Preparation method of high-scandium aluminum oxide

Abstract

The invention provides a preparation method of high-scandium aluminum oxide, and belongs to the field of aluminum oxide production. The method comprises the following steps: S1, adding an aluminum hydroxide seed crystal into a scandium-containing sodium aluminate solution to obtain mixed slurry; s2, carrying out solid-liquid separation on the mixed slurry to obtain scandium-containing aluminum hydroxide; s3, carrying out size grading on the scandium-containing aluminum hydroxide to obtain fine-particle scandium-containing aluminum hydroxide and coarse-particle scandium-containing aluminum hydroxide; s4, judging whether the scandium content in the coarse-particle scandium-containing aluminum hydroxide is not less than the set scandium content, if not, taking the fine-particle scandium-containing aluminum hydroxide as a seed crystal, and circulating the steps S1 to S3 until the scandium content in the coarse-particle scandium-containing aluminum hydroxide is not less than the set scandium content; and S5, roasting the high-scandium aluminum hydroxide to obtain the high-scandium aluminum oxide. The high-scandium aluminum oxide with uniform distribution is directly prepared in the Bayer process aluminum oxide production process, and the problem of non-uniform scandium distribution in an aluminum-scandium alloy product caused by non-uniform mixing of raw materials is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of alumina production, and in particular to a method for preparing high-scandium alumina. Background Art

[0002] Aluminum-scandium alloys are widely used in aviation, aerospace, national defense, electronic information, new energy vehicles and other fields due to their excellent mechanical properties, high-temperature resistance and lightweight advantages. There are three main processes for preparing aluminum-scandium alloys today, namely the cross-doping method, molten salt electrolysis method and metal thermal reduction method. The cross-doping method is a traditional process for preparing aluminum-scandium intermediate alloys. It wraps a certain proportion of high-purity Sc with aluminum foil, adds it to the aluminum melt under argon protection, keeps it warm for a sufficient time, stirs it thoroughly, and then injects it into an iron mold or copper mold to produce an aluminum-scandium alloy. The principle of this method is simple, but because the melting points of Sc and Al are very different, the aluminum melt must be superheated to a higher temperature, making it difficult to prepare alloy products with stable composition and uniform structure. The thermal reduction method uses scandium-containing compounds, including scandium fluoride, scandium chloride, and scandium oxide, as raw materials. It uses active metals such as aluminum, magnesium, and calcium as reducing agents to produce aluminum-scandium alloys at high temperatures. This method offers the advantages of simple processing and high scandium content in the aluminum-scandium alloy product. However, this method is an intermittent operation, resulting in low efficiency and large amounts of waste residue. The molten salt electrolysis method involves adding scandium-containing compounds and aluminum-containing compounds to a specific molten salt electrolyte system to produce aluminum-scandium alloys through electrolysis. This method features continuous production, high production efficiency, and ease of automated production. Therefore, the molten salt electrolysis method is the most commonly used method for preparing aluminum-scandium alloys.

[0003] However, the molten salt system currently used in the molten salt electrolysis method is generally a chloride system. The electrolysis preparation of aluminum-scandium alloy using scandium chloride as the raw material is characterized by low electrolysis temperature and the electrolyte being easily soluble in water for easy recycling; however, the preparation process of anhydrous scandium chloride is complicated, it is easy to absorb water, easy to volatilize, and difficult to store. The prior art discloses a method for producing aluminum-scandium alloy using aluminum and scandium oxides as raw materials and sodium fluoride and aluminum fluoride as electrolytes. This method does not require the use of metallic scandium, has a short process flow, and can greatly reduce the production cost of aluminum-scandium alloy. However, there is a problem of uneven mixing of the raw materials scandium oxide and aluminum oxide, which can easily cause uneven distribution of scandium in the aluminum-scandium alloy product. Therefore, how to solve the problem of uneven distribution of scandium caused by uneven mixing of raw materials when using aluminum and scandium oxides as raw materials for electrolysis to produce aluminum-scandium alloy is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] The present application provides a method for preparing high-scandium alumina to solve the problem of uneven scandium distribution caused by uneven mixing of raw materials when aluminum and scandium oxides are used as raw materials for electrolytic production of aluminum-scandium alloy.

