A method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions

Abstract

The application provides a method for preparing metallic tungsten by electrolyzing sodium tungstate under alkaline conditions, comprising the following steps: preparing an electrolyte; the electrolyte comprises the following components: 0.3-0.8 mol / L of sodium tungstate, 0.1-2.2 mol / L of alkaline substances, 0.05-0.3 mol / L of chlorate oxidants and 0.01-0.4 mol / L of nitrate; the pH of the electrolyte is 13-14; titanium mesh is used as an anode, stainless steel is used as a cathode, the electrolyte is injected into an electrolytic cell, and electrolysis is carried out under the current density of 120-220 A / m 2 The application significantly improves the electrolysis efficiency and reduces the energy consumption per unit product by introducing a chlorate and nitrate compound system and simultaneously optimizing electrolysis process parameters, and provides an efficient, stable and easy-to-industrialize technical scheme for preparing metallic tungsten by electrolysis under alkaline conditions.

Description

Technical Field

[0001] This invention relates to the field of electrodeposition technology, and more specifically to a method for preparing metallic tungsten by electrolyzing sodium tungstate under alkaline conditions. Background Technology

[0002] In the tungsten metallurgical industry, electrolysis of tungsten under alkaline conditions is one of the key processes for producing high-purity tungsten products. Its core principle is that in an alkaline electrolyte system, an external electric field causes tungstate ions to undergo a reduction reaction on the electrode surface, ultimately depositing to form metallic tungsten. In existing technologies, to improve tungsten deposition efficiency, reduce electrolysis energy consumption, and improve product purity during electrolysis, a single type of oxidant is typically added to the alkaline electrolyte to regulate the redox potential of the electrolyte and promote the stable existence and directional migration of tungstate ions.

[0003] However, adding a single oxidant often fails to balance electrolyte stability and tungsten reducing activity, leading to side reactions during electrolysis that generate impurities such as tungsten oxides or hydroxides, affecting the purity and deposition rate of metallic tungsten. Furthermore, traditional processes require precise control of electrolysis parameters (such as current density, temperature, and pH), making stable and efficient tungsten preparation difficult in actual production.

[0004] Therefore, developing an alkaline electrolytic tungsten preparation method that can effectively and synergistically regulate electrolyte performance and suppress side reactions is of great significance for promoting the green and efficient development of the tungsten metallurgical industry. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a method for preparing metallic tungsten by electrolyzing sodium tungstate under alkaline conditions, aiming to solve the technical problems of low electrolysis efficiency, high energy consumption and poor purity of tungsten metal in the existing alkaline electrolysis tungsten process.

[0006] In a first aspect, the present invention provides a method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, comprising the following steps: Prepare the electrolyte; the electrolyte comprises the following components: sodium tungstate 0.3~0.8 mol / L, alkaline substance 0.1~2.2 mol / L, chlorate oxidant 0.05~0.3 mol / L, nitrate 0.01~0.4 mol / L; the pH of the electrolyte is 13~14; Using titanium mesh as the anode and stainless steel as the cathode, electrolyte is injected into the electrolytic cell at a pressure of 120~220 A / m. 2 Electrolysis was performed at a certain current density to obtain a tungsten metal deposition layer.

[0007] Preferably, the alkaline substance includes sodium hydroxide and / or potassium hydroxide.

[0008] Preferably, the chlorate oxidant includes sodium chlorate and / or potassium chlorate.

[0009] Preferably, the chlorate oxidant is sodium chlorate and potassium chlorate, wherein the molar percentage of potassium chlorate is 30% to 50%.

[0010] Preferably, the nitrate includes sodium nitrate and / or potassium nitrate.

[0011] Preferably, the cell voltage during electrolysis is 2~3V.

[0012] Preferably, the temperature during electrolysis is 45~55℃ and the electrolysis time is 12~16h.

[0013] Preferably, a gradient temperature control is adopted during the electrolysis process. The temperature is controlled at 45-48℃ in the initial 0-3h stage of electrolysis, 50-55℃ in the middle 3-10h stage of electrolysis, and 48-50℃ in the later 10-16h stage of electrolysis.

