Process for preparing ammonium molybdate with low potassium content by an auxiliary agent crystallization method

Abstract

The present invention belongs to the technical field of the preparation of ammonium molybdate with low potassium content, and relates to a process for preparing ammonium molybdate with low potassium content by an auxiliary crystallization method, which comprises the following steps: S1. Preparation of ammonium molybdate solution: Using industrial molybdenum oxide as a raw material, an ammonium molybdate solution is obtained by an ammonia leaching method; S2. Preparation of ammonium molybdate with low potassium content by auxiliary crystallization: At room temperature, a crystallization aid is added to the ammonium molybdate solution in step S1, and stirred evenly to make the ammonium molybdate quickly crystallize into a solid, leaving the potassium ions in the ammonium molybdate solution in the liquid phase, realizing the rapid separation of ammonium molybdate from potassium ions, and then obtaining ammonium molybdate with low potassium content through centrifugation and drying. By adding a crystallization aid, the present invention realizes the rapid separation of ammonium molybdate from potassium ions, prepares ammonium molybdate with low potassium content, without introducing other impurities, and is more environmentally friendly.

Description

Technical Field

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

[0002] Molybdenum targets are widely used in physical vapor deposition (PVD) and magnetron sputtering technologies, mainly for making thin film electrodes, which play a key role in devices such as display screens, solar cells, and semiconductors. However, in applications, the potassium element contained in the molybdenum target belongs to harmful impurities because under high-temperature and high-pressure production conditions, the potassium element in the molybdenum target is easily broken down into bad points, affecting the qualification rate of the device. In addition, during the high-temperature sintering process or when used as an electro-light source material, the potassium element will volatilize in a gaseous state and corrode heating elements, refractory materials, and thermal insulation materials in the form of a strong base after absorbing moisture, thus contaminating the product surface.

[0003] Currently, the raw material for preparing molybdenum targets 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, strict control of potassium elements can be carried out from the source, that is, strict control of the potassium content in ammonium molybdate; however, since the potassium element in ammonium molybdate mainly comes from molybdenum ore, and the concentration of potassium elements in different molybdenum ores is difficult to predict. Therefore, strict control of potassium content is a key technical issue for the ammonium molybdate industry and has important scientific and economic significance.

[0004] Currently, the method for preparing ammonium molybdate with low potassium content is as follows: First, roast molybdenum concentrate to obtain industrial molybdenum oxide, then reduce the potassium element content in industrial molybdenum oxide by pickling or water washing, and then obtain ammonium molybdate with low potassium content through ammonia leaching and evaporation crystallization. However, pickling or water washing has the following problems:

[0005] (1) When pickling reduces the potassium element content, since molybdenum dioxide will react to form hydrates and molybdenum trioxide soluble in water under acidic conditions, it is not conducive to subsequent solid-liquid separation; in addition, the pickling process will introduce anions such as nitrate ions and chloride ions into the production process, thus causing uncontrollable environmental protection problems;

[0006] (2) When water washing reduces the potassium element content, since ammonium molybdate uses industrial molybdenum oxide as a raw material, water washing is adopted, and then through a series of processes such as ammonia leaching and crystallization, the process route is slightly longer, and water washing requires a large amount of water resources. At the same time, water washing will also wash out molybdenum elements, reducing the molybdenum recovery rate; when the potassium content in industrial molybdenum oxide is high, it is difficult to obtain a product with a qualified potassium content by the water washing process.

[0007] In summary, the existing methods for reducing the potassium element content not only introduce other impurities in the process, resulting in environmental unfriendliness, but also make it difficult to separate potassium ions from ammonium molybdate solution during the subsequent crystallization process of ammonium molybdate, leading to an excessive potassium element content in ammonium molybdate. Therefore, developing a new process for preparing low-potassium ammonium molybdate is the current research focus. Summary of the Invention

[0008] Aiming at the technical problems of environmental unfriendliness caused by introducing other impurities and excessive potassium element content in the existing preparation of low-potassium ammonium molybdate, the present invention provides a process for preparing low-potassium ammonium molybdate by an auxiliary crystallization method.

[0009] The present invention first obtains ammonium molybdate solution by an ammonia leaching method, and then adds a crystallization aid to the ammonium molybdate solution to rapidly separate ammonium molybdate from potassium ions at room temperature, thereby preparing low-potassium ammonium molybdate with a qualified potassium element content without introducing other impurities, which is more environmentally friendly.

