforts predominantly revolve around pyrometal lurgi cal and hydrometallurgical processes. Pyrometallurgical methods, though effective, are marked by high-temperature operations that escalate both cost and environmental footprint. Conversely, hydrometallurgical processes offer a more environmentally friendly approach, operating at moderate temperatures and requiring smaller facilities. However, they are not without drawbacks, such as the need for large volumes of chemicals and the potential loss of rare earth elements during solution leaching.

[0006] The industry faces significant challenges in reducing operating costs while maintaining high product yields. Current techniques, including hydrogen decrepitation, chemical vapor transport, and liquid metal extraction, are complex and often entail safety concerns, high chemical usage, and fluctuating yields. The focus has now shifted towards developing a feasible and efficient end-of-life neodymium-iron-boron permanent magnet recycling technique that addresses these challenges.

[0007] With the rising demand for rare earth elements in sectors such as clean energy, lifestyle, and defense, coupled with the challenges in mining and the geochemical and environmental concerns it raises, there is an urgent need for sustainable solutions. The shortage of natural depositsand the overproduction of less-demanded rare earth elements further complicate the supply chain, propelling the need for efficient recycling of end-of-life products containing these elements.

[0008] Current recycling technologies, while promising, are hampered by limitations such as the requirement for iron oxidation for iron removal and acid recovery, which necessitates additional energy inputs. The exploration of electrodeposition of metallic iron from iron-rich solutions as a viable alternative for closed-loop recycling has seen recent advances. However, challenges such as energy inefficiency in undivided electrochemical cells and the need for improved methods for rare earth element separation remain.

[0009] Accordingly, there is a need for a system and method using an electrolytic cell to leach and selectively recover rare earth elements, iron, and cobalt during the permanent magnet recycling process. This would address the current limitations in the recycling of rare earth elements from end-of-life permanent magnets, providing a more efficient, cost-effective, and environmentally sustainable solution.SUMMARY OF THE DISCLOSURE

[0010] The present disclosure is directed to systems and methods for the recovery of rare earth elements, iron, and cobalt from neodymium -iron-boron (NdFeB) permanent magnets at the end of their life cycle. This is achieved through a low-temperature, closed-loop, electro- hydrometallurgical process. The method encompasses a series of steps that may include chemical dissolution of NdFeB permanent magnets, filtration to remove impurities, precipitation reactions for rare earth element recovery, and electrowinning for the extraction of metals.

[0011] To address the needs disclosed above, the disclosure proposes a process that begins with the chemical dissolution of NdFeB permanent magnets. This dissolution may be performed usinga variety of suitable acids, under conditions that can vary depending on specific requirements. The dissolution process results in a solution from which various elements can be extracted. The subsequent filtration step is designed to separate impurities from the solution, preparing it for the recovery of valuable materials.

[0012] A disclosed system and method can, in some embodiments, utilize a double salt precipitation reaction, which allows for the selective recovery of rare earth elements from the solution. Various compounds may be added to facilitate this precipitation, resulting in the formation of salts that contain the desired rare earth elements. This process is designed to maximize the recovery of rare earth elements while minimizing the co-precipitation of other materials.

[0013] Electrowinning is another step that may be included in the process. This involves the recovery of metals such as iron and cobalt by electrodeposition. The specifics of the electrowinning step, such as the materials used for the anode and cathode, the composition of the electrolyte, and the operating conditions, can be varied according to the requirements of the particular application.

[0014] The present disclosure can provide a process with an emphasis on sustainability, with options for recycling the chemicals used in the process. For instance, acids utilized in the dissolution step may be captured and reused, contributing to the overall efficiency and environmental friendliness of the method. The disclosed approach thus provides a broad framework for the recycling of rare earth elements from NdFeB permanent magnets, offering flexibility in implementation and optimization for different applications.

[0015] In general, in one embodiment, the disclosure features a method for recovering rare earth elements, cobalt, and electrolytic iron from magnets can include several steps. The method can involve dissolving magnet particulates in a sulfuric acid solution. Following dissolution, the method can include filtering the solution to remove impurities. Another step can involveprecipitating rare earth elements from the solution using a sulfate salt as a precipitating agent. The method can also include subjecting the solution to electrowinning to recover metallic iron and cobalt. The method can also involve recycling the remaining acidic solution.

[0016] In general, in another embodiment, the disclosure features a system for the recovery of rare earth elements, cobalt, and electrolytic iron from magnets can comprise various components. The system can include an electrochemical cell assembly, configured to dissolve the magnets in an acid solution. The system can also feature a filtration unit operatively connected to the electrochemical cell assembly for removing impurities from the dissolved magnet solution. Additionally, the system can encompass a precipitation unit, operatively connected to the filtration unit, equipped with means for adding precipitating agents. Another part of the system can be an electrowinning cell, operatively connected to the precipitation unit and configured for the electrodeposition of metallic iron from the iron-rich solution remaining after rare earth elements recovery. The system can also include a recycling unit for regenerating sulfuric acid from the process effluent, operatively connected to the electrowinning cell.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other advantages of the present disclosure will be apparent from the following detailed description of the disclosure in conjunction with embodiments as illustrated in the accompanying drawings, in which:

[0018] FIG. 1 depicts an experimental setup for electrochemically oxidizing iron on the anode side or reducing iron on the cathode side, in accordance with certain embodiments of the present disclosure.

[0019] FIG. 2 depicts a schematic of the electrochemical cell, in accordance with certain embodiments of the present disclosure.

[0020] FIG. 3 depicts a front view of anode side graphite plate as part of the electrochemical cell, in accordance with certain embodiments of the present disclosure.

[0021] FIG. 4 depicts a front view of cathode side graphite plate as part of the electrochemical cell, in accordance with certain embodiments of the present disclosure.

[0022] FIG. 5 depicts an exemplary design of gaskets, as used on the anode and cathode sides, as part of the electrochemical cell, in accordance with certain embodiments of the present disclosure.

[0023] FIG. 6 depicts parts of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure.

[0024] FIGS. 7A-7E depict components of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7A depicts a front view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7B depicts a rear view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7C depicts a right side view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7D depicts a left side view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7E depicts a top view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure.

[0025] FIG. 8 depicts a schematic showing dimensions of part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure.

[0026] FIG. 9 depicts an exemplary design of gaskets, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure.

[0027] FIG. 10 depicts a graph of the leaching rate of neodymium at room temperature in a sulfuric acid solution, in accordance with certain embodiments of the present disclosure.