[0014] Preferably, the electrolyte is continuously stirred during the electrolysis process, and the stirring rate is controlled at 200~400 r / min.

[0015] Preferably, when the WO3 concentration is below 0.1 mol / L during electrolysis, sodium tungstate solution is added to bring the concentration up to 0.3~0.8 mol / L.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for preparing metallic tungstate by electrolysis of sodium tungstate under alkaline conditions provided by this invention significantly improves electrolysis efficiency and reduces energy consumption per unit product by synergistically controlling electrolyte composition and electrolysis process parameters. It provides an efficient, stable and easily industrially applicable technical solution for the electrolytic preparation of metallic tungstate under alkaline conditions. 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 problems of low electrolysis efficiency, high energy consumption, and poor tungsten metal purity in existing alkaline electrolysis tungsten processes, this invention provides a method for preparing metallic tungsten by electrolyzing sodium tungstate under alkaline conditions. This method improves electrolysis efficiency by introducing a chlorate and nitrate complex system into the electrolyte to achieve a synergistic effect.

[0019] In a first aspect, embodiments of the present invention provide a method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, comprising the following steps: Prepare the electrolyte; the electrolyte comprises the following components: sodium tungstate 0.3~0.8 mol / L, alkaline substance 0.1~2.2 mol / L, chlorate oxidant 0.05~0.3 mol / L, nitrate 0.01~0.4 mol / L; the pH of the electrolyte is 13~14; Using titanium mesh as the anode and stainless steel as the cathode, electrolyte is injected into the electrolytic cell at a pressure of 120~220 A / m. 2 Electrolysis was performed at a certain current density to obtain a tungsten metal deposition layer.

[0020] In the technical solution of this invention embodiment, the high concentration of tungstate ions in the strongly alkaline electrolyte can preferentially and densely adsorb onto the cathode surface and rapidly gain electrons for reduction and deposition into metallic tungsten. Simultaneously, chlorate and nitrate ions, due to their slower reaction kinetics and lower content, accumulate less at the cathode, and the alkaline environment can inhibit their reduction to some extent. The main functions of introducing chlorate and nitrate ions in this solution are: chlorate ions can remove the active hydrogen intermediates generated by the hydrogen evolution side reaction, and chlorate ions can promptly remove the low-valent tungsten (W) generated during electrolysis. 5+ W 4+ ) oxidized to WO4 2- To prevent its deposition on the electrode surface; nitrates can be prevented by NO3. - The mild reduction reaction maintains the overall redox potential stability of the electrolyte, which can both inhibit the devalence of tungsten and avoid NO3. - Excessive reduction reduces the introduction of nitrogen impurities.

[0021] Furthermore, in some embodiments, the alkaline substance includes sodium hydroxide and / or potassium hydroxide.

[0022] Furthermore, in some embodiments, the alkaline substances are sodium hydroxide and potassium hydroxide, wherein the molar percentage of potassium hydroxide is 20% to 40%.

[0023] In the technical solution of this invention embodiment, potassium hydroxide and sodium hydroxide are both strong bases and can provide an alkaline environment. Moreover, the migration rate of potassium ions is slightly higher than that of sodium ions. Replacing 20% ​​to 40% of sodium hydroxide (calculated by molar amount) with potassium hydroxide can improve the conductivity of the electrolyte and reduce the cell voltage.

[0024] Furthermore, in some embodiments, the chlorate oxidant includes sodium chlorate and / or potassium chlorate.

[0025] Furthermore, in some embodiments, the chlorate oxidant is sodium chlorate and potassium chlorate, wherein the molar percentage of potassium chlorate is 30% to 50%.

