Synergistic extractant and preparation method thereof

Abstract

The invention relates to a synergistic extraction agent and a preparation method thereof, the extraction agent has good extraction efficiency and selectivity, and the problem that reverse extraction is difficult after an acidic phosphorus extraction agent is adopted for extraction can be solved; according to the preparation method, a phosphoric acid extraction agent reacts with amines to form a stable amine-phosphoric acid compound, so that the extraction characteristics of the phosphoric acid extraction agent and the amines are maintained, the application acidic range of the extraction agent is widened, and the pretreatment cost is reduced; a neutral phosphine compound is added, so that during subsequent extraction, a complex structure is regulated and controlled through steric hindrance, the neutral phosphine compound and the main extractant form a ternary complex, the selectivity of scandium is improved, co-extraction of aluminum and iron is inhibited, the hydrophobicity of the complex is enhanced, emulsification is reduced, and meanwhile the reverse extraction rate of scandium is increased; the problem that the scandium element is efficiently extracted through a follow-up extraction agent is effectively solved, and the problem that reverse extraction is difficult after extraction is avoided.

Description

Technical Field

[0001] This application relates to the field of rare earth metal separation technology, and in particular to a synergistic extractant and its preparation method. Background Technology

[0002] Rare earth metals have important applications in modern high-tech industries, such as aerospace, electronic devices, and catalysts. However, due to the similar chemical properties of rare earth elements, the separation and purification processes are complex and costly. Scandium, as a rare earth element, also requires particularly advanced separation and purification technologies.

[0003] In scandium separation and purification techniques, solvent extraction offers advantages such as high extraction efficiency and ease of large-scale operation, making it the most widely used technique for recovering trace scandium from solutions containing numerous impurity elements. Currently used extractants (such as (2-ethylhexyl)phosphoric acid (P204) or a synergistic extraction system of 2-ethylhexyl phosphate mono-2-ethylhexyl ester (P507) and tributyl phosphate (TBP)) exhibit high scandium extraction efficiency, but also high impurity co-extraction rates. Organic phase components may enter the aqueous phase, leading to emulsification in some systems, making washing and impurity removal difficult, and requiring stringent back-extraction conditions. This is because acids have poor back-extraction efficiency on the supported organic phase, thus limiting their industrial application.

[0004] A related technology provides a method for selectively extracting scandium from leachate based on microemulsion. This method uses P2O4, TBP, and alkali to prepare a microemulsion for scandium separation, followed by back-extraction with NaOH or Na2CO3 to separate the scandium-rich aqueous phase and the microemulsion phase. Although the scandium-iron separation coefficient of this co-extraction system can be increased to over 2000, this process is only suitable for feed solutions with similar Sc and Fe concentrations, and the back-extraction process still requires 3-5 mol / L NaOH solution, which places high demands on equipment and limits its application in actual industry. Patent CN115786744A discloses a method for co-extracting scandium from titanium dioxide waste acid and molten salt chlorination sediment. This method adds reduced iron powder before co-extraction to remove Fe... 3+ Reduced to Fe 2+ This reduces interference with the scandium separation process, but the process increases processing costs and the excess Fe... 2+ This also increases the complexity of the acid leaching solution components, affecting subsequent product preparation.

[0005] In view of this, it is necessary to design a synergistic extractant and its preparation method to solve the above problems. Summary of the Invention

[0006] This application provides a synergistic extractant and its preparation method to address the issue of considering both the extractant's ability to extract scandium and its ability to back-extract, thereby reducing separation costs.

[0007] In a first aspect, this application provides a synergistic extractant, which includes: a main extractant, a synergistic extractant, and a diluent;

[0008] The main extractant includes phosphate extractants and amine extractants;

[0009] The co-extractant includes neutral phosphine compounds.

[0010] In some embodiments, the volume ratio of the primary extractant to the co-extractant is (5:1) to (1:2); and / or,

[0011] In the synergistic extractant, the total volume percentage of the main extractant and the synergistic extractant is 10% to 30%, and the volume percentage of the diluent is 70% to 90%.

[0012] In some embodiments, the phosphoric acid extractant is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester; and / or,

[0013] The neutral phosphine compounds include one or more of dimethylheptyl methylphosphonate and tributylphosphine oxide; and / or

[0014] The amine extractant is a secondary primary amine; and / or...

[0015] The diluent is 260# kerosene.

[0016] In some embodiments, in the main extractant, the volume ratio of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine is (9:2) to (2:9).

[0017] In some embodiments, the volume ratio of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to the secondary primary amine in the main extractant is (7:4) to (3:8).

[0018] Secondly, this application provides a method for preparing the above-mentioned synergistic extractant, wherein the diluent is divided into diluent one and diluent two by volume ratio, and the preparation method includes the following steps:

[0019] The diluent and the amine extractant are mixed to obtain a mixture;

[0020] The phosphoric acid extractant is added dropwise to the mixture and reacted under first conditions to obtain a first intermediate extractant;

[0021] The neutral phosphine compound is added to the first intermediate extractant and reacted under second conditions to obtain the second intermediate extractant;

[0022] The second diluent is added to the second intermediate extractant and stirred until transparent to obtain the synergistic extractant for extracting scandium.

