Method for crystallizing scandium oxalate from low-concentration scandium-containing solution in one step

Abstract

The embodiment of the invention provides a method for one-step crystallization of scandium oxalate in a scandium-containing solution, the mass concentration of scandium in the scandium-containing solution is smaller than or equal to 1 g / L. The method comprises the steps that the pH value of the scandium-containing solution is adjusted to 0.5-2, and a pretreated scandium-containing solution is obtained; under the heating and stirring conditions, oxalic acid and a solventing-out agent are added into the pretreated scandium-containing liquid for a crystallization reaction, and crystallized slurry is obtained; carrying out solid-liquid separation on the crystallized slurry to obtain scandium oxalate crystals; and washing and drying the scandium oxalate crystal to obtain scandium oxalate. The crystallization process of scandium oxalate is optimized chemically and physically through key steps of adjusting the pH value, adding a solvating-out agent, controlling the dosage of oxalic acid, heating, stirring and the like. According to the process conditions, the complex process difficulty of crystallizing scandium oxalate from the low-concentration scandium-containing solution is overcome, the energy consumption of an evaporation and concentration procedure and the large consumption of materials such as an extracting agent in a multi-time extraction process are reduced, and low-consumption and rapid crystallization of scandium oxalate is realized.

Description

Technical Field

[0001] The present application relates to the technical field of metal compound preparation, and in particular to a method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution. Background Art

[0002] Scandium and its alloys, due to their exceptional properties, are widely used in high-tech applications such as specialty glass, alloys, and aerospace products, making them key materials in modern industry. Scandium is often found in nature as an associated element, primarily in other mineral deposits and rare earth element mixed ores, such as laterite nickel ore. This poses numerous challenges to its extraction, separation, processing, and utilization.

[0003] Due to the low scandium content in the raw materials and the low scandium concentration in the leached or extracted solution, the concentration must be increased through complex processes such as multiple extractions, stripping, and evaporation before crystallization and separation can be achieved. Currently, three main scandium crystallization processes exist: evaporation crystallization, oxalic acid crystallization, and membrane crystallization. For example, the "Method for Recovering Scandium Oxide from Scandium-Containing Oxalic Acid Wastewater" utilizes evaporation, precipitation, and acid washing. This method requires high oxalic acid consumption, requiring the scandium-containing wastewater to be evaporated and concentrated to a scandium concentration of 3-5 g / L. This results in high energy consumption and large purity fluctuations, making it suitable only for the production of low-value-added scandium salts. The "Method for Producing High-Purity Scandium Oxide" requires two oxalation treatments, requiring high oxalic acid consumption, a complex process, and low efficiency. Another method, the "Method for Recovering Scandium Oxide from Scandium-Containing Oxalic Acid Wastewater," utilizes membrane crystallization technology. While this method reduces energy consumption by 50%, membrane fouling remains a significant issue, leading to high operating costs. Furthermore, the process is complex and energy-intensive, and it also produces alkaline wastewater. Although there is currently no mature process for directly crystallizing scandium oxalate from scandium solutions with scandium concentrations below 1.0 g / L, the preparation of scandium oxalate crystals is possible through the control of specific process conditions, such as liquid-phase precipitation, and precise control of the oxalation treatment and calcination temperature. Energy-efficient and efficient recycling of low-concentration scandium solutions is an important development direction in the field of scandium extraction and separation. Summary of the Invention

[0004] The present application provides a method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution to solve the following technical problem: how to one-step crystallize scandium oxalate from a low-concentration scandium-containing solution (scandium mass concentration ≤ 1 g / L).

[0005] The present invention provides a method for one-step crystallization of scandium oxalate from a scandium-containing solution, wherein the mass concentration of scandium in the scandium-containing solution is ≤1 g / L. The method comprises:

[0006] Adjusting the pH value of the scandium-containing solution to 0.5-2 to obtain a pretreated scandium-containing solution;

[0007] Under heating and stirring conditions, adding oxalic acid and a dissolving agent to the pretreated scandium-containing solution to perform a crystallization reaction to obtain a crystal slurry; the volume ratio of the dissolving agent to the pretreated scandium-containing solution is (1-3):1, and the molar ratio of the oxalic acid to the scandium in the pretreated scandium-containing solution is (2-3):1;

[0008] performing solid-liquid separation on the crystal slurry to obtain scandium oxalate crystals;

[0009] The scandium oxalate crystals are washed and dried to obtain scandium oxalate.

