A production process of ammonium molybdate

Abstract

The present application relates to the technical field of ammonium molybdate preparation, and specifically discloses a production process of ammonium molybdate. A production process of ammonium molybdate comprises the following preparation steps: (1) roasting and impregnating molybdenite to obtain a leachate; (2) mixing the leachate and a chelating purifier, filtering the mixture, and passing the filtrate through an ion exchange resin to obtain a sodium molybdate solution after elution; (3) crystallizing the sodium molybdate solution to obtain ammonium molybdate. The ammonium molybdate prepared by the present application has the advantages of low impurity content and high purity.

Description

Technical Field

[0001] The present application relates to the technical field of ammonium molybdate preparation, and more specifically, to a production process of ammonium molybdate. Background Art

[0002] Molybdenum is an important strategic metal, mainly used in steel, chemical industry, electronics and other fields. With the development of these industries, the consumption and utilization of molybdenum by human society has continued to increase, prompting people to develop efficient ammonium molybdate production processes to extract more molybdenum from molybdenum ore resources to meet market demand.

[0003] Among molybdenum products, ammonium molybdate is a basic product. Ammonium molybdate is easy to purify, dissolve, and thermally dissociate. Moreover, the ammonia produced by thermal dissociation can be fully released when heated and will no longer pollute the molybdenum product. Therefore, ammonium molybdate is the raw material for the production of molybdenum metal products, which is related to the performance and quality of the final product produced by molybdenum.

[0004] In some high-end application fields, such as the electronics industry, the purity requirements for ammonium molybdate are getting higher and higher. For this reason, we need to continuously improve and innovate the production process of ammonium molybdate.

[0005] A Chinese patent application document with application publication number CN115650293A discloses a method for producing ammonium molybdate. The patent application document specifically relates to a method for producing ammonium molybdate, comprising the steps of: S1: performing pickling operation on solid industrial molybdenum oxide and performing solid-liquid separation after the pickling operation to obtain pickling liquid and filter cake; S2: recovering molybdenum in the pickling liquid and treating the filter cake with an ammonia leaching process to obtain ammonia leaching liquid and ammonia leaching residue; S3: performing acid precipitation treatment on the ammonia leaching liquid obtained in S2 to obtain ammonium molybdate and acid precipitation mother liquor, and the acid precipitation mother liquor is returned to the pickling operation for reuse.

[0006] In the above document, the ammonium molybdate production method is to destroy the molecular structure of low-cost insoluble molybdate under high temperature and high pressure conditions, and use potassium permanganate as an oxidant to make up for the defect of insufficient oxidation strength of nitric acid in the pickling process, so as to promote the molybdate that is insoluble in ammonia water to obtain sufficient oxidation reaction under new process conditions, thereby completely converting it into soluble molybdic acid, thereby increasing the yield of ammonium molybdate. However, this process cannot ensure that the prepared ammonium molybdate has a high purity. Summary of the invention

[0007] In order to further improve the purity of ammonium molybdate, the present application provides a production process of ammonium molybdate.

[0008] In a first aspect, the present application provides a production process of ammonium molybdate, which adopts the following technical solution: A production process of ammonium molybdate comprises the following steps: (1) roasting molybdenite, heating it to 300-400°C at a heating rate of 2-4°C / min, keeping it warm for 1-1.5h, then heating it to 600-620°C at a heating rate of 3-5°C / min, keeping it warm for 1.5-2.5h, mixing the roasted molybdenite with alkali solution, introducing ozone, impregnating, filtering, and obtaining a leachate; (2) mixing the leaching solution and the chelating agent, filtering, and passing the filtrate through an ion exchange resin for elution to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at a temperature of 70-90°C, crystallized, filtered, and dried to obtain ammonium molybdate. Preferably, in step (2), the preparation method of the chelating purifier comprises the following steps: S1: mixing halloysite and sodium hydroxide solution, ultrasonically dispersing, filtering, washing, and then mixing evenly with sodium hexaphosphate, standing for 20-30 minutes, taking the upper layer of liquid, centrifugally washing, and drying to obtain pretreated halloysite; S2: Mix toluene, mercaptopropyltrimethoxysilane and pretreated halloysite evenly, react at 80-90° C. for 15-20 h under a nitrogen atmosphere, centrifuge, wash, and dry to obtain an intermediate; S3: Mix toluene, γ-aminopropyltriethoxysilane and the intermediate evenly, react at 90-100° C. for 6-12 hours under a nitrogen atmosphere, centrifuge, wash, and dry to obtain a chelating purifier.

