Method for preparing magnesium spinel zirconium material by using salt lake water bischofite

Abstract

The application provides a method for preparing magnesia spinel zirconium material by using salt lake bischofite, and the method comprises the following steps: dissolving the bischofite, filtering, and dissolving the filtrate after recrystallization to obtain a pure magnesium chloride solution; adding the magnesium chloride solution and a sodium hydroxide solution into a sodium chloride solution at the same time to perform a precipitation reaction, filtering and washing to obtain a high-purity magnesium hydroxide precipitate, and preparing light-burned magnesia by middle-temperature calcination; mixing the light-burned magnesia, aluminum raw material, zirconium raw material and a binder solution, and pressing to form a green body; drying and middle-temperature heat treating the green body, and vacuum sintering to prepare the magnesia spinel zirconium material. The magnesia spinel zirconium material prepared by using the salt lake bischofite has excellent performances such as high purity and high density, effectively solves the problem of high-value utilization of the by-product bischofite in the production process of salt lake potassium salt, greatly improves the utilization efficiency of salt lake magnesium resources, and reduces the adverse effects on the environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of comprehensive utilization of salt lake magnesium resources, and in particular relates to a preparation method of magnesia-spinel zirconia material which is widely used in the field of refractory materials, and more particularly relates to a method for preparing magnesia-spinel zirconia material by using salt lake bischofite. BACKGROUND

[0002] Magnesia-spinel zirconia material has good slag corrosion resistance and thermal shock resistance, and is widely used in key parts of high-temperature kiln such as RH vacuum furnace immersion tube, refining ladle slag line, cement kiln firing belt, etc. It is also an excellent material for preparing functional refractory materials such as metallurgical water nozzle brick, filter, air permeable element, sliding plate, etc. In the metallurgical refining process, the reliability of magnesia-spinel zirconia material is comparable to that of fused recoupled magnesia-chrome brick, and high-purity directly bonded magnesia-spinel zirconia material can replace zirconia-carbon brick for sizing water nozzle, effectively promoting the development of chrome-free and low-carbon refractory materials.

[0003] With the increasing demand for special steel and special cement and the development of emerging high-temperature technologies, people have higher requirements for the purity and high-temperature performance of magnesia-spinel zirconia material. Magnesia-spinel material is usually synthesized at high temperature by high-purity magnesite magnesia sand and spinel sand. However, there are usually a small amount of impurities such as CaO, SiO2 and FeO in magnesite magnesia sand, which are difficult to eradicate, significantly affecting the direct bonding degree of the material and thus affecting the high-temperature performance of the material. Moreover, there are problems of carbon dioxide and high-temperature flue gas emissions in the production process. In addition, with the year-by-year shortage of high-quality magnesite, there will be a problem of stable supply of high-purity magnesite magnesia sand in the future.

[0004] China's Qarhan Salt Lake contains nearly 165 million tons of magnesium chloride, and a large amount of bischofite is produced as a byproduct in the process of potassium fertilizer production. The purity of magnesium oxide prepared by bischofite precipitation method can be higher than 99%, which is a potential resource for preparing high-purity magnesia-spinel zirconia material. Therefore, developing a process route for preparing magnesia-spinel zirconia material from bischofite can not only realize the high-value comprehensive utilization of salt lake magnesium resources, but also avoid the problems of carbon dioxide and dust emissions in the traditional preparation process of magnesite refractory products, and ensure the long-term stable supply of high-performance refractory products. SUMMARY

[0005] The present application aims to overcome the deficiencies in the prior art, and provides a method for preparing magnesia-spinel zirconia material from salt lake bischofite, which can prepare magnesia-spinel zirconia material with high purity and high density, etc., realize the high-value utilization of salt lake waste bischofite, and reduce the adverse effects on the environment.

[0006] In order to achieve the above-mentioned application purposes, the present application adopts the following technical solutions:

[0007] A method for preparing magnesium spinel zircon material using magnesium chloride from salt lake water includes the following steps:

[0008] (1) Impurity removal: dissolve and filter magnesium chloride to remove insoluble impurities. The filtrate is recrystallized to remove soluble impurities to prepare high-purity magnesium chloride hexahydrate solid. After dissolving, a pure magnesium chloride solution is obtained.