[0010] Optionally, the pH value is adjusted by adding an alkaline solution dropwise to the scandium-containing solution, wherein the alkaline solution includes a sodium hydroxide solution or aqueous ammonia.

[0011] Optionally, the temperature of the crystallization reaction is 40 to 80° C., and the time of the crystallization reaction is 0.5 to 2 hours.

[0012] Optionally, the heating method is water bath heating, and the stirring method is magnetic stirring.

[0013] Optionally, the stirring speed is 100 to 500 r / min.

[0014] Optionally, the solvent is one of ethanol, methanol or acetone.

[0015] Optionally, the purity of the scandium oxalate product is 86-90.2%.

[0016] Optionally, the washing includes, in sequence: washing with dilute oxalic acid solution and rinsing with pure water, the volume of the dilute oxalic acid solution in the washing with dilute oxalic acid solution is 1 to 3 times the volume of the scandium oxalate crystals, and the volume of pure water in the rinsing with pure water is 1 to 3 times the volume of the scandium oxalate crystals.

[0017] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0018] The present invention provides a method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution. First, the pH value of the scandium-containing solution is adjusted to 0.5-2, so that the scandium ions (Sc 3+) is in a relatively stable chemical environment. Under the condition of pH value of 0.5-2, the degree of hydrolysis of scandium ions is low, which is conducive to its reaction with oxalic acid to form scandium oxalate precipitate. At the same time, the lower pH value helps to suppress the interference of other impurity ions and improve the recovery rate and purity of scandium. Secondly, a solvent is added. The function of the solvent is to reduce the solubility of scandium in the solution, thereby promoting the crystallization and precipitation of scandium oxalate. Thirdly, heating and stirring are important conditions for promoting scandium oxalate crystals. Heating can increase the reaction rate and make the reaction between oxalic acid and scandium ions more rapid and complete. Stirring can maintain the uniformity of the solution, prevent local concentration from being too high or too low, and ensure the uniform progress of the reaction. Finally, after the crystallization reaction is completed, the scandium oxalate crystals are separated from the solution by solid-liquid separation. The washing step can remove impurities on the surface of the crystal and improve the purity of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 This is a flow chart of a method for one-step crystallization of scandium oxalate from a scandium-containing solution provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] The range descriptions described in this article, such as numerical ranges, ratio ranges, etc., include all possible sub-ranges and single numerical values ​​within the range. For example, the range description of "1 to 6" or "1~6" covers all sub-ranges from 1 to 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including", "comprising", etc. used in this article mean "including but not limited to"; relational terms such as "first" and "second" are only used to distinguish different entities or operations, and do not imply an actual sequence or association relationship; "and / or" means that multiple situations can exist alone or at the same time; expressions such as "at least one", "multiple", and "at least one" refer to any combination of corresponding objects, including a combination of single or multiple objects. The proportional relationships involved in the article, such as mass ratios, molar ratios, etc., should be understood as the corresponding relationship between the first and second terms of the proportional formula in the order of description. The raw materials, reagents, instruments and equipment used in this article can be purchased on the market or prepared by existing methods.

[0024] Figure 1 This is a flow chart of a method for one-step crystallization of scandium oxalate from a scandium-containing solution provided in an embodiment of the present application.

[0025] See Figure 1 The present invention provides a method for one-step crystallization of scandium oxalate from a scandium-containing solution, wherein the mass concentration of scandium in the scandium-containing solution is ≤1 g / L, and the method comprises:

[0026] S1. The scandium-containing solution is adjusted to a pH value of 0.5 to 2 to obtain a pretreated scandium-containing solution;

[0027] S2 under heating and stirring conditions, adding oxalic acid and a dissolving agent to the pretreated scandium-containing solution to carry out a crystallization reaction to obtain a crystal slurry;

[0028] S3. The crystal slurry is subjected to solid-liquid separation to obtain scandium oxalate crystals;

[0029] S4. Washing and drying the scandium oxalate crystals to obtain a scandium oxalate product.

