Multidimensional ligand-assisted chromatography method for the purification of rare earth elements and other metal ions from waste magnets

Abstract

This invention provides a method for selecting substantially pure rare earth metals Dy, Nd, and Pr from waste magnet sources. [Solution] A method for selecting rare earth metals Dy, Nd, and Pr is: a) A step of preparing a solution containing multiple Dy, Nd, and Pr ions, b) A step of selectively capturing Dy, Nd, and Pr ions with ligands bound to the adsorbent in at least one chromatographic column containing an adsorbent to define a plurality of distinct bands, each of which distinct band contains a plurality of captured Dy, Nd, or Pr ions, c) Elute the captured Dy, Nd, and Pr ions separately from each distinct band of at least one chromatographic column to obtain multiple purified solutions, wherein each purified solution has a high concentration of either Dy, Nd, or Pr ions. Includes.

Description

[Technical Field]

[0001] Government funding This invention was developed with government support under SP8000-18-P-0007, granted by the Defense Supply Administration. The government has certain rights to this invention. Cross-reference of related applications This patent application claims priority to concurrently pending U.S. Provisional Patent Application No. 62 / 982,807, filed on 28 February 2020. This novel technology relates to a method for recovering rare earth elements Nd, Pr, and / or Dy from waste materials, generally applicable to the chemical industry. [Background technology]

[0002] Rare earth elements (REEs) are valuable to high-tech and clean energy industries. The three REEs, Pr, Nd, and Dy, are useful components of magnets and are widely used, particularly in the electronics, automotive, and wind energy industries. Because REE production is highly concentrated in a few countries, the supply chains for REEs, especially Pr, Nd, and Dy, are generally at risk. Once produced and used, waste magnets are almost without exception disposed of in landfills. Such disposal of REE (Recyclable Energy) into landfills represents a recoverable local resource of REE, but there is no efficient recovery mechanism. Therefore, there remains a need to develop alternative supply flows for REE in general, particularly for Pr, Nd, and Dy. This novel technology addresses this need. [Overview of the Initiative]

[0003] The three rare earth elements (REE), neodymium (Nd), praseodymium (Pr), and dysprosium (Dy), are essential components of permanent magnets widely used in electronics, motors, hybrid vehicles, generators, televisions, sensors, and wind turbines. Conventional production methods for high-purity REE utilize two-phase liquid-liquid extraction, which require thousands of mixer-settler units arranged in series or parallel, generating large amounts of toxic waste. This novel technology relates to a novel ligand-based chromatography (LBC) zone separation method developed to produce high-purity (>99%) Nd, Pr, and Dy from crude REE mixtures derived from waste magnets with high yield (>99%) and high sorbent productivity. By adding a ligand selective for REE to the mobile phase, ligand-assisted substitution (LAD) can be enabled, and the REE can be recovered in the ligand-assisted elution (LAE) step, or the ligand can be immobilized on the stationary phase to enable ligand-binding substitution (LBD) in continuous elution mode (LB-SMB). Ligands having affinity for one or more REEs include citric acid, aminopolycarboxylic acids (e.g., ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), etc.), bicine, and other REE selective extractants such as HDEHP, DGA, etc., as well as combinations thereof.

[0004] The new method introduces a two-zone ligand-assisted substitution chromatography (LAD) system that uses improved correlation to predict the minimum column length required to achieve a consistent pattern state in LAD. By using a zone division method based on selectivity-weighted composition factors, the two-zone design can achieve productivity two orders of magnitude higher than single-column designs. The design and simulation methods are based on first-principles and inherent (or scale-independent) engineering parameters. These can be used to design processes for a wide range of feed material compositions or production scales. The total productivity of two-zone LAD can exceed a REE of 100 kg / m3 / day, which is 100 times higher than conventional extraction methods.

[0005] In the case of LAD, sorbents include micropores, sulfonic acids, and aminosulfonic acid functional groups. For LBD, the sorbent IDA resin has high selectivity for Cu, Ni, and Co, but low selectivity for REE; EDTA, DTPA and / or phosphate ligand-bound porous silica, DGA bound to PMMA, and EDTA bound to PS or polymer resins having amine functional groups. LAD and / or LBD for the purification of three-component mixtures require only three chromatography columns, a safe extractant, EDTA, and other environmentally friendly chemicals. Most of the chemicals are recyclable, and it generates very little waste. This method has the potential to efficiently and environmentally purify REE from waste magnets. This method could also help transform the current linear REE economy (from ore to pure REE, products, and landfill waste) into a circular and sustainable REE economy.

[0006] [Table 1] [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows the breakdown of REE (by mass) in various applications. [Figure 2] This graph shows Sherwood's forecast regarding the process costs for refining REE from magnets. [Figure 3] This diagram shows how this new technology will impact the REE magnet supply chain. [Figure 4] This graph shows the prices of REEs Nd, Pr, and Dy as functions of mass fraction. [Figure 5] This graph compares the REE recovery yield between known methods and novel technologies. [Figure 6A] This graph shows the LAD (Low-Acid Dioxide) loaded with free ions, where REE (Reactive Effect Enzyme) with the highest affinity is the first to elute. [Figure 6B] This graph shows the LAD (Liquid Allocation Diagram) loaded with ligand-chelated REE ions, where REE with high ligand affinity is the first to elute. [Figure 6C] This graph shows the LBD loaded with free REE ions, where the REE with the lowest ligand affinity is the first to elute. [Figure 7] This graph shows a general map of a certain pattern for the recovery of REE LCDs. [Figure 8] This graph shows productivity versus yield for REE recovery for a constant pattern LAD design to produce a 99% pure product from a selected three-component composite REE mixture using a single column with a fixed breakthrough cut (θ=0.05). [Figure 9] This is a schematic diagram illustrating the overall structure of a new multi-zone constant pattern design method. [Figure 10] This diagram shows a schematic design of a two-zone LAD for separating REE crude material simulating waste magnets. Zone I is intended to recover high-purity Nd. In Zone II, column II-A is intended to recover high-purity Dy and Nd. Column II-B is intended to recover high-purity Nd and Pr. [Figure 11]This graph shows a function of ligand elution time and concentration. [Figures 12A-12F] This figure shows the separation of an equimolar mixture (0.3N) of Nd and Pr using 0.09M EDTA-Na (pH9). The experiment was designed for various X values: (a) 8.40; (b) 10.52; (c) 14.04; (d) 20.98; (e) 32.15. The mass transfer zone lengths in the experiment and simulation are compared in (f). [Figure 13A-13C] This graph shows the elution profile of the LAD test. (a) Zone I: Obtains the majority of Nd. Two mixed bands, Dy-Nd and Nd-Pr (monochromatic), are sent to Zone II for further separation. (b) Zone II Column A: Separates Dy and Nd from the mixed band generated in Zone I. (c) Zone II Column B: Separates Nd and Pr from the mixed band generated in Zone I. In both Zone II Column A and Zone II Column B, the mixed bands are recycled back into their original feed material solution (the mixed bands from Zone I). [Figure 14] This is a schematic diagram illustrating the separation mechanism of LAD for rare earth elements. [Figure 15] This graph shows that the mass transfer zone length of a given system initially decreases with increasing column length, and then stops decreasing after the column length reaches a minimum and forms a constant pattern. [Figure 16] This graph shows a general map with a certain pattern. [Figure 17] This is a flowchart for optimizing productivity in a fixed pattern design. [Figure 18] This graph shows the calculated yield (dashed line curve) and productivity (solid line curve) of Nd against linear velocity u0 for a fixed column length used to separate a three-component REE mixture. [Figure 19] This graph shows the breakthrough cut θ for collecting products from column effluent in LAD, with elution time expressed as a function of concentration. [Figure 20] This figure shows impurities from adjacent components. [Figure 21A-21E] This figure shows the parameters from Example A. [Figures 22A-22D] This figure shows the parameters from Example B. [Figures 23A-23B] The parameters from Example C are shown in the figure. [Figures 24A-24C] This figure shows the parameters from Example D. [Figure 25] This flowchart shows a first splitting strategy for recovering all components of the mixture. [Figure 26] This flowchart shows a second splitting strategy for recovering all components of the mixture. [Figure 27] This flowchart shows a partitioning strategy for recovering adjacent components from one group of a mixture. [Figure 28] This is a flowchart showing a partitioning strategy for recovering adjacent components from multiple groups of a mixture. [Modes for carrying out the invention]

