Method for preparing sodium tungstate by electrolyzing waste tungsten material under alkaline condition
By adding a primary oxidant, a secondary oxidant, and a complexing agent to the electrolyte and optimizing the electrolysis conditions, the problem of low electrolysis efficiency was solved, and the full dissolution and efficient recovery of tungsten were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUBEI GREEN TUNGSTEN CO LTD
- Filing Date
- 2026-02-28
- Publication Date
- 2026-06-16
Abstract
Description
Technical Field
[0001] This invention relates to the field of waste cemented carbide recycling technology, specifically to a method for preparing sodium tungstate by electrolyzing waste tungsten materials under alkaline conditions. Background Technology
[0002] In the field of tungsten resource recycling and utilization, the preparation of sodium tungstate by electrolysis of waste tungsten materials under alkaline conditions is an important process. Currently, the core of this process in existing technologies is to construct an alkaline electrolysis system, using waste tungsten materials as the anode and inert electrodes as the cathode, achieving tungsten dissolution under the influence of an electric field. During electrolysis, the tungsten on the anode surface mainly undergoes the following reaction: W + 8OH⁻ - - 6e - =WO4 2- + 4H2O.
[0003] Traditional electrolysis systems rely solely on an alkaline environment and electric field to promote the dissolution of tungsten in waste tungsten materials. They lack effective oxidants to accelerate the oxidation and dissolution reaction of tungsten on the anode surface, resulting in incomplete dissolution of tungsten, especially for complex and dense waste tungsten materials (such as tungsten-based high-density alloys and waste tungsten electrodes). Often, some tungsten fails to dissolve into the electrolyte. On one hand, the lack of effective oxidants makes it difficult to oxidize some stable tungsten compounds in the waste tungsten materials into soluble tungstate ions. On the other hand, the products generated during electrolysis may form a dense passivation film on the anode surface, such as sodium tungstate crystals or other oxide films. This passivation film hinders the contact between the electrolyte and the tungsten on the anode surface, inhibiting subsequent dissolution reactions. Although adding oxidants can improve electrolysis efficiency to some extent in actual electrolysis processes, the efficiency remains low when applied in production.
[0004] Therefore, improving electrolysis efficiency and promoting full dissolution of tungsten are urgent problems to be solved in the process of preparing sodium tungstate from waste tungsten materials. Summary of the Invention
[0005] In view of the technical problems existing in the background art, the present invention provides a method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions, aiming to solve the technical problem of poor electrolysis effect in the existing process of preparing sodium tungstate by electrolysis of waste tungsten material.
[0006] In a first aspect, the present invention provides a method for preparing sodium tungstate by electrolyzing waste tungsten material under alkaline conditions, comprising the following steps: An electrolytic cell is provided, an electrolyte is added to the electrolytic cell, and waste tungsten material is immersed in the electrolyte for electrolysis to obtain a crude sodium tungstate solution; In this process, waste tungsten material is used as the anode, and the cathode is an inert electrode. The raw materials for preparing the electrolyte include a sodium hydroxide solution with a concentration of 2-4 mol / L, as well as a primary oxidant, a secondary oxidant, and a complexing agent; the total mass of the primary oxidant, secondary oxidant, and complexing agent is 5%-8% of the mass of the sodium hydroxide solution. The primary oxidant includes at least one of sodium chlorate, hypochlorous acid, and hydrogen peroxide; the secondary oxidant includes at least one of sodium nitrate and sodium nitrite.
[0007] Preferably, the complexing agent includes at least one of sodium phosphate, sodium pyrophosphate, and sodium hexametaphosphate.
[0008] Preferably, the mass ratio of the main oxidant, the auxiliary oxidant and the complexing agent is (2~4):(2~3):(1~2).
[0009] Preferably, the waste tungsten material is pretreated before electrolysis. The pretreatment specifically involves cutting the waste tungsten material into anode plates, soaking them in hydrochloric acid solution for 20-40 minutes, rinsing them with deionized water, and then ultrasonically cleaning them for 20-30 minutes.