[0005] The present invention provides a method for preparing high-scandium alumina, which comprises:

[0006] S1, adding aluminum hydroxide seed crystals to a scandium-containing sodium aluminate solution to perform a decomposition and agglomeration reaction to obtain a mixed slurry;

[0007] S2, performing solid-liquid separation on the mixed slurry to obtain scandium-containing aluminum hydroxide;

[0008] S3, classifying the scandium-containing aluminum hydroxide to obtain fine particles of scandium-containing aluminum hydroxide and coarse particles of scandium-containing aluminum hydroxide;

[0009] S4, determining whether the scandium content in the coarse-grained scandium-containing aluminum hydroxide satisfies a set scandium content or not; if not, using the fine-grained scandium-containing aluminum hydroxide as a seed crystal, and looping through steps S1 to S3 until the scandium content in the coarse-grained scandium-containing aluminum hydroxide satisfies a set scandium content or not; if so, using the coarse-grained scandium-containing aluminum hydroxide as high-scandium aluminum hydroxide; and

[0010] S5. calcining the high-scandium aluminum hydroxide to obtain high-scandium aluminum oxide.

[0011] Optionally, the method for preparing the scandium-containing sodium aluminate solution includes:

[0012] dissolving scandium oxide or a soluble scandium salt and adjusting the pH value to a set pH value so as to precipitate scandium hydroxide to obtain colloidal scandium hydroxide;

[0013] The colloidal scandium hydroxide is dissolved in a sodium aluminate solution to obtain a scandium-containing sodium aluminate solution.

[0014] Optionally, the set pH value is 8-10.

[0015] Optionally, the caustic soda concentration of the sodium aluminate solution is Na2O K The molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α K It is 1.35 to 1.60.

[0016] Optionally, based on 1 L of sodium aluminate solution, the added amount of the colloidal scandium hydroxide is ≥2 g.

[0017] Optionally, the dissolution temperature is 40°C to 60°C, and the dissolution time is ≥2h.

[0018] Optionally, the temperature of the decomposition and agglomeration reaction is 65° C. to 80° C., and the time of the decomposition and agglomeration reaction is 4 h to 10 h.

[0019] Optionally, based on 1 L of scandium-containing sodium aluminate solution, the amount of the aluminum hydroxide seed crystal added is 50 g to 200 g.

[0020] Optionally, the particle size of the fine-particle scandium-containing aluminum hydroxide is less than 45 μm, and the particle size of the coarse-particle scandium-containing aluminum hydroxide is greater than or equal to 45 μm.

[0021] Optionally, the calcination temperature is 900° C. to 1200° C., and the calcination time is 5 min to 30 min.

[0022] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0023] The present application provides a method for preparing high-scandium aluminum oxide, which includes the following steps: S1, adding aluminum hydroxide seed crystals to a sodium aluminate solution containing scandium to perform a decomposition and agglomeration reaction to obtain a mixed slurry; S2, performing solid-liquid separation on the mixed slurry to obtain scandium-containing aluminum hydroxide; S3, performing particle size classification on the scandium-containing aluminum hydroxide to obtain fine-grained scandium-containing aluminum hydroxide and coarse-grained scandium-containing aluminum hydroxide; S4, determining whether the scandium content in the coarse-grained scandium-containing aluminum hydroxide meets or exceeds a set scandium content; if not, using the fine-grained scandium-containing aluminum hydroxide as a seed crystal, and repeating steps S1 to S3 until the scandium content in the coarse-grained scandium-containing aluminum hydroxide meets or exceeds a set scandium content; if so, using the coarse-grained scandium-containing aluminum hydroxide as high-scandium aluminum hydroxide; S5, calcining the high-scandium aluminum hydroxide to obtain high-scandium aluminum oxide. First, the aluminum hydroxide seed crystals induce the decomposition of the sodium aluminate solution. The seed crystals adsorb Sc through van der Waals forces 3+ Initial agglomerates are formed, and then Al(OH)3 precipitates in the gaps between the agglomerates, 3+ The scandium content is gradually enriched through multiple cycles to increase the Sc content of the coarse particles of scandium-containing aluminum hydroxide to the required content. Finally, Sc2O3 and Al2O3 are calcined to form a uniform solid solution. 3+ Replace Al 3+ The scandium enters the corundum lattice, forming high-scandium alumina, which can be used as the raw material for aluminum-scandium alloy products. This allows the direct production of evenly distributed high-scandium alumina during the Bayer process, avoiding the problem of uneven scandium distribution in aluminum-scandium alloy products caused by uneven mixing of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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.

