CN113697831A - Method for purifying and removing magnesium from industrial wastewater with high sodium-magnesium ratio and preparing magnesium hydroxide fire retardant - Google Patents
Method for purifying and removing magnesium from industrial wastewater with high sodium-magnesium ratio and preparing magnesium hydroxide fire retardant Download PDFInfo
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- 229910001862 magnesium hydroxide Inorganic materials 0.000 title claims abstract description 43
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 title claims abstract description 42
- 239000000347 magnesium hydroxide Substances 0.000 title claims abstract description 42
- 239000011777 magnesium Substances 0.000 title claims abstract description 40
- 239000003063 flame retardant Substances 0.000 title claims abstract description 34
- 229910052749 magnesium Inorganic materials 0.000 title claims abstract description 33
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 239000010842 industrial wastewater Substances 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims abstract description 23
- NEMFQSKAPLGFIP-UHFFFAOYSA-N magnesiosodium Chemical compound [Na].[Mg] NEMFQSKAPLGFIP-UHFFFAOYSA-N 0.000 title claims abstract description 20
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 36
- 238000006243 chemical reaction Methods 0.000 claims abstract description 34
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000002244 precipitate Substances 0.000 claims abstract description 14
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 11
- 238000001556 precipitation Methods 0.000 claims abstract description 10
- 238000002360 preparation method Methods 0.000 claims abstract description 10
- 238000000967 suction filtration Methods 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 8
- 239000006228 supernatant Substances 0.000 claims abstract description 8
- 239000000706 filtrate Substances 0.000 claims abstract description 7
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 7
- 238000001914 filtration Methods 0.000 claims abstract description 6
- 238000005406 washing Methods 0.000 claims abstract description 6
- 238000001035 drying Methods 0.000 claims abstract description 4
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 3
- 239000000047 product Substances 0.000 claims description 19
- 238000005119 centrifugation Methods 0.000 claims description 9
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- 238000004062 sedimentation Methods 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 6
- 239000002002 slurry Substances 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims description 4
- 235000019341 magnesium sulphate Nutrition 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 230000032798 delamination Effects 0.000 claims description 2
- 238000004537 pulping Methods 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 239000012153 distilled water Substances 0.000 abstract description 4
- 239000011734 sodium Substances 0.000 abstract description 4
- 229910052708 sodium Inorganic materials 0.000 abstract description 4
- 239000000654 additive Substances 0.000 abstract 1
- 230000000996 additive effect Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 13
- 239000002440 industrial waste Substances 0.000 description 5
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 229910001425 magnesium ion Inorganic materials 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 229910001415 sodium ion Inorganic materials 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000012267 brine Substances 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000012796 inorganic flame retardant Substances 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical group O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 2
- 229920002994 synthetic fiber Polymers 0.000 description 2
- 239000007832 Na2SO4 Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000004043 dyeing Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 235000011167 hydrochloric acid Nutrition 0.000 description 1
- -1 hydroxide ions Chemical class 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- 235000014380 magnesium carbonate Nutrition 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- DXZMANYCMVCPIM-UHFFFAOYSA-L zinc;diethylphosphinate Chemical compound [Zn+2].CCP([O-])(=O)CC.CCP([O-])(=O)CC DXZMANYCMVCPIM-UHFFFAOYSA-L 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
- C01F5/22—Magnesium hydroxide from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K21/00—Fireproofing materials
- C09K21/02—Inorganic materials
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a method for purifying and removing magnesium from industrial wastewater with a high sodium-magnesium ratio and preparing a magnesium hydroxide flame retardant, belonging to the field of magnesium hydroxide preparation methods. The method comprises the steps of carrying out precipitation reaction on low-magnesium industrial wastewater in a high-sodium content environment and a sodium hydroxide solution, settling for a certain time after the reaction is finished, carrying out suction filtration on a supernatant after the settlement, centrifuging a lower-layer precipitate, and obtaining a filtrate and a centrifugate as a purified high-purity sodium sulfate solution. Adding distilled water into the centrifuged precipitate, repulping, transferring the precipitate into a high-pressure reaction kettle for hydrothermal reaction, filtering, washing and drying to obtain the magnesium hydroxide flame retardant with the hexagonal sheet shape. The method solves the problem of green resource utilization of industrial wastewater with high sodium-magnesium ratio, has simple process flow and low production cost, and can prepare high-purity saturated sodium sulfate solution and nano-scale magnesium hydroxide flame retardant with regular appearance without any additive.