[0030] Scandium-containing solution refers to a solution containing scandium ions (Sc 3+) solution, wherein the mass concentration of scandium is ≤1g / L, which is a low-concentration solution. One-step crystallization refers to obtaining scandium oxalate crystals directly from the scandium-containing solution through a single crystallization process, without the need for multiple crystallizations or complex separation steps. The pH value of the scandium-containing solution is adjusted to 0.5-2, so that the scandium ions can exist stably under acidic conditions, and at the same time, a suitable acidic environment is created for subsequent crystallization reactions. Under heating and stirring conditions, oxalic acid and a solvent are added to the pretreated scandium-containing solution. Oxalic acid reacts chemically with the scandium ions to form scandium oxalate. The solvent reduces the solubility of scandium oxalate and promotes its crystallization. The scandium oxalate crystals in the crystal slurry are separated from the solution to obtain pure scandium oxalate crystals. Impurities on the surface of the crystals are removed by washing, and the water is removed by natural drying to obtain the final scandium oxalate product. In this application, the scandium-containing solution is derived from the leachate of red mud. After impurity removal, the scandium-containing solution within the applicable scope of the method is obtained. Scandium oxalate crystals are directly obtained from the low-concentration scandium-containing solution through a one-step crystallization method. This method simplifies the process flow and improves production efficiency.

[0031] The pH value of the scandium-containing solution can be adjusted to 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, etc.

[0032] In some embodiments, the volume ratio of the dissolving agent to the pretreated scandium-containing solution is (1-3):1.

[0033] By controlling the volume ratio of the dissolving agent to the pretreated scandium-containing solution (1 to 3):1, the saturation of the solution can be effectively adjusted so that scandium oxalate can reach a supersaturated state at a lower concentration, thereby rapidly crystallizing. Exemplary: the volume ratio of the dissolving agent to the pretreated scandium-containing solution can be: 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, etc.

[0034] In some embodiments, the molar ratio of the oxalic acid to the scandium in the pretreated scandium-containing solution is (2-3):1.

[0035] The molar ratio of oxalic acid to scandium is controlled at (2-3):1, which can ensure sufficient precipitation of scandium ions and avoid excessive use of oxalic acid. If oxalic acid is used excessively, it will not only increase production costs, but may also induce precipitation of impurities and reduce the purity of scandium oxalate. Exemplary: the molar ratio of oxalic acid to scandium in the pretreated scandium-containing solution can be: 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, etc.

[0036] In some embodiments, the pH value is adjusted by adding an alkaline solution dropwise to the scandium-containing solution, wherein the alkaline solution includes a sodium hydroxide solution or concentrated ammonia water.

[0037] Alkali refers to an alkaline solution, such as sodium hydroxide solution or ammonia water, which is used to adjust the pH value of the solution. By adding alkali solution to the scandium-containing solution, the pH value of the solution is adjusted to 0.5-2, so that the scandium ions can exist stably under acidic conditions, and at the same time create a suitable acidic environment for the subsequent crystallization reaction. In addition to sodium hydroxide solution and ammonia water, other alkaline substances (such as sodium carbonate solution, etc.) can also be explored as pH regulators to compare their effects on the crystallization process and product quality. Technical effects include: 1. Precise control of pH value: The use of alkali solution can accurately control the pH value of the solution, ensure that the crystallization reaction is carried out under optimal conditions, and improve the crystallization quality and yield of scandium oxalate. 2. Avoid the introduction of impurities: Selecting a suitable alkali solution can avoid the introduction of too many impurity ions, thereby ensuring the purity of the final product. Exemplary:

[0038] The mass concentration of scandium in the scandium-containing solution is 0.4 g / L, and the pH value is adjusted to 1.2 using 0.1 mol / L sodium hydroxide solution.

[0039] The mass concentration of scandium in the scandium-containing solution is 0.6 g / L, and the pH value is adjusted to 1.5 using concentrated ammonia water.

