Tungsten-molybdenum separation method based on tungsten coprecipitation inhibition
By selectively precipitating molybdenum by sulfidation and using a complexing agent, tungsten co-precipitation is suppressed, achieving efficient separation of tungsten and molybdenum. This solves the problems of tungsten loss and difficulty in controlling the amount of sulfiding agent, thereby improving production efficiency and purity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-07
AI Technical Summary
Existing sulfide precipitation methods suffer from severe tungsten loss, difficulty in controlling the amount of sulfide agent used, and low precipitation separation efficiency during tungsten-molybdenum separation. They fail to effectively address the fundamental issues of tungsten co-precipitation loss and difficulty in controlling the amount of sulfide agent used.
A selective sulfidation precipitation method for molybdenum was adopted. At the same time, a complexing agent was used to form a stable and soluble complex with tungsten ions. The pH, temperature and amount of sulfiding agent were controlled to inhibit the formation of tungstate colloid and ensure the selective precipitation of molybdenum.
It achieves efficient separation of tungsten and molybdenum, reducing tungsten loss rate to ≤0.5%, molybdenum sulfide purity to ≥98.5%, reducing sulfiding agent usage by 30-40%, increasing production efficiency by 3-4 times, and reducing process costs and environmental pressure.
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of hydrometallurgy and metal resource recycling, and particularly relates to a tungsten-molybdenum separation method based on tungsten co-precipitation inhibition. BACKGROUND
[0002] Tungsten and molybdenum are important refractory metals and are widely used in metallurgy, electronics, new energy and other fields. In the process of tungsten-molybdenum resource development and waste recycling, they often coexist in the same solution system (such as black tungsten ore and molybdenite associated ore leaching solution, tungsten-molybdenum catalyst after recycling solution), and need to be separated by separation process. In the current mainstream tungsten-molybdenum separation method, sulfidation precipitation method is a common technology for separating molybdenum in industry due to its simple operation and low cost. The principle is to add sulfidation agent (such as sodium sulfide, hydrogen sulfide) to the solution under acidic conditions, so that molybdenum is precipitated in the form of molybdenum sulfide (MoS3), while tungsten is theoretically retained in the solution.
[0003] However, the existing sulfidation precipitation method has the following significant technical bottlenecks: (1) serious tungsten co-precipitation loss: under acidic conditions (traditional process pH = 1-3), tungstic acid (WO4 2- ) is easy to combine with hydrogen ions to form tungstic acid (H2WO4) colloid, which is easy to adsorb on the surface of molybdenum sulfide precipitate or agglomerate with the precipitate, resulting in a high tungsten loss rate of 5-15%, which not only wastes tungsten resources, but also reduces the purity of molybdenum sulfide precipitate (tungsten impurity content exceeds 2%); (2) difficult to control the amount of sulfidation agent: in order to ensure complete molybdenum precipitation, the traditional process needs to add excessive sulfidation agent (molar ratio S / Mo = 3-5), and the excessive sulfidation agent is easy to generate sulfide precipitate with impurities such as Fe 3+ , Cu 2+ , etc. in the solution, further entrap tungsten ions, and increase the difficulty of subsequent wastewater treatment; (3) low separation efficiency of precipitation: molybdenum sulfide precipitate particles are fine (particle size is mostly <1 μm), which is easy to form colloidal suspension, and long time standing (8-12 h) or adding flocculants (such as polyacrylamide) is needed to realize solid-liquid separation, and the filter cake is difficult to wash, resulting in long molybdenum separation cycle and high energy consumption.
[0004] In view of the above problems, the existing technology improves from the single dimension of “adjusting pH” and “optimizing sulfidation agent type”, but does not construct a coordinated system from the essential requirements of “inhibiting tungsten colloid generation” and “strengthening molybdenum selective precipitation”, and the problem of tungsten co-precipitation has not been fundamentally solved. SUMMARY
[0005] In view of the above deficiencies, the present application aims to provide a tungsten-molybdenum separation method based on tungsten co-precipitation inhibition, which is used to solve the technical problems of serious tungsten loss, difficult control of sulfidation agent amount and low separation efficiency of precipitation existing in the existing sulfidation precipitation method.