[0025] 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.

[0026] Figure 1 A schematic flow chart of a method for preparing high-scandium alumina provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] 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.

[0028] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0029] In addition, in the description of the specification of this application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass represent the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] Figure 1 A schematic flow chart of a method for preparing high-scandium alumina provided in an embodiment of the present application.

[0032] like Figure 1 As shown, the present application provides a method for preparing high-scandium alumina, the method comprising:

[0033] S1, adding aluminum hydroxide seed crystals to a scandium-containing sodium aluminate solution to perform a decomposition and agglomeration reaction to obtain a mixed slurry;

[0034] In some embodiments, the temperature of the decomposition agglomeration reaction is 65° C. to 80° C., and the time of the decomposition agglomeration reaction is 4 h to 10 h.

[0035] By limiting the temperature range to 65°C to 80°C and the reaction time to 4 to 10 hours, the decomposition kinetics and crystallization agglomeration process of the sodium aluminate solution are regulated, achieving efficient agglomeration and growth of fine crystals and ensuring uniform elemental distribution in the scandium-containing system. For example, the decomposition and agglomeration reaction temperature can be 65°C, 70°C, 75°C, 78°C, 80°C, etc., and the decomposition and agglomeration reaction time can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.

[0036] In some embodiments, the method for preparing the scandium-containing sodium aluminate solution comprises:

[0037] dissolving scandium oxide or a soluble scandium salt and adjusting the pH value to a set pH value so as to precipitate scandium hydroxide to obtain colloidal scandium hydroxide;

[0038] The colloidal scandium hydroxide is dissolved in a sodium aluminate solution to obtain a sodium aluminate solution.

[0039] It should be noted that the chemical formula of scandium hydroxide is Sc(OH)3. The scandium hydroxide prepared by adjusting the pH is in a gel-like state, and the gel-like scandium hydroxide is easy to dissolve in the sodium aluminate solution.

[0040] In some embodiments, the set pH value is 8-10.

[0041] Ammonia or sodium hydroxide is added to the scandium salt solution to control the pH to 8-10 to precipitate scandium hydroxide. Scandium hydroxide cannot precipitate at a pH below 8, as it is an amphoteric substance. Scandium hydroxide may dissolve again at a pH above 10. For example, the pH of the scandium salt solution can be adjusted to 8, 8.5, 8.8, 9, 9.5, 10, and the like.

[0042] In some embodiments, the caustic soda concentration of the sodium aluminate solution is Na2O K The molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α K It is 1.35 to 1.60.

[0043] The concentration of sodium aluminate solution is the concentration of the seminal fluid in the alumina production process, which can directly decompose aluminum hydroxide. For example, the caustic soda concentration of sodium aluminate solution is Na2O K The molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α, which is 100g / L, 110g / L, 120g / L, 130g / L, 140g / L, 160g / L, 170g / L, etc. K It can be 1.35, 1.40, 1.45, 1.50, 1.60, etc.

[0044] In some embodiments, based on 1 L of sodium aluminate solution, the amount of the colloidal scandium hydroxide added is ≥ 2 g.

[0045] In 1L of sodium aluminate solution, the amount of colloidal scandium hydroxide added is ≥2g. Adding an excess of scandium hydroxide is beneficial for preparing a sodium aluminate solution with a high scandium concentration. For example, the amount of colloidal scandium hydroxide added can be 2g, 2.2g, 2.4g, 2.6g, 2.8g, 3.0g, etc.

[0046] In some embodiments, the dissolution temperature is 40° C. to 60° C., and the dissolution time is ≥ 2 h.

[0047] A temperature of 40-60°C is beneficial for the dissolution of colloidal scandium hydroxide. If the temperature is above 60°C, the solubility of scandium in the sodium aluminate solution decreases. If the temperature is below 40°C, the sodium aluminate solution becomes unstable and easily decomposes. Furthermore, it takes at least 2 hours for scandium to dissolve in the sodium aluminate solution. For example, the dissolution temperature can be 40°C, 45°C, 50°C, 55°C, 60°C, etc., and the dissolution time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc.

