Method for smelting ammonium paratungstate by tungsten without high-salinity wastewater discharge

Abstract

The invention relates to the technical field of tungsten ore smelting, and provides a method for smelting ammonium paratungstate from tungsten without high-salinity wastewater discharge. According to the method, wolframite is decomposed through alkali pressure boiling, scheelite is decomposed through acid leaching, an obtained initial sodium tungstate solution reacts with tungstic acid to obtain a crude sodium tungstate solution, and ammonium paratungstate is obtained through impurity removal, molybdenum removal, extraction, reverse extraction and evaporative crystallization; sodium sulfate wastewater generated by extraction is subjected to impurity removal and then subjected to bipolar membrane electrodialysis treatment, a sulfuric acid solution and a sodium hydroxide solution are obtained, the sulfuric acid solution is used for extracting agent regeneration, and the sodium hydroxide solution is used for alkali autoclaving. According to the method provided by the invention, no high-salinity wastewater is generated, so that the wastewater treatment problem is fundamentally avoided; moreover, the wolframite and the scheelite are treated according to the mineral characteristic difference of the two kinds of ore, it can be guaranteed that the wolframite and the scheelite are fully decomposed, oxalic acid generated by acid leaching of the scheelite can be reused in the process, and the cost can be further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tungsten ore smelting, and in particular to a method for smelting ammonium paratungstate from tungsten without discharging high-salt wastewater. Background Art

[0002] Currently, tungsten smelting companies generally use traditional processes such as alkaline autoclave-ion exchange, alkaline autoclave-extraction, and acid decomposition-extraction to produce ammonium paratungstate (APT). These processes generate large amounts of high-salt wastewater (usually with a salt concentration greater than 5%) containing sodium chloride (NaCl) or sodium sulfate (Na2SO4) during the leaching, neutralization, and crystallization stages.

[0003] In recent years, the treatment of high-salinity wastewater has become a major challenge for the tungsten smelting industry. On the one hand, the high salt concentration in high-salinity wastewater can lead to environmental problems such as soil salinization and water ecological damage if discharged directly. On the other hand, traditional treatment methods, such as evaporation and crystallization, are not only energy-intensive and require significant equipment investment, but also prone to secondary pollution during the treatment process, making it difficult to achieve a balance between economic and environmental benefits. Furthermore, the sodium salts in high-salinity wastewater are not effectively recycled, resulting in resource loss.

[0004] In the existing technology, although some studies have attempted to reduce wastewater discharge by improving process flow or adopting new materials, the problem of high-salt wastewater discharge has not been fundamentally solved. Summary of the Invention

[0005] In view of this, the present invention provides a method for smelting ammonium paratungstate from tungsten without discharging high-salt wastewater. The method provided by the present invention does not produce high-salt wastewater, which can fundamentally avoid the problem of high-salt wastewater treatment.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A method for smelting ammonium paratungstate from tungsten without discharging high-salt wastewater, comprising the following steps:

[0008] Wolframite and sodium hydroxide solution are mixed and then subjected to alkaline autoclave cooking to obtain initial sodium tungstate solution and tungsten slag;

[0009] The scheelite is mixed with a sulfuric acid-oxalic acid mixed solution for acid leaching to obtain calcium sulfate slag and an oxalic acid-tungsten complex solution; the oxalic acid-tungsten complex solution is heated and decomposed to obtain tungstic acid and an oxalic acid solution; the oxalic acid solution is returned to the acid leaching step to prepare a sulfuric acid-oxalic acid mixed solution;

[0010] The initial sodium tungstate solution and tungstic acid are mixed and reacted to obtain a crude sodium tungstate solution;

[0011] The crude sodium tungstate solution and the magnesium compound are mixed to remove impurities, thereby obtaining a cleaned sodium tungstate solution and cleaned slag;

[0012] The impurity-removed sodium tungstate solution is mixed with hydrogen sulfide to remove molybdenum, thereby obtaining a refined sodium tungstate solution and a molybdenum-removed slag;

[0013] Extracting the refined sodium tungstate solution with an extractant to obtain an extract phase and sodium sulfate wastewater;

[0014] The extract phase is stripped with aqueous ammonia to obtain an ammonium tungstate solution; the ammonium tungstate solution is evaporated and crystallized to obtain ammonium paratungstate;

[0015] The sodium sulfate wastewater is subjected to activated carbon adsorption to remove impurities to obtain impurity-removed wastewater; the impurity-removed wastewater is subjected to electrodialysis treatment using a bipolar membrane to obtain a sulfuric acid solution and a sodium hydroxide solution, wherein the sulfuric acid solution is used to regenerate the extractant, and the sodium hydroxide solution is concentrated and used in the alkaline autoclave.

[0016] Preferably, the wolframite has a tungsten content of 50 to 60 degrees and a mesh size of 300 to 325 meshes; the concentration of the sodium hydroxide solution used in the alkali autoclave is 450 to 500 g / L; and the mass ratio of tungsten in the wolframite to sodium hydroxide in the sodium hydroxide solution used in the alkali autoclave is 1:1 to 3;

[0017] The temperature of the alkaline autoclave is 150-180° C., the pressure is 0.8-1 MPa, and the heat preservation and pressure holding time is 3-4 hours.

[0018] Preferably, the tungsten degree of the scheelite is 20 to 60 degrees, and the mesh size is 200 to 325 meshes; the concentration of oxalic acid in the sulfuric acid-oxalic acid mixed solution is 0.5 to 2.5 mol / L, and the concentration of sulfuric acid is 0.5 to 2.5 mol / L; the liquid-solid ratio of the sulfuric acid-oxalic acid mixed solution to the scheelite is 5 to 25 mL:1 g, the temperature of the acid leaching is 50 to 80° C., and the time is 4 to 8 h; the temperature of the thermal decomposition is 85 to 100° C., and the time is 1 to 4 h.

