Large-particle-size aluminum hydroxide with high acid solubility and preparation method thereof

Abstract

The acid solubility of the product is larger than 95%, the median diameter is larger than or equal to 80 micrometers, the silicon content is smaller than or equal to 0.01%, and the product can be well applied to the industries of polyaluminum chloride and aluminum sulfate. The preparation method comprises the following steps: mixing an aluminum hydroxide source with a solvent, grinding until the median diameter of aluminum hydroxide in a seed crystal slurry is controlled in a range of 12-35 microns, adding the seed crystal slurry into a sodium aluminate fine liquid, carrying out seed decomposition while controlling parameters during seed decomposition, collecting the aluminum hydroxide with the median diameter of more than or equal to 80 microns, and carrying out vacuum drying, thereby obtaining the aluminum hydroxide powder with the median diameter of more than or equal to 80 microns. And washing and drying to obtain the aluminum hydroxide with high acid solubility and large particle size.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aluminum hydroxide preparation, and particularly relates to a coarse-grained aluminum hydroxide with high acid solubility and a preparation method thereof. BACKGROUND

[0002] The high-acid-solubility neutral aluminum hydroxide has the characteristics of loose crystal structure and irregular shape, has the advantages of high acid solubility, fast reaction rate, low reaction temperature, small waste residue discharge, easy dissolution in acid, and the like, has gradually replaced ordinary aluminum hydroxide, and is widely applied to the production of chemical products such as aluminum sulfate, polyaluminum chloride, aluminum fluoride, sodium aluminate and synthetic zeolite, and has a very broad application prospect. However, with the development of the downstream industry, the market puts forward new requirements for the particle size of the product - under the premise of maintaining high acid solubility, the median diameter of the product needs to be greater than or equal to 80 mu m.

[0003] At present, the mainstream preparation method of the high-acid-solubility neutral aluminum hydroxide mainly includes carbon fraction decomposition and seed fraction decomposition.

[0004] The carbon fraction decomposition method is to pass carbon dioxide into a sodium aluminate solution for decomposition, has the advantage of fast decomposition speed, but the silicon content of the product is relatively high, so that the highest acid solubility is only 93%, and it is difficult to meet the needs of high-end applications.

[0005] The seed fraction decomposition method is to add specific seeds to the sodium aluminate solution for decomposition to prepare the high-acid-solubility aluminum hydroxide, and the seeds mainly include two types: one is an aluminum oxide hydrate prepared by neutralization (one or a mixture of pseudo-boehmite, amorphous aluminum hydroxide and beta-aluminum gel), and the other is carbon fraction aluminum hydroxide ground to a particle size of less than 10 mu m. Among them, the aluminum oxide hydrate prepared by neutralization has a relatively fast neutralization reaction rate, and if not properly controlled, the product performance is prone to fluctuation; and in order to obtain a coarse-grained product, the number of cyclic decompositions needs to be increased, which not only increases the production cost, but also is not conducive to industrialization promotion. The carbon fraction aluminum hydroxide grinding seed becomes the mainstream seed type in the seed fraction decomposition method due to its unique structure, but since it contains high-silicon impurities, the silicon content of the final product is relatively high, and the acid solubility is only maintained at 93% to 95%, which is at a disadvantage in the current market competition.

[0006] Therefore, it is necessary to design a coarse-grained aluminum hydroxide with high acid solubility and a preparation method thereof to solve the above problems. SUMMARY

[0007] The application provides a coarse-grained aluminum hydroxide with high acid solubility and a preparation method thereof, to solve the problem that the acid solubility of the aluminum hydroxide particles is greater than 95% and the median diameter is greater than or equal to 80 mu m at the same time. In a first aspect, the present application provides a high-acid-solubility coarse-particle-size aluminum hydroxide, wherein the high-acid-solubility coarse-particle-size aluminum hydroxide has an acid solubility of > 95%; the high-acid-solubility coarse-particle-size aluminum hydroxide has a median particle size of ≥ 80 μm; and the high-acid-solubility coarse-particle-size aluminum hydroxide has a silicon content of ≤ 0.01%.

