CN115140751B - Preparation method of high-purity aluminum hydroxide - Google Patents
Preparation method of high-purity aluminum hydroxide Download PDFInfo
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- CN115140751B CN115140751B CN202210912076.6A CN202210912076A CN115140751B CN 115140751 B CN115140751 B CN 115140751B CN 202210912076 A CN202210912076 A CN 202210912076A CN 115140751 B CN115140751 B CN 115140751B
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- C01F7/00—Compounds of aluminium
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
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- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
The invention belongs to the technical field of mineral processing, and particularly relates to a preparation method of high-purity aluminum hydroxide. Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake; reconfiguring the white precipitate into a slurry, and stirring the slurry; and pumping the slurry to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after spray drying is the high-purity aluminum hydroxide product. According to the preparation method of the high-purity aluminum hydroxide, disclosed by the invention, thorough hydrolysis of aluminum salt can be realized under a mild test condition, and meanwhile, the generated product can appear as an aluminum hydroxide phase without forming an aluminum polymerization form in the reaction process.
Description
Technical Field
The invention belongs to the technical field of mineral processing, and particularly relates to a preparation method of high-purity aluminum hydroxide.
Background
The aluminum hydroxide having a purity of 99.9% or more is called high-purity aluminum hydroxide. Since aluminum hydroxide is easily gelled during formation, impurity ions in aluminum hydroxide are difficult to remove. At present, two methods for preparing high-purity aluminum hydroxide are mainly adopted, one method is an aluminum powder direct hydrolysis method, aluminum powder is used as a raw material, aluminum powder is hydrolyzed and converted into aluminum hydroxide under certain catalytic conditions, the purity of the product of the method depends on the purity of the raw material aluminum powder, and hydrogen is generated in the reaction process, so that potential safety hazards exist. The other method is an aluminum alkoxide hydrolysis method, aluminum alkoxides are hydrolyzed to prepare a high-purity aluminum hydroxide product, and the aluminum alkoxides are very expensive, so that the product has no advantage in the market, and meanwhile, organic matters generated after the aluminum alkoxides are hydrolyzed need to be further recovered, so that the process is complex.
In the synthesis of high purity aluminum hydroxide, if the hydrolysis of aluminum salt can be controlled, a high purity aluminum hydroxide product can be obtained. However, in the process of aluminum salt hydrolysis, the hydrolysis often cannot be performed spontaneously and completely, and meanwhile, in the hydrolysis process, aluminum salts such as aluminum chloride and aluminum sulfate are easy to undergo polymerization reaction to generate products such as polyaluminum chloride and polyaluminum sulfate, so that the synthesis of high-purity aluminum hydroxide is influenced.
Therefore, a new preparation method of high-purity aluminum hydroxide is needed to be found.
Disclosure of Invention
The purpose of the invention is that: provides a preparation method of high-purity aluminum hydroxide. The preparation method can realize thorough hydrolysis of aluminum salt under mild test conditions, and simultaneously can lead the generated product to appear in an aluminum hydroxide phase.
The preparation method of the high-purity aluminum hydroxide provided by the invention comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) And (3) pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product.
Wherein:
the aluminum salt in the step (1) is one of aluminum chloride hexahydrate, anhydrous aluminum chloride or aluminum nitrate nonahydrate, and the aluminum salt is analytically pure.
In step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:1 to 50 was prepared as a solution.
The addition amount of the shell in the step (1) is added according to the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt of 3:2-2.05, namely n (Ca 2+ ):n(Al 3+ )＝3:2～2.05。
The stirring rotating speed in the step (1) is 30-300 r/min.
In the step (1), carbon dioxide gas is generated in the reaction system in the stirring reaction process, so that a large amount of bubbles emerge, and the reaction is stopped until no bubbles are generated in the reaction system in the reaction process.
And (3) recycling the gas generated in the reaction process of the step (1) to obtain carbon dioxide gas.
Evaporating the filtrate filtered in the step (1) to saturated solution through a high-efficiency evaporator, cooling and crystallizing to obtain a calcium chloride dihydrate product or a calcium nitrate product, and heating the calcium chloride dihydrate to 260-360 ℃ to obtain an anhydrous calcium chloride product.
The filter cake was washed 3 times in step (1).