Description
Technical Field
The invention relates to the field of magnesium hydroxide preparation methods, in particular to a preparation method of a nano magnesium hydroxide flame retardant.
Background
With the improvement of environmental protection standards in recent years in China, the green resource utilization of industrial waste liquid is greatly developed. At the present stage, the large-scale treatment of the high-salinity wastewater still has the characteristics of low treatment efficiency and high operation cost, and has a plurality of key technical problems which need to be broken through and solved. The industrial wastewater with high sodium-magnesium ratio is mainly derived from drainage generated in the production processes of enterprises such as printing and dyeing, refining, pharmacy, salt manufacturing and the like, and has the characteristics of high content of sodium sulfate and a small amount of magnesium sulfate. If the direct evaporation crystallization is not processed, the purity of the sodium sulfate is too low, and the magnesium resource cannot be comprehensively utilized, so that the resource is seriously wasted. If the waste water is directly discharged, the waste water can cause serious pollution to soil and water quality.
Magnesium hydroxide, as an inorganic material, has the characteristics of no toxicity, no odor, no corrosiveness, high decomposition temperature and the like, and has very important application in the fields of flame retardance, environmental protection, medical use, food, ceramics, cosmetics and the like. The advantages of magnesium hydroxide as an inorganic flame retardant are particularly prominent with the increasing demand for halogen-free flame retardants in recent years. The magnesium hydroxide flame retardant has a high decomposition temperature, generates water after decomposition, absorbs a large amount of heat to lower the surface temperature of a synthetic material filled therein in a flame, and has the effects of inhibiting the decomposition of a polymer and cooling the generated combustible gas, as with the aluminum hydroxide flame retardant. The magnesium oxide generated by decomposing the magnesium hydroxide is a good refractory material, can also help to improve the fire resistance of the synthetic material, and simultaneously, the water vapor emitted by the magnesium oxide can also be used as a smoke suppressant. Compared with similar inorganic flame retardants, the magnesium hydroxide has better smoke suppression effect, does not discharge harmful substances in the production, use and waste processes of the magnesium hydroxide, and can neutralize acidic and corrosive gases generated in the combustion process.
The main process for the preparation of magnesium hydroxide of the prior art is brine (MgCl)2) And hydrated limeThe reaction is carried out to obtain; brine (MgCl)2) Reacting with ammonia water to obtain the product; magnesite, hydrochloric acid and ammonia water. The process for purifying and removing magnesium from industrial wastewater containing magnesium and simultaneously producing the flame retardant magnesium hydroxide is not reported.
Disclosure of Invention
The invention aims to provide a preparation method of a nano magnesium hydroxide flame retardant, which aims to solve the problem of preparing flame-retardant magnesium hydroxide from magnesium-containing industrial wastewater in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the method for purifying and removing magnesium from industrial wastewater with high sodium-magnesium ratio and preparing the magnesium hydroxide flame retardant comprises the following steps:
step 1, adding 0.5-2.5mol/L sodium hydroxide solution into industrial wastewater of sodium sulfate with high sodium-magnesium ratio at a constant reaction temperature of 25-100 ℃ and a certain stirring speed at a certain dropping speed for precipitation reaction for 30-60 min;
step 3, placing the slurry repulped in the step 2 in a high-pressure reaction kettle for hydrothermal reaction at the temperature of 120 ℃ and 180 ℃ for 2-10 h;
and 4, after the reaction in the step 3 is finished, filtering and washing a product obtained in the high-pressure reaction kettle, and then drying the product at the temperature of 80-110 ℃ for 3-8h to obtain the hexagonal flaky nano-scale magnesium hydroxide flame retardant.