[0048] S2, performing solid-liquid separation on the mixed slurry to obtain scandium-containing aluminum hydroxide;

[0049] In some embodiments, based on 1 L of scandium-containing sodium aluminate solution, the amount of the aluminum hydroxide seed crystal added is 50 g to 200 g.

[0050] In 1L of sodium aluminate solution containing scandium, the amount of aluminum hydroxide seed crystals added is 50g to 200g. Adding seed crystals to the sodium aluminate solution can induce the decomposition and agglomeration of aluminum hydroxide, making the particle size of the aluminum hydroxide product coarser. If the amount of aluminum hydroxide seed crystals added is less than 50g / L, the amount of aluminum hydroxide product is too small. If the amount of aluminum hydroxide seed crystals added is higher than 200g / L, the scandium content in the product will be reduced. Exemplarily, in 1L of sodium aluminate solution containing scandium, the amount of aluminum hydroxide seed crystals added can be 50g, 70g, 100g, 120g, 150g, 180g, 200g, etc.

[0051] S3, classifying the scandium-containing aluminum hydroxide to obtain fine particles of scandium-containing aluminum hydroxide and coarse particles of scandium-containing aluminum hydroxide;

[0052] In some embodiments, the particle size of the fine particles of scandium-containing aluminum hydroxide is less than 45 μm, and the particle size of the coarse particles of scandium-containing aluminum hydroxide is greater than or equal to 45 μm.

[0053] Fine particles (<45 μm) have a larger specific surface area and higher surface activity. They act as seeds during the decomposition of the sodium aluminate solution, accelerating the agglomeration and crystal growth of aluminum hydroxide. Therefore, if the scandium content in the coarse particles does not meet the standard (e.g., below the set value), the fine particles can be returned to the system as seeds for recycling (steps S1 to S3). Scandium is enriched through multiple agglomeration processes, ultimately increasing the scandium content of the coarse particles.

[0054] Coarse particles (≥45μm) are calcined to form high-scandium alumina, which can be used as a raw material for the electrolytic production of aluminum-scandium alloys. At the same time, coarse particles of scandium-containing aluminum hydroxide that do not reach the required scandium content can be crushed to form fine particles of scandium-containing aluminum hydroxide used as seed crystals.

[0055] S4, determining whether the scandium content in the coarse-grained scandium-containing aluminum hydroxide satisfies a set scandium content or not; if not, using the fine-grained scandium-containing aluminum hydroxide as a seed crystal, and looping through steps S1 to S3 until the scandium content in the coarse-grained scandium-containing aluminum hydroxide satisfies a set scandium content or not; if so, using the coarse-grained scandium-containing aluminum hydroxide as high-scandium aluminum hydroxide;

[0056] It should be noted that during the Bayer process, aluminum hydroxide is added as seed crystals to induce decomposition and increase the decomposition rate of aluminum hydroxide. The seed crystals added in the first experiment were not aluminum hydroxide containing scandium. After decomposition and agglomeration in the sodium aluminate solution containing scandium, the seed crystals will become aluminum hydroxide containing scandium. However, the scandium content in one cycle is low. Therefore, the fine aluminum hydroxide particles obtained in the first cycle are returned for a second decomposition and agglomeration. The scandium content in the aluminum hydroxide will increase, and multiple cycles will produce an aluminum hydroxide product with a high scandium content.

[0057] S5. calcining the high-scandium aluminum hydroxide to obtain high-scandium aluminum oxide.

[0058] In some embodiments, the calcination temperature is 900° C. to 1200° C., and the calcination time is 5 min to 30 min.

[0059] Under the calcination conditions of 900℃~1200℃ and 5min~30min, Sc2O3 and Al2O3 form a uniform solid solution (Al2O3-Sc), Sc 3+ Replace Al 3+ The scandium enters the alumina lattice, thus avoiding the segregation problem of metallic scandium in traditional electrolysis. For example, the calcination temperature can be 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, etc., and the calcination time can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.