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing alkaline solution with the mass content of 7-20%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the stacked objects of the soaked shells is exceeded by the liquid level of the alkaline solution;
(2) washing the soaked shells with distilled water, stirring at room temperature in the washing process, wherein the stirring speed is 60-300 r/min, the washing time is 10-30 min each time, the washing is 3 times, the washed shells are filtered, and the shells are dried for 2h at 150 ℃.
The alkaline solution in the step (1) is sodium hydroxide or potassium hydroxide solution.
The shell in the step (1) is one of conch shell, field conch shell, sea iris shell or sea conch shell.
The total soaking time in the step (1) is 5-30 days.
During cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:3 to 10.
The shell is soaked by sodium hydroxide or potassium hydroxide, so that not only can the organic matters and impurities on the surface of the shell be removed, but also siliceous matters contained in the outer surface and inner surface layers of the shell can be dissolved out, thereby achieving the purpose of removing silicon dioxide in the shell. In the process, the shells do not need to be crushed, powder and calcined, so that the energy consumption is saved, and the operation is convenient.
In step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:5 to 10, and the slurry was prepared by mixing.
In the step (2), the stirring speed is 600-3000 r/min, the stirring time is 0.5-3 h, and the stirring temperature is room temperature.
In the step (3), the temperature of an air inlet of the spray dryer is 280-400 ℃ and the temperature of an air outlet of the spray dryer is 105-110 ℃.
The mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.9-99.95%.
The invention takes pure salt of aluminum as a research object, and realizes the complete hydrolysis of the pure salt of aluminum by controlling test conditions, thus obtaining a high-purity aluminum hydroxide product. The chemical reactions occurring during this period were as follows:
SiO 2 +2NaOH＝Na 2 SiO 3 +H 2 O；
SiO 2 +2KOH＝K 2 SiO 3 +H 2 O；
2AlCl 3 +3CaCO 3 +3H 2 O＝2Al(OH) 3 ↓+3CO 2 ↑+3CaCl 2 ；
2Al(NO 3 ) 3 +3CaCO 3 +3H 2 O＝2Al(OH) 3 ↓+3CO 2 ↑+3Ca(NO 3 ) 2 。
the invention provides a preparation method of high-purity aluminum hydroxide, which has the core idea that clean shells are added into a reaction system in the process of pure salt hydrolysis of aluminum, so that the pure salt hydrolysis of aluminum is promoted to be complete. Another object is to add shells in order to slow down the formation of large amounts of calcium salts in the reaction system in a short time. If a large amount of calcium salt is formed in a short time, polymerization reaction easily occurs in the pure salt hydrolysis process of aluminum to produce a polymer; the third purpose is that during the reaction, due to the presence of CO 2 Gas generation, which can make calcium chloride coated between aluminum hydroxide crystals follow CO 2 The air flow is blown out of the aluminum hydroxide sheet layer and directly enters the reaction solution, so that the dissolution of the calcium element can be efficiently realized, and the calcium element is removed by washing.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the preparation method of the high-purity aluminum hydroxide, disclosed by the invention, thorough hydrolysis of aluminum salt can be realized under a mild test condition, and meanwhile, the generated product can appear as an aluminum hydroxide phase without forming an aluminum polymerization form in the reaction process.
(2) The preparation method of the high-purity aluminum hydroxide reduces the production cost of aluminum hydroxide, simplifies production equipment, can increase the economic benefit of enterprises, is beneficial to environmental protection and has wide development prospect.
(3) The preparation method of the high-purity aluminum hydroxide, disclosed by the invention, has the advantages of simple production process and equipment, low cost, no environmental pollution, environment-friendly production process and easiness in realizing industrial production.
Drawings
FIG. 1 is a flow chart of a process for preparing high purity aluminum hydroxide according to the present invention;
FIG. 2 is an SEM photograph of high purity aluminum hydroxide prepared in example 4;
fig. 3 is an XRD spectrum of the high purity aluminum hydroxide prepared in example 4.
Detailed Description
Aluminum chloride hexahydrate, aluminum chloride anhydrous, and aluminum nitrate nonahydrate used in the examples below were all online purchased reagents, analytical grade.
The invention is further described below with reference to examples.
Example 1
The preparation method of the high-purity aluminum hydroxide described in the present example 1 comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) And (3) pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product.