[0026] In the technical solution of this invention embodiment, potassium chlorate and sodium chlorate both belong to the chlorate family and have similar oxidizing properties under alkaline conditions, both of which can oxidize low-valence tungsten ions. Replacing 30% to 50% of sodium chlorate (calculated by molar amount) with potassium chlorate can reduce the concentration of sodium ions in the electrolyte while maintaining oxidation efficiency, thus avoiding the problem of loose deposition layer caused by sodium ion adsorption on the electrode surface.

[0027] Furthermore, in some embodiments, the nitrate includes sodium nitrate and / or potassium nitrate.

[0028] Furthermore, in some embodiments, the cell voltage during electrolysis is 2~3V.

[0029] Furthermore, in some embodiments, the temperature during electrolysis is 45~55°C; the electrolysis time is 12~16h.

[0030] Furthermore, in some embodiments, a gradient temperature control is adopted during the electrolysis process. The temperature is controlled at 45-48°C during the initial 0-3 hours of electrolysis, at 50-55°C during the middle 3-10 hours of electrolysis, and at 48-50°C during the later 10-16 hours of electrolysis.

[0031] In the technical solution of this invention embodiment, the gradient temperature control process can adjust the temperature according to the needs of different stages of electrolysis, further optimizing the activity of the oxidant and the migration rate of tungsten ions. In the initial stage of electrolysis (0-3h), the temperature is controlled at 45~48℃. At this time, the concentration of WO3 in the electrolyte is high, and the lower temperature can prevent sodium nitrate from decomposing prematurely. In the middle stage of electrolysis (3~10h), the temperature is raised to 50~55℃ to increase the oxidation rate of sodium chlorate and adapt to the decrease in tungsten ion concentration. In the later stage of electrolysis (10~15h), the temperature is lowered to 48~50℃ to reduce energy consumption and avoid excessive product growth.

[0032] Furthermore, in some embodiments, the electrolyte is continuously stirred during the electrolysis process, with the stirring rate controlled at 200~400 r / min.

[0033] Furthermore, in some embodiments, when the WO3 concentration is below 0.1 mol / L during electrolysis, sodium tungstate solution is added to bring the concentration up to 0.3~0.8 mol / L.

[0034] 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.

[0035] Example 1 A method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, the specific steps of which are as follows: (1) Electrolyte preparation: At 25℃, 5.76g sodium hydroxide (0.14mol, concentration 0.14mol / L) was added to 1000mL of deionized water and stirred for 30 minutes until completely dissolved; then 82.4g sodium tungstate (0.3mol, concentration 0.3mol / L) was added and stirred for 40 minutes; then 10.65g sodium chlorate (0.1mol, concentration 0.1mol / L) and 2.55g sodium nitrate (0.03mol, concentration 0.03mol / L) were added and stirred for 60 minutes, wherein the molar ratio of sodium chlorate to sodium nitrate was 10:3; finally, the pH of the electrolyte was adjusted to 13.5 with sodium hydroxide solution to obtain the compound electrolyte; (2) Electrolysis process: A stainless steel cathode (100mm×150mm×5mm) and a titanium mesh anode were used, with an electrode spacing of 8mm. 800mL of the above-mentioned compound electrolyte was injected; the current density was set to 180A / m. 2 The cell voltage was 2.5V, the electrolysis temperature was 50℃, and the stirring rate was 250r / min. During the electrolysis process, samples were taken for analysis every 2 hours. When the WO3 concentration was lower than 0.1mol / L, sodium tungstate solution was added to bring the concentration up to 0.3mol / L. The electrolysis lasted for 12 hours.

[0036] After electrolysis, the tungsten metal deposit on the cathode surface was collected, dried, and tested. The product purity was 99.98%, the oxygen content was 0.015%, the current efficiency was 87%, and the energy consumption to produce 1 ton of tungsten metal was 250 kWh.