[0008] For the purpose of facilitating an understanding of the principles of the novel technology and presenting the best known form of its implementation, embodiments illustrated in the drawings will be referred to and described using specific terminology. However, it is not intended to limit the scope of the novel technology, and it will be understood that such changes and further modifications in the illustrated apparatus, as well as such further applications of the principles of the novel technology illustrated herein, will be commonly recognized by those skilled in the art to which the novel technology relates. Rare earth elements (REEs) include the 15 elements of the lanthanum series, as well as scandium (Sc) and yttrium (Y). They are in demand for use in magnets, metal alloys, abrasives, catalysts, ceramics, and phosphorescent materials, which are crucial in high-tech and clean energy applications. While the market capitalization of REEs is only $1.5 billion, the market value of products requiring REEs exceeds $5 trillion.

[0009] Approximately 30% by mass of rare earth elements is used in the production of NdFeB permanent magnets, which are widely used in hard drive disks, wind turbines, and electric vehicle motors. The three most common REEs (Rare Earth Elements) found in NdFeB magnets are Nd, Dy, and Pr. The first two are classified as critical materials by the U.S. Department of Energy, which aims to produce 20% of its electricity from wind energy by 2030. Each direct-drive permanent generator for 1 MW of power requires 160–650 kg of permanent magnets made from Nd, Pr, and Dy. Such generators are increasingly used in offshore and large-scale onshore facilities due to their high energy efficiency. Rare earth permanent magnets are also used in motors for hybrid and electric vehicles. Each hybrid or electric vehicle is estimated to require 1.5–2.5 kg of REE-based permanent magnets. The market for rare earth elements (REEs), which are crucial for magnets, is highly volatile because their production is concentrated in only a few regions worldwide. Currently, China controls over 80% of the global REE supply and over 95% of the supply of rare earth alloys and magnets. This dominance could lead to over 90% of high-tech products being produced in China by 2040. REE production in other regions is limited by a lack of technical expertise in production, high capital costs, and the significant environmental impact of conventional methods.

[0010] REE production begins with the beneficiation and concentration of REE ore, such as bastnäsite, a rare earth fluorocarbonate containing approximately 7-8% rare earth oxides (REO). After crushing and grinding, chemical steam conditioning, flotation, and washing, bastnäsite can be upgraded to concentrated REE crude containing approximately 60% REO. The REE crude is further digested, refined, and smelted to pure metal. Because the REE present in the crude product has similar physical and chemical properties, the REE purification process is the most difficult step. Current industrial purification procedures still use liquid-liquid extraction methods developed in the 1950s. Such methods require thousands of mixer-settler units to produce high-purity REE. Liquid-liquid extraction methods are difficult to adapt to different feedstocks or production scales. These methods are energy-intensive and chemical-intensive, requiring toxic extractants, organic solvents, and concentrated acid for extraction, generating large amounts of acidic and toxic waste. Approximately 30 tons of wastewater are released into the environment to produce 1 ton of rare earth oxides. The extraction process also consumes large amounts of ammonia to saponify the organophosphorus extractant and large amounts of hydrochloric acid to extract the extractant. On average, only 35% of the ammonia used in this process is recovered as ammonium chloride. Life cycle analysis studies have revealed that in the production of REE from bastnäsite, the purification steps in conventional processes account for approximately one-third of the total environmental impacts, including global warming, toxicity of carcinogens and non-carcinogens to humans, eutrophication, and ecotoxicity. Furthermore, these contribute to 70% of the ozone depletion impacts in the production process.

[0011] Recycling waste magnets is a viable method for producing valuable REE material. Approximately 300,000 tons of REE are present in permanent magnets produced to date, and approximately 3,300 to 6,600 tons of REE can be recovered from waste magnets annually. As solid-state disks (SSDs) begin to dominate the market, many HDDs containing REE are expected to be available for recycling. Refined REE derived from waste magnets can be reused in other energy and defense applications.

[0012] Recycling of REE from waste materials, such as waste magnets, can reduce environmental risks associated with mining. Producing heavy rare earth oxides from clay containing adsorbed REE ions can lead to groundwater contamination and severe removal of vegetation and topsoil. Large-scale discharges of mine waste and wastewater into the environment can result in permanent damage to ecosystems, loss of biodiversity, and human health problems. The recovery of REE from waste magnets is potentially profitable, according to Sherwood analysis, which predicts the magnitude of price or production cost as a function of the concentration of the target product in the supply material. Generally, higher concentrations result in lower production costs and, therefore, lower market prices. A Sherwood correlation line was obtained by fitting the prices of 10 metals and their mass fractions in the ore. Estimates of supply material costs, as well as the refining costs of Nd, Pr, and Dy from waste magnets, are summarized in Table 1. Sherwood analysis shows that waste magnets are a promising supply material for producing Dy, Nd, and Pr, with a potential profit of approximately $5 per kg of waste magnets.

[0013] [Table 2]

[0014] Various methods have been developed to recover crude REE mixtures from waste magnets. The most commonly used method involves oxidizing the metal to obtain metal oxides followed by selective acid leaching. The waste magnets are crushed into fine particles and oxidized at high temperatures. The metal oxides are then dissolved in acid. Other metal oxides (Fe, Ni, Co, B) are also removed by selective leaching or precipitation, membrane-assisted solvent extraction, or ionic liquid extraction. REE in waste magnets can also be converted to soluble chloride salts by various methods, including roasting with ammonium chloride under an inert atmosphere, chlorination using chlorine gas, or selective extraction using molten magnesium chloride and potassium chloride salts. Other methods for converting REE in waste magnets to hydroxides, including hydrothermal treatment and hydrolysis after vacuum induction melting, have also been tested. In most prior art recovery methods, more than 90% of the REE in waste magnets can be extracted as a mixture of REE chlorides or hydroxides, with little contamination of other elements in the waste magnets.

[0015] The separation of crude REE mixtures derived from waste magnets into pure individual REEs is useful for the production of metal alloys or other applications. Solvent extraction using organophosphorus extractants in ionic liquids has been previously tested. However, only two types of REE (Rd and Dy) were recovered in high purity, and liquid-liquid extraction is inefficient for REE purification because the interfacial area per unit processing volume for mass transfer is 2-3 orders of magnitude smaller than that of adsorption or chromatography. Functionalized silica adsorbents were tested to separate Dy from other REEs derived from waste magnets, but these adsorbents were costly, had limited stability, and resulted in low Dy purity (approximately 70%). Conventional low-cost adsorbents or ion exchangers have insufficient selectivity for REE purification; therefore, the use of chelating agents (or ligands) in the mobile phase can substantially increase selectivity. The feasibility of ligand-assisted substitution chromatography for REE purification was first reported in the 1950s. However, because process simulations or systematic design methods were not available, the LAD separation methods in the literature were designed empirically. Some experiments for the separation of three types of REE took several months. Therefore, it is impractical to use empirical methods to develop efficient LADs for large-scale REE separation.