[0008] In a second aspect, the present application provides a method for preparing the high-acid-solubility coarse-particle-size aluminum hydroxide, comprising the following steps: providing an aluminum hydroxide source and a solvent; mixing the aluminum hydroxide source and the solvent to obtain a mixed slurry; grinding the mixed slurry to obtain a seed slurry; adding the seed slurry to a sodium aluminate liquor for seed precipitation and decomposition to obtain an aluminum hydroxide slurry; performing solid-liquid separation on the aluminum hydroxide slurry to obtain a filter cake; screening the filter cake to obtain a first filter cake and a second filter cake, wherein the first filter cake is the high-acid-solubility coarse-particle-size aluminum hydroxide; the median particle size of the aluminum hydroxide in the first filter cake is ≥ 80 μm; and the median particle size of the aluminum hydroxide in the second filter cake is < 80 μm; adding the second filter cake to the sodium aluminate liquor for cyclic seed precipitation and decomposition until the first filter cake is obtained.

[0009] In some embodiments, the median particle size of the aluminum hydroxide in the seed slurry is 12 μm to 35 μm.

[0010] In some embodiments, the concentration of aluminum oxide in the sodium aluminate liquor is 140 g / L to 180 g / L; and / or, the α K of the sodium aluminate liquor is 1.4 to 2.0.

[0011] In some embodiments, the solvent comprises any one of a sodium aluminate solution, water; and the α K of the sodium aluminate solution is 2.4 to 3.5.

[0012] In some embodiments, the initial temperature during the seed precipitation and decomposition is 65°C to 85°C.

[0013] In some embodiments, the initial seed ratio during the seed precipitation and decomposition is 0.5% to 10%.

[0014] In some embodiments, the decomposition time during the seed precipitation and decomposition is 20 h to 40 h.

[0015] In some embodiments, the solid content of the mixed slurry is 300 g / L to 450 g / L.

[0016] In some embodiments, the source of the aluminum hydroxide source comprises aluminum hydroxide generated from a Bayer process seed precipitation decomposition; and / or, The source of the aluminum hydroxide source comprises a slurry generated from an aluminum hydroxide seed precipitation process; and / or, The source of the aluminum hydroxide source further comprises a discharge slurry generated from an aluminum hydroxide seed precipitation process.

[0017] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art: 1. The coarse particle size aluminum hydroxide with high acid solubility provided by the embodiments of the present application has an acid solubility of > 95%, a median diameter of ≥ 80 μm, and can be well applied in the polyaluminum chloride and aluminum sulfate industry.

[0018] 2. The preparation method of the above coarse particle size aluminum hydroxide with high acid solubility provided by the embodiments of the present application, by mixing the aluminum hydroxide source with the solvent, then grinding until the median diameter of the aluminum hydroxide in the seed slurry is controlled in the range of 12 μm to 35 μm, then adding the seed slurry to the sodium aluminate liquor for seed precipitation decomposition, while controlling the parameters during the seed precipitation decomposition, thus, collecting the aluminum hydroxide with a median diameter of ≥ 80 μm, and then washing and drying to obtain the coarse particle size aluminum hydroxide with high acid solubility; wherein the coarse particle size aluminum hydroxide with high acid solubility has an acid solubility of > 95%, a median diameter of ≥ 80 μm, and a silicon content of ≤ 0.01%. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0021] Figure 1 A microstructure diagram of the coarse particle size aluminum hydroxide with high acid solubility provided by the embodiment 1 of the present application is shown. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] It should be understood that the descriptions of the ranges by use of "between" with respect to a range of values inclusively describe all of the possible sub-ranges within the described range and individual numerical values within the range. For example, a range description from 1 to 6 is to be understood to have specifically disclosed sub-ranges, for example, 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 individual numbers, for example, 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this application, what is meant is including any cited number (fraction or integer) within the indicated range. Unless specifically stated otherwise, all materials, reagents, instruments and equipment used in this application were commercially available or were prepared by known methods. In this application, unless otherwise indicated, the directional terms such as "upper" and "lower" are specifically the directions of the drawing surface. In this application, the terms "comprise", "contain", and the like are intended to mean "including but not limited to". In this application, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another, without necessarily requiring or implying any such actual relationship or order between such entities or actions. In this application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. In this application, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following", or the like, means any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0024] The high-acid-solubility coarse-particle-size aluminum hydroxide provided by the embodiments of the present application has an acid solubility of > 95%, a median particle size of ≥ 80 μm, and a silicon content of ≤ 0.01%.

