Preparation method of ultralow-potassium ammonium molybdate and ultralow-potassium derivative thereof

Abstract

The invention relates to the technical field of hydrometallurgy, and particularly discloses preparation methods of ultralow-potassium ammonium molybdate and ultralow-potassium derivatives thereof. The preparation method of the ultralow-potassium ammonium molybdate comprises the following steps that S1, roasted molybdenum concentrate is subjected to primary screening, smashing and re-screening, and a raw material is obtained; s2, adding the raw materials and pure water into a reaction kettle, uniformly mixing, adding an acid solution, adjusting the pH value, introducing compressed air, heating, adjusting the pressure in the kettle, cooling and depressurizing, washing, and carrying out solid-liquid separation to obtain hydrated molybdenum trioxide; s3, mixing molybdenum trioxide hydrate with an ammonia water solution, adding ammonium sulfide, mixing for 1-2 hours, carrying out solid-liquid separation, then adding an adsorbent, mixing for 1-2 hours, cooling, aging for 24-48 hours, and carrying out solid-liquid separation to obtain an ammonium molybdate solution; and S4, concentrating the ammonium molybdate solution according to the specific gravity, and then carrying out cooling crystallization, solid-liquid separation, washing and drying to obtain the ultralow-potassium ammonium molybdate. The ammonium molybdate and the derivatives thereof prepared by the invention have relatively low content of potassium.

Description

Technical Field

[0001] The present application relates to the technical field of hydrometallurgy, and more specifically, to a method for preparing ultra-low potassium ammonium molybdate and its ultra-low potassium derivatives. Background Art

[0002] Metallic molybdenum has excellent physical and chemical properties such as high melting point, high wear resistance, good thermal conductivity, electrical conductivity and low expansion coefficient, and is used in metallurgy, electronics, electric light sources, metal precision processing, chemical medicine and other industrial production. In recent years, with the rapid development of high-tech, the performance requirements of many high-tech industries for molybdenum and its alloy materials have exceeded the traditional index range in many aspects. In particular, strict requirements are put forward for the potassium content in molybdenum powder and its derivatives. This is mainly because in the fields of ultra-large integrated circuits, liquid crystal display targets, etc., "potassium" is easily broken down and becomes a bad point under high temperature and high pressure conditions, affecting the use effect; in addition, during high-temperature sintering or as an electric light source material, potassium will evaporate in the gaseous state, and after absorbing moisture, it will corrode heating elements, refractory materials, and thermal insulation materials in the form of strong alkali, polluting the surface of the product. Therefore, how to prepare low-potassium molybdenum powder and its derivatives is particularly important.

[0003] As an important precursor for the preparation of molybdenum powder and other derivatives, the quality index and physical and chemical properties of ammonium molybdate have an important impact on the quality and performance of the final product. Potassium is one of the impurity elements with a relatively high content in ammonium molybdate products, which seriously affects the quality of subsequent products. The existing molybdenum powder preparation process uses ammonium molybdate as the raw material, undergoes a low-temperature hydrogen reduction to generate molybdenum dioxide, undergoes a secondary high-temperature hydrogen reduction after screening, and then undergoes screening and mixing to batch out the finished molybdenum powder, which has a relatively high potassium residue ratio.

[0004] The patent application document with publication number CN101020239A discloses a process for preparing low-potassium molybdenum powder, which comprises the following steps: (1) reducing ammonium molybdate with hydrogen to generate molybdenum dioxide; (2) screening the reduced molybdenum dioxide; (3) washing the screened molybdenum dioxide with water or acid; (3) performing solid-liquid separation and drying of the molybdenum dioxide after water washing or acid washing; (4) performing secondary hydrogen reduction of the molybdenum dioxide after solid-liquid separation and drying to generate molybdenum powder; (5) screening the molybdenum powder to obtain finished molybdenum powder.

[0005] This patent application document only uses physical screening and acid washing or water washing, and the removal rate is low. Summary of the invention

[0006] In order to improve the removal rate of potassium in ammonium molybdate and its derivatives, the present application provides a preparation method of ultra-low potassium ammonium molybdate and its ultra-low potassium derivatives.

[0007] In the first aspect, the present application provides a method for preparing ultra-low potassium ammonium molybdate, using the following technical solution: A method for preparing ultra-low potassium ammonium molybdate comprises the following steps: S1: Preliminarily screening, crushing, and then screening the roasted molybdenum concentrate to obtain a raw material; S2: Add the raw materials and water into the reactor, mix them evenly, add the acid solution, adjust the pH to 0.5-0.8, introduce compressed air, heat to 150-170°C, adjust the pressure in the reactor to 0.6-0.8MPa, react for 3-5h, reduce the temperature and pressure, wash, separate the solid and liquid, and obtain hydrated molybdenum trioxide; S3: After mixing hydrated molybdenum trioxide and ammonia solution at 50-70°C for 3-5 hours, add ammonium sulfide, mix for 1-2 hours, separate the solid and liquid, then add adsorbent, mix for 1-2 hours, cool, and age for 24-48 hours. After solid-liquid separation, obtain ammonium molybdate solution; S4: Concentrate the specific gravity of the ammonium molybdate solution to 1.30~1.35g / cm 3 , adjust the pH to 6.5-7, then cool and crystallize for 3-5 hours, separate the solid and liquid, wash and dry to obtain ultra-low potassium ammonium molybdate; The adsorbent is any one of modified molecular sieves and modified polyurethane microspheres. The modified molecular sieve is a crown ether compound A modified molecular sieve, and the modified polyurethane microspheres are crown ether compound B modified polyurethane microspheres.

[0008] Preferably, in step S2, after solid-liquid separation, hot pure water with a temperature of 70-80° C. is used for washing.

[0009] Preferably, the acid solution is a nitric acid solution, and the mass fraction of nitric acid in the nitric acid solution is 27% to 30%; the mass fraction of ammonia water in the ammonia solution is 20% to 25%.

[0010] Preferably, the mass ratio of the raw material, water, aqueous ammonia, ammonium sulfide and adsorbent is 1:5~6:0.48~0.51:0.001~0.002:0.015~0.025.

[0011] By adopting the above technical scheme, first, the roasted molybdenum concentrate is crushed and sieved, so that the particle size distribution of the raw material is uniform and the surface area is significantly increased. In the subsequent process, the sufficiency and uniformity of the reaction between the raw material and nitric acid are improved, and the reaction rate is increased. It is also promoted that potassium ions and certain metal compounds are more easily dissolved from the main body of the raw material, providing a better basis for the subsequent potassium ion removal step, and indirectly improving the potassium ion removal efficiency in the entire process.

[0012] Secondly, under high temperature and high pressure, the strong acid medium is introduced with compressed air, and the process of converting it into hydrated molybdenum trioxide is helpful for the deep separation of molybdenum and potassium. This is mainly due to the following reasons: on the one hand, high temperature and high pressure help to intensify the thermal motion of potassium ions, enhance their activity, and make it easier to break away from the lattice structure of molybdenum trioxide. At the same time, the crystal structure of molybdenum trioxide may be distorted or deformed to a certain extent, which changes the lattice environment of potassium ions and weakens the chemical bond between potassium ions and molybdenum trioxide to a certain extent, further promoting the separation of potassium ions. On the other hand, the airflow impact generated by compressed air can break the adsorption equilibrium between potassium ions and molybdenum trioxide to a certain extent, which is conducive to the desorption of potassium ions from the surface of molybdenum trioxide particles and entering the liquid phase or gas phase, thereby achieving the separation of the two.