[0010] The crystallization aid provided by the present invention can be used to reduce the solubility of ammonium molybdate in solution; it can also be used to prepare low-potassium ammonium molybdate.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A process for preparing low-potassium ammonium molybdate by an auxiliary crystallization method, comprising the following steps:

[0013] S1. Prepare ammonium molybdate solution

[0014] Using industrial molybdenum oxide as raw material, obtain ammonium molybdate solution by an ammonia leaching method;

[0015] S2. Prepare low-potassium ammonium molybdate by auxiliary crystallization

[0016] At room temperature, add a crystallization aid to the ammonium molybdate solution in step S1, stir evenly and make ammonium molybdate rapidly crystallize into a solid, leaving potassium ions in the ammonium molybdate solution in the liquid phase to achieve rapid separation of ammonium molybdate from potassium ions, and then obtain low-potassium ammonium molybdate through centrifugation and drying.

[0017] In step S2, the crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isoamyl alcohol, isoamylene glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid.

[0018] Further limited, in step S2, the volume ratio of ammonium molybdate solution to crystallization aid is (0.5 - 3):1; in the ammonium molybdate solution, the molybdenum content is greater than 120 g / L.

[0019] Further limited, in step S2, the pH value of the ammonium molybdate solution is between 5 and 11.

[0020] Further limitation: in the step S2, the stirring time is not less than 20 min.

[0021] Further limitation: in the ammonium molybdate with low potassium in the step S2, the mass concentration of potassium element reaches at least 0.0082%.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. In the present invention, ammonium molybdate solution is first formed by ammonia leaching of molybdenum trioxide, and then a crystallization aid is added to the ammonium molybdate solution. Since ammonium molybdate is a polar molecule and is easily soluble in polar solvents, while the crystallization aid is a weakly polar compound. Therefore, after adding the crystallization aid to the ammonium molybdate solution, the overall polarity of the ammonium molybdate solution decreases, resulting in a decrease in 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, cause ammonium molybdate to quickly crystallize into a solid, leave potassium ions in the ammonium molybdate solution in the liquid phase, realize the rapid separation of ammonium molybdate and potassium ions, and thus prepare ammonium molybdate with qualified potassium element without introducing other impurities, which is more environmentally friendly.

[0024] 2. The present invention uses inexpensive and easily available chemical reagents as the crystallization aid, which can cause ammonium molybdate in the ammonium molybdate solution to quickly crystallize at room temperature, reduce the energy consumption of ammonium molybdate crystallization, and at the same time can leave potassium ions with good water solubility in the liquid phase, realizing the separation of ammonium molybdate and potassium ions, and can be well used for preparing ammonium molybdate with low potassium and reducing the solubility of ammonium molybdate in the solution.

[0025] 3. The preparation process of the present invention is simple in operation, low in energy consumption, good in safety and high in potassium removal rate, providing a new method for preparing ammonium molybdate with low potassium, which is beneficial to realizing industrial production.

[0026] 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 ammonium molybdate with low potassium, and improve the recovery rate of metallic molybdenum.

[0027] 5. When preparing ammonium molybdate with low potassium by using the crystallization aid in the present invention, the pH value of the ammonium molybdate solution is between 5 and 11, indicating that the method of the present invention has a wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the process flow chart of the preparation process of ammonium molybdate with low potassium of the present invention;

[0029] Figure 2 is the XRD diffraction structure diagram of the ammonium molybdate with low potassium prepared in Example 1 and the standard sample of diammonium molybdate;

[0030] Figure 3 is the scanning electron microscope image of the ammonium molybdate with low potassium prepared in Example 1. Detailed Embodiments

[0031] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs.

[0033] For technologies, methods, and devices known to those of ordinary skill in the relevant fields, they may not be discussed in detail, but in appropriate cases, the said technologies, methods, and devices should be regarded as part of the specification.

[0034] 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 person skilled in the art within the technical scope disclosed by the present invention, according to the technical solutions and inventive concepts of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

[0035] See Figure 1 , the present invention provides a process for preparing ammonium molybdate with low potassium content by an auxiliary crystallization method, which includes the following steps:

[0036] S1. Preparation of ammonium molybdate solution

[0037] Using industrial molybdenum oxide as the raw material, ammonium molybdate solution is obtained by ammonia leaching method.

