CN115771908A - Preparation method of low-chlorine magnesium hydroxide - Google Patents
Preparation method of low-chlorine magnesium hydroxide Download PDFInfo
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- CN115771908A CN115771908A CN202211471475.XA CN202211471475A CN115771908A CN 115771908 A CN115771908 A CN 115771908A CN 202211471475 A CN202211471475 A CN 202211471475A CN 115771908 A CN115771908 A CN 115771908A
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- ammonia
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- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 title claims abstract description 101
- 239000000347 magnesium hydroxide Substances 0.000 title claims abstract description 101
- 229910001862 magnesium hydroxide Inorganic materials 0.000 title claims abstract description 101
- 239000000460 chlorine Substances 0.000 title claims abstract description 25
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 229910052801 chlorine Inorganic materials 0.000 title claims abstract description 10
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 63
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 61
- 238000005406 washing Methods 0.000 claims abstract description 55
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims abstract description 50
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 49
- 239000002002 slurry Substances 0.000 claims abstract description 45
- 229910001629 magnesium chloride Inorganic materials 0.000 claims abstract description 25
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 238000005119 centrifugation Methods 0.000 claims abstract description 16
- 238000006243 chemical reaction Methods 0.000 claims abstract description 15
- 238000000975 co-precipitation Methods 0.000 claims abstract description 7
- 238000005216 hydrothermal crystallization Methods 0.000 claims abstract description 7
- 238000001035 drying Methods 0.000 claims abstract description 6
- 238000001914 filtration Methods 0.000 claims abstract description 6
- 230000007935 neutral effect Effects 0.000 claims abstract description 6
- 238000003756 stirring Methods 0.000 claims abstract description 5
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 3
- 238000004064 recycling Methods 0.000 claims abstract 2
- 239000000243 solution Substances 0.000 claims description 42
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 15
- 229910021529 ammonia Inorganic materials 0.000 claims description 8
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 claims description 4
- 125000004122 cyclic group Chemical group 0.000 claims description 4
- 229910001425 magnesium ion Inorganic materials 0.000 claims description 4
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 3
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 abstract description 5
- 239000000047 product Substances 0.000 description 44
- 239000002245 particle Substances 0.000 description 6
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 5
- 238000009792 diffusion process Methods 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 239000011777 magnesium Substances 0.000 description 5
- 229910052749 magnesium Inorganic materials 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000012761 high-performance material Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 229940072033 potash Drugs 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Substances [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 1
- 235000015320 potassium carbonate Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Abstract
The invention discloses a preparation method of low-chlorine magnesium hydroxide. Adding a magnesium chloride solution into an ammonia water solution to carry out coprecipitation reaction to prepare magnesium hydroxide slurry, then carrying out hydrothermal crystallization growth under stirring, carrying out circulating washing centrifugation on the magnesium hydroxide slurry obtained after centrifugation by adopting the ammonia water solution, finally washing by pure water until the washing water is neutral, filtering and drying to obtain the magnesium hydroxide product with low chlorine content. And the ammonia water solution for washing is recycled in a grading way and is used for producing the magnesium hydroxide, so that the recycling is realized. The invention starts from the double-electric layer theory of the solid surface solution, adopts ammonia water solutions with different concentration gradients for washing the chloride ion content in different washing stages, obviously improves the washing efficiency of the chloride ion in the washing process, reduces the using amounts of the ammonia water and pure water, and reduces the chloride ion content in the product to be less than 0.05 percent.
Description
Technical Field
The invention belongs to the technical field of preparation of inorganic functional materials, and particularly relates to a preparation method of low-chlorine magnesium hydroxide.
