An extractant and a method for extracting and separating scandium.

Abstract

This invention provides an extractant and a method for extracting and separating scandium. The extractant has a stronger extraction capacity, and the extraction process does not require saponification, which effectively reduces the consumption of alkali during saponification and avoids the generation of saponification wastewater. The extractant has high selectivity for scandium, resulting in good separation of scandium from other elements (such as rare earth elements, transition metal elements, alkali metal elements, and alkaline earth metal elements), which is beneficial for shortening the scandium separation and purification process. The extractant provides a stable extraction phase during use, without emulsification or the formation of a third phase. The extractant is also easy to back-extract and regenerate, with a high back-extraction rate. This makes the process of extracting and separating scandium using the extractant economical, environmentally friendly, and highly efficient.

Description

Technical Field

[0001] This invention belongs to the field of rare earth hydrometallurgical technology, specifically relating to an extractant and a method for extracting and separating scandium. Background Technology

[0002] Scandium (Sc) is a widely used and highly valuable rare earth element. With the development of modern technology, the market demand for scandium is constantly increasing, and it is widely used in alloy materials, fuel cells, and novel luminescent materials. Although scandium's abundance in the Earth's crust is second only to lanthanum, cerium, neodymium, and yttrium, it is rare as a standalone mineral, usually occurring in trace amounts as an associated mineral with other metallic mineral resources (such as rare earth ores, laterite nickel ore, bauxite, and ilmenite). Therefore, the clean and efficient separation and purification of scandium from complex minerals or beneficiation byproducts has become a key challenge in existing technologies.

[0003] Currently, extraction processes are widely used in industry for the separation and purification of scandium. However, while commonly used organophosphate extractants (such as P507, P204, and C272) have good extraction effects on scandium, their selectivity remains limited. They often co-extract with rare earth elements, cobalt, nickel, and other metals, leading to complex subsequent separation processes and making it difficult to achieve efficient scandium purification. More importantly, phosphate extractants have an excessively strong complexing ability for scandium, making scandium difficult to back-extract and extractant regeneration. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides an extractant and a method for extracting and separating scandium. The extractant has a stronger extraction capacity, and the extraction process does not require saponification, which effectively reduces alkali consumption during saponification and avoids the generation of saponification wastewater. The extractant exhibits high selectivity for scandium, resulting in good separation of scandium from other elements (such as rare earth elements, transition metal elements, alkali metal elements, and alkaline earth metal elements), thus shortening the scandium separation and purification process. The extractant provides a stable extraction phase during use, without emulsification or the formation of a third phase. The extractant is also easy to back-extract and regenerate, with a high back-extraction rate. This makes the process of extracting and separating scandium using this extractant economical, environmentally friendly, and highly efficient.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] An extractant for the extraction and separation of scandium, the extractant having the structural formula shown in Formula I:

[0007]

[0008] In Equation I, R1 and R2 may be the same or different, and are independently selected from C4-C 18 Straight-chain or branched alkyl groups, C4-C 18 Straight-chain or branched alkenyl groups, C6-C18 Aryl groups.

[0009] According to an embodiment of the present invention, R1 and R2 may be the same or different, and are independently selected from C4-C. 12 Straight-chain or branched alkyl groups, C4-C 12 Straight-chain or branched alkenyl groups, C6-C 12 Aryl groups.

[0010] According to an embodiment of the present invention, R1 is selected from C6-C. 12 Straight-chain or branched alkyl groups, C6-C 12 R2 is a straight-chain or branched alkenyl group or a C6-C8 aryl group; R2 is selected from a C4-C8 straight-chain or branched alkyl group, a C4-C8 straight-chain or branched alkenyl group, or a C6-C8 aryl group.

[0011] According to an embodiment of the present invention, R1 is selected from C7-C 11 Straight-chain or branched alkyl groups, C7-C 11 R2 is a straight-chain or branched alkenyl group; R2 is selected from C4-C8 straight-chain or branched alkyl groups and C6-C8 aryl groups.

