Method for preparing high-purity ammonium molybdate by using waste cobalt-molybdenum catalyst

Abstract

The invention discloses a method for preparing high-purity ammonium molybdate by using a waste cobalt-molybdenum catalyst, which comprises the following steps: carrying out ball-milling treatment on the waste cobalt-molybdenum catalyst, putting the waste cobalt-molybdenum catalyst into a beaker, carrying out magnetization in magnetization equipment under a stirring condition, adding sodium carbonate into the magnetized material for alkaline leaching, and carrying out liquid-solid separation on the mixed solution to obtain an alkaline leaching solution; adjusting the pH value of the alkaline leaching solution with dilute sulfuric acid, purifying and precipitating molybdenum, carrying out liquid-solid separation to obtain molybdic acid, dissolving and clarifying the molybdic acid with stronger ammonia water, adjusting the pH value of the dissolved and clarified ammonium molybdate solution with dilute acid, and purifying and precipitating molybdenum again to obtain pure molybdic acid; pure molybdic acid is dissolved and clarified with strong ammonia water, the dissolved and clarified ammonium molybdate solution is subjected to evaporation, concentration and high-temperature thermal crystallization under the micro-pressure ultrasonic action, and the crystallized mixed solution is subjected to centrifugal separation to obtain a 4N-grade or above high-purity ammonium molybdate product. The method for preparing high-purity ammonium molybdate by using the waste cobalt-molybdenum catalyst has the characteristics of good product quality, simple process and high molybdenum recovery efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of ammonium molybdate preparation, in particular to a method for preparing high-purity ammonium molybdate by using a waste cobalt-molybdenum catalyst. Background Art

[0002] Ammonium molybdate, a compound composed of ammonium cations and molybdenum heteropolyacid anions, is a key molybdenum chemical product. It is not only a primary raw material for the production of molybdenum powder and molybdenum metal products, but is also used in chemical reagents, catalysts, flame retardants, micro-fertilizers, and pharmaceuticals. Diverse ammonium molybdates vary in solubility, particle size, thermal decomposition temperature, and crystal form. They are used as catalysts in the petroleum industry, in the metallurgical industry to produce molybdenum, and as a raw material for ceramic glazes, pigments, and other molybdenum compounds. They have a wide range of applications.

[0003] Spent cobalt-molybdenum catalysts are products of used cobalt-molybdenum catalysts that have lost their catalytic effectiveness. These catalysts contain a carrier and a chemical component that contributes to their catalytic effectiveness. These carriers and chemical components vary from catalyst to catalyst. Spent cobalt-molybdenum catalysts cannot be directly reused as chemical products. To avoid waste, they must be comprehensively recovered to extract molybdenum and produce high-purity ammonium molybdate.

[0004] Patent CN103553132B discloses a method for preparing ammonium tetramolybdate by treating molybdenum-rich wastewater and waste residue. The method comprises the following steps: 1. Concentrating molybdenum calcined sand washing wastewater and mixing it evenly with the acid precipitation crystallization mother liquor from the ammonium molybdate production process to obtain a mixed liquor; 2. Adding molybdenum calcined sand to the water-washed molybdenum calcined sand ammonia leaching waste residue, then adding it to the mixed liquor, adjusting the pH value, subjecting it to magnetization treatment, and stirring the reaction to obtain a solid-liquid mixed slurry; 3. Solid-liquid separation, subjecting the filter cake to ammonia leaching; 4. Solid-liquid separation, obtaining an ammonia leaching solution and ammonia leaching residue; 5. Ammonia leaching the ammonia leaching residue; 6. Removing impurities from the ammonia leaching solution, purifying it, acid precipitating it, and filtering it to obtain solid ammonium tetramolybdate. This invention utilizes the addition of molybdenum calcined sand ammonia leaching waste residue doped with molybdenum calcined sand to the wastewater and acid precipitation mother liquor. Through liquid-phase magnetization treatment, the molybdenum resources in the wastewater and waste residue are efficiently utilized, significantly reducing the cost of treating molybdenum-containing waste residue and wastewater, achieving energy conservation and environmental protection, and effectively improving the molybdenum resource utilization rate of the molybdenum calcined sand washing concentrated wastewater and ammonia leaching waste residue.