[0019] Preferably, the concentration of the initial sodium tungstate solution is 30-40 g / L; the mass ratio of the initial sodium tungstate solution to tungstic acid is 2-3:1; the reaction temperature is 80-110° C., and the reaction time is 1-2 h.

[0020] Preferably, the molar ratio of the magnesium compound to arsenic in the crude sodium tungstate solution is 1.2 to 1.5:1; the magnesium compound includes one or more of magnesium oxide and magnesium salts, and the magnesium salts include one or both of basic magnesium carbonate and magnesium sulfate; the impurity removal includes a first-stage impurity removal and a second-stage impurity removal performed sequentially, the pH value of the first-stage impurity removal is 8 to 12, and the reaction time is 1 to 2 hours, and the pH value of the second-stage impurity removal is 6 to 8, and the reaction time is 0.5 to 1.5 hours.

[0021] Preferably, the MoO4 in the sodium tungstate solution is removed 2- The molar ratio of molybdenum to H2S is 1:3-4.5; the pH value of the molybdenum removal is 2-3.5, the temperature is 20-50°C, and the time is 30-120 minutes.

[0022] Preferably, the pH value of the refined sodium tungstate solution is adjusted to 2-3 before the extraction; the volume ratio of the extractant to the refined sodium tungstate solution is 1-1.5:1; the volume ratio of the ammonia water to the extraction phase is 2-3:1, and the concentration of the ammonia water is 10-20wt%; and the extractant is N235.

[0023] Preferably, in the activated carbon adsorption, the flow rate of the sodium sulfate wastewater into the activated carbon is 2 to 4 m 3 / h; the volume of sodium sulfate wastewater and the mass ratio of activated carbon introduced per hour is 1m 3 :(200~500)kg.

[0024] Preferably, the electrodialysis treatment conditions include: a current density of 700 to 900 A / m 2 , the concentration of polar water is 3 to 5 wt%; the concentration of the sulfuric acid solution obtained by the electrodialysis treatment is 1 to 1.5 mol / L, and the concentration of the sodium hydroxide solution is 2 to 2.5 mol / L.

[0025] Preferably, the temperature of the evaporation crystallization is 80 to 95° C., the time is 9 to 10 hours, and the vacuum degree is -0.08 to -0.06 MPa.

[0026] The present invention provides a method for smelting ammonium paratungstate from tungsten without high-salt wastewater discharge, comprising the following steps: mixing wolframite and sodium hydroxide solution and performing alkaline autoclaving to obtain an initial sodium tungstate solution and tungsten slag; mixing scheelite and a sulfuric acid-oxalic acid mixed solution and performing acid leaching to obtain calcium sulfate slag and an oxalic acid-tungsten complex solution; heating and decomposing the oxalic acid-tungsten complex solution to obtain tungstic acid and oxalic acid solution; returning the oxalic acid solution to the acid leaching step to prepare a sulfuric acid-oxalic acid mixed solution; mixing the initial sodium tungstate solution and tungstic acid to react to obtain a crude sodium tungstate solution; mixing the crude sodium tungstate solution and a magnesium compound to remove impurities to obtain the impurity-removed tungstic acid. The method comprises the following steps: extracting the refined sodium tungstate solution with an extractant to obtain an extract phase and sodium sulfate wastewater; back-extracting the extract phase with aqueous ammonia to obtain an ammonium tungstate solution; evaporating and crystallizing the ammonium tungstate solution to obtain ammonium paratungstate; subjecting the sodium sulfate wastewater to activated carbon adsorption to remove impurities to obtain impurity-removed wastewater; and subjecting the impurity-removed wastewater to electrodialysis treatment using a bipolar membrane to obtain a sulfuric acid solution and a sodium hydroxide solution. The sulfuric acid solution is used to regenerate the extractant, and the sodium hydroxide solution is concentrated and used in the alkaline autoclave. In the method provided by the present invention, sodium sulfate wastewater is treated by a bipolar membrane, and the generated acid-base solution can be reused in the process, thereby avoiding the generation of high-salt wastewater, fundamentally avoiding the problem of wastewater treatment, and reducing process costs. In addition, the present invention treats wolframite and scheelite separately according to the differences in the mineral properties of the two ores, which can ensure that the wolframite and scheelite are fully decomposed and has wide adaptability. In addition, sodium carbonate is usually used to decompose scheelite in traditional methods, and high-salt wastewater is generated during the treatment process. In the present invention, a sulfuric acid-oxalic acid mixed solution is used to acid-leach the scheelite, which has low cost, and the generated oxalic acid can be reused in the process, which can further reduce process costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a process flow chart of the method for smelting ammonium paratungstate from tungsten without discharging high-salt wastewater provided by the present invention. DETAILED DESCRIPTION

[0028] The present invention provides a method for smelting ammonium paratungstate from tungsten without discharging high-salt wastewater, comprising the following steps:

[0029] Wolframite and sodium hydroxide solution are mixed and then subjected to alkaline autoclave cooking to obtain initial sodium tungstate solution and tungsten slag;

[0030] The scheelite is mixed with a sulfuric acid-oxalic acid mixed solution for acid leaching to obtain calcium sulfate slag and an oxalic acid-tungsten complex solution; the oxalic acid-tungsten complex solution is heated and decomposed to obtain tungstic acid and an oxalic acid solution; the oxalic acid solution is returned to the acid leaching step to prepare a sulfuric acid-oxalic acid mixed solution;