[0009] By adopting the above technical scheme, the halloysite is pretreated to increase its specific surface area, thereby increasing the number of mercaptopropyltrimethoxysilane grafted on the halloysite surface, so that the chelating purifier can chelate more metal ions in the process of taking effect. At the same time, the increase in the specific surface area of ​​the halloysite makes its contact with the metal ions more sufficient, thereby increasing the adsorption amount of the chelating purifier on the metal ions. Mercaptopropyltrimethoxysilane and γ-aminopropyltriethoxysilane form a synergistic chelating network around the metal ions, so that the metal ions are more stably fixed in the system, thereby achieving the purpose of improving the purity of ammonium molybdate.

[0010] The thiol group forms a strong coordination bond with the metal ion through the sulfur atom to achieve the initial chelation of the metal ion. At the same time, the amino group uses the lone pair of electrons on the nitrogen atom to coordinate with the metal ion to form a coordination bond. Since the two silane coupling agents have different binding sites and modes of action with metal ions, they form a synergistic chelating network around the metal ions, making the metal ions more stably fixed in the system.

[0011] Preferably, in step S1, the mass ratio of halloysite, sodium hydroxide solution and sodium hexaphosphate solution is 1:(1-1.5):(10-11).

[0012] By adopting the above technical solution, the dispersibility of halloysite in the solution is increased, so that the sodium hydroxide solution can uniformly surround and act on the halloysite, avoiding the uneven etching phenomenon caused by excessively high or low local concentration, thereby increasing the specific surface area of ​​the halloysite, and at the same time, the surface active sites are increased, the adsorption of metal ions is enhanced, thereby reducing the impurity content of ammonium molybdate and improving the purity of ammonium molybdate.

[0013] Preferably, in step S2, the mass ratio of toluene, mercaptopropyltrimethoxysilane and pretreated halloysite is (9-11):(2-2.5):1.

[0014] By adopting the above technical scheme, a good reaction environment is provided for the grafting reaction of mercaptopropyltrimethoxysilane and halloysite, so that mercaptopropyltrimethoxysilane is fully dissolved and evenly dispersed, which is beneficial for its full contact with the surface of halloysite, improves the efficiency and uniformity of the grafting reaction, and further provides a large number of active sites for chelating metal ions, thereby significantly improving the chelating ability of the chelating purifier for metal ions, thereby reducing the content of metal ions in ammonium molybdate.

[0015] Preferably, in step (1), the average particle size of the molybdenite is 100-200 mesh.

[0016] Preferably, in step (1), the alkali solution is composed of sodium hydroxide, sodium carbonate and water, and the mass ratio of the sodium hydroxide, sodium carbonate and water is 1:(0.2-0.44):(12-16).

[0017] Preferably, in step (1), the immersion temperature is 90-95° C. and the immersion time is 1-2 h.

[0018] By adopting the above technical scheme, the chemical reaction rate of molybdenum oxide and alkali solution is accelerated, so that molybdate ions are dissolved from molybdenum oxide into the solution more quickly, a higher leaching rate is achieved in a shorter time, and impurity residues that may be caused by incomplete reaction are reduced, which helps to improve the purity of ammonium molybdate; in addition, molybdenite is heated evenly during the roasting process, avoiding incomplete local reaction or overreaction, which helps to improve the purity and quality stability of ammonium molybdate products; at the same time, sodium hydroxide and sodium carbonate work synergistically, so that the molybdenum oxide product after the molybdenite is roasted can more easily enter the solution in the form of molybdenum ions, thereby improving the leaching rate of molybdenum and reducing the residual molybdenum in the residue, thereby improving the purity of ammonium molybdate.