[0038] In this step, industrial molybdenum oxide is obtained by roasting molybdenum concentrate. The roasting method is a conventional method in the prior art.

[0039] In this step, the method of obtaining ammonium molybdate solution by ammonia leaching is a conventional method in the prior art.

[0040] S2. Preparation of ammonium molybdate with low potassium content by auxiliary crystallization

[0041] At room temperature, a crystallization aid is added to the ammonium molybdate solution in step S1, stirred evenly to make ammonium molybdate quickly crystallize into a solid, leaving potassium ions in the ammonium molybdate solution in the liquid phase, realizing the rapid separation of ammonium molybdate from potassium ions, and then obtaining ammonium molybdate with low potassium content through centrifugation and drying.

[0042] In this step, the stirring time is not less than 20 min.

[0043] Preferably, the stirring time is 20 min - 60 min; in practice, the stirring time is 20 min, 30 min, 40 min, 50 min or 60 min. In the process of stirring in the present invention, ammonium molybdate completes rapid crystallization, thus realizing the rapid separation of ammonium molybdate from potassium ions.

[0044] In this step, the crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isoamyl alcohol, isopentyl glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol, and phytic acid.

[0045] Preferably, the crystallization aid is methanol, ethanol, tetrahydrofuran, or N,N-dimethylformamide.

[0046] In this step, the volume ratio of the ammonium molybdate solution to the crystallization aid is (0.5 - 3):1. In the ammonium molybdate solution, the molybdenum content is greater than 120 g / L.

[0047] In 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.

[0048] In this step, the pH value of the ammonium molybdate solution is between 5 and 11.

[0049] 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 for the pH value within the above values is ±0.2.

[0050] Through the above preparation process of the present invention, in the obtained low-potassium ammonium molybdate, the potassium element content meets the standard, and the potassium element reaches a minimum of 0.0082%.

[0051] An application of a crystallization aid in the preparation of low-potassium ammonium molybdate.

[0052] Preferably, the crystallization aid is one or more of methanol, ethanol, isopropanol, isobutanol, isoamyl alcohol, isopentyl glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol, phytic acid.

[0053] The following uses several examples to illustrate in detail the preparation process of low-potassium ammonium molybdate provided by the present invention.

[0054] It should be noted that in the following examples, unless otherwise specified, the chemical drugs and chemical reagents used are all conventional commercially available products in the art.

[0055] It should be noted that in the following examples, unless otherwise specified, the operations used are all conventional operations; for example, unless otherwise specified, the operating temperature is at room temperature.

[0056] Example 1

[0057] This example provides a process for preparing low-potassium ammonium molybdate by the crystallization aid method, including the following steps:

[0058] S1. Preparation of ammonium molybdate solution

[0059] Using industrial molybdenum oxide as raw material, ammonium molybdate solution is obtained by ammonia leaching method.

[0060] In this step, the method of obtaining ammonium molybdate solution by ammonia leaching is a conventional existing method.

[0061] In this step, the method of obtaining ammonium molybdate solution by ammonia leaching is to crush industrial molybdenum oxide to a particle size less than 75 microns, 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, ammonia water reacts with the molybdenum component (such as molybdate) in molybdenum concentrate, and the molybdenum in molybdenum concentrate forms an ammonia complex of molybdenum through reaction with ammonia water. For example, ammonium molybdate complex dissolves in ammonia water, and then the supernatant is separated to obtain ammonium molybdate solution.

[0062] S2. Preparation of low-potassium ammonium molybdate by crystallization with additives

[0063] At room temperature, crystallization additives are added to the ammonium molybdate solution in step S1, stirred for 20 minutes until crystallization is complete, and then low-potassium ammonium molybdate is obtained by centrifugation and drying.

[0064] At room temperature, the crystallization additives can significantly reduce the solubility of ammonium molybdate in the solution, cause ammonium molybdate to quickly crystallize into a solid, leave the potassium ions in the ammonium molybdate solution in the liquid phase, and achieve the rapid separation of ammonium molybdate and potassium ions, thereby preparing low-potassium ammonium molybdate.