[0031] The initial sodium tungstate solution and tungstic acid are mixed and reacted to obtain a crude sodium tungstate solution;

[0032] The crude sodium tungstate solution and the magnesium compound are mixed to remove impurities, thereby obtaining a cleaned sodium tungstate solution and cleaned slag;

[0033] The impurity-removed sodium tungstate solution is mixed with hydrogen sulfide to remove molybdenum, thereby obtaining a refined sodium tungstate solution and a molybdenum-removed slag;

[0034] Extracting the refined sodium tungstate solution with an extractant to obtain an extract phase and sodium sulfate wastewater;

[0035] The extract phase is stripped with aqueous ammonia to obtain an ammonium tungstate solution; the ammonium tungstate solution is evaporated and crystallized to obtain ammonium paratungstate;

[0036] The sodium sulfate wastewater is subjected to activated carbon adsorption to remove impurities to obtain impurity-removed wastewater; the impurity-removed wastewater is subjected to electrodialysis treatment using a bipolar membrane to obtain a sulfuric acid solution and a sodium hydroxide solution; the sulfuric acid solution is used to regenerate the extractant, and the sodium hydroxide solution is concentrated and used in the alkaline autoclave.

[0037] The present invention mixes wolframite and sodium hydroxide solution and performs alkaline autoclaving to obtain an initial sodium tungstate solution and tungsten slag. In the present invention, the tungsten degree of the wolframite is preferably 50 to 60 degrees, specifically 50 degrees, 55 degrees or 60 degrees, and the mesh number of the wolframite is preferably 300 to 325 meshes, specifically 300 meshes, 310 meshes or 325 meshes; the wolframite is preferably ball-milled before use to meet the above mesh number requirements; the concentration of the sodium hydroxide solution used in the alkaline autoclaving is preferably 450 to 500 g / L, specifically 450 g / L, 470 g / L or 500 g / L; the tungsten in the wolframite and the alkali The mass ratio of sodium hydroxide in the sodium hydroxide solution used for autoclaving (referred to as the tungstate-to-alkali ratio) is preferably 1:1-3, specifically 1:1, 1:2, or 1:3; the temperature of the alkali autoclaving is preferably 150-180°C, and in the embodiment, it can be 150°C, 160°C, or 180°C; the pressure of the alkali autoclaving is preferably 0.8-1 MPa, and in the embodiment, it can be 0.8 MPa, 0.9 MPa, or 1 MPa; the holding time of the alkali autoclaving is preferably 3-4 hours, specifically 3 hours, 3.5 hours, or 4 hours. After the alkali autoclaving is completed, the present invention preferably performs solid-liquid separation on the obtained feed liquid to obtain an initial sodium tungstate solution.

[0038] In the present invention, the concentration of the initial sodium tungstate solution is preferably 30-40 g / L.

[0039] The present invention mixes scheelite with a sulfuric acid-oxalic acid mixed solution for acid leaching to obtain calcium sulfate slag and an oxalic acid-tungsten complex solution; the oxalic acid-tungsten complex solution is heated and decomposed to obtain tungstic acid and oxalic acid solution; the oxalic acid solution is returned to the acid leaching step to prepare the sulfuric acid-oxalic acid mixed solution. In the present invention, the tungsten content of the scheelite is preferably 20 to 60 degrees, specifically 20 degrees, 30 degrees, or 50 degrees; the mesh size of the scheelite is preferably 200 to 325 mesh, specifically 200 mesh, 280 mesh, or 325 mesh; the concentration of oxalic acid in the sulfuric acid-oxalic acid mixed solution is preferably 0.5 to 2.5 mol / L, specifically 0.5 mol / L, 1 mol / L, or 2.5 mol / L; the concentration of sulfuric acid in the sulfuric acid-oxalic acid mixed solution is 0. 5 to 2.5 mol / L, specifically 0.5 mol / L, 1 mol / L or 2.5 mol / L; the liquid-to-solid ratio of the sulfuric acid-oxalic acid mixed solution to scheelite is preferably 5 to 25 mL:1 g, specifically 10 mL:1 g, 15 mL:1 g or 25 mL:1 g; the acid leaching temperature is preferably 50 to 80 ° C, specifically 50 ° C, 60 ° C or 80 ° C, and the acid leaching time is preferably 4 to 8 hours, specifically 4 hours, 6 hours or 8 hours. After the acid leaching is completed, the present invention preferably performs solid-liquid separation on the obtained acid leaching liquid to obtain calcium sulfate slag and oxalic acid-tungsten complex solution, and the solid-liquid separation method is preferably filter press.

[0040] In the present invention, the thermal decomposition temperature is preferably 85-100°C, specifically 90°C or 100°C, and the thermal decomposition time is preferably 1-4 hours, specifically 3 hours or 4 hours. During the thermal decomposition process, the complex decomposes, and tungstic acid precipitates from the system to form a solid precipitate. After the thermal decomposition is completed, the present invention performs solid-liquid separation on the decomposed liquid to obtain an oxalic acid solution and tungstic acid.

