A process for producing ammonium molybdate by ion exchange method

Abstract

The present invention belongs to the technical field of molybdenum metallurgy, and specifically relates to a process for producing ammonium molybdate by ion exchange, including processes such as "sodium roasting - water leaching - ion exchange enrichment and conversion - impurity removal - deep impurity removal by ion exchange - evaporation, concentration and crystallization". The present invention fully recovers molybdenum resources through the sodium roasting - water leaching process of molybdenum-containing ores, greatly improving the recovery rate of molybdenum resources; selects a modified anion exchange resin to achieve the separation, enrichment and conversion of low-concentration molybdenum resources; and deeply removes impurities from the ammonium molybdate solution, improving the quality of the ammonium molybdate product.

Description

Technical Field

[0001] The present invention belongs to the technical field of molybdenum metallurgy, and particularly relates to a process for producing ammonium molybdate by an ion exchange method. Background Art

[0002] Molybdenum is an important non-renewable strategic resource, which has the characteristics of high melting point and excellent ductility, and can be applied to industries such as industrial catalysis, new energy, aerospace, electronic information, nuclear power, etc. The distribution of molybdenum is very small, and it mainly exists in the form of molybdenum sulfide or molybdate symbiotic with other minerals. It needs to go through processes such as ore dressing enrichment, smelting, and chemical purification to produce molybdenum products with excellent performance for various fields.

[0003] The processes for producing ammonium molybdate mainly include: (1) classical process: using high-soluble roasted molybdenum concentrate as raw material, and preparing ammonium molybdate through processes such as "acid washing - ammonia leaching - purification - acid precipitation"; (2) water washing and acid-free process: using high-soluble roasted molybdenum concentrate as raw material, and preparing ammonium molybdate through processes such as "water washing - ammonia leaching purification - concentration and crystallization"; (3) high-pressure oxygen leaching process: using molybdenum concentrate as raw material, and preparing ammonium molybdate through processes such as "high-pressure oxidation - ammonia leaching - purification - crystallization". Traditional processes for producing ammonium molybdate have relatively high requirements for the quality indicators of the raw material molybdenum concentrate. If the raw material quality indicators do not meet the standards, problems such as too high production costs and low molybdenum metal recovery rate may occur.

[0004] The Chinese patent application document with the application publication number CN1940096A discloses a process for wet recycling of low-grade molybdenum oxide concentrate. In this process, the molybdenum rough concentrate mainly goes through processes such as "grinding the molybdenum rough concentrate, adding sodium carbonate and sodium hydroxide agents for leaching, solid-liquid separation, flotation of the leaching residue to produce molybdenum concentrate, removing silicon with nitric acid, extracting the filtered filtrate with a mixed solvent of N235, secondary octanol and kerosene, back-extracting with ammonia water, and acid-precipitating the obtained ammonium molybdate solution" to obtain ammonium molybdate products. In this process, the solubility of N235 in kerosene is relatively low, and it is easy to precipitate to form a third phase. Although secondary octanol as a cosolvent can improve the phase separation effect, the presence of secondary octanol will increase the viscosity of the organic phase, resulting in a slower two-phase separation speed; at the same time, secondary octanol easily reduces the interfacial tension between the aqueous phase and the organic phase, and it is easy to form an emulsion during the extraction process, resulting in difficult separation of the aqueous phase and the organic phase. Summary of the Invention

[0005] Problems such as difficult separation exist in the existing processes for producing ammonium molybdate; to solve this problem, the present invention provides a process for producing ammonium molybdate by an ion exchange method.