[0005] The leaching method of this invention is to magnetize the molybdenum roasted sand ammonia leaching waste residue and the molybdenum roasted sand mixed solution with a mixture of water washing solution and molybdenum precipitation mother solution, mainly to improve the utilization of molybdenum and reduce the treatment cost of molybdenum-containing waste residue and wastewater. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst to solve the problems existing in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: Grind the waste cobalt-molybdenum catalyst into a powder of 100-200 mesh using a ball mill, add the waste cobalt-molybdenum catalyst powder into a beaker, and place the beaker on a magnetizing device for magnetization for 30-40 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed with deionized water at a solid-liquid mass ratio of 1:4-5, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 1.2-1.3 times the theoretical amount of sodium carbonate in the recyclable molybdenum raw material that reacts with molybdenum. The mixed solution is heated for leaching at a leaching temperature of 80-90° C. for 1.5-2 hours. After leaching is completed, the mixture is filtered, the residue and liquid are separated, and the filtrate is collected; Step 3, add dilute sulfuric acid with a mass percent concentration of 50% to the filtrate collected in step 2, stirring while adding, adjust the pH value of the filtrate to 0.5-1.0, filter after stirring for 30-60 minutes, solid-liquid separation, the solid state is molybdic acid, and the collected molybdic acid is molten with analytical pure concentrated ammonia. After the molybdic acid is molten, add dilute sulfuric acid with a mass percent concentration of 50% while stirring in the molten solution, adjust the pH value of the solution to 0.5-1.0, continue stirring for 30-60 minutes and carry out solid-liquid separation again, and the collected solid is light yellow pure molybdic acid; Step 4: dissolving the pure molybdic acid obtained in step 3 with analytical pure concentrated ammonia water, heating and concentrating the dissolved solution in a water bath with an ultrasonic generator, turning on the ultrasonic generator, and evaporating the pressure in the water bath to 0.1-0.2Kpa, with a boiling point of 85-95°C. After evaporation and concentration until a large amount of white crystals precipitate in the solution, heating and evaporation are stopped. When the solution temperature drops to 30°C, the ultrasonic generator is turned off, centrifuged, and the mother liquor is collected. The white crystals are pure ammonium molybdate; the mother liquor is returned to step 3 for purification and recovery again, and the evaporated ammonia is collected for reuse; The purity of the prepared ammonium molybdate is ≥4N grade and the crystallization rate is 70-80%.

[0008] Preferably, the magnetization equipment for the waste cobalt-molybdenum catalyst in step 1 is a magnetic coil with a magnetic field strength of 15,000-30,000 Gauss and a magnetization time of 30-40 minutes.

[0009] Preferably, the weight percentages of the elements contained in the waste cobalt-molybdenum catalyst are as follows: 35-40% molybdenum, 1.5-2.0% cobalt, 25-30% aluminum, 18-20% silicon, and the rest are impurities.

[0010] Preferably, the sodium carbonate is of reagent grade.

[0011] Preferably, the mass percentage concentration of the analytically pure concentrated ammonia water is 25-30%.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The cobalt ions and aluminum ions in the magnetized waste cobalt-molybdenum catalyst in step 1 are in a stable state, and the cobalt ions, aluminum ions, etc. will not enter the liquid phase during alkaline leaching; The leaching rate of molybdenum in step 2 alkaline leaching can reach more than 98%; The present invention utilizes micro-pressure ultrasound during the evaporation and high-temperature thermal crystallization process in step 4 to increase the activity of molybdenum ions. This prevents impurity ions from adhering to ammonium molybdate crystals during their formation, resulting in ammonium molybdate crystals with uniform particle size, high purity, and enhanced activity. The present invention also utilizes high-temperature thermal crystallization to effectively separate the crystals from impurity particles and improve the crystallization rate.