[0016] It is known that constant pattern substitution trains can form in non-ideal LAD systems (i.e., systems with diffusion or dispersion effects) when the column length is sufficiently long. General correlations enable the design of LAD systems with minimum column lengths to reach a constant pattern state where high-purity bands with sharp boundaries are formed as a result of the substitution effect. Operation in a constant pattern state can help achieve high-purity products with high yield and high sorbent productivity. A constant pattern design method was developed for non-ideal systems based on general correlations and equations relating to the yield of the target component. The yield is a function of several key dimensionless groups that control the constant pattern mass transfer zone length. The design method was tested and validated using simulations and experiments for different target yields, ligand concentrations, and feed material compositions. The productivity achieved using this design method on a single column was more than 800 times higher than prior art results for three-component separation at the same purity and similar yield.

[0017] General correlations were derived from rate model simulations based on a constant separation factor (CSF) isotherm model applicable to ligand-containing REE feed material mixtures. When the REE feed material mixture does not contain ligands, the feed material REE does not separate in the loading zone, as most adsorbents have negligible selectivity for different REEs. REE separation occurs only after ligands are introduced following loading. In such cases, the loading zone is shorter, and the loading time can be reduced using faster loading rates. Here, an improved isotherm model and simulation are presented to more closely simulate the separation process for ligand-free crude REE. Modified general correlations are constructed for the conditions required to reach a constant pattern state.

[0018] Prior art has focused on the separation of equimolar three-component REE mixtures. However, the REE concentration in feedstock derived from waste magnets differs by an order of magnitude (Table 1). To obtain high-purity Dy (minor component) in high yield in a single column, an extremely narrow mass transfer zone between two adjacent elution bands is required, along with a low linear velocity relative to fixed selectivity and mass transfer coefficient. Due to the low linear velocity, the total elution time is long, resulting in low productivity. To address these shortcomings, this novel technology introduces a design containing more than one column or more zones. We develop an efficient separation strategy for separating composite feedstock mixtures to obtain high-purity REE in high yield and high productivity.

[0019] The new technologies shown in Figures 1-28 have the potential to transform current REE separation and purification processes into environmentally friendly and clean processes, provide a driving force for producing high-purity REE from waste magnets, and contribute to achieving a circular REE economy.

[0020] constant-pattern constant-speed train and general constant-pattern correlation Ligand-assisted substitution chromatography uses a ligand (chelating agent) in the mobile phase to separate a mixture of different REEs into distinct REE-specific components. The separation mechanism is detailed below. A distinct characteristic of substitution chromatography is the formation of isokinetic (constant velocity) trains in a long column. In an ideal system, all components form rectangular solute bands and move at the same velocity. In a non-ideal system, the boundaries (or concentration waves) between adjacent solute bands broaden due to diffusion or dispersion effects. As the bands move at different velocities, the overlapping region decreases as the bands begin to separate. Ultimately, the broadening of the waves due to diffusion or dispersion effects is offset by the sharpening of the waves due to the substitution effect, and the concentration waves reach a "constant pattern," with each mass migration zone length being fixed, L MTZ,CP It reaches. This novel technology presents a new general correlation (Equation (1)) constructed using a modulated Langmuir isotherm, which can more closely simulate the LAD process for ligand-free REE crude. The detailed derivation of the mass transfer zone length and the construction of the new general correlation, Equation (1), are described in Supplementary Document B.

[0021]

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[0022] Constant-Pattern Constant-Velocity Trains and General Constant-Pattern Correlation in LBDs In an LBD system where the ligand is immobilized on the stationary phase, the REE mixture can also be separated into distinct substitution bands, forming a constant-pattern isokinetic train. The ligand on the stationary phase provides selectivity for separation. The column is pre-saturated with a component (Na+) with lower affinity than all components in the feed material, and the displacer (H+) has higher affinity for the ligand than all components in the feed material. The feed material component with the lowest affinity for the immobilized ligand elutes first. In LBD, the regeneration of the sorbent and the regeneration of the ligand are combined into a single step, whereas LAD requires a separate step to regenerate the ligand in the mobile phase. Therefore, LBD is expected to have lower processing costs than LAD.

[0023] Similar to the LAD, a general correlation, equation (2), is constructed to predict the formation of a constant-velocity train pattern in the LBD.

[0024]

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[0025] When the objective is to recover only one type of REE with a target yield using a single column, the design results for a REE mixture with a mole fraction of Nd at 0.83, Pr at 0.12, and Dy at 0.05 are shown. The curve was created based on a constant pattern design with a fixed breakthrough cut θ of 0.05. In practice, the breakthrough curve can be monitored using an online detector. Designs with a fixed breakthrough cut are easy to implement for product recovery. However, to satisfy the mass balance requirements of the components in a constant pattern state, only two of the three variables (purity, yield, and breakthrough cut θ) can be specified in a single-column design. The yield, productivity, and product purity when recovering a single REE (Dy, Pr, or Nd) from a REE mixture are shown for a fixed θ of 0.05. If the target yield is greater than 63.5%, the purity of the target component is greater than 99%. Since the purity of the target product is not fixed and fluctuates slightly from 99% to over 99.9%, the curve is an "approximate" trade-off curve.

[0026] When designing a single column to recover small amounts of component Dy with high purity (99.9%) and high yield (95%), the rate must be very slow to sharpen the concentration wave and minimize the mass transfer zone length (the overlapping region of two adjacent bands), resulting in an sorbent productivity of 0.04 kg / m³ of Dy. 3 The yield is extremely low at 64.2 kg / m³. In contrast, when producing a large amount of Nd from the same raw material with the same purity and yield, the productivity is 64.2 kg / m³.3 / day, which is 1,600 times higher than the productivity of Dy. When the target yield of Nd is reduced from 95% to about 77%, even though the purity of Nd is 99.5%, the productivity of Nd can be further increased to Nd 120 kg / m 3 / day. These results indicate that for the production of high-purity products (>99%) from composite feedstocks, the sorbent productivity strongly depends on the target component. Generally, when using a single column for the recovery of a single component from a composite mixture, the purity of the product is controlled by the breakthrough cut θ and the yield of the target component. The productivity of the sorbent is controlled by the selectivity-weighted composition coefficient γ i as defined by Equation (2).

[0027]

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[0028]

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[0029] For composite mixtures, if the selectivity between each pair of adjacent components is the same, the length of the constant pattern mass transfer zone will be the same for all solute bands. i As x increases, the substitution band widens. The component with the highest mole fraction has the highest yield because it has the smallest overlap region with respect to the total substitution band width and the smallest yield loss due to the mixed band relative to the total amount. i Value or maximum γ i The component with the highest value exhibits the highest yield and highest productivity. Therefore, selectivity-weighted composition coefficient γ i The effects of composition and selectivity are explained by the maximum γ i The component with a value can be separated from the mixture with maximum productivity using a single column. γ of a three-component mixture i The values ​​are listed in Table 2. In this mixture, Dy is the minimum γ i It has a value, and therefore it is separated from the mixture with minimum productivity, whereas with maximum γ i Nd with a value is separated from the mixture with maximum productivity.