[0009] (2) Preparation of magnesia: Magnesium chloride solution and sodium hydroxide solution are added to sodium chloride solution at the same time to carry out precipitation reaction. After filtration and washing, high-purity magnesium hydroxide precipitate is obtained, and lightly calcined magnesia is prepared by medium-temperature roasting.

[0010] (3) Mixing and billet preparation: Lightly calcined magnesia, aluminous raw materials, zirconium raw materials and binder solution are mixed in a certain proportion and uniaxial pressure is applied to prepare the billet;

[0011] (4) Sintering: After drying and medium-temperature heat treatment, the green body is placed in a vacuum sintering furnace at a vacuum degree ≤10. -3 Magnesium spinel zirconium material was prepared by vacuum sintering under Pa conditions for a certain time.

[0012] The present invention is further configured such that, in step (1), the water magnesium chloride solution is filtered 1 to 3 times to remove insoluble impurities.

[0013] The present invention is further configured such that, in step (1), the recrystallization temperature of the filtrate is 25-110°C, the evaporation mass of the filtrate is 10%-30% of the mass of the filtrate before evaporation, and the recrystallization is performed 1-3 times.

[0014] The present invention is further configured such that, in step (2), the concentration of the magnesium chloride solution is 1–3 mol / L, the molar ratio of magnesium chloride to sodium hydroxide is 1:1–1:3, and the molar ratio of magnesium chloride to sodium chloride is 1:0.5–1:2. The feed rate of the magnesium chloride solution and the sodium hydroxide solution is 0.5–2.0 ml / min, the stirring rate during the precipitation reaction is controlled at 300–600 r / min, the precipitation reaction temperature is 60–100 °C, and the precipitation reaction time is 0.5–3 h.

[0015] The present invention is further configured such that, in step (2), the number of washing cycles is 3 to 5, and the amount of water used for each sediment washing cycle is 3 to 6 times the mass of the sediment.

[0016] This invention uses magnesium chloride from salt lake water and sodium hydroxide as raw materials. A sodium chloride solution is added to the reaction substrate, and magnesium hydroxide is prepared through a process of recrystallization-precipitation-washing of the magnesium chloride solution. The efficient impurity removal process involving several recrystallizations and water washing avoids the presence of potassium (K) in the magnesium chloride solution. + Na + SO4 2- B 3+ Ca2+ The impurities such as magnesium hydroxide are remained in the magnesium hydroxide product, thereby seriously affecting the high-temperature performance of the downstream product magnesium spinel material. The magnesium hydroxide prepared by the method has a purity of greater than or equal to 99% and an average particle size of 5-15 μm.

[0017] The present application is further provided that, in step (2), the calcination temperature for preparing the calcined magnesia from the magnesium hydroxide precipitation is 400-600 ℃, and the calcination time is 1-3 h.

[0018] The present application is further provided that, in step (3), the mass fraction of the calcined magnesia in the mixture of the calcined magnesia, the aluminum raw material and the zirconium raw material is 60%-90%, the mass fraction of the aluminum raw material is 5%-30%, the mass fraction of the zirconium raw material is 2%-15%, and the mass ratio of the mixture to the binder solution is 100:1-10:1.

[0019] Further, in step (3), the aluminum raw material is one or more of white corundum, industrial alumina, bauxite, diaspore, hard gibbsite, pseudo-boehmite, and has an average particle size of 20%-70% of the average particle size of the magnesium hydroxide. Specifically, the average particle size of the aluminum raw material is 2-10 μm.

[0020] Further, in step (3), the zirconium raw material is one or more of monoclinic zirconium and desiliconized zirconium, and has an average particle size of 20%-50% of the average particle size of the magnesium hydroxide. Specifically, the average particle size of the zirconium raw material is 1-5 μm.

[0021] Further, in step (3), the binder is one or more of polyvinyl alcohol, polyethylene glycol, starch and carboxymethyl cellulose.

[0022] The present application is further provided that, in step (3), the forming pressure for preparing the green body is 200-400 MPa, and the pressure holding time is 3-5 min.

