Optimized method for preparing high-purity ammonium molybdate by taking crude molybdic acid as raw material

Abstract

The invention discloses a method for optimizing preparation of high-purity ammonium molybdate by taking crude molybdic acid as a raw material, and relates to the technical field of preparation of high-purity ammonium molybdate, the method comprises the following steps: adding an organic acid solution into crude molybdic acid for washing, and filtering to obtain a molybdic acid filter cake and a washing solution; adding an ammonia water solution into the molybdic acid filter cake for leaching, and filtering and washing to obtain ammonia leaching liquid and ammonia insoluble slag; and adsorbing the ammonia leaching solution by using tungsten resin, resolving by using ammonia water with the mass fraction of 10% after the tungsten removal resin is saturated to obtain an ammonium tungstate solution and a tungsten removal tail solution, and recovering tungsten salt from the ammonium tungstate solution. The quality of the ammonium molybdate product prepared by the process disclosed by the invention meets the MSA-0 standard; the method has the advantages of simple process control, high molybdenum recovery rate, stable product quality, no pollution to the environment, repeated use of the washing liquid, reduction of wastewater discharge, meeting of clean production requirements and the like, and is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of high-purity ammonium molybdate preparation, and in particular to a method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material. Background Art

[0002] Ammonium dimolybdate, commonly known as ADM, is a white powder crystalline substance whose chemical expression is usually expressed as (NH4)2Mo2O7. It is mainly produced by evaporation crystallization and has shown wide application potential in many industrial fields. Specifically, ammonium dimolybdate is suitable for roasting to produce pure molybdenum trioxide, reducing to prepare molybdenum powder, and manufacturing molybdenum sheets, molybdenum wires, molybdenum components, etc. These products are widely used in steel, metal ceramics, electric light sources, metallurgy, aerospace and military industries. In addition, ammonium dimolybdate is also an important raw material for the production of petroleum refining catalysts such as hydrogenation and desulfurization, fertilizer catalysts and dyes.

[0003] Currently, the secondary resource utilization and high-value utilization of molybdenum have become important directions for the research and development of molybdenum hydrometallurgical technology. The sources of secondary resource molybdenum are diverse, including but not limited to the molybdenum removal slag and raffinate from tungsten metallurgical processes, molybdenum-containing catalysts, low-grade molybdenum roasted sand leaching residues, potassium removal washes in molybdate production, small amounts of molybdenum in various tail liquids, metal molybdenum waste, and electro-light source etching waste liquid. These secondary molybdenum resource raw materials have complex sources and are difficult to process.

[0004] Liquid molybdenum-containing waste is usually converted into crude molybdic acid in solid form by precipitation or adsorption. For solid molybdenum-containing waste, it is generally leached with alkali after high-temperature roasting pretreatment, or directly leached with alkali to obtain molybdenum alkaline leachate. However, these alkaline leachates often contain other monovalent to trivalent metal ions, as well as impurities such as chromium, silicon, aluminum, and phosphorus. Crude molybdic acid can be obtained by simple magnesium salt purification and separation treatment and precipitation under acidic conditions. However, factors such as improper operation or incomplete washing may cause a small amount of impurities such as magnesium salts, aluminum hydroxide, and silicate to be entrained in the molybdenum acid precipitate, resulting in a high content of molybdenum acid impurities.

[0005] Crude molybdic acid from different sources often contains a considerable amount of monovalent and divalent metal ion impurities, as well as some organic impurities. If these crude molybdic acids are used as a secondary resource source of molybdenum to prepare high-value-added ammonium molybdate products, the impurities, especially various metal cations, must be effectively removed to produce ammonium molybdate products that meet national standards. It is worth noting that when the iron in molybdic acid reacts with ammonia water, a covering film Fe(OH)2 or Fe(OH)3 will be formed, resulting in a slow reaction. The divalent iron part enters the solution in the form of an iron-ammine complex, while most of the iron exists in the form of ferrous hydroxide (in a colloidal state, which is difficult to precipitate). This ferric hydroxide coats the roasted sand particles in the form of a film, hindering the dissolution of molybdenum.