[0012] According to embodiments of the present invention, R1 is selected from n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, isoheptyl, isooctyl, isononyl, isodecyl, isoundecyl, n-heptenyl, n-octenyl, n-nonenyl, n-decenyl, or n-undecenyl.

[0013] According to an embodiment of the present invention, R2 is selected from isobutyl, tert-butyl, n-hexyl, n-octyl or benzyl.

[0014] According to embodiments of the present invention, the extractant is preferably at least one of isooctyl phenylalanine (EPA) and undecenoyl phenylalanine (UPA).

[0015] According to an embodiment of the present invention, the structural formula of the undecenoylphenylalanine is:

[0016]

[0017] According to an embodiment of the present invention, the structural formula of the isooctyl phenylalanine is:

[0018]

[0019] The present invention also provides the use of compounds of the structural formula shown in Formula I as extractants;

[0020]

[0021] In Equation I, R1 and R2 are defined as described above.

[0022] According to an embodiment of the present invention, the compound with the structure shown in Formula I is used as an extractant for the extraction and separation of scandium.

[0023] According to an embodiment of the present invention, the compound of the structure shown in Formula I is used as an extractant for extracting and separating scandium from at least one of rare earth elements, transition metal elements, alkali metal elements and alkaline earth metal elements.

[0024] According to embodiments of the present invention, the rare earth element includes at least one selected from yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0025] According to an embodiment of the present invention, the transition metal element includes at least one selected from nickel, cobalt, manganese, zinc, and aluminum.

[0026] According to an embodiment of the present invention, the alkali metal element includes at least one selected from lithium, sodium, and potassium.

[0027] According to an embodiment of the present invention, the alkaline earth metal element includes at least one of calcium, magnesium and barium.

[0028] According to embodiments of the present invention, the extractant can be obtained through commercial purchase or prepared by methods known in the art.

[0029] This invention provides a method for the extraction and purification of scandium, the method comprising the following steps:

[0030] a) Mix the extractant, diluent, and cosolvent having the structure shown in Formula I to obtain an organic phase;

[0031] b) The organic phase from step a) is mixed with an aqueous solution containing scandium and extracted to prepare a supported organic phase containing scandium and an aqueous raffinate containing other metal elements besides scandium.

[0032] According to an embodiment of the present invention, in step a), the diluent is selected from at least one of alkanes, aromatics, sulfonated kerosene, m-nitrotrifluorotoluene, thymol, menthol, octanol, petroleum ether, dodecanol, chloroform, and methyl isobutyl ketone. Exemplarily, the alkanes are selected from one or more of heptane, octane, hexadecane, aviation kerosene, and 260# solvent kerosene, and the aromatics are selected from one or more of benzene, toluene, and xylene.

[0033] According to an embodiment of the present invention, in step a), the co-solvent can increase the solubility of the extractant in the diluent. The co-solvent is selected from at least one of diisooctyl phosphite, tributylphosphine, tributyl phosphate, trioctyl phosphate, trioctylphosphine oxide, isooctyl alcohol, n-octyl alcohol, N,N-diethyllauramide, N,N-bis(1-methylheptyl)acetamide, N503, etc.

[0034] According to an embodiment of the present invention, in step a), the concentration of the extractant in the organic phase (the percentage of the amount of extractant in the total volume of the organic phase) is 0.05-1.5 mol / L, preferably 0.5-1.2 mol / L, for example 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, or 1.2 mol / L.

[0035] According to an embodiment of the present invention, in step a), the concentration of the co-solvent in the organic phase (the percentage of the volume of the co-solvent to the total volume of the organic phase) is 1-30 vol%, preferably 5-20 vol%, for example, 1 vol%, 2 vol%, 3 vol%, 4 vol%, 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, 10 vol%, 12 vol%, 15 vol%, 16 vol%, 18 vol%, 20 vol%, 22 vol%, 24 vol%, 25 vol%, 26 vol%, 28 vol%, or 30 vol%.

