Purification of Scandium Concentrate

Abstract

For the purpose of reducing contamination of scandium oxide products, the present disclosure provides a method for removing at least one metal contaminant from a scandium (Sc) concentrate. The method is based on contacting the Sc concentrate with an ion exchange resin to obtain a purified Sc eluate or raffinate. The first and second ion exchange resins are strong acid cation resins having sulfonic acid functional groups in the potassium or sodium form. The purified Sc eluate or raffinate can be used to produce a scandium oxide product having reduced amounts of metal ion contaminants.

Description

Technical Field

[0001] Cross - reference to related applications This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 926,708, filed on October 28, 2019, the entire content of which is incorporated herein by reference.

[0002] The present disclosure relates to a method for reducing contamination in scandium concentrates using ion - exchange resins.

Background Art

[0003] Scandium oxide (Sc) products may be contaminated with metal contaminants that can be radioactive in some embodiments. Contamination, particularly by radioactive metal contaminants, is a problem because it can limit the transport of Sc oxide products and reduce their market value.

[0004] There is a strong desire for a method for reducing the contamination of metal contaminants in Sc concentrates in order to produce Sc oxide products with metal contaminant levels of 500 ppm (or less than 500 ppm).

Summary of the Invention

[0005] The present disclosure relates to the use of strongly acidic cation resins (such as sulfonic acid ion - exchange resins) for reducing contamination in scandium concentrates. In a first aspect, the present disclosure provides a method for removing at least one metal contaminant from a scandium (Sc) concentrate. The method includes contacting the Sc concentrate with an acidic solution to produce an unpurified Sc solution. In one embodiment of the method, the method includes contacting the unpurified Sc solution with a first ion exchange resin having a higher affinity for at least one metal contaminant than for Sc, which captures at least one metal contaminant, to produce a first ion exchange resin complex and a purified Sc raffinate solution, and optionally, eluting Sc from the first ion exchange resin complex with a first eluent to obtain a first Sc eluate, and combining the first Sc eluate with a first Sc raffinate. In another embodiment of the method, the method also includes contacting the unpurified Sc solution with a second ion exchange resin that captures at least one metal contaminant and Sc to produce a second ion exchange resin complex; and eluting Sc from the second ion exchange resin complex with a second eluent to produce a purified Sc eluate. In the method of the present disclosure, the concentration of at least one metal contaminant in the purified Sc eluate or the purified Sc raffinate is lower than the concentration of at least one metal contaminant in the unpurified Sc solution. Further, in the method of the present disclosure, the first ion exchange resin and the second ion exchange resin are strongly acidic cation resins having a sulfonic acid functional group in the potassium or sodium form. In one embodiment, the Sc concentrate is in a dry solid form, or in an aqueous solid suspension or slurry form. In yet another embodiment, the sulfonic acid functional group is in the sodium form. In still further embodiments, the at least one metal contaminant has at least three oxidation numbers. In still further embodiments, the at least one metal contaminant is thorium (Th) or zirconium (Zr). In a specific embodiment, the at least one metal contaminant is Th. In yet another embodiment, the unpurified Sc solution has a pH of from about 1.5 to about 3.5, such as from about 3.0 to about 3.5. In yet another embodiment, the acidic solution is an HCl solution.In a further embodiment, the method includes eluting Sc from the first ion exchange resin complex with a first eluent to obtain a first Sc eluate, and combining the first Sc eluate with a purified Sc raffinate. In yet another embodiment, the second eluent or the second eluent is an HCl solution. In yet another embodiment, the second ion exchange resin is a gel. In yet another embodiment, the first ion exchange resin is a macroporous resin. In one embodiment, the method further includes eluting at least one metal contaminant from the first ion exchange resin complex or the second ion exchange resin complex. In another embodiment, the method further includes regenerating the first ion exchange resin or the second ion exchange resin to the sodium form or the potassium form.

