Application and application method of synergistic extractant

Abstract

According to the application, a synergistic extraction system of a phosphoric acid extraction agent and an amine extraction agent is adopted, a neutral phosphine compound and a scandium element are adopted to form a neutral coordination layer, and water molecule competition is inhibited; therefore, it is guaranteed that the prepared synergistic extraction agent has good extraction efficiency and selectivity, the problem that reverse extraction is difficult after an acidic phosphorus agent is adopted for extraction can be solved, and the separation cost can be reduced; according to the application method, a reducing agent is firstly added to inhibit the influence of other interfering ions in a solution, so that the interfering ions are prevented from competing with scandium ions for extraction sites; the synergistic extraction agent is added, and the extraction efficiency of scandium ions is improved through multiple reverse contact of an organic phase and a water phase by virtue of the combination effect and a counter-current extraction mode; and finally, adding an acidic stripping agent, and efficiently transferring scandium from an organic phase to a water phase in combination with a countercurrent stripping technology, so that complete stripping is ensured, and finally, the scandium-rich solution is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth metal separation, and particularly relates to application of a synergistic extractant and a method thereof. BACKGROUND

[0002] Rare earth metals have important applications in modern high-tech industries, such as aerospace, electronic devices, catalysts, and other fields. However, due to the similar chemical properties of rare earth elements, the separation and purification process is complex and costly. As a rare rare earth element, the separation and purification technology of scandium is also particularly important.

[0003] In the separation and purification technology of scandium, solvent extraction has the advantages of high extraction capacity, easy large-scale operation, and is the most widely used technology for recovering trace scandium from solutions containing a large amount of impurity elements. The commonly used extractant (such as the synergistic extraction system of extractant (2-ethylhexyl) phosphoric acid (P204) or 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507) and tributyl phosphate (TBP)) has high extraction efficiency for scandium, but the impurity co-extraction rate is also high. The organic phase components will enter the aqueous phase, and emulsification phenomenon is easy to occur in some systems, it is difficult to wash out impurities, and the stripping conditions are harsh. The reason is that the acid has poor stripping efficiency for the loaded organic phase, so it also limits its application in industry.

[0004] The related technology provides a method for selectively extracting scandium from leaching solution based on microemulsion. The method uses P204, TBP and alkali solution to prepare microemulsion to separate scandium, and then uses NaOH or Na2CO3 to separate the scandium-rich aqueous phase and the microemulsion phase. Although the scandium-iron separation coefficient of the synergistic system can be increased to more than 2000, this process is only suitable for Sc and Fe solutions with similar concentrations, and the stripping process still requires 3-5 mol / L NaOH solution, which has high requirements for equipment and limits its application in actual industry. The patent with publication number CN115786744A provides a method for cooperatively extracting scandium from titanium white waste acid and molten salt chlorination dust residue. The method reduces the interference of Fe 3+ to Fe 2+ in the scandium separation process by adding reduced iron powder before synergistic extraction, but the process increases the processing cost, and excessive Fe 2+ also increases the complexity of the acid leaching solution components, affecting the subsequent product preparation.

[0005] Therefore, it is necessary to design an application of a synergistic extractant and a method thereof to solve the above problems. SUMMARY

[0006] The present application provides an application of a synergistic extractant and a method thereof to solve the problem of considering the extraction capacity of the extractant for scandium while also considering the stripping capacity, in order to reduce the separation cost.

[0007] In a first aspect, the application provides a use of a synergistic extractant, the synergistic extractant comprising: a primary extractant, a synergistic extractant, and a diluent;

[0008] The primary extractant comprises a phosphoric acid-based extractant and an amine-based extractant;

[0009] The synergistic extractant comprises a neutral phosphine compound;

[0010] The synergistic extractant is used for extracting scandium.

[0011] In some embodiments, the volume ratio of the primary extractant to the synergistic extractant is (5:1) to (1:2); and / or,

[0012] In the synergistic extractant, the total volume ratio of the primary extractant to the synergistic extractant is 10% to 30%, and the volume ratio of the diluent is 70% to 90%.