Further, in the step 1, the content of magnesium sulfate in the industrial wastewater with high sodium magnesium ratio is 0.1-0.2mol/L, and the sodium magnesium ratio is 20-40.
Further, in step 1, the ratio of the amount of the substance of sodium hydroxide to the amount of the substance of magnesium added is n (Mg)2+)：n(OH-) =1:1.2-1:2.4, and the pH range for complete precipitation is 10.5-12.5.
Further, in the step 1, the stirring speed is 200-600r/min, and the dropping speed of the sodium hydroxide is 2.5-7.5 ml/min.
Further, in step 2, after the reaction is finished and the sedimentation is finished, the supernatant is filtered, the lower layer is precipitated and centrifuged, the sedimentation time is 60-300min, the centrifugation speed is 3000-4000r/min, and the centrifugation time is 3-8 min.
Further, in the step 2, a solid-liquid separation method combining sedimentation, suction filtration and centrifugation is adopted after reaction precipitation, sedimentation and delamination.
Further, in the step 2, the filtrate and the centrifugate are high-purity saturated sodium sulfate solution.
Further, in the step 3, the hydrothermal temperature is 120-180 ℃, and the hydrothermal time is 2-10 h.
Further, in the step 4, the prepared magnesium hydroxide flame retardant is hexagonal sheet-shaped.
The preparation method of the nano-scale magnesium hydroxide flame retardant comprises the following steps of (1) carrying out precipitation reaction between industrial wastewater containing sodium sulfate with a high sodium-magnesium ratio and strong base (sodium hydroxide), and reacting magnesium ions and hydroxide ions to generate magnesium hydroxide precipitate: the reaction equation is as follows:
MgSO4+2NaOH=Na2SO4+Mg(OH)2↓
compared with the prior art, the invention has the advantages that: the method solves the problem of green resource utilization of the industrial wastewater with high sodium-magnesium ratio, and converts magnesium into the magnesium hydroxide flame retardant with use value while purifying and removing magnesium to obtain high-purity sodium sulfate; compared with the prior art, the raw materials are easy to obtain, the process flow for preparing the magnesium hydroxide flame retardant by purifying and removing magnesium is simple, the production cost is low, and the problem of slow filtration in the strong alkali method for producing the magnesium hydroxide is solved by a solid-liquid separation mode of sedimentation, filtration and centrifugation.
Drawings
FIG. 1 shows the ratio of the amount of sodium hydroxide material to the amount of magnesium material added in the present invention is n (Mg)2+)：n(OH-) Graph of magnesium content in filtrate at 1:1.2-1: 2.4.
FIG. 2 is an X-ray diffraction pattern of the product of example 1 of the present invention.
FIG. 3 is a scanning electron micrograph of a product according to example 1 of the present invention.
FIG. 4 is an X-ray diffraction pattern of the product of example 2 of the present invention.
FIG. 5 is a scanning electron micrograph of a product of example 2 of the present invention.
FIG. 6 is an X-ray diffraction pattern of the product of example 3 of the present invention.
FIG. 7 is a scanning electron micrograph of a product according to example 3 of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
Example 1
Preparation of the nano magnesium hydroxide flame retardant: measuring 300ml of industrial waste liquid with magnesium ion concentration of 0.1mol/L and sodium ion concentration of 3mol/L, heating to 60 ℃, measuring 120ml of 0.5mol/L sodium hydroxide solution, adding the solution into the high-sodium magnesium-containing solution, stirring for reaction for 1h, settling for 2h after the reaction is finished, carrying out suction filtration on the settled supernatant, measuring the magnesium content of the filtrate, carrying out lower-layer precipitation centrifugation, and adding distilled water into the centrifuged precipitate for repulping. And transferring the slurry into a high-pressure reaction kettle to react for 6 hours at 140 ℃, and filtering and washing after the reaction kettle is naturally cooled. Drying the washed product at 95 ℃ for 4h to obtain Mg (OH)2And (3) a flame retardant.