[0006] According to a second aspect, the present disclosure provides a purified scandium (Sc) eluate obtainable or obtained by the methods described herein. According to a third aspect, the present disclosure provides a purified scandium (Sc) raffinate obtainable or obtained by the methods described herein.

[0007] According to a fourth aspect, the present disclosure provides a method for producing a purified scandium (Sc) oxide product. The method includes precipitating the purified Sc eluate described herein or the purified Sc raffinate described herein with oxalic acid to obtain a precipitate slurry having a solid fraction and a liquid fraction. The method also includes separating the solid fraction of the precipitate slurry from the liquid fraction of the precipitate slurry to obtain a separated solid fraction. The method further includes calcining the separated solid fraction to obtain a purified Sc oxide product. The concentration of at least one metal contaminant in the obtained purified Sc oxide product is less than 500 ppm.

[0008] According to a fifth aspect, the present disclosure provides a purified scandium (Sc) oxide product obtainable or obtained by the methods described herein. The concentration of at least one metal contaminant in the purified Sc oxide product is less than 500 ppm.

[0009] Although the nature of the present invention has been described generally, reference will hereinafter be made to the accompanying drawings which illustrate preferred embodiments by way of example.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0011] The present disclosure relates to a method for reducing the presence of contaminant metal elements in a scandium concentrate. As used in the context of the present disclosure, the expression "scandium concentrate" means an amorphous (e.g., aqueous solid suspension or slurry) or crystalline (e.g., dry solid form) scandium carbonate-bicarbonate-hydroxide precipitate. This precipitate can be obtained from the treatment of scandium-containing feed materials such as liquid effluents and solid residues from titanium dioxide (TiO 2 ) feedstock upgrading plants (such as the UGS process), TiO 2 pigment production (sulfuric acid method or chlorine method), alumina (Al 2 O 3 ) production (Bayer process), nickel ore treatment, zirconium feedstock treatment, uranium ore treatment, tungsten ore treatment, etc. The expression "scandium concentrate" also means scandium oxide or any other scandium-containing solid compound containing significant amounts of impurities such as thorium and zirconium.

[0012] In some embodiments, the scandium concentrate can be obtained by neutralizing a scandium carbonate solution from an initial pH of about 11.0 to a final pH of 6.5 by adding a strong acid such as HCl. The scandium concentrate may be repulped and washed with deionized water and recovered by filtration, if desired. Embodiments of the process for obtaining the scandium concentrate are described in International Publication No. WO 2019 / 213753, the entire contents of which are incorporated herein by reference.

[0013] In the first step of the method, the Sc concentrate is treated with a strong acid such as HCl to obtain a solution (referred to herein as the unpurified Sc solution) having a pH of about 1.5 to 3.5, and in some embodiments, about 3.0 to about 3.5, or about 3.0. In one embodiment, the unpurified Sc solution has a pH of at least about 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, or 3.4. In another embodiment, the unpurified Sc solution has a pH of about 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, or 1.6 or less. In a further embodiment, the unpurified Sc solution has a pH ranging from about 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, or 3.4 to about 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, or 1.6. In one embodiment, the unpurified Sc solution has a pH of at least about 3.0, 3.1, 3.2, 3.3, or 3.4. In another embodiment, the unpurified Sc solution has a pH of about 3.5, 3.4, 3.3, 3.2, or 3.1 or less. In a further embodiment, the unpurified Sc solution has a pH ranging from about 3.0, 3.1, 3.2, 3.3, or 3.4 to about 3.5, 3.4, 3.3, 3.2, or 3.1. In yet another embodiment, the unpurified Sc solution has a pH of about 3.0. In one embodiment, the unpurified Sc solution has a Sc concentration of about 1 to 20 g / L, and in some embodiments, a Sc concentration of about 1 to 10 g / L, 2 to 6 g / L, or 4 to 5 g / L.

