Preparation method of high-whiteness aluminum hydroxide

Abstract

The invention provides a preparation method of high-whiteness aluminum hydroxide, and belongs to the field of aluminum hydroxide preparation. The method comprises the following steps: carrying out light burning on aluminum hydroxide to decompose organic matters in the aluminum hydroxide so as to obtain light-burned aluminum oxide; pulping the light calcined alumina and liquid caustic soda to obtain first mixed slurry; under a closed condition, carrying out reaction dissolution on the first mixed slurry to obtain a dissolution solution; carrying out solid-liquid separation on the dissolved solution to obtain a sodium aluminate solution with set alpha k; adding high-whiteness aluminum hydroxide seeds into the sodium aluminate solution for seed decomposition to obtain second mixed slurry; and carrying out solid-liquid separation on the second mixed slurry to obtain the high-whiteness aluminum hydroxide. Compared with the traditional sintering process, the method provided by the invention has the advantages of low energy consumption, small pollution and good decolorization effect, and can reach the whiteness of aluminum hydroxide prepared by the sintering process.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum hydroxide preparation, and in particular to a method for preparing high-white aluminum hydroxide. Background Art

[0002] In some products with high color requirements, such as high-end cosmetics, white paper, plastic products, etc., when aluminum hydroxide is used as a raw material or filler, its whiteness directly affects the appearance quality of the final product. Aluminum hydroxide with high whiteness can ensure that the product has a purer and brighter white appearance, improving the product's aesthetics and market competitiveness. At the same time, the higher the whiteness of aluminum hydroxide, the higher the transparency of the product with aluminum hydroxide as filler, the smaller the color deviation, and the higher the aesthetics of the product. This is crucial for products that require high transparency and uniform color. In addition, aluminum hydroxide with high whiteness usually has better physical properties, such as hardness, wear resistance, thermal stability, etc. The improvement of these properties can further extend the service life of the product and reduce maintenance costs.

[0003] At present, the well-known traditional preparation method of high-white aluminum hydroxide is the sintering process, but the sintering process requires aluminum ore and coal to be roasted at 1000℃~1100℃ to generate sodium aluminate clinker, and the clinker is then dissolved to prepare sodium aluminate solution and seeded to produce high-white filler. The sintering process is thorough in decolorization and is the best preparation process for high-white aluminum hydroxide. However, the high-temperature roasting of aluminum ore and coal is a high-energy consumption and high-pollution process, and the process is facing elimination. In recent years, there has also been a method of using strong oxidants to oxidize and decolorize organic matter in sodium aluminate to prepare a solution, and then seeding to obtain high-white aluminum hydroxide, but chemical decolorization is not thorough, and strong alumina agents need to be added during the process. After decolorization, the whiteness of the sintering process cannot be achieved. Summary of the invention

[0004] The present application provides a method for preparing high-white aluminum hydroxide to solve the following technical problems: providing a new method for preparing high-white aluminum hydroxide.

[0005] The present application provides a method for preparing high white aluminum hydroxide, the method comprising:

[0006] Lightly calcining aluminum hydroxide to decompose organic matter in the aluminum hydroxide to obtain lightly calcined aluminum oxide;

[0007] Slurrying the light-burned alumina and liquid alkali to obtain a first mixed slurry;

[0008] Under closed conditions, subjecting the first mixed slurry to reaction dissolution to obtain a dissolution solution;

[0009] The dissolved liquid is subjected to solid-liquid separation to obtain a sodium aluminate solution having a set αk;

[0010] adding high white aluminum hydroxide seeds to the sodium aluminate solution to perform seed decomposition to obtain a second mixed slurry; and

[0011] The second mixed slurry is subjected to solid-liquid separation to obtain high-white aluminum hydroxide.

[0012] Optionally, the light burning temperature is 400°C to 800°C, and the light burning time is 20min to 90min.

[0013] Optionally, the light burning temperature is 550°C to 650°C, and the light burning time is 40min to 60min.

[0014] Optionally, the heating temperature of the reaction dissolution is 180° C. to 220° C., and the insulation time of the reaction dissolution is 30 min to 90 min.

[0015] Optionally, the setting αk is 1.2 to 1.8.