[0006] In the secondary resource production process of ammonium molybdate, crude molybdic acid not only contains a large amount of divalent metal ions, but also often contains high content of monovalent metal ions (such as sodium and potassium ions). This is mainly due to the common method of treating waste molybdenum raw materials, which is the alkaline roasting process, resulting in a high sodium content in crude molybdic acid. In addition, in the process of producing ammonium molybdate using high-potassium molybdenum roasted sand as raw material, the process step of water washing and potassium reduction will also make the crude potassium molybdate recovered from the potassium reduction solution have a high content.

[0007] The existing process routes usually use nitric acid pickling to dissolve and remove the impurity metal ions, but this method will produce a large amount of nitrate wastewater, which puts pressure on environmental protection treatment. With increasingly stringent environmental protection requirements, the existing process routes are subject to many restrictions. Chinese patent CN201710530123.X discloses a method for purifying ammonium molybdate in a crude sodium molybdate solution, that is, exchanging molybdate ions with an ion resin, and then resolving with ammonia water to obtain ammonium molybdate. However, this method requires the exchange column to have a large carrying capacity. In addition, the recovered crude molybdic acid from the extraction process route often contains different amounts of organic impurities, which have an adverse effect on the production of ammonium molybdate.

[0008] The traditional ammonium molybdate production method (ammonia leaching-purification-concentration crystallization) has the problems of incomplete impurity removal, unstable product quality and difficulty in control. Taking the molybdic acid produced in the waste hydrogenation catalyst recovery process as an example, its composition is complex, containing 45% molybdenum, 0.15% silicon, 0.1% aluminum, 0.05% iron, 0.05% copper, 0.05% magnesium, 0.05% manganese, 0.02% phosphorus, 0.1% potassium, 0.2% sodium, 0.3% calcium, 0.02% tin, 0.68% chlorine, 0.05% tungsten, 0.05% nickel, 0.01% titanium, 0.01% chromium, 0.01% arsenic, etc. Therefore, the development of efficient and environmentally friendly ammonium molybdate preparation technology to realize the secondary resource and high-value utilization of molybdenum is still the focus of current research. Summary of the invention

[0009] In order to solve the above problems, the present invention provides a method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material.

[0010] The present invention provides a method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material. Figure 1 As shown, the method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material comprises the following steps:

[0011] Adding an organic acid solution to the crude molybdic acid for washing, filtering to obtain a molybdic acid filter cake and a washing liquid;

[0012] Adding an ammonia solution to the molybdic acid filter cake for leaching, filtering and washing to obtain an ammonia leaching solution and an ammonia insoluble residue;

[0013] The ammonia leaching solution is adsorbed with tungsten resin, and after the tungsten removal resin is saturated, it is analyzed with 10% ammonia water by mass to obtain ammonium tungstate solution and tungsten removal tail liquid, and the ammonium tungstate solution is used to recover tungsten salt;

[0014] Adsorbing and decolorizing the tungsten removal tail liquid with a composite adsorbent to obtain a refined ammonium molybdate solution;

[0015] The refined ammonium molybdate solution is concentrated and crystallized to obtain an ammonium molybdate product.

[0016] Furthermore, the crude molybdic acid is washed with 2-5% organic acid solution at 30-50° C. pure water, and filtered to obtain a molybdic acid filter cake and a washing liquid.

[0017] Furthermore, the molybdic acid filter cake is dissolved in ammonia water with a mass fraction of 15-25%.

[0018] Furthermore, the ammonia leaching solution is adsorbed with tungsten resin, and after the tungsten resin is saturated, it is analyzed with 10% ammonia water by mass to obtain ammonium tungstate solution and tungsten-removed liquid, and the ammonium tungstate solution is used to recover tungsten salt.