[0036] According to an embodiment of the present invention, in step a), the organic phase obtained after mixing the extractant, diluent and cosolvent does not need to undergo saponification treatment and can be directly used for the extraction and separation of yttrium and lanthanides.

[0037] According to an embodiment of the present invention, in step b), the source of the aqueous solution containing scandium is not particularly limited. For example, it can be various mineral leachates containing scandium, smelting by-product leachates, secondary resource leachates, etc., such as scandium-containing nickel-cobalt hydroxide leachates and iron-aluminum impurity removal slag leachates during the hydrometallurgical process of laterite nickel ore, Baotou rare earth tailings leachates, titanium dioxide waste acid solutions, red mud leachates, etc.

[0038] According to an embodiment of the present invention, in step b), the aqueous solution containing scandium may contain at least one of other rare earth elements, transition metal elements, alkali metal elements, and alkaline earth metal elements in addition to scandium.

[0039] According to an embodiment of the present invention, in step b), the concentration of scandium in the aqueous solution containing scandium is not specifically defined and can be within a concentration range known in the art; for example, the concentration of scandium in the aqueous solution containing scandium is 0.001 mol / L or higher.

[0040] According to an embodiment of the present invention, in step b), the concentration of other metal elements in the aqueous solution containing scandium is not specifically defined and can be within a concentration range known in the art; for example, the concentration of other metal elements in the aqueous solution containing scandium is 0.001 mol / L or higher.

[0041] According to an embodiment of the present invention, in step b), the pH value of the aqueous solution containing scandium is 1-6, preferably 3-5, for example, 4. Exemplarily, the pH value of the aqueous solution containing scandium is adjusted by adding an acid solution to the aqueous solution containing scandium.

[0042] According to an embodiment of the present invention, in step b), the equilibrium pH value of the extraction is 1-6, preferably 3-5, for example 4.

[0043] According to an embodiment of the present invention, in step b), the scandium-containing loaded organic phase obtained after extraction is a scandium-rich organic phase; the raffinate aqueous solution containing other metal elements besides scandium obtained after extraction is a scandium-poor aqueous phase containing other metal elements besides scandium.

[0044] According to an embodiment of the present invention, in step b), the extraction is a single-stage extraction or a multi-stage countercurrent extraction.

[0045] According to an embodiment of the present invention, the number of stages of the multi-stage countercurrent extraction is 2-10 stages, preferably 2-5 stages, for example, 3 stages or 4 stages.

[0046] According to an embodiment of the present invention, when multi-stage countercurrent extraction is used, the organic phase (the organic phase of step a) is added from the first stage, and the aqueous phase (an aqueous solution containing scandium) is added from the nth stage, where n is an integer between 2 and 10.

[0047] According to an embodiment of the present invention, in step b), during the extraction process, the volume ratio of the organic phase (the organic phase in step a) to the aqueous phase (an aqueous solution containing scandium) is 1:10-10:1, for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1 or 2:1.

[0048] According to an embodiment of the present invention, in step b), the extraction enables other metal elements besides scandium to remain in the aqueous phase, while scandium enters the organic phase, thus achieving the extraction, separation, and purification of scandium.

[0049] According to an embodiment of the present invention, the method further includes the following steps:

[0050] c) The scandium-containing organic phase obtained in step b) is mixed with detergent and washed to prepare a high-concentration scandium-containing organic phase.

[0051] According to an embodiment of the present invention, in step c), the washing can remove small amounts of impurity elements entrained or co-extracted in the scandium-containing organic phase obtained in step b), thereby obtaining an organic phase containing scandium with improved purity.

[0052] According to an embodiment of the present invention, in step c), the washing is a single-stage washing or a multi-stage countercurrent washing.

[0053] According to an embodiment of the present invention, the number of stages of the multi-stage countercurrent washing is 2-20 stages, preferably 2-5 stages, for example, 3 stages or 4 stages.