[0023] In some embodiments, the phosphate extractant is added to the mixture at a rate of 1 mL / min to 3 mL / min.

[0024] In some embodiments, the volume ratio of the diluent to the secondary amine is (10–30):(5–10); and / or, the volume ratio of the phosphate extractant to the amine extractant is (9:2)–(2:9); and / or,

[0025] The total volume ratio of the phosphoric acid extractant and the amine extractant to the neutral phosphine compound is (5:1) to (1:2); and / or,

[0026] In the synergistic extractant, the volume percentage of diluent one is 10% to 30%; the volume percentage of diluent two is 40% to 80%; and the volume percentage of the diluent in the synergistic extractant is 70% to 90%.

[0027] In some embodiments, the first condition satisfies the following requirement: stirring at 400 rpm for 30 min to 60 min at a temperature of 35°C to 45°C.

[0028] In some embodiments, the second condition satisfies the following requirement: stirring at 400 rpm for 10 min to 30 min.

[0029] The technical solutions provided in this application have the following advantages compared with the prior art:

[0030] 1. The synergistic extractant provided in this application adopts a synergistic extraction system of phosphoric acid extractant and amine extractant. It improves the extraction efficiency of scandium through a dual mechanism of cation exchange and amine coordination. At the same time, a neutral phosphine compound is used to form a neutral coordination layer with scandium to suppress water molecule competition. This ensures that the prepared synergistic extractant has good extraction efficiency and selectivity, and avoids the problem of back-extraction difficulties that occur after extraction with acidic phosphine agents, thereby reducing separation costs.

[0031] 2. The synergistic extractant preparation method provided in this application first mixes a phosphate extractant and an amine extractant, maintaining the extraction characteristics of both while broadening the application pH range of the extractant. The extractant prepared by this method achieves a hydrogen ion concentration of 10 during extraction. -3.5 moL / L~10 0.5 The concentration is reduced to mol / L, thus lowering pretreatment costs; then, neutral phosphine compounds are added to react with Sc during subsequent extraction.3+ A neutral coordination layer is formed, inhibiting competition for water molecules. This effectively solves the problem of efficient extraction of scandium by subsequent extractants and avoids the difficulties of back-extraction after extraction. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] Various embodiments of this application may exist in the form of a range. It should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application. Therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this application, it means including any referenced number (fraction or integer) within the indicated range. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application can be purchased commercially or prepared by existing methods. In addition, in this application, the terms "comprising," "including," etc., mean "including but not limited to." In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this application, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0034] This application provides a synergistic extractant, which includes: a main extractant, a co-extractant, and a diluent;

[0035] The main extractant includes phosphate extractants and amine extractants;

[0036] The co-extractant includes neutral phosphine compounds.

[0037] Thus, by employing a synergistic extraction system using phosphate and amine extractants, the extraction efficiency of scandium is improved through a dual mechanism of cation exchange and amine coordination. Simultaneously, a neutral phosphine compound is used to form a neutral coordination layer with scandium, suppressing competition for water molecules. This ensures that the prepared synergistic extractant has good extraction efficiency and selectivity, and also avoids the difficulties in back-extraction that occur after extraction with acidic phosphate extractants, thereby reducing separation costs.

[0038] As an optional implementation, in this embodiment of the application, the volume ratio of the main extractant to the co-extractant is (5:1) to (1:2);

[0039] In the synergistic extractant, the total volume percentage of the main extractant and the synergistic extractant is 10% to 30%, and the volume percentage of the diluent is 70% to 90%.

[0040] This approach improves the solubility of the co-extractant, facilitating the full extraction of scandium and reducing the formation of the third phase. On the other hand, it avoids excessive dilution or concentration, thus preventing a decrease in the scandium extraction rate or an increase in the co-extraction of other metal impurities.

[0041] As an optional implementation, in this embodiment of the application, the phosphoric acid extractant includes 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507).

[0042] As an optional implementation, in the embodiments of this application, the neutral phosphine compound includes one or more of dimethylheptyl methylphosphonate (P350) and tributylphosphine oxide.

[0043] Thus, during extraction, P350 or tributylphosphine oxide forms a neutral coordination layer with scandium to suppress competition for water molecules.

[0044] As an optional implementation, in this embodiment of the application, the amine extractant is a secondary primary amine (N1923).

[0045] As an optional implementation, in this embodiment of the application, the diluent is 260# kerosene.

[0046] Thus, 260# kerosene, as an inert diluent, can reduce the viscosity of the extractant and improve its phase separation performance.

[0047] As an optional implementation, in the embodiments of this application, the volume ratio of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine in the main extractant can be selected as (9:2) to (2:9).

[0048] As an optional implementation, in this embodiment of the application, in order to ensure better effect of the synergistic extractant, the volume ratio of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine in the main extractant can be selected as (7:4) to (3:8).