[0019] Furthermore, the tungsten-removed liquid is adsorbed and decolorized by a composite adsorbent, and after standing, it is filtered and washed to obtain a refined ammonium molybdate solution.

[0020] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0021] The embodiment of the present invention provides a method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material. The present invention has the advantages of high molybdenum recovery rate, stable product quality, no pollution to the environment, compliance with clean production requirements, etc., less wastewater, and is suitable for large-scale production. Compared with the prior art, the advantages of the present invention are: (1) the method provided by the present invention utilizes organic acids to have good water solubility for alkaline earth metal salts, such as: aluminum salts, sodium salts, magnesium salts, calcium salts, iron salts, zinc salts, lead salts, copper salts, nickel salts, chromium salts, etc. of aminosulfonic acid have large solubility at room temperature, and the aminosulfonic acid washing liquid is supplemented with an appropriate amount of reagents to repeatedly wash the next batch of materials. After the cyclic washing reaches a certain number of times, when the aminosulfonic acid wastewater needs to be treated, the aminosulfonic acid washing wastewater can be adjusted to pH and heavy metal elements can be added to the heavy metal collecting agent to recover the heavy metal elements, and the liquid after de-weighting is concentrated and crystallized into sodium aminosulfonate, or sodium nitrite is added in an equimolar amount, and the oxidizing property of sodium nitrite is used to convert aminosulfonic acid into harmless sodium bisulfate, which is reduced to nitrogen by itself to reduce the amount of wastewater discharged. The main reaction equation is:

[0022] Ca 2+ +2NH2SO3H→Ca(NH2SO3)2+2H +

[0023] Mg 2++2NH2SO3H→Mg(NH2SO3)2+2H +

[0024] Cu 2+ +2NH2SO3H→Cu(NH2SO3)2+2H +

[0025] Ni 2+ +2NH2SO3H→Ni(NH2SO3)2+2H +

[0026] Fe 2+ +2NH2SO3H→Fe(NH2SO3)2+2H +

[0027] Na + +NH2SO3H→NaNH2SO3+H +

[0028] Fe 2+ +2NH2SO3H→Fe(NH2SO3)2+2H +

[0029] Al 3+ +3NH2SO3H→Al(NH2SO3)3+6H +

[0030] Fe 3+ +3NH2SO3H→Fe(NH2SO3)3+6H +

[0031] Cr 3+ +3NH2SO3H→Cr(NH2SO3)3+6H +

[0032] Phosphates and silicates also react as follows

[0033] Mg3(PO4)2+6NH2SO3H→3Mg(NH2SO3)2+2H3PO4

[0034] MgSiO3+2NH2SO3H→Mg(NH2SO3)2+2H4SiO4

[0035] When disposing of waste liquid

[0036] NH2SO3H+ NaOH →NaNH2SO3+H2O

[0037] NH2SO3H+ NaNO 2=NaHSO4+N2↑+H2O

[0038] (2) The method provided by the present invention: using a macroporous anion resin containing an alkaline group of an amine complex, after regeneration with ammonia water or sodium hydroxide, it has an excellent regeneration effect and has extremely low requirements for flushing. It can resist high organic pollution and selectively deeply adsorb tungsten. The resin capacity for adsorbing tungstate can reach 100-120g / L, and the tungsten in the tungsten removal tail liquid is ≤1.0mg / L. The exchange and regeneration process does not require resin transformation to reduce wastewater discharge.

[0039] (3) The method provided by the present invention: using a specially prepared activated carbon composite adsorbent loaded with Fe(OH)3 for adsorption and decolorization, in addition to decolorization, it can also have a good removal effect on phosphorus and colloidal silicon in the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0042] Figure 1 The present invention is a flowchart of a method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material in an embodiment of the present invention.

[0043] Figure 2 The present invention is a flowchart of the method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as a raw material in Example 3 of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0046] It should be noted that the component raw materials involved in the method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as raw material provided in the embodiment of the present invention, unless otherwise specified or specified, can be directly commercially available products or homemade using existing public preparation methods; at the same time, the steps and parameters involved, unless otherwise specified or specified, can be carried out according to the process steps and parameters disclosed in the prior art or directly using existing equipment according to the instruction manual, and the present invention document will not repeat them one by one.

