Process for preparing low-potassium ammonium molybdate by aid of crystallization method

Abstract

The invention belongs to the technical field of preparation of low-potassium ammonium molybdate, and relates to a process for preparing low-potassium ammonium molybdate by an aid crystallization method, which comprises the following steps: S1, preparing an ammonium molybdate solution: taking industrial molybdenum oxide as a raw material, and obtaining the ammonium molybdate solution by an ammonia leaching method; s2, preparation of low-potassium ammonium molybdate by aid crystallization: at normal temperature, adding a crystallization aid into the ammonium molybdate solution in the step S1, uniformly stirring to quickly crystallize ammonium molybdate into a solid, leaving potassium ions in the ammonium molybdate solution in a liquid phase to realize quick separation of ammonium molybdate and the potassium ions, and then centrifuging and drying to obtain the low-potassium ammonium molybdate. According to the method, the crystallization aid is added, so that rapid separation of ammonium molybdate and potassium ions is realized, the low-potassium ammonium molybdate is prepared, other impurities do not need to be introduced, and the method is more environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of low-potassium ammonium molybdate and relates to a process for preparing low-potassium ammonium molybdate by an auxiliary agent crystallization method. Background Art

[0002] Molybdenum targets are widely used in physical vapor deposition (PVD) and magnetron sputtering technologies, mainly to make thin film electrodes, which play a key role in display screens, solar cells, semiconductors and other devices. However, in applications, the potassium contained in molybdenum targets is a harmful impurity. This is because under high temperature and high pressure production conditions, the potassium in the molybdenum target can easily be broken down to become a bad point, affecting the qualified rate of the device. In addition, during high-temperature sintering or when used 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, thereby contaminating the surface of the product.

[0003] At present, the raw material for preparing molybdenum target materials is molybdenum powder, and ammonium molybdate is an important raw material for preparing molybdenum powder. Therefore, in order to reduce the potassium content in molybdenum powder, the potassium element can be strictly controlled from the source, that is, the potassium content in ammonium molybdate can be strictly controlled; however, since the potassium element in ammonium molybdate mainly comes from molybdenum ore, and the concentration of potassium in different molybdenum ores is difficult to predict. Therefore, strict control of potassium content is a key technical issue for the ammonium molybdate industry, which has important scientific and economic significance.

[0004] The current method for preparing low-potassium ammonium molybdate is: first roast molybdenum concentrate to obtain industrial molybdenum oxide, then reduce the potassium content in the industrial molybdenum oxide by acid washing or water washing, and then obtain low-potassium ammonium molybdate by ammonia leaching, evaporation and crystallization. However, acid washing or water washing has the following problems: (1) When acid washing is used to reduce the potassium content, molybdenum dioxide will react under acidic conditions to form hydrates and molybdenum trioxide that is soluble in water, which is not conducive to subsequent solid-liquid separation. In addition, the acid washing process will introduce anions such as nitrate ions and chloride ions into the production process, thus causing uncontrollable environmental problems. (2) When water washing is used to reduce the potassium content, since ammonium molybdate is made from industrial molybdenum oxide, it is washed with water and then goes through a series of processes such as ammonia leaching and crystallization, which results in a slightly longer process line. In addition, water washing requires a large amount of water resources. At the same time, water washing will also wash out the molybdenum element, reducing the yield of molybdenum. When the potassium content in industrial molybdenum oxide is high, it is difficult to obtain a product with a potassium content that meets the standard through the water washing process.

[0005] In summary, the existing method of reducing potassium content not only introduces other impurities into the process, which is not environmentally friendly; but also in the subsequent crystallization process of ammonium molybdate, it is difficult to separate potassium ions from ammonium molybdate in the ammonium molybdate solution, resulting in excessive potassium content in ammonium molybdate. Therefore, the development of a new process for preparing low-potassium ammonium molybdate is the focus of current research. Summary of the invention

[0006] Aiming at the technical problems of introducing other impurities into the existing preparation of low-potassium ammonium molybdate, which leads to environmental pollution and excessive potassium, the present invention provides a process for preparing low-potassium ammonium molybdate by an auxiliary agent crystallization method.