Example 2
Preparation of the nano magnesium hydroxide flame retardant: measuring 300ml of industrial waste liquid with magnesium ion concentration of 0.1mol/L and sodium ion concentration of 3mol/L, heating to 60 ℃, measuring 120ml of 0.5mol/L sodium hydroxide solution, adding the solution into the high-sodium magnesium-containing solution, stirring for reaction for 1h, settling for 2h after the reaction is finished, carrying out suction filtration on the settled supernatant, measuring the magnesium content of the filtrate, carrying out lower-layer precipitation centrifugation, and adding distilled water into the centrifuged precipitate for repulping. And transferring the slurry into a high-pressure reaction kettle to react for 8 hours at the temperature of 140 ℃, and performing suction filtration and washing after the reaction kettle is naturally cooled. The washed product is placed at the temperature of 95 ℃ for 4 hours to obtain Mg (OH)2And (3) a flame retardant.
Example 3
Preparation of the nano magnesium hydroxide flame retardant: measuring 300ml of industrial waste liquid with magnesium ion concentration of 0.1mol/L and sodium ion concentration of 3mol/L, heating to 60 ℃, measuring 120ml of 0.5mol/L sodium hydroxide solution, and adding into high-sodium magnesium-containing solutionStirring the solution for reaction for 1h, settling for 2h after the reaction is finished, carrying out suction filtration on the settled supernatant, measuring the magnesium content of the filtrate, centrifuging the lower-layer precipitate, adding distilled water into the centrifuged precipitate, and repulping. And transferring the slurry into a high-pressure reaction kettle to react for 6 hours at 180 ℃, and performing suction filtration and washing after the reaction kettle is naturally cooled. The washed product is placed at the temperature of 95 ℃ for 4 hours to obtain Mg (OH)2And (3) a flame retardant.
As shown in FIG. 1, the analysis of FIG. 1 by inductively coupled plasma spectrometer can show that the magnesium content in the original solution is gradually reduced when the added precipitant is gradually increased, and when n (Mg)2+)：n(OH-) And when the ratio is 1:1.4-1:2.4, the magnesium content in the solution is 5-10 ppm. This shows that the process can remove the magnesium in the industrial waste liquid with high sodium-magnesium ratio.
The X-ray diffraction pattern analysis in fig. 2, 4 and 6 shows that the prepared sample is consistent with the standard card of magnesium hydroxide, which indicates that the product obtained by the above method is consistent with the product of the present invention.
As can be seen from the scanning electron micrographs at 8 ten thousand times magnification in fig. 3, 5 and 7, the morphology of the product is a regular hexagonal sheet shape and the size is in the nanometer level, which indicates that the product obtained by the above method is consistent with the product of the present invention.
The embodiments of the present invention are described only for the preferred embodiments of the present invention, and not for the limitation of the concept and scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the design concept of the present invention shall fall into the protection scope of the present invention, and the technical content of the present invention which is claimed is fully set forth in the claims.
Claims (9)
1. The method for purifying and removing magnesium from industrial wastewater with high sodium-magnesium ratio and preparing the magnesium hydroxide flame retardant is characterized by comprising the following steps of:
step 1, adding 0.5-2.5mol/L sodium hydroxide solution into industrial wastewater of sodium sulfate with high sodium-magnesium ratio at a constant reaction temperature of 25-100 ℃ and a certain stirring speed at a certain dropping speed for precipitation reaction for 30-60 min;
step 2, settling for 2-5 hours after the reaction in the step 1 is finished, carrying out suction filtration on the settled supernatant to leave a lower-layer precipitate, centrifuging the precipitate, adding water into the centrifuged precipitate, and then pulping;
step 3, placing the slurry repulped in the step 2 in a high-pressure reaction kettle for hydrothermal reaction at the temperature of 120 ℃ and 180 ℃ for 2-10 h;
and 4, after the reaction in the step 3 is finished, filtering and washing a product obtained in the high-pressure reaction kettle, and then drying the product at the temperature of 80-110 ℃ for 3-8h to obtain the hexagonal flaky nano-scale magnesium hydroxide flame retardant.