[0010] Preferably, the inert electrode includes a titanium-based lead dioxide coated electrode or a titanium-based iridium-tantalum coated electrode.
[0011] Preferably, the distance between the cathode and the anode is controlled at 6~7cm.
[0012] Preferably, during the electrolysis process, the current density is controlled to be 150~180 A / m. 2 .
[0013] Preferably, the electrolysis temperature is controlled at 60~80℃ during the electrolysis process.
[0014] Preferably, the electrolysis time is 3 to 8 hours.
[0015] Preferably, during the electrolysis process, the electrolyte is continuously stirred at a stirring rate of 250~400 r / min.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for preparing sodium tungstate from waste tungsten materials under alkaline conditions. By synergistically introducing a primary oxidant, a secondary oxidant, and a complexing agent into the electrolyte, the electrolysis efficiency is significantly improved. The primary oxidant possesses strong oxidizing properties and can directly participate in the oxidation reaction of tungsten on the anode surface, accelerating tungsten dissolution. The secondary oxidant significantly increases the ionic strength of the solution and improves the conductivity of the electrolyte. The complexing agent can form stable, soluble complexes with tungsten in the electrolyte, inhibiting tungsten passivation during electrolysis and effectively improving electrolysis efficiency. However, the amount of complexing agent added should not be excessive, otherwise it will increase the cost of subsequent impurity removal. This invention effectively solves the problems of low electrolysis efficiency and insufficient tungsten dissolution in existing technologies, providing a practical and feasible method for the high-value recycling and utilization of waste tungsten resources. Detailed Implementation
[0017] The embodiments of the technical solution of the present invention will be described in detail below. These embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.
[0018] To address the technical problem of poor electrolysis efficiency in the existing process of preparing sodium tungstate from waste tungsten materials, this invention provides a method for preparing sodium tungstate from waste tungsten materials under alkaline conditions. In this method, by adding an oxidant and a complexing agent to the alkaline electrolysis system, the tungsten is fully dissolved, significantly improving the electrolysis efficiency.
[0019] In a first aspect, embodiments of the present invention provide a method for preparing sodium tungstate by electrolyzing waste tungsten material under alkaline conditions, comprising the following steps: An electrolytic cell is provided, an electrolyte is added to the electrolytic cell, and waste tungsten material is immersed in the electrolyte for electrolysis to obtain a crude sodium tungstate solution; In this process, waste tungsten material is used as the anode, and the cathode is an inert electrode. The raw materials for preparing the electrolyte include a sodium hydroxide solution with a concentration of 2-4 mol / L, as well as a primary oxidant, a secondary oxidant, and a complexing agent; the total mass of the primary oxidant, secondary oxidant, and complexing agent is 5%-8% of the mass of the sodium hydroxide solution. The primary oxidant includes at least one of sodium chlorate, hypochlorous acid, and hydrogen peroxide; the secondary oxidant includes at least one of sodium nitrate and sodium nitrite.
[0020] In the technical solution of this invention, the addition of oxidants and complexing agents to the electrolyte improves electrolysis efficiency in several ways. First, the primary oxidant (taking sodium hypochlorite as an example) has strong oxidizing properties under alkaline conditions and can undergo rapid oxidation reactions with tungsten on the anode surface, for example: W + NaClO3 + 4NaOH = Na2WO4 + NaCl + 2H2O, WC + NaClO3 + 6NaOH = Na2WO4 + NaCl + Na2CO3 + 3H2O. The kinetic rate of these reactions is higher than that of tungsten dissolution reactions relying solely on an electric field, thus accelerating the dissolution rate of tungsten. Second, the auxiliary oxidant can increase the ionic strength of the solution, improve the conductivity of the electrolyte, and stabilize the pH value of the electrolyte. The complexing agent can form stable soluble complexes with tungsten in the electrolyte, inhibiting tungsten passivation during electrolysis and effectively improving electrolysis efficiency.
[0021] Furthermore, in some embodiments, the complexing agent includes at least one of sodium phosphate, sodium pyrophosphate, and sodium hexametaphosphate.