[0049] It is easy to understand that in the extraction system, P507 undergoes proton H... + The dissociation of P507 produces anions that react with Sc in the aqueous phase. 3+ Through coordination bonds, neutral complexes are formed, thereby enabling Sc to bind. 3+ The extractant is transferred from the aqueous phase to the organic phase (the organic phase in which it dissolves). In acidic systems, the amine groups of amine extractants protonate to form cations, which can react with Sc in the aqueous phase. 3+ The anionic complexes of N1923 bind together via electrostatic attraction to form ion-paired compounds. The protonated cation of N1923 binds to Sc3. - The anionic complexes bind Sc through coordination (electrostatic attraction). 3+ Introducing scandium into the organic phase; the partitioning of scandium by P507 and N1923 can be improved by 3 to 5 times compared with single extractants, thereby further enhancing the extraction effect of scandium ions. P507's H... + The anion coordination of exchange with N1923 forms a stable mixed complex through "double coordination," while the co-extractant regulates the complex structure through steric hindrance and forms a ternary complex with P507 and N1923, improving the selectivity of scandium, inhibiting the co-extraction of impurity elements such as aluminum and iron, enhancing the hydrophobicity of the complex, reducing emulsification, and increasing the scandium back-extraction rate. This avoids emulsification caused by disordered aggregation and reduces the stability of the complex to facilitate back-extraction. The three work together to ultimately achieve efficient and stable separation of scandium.

[0050] Based on a general inventive concept, this application provides a method for preparing the above-mentioned synergistic extractant, wherein the diluent is divided into diluent one and diluent two by volume ratio, and the diluent is 260# kerosene. The preparation method includes the following steps:

[0051] Step S1: Mix the diluent and the amine extractant to obtain a mixture; the amine extractant is a secondary primary amine (N1923);

[0052] Step S2: The phosphoric acid extractant is added dropwise to the mixture and reacted under the first condition to obtain the first intermediate extractant; the phosphoric acid extractant is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507);

[0053] Step S3: Add the neutral phosphine compound to the first intermediate extractant and react under the second conditions to obtain the second intermediate extractant; the neutral phosphine compound includes one or more of dimethylheptyl methylphosphonate (P350) and tributylphosphine oxide;

[0054] Step S4: Add the second diluent to the second intermediate extractant and stir until transparent to obtain the synergistic extractant for extracting scandium.

[0055] Although phosphate extractants exhibit high selectivity for trivalent rare earth elements (such as scandium), they require a low pH environment (pH < 2). Given that amine extractants can be used to extract metals under neutral conditions by forming amine salt complexes, this method experimentally mixes phosphate and amine extractants to maintain their extraction properties while broadening the applicable pH range of the extractants. The extractant prepared using this method achieves a hydrogen ion concentration of 10 during extraction. -3.5 moL / L~10 0.5 This reduces pretreatment costs by using mol / L. Adding neutral phosphine compounds further ensures that they react with Sc during subsequent extraction. 3+ A neutral coordination layer is formed, inhibiting competition for water molecules. The diluent acts as an inert diluent, reducing the viscosity of the extractant and improving phase separation performance. The reason for adding the diluent in batches is twofold: the first batch is to dilute the secondary carbon amine, allowing it to react better with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester; the second batch is to dilute and dissolve the second intermediate extractant, thereby improving the extraction efficiency of scandium and reducing the co-extraction of other metal impurities. This effectively ensures efficient extraction of scandium by subsequent extractants and avoids the difficulties of back-extraction after extraction.

[0056] As an optional implementation, in this embodiment of the application, the rate at which the phosphate extractant is added to the mixture is 1 mL / min to 3 mL / min.

[0057] In this way, on the one hand, it can achieve gradual protonation: the amine (R-NH2) slowly accepts a proton from the phosphate (HA) to form R-NH3. + ·A - Ion pairs help prevent localized over-acidity from causing amine degradation.

[0058] On the other hand, it can avoid side reactions caused by excessively high local concentrations of phosphoric acid, and the hydrogen bonds are controllable: hydrogen bonds between P=O and NH are gradually formed, reducing by-products (such as phosphate diesters or amine oxides).

[0059] It is worth noting that if the rate at which the phosphoric acid extractant is added to the mixture is greater than 3 mL / min, the local pH will drop sharply due to the excessively rapid dropping speed, causing side reactions. If the rate at which the phosphoric acid extractant is added to the mixture is less than 1 mL / min, the interface will be slow due to the excessively slow dropping speed, resulting in low mass transfer efficiency.

[0060] As an optional implementation, in this embodiment of the application, the volume ratio of the diluent and the secondary amine is (10-30):(5-10);

[0061] The volume ratio of the phosphoric acid extractant to the amine extractant is (9:2) to (2:9);

[0062] The total volume ratio of the phosphoric acid extractant and the amine extractant to the volume ratio of the neutral phosphine compound is (5:1) to (1:2);

[0063] In the synergistic extractant, the volume percentage of diluent one is 10% to 30%; the volume percentage of diluent two is 40% to 80%; and the volume percentage of the diluent in the synergistic extractant is 70% to 90%.