[0006] To achieve the purpose of the present invention, the following technical solutions are adopted in the present invention:

[0007] The present invention provides a process for producing ammonium molybdate by an ion exchange method, including the following steps:

[0008] S1: Subject the molybdenum-containing ore to sodium roasting and water leaching processes to obtain a sodium molybdate solution;

[0009] S2: Adjust the pH of the sodium molybdate solution and then adsorb it using a modified anion exchange resin to obtain the adsorbed modified anion exchange resin and the post-exchange solution;

[0010] S3: Desorb the adsorbed modified anion exchange resin to obtain an ammonium molybdate solution;

[0011] S4: Adjust the pH of the ammonium molybdate solution, add a precipitating agent to the ammonium molybdate solution, and filter to obtain a purified ammonium molybdate solution after impurity removal;

[0012] S5: Adsorb the purified ammonium molybdate solution after impurity removal using a cation exchange resin to obtain a purified ammonium molybdate solution;

[0013] S6: Evaporate, concentrate, and crystallize the purified ammonium molybdate solution to obtain ammonium molybdate;

[0014] In the said step S1, the sodium agent used in the sodium roasting is sodium carbonate, and the mass ratio of the molybdenum-containing ore to sodium carbonate is 1:1.25; the temperature of the sodium roasting is 600 - 750 °C, and the time of the sodium roasting is 1 - 4 h; the temperature of the water leaching is 75 - 90 °C, and the time of the water leaching is 1.5 - 2 h.

[0015] By adopting the above technical solution, subjecting the molybdenum concentrate to sodium roasting can convert molybdenum into compounds such as sodium molybdate, and the sulfur present in the molybdenum concentrate is transferred into sodium sulfate, reducing the generation of SO 2 ; within the temperature range of 600 - 750 °C, molybdenum in the molybdenum concentrate can fully react with sodium carbonate and be completely converted, which is beneficial to subsequent water leaching extraction; when the water leaching temperature is 75 - 90 °C, the dissolution rate of soluble substances such as sodium molybdate in water can be accelerated.

[0016] Preferably, in the said step S2, the preparation method of the modified anion exchange resin includes the following steps:

[0017] (1) Under an oxygen-free atmosphere, uniformly mix an anion exchange resin, benzylvinyltrimethylammonium chloride, and N,N-dimethylformamide, add ammonium persulfate, heat up to 35 - 45 °C and react for 1 - 3 h, then continue to heat up to 50 - 60 °C and react for 10 - 15 h, carry out suction filtration, washing, and drying to obtain a quaternized modified anion exchange resin;

[0018] (2) Uniformly mix the quaternized modified anion exchange resin, 1-vinyl-3-butylimidazolium chloride, and absolute ethanol, wash and dry to obtain the modified anion exchange resin.

[0019] Preferably, in the said step (1), the anion exchange resin is selected from one of D201 resin and D301 resin.

[0020] Preferably, in the step (1), the dosage ratio of the anion exchange resin, benzylvinyltrimethylammonium chloride and N,N-dimethylformamide is 1 g∶(0.3-0.7) g∶80 mL.

[0021] By adopting the above technical solution, at this ratio, the dosage of benzylvinyltrimethylammonium chloride is appropriate. Under the initiation of ammonium persulfate, it can be smoothly grafted onto the resin surface, improving the resin performance, enhancing the adsorption efficiency of molybdenum, and at the same time better maintaining the original pore structure of the resin.

[0022] Preferably, in the step (1), the dosage of ammonium persulfate is 0.8%-1.2% of the total mass of the anion exchange resin and benzylvinyltrimethylammonium chloride.

[0023] By adopting the above technical solution, within this dosage range, the number of free radicals generated by the decomposition of ammonium persulfate can better meet the requirements of the grafting reaction, enabling benzylvinyltrimethylammonium chloride to be effectively grafted onto the resin surface and avoiding uneven distribution of the grafted chains.

[0024] Adopting a stepwise temperature increase reaction in the step (1) can ensure the smooth progress of the grafting reaction, improve the grafting rate, and avoid the occurrence of side reactions such as excessive growth of the grafted chains and crosslinking.

[0025] Preferably, in the step (2), the dosage ratio of the quaternized modified anion exchange resin, 1-vinyl-3-butylimidazolium chloride and absolute ethanol is 1 g∶(0.1-0.3) g∶120 mL.