[0028] FIG. 11 depicts a graph of the leaching rate of iron at room temperature in a sulfuric acid solution, in accordance with certain embodiments of the present disclosure.

[0029] FIG. 12 depicts a graph of the change in pH and temperature during acid leaching of magnet powder in a sulfuric acid solution, in accordance with certain embodiments of the present disclosure.

[0030] FIG. 13 depicts a graph showing the effect of adding the precipitant sodium sulfate into 2M sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure.

[0031] FIG. 14 depicts a graph showing the effect of adding the precipitant sodium sulfate into IM sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure.

[0032] FIG. 15 depicts a graph showing the effect of adding the precipitant sodium hydroxide into 2M sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure.

[0033] FIG. 16 depicts a graph showing the effect of adding the precipitant sodium hydroxide into IM sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure.

[0034] FIG. 17 depicts a graph showing the effect of adding the precipitant sodium sulfate into sulfuric acid leachate containing fully oxidized iron on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure.

[0035] FIG. 18 depicts a graph showing the effect of adding the precipitant sodium sulfate into sulfuric acid leachate containing fully reduced iron on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure.

[0036] FIG. 19 depicts XRD patterns of the salts obtained by precipitation using sodium sulfate from sulfuric acid leachate, in accordance with certain embodiments of the present disclosure.

[0037] FIG. 20 depicts the chronoamperometric response of Fe(II) oxidation reaction under applied cell voltage at room temperature, in accordance with certain embodiments of the present disclosure.

[0038] FIG. 21 depicts the chronoamperometric response of Fe(III) oxidation reaction under applied cell voltage at room temperature, in accordance with certain embodiments of the present disclosure.

[0039] FIG. 22 depicts a graph showing the concentration of iron in catholyte and faradaic efficiency of the iron reduction process, in accordance with certain embodiments of the present disclosure.

[0040] FIG. 23 depicts a graph showing galvanostatic response of iron electrodeposition in a divided flow cell, in accordance with certain embodiments of the present disclosure.

[0041] FIG. 24 depicts a process flowsheet for a circular recycling method, in accordance with certain embodiments of the present disclosure.NOTATION AND NOMENCLATURE

[0042] Various terms are used to refer to particular system components. Different companies may refer to a component by different names - this document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections.

[0043] The terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. Following long-standing patent law convention, the terms “a” and “an” mean “one or more” when used in this application, including the claims.

[0044] As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0045] The terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections; however, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Terms such as “first,” “second,” and other numerical terms, when used herein, do not imply a sequenceor order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. As used herein, the term “and / or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and / or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D. Accordingly, as an example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. In another example, the phrase “one or more” when used with a list of items means there may be one item or any suitable number of items exceeding one.

[0046] Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” “top,” “bottom,” and the like, may be used herein. These spatially relative terms can be used for ease of description to describe one element’s or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms may also be intended to encompass different orientations of the device in use, or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein interpreted accordingly.

[0047] Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in this specification are approximations that can vary depending upon the desired properties sought to be obtained by the presently disclosed subject matter.DETAILED DESCRIPTION OF THE DISCLOSURE

[0048] The present disclosure is directed to systems and methods for the recovery of rare earth elements, iron, and cobalt from neodymium-iron-boron (NdFeB) permanent magnets at the end of their life cycle. This is achieved through a low-temperature, closed-loop, electro- hydrometallurgical process. The method encompasses a series of steps that may include chemical dissolution of NdFeB permanent magnets, filtration to remove impurities, precipitation reactions for rare earth element recovery, and electrowinning for the extraction of metals.

[0049] In certain embodiments, rare earth elements, known for their unique physical and chemical properties, can be utilized in a wide range of sectors. These sectors may include, but are not limited to, clean energy, lifestyle, and defense. Various commodities, such as wind turbines, hybrid and electric vehicles, rechargeable batteries, cellphones, hard disk drives, industrial motors, and magnetic resonance imaging machines, can potentially incorporate rare earth elements. With the evolving landscape of technology and energy, there is an anticipated increase in the demand for rare earth elements. However, challenges such as the limitations of natural deposits and the environmental considerations of mining present opportunities for alternative approaches to acquiring these elements.

[0050] The present disclosure provides methods and systems for addressing the demand for rare earth elements involving the recycling of end-of-life products that contain these elements. For instance, neodymium-iron-boron permanent magnets, which may exhibit high energy density, can be found in a variety of applications. The life cycles of these magnets can vary, and they may contain a mixture of rare earth elements, iron, boron, and other metals. The recycling of these magnets, particularly from sources like the wind industry, could provide a means to recover rare earth elements, contributing to economic and environmental sustainability.

[0051] In certain embodiments, various processes can be employed for the recycling of rare earth elements from end-of-life magnets or magnet scraps. These processes might include, but are not limited to, hydrometallurgical and pyrometallurgical methods, each offering different potential benefits and challenges. For example, in some instances, a hydrometallurgical process may be employed, which could involve either the complete or partial dissolution of magnets in an acidic solution. This process might also include the co-extraction of iron, predominantly in the Fe(II) state, from the neodymium-iron-boron magnet into the resulting solution. The flexibility and adaptability of such a process could allow for customization based on the specific composition of the magnets and the targeted recovery outcomes.

[0052] In some embodiments of the present disclosure, the process of leaching rare earth elements using sulfuric acid can be described by the following reactions:2REE + 3H2O4REE2SO4)~3+ 3H2Fe + H2SO4— > FeS04-I- H2

[0053] In the equations above, REE represents elements such as neodymium (Nd), dysprosium (Dy), praseodymium (Pr), and terbium (Tb). These reactions illustrate potential pathways for the dissolution of rare earth elements and iron in a sulfuric acid medium.

[0054] The speciation of iron plays an important role in the recycling process. Iron in the Fe(II) form may be more stable and not precipitate until reaching a pH of around 6. In this pH range, rare earth elements could also precipitate via hydrolysis. Therefore, selective precipitation of either Fe(II) or rare earth elements may be challenging. Conversely, Fe(III) may precipitate at a lower pH, around 2-3. In certain embodiments, oxidation of Fe(II) to Fe(III) can be essential for recovering iron from the leachate. Various methods, such as roasting pre-treatment, chemical oxidation, and electrochemical oxidation, might be used for this oxidation step. However, it is possible for iron to be commonly recovered as waste forms like Fe(III) hydroxide or Fe(III) oxide hydroxides.