[0016] Optionally, the ratio V:M of the volume V of the sodium aluminate solution to the mass M of the high white aluminum hydroxide seed is 1:(4-10), wherein the unit of V is L and the unit of M is g.

[0017] Optionally, the aluminum oxide concentration of the sodium aluminate solution is 70 g / L to 150 g / L.

[0018] Optionally, the particle size d50 of the high white aluminum hydroxide seeds is 8 μm to 15 μm, and the whiteness of the high white aluminum hydroxide seeds is ≥95%.

[0019] Optionally, the temperature of the seed decomposition is 60°C to 70°C, and the time of the seed decomposition is ≥30h.

[0020] Optionally, the high white aluminum hydroxide meets the following properties: particle size d50 is 70 μm to 80 μm, and whiteness is ≥ 92%.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] An embodiment of the present application provides a method for preparing high-white aluminum hydroxide, which includes: lightly calcining aluminum hydroxide to decompose organic matter in the aluminum hydroxide to obtain light-calcined aluminum oxide; slurrying the light-calcined aluminum oxide and liquid alkali to obtain a first mixed slurry; under closed conditions, reacting and dissolving the first mixed slurry to obtain an eluate; performing solid-liquid separation on the eluate to obtain a sodium aluminate solution with a set αk; adding high-white aluminum hydroxide seeds to the sodium aluminate solution to perform seed decomposition to obtain a second mixed slurry; and performing solid-liquid separation on the second mixed slurry to obtain high-white aluminum hydroxide. First, by lightly burning aluminum hydroxide, the organic matter in aluminum hydroxide is decomposed to prevent the organic matter from affecting the purity and whiteness of the product, and at the same time optimize the crystal phase of aluminum oxide; secondly, by reacting and dissolving lightly burned aluminum oxide with liquid alkali, the full dissolution of aluminum oxide can be ensured, and undissolved impurities can be reduced, thereby obtaining a colorless and transparent sodium aluminate solution, which provides a pure reaction environment for subsequent seed decomposition and helps to obtain high-whiteness aluminum hydroxide products; finally, by adding high-white aluminum hydroxide seeds to the sodium aluminate solution, the addition of high-white aluminum hydroxide seeds not only provides active sites for inducing crystallization, but also promotes the uniform precipitation and growth of aluminum hydroxide crystals through its high whiteness and suitable particle size, thereby helping to obtain aluminum hydroxide products with uniform particle size, dense structure and high whiteness. Compared with the traditional sintering process, this method has low energy consumption, low pollution, good decolorization effect, and can achieve the whiteness of aluminum hydroxide prepared by the sintering process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the description, are used to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A schematic flow chart of a method for preparing high white aluminum hydroxide provided in an embodiment of the present application;

[0026] Figure 2 This is a color comparison chart of the sodium aluminate solution provided in Example 1 of the present application and the Bayer process aluminum hydroxide heavy solution stock solution. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work 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 rigid 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 numerical values ​​within the range. For example, the range description 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 apply 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 the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only 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" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (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 indicate 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, 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 with 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, various 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-white aluminum hydroxide provided in an embodiment of the present application.

[0032] like Figure 1 As shown, the present application provides a method for preparing high white aluminum hydroxide, the method comprising:

[0033] S1, lightly calcining aluminum hydroxide to decompose organic matter in the aluminum hydroxide to obtain lightly calcined aluminum oxide;

[0034] In some embodiments, the aluminum hydroxide is Bayer process aluminum hydroxide.

[0035] In some embodiments, the light calcination temperature is 400° C. to 800° C., and the light calcination time is 20 min to 90 min.