[0026] By adopting the above technical solution, 1-vinyl-3-butylimidazolium chloride is impregnated onto the resin surface, introducing positively charged 1-vinyl-3-butylimidazolium cations onto the resin surface, increasing the adsorption active sites of the resin for molybdate ions, and enhancing the electrostatic attraction between the resin surface and molybdate ions; the 1-vinyl-3-butylimidazolium chloride impregnated on the resin surface can also complex with molybdate ions, thereby improving the adsorption capacity for molybdate ions.

[0027] Preferably, in the step (2), the mixing temperature is 25-35 °C and the mixing time is 20-26 h.

[0028] Preferably, in the step S2, the pH is 6.5-8.

[0029] Preferably, in the step S2, the post-crossing liquid is sent to a reverse osmosis unit for concentration. The concentrated liquid after reverse osmosis can be sent to a recovery device for the recovery of sodium salts, and the purified water separated by reverse osmosis is returned to the water leaching process for reuse.

[0030] By adopting the above technical solution, the sodium salts in the post-treatment liquid can be effectively enriched, and after further processing, they can be re-introduced into the production process or used for other purposes, reducing the waste liquid discharge and realizing the recycling of resources.

[0031] Preferably, in the step S4, the pH is 7-9; the precipitant is composed of polyaluminum chloride, polyacrylamide and magnesium sulfate according to the mass ratio of (1-2):(0.01-0.05):(3-3.6).

[0032] By adopting the above technical solution, the impurity removal effect is good within the pH range of 7-9. When the pH exceeds this range, Mg(OH) 2 precipitation is likely to occur, consuming the dosage of the precipitant, resulting in a decrease in the precipitation rates of magnesium ammonium phosphate, magnesium silicate and magnesium arsenate, and a deterioration in the impurity removal effect.

[0033] By adopting the above technical solution, polyaluminum chloride can be hydrolyzed into aluminum hydroxide colloid in water, adsorbing impurities such as arsenic and phosphorus on the surface of the colloid; the magnesium ions provided by magnesium sulfate react with arsenate, silicate, phosphate, etc. to form insoluble magnesium arsenate, magnesium silicate and magnesium phosphate precipitates, reducing the concentrations of arsenic, silicon and phosphorus ions in the solution; polyacrylamide further aggregates the small particle flocs formed under the action of polyaluminum chloride and magnesium sulfate, accelerating the precipitation separation, and the synergistic effect of the three improves the removal rate of impurity ions such as arsenic, silicon and phosphorus.

[0034] In summary, the beneficial effects of the present invention are as follows:

[0035] (1) In the present invention, benzylvinyltrimethylammonium chloride is grafted onto the anion exchange resin, introducing a positively charged quaternary ammonium salt group, providing more exchange sites for molybdate ions and increasing the adsorption amount of molybdate ions; 1-vinyl-3-butylimidazolium chloride impregnated on the resin surface can complex with molybdate ions, and at the same time, it can also further increase the adsorption of molybdate ions through electrostatic interaction; the synergistic effect of grafting and impregnation improves the adsorption efficiency of the modified anion exchange resin for molybdate ions;

[0036] (2) In the present invention, a composite precipitant is used for impurity removal. Polyaluminum chloride hydrolyzes and adsorbs arsenic, silicon and phosphorus ions, magnesium sulfate reacts with it to form a precipitate, and polyacrylamide strengthens flocculation. The synergistic effect of the three can significantly improve the removal rates of arsenic, silicon and phosphorus;

[0037] (3) In the present invention, molybdenum resources are fully recovered through the sodium roasting - water leaching process for molybdenum-containing ores, greatly improving the recovery rate of molybdenum resources; the selected modified anion exchange resin can realize the separation, enrichment and conversion of low-concentration molybdenum resources; and the molybdate solution is purified to improve the quality of ammonium molybdate products. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1This is the process flow diagram of producing ammonium molybdate by the ion exchange method of the present invention. Specific Embodiments

[0039] The technical solutions of the present invention will be elaborated in detail below with reference to several representative embodiments of the present invention.

