A method for preparing high-purity scandium oxide products from crude scandium oxide.

Abstract

This invention discloses a method for preparing high-purity scandium oxide from crude scandium oxide, comprising the following steps: dissolving crude scandium oxide with hydrochloric acid; adding an amine extractant to remove impurities such as iron and zinc, obtaining a purified solution after primary impurity removal; adding a complexing agent to the raffinate to complex scandium, followed by extraction of major impurities such as calcium, aluminum, magnesium, and manganese using a phosphate ester acidic extractant, obtaining a purified solution after secondary impurity removal; adding a decomplexing agent to the scandium-containing back-extraction solution to decomplex, adding a precipitating agent to the decomplexed scandium-containing solution to precipitate scandium, and subjecting the precipitate to filtration, washing, and calcination to obtain refined high-purity scandium oxide (>99.99%). The process of this invention has the advantages of short process flow, low cost, and high product quality, providing an effective impurity removal method for the preparation of high-purity scandium oxide.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of rare earth metal metallurgy, and particularly relates to a method for preparing high-purity scandium oxide product from coarse scandium oxide. BACKGROUND

[0002] Scandium is an excellent alloy material with wide application in many fields. In nature, large independent scandium ore is rarely seen, so scandium usually exists in association with other substances. The main source of scandium recovery in industry is scandium-containing secondary resources, such as titanium white waste acid, red mud, Baiyunebo ore, chlorinated smoke dust, etc. Low-grade scandium in the above-mentioned raw materials can be enriched by wet metallurgical methods such as solvent extraction, precipitation, ion exchange, etc., so as to obtain coarse scandium oxide product or enriched scandium solution, and then high-purity scandium oxide product is prepared by other means.

[0003] Coarse scandium oxide contains a large amount of impurities such as calcium, iron, magnesium, lithium, zinc, aluminum, manganese and nickel. Therefore, before preparing high-purity scandium oxide, the coarse scandium oxide needs to be converted into scandium-containing acid solution after acid dissolution, and then the impurity ions are removed.

[0004] At present, there has been a certain research basis for the deep removal of impurities from scandium-containing acid solution. For example, in the invention patent 202011143998.2, neutral extractant P350 is used to purify scandium in coarse scandium oxide leaching solution, and high-purity scandium oxide product is prepared after oxalic acid precipitation. However, P350 production process will cause serious environmental pollution, so it is facing the problem of interruption of extractant production and difficulty in procurement. In the invention patent CN201410809499.0, ion exchange method is used to purify scandium-containing solution, and the method of complexing scandium first and then adsorbing impurities is used to remove iron, aluminum, calcium and part of titanium, zirconium, magnesium, manganese and other impurities. The problem of this invention is that the ion exchange method is relatively complicated and has low efficiency.

[0005] In addition to solvent extraction and ion exchange technology, there is also a chemical precipitation method for purifying scandium, such as the invention of CN202310726842.4, a method for purifying scandium hydroxide to prepare high-purity scandium oxide. The method removes impurities by phosphate precipitation first, and then further purifies by solvent extraction, and obtains 3N grade high-purity scandium oxide product after scandium oxalate precipitation. This method has obvious effect on iron, zirconium, calcium, etc., but has poor effect on other impurity ions.

[0006] In view of the above problems, the present application is proposed. SUMMARY

[0007] This invention proposes a method for preparing high-purity scandium oxide from crude scandium oxide. This method effectively removes major impurities such as calcium, iron, magnesium, lithium, zinc, aluminum, manganese, and nickel, ultimately yielding a high-purity scandium oxide product with a purity exceeding 99.99%. The method primarily utilizes solvent extraction, is simple to operate, highly efficient, effective, low-cost, and produces superior product quality.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for preparing high-purity scandium oxide from crude scandium oxide, comprising the steps of:

[0010] (1) Acid dissolution of crude scandium: crude scandium oxide is dissolved in hydrochloric acid to obtain a scandium-containing solution;

[0011] (2) First stage extraction to remove impurities: Add inorganic acid to adjust the acidity of the scandium-containing solution, and use amine extractant to extract impurities trivalent iron and zinc ions to obtain a first stage purified solution after preliminary impurity removal;

[0012] (3) Complexation: Add a complexing agent, scandium, to the purified liquid after preliminary impurity removal in step (2);

[0013] (4) Two-stage extraction to remove impurities: Add an alkaline reagent to the scandium-containing solution after complexation in step (3) to adjust the pH value of the solution, and then use a phosphate ester acidic extractant to further extract the calcium, magnesium, aluminum and manganese impurities to obtain a two-stage purified solution after further impurity removal.