[0064] Thus, diluent one is used to dilute and dissolve the secondary carbon primary amine, which helps to improve the reaction efficiency of the amine with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester; diluent two is used to dilute and dissolve the second intermediate extractant to improve the extraction efficiency of scandium, while reducing the co-extraction of other metal impurities.

[0065] As an optional implementation, in this embodiment of the application, the first condition satisfies the following requirement: stirring at a temperature of 35℃ to 45℃ for 30 min to 60 min at a speed of 400 rpm.

[0066] This matching of stirring speed and dropping rate promotes mass transfer, balances reaction rate and stability, and ensures stable hydrogen bonds and high mass transfer rate. It is worth noting that below this temperature, mass transfer is slow and reaction efficiency is low; above 45°C, it may lead to amine decomposition (such as oxidation or dealkylation).

[0067] As an optional implementation, in this embodiment of the application, the second condition satisfies the following requirement: stirring at a speed of 400 rpm for 10 min to 30 min.

[0068] In this way, the diffusion layer at the liquid-liquid interface can be broken by shear force, allowing the components to be distributed quickly and evenly, increasing the frequency of molecular collisions, and accelerating key reactions.

[0069] Based on a general inventive concept, embodiments of this application provide an application of a synergistic extractant, wherein the synergistic extractant is a scandium extractant.

[0070] This extractant can achieve an extraction rate of over 99% when extracting scandium from subsequent scandium-containing solutions (and even trace scandium-containing solutions), with an extraction rate of less than 8% for iron, a scandium back-extraction rate of over 85%, and a titanium back-extraction rate of less than 10%.

[0071] Based on a general inventive concept, embodiments of this application provide a method for applying the above-mentioned synergistic extractant, wherein the method of using the synergistic extractant as a scandium extractant includes the following steps:

[0072] Step Sa: Provide a scandium-containing solution, add a reducing agent to the scandium-containing solution to obtain a first mixed solution; the concentration of scandium in the scandium-containing solution is ≤0.03 g / L; the concentration of hydrogen ions in the scandium-containing solution is 10. -3.5 moL / L~10 0.5 moL / L;

[0073] Step Sb: Add the synergistic extractant to the first mixed solution and perform countercurrent extraction to separate the first aqueous phase and the first organic phase;

[0074] Step Sc: Add an acidic back-extraction agent to the first organic phase for countercurrent back-extraction to separate a second organic phase and a second aqueous phase. The second aqueous phase is a collected scandium-rich solution. The concentration of scandium in the scandium-rich solution is 0.67 g / L to 0.70 g / L. The scandium back-extraction rate can be calculated based on the concentration of scandium in the scandium-rich solution.

[0075] Understandably, this method first effectively suppresses other easily oxidized interfering ions in the solution (such as Fe) by adding a reducing agent. 3+ To mitigate the impact of factors such as (etc.), and avoid competition with scandium ions for extraction sites, thereby reducing the incorporation of impurities into the organic phase, a specially formulated synergistic extractant is added. Leveraging its combined effect and employing countercurrent extraction, the extraction efficiency of scandium ions is significantly improved through multiple countercurrent contacts between the organic and aqueous phases, reducing scandium residue in the aqueous phase. Finally, an acidic back-extraction agent is added, combined with countercurrent back-extraction technology, to efficiently transfer scandium from the organic phase to the aqueous phase, ensuring complete back-extraction and ultimately achieving the acquisition of a scandium-rich solution, thus guaranteeing the overall recovery rate.

[0076] Furthermore, this method has a wide range of hydrogen ion concentrations applicable to scandium-containing solutions (10). -3.5 mol / L~10 0.5The concentration of scandium in the solution is approximately mol / L (pH range of -0.5 to 3.5), indicating that this method has low requirements for the acidity of the feed solution and does not require strict pH adjustment to a narrow range. This simplifies the pretreatment process and reduces dependence on the stability of the feed solution. The resulting scandium-rich solution has a significantly increased scandium concentration, which can be directly used as a raw material for the subsequent preparation of high-purity scandium compounds, reducing energy consumption and cost in subsequent concentration steps and improving the overall economic efficiency of the process.

[0077] The extraction rate of scandium in scandium-containing solutions (especially those containing trace amounts of scandium) reaches over 99%, the extraction rate of iron can be controlled below 8%, the back-extraction rate of scandium can reach over 85%, and the back-extraction rate of titanium can be controlled below 10%.

[0078] In summary, this method, through the combination of synergistic extraction and countercurrent operation, ensures high selectivity and high recovery rate of scandium while taking into account operational flexibility and industrial feasibility, providing a practical solution for the efficient extraction of high-purity scandium from low-grade or complex systems.

[0079] As an optional implementation, in this embodiment of the application, the reducing agent includes one of ascorbic acid and sodium sulfite;

[0080] In the first mixed solution, the concentration of the reducing agent is 0.05 mol / L to 0.5 mol / L.