[0060] The embodiments of the present application provide a method for preparing high-scandium alumina, which directly prepares uniformly distributed high-scandium alumina during the Bayer process alumina production process. This can not only avoid the problem of uneven scandium distribution in the aluminum-scandium alloy product caused by uneven mixing of raw materials, but also shorten the process flow and reduce production costs.

[0061] In summary, the present application solves the problem of uneven scandium distribution caused by uneven mixing when using aluminum and scandium oxide as raw materials in the traditional electrolysis method through the following core mechanisms:

[0062] (1) Uniform pre-dispersion of scandium element (solution stage)

[0063] Colloidal scandium hydroxide dissolution technology: By adjusting the pH of the scandium salt solution to 8-10, colloidal Sc(OH)3 is generated. Its gel-like properties make it easier to disperse in the sodium aluminate solution, avoiding the agglomeration problem during physical mixing of traditional oxide powders.

[0064] Optimization of dissolution temperature and time: dissolution conditions of 40-60℃ and ≥2h to ensure that Sc(OH)3 is fully dissolved into Sc 3+ It exists in ionic form rather than in the form of solid particles, ensuring the molecular-level dispersion of scandium from the source.

[0065] Sodium aluminate solution system adaptability: The caustic ratio (αk = 1.35 ~ 1.60) and concentration (Na2O100 ~ 170g / L) of sodium aluminate solution are controlled to make Sc 3+ With AlO2 - Form stable complexes such as [Sc(AlO2)n] 3- , suppressing local concentration gradients and further enhancing uniformity.

[0066] (2) Seed-induced uniform agglomeration (reaction stage)

[0067] Dynamic decomposition and agglomeration process: Under the conditions of 65-80℃ and 4-10h, aluminum hydroxide seeds (50-200g / L) induce the decomposition of sodium aluminate solution, and scandium elements (Sc 3+ ) is uniformly embedded in the aluminum hydroxide lattice through the following mechanisms: Physical flocculation: fine crystal seeds (<45μm) adsorb Sc through van der Waals forces 3+ , forming initial agglomerates; crystallization agglomeration: Al(OH)3 in the solution precipitates in the gaps between the agglomerates, 3+ Fixed in the crystal lattice to form dense composite particles.

[0068] Coordinated regulation of temperature and time: low temperature (65-75℃) prolongs the nucleation period and promotes Sc 3+ Uniform adsorption; the high temperature section (75-80°C) accelerates crystal growth and reduces the generation of secondary crystal nuclei.

[0069] (3) Particle size classification and cyclic enrichment (post-processing stage)

[0070] Particle size classification (fine particles <45μm circulation): crush the coarse particles that do not meet the standards (≥45μm) into fine particles and then recycle them back to the system. Through multiple decomposition and agglomeration, the scandium is gradually enriched. Specific surface area effect: the high specific surface area of fine particles (>5m 2 / g) provides more active sites and accelerates Sc 3+ adsorption and co-deposition.

[0071] Feedback control mechanism: The scandium content of coarse particles is dynamically detected, and only particles that meet the standards enter the roasting process, while particles that do not meet the standards continue to circulate, ensuring the uniformity of Sc distribution in the final product.

[0072] (4) Solid solution strengthening during the roasting process (final product stage)

[0073] High temperature solid solution formation: Sc2O3 and Al2O3 form a uniform solid solution (Al2O3-Sc) when calcined at 900℃~1200℃. 3+ Replace Al 3+ It enters the alumina lattice, avoiding the segregation problem of metallic scandium in traditional electrolysis.

[0074] Lattice matching: Sc 3+ (ionic radius ) and Al 3+ The size difference is compensated by lattice distortion to form a stable doping structure.

[0075] 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.