[0022] Furthermore, in some embodiments, the mass ratio of the primary oxidant, the secondary oxidant, and the complexing agent is (2~4):(2~3):(1~2).
[0023] In the technical solution of this invention, the ratio of the main oxidant, auxiliary oxidant, and complexing agent can be adjusted according to the specific composition of the waste tungsten material. For example, when the content of stable tungsten compounds (such as tungsten carbide) in the waste tungsten material is high, the ratio of the main oxidant can be appropriately increased, adjusting the mass ratio of the three to 4:2:1 to enhance the oxidizing power of the main oxidant and ensure the full dissolution of the stable tungsten compounds. When it is necessary to further improve the current efficiency, the ratio of the auxiliary oxidant can be appropriately increased, adjusting the mass ratio to 3:3:1. When slight passivation signs are found on the anode surface during electrolysis, the ratio of the complexing agent can be appropriately increased, adjusting it to 2:2:2. Through the complexing effect of the complexing agent and tungsten ions, the precursors of the passivation film that may be formed can be effectively dispersed, maintaining the active dissolution state of the anode surface. In actual operation, the ratio of the three can be dynamically optimized by monitoring the changes in cell voltage and the concentration of tungsten ions in the electrolyte during the electrolysis process to achieve the best electrolysis effect.
[0024] Furthermore, in some embodiments, the waste tungsten material is pretreated before electrolysis. The pretreatment specifically involves cutting the waste tungsten material into anode plates, soaking them in hydrochloric acid solution for 20-40 minutes, rinsing them with deionized water, and then ultrasonically cleaning them for 20-30 minutes.
[0025] In the technical solution of this invention, soaking in hydrochloric acid solution can remove oxides from the surface of waste tungsten materials; ultrasonic cleaning can thoroughly remove oil and fine impurities from the surface, ensuring the cleanliness and activity of the anode surface, which is beneficial to the dissolution of tungsten during electrolysis.
[0026] Furthermore, in some embodiments, the inert electrode includes a titanium-based lead dioxide coated electrode or a titanium-based iridium-tantalum coated electrode.
[0027] In the technical solution of this invention embodiment, a titanium-based lead dioxide coated electrode or a titanium-based iridium-tantalum coated electrode is selected as the cathode. Compared with the nickel electrode and stainless steel electrode of the prior art, the cathode has higher inertness and stability. It hardly undergoes a dissolution reaction during the electrolysis process, which can effectively avoid the impact of cathode metal ion dissolution on the electrolyte and product purity.
[0028] Furthermore, in some embodiments, the distance between the cathode and the anode is controlled at 6-7 cm.
[0029] In the technical solution of this invention embodiment, a suitable distance setting can ensure good convection of electrolyte, reduce the resistance between electrodes, and improve energy utilization.
[0030] Furthermore, in some embodiments, the current density is controlled to be 150~180 A / m during electrolysis. 2 .
[0031] Furthermore, in some embodiments, the electrolysis temperature is controlled at 60~80°C during the electrolysis process.
[0032] Furthermore, in some embodiments, the electrolysis time is 3 to 8 hours.
[0033] Furthermore, in some embodiments, the electrolyte is continuously stirred during the electrolysis process, with the stirring rate controlled at 250~400 r / min.
[0034] In the technical solution of this invention embodiment, stirring can promote the uniform mixing of electrolyte, accelerate the diffusion of products (tungstate ions) on the anode surface, prevent products from accumulating on the anode surface to form a passivation film, and at the same time enable oxidants and complexing agents to be evenly distributed in the electrolyte and fully exert their effects.
[0035] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.
[0036] Example 1 A method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions, the specific steps of which are as follows: (1) Pretreatment of waste tungsten materials: Select waste tungsten-cobalt alloy materials (tungsten content is 85%, cobalt content is 15%) and cut them into anode plates with dimensions of 5cm×10cm×2cm; immerse the anode plates in a 5% hydrochloric acid solution for 30 minutes, then rinse them with deionized water until neutral; then place the anode plates in an ultrasonic cleaner and clean them for 20 minutes at 40℃ and 40kHz, and then air dry them for later use.