[0014] The method of the present disclosure is designed to at least partially remove some of the metal contaminants from the Sc concentrate by treating the unpurified Sc solution. The metal contaminants that can be removed from the unpurified Sc solution by the method of the present disclosure have an oxidation number of at least 3 (in the unpurified Sc solution). For example, they can include, but are not limited to, thorium (Th), iron (Fe), chromium (Cr), and zirconium (Zr). In a specific embodiment, the metal contaminants that can be removed from the unpurified Sc solution by the method of the present disclosure can include thorium (Th) and zirconium (Zr) (in some embodiments, they can be limited to these). In a specific embodiment, the metal contaminants that can be removed from the unpurified Sc solution by the method of the present disclosure can include thorium (Th) (in some embodiments, it can be limited to this). In some embodiments, the concentration of each metal contaminant in the unpurified Sc solution is about 10 - 500 mg / L. In one embodiment, the concentration of each metal contaminant in the unpurified Sc solution is at least about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 mg / mL, or more. In another embodiment, the concentration of each metal contaminant in the unpurified Sc solution is 500, 450, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20 mg / L or less, or less than that. In another embodiment, the concentration of each metal contaminant in the unpurified Sc solution is from about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450 mg / mL to about 500, 450, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20 mg / L.

[0015] Once the crude Sc solution is obtained, it is contacted with an ion exchange resin. The "ion exchange resin" is understood as a resin having an affinity for the target metal ions. The ion exchange resin that can be used in the method of the present disclosure can be made of particles of so-called "chromatography size" (e.g., an average diameter of about 200 - 400 μm) or "standard size" (e.g., an average diameter of about 300 - 1200 μm). The particles of the ion exchange resin may be cross-linked before being subjected to the method.

[0016] The ion exchange resin used in the method of the present disclosure is a strongly acidic cation resin such as a sulfonic acid cation resin. In the context of the present disclosure, such an ion exchange resin contains a sulfonic acid moiety that can capture metal ion contaminants and, in some embodiments, Sc as well. As is known in the art, strong cation resins show little or no variation in ion exchange capacity (e.g., charge) due to changes in pH. In some embodiments, the strong cation exchange resin shows little or no variation over a pH range of 1 - 14, exemplified by 2 - 14. This is in contrast to weak cation exchange resins that ionize only within a limited pH range (e.g., 2 - 9).

[0017] The ion exchange resin used in the method of the present disclosure is in the potassium form or the sodium form. As is known in the art, the "form" of an ion exchange resin means the counter ion absorbed on the sulfonic acid functional group before the method. In the present disclosure, it is preferred that the ion exchange resin contains a potassium or sodium counter ion. In a specific embodiment, the ion exchange resin of the present disclosure contains a sodium counter ion (e.g., in a sodium form resin).

[0018] In some embodiments of the present disclosure, it is possible to use an ion exchange resin in the form of a gel. Gel resins generally have small pores (e.g., about 1-2 nm when hydrated). Embodiments of gel ion exchange resins that can be used in the context of the present disclosure include, but are not limited to, Purolite PCR642 (trademark) or SSTC60 (trademark), Diaion UBK(8) (trademark).

[0019] In other embodiments of the present disclosure, it is possible to use an ion exchange resin in the macroporous form. Macroporous resins generally have large pores (e.g., about 20-100 nm when hydrated). Embodiments of macroporous ion exchange resins that can be used in the context of the present disclosure include, but are not limited to, Purolite C150 (trademark) or PCR145K (trademark).

[0020] In the method of the present disclosure, two different types of ion exchange resins may be used. In a first embodiment, the method uses a first ion exchange resin that preferentially captures metal contaminants but does not capture Sc (at least substantially does not capture Sc). In this first embodiment, the metal contaminants form a complex with the first ion exchange resin (e.g., an adsorption resin, or a second ion exchange resin complex). Further, when the first ion exchange resin is used, a Sc raffinate is obtained. In this first aspect, since some Sc can be captured by the resin, it is possible to elute Sc from the first ion exchange resin complex (e.g., an adsorption resin) to obtain a first Sc eluate that can be combined with the Sc raffinate as desired. In a first aspect of the method using the first ion exchange resin, a macroporous resin can be used.