[0023] The present application is further provided that, in step (4), the green body is first dried at 20-40 ℃ for 10-30 h, and then dried at 80-120 ℃ for 15-30 h; the temperature for the medium-temperature heat treatment is 300-600 ℃, and the heat treatment time is 2-5 h, so as to remove the residual carbon in the binder.

[0024] The present application is further provided that, in step (4), the temperature for the vacuum sintering is 1400-2000 ℃, and the sintering time is 2-5 h.

[0025] The present application also provides a magnesium spinel zirconium material prepared by the method for preparing the magnesium spinel zirconium material from the bischofite in the salt lake water.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The present application uses salt lake bischofite as raw material to prepare flower-shaped magnesium hydroxide aggregate structure with rich surface voids, so that the aluminum raw material and zirconium raw material are uniformly distributed on the surface of the loose structure during the mixing process, and the spinel-zirconia wrapped periclase structure (MgO@MgAl2O4-ZrO2 structure) is obtained through in-situ reaction sintering. The wrapping structure strengthens the pinning effect of spinel, promotes the sintering of periclase, improves the densification degree of magnesia spinel zirconium material, and prepares magnesia spinel zirconium material with high purity, high density and other excellent properties.

[0028] (2) The process for preparing magnesia spinel zirconium material using salt lake bischofite provided by the present application has the advantages of green, low carbon and environmental protection, which can effectively avoid the problems of carbon dioxide emission and dust pollution faced by the traditional process for preparing magnesia spinel zirconium material from magnesite, realizes high-value utilization of abandoned salt lake bischofite, greatly improves the utilization efficiency of salt lake magnesium resources, and reduces the pollution to the environment.

[0029] (3) Compared with the traditional process for preparing magnesia spinel zirconium material by calcining magnesite and spinel, the process for preparing magnesia spinel zirconium material using salt lake bischofite provided by the present application has fewer high-temperature sintering times, and excellent magnesia spinel zirconium material can be prepared through one high-temperature sintering process, which greatly reduces the energy consumption of the preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The process flow chart for preparing magnesia spinel zirconium material of the present application;

[0031] Figure 2 The SEM image of magnesium hydroxide prepared in Example 1;

[0032] Figure 3 The SEM image of light magnesium sand prepared in Example 1;

[0033] Figure 4 The SEM image of magnesia spinel zirconium material prepared in Example 1. DETAILED DESCRIPTION

[0034] The technical solutions of the present application will be described in detail below with specific examples. It should be understood that the described examples are only a part of the examples of the present application, not all examples. Based on the examples of the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of the present application. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as familiar to those skilled in the art.

[0035] Example 1

[0036] (1) Take 190g of natural brine from Chai' erhan salt lake in Qinghai province, which is evaporated and crystallized by sunlight, and its elemental composition is 11.06wt.% Mg, 34.67wt.% Cl, 0.202wt.% Na, 0.0917wt.% K, 0.00768wt.% S, 0.00026wt.% Ca, and 0.00032wt.% B. Dissolve it in water, filter twice to remove insoluble impurities, and evaporate the filtrate at 110°C to recrystallize. Evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid, and dissolve it to obtain a pure magnesium chloride solution.

[0037] (2) Prepare a 3mol / L magnesium chloride solution, and simultaneously add it to a 3mol / L sodium chloride solution with a 6mol / L sodium hydroxide solution. The feeding rate is 1.125ml / min, the stirring rate is 400r / min, the precipitation reaction temperature is 80°C, the reaction time is 120min, the suspension is naturally cooled and filtered to obtain a magnesium hydroxide precipitate, which is washed with deionized water three times. The mass ratio of deionized water to precipitate in a single washing is 5:1. A pure magnesium hydroxide precipitate is obtained by washing, with a purity of 99.2% and an average particle size of 7.58μm. The precipitate is calcined at 500°C for 2h to obtain calcined magnesia.

[0038] (3) Grind and mix calcined magnesia, white corundum (average particle size of 3μm), and monoclinic zircon (average particle size of 3.42μm) for 3min. The mass fraction of calcined magnesia in the mixture is 81%, the mass fraction of white corundum is 16%, and the mass fraction of zirconia powder is 3%. Add polyvinyl alcohol solution to the mixture, and the mass ratio of the mixture to the binder solution is 100:7. After grinding and mixing for 3min, the mixture is formed into a green body under a uniaxial pressing pressure of 350MPa, and the pressure holding time is 3min.