[0013] The present invention uses waste cobalt-molybdenum catalyst as raw material. Ball milling and magnetization of the waste cobalt-molybdenum catalyst prevents cobalt and aluminum from entering the liquid phase during alkaline leaching. The liquid, after pure molybdic acid is dissolved in concentrated ammonia, is evaporated and concentrated under the action of an ultrasonic generator, resulting in uniform and highly active ammonium molybdate crystals. High-temperature crystallization facilitates efficient separation of impurities from ammonium molybdate, resulting in a higher-purity product, producing high-purity ammonium molybdate of grade 4N or higher. The method is simple and highly efficient in molybdenum recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flow chart of the present invention; Figure 2 This is a physical picture of ammonium molybdate prepared in Example 1; Figure 3 This is a physical picture of the ammonium molybdate produced in Comparative Example 2. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0016] Example 1 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: The waste cobalt-molybdenum catalyst is ball-milled to a 100-mesh powder, the waste cobalt-molybdenum catalyst powder is added to a beaker and mixed evenly, and the beaker is placed on a magnetizing coil for magnetization treatment. The magnetic field strength of the coil is 15,000 gauss for 30 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed evenly with deionized water at a solid-liquid mass ratio of 1:4, and pure sodium carbonate is added as a reagent under stirring. The amount of sodium carbonate added is 1.2 times the theoretical amount of sodium carbonate in the raw material that reacts with molybdenum. After stirring evenly, the mixture is heated and leached at a leaching temperature of 80° C. for 1.5 hours. After leaching is completed, the mixture is filtered, the residue and liquid are separated, and the filtrate is collected; Step 3: add 50% by mass concentration of dilute sulfuric acid to the filtrate collected in step 2, adjust the pH value of the filtrate to 0.5 under stirring, stir for 30 minutes, and perform solid-liquid separation. The solid is molybdic acid, and the molybdic acid is dissolved with 25% by mass concentration of concentrated ammonia. After the molybdic acid is dissolved, add 50% by mass concentration of dilute sulfuric acid to adjust the pH value of the melt to 0.5 under stirring, stir for 30 minutes to perform solid-liquid separation, and the solid is light yellow pure molybdic acid; Step 4, the pure molybdic acid obtained in step 3 is dissolved in concentrated ammonia with a mass percentage concentration of 25%, and the dissolved solution is placed in a water bath with a micro-pressure ultrasonic generator for heating and concentration. The ultrasonic generator is turned on, the pressure during evaporation is 0.1Kpa, the boiling point of the solution is 85°C, and the heating and evaporation are stopped when a large amount of white crystals are precipitated in the solution. When the solution temperature drops to 30°C, the ultrasonic generator is turned off and centrifuged to obtain pure ammonium molybdate; The physical photo of the ammonium molybdate product prepared in this embodiment is as follows Figure 2 As shown. Figure 2 It can be seen that the prepared ammonium molybdate product has small and uniform particles and is white and pure in color.

[0017] The purity of ammonium molybdate was tested to be ≥99.996%, the mass percentage contents of each element in ammonium molybdate were: Co<0.0007%, Al<0.0022%, Si<0.001%, the crystallization rate was 70.80%, the molybdenum alkali leaching recovery rate was 98.20%, and the comprehensive yield was 95.19%.

[0018] Example 2 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: ball-milling the waste cobalt-molybdenum catalyst to a 200-mesh powder, adding the waste cobalt-molybdenum catalyst powder to a beaker and mixing evenly, placing the beaker on a magnetizing device and magnetizing it at a magnetic field strength of 15,000 Gauss for 40 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed evenly with deionized water at a solid-liquid mass ratio of 1:5, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 1.3 times the theoretical amount of sodium carbonate that reacts with molybdenum in the raw material. After adding sodium carbonate, heating and leaching are performed at a leaching temperature of 90° C. and a leaching time of 2 hours. After leaching is completed, filtering is performed, the residue and liquid are separated, and the filtrate is collected; Step 3, adding 50% by mass concentration of dilute sulfuric acid to the filtrate collected in step 2, adjusting the pH value of the filtrate to 1.0 under stirring, stirring for 60 minutes, and performing solid-liquid separation. The solid is molybdic acid, and the molybdic acid is dissolved with 30% by mass concentration of concentrated ammonia. After the molybdic acid is dissolved, dilute sulfuric acid is added under stirring to adjust the pH value of the melt to 1.0. Stir for 60 minutes for solid-liquid separation, and the solid is light yellow pure molybdic acid; Step 4: The pure molybdic acid obtained in step 3 was dissolved in 30% concentrated ammonia water by mass. The dissolved solution was placed in a water bath with a micro-pressure ultrasonic generator and heated and concentrated. The ultrasonic generator was turned on, the pressure during evaporation was 0.2 kPa, and the boiling point of the solution was 95 ° C. When a large amount of white crystals precipitated in the solution, the heating and evaporation were stopped. When the solution temperature dropped to 30 ° C, the ultrasonic generator was turned off and centrifuged to obtain pure ammonium molybdate. The purity of ammonium molybdate was tested to be ≥99.992%. The mass percentage content of each element in ammonium molybdate was: Co <0.0005%, Al <0.0018%, Si <0.0009%, and the crystallization rate was 80%. The molybdenum alkali leaching rate was 98.6%, and the comprehensive yield was 95.4%.