[0006] This invention innovatively proposes a dual-functional technical route of "selective sulfidation precipitation of molybdenum + in-situ complexation stabilization of tungsten". By precisely controlling the reaction environment and optimizing the reagent system, it achieves efficient separation of tungsten and molybdenum and zero waste of tungsten resources.
[0007] The core idea of this invention is to form a stable and soluble complex with tungsten ions through a "compound complexing agent" while simultaneously precipitating molybdenum by sulfidation, thereby inhibiting the formation of tungstic acid colloids; and to simultaneously control parameters such as reaction pH, temperature, and amount of sulfiding agent to ensure selective precipitation of molybdenum and avoid co-precipitation of tungsten.
[0008] The objective of this invention is achieved through the following technical solution: A method for separating tungsten and molybdenum based on inhibiting tungsten co-precipitation includes the following steps: S1. Measuring WO4 in tungsten-molybdenum mixture 2- MoO4 2- Fe 3+ Cu 2+ Si 4+ The content; When Fe 3+ +Cu 2+ When the concentration is >0.5 g / L, add disodium ethylenediaminetetraacetate solution for complexation. After the reaction is complete, filter to obtain the pretreated solution. When Si 4+ When the concentration is >0.1g / L, sodium aluminate solution is added and the pH is adjusted to 8~9 to carry out the reaction. After the reaction is completed, the solution is filtered to obtain the pretreated solution. S2. Adjust the pH of the pretreated solution to 4.5~6.0 and heat it to 40~55℃. Under stirring, add the compound complexing agent and precipitation promoter and react for 20~30 min. Then add ammonium sulfide solution and maintain the pH of the system during the reaction. Continue the reaction until the end. Separate the product into solid and liquid to obtain filtrate and filter residue. S3. The filter residue is washed and dried to obtain molybdenum sulfide; the washing liquid of the filter residue and the filtrate are combined and tungsten products are recovered by ion exchange.
[0009] In this invention, in step S1, when Fe 3+ +Cu 2+ When the concentration is >0.5 g / L, add disodium ethylenediaminetetraacetate (EDTA-2Na) solution for complexation, so that Fe... 3+ Cu 2+ They form stable complexes (water-soluble five-membered ring chelates) with EDTA-2Na, "encapsulating" metal ions in a water-soluble structure, thereby reducing the concentration of free metal ions and preventing them from reacting with the sulfiding agent to form sulfides.
[0010] The purpose of filtration after the reaction is to remove a small amount of uncomplexed impurities as precipitate. This is because, in actual industrial solutions, besides Fe... 3+ Cu 2+ There may also be other trace impurity ions that are not complexed by EDTA-2Na (such as a small amount of Ca). 2+ Mg 2+ (or hydroxides of other metal ions). These impurities will form precipitates under reaction conditions, so the purpose of filtration is to remove these "uncomplexed impurity precipitates".
[0011] In summary, the core function of EDTA-2Na is to react with Fe. 3+ Cu 2+ The process involves forming water-soluble complexes (to prevent them from reacting with the vulcanizing agent to form impurity sulfides), while the filtration step is to remove other uncomplexed trace impurities from the system.
[0012] In this invention, the criteria for detecting and determining the completeness of complexation of elements such as Fe and Cu are as follows: Detection method: Ultraviolet spectrophotometry combined with complexometric titration (such as EDTA back titration) is commonly used to detect free Fe. 3+ Cu 2+ Concentration. Ultraviolet spectrophotometry can detect concentrations through characteristic absorption peaks (such as Fe). 3+ In qualitative / quantitative analysis (absorbing at a specific wavelength), complexometric titration can more accurately determine the concentration of free ions.
[0013] The standard for complete complexation: It is generally believed in the industry that when free Fe... 3+ Concentration ≤ 0.01 g / L, free Cu 2+ When the concentration is ≤0.005g / L, it can be considered as EDTA-2Na and Fe. 3+ Cu 2+ Complete complexation. This standard stems from the tolerance of subsequent sulfidation reactions to impurity ions: if the concentration of free metal ions is too high, they will react with the sulfiding agent to form impurity sulfides, affecting product purity.
