Method for electrolytic preparation of low-arsenic antimony in alkaline system

Abstract

This application relates to an electrolytic preparation method for low-arsenic antimony in an alkaline system, belonging to the field of hydrometallurgical technology. The method includes: separating the anode and cathode chambers using an anion exchange membrane; injecting sodium thiostite solution into the cathode chamber and sodium hydroxide solution into the anode chamber; using a stainless steel plate or mesh as the anode and a stainless steel plate as the cathode, and connecting it to a power source after pretreatment; performing pre-electrolysis to preferentially co-deposit impurities such as arsenic, which have similar electrode potentials to antimony, on the cathode to obtain a purified electrolyte; replacing the cathode plate after a period of settling, and then performing formal electrolysis to obtain a low-arsenic cathode antimony product. This application achieves deep removal of impurities such as arsenic through the synergistic effect of pre-electrolysis and the anion exchange membrane, avoiding the burial and contamination of impurities in the cathode antimony, while improving the deposition morphology of the cathode antimony, resulting in a high-quality cathode antimony product with a dense and smooth surface, extremely low arsenic content, and low levels of impurities such as copper, lead, and bismuth.

Description

Technical Field

[0001] This application relates to the field of hydrometallurgical technology, and in particular to an electrolytic preparation method for low-arsenic antimony in an alkaline system. Background Technology

[0002] With the increasing demands for purity and stability in downstream antimony product applications, especially the continued growth in demand for low-arsenic antimony products, effectively controlling arsenic content during antimony production has become one of the key issues that the antimony metallurgical industry urgently needs to address.

[0003] Currently, antimony smelting in China is still dominated by traditional pyrometallurgical processes. While these processes are technically mature, they generally suffer from high energy consumption and significant pressure in treating smelting solid waste. Pyrometallurgical antimony smelting generates large amounts of high-arsenic-containing antimony dust, and because antimony and arsenic have similar chemical properties, the antimony recovery rate is low when using traditional methods, easily causing environmental pollution. Antimony pyrometallurgy mainly employs blast furnaces and reverberatory furnaces, generating a large amount of metallurgical solid waste during the smelting process. When the arsenic content in the raw materials is high, arsenic is prone to migration and accumulation during roasting, volatilization, reduction, and refining, not only affecting the quality of the final product but also greatly increasing the difficulty of environmental remediation due to its high toxicity.

[0004] To obtain low-arsenic and antimony products, existing technologies typically employ methods such as pyrometallurgical arsenic removal, alkaline refining, oxidative refining, or wet purification. However, pyrometallurgical arsenic removal usually requires high temperatures, resulting in significant energy consumption, and arsenic easily enters the flue dust or secondary slag, making subsequent harmless treatment complex. Alkaline refining and conventional wet purification often involve lengthy processes and high reagent consumption. Furthermore, due to the similar chemical properties of antimony and arsenic, their separation is challenging, often leading to problems such as high antimony loss or incomplete arsenic removal.

[0005] Sodium thiostite solution electrowinning is a crucial component of alkaline hydrometallurgical antimony refining and holds an irreplaceable position in the metal recovery field. When processing arsenic-containing feedstocks, arsenic enters the solution system in the form of sulfur-containing complexes. Substances in the cathode and anodic regions readily migrate between each other, leading to increased fluctuations in system composition, more side reactions, decreased current efficiency, and unstable purity of the cathode antimony product. Particularly in alkaline sulfur-containing systems, the anodic oxidation reaction and the cathode deposition reaction are significantly coupled, hindering stable control of selective antimony precipitation and deep arsenic removal.

[0006] Therefore, how to achieve efficient electrodeposition of high-purity antimony in an alkaline electrolysis system, while controlling the deep removal of impurity metals such as arsenic that have similar electrode potentials to antimony, so as to stably obtain cathode antimony products with low arsenic and excellent deposition quality, has always been a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] To address or partially address the problems existing in related technologies, this application provides an electrolytic preparation method for low-arsenic antimony in an alkaline system.