[0007] The invention first obtains an ammonium molybdate solution by an ammonia leaching method, then adds a crystallization aid into the ammonium molybdate solution, and realizes rapid separation of ammonium molybdate and potassium ions at room temperature, thereby preparing low-potassium ammonium molybdate with potassium element reaching the standard, without introducing other impurities, and is more environmentally friendly.

[0008] The crystallization aid provided by the invention can be used to reduce the solubility of ammonium molybdate in a solution; and can also be used to prepare low-potassium ammonium molybdate.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is: A process for preparing low-potassium ammonium molybdate by an auxiliary agent crystallization method comprises the following steps: S1. Preparation of ammonium molybdate solution Using industrial molybdenum oxide as raw material, ammonium molybdate solution is obtained through ammonia leaching; S2. Preparation of low potassium ammonium molybdate by crystallization of auxiliary agent At room temperature, a crystallization aid is added to the ammonium molybdate solution in step S1, and the mixture is stirred evenly to allow the ammonium molybdate to crystallize rapidly into a solid, leaving potassium ions in the ammonium molybdate solution in the liquid phase to achieve rapid separation of ammonium molybdate and potassium ions, and then low-potassium ammonium molybdate is obtained by centrifugation and drying.

[0010] In step S2, the crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isopentanol, isopentyl glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid.

[0011] It is further defined that in step S2, the volume ratio of the ammonium molybdate solution to the crystallization aid is (0.5-3):1; and the molybdenum content in the ammonium molybdate solution is greater than 120 g / L.

[0012] It is further defined that in step S2, the pH value of the ammonium molybdate solution is between 5 and 11.

[0013] It is further defined that in step S2, the stirring time is not less than 20 minutes.

[0014] It is further defined that the mass concentration of potassium element in the low-potassium ammonium molybdate in step S2 is as low as 0.0082%.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention first leaches molybdenum oxide with ammonia to form an ammonium molybdate solution, and then adds a crystallization aid to the ammonium molybdate solution. Since ammonium molybdate is a polar molecule and is easily soluble in polar solvents; and the crystallization aid is a weakly polar compound, after the crystallization aid is added to the ammonium molybdate solution, the overall polarity of the ammonium molybdate solution is reduced, thereby reducing the solubility of ammonium molybdate in the solution. It can be seen that the crystallization aid can significantly reduce the solubility of ammonium molybdate in the solution, allowing ammonium molybdate to quickly crystallize into a solid, leaving the potassium ions in the ammonium molybdate solution in the liquid phase, and realizing the rapid separation of ammonium molybdate and potassium ions, thereby preparing low-potassium ammonium molybdate with potassium elements that meet the standards, without the need to introduce other impurities, and more environmentally friendly.

[0016] 2. The present invention uses cheap and readily available chemical reagents as crystallization aids, can rapidly crystallize ammonium molybdate in an ammonium molybdate solution at room temperature, reduces the energy consumption of ammonium molybdate crystallization, and can simultaneously retain potassium ions with good water solubility in the liquid phase, thereby achieving separation of ammonium molybdate and potassium ions, and can be well used in preparing low-potassium ammonium molybdate and reducing the solubility of ammonium molybdate in a solution.

[0017] 3. The preparation process of the present invention has the advantages of simple operation, low energy consumption, good safety and high potassium removal rate, and provides a new method for preparing low-potassium ammonium molybdate, which is conducive to realizing industrial production.

[0018] 4. The crystallization aid provided by the present invention can be used to reduce the solubility of ammonium molybdate in the solution, can be used to prepare low-potassium ammonium molybdate, and improve the yield of metallic molybdenum.