[0047] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0048] Example 1

[0049] Step 1. Add 2000 ml of 2% aminosulfonic acid aqueous solution to 1 kg of crude molybdic acid, control the end point pH to 2.0, wash at 30°C for 2 h, and filter to obtain 1636.7 g of molybdic acid filter cake (40% moisture, equivalent to 982 g on dry basis) and 2000 ml of washing liquid.

[0050] Step 2. Add 1636.7g of molybdic acid filter cake to 2342ml (20%) ammonia water at a solid-liquid ratio of 1:3 and control the pH to 8.0 at 55°C for leaching for 2h. After the reaction is completed, filter and wash with pure water to obtain 3100ml of ammonia leaching solution and 12.5g (40% water content, equivalent to 7.52g on a dry basis) of ammonia insoluble residue.

[0051] Step 3. Use 15ml of tungsten resin to adsorb tungsten from 3100ml of ammonia leaching solution to obtain 3080ml of tungsten removal tail liquid (WO3≤1.0mg / L)

[0052] Step 4. Add 5g of activated carbon composite adsorbent to 3080ml of tungsten removal tail liquid, let it stand, filter it and wash it with pure water to obtain filter residue and 3100ml of refined ammonium molybdate solution.

[0053] Step 4. 3100 ml of the obtained filtrate was concentrated to 1.568 g / cm3, pH 7-8, and the concentrated solution was crystallized to obtain 834.15 g (5% water, equivalent to 792.44 g on a dry basis) of ammonium dimolybdate product. The impurities were calculated as shown in Table 1 after analysis.

[0054] Table 1

[0055]

[0056] According to calculation, crude molybdic acid is washed with 2% aminosulfonic acid aqueous solution to control the end point PH2.0, the elution rate of harmful metal elements is 88.12%, and the loss of molybdic acid is ≤0.5%. The molybdic acid filter cake after washing is leached with 15% ammonia water, and the leaching rate of molybdenum in the crude molybdic acid is 99.5%. The ammonia leaching liquid is refined by activated carbon composite adsorbent, and the refined ammonium molybdate solution is concentrated and crystallized into ammonium molybdate product with a total mass of 0.0096%, a purity of ≥99.99%, and a direct recovery rate of molybdenum of 99.0%. Example 2

[0057] Step 1. Add 2000 ml of 1.5% sulfamic acid aqueous solution to 1 kg of crude molybdic acid and control the end point pH to 2.5, wash at 30°C for 2 hours, filter after the reaction to obtain 1642 g of molybdic acid filter cake (40% moisture, equivalent to 980.6 g on a dry basis) and 2000 ml of washing liquid.

[0058] Step 2. Add 3000ml (15%) ammonia water to 1kg of crude molybdic acid at a solid-liquid ratio of 1:3 and leaching for 2h at 55℃ with pH 8.0. After the reaction is completed, 3100ml ammonia leaching solution and 16.5g ammonia insoluble residue are obtained by washing and filtration.

[0059] Step 3. 3100 ml of ammonia leaching solution is further adsorbed with the tungsten resin in Example 1 to obtain 3080 ml of tungsten-removed tail liquid (WO3≤1.0 mg / L).

[0060] Step 4: Add 5 g of activated carbon composite adsorbent to 3080 ml of tungsten removal tail liquid, let it stand, filter and wash to obtain filter residue and 3100 ml of refined ammonium molybdate solution.

[0061] Step 5. Concentrate 3100 ml of the obtained filtrate to 1.568 g / cm3, pH 7-8, and evaporate and crystallize the concentrated solution to obtain 829.3 g (5% water content, equivalent to 787.8 g on a dry basis) of ammonium dimolybdate product.