[0036] In the process of preparing high white aluminum hydroxide, light calcination is a key step. The purpose of light calcination is to heat the aluminum hydroxide raw material, decompose the organic matter in it, and obtain light calcined aluminum oxide. This process has a direct impact on the preparation of sodium aluminate solution and the color of the aluminum hydroxide in the subsequent steps. The light calcination temperature is limited to 400℃~800℃, and the light calcination time is 20min~90min. The organic matter in the aluminum hydroxide can be effectively oxidized and decomposed to generate harmless CO 2 and H 2 O. This ensures the purity of the subsequent sodium aluminate solution system and reduces the color problem caused by residual organic matter. At the same time, within this temperature and time range, the main crystal phase of alumina is the γ phase. γ-phase alumina has high activity, which is conducive to rapid and complete dissolution in liquid alkali in the subsequent dissolution step to form a high-quality sodium aluminate solution. In addition, excessively high temperatures (over 800°C) will lead to the formation of δ-phase alumina, which has a low dissolution activity for alumina and is difficult to completely dissolve in the dissolution step. By controlling the temperature within this range, the formation of the δ phase can be effectively avoided, thereby ensuring the solubility performance and output of the product. In this way, organic matter can be completely removed and the alumina crystal phase can be optimized, which can significantly improve the whiteness and quality of the final product. Exemplarily, the light firing temperature can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, etc., and the light firing time can be 20 min, 40 min, 50 min, 60 min, 80 min, 90 min, etc.

[0037] In some embodiments, the light calcination temperature is 550° C. to 650° C., and the light calcination time is 40 min to 60 min.

[0038] The light calcination temperature is limited to 550° C. to 650° C., and the light calcination time is 40 min to 60 min, which can further remove organic matter and optimize the alumina crystal phase, thereby improving the whiteness and quality of the final product.

[0039] S2, slurrying the light-burned alumina and liquid caustic soda to obtain a first mixed slurry;

[0040] S3, under closed conditions, subjecting the first mixed slurry to reaction dissolution to obtain a dissolution solution;

[0041] In some embodiments, the heating temperature of the reaction dissolution is 180° C. to 220° C., and the insulation time of the reaction dissolution is 30 min to 90 min.

[0042] The reaction dissolution temperature mentioned in the embodiment of the present application refers to the reaction temperature at which lightly burned alumina and liquid alkali are dissolved to form a sodium aluminate solution, and the holding time refers to the continuous reaction time at the controlled temperature, and the timing starts after reaching the controlled temperature. The heating temperature of the reaction dissolution is limited to 180°C to 220°C, and the holding time of the reaction dissolution is 30min to 90min, which can significantly improve the dissolution efficiency of alumina in liquid alkali, thereby ensuring that alumina can be fully dissolved in liquid alkali to form a high-quality sodium aluminate solution. Exemplarily, the heating temperature of the reaction dissolution can be 180°C, 190°C, 200°C, 210°C, 220°C, etc., and the holding time of the reaction dissolution can be 30min, 40min, 50min, 60min, 70min, 80min, 90min, etc.

[0043] S4, performing solid-liquid separation on the dissolving solution to obtain a sodium aluminate solution with a set αk;

[0044] In some embodiments, after the dissolution is completed, the temperature is lowered to below 100° C. and the material is discharged for solid-liquid separation. Solid-liquid separation refers to filtering the dissolution liquid to separate insoluble impurities. Filtration is also part of solution purification. Use 3 layers of filter paper to filter twice to complete the fine filtration.

[0045] In some embodiments, the setting αk is 1.2-1.8.

[0046] The set αk (caustic ratio) of the sodium aluminate solution is limited to 1.2 to 1.8. Within this αk range, the stability of the sodium aluminate solution is relatively high. This helps to reduce the spontaneous decomposition of the solution during the seeding process, thereby ensuring the orderly progress of the decomposition process. At the same time, it can promote the growth and precipitation of crystals, thereby improving the efficiency of seed decomposition. In addition, it helps to obtain aluminum hydroxide products with uniform particle size and high purity. Exemplarily, the set αk of the sodium aluminate solution can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, etc.

[0047] In some embodiments, the sodium aluminate solution has an aluminum oxide concentration of 70 g / L to 150 g / L.

[0048] The concentration of alumina in sodium aluminate solution is limited to 70g / L to 150g / L. The dissolution and precipitation process of alumina is relatively balanced, which can ensure a high output rate while avoiding excessive energy consumption and material waste. When the concentration is lower than 70g / L, the production efficiency will be affected due to the low solute content; and when the concentration exceeds 150g / L, although it can theoretically accommodate more alumina, the alkali concentration (Na 2O) is too high, the decomposed high white filler Na will increase. Exemplarily, the alumina concentration of the sodium aluminate solution is 70g / L, 80g / L, 90g / L, 100g / L, 110g / L, 120g / L, 140g / L, 150g / L, etc.