[0019] Preferably, in step (2), the ion exchange resin is one of 201×7 resin, D296 resin and LS-32 resin.

[0020] Preferably, in step (2), the rate at which the filtrate passes through the ion exchange resin is 1-2 mL / min, and the elution rate is 2-2.5 mL / min.

[0021] By adopting the above technical scheme, the equilibrium stability of the ion exchange process is maintained, so that the resin has a more selective adsorption of molybdate ions, and then the molybdate ions are separated from the filtrate, and the impurity ions flow out with the filtrate, thereby improving the purity of ammonium molybdate; at the same time, 201×7 resin, D296 resin and LS-32 resin have a strong selective adsorption capacity for molybdate ions, effectively adsorb molybdate ions from the filtrate, and exclude many other impurity ions, thereby playing a role in purification and improving the purity of ammonium molybdate; at the same time, they have good stability, are not prone to degradation or other chemical reactions, can maintain the stability of their ion exchange function, continuously and effectively adsorb and separate molybdate ions, and ensure the purity stability of the ammonium molybdate product.

[0022] Preferably, in step (3), the crystallization temperature is 55-65° C. and the pH is 2-2.5.

[0023] In summary, this application has the following beneficial effects: 1. By using alkaline solution to etch halloysite, the specific surface area of ​​halloysite is increased, thereby increasing the number of surface active sites, which is conducive to chelating more impurity metal ions and achieving good impurity removal and purification effects; at the same time, some defects and unstable parts in the halloysite structure can be removed, making the overall structure more regular and stable. During the chelation purification process, this stable structure can withstand greater external forces and environmental changes, and is not prone to structural collapse or deformation, thereby ensuring the stability and sustainability of the purification process and extending the service life of the chelating purifier.

[0024] 2. Mercaptopropyltrimethoxysilane can introduce mercapto groups into the surface and pores of halloysite, greatly enhancing the chelating ability of halloysite to metal ions. In addition, after treating halloysite with mercaptopropyltrimethoxysilane, the surface properties of halloysite can be improved, its surface energy can be reduced, and its dispersibility in the solution can be significantly improved, so that halloysite can contact with metal ions more evenly, give full play to its chelating effect, and thus improve the impurity removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the purity and molybdenum content of ammonium molybdate prepared in Examples 1-3 and Comparative Examples 1-2 of the present application.

[0026] Figure 2 It is a schematic diagram of the metal impurity content of ammonium molybdate prepared in Examples 1-3 and Comparative Examples 1-2 of the present application. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to the embodiments.

[0028] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0029] Example 1 The production process of ammonium molybdate of the present embodiment comprises the following steps: (1) 45 g of molybdenite with an average particle size of 200 mesh was put into a muffle furnace, and the temperature was raised to 300°C at a heating rate of 2°C / min, and the temperature was kept for 1.5 h. The temperature was then raised to 600°C at a heating rate of 3°C / min, and the temperature was kept for 2.5 h. After the calcination was completed, 10 g of sodium hydroxide, 2 g of sodium carbonate and 120 g of water were mixed evenly, and the calcined molybdenite was added. The mixture was stirred at a stirring rate of 300 rpm, ozone was introduced, and the mixture was immersed at a temperature of 90°C for 2 h. The mixture was filtered to obtain a leachate. (2) 200 g of the leachate and 8 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through 201×7 resin at a rate of 1 mL / min. The exchanged resin was rinsed with deionized water, and then eluted with 150 mL of 10% ammonia water at a flow rate of 2 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 70°C, then the temperature is adjusted to 55°C, nitric acid is added to adjust the pH to 2, and crystallization is performed. After the crystallization is completed, the solution is filtered and dried to obtain ammonium molybdate.