[0025] The high-acid-solubility coarse-particle-size aluminum hydroxide provided by the embodiments of the present application has an acid solubility of > 95%, a median particle size of ≥ 80 μm, and a silicon content of ≤ 0.01%.

[0026] Based on a general inventive concept, this application provides a method for preparing the above-mentioned high acid solubility coarse-particle-size aluminum hydroxide, comprising the following steps: Step 1: Provide aluminum hydroxide source and solvent; Step 2: Mix the aluminum hydroxide source with the solvent to obtain a mixed slurry; Step 3: Grind the mixed slurry to obtain a seed slurry; Step 4: Add the seed slurry to sodium aluminate concentrate for seed decomposition to obtain aluminum hydroxide slurry; Step 5: Perform solid-liquid separation on the aluminum hydroxide slurry to obtain filter cake and filtrate; Step 6: The filter cake is sieved to obtain a first filter cake and a second filter cake. The first filter cake is coarse-grained aluminum hydroxide with high acid solubility. The median diameter of the aluminum hydroxide in the first filter cake is ≥80μm. The median diameter of the aluminum hydroxide in the second filter cake is <80μm. The second filter cake is added to the sodium aluminate concentrate and circulated for seed decomposition until the first filter cake is obtained; Step 7: Wash and dry the first filter cake to obtain the coarse-particle aluminum hydroxide with high acid solubility.

[0027] The method for preparing coarse-grained aluminum hydroxide with high acid solubility provided in this application involves mixing an aluminum hydroxide source with a solvent and then grinding it until the median diameter of the aluminum hydroxide in the seed slurry is controlled within the range of 12 μm to 35 μm. The seed slurry is then added to sodium aluminate concentrate for seed decomposition, while controlling the parameters during seed decomposition. Aluminum hydroxide with a median diameter ≥ 80 μm is collected, washed, and dried to obtain coarse-grained aluminum hydroxide with high acid solubility. The coarse-grained aluminum hydroxide with high acid solubility has an acid solubility > 95%, a median diameter ≥ 80 μm, and a silicon content ≤ 0.01%.

[0028] As an optional implementation, in the embodiments of this application, the median diameter of aluminum hydroxide in the seed slurry is 12μm~35μm.

[0029] As an optional implementation, in this embodiment of the application, the concentration of alumina in the sodium aluminate semen is 140 g / L to 180 g / L; the α-alumina concentration in the sodium aluminate semen... K It ranges from 1.4 to 2.0.

[0030] As an optional implementation, in this embodiment, the solvent includes either sodium aluminate solution or water; optionally, the α-solvent in the sodium aluminate solution... K It ranges from 2.4 to 3.5.

[0031] As an optional implementation, in this embodiment of the application, the second filter cake is added to the sodium aluminate semen for cyclic decomposition, and the number of cycles is 5 to 7.

[0032] As an optional implementation, in this embodiment of the application, the initial temperature during seed decomposition is 65℃~85℃; the final temperature during seed decomposition is 53℃~56℃.

[0033] Therefore, controlling the initial temperature during seed decomposition to 65℃~85℃ is to improve the ability of aluminum hydroxide to aggregate and grow.

[0034] As an optional implementation, in this embodiment of the application, the initial seed ratio during seed decomposition is 0.5% to 10%.

[0035] Preferably, the initial seed ratio during the seed decomposition is 2% to 7%.

[0036] As an optional implementation, in this embodiment of the application, the decomposition time during seed decomposition is 20h~40h.

[0037] Preferably, the decomposition time during seed decomposition is 24h~36h.

[0038] As an optional implementation, in this embodiment of the application, the solid content of the mixed slurry is 300g / L~450g / L.