[0019] Example 3 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: ball-milling the waste cobalt-molybdenum catalyst to a 200-mesh powder, adding the waste cobalt-molybdenum catalyst powder to a beaker and mixing evenly, placing the beaker on a magnetizing device and magnetizing it at a magnetic field strength of 30,000 Gauss for 90 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed evenly with deionized water at a solid-liquid mass ratio of 1:5, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 1.3 times the theoretical amount of sodium carbonate that reacts with molybdenum in the raw material. After adding sodium carbonate, heating and leaching are performed at a leaching temperature of 90° C. and a leaching time of 2 hours. After leaching is completed, filtering is performed, the residue and liquid are separated, and the filtrate is collected; Step 3: Add 50% by mass concentration of dilute sulfuric acid to the filtrate collected in step 2, adjust the pH value of the filtrate to 1.0 while stirring, stir for 60 minutes, and perform solid-liquid separation. The solid is molybdic acid. Use 25% by mass concentration of concentrated ammonia to dissolve the molybdic acid. After the molybdic acid is dissolved, add 50% by mass concentration of dilute sulfuric acid to adjust the pH value of the melt to 1.0 while stirring. Stir for 60 minutes to perform solid-liquid separation. The solid is light yellow pure molybdic acid; Step 4: The pure molybdic acid obtained in step 3 was dissolved in 25% concentrated ammonia water by mass. The dissolved solution was placed in a water bath with a micro-pressure ultrasonic generator and heated and concentrated. The ultrasonic generator was turned on, and the pressure during evaporation was 0.2 kPa. The boiling point of the solution was 95°C. When a large amount of white crystals precipitated in the solution, the heating and evaporation were stopped. When the solution temperature dropped to 30°C, the ultrasonic generator was turned off and centrifuged to obtain pure ammonium molybdate. The purity of ammonium molybdate was tested to be ≥99.993%. The mass percentage content of each element in the ammonium molybdate was: Co <0.0006%, Al <0.0023%, Si <0.0019%, and the crystallization rate was 75%. The molybdenum alkali leaching rate was 98.44%, and the overall yield was 95.62%.

[0020] Example 4 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: ball-milling the waste cobalt-molybdenum catalyst to a 100-mesh powder, adding the waste cobalt-molybdenum catalyst powder to a beaker and mixing evenly, placing the beaker on a magnetizing device and magnetizing it at a magnetic field strength of 20,000 Gauss for 90 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed evenly with deionized water at a solid-liquid mass ratio of 1:4, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 2.0 times the theoretical amount of sodium carbonate in the raw material that reacts with molybdenum. After adding sodium carbonate, heating and leaching are performed at a leaching temperature of 90° C. and a leaching time of 3 hours. After leaching is completed, filtering is performed, the residue and liquid are separated, and the filtrate is collected; Step 3, adding 50% by mass concentration of dilute sulfuric acid to the filtrate collected in step 2, adjusting the pH value of the filtrate to 1.0 under stirring, stirring for 60 minutes, and performing solid-liquid separation. The solid is molybdic acid, and the molybdic acid is dissolved with 30% by mass concentration of concentrated ammonia water. After the molybdic acid is dissolved, dilute sulfuric acid is added under stirring to adjust the pH value of the melt to 1.0. Stir for 60 minutes for solid-liquid separation, and the solid is light yellow pure molybdic acid; Step 4: The pure molybdic acid obtained in step 3 was dissolved in 30% concentrated ammonia water by mass. The dissolved solution was placed in a water bath equipped with a micro-pressure ultrasonic generator and heated and concentrated. The ultrasonic generator was turned on, and the pressure during evaporation was 0.2 kPa. The boiling point of the solution was 95°C. When a large amount of white crystals precipitated in the solution, the heating and evaporation were stopped. When the solution temperature dropped to 30°C, the ultrasonic generator was turned off and centrifuged to obtain pure ammonium molybdate. The purity of ammonium molybdate was tested to be ≥99.995%. The mass percentage content of each element in the ammonium molybdate was: Co <0.0003%, Al <0.0019%, Si <0.0014%, and the crystallization rate was 75.83%. The molybdenum alkali leaching rate was 98.57%, and the overall yield was 95.62%.