[0013] Finally, after mixing ammonia water with hydrated molybdenum trioxide, molybdenum is transferred from the solid phase to the liquid phase, and then ammonium sulfide is added to remove lead, copper and other ions in the solution, and then an adsorbent is added to selectively adsorb potassium ions and other impurities in the complex solution, thereby reducing the potassium ion concentration and impurity concentration in the molybdate solution. After that, the ammonium molybdate solution is further concentrated, the pH of the ammonium molybdate solution is adjusted, and solid-liquid separation and washing are performed after cooling and crystallization, which can further remove potassium ions and further reduce the potassium content in the ammonium molybdate.

[0014] Preferably, in step S4, the ammonium molybdate solution is concentrated using a reverse osmosis membrane at 25-35° C. and a pressure of 6-8 MPa until the desired concentration is reached, the concentrated solution is collected, the pH is adjusted to 6.5-7, and then transferred to a crystallizer, slowly cooled to 10-12° C., kept warm for 3-5 hours, solid-liquid separation, and washing to obtain ultra-low potassium ammonium molybdate.

[0015] Preferably, after entering the crystallizer, stirring is started at a speed of 90-110 r / min until the insulation is completed, and then stirring is stopped.

[0016] Preferably, the reverse osmosis membrane is a polyamide composite membrane.

[0017] Preferably, the method for preparing the crown ether compound A modified molecular sieve, wherein the crown ether compound A is 18-crown ether-6, comprises the following steps: (1) Sintering the molecular sieve at 300-500°C for 2-4 hours, cooling, and sieving to obtain a pretreated molecular sieve; (2) uniformly mixing the pretreated molecular sieve with a γ-aminopropyltriethoxysilane solution having a mass fraction of 0.5% to 1%, performing solid-liquid separation, washing, and drying to obtain a pre-modified molecular sieve; (3) mixing the pre-modified molecular sieve with the 18-crown ether-6 aqueous solution for 2 to 4 hours, separating the solid and the liquid, washing, and drying to obtain the modified molecular sieve; The mass fraction of the 18-crown ether-6 aqueous solution is 5% to 10%, and the mass ratio of the molecular sieve to 18-crown ether-6 is 1:0.1 to 0.2.

[0018] By adopting the above technical scheme, when 18-crown ether-6 is combined with the pre-modified molecular sieve, on the one hand, the modified molecular sieve is endowed with a highly selective complexing ability for potassium ions, thereby improving the efficiency of potassium ion separation and purification. On the other hand, the modified molecular sieve is endowed with a weak interaction with ammonium ions, which can significantly reduce the competitive ability of ammonium ions in the potassium ion adsorption process. At the same time, 18-crown ether-6 can be firmly attached to the molecular sieve, and has little effect on the subsequent purity of ammonium molybdate.

[0019] In addition, in the ammonium molybdate solution, potassium ions are first complexed by 18-crown-6 and then adsorbed and fixed by the molecular sieve. This dual effect can effectively reduce the potassium ion content in the ammonium molybdate solution and improve the purity of ammonium molybdate. At the same time, this combination can also reduce the loss of 18-crown-6, allowing it to maintain its ability to remove potassium ions for a longer period of time.

[0020] Preferably, the method for preparing the crown ether compound B modified polyurethane microspheres, wherein the crown ether compound B is dibenzo-18-crown-6, comprises the following steps: S11: dibenzo-18-crown-6 and formic acid are mixed evenly to obtain dispersion A; then, at 30-40°C, polyformaldehyde and formic acid are mixed evenly to obtain dispersion B; at 30-40°C, solution B is added to solution A, mixed evenly until precipitation occurs, and the mixture is mixed for 10-12 hours, cooled, allowed to stand for 1-2 hours, separated from the solid and the liquid, washed until neutral, and dried to obtain dibenzo-18-crown-6 formaldehyde polymer; S12: polyethylene glycol and dibenzo-18-crown-6-formaldehyde polymer are mixed evenly to obtain a mixed solution A, toluene diisocyanate, Tween 80, dibutyltin dilaurate and water are mixed evenly to obtain a mixed solution B, and then the mixed solution B is added to the mixed solution A, mixed evenly, heated to 20-40°C for reaction for 4-6 hours, and then 1,4-butanediol is added, and the mixture is kept warm for 20-40 minutes, and then the mixture is heated to 60-80°C, and the mixture is kept warm for 1.5-2.5 hours, and then a foaming agent is added, and the mixture is mixed evenly. After keeping warm for 2-4 hours, the reaction solution is added to an ethanol aqueous solution, cooled, sodium dodecyl sulfate is added, and the mixture is mixed evenly, and triethylamine is added to adjust the pH to neutral, and the mixture is separated into solid and liquid, washed, and dried to obtain modified polyurethane microspheres; The foaming agent is n-pentane; The mass ratio of the dibenzo-18-crown-6 to polyformaldehyde is 8-10:1.5-2.5; the mass ratio of the polyethylene glycol, toluene diisocyanate, dibenzo-18-crown-6 formaldehyde polymer, 1,4-butanediol and sodium dodecyl sulfate is 1:0.5-0.7:0.2-0.4:0.1-0.2:0.05-0.07.

[0021] Preferably, the Tween 80 accounts for 1% to 2% of the total mass of the polyethylene glycol, toluene diisocyanate and dibenzo-18-crown-6-formaldehyde polymer.

[0022] Preferably, the dibutyltin dilaurate accounts for 3% to 5% of the total mass of the polyethylene glycol, toluene diisocyanate and dibenzo-18-crown-6-formaldehyde polymer.

[0023] Preferably, the pure water accounts for 0.1% to 0.5% of the total mass of the polyethylene glycol, toluene diisocyanate and dibenzo-18-crown-6-formaldehyde polymer.

[0024] Preferably, the foaming agent accounts for 5% to 10% of the total mass of polyethylene glycol, toluene diisocyanate and dibenzo-18-crown-6-formaldehyde polymer.

[0025] Preferably, the mass volume ratio of the dibenzo-18-crown ether-6 to formic acid is 1 g:10-15 ml.

[0026] Preferably, the mass volume ratio of the paraformaldehyde to formic acid is 1 g:40-50 ml.

[0027] Preferably, the mass fraction of the ethanol aqueous solution is 70% to 80%.

[0028] By adopting the above technical scheme and the above synthesis steps, a strong interaction is formed between dibenzo-18-crown-6 and polyurethane microspheres, thereby ensuring the stability of dibenzo-18-crown-6 on the microspheres. In the ammonium molybdate solution, the polyurethane microspheres can fix the dibenzo-18-crown-6 complexed with potassium ions on the surface or inside thereof, preventing the complex with potassium ions from being free in the solution, and facilitating subsequent separation and removal.

[0029] Dibenzo-18-crown-6 selectively complexes potassium ions, while polyurethane microspheres provide carrier and fixation functions. The two cooperate with each other, allowing the modified polyurethane microspheres to effectively remove potassium ions from ammonium molybdate solution. This synergistic effect not only improves the efficiency of potassium ion removal, but also reduces the cost and difficulty of potassium ion removal.

