Method for smelting ammonium paratungstate from tungsten by recycling wastewater
Through steps such as alkaline pressure cooking, impurity removal, extraction and electrodialysis, the problem of high-salt wastewater treatment in traditional tungsten smelting process has been solved, the resource reuse of wastewater has been realized, environmental pollution has been reduced, and the smelting needs of different tungsten ores have been adapted.
Patent Information
- Application Number
- CN202510921805.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-04
- Publication Date
- 2025-10-14
AI Technical Summary
The traditional tungsten smelting process for preparing ammonium paratungstate produces a large amount of high-salt wastewater, which is difficult to recycle. Moreover, since harmful substances are difficult to degrade, direct discharge causes environmental pollution. In addition, the smelting processes of different tungsten ores vary greatly, making it difficult to establish a unified wastewater treatment method.
The process of alkaline pressure cooking, impurity removal, extraction, electrodialysis and other steps is adopted to mix the black and white tungsten ore with sodium hydroxide solution. The wastewater is then treated by magnesium compound impurity removal, hydrogen sulfide molybdenum removal, extraction agent extraction, activated carbon adsorption and electrodialysis to achieve wastewater resource reuse. The process is short and has wide adaptability.
It achieves efficient resource reuse of wastewater, reduces environmental pollution, and can process wolframite and scheelite at the same time, with a short process and strong adaptability.
Smart Images
Figure CN120776145A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of tungsten ore smelting, and particularly relates to a method for recycling wastewater in tungsten smelting ammonium paratungstate. BACKGROUND
[0002] Ammonium paratungstate (APT) is an important tungsten compound and occupies a core position in the tungsten smelting and processing industry chain. Ammonium paratungstate is usually prepared by tungsten ore smelting. The traditional tungsten smelting process mainly includes steps of tungsten ore decomposition, impurity removal, transformation, evaporation crystallization, etc.
[0003] At present, a large amount of high-salt wastewater is generated in the traditional process of preparing ammonium paratungstate by tungsten smelting. The salt in the high-salt wastewater is mainly sodium chloride or sodium sulfate. The wastewater contains high-concentration salt and harmful substances, which is difficult to directly recycle and utilize. At the same time, since the harmful substances contained in the wastewater are difficult to degrade, direct discharge will cause long-term pollution to water, soil and ecological system, and seriously affect the ecological balance and human health.
[0004] In addition, different smelting processes are often used for the two main tungsten ore raw materials, i.e. wolframite and scheelite. This not only requires the configuration of equipment and reagents for specific purposes, but also results in significant differences in the composition of the generated wastewater, making it difficult to establish a unified and efficient wastewater treatment method, and increasing the amount of wastewater generated and the difficulty of treatment. SUMMARY
[0005] Therefore, the present application provides a method for recycling wastewater in tungsten smelting ammonium paratungstate. The method provided by the present application can realize the recycling of wastewater, there is no discharge of high-salt wastewater, and it can simultaneously treat wolframite and scheelite, the treatment process is short, and the adaptability is wide.
[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:
[0007] A method for recycling wastewater in tungsten smelting ammonium paratungstate, comprising the following steps:
[0008] Mixing wolframite-scheelite mixed ore and sodium hydroxide solution for alkali pressure boiling to obtain a crude sodium tungstate solution and a tungsten residue;
[0009] Mixing the crude sodium tungstate solution and a magnesium compound for impurity removal to obtain a sodium tungstate solution and an impurity removal residue;
[0010] Mixing the sodium tungstate solution and hydrogen sulfide for molybdenum removal to obtain a refined sodium tungstate solution and a molybdenum removal residue;
[0011] Extracting the refined sodium tungstate solution with an extractant to obtain an extraction phase and sodium sulfate wastewater;
[0012] The extraction phase is back-extracted with ammonia water to obtain an ammonium tungstate solution; the ammonium tungstate solution is subjected to evaporation crystallization to obtain ammonium paratungstate;
[0013] 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 by using a bipolar membrane to obtain a sulfuric acid solution and a sodium hydroxide solution; the sulfuric acid solution obtained by the electrodialysis treatment is used for regeneration of an extractant, and the sodium hydroxide solution after concentration is used in the alkali pressure boiling.