Background
China has abundant salt lake resources and stores a large amount of metal ions such as magnesium, potassium, sodium, lithium and the like. In the process of salt lake resource development, especially in the process of producing potash fertilizer, a large amount of magnesium chloride is produced as a byproduct. Most of the magnesium-rich salt lake is sold only as a primary product or is placed in a salt lake area in a large quantity, and the magnesium harm is formed, so that the comprehensive development and utilization of salt lake resources are seriously hindered. Therefore, the effective utilization of magnesium chloride is one of the keys for promoting the efficient utilization of magnesium resources in salt lakes. Magnesium hydroxide is a chemical product with high added value and wide application, and is widely concerned due to great effect in the fields of flame retardance and environmental protection. The magnesium hydroxide product produced by using the salt lake magnesium chloride can effectively solve the problem of surplus magnesium resources and change waste into valuable. Compared with the magnesium hydroxide prepared by an ore method, the purity of the product prepared by adopting the magnesium chloride can reach more than 99 percent, so the method has obvious advantages in the field of high-performance materials.
At present, magnesium hydroxide is mainly prepared in a salt lake region by adopting a precipitation reaction of magnesium chloride. However, in the preparation process, due to the special properties of chloride ions, magnesium hydroxide is easy to generate surface adsorption and intercrystalline entrainment to the chloride ions in the nucleation and growth processes, so that the content of the chloride ions in the product is far higher than the industrial standard of high-quality magnesium hydroxide, generally more than 0.5 percent and maximally more than 1 percent. The national standard (GB/T3050-2000) of industrial magnesium hydroxide requires that the content of chloride ions in high-quality magnesium hydroxide is not higher than 0.1 percent. Therefore, the content of chloride ions is difficult to reach the standard, and the sale of magnesium hydroxide products produced by taking magnesium chloride as a raw material and the utilization of magnesium chloride in salt lakes are seriously influenced.
In order to reduce the content of chloride ions in magnesium hydroxide products, the traditional magnesium hydroxide preparation is based on the ion diffusion principle, and a large amount of pure water is adopted for multiple and continuous washing to remove the chloride ions in the products. Recent studies have found that according to the theory of the electric double layer of the solid surface solution, magnesium hydroxide is dispersed in water to form an electric double layer on the surface, the surface of magnesium hydroxide is charged positively, and OH in the aqueous solution - And Cl - The plasma will adsorb to form a tight layer on the surface and also form a diffusion layer near the surface. After the reaction of the magnesium hydroxide, OH - Enters into octahedral crystal lattice of magnesium hydroxide through reaction, OH - Cl which is less in solution and does not participate in the reaction - Ions are present in large amounts in solution and Cl - Has higher electronegativity, and can adsorb a large amount of Cl in a compact layer on the surface of magnesium hydroxide by electrostatic attraction - Counter ion and strong stability, and is difficult to remove by simply adopting pure water and taking ion diffusion as driving force. At the same time, since Cl - Has the characteristics of lone electron pair and the like, has strong adsorption performance, is easy to cause product intercrystalline entrainment in the preparation process, is difficult to remove in the subsequent washing process, and further causes Cl in the product - The content exceeds the standard.
Disclosure of Invention
The invention provides a preparation method of low-chlorine magnesium hydroxide, which aims to reduce the content of residual chloride ions in a magnesium hydroxide product produced by taking magnesium chloride as a raw material.
The preparation method of the low-chlorine magnesium hydroxide comprises the following steps: adding the magnesium chloride solution into an ammonia water solution for coprecipitation reaction to prepare magnesium hydroxide slurry, then carrying out hydrothermal crystallization growth under stirring, carrying out circulating washing centrifugation on the magnesium hydroxide slurry obtained after centrifugation by adopting the ammonia water solution, finally washing by pure water until the washing water is neutral, filtering and drying to obtain the magnesium hydroxide product with low chlorine content.
The concentration of magnesium ions in the magnesium chloride solution is 0.01-4mol/L, preferably 2-3mol/L.
The concentration of the ammonia aqueous solution used in the coprecipitation reaction is 0.1 to 12mol/L, preferably 4 to 6mol/L.