[0030] In a second aspect, the present application also provides a method for preparing an ultra-low potassium derivative, using the ultra-low potassium ammonium molybdate as the initial raw material to prepare molybdenum powder or molybdenum trioxide.

[0031] Preferably, the molybdenum trioxide is prepared by the following steps: crushing and sieving the ultra-low potassium ammonium molybdate, heating to 400-500° C. in an inert atmosphere, sintering for 90-150 min, cooling, sieving, and mixing uniformly to obtain molybdenum trioxide.

[0032] Preferably, the heating rate is 2-4°C / min, and the cooling rate is 3-5°C / min.

[0033] Preferably, the inert atmosphere is nitrogen, and the flow rate of the nitrogen is 2-3 L / min.

[0034] Preferably, the molybdenum trioxide is prepared by the following steps: after the ultra-low potassium ammonium molybdate is crushed and sieved, the temperature is raised to 450-500°C under an inert atmosphere, sintered for 90-110 min, the temperature is kept constant, and then a mixed gas of hydrogen chloride gas and part of nitrogen is introduced at 2.5-3 L / min, and then nitrogen is continuously introduced at 2.5-3 L / min for 10-15 min, the temperature is lowered, washed, dried, and sieved to obtain molybdenum trioxide; the mass of the hydrogen chloride gas accounts for 0.8%-1% of the total mass of the ultra-low potassium ammonium molybdate.

[0035] Preferably, the weighing standard of the hydrogen chloride gas is: standard atmospheric pressure and room temperature (20±1° C.).

[0036] By adopting the above technical solution, after hydrogen chloride gas enters the system, it can react chemically with potassium ions in ultra-low potassium ammonium molybdate by virtue of its acidity and chemical activity to generate potassium chloride, and potassium chloride is more likely to exist in gaseous form under high temperature and inert atmosphere. Under the continuous purge of nitrogen, gaseous potassium chloride will be taken out of the reaction system with the airflow, thereby effectively reducing the concentration of potassium ions in the final product, molybdenum trioxide. At the same time, the introduction of hydrogen chloride gas may also have a certain effect on the surface properties of molybdenum trioxide, change its surface adsorption characteristics, reduce the possibility of potassium ions adsorbing on the surface of molybdenum trioxide, and further help potassium ions be removed from the entire system.

[0037] Preferably, the molybdenum powder is prepared by the following steps: In a hydrogen atmosphere, the temperature is raised to 450-650°C in the first stage, and the molybdenum trioxide is sintered for 2-4 hours. In the second stage, the temperature is raised to 900-1100°C, and sintered for 3-5 hours. The temperature is then lowered, sieved, and mixed evenly to obtain molybdenum powder.

[0038] Preferably, the heating rate is 2-4°C / min, the hydrogen flow rate in the first stage is 0.4-0.6 L / min, the hydrogen flow rate in the second stage is 0.7-1 L / min, and the cooling rate is 3-5°C.

[0039] Preferably, the dew point of the hydrogen is -40 to -50°C.

[0040] In summary, this application has the following beneficial effects: 1. The present invention promotes the effective separation of potassium ions and hydrated molybdenum trioxide in a high temperature and high pressure strong acid medium and introduces compressed air. After ammonia leaching, ammonium sulfide is added to remove impurity ions such as lead and copper, and then an adsorbent is added to effectively reduce the potassium content in ammonium molybdate.

[0041] 2. The adsorbent prepared in this application exhibits a highly selective complexing ability for potassium ions, and the separation process is simple and fast, and almost no new impurities are introduced. This feature not only reduces the cost of removing potassium ions, but also simplifies the operation process. In addition, the adsorbent also has good reusability, which further enhances its economic value.

[0042] 3. When preparing molybdenum trioxide, the present application mixes a small amount of hydrogen chloride gas into part of the inert gas, which can not only further reduce the potassium content in the molybdenum trioxide and improve the purity of the molybdenum trioxide, but also hardly cause any damage to the performance of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 : The morphology of roasted molybdenum concentrate in Example 1 of the present application; Figure 2 : Morphology diagram of hydrated molybdenum trioxide in Example 1 of the present application. DETAILED DESCRIPTION

[0044] The present application is further described in detail below with reference to the embodiments.

[0045] Unless otherwise specified, the raw materials used in the preparation examples, embodiments and comparative examples of the present application are all commercially available.

[0046] In the embodiment, the main component of the roasted molybdenum concentrate is molybdenum trioxide; MCM-41 molecular sieve (abbreviated as molecular sieve), all silicon, spherical, 1-2 mm in diameter, pore diameter maintained between 3-5 nm, purchased from Zhuoran Environmental Protection Technology Co., Ltd.; Paraformaldehyde, 99.6%, was purchased from Shandong Wenhui Chemical Co., Ltd.; 18-Crown ether-6, 99%, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Dibenzo-18-crown-6, 97%, purchased from Shanghai Darui Fine Chemicals Co., Ltd.; The weighing standard of hydrogen chloride gas is: under standard atmospheric pressure, room temperature (20±1℃), the density is about 1.48g / L.

[0047] The purity of hydrogen is not less than 99.5%; formic acid is analytical grade.

[0048] The roasted molybdenum concentrate was tested and analyzed according to the testing standard GB / T24482-2009. The test results are shown in Table 1.

[0049] Table 1 Analysis and testing indicators of roasted molybdenum concentrate

[0050] Preparation Examples 1~3 Modified Molecular Sieve Preparation Example 1 (1) Place 100 g of molecular sieve in a muffle furnace and sinter at 300 ° C for 4 h. After cooling in the furnace, grind and disperse it slightly, first pass it through a 10-mesh Taylor standard sieve to take the sieve underflow, and then pass it through a 18-mesh Taylor standard sieve to take the sieve overflow to obtain a pretreated molecular sieve; (2) The pretreated molecular sieve was mixed with 500 ml of 0.5% by mass γ-aminopropyltriethoxysilane solution under stirring for 60 min, filtered, washed twice with pure water, each time with 500 ml of pure water, filtered, transferred to a vacuum drying oven, and dried at 80 ° C for 3 h to obtain a pre-modified molecular sieve; (3) Add 10 g of 18-crown ether-6 into 190 g of pure water, stir until completely dissolved, and continue stirring for 10 min to obtain a 5% mass fraction of 18-crown ether-6 aqueous solution; (4) The pre-modified molecular sieve and the 18-crown ether-6 aqueous solution were stirred for 2 h, filtered and separated, and washed twice with anhydrous ethanol, each time using 300 ml of anhydrous ethanol. After filtering, the filter residue was dried at 80° C. to constant weight to obtain a modified molecular sieve.