[0054] According to an embodiment of the present invention, when multi-stage countercurrent washing is used, the organic phase (organic phase containing scandium obtained in step b) is added from the first stage, and the aqueous phase (detergent) is added from the pth stage, where p is an integer between 2 and 20.

[0055] According to an embodiment of the present invention, in step c), during the washing process, the volume ratio of the organic phase (the scandium-containing organic phase obtained in step b) to the aqueous phase (detergent) is 10:1-1:10, preferably 5:1-1:1, for example 5:1, 4:1, 3:1, 2:1 or 1:1.

[0056] According to an embodiment of the present invention, in step c), the detergent is deionized water or a dilute acid solution, preferably an aqueous solution of hydrochloric acid or nitric acid with a concentration of 0.01-1 mol / L.

[0057] According to an embodiment of the present invention, the method further includes the following steps:

[0058] d) The high-concentration scandium-containing organic phase obtained in step c) is mixed with a back-extraction agent and back-extracted to prepare an organic phase and an aqueous solution containing scandium.

[0059] According to an embodiment of the present invention, in step d), the back-extraction enables the scandium element in the high-concentration scandium-containing organic phase obtained in step c) to enter the aqueous phase, thereby obtaining an organic phase containing the extractant and realizing the reuse of the extractant.

[0060] According to an embodiment of the present invention, in step d), the back-extraction is a single-stage back-extraction or a multi-stage countercurrent back-extraction.

[0061] According to an embodiment of the present invention, the number of stages of the multi-stage countercurrent back-extraction is 2-5 stages, preferably 2-3 stages.

[0062] According to an embodiment of the present invention, when multi-stage countercurrent back-extraction is used, the high-concentration scandium-containing organic phase obtained in step c is added from stage 1, and the aqueous phase (back-extraction agent) is added from stage q, where q is an integer between 2 and 5.

[0063] According to an embodiment of the present invention, in step d), during the back-extraction process, the volume ratio of the high-concentration scandium-containing organic phase obtained in step c to the aqueous phase (back-extraction agent) is 10:1-1:1, preferably 5:1-10:1, for example, 10:1, 9:1, 8:1, 7:1, 6:1 or 5:1. Studies have found that increasing the volume ratio of the high-concentration scandium-containing organic phase obtained in step c to the aqueous phase (back-extraction agent) during the back-extraction process can enrich the scandium element in the back-extraction solution, obtaining a high-concentration scandium-rich aqueous solution, which is beneficial for the subsequent preparation of scandium oxide and other products.

[0064] According to an embodiment of the present invention, in step d), the stripping agent is a dilute acid solution, preferably an aqueous solution of hydrochloric acid and / or nitric acid with a concentration of 1-3 mol / L.

[0065] According to an embodiment of the present invention, the method further includes the following steps:

[0066] e) Adjust the pH of the scandium-containing aqueous solution obtained in step d) to alkaline to cause scandium hydrolysis and precipitation, then calcine the precipitate to obtain scandium oxide; or...

[0067] The scandium-containing aqueous solution obtained in step d) is mixed with oxalic acid, sodium oxalate, or ammonium oxalate to precipitate, and the precipitate is then calcined to obtain scandium oxide; or,

[0068] The aqueous solution containing scandium obtained in step d) is subjected to crystallization and evaporation to obtain scandium chloride or scandium nitrate.

[0069] According to an embodiment of the present invention, in step e), the pH value is adjusted to alkaline (e.g., pH value is 7.5-9) using ammonia, ammonium bicarbonate, sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, etc.

[0070] According to an embodiment of the present invention, the method further includes the following steps:

[0071] f) Wash the organic phase obtained in step d) with deionized water, and return the washed organic phase to step b) to replace the organic phase obtained in step a), thereby realizing the recycling of the organic phase.