[0062] According to calculation, crude molybdic acid is washed with 1.5% aminosulfonic acid aqueous solution to control the end point PH2.5, the elution rate of harmful metal elements is 88.0%, and the loss of molybdic acid is ≤0.8%. The molybdic acid filter cake after washing is leached with 15% ammonia water, and the leaching rate of molybdenum in the crude molybdic acid is 99.0%. The ammonia leaching solution is refined by activated carbon composite adsorbent, and the refined ammonium molybdate solution is concentrated and crystallized into ammonium molybdate product with total impurities of 0.012%, purity of ≥99.99%, and direct recovery rate of molybdenum is 98.2%, as shown in Table 2.

[0063] Table 2

[0064]

[0065] Example 3

[0066] like Figure 2As shown, step 1. add 2000 ml of the sulfamic acid aqueous solution produced in implementation 1 to 1 kg of crude molybdic acid and add a small amount of fresh sulfamic acid, and wash at 30° C. at an end point pH of 2.0, and filter to obtain 1635.8 g of molybdic acid filter cake (40% moisture, equivalent to 981.5 g on a dry basis) and 2000 ml of washing liquid.

[0067] Step 2. Add 3000 ml (15%) ammonia water to 1 kg of crude molybdic acid at a solid-liquid ratio of 1:3 and leaching for 2 hours at 55°C with pH controlled at 8.0. After the reaction is completed, 3100 ml of ammonia leaching liquid and 20.1 g of ammonia insoluble slag (40% water content, equivalent to 12.06 g on a dry basis) are obtained by washing and filtration.

[0068] Step 3. 3100 ml of ammonia leaching solution was further adsorbed with the tungsten resin in Example 2 to obtain 3080 ml of tail liquid (WO31.0 mg / L), and the tungsten-loaded resin was regenerated by soaking and analyzing with 50 ml of ammonia water (10%), filtered and washed to obtain 50 ml of ammonium tungstate analysis solution, and sampled for analysis, WO3≤29.94 g / L.

[0069] Step 4: Add 5 g of activated carbon composite adsorbent to 3080 ml of tungsten removal tail liquid, let it stand, filter and wash to obtain filter residue and 3100 ml of refined ammonium molybdate solution.

[0070] Step 5. Concentrate 3100 ml of refined ammonium molybdate solution to 1.568 g / cm3, pH 7-8, and evaporate and crystallize the concentrated solution to obtain 833.32 g (5% moisture, equivalent to 791.65 g on a dry basis) of ammonium dimolybdate product, as shown in Table 3.

[0071] Table 3

[0072]

[0073] According to calculation, the crude molybdic acid is washed with the aminosulfonic acid washing solution produced in Implementation 1 and supplemented with a small amount of fresh aminosulfonic acid, and the end point pH is 2.0, the elution rate of harmful metal elements is 88.1%, and the loss of molybdic acid is ≤0.6%. The molybdic acid filter cake after washing is leached with 15% ammonia water, and the leaching rate of molybdenum in the crude molybdic acid is 99.5%. The ammonia leaching solution is refined by using a composite adsorbent, and the refined ammonium molybdate solution is concentrated and crystallized into an ammonium molybdate product, with a total impurity of 0.0095%, a purity of ≥99.99%, and a direct recovery rate of molybdenum of 98.9%.

[0074] Comparative Example 1

[0075] Step 1. Add 2000 ml of 1.5% aminosulfonic acid aqueous solution to 1 kg of crude molybdic acid and wash at 60°C. Filter to obtain 1641.5 g of molybdic acid filter cake (40% moisture, equivalent to 984.9 g on a dry basis) and 2000 ml of washing liquid, as shown in Table 4.