[0030] [Table 3]

[0031] When recovering all three components from a mixture in high yield and high purity using a single column, the rate or flow rate is minimum γ i The yield requirement for Dy, a component with a value, is limited. If the design aims to recover Dy with a 95% yield, the productivity of Nd and Pr will also be low due to the slow rate. As a result, the total REE productivity is only 0.7 kg / m³ 3 / day However, if the separation of the three types of REE is performed in two separate zones, high-purity REE can be recovered in high yield and high productivity. Develop a systematic separation strategy. Maximum γ i Nd, a component with a value, is initially recovered in Zone I with high purity and productivity. The two mixed bands from Zone I, Dy / Nd and Nd / Pr, are then sent to Zone II for further separation. The mixed band material in Zone II is then recycled back to the Zone II inlet to achieve high yields (99%) for all three components. In this method, the productivity and yield of each component are no longer limited by the single-column trade-off curve. The total productivity of the two-zone design, with high purity (>99.5%) and high yield (>99%) for all three REEs, is 100 times higher than that of a single-column design with similar product purity and a 95% Dy yield. The two-zone design is described in more detail below.

[0032] Constant pattern design of a 2-zone LAD for the separation of a three-component REE mixture of Dy, Nd, and Pr. Here, we present a previously reported method for designing a constant pattern for a single column. 38 This represents a new general correlation, the γ of equation (1) and equation (2). i The method was modified by incorporating a new value-based zoning strategy. The multi-zone constant pattern design method is based on advanced wave theory, general zoning strategies, and inherent (or scale-independent) parameters. This method is suitable for many production scales and can handle complex feed material mixtures containing multiple components and significantly different concentrations. With respect to the desired purity and yield of the product, given that the inherent parameters, feed material composition, and volume are known, this method can generate the zone configuration, column size, and optimal operating rate for each zone to achieve maximum sorbent productivity.

[0033] Regarding the separation of the three-component mixture of Dy (5%), Nd (83%), and Pr (12%), a schematic diagram of this design is shown in the drawing. Zone I has the highest γ in the original feed material. iDesigned to recover most of the Nd containing Cu. Zone I, step 1, the column is Cu 2+ Pre-equilibrium with solution. In step 2, the supply material mixture is Cu 2+ The material is supplied to the loaded column. In steps 3-7, the ligand solution (EDTA-Na) is loaded onto the column to separate the feed material mixture into three fractions: a Dy / Nd mixed band, a pure Nd band (target product in zone I), and an Nd / Pr mixed band. After all of the REE has been eluted from the column, the column is Na + It is a type, and then, it again Cu 2+ Pre-saturate with the solution. Send the Dy / Nd mixed band from step 5 and the Nd / Pr mixed band from step 7 to columns II-A and II-B in Zone II, respectively. Collect the mixed band from the Zone II columns and recirculate it directly back to columns II-A and II-B to further increase the yield. For simplification, the recirculation flow and column washing steps within Zone II are not illustrated.

[0034] Velocity model simulations were constructed for zones I and II. Batch LAD experiments were performed first to test the velocity model based on the modulated multi-component Langmuir isotherm and intrinsic parameters. Using the validated isotherm and parameters, a two-zone LAD system was designed to separate a three-component mixture having a REE composition similar to that of the waste magnet. Before LAD purification, it is convenient to first convert the metals in waste magnets into soluble salts. Common conversion methods include (1) wet metallurgy, (2) high-temperature metallurgy, (3) hydrothermal method, and (4) electrochemical method.

[0035] In the wet metallurgy process, waste magnets are dissolved in concentrated (up to 8M) nitric acid or hydrochloric acid. REE and other metals in the waste magnets can be completely dissolved and converted into soluble salts. Impurities, such as Fe, can be removed by adjusting the pH of the solution. Any excess acid remaining in the dissolution solution must be neutralized before loading it onto a chromatography column for purification. Waste magnets can also be processed using high-temperature metallurgy. The magnets are demagnetized, crushed, and pulverized at 300-400°C to produce small particles. Alternatively, waste magnets can be converted into small particles (100 μM) by hydrogen decrepitation. The magnet particles are then roasted at high temperatures (>800°C) to form metal oxides. Dilute acid (<2M) is used to selectively dissolve REE, Co, and other metal oxides to produce a solution of metal ions for further purification.

[0036] The following describes a hydrothermal method for converting waste magnets into soluble salts. A waste magnet (10g) may be placed in a hydrothermal reactor (50mL) containing water (30g) and a small amount of salt (NaCl 0.01g or 0.03% by mass) at 250°C and 550psi for a period of time, for example, about 18 hours. The Nd-rich phase reacts with water to form Nd(OH)3. Hydrogen is absorbed by the Nd2FeB phase, causing volume expansion and phase breakdown into fine powder. The metal alloy is oxidized to Fe3O4 and REE(OH)3. The metal coating is broken down and separated from the powder by sieving. The majority of the Fe3O4 powder can be separated using magnetic separation. The REE hydroxide typically contains less than 5% impurities and can be dissolved in dilute acid (<0.5M) for further purification. Electrochemical methods can also be used to dissolve waste magnets. The magnets can be used as sacrificial anodes to oxidize REE and other metals to form metal hydroxides. Dilute acid (0.2 M) is used to selectively dissolve the REE into an aqueous solution, while Fe(OH)3 remains in the solid residue. The solution containing REE and other metal ions is typically used as feedstock for LAD separation after filtration.

[0037] (Example 1) Two packed columns were connected to achieve a total column length of 127 cm. A three-component mixture mimicking the crude REE material derived from waste magnets was prepared and separated using LAD. Detailed experimental conditions and simulation parameters are summarized in Table 9. In Zone I, the feed material concentrations were 0.05 N Dy, 0.83 N Nd, and 0.12 N Pr. Column effluent was monitored with an Agilent PDA detector. The effluent was also collected as multiple fractions using an Agilent 440-LC fraction collector. Dy concentration was analyzed by ICP-OES. In Zone I, two mixed bands were generated, one containing Cu / Dy / Nd and the other containing Nd / Pr. More than 10 runs of Zone I were required to generate enough mixed band material to test the separation in Zone II. The elution history of the mixed band separation in Zone II was investigated using a synthetic mixture. The REE concentration in the mixed band was calculated from the elution profile from Zone I. Note that the collected REE mixed bands from the LAD test were a mixture of EDTA-REE composites, not aqueous solutions of free REE ions.

[0038] To prepare a mixed band of Cu / Dy / Nd, 3.143 g of Dy(NO3)3·5H2O and 3.872 g of Nd(NO3)3·6H2O were first dissolved in DI water. The mixture was loaded onto a copper-loaded column. REE was withdrawn from the column using 0.09 M EDTA at pH=9. The mixed band was collected before a decrease in Cu concentration was observed. The loaded REE was collected within the mixed band. When this mixed band was diluted to 500 ml, the final concentrations of Dy and Nd were 0.043 N and 0.053 N, respectively. The experimental conditions and simulation parameters for the separation of Dy and Nd are summarized in Supplementary Material E, Table 10. The effluent was monitored using a PDA detector and collected as multiple fractions to measure the Dy concentration using ICP analysis. To prepare a mixed band of Nd / Pr, 2.513 g of Nd(NO3)3·6H2O and 2.146 g of Pr(NO3)3·6H2O were dissolved in a 0.09 M EDTA solution (pH=9). To prevent EDTA precipitation at low pH, approximately 1.04 g of NaOH was added to the solution. The final solution volume was 200 ml, and the concentrations of Nd and Pr were 0.086 N and 0.074 N, respectively. The conditions for separating Nd and Pr are summarized in Table 11.