[0072] According to an embodiment of the present invention, in step f), the washing can remove residual acid from the organic phase obtained in step d), thereby obtaining an organic phase with higher purity and realizing multiple recycling of the organic phase while ensuring the extraction effect.

[0073] According to an embodiment of the present invention, in step f), the number of times the cycle is used is at least 15 times.

[0074] According to an embodiment of the present invention, in step f), during the washing process, the volume ratio of the organic phase (obtained in step d) to the aqueous phase (deionized water) is 10:1-1:1, preferably 5:1-1:1, for example 5:1, 4:1, 3:1, 2:1 or 1:1.

[0075] Beneficial effects:

[0076] This invention provides an extractant and a method for extracting and separating scandium. The extractant has a stronger extraction capacity, and the extraction process does not require saponification, which effectively reduces the consumption of alkali during saponification and avoids the generation of saponification wastewater. The extractant has high selectivity for scandium, resulting in good separation of scandium from other elements (such as rare earth elements, transition metal elements, alkali metal elements, and alkaline earth metal elements), which is beneficial for shortening the scandium separation and purification process. The extractant provides a stable extraction phase during use, without emulsification or the formation of a third phase. The extractant is also easy to back-extract and regenerate, with a high back-extraction rate. This makes the extractant economical, environmentally friendly, and highly efficient in the extraction and separation of scandium. Attached Figure Description

[0077] Figure 1 This is a diagram showing the separation effect of scandium with other rare earth elements in Example 1;

[0078] Figure 2 This is a diagram showing the separation effect of scandium with other rare earth elements in Example 2;

[0079] Figure 3 This is a diagram showing the separation effect of scandium with other rare earth elements in Example 3;

[0080] Figure 4 The image shows the extraction effect of different extractants on scandium in Example 4. Detailed Implementation

[0081] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0082] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0083] The extraction rate calculation formula involved in the following examples is: E% = (C i -C e ) / C e C i and C e The initial concentrations of the elements in the solution (C) are respectively. i ) and the concentration after extraction (C e );

[0084] The formula for calculating the allocation ratio (D) involved in the following embodiments is: D = C o / C e C o and C e These represent the concentrations of the elements in the organic phase after extraction (C0). o ) and the concentration in the aqueous phase (C e );

[0085] The separation coefficient (SF) involved in the following embodiments is calculated as follows: SF = D2 / D1, where D2 and D1 are the distribution ratio of scandium (D2) and the distribution ratio of other metal elements (D1), respectively.

[0086] Example 1

[0087] First, the extractant undecenoylphenylalanine and the co-solvent tributylphosphine were dissolved in sulfonated kerosene as a diluent to prepare the organic phase. The concentration of the extractant was 0.2 mol / L, and the concentration of the co-solvent was 20 vol%. The solution to be extracted was a mixed rare earth chloride solution, in which the molar concentration of scandium and other rare earth elements was 0.002 mol / L. The initial pH of the solution to be extracted was adjusted to 5.0. Single-stage extraction was performed on the organic phase and the aqueous phase at a volume ratio of 1:1. The extraction results are as follows: Figure 1 As shown, the extractant can effectively extract scandium and other rare earth elements under unsaponified conditions. The extraction rate of scandium is close to 100%, while among the other rare earth elements, samarium has the highest extraction rate, reaching 41.5%. Nevertheless, as shown in Table 1, the separation coefficient of scandium / samarium is still relatively high, reaching 1874, indicating that scandium has excellent separation performance from other rare earth elements.

[0088] Table 1 Separation coefficients of scandium with other rare earth elements

[0089] Separation coefficient 3738 2331 2045 2149 1874 2163 3420 3500 element Dy Ho Y Er Tm Yb Lu - Separation coefficient 4178 5288 10370 6093 6330 5988 6776 -

[0090] Example 2

[0091] The other operations are the same as in Example 1, except that the initial pH of the solution to be extracted is adjusted to 1.88.