[0021] In a second embodiment, the method uses a second ion exchange resin that can capture both the metal contaminants and Sc present in the unpurified Sc solution and form a complex with them. When the second ion exchange resin is used, it is necessary to elute the captured Sc from the resin to obtain a second Sc eluate. The elution step can be performed, for example, by contacting the second ion exchange resin complex (e.g., adsorption resin) with a second eluent. One skilled in the art will know how to select an eluent suitable for obtaining the second Sc eluate. In one embodiment, the eluent is a strong acid eluent, such as an HCl solution (e.g., 1N HCl solution, 2N HCl solution, or 3N HCl solution). In a second embodiment of the method using the first ion exchange resin, a macroporous resin or a gel resin can be used.

[0022] In the method of the present disclosure, when a Sc eluate and / or a Sc raffinate is obtained, it is possible to regenerate the resin to perform a new ion exchange cycle. In such an embodiment, the first and / or second ion exchange resin may be subjected to an elution step with a further eluent to remove metal contaminants that may have been captured by the resin. One skilled in the art will know how to select an eluent suitable for removing at least a portion or most of the captured metal contaminants. In one embodiment, the eluent is a strong acid eluent, such as an HCl solution (e.g., 4N HCl solution, 5N HCl solution, 6N HCl solution, or 8N HCl solution). The eluted metal contaminants may be further processed or may be discarded.

[0023] The method of the present disclosure may further include steps for making a purified scandium oxide product. The level of each metal ion contaminant (e.g., metal contaminant) of scandium oxide obtained using the purified Sc eluate and / or Sc raffinate described herein may, in some embodiments, be less than about 500, 450, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, or 10 ppm. In embodiments where the scandium concentrate contains Th as a metal ion contaminant, the Th level of scandium oxide obtained using the purified Sc eluate and / or Sc raffinate described herein may, in some embodiments, be less than about 500, 450, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, or 10 ppm.

[0024] An embodiment of a first embodiment of a method using a first ion exchange resin that can preferentially capture metal contaminants and Sc is shown in step 130 of FIG. 1. In a preliminary step, the untreated Sc concentrate 105 is dissolved in step 110 at a pH of 1.5 to 3.5, exemplified by pH 3.0, and can be heated to a temperature of 20 to 100 °C, such as about 90 °C. The dissolution step 110 can be carried out using a concentrated acid such as HCl. By the dissolution step, a slurry 115 is produced, which is fed to a solid-liquid separation step 120. The solid residue obtained after step 120 (which may contain, for example, Fe, Ti, Zr, Th, etc.) can be discarded as waste solid. The separated liquid obtained in step 120 is regarded as the unpurified Sc solution 125. In FIG. 1, an unpurified Sc solution containing Th as a metal ion contaminant is shown. The unpurified Sc solution is adsorbed onto the first ion exchange resin in step 130 to produce an adsorbed resin 133-A (also referred to as a first ion exchange resin complex) containing the metal ion contaminant (Th in FIG. 1). Since the first ion exchange resin does not substantially capture Sc, step 130 produces a purified Sc raffinate 135-B. The adsorbed resin 133-A can be subjected to an elution step (not shown in FIG. 1) to collect Sc metal ions that may have been captured on the first ion exchange resin. The purified Sc raffinate 135-B (optionally combined with the obtained Sc eluate) can be fed to a precipitation step 140 to which oxalic acid 143 is added. The precipitation step 140 can be carried out at a temperature of 20 to 100 °C, such as about 60 °C. By the precipitation step, a slurry 145 that can be fed to a solid-liquid separation step 150 can be produced. The solid 155 obtained from the separation step 150 may be fed to a calcination step 160, and the used oxalic acid solution may be discarded or reused. The calcination step 160 may include subjecting the solid 155 to a temperature of 600 to 1000 °C (such as about 900 °C) until a purified scandium oxide product 165 is obtained.