[0014] Preferably, the tungsten grade of the black and white tungsten mixed ore is 50-60 degrees, and the mesh number is 300-325 meshes;
[0015] The concentration of the sodium hydroxide solution used in the alkali pressure boiling is 450-500 g / L; the mass ratio of tungsten in the black and white tungsten mixed ore to sodium hydroxide in the sodium hydroxide solution used in the alkali pressure boiling is 1:1-3;
[0016] The temperature of the alkali pressure boiling is 150-180℃, the pressure is 0.8-1 MPa, and the holding time is 3-4 h.
[0017] Preferably, the compound includes one or more of magnesium oxide and magnesium salt, the magnesium salt includes one or both of basic magnesium carbonate and magnesium sulfate; the molar ratio of the magnesium salt to arsenic in the crude sodium tungstate solution is 1.2-1.5:1; the impurity removal includes sequentially performing a first stage and a second stage, the pH value of the first stage is 8-12, the reaction time is 1-2 h, and the pH value of the second stage is 6-8, the reaction time is 0.5-1.5 h.
[0018] Preferably, the molar ratio of MoO4 2- in the sodium tungstate solution to H2S is 1:3-4.5; the pH value of the molybdenum removal is 2-3.5, the temperature is 20-50℃, and the time is 30-120 min.
[0019] Preferably, the volume ratio of the extractant to the refined sodium tungstate solution is 1-1.5:1; the pH value of the refined sodium tungstate solution is adjusted to 2-3 before extraction; the volume ratio of the ammonia water to the extraction phase is 4-5:1, the concentration of the ammonia water is 10-20 wt%; and the extractant is N235.
[0020] Preferably, in the activated carbon adsorption to remove impurities, the flow rate of the sodium sulfate wastewater into the activated carbon is 2-4 m 3 / h; the ratio of the volume of the sodium sulfate wastewater introduced per hour to the mass of the activated carbon is 1 m 3 :(200-500) kg.
[0021] Preferably, the conditions of the electrodialysis treatment include: the current density is 700-900 A / m2 The concentration of the sulfuric acid solution obtained by the electrodialysis treatment is 3-5wt%.
[0022] Preferably, the concentration of the sulfuric acid solution obtained by the electrodialysis treatment is 1-1.5mol / L, and the concentration of the sodium hydroxide solution is 2-2.5mol / L.
[0023] Preferably, the temperature of the evaporation crystallization is 80-95℃, the time is 9-10h, and the vacuum degree is -0.08--0.06MPa.
[0024] Preferably, the evaporation crystallization obtains a crystallization solution, and after obtaining the crystallization solution, the method further comprises: solid-liquid separation of the crystallization solution to obtain a primary product, washing and drying of the primary product to obtain the ammonium paratungstate product.
[0025] The method for recycling wastewater in tungsten smelting ammonium paratungstate provided by the application comprises the following steps: mixing black and white tungsten mixed ore and a sodium hydroxide solution to perform alkali pressure digestion to obtain a crude sodium tungstate solution and a tungsten residue; mixing the crude sodium tungstate solution and a magnesium compound to remove impurities to obtain a sodium tungstate solution and a removal residue; mixing the sodium tungstate solution and hydrogen sulfide to remove molybdenum to obtain a refined sodium tungstate solution and a molybdenum removal residue; using an extractant to extract the refined sodium tungstate solution to obtain an extraction phase and a sodium sulfate wastewater; using ammonia water to back-extract the extraction phase to obtain an ammonium tungstate solution; performing evaporation crystallization on the ammonium tungstate solution to obtain ammonium paratungstate (APT); using activated carbon adsorption to remove impurities from the sodium sulfate wastewater to obtain a wastewater after impurity removal; using 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 obtained by the electrodialysis treatment is used for regenerating the extractant, and the sodium hydroxide solution is concentrated and then used in the alkali pressure digestion. The method provided by the application can return all the sodium sulfate wastewater to the process flow, no high-salinity wastewater is discharged in the whole process, efficient recycling of the wastewater is achieved, and environmental pollution is reduced. Moreover, the method provided by the application can simultaneously process white tungsten ore and black tungsten ore, the processing flow is short, and the adaptability is wide. BRIEF DESCRIPTION OF DRAWINGS