[0092] Extraction experiment results as follows Figure 2 As shown, compared with the extraction results in Example 1, the extractant can still extract scandium well under the current conditions (the initial pH of the solution to be extracted is 1.88), with an extraction rate of 68.7%, while other rare earth elements are not extracted. The experimental results indicate that under suitable pH conditions, high selective separation of scandium from other rare earth elements can be achieved. Single-stage back-extraction of the extracted organic phase using 0.5 mol / L hydrochloric acid solution resulted in a scandium back-extraction rate of 98.5%, demonstrating that the extractant is easily regenerated through back-extraction.

[0093] Example 3

[0094] The other operations are the same as in Example 1, except that isooctylphenylalanine is chosen as the extractant.

[0095] Extraction experiment results as follows Figure 3 As shown, the isooctanoyl phenylalanine extractant can effectively extract scandium under unsaponified conditions, with an extraction rate of 82.1%, while other rare earth elements are not extracted. The separation performance of scandium from other rare earth elements is excellent. Using a 0.5 mol / L hydrochloric acid solution for single-stage back-extraction, the scandium back-extraction rate reaches 99%, proving that the isooctanoyl phenylalanine extractant is easy to back-extract and regenerate.

[0096] Example 4

[0097] The other operations are the same as in Example 1, except that the solution to be extracted contains scandium, sodium, lithium, calcium, magnesium, cobalt, nickel, and manganese, with a molar concentration of 0.002 mol / L for each element. The extraction results are shown in Table 2. After single-stage extraction, the extraction rate of scandium was 98.6%, while the extraction rates of the other elements were all less than 1%, demonstrating the high selectivity of the extractant for scandium.

[0098] Table 2 Extraction rates (%) of different elements

[0099] 98.6 0.01 0.00 0.03 0.00 0.06 0.03 0.02

[0100] Example 5

[0101] The practical application performance of the extractant was verified by countercurrent cascade extraction.

[0102] First, the extractant undecylenoyl phenylalanine and the co-solvent tributyl phosphate were dissolved in sulfonated kerosene as a diluent to prepare the organic phase. The concentration of the extractant was 0.2 mol / L, and the concentration of the co-solvent was 20 vol%. The solution to be extracted was a mixed rare earth chloride solution, in which the molar concentration of scandium and other rare earth elements was 0.004 mol / L. The initial pH of the solution to be extracted was adjusted to 4.5. A three-stage extraction-two-stage washing-one-stage back-extraction process was used for the extraction, purification, and back-extraction enrichment of scandium. During the extraction process, the volume ratio of organic phase:aqueous phase:wash solution was 1:8:0.5. The scandium-loaded organic phase obtained after extraction was back-extracted using 0.5 M HCl. During the back-extraction process, the volume ratio of organic phase:aqueous phase was 1:1. The content of each element in the resulting back-extraction solution is shown in Table 3. Through countercurrent cascade extraction, the concentration of Sc in the back-extraction solution can be enriched to about 6.5 g / L, with a purity of 99.4%. This effectively achieves short-process enrichment and purification of Sc, demonstrating the high selectivity and extraction capability of the extractant for Sc.

[0103] Table 3. Concentrations (mg / L) of various elements in the countercurrent cascade extraction backfill solution.

[0104] 1.40 - - 0.20 - 0.10 0.30 - Dy Ho Er Tm Yb Lu Y Sc - - - 0.10 0.10 0.10 0.20 6550.9