[0081] Thus, by adding a reducing agent, the Fe in the scandium-containing solution can be removed. 3+ Reduced to Fe 2+ Ti 4+ Transformed into a low-valence state (such as Ti) 3+ This reduces the affinity of these impurity elements for the extractant, decreases co-extraction, improves phase separation and emulsification, and increases separation efficiency. On the other hand, it maintains the reducibility of the system, ensuring that scandium always exists in its trivalent state, avoiding the formation of difficult-to-extract heteropolyacids or other complexes. Simultaneously, the addition of a reducing agent can optimize the synergistic extraction system—that is, when N1923 and P507 are used synergistically, N1923's effect on Sc... 3+ P507 exhibits high selectivity, demonstrating strong extraction capabilities for trivalent metals, while reducing agents can inhibit the extraction of Fe by P507. 3+ Extraction of N1923 can better leverage its selective advantage.

[0082] As an optional implementation, in this embodiment of the application, the volume ratio of the scandium-containing solution to the synergistic extractant is (5-40):1.

[0083] As an optional implementation, in this embodiment of the application, the volume ratio of the acidic back-extraction agent to the first organic phase is 1:(1-6);

[0084] The acidic back-extraction agent comprises an aqueous solution of an inorganic acid containing a salting-out agent; the salting-out agent in the acidic back-extraction agent comprises sodium fluoride, and the inorganic acid comprises sulfuric acid and hydrochloric acid.

[0085] As an optional implementation, in the embodiments of this application, the concentration of the salting-out agent in the acidic stripping agent is 0.05 mol / L to 0.5 mol / L, the concentration of the sulfuric acid is 1.5 mol / L to 2.5 mol / L, and the concentration of the hydrochloric acid is 0.1 mol / L to 0.5 mol / L.

[0086] Thus, the back-extraction rate can be further improved by introducing a salting-out agent.

[0087] As an optional implementation, in this embodiment of the application, the second organic phase can be regenerated and returned to step Sa as a co-extractant for recycling.

[0088] In this way, a "closed-loop cycle" of the extractant can be achieved, avoiding the loss of valuable reagents with waste liquid, improving the overall resource conversion rate of the process, and conforming to the industrial trend of sustainable development.

[0089] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0090] Examples 1-5

[0091] Examples 1-5 provide a method for preparing a synergistic extractant, wherein 260# kerosene is divided into 260# kerosene one and 260# kerosene two by volume ratio, and the preparation method includes the following steps:

[0092] S1. Add 260# kerosene and N1923 to a round-bottom flask, mix, and obtain a mixture;

[0093] The volume ratio of the 260# kerosene to N1923 is (10-30):(5-10);

[0094] S2. P507 is added dropwise to the mixture at a rate of 1.5 mL / min, and the mixture is stirred at 400 rpm for 40 min at a temperature of 40°C to carry out the reaction and obtain the first intermediate extractant.

[0095] The volume ratio of P507 to N1923 is (9:2) to (2:9);

[0096] S3. Add P350 to the first intermediate extractant and stir at 400 rpm for 15 min to react and obtain the second intermediate extractant.

[0097] The ratio of the total volume of P507 and N1923 to the volume of P350 is (5:1) to (1:2);

[0098] S4. Add 260# kerosene II to the second intermediate extractant and stir until transparent to obtain the synergistic extractant used for extracting scandium;

[0099] In the synergistic extractant, the volume percentage of 260# kerosene one is 20%; the volume percentage of 260# kerosene two is 66%.

[0100] The specific process parameters are shown in Table 1.

[0101] Comparative Examples 1-4

[0102] Comparative Examples 1-4 each provide a method for preparing a synergistic extractant, differing from Example 1 in the volume ratio of P507 and N1923. Specific processes are shown in Table 1. The remaining steps are consistent with Example 1 and will not be repeated here.

[0103] Examples 6-7 and Comparative Examples 5-6

[0104] Examples 6-7 and Comparative Examples 5-6 each provide a method for preparing a synergistic extractant. The difference from Example 5 lies in the ratio of the total volume of P507 and N1923 to the volume of P350. The specific process is shown in Table 1. The remaining steps are the same as in Example 1 and will not be repeated here.

[0105] Table 1. Process parameters for Examples 1-7 and Comparative Examples 1-6

[0106]

[0107] The synergistic extractants prepared in Examples 1-7 and Comparative Examples 1-6 were used to perform extraction experiments on scandium, specifically including the following steps:

[0108] Sa, a scandium-containing solution is provided, and a reducing agent is added to the scandium-containing solution to obtain a first mixed solution; the concentration of scandium in the scandium-containing solution is 0.02 g / L; the concentration of hydrogen ions in the scandium-containing solution is 10. -2 moL / L;

[0109] The reducing agent is ascorbic acid;

[0110] In the first mixed solution, the concentration of ascorbic acid is 0.1 mol / L;

[0111] Sb, the synergistic extractant is added to the first mixed solution for countercurrent extraction to separate the first aqueous phase and the first organic phase; the volume ratio of the scandium-containing solution to the synergistic extractant is 25:1 (i.e., the extraction A / O ratio is 25:1);

[0112] Sc. An acidic back-extraction agent is added to the first organic phase for countercurrent back-extraction to separate the second organic phase and the second aqueous phase; the second aqueous phase is the collected scandium-rich solution.