[0026] Figure 1 The method for recycling wastewater in tungsten smelting ammonium paratungstate provided by the application is shown in the process flowchart. DETAILED DESCRIPTION
[0027] The method for recycling wastewater in tungsten smelting ammonium paratungstate provided by the application comprises the following steps:
[0028] Mixing black and white tungsten mixed ore and a sodium hydroxide solution to perform alkali pressure digestion to obtain a crude sodium tungstate solution and a tungsten residue;
[0029] Mixing the crude sodium tungstate solution and a magnesium compound to remove impurities to obtain a sodium tungstate solution and a removal residue;
[0030] The sodium tungstate solution and hydrogen sulfide are mixed to remove molybdenum, thereby obtaining a refined sodium tungstate solution and a molybdenum-removed slag;
[0031] Extracting the refined sodium tungstate solution with an extractant to obtain an extract phase and sodium sulfate wastewater;
[0032] 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;
[0033] 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 obtained by the electrodialysis treatment is used to regenerate the extractant, and the sodium hydroxide solution is concentrated and used in the alkaline autoclave.
[0034] Figure 1 The process flow chart of the method for smelting ammonium paratungstate by recycling wastewater provided by the present invention is as follows: Figure 1 Provide detailed explanation.
[0035] In the present invention, a mixed wolframite and scheelite ore is mixed with a sodium hydroxide solution and then subjected to alkaline autoclaving to obtain a crude sodium tungstate solution and a tungsten slag. In the present invention, the wolframite and scheelite ore preferably has a tungsten content of 50 to 60 degrees, specifically 50, 55, or 60 degrees. The present invention has no requirements for the ratio of wolframite to scheelite in the mixed wolframite and scheelite ore. The mesh size of the mixed wolframite and scheelite ore is preferably 300 to 325 mesh. The mixed wolframite and scheelite ore is preferably ball-milled before use to meet the aforementioned mesh size requirements. The concentration of the sodium hydroxide solution used in the alkali autoclave is preferably 450-500 g / L, specifically 450 g / L, 470 g / L or 500 g / L; the mass ratio of tungsten in the black and white tungsten mixed ore to sodium hydroxide in the sodium hydroxide solution used in the alkali autoclave (denoted as the tungsten-alkali ratio) is preferably 1:1-3, specifically 1:1, 1:2 or 1:3; the temperature of the alkali autoclave is preferably 150-180°C, specifically 150°C, 160°C or 180°C; the pressure of the alkali autoclave is preferably 0.8-1 MPa, specifically 0.8 MPa, 0.9 MPa or 1 MPa; the heat preservation and pressure holding time of the alkali autoclave is preferably 3-4 h, specifically 3 h, 3.5 h or 4 h.
[0036] After the alkaline autoclave is completed, the present invention preferably performs solid-liquid separation on the resulting feed liquid to obtain a filtrate and a tungsten slag; the solid-liquid separation is preferably performed using a filter press. The present invention preferably performs multiple-effect evaporation on the filtrate to precipitate sodium tungstate in the form of crystals, and then centrifuges to obtain crude sodium tungstate crystals and an alkali solution. The alkali solution is recovered and returned to the alkaline autoclave step for reuse. The crude sodium tungstate crystals are dissolved in water to obtain a crude sodium tungstate solution; the concentration of the crude sodium tungstate solution is preferably 30-40 g / L.