[0037] (2) Electrolyte preparation: In a 10L electrolytic cell, add 6L of deionized water, slowly add 840g of sodium hydroxide solid (analytical grade), and stir until completely dissolved to obtain a 3.5mol / L sodium hydroxide solution; then, according to 6% of the electrolyte mass (the total mass of the electrolyte is about 6840g, so the total amount of oxidant added is about 410.4g), and according to the mass ratio of sodium chlorate, sodium nitrate, and sodium phosphate of 3:2:1, add 205.2g of sodium chlorate, 136.8g of sodium nitrate, and 68.4g of sodium phosphate respectively, and continue stirring for 30 minutes to obtain a uniform electrolyte.
[0038] (3) Electrode installation and electrolysis operation: The pretreated waste tungsten anode plate and titanium-based lead dioxide coated cathode plate (the same size as the anode plate) are fixed on both sides of the electrolytic cell, with a distance of 6 cm between the two electrodes; the anode is connected to the positive terminal of the DC power supply, and the cathode is connected to the negative terminal; the heating device is turned on to raise the electrolyte temperature to 70°C, the magnetic stirrer is turned on, and the stirring rate is set to 350 r / min; the DC power supply is turned on, the current density is set to 160 A / m², and constant current electrolysis is performed.
[0039] (4) Monitoring and subsequent treatment of electrolysis process: During the electrolysis process, samples are taken every hour. When the concentration of sodium tungstate in the electrolyte reaches 230 g / L after 6 hours of electrolysis, the electrolysis is stopped.
[0040] According to the test results, the tungsten dissolution rate in the waste tungsten material in this embodiment is 97.2%, and the current efficiency is 88.5%.
[0041] Example 2 The difference between this embodiment and embodiment 1 is that the waste tungsten material selected in step (1) is waste tungsten carbide (tungsten content is 90%); in step (2), oxidant is added according to the mass ratio of sodium chlorate, sodium nitrate and sodium phosphate of 4:2:1, which is 6% of the electrolyte mass; the remaining steps are the same as in embodiment 1.
[0042] Testing revealed that the tungsten dissolution rate in the waste tungsten carbide in this embodiment was 96.8%, and the current efficiency was 87.2%. Since the waste tungsten carbide contained a high amount of stable tungsten carbide, even after appropriately increasing the proportion of sodium chlorate, sufficient dissolution of tungsten was still achieved, indicating that adjusting the proportion of the compound oxidant can meet the needs of different types of waste tungsten materials.
[0043] Example 3 The difference between this embodiment and embodiment 1 is that in step (2), the cathode material is replaced by a titanium-based iridium-tantalum coated electrode instead of a titanium-based lead dioxide coated electrode; the remaining steps are the same as in embodiment 1.
[0044] Testing revealed that the tungsten dissolution rate in the waste tungsten material in this embodiment was 97.0%, and the current efficiency was 88.0%, which are similar to the performance indicators in Example 1. This indicates that the titanium-based iridium-tantalum coated electrode, as an alternative cathode material, can meet the requirements of this process.
[0045] Example 4 The mother liquor (approximately 5 L) after electrolysis in Example 1 was collected and returned to the electrolyte preparation step. Appropriate amounts of sodium hydroxide, sodium chlorate, sodium nitrate, and sodium phosphate were added to restore the electrolyte composition to the initial state of Example 1 (3.5 mol / L sodium hydroxide, and the total amount of compound oxidant added was 6% of the electrolyte mass, in a ratio of 3:2:1). Then, the second electrolysis experiment was conducted according to the operating steps of Example 1, and the mother liquor circulation process was repeated 5 times.
[0046] After five cycles of mother liquor recycling, the dissolution rate of tungsten in the waste tungsten material was 96.5% and the current efficiency was 87.5% in the fifth electrolysis experiment. The performance indicators showed little change compared with the first electrolysis experiment, indicating that the mother liquor recycling process has good feasibility and stability, and can achieve efficient recovery of tungsten resources and sustainable operation of the process.