The molar ratio of magnesium ions to ammonia in ammonia water in the coprecipitation reaction is 1.05 to 3.0, preferably 1.
The temperature of the hydrothermal crystallization is 60-100 ℃, preferably 80-90 ℃; the time of hydrothermal crystallization is 0.1-10h, preferably 0.5-2h.
The cycle number of the circulating washing centrifugation is 1-4.
The molar concentration of the ammonia water solution used for the circular washing centrifugation is 2-5 times of the molar concentration of chloride ions in the magnesium hydroxide slurry at the beginning of each circular washing centrifugation, and the volume of the ammonia water solution is 1-3 times of the volume of the magnesium hydroxide slurry.
The content of chloride ions in the magnesium hydroxide slurry after the circular washing and centrifugation is lower than 0.1 percent.
The ammonia water solution recovered by the circular washing and centrifugation is used for producing magnesium hydroxide, so that the circular utilization is realized; and when the chloride ion content in the ammonia water solution exceeds 20%, sending the ammonia water solution to an ammonia still to recover ammonia gas, and continuously using the ammonia gas in the production of magnesium hydroxide.
Based on the double-electric-layer theory that the solid surface can preferentially adsorb counter ions with the same composition in solution, when high-concentration excessive ammonia water is used for reaction to generate magnesium hydroxide, a large amount of OH can be adsorbed on the surface - Can reduce the Cl in the reaction process - The adsorption reduces the intercrystalline entrainment of chloride ions in the preparation process, and is further convenient for washing; meanwhile, after the precipitation reaction, the magnesium hydroxide is subjected to hydrothermal growth under a certain temperature condition, so that the number of defect sites on the surface of the magnesium hydroxide can be effectively reduced, and the Cl of a defect structure is further reduced - The adsorption effect of (2) reduces Cl in the product - And (4) content. After the precipitation reaction is finished, excess ammonia water with different concentration gradients is adopted to wash the magnesium hydroxide slurry, so that OH in the solution is always ensured - The content is far higher than Cl - Content of OH in high concentration - Under the condition of OH - Will enter a solid surface compact layer to replace Cl - Reacting Cl - Quickly separated from the surface of the magnesium hydroxide solid, enters the solution and is carried out of a slurry system along with the washing solution, thus realizing the separation of Cl - Removing; furthermore, due to the high concentration of OH - The thickness of the surface double-electrode layer is obviously reduced by entering the compact layer and the diffusion layer, and the Cl pair is greatly weakened - Compared with the traditional method of washing with water and relying on ion diffusion, the adsorption effect of the method greatly improves Cl - The removal efficiency and the effect remarkably improve the washing efficiency. The washed ammonia water is recycled in a grading way and is used for producing the magnesium hydroxide, thereby realizing closed cycle. And a small amount of pure water is used for washing and removing slightly excessive ammonia water in the slurry after the last ammonia water washing in the later period, so that the water consumption is greatly reduced compared with the traditional pure water washing. The content of chloride ions in the magnesium hydroxide product prepared by the method can be reduced to be below 0.05 percent, and the requirement of industrial magnesium hydroxide on the first-grade magnesium hydroxide product is met.
Drawings
FIG. 1 is an XRD spectrum of magnesium hydroxide obtained in example 1.
FIG. 2 is an SEM photograph of magnesium hydroxide obtained in example 2.
FIG. 3 is a laser particle size distribution diagram of magnesium hydroxide obtained in example 3.
Detailed Description
Example 1:
40.66g of MgCl were weighed 2 ·6H 2 O and 32.67g of ammonia water (25 wt%), adding deionized water to prepare 100mL of magnesium chloride solution and ammonia water solution respectively, wherein the concentration of magnesium chloride is 2mol/L, and the molar ratio of magnesium chloride to ammonia water is 1. Then placing the ammonia water solution in a 500mL flask, adding the magnesium chloride solution into the ammonia water solution at the speed of 60mL/min, stirring simultaneously, crystallizing at 80 ℃ for 3h, and centrifuging the obtained slurry once to obtain 60mL magnesium hydroxide slurry with the chloride ion concentration of 2 mol/L.