[0025] FIG. 1 also includes several steps for regenerating the resin after the purified Sc raffinate 135-B and optionally the Sc eluate are obtained. To do so, the resin 133-A can be subjected to an elution step 134 using a strong acid solution such as, for example, a 6N HCl solution as shown in FIG. 1. The eluate from step 134 can be further processed. The resin 133-B obtained after step 134 can be washed in step 136 with an aqueous solution such as, for example, water as shown in FIG. 1. The washed resin 133-C obtained from step 136 can be regenerated in step 138 using a basic solution such as, for example, a 5-10% NaOH solution. The basic solution added in step 138 contains sodium ions or potassium ions. The regenerated resin 139 can be used in step 130 for performing the ion exchange step.

[0026] An embodiment of a second embodiment of a method using a second ion exchange resin capable of capturing both metal contaminants and Sc is shown in steps 130 and 132 of FIG. 2. Prior to steps 130 and 132, the untreated Sc concentrate 105 may be dissolved in step 110 at a pH of 1.5 to 3.5, exemplified by pH 3.0, and heated to a temperature of 20 to 100 °C, such as about 90 °C. The dissolution step 110 can be carried out using a concentrated acid such as HCl, for example. By the dissolution step, a slurry 115 that can be fed to the solid-liquid separation step 120 is produced. The solid residue obtained after step 120 (which may contain, for example, Fe, Ti, Zr, Th, etc.) can be discarded as waste solid. The separated liquid obtained in step 120 is regarded as the unpurified Sc solution 125. In FIG. 2, an unpurified Sc solution containing Th as a metal ion contaminant is shown. The unpurified Sc solution is adsorbed onto the first ion exchange resin in step 130 to produce an adsorption resin 131-A (also referred to as a second ion exchange resin complex) containing both Sc and Th. To separate Sc from the metal ion contaminant (e.g., Th in FIG. 2), the resin is subjected to an elution step 132. In the elution step 132, a strong acid such as a 3N HCl solution as shown in FIG. 2 is applied to the adsorption resin 131-A to obtain a purified Sc eluate 135-A. The acid used for eluting Sc must be strong enough to remove Sc from the resin while leaving most of the metal ion contaminant (e.g., Th in FIG. 2) and most of the other contaminants. The purified Sc eluate 135-A can be fed to a precipitation step 140 to which oxalic acid 143 is added. The precipitation step 140 can be carried out at a temperature of 20 to 100 °C, such as about 60 °C, for example. By the precipitation step 140, a slurry 145 that can be fed to the solid-liquid separation step 150 is produced. The solid 155 obtained from the separation step 150 may be subjected to a calcination step 160, and the used oxalic acid solution may be discarded or reused. The calcination step 160 may include subjecting the solid 155 to a temperature of 600 to 1000 °C, such as about 900 °C, until a purified scandium oxide product 165 is obtained.

[0027] Figure 2 also includes several steps for regenerating the resin after the purified Sc eluate 135-A is obtained. To do this, the resin 133-A can be subjected to an elution step 134 using a strong acid solution such as, for example, 6N HCl solution as shown in Figure 2. Since the second ion exchange resin has a higher affinity for metal ion contaminants than for Sc, the acidic solution used to elute the metal ion contaminants of the resin 133-A is a solution with a higher normality than the acidic solution used to elute Sc from the resin 131-A. The eluate from step 134 can be further processed. The resin 133-B obtained after step 134 can be washed with an aqueous solution such as, for example, water in step 136 as shown in Figure 2. The washed resin 133-C obtained from step 136 can be regenerated in step 138 using a basic solution such as, for example, a 5-10% NaOH solution. The basic solution in step 138 contains sodium ions or potassium ions (not specifically shown in Figure 2). The regenerated resin 139 can be used in step 130 for performing the ion exchange process.