[0113] The volume ratio of the acidic back-extraction agent to the first organic phase is 1:4 (i.e., the back-extraction A / O ratio is 1:4); the acidic back-extraction agent is an aqueous solution of an inorganic acid containing a salting-out agent; the salting-out agent in the acidic back-extraction agent is sodium fluoride with a concentration of 0.1 mol / L, and the inorganic acid is sulfuric acid with a concentration of 2 mol / L and hydrochloric acid with a concentration of 0.5 mol / L.

[0114] The extraction results are shown in Table 2.

[0115] Table 2 shows the results of scandium extraction using various extractants in Examples 1-7 and Comparative Examples 1-7.

[0116] Scandium extraction rate (%) Iron extraction rate (%) Scandium back-extraction rate (%) Titanium back-extraction rate (%) Example 1 99 7.88 85.24 9.87 Example 2 99 7.45 86.11 9.67 Example 3 99 7.23 86.54 9.24 Example 4 99 7.05 87.24 9.02 Example 5 99.57 6.8 87.5 8.85 Comparative Example 1 99 10.79 80.14 9.98 Comparative Example 2 96.82 8.23 82.05 9.87 Comparative Example 3 99 15.76 75.02 9.03 Comparative Example 4 86.92 6.83 88.11 10.0 Example 6 99 7.79 86.99 9.54 Example 7 99.04 6.89 87.88 9.12 Comparative Example 5 92.91 9.19 80.88 14.89 Comparative Example 6 99 15.41 77.85 11.39 Comparative Example 7 97.67 9.83 85.58 10.66

[0117] As shown in Table 2, the synergistic extractants provided in Examples 1-7 achieve a scandium extraction rate of over 99% while maintaining a scandium back-extraction rate of over 85.24%. Comparing Examples 1-5, it is evident that as the ratio of P507 to N1923 (within the range of (9:2) to (2:9)) decreases, the scandium extraction rate initially increases and then decreases, while the scandium back-extraction rate initially increases and then decreases, followed by a period of increase. Comparative Examples 1-4 show that when the P507 to N1923 ratio is outside the range of (9:2) to (2:9), the prepared extractants cannot guarantee the scandium extraction rate and scandium back-extraction rate, nor can they guarantee the extraction of scandium from other impurity elements such as iron and titanium. For example, the higher the extraction or back-extraction rate of iron and titanium, the greater the interference with subsequent scandium purification.

[0118] Comparative Examples 5-7 show that as the ratio of the total volume of P507 and N1923 to the volume of P350 (within the range of (5:1) to (1:2)) continuously decreases, the extraction efficiency of the extractant for scandium first increases and then decreases, while the back-extraction rate of the extractant for scandium increases. Comparative Examples 5-6 show that when the ratio of the total volume of P507 and N1923 to the volume of P350 is not within the range of (5:1) to (1:2), the prepared extractant also cannot simultaneously guarantee both the extraction efficiency and the back-extraction rate of scandium.

[0119] Comparative Example 7

[0120] Comparative Example 7 also provides a method for preparing a synergistic extractant, which differs from Example 5 in that the rate at which P507 is added to the mixture in step S2 is different. In Comparative Example 7, P507 is added to the mixture at a rate of 4 mL / min. The remaining steps are the same as in Example 5 and will not be repeated here.

[0121] Furthermore, as shown in Comparative Examples 3 and 4, if neither N1923 nor P507 is added during the preparation of the extractant, the extraction rate of scandium using this extractant is below 90%, or the back-extraction rate is below 76%. Additionally, combined with Comparative Examples 1 to 7, it can be demonstrated that the extractant provided by this invention has a good extraction effect on scandium, especially on solutions containing trace amounts of scandium, based on the combined effect of the components in the extractant and its preparation process.

[0122] Examples 8-10

[0123] The difference between Examples 8-10 and Example 5 lies in the application method of the prepared synergistic extractant as a scandium extractant, but the extractant used is the same (including the process and related parameters). The difference between Examples 8-10 and Example 5 is that the volume ratio of the scandium-containing solution to the synergistic extractant is different (i.e., the extraction A / O ratio is different), and the specific parameters are shown in Table 3. The remaining steps and parameters are consistent with Example 5 and will not be repeated here.

[0124] Comparative Examples 8-9

[0125] The difference between Comparative Examples 8-9 and Example 5 lies in the application method of the prepared synergistic extractant as a scandium extractant, but the extractant used is the same (including the process and related parameters). The difference between Examples 8-10 and Example 5 is that the volume ratio of the scandium-containing solution to the synergistic extractant is different (i.e., the extraction A / O ratio is different), and the specific parameters are shown in Table 3. The remaining steps and parameters are consistent with Example 5 and will not be repeated here.