[0065] In this step S2, the crystallization additive is ethanol.

[0066] In step S2 of this embodiment, the process of preparing low-potassium ammonium molybdate by crystallization with additives is specifically as follows:

[0067] S2.1. Inject 8.33 L of ammonium molybdate solution into a 50 L glass reaction kettle;

[0068] In this step, the pH value of the ammonium molybdate solution is 9, and it can also be any value within 5 - 11;

[0069] S2.2. Under stirring conditions, add 15 L of crystallization additives to the 50 L reaction kettle and mix with the ammonium molybdate solution, then stir for 20 minutes until crystallization is complete; It shows that 20 minutes makes ammonium molybdate quickly crystallize into a solid, thereby achieving the rapid separation of ammonium molybdate and potassium ions.

[0070] S2.3. Use suction filtration for solid-liquid separation to obtain a filter cake.

[0071] S2.4. After drying the filter cake, a low-potassium ammonium molybdate product is obtained, and the mass of the filter cake is weighed.

[0072] In this embodiment, the concentrations of potassium and molybdenum elements in the filter cake after drying are detected, as well as the concentrations of potassium and molybdenum elements in the ammonium molybdate solution, and the potassium removal rate and the direct recovery rate of molybdenum are calculated.

[0073] During the detection and calculation of the potassium removal rate and the direct recovery rate of molybdenum, in order to illustrate the stability of the method of this embodiment, the process of Example 1 is repeated three groups, which are respectively recorded as crystallization 1, crystallization 2, and crystallization 3. Then, the potassium removal rate and the direct recovery rate of molybdenum are obtained through the following test methods, and the results are shown in Table 1 and Table 2.

[0074] The test method is as follows:

[0075] (1)Use X-ray diffraction (XRD) analysis to determine the crystal form of the crystal.

[0076] (2)Use inductively coupled plasma ICP elemental analysis to detect the concentration of molybdenum element (Mo element) and potassium element (K element) in the ammonium molybdate product after drying the filter cake.

[0077] (3)Use inductively coupled plasma ICP elemental analysis to detect the concentration of molybdenum element (Mo element) and potassium element (K element) in the ammonium molybdate solution.

[0078] The specific operations are as follows:

[0079] 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 at a low temperature on a hot plate, evaporate until about 5 mL remains, add 15 mL of nitric acid, continue heating until it is nearly viscous, add 5 mL of hydrofluoric acid and continue heating, and finally add 2 mL of perchloric acid and heat until the white smoke basically disappears. Rinse the inner wall and the beaker with nitric acid solution, warm it to dissolve the residue, cool it, and make the volume up to 25 mL with 1% nitric acid, and shake well for testing.

[0080] b) Prepare molybdenum standard solutions using national standard substances, and the concentration gradients are: 0, 5, 10, 15, 20 mg / L.

[0081] c) Prepare potassium standard solutions using national standard substances, and the concentration gradients are: 0.01, 0.02, 0.04, 0.06 mg / L.

[0082] d) Use an ICP-OES instrument to sequentially measure the standard solutions of molybdenum and potassium elements, and draw a calibration curve.

[0083] e) Introduce the solution to be tested into the ICP-OES instrument, and sequentially measure the signal intensities of molybdenum and potassium elements.

[0084] f) Calculate the concentrations of molybdenum and potassium elements in the sample according to the calibration curve, and calculate their contents in combination with the sample mass.

[0085] (4) Calculate the mass of Mo element input = concentration of Mo element in ammonium molybdate solution × volume of ammonium molybdate solution input.

[0086] (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.

[0087] (6) Direct recovery rate of molybdenum = (mass of Mo element in the filter cake / mass of Mo element input) × 100%.

[0088] (7) Calculate the mass of K element input = concentration of K element in ammonium molybdate solution × volume of ammonium molybdate solution input.

[0089] (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.

[0090] (9) Potassium removal rate = [1 - (mass of K element in the filter cake / mass of K element input)] × 100%;

[0091] (10) Use a scanning electron microscope to observe the dispersion of the crystals.

[0092] Specifically, use the low-potassium ammonium molybdate prepared in this example as the Mo experimental sample, and use the standard ammonium di-molybdate crystal as the Mo standard sample to test the XRD diffraction pattern diagrams of the two groups of samples respectively, as Figure 2 shown; also test the scanning electron microscope image of the low-potassium ammonium molybdate prepared in this example, as Figure 3 shown.