[0028] One skilled in the art will understand that the final purity of the scandium oxide product 165 is directly affected by the initial purity of the scandium eluate or raffinate obtained after the ion exchange step 130 (and 132 if desired). The method described herein increases the final purity of the scandium oxide product by increasing the purity of the scandium eluate.

[0029] Examples Example I - Influence of Resin Conditions (H + form or Na + form) on Its Selectivity for Scandium and Thorium The selectivity test was performed on H + form (i.e., the active sites of the resin are occupied by protons) and Na +Performed using two strong cation (sulfonic acid) gel type resins of the H (i.e., the sodium cation occupies the active site of the resin) type. In each test, 15 mL of the resin and 100 mL of an unpurified scandium solution containing 4 - 5 g / L of Sc and having a pH of 3.0 were mixed in a beaker at ambient temperature for 12 hours to reach equilibrium. The resin was initially received in the H + type. For tests with Na + type resin, the resin was pre-conditioned with sodium hydroxide solution (5 wt / wt% NaOH) for several hours. After each test, the solution was recovered by filtration and analyzed for its scandium and thorium contents. As shown in Table 1, the Na + type resin was more selective for scandium compared to thorium. For the H + type resin, approximately 98% of the thorium was adsorbed, while for the Na + type resin, only 15% - 20% of the thorium was adsorbed.

[0030]

Table 1

[0031] Example II - Influence of the pH of the unpurified scandium solution on the resin selectivity for scandium and thorium To evaluate the influence of the pH of the unpurified scandium solution on the selectivity of strong cation (sulfonic acid) resins for scandium and thorium, tests were conducted using the gel type chromatographic resin Purolite PCR642 and unpurified scandium solutions containing 4 - 5 g / L of Sc and acidified with HCl to various pH values. All tests were performed by mixing 15 mL of the resin and 100 mL of the unpurified scandium solution together in a beaker at ambient temperature for 12 hours to reach equilibrium. Prior to the tests, the resin was contacted with sodium hydroxide solution (5 wt / wt% NaOH) for several hours to convert it to the Na +Conditioned in the Na form. After each test, the solution was recovered by filtration and analyzed for its scandium and thorium contents. As shown in Table 2, the selectivity of the resin for scandium is higher at relatively high pH values. The optimal pH for the best selectivity exists between pH 3.0 and 3.5. At these pH values, 75% of the scandium was adsorbed as compared to less than 25% of the thorium being adsorbed. At pH > 3.5, significant loss of scandium occurred as it began to precipitate in solid form.

[0032]

Table 2

[0033] Example III - Influence of resin type (gel type or macroporous) and particle size (standard or chromatography grade) on its selectivity for scandium and thorium To evaluate the influence of resin type (gel type or macroporous) and resin particle size (standard 300 - 1200 μm or chromatography grade 200 - 400 μm) on the selectivity for scandium and thorium, tests were conducted using various strong cation (sulfonic acid) resins and an unpurified scandium solution containing 4 - 5 g / L Sc and acidified to pH 3.0 with HCl. All tests were performed by mixing 15 mL of resin and 100 mL of the unpurified scandium solution together in a beaker at ambient temperature for 12 hours to reach equilibrium. Before the tests, the resin was conditioned in the Na form by contacting it with a sodium chloride (5 wt / wt% NaOH) solution over several hours. After each test, the solution was recovered by filtration and analyzed for its scandium and thorium contents. + Conditioned in the Na form. After each test, the solution was recovered by filtration and analyzed for its scandium and thorium contents. As shown in Table 3, the macroporous resin adsorbed nearly 100% of the thorium in the solution. Also, the results in Table 3 showed that the resin with particle size for chromatography exhibited higher selectivity for thorium than for scandium.