[0126] Example 11

[0127] The difference between Example 11 and Example 9 lies in the application method of the prepared synergistic extractant as a scandium extractant, but the extractant used is the same (including the process and related parameters). The difference between Example 11 and Example 9 is that the type of reducing agent used is different; specific parameters are shown in Table 3. The remaining steps and parameters are consistent with Example 5 and will not be repeated here.

[0128] Table 3. Process parameters for Examples 8-11 and Comparative Examples 8-9

[0129]

[0130] Note: "-" indicates that the reagent was not added.

[0131] The extraction results of Examples 8-11 and Comparative Examples 8-9 are shown in Table 4.

[0132] Table 4 shows the results of scandium extraction using various extractants in Examples 8-11 and Comparative Examples 8-9.

[0133] Scandium extraction rate (%) Iron extraction rate (%) Scandium back-extraction rate (%) Titanium back-extraction rate (%) Example 8 99.55 9.82 86.74 7.93 Example 9 99.57 6.8 87.5 8.85 Example 10 99.09 6.27 86.88 8.68 Comparative Example 8 99.86 13.87 84.80 10.15 Comparative Example 9 94.35 9.64 82.55 9.67 Example 11 99.55 6.88 87.45 8.75

[0134] As shown in Table 4, the extraction methods provided in Examples 8-11 can achieve an extraction rate of over 99% for scandium, a back-extraction rate of over 86% for scandium, an extraction rate of iron below 10%, and a back-extraction rate of titanium below 10%. However, in Comparative Examples 8-9, even when using the optimal extractant from Example 5, the extraction rate or back-extraction rate of scandium decreases to varying degrees when the volume ratio of the scandium-containing solution to the synergistic extractant (i.e., extraction A / O) is not within the range of (5-40):1. Moreover, the extraction rate of iron reaches over 13%, making it impossible to simultaneously guarantee both the extraction rate and the back-extraction rate of scandium.

[0135] This demonstrates that the method of using the synergistic extractant as a scandium extractant provided by the present invention significantly improves the extraction selectivity of scandium while also increasing the back-extraction efficiency of scandium.

[0136] Examples 12-14

[0137] The difference between Examples 12-14 and Example 5 lies in the application method of the prepared synergistic extractant as a scandium extractant, but the extractant used is the same (including the process and related parameters). The difference between Examples 12-14 and Example 5 is that the volume ratio of the acidic back-extractant to the first organic phase is different during countercurrent back-extraction (i.e., the A / O ratio is different), and the specific parameters are shown in Table 5. The remaining steps and parameters are consistent with Example 5 and will not be repeated here.

[0138] Comparative Examples 10-11

[0139] The difference between Comparative Examples 10-11 and Example 5 lies in the application method of the prepared synergistic extractant as a scandium extractant, but the extractant used is the same (including the process and related parameters). The difference between Comparative Examples 10-11 and Example 5 is that the volume ratio of the acidic back-extractant to the first organic phase is different during countercurrent back-extraction (i.e., the A / O ratio is different), and the specific parameters are shown in Table 5. The remaining steps and parameters are consistent with Example 5 and will not be repeated here.

[0140] Comparative Example 12

[0141] The difference between Comparative Example 12 and Example 12 lies in the application method of the prepared synergistic extractant as a scandium extractant, but the extractant used is the same (including the process and related parameters). The difference between Comparative Example 12 and Example 12 is that sodium fluoride was not added to the acidic back-extraction agent; specific parameters are shown in Table 5. The remaining steps and parameters are consistent with Example 12 and will not be repeated here.

[0142] Table 5. Process parameters for Examples 12-14 and Comparative Examples 10-12

[0143] Sodium fluoride (mol / L) Stripping A / O Sulfuric acid (mol / L) Hydrochloric acid (mol / L) Example 12 0.1 1:4 2 0.5 Example 13 0.1 1:1 2 0.5 Example 14 0.1 1:6 2 0.5 Comparative Example 10 0.1 1:0.5 2 0.5 Comparative Example 11 0.1 1:7 2 0.5 Comparative Example 12 - 1:4 2 0.5

[0144] Note: "-" indicates that the reagent was not added.

[0145] The extraction results of Examples 12-14 and Comparative Examples 10-12 are shown in Table 6.

[0146] Table 6 shows the results of scandium extraction using various extractants in Examples 12-14 and Comparative Examples 10-12.

[0147] Scandium extraction rate (%) Iron extraction rate (%) Scandium back-extraction rate (%) Titanium back-extraction rate (%) Example 12 99.57 6.8 87.5 8.85 Example 13 99.60 7.24 85.85 9.84 Example 14 99.48 7.06 86.85 9.39 Comparative Example 10 99.58 7.53 79.84 15.65 Comparative Example 11 99.49 7.41 83.12 11.34 Comparative Example 12 99.61 7.39 83.90 10.19

[0148] As shown in Table 6, the extraction methods provided in Examples 12-14 can achieve an extraction rate of over 99% for scandium, an extraction rate of less than 8% for iron, a back-extraction rate of over 85% for scandium, and a back-extraction rate of less than 10% for titanium. However, in Comparative Examples 10-11, even when using the optimal extractant from Example 5, the back-extraction rate of scandium decreases to varying degrees whenever the volume ratio of the acidic back-extractant to the first organic phase is not within the range of 1:(1-6) during countercurrent back-extraction, and the back-extraction rate of titanium reaches over 10%. Therefore, it is also impossible to simultaneously guarantee both the extraction rate and the back-extraction rate of scandium.