[0039] Verification of velocity model simulation The results of the velocity model simulation were compared with literature data using erbium (Er) as a presaturant and EDTA as a ligand. The simulation parameters are summarized in Table 12. The sorbent was AG 50X12, a cation exchange resin with sulfonic acid functional groups. The simulation results were in good agreement with the experimental data, indicating the accuracy of the velocity model simulation and model parameters. Er was used as a presaturant instead of Cu. The selectivity between REE and Er in the feed material was 1.1 during loading and increased to 1.95 after the ligand was introduced into the column.

[0040] Velocity model simulations and general maps were compared with the separation data. A two-component mixture (0.3N Nd, 0.3N Pr) was prepared and fed into a 38 cm column. The Nd / Pr selectivity was 1.8, as previously measured. The mass transfer coefficient was estimated in our previous study. Different loading rates (L) were obtained by changing the loading capacity. f The ) and the dimensionless column length (Φ) were obtained. The X value corresponding to the Φ value was calculated from the general correlation. Dimensionless mass transfer coefficient

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[0041] Design and testing of Zone I Using improved general correlations, a three-component separation system was designed using a synthetic mixture with a composition similar to that of REE crude derived from waste magnets (0.05N Dy, 0.83N Nd, 0.12N Pr). The actual effective selectivity between Dy and Nd should be extremely high due to the large difference in ligand affinity. The Dy / Nd selectivity in this design was set to 5. This is sufficient to generate sharp waves in this design and simulation.

[0042] The Zone I design aimed to maximize Nd productivity in a single column. The yield for the highest Nd productivity was predicted to be 77.5%. Detailed experimental conditions are listed in Table 9. The ligand solution pH was maintained at 9. Experimental elution profiles were compared with simulations. Table 3 summarizes the design target yield of Nd in Zone I, as well as the experimental yield and productivity of Nd for each test. The target yield was in agreement with the experimental yield within 1%. Nd productivity exceeded 100 kg / m3 / day in Zone I.

[0043] [Table 4]

[0044] Design and testing of Zone II To increase the yield of Nd and collect high-purity Dy and Pr, the mixed bands of Dy / Nd and Nd / Pr in Zone I (monochromatic region of the elution profile) were collected and further separated in Zone II. A dummy material of similar concentration was run to demonstrate Zone II separation. In Zone I, an aqueous solution containing REE ions was directly supplied to the column. The mixed band collected from Zone I was then supplied to Zone II. In Zone I, the REE ions were adsorbed together without separation, forming a uniform mixed band near the column inlet. This was because the selectivity was negligible. After introducing the EDTA ligand solution into the column, the REE ions began to separate. In theoretical models and simulations, the change in selectivity was revealed by a modulated Langmuir isotherm, as described below.

[0045] REE ions in the feed material in Zone II were bound to EDTA, and apparent substitution occurred during the loading of the feed material. Because EDTA has different selectivity for different REEs, the REEs begin to separate during loading. Since EDTA binds to the REEs as they move, the REE-loaded region was wider in Zone II than in Zone I. To leave sufficient column length for further separation after loading, it was important to limit the REEs to the shorter portion of the column length during loading. For this reason, a safety factor of 100% additional column length was incorporated into the Zone II design. Although separation in Zone II was demonstrated using such a large safety factor, in reality, the actual safety factor may have been smaller. The same design algorithm was used for both columns used in Zone II. The column length in the design program was 89 cm, which is 50% of the actual column length in the experiment.

[0046] The elution profile is shown in the diagram, and the experimental yield and productivity are summarized in Table 3. Detailed experimental conditions and simulation parameters are shown in the experimental section below. In column A of Zone II, the Nd yield target in the design was 73.4% to maximize productivity, and the experimental Nd yield was 89%. In practice, Nd can be easily separated from Na by precipitating it as oxalate or carbonate, so in the experiment, the mixed band between the Nd band and the Na band was defined as "pure" Nd. In column B of Zone II, the Nd yield target was 74.6%, and the experimental yield was 74%. By recirculating the mixed band from the two columns of Zone II back into the Zone II feed material, the yield of all components can be further increased to over 99%.

[0047] Theoretical prediction of REE yield in 2-zone LAD Established theoretical and velocity model simulations for both Zones I and II agree well with the presented results. Experimental yields closely match or exceed the design target yields, and all components have a purity of over 99%. A key condition for achieving a 99% yield for each component is the recirculation and refeeding of the mixed band in Zone II. Since experimental demonstration of mixed band recirculation in Zone II is redundant, a VERSE simulation of the LAD process was performed instead. The column length was 100 cm in the design, and 120 cm in the simulation with a safety factor of 20%. The Dy / Nd mixed band from a single run in Zone I was used as feed material for column A in Zone II, and the Nd / Pr mixed band from Zone I was used as feed material for column B in Zone II.

[0048] In Zone II, column A collected two mixed bands, Cu / Dy and Dy / Nd, and mixed them with the original feed material for column A. The new mixture was used as the feed material for Zone II column A in run 2. The load capacity and flow rate remained the same. In run 3, the feed material for Zone II column A contained the Cu / Dy and Dy / Nd bands collected from run 2, mixed with the original feed material. In run 3, the column output, yield, and component purity remained the same as in run 2. The results showed that the system reached a circulating steady state after run 3 (Table 4). A similar process was performed on Zone II column B for the separation of the Nd / Pr mixed band. The system also reached a circulating steady state after run 3. By continuously recirculating the mixed bands in the two-zone LAD, almost no REE was lost in the mixture. The total yield for all components was over 99%.

[0049] [Table 5]

[0050] Table 5 summarizes the total yield and productivity for the three components and compares them to those of a single-column design with a fixed breakthrough cut. To achieve a total REE yield of 99% and a purity of over 99.5% for each component using a similar column length (approximately 1.2 m), the productivity of the single-column process was more than two orders of magnitude lower than that of the two-zone LAD process. The average sorbent productivity of the two-zone design was 0.7 kg REE / m², compared to the average sorbent productivity of the single-column design. 3 This is approximately 159 times the rate per day.

[0051] [Table 6]

[0052] Comparison of LAD and conventional liquid-liquid extraction The most widely used REE separation technique in this industry is multi-stage liquid-liquid extraction. In this method, organophosphorus extractants dissolved in kerosene are used to extract REE from the aqueous phase. A concentrated HCl solution (up to 6 M) is required to remove REE from the extractant, and concentrated ammonia water is used as a saponifier. Most of the acids and bases used cannot be recovered, resulting in large amounts of acidic wastewater containing high concentrations of ammonia salts. Furthermore, kerosene is highly flammable, and organophosphorus extractants are toxic.

[0053] In contrast, LAD uses only environmentally friendly chemicals, resulting in significantly improved process safety and much less environmental impact. The LAD process generates sodium salt byproducts, which can be electrochemically converted to bases and acids. The EDTA-Cu complex eluted from the column can be easily recovered as EDTA and copper salts. The recovery yield of EDTA and Cu is extremely high (>95%). High-purity REE can be precipitated from the EDTA-REE complex using oxalates, and the ligand can be recovered in high yield and reused. Therefore, very little waste is generated. Table 6 summarizes the advantages of LAD over extraction processes.

