A method for separating and purifying scandium from crude nickel-cobalt hydroxide

Abstract

The application belongs to the technical field of scandium separation and purification, and particularly relates to a method for separating and purifying scandium from crude nickel-cobalt hydroxide, which comprises the following steps: using 0.1-0.5 mol / L dilute sulfuric acid to leach the crude nickel-cobalt hydroxide, and filtering to obtain a scandium-containing leaching solution, wherein the ratio of the dilute sulfuric acid to the crude nickel-cobalt hydroxide is (3-5) mL:1 g, and the molar ratio of sulfuric acid to scandium is (3-5):1; using an extractant comprising Cyanex572 and Aliquat336 to treat the scandium-containing leaching solution to obtain a scandium-containing organic phase; using an oxalic acid solution to back-extract the scandium-containing organic phase to obtain scandium oxalate precipitation; and calcining the scandium oxalate precipitation to obtain scandium oxide. The technical scheme adopts a selective leaching process to realize efficient separation of scandium from main metals nickel and cobalt at the front end, has low reagent consumption, a short process, and great cost advantages; a new type of synergistic extraction technology is adopted, which has super-high selectivity and extraction capacity for scandium, the prepared scandium oxide has a purity of greater than or equal to 96%, and the scandium recovery rate is greater than or equal to 89%.

Description

Technical Field

[0001] This application belongs to the field of scandium separation and purification technology, specifically a method for separating and purifying scandium from crude nickel-cobalt hydroxide. Background Technology

[0002] Crude nickel-cobalt hydroxide (MHP) is an intermediate product used in the production of nickel and cobalt from laterite nickel ore. Since laterite nickel ore contains scandium, a scarce strategic resource, it accumulates in crude MHP during hydrometallurgical processes. Currently, hydrometallurgical processes for crude MHP often focus on the recovery and purification of the main nickel and cobalt metals, paying insufficient attention to the low-content scandium. Traditional scandium extraction processes involve first completely dissolving the crude MHP in concentrated sulfuric acid, leaching out all metals, and then separating and purifying scandium through extraction and ion exchange. However, the significant difference in concentration between the dissolved nickel and cobalt and scandium severely affects the subsequent separation and purification of trace scandium, resulting in low scandium recovery rates and product purity. Furthermore, this process can interfere with the main nickel-cobalt recovery process. Therefore, developing a low-cost and efficient method for separating and purifying scandium from crude MHP is of significant practical importance. Summary of the Invention

[0003] To address the aforementioned issues, this application provides a method for separating and purifying scandium from crude nickel-cobalt hydroxide. The method aims to preferentially extract scandium from the upstream of crude nickel-cobalt hydroxide. Its core lies in selectively leaching scandium under conditions that minimize the dissolution of the main metals nickel and cobalt. The scandium separation and purification process is set before the main nickel and cobalt recovery line to achieve seamless integration with the main process and directly produce pure scandium oxide.

[0004] This application discloses a method for separating and purifying scandium from crude nickel-cobalt hydroxide, comprising the following steps:

[0005] S1. Obtain crude nickel-cobalt hydroxide, wherein the crude nickel-cobalt hydroxide contains scandium, and leach the crude nickel-cobalt hydroxide with dilute sulfuric acid, and filter to obtain a scandium-containing leachate, wherein the concentration of the dilute sulfuric acid is 0.1~0.5mol / L, the ratio of the dilute sulfuric acid to the crude nickel-cobalt hydroxide is (3~5)mL:1g, and the molar ratio of the sulfuric acid to the scandium in the dilute sulfuric acid is (3~5):1;

[0006] S2. The scandium-containing leachate is subjected to scandium extraction treatment using an extractant to obtain a scandium-containing organic phase, wherein the extractant includes Cyanex 572 and Aliquat 336;

[0007] S3. The scandium-containing organic phase is back-extracted using oxalic acid solution to obtain scandium oxalate precipitate;

[0008] S4. Calcining the scandium oxalate precipitate to obtain scandium oxide.

[0009] Furthermore, in step S1, the leaching temperature is 20~60℃ and the leaching time is 1~3h.

[0010] Furthermore, in step S2, the volume ratio of Cyanex572 to Aliquat336 in the extractant is 4:1.