[0013] In some embodiments, the phosphoric acid-based extractant is 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester; and / or,

[0014] The neutral phosphine compound comprises one or more of dimethylheptyl phosphonate, tributylphosphine oxide; and / or,

[0015] The amine-based extractant is a secondary carbon primary amine; and / or,

[0016] The diluent is 260# kerosene.

[0017] In some embodiments, in the primary extractant, the volume ratio of the 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine is (9:2) to (2:9).

[0018] In some embodiments, in the primary extractant, the volume ratio of the 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester to the secondary carbon primary amine is (7:4) to (3:8).

[0019] In a second aspect, the application provides a method for the use of the above-mentioned synergistic extractant, the method for using the synergistic extractant as a scandium extractant comprising the following steps:

[0020] Providing a scandium-containing solution, adding 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 to 10 0.5 moL / L;

[0021] The counter-current extraction is performed by adding the synergistic extractant into the first mixed solution, and a first water phase and a first organic phase are separated;

[0022] The counter-current stripping is performed by adding an acidic stripping agent into the first organic phase, and a second organic phase and a second water phase are separated, wherein the second water phase is the collected scandium-rich solution, and the concentration of scandium in the scandium-rich solution is 0.67 g / L to 0.70 g / L.

[0023] In some embodiments, the reducing agent comprises one of ascorbic acid and sodium sulfite; and / or,

[0024] In the first mixed solution, the concentration of the reducing agent is 0.05 mol / L to 0.5 mol / L.

[0025] In some embodiments, the volume ratio of the scandium-containing solution to the synergistic extractant is (5 to 40):1.

[0026] In some embodiments, the volume ratio of the acidic stripping agent to the first organic phase is 1:(1 to 6); and / or,

[0027] The acidic stripping agent comprises an aqueous solution of an inorganic acid containing a salting-out agent, wherein the salting-out agent in the acidic stripping agent comprises sodium fluoride, and the inorganic acid comprises sulfuric acid and hydrochloric acid.

[0028] In some embodiments, in the acidic stripping agent, the concentration of the salting-out 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.

[0029] Compared with the prior art, the above technical solutions provided by the embodiments of the present application have the following advantages:

[0030] 1. The application of the synergistic extractant provided by the embodiments of the present application uses a synergistic extraction system of phosphoric acid extractant and amine extractant, and improves the extraction efficiency of scandium in the subsequent process through the double mechanisms 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 inhibit the competition of water molecules. In this way, the prepared synergistic extractant has good extraction efficiency and selectivity, and can avoid the stripping difficulty problem after using an acidic phosphine agent for extraction, thereby reducing the separation cost. When the synergistic extractant is used to extract scandium in the subsequent scandium-containing solution, especially in the scandium-containing solution containing trace amounts of scandium, the extraction rate can be more than 99%, the extraction rate of iron can be controlled to be less than 8%, the stripping rate of scandium can be more than 85%, and the stripping rate of titanium can be controlled to be less than 10%.

[0031] 2. The method for applying the synergistic extractant provided in the embodiments of this application first effectively suppresses other easily oxidized interfering ions (such as Fe) in the solution by adding a reducing agent. 3+ To mitigate the influence of (etc.) on scandium ions and avoid competition for extraction sites with them, thus 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. Using the above extractant, this method can extract scandium from scandium-containing solutions (especially those containing trace amounts of scandium), achieving an extraction rate of over 99%. The extraction rate for iron can be controlled below 8%, the back-extraction rate for scandium can reach over 85%, and the back-extraction rate for titanium can be controlled below 10%. 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. 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. Furthermore, 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 an application of 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] The synergistic extractant is used to extract scandium.

[0038] Thus, a synergistic extraction system employing both phosphoric acid and amine extractants 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 from 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, thereby reducing separation costs. This extractant can achieve an extraction rate of over 99% for scandium in subsequent scandium-containing solutions (even trace scandium-containing solutions), with an extraction rate for iron controlled below 8%, a scandium back-extraction rate exceeding 85%, and a titanium back-extraction rate controlled below 10%.

[0039] 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);

[0040] 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%.

[0041] 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.

[0042] As an optional implementation, in this embodiment of the application, the phosphoric acid extractant is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507).