[0014] Furthermore, when checking the completeness of subsequent reactions (such as molybdenum sulfide precipitation reaction, tungsten solution purity reaction, etc.) in this invention, ultraviolet spectrophotometry can be used; for the molybdenum sulfide precipitation reaction, residual MoO4 in the supernatant can be detected. 2- A concentration ≤ 0.05 g / L is considered a complete reaction. For tungsten solutions, free WO4 can be detected. 2- The concentration and impurity ion concentration, combined with the purity of the APT product, are used to infer the completeness of the reaction.
[0015] In this invention, in step S1, when Si 4+When the concentration is >0.1 g / L, sodium aluminate solution is added and the pH is adjusted to 8-9 to proceed with the reaction, so that Si 4+ With Al 3+ Sodium aluminosilicate precipitate is formed, which is then removed by filtration to prevent the silica gel from carrying tungsten ions.
[0016] Preferably, in step S1, an inductively coupled plasma atomic emission spectrometer is used to test the content of each ion in the tungsten-molybdenum mixture.
[0017] Preferably, the concentration of the disodium ethylenediaminetetraacetate solution in step S1 is 0.1~0.3 mol / L; and the concentration of the sodium aluminate solution is 0.05~0.1 mol / L.
[0018] Preferably, in step S2, the pH of the pretreated solution is adjusted to 4.5-6.0 by adding sulfuric acid solution or sodium hydroxide solution. More preferably, the concentration of both the sulfuric acid solution and the sodium hydroxide solution is 2 mol / L. Unlike traditional acidic conditions, this pH range can reduce the formation of tungstate colloids.
[0019] In this invention, the pH of the pretreated solution is adjusted to 4.5~6.0 and the temperature is raised to 40~55℃, which provides a suitable environment for the subsequent sulfidation and complexation reactions (if the temperature is too low, the precipitation rate of molybdenum sulfide will be slow, and if the temperature is too high, the stability of the complex will decrease).
[0020] Preferably, the complexing agent in step S2 is a mixed aqueous solution of sodium citrate and potassium sodium tartrate; the precipitation promoter is an aqueous solution of polyvinylpyrrolidone.
[0021] Preferably, the polyvinylpyrrolidone in the aqueous solution has a molecular weight of 10,000, and its surface-active groups can be adsorbed on the surface of molybdenum sulfide particles, promoting particle aggregation (increasing the particle size to 5-8 μm) and accelerating precipitation separation.
[0022] Preferably, in the compound complexing agent, the concentration of sodium citrate is 0.3~0.6 mol / L and the concentration of potassium sodium tartrate is 0.1~0.2 mol / L.
[0023] In this invention, sodium citrate and potassium sodium tartrate synergistically form a stable, soluble complex with tungsten ions (sodium citrate and WO4). 2- A complex with logK=12.5 is formed, and potassium sodium tartrate further enhances stability and prevents the formation of tungstate colloids.
[0024] Preferably, in step S2, the amount of the complexing agent added is sufficient to satisfy the requirement of free WO4 in the reaction solution. 2- The concentration should be ≤0.1g / L; the volume ratio of the precipitation promoter to the compound complexing agent is 1:5~10.
[0025] Preferably, the concentration of the ammonium sulfide solution in step S2 is 2~4 mol / L, and the molar ratio of S in the ammonium sulfide solution to Mo in the reaction system is 3.2~3.5:1.
[0026] In this invention, ammonium sulfide is selected as the sulfiding agent. Compared with sodium sulfide, the molybdenum sulfide precipitate particles generated by ammonium sulfide are larger (particle size 1-3 μm) and are less likely to adsorb with tungsten ions.
[0027] Preferably, the solid-liquid separation method in step S2 is pressure filtration, with a pressure of 0.4~0.6MPa and a time of 30~45min.