[0011] Furthermore, in step S2, the extractant further includes sulfonated kerosene, and the volume ratio of Cyanex572, Aliquat336, and sulfonated kerosene in the extractant is 4:1:15.

[0012] Furthermore, in step S2, the volume ratio of the extractant to the scandium-containing leachate is 1:(5~10).

[0013] Furthermore, in step S3, the concentration of the oxalic acid solution is 4wt%~10wt%.

[0014] Furthermore, in step S3, the volume ratio of the oxalic acid solution to the scandium-containing organic phase is 1:(1~2).

[0015] Furthermore, step S4 also includes washing the scandium oxalate precipitate with pure water, heating the washed scandium oxalate precipitate to 340~360℃ and holding it at that temperature for 1.0~1.5h, and then calcining it at 800~900℃ to obtain scandium oxide.

[0016] Furthermore, in step S4, the calcination time is 1-2 hours.

[0017] Furthermore, the purity of the scandium oxide is greater than or equal to 96%, and the recovery rate of the scandium element is greater than or equal to 89%.

[0018] This application proposes a method for separating and purifying scandium from crude nickel-cobalt hydroxide, which produces the following beneficial effects: the selective leaching process achieves efficient separation of scandium from the main metals nickel and cobalt at the front end, with low reagent consumption, short process, and significant cost advantages; the novel synergistic extraction technology has ultra-high selectivity and extraction capacity for scandium, and the prepared scandium oxide has high purity and high recovery rate. Detailed Implementation

[0019] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] This application discloses a method for separating and purifying scandium from crude nickel-cobalt hydroxide, comprising the following steps:

[0021] S1. Obtain crude nickel-cobalt hydroxide, which contains scandium. Leach the crude nickel-cobalt hydroxide with dilute sulfuric acid and filter to obtain a scandium-containing leachate. The concentration of the dilute sulfuric acid is 0.1~0.5 mol / L, the ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide is (3~5) mL:1 g, and the molar ratio of sulfuric acid to scandium in the dilute sulfuric acid is (3~5):1.

[0022] In some preferred embodiments of this application, the leaching temperature is 20~60°C and the leaching time is 1~3 hours;

[0023] Specifically, the concentration of dilute sulfuric acid can be any one or any two of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L; the ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide can be any one or any two of 3 mL:1 g, 3.5 mL:1 g, 4 mL:1 g, 4.5 mL:1 g, and 5 mL:1 g; the molar ratio of sulfuric acid to scandium in the dilute sulfuric acid can be any one or any two of 3:1, 3.5:1, 4:1, 4.5:1, and 5:1; the leaching temperature can be any one or any two of 20℃, 30℃, 40℃, 50℃, and 60℃; and the leaching time can be any one or any two of 1 h, 1.5 h, 2 h, 2.5 h, and 3 h.

[0024] This step uses dilute sulfuric acid to leach crude nickel-cobalt hydroxide. By controlling the concentration of dilute sulfuric acid, the ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide (liquid-solid ratio), the molar ratio of sulfuric acid to scandium, the leaching temperature, and the inlet and outlet times, selective leaching of scandium can be achieved. The reasons for this are as follows: 1. From a thermodynamic perspective: In nickel-cobalt hydroxide (MHP), scandium usually exists as scandium hydroxide (Sc(OH)3) or scandium hydroxide (ScOOH), both of which are amphoteric hydroxides. Nickel and cobalt mainly exist as nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2). Due to the high solubility product (K) of scandium and nickel-cobalt hydroxides... sp1. Unlike the equilibrium pH value, the pH at which scandium hydroxide begins to dissolve significantly is much higher than that of nickel hydroxide and cobalt hydroxide. That is, under the same acidity, the driving force for the dissolution of scandium hydroxide is much greater than that for the dissolution of nickel hydroxide and cobalt hydroxide. 2. From a kinetic perspective: Once a weakly acidic environment is provided, the dissolution reaction of scandium proceeds at a relatively fast rate, while the dissolution reaction rate of nickel and cobalt is slower under the same weakly acidic environment. Therefore, by controlling the appropriate acidity and reaction time, the kinetic differences can be fully utilized. 3. Physical morphology and surface passivation: Nickel-cobalt hydroxides in MHP are usually microcrystalline or amorphous fine particles. In practice, a passivation layer may form on the surface of nickel-cobalt hydroxides under weakly acidic conditions, further inhibiting their dissolution reaction. However, the dissolution of scandium hydroxide or scandium hydroxide does not have this problem. If the amount of dilute sulfuric acid is sufficient, the leaching rate of scandium will be low if the concentration is too low, and the dissolution of nickel and cobalt will be accelerated if the concentration is too high. If the liquid-to-solid ratio is too low, the local reaction will be uneven and impurities will be easily dissolved. If the liquid-to-solid ratio is too high, the solution will be diluted and it will not be conducive to the enrichment of scandium. Therefore, in addition to keeping the amount of dilute sulfuric acid sufficient, the concentration of dilute sulfuric acid and the liquid-to-solid ratio should be controlled within a suitable range during leaching.