[0041] After obtaining an initial sodium tungstate solution and tungstic acid, the present invention mixes the initial sodium tungstate solution and tungstic acid to react and obtain a crude sodium tungstate solution. In the present invention, the mass ratio of the initial sodium tungstate solution to tungstic acid is preferably 2-3:1, specifically 2:1, 2.5:1, or 3:1; the reaction temperature is preferably 80-110°C, specifically 80°C, 100°C, or 110°C; and the reaction time is preferably 1-2 hours, specifically 1 hour, 1.5 hours, or 2 hours. After the initial sodium tungstate solution and tungstic acid are mixed, the tungstic acid first undergoes an acid-base neutralization reaction with the excess sodium hydroxide in the initial sodium tungstate solution to produce soluble sodium tungstate and water. The remaining tungstic acid then undergoes an acid-salt condensation reaction with the sodium tungstate to produce sodium dodecanotungstate. The main components of the crude sodium tungstate solution are sodium tungstate and sodium dodecanotungstate.

[0042] After obtaining a crude sodium tungstate solution, the present invention mixes the crude sodium tungstate solution with a magnesium compound to remove impurities, thereby obtaining a decontaminated sodium tungstate solution and decontaminated slag. In the present invention, the molar ratio of the magnesium compound to arsenic in the crude sodium tungstate solution is preferably 1.2 to 1.5:1, specifically 1.2:1, 1.3:1, or 1.5:1. The magnesium compound comprises one or more of magnesium oxide and a magnesium salt, preferably one or both of basic magnesium carbonate and magnesium sulfate. The decontamination comprises a first-stage decontamination and a second-stage decontamination, performed sequentially. The pH value of the first-stage decontamination is preferably 8 to 12, specifically 8, 10, or 12. The reaction time of the first-stage decontamination is preferably 1 to 2 hours, specifically 1 hour, 1.5 hours, or 2 hours. The pH value of the second-stage decontamination is preferably 6 to 8, specifically 6, 7, or 8. The reaction time of the second-stage decontamination is preferably 0.5 to 1.5 hours, specifically 0.5 hours, 1 hour, or 1.5 hours. The decontamination can be performed at room temperature. In a specific embodiment of the present invention, the pH value of the crude sodium tungstate solution is preferably adjusted to 8-12 before adding a magnesium compound for the first stage of impurity removal, and then the pH value is adjusted to 6-8 for the second stage of impurity removal. After the impurity removal is completed, the present invention preferably performs solid-liquid separation on the resulting liquid to obtain a cleaned sodium tungstate solution and cleaned residue; the solid-liquid separation is preferably performed using a filter press.

[0043] After obtaining the impurity-removed sodium tungstate solution, the present invention mixes the impurity-removed sodium tungstate solution with hydrogen sulfide to remove molybdenum, thereby obtaining a refined sodium tungstate solution and a molybdenum-removed slag. In the present invention, the MoO4 in the sodium tungstate solution 2- The molar ratio of the molybdenum to H2S is preferably 1:3 to 4.5, and in the embodiment, it can be 1:3.5, 1:3 or 1:4.5; the pH value of the molybdenum removal is preferably 2 to 3.5, and in the embodiment, it can be 2, 3 or 3.5; the temperature of the molybdenum removal is preferably 20 to 50°C, and in the embodiment, it can be 20°C, 30°C or 50°C; the time of the molybdenum removal is preferably 30 to 120 minutes, and in the embodiment, it can be 30 minutes, 60 minutes or 120 minutes; in a specific embodiment of the present invention, the pH value of the sodium tungstate solution is preferably adjusted to 2 to 3.5, and then hydrogen sulfide gas is introduced to remove the molybdenum. After the molybdenum removal is completed, the present invention preferably uses a filter press to separate the obtained feed liquid into solid and liquid to obtain a refined sodium tungstate solution and a molybdenum removal slag.

[0044] After obtaining the refined sodium tungstate solution, the present invention extracts the refined sodium tungstate solution with an extractant to obtain an extract phase and sodium sulfate wastewater. In the present invention, the extractant is preferably N235, and the volume ratio of the extractant to the refined sodium tungstate solution is preferably 1 to 1.5:1, specifically 1.5:1, 1.3:1, or 1:1. Prior to the extraction, the pH of the refined sodium tungstate solution is preferably adjusted to 2 to 3, specifically 2, 2.5, or 3.

[0045] After the extraction phase is obtained, the extraction phase is back-extracted with ammonia water to obtain an ammonium tungstate solution; the ammonium tungstate solution is evaporated and crystallized to obtain ammonium paratungstate. In the present application, the volume ratio of the ammonia water to the extractant is preferably 2-3:1, and can be 2:1, 2.5:1 or 3:1, and the concentration of the ammonia water is preferably 10-20%; the water phase obtained after back-extraction is an ammonium tungstate solution, and the organic phase obtained is the used extractant, and the present application preferably uses a sulfuric acid solution to regenerate the used extractant, and the regenerated extractant is returned to the extraction step for reuse; the temperature of the regeneration is preferably 15-30℃, and the time is preferably 1-2h.

[0046] In the present application, the temperature of the evaporation and crystallization is preferably 80-95℃, and can be 80℃, 90℃ or 95℃, the time of the evaporation and crystallization is preferably 9-10h, and can be 9h, 9.5h or 10h, and the vacuum degree of the evaporation and crystallization is preferably -0.08 to -0.06MPa, and can be -0.08MPa, -0.07MPa or -0.06MPa; the evaporation and crystallization is preferably evaporated until the WO3 concentration in the mother liquor is 8-11g / L, at which time the obtained material liquid is the crystallization liquid. After the evaporation and crystallization obtains the crystallization liquid, the present application preferably separates the crystallization liquid into solid and liquid to obtain the primary product, washes the primary product and dries it to obtain the ammonium paratungstate finished product, which is a zero-grade product; the method of solid-liquid separation is preferably vacuum filtration, the washing agent is preferably deionized water, and the washing is carried out until the conductivity of the washing liquid is ≤50μS / cm; the drying is preferably microwave drying, the temperature of the drying is preferably 60-70℃, and the drying time is 0.2-0.5h.