[0076] Table 4

[0077]

[0078] The difference between this comparative example and Example 1 is that the crude molybdic acid is washed with a 1.5% sulfamic acid aqueous solution at 60°C. After calculation, the crude molybdic acid is washed with a 1.5% sulfamic acid aqueous solution to control the endpoint pH value to 2, and the elution rate of harmful metal elements is 71.9%. The washing effect of harmful metal elements in the crude molybdic acid is not friendly, and the loss of molybdenum is ≥0.05%. According to analysis, when the sulfamic acid aqueous solution is heated to ≥60°C, part of the sulfamic acid is hydrolyzed into sulfate, which reduces the washing effect of harmful metal elements, and the sulfamic acid has a side reaction:

[0079] NH2SO3H+H2O=NH4HSO4

[0080] Comparative Example 2

[0081] Step 1. Add 1 kg of crude molybdic acid to 2000 ml of 3% aminosulfonic acid washing solution, wash at 30°C for 2 h at an end point pH of 1.5, and filter to obtain 1617.8 g of molybdic acid filter cake (equivalent to 970.7 g on a dry basis) and 2000 ml of washing solution.

[0082] Step 2. Add 3000 ml (15%) ammonia water to 1 kg of crude molybdic acid at a solid-liquid ratio of 1:3 and leach for 2 hours at 55°C and pH 8.0. After the reaction is completed, wash and filter to obtain 3100 ml of ammonia leaching liquid and 20.2 g of ammonia insoluble slag (40% water content, equivalent to 16.53 g on dry basis).

[0083] Step 3. Continue to adsorb the tungsten resin in Example 3 in 3100ml of ammonia leaching solution to obtain 3080ml of tail liquid (WO3≤1.0mg / L).

[0084] Step 4: Add 5 g of activated carbon composite adsorbent to 3080 ml of tungsten removal tail liquid, let it stand, filter and wash to obtain filter residue and 3100 ml of refined ammonium molybdate solution.

[0085] Step 5. Concentrate 3100 ml of refined ammonium molybdate solution to 1.568 g / cm3, pH 7-8, and evaporate and crystallize the concentrated solution to obtain 813.37 g (5% moisture, equivalent to 772.7 g on a dry basis) of ammonium dimolybdate product.

[0086] This comparative example is different from comparative example 4 in that 3% aminosulfonic acid washing solution is used to wash the crude molybdic acid. According to calculation, the elution rate of harmful metal elements reaches 88.34% when the aminosulfonic acid washing solution is used to wash the crude molybdic acid at the end point pH 1.5, and the molybdic acid loss is ≥3%. The molybdic acid filter cake after washing is leached with 15% ammonia water, and the leaching rate of molybdenum in the crude molybdic acid is 99.5%. The concentrated crystallization is pure ammonium molybdate product, the total impurities are 0.00593%, the purity is ≥99.99%, and the direct recovery rate of molybdenum is 96.52%, as shown in Table 5.

[0087] Table 5

[0088]

[0089] Comparative Example 3

[0090] Step 1. Add 2000 ml of 2% citric acid aqueous solution to 1 kg of crude molybdic acid, wash for 2 h at 30 ° C with an end point pH of 2.0, and filter to obtain 1635.8 g of molybdic acid filter cake (40% moisture, equivalent to 981.5 g on a dry basis) and 2000 ml of washing liquid.

[0091] Step 2. Add 3000 ml (15%) ammonia water to 1 kg of crude molybdic acid at a solid-liquid ratio of 1:3 and leaching for 2 hours at 55°C with pH 8.5. After the reaction is completed, 3100 ml of ammonia leaching liquid and 69.8 g of ammonia insoluble slag (40% water content, equivalent to 41.88 g on a dry basis) are obtained by washing and filtration.

[0092] Step 3. 3100 ml of ammonia leaching solution is further adsorbed with the tungsten resin in Example 3 to obtain 3080 ml of tailing liquid (WO3≤1.0 mg / L).

[0093] Step 4: Add 5 g of activated carbon composite adsorbent to 3080 ml of tungsten removal tail liquid, let it stand, filter and wash to obtain filter residue and 3100 ml of refined ammonium molybdate solution.