[0039] (4) The green body is naturally dried at 25°C for 24h, and then placed in an oven at 110°C for 24h. The dried green body is heat treated at 600°C for 4h, and then placed in a vacuum sintering furnace. The vacuum degree is 10 -4 pa, and the sintering temperature is 1600°C. The sintering time is 3h, and the natural cooling time is 6h. A magnesium spinel zirconium material is obtained.

[0040] The SEM images of the prepared magnesium hydroxide, calcined magnesia, and the product magnesium spinel zirconium material are shown in Figures 2-4 , respectively. The magnesium hydroxide is in the form of flower-like agglomerates, the obtained calcined magnesia has abundant surface pores, and the product magnesium spinel zirconium material has a spinel-zirconia-encapsulated periclase encapsulation structure. The density of the prepared magnesium spinel zirconium material is 3.58g / cm 3 , the porosity is 2.2%, and the linear shrinkage rate is 14.11%.

[0041] Example 2

[0042] (1) Take 190g of natural day-sunning heap mineral of Qinghai Chai' erhan salt lake brine, its elemental composition is 11.06wt.% Mg, 34.67wt.% Cl, 0.202wt.% Na, 0.0917wt.% K, 0.00768wt.% S, 0.00026wt.% Ca, and 0.00032wt.% B. Dissolve it with water, filter twice to remove insoluble impurities, evaporate the filtrate at 110°C to recrystallize, evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid, and dissolve to obtain pure magnesium chloride solution.

[0043] (2) Prepare 3mol / L magnesium chloride solution, and add it into 3mol / L sodium chloride solution at the same time as 6mol / L sodium hydroxide solution, the feeding rate is 1.125ml / min, the stirring rate is 400r / min, the precipitation reaction temperature is 80°C, the reaction time is 120min, the suspension is naturally cooled and filtered to obtain magnesium hydroxide precipitate, which is washed with deionized water for 3 times, the mass ratio of deionized water to precipitate in single washing is 5:1, and the pure magnesium hydroxide precipitate with a purity of 99.2% and an average particle size of 7.58μm is obtained through washing, and the precipitate is calcined at 500°C for 2h to obtain calcined magnesia.

[0044] (3) Grind and mix calcined magnesia, white corundum (average particle size is 3μm) and monoclinic zircon (average particle size is 3.42μm) for 3min, the mass fraction of calcined magnesia in the mixture is 78%, the mass fraction of white corundum is 16%, and the mass fraction of zirconia powder is 6%, add polyvinyl alcohol solution to the mixture, the mass ratio of the mixture to the binder solution is 100:7, grind and mix for 3min, and then uniaxially press the mixture to form a blank under a forming pressure of 300MPa, and the pressure maintaining time is 5min.

[0045] (4) The blank is naturally dried at 30°C for 22h, and then is placed into a 100°C oven for drying for 24h. The dried blank is heat treated at a temperature of 600°C for 4h, and then is placed into a vacuum sintering furnace, the vacuum degree is 10 -4 pa, and the sintering is carried out at a temperature of 1600°C for 3h, and the magnesium spinel zirconium material is obtained after natural cooling.

[0046] The SEM images of the prepared magnesium hydroxide, calcined magnesia and the product magnesium spinel zirconium material are similar to those of Example 1, the density of the prepared magnesium spinel zirconium material is 3.65g / cm 3 , the porosity is 2.13%, and the linear shrinkage rate is 12.89%.

[0047] Example 3

[0048] (1) Take 190g of the natural day sun heap mineral of Qinghai Chai' erhan salt lake brine, its element composition is 11.06wt.% Mg, 34.67wt.% Cl, 0.202wt.% Na, 0.0917wt.% K, 0.00768wt.% S, 0.00026wt.% Ca, and 0.00032wt.% B. Dissolve it with water, filter twice to remove insoluble impurities, evaporate the filtrate at 110°C to recrystallize, evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid, and dissolve to obtain a pure magnesium chloride solution.