[0019] 5. In the present invention, when low-potassium ammonium molybdate is prepared by using a crystallization aid, the pH value of the ammonium molybdate solution is between 5 and 11, indicating that the method of the present invention has a wide range of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a process flow chart for preparing low-potassium ammonium molybdate according to the present invention; Figure 2 XRD diffraction structure diagram of the standard samples of low potassium ammonium molybdate and diammonium molybdate prepared in Example 1; Figure 3 This is a scanning electron microscope image of the low-potassium ammonium molybdate prepared in Example 1. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0022] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0023] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0024] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0025] See also Figure 1 The present invention provides a process for preparing low-potassium ammonium molybdate by an auxiliary agent crystallization method, comprising the following steps: S1. Preparation of ammonium molybdate solution Using industrial molybdenum oxide as raw material, ammonium molybdate solution is obtained through ammonia leaching.

[0026] In this step, industrial molybdenum oxide is obtained by roasting molybdenum concentrate. The roasting method is an existing conventional method.

[0027] In this step, the ammonium molybdate solution is obtained by ammonia leaching, which is a conventional method.

[0028] S2. Preparation of low potassium ammonium molybdate by crystallization of auxiliary agent At room temperature, a crystallization aid is added to the ammonium molybdate solution in step S1, and the mixture is stirred evenly to allow the ammonium molybdate to crystallize rapidly into a solid, leaving potassium ions in the ammonium molybdate solution in the liquid phase to achieve rapid separation of ammonium molybdate and potassium ions, and then low-potassium ammonium molybdate is obtained by centrifugation and drying.

[0029] In this step, the stirring time is not less than 20 min.

[0030] Preferably, the stirring time is 20 min to 60 min; in practice, the stirring time is 20 min, 30 min, 40 min, 50 min or 60 min. In the present invention, ammonium molybdate completes rapid crystallization during the stirring process, thereby achieving rapid separation of ammonium molybdate and potassium ions.

[0031] In this step, the crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isopentanol, isopentyl glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid.

[0032] Preferably, the crystallization aid is methanol, ethanol, tetrahydrofuran or N,N-dimethylformamide.

[0033] In this step, the volume ratio of the ammonium molybdate solution to the crystallization aid is (0.5-3): 1. The molybdenum content in the ammonium molybdate solution is greater than 120 g / L.

[0034] During implementation, the volume ratio of the ammonium molybdate solution to the crystallization aid is 0.5:1, 0.555:1, 0.75:1, 1:1, 1.25:1, 1.5:1, 2:1, 2.25:1, 2.5:1, 2.75:1 or 3:1.

[0035] In this step, the pH value of the ammonium molybdate solution is between 5 and 11.

[0036] In implementation, the pH value of the ammonium molybdate solution is 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5 or 11. The allowable error range of the pH value when taking the above values ​​is ±0.2.

[0037] The potassium content of the low-potassium ammonium molybdate obtained by the preparation process of the present invention meets the standard, and the lowest potassium content reaches 0.0082%.

[0038] The invention discloses an application of a crystallization aid in the preparation of low-potassium ammonium molybdate.

[0039] Preferably, the crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isopentanol, isopentyl glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol, and phytic acid.

[0040] The following is a detailed description of the preparation process of low-potassium ammonium molybdate provided by the present invention with reference to several groups of embodiments.

[0041] It should be noted that, in the following examples, unless otherwise specified, the chemicals and reagents used are all conventional commercial products in the art.

[0042] It should be noted that, in the following embodiments, unless otherwise specified, the operations adopted are all conventional operations; for example, the operating temperature is all room temperature operation unless otherwise specified.

[0043] Example 1 This embodiment provides a process for preparing low-potassium ammonium molybdate by an auxiliary crystallization method, comprising the following steps: S1. Preparation of ammonium molybdate solution Using industrial molybdenum oxide as raw material, ammonium molybdate solution is obtained through ammonia leaching.

[0044] In this step, the ammonium molybdate solution is obtained by ammonia leaching, which is a conventional method.