Wherein:
the aluminum salt in step (1) is aluminum chloride hexahydrate, and the aluminum salt is analytically pure.
In step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:30 was configured as a solution.
The addition amount of the shell in the step (1) was added in such a manner that the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt was 3:2.02, namely, n (Ca 2+ ):n(Al 3+ )＝3:2.02。
In the step (1), the stirring rotating speed is 300r/min.
In the step (1), carbon dioxide gas is generated in the reaction system in the stirring reaction process, so that a large amount of bubbles emerge, and the reaction is stopped until no bubbles are generated in the reaction system in the reaction process.
And (3) recycling the gas generated in the reaction process of the step (1) to obtain carbon dioxide gas.
Evaporating the filtrate filtered in the step (1) to saturated solution through a high-efficiency evaporator, cooling and crystallizing to obtain a calcium chloride dihydrate product, and heating the calcium chloride dihydrate to 280 ℃ to obtain an anhydrous calcium chloride product.
The filter cake was washed 3 times in step (1).
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing an alkaline solution with the mass content of 10%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the accumulated objects of the soaked shells is higher than the liquid surface of the alkaline solution;
(2) washing soaked shell with distilled water, stirring at room temperature for 3 times at stirring rate of 150r/min for 10min each time, filtering, and oven drying at 150deg.C for 2 hr.
The alkaline solution in the step (1) is sodium hydroxide solution.
The shell in the step (1) is a clam shell. Clam shellThe chemical composition in percentage by weight is as follows: siO (SiO) 2 0.66％、Al 2 O 3 0.15％、Fe 2 O 3 0.09％、CaO 53.36％、MgO 0.03％、SO 3 0.19％、K 2 O 0.08％、Na 2 O0.85% and loss on ignition 44%.
The total soaking time in the step (1) is 5 days.
During cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:5.
The shell is soaked by sodium hydroxide, so that not only can the organic matters and impurities on the surface of the shell be removed, but also siliceous matters contained in the outer surface and inner surface layer of the shell can be dissolved out, thereby achieving the purpose of removing silicon dioxide in the shell. In the process, the shells do not need to be crushed, powder and calcined, so that the energy consumption is saved, and the operation is convenient.
In step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:7, and is mixed to form a slurry.
In the step (2), the stirring speed is 600r/min, the stirring time is 0.5h, and the stirring temperature is room temperature.
In the step (3), the temperature of the air inlet of the spray dryer is 310 ℃, and the temperature of the air outlet is 106 ℃.
The mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.9 percent.
Example 2
The preparation method of the high-purity aluminum hydroxide described in the embodiment 2 comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) And (3) pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product.
Wherein:
the aluminum salt in step (1) is anhydrous aluminum chloride and the aluminum salt is analytically pure.
In step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:50 was configured as a solution.
The addition amount of the shell in the step (1) was added in such a manner that the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt was 3:2.05, namely, n (Ca 2+ ):n(Al 3+ )＝3:2.05。
In the step (1), the stirring rotating speed is 100r/min.
In the step (1), carbon dioxide gas is generated in the reaction system in the stirring reaction process, so that a large amount of bubbles are generated, and the reaction is stopped until no bubbles are generated in the reaction system in the reaction process.
And (3) recycling the gas generated in the reaction process of the step (1) to obtain carbon dioxide gas.
Evaporating the filtrate filtered in the step (1) to saturated solution through a high-efficiency evaporator, cooling and crystallizing to obtain a calcium chloride dihydrate product, and heating the calcium chloride dihydrate to 360 ℃ to obtain an anhydrous calcium chloride product.
The filter cake was washed 3 times in step (1).
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing an alkaline solution with the mass content of 20%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the accumulated objects of the soaked shells is higher than the liquid surface of the alkaline solution;
(2) washing soaked shell with distilled water, stirring at room temperature for 30min at stirring rate of 300r/min, washing for 3 times, filtering, and oven drying at 150deg.C for 2 hr.
The alkaline solution in the step (1) is potassium hydroxide solution.
The shell in the step (1) is a field snail shell.
The field snail shell comprises the following chemical components in percentage by mass: siO (SiO) 2 0.06％、Al 2 O 3 0.22％、CaO 54.61％、SO 3 0.14％、K 2 O 0.04％、Na 2 O0.76% and loss on ignition 44.26%.