Centrifuging and washing the obtained 60mL of magnesium hydroxide slurry for 1 time by sequentially using 100mL of 6mol/L ammonia water to obtain 60mL of magnesium hydroxide slurry with the chloride ion concentration of 0.11 mol/L; centrifugally washing the slurry for the 2 nd time by 100mL of 0.33 mol/L ammonia water to obtain 60mL of magnesium hydroxide slurry with the chloride ion concentration of 0.041 mol/L; centrifuging and washing the product by 100mL0.124 mol/L ammonia water for 3 times to obtain 60mL of magnesium hydroxide slurry with the chloride ion concentration of 0.0051mol/L, centrifuging and washing the product by 100mL0.0153 mol/L ammonia water for 4 times to obtain 60mL of magnesium hydroxide slurry with the chloride ion concentration of 0.0023mol/L, and reducing the chloride ion content of the product to 0.044%. During washing, ammonia water is recycled according to the concentration each time for producing magnesium hydroxide, so that the cyclic utilization is realized; and when the chloride ion content in the ammonia water solution exceeds 20%, sending the ammonia water solution to an ammonia still to recover ammonia gas, and continuously using the ammonia gas in the production of magnesium hydroxide. And finally, washing the magnesium hydroxide product to be neutral by pure water, filtering and drying the magnesium hydroxide product to obtain the magnesium hydroxide product, wherein the final chloride ion content of the product is 0.043%.
The crystal structure of the product is characterized by adopting an X-ray powder diffractometer model DX-2600 manufactured by the Dandong Haoyuan company. And comparing with a magnesium hydroxide standard spectrogram, wherein the product is magnesium hydroxide.
Example 2:
49.28g of MgCl were weighed 2 ·6H 2 O and 40.80g of ammonia water (25 wt%), adding deionized water to prepare 80mL of magnesium chloride solution and ammonia water solution respectively, wherein the concentration of magnesium chloride is 3mol/L, and the molar ratio of magnesium chloride to ammonia water is 1. Then the ammonia solution is placed in a 250mL flask, the magnesium chloride solution is added into the ammonia solution according to the speed of 40mL/min, and the same is carried outThe mixture was stirred, crystallized at 100 ℃ for 2.5 hours, and the resulting slurry was centrifuged once to obtain about 80mL of magnesium hydroxide slurry having a chloride ion concentration of 3mol/L.
Carrying out centrifugal washing on the obtained 80mL of magnesium hydroxide slurry for the 1 st time by using 160mL7.5 mol/L ammonia water in sequence to obtain 80mL of magnesium hydroxide slurry with the chloride ion concentration of 0.12 mol/L; carrying out centrifugal washing for the 2 nd time by using 160mL0.36 mol/L ammonia water to obtain 80mL of magnesium hydroxide slurry with the chloride ion concentration of 0.045 mol/L; carrying out centrifugal washing with 160mL0.135 mol/L ammonia water for the 3 rd time to obtain 80mL magnesium hydroxide slurry with the chloride ion concentration of 0.0048mol/L, wherein the chloride ion content of the product is 0.35%; the magnesium hydroxide slurry with the chloride ion concentration of 0.0033mol/L is obtained by carrying out centrifugal washing on the magnesium hydroxide slurry with 160mL0.0144 mol/L ammonia water for the 4 th time, and the chloride ion content of the product is reduced to 0.049%. Ammonia water is recovered according to the concentration each time during washing for producing magnesium hydroxide, so that the cyclic utilization is realized; and when the chloride ion content in the ammonia water solution exceeds 20%, sending the ammonia water solution to an ammonia still to recover ammonia gas, and continuously using the ammonia gas in the production of magnesium hydroxide. And finally, washing the magnesium hydroxide product to be neutral by pure water, filtering and drying the magnesium hydroxide product to obtain the magnesium hydroxide product, wherein the final chloride ion content of the product is 0.047%.