[0039] As an optional implementation, in this embodiment of the application, the source of the aluminum hydroxide includes aluminum hydroxide generated by the Bayer process. The sources of the aluminum hydroxide source also include the slurry generated during the aluminum hydroxide seeding process; The source of aluminum hydroxide also includes the slurry generated during the aluminum hydroxide seeding process; the slurry includes the aluminum hydroxide mixture that has not been separated from the solid after the seeding decomposition is completed.

[0040] Where, α K This represents the molar ratio of caustic alkali (Na2O) to aluminum oxide (Al2O3).

[0041] In this embodiment, the filtrate enters the conventional Bayer process to continue participating in decomposition.

[0042] As an optional implementation, in this embodiment, the sodium aluminate concentrate can be sourced from any one or more mixtures of sodium aluminate solution from the Bayer process and seed mother liquor. Before adding the sodium aluminate concentrate to the seed slurry, the concentrate needs to be filtered using a conventional filtration device.

[0043] As an optional implementation, in this embodiment of the application, the mill used to grind the mixed slurry is a conventional industrial mill.

[0044] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0045] Example 1 Example 1 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility, comprising the following steps: Step 1: Provide an aluminum hydroxide source and a sodium aluminate solution; the aluminum hydroxide source includes aluminum hydroxide produced by the Bayer process; the sodium aluminate solution contains α-aluminum hydroxide. K The molar ratio of caustic alkali to alumina is 3.1; Step 2: Mix the aluminum hydroxide source with the sodium aluminate solution to obtain a mixed slurry; the solid content of the mixed slurry is 450 g / L; Step 3: Grind the mixed slurry to obtain a seed slurry; the median diameter of the aluminum hydroxide in the seed slurry is 30 μm; Step 4: Add the seed slurry to sodium aluminate concentrate for seed decomposition to obtain aluminum hydroxide slurry; the initial seed ratio during seed decomposition is 2%, the initial temperature during seed decomposition is 70℃, the final temperature during seed decomposition is 55℃, the decomposition time is 24 hours, the concentration of alumina in the sodium aluminate concentrate is 151 g / L, and the α-alumina concentration in the sodium aluminate concentrate... K The molar ratio of caustic alkali to alumina is 1.5; Step 5: Perform solid-liquid separation on the aluminum hydroxide slurry to obtain filter cake and filtrate; Step 6: Screen the filter cake to obtain a first filter cake and a second filter cake. The first filter cake is coarse-grained aluminum hydroxide with high acid solubility. The median diameter of the aluminum hydroxide in the first filter cake is ≥80μm. The median diameter of the aluminum hydroxide in the second filter cake is <80μm. The second filter cake is added to the sodium aluminate concentrate and circulated for seed decomposition until the first filter cake is obtained; Step 7: Wash and dry the first filter cake to obtain coarse-particle aluminum hydroxide with high acid solubility.

[0046] The filtrate enters the conventional Bayer process to continue participating in decomposition.

[0047] The entire process loops 5 times.

[0048] In this embodiment, coarse-grained aluminum hydroxide with high acid solubility was mixed with hydrochloric acid with a mass concentration of 21% and reacted for 1 hour. The results showed that the acid solubility was 95.23%.

[0049] The coarse-grained aluminum hydroxide with high acid solubility, prepared by the above method, has an acid solubility of 95.23% and a median diameter (D). 50 The particle size is 83.246 μm; the silicon content of coarse-grained aluminum hydroxide with high acid solubility is 0.008%.

[0050] In addition, electron microscopy analysis was performed on the coarse-grained aluminum hydroxide with high acid solubility in Example 1, and the results are as follows: Figure 1 As shown, the coarse-grained aluminum hydroxide with high acid solubility is porous and has a large particle size.