2. The preparation method of the nano magnesium hydroxide fire retardant according to claim 1, wherein in the step 1, the content of magnesium sulfate in the industrial wastewater with high sodium-magnesium ratio is 0.1-0.2mol/L, and the sodium-magnesium ratio is 20-40.
3. The method for purifying and removing magnesium and preparing magnesium hydroxide fire retardant for industrial wastewater with high sodium-magnesium ratio as claimed in claim 1, wherein in step 1, the ratio of the amount of the substance of sodium hydroxide to the amount of the substance of magnesium is n (Mg)2+)：n(OH-) =1:1.2-1:2.4, and the pH range for complete precipitation is 10.5-12.5.
4. The method for purifying and removing magnesium from industrial wastewater and preparing magnesium hydroxide fire retardant according to claim 1, wherein in step 1, the stirring speed is 200-600r/min, and the dropping speed of sodium hydroxide is 2.5-7.5 ml/min.
5. The method for purifying and removing magnesium from industrial wastewater and preparing magnesium hydroxide fire retardant according to claim 1, wherein in step 2, after the reaction is finished and settled, the supernatant is filtered, the lower layer is precipitated and centrifuged, the settling time is 2-5h, the centrifugation speed is 3000-4000r/min, and the centrifugation time is 3-8 min.
6. The method for purifying and removing magnesium and preparing the magnesium hydroxide fire retardant for the industrial wastewater with the high sodium-magnesium ratio as claimed in claim 1, wherein in the step 2, a solid-liquid separation method combining sedimentation, suction filtration and centrifugation is adopted after reaction precipitation, sedimentation and delamination.
7. The method for purifying and removing magnesium and preparing magnesium hydroxide fire retardant for industrial wastewater with high sodium-magnesium ratio as claimed in claim 1, wherein in step 2, the filtrate and the centrifugate are high-purity saturated sodium sulfate solution.
8. The method for purifying and removing magnesium and preparing magnesium hydroxide fire retardant for industrial wastewater with high sodium-magnesium ratio as claimed in claim 1, wherein the hydrothermal temperature is 120-180 ℃ and the hydrothermal time is 2-10 h.
9. The method for purifying and removing magnesium from industrial wastewater and preparing magnesium hydroxide fire retardant according to claim 1, wherein the magnesium hydroxide prepared in step 4 is hexagonal and flaky.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114804163A (en) * | 2022-05-16 | 2022-07-29 | 安徽大学绿色产业创新研究院 | Method for preparing flame retardant magnesium hydroxide by wet dechlorination of industrial-grade magnesium hydroxide |
| CN114853212A (en) * | 2022-05-09 | 2022-08-05 | 纪宏轩 | Zero-emission recycling treatment method for magnesium sulfate wastewater |
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| CN1740269A (en) * | 2005-09-23 | 2006-03-01 | 清华大学 | Liquid amonia pressurized precipitation and hydrothermal modification process for preparing magnesium hydroxide fire retardant |
| CN101700899A (en) * | 2009-10-28 | 2010-05-05 | 钟辉 | Technology for producing and preparing high-purity lamellar magnesium hydroxide |
| CN102205980A (en) * | 2011-04-07 | 2011-10-05 | 中国科学院青海盐湖研究所 | Method for preparing monodisperse flaky magnesium hydroxide flame retardant |
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| CN114804163B (en) * | 2022-05-16 | 2024-02-13 | 安徽大学绿色产业创新研究院 | Method for preparing flame retardant magnesium hydroxide by wet dechlorination of industrial magnesium hydroxide |
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