The morphology of the product was observed by scanning electron microscopy using model supra55 from ZEISS, germany. FIG. 2 is an SEM photograph of the product, and it can be seen from the figure that the prepared product is in a sheet structure and regular, and has a uniform particle size.
Example 3:
51.33g of MgCl were weighed 2 ·6H 2 O and 51.00g of ammonia water (25 wt%), adding deionized water to prepare 100mL of magnesium chloride solution and ammonia water solution respectively, wherein the concentration of magnesium chloride is 2.5mol/L, and the molar ratio of magnesium chloride to ammonia water is 1. Then placing the ammonia water solution in a 500mL flask, adding the magnesium chloride solution into the ammonia water solution at the speed of 50mL/min while stirring, crystallizing at 90 ℃ for 4 hours, and centrifuging the obtained slurry once to obtain magnesium hydroxide slurry with the concentration of chloride ions of about 70mL and 2.5 mol/L.
The obtained 70mL of magnesium hydroxide slurry is sequentially washed 1 st by 70mL10 mol/L ammonia water in a centrifugal way to obtain 70mL of magnesium hydroxide slurry with the chloride ion concentration of 0.11 mol/L; centrifugally washing the slurry for the 2 nd time by 70mL0.44mol/L ammonia water to obtain 70mL of magnesium hydroxide slurry with the chloride ion concentration of 0.041 mol/L; centrifugally washing the slurry for the 3 rd time by using 70mL0.164mol/L ammonia water to obtain 70mL of magnesium hydroxide slurry with the chloride ion concentration of 0.0052 mol/L; the magnesium hydroxide slurry with the chloride ion concentration of 70mL and the concentration of 0.0036mol/L is obtained by centrifugal washing with 70mL0.0208mol/L ammonia water for the 4 th time, and the chloride ion content of the product is reduced to 0.051 percent. During washing, ammonia water is recycled according to the concentration each time for producing magnesium hydroxide, so that the cyclic utilization is realized; and when the chloride ion content in the ammonia water solution exceeds 20%, sending the ammonia water solution to an ammonia still to recover ammonia gas, and continuously using the ammonia gas in the production of magnesium hydroxide. And finally, washing the magnesium hydroxide product to be neutral by adopting pure water, filtering and drying the magnesium hydroxide product to obtain a magnesium hydroxide product, wherein the final chloride ion content of the magnesium hydroxide product is 0.049%.
The particle size of the samples was measured using a laser particle sizer, malvern 2000, uk. FIG. 3 is a laser particle size distribution diagram, from which it can be seen that the particle size distribution D of the product 50 0.220 μm, D 90 And was 0.672 μm.
Comparative example:
magnesium hydroxide slurry was prepared by the same method and conditions as in example 1, and the slurry was centrifuged once to obtain 60mL of magnesium hydroxide slurry having a chloride ion concentration of 2mol/L and a chloride ion content of 35.12% in the magnesium hydroxide product. And (3) centrifuging and washing the obtained 60mL magnesium hydroxide slurry for 8 times by respectively adopting 100mL pure water and 150mL pure water each time, obtaining 60mL magnesium hydroxide slurry after each centrifugation during the circulating centrifugal washing, detecting the chloride ion content of the magnesium hydroxide product after each centrifugal washing, comparing the chloride ion content with that of the magnesium hydroxide product obtained in the step of washing the magnesium hydroxide product with ammonia in example 1 for different times, and comparing the comparison table.
Comparison table for chloride ion content of products with different washing modes
The present invention has been described in detail, and it should be understood that the present invention is not limited to the precise embodiments, and that various changes and modifications can be effected therein without departing from the scope of the invention.