The total soaking time in the step (1) is 10 days.
During cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:10.
The shell is soaked by potassium hydroxide, so that not only can the organic matters and impurities on the surface of the shell be removed, but also siliceous matters contained in the outer surface and inner surface layer of the shell can be dissolved out, thereby achieving the purpose of removing silicon dioxide in the shell. In the process, the shells do not need to be crushed, powder and calcined, so that the energy consumption is saved, and the operation is convenient.
In step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:10, and is mixed to form a slurry.
In the step (2), the stirring speed is 1000r/min, the stirring time is 2h, and the stirring temperature is room temperature.
In the step (3), the temperature of an air inlet of the spray dryer is 400 ℃, and the temperature of an air outlet of the spray dryer is 110 ℃.
The mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.92 percent.
Example 3
The preparation method of the high-purity aluminum hydroxide described in the embodiment 3 comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) And (3) pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product.
Wherein:
the aluminum salt described in step (1) is aluminum nitrate nonahydrate and the aluminum salt is analytically pure.
In step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:45 was configured as a solution.
The addition amount of the shell in the step (1) was added in such a manner that the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt was 3:2.04, namely, n (Ca 2+ ):n(Al 3+ )＝3:2.04。
In the step (1), the stirring rotating speed is 200r/min.
In the step (1), carbon dioxide gas is generated in the reaction system in the stirring reaction process, so that a large amount of bubbles are generated, and the reaction is stopped until no bubbles are generated in the reaction system in the reaction process.
And (3) recycling the gas generated in the reaction process of the step (1) to obtain carbon dioxide gas.
Evaporating the filtrate filtered in the step (1) to saturated solution through a high-efficiency evaporator, and then cooling and crystallizing to obtain a calcium nitrate product.
The filter cake was washed 3 times in step (1).
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing an alkaline solution with the mass content of 18%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the accumulated objects of the soaked shells is higher than the liquid surface of the alkaline solution;
(2) washing soaked shell with distilled water, stirring at room temperature for 30min at stirring rate of 250r/min, washing for 3 times, filtering, and oven drying at 150deg.C for 2 hr.
The alkaline solution in the step (1) is sodium hydroxide solution.
The shell in the step (1) is a clam shell.
The clam shell comprises the following chemical components in percentage by mass: al (Al) 2 O 3 0.14％、Fe 2 O 3 0.05％、CaO 54.05％、SO 3 0.13％、K 2 O 0.07％、Na 2 O0.82% and loss on ignition 44.52%.
The total soaking time in the step (1) is 15 days.
During cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:8.
The shell is soaked by sodium hydroxide, so that not only can the organic matters and impurities on the surface of the shell be removed, but also siliceous matters contained in the outer surface and inner surface layer of the shell can be dissolved out, thereby achieving the purpose of removing silicon dioxide in the shell. In the process, the shells do not need to be crushed, powder and calcined, so that the energy consumption is saved, and the operation is convenient.
In step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:8, and is mixed to form a slurry.
In the step (2), the stirring speed is 1500r/min, the stirring time is 1h, and the stirring temperature is room temperature.
In the step (3), the temperature of an air inlet of the spray dryer is 380 ℃ and the temperature of an air outlet of the spray dryer is 109 ℃.
The mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.93 percent.
Example 4
The preparation method of the high-purity aluminum hydroxide described in the embodiment 4 comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) And (3) pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product.
Wherein:
the aluminum salt in step (1) is aluminum chloride hexahydrate, and the aluminum salt is analytically pure.
In step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:25 was configured as a solution.
The addition amount of the shell in the step (1) was added in such a manner that the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt was 3:2, namely n (Ca 2+ ):n(Al 3+ )＝3:2。
In the step (1), the stirring rotating speed is 300r/min.
In the step (1), carbon dioxide gas is generated in the reaction system in the stirring reaction process, so that a large amount of bubbles are generated, and the reaction is stopped until no bubbles are generated in the reaction system in the reaction process.
And (3) recycling the gas generated in the reaction process of the step (1) to obtain carbon dioxide gas.
Evaporating the filtrate filtered in the step (1) to saturated solution through a high-efficiency evaporator, cooling and crystallizing to obtain a calcium chloride dihydrate product, and heating the calcium chloride dihydrate to 260 ℃ to obtain an anhydrous calcium chloride product.