[0040] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. Unless otherwise specified, the materials, reagents, etc. used in the following examples can all be obtained from commercial channels.

[0041] The resins used in the following examples have all undergone a pretreatment process, specifically as follows: Place the resin in a sulfuric acid aqueous solution with a mass fraction of 5% that is 3 times the volume of the resin, soak for 12 h, wash with water until neutral, and then soak the resin in a sodium hydroxide aqueous solution with a mass fraction of 5% that is 3 times the volume of the resin for 12 h, wash with water until neutral, and dry in a vacuum drying oven at 55 °C for 10 h for standby.

[0042] In the present invention, the "post-exchange liquid" refers to the liquid flowing out after the modified anion exchange resin completes the ion exchange process in step S2.

[0043] Example 1

[0044] The process of producing ammonium molybdate by the ion exchange method in this example is as follows:

[0045] S1: Mix 1 kg of molybdenum concentrate (the mass percentage content of Mo is 33.74%) with 1.25 kg of sodium carbonate, crush to 60 mesh, transfer to a muffle furnace, heat up to 650 °C and roast for 3 h; crush the roasted molybdenum concentrate to 60 mesh, add it to the leaching reaction kettle, stir, heat up to 90 °C, the water leaching time is 1.5 h, filter by suction, transfer the separated solid to the leaching reaction kettle again for the water leaching process, repeat the water leaching 3 times, filter by suction to obtain a sodium molybdate solution, and recycle the leaching residue;

[0046] S2: After adjusting the pH of the sodium molybdate solution to 6.5, adsorb it with a modified anion exchange resin at 35 °C to obtain the adsorbed modified anion exchange resin and the post-exchange liquid. The post-exchange liquid is sent to a reverse osmosis unit for concentration. The concentrated liquid after reverse osmosis is sent to a recovery device for recovering sodium salts, and the purified water separated by reverse osmosis is returned to the water leaching process for reuse. The molybdenum adsorption rate is 98.74%;

[0047] S3: After rinsing the adsorbed modified anion exchange resin in step S2 with clear water, desorb it with an ammonia aqueous solution with a mass fraction of 10% to obtain an ammonium molybdate solution;

[0048] S4: After adjusting the pH of the ammonium molybdate solution to 8, add 2 g of polyaluminum chloride to the ammonium molybdate solution and stir for 30 min, then add 6.5 g of magnesium sulfate and stir for 1 h. Next, add 0.04 g of polyacrylamide and stir for 30 min. Filter to obtain the ammonium molybdate solution after impurity removal;

[0049] S5: After adjusting the pH of the ammonium molybdate solution after impurity removal to 7, perform adsorption using D112 resin at 30 °C to obtain a purified ammonium molybdate solution;

[0050] S6: Evaporate, concentrate, and crystallize the purified ammonium molybdate solution to obtain ammonium molybdate; the steam condensate generated during the evaporation and concentration process is returned to the water leaching process for reuse.

[0051] The process flow diagram of producing ammonium molybdate by the ion exchange method is shown in Figure 1 。

[0052] The preparation method of the modified anion exchange resin in this example is as follows:

[0053] (1) Under a nitrogen atmosphere, add 10 g of D201 resin, 4 g of benzylvinyltrimethylammonium chloride, and 80 mL of N,N-dimethylformamide to a four-necked flask and stir for 20 min. Add 0.14 g of ammonium persulfate, raise the temperature to 45 °C, and react for 2 h. Then continue to raise the temperature to 50 °C and react for 15 h. Perform suction filtration, extract with acetone for 24 h, and dry in a vacuum drying oven at 60 °C for 10 h to obtain a quaternized modified anion exchange resin;

[0054] (2) Add 10 g of the quaternized modified anion exchange resin, 1.5 g of 1-vinyl-3-butylimidazolium chloride, and 120 mL of absolute ethanol to a flask and stir for 15 min. Oscillate in a water bath constant temperature oscillator at 25 °C for 24 h, wash, and dry in a vacuum drying oven at 40 °C for 12 h to obtain a modified anion exchange resin.