[0030] The preparation method of the chelating purifier of the present embodiment is as follows: S1: 10 g of halloysite and 10 g of a sodium hydroxide solution with a mass percentage concentration of 18% were mixed, ultrasonically dispersed at a frequency of 20 kHz for 1 hour, filtered, washed, and then mixed evenly with 100 g of a sodium hexaphosphate aqueous solution with a mass percentage concentration of 0.05%, allowed to stand for 20 minutes, filtered, washed, and dried to obtain pretreated halloysite; S2: 90 g of toluene, 20 g of mercaptopropyltrimethoxysilane and 10 g of pretreated halloysite were mixed evenly, reacted at 80° C. for 20 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain an intermediate; S3: 80 g of toluene, 25 g of γ-aminopropyltriethoxysilane and the intermediate were mixed evenly, reacted at 90° C. for 12 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain a chelating purifier.

[0031] Example 2 The production process of ammonium molybdate of the present embodiment comprises the following steps: (1) 45 g of molybdenite with an average particle size of 100 mesh was put into a muffle furnace, and the temperature was raised to 400°C at a heating rate of 4°C / min, and the temperature was kept for 1 hour. Then, the temperature was raised to 620°C at a heating rate of 5°C / min, and the temperature was kept for 1.5 hours to complete the roasting. 10 g of sodium hydroxide, 4.4 g of sodium carbonate and 160 g of water were mixed evenly, and the roasted molybdenite was added. The mixture was stirred at a stirring rate of 400 rpm, ozone was introduced, and the mixture was immersed at a temperature of 95°C for 1 hour. The mixture was filtered to obtain a leachate. (2) 200 g of the leachate and 5 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through the D296 resin at a rate of 2 mL / min. The exchanged resin was rinsed with deionized water, and then eluted with 200 mL of 10% by mass ammonia water at a flow rate of 2.5 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 90°C, then the temperature is adjusted to 65°C, nitric acid is added to adjust the pH to 2.5, and crystallization is performed. After the crystallization is completed, it is filtered and dried to obtain ammonium molybdate.

[0032] The preparation method of the chelating purifier of the present embodiment is as follows: S1: 10 g of halloysite and 15 g of a sodium hydroxide solution with a mass percentage concentration of 18% were mixed, ultrasonically dispersed at a frequency of 60 kHz for 0.5 h, filtered, washed, and then mixed evenly with 110 g of a sodium hexaphosphate aqueous solution with a mass percentage concentration of 0.05%, allowed to stand for 30 min, filtered, washed, and dried to obtain pretreated halloysite; S2: 110 g of toluene, 25 g of mercaptopropyltrimethoxysilane and 10 g of pretreated halloysite were mixed evenly, reacted at 90° C. for 15 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain an intermediate; S3: 90 g of toluene, 30 g of γ-aminopropyltriethoxysilane and the intermediate were mixed evenly, reacted at 100° C. for 6 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain a chelating purifier.

[0033] Example 3 The production process of ammonium molybdate of the present embodiment comprises the following steps: (1) 45 g of molybdenite with an average particle size of 150 mesh was put into a muffle furnace, and the temperature was raised to 320°C at a heating rate of 3°C / min, and the temperature was kept for 1.2 h. The temperature was then raised to 610°C at a heating rate of 4°C / min, and the temperature was kept for 2 h to complete the roasting. 10 g of sodium hydroxide, 3 g of sodium carbonate and 140 g of water were mixed evenly, and the roasted molybdenite was added. The mixture was stirred at a stirring rate of 320 rpm, ozone was introduced, and the mixture was immersed at a temperature of 902°C for 1.2 h. The mixture was filtered to obtain a leachate. (2) 200 g of the leachate and 56 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through an LS-32 resin at a rate of 1.5 mL / min. The exchanged resin was rinsed with deionized water and then eluted with 170 mL of 10% ammonia water at a flow rate of 2.3 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 75°C, then the temperature is adjusted to 60°C, nitric acid is added to adjust the pH to 2.2, and crystallization is performed. After the crystallization is completed, it is filtered and dried to obtain ammonium molybdate.