[0045] In this step, the ammonium molybdate solution is obtained by ammonia leaching method, which is to crush industrial molybdenum oxide to a particle size of less than 75 microns, and soak it in ammonia water with a volume fraction of 15%-25% for 3 hours under heating conditions (temperature controlled at 50°C-90°C). At this time, the ammonia water reacts with the molybdenum component (such as molybdate) of the molybdenum concentrate, and the molybdenum in the molybdenum concentrate reacts with the ammonia water to form a molybdenum ammonia complex, such as molybdic acid ammonia complex dissolved in ammonia water, and then separated to obtain the supernatant, that is, the ammonium molybdate solution.

[0046] S2. Preparation of low potassium ammonium molybdate by crystallization of auxiliary agent At room temperature, a crystallization aid is added to the ammonium molybdate solution in step S1, and the mixture is stirred for 20 minutes until the crystallization is complete, and then low-potassium ammonium molybdate is obtained by centrifugation and drying.

[0047] At room temperature, the crystallization aid can significantly reduce the solubility of ammonium molybdate in the solution, causing the ammonium molybdate to quickly crystallize into a solid, leaving the potassium ions in the ammonium molybdate solution in the liquid phase, and achieving rapid separation of ammonium molybdate and potassium ions, thereby preparing low-potassium ammonium molybdate.

[0048] In this step S2, the crystallization aid is ethanol.

[0049] In step S2 of this embodiment, the process of preparing low-potassium ammonium molybdate by crystallization of the auxiliary agent is specifically as follows: S2.1, inject 8.33 L of ammonium molybdate solution into a 50 L glass reactor; In this step, the pH value of the ammonium molybdate solution is 9, and can also be any value within the range of 5-11; S2.2. Under stirring conditions, 15 L of crystallization aid was added into a 50 L reactor and mixed with the ammonium molybdate solution, and then stirred for 20 min until crystallization was complete; this indicated that ammonium molybdate could be rapidly crystallized into a solid in 20 min, thereby achieving rapid separation of ammonium molybdate and potassium ions.

[0050] S2.3, use suction filtration to separate the solid and liquid to obtain a filter cake.

[0051] S2.4. After drying the filter cake, low-potassium ammonium molybdate product is obtained, and the mass of the filter cake is weighed.

[0052] In this embodiment, the potassium concentration and the molybdenum concentration in the filter cake after drying, as well as the potassium concentration and the molybdenum concentration in the ammonium molybdate solution are detected, and the potassium removal rate and the direct recovery rate of molybdenum are calculated.

[0053] During the detection, when calculating the potassium removal rate and the direct recovery rate of molybdenum, in order to illustrate the stability of the method of this embodiment, three groups were repeated according to the process of Example 1, which were respectively recorded as Crystallization 1, Crystallization 2 and Crystallization 3. Then the potassium removal rate and the direct recovery rate of molybdenum were obtained by the following test method, and the results are shown in Tables 1 and 2.

[0054] The test method is as follows: (1) X-ray diffraction (XRD) analysis was used to determine the crystal form.

[0055] (2) Inductively coupled plasma (ICP) elemental analysis was used to detect the concentration of molybdenum element (Mo element) and potassium element (K element) in the ammonium molybdate product after filter cake drying.

[0056] (3) Inductively coupled plasma (ICP) elemental analysis was used to detect the concentration of molybdenum (Mo) and potassium (K) in the ammonium molybdate solution.

[0057] The specific operations are as follows: a) First, prepare the sample to be tested. Use an analytical balance to accurately weigh about 65 mg of the sample, place it in a polytetrafluoroethylene beaker, add a small amount of water to moisten the sample, add 5 mL of hydrochloric acid, heat it on a hot plate at low temperature, and add 15 mL of nitric acid when it evaporates to about 5 mL. Continue heating and evaporate until it is almost viscous. Add 5 mL of hydrofluoric acid and continue heating. Finally, add 2 mL of perchloric acid and heat until the white smoke is basically gone. Rinse the inner wall and beaker with nitric acid solution, dissolve the residue with warm water, cool it, dilute it to 25 mL with 1% nitric acid, and shake it well for testing.