[0025] S2. Scandium-containing leachate is extracted using extractants to obtain a scandium-containing organic phase. The extractants include Cyanex 572 and Aliquat 336.

[0026] In some preferred embodiments of this application, the volume ratio of Cyanex572 to Aliquat336 in the extractant is 4:1, the extractant also includes sulfonated kerosene, and the volume ratio of Cyanex572, Aliquat336 and sulfonated kerosene is 4:1:15; the volume ratio of the extractant to the scandium-containing leachate is 1:(5~10).

[0027] Specifically, the volume ratio of the extractant to the scandium-containing leachate can be any one of 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, or any range between two of them.

[0028] In this step, extractants including Cyanex 572 and Aliquat 336 are used to extract scandium from the scandium-containing leachate. Cyanex 572, as the scandium extractant, exhibits better selective extraction and enrichment effects for scandium. Aliquat 336 (a quaternary ammonium salt), as a co-extractant and phase modifier, improves recovery rate and purity at both physical and chemical levels. Its effects are manifested in: 1. Improved extraction efficiency: Scandium in solution forms complex anions with sulfate ions. Aliquat 336 can participate in the chemical reaction through anion exchange mechanism to extract these complex anions, forming more hydrophobic ion-pair complexes with scandium. Simultaneously, Aliquat 336 and Cyanex 572 act together on a single scandium ion, forming an electrically neutral, highly hydrophobic mixed coordination complex. 1. **Improved Extraction Efficiency:** This complex is more stable and soluble in the organic phase than the complex formed by Cyanex 572 alone, thus achieving higher extraction efficiency over a wider pH range and at lower acidity. 2. **Impurification Capability:** Aliquat 336 preferentially extracts sulfate anions formed by impurities such as iron and zinc, removing some potentially interfering impurities. 3. **Improved Organic Phase Physical Properties:** As a phase modifier, Aliquat 336 significantly reduces the interfacial tension between the organic and aqueous phases, improving phase separation, reducing impurities and scandium entrainment, and increasing phase purity. Simultaneously, it provides rapid phase separation with almost no third phase formation, ensuring the stability of continuous production. 4. **Expanded Extraction pH Range:** It can suppress impurity extraction over a wider pH range and has greater tolerance to fluctuations in feed acidity. Controlling the volume ratio of extractant to scandium-containing leachate within the range of 1:(5~10) can further improve the recovery rate and purity of scandium. If the volume ratio is too small (too little extractant), the scandium in the leachate cannot be completely extracted, resulting in a decrease in the scandium recovery rate. If the volume ratio is too large (too much extractant), impurities such as calcium, magnesium, and aluminum will be extracted along with scandium, resulting in a decrease in the purity of scandium.

[0029] S3. The scandium-containing organic phase was back-extracted using oxalic acid solution to obtain scandium oxalate precipitate;

[0030] In some preferred embodiments of this application, the concentration of the oxalic acid solution is 4wt%~10wt%, and the volume ratio of the oxalic acid solution to the scandium-containing organic phase is 1:(1~2).

[0031] Specifically, the concentration of the oxalic acid solution can be any one or any two of 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, and the volume ratio of the oxalic acid solution to the scandium-containing organic phase can be any one or any two of 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 1:2.