[0034] The preparation method of the chelating purifier of the present embodiment is as follows: S1: 10 g of halloysite and 12 g of a sodium hydroxide solution with a mass percentage concentration of 18% were mixed, ultrasonically dispersed at a frequency of 30 kHz for 50 min, filtered, washed, and then mixed evenly with 105 g of a sodium hexaphosphate aqueous solution with a mass percentage concentration of 0.05%, allowed to stand for 25 min, filtered, washed, and dried to obtain pretreated halloysite; S2: 100 g of toluene, 21 g of mercaptopropyltrimethoxysilane and 10 g of pretreated halloysite were mixed evenly, reacted at 85° C. for 17 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain an intermediate; S3: 85 g of toluene, 26 g of γ-aminopropyltriethoxysilane and the intermediate were mixed evenly, reacted at 95° C. for 10 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain a chelating purifier.

[0035] Example 4 The production process of ammonium molybdate of the present embodiment comprises the following steps: (1) 45 g of molybdenite with an average particle size of 200 mesh was put into a muffle furnace, and the temperature was raised to 350°C at a heating rate of 3°C / min, and the temperature was kept for 1.3 h. The temperature was then raised to 620°C at a heating rate of 3°C / min, and the temperature was kept for 2.5 h. After the roasting was completed, 10 g of sodium hydroxide, 4 g of sodium carbonate and 130 g of water were mixed evenly, and the roasted molybdenite was added. The mixture was stirred at a stirring rate of 320 rpm, and ozone was introduced. The mixture was immersed at a temperature of 93°C for 2 h, and filtered to obtain a leachate. (2) 200 g of the leachate and 6 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through 201×7 resin at a rate of 1 mL / min. The exchanged resin was rinsed with deionized water, and then eluted with 170 mL of 10% ammonia water at a flow rate of 2 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 70°C, then the temperature is adjusted to 55°C, nitric acid is added to adjust the pH to 2, and crystallization is performed. After the crystallization is completed, the solution is filtered and dried to obtain ammonium molybdate.

[0036] The preparation method of the chelating purifier of the present embodiment is as follows: S1: 10 g of halloysite and 13 g of a sodium hydroxide solution with a mass percentage concentration of 18% were mixed, ultrasonically dispersed at a frequency of 50 kHz for 1 hour, filtered, washed, and then mixed evenly with 102 g of a sodium hexaphosphate aqueous solution with a mass percentage concentration of 0.05%, allowed to stand for 20 minutes, filtered, washed, and dried to obtain pretreated halloysite; S2: 95 g of toluene, 20 g of mercaptopropyltrimethoxysilane and 10 g of pretreated halloysite were mixed evenly, reacted at 80° C. for 20 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain an intermediate; S3: 83 g of toluene, 25 g of γ-aminopropyltriethoxysilane and the intermediate were mixed evenly, reacted at 98° C. for 12 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain a chelating purifier.

[0037] Example 5 The production process of ammonium molybdate of the present embodiment comprises the following steps: (1) 45 g of molybdenite with an average particle size of 120 mesh was put into a muffle furnace, and the temperature was raised to 380°C at a heating rate of 4°C / min, and the temperature was kept for 1 hour. Then, the temperature was raised to 620°C at a heating rate of 5°C / min, and the temperature was kept for 1.5 hours to complete the roasting. 10 g of sodium hydroxide, 4 g of sodium carbonate and 160 g of water were mixed evenly, and the roasted molybdenite was added. The mixture was stirred at a stirring rate of 400 rpm, ozone was introduced, and the mixture was immersed at a temperature of 94°C for 1 hour. The mixture was filtered to obtain a leachate. (2) 200 g of the leachate and 5 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through the D296 resin at a rate of 2 mL / min. The exchanged resin was rinsed with deionized water, and then eluted with 200 mL of 10% by mass ammonia water at a flow rate of 2.5 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 80°C, then the temperature is adjusted to 65°C, nitric acid is added to adjust the pH to 2.5, and crystallization is performed. After the crystallization is completed, it is filtered and dried to obtain ammonium molybdate.