[0049] S5, adding high white aluminum hydroxide seeds to the sodium aluminate solution to perform seed decomposition to obtain a second mixed slurry; and

[0050] The main factors affecting the whiteness of high-white aluminum hydroxide are the raw material - sodium aluminate solution and the seeds used in the seeding process. The embodiments of this application do not limit or discuss the secondary pollution of whiteness caused by the equipment, process operation, packaging and transportation in the seeding process.

[0051] In some embodiments, the ratio V:M of the volume V of the sodium aluminate solution to the mass M of the high white aluminum hydroxide seeds is 1:(4-10), wherein the unit of V is L and the unit of M is g.

[0052] The seed addition amount is limited to 4g / L~10g / L, and aluminum hydroxide crystals can be uniformly precipitated and appropriately grown to form crystal particles with a particle size of 70μm~80μm and stable structure. If the seed rate is too low (<4g / L), the active sites that can be used to induce crystallization in the solution are reduced, resulting in insufficient number of aluminum hydroxide crystals precipitated, and the chance of mutual collision and aggregation between crystals is reduced, thereby possibly forming crystals with coarse particle size. If the seed rate is too high (>15g / L), there are a large number of active sites in the solution, and these sites will compete to adsorb the aluminate ions in the solution, resulting in too many aluminum hydroxide crystals precipitated and fine particle size. The fine crystal particles not only increase the difficulty of filtering and washing, but also may affect the physical properties and chemical stability of the product. Exemplary, the seed addition amount can be 4g / L, 5g / L, 6g / L, 7g / L, 8g / L, 9g / L, 10g / L, etc.

[0053] In some embodiments, the particle size d50 of the high white aluminum hydroxide seeds is 8 μm to 15 μm, and the whiteness of the high white aluminum hydroxide seeds is ≥95%.

[0054] Adding high white aluminum hydroxide seeds to the sodium aluminate solution for seed decomposition is a key step aimed at promoting the precipitation of high white aluminum hydroxide crystals through seed induction. The particle size d50 (median particle size) of the high white aluminum hydroxide seeds is controlled between 8μm and 15μm, ensuring that the seed particles are neither too large to be evenly dispersed nor too small to reduce the efficiency of induced crystallization. The moderate particle size helps to form aluminum hydroxide crystals with uniform particle size and dense structure. The whiteness of high white aluminum hydroxide seeds must reach 95% or above. High whiteness means that the impurity content in the seeds is low, which helps to produce aluminum hydroxide products with higher purity and whiter color. Exemplarily, the particle size d50 of high white aluminum hydroxide seeds can be 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc., and the whiteness of high white aluminum hydroxide seeds can be 95%, 95.2%, 95.6%, 96%, 96.2%, 96.5%, 97%, etc.

[0055] In some embodiments, the temperature of the seed decomposition is 60°C to 70°C, and the time of the seed decomposition is ≥30h.

[0056] During the seed decomposition process, the temperature is in the range of 60°C to 70°C, which can accelerate the chemical reaction rate of the seed decomposition, making the decomposition process more efficient, and at the same time is conducive to the crystallization and purification of the product, thereby improving the quality and purity of the product. A decomposition time of ≥30h can ensure that the decomposition reaction is fully carried out, improve the decomposition rate, and thus increase the output. At the same time, it helps to stabilize the production process and reduce production fluctuations caused by incomplete or too fast decomposition. Exemplarily, the temperature of the seed decomposition can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, etc., and the time of the seed decomposition can be 30h, 32h, 34h, 36h, 38h, 40h, etc.

[0057] S6. Perform solid-liquid separation on the second mixed slurry to obtain high white aluminum hydroxide.

[0058] After solid-liquid separation, the filter cake is washed, and after washing to a pH value of 7, it is moved into an oven for drying to obtain a high-white aluminum hydroxide sample.

[0059] In some embodiments, the high white aluminum hydroxide meets the following properties: particle size d50 is 70 μm to 80 μm, and whiteness is ≥ 92%.