[0058] b) Use national standard substances to prepare molybdenum standard solutions with a concentration gradient of 0, 5, 10, 15, and 20 mg / L.

[0059] c) Use national standard substances to prepare potassium standard solutions with a concentration gradient of 0.01, 0.02, 0.04, and 0.06 mg / L.

[0060] d) Use ICP-OES instrument to measure the standard solutions of molybdenum and potassium in turn and draw calibration curves.

[0061] e) The solution to be tested is introduced into the ICP-OES instrument to measure the signal intensity of molybdenum and potassium elements in turn.

[0062] f) Calculate the concentration of molybdenum and potassium in the sample based on the calibration curve, and calculate their content based on the sample mass.

[0063] (4) Calculate the mass of Mo element input = Mo element concentration in ammonium molybdate solution × volume of ammonium molybdate solution input.

[0064] (5) Calculate the mass of Mo element in the filter cake = mass of dried filter cake × mass concentration of Mo element in the filter cake.

[0065] (6) Molybdenum direct recovery rate = (Mo element mass in filter cake / Mo element mass input) × 100%.

[0066] (7) Calculate the mass of K element input = K element concentration in ammonium molybdate solution × volume of ammonium molybdate solution input.

[0067] (8) Calculate the mass of K element in the filter cake = mass of dried filter cake × mass concentration of K element in the filter cake.

[0068] (9) Potassium removal rate = [1-(mass of K element in filter cake / mass of K element input)] × 100%; (10) The dispersion of the crystals was observed using a scanning electron microscope.

[0069] Specifically, the low potassium ammonium molybdate prepared in this embodiment is used as the Mo experimental sample, and the standard diammonium molybdate crystal is used as the Mo standard sample. The XRD diffraction structure diagrams of the two groups of samples are tested respectively. Figure 2 As shown; the scanning electron microscope image of the low potassium ammonium molybdate prepared in this embodiment was also tested, as shown Figure 3 shown.

[0070] according to Figure 2 From the XRD analysis of low-potassium ammonium molybdate, it can be seen that the XRD characteristic peaks of the low-potassium ammonium molybdate prepared in this embodiment are consistent with the XRD characteristic peaks of standard diammonium molybdate, indicating that the low-potassium ammonium molybdate prepared in this embodiment is diammonium molybdate. Figure 3 The scanning electron microscope image analysis shows that the low-potassium ammonium molybdate crystal particles prepared in this embodiment have good dispersibility.

[0071] Table 1 Mo element test analysis results in Example 1 Table 2 K element test analysis results in Example 1 It can be seen from Table 1 and Table 2 that, by using the process of this embodiment, the potassium removal rate is as high as 65.07%, the direct recovery rate of metal Mo is 80.47%-83.70%, and the mass concentration of potassium in the obtained low ammonium molybdate product is below 0.0098%, and the lowest can reach 0.0082%. It shows that the process for preparing low-potassium ammonium molybdate provided in this embodiment not only has a high potassium removal rate, but also a high direct recovery rate of metal Mo; at the same time, the potassium content in the obtained low-potassium ammonium molybdate product is low, which meets the potassium content requirement of the ammonium molybdate product.

[0072] In addition, through the comparison of the three sets of data, the concentration of the Mo element in the filter cake and the concentration of the K element in the filter cake are both in a stable state without large fluctuations, indicating that the process provided in this embodiment has good stability.

[0073] Example 2 This embodiment provides an application of a crystallization aid in the preparation of low-potassium ammonium molybdate.

[0074] In this embodiment, the crystallization aid can reduce the solubility of ammonium molybdate in the solution, realize the rapid crystallization of ammonium molybdate, thereby leaving potassium ions with good water solubility in the liquid phase, and realize the separation of ammonium molybdate and potassium ions; at the same time, the crystallization aid can crystallize ammonium molybdate in the ammonium molybdate solution at room temperature, and reduce the energy consumption of ammonium molybdate crystallization.