[0047] After the sodium sulfate wastewater is obtained, the present application adsorbs and removes impurities from the sodium sulfate wastewater by activated carbon to obtain wastewater after impurity removal; uses a bipolar membrane to perform electrodialysis treatment on the wastewater after impurity removal to obtain a sulfuric acid solution and a sodium hydroxide solution; the sulfuric acid solution is used for regenerating the extractant, and the sodium hydroxide solution is concentrated and used in the alkali pressure boiling. In the present application, the activated carbon adsorption and impurity removal is specifically that the sodium sulfate wastewater is introduced into the activated carbon for impurity removal, the flow rate of the sodium sulfate wastewater introduced into the activated carbon is preferably 2-4m 3 / h, and can be 2m 3 / h, 3m 3 / h or 4m 3 / h; the volume of the sodium sulfate wastewater introduced per hour and the mass of the activated carbon are preferably in a ratio of 1m 3 :(200-500)kg, and can be 1m 3 :200kg, 1m 3 :400kg or 1m 3 :500kg.

[0048] The present invention has no special requirements for the bipolar membrane device used in the electrodialysis treatment, and any device known to those skilled in the art can be used. In a specific embodiment of the present invention, the bipolar membrane device includes an anode chamber, an acid chamber, an alkali chamber, and a cathode chamber. During the electrodialysis treatment, SO4 in the sodium sulfate solution is 2- Migrate toward the anode and enter the acid chamber (positive membrane side of the bipolar membrane), where sulfuric acid solution is obtained. + It migrates toward the cathode and enters the alkali chamber (cathode side of the bipolar membrane), where it obtains a sodium hydroxide solution.

[0049] In the present invention, the conditions for the electrodialysis treatment preferably include: a current density of 900 to 700 A / m 2 , specifically 700A / m 2 , 800A / m 2 or 900A / m 2 , the concentration of polar water is preferably 3-5wt%; in a specific embodiment of the present invention, the polar water used in the electrodialysis treatment is preferably sodium hydroxide solution.

[0050] In the present invention, the concentration of the sodium hydroxide solution obtained by the electrodialysis treatment is preferably 2-2.5 mol / L, and the concentration of the sulfuric acid solution is preferably 1-1.5 mol / L. In a specific embodiment of the present invention, the concentrations of the sodium hydroxide solution and sulfuric acid solution obtained by the electrodialysis treatment are preferably tested, and the electrodialysis treatment can be stopped when the concentrations reach the above requirements. The sodium hydroxide solution obtained by the electrodialysis treatment is concentrated and used in the alkaline autoclave, and the sulfuric acid solution is returned for use in the extractant regeneration process. The equipment used for concentrating the sodium hydroxide solution is preferably an MVR device. The concentration of the sodium hydroxide solution after the concentration is 450-500 g / L. The present invention recycles all the generated sodium sulfate wastewater into the process flow, achieving the goal of no high-salt wastewater discharge.

[0051] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] Example 1

[0053] (1) Prepare 500g of wolframite with a tungsten content of 50 degrees and ball-mill it to 300 mesh. Add 450g / L sodium hydroxide solution with a tungsten-alkali ratio of 1:1 to the wolframite and perform alkaline autoclave cooking in a reactor. The reaction temperature is 150℃, the reaction pressure is 0.8MPa, and the heat and pressure are maintained for 3h. The resulting liquid is separated into solid and liquid using a filter press to obtain the initial sodium tungstate solution and tungsten slag.

[0054] (2) Prepare 500g of scheelite with a tungsten content of 20 degrees, ball-mill it to 200 mesh, prepare a sulfuric acid-oxalic acid mixed solution with sulfuric acid and oxalic acid concentrations of 0.5 mol / L respectively, add the oxalic acid-sulfuric acid mixed solution and scheelite into the reactor at a liquid-solid ratio of 25mL:1g for acid leaching, the acid leaching temperature is 80℃, the time is 8h, the material liquid obtained after acid leaching is separated into solid and liquid using a filter press to obtain calcium sulfate slag and oxalic acid-tungsten complex solution, heat the obtained oxalic acid-tungsten complex solution at 100℃ for 4h to obtain tungstic acid and oxalic acid solution, and return the obtained oxalic acid solution to prepare the sulfuric acid-oxalic acid mixed solution for acid leaching reaction with scheelite.

[0055] (3) The initial sodium tungstate solution obtained in step (1) and the tungstic acid obtained in step (2) are added into a reactor in a mass ratio of 2:1 for reaction at a reaction temperature of 80° C. for 1 h to obtain a crude sodium tungstate solution.

[0056] (4) The pH value of the crude sodium tungstate solution obtained in step 3 is adjusted to 8, and magnesium sulfate is added at a molar ratio of magnesium sulfate to arsenic in the crude sodium tungstate solution of 1.2:1 to remove impurities. The reaction is carried out for 1 hour, and then the pH value is adjusted to 6 and the reaction is carried out for 0.5 hour. After the reaction, the obtained liquid is subjected to solid-liquid separation using a filter press to obtain a decontaminated sodium tungstate solution and decontaminated residue.