[0051] Example 2 Example 2 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility, comprising the following steps: Step 1: Provide an aluminum hydroxide source and water; the source of aluminum hydroxide includes aluminum hydroxide produced by the Bayer process. Step 2: Mix the aluminum hydroxide source with water to obtain a slurry; the solid content of the slurry is 400 g / L. Step 3: Grind the mixed slurry to obtain seed slurry; the median diameter of aluminum hydroxide in the seed slurry is 20 μm; Step 4: Add the seed slurry to sodium aluminate concentrate for seed decomposition to obtain aluminum hydroxide slurry; the initial seed ratio during seed decomposition is 2%, the initial temperature during seed decomposition is 70℃, the final temperature during seed decomposition is 55℃, the decomposition time is 24 hours, the concentration of alumina in the sodium aluminate concentrate is 153 g / L, and the α-alumina concentration in the sodium aluminate concentrate... K The molar ratio of caustic alkali to alumina is 1.41. Step 5: Perform solid-liquid separation on the aluminum hydroxide slurry to obtain filter cake and filtrate; Step 6: Screen the filter cake to obtain a first filter cake and a second filter cake. The first filter cake is coarse-grained aluminum hydroxide with high acid solubility. The median diameter of the aluminum hydroxide in the first filter cake is ≥80μm. The median diameter of the aluminum hydroxide in the second filter cake is <80μm. The second filter cake is added to the sodium aluminate concentrate and circulated for seed decomposition until the first filter cake is obtained; Step 7: Wash and dry the first filter cake to obtain coarse-particle aluminum hydroxide with high acid solubility.

[0052] The filtrate enters the conventional Bayer process to continue participating in decomposition.

[0053] The entire process loops 5 times.

[0054] The coarse-grained aluminum hydroxide with high acid solubility in this embodiment was mixed with hydrochloric acid with a mass concentration of 21% and reacted for 1 hour. The results showed that the acid solubility was 95.05%.

[0055] The coarse-grained aluminum hydroxide with high acid solubility prepared by the above method has an acid solubility of 95.31% and a median diameter (D). 50 The particle size was 81.899 μm; the yield was 34.23%; the silicon content of the coarse-grained aluminum hydroxide with high acid solubility was 0.007%.

[0056] Example 3 Example 3 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 2 is that in step three, the mixed slurry is ground to obtain a different particle size of aluminum hydroxide in the seed slurry. The particle size of aluminum hydroxide in the seed slurry of Example 2 is 30 μm. The remaining steps are the same as in Example 1, and will not be repeated here.

[0057] The coarse-grained aluminum hydroxide with high acid solubility, prepared by the above method, has an acid solubility of 95.05% and a median diameter (D). 50 The particle size was 81.362 μm; the yield was 37.4%; the silicon content of the coarse-grained aluminum hydroxide with high acid solubility was 0.007%.

[0058] Comparative Example 1 Comparative Example 1 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 2 is that in step three, the mixed slurry is ground, resulting in a different particle size of aluminum hydroxide in the seed slurry. The particle size of aluminum hydroxide in the seed slurry of Comparative Example 1 is 3 μm.

[0059] The remaining steps are the same as in Example 2, and will not be repeated here.

[0060] The coarse-grained aluminum hydroxide with high acid solubility obtained by the above method has an acid solubility of 96% and a median diameter (D). 50 The particle size was 84.206 μm; the yield was 28.21%; the silicon content of the coarse-grained aluminum hydroxide with high acid solubility was 0.007%.

[0061] Comparative Example 2 Comparative Example 2 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 2 is that in step three, the mixed slurry is ground, and the aluminum hydroxide particle size in the resulting seed slurry is different. The aluminum hydroxide particle size in the seed slurry of Comparative Example 1 is 40 μm.

[0062] The remaining steps are the same as in Example 2, and will not be repeated here.

[0063] The coarse-grained aluminum hydroxide with high acid solubility prepared by the above method has an acid solubility of 94.11% and a median diameter (D). 50 The particle size was 83.992 μm; the yield was 24.22%; the silicon content of the coarse-grained aluminum hydroxide with high acid solubility was 0.008%.

[0064] Example 4 Example 4 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 3 is that in step four, the α-aluminate in the sodium aluminate concentrate... K Different, in Example 4, sodium aluminate semen, α K It is 1.81.

[0065] The remaining steps are the same as in Example 3, and will not be repeated here.

[0066] The coarse-grained aluminum hydroxide with high acid solubility prepared by the above method has an acid solubility of 95.82% and a median diameter (D). 50 The silicon content of the coarse-grained aluminum hydroxide with high acid solubility is 0.007%, with a particle size of 82.659 μm.

[0067] Comparative Example 3 Comparative Example 3 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 3 is that in step four, the α-aluminate in the sodium aluminate concentrate... K Different, in Comparative Example 3, sodium aluminate semen, α K It is 1.3.