[0032] In this step, the oxalic acid solution simultaneously provides oxalate and hydrogen ions. During the back-extraction process, the hydrogen ions back-extract scandium ions from the scandium-containing organic phase into the aqueous phase. The scandium ions immediately react with the oxalate ions to precipitate scandium oxalate. This process replaces the traditional two-step operation (acid back-extraction to obtain scandium solution, which is then transferred to a precipitation tank and oxalic acid is added for precipitation) in one step. The back-extraction and precipitation are combined, resulting in a shorter and more efficient process. At the same time, this step avoids the losses caused by multiple operation steps, thus achieving a high scandium recovery rate and reducing losses. Furthermore, impurities such as iron and aluminum can form soluble complexes with oxalic acid. During the back-extraction-precipitation process, these soluble complexes tend to remain in the aqueous phase, resulting in a higher purity scandium product. In addition, the oxalic acid back-extraction reaction has a strong driving force and high back-extraction efficiency. The regenerated organic phase after the reaction contains less oxalic acid and other impurities, which can be directly returned to the extraction process for recycling, resulting in good stability. Controlling the concentration of oxalic acid solution can further control the recovery rate and purity of scandium. If the concentration of oxalic acid is too low, the back-extraction will be incomplete and the precipitation rate will be low. If the concentration of oxalic acid is too high, impurities may enter the scandium oxalate precipitate along with it, affecting the purity of the precipitate and increasing the cost.

[0033] S4. Calcining the scandium oxalate precipitate yields scandium oxide;

[0034] In some preferred embodiments of this application, scandium oxalate precipitate is first washed with pure water, then the washed scandium oxalate precipitate is heated to 340~360℃ and held at that temperature for 1.0~1.5h, and then heated to 800~900℃ for calcination to obtain scandium oxide. The calcination time is 1~2h, the purity of the obtained scandium oxide is greater than or equal to 96%, and the recovery rate of scandium element is greater than or equal to 89%.

[0035] Preferably, the purity of scandium oxide is greater than or equal to 99.98%, and the recovery rate of scandium element is greater than or equal to 93.64%.

[0036] In this step, heating to 340~360℃ and holding for 1.0~1.5h removes the water of crystallization and organic matter entrained in the scandium oxalate precipitate, thereby improving the purity. Then, heating to 800~900℃ for calcination not only fully calcines the scandium oxalate precipitate but also prevents the obtained scandium oxide from hardening and caking.

[0037] The technical solution of this application will be further described below with reference to specific embodiments.

[0038] Example 1

[0039] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0040] S1. Crude nickel-cobalt hydroxide was leached with 0.3 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 4 mL: 1 g. The leaching temperature was 40 °C and the leaching time was 2 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 3:1.

[0041] S2. Scandium-containing leachate is extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene is 4:1:15 and the volume ratio of extractant:scandium-containing leachate is 1:5.

[0042] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:1.

[0043] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.0 h, and then calcine it at 900℃ for 2 h to obtain scandium oxide.

[0044] The scandium oxide prepared in this embodiment has a purity of 96.71% and a scandium element recovery rate of 93.29%.

[0045] Example 2

[0046] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0047] S1. Crude nickel-cobalt hydroxide was leached with 0.3 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 4 mL: 1 g. The leaching temperature was 40 °C and the leaching time was 2 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 5:1.

[0048] S2. Scandium-containing leachate was extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene was 4:1:15 and the volume ratio of extractant:scandium-containing leachate was 1:7.

[0049] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:1.

[0050] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.5h, then heat it to 900℃ and calcine it for 2h to obtain scandium oxide.

[0051] The scandium oxide prepared in this embodiment has a purity of 99.54% and a scandium element recovery rate of 93.56%.

[0052] Example 3

[0053] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0054] S1. Crude nickel-cobalt hydroxide was leached with 0.3 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 4 mL: 1 g. The leaching temperature was 40 °C and the leaching time was 2 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 4:1.

[0055] S2. Scandium-containing leachate was extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene was 4:1:15 and the volume ratio of extractant:scandium-containing leachate was 1:7.

[0056] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:1.5.

[0057] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.5h, then heat it to 900℃ and calcine it for 2h to obtain scandium oxide.