[0040] The mass concentration of scandium in the scandium-containing solution is 0.3 g / L, and the pH value is adjusted to 0.8 using 0.05 mol / L sodium hydroxide solution.

[0041] The mass concentration of scandium in the scandium-containing solution is 0.7 g / L, and the pH value is adjusted to 1.8 using concentrated ammonia water.

[0042] The mass concentration of scandium in the scandium-containing solution is 0.5 g / L, and the pH value is adjusted to 1.3 using 0.2 mol / L sodium hydroxide solution.

[0043] The mass concentration of scandium in the scandium-containing solution is 0.8 g / L, and the pH value is adjusted to 1.6 using concentrated ammonia water.

[0044] The mass concentration of scandium in the scandium-containing solution is 0.2 g / L, and the pH value is adjusted to 1.0 using 0.1 mol / L sodium hydroxide solution.

[0045] The mass concentration of scandium in the scandium-containing solution is 0.9 g / L, and the pH value is adjusted to 1.4 using concentrated ammonia water.

[0046] The mass concentration of scandium in the scandium-containing solution is 0.1 g / L, and the pH value is adjusted to 0.5 using 0.01 mol / L sodium hydroxide solution.

[0047] The mass concentration of scandium in the scandium-containing solution is 0.55 g / L, and the pH value is adjusted to 1.7 using concentrated ammonia water.

[0048] In some embodiments, the temperature of the crystallization reaction is 40 to 80° C., and the time of the crystallization reaction is 0.5 to 2 hours.

[0049] The crystallization reaction temperature refers to the temperature of the solution during the crystallization reaction, which is 40-80°C in this application. The crystallization reaction time refers to the time during which the crystallization reaction is carried out, which is 0.5-2 hours in this application. The crystallization reaction temperature has a significant impact on the reaction rate and crystal growth rate. According to crystal growth theory, the crystal growth rate is a function of supersaturation; the greater the supersaturation, the greater the growth rate. Within the temperature range of 40-80°C, the reaction rate is moderate, crystal growth is good, and impurity formation or crystal decomposition caused by excessively high temperatures is avoided. In addition, the relationship between the crystallization rate and temperature of polymers shows that temperature has different effects on nucleation and crystal growth, and the influence of crystal growth mechanism and conditions on crystal form further emphasizes the importance of factors such as temperature, raw material type, and concentration in the crystal growth process. The crystallization reaction time determines the completeness of the reaction. Within 0.5-2 hours, the reaction time is sufficient for the scandium oxalate crystals to fully grow, while avoiding excessive crystal growth or impurity accumulation caused by too long a time. The technical effects include: 1. By precisely controlling the temperature and time parameters of the crystallization reaction, we successfully obtained scandium oxalate crystals with uniform particle size and high purity, thereby significantly improving the overall quality of the product. 2. Under the condition of ensuring that the reaction temperature and time are precisely controlled, the crystallization reaction can be effectively completed, avoiding unnecessary long reaction times, thereby improving production efficiency. Example:

[0050] The temperature of the crystallization reaction can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc.; the time of the crystallization reaction can be 0.5 hour, 0.75 hour, 1 hour, 1.25 hours, 1.5 hours, 1.75 hours, or 2 hours.

[0051] In some embodiments, the heating method is water bath heating, and the stirring method is magnetic stirring.

[0052] Water bath heating is a heating method in which the reaction vessel is placed in a water bath and the heat conduction of water is used to heat the solution evenly. Magnetic stirring is a stirring method in which the magnetic field generated by the magnetic stirrer drives the stirrer to rotate, so that the solution is evenly mixed. Water bath heating can heat the solution evenly, avoid side reactions caused by local overheating, and facilitate the control of the heating temperature. Magnetic stirring can ensure that the components in the solution are evenly distributed, effectively prevent local concentration imbalances, and thus ensure the smooth progress of the reaction. In addition to water bath heating and magnetic stirring, other heating methods (such as oil bath heating, microwave heating, etc.) and stirring methods (such as mechanical stirring, ultrasonic stirring, etc.) can also be used. The technical effects include: 1. Combined with a magnetic stirring water bath equipment, uniform heating and stirring of the crystallization reaction can be achieved by precisely controlling the temperature and stirring speed, thereby improving the quality and yield of scandium oxalate crystals. 2. These two heating and stirring methods are simple to operate, easy to implement, and suitable for large-scale industrial production. Exemplary:

[0053] The mixture was heated to 60°C in a water bath and stirred at a speed of 300 r / min.