[0038] The preparation method of the chelating purifier of the present embodiment is as follows: S1: 10 g of halloysite and 14 g of a sodium hydroxide solution with a mass percentage concentration of 18% were mixed, ultrasonically dispersed at a frequency of 55 kHz for 0.5 h, filtered, washed, and then mixed evenly with 100 g of a sodium hexaphosphate aqueous solution with a mass percentage concentration of 0.05%, allowed to stand for 30 min, filtered, washed, and dried to obtain pretreated halloysite; S2: 95 g of toluene, 25 g of mercaptopropyltrimethoxysilane and 10 g of pretreated halloysite were mixed evenly, reacted at 90° C. for 15 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain an intermediate; S3: 88 g of toluene, 27 g of γ-aminopropyltriethoxysilane and the intermediate were mixed evenly, reacted at 90° C. for 8 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain a chelating purifier.

[0039] Comparative Example 1 The production process of ammonium molybdate in this comparative example comprises the following steps: (1) 45 g of molybdenite with an average particle size of 200 mesh was put into a muffle furnace, and the temperature was raised to 300°C at a heating rate of 2°C / min, and the temperature was kept for 1.5 h. The temperature was then raised to 600°C at a heating rate of 3°C / min, and the temperature was kept for 2.5 h. After the calcination was completed, 10 g of sodium hydroxide, 2 g of sodium carbonate and 120 g of water were mixed evenly, and the calcined molybdenite was added. The mixture was stirred at a stirring rate of 300 rpm, ozone was introduced, and the mixture was immersed at a temperature of 90°C for 2 h. The mixture was filtered to obtain a leachate. (2) 200 g of the leachate and 5 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through 201×7 resin at a rate of 1 mL / min. The exchanged resin was rinsed with deionized water, and then eluted with 150 mL of 10% ammonia water at a flow rate of 2 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 70°C, then the temperature is adjusted to 55°C, nitric acid is added to adjust the pH to 2, and crystallization is performed. After the crystallization is completed, the solution is filtered and dried to obtain ammonium molybdate.

[0040] The preparation method of the chelating purifier of this comparative example is as follows: S1: 90 g of toluene, 20 g of mercaptopropyltrimethoxysilane and 10 g of halloysite were mixed evenly, reacted at 80° C. for 20 h under a nitrogen atmosphere, centrifuged, washed and dried to obtain an intermediate; S2: 80 g of toluene, 25 g of γ-aminopropyltriethoxysilane and the intermediate were mixed evenly, reacted at 90° C. for 12 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain a chelating purifier.

[0041] Comparative Example 2 The production process of ammonium molybdate in this comparative example comprises the following steps: (1) 45 g of molybdenite with an average particle size of 200 mesh was put into a muffle furnace, and the temperature was raised to 300°C at a heating rate of 2°C / min, and the temperature was kept for 1.5 h. The temperature was then raised to 600°C at a heating rate of 3°C / min, and the temperature was kept for 2.5 h. After the calcination was completed, 10 g of sodium hydroxide, 2 g of sodium carbonate and 120 g of water were mixed evenly, and the calcined molybdenite was added. The mixture was stirred at a stirring rate of 300 rpm, ozone was introduced, and the mixture was immersed at a temperature of 90°C for 2 h. The mixture was filtered to obtain a leachate. (2) 200 g of the leachate and 5 g of the chelating agent were mixed evenly, filtered, and the filtrate was passed through 201×7 resin at a rate of 1 mL / min. The exchanged resin was rinsed with deionized water, and then eluted with 150 mL of 10% ammonia water at a flow rate of 2 mL / min to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at 70°C, then the temperature is adjusted to 55°C, nitric acid is added to adjust the pH to 2, and crystallization is performed. After the crystallization is completed, the solution is filtered and dried to obtain ammonium molybdate.