[0094] Step 5. Concentrate 3100 ml of refined ammonium molybdate solution to 1.568 g / cm3, pH 7-8, and evaporate and crystallize the concentrated solution to obtain 803.91 g (5% moisture, equivalent to 763.71 g on a dry basis) of ammonium dimolybdate product, as shown in Table 6.

[0095] Table 6

[0096]

[0097] According to calculation, the elution rate of harmful metal elements in crude molybdic acid reaches 79.25% when washing with 2% citric acid washing solution and the end point PH2.0, and the loss of molybdic acid is ≥1%. The molybdenum leaching rate in crude molybdic acid is 96% when the molybdenum filter cake after washing is leached with 15% ammonia water. The purity of the concentrated crystallized ammonium molybdate product is 0.013%, and the calcium, phosphorus and magnesium do not meet the product quality requirements of MSA0-3. The direct recovery rate of molybdenum is 95.04%

[0098] In summary, the molybdate washed with sulfamic acid aqueous solution, the filter cake is dissolved with ammonia water, the ammonia leachate is tungsten-removed with tungsten-removing resin, and the tungsten-removed liquid is treated with a composite adsorbent to obtain a refined ammonium molybdate solution, which is concentrated and crystallized to obtain a high-purity ammonium molybdate product. The product quality meets the MSA-0 standard; the process control of the present invention is simple, the molybdenum recovery rate is high, the product quality is stable, and there is no pollution to the environment. The sulfamic acid washing liquid can be circulated for multiple times to wash the next batch of materials by adding an appropriate amount of reagents. When the harmful metal elements in the washing liquid are nearly saturated and the sulfamic acid wastewater needs to be treated, the treatment process is simple, the sulfamic acid washing wastewater can be adjusted to pH and heavy metal elements can be recovered by adding a heavy catching agent, and the liquid after the heavy removal is concentrated and crystallized into sulfamic acid sodium salt, or sodium nitrite is added in an equimolar amount, and the oxidizing property of sodium nitrite is used to convert sulfamic acid into harmless sodium bisulfate, which is reduced to nitrogen gas by itself. The wastewater treatment process can also produce by-products, which meets the requirements of clean production and other advantages, reduces the discharge of wastewater, and is suitable for large-scale production.

[0099] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0100] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as raw material, characterized in that: The method comprises the following steps: Adding an organic acid solution to the crude molybdic acid for washing, filtering to obtain a molybdic acid filter cake and a washing liquid; Adding an ammonia solution to the molybdic acid filter cake for leaching, filtering and washing to obtain an ammonia leaching solution and an ammonia insoluble residue; The ammonia leaching solution is adsorbed with tungsten resin, and after the tungsten removal resin is saturated, it is analyzed with 10% ammonia water by mass to obtain ammonium tungstate solution and tungsten removal tail liquid, and the ammonium tungstate solution is used to recover tungsten salt; Adsorbing and decolorizing the tungsten removal tail liquid with a composite adsorbent to obtain a refined ammonium molybdate solution; The refined ammonium molybdate solution is concentrated and crystallized to obtain an ammonium molybdate product.

2. The method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as raw material according to claim 1, characterized in that: Add 2-5% organic acid solution by mass to the crude molybdic acid and wash with 30-50° C. pure water, and filter to obtain molybdic acid filter cake and washing liquid.

3. The method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as raw material according to claim 1, characterized in that: The molybdic acid filter cake is dissolved in ammonia water with a mass fraction of 15-25%.

4. The method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as raw material according to claim 1, characterized in that: The ammonia leaching solution is adsorbed with tungsten resin, and after the tungsten resin is saturated, it is analyzed with 10% ammonia water by mass to obtain ammonium tungstate solution and tungsten-removed liquid, and the ammonium tungstate solution is used to recover tungsten salt.

5. The method for optimizing the preparation of high-purity ammonium molybdate using crude molybdic acid as raw material according to claim 1, characterized in that: The tungsten-removed liquid is adsorbed and decolorized by a composite adsorbent, and after standing, it is filtered and washed to obtain a refined ammonium molybdate solution.

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