[0054] The mixture was heated to 70°C in a water bath and stirred at a speed of 400 r / min.

[0055] The mixture was heated to 50°C in a water bath and stirred at a speed of 200 r / min.

[0056] The mixture was heated to 80°C in a water bath and stirred at a speed of 500 r / min.

[0057] The mixture was heated to 40°C in a water bath and stirred at a speed of 100 r / min.

[0058] The mixture was heated to 65°C in a water bath and stirred at a speed of 350 r / min.

[0059] The mixture was heated to 75°C in a water bath and stirred at a speed of 450 r / min.

[0060] The mixture was heated to 55°C in a water bath and stirred at a magnetic stirring speed of 250 r / min.

[0061] The mixture was heated to 45°C in a water bath and stirred at a magnetic stirring speed of 150 r / min.

[0062] The mixture was heated to 58°C in a water bath and stirred at a speed of 280 r / min.

[0063] In some embodiments, the solvent is one of ethanol, methanol or acetone.

[0064] A dissolving agent refers to a substance that can change the solubility of a solute in a solution, and in this application, it is one of ethanol, methanol or acetone. After the dissolving agent is added to the solution, it will change the properties of the solution, reduce the solubility of scandium oxalate in the solution, and thus promote the precipitation of scandium oxalate crystals. Different dissolving agents have different effects on the solubility of scandium oxalate. Selecting a suitable dissolving agent can achieve selective crystallization and improve the quality and purity of scandium oxalate crystals. In addition to ethanol, methanol and acetone, other organic solvents (such as isopropanol, butanol, etc.) can also be used as dissolving agents. Technical effects include: 1. By introducing a specific dissolving agent, the solubility of scandium oxalate can be effectively reduced, thereby promoting its crystallization and precipitation, and improving crystallization efficiency. 2. Selecting a suitable dissolving agent can reduce the mixing of impurities and improve the purity of scandium oxalate crystals. Exemplary:

[0065] Ethanol was used as the dissolving agent, and the volume ratio of the dissolving agent to the scandium-containing solution was 1:1.

[0066] Methanol was used as the solvent, and the volume ratio of the solvent to the scandium-containing solution was 2:1.

[0067] Acetone was used as the dissolving agent, and the volume ratio of the dissolving agent to the scandium-containing solution was 3:1.

[0068] Ethanol was used as the solvent, and the volume ratio of the solvent to the scandium-containing solution was 1.5:1.

[0069] Methanol was used as the solvent, and the volume ratio of the solvent to the scandium-containing solution was 2.5:1.

[0070] Acetone was used as the dissolving agent, and the volume ratio of the dissolving agent to the scandium-containing solution was 1:1.

[0071] Ethanol was used as the solvent, and the volume ratio of the solvent to the scandium-containing solution was 2:1.

[0072] Methanol was used as the solvent, and the volume ratio of the solvent to the scandium-containing solution was 3:1.

[0073] Acetone was used as the dissolving agent, and the volume ratio of the dissolving agent to the scandium-containing solution was 1.5:1.

[0074] Ethanol was used as the solvent, and the volume ratio of the solvent to the scandium-containing solution was 2.5:1.

[0075] In some embodiments, the purity of the scandium oxalate crystals can reach 90%.

[0076] Purity refers to the percentage of scandium content in the scandium oxalate crystals to the total mass. By optimizing the crystallization conditions and subsequent processing steps and reducing the mixing of impurities, the purity of the scandium oxalate crystals can be significantly improved. By controlling the temperature, time, amount of solvent used and other conditions during the crystallization process, the growth rate of the scandium oxalate crystals can be adjusted. Through the process flow of this application, scandium oxalate crystals with a purity of 85-90% can be obtained, which meets the material requirements for the subsequent preparation of high-purity scandium oxide and other products.