[0055] Example 2

[0056] The process of producing ammonium molybdate by the ion exchange method in this example is as follows:

[0057] S1: Mix 1 kg of molybdenum concentrate (the mass percentage of Mo is 33.74%) with 1.25 kg of sodium carbonate, crush to 60 mesh, transfer to a muffle furnace, and roast at 750 °C for 2 h; crush the molybdenum concentrate after roasting to 60 mesh, add it to the leaching reactor, stir, raise the temperature to 75 °C, and the water leaching time is 2 h. Perform suction filtration, transfer the separated solid back to the leaching reactor for the water leaching process, repeat the water leaching 3 times, perform suction filtration to obtain a sodium molybdate solution, and recycle the leaching residue;

[0058] S2: After adjusting the pH of the sodium molybdate solution to 7, adsorb it at 35°C using a modified anion exchange resin to obtain the adsorbed modified anion exchange resin and the post-exchange solution. The post-exchange solution is sent to a reverse osmosis unit for concentration. The concentrated solution after reverse osmosis is sent to a recovery device for recovering sodium salts, and the purified water separated by reverse osmosis is returned to the water leaching process for reuse. The molybdenum adsorption rate is 98.22%;

[0059] S3: Wash the adsorbed modified anion exchange resin in step S2 with clear water, and then desorb it with a 10% ammonia water solution by mass to obtain an ammonium molybdate solution;

[0060] S4: After adjusting the pH of the ammonium molybdate solution to 7, add 2 g of polyaluminum chloride to the ammonium molybdate solution and stir for 30 min, add 7.2 g of magnesium sulfate and stir for 1 h, then add 0.02 g of polyacrylamide and stir for 30 min, and filter to obtain the ammonium molybdate solution after impurity removal;

[0061] S5: After adjusting the pH of the ammonium molybdate solution after impurity removal to 7, adsorb it at 30°C using D112 resin to obtain a purified ammonium molybdate solution;

[0062] S6: Evaporate, concentrate, and crystallize the purified ammonium molybdate solution to obtain ammonium molybdate; the steam condensate generated during the evaporation and concentration process is returned to the water leaching process for reuse.

[0063] The preparation method of the modified anion exchange resin in this example is as follows:

[0064] (1) Under a nitrogen atmosphere, add 10 g of D201 resin, 7 g of benzylvinyltrimethylammonium chloride, and 80 mL of N,N-dimethylformamide to a four-necked flask, stir for 20 min, add 0.14 g of ammonium persulfate, heat up to 40°C and react for 3 h, continue to heat up to 60°C and react for 10 h, perform suction filtration, extract with acetone for 24 h, and dry in a vacuum drying oven at 60°C for 10 h to obtain a quaternized modified anion exchange resin;

[0065] (2) Add 10 g of the quaternized modified anion exchange resin, 2 g of 1-vinyl-3-butylimidazolium chloride, and 120 mL of absolute ethanol to a flask, stir for 15 min, oscillate in a water bath constant temperature oscillator at 30°C for 20 h, wash, and dry in a vacuum drying oven at 40°C for 12 h to obtain the modified anion exchange resin.

[0066] Example 3

[0067] The process for producing ammonium molybdate by an ion exchange method in this example is as follows:

[0068] S1: Mix 1 kg of molybdenum concentrate (with a mass percentage of Mo being 56.52%) with 1.25 kg of sodium carbonate, crush it to 60 mesh, transfer it to a muffle furnace, heat it up to 700 °C and roast for 1 h; crush the roasted molybdenum concentrate to 60 mesh, add it to a leaching reactor, stir, heat it up to 80 °C, carry out water leaching for 2 h, filter by suction, transfer the separated solid back to the leaching reactor for the water leaching process, repeat the water leaching 3 times, filter by suction to obtain a sodium molybdate solution, and recycle the leaching residue;