[0037] After obtaining the crude sodium tungstate solution, the present invention mixes the crude sodium tungstate solution with a magnesium compound to remove impurities, thereby obtaining a sodium tungstate solution and a removed impurity residue. In the present invention, the magnesium compound preferably includes one or more of magnesium oxide and a magnesium salt, and the magnesium salt preferably includes one or both of basic magnesium carbonate and magnesium sulfate. The molar ratio of the magnesium salt to the 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 impurity removal preferably includes a first stage and a second stage, wherein the pH value of the first stage is preferably 8 to 12, specifically 8, 10, or 12, and the reaction time is preferably 1 to 2 hours, specifically 1 hour, 1.5 hours, or 2 hours. The pH value of the second stage is preferably 6 to 8, specifically 6, 7, or 8, and the reaction time is preferably 0.5 to 1.5 hours, specifically 0.5 hours, 1 hour, or 1.5 hours. The impurity removal can be carried out at room temperature. In a specific embodiment of the present invention, the pH of the crude sodium tungstate solution is preferably adjusted to 8-12 before adding the magnesium salt and reacting for 1-2 hours. The pH is then adjusted to 6-8 and reacted for 0.5-1 hour. After impurities are removed, the present invention preferably performs solid-liquid separation on the resulting feed liquid to obtain a sodium tungstate solution and impurity-removed residue; the solid-liquid separation is preferably performed using a filter press.
[0038] After obtaining the sodium tungstate solution, the present invention mixes the 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 sodium tungstate to H2S is preferably 1:3 to 4.5, specifically 1:3, 1:3.5 or 1:4.5; the pH value of the molybdenum removal is preferably 2 to 3.5, specifically 2, 3 or 3.5; the temperature of the molybdenum removal is preferably 20 to 50°C, specifically 20°C, 30°C or 50°C; the time of the molybdenum removal is preferably 30 to 120 minutes, specifically 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 performs solid-liquid separation on the obtained feed liquid to obtain a refined sodium tungstate solution and a molybdenum removal slag; the solid-liquid separation is preferably performed using a filter press.
[0039] 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 1:1, 1.3:1, or 1.5:1. 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.
[0040] After obtaining the extract phase, the present invention strips the extract phase with aqueous ammonia to obtain an ammonium tungstate solution; the ammonium tungstate solution is evaporated and crystallized to obtain ammonium paratungstate. In the present invention, the volume ratio of aqueous ammonia to extractant is preferably 4 to 5:1, specifically 4:1, 4.5:1, or 5:1, and the concentration of aqueous ammonia is preferably 10 to 20 wt%. The aqueous phase obtained after stripping is the ammonium tungstate solution, and the obtained organic phase is the used extractant. The present invention preferably uses sulfuric acid solution to regenerate the used extractant, and the regenerated extractant is returned to the extraction step for reuse. The regeneration temperature is preferably 15 to 30°C, and the regeneration time is preferably 1 to 2 hours.
[0041] In the present invention, the temperature of the evaporation crystallization is preferably 80 to 95°C, specifically 80°C, 90°C or 95°C; the time of the evaporation crystallization is preferably 9 to 10 hours, specifically 9 hours, 9.5 hours or 10 hours; the vacuum degree of the evaporation crystallization is preferably -0.08 to -0.06 MPa, specifically -0.08 MPa, -0.07 MPa or -0.06 MPa; the evaporation crystallization is preferably evaporated until the WO3 concentration in the mother liquor is 8 to 11 g / L, at which time the obtained feed liquid is the crystallization liquid. After the evaporation and crystallization obtain the crystal liquid, the present invention preferably separates the crystal liquid into solid and liquid to obtain a primary product, washes the primary product and then dries it to obtain a finished ammonium paratungstate product, wherein the finished ammonium paratungstate product is a zero-grade product; the solid-liquid separation method is preferably vacuum filtration, the washing reagent 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 drying temperature is preferably 60-70°C, and the drying time is preferably 0.2-0.5h.
[0042] After obtaining sodium sulfate wastewater, the present invention performs activated carbon adsorption to remove impurities from the sodium sulfate wastewater 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. In the present invention, the activated carbon adsorption and impurity removal specifically involves passing the sodium sulfate wastewater through the activated carbon for impurity removal, and the flow rate of the sodium sulfate wastewater passing through the activated carbon is preferably 2 to 4 m 3 / h, specifically 2m 3 / h、3m 3 / h or 4m 3 / h; The ratio of the volume of sodium sulfate wastewater introduced per hour to the mass of activated carbon is preferably 1m 3 :(200~500)kg, specifically 1m 3 :200kg, 1m 3 :400kg or 1m 3 :500kg.