[0014] (5) Decomposition and Scandium precipitation: Add a decomposition agent to the purified liquid after impurity removal in step (4) to decompose the complex, and then add a precipitant to precipitate the scandium;

[0015] (6) Calcination: The scandium-containing precipitate obtained in step (5) is filtered, washed and calcined to obtain refined high-purity scandium oxide.

[0016] The technical principle of this invention is as follows:

[0017] Since Fe(III) preferentially complexes with the complexing agent over Sc(III), Fe(III) needs to be removed before complexing Sc(III). Amine extractants are used to remove Fe(III) from the scandium-containing solution, which also removes zinc impurities. An appropriate amount of complexing agent is added to the scandium-containing solution after removing iron and zinc to convert cationic scandium into complex anions, thereby avoiding the extraction of scandium by acidic extractants. During the two-stage extraction process, most of the impurities such as calcium, magnesium, aluminum, manganese, and some lithium and nickel, which exist in cationic form, are extracted by acidic extractants, while scandium, which exists in complex anionic form, is not extracted, thus obtaining the scandium-containing raffinate after impurity removal. Finally, scandium is precipitated by the scandium precipitation method, and the precipitate is oxidized and roasted to obtain high-purity scandium oxide.

[0018] The crude scandium oxide product is a scandium oxide solid containing one or more oxides selected from Fe2O3, CaO, MgO, Li2O, ZnO, Al2O3, MnO2, and Ni2O, with a scandium oxide content of 30% to 99%.

[0019] Optionally, in step (1), crude scandium oxide solid is dissolved by heating with hydrochloric acid of concentration of 2-12M, the liquid-solid ratio is 10:1-50:1, the temperature is room temperature-100℃, and the time is 5-60min.

[0020] Preferably, in step (1), crude scandium oxide solid is dissolved by heating with 6-12M hydrochloric acid, the liquid-to-solid ratio is 15:1-20:1, the temperature is 80-90℃, and the time is 20-30min.

[0021] Optionally, in step (2), the inorganic acid used to adjust the acidity is hydrochloric acid with a concentration of 2-12M, and the target acidity is adjusted to 1-6M; the extractant used is N235 (tri(octyl-decyl) tertiary amine), the volume fraction of N235 is 1-15%, the ratio of O / A is 1:5-5:1, and the extraction method is multi-stage countercurrent extraction.

[0022] Preferably, in step (2), the inorganic acid used to adjust the acidity is hydrochloric acid with a concentration of 6-12M, the target acidity is adjusted to 2-4M; the N235 concentration is 5-15%, the O / A ratio is 1:1-5:1, and the extraction method is 4-6 stages of countercurrent extraction.

[0023] Optionally, the complexing agent used in step (3) is one or more of EDTA (ethylenediaminetetraacetic acid), NTA (aminotriacetic acid), HEDTA (hydroxyethylethylenediaminetetraacetic acid), diethyltriaminepentaacetic acid (DTPA), trans-1,2-cyclohexanediaminetetraacetic acid (DCTA), and lactic acid, and the amount added is 0.8 to 1.0 times the theoretical amount required to complex Sc(Ⅲ).

[0024] Preferably, the amount of complexing agent added in step (3) is 0.9 to 1.0 times the amount theoretically required to complex Sc(Ⅲ).

[0025] Optionally, in step (4), the alkaline reagent used to adjust the pH is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water, and the pH is adjusted to 2-7; the acidic extractant used is P204 or P507, and the modifier used during extraction is one or more of TBP, 2-octanol, and isooctanol, with the extractant volume fraction being 1-10%, the modifier volume fraction being 0-10%, the O / A ratio being 1:5-5:1, the extraction equilibrium pH being 2-6, and the extraction method being multi-stage countercurrent extraction.

[0026] Preferably, in step (4), the pH is adjusted to 3-5; the volume fraction of the extractant is 5-10%; the volume fraction of the modifier is 5-10%; the ratio of O / A is 1:1-5:1; the extraction equilibrium pH is 4.8-5.0; and the extraction method is 3-5 stages of countercurrent extraction.

[0027] Optionally, in step (5), one or more of hydrochloric acid, sulfuric acid, and nitric acid are selected as the complex-dissolving agent, and oxalic acid, sodium carbonate, ammonia, ammonium carbonate, and carbon dioxide are selected as the precipitating agent.

[0028] Preferably, in step (5), hydrochloric acid with a concentration of 1-6M is used as the complexing agent and oxalic acid is used as the precipitant.