[0055] For the separation of rare earth elements from the leachate, various precipitants may be used. A prevalent method might involve the formation of a double salt precipitate (RE, Na)2(SO4)2 XH2O by adding sodium sulfate, ammonium sulfate, sodium hydroxide, or similar compounds, as shown in the following reaction:2Na++ REE3++ 2SO2" + xH20 -> NaREE(SO4)2.xH2O

[0056] In certain recycling technologies, the oxidation of Fe(II) to Fe(III) may be a necessary step for iron removal and acid recovery, requiring additional heat, chemical oxidizers, or electrical energy, with iron recovered as waste. In alternative embodiments, a method or system could include the electrodeposition of metallic iron from an iron-rich solution following the removal of rare earth elements. In such an alternative embodiment, the approach could lead to the creation of a valuable byproduct and enable a closed-loop recycling route.

[0057] In some embodiments, the magnet recycling may involve the use of an undivided electrochemical cell for the dissolution of the magnet and deposition of iron on a cathode. The present disclosure, in some embodiments, utilzies a closed-loop recycling route that includes thecomplete chemical dissolution of magnets, recovery of rare earth elements by double salt precipitation, iron electrowinning, and acid recycling.

[0058] FIG. 1 depicts an experimental setup for electrochemically oxidizing iron on the anode side or reducing iron on the cathode side, in accordance with certain embodiments of the present disclosure. The setup of FIG. 1 is designed for the electrochemical oxidation of iron on the anode side and the reduction of iron on the cathode side. The detailed configuration of this setup and the specific conditions under which it operates are described in accordance with certain embodiments.

[0059] Chemicals used in various embodiments may include sulfuric acid, sodium hydroxide, and sodium sulfate anhydrous, among others. These chemicals are sourced to ensure high purity and reliability in the experimental process. Ultrapure water is utilized for the preparation of solutions and standards. Spent magnet samples, demagnetized for the purpose of these studies, are obtained from specified sources, such as the American Resources Corporation.

[0060] For the characterization and chemical analysis, several techniques may be employed. These can include inductively coupled plasma optical emission spectroscopy (ICP-OES) for measuring the concentrations of iron and rare earth elements in both magnet and test solutions. X-ray diffraction (XRD) measurements are conducted to analyze solid samples, and X-ray fluorescence (PXRF) is utilized for analyzing electrodeposited films. All measurements may be carried out multiple times to ensure accuracy, and standard deviation values are considered for error analysis.

[0061] The experimental process in some embodiments may involve reducing the particle size of magnets using specific crushing and pulverizing equipment. A sieve shaker is employed to collect magnet particles of a targeted size for the experiments. The pH levels during leaching experiments are closely monitored using specified pH meters.

[0062] The acid dissolution of magnets can be conducted with varying ratios of acid to magnet powder. Specific quantities of magnet powder are dissolved in sulfuric acid solutions of varying molarity. These tests are typically run at room temperature for a set duration, with continuous stirring to ensure uniform dissolution. The leached solution is then filtered to remove impurities, preparing it for subsequent steps in the recycling process.

[0063] An electrochemical flow cell, developed for either oxidizing or reducing iron electrochemically, is an integral part of the experimental setup. This setup, as depicted in Figures 1 and 2, includes carbon cloth electrodes and an anion exchange membrane. The electrochemical oxidation experiments are conducted under specific conditions, including cell voltage, solution recirculation, and the use of pumps for fluid movement. The potential reactions for this cell configuration are as follows:Fe2+-► Fe3++ e~ (E° = 0.77V vs. SHE)2H2O O2+ 4H++ 4e“ (E° = 1.23V vs. SHE2H++ 2e~ H2(E° = 07 vs. SHE)

[0064] The electrochemical reduction experiments are similarly conducted under specific conditions, with adjustments made to the voltage, solution compositions, and flow rates. These experiments are performed until a predetermined current threshold is reached, ensuring consistent and controlled conditions for the electrochemical processes.

[0065] The mass of oxidized iron and the energy consumption for the oxidation process are calculated using Faraday’s law and a specific formula for energy consumption, as detailed in the equations:

[0066] Where It is the total charge consumed during electrolysis, MFeis the atomic mass of iron, n is the number of electron transfers per mole of iron oxidation, is the Faraday’s constant, P is the energy consumed, and Fis the applied cell voltage.

[0067] As depicted in FIG. 1, the system for the electrochemical treatment of iron may include an assembly that features two separate electrochemical cells. In FIG. 1, each cell can be arranged to house an electrode that may be submerged in an electrolyte solution, with a configuration allowing for the electrodes to be connected to an external circuit, as required.

[0068] Accompanying the cells, as shown in the system for an electrochemical cell depicted in FIG. 1, can be a power supply with a digital readout that may be capable of supplying a regulated voltage and current to facilitate the electrochemical reactions. This power supply may be adjustable, providing the flexibility to set various voltages for the processes of oxidation or reduction.

[0069] As part of the system illustrated in FIG. 1, pumps may be placed on either side of the cells. These pumps, identified by their circular mechanisms and associated tubing, can be utilized to circulate the electrolyte solution through the cells. The tubing that connects the pumps to the cells, as indicated in FIG. 1, is purposed for the conveyance of the electrolyte solution, which may be essential for the ongoing introduction of fresh electrolyte and the removal of reaction by-products.

[0070] As shown in FIG. 1, in the system for the electrochemical cell, beneath each cell, magnetic stirrers may be positioned, which can be employed to ensure a homogenous solution within the cells for the conduct of the electrochemical reactions. Industrial scale mixers can be used instead of magnetic mixers.

[0071] The cells can be placed upon stands, as shown in FIG. 1, which are fitted with clamps that may be adjustable to secure the electrodes in a position that facilitates the reactions within the cells.

[0072] The vessels, or containers, as illustrated in FIG. 1, can be designed to be chemically resistant and appropriately proportioned to house the electrodes and permit sufficient movement of the solution. The electrical wires can provide the connections from the power supply to the electrodes, essential for supplying the electrical current for the reactions.

[0073] In some embodiments, the system for electrochemically oxidizing iron on the anode side or reducing iron on the cathode side can include a control panel with a digital display, as depicted in FIG. 1. This panel may be utilized to monitor and adjust the parameters of the electrochemical process, such as voltage and current, and in some embodiments, the duration of the experiment. This feature allows for detailed management of the conditions under which the electrochemical oxidation and reduction of iron are conducted.

[0074] FIG. 2 depicts a schematic of the electrochemical cell, in accordance with certain embodiments of the present disclosure.