[0054] [Table 7]

[0055] Rare earth elements are essential for high-tech products. Conventional mining and separation processes for producing high-purity REE can have significant environmental impacts. Recycling REE from waste flows such as waste magnets is technically feasible, potentially profitable, and reduces the need for mining processes. Two-zone ligand-assisted substitution chromatography, an environmentally friendly separation method, has been developed to produce high-purity REE in high yield and productivity.

[0056] To accurately simulate ligand-assisted substitution chromatography (RIE) feedstocks that do not contain ligands, an improved model based on a modulated Langmuir isotherm has been developed and used. A general correlation for such feedstocks was developed to predict the minimum column length for the formation of a constant pattern substitution train. A design method based on this correlation was developed. The rate models and simulations were tested and validated using literature data on the separation of seven types of RIEs. Furthermore, the general correlation was tested and validated using new experimental data on the separation of a two-component mixture of Nd and Pr.

[0057] For a two-zone LAD for the separation of a composite mixture of Dy, Nd, and Pr, selectivity-weighted composition coefficient γ i A precise zone division strategy based on this was developed and tested. In the first zone, high-purity Nd yielded 78% and 100 kg / m³. 3 Higher productivity was achieved than / day. The second zone was designed to separate the mixed band from the first zone to produce all three types of REE in high purity and high yield. The total Nd yield was 95% when the mixed band was not recirculated in zone II. By recirculating the Nd / Pr and Dy / Nd mixed bands in zone II, the total yield for all three types of REE can be further increased to over 99%. For similar product purity and yield, the total productivity of this two-zone LAD system is 111 kg / (m³) of REE. 3 The adsorbent was present in the sorbent (LAD) column per day, which was more than 100 times higher than that of single-column LAD.

[0058] Two-zone LAD requires fewer columns and boasts productivity approximately 100 times higher than the average volume productivity of conventional liquid-liquid extraction, which requires thousands of mixer-settler units. The LAD separation process requires only environmentally friendly chemicals, most of which can be recycled and reused, and generates virtually no waste. The multi-zone LAD method has the potential to transform the REE purification process into a cleaner, more environmentally friendly process. The results of this research could also help transform the current linear REE economy (from ore to pure REE, products, and landfill waste) into a circular and sustainable REE economy.

[0059] (Example 2) A two-zone LBD (general strategy 1) with three columns for separating and recovering three types of high-purity REE, Nd, Pr, and Dy from the REE mixture of Example 4. The mixture derived from waste magnets contains three components: REE, Pr, Nd, and Dy. The detailed composition is listed in Table B below. A two-zone ligand-based substitution (LBD) separation with three columns is designed to recover all three components: Pr, Nd, and Dy. A REE-selective ligand, EDTA, is immobilized as the sorbent to provide sufficient selectivity for separation. The monovalent metal ion Na has a much lower affinity than EDTA. + Select H as the pre-saturating agent. + Since it has the highest EDTA affinity, an acid such as HCl is used as a substitution agent. Of the three REEs to be separated, Pr has the lowest EDTA affinity among the three components, and therefore the lowest sorbent selectivity, and elutes first, followed by Nd, and then Dy.

[0060] [Table 8]

[0061] General partitioning strategy 1 is applied in this case. In this three-component mixture, Nd is γ iThe highest value is obtained and recovered first in Zone I. The operating conditions in Zone I are designed to achieve maximum Nd productivity. Under these conditions, neither Pr nor Dy reach plateau concentrations. Two mixed bands, Pr / Nd and Nd / Dy, are generated from Zone I and further separated in columns A and B of Zone II. The two-component mixed bands generated from the elutes of the two columns in Zone II are recirculated to the inlets of each column, IIA and IIB, respectively, to increase the yield of all three components to over 99%. The simulated elution profiles are shown in Figures 21A to 21E. Total productivity in the 3-zone design: 281 kg / m³ 3 This represents 680 times the total productivity in a single-column design.

[0062] [Table 9]

[0063] [Table 10]

[0064] [Table 11]

[0065] [Table 12]

[0066] (Example 3) A one-zone LBD including one column for the separation and recovery of two products Dy and Nd / Pr (as a mixture) from the previously disclosed REE mixture (general strategies 2 and 3). The feedstock mixture and sorbent in this embodiment are the same as those in Example 5. However, the target products in this embodiment are not three pure products, but (1) a mixture of Pr and Nd and (2) Dy. The Nd / Pr ratio in the waste magnet is the same as that of the unused magnet. The recovered Nd / Pr can be used directly in the manufacture of new magnets. Recovering Nd and Pr as single products simplifies the purification process and reduces processing costs.

[0067] In this design method, Pr and Nd are grouped together as a single component, Pr / Nd, and Dy is the other component. The mixture is treated as a two-component mixture. The composition and selectivity-weighted composition coefficient of this two-component mixture are shown in Table C. The γ of the grouped component Pr / Nd i When calculating values, the selectivity between the pre-saturating agent and Pr, and the selectivity between Nd and Dy should be used.

[0068] [Table 13]

[0069] To recover two products from this feedstock, only a single-zone LBD containing one column is required. The grouped component Pr / Nd is higher than Dy γ i Zone I is designed to achieve maximum productivity for producing Pr / Nd. Since the purity of the collected Dy meets the requirement of 99.5%, Dy can be recovered as a pure product in Zone I. The two-component mixed band generated from Zone I is recycled to the inlet of this column to prevent material loss and ensure that the yield of both components is greater than 99%. The simulated elution profiles are shown in Figures 23A and 23B.

[0070] Based on the chromatogram shown in Figure 23B, the estimated sorbent productivity of this system (including mixed band recirculation) is REE 1,800 kg / m³. 3This is per day. The selectivity between Dy and Nd is very high (α=5) (Table 5 above), resulting in very high productivity. More importantly, this separation does not require the separation of the low-selectivity pair Nd and Pr (α=1.8), as in Example 4, resulting in high sorbent productivity. The productivity of a single-column design that separates Nd, Pr, and Dy with high purity (>99.5%) and high yield (>99%) for all three REEs is only 0.4 kg / m³ of REE. 3 Please note that this is per day (Table 8, Example 5). Generally, the selectivity-weighted composition coefficient γ for the target product component i is i The higher the purity requirement, the higher the productivity of the sorbent.

[0071] (Example 4) A combination of LAD (Zones I and II) and LBD (Zone III) for separating four types of REE and Co from a crude mixture derived from waste magnets (General separation strategy 1 for LAD and General strategy 2 for LBD). Example 7 demonstrates a method for recovering three types of REE (Dy, Nd, and Pr) and Co from a crude mixture derived from waste magnets. The waste magnets are first converted into soluble salts in an aqueous solution. The major component, Fe, in the soluble salts of the waste magnets is precipitated by adjusting the pH of the solution and removed by filtration. The remaining REE and Co ions in the solution can be separated and recovered. A three-zone design is developed to recover Co and the three types of REE (Figure 24A).

[0072] A cation exchange column is used as the loading column, Zone IA. In the case of cation exchangers, trivalent ions have a higher affinity than divalent metal ions. When a mixture of REE and Co is fed to this column, the trivalent REE remains in the column, while the other divalent metal ions are replaced by trivalent ions and eluted from the column more quickly. The simulated elution profile for Zone IA is shown in the figure. Next, the REE-loaded column, Zone IA, is connected to a Cu-loaded column, and the REE separation process is carried out using a 2-zone LAD. The LAD separation design strategy is the same as in Example 4. Three types of pure REE are produced. Divalent metal ions that elute quickly from Zone IA are collected and sent to Zone III, where Co is recovered by LBD. Zone III uses an iminodiacetic acid (IDA) column, which has high selectivity between divalent metal ions. The affinity order of the IDA column is Cu > Ni > Co > B. A substitution separation is designed to recover Co as the product. Na is used as a pre-saturation agent. + Using H as a substitution agent + Use the following. The simulated dissolution profile is shown in Figure 24C.