[0029] Preferably, the roasting temperature in step (6) is 700-900℃ and the roasting time is 1-2h.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. A multi-stage extraction method is used to purify scandium in crude scandium oxide, deeply removing impurities such as iron, magnesium, lithium, zinc, aluminum, manganese and nickel, and preparing high-purity scandium oxide products.

[0032] 2. The process is simple, the cost is low, the scandium loss rate is small, and the product quality is excellent. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the method of the present invention. Detailed Implementation

[0034] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide. The main steps include acid dissolution, primary extraction to remove iron and zinc, secondary extraction to remove calcium, magnesium, aluminum, and manganese, and precipitation of scandium. To illustrate the content of the present invention in detail, specific embodiments of each part are described with examples:

[0035] I. Acid solubility of crude scandium oxide

[0036] The crude scandium oxide used in this example was recovered from scandium-containing wastewater generated during the titanium dioxide process using the chloride method. It contains 76.44% Sc2O3, and the main impurities are Fe(Ⅲ), Mg, Li, Zn, Al, Mn, and Ni.

[0037] Example 1

[0038] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, wherein acid dissolution includes the following steps:

[0039] (1) Weigh a certain amount of crude scandium oxide into a beaker, add 12M hydrochloric acid at a liquid-to-solid ratio of 20:1, and seal with plastic wrap to prevent the hydrochloric acid from evaporating.

[0040] (2) When heated and dissolved at 90°C for 30 minutes, the dissolution rate of scandium can reach 97.72%.

[0041] Example 2

[0042] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, wherein acid dissolution includes the following steps:

[0043] (1) Weigh a certain mass of crude scandium oxide into a beaker, add 8M hydrochloric acid at a liquid-to-solid ratio of 15:1, and react under sealed conditions to prevent the hydrochloric acid from evaporating.

[0044] (2) When heated to 85°C for 25 minutes, the dissolution rate of scandium can reach 92.77%.

[0045] Example 3

[0046] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, wherein acid dissolution includes the following steps:

[0047] (1) Weigh a certain amount of crude scandium oxide into a beaker, add 6M hydrochloric acid at a liquid-to-solid ratio of 15:1, and seal with plastic wrap to prevent the hydrochloric acid from evaporating.

[0048] (2) The dissolution rate of scandium can reach 86.76% when heated at 80℃ for 20 minutes.

[0049] II. Removal of iron and zinc by scandium chloride solution extraction

[0050] Example 1

[0051] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, wherein the first-stage extraction for removing iron and zinc includes the following steps:

[0052] (1) Add 12M hydrochloric acid to the scandium chloride solution obtained by acid dissolution and adjust the acidity to 4M.

[0053] (2) The scandium-containing solution with adjusted acidity was used to extract impurities iron and zinc using N235. The organic phase was acidified with 1M hydrochloric acid in advance. The volume fraction of N235 was 15%, and the remainder was sulfonated kerosene.

[0054] (3) Under the condition of O / A = 1:1, after 6 stages of countercurrent extraction, the extraction rates of ferric iron and zinc were 99.91% and 99.94%, respectively, and the extraction rate of scandium was less than 0.15%.

[0055] Example 2

[0056] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, wherein the first-stage extraction for removing iron and zinc includes the following steps:

[0057] (1) Add 6M hydrochloric acid to the scandium chloride solution obtained by acid dissolution and adjust the acidity to 2M.

[0058] (2) The scandium-containing solution with adjusted acidity was used to extract impurities iron and zinc using N235. The organic phase was acidified with 1M hydrochloric acid in advance. The volume fraction of N235 was 5%, and the remainder was sulfonated kerosene.

[0059] (3) Under the condition of O / A = 5:1, after 4 stages of countercurrent extraction, the extraction rates of ferric iron and zinc were 99.90% and 99.95%, respectively, and the extraction rate of scandium was less than 0.13%.

[0060] Example 3

[0061] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, wherein the first-stage extraction for removing iron and zinc includes the following steps:

[0062] (1) Add 8M hydrochloric acid to the scandium chloride solution obtained by acid dissolution and adjust the acidity to 3M.

[0063] (2) The scandium-containing solution with adjusted acidity was used to extract impurities iron and zinc using N235. The organic phase was acidified with 1M hydrochloric acid in advance. The volume fraction of N235 was 10%, and the remainder was sulfonated kerosene.

[0064] (3) Under the condition of O / A = 3:1, after 5 stages of countercurrent extraction, the extraction rates of ferric iron and zinc were 99.91% and 99.96%, respectively, and the extraction rate of scandium was less than 0.14%.