[0105] Example 6

[0106] Organic phases were prepared by dissolving neodecanoic acid (V10), naphthenic acid (NA), sec-octylphenoxyacetic acid (CA12), p-tert-octylphenoxyacetic acid (POAA), isooctanoylphenylalanine (EPA), and undecanoylphenylalanine (UPA) as extractants and tributylphosphine as a cosolvent in sulfonated kerosene as a diluent. The concentration of the extractants was 0.1 mol / L, and the concentration of the cosolvent was 20 vol%. The solution to be extracted was a mixed rare earth chloride solution, in which the molar concentration of scandium and other rare earth elements was 0.002 mol / L. The initial pH of the solution to be extracted was adjusted to 5.0. Single-stage extraction was performed on the organic phase and the aqueous phase at a volume ratio of 1:1. The extraction results are as follows. Figure 4 As shown in the figure. The results indicate that the extraction rates of scandium by the extractants neodecanoic acid (V10), naphthenic acid (NA), sec-octylphenoxyacetic acid (CA12), and p-tert-octylphenoxyacetic acid (POAA) are all below 10%, which proves that the extractants undecenoylphenylalanine and isooctanoylphenylalanine have superior scandium extraction and separation performance compared with the above-mentioned carboxylic acid extractants.

[0107] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for extracting and purifying scandium, the method comprising the following steps: a) The extractant, diluent, and cosolvent are mixed to obtain an organic phase; b) The organic phase from step a) is mixed with an aqueous solution containing scandium and extracted to prepare a supported organic phase containing scandium and an aqueous raffinate containing other metal elements besides scandium. The extractant has the structural formula shown in Formula I: Equation I In Equation I, R1 and R2 may be the same or different, and are independently selected from C4-C 18 Straight-chain or branched alkyl groups, C4-C 18 Straight-chain or branched alkenyl groups, C6-C 18 aryl; In step b), the pH value of the aqueous solution containing scandium is 3-6; In step b), the aqueous solution containing scandium contains at least one of other rare earth elements, transition metal elements, alkali metal elements, and alkaline earth metal elements in addition to scandium.

2. The method according to claim 1, wherein, R1 and R2 may be the same or different, and are independently selected from C4-C. 12 Straight-chain or branched alkyl groups, C4-C 12 Straight-chain or branched alkenyl groups, C6-C 12 Aryl groups.

3. The method according to claim 2, wherein, R1 is selected from C6-C 12 Straight-chain or branched alkyl groups, C6-C 12 R2 is selected from C4-C8 straight-chain or branched alkenyl groups, C6-C8 aryl groups; R2 is selected from C4-C8 straight-chain or branched alkyl groups, C4-C8 straight-chain or branched alkenyl groups, and C6-C8 aryl groups.

4. The method according to claim 3, wherein, R1 is selected from n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, isoheptyl, isooctyl, isononyl, isodecyl, isoundecyl, n-heptenyl, n-octenyl, n-nonenyl, n-decenyl, or n-undecenyl; R2 is selected from isobutyl, tert-butyl, n-hexyl, n-octyl, or benzyl.

5. The method according to claim 4, wherein, The extractant is at least one of isooctyl phenylalanine and undecenoyl phenylalanine.

6. The purification method according to any one of claims 1-5, wherein, In step a), the co-solvent is selected from at least one of diisooctyl phosphite, tributylphosphine, tributyl phosphate, trioctyl phosphate, trioctylphosphine oxide, isooctyl alcohol, n-octanol, N,N-diethyllauramide, and N,N-bis(1-methylheptyl)acetamide; And / or, in step a), the concentration of the extractant in the organic phase is 0.05-1.5 mol / L, and the concentration of the co-solvent in the organic phase is 1-30 vol.

7. The purification method according to any one of claims 1-5, wherein, In step b), the concentration of scandium in the aqueous solution containing scandium is 0.001 mol / L or higher; the concentration of other metal elements in the aqueous solution containing scandium is 0.001 mol / L or higher. And / or, in step b), the equilibrium pH of the extraction is 3-5; And / or, in step b), the extraction is a single-stage extraction or a multi-stage countercurrent extraction, wherein the number of stages in the multi-stage countercurrent extraction is 2-10; if multi-stage countercurrent extraction is used, the organic phase is added from the first stage and the aqueous phase is added from the nth stage, where n is an integer between 2 and 10. And / or, in step b), during the extraction process, the volume ratio of the organic phase to the aqueous phase is 1:10-10:

1.