[0058] The scandium oxide prepared in this embodiment has a purity of 99.87% and a scandium element recovery rate of 93.46%.

[0059] Example 4

[0060] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0061] S1. Crude nickel-cobalt hydroxide was leached with 0.3 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 4 mL: 1 g. The leaching temperature was 40 °C and the leaching time was 2 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 4:1.

[0062] S2. Scandium-containing leachate was extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene was 4:1:15 and the volume ratio of extractant:scandium-containing leachate was 1:7.

[0063] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:1.5.

[0064] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.2h, then heat it to 850℃ and calcine it for 1.5h to obtain scandium oxide.

[0065] The scandium oxide prepared in this embodiment has a purity of 99.98% and a scandium element recovery rate of 93.64%.

[0066] Example 5

[0067] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0068] S1. Crude nickel-cobalt hydroxide was leached with 0.5 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 3 mL: 1 g. The leaching temperature was 20 °C and the leaching time was 1 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 5:1.

[0069] S2. Scandium-containing leachate was extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene was 4:1:15 and the volume ratio of extractant:scandium-containing leachate was 1:10.

[0070] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:2.

[0071] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.2h, then heat it to 800℃ and calcine it for 1h to obtain scandium oxide.

[0072] The scandium oxide prepared in this embodiment has a purity of 97.85% and a scandium element recovery rate of 93.06%.

[0073] Example 6

[0074] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0075] S1. Crude nickel-cobalt hydroxide was leached with 0.1 mol / L dilute sulfuric acid and filtered to obtain a scandium-containing leachate. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 5 mL: 1 g. The leaching temperature was 60 °C and the leaching time was 3 h. The molar ratio of sulfuric acid in the dilute sulfuric acid to scandium in the crude nickel-cobalt hydroxide was 3:1.

[0076] S2. Scandium-containing leachate is extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene is 4:1:15 and the volume ratio of extractant:scandium-containing leachate is 1:5.

[0077] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:1.

[0078] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.2h, then heat it to 900℃ and calcine it for 2h to obtain scandium oxide.

[0079] The scandium oxide prepared in this embodiment has a purity of 99.84% and a scandium element recovery rate of 89.13%.

[0080] Comparative Example 1

[0081] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0082] S1. Crude nickel-cobalt hydroxide was leached with 0.1 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 3 mL: 1 g. The leaching temperature was 20 °C and the leaching time was 1 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 1:1.

[0083] S2. Scandium-containing leachate was extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene was 4:1:15 and the volume ratio of extractant:scandium-containing leachate was 1:10.

[0084] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:2.

[0085] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.5h, then heat it to 800℃ and calcine it for 1h to obtain scandium oxide.

[0086] The scandium oxide prepared in this embodiment has a purity of 99.62% and a scandium element recovery rate of 76.54%.

[0087] Comparative Example 2

[0088] A method for separating and purifying scandium from crude nickel cobalt hydroxide includes the following steps:

[0089] S1. Crude nickel-cobalt hydroxide was leached with 0.5 mol / L dilute sulfuric acid, and the solution containing scandium was obtained by filtration. The ratio of dilute sulfuric acid to crude nickel-cobalt hydroxide was 5 mL: 1 g. The leaching temperature was 60 °C and the leaching time was 3 h. The molar ratio of sulfuric acid to scandium in the dilute sulfuric acid was 6:1.

[0090] S2. Scandium-containing leachate is extracted using an extractant composed of Cyanex572, Aliquat336 and sulfonated kerosene to obtain a scandium-containing organic phase, wherein the volume ratio of Cyanex572:Aliquat336:sulfonated kerosene is 4:1:15 and the volume ratio of extractant:scandium-containing leachate is 1:5.

[0091] S3. The scandium-containing organic phase is back-extracted using a 4wt% oxalic acid solution to obtain scandium oxalate precipitate, wherein the volume ratio of oxalic acid solution to scandium-containing organic phase is 1:1.

[0092] S4. Wash the scandium oxalate precipitate with pure water, heat the washed scandium oxalate precipitate to 350℃ and keep it at that temperature for 1.0 h, and then calcine it at 900℃ for 2 h to obtain scandium oxide.