[0043] 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. Specifically, 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 converted to 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.
[0044] In the present invention, the conditions for the electrodialysis treatment preferably include: a current density of 700 to 900 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 sodium hydroxide solution.
[0045] In the present invention, the concentration of the sulfuric acid solution obtained by the electrodialysis treatment is preferably 1-1.5 mol / L, and the concentration of the sodium hydroxide solution is preferably 2-2.5 mol / L. In a specific embodiment of the present invention, the concentrations of the sulfuric acid solution and sodium hydroxide solution obtained by the electrodialysis treatment are preferably detected, and the electrodialysis treatment can be stopped when the concentrations reach the above requirements. The sulfuric acid solution obtained by the electrodialysis treatment is returned to the extractant regeneration process, and the sodium hydroxide solution is concentrated and used in the alkaline autoclave. The equipment used for the concentration is preferably an MVR device. The concentration of the sodium hydroxide solution after the concentration is 450-500 g / L.
[0046] 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.
[0047] Example 1
[0048] (1) Prepare 500g of black and white tungsten mixed ore with a tungsten content of 50 degrees and ball-mill it to 300 mesh. Add 450g / L sodium hydroxide solution at a tungsten to alkali ratio of 1:1 and perform alkaline autoclaving together with the black and white tungsten mixed ore in a reactor. The alkaline autoclaving temperature is 150℃, the pressure is 0.8MPa, and the heat preservation and pressure holding time is 3h. The liquid obtained after the reaction is subjected to solid-liquid separation using a filter press to obtain a filtrate and a tungsten slag. The filtrate is subjected to multi-effect evaporation to precipitate sodium tungstate in the form of crystals. Then, crude sodium tungstate crystals and alkali liquor are obtained by centrifugation. After the alkali liquor is recovered, it is returned to the alkaline autoclaving step for reuse. The crude sodium tungstate crystals are dissolved in water to obtain a crude sodium tungstate solution. The concentration of the crude sodium tungstate solution is 30g / L.
[0049] (2) The pH value of the crude sodium tungstate solution obtained in step (1) was adjusted to 8, and magnesium sulfate was added at a molar ratio of magnesium sulfate to arsenic in the solution of 1.2:1 to remove impurities. The reaction was carried out for 1 hour, and then the pH value was adjusted to 6 and the reaction was carried out for 0.5 hour. After the reaction, the obtained liquid was separated into solid and liquid using a filter press to obtain a sodium tungstate solution and impurity-removed residue.
[0050] (3) The pH value of the sodium tungstate solution obtained in step (2) was adjusted to 2, and the The molar ratio of hydrogen sulfide gas was introduced to remove molybdenum, the reaction temperature was 20 ° C, the reaction 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-removing slag.
[0051] (4) The refined sodium tungstate solution obtained in step (3) is extracted using N235, and the pH value of the feed solution is adjusted to 2 before extraction. The volume ratio of the extractant to the refined sodium tungstate solution is 1:1. After extraction, an extract phase and sodium sulfate wastewater are obtained. The extract phase is stripped using 10wt% ammonia water as a stripping agent. The volume ratio of ammonia water to the extract phase is 4:1. The ammonium tungstate solution is obtained by stripping. After stripping, the extractant is regenerated using the sulfuric acid solution produced in step (5). The regenerated extractant is returned to the extraction step for repeated use.
[0052] (5) The sodium sulfate wastewater produced in step (4) is heated to 2 m 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 500kg:1m 3 , then use bipolar membrane equipment at 900A / m 2Electrodialysis treatment is carried out at a current density of 1.5 mol / L (the polar water used is a 3 wt% sodium hydroxide solution) to prepare a 1.5 mol / L sulfuric acid solution and a 2.3 mol / L sodium hydroxide solution. The generated sulfuric acid solution is returned to step (4) for use in the regeneration of 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.
[0053] (6) The ammonium tungstate solution obtained in step (4) was reacted at a temperature of 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 11 g / L. After the reaction was completed, a vacuum filtration device was used to perform solid-liquid separation to obtain an APT primary product. The obtained APT primary product was washed with deionized water until the crystals had a conductivity of 48 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).