8. The purification method according to any one of claims 1-5, wherein, The method further includes the following steps: c) The scandium-containing organic phase obtained in step b) is mixed with detergent and washed to prepare a high-concentration scandium-containing organic phase.

9. The purification method according to claim 8, wherein, In step c), the washing is either single-stage washing or multi-stage countercurrent washing, and the number of stages in multi-stage countercurrent washing is 2-20. If multi-stage countercurrent washing is used, the organic phase is added from stage 1 and the aqueous phase is added from stage p, where p is an integer between 2 and 20. And / or, in step c), during the washing process, the volume ratio of the organic phase to the aqueous phase is 10:1 to 1:10; And / or, in step c), the detergent is deionized water or a dilute acid solution.

10. The purification method according to claim 8, wherein, The method further includes the following steps: d) The high-concentration scandium-containing organic phase obtained in step c) is mixed with a back-extraction agent and back-extracted to prepare an organic phase and an aqueous solution containing scandium.

11. The purification method according to claim 10, wherein, In step d), the back-extraction is either single-stage back-extraction or multi-stage countercurrent back-extraction, and the number of stages in the multi-stage countercurrent back-extraction is 2-5. If multi-stage countercurrent back-extraction is used, the organic phase is added from the 1st stage and the aqueous phase is added from the qth stage, where q is an integer between 2 and 5.

12. The purification method according to claim 11, wherein, In step d), during the back-extraction process, the volume ratio of the organic phase to the aqueous phase is 10:1 to 1:1; And / or, in step d), the stripping agent is a dilute acid solution.

13. The purification method according to claim 10, wherein, The method further includes the following steps: e) Adjust the pH of the scandium-containing aqueous solution obtained in step d) to alkaline to cause scandium hydrolysis and precipitation, then calcine the precipitate to obtain scandium oxide; or... The scandium-containing aqueous solution obtained in step d) is mixed with oxalic acid, sodium oxalate, or ammonium oxalate to precipitate, and the precipitate is then calcined to obtain scandium oxide; or, The aqueous solution containing scandium obtained in step d) is subjected to crystallization and evaporation to obtain scandium chloride or scandium nitrate.

14. The purification method according to claim 10, wherein, The method further includes the following steps: f) Wash the organic phase obtained in step d) with deionized water, and return the washed organic phase to step b) to replace the organic phase obtained in step a), thereby realizing the recycling of the organic phase.

15. The purification method according to claim 14, wherein, In step f), the cycle is used at least 15 times; And / or, in step f), during the washing process, the volume ratio of the organic phase to the aqueous phase is 10:1 to 1:

1.

16. An extractant for extracting and separating scandium, wherein, The extractant has the structural formula shown in Formula I: Equation I In Equation I, R1 is selected from C4-C 18 Straight-chain or branched alkyl groups, C4-C 18 Straight-chain or branched alkenyl groups; R2 is selected from C6-C 18 Aryl groups.

17. The extractant according to claim 16, wherein, R1 is selected from C4-C 12 Straight-chain or branched alkyl groups, C4-C 12 Straight-chain or branched alkenyl groups; R2 is selected from C6-C 12 Aryl groups.

18. The extractant according to claim 17, wherein, R1 is selected from C6-C 12 Straight-chain or branched alkyl groups, C6-C 12 The straight-chain or branched alkenyl group; R2 is selected from C6-C8 aryl groups.

19. The extractant according to claim 18, wherein, R1 is selected from C7-C 11 Straight-chain or branched alkyl groups, C7-C 11 The straight-chain or branched alkenyl group; R2 is selected from C6-C8 aryl groups.

20. The extractant according to claim 19, wherein, R1 is selected from n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, isoheptyl, isooctyl, isononyl, isodecyl, isoundecyl, n-heptenyl, n-octenyl, n-nonenyl, n-decenyl, or n-undecenyl.

21. The extractant according to claim 20, wherein, The extractant is at least one of isooctyl phenylalanine and undecenoyl phenylalanine.

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