[0037] Example 2 A method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, the specific steps of which are as follows: (1) Electrolyte preparation: At 25℃, 5.76g sodium hydroxide (0.14mol, concentration 0.14mol / L) was added to 1000mL of deionized water and stirred for 30 minutes until completely dissolved; then 82.4g sodium tungstate (0.3mol, concentration 0.3mol / L) was added and stirred for 40 minutes; then 15.98g sodium chlorate (0.15mol, concentration 0.15mol / L) and 2.55g sodium nitrate (0.03mol, concentration 0.03mol / L) were added and stirred for 60 minutes, wherein the molar ratio of sodium chlorate to sodium nitrate was 10:2; finally, the pH of the electrolyte was adjusted to 13.2 with sodium hydroxide solution to obtain the compound electrolyte; (2) Electrolysis process: A stainless steel cathode (100mm×150mm×5mm) and a titanium mesh anode were used, with an electrode spacing of 8mm. 800mL of the above-mentioned compound electrolyte was injected; the current density was set to 180A / m. 2The cell voltage was 2.5V, the electrolysis temperature was 50℃, and the stirring rate was 250r / min. During the electrolysis process, samples were taken for analysis every 2 hours. When the WO3 concentration was lower than 0.1mol / L, sodium tungstate solution was added to bring the concentration up to 0.3mol / L. The electrolysis lasted for 12 hours.

[0038] After electrolysis, the tungsten metal deposit on the cathode surface was collected, dried, and tested. The tungsten metal product had a purity of 99.97%, an oxygen content of 0.018%, a current efficiency of 85%, and an energy consumption of 260 kWh to produce 1 ton of tungsten metal.

[0039] Example 3 A method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, the specific steps of which are as follows: (1) Electrolyte preparation: At 25℃, 5.76g sodium hydroxide (0.14mol, concentration 0.14mol / L) was added to 1000mL of deionized water and stirred for 30 minutes until completely dissolved; then 82.4g sodium tungstate (0.3mol, concentration 0.3mol / L) was added and stirred for 40 minutes; then 7.1g sodium chlorate (0.067mol, concentration 0.067mol / L), 11.2g potassium chlorate (0.083mol, concentration 0.083mol / L) and 2.55g sodium nitrate (0.03mol, concentration 0.03mol / L) were added and stirred for 60 minutes. Finally, the pH of the electrolyte was adjusted to 13.5 with sodium hydroxide solution to obtain the compound electrolyte. (2) Electrolysis process: A stainless steel cathode (100mm×150mm×5mm) and a titanium mesh anode were used, with an electrode spacing of 8mm. 800mL of the above-mentioned compound electrolyte was injected; the current density was set to 180A / m. 2 The cell voltage was 2.5V, the electrolysis temperature was 50℃, and the stirring rate was 250r / min. During the electrolysis process, samples were taken for analysis every 2 hours. When the WO3 concentration was lower than 0.1mol / L, sodium tungstate solution was added to bring the concentration up to 0.3mol / L. The electrolysis lasted for 12 hours.

[0040] After electrolysis, the tungsten metal deposit layer on the cathode surface was collected, dried, and tested. The purity of the tungsten metal product was 99.99%, the oxygen content was 0.012%, the current efficiency was 89%, the density of the deposit layer was 8% higher than that in Example 2, and the energy consumption for producing 1 ton of tungsten metal was 255 kWh.

[0041] Example 4 A method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, the specific steps of which are as follows: (1) Electrolyte preparation: At 25℃, 5.76g sodium hydroxide (0.14mol, concentration 0.14mol / L) was added to 1000mL of deionized water and stirred for 30 minutes until completely dissolved; then 82.4g sodium tungstate (0.3mol, concentration 0.3mol / L) was added and stirred for 40 minutes; then 10.65g sodium chlorate (0.1mol, concentration 0.1mol / L) and 2.55g sodium nitrate (0.03mol, concentration 0.03mol / L) were added and stirred for 60 minutes, wherein the molar ratio of sodium chlorate to sodium nitrate was 10:3; finally, the pH of the electrolyte was adjusted to 13.5 with sodium hydroxide solution to obtain the compound electrolyte; (2) Electrolysis process: A stainless steel cathode (100mm×150mm×5mm) and a titanium mesh anode were used, with an electrode spacing of 8mm. 800mL of the above-mentioned compound electrolyte was injected; the current density was set to 180A / m. 2 The cell voltage was 2.5V, the stirring rate was 250r / min, the temperature was controlled at 48℃ in the initial stage of electrolysis (0~3h), the temperature was raised to 52℃ in the middle stage of electrolysis (3~10h), and the temperature was lowered to 48℃ in the later stage of electrolysis (10~15h). During the electrolysis process, samples were taken for analysis every 2h. When the WO3 concentration was lower than 0.1mol / L, sodium tungstate solution was added to 0.3mol / L. The electrolysis lasted for 12h.