[0093] According to Figure 2 the XRD analysis of the low-potassium ammonium molybdate in Figure 3 it can be seen that the XRD characteristic peaks of the low-potassium ammonium molybdate prepared in this example are consistent with those of the standard ammonium di-molybdate, indicating that the low-potassium ammonium molybdate prepared in this example is ammonium di-molybdate. From

[0094] Table 1 Test analysis results of Mo element in Example 1

[0095]

[0096] Table 2 Test analysis results of K element in Example 1

[0097]

[0098] As can be seen from Table 1 and Table 2, using the process of this embodiment, the potassium removal rate reaches a maximum of 65.07%, the direct recovery rate of metallic Mo is between 80.47% and 83.70%, the mass concentration of potassium element in the obtained ammonium molybdate product with low molybdenum is below 0.0098%, and can reach as low as 0.0082%. It shows that the process for preparing ammonium molybdate with low potassium provided by this embodiment not only has a high potassium removal rate, but also has a relatively high direct recovery rate of metallic Mo; at the same time, the potassium content in the obtained ammonium molybdate product with low potassium is low, meeting the content requirements of potassium element in ammonium molybdate products.

[0099] In addition, through the comparison of three groups of data, the concentration of Mo element in the filter cake and the concentration of K element in the filter cake are both in a stable state without significant fluctuations, indicating that the process provided by this embodiment has good stability.

[0100] Example 2

[0101] This embodiment provides an application of a crystallization aid in the preparation of ammonium molybdate with low potassium.

[0102] In this embodiment, the crystallization aid can reduce the solubility of ammonium molybdate in the solution, realize the rapid crystallization of ammonium molybdate, so as to leave the potassium ions with good water solubility in the liquid phase, realizing the separation of ammonium molybdate and potassium ions; at the same time, the crystallization aid can make ammonium molybdate in the ammonium molybdate solution crystallize at room temperature, reducing the energy consumption of ammonium molybdate crystallization.

[0103] Preferably, the crystallization aid is ethanol.

[0104] In this embodiment, when using a crystallization aid to prepare ammonium molybdate with low potassium, industrial molybdenum oxide is used as the raw material, and ammonium molybdate solution is obtained by ammonia leaching. At room temperature, a crystallization aid is added to the ammonium molybdate solution, and stirred for 20 minutes until crystallization is complete, and then ammonium molybdate with low potassium is obtained by centrifugation and drying.

[0105] In this embodiment, the step of obtaining ammonium molybdate solution by ammonia leaching can refer to Example 1. The ratio, concentration, etc. of ammonium molybdate solution and crystallization aid refer to Example 1.

[0106] Example 3

[0107] This embodiment provides an application of a crystallization aid in reducing the solubility of ammonium molybdate.

[0108] In this embodiment, the crystallization aid is ethanol.

[0109] In this embodiment, the method for reducing the solubility of ammonium molybdate is: at room temperature, a crystallization aid is added to the ammonium molybdate solution, thereby reducing the solubility of ammonium molybdate.

[0110] In this embodiment, the step of obtaining ammonium molybdate solution by ammonia leaching can refer to Example 1. The ratio, concentration, etc. of ammonium molybdate solution and crystallization aid refer to Example 1.

[0111] In the above Examples 1 to 3, the crystallization aid can also be replaced with ethanol, isopropanol, isobutanol, isoamyl alcohol, isopentylene glycol, acetone, methyl ethyl ketone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol or phytic acid, or can also be replaced with a variety of methanol, ethanol, isopropanol, isobutanol, isoamyl alcohol, isopentylene glycol, acetone, methyl ethyl ketone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid.

[0112] In the above Examples 1 and 2, the volume ratio of ammonium molybdate solution to the crystallization aid can also be any other ratio within (0.5 - 3):1.

[0113] Furthermore, in the ammonium molybdate solution obtained by the ammonia leaching method in Example 1, the concentration of potassium element is 0.10 g / L, which belongs to the normal potassium content. However, due to the different potassium element contents in molybdenum oxide ore, the potassium element content may be relatively high. Therefore, the preparation of low-potassium ammonium molybdate from high-potassium ammonium molybdate solution by the crystallization method with an aid was also verified.