The filter cake was washed 3 times in step (1).
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing an alkaline solution with the mass content of 7%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the accumulated objects of the soaked shells is higher than the liquid surface of the alkaline solution;
(2) washing soaked shell with distilled water, stirring at room temperature for 30min for 3 times at stirring rate of 60r/min, filtering, and oven drying at 150deg.C for 2 hr.
The alkaline solution in the step (1) is sodium hydroxide solution.
The shell in the step (1) is a sea-iris shell. The sea-iris shell comprises the following chemical components in percentage by mass: siO (SiO) 2 0.31％、Al 2 O 3 0.16％、Fe 2 O 3 0.01％、CaO 51.62％、SO 3 0.11％、K 2 O 0.05％、Na 2 0.60% of O and 46.86% of loss on ignition.
The total soaking time in the step (1) is 30 days.
During cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:3.
The shell is soaked by sodium hydroxide, so that not only can the organic matters and impurities on the surface of the shell be removed, but also siliceous matters contained in the outer surface and inner surface layer of the shell can be dissolved out, thereby achieving the purpose of removing silicon dioxide in the shell. In the process, the shells do not need to be crushed, powder and calcined, so that the energy consumption is saved, and the operation is convenient.
In step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:5, and is mixed to form a slurry.
In the step (2), the stirring speed is 3000r/min, the stirring time is 0.5h, and the stirring temperature is room temperature.
In the step (3), the temperature of an air inlet of the spray dryer is 280 ℃, and the temperature of an air outlet of the spray dryer is 105 ℃.
The mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.95 percent.
XRD and SEM tests were carried out on the high-purity aluminum hydroxide prepared in example 4, the SEM image of the obtained aluminum hydroxide is shown in FIG. 2, and the XRD image of the obtained aluminum hydroxide is shown in FIG. 3. As can be seen from fig. 3, the peaks of the product are sharp, bilateral symmetry, the peaks appear in phase analysis, and the diffraction indexes of characteristic peaks of aluminum hydroxide such as (001), (020), (110), (201), (111) are extremely remarkable, which indicates that the product is a single-phase aluminum hydroxide product.
Example 5
The preparation method of high purity aluminum hydroxide described in this example 5 comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) And (3) pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product.
Wherein:
the aluminum salt in step (1) is anhydrous aluminum chloride and the aluminum salt is analytically pure.
In step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:35 was configured as a solution.
The addition amount of the shell in the step (1) was added in such a manner that the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt was 3:2.03, namely, n (Ca 2+ ):n(Al 3+ )＝3:2.03。
In the step (1), the stirring rotating speed is 180r/min.
In the step (1), carbon dioxide gas is generated in the reaction system in the stirring reaction process, so that a large amount of bubbles are generated, and the reaction is stopped until no bubbles are generated in the reaction system in the reaction process.
And (3) recycling the gas generated in the reaction process of the step (1) to obtain carbon dioxide gas.
Evaporating the filtrate filtered in the step (1) to saturated solution through a high-efficiency evaporator, cooling and crystallizing to obtain a calcium chloride dihydrate product, and heating the calcium chloride dihydrate to 300 ℃ to obtain an anhydrous calcium chloride product.
The filter cake was washed 3 times in step (1).
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing an alkaline solution with the mass content of 15%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the accumulated objects of the soaked shells is higher than the liquid surface of the alkaline solution;
(2) washing soaked shell with distilled water, stirring at room temperature for 15min for 3 times at stirring rate of 150r/min, filtering, and oven drying at 150deg.C for 2 hr.
The alkaline solution in the step (1) is sodium hydroxide solution.
The shell in the step (1) is a conch shell.
The sea snail shell comprises the following chemical components in percentage by mass: al (Al) 2 O 3 0.11％、Fe 2 O 3 0.02％、CaO 53.81％、SO 3 0.08％、K 2 O 0.06％、Na 2 O0.65% and loss on ignition 44.82%.
The total soaking time in the step (1) is 25 days.
During cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:6.
The shell is soaked by sodium hydroxide, so that not only can the organic matters and impurities on the surface of the shell be removed, but also siliceous matters contained in the outer surface and inner surface layer of the shell can be dissolved out, thereby achieving the purpose of removing silicon dioxide in the shell. In the process, the shells do not need to be crushed, powder and calcined, so that the energy consumption is saved, and the operation is convenient.