[0051] Preparation Example 2 (1) Place 100 g of molecular sieve in a muffle furnace and sinter at 500 °C for 2 h. After cooling in the furnace, grind and disperse it slightly, first pass it through a 10-mesh Taylor standard sieve to take the sieve underflow, and then pass it through a 18-mesh Taylor standard sieve to take the sieve overflow to obtain a pretreated molecular sieve; (2) The pretreated molecular sieve was mixed with 500 ml of 1% by mass γ-aminopropyltriethoxysilane solution under stirring for 60 min, filtered, washed twice with pure water, each time with 500 ml of pure water, filtered, transferred to a vacuum drying oven, and dried at 80 ° C for 3 h to obtain a pre-modified molecular sieve; (3) Add 20 g of 18-crown ether-6 into 180 g of pure water, stir until completely dissolved, and continue stirring for 10 min to obtain a 10% mass fraction of 18-crown ether-6 aqueous solution; (4) The pre-modified molecular sieve and the 18-crown ether-6 aqueous solution were stirred for 3 h, filtered and separated, and washed twice with anhydrous ethanol, each time using 300 ml of anhydrous ethanol. After filtering, the filter residue was dried at 80° C. to constant weight to obtain a modified molecular sieve.

[0052] Preparation Example 3 (1) Place 100 g of molecular sieve in a muffle furnace and sinter at 450 ° C for 3 h. After cooling in the furnace, grind and disperse it slightly, first pass it through a 10-mesh Taylor standard sieve to take the sieve underflow, and then pass it through a 18-mesh Taylor standard sieve to take the sieve overflow to obtain a pretreated molecular sieve; (2) The pretreated molecular sieve was mixed with 500 ml of 0.5% by mass γ-aminopropyltriethoxysilane solution under stirring for 60 min, filtered, washed twice with pure water, each time with 500 ml of pure water, filtered, transferred to a vacuum drying oven, and dried at 80 ° C for 3 h to obtain a pre-modified molecular sieve; (3) Add 16 g of 18-crown ether-6 into 184 g of pure water, stir until completely dissolved, and continue stirring for 10 min to obtain an 8% mass fraction of 18-crown ether-6 aqueous solution; (4) The pre-modified molecular sieve and the 18-crown ether-6 aqueous solution were stirred for 4 hours, filtered and separated, and washed twice with anhydrous ethanol, each time using 300 ml of anhydrous ethanol. After filtering, the filter residue was dried at 80° C. to constant weight to obtain a modified molecular sieve.

[0053] Preparation Examples 4-6 Modified Polyurethane Microspheres Preparation Example 4 S11: 8g of dibenzo-18-crown-6 was mixed with 80ml of formic acid to obtain dispersion A; 1.5g of polyformaldehyde was mixed with 60ml of formic acid to obtain dispersion B (after mixing, the temperature can be appropriately increased until it is completely dissolved, and the temperature is generally not higher than 40°C); at 30°C, dispersion B was slowly added dropwise to dispersion A, and stirred and mixed until precipitation was produced, and the mixing was continued for 12h, and the temperature was lowered, and the solid was filtered, washed with pure water until neutral, and dried at 40°C to constant weight to obtain dibenzo-18-crown-6 formaldehyde polymer; S12: Add 2g of dibenzo-18-crown-6 formaldehyde polymer to 10g of polyethylene glycol and mix well to obtain a mixed solution A. Mix 5g of toluene diisocyanate, 0.17g of Tween 80, 0.51g of dibutyltin dilaurate and 0.02g of pure water to obtain a mixed solution B. Then slowly drop the mixed solution B into the mixed solution A, stir and mix well, heat to 20°C and react for 6h, then add 1g of 1,4-butanediol, keep warm for 40min, heat to 60°C, keep warm for 2.5h, add 0.85g of n-pentane and mix well. After keeping warm for 4h, stir continuously during the period at a stirring rate of 600r / min. Add the reaction solution into an ethanol aqueous solution, cool, add 0.5g of sodium dodecyl sulfate, mix well, add triethylamine to adjust the pH to neutral, filter, wash twice with pure water, and dry at 50°C for 2h to obtain modified polyurethane microspheres.

[0054] The mass fraction of the ethanol aqueous solution is 70%, and the volume ratio of the reaction liquid to the ethanol aqueous solution is 1:5.

[0055] Preparation Example 5 S11: 10g of dibenzo-18-crown-6 was mixed with 150ml of formic acid to obtain dispersion A; 2.5g of paraformaldehyde was mixed with 125ml of formic acid to obtain dispersion B (after mixing, the temperature can be appropriately increased until it is completely dissolved, and the temperature is generally not higher than 40°C); at 40°C, dispersion B was slowly added dropwise to dispersion A, and stirred and mixed until precipitation was produced, and the mixing was continued for 10h, and the temperature was lowered, and the solid was filtered, washed with pure water until neutral, and dried at 40°C to constant weight to obtain dibenzo-18-crown-6 formaldehyde polymer; S12: Add 4g of dibenzo-18-crown-6-formaldehyde polymer to 10g of polyethylene glycol and mix well to obtain a mixed solution A. Mix 7g of toluene diisocyanate, 0.42g of Tween 80, 1.05g of dibutyltin dilaurate and 0.11g of pure water to obtain a mixed solution B. Then slowly drop the mixed solution B into the mixed solution A, stir and mix well, heat to 40°C and react for 4h, then add 2g of 1,4-butanediol, keep warm for 20min, heat to 80°C, keep warm for 1.5h, add 2.1g of n-pentane, mix well, keep warm for 2h, stir continuously during the period, and the stirring rate is 600r / min. The reaction solution was added to an ethanol aqueous solution, cooled, 0.7 g of sodium dodecyl sulfate was added, mixed evenly, triethylamine was added to adjust the pH to neutral, filtered, washed twice with pure water, and dried at 50° C. for 2 h to obtain modified polyurethane microspheres.

[0056] The mass fraction of the ethanol aqueous solution is 80%, and the volume ratio of the reaction liquid to the ethanol aqueous solution is 1:5.

[0057] Preparation Example 6 S11: 9 g of dibenzo-18-crown-6 was mixed with 120 ml of formic acid to obtain dispersion A; 2 g of paraformaldehyde was mixed with 90 ml of formic acid to obtain dispersion B (after mixing, the temperature can be appropriately increased until it is completely dissolved, and the temperature is generally not higher than 40°C); at 40°C, dispersion B was slowly added dropwise to dispersion A, and stirred and mixed until precipitation was produced, and the mixing was continued for 12 hours, and the temperature was lowered, and the solid was filtered, washed with pure water until neutral, and dried at 40°C to constant weight to obtain dibenzo-18-crown-6 formaldehyde polymer; S12: Add 3g of dibenzo-18-crown-6-formaldehyde polymer to 10g of polyethylene glycol and mix well to obtain a mixed solution A. Mix 6g of toluene diisocyanate, 0.38g of Tween 80, 0.76g of dibutyltin dilaurate and 0.07g of pure water to obtain a mixed solution B. Then slowly drop the mixed solution B into the mixed solution A, stir and mix well, heat to 35°C and react for 5h, then add 1.5g of 1,4-butanediol, keep warm for 30min, heat to 75°C, keep warm for 2h, add 1.5g of n-pentane, mix well, keep warm for 3h, stir continuously during the period, and the stirring rate is 600r / min. The reaction solution was added to an ethanol aqueous solution, cooled, 0.6 g of sodium dodecyl sulfate was added, mixed evenly, triethylamine was added to adjust the pH to neutral, filtered, washed twice with pure water, and dried at 50° C. for 2 h to obtain modified polyurethane microspheres.