[0093] The scandium oxide prepared in this embodiment has a purity of 94.12% and a scandium element recovery rate of 93.43%.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 3 is that in step S1, the concentration of dilute sulfuric acid is 0.6 mol / L, the ratio of dilute sulfuric acid to crude nickel cobalt hydroxide is 2 mL: 1 g, and the molar ratio of sulfuric acid in dilute sulfuric acid to scandium in crude nickel cobalt hydroxide is 3:1.

[0096] The scandium oxide prepared in this comparative example has a purity of 94.12% and a scandium element recovery rate of 91.57%.

[0097] Comparative Example 4

[0098] The difference between this comparative example and Example 3 is that in step S2, only an extractant composed of Cyanex 572 extractant and sulfonated kerosene is used, without adding Aliquat 336, and the volume ratio of Cyanex 572 to sulfonated kerosene is 4:15.

[0099] The scandium oxide prepared in this comparative example has a purity of 89.97% and a scandium element recovery rate of 90.74%.

[0100] Comparative Example 5

[0101] The difference between this comparative example and Example 3 is that no extraction is performed; instead, oxalic acid solution is used directly to precipitate scandium in the scandium-containing leachate before proceeding to step S4.

[0102] The scandium oxide prepared in this comparative example has a purity of 86.54% and a scandium element recovery rate of 91.75%.

[0103] This application proposes a method for separating and purifying scandium from crude nickel-cobalt hydroxide, which produces the following beneficial effects: the selective leaching process achieves efficient separation of scandium from the main metals nickel and cobalt at the front end, with low reagent consumption, short process, and significant cost advantages; the novel synergistic extraction technology has ultra-high selectivity and extraction capacity for scandium, and the prepared scandium oxide has high purity and high recovery rate.

[0104] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for separating and purifying scandium from crude nickel-cobalt hydroxide, characterized in that, Includes the following steps: S1. Obtain crude nickel-cobalt hydroxide, which contains scandium. Leach the crude nickel-cobalt hydroxide with dilute sulfuric acid, and filter to obtain a scandium-containing leachate. The concentration of the dilute sulfuric acid is 0.1~0.5 mol / L, the ratio of the dilute sulfuric acid to the crude nickel-cobalt hydroxide is (3~5) mL:1 g, and the molar ratio of sulfuric acid to scandium in the dilute sulfuric acid is (3~5):

1. A selective leaching process is used to separate scandium from the main metals nickel and cobalt at the front end. S2. The scandium-containing leachate is subjected to scandium extraction treatment using an extractant to obtain a scandium-containing organic phase, wherein the extractant includes Cyanex 572 and Aliquat 336; S3. The scandium-containing organic phase is back-extracted using oxalic acid solution to obtain scandium oxalate precipitate; S4. Calcining the scandium oxalate precipitate to obtain scandium oxide; The scandium oxide has a purity of 96% or higher, and the scandium element recovery rate is 89% or higher.

2. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 1, characterized in that, In step S1, the leaching temperature is 20~60℃ and the leaching time is 1~3h.

3. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 1, characterized in that, In step S2, the volume ratio of Cyanex572 to Aliquat336 in the extractant is 4:

1.

4. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 3, characterized in that, In step S2, the extractant further includes sulfonated kerosene, and the volume ratio of Cyanex572, Aliquat336, and sulfonated kerosene in the extractant is 4:1:

15.

5. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 1, characterized in that, In step S2, the volume ratio of the extractant to the scandium-containing leachate is 1:(5~10).

6. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 1, characterized in that, In step S3, the concentration of the oxalic acid solution is 4wt%~10wt%.

7. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 6, characterized in that, In step S3, the volume ratio of the oxalic acid solution to the scandium-containing organic phase is 1:(1~2).

8. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 1, characterized in that, Step S4 further includes washing the scandium oxalate precipitate with pure water, heating the washed scandium oxalate precipitate to 340~360℃ and holding it at that temperature for 1.0~1.5h, and then calcining it at 800~900℃ to obtain scandium oxide.

9. The method for separating and purifying scandium from crude nickel-cobalt hydroxide according to claim 1, characterized in that, In step S4, the calcination time is 1-2 hours.