[0114] Verification Example

[0115] A process for preparing low-potassium ammonium molybdate by the crystallization method with an aid includes the following steps:

[0116] S1. Preparation of ammonium molybdate solution

[0117] Using industrial molybdenum oxide as the raw material, ammonium molybdate solution is obtained by the ammonia leaching method.

[0118] In this step, the method for obtaining ammonium molybdate solution by the ammonia leaching method is a conventional existing method.

[0119] S2. Preparation of low-potassium ammonium molybdate by crystallization with an aid

[0120] In this step, potassium is additionally added to the ammonium molybdate solution to form a high-potassium ammonium molybdate solution.

[0121] At room temperature, a crystallization aid is added to the high-potassium ammonium molybdate solution in step S1, stirred for 20 min until crystallization is complete, and then low-potassium ammonium molybdate is obtained by centrifugation and drying.

[0122] At room temperature, the crystallization aid can significantly reduce the solubility of ammonium molybdate in the solution, cause ammonium molybdate to quickly crystallize into a solid, leave the potassium ions in the ammonium molybdate solution in the liquid phase, realize the rapid separation of ammonium molybdate and potassium ions, and thus prepare low-potassium ammonium molybdate.

[0123] In this step, the crystallization aid is methanol.

[0124] In step S2 of this example, the process of preparing low-potassium ammonium molybdate by crystallization with an aid is specifically as follows:

[0125] S2.1. Inject 8.33 L of ammonium molybdate solution into a 50 L glass reactor;

[0126] In this step, the pH value of the ammonium molybdate solution is 5, or any value within 5 - 11;

[0127] S2.2. Dissolve 0.866 g of solid KOH in 50 mL of deionized water, and inject the KOH solution into the glass reactor to obtain a high - potassium ammonium molybdate solution;

[0128] S2.3. Under stirring conditions, add 15 L of crystallization aid to the 50 L reactor and mix it with the high - potassium ammonium molybdate solution, then stir for 20 min until crystallization is complete;

[0129] S2.4. Use suction filtration for solid - liquid separation to obtain a filter cake, which is the ammonium molybdate product.

[0130] S2.5. After drying the filter cake, obtain the ammonium molybdate product and weigh the mass of the filter cake.

[0131] Detect the potassium element concentration and molybdenum element concentration in the ammonium molybdate solution (here the ammonium molybdate solution is the high - potassium ammonium molybdate solution after adding KOH, that is, 8.33 + 0.05 = 8.38 L), detect the potassium element concentration and molybdenum element concentration in the dried filter cake, and calculate the potassium removal rate and the direct recovery rate of molybdenum.

[0132] During the experiment, repeat the above process three times, which are respectively recorded as crystallization 4, crystallization 5, and crystallization 6. Then, refer to the test method of the example to obtain the potassium removal rate and the direct recovery rate of molybdenum, and the results are shown in Table 3 and Table 4.

[0133] Table 3 Test analysis results of Mo element in verification examples

[0134]

[0135] Table 4 Test analysis results of K element in verification examples

[0136]

[0137] It can be seen from Table 3 and Table 4 that the direct recovery rate of metal Mo is above 77%, and the highest reaches 78.73%;

[0138] After the high-potassium ammonium molybdate solution is crystallized with the aid of additives, the potassium removal rate is between 51.15% and 58.53%; in the ammonium molybdate obtained after crystallization, the mass concentration of potassium element is between 0.0160% and 0.0178%. It can be seen that for the high-potassium ammonium molybdate solution, by using the crystallization method with additives provided by the present invention, not only the direct recovery rate of metal Mo is relatively high, but also more than 50% of potassium element can be removed, and an ammonium molybdate product with a relatively low potassium element content can be obtained. It can be seen that the preparation process of the present invention is also applicable to the preparation of low-potassium ammonium molybdate products from high-potassium ammonium molybdate solutions.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments. Those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions 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: 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, isopentyl glycol, acetone, butanone, tetrahydrofuran, N,N-dimethylformamide, acetonitrile, petroleum ether, triethanolamine, inositol and phytic acid; 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; In step S2, the pH value of the ammonium molybdate solution is between 5 and 11.

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 stirring time is not less than 20 minutes.

3. 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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