[0034]

Table 3

[0035] Example IV - Column Purification of Crude Scandium Solution Using Gel-Type Resin A continuous column test was carried out using UBK(8) resin from Diaion (a strong cation resin made of divinylbenzene cross-linked polystyrene gel (sulfonic acid of Na + type)). Adsorption was carried out in a column with a diameter of 1.5 cm and a resin volume of 12 mL at a flow rate of about 5 mL / min of the crude scandium solution. The resin was washed with 100 mL of water at a flow rate of 10 mL / min. Scandium was eluted with 100 mL of 3N HCl solution at a flow rate of 5 mL / min. The total recovery rate of scandium from the crude scandium solution to the scandium eluate was 73%, but for thorium it was only 2.7%, indicating a high selectivity of scandium compared to thorium. Thorium was finally eluted with 300 mL of 6N HCl solution at a flow rate of 5 mL / min.

[0036] Four cycles of adsorption (80 mL of acidified crude scandium solution, 5 mL / min), washing (30 mL of water, 5 mL / min), scandium elution (100 mL of 3N HCl solution, 5 mL / min), thorium elution (300 mL of 6N HCl solution, 5 mL / min), washing (100 mL of water, 5 mL / min), and conditioning (50 mL of 5 wt% NaOH solution, 5 mL / min) were carried out in the same column. The scandium eluates were combined, and 50 mL of 240 g / L hot oxalic acid solution was added to precipitate scandium as scandium oxalate. The precipitate was filtered, washed with deionized water, and calcined at 850 °C overnight. The thorium content of the final product (scandium oxide) was determined by inductively coupled plasma mass spectrometry (ICP-MS) and found to be 410 ± 25 ppm (mg / kg). Chemical analyses of the initial solution (acidified crude scandium solution), the solution treated with resin (raffinate), the scandium eluate, and the obtained precipitated product are shown in Table 4.

[0037]

Table 4

[0038] The stability of the resin after the 4-cycle process described above was determined. As shown in Figure 3, the adsorption of scandium was stably maintained at 81 ± 3% adsorbed Sc in each pass, which corresponds to an average resin capacity of Sc of about 21 g / L. Further, as shown in Figure 3, the adsorption of thorium was low, at 14 ± 3% in each pass.

[0039] Example V - Selectivity Test Using Macroporous Resin and Column Purification of Unpurified Scandium Solution A selectivity test was conducted using the PCR145K resin from Purolite (a strong cation resin made of divinylbenzene-crosslinked macroporous polystyrene beads (sulfonic acid of the Na + form)).

[0040] In the selectivity test, 5 - 15 mL of the resin was mixed with 100 - 200 mL of an unpurified scandium solution (about 5 g / L of Sc at pH 3.0) at ambient temperature for 12 - 16 hours. After each test, the solution was analyzed again for its scandium content and thorium content. Thus, it was observed that the resin adsorbed 97% of thorium and only 7% of scandium (see Table 5 below, Test 4).

[0041]

Table 5

[0042] The selectivity of the PCR145K resin for thorium was excellent compared to the selectivity of the corresponding gel-type resin (such as the resin described in Example IV, see Table 6).

[0043]

Table 6

[0044] The continuous column test was also carried out using the resin PCR145K. In a column containing 12 mL of resin with a diameter of 1.5 cm, 200 mL of the unpurified scandium solution was used for adsorption at a flow rate of 1 mL / min. The resin was washed with 30 mL of water at a flow rate of 10 mL / min. Thorium was eluted using 300 mL of 6N HCl solution at a flow rate of 5 mL / min. Conditioning was carried out using 100 mL of 5 wt / wt% NaOH solution at a flow rate of 5 mL / min.

[0045] Oxalic acid was added to the raffinate (the solution after Th was adsorbed onto the PCR145K resin) to precipitate scandium oxalate, and the purity of the final scandium oxide product was determined. The precipitation of scandium oxalate was carried out by adding 50 mL of a 240 g / L hot oxalic acid solution to approximately 200 mL of the scandium-containing raffinate. The scandium oxalate precipitate was filtered, washed with water, and calcined at 850 °C overnight to convert it to scandium oxide. The initial feed solution (the unpurified scandium solution with pH 3.0), the raffinate, and the filtrate after the precipitation of scandium oxalate were analyzed by ICP-MS. The material balance (based on chemical analysis) is shown in Table 7.