[0043] 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.

[0044] Thus, during extraction, P350 or tributylphosphine oxide forms a neutral coordination layer with scandium to suppress competition for water molecules.

[0045] As an optional implementation, in this embodiment of the application, the amine extractant is a secondary primary amine (N1923).

[0046] As an optional implementation, in this embodiment of the application, the diluent is 260# kerosene.

[0047] Thus, 260# kerosene, as an inert diluent, can reduce the viscosity of the extractant and improve its phase separation performance.

[0048] 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 is (9:2) to (2:9).

[0049] 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 is (7:4) to (3:8).

[0050] 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.

[0051] 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:

[0052] Step S1: Mix the diluent and the amine extractant to obtain a mixture; the amine extractant is a secondary primary amine (N1923);

[0053] 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);

[0054] 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;

[0055] Step S4: Add the second diluent to the second intermediate extractant and stir until transparent to obtain the synergistic extractant for extracting scandium.

[0056] 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 fully 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.

[0057] 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.

[0058] 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.

[0059] 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).

[0060] 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.

[0061] 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);

[0062] The volume ratio of the phosphoric acid extractant to the amine extractant is (9:2) to (2:9);

[0063] 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);

[0064] 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%.

[0065] 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, reduce the viscosity of the extractant, and improve the phase separation performance, so as to improve the extraction efficiency of scandium and reduce the co-extraction of other metal impurities.

[0066] 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.

[0067] This achieves a match between stirring speed and dropping speed, promoting mass transfer, balancing reaction rate and stability, and ensuring stable hydrogen bonds and a 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).

[0068] 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.

[0069] 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.

[0070] 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:

[0071] 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;

[0072] 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;

[0073] 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 is calculated based on the concentration of scandium in the scandium-rich solution.

[0074] 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.

[0075] Furthermore, this method has a wide range of hydrogen ion concentrations applicable to scandium-containing solutions (10). -3.5 mol / L~10 0.5 The 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.

[0076] 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%.

[0077] 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.

[0078] As an optional implementation, in this embodiment of the application, the reducing agent includes one of ascorbic acid and sodium sulfite;

[0079] In the first mixed solution, the concentration of the reducing agent is 0.05 mol / L to 0.5 mol / L.

[0080] 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.

[0081] 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.

[0082] 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);

[0083] 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.

[0084] 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.

[0085] Thus, the salting-out agent can be introduced to further improve the back-extraction rate.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] Examples 1-5

[0090] 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:

[0091] S1. Add 260# kerosene and N1923 to a round-bottom flask, mix, and obtain a mixture;

[0092] The volume ratio of the 260# kerosene to N1923 is (10-30):(5-10);

[0093] 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.

[0094] The volume ratio of P507 to N1923 is (9:2) to (2:9);

[0095] S3. Add P350 to the first intermediate extractant and stir at 400 rpm for 15 min to react and obtain the second intermediate extractant.

[0096] The ratio of the total volume of P507 and N1923 to the volume of P350 is (5:1) to (1:2);

[0097] S4. Add 260# kerosene II to the second intermediate extractant and stir until transparent to obtain the synergistic extractant used for extracting scandium;

[0098] In the synergistic extractant, the volume percentage of 260# kerosene one is 20%; the volume percentage of 260# kerosene two is 66%.

[0099] The specific process parameters are shown in Table 1.

[0100] Comparative Examples 1-4

[0101] 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.

[0102] Examples 6-7 and Comparative Examples 5-6

[0103] 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.

[0104] Table 1. Process parameters for Examples 1-7 and Comparative Examples 1-6

[0105]

[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 stripping agent is added to the first organic phase for countercurrent stripping to separate a second organic phase and a second aqueous phase; the second aqueous phase is a collected scandium-rich solution; the scandium stripping rate is calculated based on the concentration of scandium in the 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]

[0117]

[0118] 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.

[0119] 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.

[0120] Comparative Example 7

[0121] 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.

[0122] 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.

[0123] Examples 8-10

[0124] 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.

[0125] Comparative Examples 8-9

[0126] 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.

[0127] Example 11

[0128] 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.