[0028] In step S2 of this invention, the pH of the pretreated solution is adjusted to 4.5-6.0, and the temperature is raised to 40-55°C. Under stirring conditions, a complexing agent and a precipitation promoter are added, and the reaction is carried out for 20-30 minutes to ensure complete complexation of tungsten ions (detected by a UV spectrophotometer, showing free WO4 in the solution). 2- (Concentration ≤ 0.1 g / L is considered complete complexation); add ammonium sulfide solution dropwise, controlling the dropping rate at 1~2 mL / min (to avoid excessively high local sulfidation concentrations leading to tungsten co-precipitation), while simultaneously adding 0.5 mol / L sulfuric acid solution via an online pH monitoring system to maintain the pH of the reaction system stable at 4.5-6.0; based on precise calculation of molybdenum concentration, the molar ratio S / Mo = 3.2~3.5 (only an excess of 6.7~16.7%, far lower than the 3~5 times of traditional processes, reducing impurity generation); after the dropwise addition is complete, continue stirring for 60-90 min to ensure complete conversion of molybdenum into molybdenum sulfide precipitate.
[0029] It is worth noting that at this point, molybdenum ions will not be complexed by the complexing agent, for the following reasons: Complexing stabilizers (such as sodium citrate and potassium sodium tartrate) affect tungsten ions (WO4). 2- It has selective complexation activity, but is effective against molybdenum ions (MoO4). 2- The complexing ability of tungsten ions is extremely weak. The principle is that the stability constant of the chelate formed by tungsten ions and the complexing agent is much higher than that of molybdenum ions. Therefore, in the same system, the complexing agent will preferentially and almost completely bind to tungsten ions, while molybdenum ions exist in a free or weakly bound state and will not be complexed together.
[0030] Furthermore, the principle behind the coexistence of "compound complexing agent + precipitation promoter" is as follows: The role of the compound complexing agent: to form a stable water-soluble complex with tungsten ions, inhibit the formation of tungstic acid colloids, avoid the co-precipitation of tungsten and molybdenum in the subsequent sulfidation reaction, and ensure the recovery rate of tungsten.
[0031] The role of precipitation promoter (PVP): Through adsorption and aggregation, it enables the subsequently generated molybdenum sulfide particles to grow rapidly, accelerate precipitation and separation, and at the same time reduce the adsorption of tungsten complexes by the particles.
[0032] The logic behind their coexistence is as follows: the complexing agent "protects" tungsten from precipitation, while the precipitation promoter "accelerates" the sulfide precipitation of molybdenum, thereby achieving efficient separation of tungsten and molybdenum. Tungsten remains in the solution, while molybdenum precipitates as sulfides, and they are ultimately recycled separately.
[0033] Preferably, the washing operation in step S3 is as follows: wash 2 to 3 times with a dilute ammonia solution (concentration 0.5mol / L) at 40~50℃, with the amount of washing solution used each time being 3 to 5 times the volume of the filter residue.
[0034] Preferably, hydrogen sulfide gas (flow rate of 0.5-1 L / min) is introduced into the washing solution obtained in step S3 (the main component is dilute ammonia water, containing a small amount of unreacted ammonium sulfide) to generate an ammonium sulfide solution (concentration of 1.5-2 mol / L). This solution can be reused in step S2, reducing reagent costs by 30%.
[0035] Preferably, in step S3, the washing liquid of the filter residue (if the washing liquid of the filter residue contains molybdenum, an ammonium sulfide solution with a concentration of 0.1~0.2 mol / L can be added to allow the molybdenum to precipitate again) and the filtrate are combined, and the combined solution is passed through a D201 macroporous anion exchange resin column, where the tungsten complex is adsorbed by the resin. Subsequently, it is eluted with a sodium hydroxide solution with a concentration of 2~3 mol / L. The eluted solution is collected, concentrated, and crystallized to obtain ammonium paratungstate (APT) product (purity ≥99.8%), with a tungsten loss rate ≤0.5%.
[0036] Preferably, the waste liquid is concentrated to 1 / 3 of its original volume by vacuum distillation (temperature 70~80℃, vacuum degree -0.08MPa), and can be directly used as a compound complexing agent for recycling (after 3 cycles, the tungsten complexing efficiency is still ≥99%).