[0075] As shown in FIG. 2, the cell can be composed of various parts, each with specified dimensions and materials, which are presented in Table 1 below, which provides exemplary outer dimensions and materials of various parts of the electrochemical flow cell.TABLE 1

[0076] In FIG. 2, a backplate serves as the foundational part of the electrochemical flow cell, which, in some embodiments, measures 17.5 cm in length and width, with a thickness of 20 mm, and may be made from SS304 stainless steel. Adjacent to the backplate, as depicted in FIG. 2, the current collector, potentially measuring 20 cm by 15 cm and with a thickness of 1.4 mm, can be constructed from copper, facilitating the flow of electrons during the electrochemical process.

[0077] As shown in FIG. 2, in some embodiments of the electrochemical cell, an insulating layer can be positioned next to the current collector, which may be 17 cm long, 15 cm wide, and 0.6 mm thick, possibly made of high-temperature silicone to provide electrical insulation. Following this layer, as illustrated in FIG. 2, is a graphite plate that could measure 15.24 cm by 15.24 cm with a thickness of 1.9 cm, and may be composed of fuel cell-grade graphite, providing structural support and electrical conductivity.

[0078] Further, the electrochemical cell can include a carbon cloth, depicted in FIG. 2, which may act as the electrode material. As provided in Table 1 above, the carbon cloth can in some embodiments be 12 cm by 12 cm with a thickness of 0.406 mm. This component can be made from a hydrophilic material, as specified by its product code, to enhance its interaction with the cell’s electrolyte.

[0079] A gasket, as represented in FIG. 2, may be included in the electrochemical cell to ensure a secure seal within the cell. In some embodiments, the gasket can measure 15.24 cm by 15.24 cm and 0.25 mm thick, and in some embodiments, fabricated from high-temperature silicone capable of withstanding the operational conditions of the cell.

[0080] As shown in FIG. 2, the membrane of the electrochemical cell, which may separate the anode and cathode compartments, can have dimensions of 15.24 cm by 15.24 cm and a thicknessranging from 45 to 55 gm. In certain embodiments, this membrane, such as the FUMASEP FAS- 50, serves as a selective barrier allowing ions to pass while preventing the mixing of reactants.

[0081] The detailed assembly and arrangement of these components, as shown in FIG. 2, are critical to the function of the electrochemical cell in the disclosed recycling process.

[0082] FIG. 3 depicts a front view of anode side graphite plate as part of the electrochemical cell, in accordance with certain embodiments of the present disclosure. As depicted in FIG. 3, the present disclosure illustrates a front view of the anode side graphite plate, which is a component of the electrochemical cell in certain embodiments. The graphite plate features channels with a depth of 7.1 mm, designed to facilitate the flow of electrolyte and the distribution of reactants to the anode surface during the electrochemical process.

[0083] FIG. 4 depicts a front view of cathode side graphite plate as part of the electrochemical cell, in accordance with certain embodiments of the present disclosure. In FIG. 4, a front view of the cathode side graphite plate is shown as part of the electrochemical cell, consistent with certain embodiments of the present disclosure. This graphite plate also has channels with a depth of 7.1 mm. The distinguishing characteristic of the cathode side plate, as compared to the anode side plate shown in FIG. 3, is the positioning of the holes for the inlet and outlet tubes, which are designed to manage the introduction and exit of electrolyte solutions specific to the cathodic reactions.

[0084] FIG. 5 depicts an exemplary design of gaskets, as used on the anode and cathode sides, as part of the electrochemical cell, in accordance with certain embodiments of the present disclosure. Specifically, these gaskets can be utilized on both the anode and cathode sides of the cell and are identical in design. Their role in the cell assembly in some embodiments is to ensure a proper seal, preventing leaks and ensuring that the electrolyte solution flows through the designated channelseffectively, thus contributing to the efficiency and safety of the electrochemical reactions within the cell.

[0085] FIG. 6 depicts parts of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. As shown in FIG. 6, parts of an iron electrowinning cell are detailed, in alignment with certain embodiments of the present disclosure. The iron electrowinning process, subsequent to the separation of rare earth elements, involves the electrodeposition of iron from an iron-rich solution. This solution is prepared by dissolving magnet material in sulfuric acid, followed by a reduction process in an electrochemical cell, and precipitation using sodium sulfate. The electrowinning cell, as depicted in FIG. 6, is further described by Table 2 below, which outlines the outer dimensions and materials of various parts of the cell, including the backplate, anode / cathode compartment, gasket, and membrane.TABLE 2

[0086] In certain embodiments of the disclosure, as exemplified in FIGS. 1 and 6, the process of iron electrowinning may involve electrodeposition from an iron-rich solution subsequent to the separation of rare earth elements by precipitation. For example, 75 grams of magnet can be dissolved in 1.5 liters of a IM sulfuric acid solution. Then, in some embodiments, 600 milliliters of this leached solution may be completely reduced within an electrochemical cell.

[0087] Subsequent to the reduction step, the leached solution can be subjected to a precipitation process by adding, for example, 25.9 grams of sodium sulfate, which may correspond toapproximately 2.66 times the stoichiometric requirement. This precipitation process may continue for a duration of 12 hours. Thereafter, in certain embodiments, the pH of the collected iron-rich supernatant may be adjusted to 1.46 by adding, for example, 4 milliliters of sodium hydroxide at a 50% weight concentration.

[0088] FIG. 6 illustrates details of the electrowinning cell wherein, in some embodiments, a cathode can be made from commercial iridium oxide and tantalum oxide at a density of 2 milligrams per square centimeter, supported on a titanium plate measuring 10.16 centimeters by 10.80 centimeters. An expanded mesh, which may be used as an anode, can have the same dimensions and material as the cathode. The electrode gap between anode and cathode in the cell may be set at 3 centimeters.

[0089] An anion exchange membrane, such as the FUMASEP FAS-50, may separate the anode and cathode compartments within the electrowinning cell. In certain embodiments, the electrowinning experiment may be conducted in a galvanostatic mode, typically at a constant current of 3 amperes, recirculating 550 milliliters of IM sulfuric acid with 27.5 grams of dissolved sodium sulfate through the anodic compartment. The experiment might last for approximately 20 hours and can be performed at a temperature of 70 degrees Celsius, with a flow rate varied between 0.5 to 1.1 liters per minute using Masterflex® peristaltic pumps, for example, with model numbers 7555-00 and 77201-62.

[0090] FIGS. 7A-7E depict components of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7A depicts a front view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7B depicts a rear view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure.FIG. 7C depicts a right side view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7D depicts a left side view, as used in the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. FIG. 7E depicts a top view, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure.