[0057] (5) Adjust the pH value of the impurity-removing sodium tungstate solution to 2, and press MoO4 2- :H2S=1:3.0 molar ratio of hydrogen sulfide gas was introduced to remove molybdenum, the temperature of the molybdenum removal was 20 ° C, the time was 30 min, and after the reaction, the obtained liquid was separated into solid and liquid using a filter press to obtain refined sodium tungstate solution and molybdenum removal slag.

[0058] (6) The refined sodium tungstate solution is extracted using N235. Before extraction, the pH value of the refined sodium tungstate solution is adjusted to 2. The volume ratio of the extractant to the refined sodium tungstate solution is 1:1. After extraction, sodium sulfate wastewater and an extraction phase are generated. Ammonia water with a concentration of 15wt% is used as a stripping agent to strip the extraction phase. The volume ratio of ammonia water to the extraction phase is 2:1. Ammonium tungstate solution is obtained by stripping. After stripping, the used extractant is regenerated using the sulfuric acid solution generated in step (7). The regenerated extractant is returned to the extraction step for use.

[0059] (7) The sodium sulfate wastewater produced in step (6) is heated to 2m 3 / h flow rate to absorb the organic matter in the activated carbon. The ratio of the mass of the activated carbon to the volume of the sodium sulfate wastewater introduced per hour is 500kg:1m 3 , then use bipolar membrane equipment at 900A / m 2 Electrodialysis treatment is carried out at a current density of 400 nm (the polar water used is a 4 wt% sodium hydroxide solution) to prepare a 1.5 mol / L sulfuric acid solution and a 2.4 mol / L sodium hydroxide solution. The generated sulfuric acid solution is returned to step (6) for use in regenerating the extractant. The obtained sodium hydroxide solution is concentrated to 450 g / L using an MVR device and then returned to step (1) for use in alkaline autoclaving.

[0060] (8) The ammonium tungstate solution obtained in step (6) was reacted at 80° C. and a vacuum degree of −0.08 MPa for 9 h. The reaction was stopped when the WO3 concentration in the mother liquor reached 9 g / L. After the reaction was completed, a vacuum filtration device was used for solid-liquid separation to obtain the APT primary product. The obtained APT primary product was washed with deionized water until the crystals had a conductivity of 45 μS / cm, and the residual mother liquor on the surface was removed. Finally, the product was dried at 60° C. for 0.2 h using a microwave drying device to obtain an APT finished product (grade zero).

[0061] Example 2

[0062] (1) Prepare 500g of wolframite with a tungsten content of 55 degrees and ball-mill it to 310 mesh. Add 470g / L sodium hydroxide solution with a tungsten to alkali ratio of 1:2 and perform alkaline autoclave cooking with the wolframite in a reactor. The reaction temperature is 160℃, the reaction pressure is 0.9MPa, and the heat and pressure are maintained for 3.5h. The resulting liquid is separated into solid and liquid using a filter press to obtain the initial sodium tungstate solution and tungsten slag.

[0063] (2) Prepare 500g of scheelite with a tungsten content of 30 degrees, ball-mill it to 280 mesh, prepare a sulfuric acid-oxalic acid mixed solution with sulfuric acid and oxalic acid concentrations of 1 mol / L respectively, add the oxalic acid-sulfuric acid mixed solution and scheelite into the reactor at a liquid-solid ratio of 15mL:1g for acid leaching, the acid leaching temperature is 60℃, the time is 6h, the material liquid obtained after acid leaching is separated into solid and liquid using a filter press to obtain calcium sulfate slag and oxalic acid-tungsten complex solution, heat the obtained oxalic acid-tungsten complex solution at 90℃ for 3h to obtain tungstic acid and oxalic acid solution, and return the obtained oxalic acid solution to prepare the sulfuric acid-oxalic acid mixed solution for acid leaching reaction with scheelite.

[0064] (3) The initial sodium tungstate solution obtained in step (1) and the tungstic acid obtained in step (2) are added into a reactor at a mass ratio of 2.5:1 for reaction at a reaction temperature of 100° C. for 1.5 h to obtain a crude sodium tungstate solution.

[0065] (4) The pH value of the crude sodium tungstate solution obtained in step 3 was adjusted to 10, and basic magnesium carbonate was added at a molar ratio of basic magnesium carbonate to arsenic in the solution of 1.3:1 for impurity removal. The reaction time was 1.5 hours, and then the pH value was adjusted to 7 and the reaction was continued for 1 hour. After the reaction, the obtained liquid was subjected to solid-liquid separation using a filter press to obtain a decontaminated sodium tungstate solution and decontaminated residue.

[0066] (5) Adjust the pH value of the impurity-removing sodium tungstate solution to 3, and press MoO4 2- :H2S=1:4 molar ratio of hydrogen sulfide gas was introduced to remove molybdenum, the reaction temperature was 40 ° C, the reaction was carried out for 1 hour, and after the molybdenum was removed, the obtained liquid was separated into solid and liquid using a filter press to obtain refined sodium tungstate solution and molybdenum-removed slag.

[0067] (6) The refined sodium tungstate solution is extracted using N235. Before extraction, the pH of the feed solution is adjusted to 2.5. The molar ratio of the extractant to the refined sodium tungstate solution is 1.3:1. Sodium sulfate wastewater is generated after extraction. Ammonia water with a concentration of 10 wt% is used as a stripping agent to strip the extract phase. The volume ratio of ammonia water to the extract phase is 2.5:1. Ammonium tungstate solution is obtained by stripping. After stripping, the extractant is regenerated using the dilute sulfuric acid solution generated in step (7). The regenerated extractant is returned to the extraction for use.