[0037] Compared with the prior art, the beneficial effects of the present invention include: (1) Breakthrough in both tungsten-molybdenum separation efficiency and resource utilization The molybdenum precipitation rate is ≥99% and the molybdenum sulfide purity is ≥98.5%, meeting the raw material requirements for subsequent molybdenum purification (such as roasting to prepare molybdenum trioxide). The tungsten loss rate is reduced from 5~15% in the traditional process to ≤0.5%. For every 1 ton of tungsten-molybdenum solution processed, 5~15 kg of tungsten resources can be reduced. Based on the tungsten market price of 200,000 yuan / ton, the economic benefits per ton of solution are increased by 1,000~3,000 yuan.
[0038] (2) The process cost is significantly reduced. The amount of sulfiding agent used is reduced by 30-40% (the molar ratio S / Mo decreases from 3-5 to 3.2-3.5), and the complexing stabilizer and ammonium sulfide can be recycled (the reagent cost decreases by 30% after 3 cycles), reducing the reagent cost per ton of solution from 280-320 yuan to 190 yuan; the filtration time is shortened from 2-3 hours to 0.5-0.75 hours, the energy consumption for solid-liquid separation is reduced by 60%, and the production efficiency is increased by 3-4 times.
[0039] (3) Enhanced environmental friendliness and industrial adaptability The reaction system has a pH of 4.5~6.0 (near neutral), and there is no strong acid or alkali to corrode the equipment. The wastewater has a pH of 5~7, and only simple neutralization is required to meet the discharge standards (COD≤50mg / L), reducing solid waste generation by 50%. The core equipment (plate and frame filter press, ion exchange column, online monitoring system) are all mature industrial equipment, requiring no customized modification. Existing tungsten and molybdenum separation production lines can be directly connected, and the return on investment for modification is less than 1 year.
[0040] (4) Wide range of application scenarios It is applicable to various conventional tungsten and molybdenum solutions with tungsten concentrations of 5~30g / L and molybdenum concentrations of 1~10g / L, including tungsten ore leaching solutions, waste tungsten and molybdenum alloy recovery solutions, and tungsten and molybdenum catalyst regeneration solutions; it can be extended to the separation system of "tungsten and other sulfide precipitated metals (such as arsenic and antimony)", providing technical reference for the high-value recovery of multi-metal mixed solutions. Detailed Implementation
[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0042] Example 1 A method for separating tungsten and molybdenum based on inhibiting tungsten co-precipitation, the specific steps of which are as follows: (1) Preparation of raw material solution: Weigh out sodium tungstate, sodium molybdate, ferric sulfate, and sodium silicate respectively, add them to deionized water in sequence, stir until completely dissolved, and finally adjust the volume to 10L to obtain tungsten-molybdenum mixed raw material solution; wherein, WO4 2- The concentration was 20 g / L, MoO4 2- The concentration was 8 g / L, Fe 3+ The concentration of Si was 0.3 g / L. 4+ The concentration was 0.08 g / L; (2) Adjust the pH of the raw material solution to 5.0 and heat it to 50°C in a water bath. Under stirring conditions, add 1.32L of compound complexing agent (0.5mol / L sodium citrate + 0.15mol / L potassium sodium tartrate) and 0.165L of precipitation promoter (0.02mol / L PVP solution). React at a stirring rate of 400r / min for 25min and detect free WO4. 2- The concentration was 0.08 g / L; then, a 3 mol / L ammonium sulfide solution (calculated dosage: S / Mo = 3.3) was added at a rate of 1.5 mL / min, and the pH of the system was maintained during the reaction, and the reaction was continued for 75 min; (3) After the reaction is completed, the slurry is sent to a plate and frame filter press (filter cloth pore size 0.22μm) and filtered under a pressure of 0.5MPa. Since the molybdenum sulfide particles are promoted to agglomerate by PVP, the filtration time can be shortened to 40min; after filtration, filtrate and filter residue are obtained. Free WO4 in the filtrate (tungsten-containing solution) 2- The concentration was 19.9 g / L, and the tungsten loss rate was 0.45%.