[0091] FIGS. 7A-7E collectively provide a detailed design of the anode and cathode compartments, highlighting the mirrored configuration in the electrowinning cell.

[0092] FIG. 8 depicts a schematic showing dimensions of the Ta-Ir supported on Ti plate cathode as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. In some embodiments, the anode, which is designed with a mesh structure, shares the same material and dimensions as the cathode, consistent with certain embodiments of the present disclosure.

[0093] FIG. 9 depicts an exemplary design of gaskets, as used on the anode and cathode sides, as part of the iron electrowinning cell, in accordance with certain embodiments of the present disclosure. In certain embodiments, the anode and cathode side gaskets are identical, signifying their interchangeable use on either side of the cell.

[0094] FIGS. 10 and 11 provide data on the leaching behavior of neodymium and iron from magnet powder and the subsequent recovery of rare earth elements through various precipitation methods are illustrated, in line with certain embodiments of the present disclosure.

[0095] FIG. 10 depicts a graph of the leaching rate of neodymium at room temperature in a sulfuric acid solution, in accordance with certain embodiments of the present disclosure. FIG. 10 shows a graph of the leaching rate of neodymium at room temperature in a sulfuric acid solution. Theleaching of neodymium is characterized by a rapid dissolution, with almost 95% of the initial mass dissolving within the first 10 minutes.

[0096] FIG. 11 depicts a graph of the leaching rate of iron at room temperature in a sulfuric acid solution, in accordance with certain embodiments of the present disclosure. FIG. 11 exhibits a graph of the leaching rate of iron under similar conditions as neodymium, also at room temperature in a sulfuric acid solution. Iron displays a comparable leaching rate, with nearly 95% of the initial mass dissolving within the same time frame as neodymium.

[0097] FIGS. 10 and 11 provide results from leaching experiments conducted using IM and 2M sulfuric acid with pulp densities of 20 and 10 mL / g of magnet powder, respectively. These experiments, referenced in FIGS. 10 and 11, demonstrate that complete dissolution can be achieved under both conditions, with similar leaching rates. Further, as shown by FIGS. 10 and 11, the use of 2M sulfuric acid can reduce the water requirement.

[0098] FIG. 12 depicts a graph of the change in pH and temperature during acid leaching of magnet powder in a sulfuric acid solution, in accordance with certain embodiments of the present disclosure. As shown by FIG. 12, the final pH values obtained were well below 2, which can prevent iron oxidation and potential precipitation as Fe(OH).3.

[0099] In the context of refining the recovery process for rare earth elements from leached solutions, FIGS. 13 through 16 detail the exploration of two precipitating reagents — sodium sulfate and sodium hydroxide — with the aim of forming rare earth sodium double sulfate salts. These salts are desired for their low or absent iron coprecipitation, a key consideration in the purity of the recovered rare earth elements.

[0100] FIG. 13 depicts a graph showing the effect of adding the precipitant sodium sulfate into2M sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance withcertain embodiments of the present disclosure. Specifically, FIG. 13 demonstrates the recovery efficiency of rare earth elements from a 2M sulfuric acid leachate when sodium sulfate is used as the precipitating agent. In these experiments, sodium sulfate was added in amounts ranging from 2 to 8 times the stoichiometric quantity necessary to precipitate all the rare earth elements. The results as shown in FIG. 13 depict maximum extractions of 99.7%, 98.1%, and 97.5% for neodymium (Nd), praseodymium (Pr), and terbium (Tb), respectively.

[0101] As shown in the experimental results from FIG. 13, dysprosium (Dy) recovery was less efficient, with only 42% recovered at the highest stoichiometric amount tested. This lower recovery rate is attributed to the higher solubility of heavier rare earth double salts in the multicomponent sulfuric acid solution compared to lighter rare earths, necessitating an increased amount of sodium sulfate to improve dysprosium recovery. Furthermore, it has been reported that precipitation at a higher temperature, specifically 70°C, can enhance dysprosium recovery. The experiments depicted in FIG. 13 were performed for 1 hour at room temperature with stirring at 400 rpm, and the supernatant samples were collected after a 15-minute settling time, indicating no iron coprecipitation at even high stoichiometric amounts of sodium sulfate.

[0102] FIG. 14 depicts a graph showing the effect of adding the precipitant sodium sulfate into IM sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure. FIG. 14 illustrates the effects of adding sodium sulfate to a IM sulfuric acid leachate on the recovery of rare earth elements. These experiments also avoided iron coprecipitation, demonstrating the effectiveness of sodium sulfate as a selective precipitant for rare earth elements.

[0103] FIG. 15 depicts a graph showing the effect of adding the precipitant sodium hydroxide into 2M sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance withcertain embodiments of the present disclosure. In FIG. 15, the addition of sodium hydroxide to a 2M sulfuric acid leachate is examined. The experiments were carried out under identical conditions to those of FIG. 13 and FIG. 14. However, the addition of sodium hydroxide led to the undesirable coprecipitation of iron starting at around 3.5 times the stoichiometric amount of the hydroxide, underscoring the need for careful control of the precipitation process.

[0104] FIG. 16 depicts a graph showing the effect of adding the precipitant sodium hydroxide into IM sulfuric acid leachate on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure. Similarly, FIG. 16 presents the effects of sodium hydroxide addition into a IM sulfuric acid leachate. The pattern of coprecipitation is consistent with that observed in the 2M sulfuric acid leachate, reinforcing the conclusion that sodium hydroxide, beyond certain stoichiometric amounts, leads to the coprecipitation of iron, which is undesirable for the purity of the recovered rare earth elements.

[0105] In the progression of establishing a novel recycling route for NdFeB magnets, the detailed description section of the present disclosure covers Figures 17 through 24, addressing the steps involved in the electrooxidation and reduction of iron in the leached solution and the subsequent impact on rare earth element recovery.

[0106] FIG. 17 depicts a graph showing the effect of adding the precipitant sodium sulfate into sulfuric acid leachate containing fully oxidized iron on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure. In certain embodiments, these experiments were carried out at room temperature with stirring and showcased that iron coprecipitation remained very low even when high stoichiometric amounts of sodium sulfate were added.