[0065] III. Extraction and removal of calcium, magnesium, aluminum, and manganese from a single-stage purification solution

[0066] Example 1

[0067] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, which includes the following steps for removing calcium, magnesium, aluminum, and manganese from a purification solution:

[0068] (1) Add EDTA (ethylenediaminetetraacetic acid) to a section of the purification solution to complex scandium. The amount added is 1.0 times the amount that can theoretically complex all Sc(III).

[0069] (2) Add sodium hydroxide solid to the solution after scandium complexation to adjust the pH to 5.0. Stir and complex for 24 hours, filter the precipitate, and obtain the filtrate.

[0070] (3) The pH-adjusted scandium-containing solution was used to extract impurities of calcium, magnesium, aluminum, and manganese using P204. The volume fraction of P204 was 5%, the volume fraction of TBP was 5%, and the remainder was sulfonated kerosene.

[0071] (4) Under the condition of O / A = 5:1, after three stages of countercurrent extraction, at the equilibrium pH = 4.90, the extraction rates of calcium, magnesium, aluminum and manganese were 99.97%, 99.90%, 99.99% and 99.95%, respectively, and the scandium extraction rate was less than 0.08%.

[0072] Example 2

[0073] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, comprising the following steps: Removing calcium, magnesium, aluminum, and manganese from a first-stage raffinate.

[0074] (1) Add lactic acid-complexed scandium to a first-stage purification solution, with the amount added being 0.9 times the theoretical amount of Sc(III) complexed.

[0075] (2) Add sodium carbonate solid to the solution after scandium complexation to adjust the pH to 3.2. Stir and complex for 24 hours, filter the precipitate, and obtain the filtrate.

[0076] (3) The pH-adjusted scandium-containing solution was used to extract impurities such as calcium, magnesium, aluminum and manganese using P507. The volume fraction of P507 was 10%, the volume fraction of isooctanol was 5%, and the remainder was sulfonated kerosene.

[0077] (4) Under the condition of O / A = 3:1, after 4 stages of countercurrent extraction, at the equilibrium pH = 4.51, the extraction rates of calcium, magnesium, aluminum and manganese were 99.92%, 99.82%, 99.95% and 99.89%, respectively, and the scandium extraction rate was less than 0.4%.

[0078] Example 3

[0079] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, comprising the following steps: Removing calcium, magnesium, aluminum, and manganese from a first-stage raffinate.

[0080] (1) Add DCTA-complexed scandium to a first-stage purification solution, with the amount added being 0.95 times the theoretical amount of Sc(Ⅲ) complexed.

[0081] (2) Add sodium bicarbonate solid to the solution after scandium complexation to adjust the pH to 4.2. Stir and complex for 24 hours, filter the precipitate, and obtain the filtrate.

[0082] (3) The pH-adjusted scandium-containing solution was used to extract impurities of calcium, magnesium, aluminum and manganese using P204. The volume fraction of P204 was 10%, the volume fraction of 2-octanol was 10%, and the remainder was sulfonated kerosene.

[0083] (4) Under the condition of O / A = 1:1, after 5 stages of countercurrent extraction, at the equilibrium pH = 4.86, the extraction rates of calcium, magnesium, aluminum and manganese were 99.91%, 99.82%, 99.96% and 99.88%, respectively, and the scandium extraction rate was less than 0.29%.

[0084] IV. Preparation of high-purity scandium oxide by oxalic acid precipitation

[0085] Example 1

[0086] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, which involves removing lithium and nickel by oxalic acid precipitation to prepare high-purity scandium oxide, comprising the following steps:

[0087] (1) Add 6M hydrochloric acid to the second-stage raffinate to dissolve the complex. The amount added is 1.0 times the theoretical amount.

[0088] (2) Add 1.0 times the amount of oxalic acid dihydrate required to complex Sc(Ⅲ) to the solution after decomposition, stir and precipitate for 2 hours to obtain scandium oxalate precipitate, and remove impurities lithium and nickel.

[0089] (3) The scandium oxalate precipitate was rinsed with ultrapure water to remove sodium salt, and then calcined at 900℃ for 1 h to obtain scandium oxide solid. The purity of scandium oxide was greater than 99.99%, and the removal rates of lithium and nickel were 99.96% and 99.92%, respectively.

[0090] Example 2

[0091] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, which involves removing lithium and nickel by oxalic acid precipitation to prepare high-purity scandium oxide, comprising the following steps:

[0092] (1) Add 1M hydrochloric acid to the second-stage raffinate to dissolve the complex. The amount added is 1.1 times the theoretical amount.