[0077] In some embodiments, the washing includes, in sequence: washing with dilute oxalic acid solution and rinsing with pure water, the volume of the dilute oxalic acid solution in the washing with dilute oxalic acid solution is 1 to 3 times the volume of the scandium oxalate crystals, and the volume of pure water in the rinsing with pure water is 1 to 3 times the volume of the scandium oxalate crystals.

[0078] Washing with dilute oxalic acid solution refers to washing the scandium oxalate crystals with dilute oxalic acid solution to remove impurities on the surface of the crystals. Rinsing with pure water refers to rinsing the scandium oxalate crystals with pure water to further remove residual impurities and washing liquid. Dilute oxalic acid solution can react chemically or physically adsorb with impurities on the surface of the crystal to remove the impurities. Rinsing with pure water can further remove residual impurities and washing liquid, thereby improving the purity of the scandium oxalate crystals. The technical effects include: 1. Effectively remove impurities on the surface of the scandium oxalate crystals through washing with dilute oxalic acid solution and rinsing with pure water, thereby improving the purity of the product. 2. Ensure the purity of the scandium oxalate crystals to meet the requirements of high-purity material preparation. Exemplary:

[0079] Use 0.1 mol / L dilute oxalic acid solution to wash, the volume of the solution is 1 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 1 times the volume of the scandium oxalate crystal.

[0080] Use 0.2 mol / L dilute oxalic acid solution to wash, the volume of the solution is twice the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is twice the volume of the scandium oxalate crystal.

[0081] Use 0.3 mol / L dilute oxalic acid solution to wash, the volume of the solution is 3 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 3 times the volume of the scandium oxalate crystal.

[0082] Use 0.4 mol / L dilute oxalic acid solution to wash, the volume of the solution is 1 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 1 times the volume of the scandium oxalate crystal.

[0083] Use 0.5 mol / L dilute oxalic acid solution to wash, the volume of the solution is twice the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is twice the volume of the scandium oxalate crystal.

[0084] Use 0.6 mol / L dilute oxalic acid solution to wash, the volume of the solution is 3 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 3 times the volume of the scandium oxalate crystal.

[0085] Use 0.7 mol / L dilute oxalic acid solution to wash, the volume of the solution is 1 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 1 times the volume of the scandium oxalate crystal.

[0086] Use 0.8 mol / L dilute oxalic acid solution to wash, the volume of the solution is twice the volume of the scandium oxalate crystals, and then rinse with pure water, the volume of pure water is twice the volume of the scandium oxalate crystals.

[0087] Use 0.9 mol / L dilute oxalic acid solution to wash, the volume of the solution is 3 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 3 times the volume of the scandium oxalate crystal.

[0088] Use 1.0 mol / L dilute oxalic acid solution to wash, the volume of the solution is 1 times the volume of the scandium oxalate crystal, and then rinse with pure water, the volume of pure water is 1 times the volume of the scandium oxalate crystal.

[0089] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0090] Example 1

[0091] Step 1: Add 50mL of scandium-containing solution (scandium mass concentration is 0.32g / L) to a beaker and adjust the pH to 0.53 with ammonia water to obtain scandium-containing solution 2. Step 2: Place scandium-containing solution 2 in a 40°C constant temperature magnetic stirring water bath, add 0.048g of oxalic acid, stir and react for 30 minutes, then dropwise add 150mL of ethanol solvent, continue stirring and heating to react for 1 hour to obtain scandium oxalate crystal slurry. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature and filter using a sand core filter with a 0.45μm organic filter membrane. The filter cake is first washed with 1 volume of 0.5% dilute oxalic acid solution, then rinsed with 1 volume of pure water, and naturally dried to obtain scandium oxalate powder.

[0092] Example 2

[0093] Step 1: Add 100mL of scandium-containing solution (scandium mass concentration is 0.56g / L) to a beaker and adjust the pH to 0.86 with solid NaOH to obtain scandium-containing solution 2. Step 2: Place scandium-containing solution 2 in a 70°C constant temperature magnetic stirring water bath, add 0.15g of solid oxalic acid, stir and react for 30 minutes, then add 100mL of ethanol dropwise, continue stirring and heating to react for 50 minutes to obtain scandium oxalate crystal slurry. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature and filter using a sand core filter with a 0.45μm organic filter membrane. The filter cake is first washed with 1 volume of 0.3% dilute oxalic acid solution, then rinsed with 2 volumes of pure water, and naturally dried to obtain scandium oxalate powder.