[0107] FIG. 18 depicts a graph showing the effect of adding the precipitant sodium sulfate into sulfuric acid leachate containing fully reduced iron on the precipitation recovery of rare earth elements, in accordance with certain embodiments of the present disclosure. Here, as in certain embodiments and as shown in Table 3 below, iron coprecipitation was observed to be higher than in the oxidized state or when the leachate was not electrochemically treated. These results indicate that electrochemical treatment prior to double salt precipitation may not confer a significant advantage for rare earth element separation or iron coprecipitation.TABLE 3

[0108] FIG. 19 depicts XRD patterns of the salts obtained by precipitation using sodium sulfate from sulfuric acid leachate, in accordance with certain embodiments of the present disclosure. As shown by FIG. 19, these patterns match the peaks of sodium neodymium sulfate hydrate and do not vary with iron speciation, confirming the consistency of the double salt formation regardless of the iron's oxidation state.

[0109] FIG. 20 depicts the chronoamperometric response of Fe(II) oxidation reaction under applied cell voltage at room temperature, in accordance with certain embodiments of the present disclosure. As shown by FIG. 20, in some embodiments a significant majority of dissolved ironwas converted to Fe(III) during the oxidation process, enhancing the subsequent recovery of rare earth elements.

[0110] FIG. 21 depicts the chronoamperometric response of Fe(III) oxidation reaction under applied cell voltage at room temperature, in accordance with certain embodiments of the present disclosure. FIG. 21 depicts data evidencing the efficiency of the electrochemical reduction and the constancy of the pH in the solution throughout the process.

[0111] The work detailed in these figures emphasizes that the speciation of iron in the leach liquor does not significantly affect the formation of rare earth element sodium double salt precipitates. This finding is further corroborated by FIG. 22, which highlights the continuous decline in iron concentration within the catholyte over time during the electrowinning experiment..

[0112] Specifically, FIG. 22 depicts a graph showing the concentration of iron in catholyte and faradaic efficiency of the iron reduction process, in accordance with certain embodiments of the present disclosure. The experiment of FIG. 22 was conducted at 70°C for 20 hours and demonstrated a notable removal of iron from the solution, with an overall faradaic efficiency of the iron electrodeposition process.

[0113] FIG. 23 depicts a graph showing galvanostatic response of iron electrodeposition on Ta-Ir supported on Ti cathode in a divided flow cell, in accordance with certain embodiments of the present disclosure. FIG. 23 describes the galvanostatic response of iron electrodeposition in a divided flow cell, emphasizing the importance of maintaining high faradaic efficiency and low energy consumption throughout the process. FIG. 23 shows, as in some embodiments, that the evolution of hydrogen, a significant side reaction, can be suppressed by adjusting the pH, thereby preventing the formation of unwanted by-products such as ferrous hydroxide.

[0114] FIG. 24 depicts a process flowsheet for a circular recycling method, in accordance with certain embodiments of the present disclosure.

[0115] In certain embodiments, as shown in FIG. 24, the present disclosure involves a circular electrochemical method, developed for recycling spent NdFeB permanent magnets. In some embodiments, this method involves the recovery of rare earth elements as sodium double salts and iron in metallic form, alongside the regeneration of a sulfuric acid solution characterized by low iron and dysprosium concentration.

[0116] In the disclosed process, in certain embodiments, magnet particulates with a size of less than 212 micrometers can be leached in IM and 2M sulfuric acid solutions. The ratio of acid to magnet can be selected to ensure that the pH at the end of complete leaching remains below 1.

[0117] Sodium sulfate and sodium hydroxide may be used as precipitating agents to form rare earth element sodium double sulfate salts. The addition of sodium hydroxide as a precipitant may lead to the co-preci pitati on of iron in the double salts at higher stoichiometric quantities. Therefore, sodium sulfate, in some instances, can act as the preferred precipitating agent. Additionally, the use of 2M sulfuric acid as the leaching agent can be used in embodiments aiming to minimize water requirements.

[0118] In certain embodiments, batches of 2M sulfuric acid leachate with a determined amount of dissolved magnet can be subject to electrochemical oxidation and reduction at room temperature. In some embodiments, iron speciation may result in higher iron coprecipitation — ranging from 2- 7% — when the leachate contains fully reduced iron.

[0119] In some embodiments, using 2 to 4 times the stoichiometric quantity of sodium sulfate as a precipitant and a leachate without electrochemical treatment can effectively separate Nd, Pr, and Tb as double salts, with minimal to zero iron coprecipitation. Subsequent to the removal of rareearth elements from a IM acid leachate, the iron-rich solution can be subjected to electrowinning to recover metallic iron.

[0120] During an electrowinning process, significant amounts of the iron, for example over 77% in certain embodiments, can be removed from the leachate, leaving behind an acidic solution with minimal iron content and trace amounts of dysprosium. This solution, along with the anolyte from the electrowinning process, can be recycled back into the magnet dissolution step.

[0121] In some embodiments, use of this method and system can result in a closed-loop circular recycling process for spent NdFeB permanent magnets, as summarized in FIG. 24. The disclosed process eliminates the need for iron oxidation as a distinct step for iron removal from the leachate. Furthermore, the electrowinning stage presents the potential to recover acid, thereby minimizing the production of hazardous waste.

[0122] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it should be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It should be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

[0123] While embodiments of the disclosure have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the disclosure. The embodiments described and the examples provided herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the disclosure disclosed herein are possible and are within the scope of the disclosure. The scope of protection is not limitedby the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.

[0124] Embodiments can include be a system, a method, and / or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

[0125] Those skilled in the art will appreciate that the steps described herein may be carried out in a variety ways and that no particular ordering is required. It will be further understood from the foregoing description that modifications and changes may be made in various embodiments of the present disclosure without departing from its true spirit. The descriptions in this specification are for purposes of illustration only and are not to be construed in a limiting sense.

[0126] Consistent with the above disclosure, the examples of systems and methods enumerated in the following clauses are specifically contemplated and are intended as a non-limiting set of examples.

[0127] Clause 1. A method for recovering rare earth elements, cobalt, nickel, and electrolytic iron from magnets by dissolving magnet particulates in a sulfuric acid solution, filtering the solution to remove impurities, precipitating rare earth elements from the solution using a sulfate salt as a precipitating agent, subjecting the solution to electrowinning to recover metallic iron and cobalt, and recycling the remaining acidic solution.

[0128] Clause 2. The method of any foregoing clause, where the sulfate salt is selected from the group comprising sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, ammonium sulfate, or combinations thereof.

[0129] Clause 3. The method of any foregoing clause, where the magnets are neodymium-iron- boron (NdFeB) permanent magnets.

[0130] Clause 4. The method of any foregoing clause, where the acid solution is selected from the group comprising sulfuric acid, hydrochloric acid, nitric acid, and combinations thereof.