[0021] Example 5 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: The waste cobalt-molybdenum catalyst is ball-milled to a powder of 200 mesh, the waste cobalt-molybdenum catalyst powder is added to a beaker and mixed evenly, and the beaker is placed on a magnetizing device for magnetization treatment at a magnetic field strength of 30,000 Gauss for 30 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed evenly with deionized water at a solid-liquid mass ratio of 1:5, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 3.0 times the theoretical amount of sodium carbonate that reacts with molybdenum in the raw material. After adding sodium carbonate, heating and leaching are performed at a leaching temperature of 80° C. and a leaching time of 1.5 hours. After leaching is completed, filtering is performed, the residue and liquid are separated, and the filtrate is collected; Step 3: Add 50% by mass concentration of dilute sulfuric acid to the filtrate collected in step 2, adjust the pH value of the filtrate to 0.5 while stirring, stir for 30 minutes, and perform solid-liquid separation. The solid is molybdic acid. Use concentrated ammonia to dissolve the molybdic acid. After the molybdic acid is dissolved, add dilute sulfuric acid while stirring to adjust the pH value of the melt to 0.5. Stir for 30 minutes to perform solid-liquid separation. The solid is light yellow pure molybdic acid; Step 4: Dissolve the purified molybdic acid obtained in step 3 with concentrated ammonia water. The dissolved solution is placed in a water bath equipped with a micro-pressure ultrasonic generator and heated and concentrated. The ultrasonic generator is turned on, and the evaporation pressure is 0.1 kPa. The boiling point of the solution is 90°C. When a large amount of white crystals precipitate in the solution, heating and evaporation are stopped. When the solution temperature drops to 30°C, the ultrasonic generator is turned off. Centrifugation is performed to obtain purified ammonium molybdate. Testing shows that the purity of the ammonium molybdate is ≥99.995%, Co <0.001%, Al <0.0019%, Si <0.0028%, and the crystallization rate is 77.85%. The molybdenum alkali leaching rate is 98.52%, and the overall yield is 96.30%.

[0022] Comparative Example 1 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: Use spent cobalt-molybdenum catalyst as the raw material for alkaline leaching. Mix it evenly with deionized water at a solid-to-liquid ratio of 1:4. Add sodium carbonate while stirring. The amount of sodium carbonate added is 1.2 times the theoretical amount of sodium carbonate required to react with molybdenum in the raw material. Leaching is then carried out by heating at 90°C for 2 hours. After leaching, the residue is filtered, the liquid is separated, and the filtrate is collected. Testing shows that the leaching rates of molybdenum, cobalt, and aluminum in the filter residue are 67.4%, 35.22%, and 51.69%, respectively. This affects the molybdenum recovery rate and the subsequent impact of cobalt and aluminum on product quality.

[0023] Comparative Example 2 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: ball-milling the waste cobalt-molybdenum catalyst to a 200-mesh powder, adding the waste cobalt-molybdenum catalyst powder to a beaker and mixing evenly, placing the beaker on a magnetizing device and magnetizing it at a magnetic field strength of 30,000 Gauss for 90 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is evenly mixed with deionized water at a solid-liquid mass ratio of 1:10, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 3.0 times the theoretical amount of sodium carbonate that reacts with molybdenum in the raw material. After adding sodium carbonate, heating and leaching are performed. The leaching temperature is 90°C and the leaching time is 3 hours. After the leaching is completed, the residue and liquid are separated and the filtrate is collected. The leaching rates of molybdenum, cobalt and aluminum obtained by testing the filtrate are 98.6%, 0.002% and 0.001% respectively, and silicon is not detected, indicating that further increasing the solid-liquid ratio and increasing the amount of alkali have little effect on the leaching effect and increase the cost.