[0149] Furthermore, in Comparative Example 12, the absence of sodium fluoride in the acidic back-extraction agent led to a decrease in the scandium back-extraction rate, while the titanium back-extraction rate reached over 10%, making it impossible to simultaneously guarantee both the scandium extraction rate and the scandium back-extraction rate.

[0150] This demonstrates that the method provided by the present invention, using a synergistic extractant as a scandium extractant, significantly improves both the extraction selectivity and the back-extraction efficiency of scandium. Moreover, achieving this effect is based on the results of various processes and parameters, none of which can be omitted.

[0151] In summary, this invention provides a synergistic extractant that employs a synergistic extraction system combining phosphoric acid extractants and amine extractants. It enhances the extraction efficiency of scandium through a dual mechanism of cation exchange and amine coordination. Simultaneously, a neutral phosphine compound forms a neutral coordination layer with scandium, suppressing competition for water molecules. This ensures the prepared synergistic extractant possesses good extraction efficiency and selectivity, while avoiding the difficulties in back-extraction that occur after extraction with acidic phosphoric acid extractants, thus reducing separation costs.

[0152] This invention provides a method for preparing a synergistic extractant. By first reacting a phosphoric acid extractant and an amine extractant to form a stable amine-phosphoric acid complex, the extraction properties of both are maintained while the application pH range of the extractant is broadened. The extractant prepared by this method achieves a hydrogen ion concentration of 10 during extraction. -3.5 moL / L~10 0.5 This reduces pretreatment costs by using mol / L. Adding neutral phosphine compounds further ensures that they react with Sc during subsequent extraction. 3+ A neutral coordination layer is formed, inhibiting competition for water molecules. This effectively solves the problem of efficient extraction of scandium by subsequent extractants and avoids the difficulties of back-extraction after extraction.

[0153] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A synergistic extractant, characterized in that, The synergistic extractant includes: a primary extractant, a synergistic extractant, and a diluent; The main extractant includes phosphate extractants and amine extractants; The co-extractant includes neutral phosphine compounds.

2. The synergistic extractant according to claim 1, characterized in that, The volume ratio of the primary extractant to the co-extractant is (5:1) to (1:2); and / or, In the synergistic extractant, the total volume percentage of the main extractant and the synergistic extractant is 10% to 30%, and the volume percentage of the diluent is 70% to 90%.

3. The synergistic extractant according to claim 2, characterized in that, The phosphoric acid extractant is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester; and / or, The neutral phosphine compounds include one or more of dimethylheptyl methylphosphonate and tributylphosphine oxide; and / or The amine extractant is a secondary primary amine; and / or... The diluent is 260# kerosene.

4. The synergistic extractant according to claim 3, characterized in that, In the main extractant, the volume ratio of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine is (9:2) to (2:9).

5. The synergistic extractant according to claim 3, characterized in that, In the main extractant, the volume ratio of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine is (7:4) to (3:8).

6. A method for preparing the synergistic extractant as described in any one of claims 1 to 5, characterized in that, The diluent is divided into diluent one and diluent two by volume ratio, and the preparation method includes the following steps: The diluent and the amine extractant are mixed to obtain a mixture; The phosphoric acid extractant is added dropwise to the mixture and reacted under first conditions to obtain a first intermediate extractant; The neutral phosphine compound is added to the first intermediate extractant and reacted under second conditions to obtain the second intermediate extractant; The second diluent is added to the second intermediate extractant and stirred until transparent to obtain the synergistic extractant for extracting scandium.

7. The preparation method according to claim 6, characterized in that, The phosphate extractant is added to the mixture at a rate of 1 mL / min to 3 mL / min.

8. The preparation method according to claim 6, characterized in that, The volume ratio of the diluent and the secondary amine is (10-30):(5-10); and / or, The volume ratio of the phosphate extractant to the amine extractant is (9:2) to (2:9); and / or, The total volume ratio of the phosphoric acid extractant and the amine extractant to the neutral phosphine compound is (5:1) to (1:2); and / or, In the synergistic extractant, the volume percentage of diluent one is 10% to 30%; the volume percentage of diluent two is 40% to 80%; and the volume percentage of the diluent in the synergistic extractant is 70% to 90%.

9. The preparation method according to claim 6, characterized in that, The first condition meets the following requirements: stirring at 400 rpm for 30 min to 60 min at a temperature of 35℃ to 45℃.

10. The preparation method according to claim 6, characterized in that, The second condition must meet the following requirements: stir at 400 rpm for 10 min to 30 min.

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