[0049] (2) Prepare a 3mol / L magnesium chloride solution, and simultaneously add a 6mol / L sodium hydroxide solution to a 3mol / L sodium chloride solution, with a feeding rate of 1.125ml / min and a stirring rate of 400r / min, at a precipitation reaction temperature of 80°C, for a reaction time of 120min, and obtain a magnesium hydroxide precipitate by natural cooling and filtration of the suspension, washing the precipitate three times with deionized water, with a mass ratio of deionized water to precipitate of 5:1 for each washing, obtaining a pure magnesium hydroxide precipitate with a purity of 99.2% and an average particle size of 7.58μm, and calcining the precipitate at 500°C for 2h to obtain calcined magnesia.

[0050] (3) Grind and mix calcined magnesia, white corundum (with an average particle size of 3μm) and monoclinic zircon (with an average particle size of 3.42μm) for 3min, with a mass fraction of calcined magnesia in the mixture of 82%, a mass fraction of white corundum of 16%, and a mass fraction of zirconia powder of 2%, add polyvinyl alcohol solution to the mixture, with a mass ratio of mixture to binder solution of 100:7, grind and mix for 3min, and then form a blank under a uniaxial pressing pressure of 350MPa, with a pressure holding time of 5min.

[0051] (4) Dry the blank at 30°C for 24h, and then place it in an oven at 110°C for 24h. After drying, heat treat the blank at a temperature of 600°C for 4h, and then place it in a vacuum sintering furnace, with a vacuum degree of 10 -4 pa, sinter at a temperature of 1600°C for 3h, and then naturally cool to obtain a magnesium spinel zirconium material.

[0052] The SEM images of the prepared magnesium hydroxide, calcined magnesia and product magnesium spinel zirconium material are similar to those of Example 1, and the density of the prepared magnesium spinel zirconium material is 3.5g / cm 3 , the porosity is 2.31%, and the linear shrinkage is 13.52%.

[0053] Example 4

[0054] (1) Take 190g of the natural day-sun heap mineral of the brine of Chai' erhan salt lake in Qinghai province, its elemental composition is 11.06wt.% Mg, 34.67wt.% Cl, 0.202wt.% Na, 0.0917wt.% K, 0.00768wt.% S, 0.00026wt.% Ca, and 0.00032wt.% B. Dissolve it with water, filter twice to remove insoluble impurities, evaporate the filtrate at 110°C to recrystallize, evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid, and dissolve to obtain a pure magnesium chloride solution.

[0055] (2) Prepare a 3mol / L magnesium chloride solution, and simultaneously add it to a 3mol / L sodium chloride solution with a 6mol / L sodium hydroxide solution, the feeding rate is 1.125ml / min, the stirring rate is 400r / min, the precipitation reaction temperature is 80°C, the reaction time is 120min, the suspension is naturally cooled and filtered to obtain a magnesium hydroxide precipitate, which is washed with deionized water for 3 times, the mass ratio of deionized water to precipitate in single washing is 5:1, and a pure magnesium hydroxide precipitate is obtained through washing, the purity is 99.2%, and the average particle size is 7.58μm. The precipitate is calcined at 500°C for 2h to obtain calcined magnesia.

[0056] (3) Grind and mix the calcined magnesia, white corundum (average particle size is 3μm), and monoclinic zircon (average particle size is 3.42μm) for 3min, the mass fraction of calcined magnesia in the mixed material is 73.1%, the mass fraction of white corundum is 14.6%, and the mass fraction of zirconia powder is 12.3%, add polyvinyl alcohol solution to the mixed material, the mass ratio of mixed material to binder solution is 100:7, grind and mix for 3min, and then uniaxially press the mixture to form a blank under a forming pressure of 350MPa, and the pressure maintaining time is 5min.

[0057] (4) The blank is naturally dried at 30°C for 24h, and then is placed into a 110°C oven for drying for 24h. The dried blank is heat treated at a temperature of 600°C for 4h, and then is placed into a vacuum sintering furnace, the vacuum degree is 10 -4 pa, and the sintering is performed at a temperature of 1600°C for 3h, and then the magnesium spinel zirconium material is obtained after natural cooling.