[0069] S2: After adjusting the pH of the sodium molybdate solution to 8, adsorb it at 35 °C using a modified anion exchange resin to obtain the adsorbed modified anion exchange resin and the post-exchange solution. The post-exchange solution is sent to a reverse osmosis unit for concentration. The concentrated solution after reverse osmosis is sent to a recovery device for recovering sodium salts, and the purified water separated by reverse osmosis is returned to the water leaching process for reuse. The molybdenum adsorption rate is 99.52%;

[0070] S3: After rinsing the adsorbed modified anion exchange resin in step S2 with clear water, desorb it with a 10% ammonia aqueous solution by mass to obtain an ammonium molybdate solution;

[0071] S4: After adjusting the pH of the ammonium molybdate solution to 9, add 3 g of polyaluminum chloride to the ammonium molybdate solution and stir for 30 min, add 6 g of magnesium sulfate and stir for 1 h, then add 0.08 g of polyacrylamide and stir for 30 min, and filter to obtain the ammonium molybdate solution after impurity removal;

[0072] S5: After adjusting the pH of the ammonium molybdate solution after impurity removal to 7, adsorb it at 30 °C using D112 resin to obtain a purified ammonium molybdate solution;

[0073] S6: Evaporate, concentrate, and crystallize the purified ammonium molybdate solution to obtain ammonium molybdate; the steam condensate generated during the evaporation and concentration process is returned to the water leaching process for reuse.

[0074] The preparation method of the modified anion exchange resin in this example is as follows:

[0075] (1) Under a nitrogen atmosphere, add 10 g of D301 resin, 6 g of benzylvinyltrimethylammonium chloride, and 80 mL of N,N-dimethylformamide to a four-necked flask, stir for 20 min, add 0.19 g of ammonium persulfate, heat up to 35 °C and react for 1 h, continue to heat up to 55 °C and react for 12 h, filter by suction, extract with acetone for 24 h, and dry in a vacuum drying oven at 60 °C for 10 h to obtain a quaternized modified anion exchange resin;

[0076] (2) Add 10 g of quaternized modified anion exchange resin, 3 g of 1-vinyl-3-butylimidazolium chloride, and 120 mL of absolute ethanol to a flask, stir for 15 min, oscillate at 35 °C for 26 h in a water bath constant temperature oscillator, wash, and dry at 40 °C for 12 h in a vacuum drying oven to obtain the modified anion exchange resin.

[0077] Example 4

[0078] The process for producing ammonium molybdate by an ion exchange method in this example is as follows:

[0079] S1: Mix 1 kg of molybdenite concentrate (the mass percentage of Mo is 56.52%) with 1.25 kg of sodium carbonate, crush to 60 mesh, transfer to a muffle furnace, heat up to 600 °C and roast for 4 h; crush the roasted molybdenite concentrate to 60 mesh, add it to a leaching reactor, stir, heat up to 85 °C, leach with water for 1.5 h, filter by suction, transfer the separated solid back to the leaching reactor for the water leaching process, repeat the water leaching 3 times, filter by suction to obtain a sodium molybdate solution, and recycle the leaching residue.

[0080] S2: After adjusting the pH of the sodium molybdate solution to 7.5, adsorb it at 35 °C using the modified anion exchange resin to obtain the adsorbed modified anion exchange resin and the post-exchange solution. The post-exchange solution is sent to a reverse osmosis unit for concentration. The concentrated solution after reverse osmosis is sent to a recovery device for recovering sodium salts, and the purified water separated by reverse osmosis is returned to the water leaching process for reuse. The molybdenum adsorption rate is 99.15%.

[0081] S3: After rinsing the adsorbed modified anion exchange resin in step S2 with clear water, desorb it with a 10% ammonia water solution by mass to obtain an ammonium molybdate solution.