[0043] Filter residue (molybdenum sulfide) washing: Wash three times with a dilute ammonia solution (0.5 mol / L) at 50℃, with each washing solution being 3 to 5 times the volume of the filter residue. This removes the complexing stabilizer and a small amount of tungsten ions adsorbed on the surface of the filter residue. After washing, the residue is dried to obtain molybdenum sulfide with a purity of 98.8% and a molybdenum recovery rate of 99.2%. The washing liquid from the filter residue and the filtrate from the pressure filtration were combined, and the combined solution was passed through a D201 macroporous anion exchange resin (resin layer height 1.5m, flow rate 2BV / Hr). Tungsten complexes were adsorbed by the resin, and then eluted with a 3mol / L sodium hydroxide solution. The eluent was concentrated and crystallized to obtain ammonium paratungstate (APT) product with a purity of 99.85%.
[0044] Example 2 A method for separating tungsten and molybdenum based on inhibiting tungsten co-precipitation, the specific steps of which are as follows: (1) Preparation of raw material solution: Weigh out sodium tungstate, sodium molybdate, ferric sulfate, and sodium silicate respectively, add them to deionized water in sequence, stir until completely dissolved, and finally adjust the volume to 10L to obtain tungsten-molybdenum mixed raw material solution; wherein, WO4 2- The concentration is 10 g / L, MoO4 2- The concentration was 1.5 g / L, Fe 3+ The concentration of Si was 0.1 g / L. 4+ The concentration is 0.05 g / L; (2) Adjust the pH of the raw material solution to 5.5 and heat it to 45°C in a water bath. Under stirring conditions, add 0.45L of compound complexing agent (0.3mol / L sodium citrate + 0.1mol / L potassium sodium tartrate) and 0.09L of precipitation promoter (0.01mol / L PVP solution). React at a stirring rate of 350r / min for 20min and detect free WO4. 2- The concentration was 0.05 g / L; then, a 2 mol / L ammonium sulfide solution was added at a rate of 1.0 mL / min (calculated amount: S / Mo = 3.2), and the pH of the system was maintained during the reaction, and the reaction was continued for 60 min; (3) After the reaction is completed, the slurry is fed into a plate and frame filter press (filter cloth pore size 0.22μm) and filtered under a pressure of 0.4MPa. Since the molybdenum sulfide particles are promoted to agglomerate by PVP, the filtration time can be shortened to 30min; after filtration, filtrate and filter residue are obtained. Free WO4 in the filtrate (tungsten-containing solution) 2- The concentration was 9.98 g / L, and the tungsten loss rate was 0.2%.
[0045] Filter residue (molybdenum sulfide) washing: Wash twice with a dilute ammonia solution (concentration 0.5mol / L) at 50℃, with the volume of washing solution being 3 to 5 times the volume of the filter residue each time, to remove the complexing stabilizer and a small amount of tungsten ions adsorbed on the surface of the filter residue. After washing, dry to obtain molybdenum sulfide with a purity of 99.1% and a molybdenum recovery rate of 99.5%. The washing liquid from the combined filter residue and the filtrate from the pressure filtration were then passed through a D201 macroporous anion exchange resin (resin layer height 1.5 m, flow rate 2 BV / Hr). Tungsten complexes were adsorbed by the resin, and subsequently eluted with a 3 mol / L sodium hydroxide solution. The eluent was concentrated and crystallized to obtain ammonium paratungstate (APT) product with a purity of 99.9%.