[0054] Example 2
[0055] (1) Prepare 500g of black and white tungsten mixed ore 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 alkali autoclaving in a reactor. The reaction temperature is 160℃, the reaction pressure is 0.9MPa, and the temperature is kept for 3.5h. The liquid obtained after the reaction is separated into solid and liquid using a filter press to obtain a filtrate and a tungsten slag. The filtrate is subjected to multi-effect evaporation to precipitate sodium tungstate in the form of crystals. Then, crude sodium tungstate crystals and alkali liquor are obtained by centrifugation. After the alkali liquor is recovered, it is returned to the alkali autoclaving step for reuse. The crude sodium tungstate crystals are dissolved in water to obtain a crude sodium tungstate solution. The concentration of the crude sodium tungstate solution is 35g / L.
[0056] (2) The pH value of the crude sodium tungstate solution obtained in step (1) is adjusted to 10, and basic magnesium carbonate is added at a molar ratio of basic magnesium carbonate to arsenic in the solution of 1.3:1 to remove impurities. The reaction is carried out for 1.5 hours, and then the pH value is adjusted to 7 and the reaction is carried out for 1 hour. After the reaction, the obtained liquid is subjected to solid-liquid separation using a filter press to obtain a sodium tungstate solution and impurity-removed residue.
[0057] (3) The pH value of the sodium tungstate solution obtained in step (2) was adjusted to 3, and the The molar ratio of hydrogen sulfide gas was introduced to remove molybdenum, the reaction temperature was 30 ° C, the reaction was carried out for 1 hour, 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-removed slag.
[0058] (4) The refined sodium tungstate solution obtained in step (3) is extracted using N235, and the pH of the feed solution is adjusted to 2.5 before extraction. The volume ratio of the extractant to the refined sodium tungstate solution is 1.3:1. After extraction, an extract phase and sodium sulfate wastewater are obtained. The extract phase is stripped using 15wt% ammonia water as a stripping agent. The volume ratio of ammonia water to the extract phase is 4.5:1. The ammonium tungstate solution is obtained by stripping. After stripping, the extractant is regenerated using the sulfuric acid solution produced in step (5), and the regenerated extractant is returned for extraction.
[0059] (5) The sodium sulfate wastewater produced in step (4) was 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 400kg:1m 3 , then use bipolar membrane equipment at 800A / 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 1.2 mol / L sulfuric acid solution and a 2.3 mol / L sodium hydroxide solution. The generated sulfuric acid solution is returned to step (4) for use in the 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.
[0060] (6) The ammonium tungstate solution obtained in step (4) 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 11 g / L. After the reaction was completed, a vacuum filtration device was used to separate the solid and liquid to obtain an 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 65° C. for 0.3 h using a microwave drying device to obtain an APT finished product (grade zero).
[0061] Example 3
[0062] (1) Prepare 500g of black and white tungsten mixed ore 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 to the black and white tungsten mixed ore and perform alkaline autoclave in a reactor. The reaction temperature is 180℃, the reaction pressure is 1MPa, and the temperature is kept for 4 hours. The liquid obtained after the reaction is separated into solid and liquid using a filter press to obtain a filtrate and a tungsten slag. The filtrate is subjected to multi-effect evaporation to precipitate sodium tungstate in the form of crystals. Then, crude sodium tungstate crystals and alkali liquor are obtained by centrifugation. After the alkali liquor is recovered, it is returned to the alkaline autoclave step for reuse. The crude sodium tungstate crystals are dissolved in water to obtain a crude sodium tungstate solution. The concentration of the crude sodium tungstate solution is 40g / L.
[0063] (2) The pH value of the crude sodium tungstate solution obtained in step (1) 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 the reaction, the obtained liquid was separated into solid and liquid using a filter press to obtain a sodium tungstate solution and impurity-removed residue.
[0064] (3) The pH value of the sodium tungstate solution obtained in step (2) was adjusted to 3.5. The molar ratio of hydrogen sulfide gas was introduced to remove molybdenum, the reaction temperature was 50 ° C, the reaction was carried out for 2 hours, 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-removing slag.