In step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:7, and is mixed to form a slurry.
In the step (2), the stirring speed is 2500r/min, the stirring time is 1h, and the stirring temperature is room temperature.
In the step (3), the temperature of an air inlet of the spray dryer is 350 ℃ and the temperature of an air outlet of the spray dryer is 106 ℃.
The mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.94 percent.
Claims (8)
1. A preparation method of high-purity aluminum hydroxide is characterized in that: the method comprises the following steps:
(1) Preparing aluminum salt and water into a solution, then adding pretreated shells into the solution, slowly stirring a reaction system in the adding process, stopping the reaction when no bubbles are generated in the reaction, filtering a product, and then washing a filter cake;
(2) Reconfiguring the white precipitate obtained in the step (1) into slurry, and stirring the slurry;
(3) Pumping the slurry obtained in the step (2) to a spray dryer by using a peristaltic pump to carry out spray drying, wherein the powder material obtained after the spray drying is the high-purity aluminum hydroxide product;
wherein:
the aluminum salt in the step (1) is one of aluminum chloride hexahydrate, anhydrous aluminum chloride or aluminum nitrate nonahydrate, and the aluminum salt is analytically pure;
the addition amount of the shell in the step (1) is added according to the ratio of the amount of calcium in the shell to the amount of aluminum in the aluminum salt of 3:2-2.05, namely n (Ca 2+ ):n(Al 3+ )=3:2~2.05；
The preparation method of the pretreated shell in the step (1) comprises the following steps:
(1) preparing an alkaline solution with the mass content of 7% -20%, soaking the shells in the alkaline solution, and stirring every 4 hours in the soaking process until attachments on the outer surfaces of the shells completely fall off, wherein the highest point of the stacked objects of the soaked shells is the liquid surface of the alkaline solution;
(2) washing the soaked shells with distilled water, stirring at room temperature in the washing process, wherein the stirring speed is 60 r/min-300 r/min, the washing time is 10-30 min each time, the washing is 3 times, the washed shells are filtered, and the shells are dried for 2 hours at 150 ℃.
2. The method for producing high purity aluminum hydroxide according to claim 1, wherein: in step (1), the aluminum salt and water are mixed according to m (aluminum salt): m (H) 2 O) =1:1-50 to prepare a solution;
in the step (1), the stirring rotating speed is 30-300 r/min.
3. The method for producing high purity aluminum hydroxide according to claim 1, wherein: evaporating the filtrate filtered in the step (1) to a saturated solution through a high-efficiency evaporator, cooling and crystallizing to obtain a calcium chloride dihydrate product or a calcium nitrate product, and heating the calcium chloride dihydrate to 260-360 ℃ to obtain an anhydrous calcium chloride product;
the filter cake was washed 3 times in step (1).
4. The method for producing high purity aluminum hydroxide according to claim 1, wherein: the alkaline solution in the step (1) is sodium hydroxide or potassium hydroxide solution;
the shell in the step (1) is one of conch shell, field snail shell, clam shell, sea-iris shell or sea snail shell;
the total soaking time in the step (1) is 5-30 days;
during cleaning in the step (2), the relation between the consumption of the shells and the consumption of water is as follows: m (shell) =1:3 to 10.
5. The method for producing high purity aluminum hydroxide according to claim 1, wherein: in step (2), the white precipitate is mixed with water according to m (Al (OH)) 3 ):m(H 2 O) =1:5 to 10, and mixing to prepare slurry.
6. The method for producing high purity aluminum hydroxide according to claim 1, wherein: in the step (2), the stirring speed is 600-3000 r/min, the stirring time is 0.5-3 h, and the stirring temperature is room temperature.
7. The method for producing high purity aluminum hydroxide according to claim 1, wherein: in the step (3), the temperature of an air inlet of the spray dryer is 280-400 ℃, and the temperature of an air outlet of the spray dryer is 105-110 ℃.
8. The method for producing high purity aluminum hydroxide according to claim 1, wherein: the mass content of the aluminum hydroxide in the high-purity aluminum hydroxide product prepared in the step (3) is 99.9-99.95%.
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