[0073] Theoretical details A. Separation mechanism in ligand-assisted substitution (LAD) chromatography A schematic diagram of the separation mechanism of ligand-assisted substitution chromatography for a two-component mixture is shown. The cation exchange resin is first pre-saturated with a pre-saturating agent (P), in this case copper ions (Cu 2+ Pre-equilibrium is achieved with ). The pre-saturating agent should have a lower affinity for the sorbent than REE but a higher affinity for the ligand than REE. REE ion (Nd 3+ and Pr 3+ When the mixture of ) is supplied to the column, trivalent REE ions are converted into divalent Cu 2+ It is replaced by [another component]. The selectivity of the sorbent for REE ions is extremely low (<1.1), so no separation occurs during loading, and a uniform REE mixture band is formed near the column inlet.

[0074] When a solution of EDTA ligand is supplied to the column, the EDTA competes with the sorbent to form non-adsorbed ligand-REE (L-REE) complexes. Each complex moves downward along the column with the mobile phase, resulting in Na + REE substitution occurs effectively by EDTA. 3+ Nd 3+ Because it has high selectivity for Cu, the L-Nd complex moves before the L-Pr complex, and as a result, the Nd band is separated from the Pr band. 2+ Since it has the highest affinity for EDTA, when L-Nd reaches the boundary between the Nd band and the Cu band, the ligand becomes Nd 3+ By releasing Cu 2+ It forms a complex with Nd. 3+ The ions are re-adsorbed onto the column. As more ligand is supplied to the column, the L-Pr complex reaches the boundary between the Pr band and the Nd band. Similarly, Pr 3+ The Nd ions are released from the ligand and re-adsorbed onto the sorbent. When the adsorbed Nd ions are desorbed and form a complex with the ligand, the Nd band is replaced by the Pr band. If the column is long enough, this substitution process continues until two consecutive bands of Nd and Pr are formed, moving at the same rate within the column. The separation of these two bands is driven by EDTA, which acts as an apparent substitute. In the ideal case, where there are no mass transfer effects, this set of bands is called a "constant-velocity train." In the non-ideal case, the overlapping region between adjacent bands shrinks as the bands continue to separate. Eventually, when each mass transfer zone reaches a certain length, the system reaches a "constant pattern" state.

[0075] B. Constant velocity train, constant pattern constant velocity train, and general map Adsorbent is selectivity

number

number

number

number

number

[0076] For an ideal system (without expansion due to mass transfer), we were the first to derive the minimum column length for forming a constant velocity train in a LAD using h-transformation theory.

[0077] For non-ideal systems, a constant pattern mass transfer zone length (L) is required. MTZ,CP )teeth,

number

number

[0078] Load factor (L f )teeth,

number

[0079] Dimensionless total matter transfer coefficient

number

number

number

number

[0080] N D This is the ratio of the diffusion velocity within a particle to the convection velocity.

number

[0081] Constant pattern mass transfer zone length L MTZ,CP teeth,

number

[0082] The non-linear distribution coefficient K d is [Number] [where the phase ratio P is [Number] is defined as, ε b is the bed void fraction, ε p is the particle porosity, Δ q is the change in the stationary phase concentration, Δ c is the change in the mobile phase concentration, q d is the adsorbed concentration of the displacing agent, c d is the displacing agent concentration in the mobile phase] is. K d is usually greater than 1.

[0083] The minimum column length L required to form a constant-pattern isokinetic train iso-nid was correlated with several important dimensionless groups. The L iso-nid value was determined using velocity model simulations. The dimensionless column length Φ is the ratio of the column length in a non-ideal system to the minimum column length required to form an isokinetic train in an ideal system. When the column length is fixed, Φ is the ratio of the ideal loading rate to the non-ideal loading rate.

[0084] Using combinations of important dimensionless groups, the multidimensional design parameter space is converted to two-dimensional Φ as a function of X. X is the product of important dimensionless groups that control the mass transfer zone length [Number] [where L f is the loading rate,

Number

[0085] Use a constant separation coefficient isotherm to simulate the LAD process:

Number

Number

[0086] The multi-component Langmuir isotherm, Equation (A13), is equal to the constant separation coefficient isotherm,

Number

[0087] The sorption capacity of each component is the same and b j C p,j If the term is much greater than 1, then equation (A13) is:

number

[0088] The simplified isothermal equation corresponds to the constant separation coefficient isothermal equation, equation (A12), and the selectivity is

number

[0089] To simulate the process in which the separation coefficient changes after ligand introduction, we use a modulated Langmuir isotherm:

number

number

[0090] b j C p,j If the term is much greater than 1, the isothermal equation is

number

number

number

number

[0091] If there is no selectivity between the two components during loading, a 0,i =a 0,j Therefore, the pre-saturating agent Cu 2+ The effective selectivity between the most rapidly eluting REE (the one with the highest affinity for the ligand) was approximated as 5 in this simulation. Such high selectivity is sufficient to predict a sharp wave between the two species. After the ligand is introduced into the column, separation begins. Since each REE has a different affinity for the ligand, the modifier concentration c in the exponential term changes as the ligand is supplied to the column. m This changes to 1, and as a result, the effective selection rate is obtained.

[0092]

number

[0093] Since the sorption capacity remains the same, the ratio between all Langmuir "a" and "b" values ​​should be the same.

number

number

number

number

number

[0094] Using a new isothermal simulation, the minimum column length required to achieve a consistent pattern in a non-ideal two-component system was determined. In all cases, the two REEs (REE1 and REE2) were separated using LAD. The sorbent had negligible selectivity for these elements. REE1 had a higher affinity for the ligand, resulting in a lower effective sorbent selectivity. REE1 eluted before REE2. Various hypothetical two-component systems, including a 2-meter column, were simulated. By varying the flow rate and the effective selectivity between the two REEs, a range of X values ​​(8-41) was obtained.

[0095] α e The value was varied from 1.5 to 10. The effective selectivity between REE1 and the pre-saturating agent was set to 5, and the effective selectivity between the ligand (EDTA-Na) and REE2 was also set to 5 to simulate a sharp substitution wave. The effective volume of these systems, the ratio of a0 to b0, was 1.45 meq / ml (bed volume). The isothermal parameters of the virtual two-component system are shown in A5, Table 7.

[0096] Assuming the simulated mass transfer zone length remains fixed even as the column length increases, the minimum column length required to reach a constant pattern mass transfer zone length was identified from the column profile for each two-component system. The minimum column length was then divided by the ideal column length that forms a constant velocity train in the corresponding ideal system. The dimensionless column length Φ was plotted against various X values.

[0097] The best-fitted curve for the data points was found and plotted. This plot is a general map that predicts whether a non-ideal system is within a certain pattern region. In the nonlinear regression, where an exponential equation is fitted to the curve, the constant term was fixed at 1. This is because as the X value approaches infinity, the system approaches the ideal system, and the minimum column length approaches the minimum column length of the ideal system. Φ as a function of X min The new correlation is shown below.

number

[0098] C. Yield and productivity in a constant pattern design method for multi-component mixtures The dimensionless yield formula is:

number

number

number

[0099] In the LAD system, the productivity of sorbent P for component i is... R,i(REE production per unit volume of sorbent per unit time) was derived previously.

number

number

[0100] The design results for yield and productivity as a function of linear velocity are shown for three-component mixtures of Dy, Nd, and Pr with mole fractions of 0.05, 0.83, and 0.12, respectively. The highest productivity is 120 kg / m³ for Nd. 3 (Adsorbent) / day was observed with a yield of 77.5%.