[0068] (7) The sodium sulfate wastewater produced in step (6) is heated to 3m 3 / h flow rate to pass activated carbon to adsorb organic matter in it. The ratio of the mass of activated carbon to the volume of sodium sulfate wastewater passed per hour is 300kg:1m 3 , then use bipolar membrane equipment at 800A / m 2 Electrodialysis treatment is carried out at a current density of 500 nm (the polar water used is a 5 wt% sodium hydroxide solution) to prepare a 1.3 mol / L sulfuric acid solution and a 2.2 mol / L sodium hydroxide solution. The generated sulfuric acid solution is returned to step (6) for regeneration of the extractant. The obtained sodium hydroxide solution is concentrated to 470 g / L using an MVR device and then returned to step (1) for use in alkaline autoclaving.

[0069] (8) The ammonium tungstate solution obtained in step (6) was reacted at 90° C. and a vacuum degree of -0.07 MPa for 9.5 h. The reaction was stopped when the WO3 concentration in the mother liquor reached 7 g / L. After the reaction was completed, a vacuum filtration device was used to separate the solid and liquid to obtain the APT primary product. The obtained APT primary product was washed with deionized water until the crystals had a conductivity of 43 μS / cm, and the residual mother liquor on the surface was removed. Finally, the product was dried at 65° C. for 0.4 h using a microwave drying device to obtain an APT finished product (grade zero).

[0070] Example 3

[0071] (1) Prepare 500g of wolframite with a tungsten content of 60 degrees and ball-mill it to 325 mesh. Add 500g / L sodium hydroxide solution at a tungsten to alkali ratio of 1:3 and perform alkaline autoclave cooking with the wolframite in a reactor. The reaction temperature is 180℃, the reaction pressure is 1MPa, and the heat and pressure are maintained for 4h. The resulting liquid is separated into solid and liquid using a filter press to obtain the initial sodium tungstate solution and tungsten slag.

[0072] (2) Prepare 500g of scheelite with a tungsten content of 50 degrees, ball-mill it to 325 mesh, prepare a sulfuric acid-oxalic acid mixed solution with sulfuric acid and oxalic acid concentrations of 2.5mol / L respectively, add the oxalic acid-sulfuric acid mixed solution and scheelite into the reactor at a liquid-solid ratio of 10mL:1g for acid leaching reaction, the reaction temperature is 80℃, and the reaction is carried out for 8h. The obtained liquid after the reaction is separated into solid and liquid using a filter press to obtain calcium sulfate slag and oxalic acid-tungsten complex solution. The obtained oxalic acid-tungsten complex solution is heated and decomposed at 100℃ for 4h to obtain tungstic acid and oxalic acid solution, and the obtained oxalic acid solution is returned to prepare the sulfuric acid-oxalic acid mixed solution.

[0073] (3) The initial sodium tungstate solution obtained in step (1) and the tungstic acid obtained in step (2) are added into a reactor in a mass ratio of 3:1 for reaction at a reaction temperature of 110° C. for 2 h to obtain a crude sodium tungstate solution.

[0074] (4) The pH value of the crude sodium tungstate solution obtained in step (3) was adjusted to 12, and magnesium oxide was added at a molar ratio of magnesium oxide to arsenic in the solution of 1.5:1 to remove impurities. The reaction was carried out for 2 hours, and then the pH value was adjusted to 8 and the reaction was carried out for 1.5 hours. After impurities were removed, the obtained feed liquid was separated into solid and liquid using a filter press to obtain a decontaminated sodium tungstate solution and decontaminated residue.

[0075] (5) Adjust the pH of the sodium tungstate solution to 3.5, and press MoO4 2- :H2S=1:4.5 molar ratio of hydrogen sulfide gas was introduced to remove molybdenum, the reaction temperature was 50 ° C, the reaction time was 2h, and after the molybdenum removal, the obtained liquid was separated into solid and liquid using a filter press to obtain refined sodium tungstate solution and molybdenum-removed slag.

[0076] (6) The refined sodium tungstate solution obtained in step (5) is extracted using N235, the pH value of the feed liquid is adjusted to 3 before extraction, the ratio of the extractant to the feed liquid OA is 1.5:1, and sodium sulfate wastewater is generated after extraction. Ammonia water with a concentration of 20wt% is used as a stripping agent to strip the extract phase, and the volume ratio of ammonia water to the extract phase is 3:1. The stripping obtains an ammonium tungstate solution. After stripping, the extractant is regenerated using the dilute sulfuric acid solution generated in step (7), and the regenerated extractant is returned to the extraction for use.

[0077] (7) The sodium sulfate wastewater produced in step (6) is heated to 4 m3 / h flow rate to absorb the organic matter in the activated carbon. The ratio of the mass of the activated carbon to the volume of the sodium sulfate wastewater introduced per hour is 200kg:1m 3 , then use bipolar membrane equipment at 700A / m 2 Electrodialysis treatment is carried out at a current density of 1.1 mol / L (the polar water used is a 3 wt% sodium hydroxide solution) to prepare a 1.1 mol / L sulfuric acid solution and a 2.0 mol / L sodium hydroxide solution. The generated sulfuric acid solution is returned to step (6) for regeneration of the extractant. The obtained sodium hydroxide solution is concentrated to 500 g / L using an MVR device and then returned to step (1) for use in alkaline autoclaving.

[0078] (8) The ammonium tungstate solution obtained in step (6) was reacted at 95° C. and a vacuum degree of −0.06 MPa for 10 h. The reaction was stopped when the WO3 concentration in the mother liquor reached 7.8 g / L. After the reaction was completed, a vacuum filtration device was used to separate the solid and liquid to obtain the APT primary product. The obtained APT primary product was washed with deionized water until the crystals had a conductivity of 38 μS / cm, and the residual mother liquor on the surface was removed. Finally, the product was dried at 70° C. for 0.5 h using a microwave drying device to obtain an APT finished product (grade zero).