[0046]

Table 7

[0047] The final scandium oxide product was analyzed for its thorium content and was found to be only 56 ± 13 ppm (mg / kg), which is well below the specification for commercial use (typically less than 150 ppm Th).

[0048] Although the present invention has been described in connection with its specific embodiments, it will be understood that the scope of the claims should not be limited by the preferred embodiments shown by way of example, but rather the broadest interpretation consistent with the entire description should be given.

Claims

1. 1. A method for removing at least one metal contaminant from a scandium (Sc) concentrate, comprising: a) contacting the Sc concentrate with an acidic solution to produce a crude Sc solution; b) contacting the unpurified Sc solution with a first ion exchange resin that captures the at least one metal contaminant and has a higher affinity for the at least one metal contaminant than for Sc to produce a first ion exchange resin complex and a purified Sc raffinate solution; or contacting the unpurified Sc solution with a second ion exchange resin that captures the at least one metal contaminant and Sc to form a second ion exchange resin complex, and eluting Sc from the second ion exchange resin complex with a second eluent to form a purified Sc eluate; Including, the second ion exchange resin has a higher affinity for the at least one metal contaminant than for Sc; the concentration of the at least one metal contaminant in the purified Sc eluate or the purified Sc raffinate is less than the concentration of the at least one metal contaminant in the unpurified Sc solution; the first ion exchange resin and the second ion exchange resin are strong acid cation resins having sulfonic acid functional groups in potassium or sodium form, wherein the strong acid cation resins do not exhibit variation in ion exchange capacity over a pH range of 1 to 14; and The first ion exchange resin is a macroporous resin and does not substantially capture Sc; method.

2. The method of claim 1 , wherein the Sc concentrate is in a dry solid form or in the form of an aqueous solid suspension.

3. The method of claim 1 , wherein the sulfonic acid functional group is in the sodium form.

4. 4. The method of claim 1, wherein the at least one metal contaminant has an oxidation number of at least 3.

5. The method of claim 4 , wherein the at least one metal contaminant is thorium (Th) or zirconium (Zr).

6. The method of claim 5 , wherein the at least one metal contaminant is Th.

7. 7. The method of claim 1, wherein the unpurified Sc solution has a pH of 1.5 to 3.

5.

8. The method of claim 7, wherein the unpurified Sc solution has a pH of 3.0 to 3.

5.

9. 9. The method of claim 1, wherein the acidic solution is an HCl solution.

10. 10. The method of claim 1, further comprising: eluting Sc from the first ion exchange resin complex with a first eluent to obtain the first Sc eluate; and combining the first Sc eluate with the purified Sc raffinate.

11. 11. The method of claim 1, wherein the first eluent or the second eluent is an HCl solution.

12. 12. The method of claim 1, wherein the second ion exchange resin is a gel.

13. 13. The method of any one of claims 1 to 12, further comprising eluting the at least one metal contaminant from the first ion exchange resin complex or the second ion exchange resin complex.

14. 14. The method of claim 13, further comprising regenerating the first ion exchange resin or the second ion exchange resin to the sodium form or the potassium form.

15. 1. A method for producing a purified scandium (Sc) oxide product, comprising the steps of: (i) providing a purified Sc raffinate solution or a purified Sc eluate according to the method of claim 1; (ii) precipitating the purified Sc raffinate solution or the Sc eluate with oxalic acid to obtain a precipitated slurry having a solid fraction and a liquid fraction; (iii) separating the solid fraction of the precipitated slurry from the liquid fraction of the precipitated slurry to obtain a separated solid fraction; (iv) calcining the separated solid fraction to obtain the purified Sc oxide product; Including, The method of claim 1, wherein the purified Sc oxide product has at least one metal contaminant concentration of less than 500 ppm.

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