[0076] Example 1

[0077] This embodiment provides a method for preparing high-scandium alumina, comprising the following steps:

[0078] Sa: Scandium oxide is used as the raw material, dissolved in 30% hydrochloric acid, and then slowly added with NaOH. When the pH value is 6-7, the addition is stopped. Scandium hydroxide precipitates in a gel-like state. After filtering and washing, the scandium hydroxide is set aside;

[0079] Sb: Take 1000ml of refined sodium aluminate solution in production, and the semen Na2O k 140g / L, ak 1.4g / L, add Sa to prepare 2g of scandium hydroxide, stir and dissolve in a 40℃ water bath for 4h, then filter to obtain a sodium aluminate solution containing scandium. The scandium solution is analyzed, Sc 3+ The concentration is 0.1g / L;

[0080] Sc: Add 1000 ml of scandium-containing sodium aluminate solution into the decomposition tank, and add 50 g of aluminum hydroxide seeds, with a seed solid content of 50 g / L, an agglomeration temperature of 75 ° C, and a time of 6 hours;

[0081] Sd: After the agglomeration is completed, liquid-solid separation is performed to obtain aluminum hydroxide containing scandium. The Sc content is 0.098% after analysis.

[0082] Se: The scandium-containing aluminum hydroxide obtained by six cycles was calcined at 1050°C to obtain scandium-containing aluminum oxide with a particle size of -45 μm, a Sc content of 15%, and a Sc content of 0.15%.

[0083] Example 2

[0084] Sa: Scandium oxide is used as the raw material, dissolved in 30% hydrochloric acid, and then slowly added with NaOH. When the pH value is 6-7, the addition is stopped. Scandium hydroxide precipitates in a gel-like state. After filtering and washing, the scandium hydroxide is set aside;

[0085] Sb: Take 1000ml of refined sodium aluminate solution in production, and the semen Na2O k 150g / L, ak 1.45g / L, add Sa to prepare 3g of scandium hydroxide, stir and dissolve in a 40℃ water bath for 4h, then filter to obtain a sodium aluminate solution containing scandium. The scandium solution is analyzed, Sc 3+ The concentration is 0.17g / L;

[0086] Sc: Add 1000 ml of scandium-containing sodium aluminate solution into the decomposition tank, and add 100 g of aluminum hydroxide seed crystals, with a seed crystal solid content of 100 g / L, an agglomeration temperature of 75 ° C, and a time of 6 hours;

[0087] Sd: After the agglomeration is completed, liquid-solid separation is performed to obtain aluminum hydroxide containing scandium. The Sc content is 0.08% after analysis.

[0088] Se: The scandium-containing aluminum hydroxide obtained by six cycles was calcined at 1050° C. to obtain scandium-containing aluminum oxide with a particle size of -45 μm, a Sc content of 10%, and a Sc content of 0.12%.

[0089] Example 3

[0090] Sa: Scandium oxide is used as the raw material, dissolved in 30% hydrochloric acid, and then slowly added with NaOH. When the pH value is 6-7, the addition is stopped. Scandium hydroxide precipitates in a gel-like state. After filtering and washing, the scandium hydroxide is set aside;

[0091] Sb: Take 1000ml of refined sodium aluminate solution in production, and the semen Na2O k150g / L, ak 1.45g / L, add Sa to prepare 3g of scandium hydroxide, stir and dissolve in a 40℃ water bath for 4h, then filter to obtain a sodium aluminate solution containing scandium. The scandium solution is analyzed, Sc 3+ The concentration is 0.17g / L;

[0092] Sc: Add 1000ml of scandium-containing sodium aluminate solution into the decomposition tank, and add 150g of aluminum hydroxide seeds, with a seed solid content of 150g / L, an agglomeration temperature of 70℃, and a time of 10h;

[0093] Sd: After the agglomeration is completed, the solid-liquid separation is performed to obtain aluminum hydroxide containing scandium, and the Sc content is analyzed to be 0.06%; the aluminum hydroxide containing scandium is subjected to particle size classification, and the fine particles are returned as seeds to the sodium aluminate solution containing scandium for further agglomeration. The aluminum hydroxide containing scandium is obtained after 2 cycles with a Sc content of 0.11%; the aluminum hydroxide containing scandium is obtained after 3 cycles with a Sc content of 0.16%; and the aluminum hydroxide containing scandium is obtained after 4 cycles with a Sc content of 0.20%.

[0094] Se: The scandium-containing aluminum hydroxide obtained by six cycles was calcined at 1050°C to obtain scandium-containing aluminum oxide with a particle size of -45μm and a Sc content of 12%, respectively. The Sc content was 0.09%, 0.17%, 0.24% and 0.30%.