[0068] The remaining steps are the same as in Example 3, and will not be repeated here.

[0069] When sodium aluminate semen α K Below 1.4, the supersaturation of the system will increase with α. K The value decreases and increases significantly; although excessive supersaturation can increase the initial decomposition rate, it will exacerbate the secondary nucleation phenomenon. This not only leads to an increase in the proportion of fine particles and a wider particle size distribution in the product, but also directly affects the preparation effect of coarse-sized aluminum hydroxide, which is not conducive to obtaining large-particle products with uniform particle size.

[0070] Comparative Example 4 Comparative Example 4 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 3 is that in step four, the α-aluminate in the sodium aluminate concentrate... K Different, in Comparative Example 4, sodium aluminate semen, α K It is 2.2.

[0071] The remaining steps are the same as in Example 3, and will not be repeated here.

[0072] The entire process loops 10 times.

[0073] The coarse-grained aluminum hydroxide with high acid solubility prepared by the above method has an acid solubility of 92.2% and a median diameter (D). 50 The particle size was 81.466 μm, the yield was 12%, and the cycle time was long; the silicon content of the coarse-grained aluminum hydroxide with high acid solubility was 0.008%.

[0074] Example 5 Example 5 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference from Example 2 is that the initial temperature during seed decomposition in step four is different. In Example 5, the initial temperature during seed decomposition is 85°C.

[0075] The remaining steps are the same as in Example 2, and will not be repeated here.

[0076] The coarse-grained aluminum hydroxide with high acid solubility prepared by the above method has an acid solubility of 95.16%, and its median diameter (D) is [not specified]. 50 The silicon content of the coarse-grained aluminum hydroxide with high acid solubility is 0.007%, with a particle size of 82.61 μm.

[0077] Comparative Example 7 Comparative Example 7 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference between Comparative Example 7 and Example 2 is that the initial temperature during seed decomposition in step four is different. The initial temperature during seed decomposition in Comparative Example 7 is 55°C.

[0078] The remaining steps are the same as in Example 2, and will not be repeated here.

[0079] The coarse-grained aluminum hydroxide with high acid solubility prepared by the above method has an acid solubility of 91.87%, and its median diameter (D) is [not specified]. 50 The particle size is 83.47 μm; the silicon content of the coarse-grained aluminum hydroxide with high acid solubility is 0.008%.

[0080] Comparative Example 8 Comparative Example 8 provides a method for preparing coarse-grained aluminum hydroxide with high acid solubility. The difference between Comparative Example 8 and Example 2 is that the initial temperature during seed decomposition in step four is different. The initial temperature during seed decomposition in Comparative Example 8 is 90°C.

[0081] The remaining steps are the same as in Example 2, and will not be repeated here.

[0082] The coarse-grained aluminum hydroxide with high acid solubility, prepared by the above method, has an acid solubility of 90.65% and a median diameter (D). 50 The particle size was 73.22 μm; the yield was 5%, and the silicon content of the coarse-grained aluminum hydroxide with high acid solubility was 0.007%.

[0083] The specific process parameters in the examples and comparative examples are shown in Table 1, and the performance results of the coarse-grained aluminum hydroxide with high acid solubility prepared in the examples and comparative examples are shown in Table 2.

[0084] Table 1. Specific process parameters for the examples and comparative examples.

[0085] Table 2 Performance results of coarse-grained aluminum hydroxide with high acid solubility obtained in the examples and comparative examples.

[0086] Experimental results show that: Comparing Examples 2-3 and Comparative Examples 1-2, it can be seen that when preparing coarse-grained aluminum hydroxide with high acid solubility using the method provided in this application, although the acid solubility and median diameter of the obtained coarse-grained aluminum hydroxide with high acid solubility decrease with the increase of the aluminum hydroxide particle size in the seed slurry, the yield shows a significant upward trend. However, when the aluminum hydroxide particle size in the seed slurry continues to increase and exceeds 35 μm, the acid solubility and median diameter of the obtained product decrease, and the yield also decreases simultaneously.