[0060] The sodium aluminate solution prepared in the embodiment of the present application is colorless and transparent, and the whiteness of the aluminum hydroxide after decomposition is very high. When the particle size is 70 μm to 80 μm, the whiteness can reach more than 92%, which can reach the whiteness of aluminum hydroxide prepared by the sintering process.

[0061] The preparation method of high white aluminum hydroxide provided in the embodiment of the present application has the following significant advantages:

[0062] (1) Efficient removal of organic matter and optimization of crystal phase: Through the light calcination step, at a temperature of 400°C to 800°C (preferably 550°C to 650°C) and a time of 20min to 90min (preferably 40min to 60min), the organic matter in aluminum hydroxide can be completely removed, and the alumina crystal phase is optimized to a more active γ phase, providing high-quality raw materials for subsequent steps. This ensures the purity and whiteness of the final product.

[0063] (2) Efficient dissolution and solution stability: Under closed conditions, the efficient dissolution of alumina in liquid alkali is achieved by heating at 180°C to 220°C and keeping warm for 30min to 90min, forming a high-quality sodium aluminate solution. In addition, by setting αk to 1.2 to 1.8, the stability of the solution is improved, the possibility of spontaneous decomposition is reduced, and the orderly decomposition process is ensured.

[0064] (3) Precise control of product particle size and whiteness: By adding aluminum hydroxide seeds with moderate particle size (d50 is 8μm to 15μm) and high whiteness (≥95%) to the sodium aluminate solution and precisely controlling the seed addition amount (4g / L to 10g / L), uniform precipitation and moderate growth of aluminum hydroxide crystals are achieved, and finally an aluminum hydroxide product with uniform particle size (d50 is 70μm to 80μm) and high whiteness (≥92%) is obtained.

[0065] (4) Process optimization and cost saving: This method achieves an efficient and energy-saving production process by precisely controlling the process parameters of each step, such as temperature, time, and seed addition amount. At the same time, due to the improvement of raw material purity and product quality, energy consumption and material waste in subsequent processing are reduced, thereby reducing production costs.

[0066] (5) Environmental friendliness and sustainability: This method generates less waste during the treatment process, and can be harmlessly treated through appropriate environmental protection measures. In addition, by optimizing process parameters, energy consumption and emissions are reduced, which meets the requirements of green production and sustainable development.

[0067] (6) Superior product performance: The high-white aluminum hydroxide product prepared in the end not only has high whiteness and uniform particle size, but also has excellent physical properties and chemical stability. This makes the product have higher added value and competitiveness in various fields of application.

[0068] In summary, the preparation method of high-white aluminum hydroxide shows significant advantages in organic matter removal, crystal phase optimization, dissolution efficiency, product particle size and whiteness control, process optimization and cost saving, and environmental friendliness and sustainability. These advantages make this method have broad application prospects and market competitiveness in the production of aluminum hydroxide.

[0069] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0070] Example 1

[0071] Weigh 700g of Bayer aluminum hydroxide, put it into a crucible and move it into a muffle furnace, set the temperature to 550℃, keep warm for 40 minutes, and dissolve according to αk of 1.40. Measure 1.25L of liquid alkali with a sodium oxide content of 325g / L and add it to the light-burned product for slurrying. After slurrying evenly, move it into a 2L autoclave, set the temperature to 180℃, and set the holding time to 50 minutes. After the dissolution is completed, cool the material and transfer it to a 2-liter beaker. Take 3 pieces of filter paper, weigh them, and place them on the bottom of the funnel to start filtering the dissolution solution. After filtering twice, remove the sodium aluminate solution. The αk of the sodium aluminate solution is 1.40, and the aluminum oxide concentration is 331.53g / L; wash the filter paper (filter residue), and after washing, move the filter paper (filter residue) into an oven for drying and weighing.

[0072] The concentration of sodium aluminate solution was adjusted, and the alumina concentration was controlled at 110 g / L. 1 L of the adjusted liquid was measured, and the temperature of the adjusted liquid was controlled at 60°C. 4 g of 10 μm high white seeds (powdered) were added to start decomposition. The decomposition time was 36 hours. After the decomposition was completed, the solid and liquid were separated and washed. The filter cake was put into drying and sent for sample analysis. The whiteness was 92.6% and the particle size was 78.67 μm.