[0058] The SEM images of the prepared magnesium hydroxide, calcined magnesia, and the product magnesium spinel zirconium material are similar to those of Example 1, the density of the prepared magnesium spinel zirconium material is 3.67g / cm 3 , the porosity is 1.87%, and the linear shrinkage rate is 10.5%.

[0059] Example 5

[0060] (1) Take 190 g of the natural day sunning heap mineral of Qinghai Chai' erhan salt lake brine, its element composition is 11.06 wt.% Mg, 34.67 wt.% Cl, 0.202 wt.% Na, 0.0917 wt.% K, 0.00768 wt.% S, 0.00026 wt.% Ca, and 0.00032 wt.% B. Dissolve it with water, filter twice to remove insoluble impurities, evaporate the filtrate at 110°C to recrystallize, evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid, and dissolve to obtain a pure magnesium chloride solution.

[0061] (2) Prepare a 3 mol / L magnesium chloride solution, and simultaneously add a 6 mol / L sodium hydroxide solution to a 3 mol / L sodium chloride solution at a feeding rate of 1.125 ml / min and a stirring rate of 400 r / min, and the precipitation reaction temperature is 80°C, the reaction time is 120 min, the suspension is naturally cooled and filtered to obtain a magnesium hydroxide precipitate, which is washed with deionized water for 3 times, and the mass ratio of deionized water to the precipitate in a single washing is 5:1, and a pure magnesium hydroxide precipitate is obtained by washing, the purity is 99.2%, and the average particle size is 7.58 μm, and the precipitate is calcined at 500°C for 2 h to obtain calcined magnesia.

[0062] (3) Grind and mix the calcined magnesia, white corundum (average particle size is 3 μm), and monoclinic zircon (average particle size is 3.42 μm) for 3 min, the mass fraction of the calcined magnesia in the mixed material is 74.4%, the mass fraction of the white corundum is 14.9%, and the mass fraction of the zirconia powder is 10.7%, add a polyvinyl alcohol solution to the mixed material, the mass ratio of the mixed material to the binder solution is 100:7, grind and mix for 3 min, and then uniaxially press the mixture to form a blank at a forming pressure of 350 MPa, and the pressure maintaining time is 5 min.

[0063] (4) The blank is naturally dried at 30°C for 24 h, and then is placed into a 110°C oven for drying for 24 h. The dried blank is heat treated at a temperature of 600°C for 4 h, and then is placed into a vacuum sintering furnace, the vacuum degree is 10 -4 pa, and the sintering is performed at a temperature of 1600°C for 3 h, and the magnesium spinel zirconium material is obtained after natural cooling.

[0064] The SEM images of the prepared magnesium hydroxide, calcined magnesia, and the product magnesium spinel zirconium material are similar to those of Example 1, the density of the prepared magnesium spinel zirconium material is 3.65 g / cm 3 , the porosity is 2.03%, and the linear shrinkage rate is 12%.

[0065] Comparative Example 1

[0066] (1) Take 190 g of natural brine from Chai' erhan salt lake in Qinghai province, which is obtained by solar evaporation of brine. The elemental composition of the brine is 11.06 wt. % Mg, 34.67 wt. % Cl, 0.202 wt. % Na, 0.0917 wt. % K, 0.00768 wt. % S, 0.00026 wt. % Ca, and 0.00032 wt. % B. Dissolve the brine with water, filter twice to remove insoluble impurities, and evaporate the filtrate at 110 °C to recrystallize. Evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid. Dissolve the solid to obtain a pure magnesium chloride solution.

[0067] (2) Prepare a 3 mol / L magnesium chloride solution, and simultaneously add it to a 3 mol / L sodium chloride solution with a 6 mol / L sodium hydroxide solution. The feeding rate is 1.125 ml / min, the stirring rate is 400 r / min, the precipitation reaction temperature is 80 °C, the reaction time is 120 min, the suspension is naturally cooled and filtered to obtain a magnesium hydroxide precipitate, which is washed with deionized water three times. The mass ratio of deionized water to precipitate in a single washing is 5:1. A pure magnesium hydroxide precipitate with a purity of 99.2% and an average particle size of 7.58 μm is obtained by washing. The precipitate is calcined at 500 °C for 2 h to obtain calcined magnesia.