[0131] Clause 5. The method of any foregoing clause, where the acid solution has a concentration between 0.05M and 4M.

[0132] Clause 6. The method of any foregoing clause, where the magnet particulates are less than 212 micrometers in size.

[0133] Clause 7. The method of any foregoing clause, where the ratio of acid to magnet particulates is selected to ensure the pH at the end of leaching is between 0 and 4.

[0134] Clause 8. The method of any foregoing clause, where the electrowinning process is performed in a divided electrochemical flow cell.

[0135] Clause 9. The method of any foregoing clause, where the divided electrochemical flow cell comprises an anion exchange membrane separating anode and cathode compartments.

[0136] Clause 10. The method of any foregoing clause, where the electrowinning process includes adjusting the pH of the iron-rich solution prior to electrowinning to suppress hydrogen evolution.

[0137] Clause 11. The method of any foregoing clause, where the precipitating agent comprises sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, or ammonium sulfate, and the precipitating agent is added in amounts ranging from 2 to 10 times the stoichiometric quantity required to precipitate all rare earth elements.

[0138] Clause 12. The method of any foregoing clause, where the recovered metallic iron has a purity of at least 95.20%.

[0139] Clause 13. The method of any foregoing clause, further including reusing the residual solution following rare earth element precipitation and iron electrowinning in the magnet dissolution step, creating a closed-loop circular recycling process.

[0140] Clause 14. The method of any foregoing clause, further including adjusting the temperature between 20 C and 100 C during the electrowinning process to optimize the recovery of metallic iron.

[0141] Clause 15. The method of any foregoing clause, where the leaching step is performed at room temperature for a duration sufficient to ensure complete dissolution of magnet particulates.

[0142] Clause 16. The method of any foregoing clause, further including using sodium hydroxide, potassium hydroxide or calcium hydroxide as a precipitating agent for comparison in the recovery of rare earth elements.

[0143] Clause 17. The method of any foregoing clause, where the electrowinning process is conducted at a constant current.

[0144] Clause 18. The method of any foregoing clause, where the current density is set between 10 and 500 mA / cm2.

[0145] Clause 19. The method of any foregoing clause, where the electrowinning process is conducted at a constant voltage.

[0146] Clause 20. The method of any foregoing clause, where the constant voltage is set between 1 and 10 Volts per cell.

[0147] Clause 21. The method of any foregoing clause, further including monitoring the pH and temperature changes during the leaching process.

[0148] Clause 22. A system for the recovery of rare earth elements, cobalt, nickel, and electrolytic iron from magnets comprising an electrochemical cell assembly configured to dissolve themagnets in an acid solution, a filtration unit operatively connected to the electrochemical cell assembly for removing impurities from the dissolved magnet solution, a precipitation unit operatively connected to the filtration unit, equipped with means for adding precipitating agents, an electrowinning cell operatively connected to the precipitation unit, configured for the electrodeposition of metallic iron from the iron-rich solution remaining after rare earth elements recovery, and a recycling unit for regenerating sulfuric acid from the process effluent, operatively connected to the electrowinning cell.

[0149] Clause 23. The system of any foregoing clause, where the acid solution is selected from the group comprising sulfuric acid, hydrochloric acid, nitric acid, or combinations thereof.

[0150] Clause 24. The system of any foregoing clause, where the magnets are neodymium-iron- boron (NdFeB) permanent magnets.

[0151] Clause 25. The system of any foregoing clause, configured to operate at variable temperatures and acid concentrations in the electrochemical cell assembly.

[0152] Clause 26. The system of any foregoing clause, where the electrochemical cell assembly includes a plurality of compartments for conducting various stages of the dissolution process.

[0153] Clause 27. The system of any foregoing clause, where the precipitating agents include sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, ammonium sulfate sodium hydroxide, potassium hydroxide, calcium hydroxide, or combinations thereof to recover rare earth elements as sodium double sulfate salts from the filtered solution.

[0154] Clause 28. The system of any foregoing clause, where the electrowinning cell comprises an anode and a cathode compartment separated by an anion exchange membrane.

[0155] Clause 29. The system of any foregoing clause, where the anode is constituted by a conductive material, support, or alloy.

[0156] Clause 30. The system of any foregoing clause, where the conductive material, the support, or the alloy comprises one or more of Ti, Ti, Ta, Ir, Pb, Ru, Pt, Rh, carbon, carbon fibers, graphene, or combinations thereof.

[0157] Clause 31. The system of any foregoing clause, where the conductive material, the support, or the alloy is resistant to corrosion based on the electrolyte, cell voltage, and temperature of the system.

[0158] Clause 32. The system of any foregoing clause, where the catalyst comprises an oxide selected from the group comprising Ti, Ta, Ir, Pb, Ru, Pt, Rh, or combinations thereof.

[0159] Clause 33. The system of any foregoing clause, where the catalyst comprises composites of graphene metal combinations with loadings 0.01 mg / cm2to 5 mg / cm2of metal composition.

[0160] Clause 34. The system of any foregoing clause, where the catalyst is operably configured to act as a direct metal and / or support.

[0161] Clause 35. The system of any foregoing clause, where the cathode is constituted by a conductive material.

[0162] Clause 36. The system of any foregoing clause, where the conductive material comprises one or more of foil, mesh, gauze or wool support, Fe, stainless steel, Hastelloy, graphite, nickel foam, Cu, Co, Cr, Zn, Ti foam, Aluminum, Aluminum foam, or combinations thereof.

[0163] Clause 37. The system of any foregoing clause, where the conductive material is resistant to corrosion based on the electrolyte, cell voltage, and temperature of the system.

[0164] Clause 38. The system of any foregoing clause, where the electrowinning cell includes a power supply providing a constant current for the electrowinning process.

[0165] Clause 39. The system of any foregoing clause, where the electrowinning cell includes temperature control means for maintaining optimal conditions for iron electrodeposition.

[0166] Clause 40. The system of any foregoing clause, further including a control system integrated with the electrochemical cell assembly, fdtration unit, precipitation unit, and electrowinning cell, configured to monitor and adjust operational parameters including pH, temperature, current, and flow rate.

[0167] Clause 41. The system of any foregoing clause, where the recycling unit is designed to minimize hazardous waste production and enable a closed-loop recycling process.