[0073] Figure 2 This is a color comparison chart of the sodium aluminate solution and the Bayer process aluminum hydroxide heavy solution provided in Example 1 of the present application. Figure 2 In the figure, the left side is the sodium aluminate solution after the purification treatment of this embodiment, and the right side is the original solution of the Bayer process aluminum hydroxide heavy solution. From the comparison, it can be seen that the sodium aluminate solution of this embodiment is colorless and transparent, and the aluminum hydroxide decomposed therefrom has a very high whiteness.

[0074] Example 2

[0075] The specific operation steps are the same as those in Example 1

[0076] The light burning temperature is set at 600°C and the holding time is 50 minutes; the dissolution is based on αk of 1.50; the dissolution setting temperature is 200°C, the dissolution holding time is set at 60 minutes, and the material is discharged after the dissolution is completed by cooling.

[0077] The concentration of sodium aluminate solution was adjusted, the concentration of alumina was controlled at 110 g / L, 1 L of the adjustment solution was measured, the temperature of the adjustment solution was controlled at 65°C, 7 g of 10 μm high white seeds (powder) were added for decomposition, and the decomposition time was 36 hours. After the decomposition was completed, the solid-liquid separation and washing were performed, and the filter cake was dried and sent for sample analysis. The other conditions were the same as those in Example 1. The whiteness was 93.1%, and the particle size was 77.57 μm.

[0078] Example 3

[0079] The specific operation steps are the same as those in Example 1

[0080] The light burning temperature is set at 650°C and the holding time is 60 minutes; the dissolution is based on αk of 1.60; the dissolution setting temperature is 220°C, the dissolution holding time is set at 70 minutes, and the material is discharged after the dissolution is completed by cooling.

[0081] The concentration of sodium aluminate solution was adjusted, the concentration of alumina in the solution was controlled at 130 g / L, 1 L of the adjustment solution was measured, the temperature of the adjustment solution was controlled at 70°C, 10 g of 10 μm high white seeds (powder) were added for decomposition, and the decomposition time was 36 hours. After the decomposition was completed, the solid-liquid separation and washing were performed, and the filter cake was dried and sent for sample analysis. The other conditions were the same as those in Example 1. The whiteness was 93.5%, and the particle size was 78.23 μm.

[0082] Comparative Example 1

[0083] The light calcination temperature was 300°C, and the other conditions and steps were exactly the same as those in the embodiment. The residue after dissolution was 0 g, the solution αk was 1.46, the aluminum oxide concentration was 330.17 g / L, the whiteness of the sample was 81%, and the particle size was 77.60 μm.

[0084] Comparative Example 2

[0085] The light calcination temperature was 900°C, and the other conditions and steps were exactly the same as in the embodiment. The residue after dissolution was 90g, and αk was 1.78. The residue was too much, and the economic efficiency was poor, so no seed separation was performed.

[0086] Comparative Example 3

[0087] The light burning and holding time is 15 minutes, and the other conditions and steps are exactly the same as those in the embodiment. The solution αk is 1.46, the aluminum oxide concentration is 331.27 g / L, the whiteness after seeding is 88%, and the particle size is 78.00 μm.

[0088] Comparative Example 4

[0089] The light calcination time was 120 minutes, and the other conditions and steps were exactly the same as those in the embodiment. The αk of the dissolving solution was 1.48, the aluminum oxide concentration was residual 10 g, the whiteness was 92.3%, and the particle size was 79.00 μm.

[0090] Comparative Example 5

[0091] The dissolution temperature was 130°C, and the other conditions and steps were exactly the same as those in the embodiment. A large amount of residual solution was found. Analysis showed that 73.6 g of alumina was not dissolved. Analysis showed that the solution αk was 1.74, which had poor economic efficiency and was not subjected to seed separation.

[0092] Comparative Example 6

[0093] The dissolution holding time was 20 minutes, and the other conditions and steps were exactly the same as those in the embodiment. There was residue in the dissolution liquid. After analysis, 64.3 g of alumina was not dissolved, and there was a lot of residue, which was not feasible and was not classified.