[0068] (3) Grind and mix the calcined magnesia and white corundum (average particle size 7.85 μm) for 3 min. The mass fraction of calcined magnesia in the mixture is 67%, the mass fraction of white corundum is 33%, and the mass fraction of zirconia powder is 0%. Add a polyvinyl alcohol solution to the mixture, and the mass ratio of the mixture to the binder solution is 100:7. After grinding and mixing for 3 min, the mixture is uniaxially pressed to form a green body at a forming pressure of 350 MPa, and the pressure holding time is 3 min.

[0069] (4) The green body is naturally dried at 25 °C for 24 h, and then placed in an oven at 110 °C for 24 h. The dried green body is heat treated at 600 °C for 4 h, and then placed in a vacuum sintering furnace at a vacuum degree of 10 -4 pa, sintered at 1600 °C for 3 h, and naturally cooled to obtain a magnesia spinel material.

[0070] The density of the prepared magnesia spinel material is 3.26 g / cm 3 , the porosity is 6.61%, and the linear shrinkage is 8.43%.

[0071] Comparative Example 2

[0072] (1) Take 190 g of the natural day sun heap mineral of Qinghai Chai' erhan salt lake brine, and its elemental composition is 11.06 wt. % Mg, 34.67 wt. % Cl, 0.202 wt. % Na, 0.0917 wt. % K, 0.00768 wt. % S, 0.00026 wt. % Ca, and 0.00032 wt. % B. Dissolve it with water, filter twice to remove insoluble impurities, and evaporate the filtrate at 110°C to recrystallize. Evaporate the filtrate to 80% of the original solution mass, and filter after natural cooling to obtain high-purity magnesium chloride hexahydrate solid. Recrystallize twice to obtain a pure magnesium chloride solution.

[0073] (2) Prepare a 3 mol / L magnesium chloride solution, and simultaneously add it to a 3 mol / L sodium chloride solution with a 6 mol / L sodium hydroxide solution. The feeding rate is 1.125 ml / min, the stirring rate is 430 r / min, the precipitation reaction temperature is 80°C, the reaction time is 120 min, the suspension is naturally cooled and filtered to obtain a magnesium hydroxide precipitate, which is washed with deionized water three times. The mass ratio of deionized water to precipitate in a single washing is 5:1. A pure magnesium hydroxide precipitate is obtained through washing, with a purity of 99.2% and an average particle size of 7.58 μm. The precipitate is lightly calcined at 500°C for 2 h to obtain light calcined magnesia.

[0074] (3) Grind and mix the light calcined magnesia and white corundum (average particle size 3 μm) for 3 min. The mass fraction of light calcined magnesia in the mixture is 67%, the mass fraction of white corundum is 33%, and the mass fraction of zirconia powder is 0%. Add polyvinyl alcohol solution to the mixture, and the mass ratio of the mixture to the binder solution is 100:7. After grinding and mixing for 3 min, the mixture is uniaxially pressed to form a green body under a forming pressure of 350 MPa.

[0075] (4) The green body is naturally dried at 25°C for 24 h, and then placed in an oven at 110°C for drying for 24 h. After drying, the green body is heat treated at 600°C for 4 h, and then placed in a vacuum sintering furnace with a vacuum degree of 10 -4 pa, sintered at 1600°C for 3 h, and naturally cooled to obtain a magnesia spinel material.

[0076] The density of the prepared magnesia spinel material is 3.44 g / cm 3 , the porosity is 4.5%, and the linear shrinkage is 12.8%.

[0077] In Comparative Example 1-2, no zirconia raw material was added, and under the condition that the particle size difference of white corundum raw material was relatively small, the volume density difference of the prepared magnesia spinel material was relatively large, which was mainly due to the fact that in Comparative Example 2, the particle size of white corundum was small, and after being mixed with light-burned magnesia, it was more easily dispersed uniformly and formed a wrapped structure (MgO@MgAl2O4) of spinel wrapping periclase, while in Comparative Example 1, the particle size of white corundum was unable to form a wrapped structure after being mixed with light-burned magnesia, thereby affecting the densification degree of the material. No zirconia raw material was added in the two sets of comparative examples to eliminate the influence of the zirconia raw material on the comparison results.