[0093] (2) Add 0.9 times the amount of sodium oxalate required to complex Sc(Ⅲ) to the solution after decomposition, stir and precipitate for 2 hours to obtain scandium oxalate precipitate, and remove impurities lithium and nickel.

[0094] (3) The scandium oxalate precipitate was rinsed with ultrapure water to remove sodium salt, and then calcined at 800℃ for 1.5 h to obtain scandium oxide solid. The purity of scandium oxide was greater than 99.99%, and the removal rates of lithium and nickel were 99.94% and 99.90%, respectively.

[0095] Example 3

[0096] The present invention provides a method for preparing high-purity scandium oxide from crude scandium oxide, which involves removing lithium and nickel by oxalic acid precipitation to prepare high-purity scandium oxide, comprising the following steps:

[0097] (1) Add 3M hydrochloric acid to the second-stage raffinate to dissolve the complex. The amount added is 1.0 times the theoretical amount.

[0098] (2) Add 1.1 times the amount of oxalic acid dihydrate required to complex Sc(Ⅲ) to the solution after decomposition, stir and precipitate for 2 hours to obtain scandium oxalate precipitate, and remove impurities lithium and nickel.

[0099] (3) The scandium oxalate precipitate was rinsed with ultrapure water to remove the sodium salt, and then calcined at 700℃ for 2 hours to obtain scandium oxide solid. The purity of scandium oxide was greater than 99.99%, and the removal rates of lithium and nickel were 99.95% and 99.91%, respectively.

[0100] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity scandium oxide products from crude scandium oxide, characterized in that, Including the following steps: (1) Acid dissolution of crude scandium: crude scandium oxide is dissolved in hydrochloric acid to obtain a scandium-containing chloride solution; (2) First stage extraction to remove impurities: Add inorganic acid to adjust the acidity of the scandium chloride solution, and use amine extractant to extract the impurities trivalent iron and zinc ions to obtain a first stage purified solution after preliminary impurity removal; (3) Complexation: Add a complexing agent, scandium, to the purified liquid after impurity removal in step (2); (4) Two-stage extraction to remove impurities: Add an alkaline reagent to the scandium-containing solution after complexation in step (3) to adjust the pH value of the solution, and then use a phosphate ester acidic extractant to further extract the calcium, magnesium, aluminum and manganese impurities. (5) Decomposition and Scandium precipitation: Add a decomposition agent to the purified liquid after impurity removal in step (4) to decompose the complex, and then add a precipitant to precipitate the scandium; (6) Calcination: The scandium-containing precipitate is filtered, washed and calcined to obtain refined high-purity scandium oxide; In step (4), the pH is adjusted to 3-5; the acidic extractant used is P204 or P507; the modifier used during extraction is one or more of TBP, 2-octanol, and isooctanol; the volume fraction of the extractant is 5-10%; the volume fraction of the modifier is 5-10%; the ratio of O / A is 1:1-5:1; the extraction equilibrium pH is 4.8-5.0; and the extraction method is 3-5 stages of countercurrent extraction.

2. The method according to claim 1, characterized in that, The crude scandium oxide is a solid powder or granules with a scandium oxide mass fraction of 30% to 99%.

3. The method according to claim 1, characterized in that, In step (1), hydrochloric acid is used to heat and dissolve the crude scandium oxide solid.

4. The method according to claim 1, characterized in that, In step (2), the inorganic acid used to adjust the acidity is 2-12M concentrated hydrochloric acid, and the target acidity is 1-6M.

5. The method according to claim 1, characterized in that, The extractant used in step (2) is tri(octyl-decyl)alkyl tertiary amine, and the extraction method is multi-stage countercurrent extraction.

6. The method according to claim 1, characterized in that, The complexing agent used in step (3) is one or more of ethylenediaminetetraacetic acid, aminotriacetic acid, hydroxyethyl ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, and lactic acid, and the amount added is 0.8 to 1.0 times the theoretical amount required to complex scandium (III).

7. The method according to claim 1, characterized in that, The alkaline reagent used to adjust the pH in step (4) is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water.

8. The method according to claim 1, characterized in that, In step (5), one or more of hydrochloric acid, sulfuric acid, and nitric acid are selected as the complex-dissolving agent, and oxalic acid, sodium carbonate, ammonia, ammonium carbonate, and carbon dioxide are selected as the precipitating agent.

9. The method according to claim 1, characterized in that, In step (6), the roasting temperature is 700~900℃ and the roasting time is 1~2h.

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