[0129] Table 3. Process parameters for Examples 8-11 and Comparative Examples 8-9

[0130]

[0131] Note: "-" indicates that the reagent was not added.

[0132] The extraction results of Examples 8-11 and Comparative Examples 8-9 are shown in Table 4.

[0133] Table 4 shows the results of scandium extraction using various extractants in Examples 8-11 and Comparative Examples 8-9.

[0134]

[0135]

[0136] 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.

[0137] 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.

[0138] Examples 12-14

[0139] 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.

[0140] Comparative Examples 10-11

[0141] 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.

[0142] Comparative Example 12

[0143] 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.

[0144] Table 5. Process parameters for Examples 12-14 and Comparative Examples 10-12

[0145] Sodium fluoride (mol / L) Strip 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

[0146] Note: "-" indicates that the reagent was not added.

[0147] The extraction results of Examples 12-14 and Comparative Examples 10-12 are shown in Table 6.

[0148] Table 6 shows the results of scandium extraction using various extractants in Examples 12-14 and Comparative Examples 10-12.

[0149] Extraction rate of scandium (%) Extraction rate of iron (%) Strip rate of scandium (%) Strip rate of titanium (%) 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

[0150] 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.

[0151] 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.

[0152] 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.

[0153] In summary, this invention provides an application of a synergistic extractant. By employing a synergistic extraction system of phosphoric acid extractants 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 avoids the problem of difficult back-extraction that occurs after extraction with acidic phosphoric acid extractants, thus reducing separation costs. When this extractant is used to extract scandium from subsequent scandium-containing solutions, especially those containing trace amounts of scandium, the extraction rate can reach 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%.

[0154] This invention also provides a method for applying the above-mentioned synergistic extractant, which first involves adding a reducing agent to effectively suppress other easily oxidized interfering ions (such as Fe) in the solution. 3+ To mitigate the influence of (etc.) on scandium ions and avoid competition for extraction sites with them, thus 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. Using the above extractant, this method can extract scandium from scandium-containing solutions (especially those containing trace amounts of scandium), achieving an extraction rate of over 99%. The extraction rate for iron can be controlled below 8%, the back-extraction rate for scandium can reach over 85%, and the back-extraction rate for titanium can be controlled below 10%. Furthermore, this application method features low acid and alkali consumption. Acid extractants require early saponification, and alkali extractants require protonation with acid. This invention eliminates the need for acid or alkali treatment, offers high selectivity, effectively shortens the extraction process, and effectively avoids emulsification or three-phase formation in the extraction system. The extracted organic phase is easily back-extracted and regenerated using dilute acid, and extraction conditions are easily controlled, combining economic efficiency, environmental friendliness, and high efficiency. Therefore, this method, through the combination of synergistic extraction and countercurrent operation, ensures high selectivity and high recovery rate of scandium while also considering operational flexibility and industrial feasibility, providing a practical solution for the efficient extraction of high-purity scandium from low-grade or complex systems.

[0155] 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. The application of 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; The synergistic extractant is used to extract scandium.

2. The application of 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 application of 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 application of 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 application of 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 using the synergistic extractant as described in any one of claims 1 to 5, characterized in that, The method of using the synergistic extractant as a scandium extractant includes the following steps: 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 ≤0.03 g / L; the concentration of hydrogen ions in the scandium-containing solution is 10. -3.5 moL / L~10 0.5 moL / L; The synergistic extractant was added to the first mixed solution for countercurrent extraction to separate the first aqueous phase and the first organic phase. An acidic back-extraction agent is added 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.

7. The method according to claim 6, characterized in that, The reducing agent includes one of ascorbic acid and sodium sulfite; and / or, In the first mixed solution, the concentration of the reducing agent is 0.05 mol / L to 0.5 mol / L.

8. The method according to claim 6, characterized in that, The volume ratio of the scandium-containing solution to the synergistic extractant is (5-40):

1.

9. The method according to claim 6, characterized in that, The volume ratio of the acidic stripping agent to the first organic phase is 1:(1-6); and / or, 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.

10. The method according to claim 9, characterized in that, In the acidic stripping agent, the concentration of the salting-out 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.

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