[0082] S4: After adjusting the pH of the ammonium molybdate solution to 9, add 2 g of polyaluminum chloride to the ammonium molybdate solution and stir for 30 min, add 6.5 g of magnesium sulfate and stir for 1 h, then add 0.04 g of polyacrylamide and stir for 30 min, and filter to obtain the ammonium molybdate solution after impurity removal.

[0083] S5: After adjusting the pH of the ammonium molybdate solution after impurity removal to 7, adsorb it at 30 °C using D112 resin to obtain a purified ammonium molybdate solution.

[0084] S6: Evaporate, concentrate, and crystallize the purified ammonium molybdate solution to obtain ammonium molybdate; the steam condensate generated during the evaporation and concentration process is returned to the water leaching process for reuse.

[0085] The preparation method of the modified anion exchange resin in this example is as follows:

[0086] (1) Under a nitrogen atmosphere, 10 g of D201 resin, 3 g of benzylvinyltrimethylammonium chloride, and 80 mL of N,N-dimethylformamide were added to a four-necked flask and stirred for 20 min. 0.13 g of ammonium persulfate was added, and the temperature was raised to 30 °C for reaction for 2 h. Then the temperature was further raised to 50 °C for reaction for 15 h. Filtration was carried out, and extraction with acetone was performed for 24 h. Drying was carried out in a vacuum drying oven at 60 °C for 10 h to obtain a quaternized modified anion exchange resin;

[0087] (2) 10 g of the quaternized modified anion exchange resin, 1 g of 1-vinyl-3-butylimidazolium chloride, and 120 mL of absolute ethanol were added to a flask and stirred for 15 min. Oscillation was carried out at 25 °C for 22 h in a water bath constant temperature oscillator, followed by washing. Drying was carried out in a vacuum drying oven at 40 °C for 12 h to obtain a modified anion exchange resin.

[0088] The ammonium molybdate products prepared in Examples 1 - 4 of the present invention all meet the detection standards of "GB / T 3460 - 2017 Ammonium Molybdate".

[0089] Comparative Example 1

[0090] The difference from Example 1 is that in the preparation of the modified anion exchange resin in this comparative example, the preparation of step (2) is not carried out, and the rest is the same as in Example 1;

[0091] In this comparative example, the molybdenum adsorption rate is 94.34%; the lack of impregnation of the resin reduces the sites for molybdate ions adsorbed on the resin surface; at the same time, the substances complexed with molybdate ions on the resin surface are reduced. Therefore, the molybdenum adsorption rate of the resin is decreased.

[0092] Comparative Example 2

[0093] The difference from Example 1 is that in the preparation of the modified anion exchange resin in this comparative example, the preparation of step (1) is not carried out, and the rest is the same as in Example 1;

[0094] In this comparative example, the molybdenum adsorption rate is 92.52%; introducing benzylvinyltrimethylammonium chloride onto the resin, the quaternary ammonium cations present in its molecule can form electrostatic attraction with molybdate ions. Compared with the case without introduction, the sites on the resin that can adsorb molybdate ions increase, effectively improving the molybdate ion adsorption rate of the resin.

[0095] Comparative Example 3

[0096] The difference from Example 1 is that in step S2 of this comparative example, D201 resin is used instead of the modified anion exchange resin, and the rest is the same as in Example 1;

[0097] In this comparative example, the molybdenum adsorption rate was 90.02%. Comparing with the unmodified D201 resin, it can be seen that the modified D201 resin increased the adsorption sites for molybdate ions, and there was a complexation effect on molybdate ions on the resin surface. Therefore, the molybdenum adsorption rate of the modified D201 resin was stronger than that of the D201 resin.

[0098] Comparative Examples 4 - 6

[0099] The difference from Example 1 was that in this comparative example, the dosage of the precipitant in step S4 was changed. Specifically, see Table 1, and the removal rate results of arsenic, silicon, and phosphorus are shown in Table 2. The rest were the same as in Example 1.