[0058] The mass fraction of the ethanol aqueous solution is 75%, and the volume ratio of the reaction liquid to the ethanol aqueous solution is 1:5.

[0059] Example 1 This embodiment provides a method for preparing ultra-low potassium ammonium molybdate, comprising the following steps: S1: After the roasted molybdenum concentrate is preliminarily screened mechanically, it is transferred into a ball mill for crushing until it completely passes through a 40-mesh Taylor standard sieve (d≤0.38mm) to obtain a raw material; S2: 1 kg of raw material and 5 kg of pure water were added into the reactor, and the double-layer turbine stirring paddle was turned on at a stirring rate of 2000 r / min, so that the solid-liquid slurry formed by the raw material and pure water formed a continuous cyclone loop, and the solid raw material basically did not sink to the bottom, and then a nitric acid solution with a mass fraction of 27% was added, and the pH distribution was adjusted to between 0.5 and 0.8, and compressed air was blown into the reactor, and the temperature was raised to 150°C, and the pressure in the reactor was adjusted to 0.6 MPa, and the reaction was carried out for 5 hours, and the temperature was lowered to 85°C, and filtered, and washed twice with pure water at a temperature of 70°C to obtain hydrated molybdenum oxide with uniform particle size distribution; S3: immerse the hydrated molybdenum oxide in 2.4 kg of 20% ammonia water, heat to 50°C, stir and mix thoroughly for 5 hours at a stirring rate of 800 r / min, cool to room temperature, add 1 g of ammonium sulfide, stir and mix for 1 hour, filter, then add 15 g of modified molecular sieve, stir and mix for 1 hour, age for 24 hours, filter, and obtain an ammonium molybdate solution; S4: At 25°C and a pressure of 6 MPa, the ammonium molybdate solution is concentrated using a reverse osmosis membrane until the density reaches 1.30 g / cm 3 , adjust the pH to 6.5 with 5% mass fraction of dilute nitric acid, then transfer it to the crystallizer, start stirring, the stirring speed is 110r / min, cool to 10℃, keep warm for 3h, transfer the crystal slurry to an automatic centrifuge for solid-liquid separation, wash the filter cake twice with pure water, send it to a tunnel microwave dryer at 60℃, dry, grind and disperse, pass through a 325-mesh Taylor standard sieve, and mix evenly to obtain ultra-low potassium ammonium molybdate.

[0060] Among them, the roasted molybdenum concentrate comes from batch 1; the modified molecular sieve comes from preparation example 1; and the reverse osmosis membrane is a polyamide composite membrane.

[0061] Depend on Figure 1 It can be seen that roasted molybdenum concentrate contains large particles of sintered melt and raw material. Before use, it needs to be mechanically screened, then ground and sieved to obtain raw materials with smaller particle size and uniform distribution.

[0062] Depend on Figure 2 It can be seen that hydrated molybdenum trioxide not only has uniform particle size distribution but also uniform color. When it subsequently reacts with ammonia water to generate ammonium molybdate, smaller and more uniform particles can dissolve faster and participate in the reaction, which not only reduces the reaction time and energy consumption, but also helps to effectively remove impurities. The crystal structure and chemical composition of ammonium molybdate are more consistent, so that the purity of the generated ammonium molybdate can be significantly improved.

[0063] This embodiment also provides a method for preparing molybdenum trioxide using the ultra-low potassium ammonium molybdate, comprising the following steps: 1 kg of ultra-low potassium ammonium molybdate was transferred into a ball mill, ground and crushed until it completely passed through a 500-mesh Taylor standard sieve, and then transferred into a sintering furnace. In a high-purity nitrogen atmosphere, the nitrogen flow rate was 2 L / min, and the temperature was increased to 400°C at 2°C / min. After sintering for 150 minutes, the temperature was lowered to room temperature at 3°C / min, ground, vibrated and screened, and stirred to mix evenly to obtain molybdenum trioxide.

[0064] The present embodiment also provides a method for preparing molybdenum powder using the above-mentioned molybdenum trioxide, comprising the following steps: transferring 0.5 kg of molybdenum trioxide into a tubular furnace, heating to 450° C. at 2° C. / min under a hydrogen atmosphere at a hydrogen flow rate of 0.4 L / min, sintering for 4 hours, adjusting the hydrogen flow rate to 0.7 L / min, then heating to 900° C. at 2° C. / min, sintering for 5 hours, cooling to room temperature at 3° C. / min, grinding, vibrating and screening, and stirring to mix evenly to obtain molybdenum powder.

[0065] Among them, the dew point of hydrogen is -40℃.

[0066] Example 2 This embodiment provides a method for preparing ultra-low potassium ammonium molybdate, comprising the following steps: S1: After the roasted molybdenum concentrate is preliminarily screened mechanically, it is transferred into a ball mill for crushing until it completely passes through a 40-mesh Taylor standard sieve (d≤0.38mm) to obtain a raw material; S2: 1 kg of raw material and 6 kg of pure water were added into the reactor, and the double-layer turbine stirring paddle was turned on at a stirring rate of 2000 r / min, so that the solid-liquid slurry formed by the raw material and pure water formed a continuous cyclone loop, and the solid raw material basically did not sink to the bottom, and then a 30% mass fraction of nitric acid solution was added, and the pH distribution was adjusted to between 0.5 and 0.8, and compressed air was blown into the reactor, and the temperature was raised to 170°C, and the pressure in the reactor was adjusted to 0.8 MPa, and the reaction was carried out for 3 hours, and the temperature was lowered to 85°C, and filtered, and washed twice with pure water at a temperature of 80°C to obtain hydrated molybdenum oxide with uniform particle size distribution; S3: immerse hydrated molybdenum oxide in 2.04 kg of 25% ammonia water, heat to 70°C, stir and mix thoroughly for 3 h at a stirring rate of 800 r / min, cool to room temperature, add 2 g of ammonium sulfide, stir and mix for 2 h, filter, then add 25 g of modified molecular sieve, stir and mix for 2 h, age for 48 h, filter, and obtain an ammonium molybdate solution; S4: At 35°C and 8 MPa, the ammonium molybdate solution was concentrated using a reverse osmosis membrane until the density reached 1.35 g / cm 3 , adjust the pH to 7 with 5% mass fraction of dilute nitric acid, then transfer it to the crystallizer, start stirring, the stirring speed is 90r / min, cool to 12°C, keep warm for 5h, transfer the crystal slurry to an automatic centrifuge for solid-liquid separation, wash the filter cake twice with pure water, send it to a tunnel microwave dryer at 60°C, dry, grind and disperse, pass through a 325-mesh Taylor standard sieve, and mix evenly to obtain ultra-low potassium ammonium molybdate.

[0067] Among them, the roasted molybdenum concentrate comes from Batch No. 2; the modified molecular sieve comes from Preparation Example 2; and the reverse osmosis membrane is a polyamide composite membrane.

[0068] This embodiment also provides a method for preparing molybdenum trioxide using the ultra-low potassium ammonium molybdate, comprising the following steps: 1 kg of ultra-low potassium ammonium molybdate was transferred into a ball mill, ground and crushed until it completely passed through a 500-mesh Taylor standard sieve, and then transferred into a sintering furnace. In a high-purity nitrogen atmosphere, the nitrogen flow rate was 3 L / min, and the temperature was raised to 500°C at 4°C / min. After sintering for 90 minutes, the temperature was lowered to room temperature at 5°C / min, ground, vibrated and sieved, and stirred to mix evenly to obtain molybdenum trioxide.