[0094] Example 3

[0095] Step 1: Add 300mL of scandium-containing solution (mass concentration of scandium is 0.84g / L) to a beaker and adjust the pH to 1.2 with solid NaOH to obtain scandium-containing solution 2. Step 2: Place scandium-containing solution 2 in a 50°C constant temperature magnetic stirring water bath, add 0.7g of oxalic acid solid, stir and react for 40 minutes, then add 150mL of ethanol dropwise, continue stirring and heating to react for 30 minutes to obtain scandium oxalate crystal slurry. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature and filter using a sand core filter with a 0.45μm organic filter membrane. The filter cake is first washed with 3 volumes of 0.2% dilute oxalic acid solution, then rinsed with 1 volume of pure water and naturally dried to obtain scandium oxalate powder.

[0096] Example 4

[0097] Step 1: Add 600mL of scandium-containing solution (with a scandium mass concentration of 0.96g / L) to a beaker and adjust the pH to 1.6 with ammonia water to obtain scandium-containing solution 2. Step 2: Place scandium-containing solution 2 in a 60°C constant temperature magnetic stirring water bath, add 1.1g of oxalic acid solid, stir and react for 30 minutes, then add 200mL of ethanol solvent dropwise, continue stirring and heating to react for 1 hour, and obtain scandium oxalate crystal slurry. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature and filter using a sand core filter with a 0.45μm organic filter membrane. The filter cake is first washed with 2 volumes of 0.1% dilute oxalic acid solution, then rinsed with 2 volumes of pure water, and naturally dried to obtain scandium oxalate powder.

[0098] Example 5

[0099] Step 1: Add 500mL of scandium-containing solution (with a scandium mass concentration of 0.45g / L) to a beaker and adjust the pH to 2 with solid NaOH to obtain scandium-containing solution 2. Step 2: Place scandium-containing solution 2 in a 55°C constant temperature magnetic stirring water bath, add 0.65g of solid oxalic acid, stir and react for 50 minutes, then add 150mL of ethanol dropwise, continue stirring and heating to react for 40 minutes to obtain scandium oxalate crystal slurry. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature and filter using a sand core filter with a 0.45μm organic filter membrane. Wash the filter cake with 2 volumes of 0.4% dilute oxalic acid solution, then rinse with 3 volumes of pure water, and air dry to obtain scandium oxalate powder.

[0100] Example 6

[0101] Step 1: Add 200mL of scandium-containing solution (scandium mass concentration is 0.63g / L) to a beaker and adjust the pH to 1.2 with solid NaOH to obtain scandium-containing solution 2. Step 2: Place scandium-containing solution 2 in a constant temperature magnetic stirring water bath at 80°C, add 0.31g of solid oxalic acid, stir and react for 50 minutes, then add 150mL of ethanol dropwise, continue stirring and heating to react for 40 minutes to obtain scandium oxalate crystal slurry. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature and filter using a sand core filter with a 0.45μm organic filter membrane. Wash the filter cake with 2 volumes of 0.4% dilute oxalic acid solution, then rinse with 3 volumes of pure water, and air dry to obtain scandium oxalate powder.

[0102] Comparative Example 1

[0103] Step 1: Add 50mL of scandium solution (mass concentration of scandium is 0.32g / L) to a beaker, and the pH is measured to be -0.05. No alkali solution is required for adjustment. Step 2: Place the scandium solution in a 40°C constant temperature magnetic stirring water bath, add 0.048g of oxalic acid, and stir to react for 30 minutes. Step 3: Allow the scandium oxalate crystal slurry obtained in step 2 to cool to room temperature, and filter it using a sand core filter with a 0.45μm organic filter membrane. Wash the filter cake with 1 volume of 0.5% dilute oxalic acid solution, then rinse with 1 volume of pure water, and air dry to obtain scandium oxalate powder.