[0078] The present application has been described in detail to enable those skilled in the art to understand and implement it, and is not intended to limit the scope of protection of the present application, and any equivalent changes or modifications made in accordance with the spirit of the present application should be covered within the scope of protection of the present application.

Claims

1. A method for preparing magnesia spinel zirconia material from salt lake water using bischofite, characterized in that, The method comprises the following steps: (1) dissolving, filtering the bischofite, dissolving the filtrate after recrystallization to obtain a pure magnesium chloride solution; (2) adding the magnesium chloride solution and sodium hydroxide solution into the sodium chloride solution to carry out a precipitation reaction, filtering and washing to obtain a high-purity magnesium hydroxide precipitate, and preparing light-burned magnesia by medium-temperature calcination; (3) mixing the light-burned magnesia, aluminum raw material, zirconium raw material and binder solution and pressing to prepare a green body; (4) drying and medium-temperature heat treating the green body, and then vacuum sintering to prepare the magnesia spinel zirconium material; In step (2), the average particle size of the magnesium hydroxide precipitate is 5-15 μm, and the medium-temperature calcination temperature is 400-600 ℃, and the calcination time is 1-3 h; In step (3), the average particle size of the aluminum raw material is 20%-70% of the average particle size of the magnesium hydroxide, and the average particle size of the zirconium raw material is 20%-50% of the average particle size of the magnesium hydroxide; the average particle size of the aluminum raw material is 2-10 μm, and the average particle size of the zirconium raw material is 1-5 μm; In step (3), in the mixture of the light-burned magnesia, aluminum raw material and zirconium raw material, the mass fraction of the light-burned magnesia is 60%-90%, the mass fraction of the aluminum raw material is 5%-30%, and the mass fraction of the zirconium raw material is 2%-15%; the mass ratio of the mixture to the binder solution is 100:1-10:1; the aluminum raw material is one or more of white corundum, industrial alumina, bauxite, one water soft alumina, hard water alumina, pseudo-thin alumina; the zirconium raw material is one or more of monoclinic zirconium and desilicon zirconium; the binder is one or more of polyvinyl alcohol, polyethylene glycol, starch and carboxymethyl cellulose; the forming pressure of the green body is 200-400 MPa, and the pressure holding time is 3-5 min; In step (4), the green body is dried at 20-40 ℃ for 10-30 h, and then dried at 80-120 ℃ for 15-30 h; the temperature of the medium-temperature heat treatment is 300-600 ℃, and the heat treatment time is 2-5 h; the vacuum sintering is performed under a vacuum degree ≤10 -3 Pa condition, the temperature of the vacuum sintering is 1400-2000 ℃, and the sintering time is 2-5 h.

2. The method of making magnesia-spinel zirconia material according to claim 1, wherein, In step (1), the bischofite solution is filtered for 1-3 times to remove insoluble impurities; the recrystallization temperature of the filtrate is 25-110 ℃, the evaporation mass of the filtrate is 10%-30% of the mass of the filtrate before evaporation, and the recrystallization is carried out for 1-3 times.

3. The method of making magnesia-spinel zirconia material of claim 1, wherein, In step (2), the concentration of the magnesium chloride solution is 1-3 mol / L, the molar ratio of magnesium chloride to sodium hydroxide is 1:1-1:3, and the molar ratio of magnesium chloride to sodium chloride is 1:0.5-1:2; the feeding rate of the magnesium chloride solution and the sodium hydroxide solution is 0.5-2.0 mL / min, the stirring rate in the precipitation reaction process is controlled to be 300-600 r / min, the precipitation reaction temperature is 60-100 ℃, and the precipitation reaction time is 0.5-3 h.

4. The method of making magnesia-spinel zirconia material of claim 1, wherein, In step (2), the washing is carried out for 3-5 times, and the single-time water consumption for washing the precipitate is 3-6 times the mass of the precipitate.

5. A magnesia-spinel zirconia material characterized by, The method is prepared by the method for preparing the magnesia spinel zirconium material in any one of claims 1-4.

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