[0100] Table 1 Dosage of the Precipitant

[0101]

[0102] Table 2 Removal Rate Results

[0103]

[0104] As can be seen from Table 1 and Table 2, the components and dosage ratios of polyaluminum chloride, magnesium sulfate, and polyacrylamide in the precipitant have been optimized. Any change in the components and dosage ratios will affect the removal rates of arsenic, silicon, and phosphorus impurities.

[0105] The above has made an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent replacement that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. A process for producing ammonium molybdate by ion exchange, characterized in that: The steps include: S1: subjecting the molybdenum-containing ore to sodium roasting and water leaching to obtain a sodium molybdate solution; S2: adjusting the pH of the sodium molybdate solution and then adsorbing it with a modified anion exchange resin to obtain an adsorbed modified anion exchange resin and a post-exchange liquid; S3: desorbing the adsorbed modified anion exchange resin to obtain an ammonium molybdate solution; S4: After adjusting the pH of the ammonium molybdate solution, adding a precipitant to the ammonium molybdate solution, filtering, and obtaining a decontaminated ammonium molybdate solution; S5: Adsorbing the ammonium molybdate solution after impurities removal by cation exchange resin to obtain purified ammonium molybdate solution; S6: evaporating, concentrating and crystallizing the purified ammonium molybdate solution to obtain ammonium molybdate; In the step S1, the sodium-forming agent used in the sodium-forming roasting is sodium carbonate, and the mass ratio of the molybdenum-containing ore to the sodium carbonate is 1:1.25; the temperature of the sodium-forming roasting is 600-750° C., and the time of the sodium-forming roasting is 1-4 hours; The preparation method of the modified anion exchange resin comprises the following steps: (1) In an oxygen-free atmosphere, an anion exchange resin, benzyltrimethylammonium chloride and N,N-dimethylformamide are uniformly mixed, ammonium persulfate is added, the temperature is raised to 35-45°C for reaction, the temperature is further raised to 50-60°C for reaction, and then the mixture is filtered, washed and dried to obtain a quaternary ammonium modified anion exchange resin; (2) The quaternary ammonium modified anion exchange resin, 1-vinyl-3-butyl imidazole chloride and anhydrous ethanol are uniformly mixed, washed and dried to obtain a product.

2. The process for producing ammonium molybdate by an ion exchange method according to claim 1, characterized in that: In step S1, the water immersion temperature is 75-90° C., and the water immersion time is 1.5-2 hours.

3. The process for producing ammonium molybdate by an ion exchange method according to claim 1, characterized in that: In the step (1), the reaction time at 35-45°C is 1-3 hours, and the reaction time at 50-60°C is 10-15 hours.

4. The process for producing ammonium molybdate by an ion exchange method according to claim 1, characterized in that: In the step (1), the usage ratio of anion exchange resin, benzyltrimethylammonium chloride and N,N-dimethylformamide is 1 g: (0.3-0.7) g: 80 mL.

5. The process for producing ammonium molybdate by an ion exchange method according to claim 1, characterized in that: In the step (1), the amount of ammonium persulfate used is 0.8%-1.2% of the total mass of the anion exchange resin and benzyltrimethylammonium chloride.

6. The process for producing ammonium molybdate by an ion exchange method according to claim 1, characterized in that: In the step (2), the ratio of the quaternary ammonium modified anion exchange resin, 1-vinyl-3-butyl imidazole chloride and anhydrous ethanol is 1 g: (0.1-0.3) g: 120 mL.

7. The process for producing ammonium molybdate by an ion exchange method according to claim 1, characterized in that: In the step (2), the mixing time is 20-26 hours.

8. The process for producing ammonium molybdate by ion exchange according to claim 1, characterized in that: In step S2, the pH is 6.5-8.

9. The process for producing ammonium molybdate by ion exchange according to claim 1, characterized in that: In the step S4, the pH is 7-9; the precipitant is composed of polyaluminium chloride, polyacrylamide and magnesium sulfate in a mass ratio of (1-2): (0.01-0.05): (3-3.6).

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