[0104] Comparative Example 2

[0105] Step 1: Add 100 mL of scandium solution (scandium concentration of 0.56 g / L) to a beaker and adjust the pH to 2.5 with solid NaOH to obtain scandium solution 2. Step 2: Place scandium solution 2 in a 70°C constant temperature magnetic stirring water bath, add 0.15 g of solid oxalic acid, and stir to react for 30 minutes. Step 3: Filter the scandium oxalate crystal slurry obtained in Step 2 using a sand core filter with a 0.45 μm organic filter membrane. Wash the filter cake with 1 volume of 1% dilute oxalic acid solution and air dry to obtain scandium oxalate powder.

[0106] The product purity effect experiment was carried out on Examples 1-6 and Comparative Examples 1-2, and the product detection method was as follows:

[0107] The content of scandium in scandium oxalate powder was determined by chemical analysis method and the purity of the product was calculated.

[0108] Experimental data effect table of scandium oxalate product purity

[0109] Example 1 87.25 Example 2 86 Example 3 89.3 Example 4 89.6 Example 5 90.2 Example 6 88.9 Comparative Example 1 60 Comparative Example 2 57

[0110] The experimental data table clearly shows the differences between different examples and comparative examples, which helps us evaluate the specific effects of various process conditions on the quality and performance of scandium oxalate powder. The specific analysis is as follows:

[0111] Product purity:

[0112] The product purities of Examples 1 to 6 all exceeded 86%, and in particular, the purity of Example 5 reached 90.2%, which fully demonstrated that the optimized process conditions can significantly improve the purity of scandium oxalate powder.

[0113] Comparative Examples 1 and 2: The product purity is generally lower than that of the examples. This indicates that under the unoptimized process conditions, the crystallization rate of scandium is significantly reduced, and the product purity is significantly lower than that of the optimized process.

[0114] Comparing the data from the Examples and Comparative Examples shows that optimized process conditions (such as the addition of an ethanol solvent, pH adjustment, and washing) significantly improve the purity of scandium oxalate powder. These optimization measures can effectively reduce the incorporation of impurities, promote the uniform growth of scandium oxalate crystals, and thus improve product quality.

[0115] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present 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 the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for one-step crystallization of scandium oxalate from a scandium-containing solution, wherein the scandium concentration in the scandium-containing solution is ≤1 g / L, the method comprising: Adjusting the pH value of the scandium-containing solution to 0.5-2 to obtain a pretreated scandium-containing solution; adding oxalic acid and a dissolving agent to the pretreated scandium-containing solution under heating and stirring conditions to perform a crystallization reaction to obtain a crystal slurry; performing solid-liquid separation on the crystal slurry to obtain scandium oxalate crystals; The scandium oxalate crystals are washed and dried to obtain a scandium oxalate product.

2. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The volume ratio of the dissolving agent to the pretreated scandium-containing solution is (1-3):

1.

3. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The molar ratio of the oxalic acid to the scandium in the pretreated scandium-containing solution is (2-3):

1.

4. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The pH value is adjusted by dripping an alkali solution into the scandium-containing solution, wherein the alkali solution includes a sodium hydroxide solution or an ammonia solution.

5. The temperature of the crystallization reaction is 40-80°C, and the time of the crystallization reaction is 0.5-2 hours.

6. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The heating method is water bath heating, and the stirring method is magnetic stirring.

7. A method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1 or 6, characterized in that: The stirring speed is 100-500 r / min.

8. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The solvent is one of ethanol, methanol or acetone.

9. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The purity of the scandium oxalate crystals is 86-90.2%.

10. The method for one-step crystallization of scandium oxalate from a low-concentration scandium-containing solution according to claim 1, characterized in that: The washing includes: washing with dilute oxalic acid solution and rinsing with pure water. The volume of the dilute oxalic acid solution in the washing with dilute oxalic acid solution is 1 to 3 times the volume of the scandium oxalate crystals, and the volume of the pure water in the rinsing with pure water is 1 to 3 times the volume of the scandium oxalate crystals.

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