[0101] D. Relationship between yield, purity, and breakthrough cut θ in constant pattern design In recovering the product from the column effluent, the breakthrough cut θ, which controls the width of the product band, is set to the minimum concentration c bot Maximum band concentration c d This is defined as the ratio to . This cut controls the yield of the product component because it determines the amount in the collected product relative to the total amount of this component in the feed material. This cut also controls the purity of the product because it determines the amount of impurities from adjacent bands. The collected product is the band region between the two mass transfer zones. From the elution profile, the yield of component i is:

number

[0102] To calculate the purity of the product, the amount of impurities from two adjacent bands is first calculated. The impurities from the adjacent band on the right are shown enlarged. It is difficult to find an analytical function that can show the change in concentration over time, but the elution time t MTZ,CP corresponding to the mass transfer zone length is related to θ by the analytical solutions, equations (A2) and (A8). Combining equation (A2) and equation (A8),

Equation

Equation

[0103] The area within the curve region is

Equation

[0104] Combining equation (A30) and equation (A31), t(θ) is

Equation

[0105] In that case, the area is

Number

Number

Number

[0106] In that case

Number

[0107] In the limit as θ0 → 0

Number

Number

[0108] To relate the yield to the purity and cut, first simplify the k-th term by substituting Q f and K d :

Number

[0109] The loading rate L f is

Number

[0110] Purity is calculated by combining formulas (29), (A40), and (A41) to determine yield and breakthrough cut θ. d Associated with:

number

[0111] E. Table of System and Simulation Parameters [Table 14]

[0112] [Table 15]

[0113] [Table 16]

[0114] [Table 17]

[0115] [Table 18]

[0116] [Table 19]

[0117] [Table 20]

[0118] While the novel technology has been illustrated and described in detail in the drawings and the aforementioned specification, it should be understood that this is illustrative and not restrictive in nature. It is understood that the best mode and embodiments that satisfy the enablement requirements are shown and described in the aforementioned specification. A person skilled in the art will understand that an almost infinite number of non-substantial changes and modifications can be easily made to the embodiments, and that it is impractical to describe all such variations of the embodiments in this specification. Therefore, it is understood that it is desirable that all changes and modifications that fall within the scope of the novel technology be protected.

Claims

1. A method for substantially recovering rare earth elements (REEs) from magnets, a) A step of dissolving the magnet to obtain a solution containing Nd, Pr and Dy, b) Equilibrium the first column with a pre-saturating agent to obtain the first equilibrium column, c) The step of introducing the solution into the first equilibrium column, d) The step of introducing the ligand solution into the first equilibrium column, e) A step of establishing three mobile bands of different solution compositions in the column, wherein the three mobile bands include a Dy / Nd mixed band, a first pure Nd band, and an Nd / Pr mixed band. f) A step of sending the Dy / Nd mixed band to a second column containing the pre-saturating agent, g) The step of introducing the ligand solution into the second column, h) The step of establishing a pure Dy band and a second pure Nd band in the second column, i) A step of sending an Nd / Pr mixed band to a third column containing the pre-saturating agent, j) The step of introducing the ligand solution into the third column, k) A step of establishing a third pure Nd band and a pure Pr band in the third column, l) A step of eluting each pure Nd band and recovering Nd, m) A step of eluting the pure Dy band and recovering Dy, n) A step of eluting the pure Pr band and recovering Pr. The method, including the method described above.

2. The method according to claim 1, wherein the second column and the third column are integrated, step h) is performed in a first zone of the second column, and step k) is performed in a second, spaced zone in the second column.

3. Step a) is, a1) A step of converting waste magnets into a mixture of soluble metal salts, a2) The step of dissolving a mixture of soluble metal salts to obtain a solution containing Nd, Pr, and Dy. The method according to claim 1, further comprising:

4. The method according to claim 1, wherein the ligand is EDTA and the pre-saturating agent is a Cu2+ solution.

5. The method according to claim 1, wherein the three bands define a constant-pattern constant-velocity train.

6. The method according to claim 1, wherein the pre-saturating agent is selected from the group including sodium, copper, erbium, and combinations thereof.

7. The method according to claim 1, further comprising the step of introducing a substitution agent into each column after k) and before l).

8. The method according to claim 7, wherein the substitution agent is hydrogen.

9. The method according to claim 1, wherein each of the ligands is EDTA.

10. The method according to claim 1, wherein the ligand moves through each column.

11. A method for recovering rare earth elements from magnets, a. A step of introducing a solution containing multiple rare earth element ions obtained from waste magnets into a first chromatography column, b. A step in which the remaining rare earth element ions are passed through the column while the first rare earth element ions are captured with the first ligand, c. The step of eluting the first rare earth element ions to obtain a first portion of the concentrated first rare earth element, d. A step of capturing a second rare earth element ion with a second ligand, e. A step of eluting the second rare earth element ion to obtain a second portion of the concentrated second rare earth element, f. A step of capturing a third rare earth element ion with a third ligand, g. The step of eluting the third rare earth element ion to obtain the third portion of the concentrated third rare earth element. The method, including the method described above.

12. h. Before step a, the step of calculating the selectivity-weighted composition coefficient for each rare earth element, i. After step h and before step a, a first ligand having high selectivity for a first rare earth element is selected, where the first rare earth element has the highest selectivity-weighted composition coefficient; a second ligand having high affinity for a second rare earth element is selected, where the second rare earth element has the second highest selectivity-weighted composition coefficient; and a third ligand having high affinity for a third rare earth element is selected, where the third rare earth element has the third highest selectivity-weighted composition coefficient, and The method according to claim 11, further comprising:

13. The method according to claim 12, wherein the first, second, and third ligands are present in the respective, spaced-out first, second, and third mobile bands.

14. The method according to claim 13, wherein the first mobile band is present in a first chromatography column and the second mobile band is present in a second separated chromatography column.

15. The method according to claim 13, wherein the third mobile band is present in the second chromatography column.

16. j. Before step a, the step of calculating the selectivity-weighted composition coefficient for each rare earth element, k. After step j and before step a, a first ligand having high selectivity for a first rare earth element is selected, where the first rare earth element has the lowest selectivity weighted composition coefficient; a second ligand having high affinity for a second rare earth element is selected, where the second rare earth element has the second lowest selectivity weighted composition coefficient; and a third ligand having high affinity for a third rare earth element is selected, where the third rare earth element has the third lowest selectivity weighted composition coefficient. The method according to claim 11, further comprising:

17. The method according to claim 16, wherein the first, second, and third ligands are present in the respective fixed first, second, and third zones, the first ligand being bound to the first adsorbent, the second ligand being bound to the second adsorbent, and the third ligand being bound to the third adsorbent.

18. The method according to claim 17, wherein steps b and c are performed in a first chromatography column, steps d and e are performed in a second chromatography column, and steps f and g are performed in a third chromatography column.

19. The method according to claim 11, wherein each ligand is EDTA.

20. The method according to claim 11, wherein each ligand is selected from the group comprising citric acid, aminopolycarboxylic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, bicine, HDEHP, DGA, and combinations thereof.

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