[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that no sodium chlorate, sodium nitrate, and sodium phosphate compound oxidant was added to the electrolyte; all other operating steps were the same as in Example 1.
[0048] The test results showed that the tungsten dissolution rate in the waste tungsten material in this comparative example was 82.5%, and the current efficiency was 65.3%.
[0049] The comparison between this comparative example and Example 1 shows that the addition of the compound oxidant in Example 1 significantly improved the solubility of tungsten and the current efficiency.
[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (2), an oxidant (excluding sodium phosphate) is added at 6% of the electrolyte mass, based on a mass ratio of sodium chlorate to sodium nitrate of 3:2; the remaining steps are the same as in Example 1.
[0051] Testing revealed that the tungsten dissolution rate in the waste tungsten material in this comparative example was 93.2%, and the current efficiency was 84.0%. Compared to Example 1, both the tungsten dissolution rate and current efficiency decreased when sodium phosphate was not added.
[0052] Comparative Example 3 The difference between this comparative example and Example 1 is that in step (2), an oxidant (excluding sodium nitrate) is added at 6% of the electrolyte mass, based on a mass ratio of sodium chlorate to sodium phosphate of 3:1; the remaining steps are the same as in Example 1.
[0053] Testing revealed that the tungsten dissolution rate in the waste tungsten material in this comparative example was 91.5%, and the current efficiency was 82.2%. Compared to Example 1, the compound system lacking sodium nitrate still showed lower tungsten dissolution rate and current efficiency.
[0054] Comparative Example 4 The difference between this comparative example and Example 1 is that only sodium chlorate is added as an oxidant in step (2) (the amount added is 6% of the electrolyte mass), and the rest of the steps are the same as in Example 1.
[0055] Testing revealed that the tungsten dissolution rate in the waste tungsten material in this comparative example was 89.3%, and the current efficiency was 77.8%. Compared to Example 1, although sodium chlorate alone can improve the tungsten dissolution effect to some extent, its tungsten dissolution rate and current efficiency are still lower than those achieved when all three reagents are used in combination.
[0056] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.
Claims
1. A method for preparing sodium tungstate by electrolyzing waste tungsten material under alkaline conditions, characterized in that, Includes the following steps: An electrolytic cell is provided, an electrolyte is added to the electrolytic cell, and waste tungsten material is immersed in the electrolyte for electrolysis to obtain a crude sodium tungstate solution; The waste tungsten material serves as the anode, and the cathode is an inert electrode. The electrolyte is prepared from a sodium hydroxide solution with a concentration of 2-4 mol / L, a primary oxidant, a secondary oxidant, and a complexing agent; the total mass of the primary oxidant, secondary oxidant, and complexing agent is 5%-8% of the mass of the sodium hydroxide solution. The primary oxidant includes at least one of sodium chlorate, hypochlorous acid, and hydrogen peroxide; the secondary oxidant includes at least one of sodium nitrate and sodium nitrite.
2. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, The complexing agent includes at least one of sodium phosphate, sodium pyrophosphate, and sodium hexametaphosphate.
3. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, The mass ratio of the main oxidant, the auxiliary oxidant and the complexing agent is (2~4):(2~3):(1~2).
4. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, The waste tungsten material is pretreated before electrolysis. The pretreatment specifically involves cutting the waste tungsten material into anode plates, soaking them in hydrochloric acid solution for 20-40 minutes, rinsing them with deionized water, and then ultrasonically cleaning them for 20-30 minutes.
5. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, The inert electrode includes a titanium-based lead dioxide coated electrode or a titanium-based iridium-tantalum coated electrode.
6. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, The distance between the cathode and the anode is controlled at 6-7 cm.
7. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, During the electrolysis process, the current density is controlled at 150~180 A / m. 2 .
8. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, During the electrolysis process, the electrolysis temperature is controlled at 60~80℃.
9. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, The electrolysis time is 3 to 8 hours.
10. The method for preparing sodium tungstate by electrolysis of waste tungsten material under alkaline conditions according to claim 1, characterized in that, During the electrolysis process, the electrolyte is continuously stirred at a rate of 250-400 r / min.