[0042] After electrolysis, the tungsten metal deposit on the cathode surface was collected, dried, and tested. The product purity was 99.999%, the oxygen content was 0.001%, the current efficiency was 92%, and the energy consumption to produce 1 ton of tungsten metal was 200 kWh.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that sodium nitrate is not added to the electrolyte, and the amount of sodium chlorate added is 31.95g (0.3mol, concentration 0.3mol / L). The other electrolyte preparation steps are the same as in Example 1, the electrolysis parameters are the same as in Example 1, and the electrolysis lasts for 12 hours.

[0044] After electrolysis, the tungsten metal deposit on the cathode surface was collected, dried, and tested. The tungsten metal product had a purity of 99.7%, an oxygen content of 0.008%, a current efficiency of 72%, and an energy consumption of 340 kWh to produce 1 ton of tungsten metal.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that sodium chlorate is not added to the electrolyte, and the amount of sodium nitrate added is 51g (0.6mol, concentration 0.6mol / L). The other electrolyte preparation steps are the same as in Example 1, the electrolysis parameters are the same as in Example 1, and the electrolysis lasts for 12 hours.

[0046] After electrolysis, the tungsten metal deposit on the cathode surface was collected, dried, and tested. The tungsten metal product had a purity of 99.6%, an oxygen content of 0.08%, a current efficiency of 78%, and an energy consumption of 310 kWh to produce 1 ton of tungsten metal.

[0047] 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 metallic tungsten by electrolysis of sodium tungstate under alkaline conditions, characterized in that, Includes the following steps: Preparation of electrolyte; The electrolyte comprises the following components: sodium tungstate 0.3~0.8 mol / L, alkaline substance 0.1~2.2 mol / L, chlorate oxidant 0.05~0.3 mol / L, and nitrate 0.01~0.4 mol / L; the pH of the electrolyte is 13~14. Using a titanium mesh as the anode and stainless steel as the cathode, the electrolyte is injected into the electrolytic cell at a pressure of 120~220 A / m. 2 Electrolysis was performed at a certain current density to obtain a tungsten metal deposition layer.

2. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, The alkaline substances include sodium hydroxide and / or potassium hydroxide.

3. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, The chlorate oxidant includes sodium chlorate and / or potassium chlorate.

4. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 3 is characterized in that, The chlorate oxidant is sodium chlorate and potassium chlorate, wherein the molar percentage of potassium chlorate is 30% to 50%.

5. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, The nitrates include sodium nitrate and / or potassium nitrate.

6. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, The cell voltage during the electrolysis process is 2~3V.

7. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, The electrolysis process is carried out at a temperature of 45~55℃ for 12~16h.

8. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 7, characterized in that, The electrolysis process employs gradient temperature control. During the initial 0-3 hours of electrolysis, the temperature is controlled at 45-48℃; during the middle 3-10 hours of electrolysis, the temperature is controlled at 50-55℃; and during the later 10-16 hours of electrolysis, the temperature is controlled at 48-50℃.

9. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, During the electrolysis process, the electrolyte is continuously stirred at a rate of 200-400 r / min.

10. The method for preparing metallic tungsten by electrolysis of sodium tungstate under alkaline conditions according to claim 1, characterized in that, During the electrolysis process, when the WO3 concentration is below 0.1 mol / L, sodium tungstate solution is added to bring the concentration up to 0.3~0.8 mol / L.