[0069] The present embodiment also provides a method for preparing molybdenum powder using the above-mentioned molybdenum trioxide, comprising the following steps: transferring 0.5 kg of molybdenum trioxide into a tubular furnace, heating to 650° C. at 4° C. / min under a hydrogen atmosphere at a hydrogen flow rate of 0.6 L / min, sintering for 2 h, adjusting the hydrogen flow rate to 1 L / min, then heating to 1100° C. at 4° C. / min, sintering for 3 h, cooling to room temperature at 5° C. / min, grinding, vibrating and screening, and stirring to mix evenly to obtain molybdenum powder.

[0070] Among them, the dew point of hydrogen is -50℃.

[0071] Example 3 This embodiment provides a method for preparing ultra-low potassium ammonium molybdate, comprising the following steps: S1: After the roasted molybdenum concentrate is preliminarily screened mechanically, it is transferred into a ball mill for crushing until it completely passes through a 40-mesh Taylor standard sieve (d≤0.38mm) to obtain a raw material; S2: 1 kg of raw material and 5.5 kg of pure water were added into the reactor, and the double-layer turbine stirring paddle was turned on at a stirring rate of 2000 r / min, so that the solid-liquid slurry formed by the raw material and pure water formed a continuous cyclone loop, and the solid raw material basically did not sink to the bottom, and then a nitric acid solution with a mass fraction of 28% was added, and the pH distribution was adjusted to between 0.5 and 0.8, and compressed air was blown into the reactor, and the temperature was raised to 160°C, and the pressure in the reactor was adjusted to 0.7 MPa, and the reaction was carried out for 4 hours, and the temperature was lowered to 85°C, and filtered, and washed twice with pure water at a temperature of 80°C to obtain hydrated molybdenum oxide with uniform particle size distribution; S3: immerse hydrated molybdenum oxide in 2 kg of 25% ammonia water, heat to 60°C, stir and mix thoroughly for 4 h at a stirring rate of 800 r / min, cool to room temperature, add 1.5 g of ammonium sulfide, stir and mix for 1.5 h, filter, then add 20 g of modified molecular sieve, stir and mix for 1.5 h, age for 36 h, filter, and obtain ammonium molybdate solution; S4: At 30°C and a pressure of 7 MPa, the ammonium molybdate solution was concentrated using a reverse osmosis membrane until the density reached 1.30 g / cm 3, adjust the pH to 7 with 5% mass fraction of dilute nitric acid, then transfer it to the crystallizer, start stirring, the stirring speed is 100r / min, cool to 12°C, keep warm for 4h, transfer the crystal slurry to an automatic centrifuge for solid-liquid separation, wash the filter cake twice with pure water, send it to a tunnel microwave dryer at 60°C, dry, grind and disperse, pass through a 325-mesh Taylor standard sieve, and mix evenly to obtain ultra-low potassium ammonium molybdate.

[0072] Among them, the roasted molybdenum concentrate comes from batch number 3; the modified molecular sieve comes from preparation example 3; and the reverse osmosis membrane is a polyamide composite membrane.

[0073] This embodiment also provides a method for preparing molybdenum trioxide using the ultra-low potassium ammonium molybdate, comprising the following steps: 1 kg of ultra-low potassium ammonium molybdate was transferred into a ball mill, ground and crushed until it completely passed through a 500-mesh Taylor standard sieve, and then transferred into a sintering furnace. In a high-purity nitrogen atmosphere, the nitrogen flow rate was 3 L / min, and the temperature was increased to 450°C at 3°C / min. After sintering for 120 minutes, the temperature was lowered to room temperature at 4°C / min, ground, vibrated and sieved, and stirred to mix evenly to obtain molybdenum trioxide.

[0074] The present embodiment also provides a method for preparing molybdenum powder using the above-mentioned molybdenum trioxide, comprising the following steps: transferring 0.5 kg of molybdenum trioxide into a tubular furnace, heating to 600° C. at 3° C. / min under a hydrogen atmosphere at a hydrogen flow rate of 0.5 L / min, sintering for 3 h, adjusting the hydrogen flow rate to 0.8 L / min, then heating to 1000° C. at 3° C. / min, sintering for 4 h, cooling to room temperature at 4° C. / min, grinding, vibrating and screening, stirring and mixing evenly to obtain molybdenum powder.

[0075] Among them, the dew point of hydrogen is -50℃.

[0076] Example 4 The difference between this embodiment and embodiment 3 is that the modified polyurethane microspheres in preparation example 4 are used to replace the modified molecular sieve.

[0077] The rest is the same as in Example 3.

[0078] Example 5 The difference between this embodiment and embodiment 4 is that the modified polyurethane microspheres come from preparation example 4.

[0079] The rest is the same as Example 4.

[0080] Example 6 The difference between this embodiment and embodiment 5 is that the modified polyurethane microspheres come from preparation example 5.

[0081] The rest is the same as Example 5.

[0082] Example 7 The difference between this embodiment and embodiment 6 is that: This embodiment also provides a method for preparing molybdenum trioxide using the ultra-low potassium ammonium molybdate, comprising the following steps: 1 kg of ultra-low potassium ammonium molybdate was transferred into a ball mill, ground and crushed until it completely passed through a 500-mesh Taylor standard sieve, and then transferred into a sintering furnace. In a high-purity nitrogen atmosphere, the nitrogen flow rate was 2 L / min, the temperature was raised to 500°C at 3°C / min, sintered for 90 min, and the temperature was kept constant. Then, a mixed gas of nitrogen and hydrogen chloride was introduced at 2.5 L / min, and then nitrogen was continued to be introduced at 2.5 L / min for 15 min, and then the temperature was lowered to 40°C at 4°C / min, washed twice with 40°C pure water, and then dried at 110°C in a high-purity nitrogen atmosphere for 8 h, ground, vibrated and sieved, and stirred to mix evenly to obtain molybdenum trioxide.

[0083] Among them, the total amount of the mixed gas is 90L, and the content of hydrogen chloride gas is 5.3L.

[0084] The rest is the same as Example 6.

[0085] Example 8 The difference between this embodiment and embodiment 7 is that: This embodiment also provides a method for preparing molybdenum trioxide using the ultra-low potassium ammonium molybdate, comprising the following steps: 1 kg of ultra-low potassium ammonium molybdate was transferred into a ball mill, ground and crushed until it completely passed through a 500-mesh Taylor standard sieve, and then transferred into a sintering furnace. In a high-purity nitrogen atmosphere, the nitrogen flow rate was 2 L / min, the temperature was raised to 450°C at 3°C / min, sintered for 110 min, the temperature was kept constant, and then a mixed gas of nitrogen and hydrogen chloride was introduced at 3 L / min, and then nitrogen was continued to be introduced at 3 L / min for 10 min, the temperature was lowered to 40°C at 4°C / min, and washed 3 times with 40°C pure water, and then dried at 110°C in a high-purity nitrogen atmosphere for 8 h, ground, vibrated and sieved, and stirred to mix evenly to obtain molybdenum trioxide.