[0042] The preparation method of the chelating purifier of this comparative example is as follows: S1: 10 g of halloysite and 10 g of a sodium hydroxide solution with a mass percentage concentration of 18% were mixed, ultrasonically dispersed at a frequency of 20 kHz for 1 hour, filtered, washed, and then mixed evenly with 100 g of a sodium hexaphosphate aqueous solution with a mass percentage concentration of 0.05%, allowed to stand for 20 minutes, filtered, washed, and dried to obtain pretreated halloysite; S2: 90 g of toluene, 20 g of mercaptopropyltrimethoxysilane and 10 g of pretreated halloysite were mixed evenly, reacted at 80° C. for 20 h under a nitrogen atmosphere, centrifuged, washed and dried to obtain a chelating purifier.

[0043] Performance testing The molybdenum content, purity and other impurity contents of the ammonium molybdate prepared in Example 1-3 and Comparative Example 1-2 were tested with reference to GB / T 3460-2017. The test results are as follows: Figure 1 and Figure 2 shown.

[0044] Analyze Examples 1-3 and Comparative Examples 1-2 and combine Figure 1 It can be seen that the chelating purifier prepared by treating and modifying halloysite can play a good role in purifying metal ions in the process of preparing ammonium molybdate, thereby improving the product purity of ammonium molybdate.

[0045] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A production process for ammonium molybdate, characterized in that: The method comprises the following preparation steps: (1) roasting molybdenite with an average particle size of 100-200 mesh, heating it to 300-400°C at a heating rate of 2-4°C / min, keeping it warm for 1-1.5h, then heating it to 600-620°C at a heating rate of 3-5°C / min, keeping it warm for 1.5-2.5h, mixing the roasted molybdenite with alkali solution, introducing ozone, impregnating, filtering, and obtaining a leachate; (2) mixing the leaching solution and the chelating agent, filtering, and passing the filtrate through an ion exchange resin for elution to obtain a sodium molybdate solution; (3) The sodium molybdate solution is concentrated at a temperature of 70-90°C, crystallized, filtered, and dried to obtain ammonium molybdate; The preparation method of the chelating purifier comprises the following steps: S1: mixing halloysite and sodium hydroxide solution, ultrasonically dispersing, filtering, washing, and then mixing evenly with sodium hexaphosphate, standing for 20-30 minutes, taking the upper layer of liquid, centrifugally washing, and drying to obtain pretreated halloysite; S2: Toluene, mercaptopropyltrimethoxysilane and pretreated halloysite are mixed uniformly in a mass ratio of (9-11):(2-2.5):1, reacted at 80-90° C. for 15-20 h under a nitrogen atmosphere, centrifuged, washed, and dried to obtain an intermediate; S3: mixing toluene, γ-aminopropyltriethoxysilane and the intermediate evenly, reacting at 90-100° C. for 6-12 hours under a nitrogen atmosphere, centrifuging, washing, and drying to obtain a chelating purifier; The mass ratio of the halloysite, the sodium hydroxide solution and the sodium hexaphosphate solution is 1:(1-1.5):(10-11).

2. A production process for ammonium molybdate according to claim 1, characterized in that: In the step (1), the alkali solution is composed of sodium hydroxide, sodium carbonate and water, and the mass ratio of the sodium hydroxide, sodium carbonate and water is 1:(0.2-0.44):(12-16).

3. A production process for ammonium molybdate according to claim 1, characterized in that: In the step (1), the immersion temperature is 90-95° C. and the immersion time is 1-2 h.

4. The production process of ammonium molybdate according to claim 1, characterized in that: In the step (2), the ion exchange resin is one of 201×7 resin, D296 resin and LS-32 resin.

5. The production process of ammonium molybdate according to claim 1, characterized in that: In the step (2), the rate at which the filtrate passes through the ion exchange resin is 1-2 mL / min, and the elution rate is 2-2.5 mL / min.

6. The production process of ammonium molybdate according to claim 1, characterized in that: In the step (3), the crystallization temperature is 55-65°C and the pH is 2-2.5.

Images