[0168] Clause 42. The system of any foregoing clause, where the filtration unit includes a mechanism for selectively separating different metallic and non-metallic components based on their chemical and physical properties.REFERENCES

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Claims

CLAIMSWHAT IS CLAIMED IS:

1. A method for recovering rare earth elements, cobalt, nickel, and electrolytic iron from magnets, comprising:(a) dissolving magnet particulates in an acid solution;(b) filtrating the solution to remove impurities;(c) precipitating rare earth elements from the solution using a sulfate salt as a precipitating agent;(d) subjecting the solution to electrowinning to recover metallic iron and cobalt; and(e) recycling the remaining acidic solution.

2. The method of Claim 1, wherein the sulfate salt is selected from the group comprising sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, ammonium sulfate, or combinations thereof.

3. The method of Claim 1, wherein the magnets are neodymium-iron-boron (NdFeB) permanent magnets.

4. The method of Claim 1, wherein the acid solution is selected from the group comprising sulfuric acid, hydrochloric acid, nitric acid, and combinations thereof.

5. The method of Claim 1, wherein the acid solution has a concentration between 0.05M and 4M.

6. The method of Claim 1, wherein the magnet particulates are less than 212 micrometers in size.

7. The method of Claim 1, wherein the ratio of acid to magnet particulates is selected between 10g and 200g of magnet powder per liter of acid to ensure the pH at the end of leaching is between 0 and 4.

8. The method of Claim 1, wherein the electrowinning process is performed in a divided electrochemical flow cell.

9. The method of Claim 8, wherein the divided electrochemical flow cell comprises an anion exchange membrane separating anode and cathode compartments.

10. The method of Claim 1, wherein the electrowinning process includes adjusting the pH of the iron-rich solution prior to electrowinning to suppress hydrogen evolution.

11. The method of Claim 1, wherein the precipitating agent comprises sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, or ammonium sulfate, and the precipitating agent is added in amounts ranging from 2 to 10 times the stoichiometric quantity required to precipitate all rare earth elements.

12. The method of Claim 1, wherein the recovered metallic iron has a purity of at least 95.20%.

13. The method of Claim 1, wherein the residual solution following rare earth element precipitation and iron electrowinning is reused in the magnet dissolution step, creating a closed-loop circular recycling process.

14. The method of Claim 1 further comprising the step of adjusting the temperature between 20 C and 100 C during the electrowinning process to optimize the recovery of metallic iron.

15. The method of Claim 1, wherein the leaching step is performed at room temperature for a duration sufficient to ensure complete dissolution of magnet particulates.

16. The method of Claim 1 further comprising the step of using sodium hydroxide, potassium hydroxide or calcium hydroxide as a precipitating agent for comparison in the recovery of rare earth elements.

17. The method of Claim 1, wherein the electrowinning process is conducted at a constant current.

18. The method of Claim 17, wherein the current density is set between 10 and 500 mA / cm2.

19. The method of Claim 1, wherein the electrowinning process is conducted at a constant voltage.

20. The method of Claim 19, wherein the constant voltage is set between 1 and 10 Volts per cell.

21. The method of Claim 1, further including the step of monitoring the pH and temperature changes during the leaching process.

22. A system for the recovery of rare earth elements, cobalt nickel, and electrolytic iron from magnets, the system comprising:(a) an electrochemical cell assembly configured to dissolve the magnets in an acid solution;(b) a filtration unit operatively connected to the electrochemical cell assembly for removing impurities from the dissolved magnet solution;(c) a precipitation unit operatively connected to the filtration unit, equipped with means for adding precipitating agents;(d) an electrowinning cell operatively connected to the precipitation unit, configured for the electrodeposition of metallic iron from the iron-rich solution remaining after rare earth elements recovery; and(e) a recycling unit for regenerating the acid from the process effluent, operatively connected to the electrowinning cell.

23. The system of Claim 22, wherein the acid solution is selected from the group comprising sulfuric acid, hydrochloric acid, nitric acid, or combinations thereof.

24. The system of Claim 22, wherein the magnets are neodymium-iron-boron (NdFeB) permanent magnets.

25. The system of Claim 22, wherein the system is configured to operate at variable temperatures and acid concentrations in the electrochemical cell assembly.

26. The system of Claim 22, wherein the electrochemical cell assembly includes a plurality of compartments for conducting various stages of the dissolution process.

27. The system of Claim 22, wherein the precipitating agents include sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, ammonium sulfate sodium hydroxide, potassium hydroxide, calcium hydroxide, or combinations thereof to recover rare earth elements as sodium double sulfate salts from the fdtered solution.

28. The system of Claim 22, wherein the electrowinning cell comprises an anode and a cathode compartment separated by an anion exchange membrane.

29. The system of Claim 28, wherein the anode is constituted by a conductive material, support, or alloy.

30. The system of Claim 29, wherein the conductive material, the support, or the alloy comprises one or more of Ti, Ti, Ta, Ir, Pb, Ru, Pt, Rh, carbon, carbon fibers, graphene, or combinations thereof.

31. The system of Claim 29, wherein the conductive material, the support, or the alloy is resistant to corrosion based on the electrolyte, cell voltage, and temperature of the system.

32. The system of Claim 28, wherein the catalyst comprises an oxide selected from the group comprising Ti, Ta, Ir, Pb, Ru, Pt, Rh, or combinations thereof.

33. The system of Claim 28, wherein the catalyst comprises composites of graphene metal combinations with loadings 0.01 mg / cm2to 5 mg / cm2of metal composition.

34. The system of Claim 28, wherein the catalyst is operably configured to act as a direct metal and / or support.

35. The system of Claim 28, wherein the cathode is constituted by a conductive material.

36. The system of Claim 35, wherein the conductive material comprises one or more of foil, mesh, gauze or wool support, Fe, stainless steel, Hastelloy, graphite, nickel foam, Cu, Co,Cr, Zn, Ti foam, Aluminum, Aluminum foam, or combinations thereof.

37. The system of Claim 35, wherein the conductive material is resistant to corrosion based on the electrolyte, cell voltage, and temperature of the system.

38. The system of Claim 22, wherein the electrowinning cell includes a power supply providing a constant current for the electrowinning process.

39. The system of Claim 22, wherein the electrowinning cell includes temperature control means for maintaining optimal conditions for iron electrodeposition.

40. The system of Claim 22, further comprising a control system integrated with the electrochemical cell assembly, filtration unit, precipitation unit, and electrowinning cell, configured to monitor and adjust operational parameters including pH, temperature, current, and flow rate.

41. The system of Claim 22, wherein the recycling unit is designed to minimize hazardous waste production and enable a closed-loop recycling process.

42. The system of Claim 22, wherein the filtration unit includes a mechanism for selectively separating different metallic and non-metallic components based on their chemical and physical properties

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