[0087] Comparing Examples 3-4 and Comparative Examples 3-4, it can be seen that when preparing coarse-grained aluminum hydroxide with high acid solubility using the method provided in this application, as the α-particles in the sodium aluminate concentrate increase... K An increase in the value leads to an increase in the acid solubility and median diameter of the product; however, if the α-value in sodium aluminate semen increases... K When the value exceeds 2, the acid solubility of the product decreases and the median diameter decreases.

[0088] Comparing Examples 2, 5, and 7-8, it can be seen that when preparing coarse-grained aluminum hydroxide with high acid solubility using the method provided in this application, the acid solubility of the product increases with the increase of the initial temperature during seed decomposition, and the median diameter first increases and then decreases; and as the initial temperature during seed decomposition exceeds 85°C, the acid solubility of the product decreases significantly, and the median diameter decreases.

[0089] It is evident that the method for preparing coarse-grained aluminum hydroxide with high acid solubility provided in this application is formed under the combined effect of various parameters, none of which can be omitted.

[0090] In summary, this invention provides a coarse-grained aluminum hydroxide with high acid solubility (>95%) and a median diameter (>80μm), which can be well applied in the polyaluminum chloride and aluminum sulfate industries. This invention also provides a method for preparing this coarse-grained aluminum hydroxide with high acid solubility. The method involves mixing an aluminum hydroxide source with a solvent, followed by grinding until the median diameter of the aluminum hydroxide in the seed slurry is controlled within the range of 12μm to 35μm. This seed slurry is then added to sodium aluminate concentrate for seed decomposition, while controlling the parameters during seed decomposition. Aluminum hydroxide with a median diameter >80μm is collected, washed, and dried to obtain the coarse-grained aluminum hydroxide with high acid solubility.

[0091] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this 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 this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A coarse-grained aluminum hydroxide with high acid solubility, characterized in that, The high acid solubility coarse-grained aluminum hydroxide has an acid solubility > 95%; a median diameter ≥ 80 μm; and a silicon content ≤ 0.01%.

2. A method for preparing coarse-grained aluminum hydroxide with high acid solubility as described in claim 1, characterized in that, Includes the following steps: Provide aluminum hydroxide source and solvent; The aluminum hydroxide source is mixed with the solvent to obtain a mixed slurry; The mixture slurry is ground to obtain a seed slurry; The seed slurry is added to sodium aluminate concentrate for seed decomposition to obtain aluminum hydroxide slurry; The aluminum hydroxide slurry was subjected to solid-liquid separation to obtain a filter cake; The filter cake is sieved to obtain a first filter cake and a second filter cake. The first filter cake is coarse-grained aluminum hydroxide with high acid solubility. The median diameter of the aluminum hydroxide in the first filter cake is ≥80μm. The median diameter of the aluminum hydroxide in the second filter cake is <80μm. The second filter cake is added to the sodium aluminate concentrate and circulated for decomposition until the first filter cake is obtained.

3. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 2, characterized in that, The median diameter of the aluminum hydroxide in the seed slurry is 12 μm to 35 μm.

4. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 2, characterized in that, The concentration of alumina in the sodium aluminate semen is 140 g / L to 180 g / L; and / or, α in sodium aluminate semen K It ranges from 1.4 to 2.

0.

5. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 2, characterized in that, The solvent includes either sodium aluminate solution or water; the sodium aluminate solution has an α... K It ranges from 2.4 to 3.

5.

6. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 2, characterized in that, The initial temperature during the decomposition of the species is 65℃~85℃.

7. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 6, characterized in that, The initial seed ratio during the seed decomposition is 0.5% to 10%.

8. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 7, characterized in that, The decomposition time during the seed decomposition is 20h~40h.

9. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 6, characterized in that, The solid content of the mixed slurry is 300g / L~450g / L.

10. The method for preparing coarse-grained aluminum hydroxide with high acid solubility according to claim 6, characterized in that, The source of the aluminum hydroxide includes aluminum hydroxide generated by the Bayer process; and / or, The aluminum hydroxide source includes the slurry generated during the aluminum hydroxide seeding process; and / or, The sources of aluminum hydroxide also include the slurry generated during the aluminum hydroxide seeding process.

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