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for smelting ammonium paratungstate from tungsten without discharging high-salt wastewater, characterized in that: The following steps are involved: Wolframite and sodium hydroxide solution are mixed and then subjected to alkaline autoclave cooking to obtain initial sodium tungstate solution and tungsten slag; The scheelite is mixed with a sulfuric acid-oxalic acid mixed solution for acid leaching to obtain calcium sulfate slag and an oxalic acid-tungsten complex solution; heating and decomposing the oxalic acid-tungsten complex solution to obtain tungstic acid and oxalic acid solution; returning the oxalic acid solution to the acid leaching step to prepare a sulfuric acid-oxalic acid mixed solution; The initial sodium tungstate solution and tungstic acid are mixed and reacted to obtain a crude sodium tungstate solution; The crude sodium tungstate solution and the magnesium compound are mixed to remove impurities, thereby obtaining a cleaned sodium tungstate solution and cleaned slag; The impurity-removed sodium tungstate solution is mixed with hydrogen sulfide to remove molybdenum, thereby obtaining a refined sodium tungstate solution and a molybdenum-removed slag; Extracting the refined sodium tungstate solution with an extractant to obtain an extract phase and sodium sulfate wastewater; The extract phase is stripped with aqueous ammonia to obtain an ammonium tungstate solution; the ammonium tungstate solution is evaporated and crystallized to obtain ammonium paratungstate; The sodium sulfate wastewater is subjected to activated carbon adsorption to remove impurities to obtain impurity-removed wastewater; the impurity-removed wastewater is subjected to electrodialysis treatment using a bipolar membrane to obtain a sulfuric acid solution and a sodium hydroxide solution, wherein the sulfuric acid solution is used to regenerate the extractant, and the sodium hydroxide solution is concentrated and used in the alkaline autoclave.

2. The method according to claim 1, characterized in that The wolframite has a tungsten content of 50 to 60 degrees and a mesh size of 300 to 325 meshes; the concentration of the sodium hydroxide solution used in the alkali autoclaving is 450 to 500 g / L; the mass ratio of tungsten in the wolframite to sodium hydroxide in the sodium hydroxide solution used in the alkali autoclaving is 1:1 to 3; The temperature of the alkaline autoclave is 150-180° C., the pressure is 0.8-1 MPa, and the heat preservation and pressure holding time is 3-4 hours.

3. The method according to claim 1, characterized in that The tungsten content of the scheelite is 20 to 60 degrees, and the mesh size is 200 to 325 meshes; the concentration of oxalic acid in the sulfuric acid-oxalic acid mixed solution is 0.5 to 2.5 mol / L, and the concentration of sulfuric acid is 0.5 to 2.5 mol / L; the liquid-solid ratio of the sulfuric acid-oxalic acid mixed solution to the scheelite is 5 to 25 mL:1 g, the temperature of the acid leaching is 50 to 80° C., and the time is 4 to 8 hours; the temperature of the thermal decomposition is 85 to 100° C., and the time is 1 to 4 hours.

4. The method according to claim 1, wherein The concentration of the initial sodium tungstate solution is 30-40 g / L; the mass ratio of the initial sodium tungstate solution to tungstic acid is 2-3:1; the reaction temperature is 80-110° C., and the reaction time is 1-2 hours.

5. The method according to claim 1, wherein The molar ratio of the magnesium compound to arsenic in the crude sodium tungstate solution is 1.2-1.5:1; the magnesium compound includes one or more of magnesium oxide and magnesium salts, and the magnesium salts include one or both of basic magnesium carbonate and magnesium sulfate; the impurity removal includes a first-stage impurity removal and a second-stage impurity removal performed sequentially, wherein the pH value of the first-stage impurity removal is 8-12 and the reaction time is 1-2 hours, and the pH value of the second-stage impurity removal is 6-8 and the reaction time is 0.5-1.5 hours.

6. The method according to claim 1, characterized in that The MoO4 in the sodium tungstate solution 2- The molar ratio of molybdenum to H2S is 1:3-4.5; the pH value of the molybdenum removal is 2-3.5, the temperature is 20-50°C, and the time is 30-120 minutes.

7. The method according to claim 1, characterized in that Before the extraction, the pH value of the refined sodium tungstate solution is adjusted to 2-3; the volume ratio of the extractant to the refined sodium tungstate solution is 1-1.5:1; the volume ratio of the ammonia water to the extraction phase is 2-3:1, and the concentration of the ammonia water is 10-20wt%; the extractant is N235.

8. The method according to claim 1, characterized in that In the activated carbon adsorption, the flow rate of sodium sulfate wastewater into the activated carbon is 2 to 4 m 3 / h; the volume of sodium sulfate wastewater and the mass ratio of activated carbon introduced per hour is 1m 3 :(200~500)kg.

9. The method according to claim 1, characterized in that The conditions of the electrodialysis treatment include: a current density of 700 to 900 A / m 2 , the concentration of polar water is 3 to 5 wt%; the concentration of the sulfuric acid solution obtained by the electrodialysis treatment is 1 to 1.5 mol / L, and the concentration of the sodium hydroxide solution is 2 to 2.5 mol / L.

10. The method according to claim 1, characterized in that The temperature of the evaporation crystallization is 80-95° C., the time is 9-10 hours, and the vacuum degree is -0.08-0.06 MPa.

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