[0095] Example 4

[0096] Sa: Scandium oxide is used as the raw material, dissolved in 30% hydrochloric acid, and then slowly added with NaOH. When the pH value is 6-7, the addition is stopped. Scandium hydroxide precipitates in a gel-like state. After filtering and washing, the scandium hydroxide is set aside;

[0097] Sb: Take 1000ml of refined sodium aluminate solution in production, and the semen Na2O k 160g / L, ak 1.50 / L, add Sa to prepare 4g of scandium hydroxide, stir and dissolve in a 45℃ water bath for 6h, then filter to obtain a sodium aluminate solution containing scandium. The scandium solution is analyzed, Sc 3+ The concentration is 0.19g / L;

[0098] Sc: Add 1000ml of scandium-containing sodium aluminate solution into the decomposition tank, and add 200g of aluminum hydroxide seeds, with a seed solid content of 100g / L, an agglomeration temperature of 70℃, and a time of 10h;

[0099] Sd: After the agglomeration is completed, the solid-liquid separation is performed to obtain aluminum hydroxide containing scandium, and the Sc content is 0.05% after analysis; the aluminum hydroxide containing scandium is subjected to particle size classification, and the fine particles are returned to the sodium aluminate solution containing scandium as seeds for further agglomeration. The aluminum hydroxide containing scandium is subjected to two cycles to obtain an Sc content of 0.09%; the aluminum hydroxide containing scandium is subjected to three cycles to obtain an Sc content of 0.13%; the aluminum hydroxide containing scandium is subjected to four cycles to obtain an Sc content of 0.17%; the aluminum hydroxide containing scandium is subjected to five cycles to obtain an Sc content of 0.21%; and the aluminum hydroxide containing scandium is subjected to six cycles to obtain an Sc content of 0.25%.

[0100] Se: The scandium-containing aluminum hydroxide obtained by six cycles was calcined at 1050°C to obtain scandium-containing aluminum oxide with a particle size of -45μm and a Sc content of 0.076%, 0.14%, 0.20%, 0.26%, 0.32% and 0.38% respectively.

[0101] Example 5

[0102] Sa: Scandium oxide is used as the raw material, dissolved in 30% hydrochloric acid, and then slowly added with NaOH. When the pH value is 6-7, the addition is stopped. Scandium hydroxide precipitates in a gel-like state. After filtering and washing, the scandium hydroxide is set aside;

[0103] Sb: Take 1000ml of refined sodium aluminate solution in production, and the semen Na2O k 170g / L, ak1.50 / L, add Sa to prepare 5g of scandium hydroxide, stir and dissolve in a 45℃ water bath for 6h, then filter to obtain a sodium aluminate solution containing scandium. The scandium solution is analyzed, Sc 3+ The concentration is 0.20g / L;

[0104] Sc: Add 1000ml of scandium-containing sodium aluminate solution into the decomposition tank, and add 100g of aluminum hydroxide seeds, with a seed solid content of 80g / L, an agglomeration temperature of 70℃, and a time of 10h;

[0105] Sd: After the agglomeration is completed, the solid-liquid separation is performed to obtain aluminum hydroxide containing scandium, and the Sc content is analyzed to be 0.10%; the aluminum hydroxide containing scandium is subjected to particle size classification, and the fine particles are returned as seeds to the sodium aluminate solution containing scandium for further agglomeration. The cycle is repeated twice to obtain aluminum hydroxide containing scandium with a Sc content of 0.15%; the cycle is repeated three times to obtain aluminum hydroxide containing scandium with a Sc content of 0.20%; and the cycle is repeated four times to obtain aluminum hydroxide containing scandium with a Sc content of 0.25%;

[0106] Se: The scandium-containing aluminum hydroxide obtained by six cycles was calcined at 1050°C to obtain scandium-containing aluminum oxide with a particle size of -45μm and a Sc content of 12%, respectively. The Sc content was 0.15%, 0.23%, 0.30% and 0.38%.

[0107] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0108] In the embodiment of the present application, scandium doping is combined with the Bayer process alumina production to directly introduce scandium element (Sc) into the sodium aluminate solution. 3+ ), eliminating the need for metallic scandium in the traditional aluminum-scandium alloy preparation, significantly reducing raw material costs. Furthermore, compared to traditional sol-gel methods or inorganic salt thermal decomposition methods, this method requires no additional organic solvents or high-temperature sintering equipment, shortening the process by over 30%.