[0094] Comparative Example 7

[0095] The seed particle size d50 used in the seeding is 10 μm, and the seed is prepared by crushing aluminum hydroxide by the Bayer process. The seed whiteness is 90%. The other conditions and steps are exactly the same as those in the embodiment. The particle size is 78.34 μm and the whiteness is 91.4%.

[0096] It should be noted that:

[0097] (1) The dissolution temperature or dissolution time is greater than the condition range of the best embodiment of the patent, and no comparative examples are listed. This is because it is well known in the industry that the dissolution effect is improved when the dissolution temperature and time increase, so no comparative examples are listed.

[0098] (2) No comparative examples are given for the temperature and concentration during the seeding process because, from a process perspective, these conditions have little effect on whiteness. Whiteness is caused by secondary contamination from raw materials (sodium aluminate solution, seed crystals) or intermediate operations, and the seeding production itself has little effect on whiteness.

[0099] The process parameters and product performances of Examples 1 to 3 and Comparative Examples 1 to 7 are summarized, and the results are shown in Table 1.

[0100] Table 1 Process parameters and product performance of the embodiments and comparative examples

[0101]

[0102] Note: The bold contents in the data table are comparative items. It is specially noted that the solutions with residual solution after dissolution were not classified.

[0103] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0104] In the embodiments of the present application, the energy consumption is low, the pollution is small, and the decolorization effect is good. The prepared sodium aluminate solution is colorless and transparent, and the whiteness of the aluminum hydroxide after decomposition is very high. When the particle size is 70μm to 80μm, the whiteness can reach more than 92%, which can reach the whiteness of aluminum hydroxide prepared by the sintering process.

[0105] In the embodiments of the present application, the green preparation method of high-white aluminum hydroxide provided can not only reduce energy consumption and pollution, but also make the whiteness index of aluminum hydroxide reach the whiteness index of high-white aluminum hydroxide produced by sintering.

[0106] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing high white aluminum hydroxide, the method comprising: Lightly calcining aluminum hydroxide to decompose organic matter in the aluminum hydroxide to obtain lightly calcined aluminum oxide; Slurrying the light-burned alumina and liquid alkali to obtain a first mixed slurry; Under closed conditions, subjecting the first mixed slurry to reaction dissolution to obtain a dissolution solution; The dissolved liquid is subjected to solid-liquid separation to obtain a sodium aluminate solution having a set αk; Adding high white aluminum hydroxide seeds to the sodium aluminate solution to perform seed decomposition to obtain a second mixed slurry; as well as The second mixed slurry is subjected to solid-liquid separation to obtain high-white aluminum hydroxide.

2. The method according to claim 1, characterized in that The light calcination temperature is 400° C. to 800° C., and the light calcination time is 20 min to 90 min.

3. The method according to claim 2, characterized in that The light calcination temperature is 550° C. to 650° C., and the light calcination time is 40 min to 60 min.

4. The method according to claim 1, characterized in that: The heating temperature of the reaction dissolution is 180° C. to 220° C., and the insulation time of the reaction dissolution is 30 min to 90 min.

5. The method according to claim 1, characterized in that The setting αk is 1.2 to 1.

8.

6. The method according to claim 1, characterized in that The ratio V:M of the volume V of the sodium aluminate solution to the mass M of the high white aluminum hydroxide seed is 1:(4-10), wherein the unit of V is L and the unit of M is g.

7. The method according to claim 6, characterized in that The aluminum oxide concentration of the sodium aluminate solution is 70 g / L to 150 g / L.

8. The method according to claim 6, characterized in that The particle size d50 of the high white aluminum hydroxide seeds is 8 μm to 15 μm, and the whiteness of the high white aluminum hydroxide seeds is ≥95%.

9. The method according to claim 1, characterized in that: The temperature for decomposing the seed component is 60° C. to 70° C., and the time for decomposing the seed component is ≥30 hours.

10. The method according to claim 1, characterized in that The high white aluminum hydroxide meets the following properties: particle size d50 is 70 μm to 80 μm, and whiteness is ≥ 92%.

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