[0046] Example 3 A method for separating tungsten and molybdenum based on inhibiting tungsten co-precipitation, the specific steps of which are as follows: (1) Preparation of raw material solution: Weigh out sodium tungstate, sodium molybdate, ferric sulfate, and sodium silicate respectively, add them to deionized water in sequence, stir until completely dissolved, and finally adjust the volume to 10L to obtain tungsten-molybdenum mixed raw material solution; wherein, WO4 2- The concentration was 15 g / L, MoO4 2- The concentration was 4 g / L, Fe 3+ The concentration was 0.6 g / L, and Si 4+ The concentration was 0.12 g / L; (2) Add 600 mL of 0.25 mol / L EDTA-2Na solution to the raw material solution and react at 32℃ and 280 r / min for 50 min; add 0.08 mol / L sodium aluminate solution and adjust pH to 8.5, stir for 30 min, filter to remove sodium aluminosilicate precipitate after the reaction, and obtain the pretreated solution; (3) Adjust the pH of the pretreated solution to 5.2 and heat it to 48°C in a water bath. Under stirring, add 0.88 L of compound complexing agent (0.4 mol / L sodium citrate + 0.18 mol / L potassium sodium tartrate) and 0.098 L of precipitation promoter (0.025 mol / L PVP solution). React at a stirring rate of 380 r / min for 28 min and detect free WO4. 2- The concentration was 0.07 g / L; then, a 2.5 mol / L ammonium sulfide solution (calculated dosage: S / Mo = 3.4) was added at a rate of 1.3 mL / min, and the pH of the system was maintained during the reaction, and the reaction was continued for 80 min; (4) After the reaction is completed, the slurry is fed into a plate and frame filter press (filter cloth pore size 0.22μm) and filtered under a pressure of 0.5MPa. Since the molybdenum sulfide particles are promoted to agglomerate by PVP, the filtration time can be shortened to 35min. After filtration, filtrate and filter residue are obtained. Free WO4 in the filtrate (tungsten-containing solution) 2- The concentration was 14.96 g / L, and the tungsten loss rate was 0.27%.
[0047] Filter residue (molybdenum sulfide) washing: Wash three times with a dilute ammonia solution (0.5 mol / L) at 50℃, with each washing solution being 3 to 5 times the volume of the filter residue. This removes the complexing stabilizer and a small amount of tungsten ions adsorbed on the surface of the filter residue. After washing, the residue is dried to obtain molybdenum sulfide with a purity of 98.9% and a molybdenum recovery rate of 99.3%. The washing liquid from the filter residue and the filtrate from the pressure filtration were combined, and the combined solution was passed through a D201 macroporous anion exchange resin (resin layer height 1.5m, flow rate 2BV / Hr). Tungsten complexes were adsorbed by the resin, and then eluted with a 3mol / L sodium hydroxide solution. The eluent was concentrated and crystallized to obtain ammonium paratungstate (APT) product with a purity of 99.88%.
[0048] Comparative Example 1 Compared with Example 1, the only difference is that PVP solution is not added in step S2, while the rest of the steps are exactly the same as in Example 1.
[0049] Experimental results: The particle size of the molybdenum sulfide precipitate is 0.8~1.2μm, and the plate and frame filtration time is 2.5h (only 40min in Example 1). The purity of molybdenum sulfide was 96.2% (with tungsten impurities of 1.8%), and the molybdenum recovery rate was 97.5%. The tungsten loss rate was 3.8% (only 0.45% in Example 1).
[0050] By comparing Example 1 and Comparative Example 1, we can see that PVP can effectively promote the agglomeration of molybdenum sulfide particles, shorten the filtration time, and at the same time reduce the adsorption of tungsten impurities and reduce tungsten loss.
[0051] Comparative Example 2 Compared with Example 2, the only difference is that the sodium citrate-sodium potassium tartrate compound system is not added in step S2, and the other steps are completely the same as in Example 1.
[0052] Experimental results: A large amount of tungstic acid colloid is generated in the solution, resulting in a turbid precipitate that is visible to the naked eye; The purity of the molybdenum sulfide precipitate was 94.7% (with tungsten impurities of 3.2%), and the molybdenum recovery rate was 96.8%. The tungsten loss rate was 8.5% (only 0.2% in Example 2).
[0053] By comparing Example 2 and Comparative Example 2, we can see that complexation is the key to inhibiting the formation of tungstate colloids and avoiding tungsten co-precipitation, which directly determines the utilization rate of tungsten resources.
[0054] Comparative Example 3 Compared with Example 3, the only difference is that in step (3), the pH of the pretreated solution is adjusted to 2.5 (the commonly used range of traditional processes), and the other steps are completely the same as in Example 3.