[0086] Among them, the total amount of the mixed gas is 90L, and the content of hydrogen chloride gas is 6.7L.

[0087] The rest is the same as Example 7.

[0088] Comparative Example 1 The difference between this comparative example and Example 1 is: S3: immerse the hydrated molybdenum oxide in 2.4 kg of 20% ammonia water, heat to 50°C, stir and mix for 5 hours at a stirring rate of 800 r / min, cool to room temperature, add 1 g of ammonium sulfide, stir and mix for 1 hour, age for 24 hours, filter, and obtain an ammonium molybdate solution; The rest is the same as in Example 1.

[0089] Comparative Example 2 The difference between this comparative example and comparative example 1 is: S2: 1 kg of raw material and 5 kg of pure water were added into the reactor, and the double-layer turbine stirring paddle was turned on at a stirring rate of 2000 r / min, so that the solid-liquid slurry formed by the raw material and pure water formed a continuous cyclone loop, and the solid raw material basically did not sink to the bottom, and then a nitric acid solution with a mass fraction of 27% was added, and the pH distribution was adjusted to between 0.5 and 0.8, and compressed air was blown into the reactor, and the temperature was raised to 100°C, and the pressure in the reactor was adjusted to 0.6 MPa, and the reaction was carried out for 5 hours, and the temperature was lowered to 85°C, and the mixture was filtered and washed twice with pure water at a temperature of 70°C to obtain hydrated molybdenum oxide with uniform particle size distribution; Other details are the same as those in Comparative Example 1.

[0090] Comparative Example 3 The difference between this comparative example and comparative example 2 is that: S2: 1 kg of raw materials and 5 kg of pure water were added into the reactor, and a single-layer turbine stirring blade was used with a stirring rate of 2000 r / min, and then a nitric acid solution with a mass fraction of 27% was added, and the pH distribution was adjusted between 0.5 and 0.8, and compressed air was blown into the reactor, and the temperature was raised to 100°C, and the pressure in the reactor was adjusted to 0.6 MPa, and the reaction was carried out for 5 hours, and the temperature was lowered to 85°C, and filtered, and washed twice with pure water at a temperature of 70°C to obtain hydrated molybdenum oxide with uniform particle size distribution; The rest is the same as Comparative Example 2.

[0091] Performance Testing The content of molybdenum (abbreviated as ammonium molybdate-Mo) in the ultra-low potassium ammonium molybdate in Examples 1 to 6 and Comparative Examples 1 to 3 was analyzed and tested according to the testing standard GB / T3460-2017, and the results are shown in Tables 2 and 5; the molybdenum trioxide in Examples 1 to 8 was analyzed and tested according to the testing standard GB / T23439-2009, and the results are shown in Tables 2 and 4; the molybdenum powder in Examples 1 to 8 was analyzed and tested according to the testing standard GB / T3461-2016, and the results are shown in Tables 3 and 4.

[0092] Table 2 Content of ammonium molybdate-Mo and purity of molybdenum trioxide and impurity content of Examples 1 to 6

[0093] Table 3 Purity and impurity content of molybdenum powder in Examples 1 to 6

[0094] Table 4 Purity of molybdenum trioxide, purity of molybdenum powder and potassium content in Examples 7-8

[0095] Table 5 Content of ammonium molybdate-Mo and impurity content in comparative examples 1 to 3

[0096] From the test data in Table 1 to Table 5, it can be seen from the comparative analysis of Example 1 and Comparative Examples 1 to 3 that: By using a double-layer turbine stirring paddle in step S2, increasing the acid leaching temperature and adding a modified molecular sieve in step S3, not only the content of ammonium molybdate-Mo is increased, but also the content of impurities is reduced. This is because: the use of a double-layer turbine stirring paddle can make the acid leaching reaction system in step S2 fully mixed in both the horizontal and vertical directions, which can better disperse the raw material particles, make the raw material particles more fully contact with the acid solution, reduce local concentration differences and insufficiently acidified raw material areas, and pre-separate impurities such as potassium as much as possible. Appropriately increasing the temperature of the reaction system in step S2 increases the dissolution probability of impurities, allowing the impurities to be more smoothly separated from the raw materials and enter the solution, preparing for the subsequent impurity removal step.

[0097] In step S3, based on the loading of 18-crown ether-6 on the modified molecular sieve, the modified molecular sieve has a preferential selective coordination ability for metal cations such as potassium, copper, and calcium in the solution, and the interaction between ammonium ions and the modified molecular sieve is weakened, so that the ammonium ions are at a disadvantage in competitive adsorption, thereby increasing the relative content of ammonium molybdate in the solution, and also increasing the molybdenum content. In addition, the removal of metal cation impurities by the modified molecular sieve improves the chemical environment of the ammonium molybdate solution, is conducive to the stable existence of ammonium molybdate, and indirectly increases the molybdenum content.

[0098] In addition to being able to form coordination compounds with some metal cations, modified molecular sieves can also use their own pore structure and surface adsorption to remove impurities. In subsequent filtration and other operations, those modified molecular sieves that form coordination compounds with metal cations will be separated. At the same time, the pore structure of the molecular sieve is like a tiny "sieve" that can screen and adsorb impurities in the solution, and its surface can also adsorb some impurities. This synergistic approach allows impurities in the solution to be removed more comprehensively and thoroughly, further improving the purity of ammonium molybdate.

[0099] Comparative analysis of Examples 1 to 3 shows that although different batches of roasted molybdenum concentrates were used and modified molecular sieves in different preparation examples were used, the test results show that the content of ammonium molybdate-Mo, the purity of molybdenum trioxide and molybdenum powder, and the removal of metal impurities such as potassium, copper, and calcium all reached a good level. The process shows good stability and effectiveness in the face of changes in raw materials and key materials, and can stably produce high-quality, high-purity, and low-impurity ultra-low potassium ammonium molybdate and its ultra-low potassium derivatives.

[0100] Comparative analysis of Examples 3 to 6 shows that by using modified polyurethane microspheres instead of modified molecular sieves, the molybdenum content in the prepared ultra-low potassium ammonium molybdate and its ultra-low potassium derivatives have a slightly lower purity and a slightly higher impurity content. This may be due to the fact that the active oxygen atoms of some crown ether units in the modified polyurethane microspheres are blocked, resulting in impurities such as potassium ions not being effectively removed by complexation. These impurities such as potassium ions are mixed in the crystals during the subsequent crystallization of ammonium molybdate, reducing the purity of ammonium molybdate and causing a corresponding decrease in the content of ammonium molybdate-Mo.

[0101] In addition, the modified polyurethane microspheres may contain certain functional groups or active sites that can react with ammonium molybdate, such as carboxyl, hydroxyl, etc. These functional groups may react with the molybdenum ions in ammonium molybdate by complexation, chelation or ion exchange, thereby changing the content and distribution of molybdenum in ammonium molybdate. The complexation or chelation reaction may cause a part of the molybdenum ions to be fixed in the complex or chelate on the surface of the polyurethane microspheres, which will be taken out with the polyurethane microspheres during the subsequent filtration process, thereby reducing the molybdenum content in the original ammonium molybdate solution. Due to the reduction in molybdenum content, the proportion of molybdenum in the subsequently prepared molybdenum trioxide may decrease, resulting in a decrease in purity.