Claims (9)
1. A preparation method of low-chlorine magnesium hydroxide is characterized by comprising the following specific operations: adding the magnesium chloride solution into an ammonia water solution for coprecipitation reaction to prepare magnesium hydroxide slurry, then carrying out hydrothermal crystallization growth under stirring, carrying out circulating washing centrifugation on the magnesium hydroxide slurry obtained after centrifugation by adopting the ammonia water solution, finally washing by using pure water until the washing water is neutral, filtering and drying to obtain the magnesium hydroxide product with low chlorine content.
2. The method according to claim 1, wherein the concentration of magnesium ions in the magnesium chloride solution is 0.01 to 4mol/L, preferably 2 to 3mol/L.
3. The method according to claim 1, wherein the concentration of the aqueous ammonia solution used in the coprecipitation reaction is 0.1 to 12mol/L, preferably 4 to 6mol/L.
4. The process according to claim 1, wherein the molar ratio of magnesium ions to ammonia in aqueous ammonia in the coprecipitation reaction is 1.05 to 3.0, preferably 1.4 to 3.0.
5. The method of claim 1, wherein the temperature of the hydrothermal crystallization is 60-100 ℃, preferably 80-90 ℃; the time of the hydrothermal crystallization is 0.1-10h, preferably 0.5-2h.
6. The method of claim 1, wherein the number of cycles of the cyclic washing centrifugation is 1 to 4.
7. The preparation method according to claim 1, wherein the ammonia aqueous solution used in the circulation washing centrifugation has a molar concentration 2 to 5 times that of chloride ions in the magnesium hydroxide slurry at the beginning of each circulation washing centrifugation, and a volume 1 to 3 times that of the magnesium hydroxide slurry.
8. The method according to claim 1, wherein the chloride ion content of the magnesium hydroxide slurry after the circulating washing and centrifuging is less than 0.1%.
9. The preparation method according to claim 1, wherein the ammonia water solution recovered by the circular washing and centrifugation is used for producing magnesium hydroxide to realize recycling; when the content of chloride ions in the ammonia water solution exceeds 20 percent, the ammonia water solution is sent to an ammonia still to recover ammonia gas and is continuously used for producing magnesium hydroxide.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101475197A (en) * | 2009-01-09 | 2009-07-08 | 中国科学院青海盐湖研究所 | Method for preparing ultra-fine high dispersing magnesium hydrate flame retardant from saline lake bittern or bischofite |
| CN106477602A (en) * | 2016-10-13 | 2017-03-08 | 青海百事特镁业有限公司 | A kind of preparation technology of high-purity low oxychloride magnesium |
| CN111137910A (en) * | 2020-01-03 | 2020-05-12 | 合肥中科阻燃新材料有限公司 | Method for preparing high-purity superfine magnesium hydroxide flame retardant by chemical method |
| CN115231593A (en) * | 2022-03-31 | 2022-10-25 | 定西凯美特新材料科技有限公司 | Method for preparing hexagonal magnesium hydroxide flame retardant by one-step hydrothermal method |
-
2022
- 2022-11-23 CN CN202211471475.XA patent/CN115771908A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101475197A (en) * | 2009-01-09 | 2009-07-08 | 中国科学院青海盐湖研究所 | Method for preparing ultra-fine high dispersing magnesium hydrate flame retardant from saline lake bittern or bischofite |
| CN106477602A (en) * | 2016-10-13 | 2017-03-08 | 青海百事特镁业有限公司 | A kind of preparation technology of high-purity low oxychloride magnesium |
| CN111137910A (en) * | 2020-01-03 | 2020-05-12 | 合肥中科阻燃新材料有限公司 | Method for preparing high-purity superfine magnesium hydroxide flame retardant by chemical method |
| CN115231593A (en) * | 2022-03-31 | 2022-10-25 | 定西凯美特新材料科技有限公司 | Method for preparing hexagonal magnesium hydroxide flame retardant by one-step hydrothermal method |
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