[0109] In the embodiments of the present application, uniformly distributed high-scandium alumina is directly prepared during the Bayer process alumina production process, which can not only avoid the problem of uneven scandium distribution in the aluminum-scandium alloy product caused by uneven mixing of raw materials, but also shorten the process flow and reduce production costs.

[0110] In the examples of this application, by precisely controlling the temperature and time of the deagglomeration reaction, as well as the composition of the sodium aluminate solution, this method ensures uniform elemental distribution in the scandium-containing system. This avoids the problem of uneven scandium distribution in the aluminum-scandium alloy product that can result from uneven mixing of the raw materials.

[0111] In the examples of this application, scandium-containing aluminum hydroxide is separated into fine and coarse particles through particle size classification. The fine particles are then recycled back into the system as seeds, where they are enriched with scandium through multiple agglomeration processes, ultimately increasing the scandium content of the coarse particles. This cyclic enrichment mechanism ensures the stable production of high-scandium aluminum hydroxide products.

[0112] In the examples of this application, existing equipment and processes for Bayer-process alumina production are utilized, eliminating the need for significant additional capital investment in equipment modification or new production lines. Furthermore, by optimizing process parameters and recycling mechanisms, raw material utilization and product yield are improved, thereby reducing production costs.

[0113] 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 preparing high-scandium alumina, the method comprising: S1, adding aluminum hydroxide seed crystals to a scandium-containing sodium aluminate solution to perform a decomposition and agglomeration reaction to obtain a mixed slurry; S2, performing solid-liquid separation on the mixed slurry to obtain scandium-containing aluminum hydroxide; S3, classifying the scandium-containing aluminum hydroxide to obtain fine particles of scandium-containing aluminum hydroxide and coarse particles of scandium-containing aluminum hydroxide; S4, determining whether the scandium content in the coarse-grained scandium-containing aluminum hydroxide satisfies a set scandium content or not; if not, using the fine-grained scandium-containing aluminum hydroxide as a seed crystal, and looping through steps S1 to S3 until the scandium content in the coarse-grained scandium-containing aluminum hydroxide satisfies a set scandium content or not; if so, using the coarse-grained scandium-containing aluminum hydroxide as high-scandium aluminum hydroxide; and S5. calcining the high-scandium aluminum hydroxide to obtain high-scandium aluminum oxide.

2. The method according to claim 1, characterized in that The preparation method of the scandium-containing sodium aluminate solution comprises: dissolving scandium oxide or a soluble scandium salt and adjusting the pH value to a set pH value so as to precipitate scandium hydroxide to obtain colloidal scandium hydroxide; The colloidal scandium hydroxide is dissolved in a sodium aluminate solution to obtain a scandium-containing sodium aluminate solution.

3. The method according to claim 2, characterized in that The set pH value is 8-10.

4. The method according to claim 2, characterized in that The caustic soda concentration of the sodium aluminate solution is Na2O K The molecular ratio of sodium oxide to aluminum oxide in the sodium aluminate solution is α K It is 1.35 to 1.

60.

5. The method according to claim 2, characterized in that Based on 1L of sodium aluminate solution, the added amount of the colloidal scandium hydroxide is ≥2g.

6. The method according to claim 2, characterized in that The dissolution temperature is 40° C. to 60° C., and the dissolution time is ≥2 h.

7. The method according to claim 1, characterized in that The temperature of the decomposition and agglomeration reaction is 65° C. to 80° C., and the time of the decomposition and agglomeration reaction is 4 hours to 10 hours.

8. The method according to claim 1, characterized in that Based on 1L of scandium-containing sodium aluminate solution, the amount of the aluminum hydroxide seed crystal added is 50g to 200g.

9. The method according to claim 1, characterized in that The particle size of the fine-particle scandium-containing aluminum hydroxide is less than 45 μm, and the particle size of the coarse-particle scandium-containing aluminum hydroxide is greater than or equal to 45 μm.

10. The method according to claim 1, characterized in that The calcination temperature is 900° C. to 1200° C., and the calcination time is 5 min to 30 min.

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