[0024] Comparative Example 3 A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst comprises the following steps: Step 1: The waste cobalt-molybdenum catalyst is ball-milled to a 100-mesh powder, the waste cobalt-molybdenum catalyst powder is added to a beaker and mixed evenly, and the beaker is placed on a magnetizing device and magnetized at a magnetic field strength of 15,000 gauss for 30 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed evenly with deionized water at a solid-liquid mass ratio of 1:4, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 1.2 times the theoretical amount of sodium carbonate that reacts with molybdenum in the raw material. After adding sodium carbonate, heating and leaching are performed at a leaching temperature of 80° C. and a leaching time of 1.5 hours. After leaching is completed, filtering is performed, the residue and liquid are separated, and the filtrate is collected; Step 3: add 50% by mass percent dilute sulfuric acid to the filtrate collected in step 2, adjust the pH value of the filtrate to 0.5 under stirring, stir for 30 minutes, and perform solid-liquid separation. The solid is molybdic acid. Dissolve the molybdic acid with concentrated ammonia water. After the molybdic acid is dissolved, add dilute sulfuric acid under stirring to adjust the pH value of the melt to 0.5. Stir for 30 minutes to perform solid-liquid separation. The solid is light yellow pure molybdic acid. Step 4: Dissolve the pure molybdic acid obtained in step 3 with concentrated ammonia water, heat and concentrate normally until the solution has a specific gravity of 1.33 g / cm 3 Cooling crystallization was carried out at 37°C, and the crystallization rate of the ammonium molybdate product was 65%, the purity was 99.85%, and the mass percentage contents of pure cobalt, aluminum, and silicon were 0.032%, 0.063%, and 0.049%, respectively.

[0025] The actual photo of the prepared ammonium molybdate product is as follows Figure 3 As shown. Figure 3 It can be seen that the prepared ammonium molybdate particles are uneven in size, impure in color, and have a lower whiteness than the ammonium molybdate produced in Example 1.

Claims

1. A method for preparing high-purity ammonium molybdate using waste cobalt-molybdenum catalyst, characterized in that: The following steps are involved: Step 1: Grind the waste cobalt-molybdenum catalyst into a powder of 100-200 mesh using a ball mill, add the waste cobalt-molybdenum catalyst powder into a beaker, and place the beaker on a magnetizing device for magnetization for 30-40 minutes to obtain a recyclable molybdenum raw material; Step 2: The recyclable molybdenum raw material prepared in step 1 is mixed with deionized water at a solid-liquid mass ratio of 1:4-5, and sodium carbonate is added under stirring. The amount of sodium carbonate added is 1.2-1.3 times the theoretical amount of sodium carbonate in the recyclable molybdenum raw material that reacts with molybdenum. The mixed solution is heated for leaching at a leaching temperature of 80-90° C. for 1.5-2 hours. After leaching is completed, the mixture is filtered, the residue and liquid are separated, and the filtrate is collected; Step 3, add dilute sulfuric acid with a mass percent concentration of 50% to the filtrate collected in step 2, stirring while adding, adjust the pH value of the filtrate to 0.5-1.0, filter after stirring for 30-60 minutes, solid-liquid separation, the solid state is molybdic acid, and the collected molybdic acid is molten with analytical pure concentrated ammonia. After the molybdic acid is molten, add dilute sulfuric acid with a mass percent concentration of 50% while stirring in the molten solution, adjust the pH value of the solution to 0.5-1.0, continue stirring for 30-60 minutes and carry out solid-liquid separation again, and the collected solid is light yellow pure molybdic acid; Step 4: dissolving the pure molybdic acid obtained in step 3 with analytical pure concentrated ammonia water, heating and concentrating the dissolved solution in a water bath with an ultrasonic generator, turning on the ultrasonic generator, and evaporating the pressure in the water bath to 0.1-0.2Kpa, with a boiling point of 85-95°C. After evaporation and concentration until a large amount of white crystals precipitate in the solution, heating and evaporation are stopped. When the solution temperature drops to 30°C, the ultrasonic generator is turned off, centrifuged, and the mother liquor is collected. The white crystals are pure ammonium molybdate; the mother liquor is returned to step 3 for purification and recovery again, and the evaporated ammonia is collected for reuse; The purity of the prepared ammonium molybdate is ≥4N grade and the crystallization rate is 70-80%.

2. The method according to claim 1, wherein: In the step 1, the magnetization equipment for the waste cobalt-molybdenum catalyst is a magnetic coil with a magnetic field strength of 15,000-30,000 Gauss and a magnetization time of 30-40 minutes.

3. The method according to claim 1, wherein: The waste cobalt-molybdenum catalyst contains the following elements in percentage by mass: 35-40% molybdenum, 1.5-2.0% cobalt, 25-30% aluminum, 18-20% silicon, and the rest are impurities.

4. The method according to claim 1, wherein: The sodium carbonate is of reagent pure grade.

5. The method according to claim 1, wherein: The mass percentage concentration of the analytical pure concentrated ammonia water is 25-30%.

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