[0102] Comparative analysis of Examples 6 to 8 shows that when ultra-low potassium ammonium molybdate is used to prepare molybdenum trioxide, a small amount of a mixed gas of hydrogen chloride and nitrogen is introduced in the later stage of the reaction, so that the potassium content in the molybdenum trioxide is reduced and the purity is improved. This is because: hydrogen chloride may react with potassium ions and other impurities contained in the ultra-low potassium ammonium molybdate to generate volatile substances and the dilution and carrying effect of nitrogen, which effectively reduces the potassium content in the molybdenum trioxide, thereby improving its purity.

Claims

1. A method for preparing ultra-low potassium ammonium molybdate, characterized in that: The steps include: S1: Preliminarily screening, crushing, and then screening the roasted molybdenum concentrate to obtain a raw material; S2: Add the raw materials and water into the reactor, mix them evenly, add the acid solution, adjust the pH to 0.5-0.8, introduce compressed air, heat to 150-170°C, adjust the pressure in the reactor to 0.6-0.8MPa, react for 3-5h, reduce the temperature and pressure, wash, separate the solid and liquid, and obtain hydrated molybdenum trioxide; S3: After mixing hydrated molybdenum trioxide and ammonia solution at 50-70°C for 3-5 hours, add ammonium sulfide, mix for 1-2 hours, separate the solid and liquid, then add adsorbent, mix for 1-2 hours, cool, and age for 24-48 hours. After solid-liquid separation, obtain ammonium molybdate solution; S4: Concentrate the specific gravity of the ammonium molybdate solution to 1.30~1.35g / cm 3 , adjust the pH to 6.5-7, then cool and crystallize for 3-5 hours, separate the solid and liquid, wash and dry to obtain ultra-low potassium ammonium molybdate; The adsorbent is any one of modified molecular sieves and modified polyurethane microspheres. The modified molecular sieve is a crown ether compound A modified molecular sieve, and the modified polyurethane microspheres are crown ether compound B modified polyurethane microspheres.

2. The method for preparing ultra-low potassium ammonium molybdate according to claim 1, characterized in that: The acid solution is a nitric acid solution, in which the mass fraction of nitric acid is 27% to 30%; the mass fraction of ammonia water in the ammonia solution is 20% to 25%.

3. The method for preparing ultra-low potassium ammonium molybdate according to claim 2, characterized in that: The mass ratio of the raw material, water, ammonia water, ammonium sulfide and adsorbent is 1:5-6:0.48-0.51:0.001-0.002:0.015-0.

025.

4. The method for preparing ultra-low potassium ammonium molybdate according to claim 3, characterized in that: The method for preparing the crown ether compound A modified molecular sieve, wherein the crown ether compound A is 18-crown ether-6, comprises the following steps: (1) Sintering the molecular sieve at 300-500°C for 2-4 hours, cooling, and sieving to obtain a pretreated molecular sieve; (2) uniformly mixing the pretreated molecular sieve with a γ-aminopropyltriethoxysilane solution having a mass fraction of 0.5% to 1%, performing solid-liquid separation, washing, and drying to obtain a pre-modified molecular sieve; (3) mixing the pre-modified molecular sieve with the 18-crown ether-6 aqueous solution for 2 to 4 hours, separating the solid and the liquid, washing, and drying to obtain the modified molecular sieve; The mass fraction of the 18-crown ether-6 aqueous solution is 5% to 10%, and the mass ratio of the molecular sieve to 18-crown ether-6 is 1:0.1 to 0.

2.

5. The method for preparing ultra-low potassium ammonium molybdate according to claim 3, characterized in that: The preparation method of the crown ether compound B modified polyurethane microspheres, wherein the crown ether compound B is dibenzo-18-crown ether-6, comprises the following steps: S11: dibenzo-18-crown-6 and formic acid are mixed evenly to obtain dispersion A; then, at 30-40°C, polyformaldehyde and formic acid are mixed evenly to obtain dispersion B; at 30-40°C, solution B is added to solution A, mixed evenly until precipitation occurs, and the mixture is mixed for 10-12 hours, cooled, allowed to stand for 1-2 hours, separated from the solid and the liquid, washed until neutral, and dried to obtain dibenzo-18-crown-6 formaldehyde polymer; S12: polyethylene glycol and dibenzo-18-crown-6-formaldehyde polymer are mixed evenly to obtain a mixed solution A, toluene diisocyanate, Tween 80, dibutyltin dilaurate and water are mixed evenly to obtain a mixed solution B, and then the mixed solution B is added to the mixed solution A, mixed evenly, heated to 20-40°C for reaction for 4-6 hours, and then 1,4-butanediol is added, and the mixture is kept warm for 20-40 minutes, and then the mixture is heated to 60-80°C, and the mixture is kept warm for 1.5-2.5 hours, and then a foaming agent is added, and the mixture is mixed evenly. After keeping warm for 2-4 hours, the reaction solution is added to an ethanol aqueous solution, cooled, sodium dodecyl sulfate is added, and the mixture is mixed evenly, and triethylamine is added to adjust the pH to neutral, and the mixture is separated into solid and liquid, washed, and dried to obtain modified polyurethane microspheres; The foaming agent is n-pentane; The mass ratio of the dibenzo-18-crown-6 to polyformaldehyde is 8-10:1.5-2.5; the mass ratio of the polyethylene glycol, toluene diisocyanate, dibenzo-18-crown-6 formaldehyde polymer, 1,4-butanediol and sodium dodecyl sulfate is 1:0.5-0.7:0.2-0.4:0.1-0.2:0.05-0.

07.

6. A method for preparing an ultra-low potassium derivative, characterized in that: Molybdenum powder or molybdenum trioxide is prepared using the ultra-low potassium ammonium molybdate described in any one of claims 1 to 5 as an initial raw material.

7. The method for preparing the ultra-low potassium derivative according to claim 6, characterized in that: The molybdenum trioxide is prepared by the following steps: crushing and sieving the ultra-low potassium ammonium molybdate, heating it to 400-500° C. in an inert atmosphere, sintering it for 90-150 minutes, cooling it, sieving it, and mixing it evenly to obtain molybdenum trioxide.

8. The method for preparing the ultra-low potassium derivative according to claim 6, characterized in that: The molybdenum trioxide is prepared by the following steps: crushing and sieving the ultra-low potassium ammonium molybdate, heating it to 450-500° C. in an inert atmosphere, sintering it for 90-110 min, keeping the temperature constant, then introducing a mixed gas of hydrogen chloride gas and part of nitrogen at 2.5-3 L / min, then continuously introducing nitrogen at 2.5-3 L / min for 10-15 min, cooling, washing, drying, and sieving to obtain molybdenum trioxide; the mass of the hydrogen chloride gas accounts for 0.8%-1% of the total mass of the ultra-low potassium ammonium molybdate.

9. The method for preparing the ultra-low potassium derivative according to claim 7, characterized in that: The molybdenum powder is prepared by the following steps: In a hydrogen atmosphere, the temperature is raised to 450-650° C. in the first stage, and the molybdenum trioxide is sintered for 2-4 hours. In the second stage, the temperature is raised to 900-1100° C., and sintered for 3-5 hours. The temperature is lowered, sieved, and mixed uniformly to obtain molybdenum powder.

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