[0055] Experimental results: A large amount of tungstate colloids are generated and tightly aggregate with molybdenum sulfide precipitate; The purity of molybdenum sulfide was 95.3% (with tungsten impurities of 2.6%), and the molybdenum recovery rate was 98.1%. The tungsten loss rate was 6.2% (only 0.27% in Example 3).
[0056] Comparing Example 3 and Comparative Example 3, we can see that a near-neutral environment with pH = 4.5~6.0 can reduce the formation of tungstate colloids from the source and achieve efficient tungsten stabilization in conjunction with complexing stabilizers.
[0057] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A method for separating tungsten and molybdenum based on inhibiting tungsten co-precipitation, characterized in that, Includes the following steps: S1. Measuring WO4 in tungsten-molybdenum mixture 2- MoO4 2- Fe 3+ Cu 2+ Si 4+ The content; When Fe 3+ +Cu 2+ When the concentration is >0.5 g / L, add disodium ethylenediaminetetraacetate solution for complexation. After the reaction is complete, filter to obtain the pretreated solution. When Si 4+ When the concentration is >0.1g / L, sodium aluminate solution is added and the pH is adjusted to 8~9 to carry out the reaction. After the reaction is completed, the solution is filtered to obtain the pretreated solution. S2. Adjust the pH of the pretreated solution to 4.5~6.0 and heat it to 40~55℃. Under stirring, add the compound complexing agent and precipitation promoter and react for 20~30 min. Then add ammonium sulfide solution and maintain the pH of the system during the reaction. Continue the reaction until the end. Separate the product into solid and liquid to obtain filtrate and filter residue. S3. The filter residue is washed and dried to obtain molybdenum sulfide; the washing liquid of the filter residue and the filtrate are combined and tungsten products are recovered by ion exchange.
2. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 1, characterized in that, The concentration of the disodium ethylenediaminetetraacetate solution in step S1 is 0.1~0.3 mol / L; the concentration of the sodium aluminate solution is 0.05~0.1 mol / L; and / or In step S2, the pH of the pretreated solution is adjusted to 4.5-6.0 by adding sulfuric acid solution or sodium hydroxide solution.
3. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 1, characterized in that, The complexing agent mentioned in step S2 is a mixed aqueous solution of sodium citrate and potassium sodium tartrate; the precipitation promoter is an aqueous solution of polyvinylpyrrolidone.
4. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 3, characterized in that, In the compound complexing agent, the concentration of sodium citrate is 0.3~0.6 mol / L and the concentration of potassium sodium tartrate is 0.1~0.2 mol / L.
5. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 4, characterized in that, In step S2, the amount of complexing agent added is sufficient to satisfy the requirement of free WO4 in the reaction solution. 2- The concentration should be ≤0.1 g / L; the volume ratio of the precipitation promoter to the compound complexing agent should be 1:5~10; and / or The concentration of the ammonium sulfide solution in step S2 is 2~4 mol / L, and the molar ratio of S in the ammonium sulfide solution to Mo in the reaction system is 3.2~3.5:
1.
6. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 1, characterized in that, The solid-liquid separation method described in step S2 is pressure filtration, with a pressure of 0.4~0.6MPa and a time of 30~45min.
7. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 1, characterized in that, The specific washing operation in step S3 is as follows: wash 2 to 3 times with a dilute ammonia solution at 40 to 50°C, with the amount of washing solution used each time being 3 to 5 times the volume of the filter residue.
8. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 7, characterized in that, Hydrogen sulfide gas is introduced into the washing liquid obtained in step S3 to generate an ammonium sulfide solution, which can be reused in step S2.
9. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 1, characterized in that, In step S3, the washing liquid of the filter residue and the filtrate are combined, and the combined solution is passed through a D201 macroporous anion exchange resin column, where the tungsten complex is adsorbed by the resin. Subsequently, it is desorbed with a sodium hydroxide solution with a concentration of 2-3 mol / L. The elution solution is collected, concentrated, and crystallized to obtain ammonium paratungstate product.
10. The tungsten-molybdenum separation method based on inhibiting tungsten co-precipitation according to claim 9, characterized in that, After analysis, the waste liquid is concentrated to 1 / 3 of its original volume by vacuum distillation and can be directly recycled as a compound complexing agent.