[0075] Preferably, the crystallization aid is ethanol.

[0076] In this embodiment, when a crystallization aid is used to prepare low-potassium ammonium molybdate, industrial molybdenum oxide is first used as a raw material to obtain an ammonium molybdate solution by an ammonia leaching method. At room temperature, a crystallization aid is added to the ammonium molybdate solution, and the mixture is stirred for 20 minutes until crystallization is complete. Low-potassium ammonium molybdate is then obtained by centrifugation and drying.

[0077] In this embodiment, the step of obtaining the ammonium molybdate solution by ammonia leaching can refer to Example 1. The ratio and concentration of the ammonium molybdate solution and the crystallization aid can refer to Example 1.

[0078] Example 3 This embodiment provides an application of a crystallization aid in reducing the solubility of ammonium molybdate.

[0079] In this embodiment, the crystallization aid is ethanol.

[0080] In this embodiment, the method for reducing the solubility of ammonium molybdate is: adding a crystallization aid to the ammonium molybdate solution at room temperature, thereby reducing the solubility of ammonium molybdate.

[0081] In this embodiment, the step of obtaining the ammonium molybdate solution by ammonia leaching can refer to Example 1. The ratio and concentration of the ammonium molybdate solution and the crystallization aid can refer to Example 1.

[0082] In the above-mentioned Examples 1 to 3, the crystallization aid can also be replaced by ethanol, isopropanol, isobutanol, isopentanol, isopentanol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol or phytic acid, and can also be replaced by methanol, ethanol, isopropanol, isobutanol, isopentanol, isopentanol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid.

[0083] In the above-mentioned Example 1 and Example 2, the volume ratio of the ammonium molybdate solution to the crystallization aid may also be any other ratio within (0.5-3):1.

[0084] Furthermore, the concentration of potassium in the ammonium molybdate solution obtained by the ammonia leaching method in Example 1 is 0.10 g / L, which is a normal potassium content. However, due to the different potassium contents in the molybdenum oxide ore, the potassium content may be higher. Therefore, it is also verified that low-potassium ammonium molybdate is prepared from high-potassium ammonium molybdate solution by the auxiliary crystallization method.

[0085] Verification Example A process for preparing low-potassium ammonium molybdate by an auxiliary agent crystallization method comprises the following steps: S1. Preparation of ammonium molybdate solution Using industrial molybdenum oxide as raw material, ammonium molybdate solution is obtained through ammonia leaching.

[0086] In this step, the ammonium molybdate solution is obtained by ammonia leaching, which is a conventional method.

[0087] S2. Preparation of low potassium ammonium molybdate by crystallization of auxiliary agent In this step, potassium is additionally added to the ammonium molybdate solution to form a high potassium ammonium molybdate solution.

[0088] At room temperature, a crystallization aid is added to the high potassium ammonium molybdate solution in step S1, and the mixture is stirred for 20 minutes until the crystallization is complete, and then low potassium ammonium molybdate is obtained by centrifugation and drying.

[0089] At room temperature, the crystallization aid can significantly reduce the solubility of ammonium molybdate in the solution, causing the ammonium molybdate to quickly crystallize into a solid, leaving the potassium ions in the ammonium molybdate solution in the liquid phase, and achieving rapid separation of ammonium molybdate and potassium ions, thereby preparing low-potassium ammonium molybdate.

[0090] In this step, the crystallization aid is methanol.