[0065] (4) The refined sodium tungstate solution obtained in step (3) is extracted using N235, and the pH value of the feed solution is adjusted to 3 before extraction. The volume ratio of the extractant to the refined sodium tungstate solution is 1.5:1. After extraction, an extract phase and sodium sulfate wastewater are obtained. 20wt% ammonia water is used as a stripping agent to strip the extract phase. The volume ratio of ammonia water to the extract phase is 5:1. Ammonium tungstate solution is obtained by stripping. After stripping, the extractant is regenerated using the sulfuric acid solution produced in step (5). The regenerated extractant is returned for extraction.
[0066] (5) The sodium sulfate wastewater produced in step (4) was heated to 4 m 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 solution passed in 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 500 (the polar water used is a 5 wt% sodium hydroxide solution) to prepare a 1.1 mol / L sulfuric acid solution and a 2.1 mol / L sodium hydroxide solution. The generated sulfuric acid solution is returned to step (4) for use in the 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.
[0067] (6) The ammonium tungstate solution obtained in step (4) 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 11 g / L. After the reaction was completed, a vacuum filtration device was used for solid-liquid separation to obtain an APT primary product. The obtained APT primary product was washed with deionized water until the crystals had a conductivity of 40 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).
[0068] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.
Claims
1. A method for smelting ammonium paratungstate from tungsten by recycling wastewater, characterized in that: The following steps are involved: Mix the black and white tungsten mixed ore with sodium hydroxide solution and perform alkaline autoclaving to obtain crude sodium tungstate solution and tungsten slag; The crude sodium tungstate solution and the magnesium compound are mixed and impurities are removed to obtain a sodium tungstate solution and impurity-removed slag; The sodium tungstate solution and hydrogen sulfide are mixed 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, thereby obtaining impurity-removed wastewater; The wastewater after impurity removal is subjected to electrodialysis treatment using a bipolar membrane to obtain a sulfuric acid solution and a sodium hydroxide solution; the sulfuric acid solution obtained by the electrodialysis treatment 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 tungsten content of the black and white tungsten mixed ore is 50-60 degrees and the mesh size is 300-325 meshes; The concentration of the sodium hydroxide solution used in the alkaline autoclave is 450-500 g / L; the mass ratio of tungsten in the black and white tungsten mixed ore to sodium hydroxide in the sodium hydroxide solution used in the alkaline autoclave is 1:1-3; 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 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 molar ratio of the magnesium salt to arsenic in the crude sodium tungstate solution is 1.2 to 1.5:
1. The impurity removal includes sequentially performing a first stage and a second stage, wherein the pH value of the first stage is 8 to 12, and the reaction time is 1 to 2 hours, and the pH value of the second stage is 6 to 8, and the reaction time is 0.5 to 1.5 hours.
4. The method according to claim 1, wherein 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.
5. The method according to claim 1, wherein The volume ratio of the extractant to the refined sodium tungstate solution is 1-1.5:1; the pH value of the refined sodium tungstate solution is adjusted to 2-3 before the extraction; the volume ratio of the ammonia water to the extraction phase is 4-5:1, and the concentration of the ammonia water is 10-20wt%; the extractant is N235.
6. The method according to claim 1, characterized in that In the activated carbon adsorption and impurity removal, the flow rate of sodium sulfate wastewater into the activated carbon is 2 to 4 m 3 / h; the ratio of the volume of sodium sulfate wastewater introduced per hour to the mass of activated carbon is 1m 3 :(200~500)kg.
7. 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 extreme water concentration is 3 to 5 wt%.
8. The method according to claim 1, characterized in that The concentration of the sulfuric acid solution obtained by the electrodialysis treatment is 1-1.5 mol / L, and the concentration of the sodium hydroxide solution is 2-2.5 mol / L.
9. 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.
10. The preparation method according to claim 1 or 9, characterized in that: The evaporation crystallization obtains a crystal liquid, and after obtaining the crystal liquid, the method further comprises: separating the crystal liquid into a solid and a liquid to obtain a primary product, washing the primary product and then drying it to obtain a finished ammonium paratungstate product.