[0091] In step S2 of this embodiment, the process of preparing low-potassium ammonium molybdate by crystallization of the auxiliary agent is specifically as follows: S2.1, inject 8.33 L of ammonium molybdate solution into a 50 L glass reactor; In this step, the pH value of the ammonium molybdate solution is 5, or any value within the range of 5-11; S2.2, dissolve 0.866 g of KOH solid in 50 mL of deionized water, inject the KOH solution into a glass reactor to obtain a high potassium ammonium molybdate solution; S2.3, under stirring conditions, add 15 L of crystallization aid into a 50 L reactor and mix with the high potassium ammonium molybdate solution, and stir for 20 min until crystallization is complete; S2.4, use suction filtration to separate the solid and liquid to obtain a filter cake, i.e., ammonium molybdate product.

[0092] S2.5. After drying the filter cake, the ammonium molybdate product is obtained, and the mass of the filter cake is weighed.

[0093] The potassium and molybdenum concentrations in the ammonium molybdate solution (the ammonium molybdate solution here is a high-potassium ammonium molybdate solution after additional KOH is added, i.e. 8.33+0.05=8.38L) are detected, and the potassium and molybdenum concentrations in the filter cake after drying are detected, and the potassium removal rate and the direct recovery rate of molybdenum are calculated.

[0094] During the test, the above process was repeated for three groups, which were respectively recorded as Crystallization 4, Crystallization 5 and Crystallization 6. Then, the potassium removal rate and the direct recovery rate of molybdenum were obtained by referring to the test method of the embodiment. The results are shown in Tables 3 and 4.

[0095] Table 3 Test and analysis results of Mo element in verification example Table 4 Verification example K element test analysis results It can be seen from Tables 3 and 4 that the direct recovery rate of metal Mo is above 77%, with the highest reaching 78.73%; After the high-potassium ammonium molybdate solution is crystallized with an auxiliary agent, the potassium removal rate is 51.15%-58.53%; in the ammonium molybdate obtained after crystallization, the mass concentration of potassium element is 0.0160%-0.0178%. It can be seen that for the high-potassium ammonium molybdate solution, the auxiliary agent crystallization method provided by the present invention not only has a high direct yield of metal Mo, but also can remove more than 50% of the potassium element, and obtain an ammonium molybdate product with a low potassium content. It can be seen that the preparation process of the present invention is also suitable for preparing a low-potassium ammonium molybdate product from a high-potassium ammonium molybdate solution.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the present invention, although the present invention has been described in detail with reference to the preferred embodiments. It should be understood by those skilled in the art that the technical solutions of the present invention can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A process for preparing low-potassium ammonium molybdate by an auxiliary crystallization method, characterized in that: The following steps are involved: S1. Preparation of ammonium molybdate solution Using industrial molybdenum oxide as raw material, ammonium molybdate solution is obtained through ammonia leaching; S2. Preparation of low potassium ammonium molybdate by crystallization of auxiliary agent At room temperature, a crystallization aid is added to the ammonium molybdate solution in step S1, the mixture is stirred evenly and the ammonium molybdate is rapidly crystallized into a solid, the potassium ions in the ammonium molybdate solution are retained in the liquid phase, the ammonium molybdate and the potassium ions are rapidly separated, and low-potassium ammonium molybdate is obtained by centrifugation and drying; The crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isopentanol, isopentandiol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid.

2. The process for preparing low-potassium ammonium molybdate by the auxiliary agent crystallization method according to claim 1, characterized in that: In step S2, the volume ratio of the ammonium molybdate solution to the crystallization aid is (0.5-3):1; the molybdenum content in the ammonium molybdate solution is greater than 120 g / L.

3. The process for preparing low-potassium ammonium molybdate by the auxiliary agent crystallization method according to claim 1, characterized in that: In step S2, the pH value of the ammonium molybdate solution is between 5 and 11.

4. The process for preparing low-potassium ammonium molybdate by the auxiliary agent crystallization method according to claim 1, characterized in that: In step S2, the stirring time is not less than 20 minutes.

5. The process for preparing low-potassium ammonium molybdate by the auxiliary agent crystallization method according to claim 1, characterized in that: In the low-potassium ammonium molybdate of step S2, the mass concentration of potassium element reaches as low as 0.0082%.

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