[0008] The electrolytic preparation method of low-arsenic antimony in an alkaline system disclosed in this application includes the following steps: (1) An anion exchange membrane is used as a diaphragm to separate the anode and cathode chambers. A sodium thioantimonate solution with an antimony ion concentration of 60-120 g / L is injected into the cathode chamber, and a sodium hydroxide solution with a concentration of 40-100 g / L is injected into the anode chamber. (2) Use stainless steel plate or stainless steel mesh as anode and stainless steel plate as cathode. Before electrolysis, pre-treat the anode and cathode plates, connect the anode to the positive terminal of the power supply, and connect the cathode to the negative terminal of the power supply. (3) Using the electrolysis system of steps (1) and (2), select appropriate electrolysis process parameters for pre-electrolysis to remove target impurities such as arsenic that have similar electrode potentials to antimony, and obtain highly purified post-electrolysis liquid; (4) After the pre-electrolysis described in step (2) is completed, the electrolyzed liquid is left to stand for a certain period of time, and then a new stainless steel cathode plate is replaced. Appropriate electrolysis process parameters are selected to carry out formal electrolysis and obtain a low-arsenic cathode antimony product.

[0009] Furthermore, the anion exchange membrane used in step (1) is either AE2 or AE4.

[0010] Furthermore, in step (2), the cathode and anode are pretreated before electrolysis. The pretreatment steps include: sanding the cathode and anode with sandpaper, removing surface oxides and oil stains with sulfuric acid solution, rinsing with pure water, and finally drying for later use.

[0011] Furthermore, the pre-electrolysis process parameters in step (3) are: current density 50-300 A / m², electrolysis temperature 40-80℃, electrolysis cycle 6-24 h, and electrolyte circulation rate 100-300 mL / min. Under the above pre-electrolysis conditions, impurities such as arsenic with electrode potentials similar to antimony are preferentially co-deposited with antimony at the cathode, thereby achieving deep removal.

[0012] Furthermore, in step (4), the settling time of the pre-electrolyzed liquid is 20-30 h.

[0013] Furthermore, the process conditions for formal electrolysis in step (4) are: current density 100-250 A / m 2 The electrolysis temperature is 40-80℃, the electrolysis cycle is 6-24h, and the electrolyte circulation rate is 100-300mL / min.

[0014] The mechanism of this application is as follows: In the alkaline electrodeposition system of sodium thiostite, the removal of target impurities is achieved by synergistically utilizing pre-electrolysis and anion exchange membrane. First, a pre-electrolysis process is used before formal electrolysis to promote the preferential co-deposition of impurities such as arsenic with antimony, which have similar electrode potentials to antimony, thereby achieving deep purification and impurity removal of the electrolyte. Then, the barrier effect of the anion exchange membrane is used to regulate the migration behavior of polysulfide species generated after the discharge of thiostite ions in the cathode chamber between the cathode and anode chambers, ensuring that metals such as arsenic, antimony, and bismuth exist as trivalent ions during the electrolysis process and do not generate high-valence ions. This prevents the formation of flocculent high-valence complex precipitates and avoids the burial and contamination of impurities in the antimony at the cathode during the electrolysis process, thereby achieving deep removal of target impurities such as arsenic with similar electrode potentials to antimony.

[0015] The beneficial effects of this application are: 1. Achieve deep removal of arsenic impurities: By introducing a synergistic process of "pre-electrolysis + anion exchange membrane isolation", the pre-electrolysis process allows impurities such as arsenic with electrode potentials similar to antimony to preferentially co-deposit at the cathode, achieving efficient purification of the electrolyte; at the same time, combined with the directional migration regulation of intermediate products such as polysulfides by the anion exchange membrane, the embedding and inclusion of impurities in the antimony of the cathode are effectively avoided, thereby significantly reducing the arsenic content in the antimony product of the cathode.

[0016] 2. Improve the deposition morphology and density of antimony on the cathode: Due to the deep removal of harmful impurities during the electrolysis process, the electrocrystallization environment on the cathode surface is optimized, inhibiting the formation of undesirable deposition morphologies such as dendrites and looseness, and a cathode antimony deposition layer with a smooth surface, dense structure and good adhesion can be obtained.

[0017] 3. Improve the overall purity of cathode antimony products: This method can not only effectively remove arsenic, but also synergistically reduce the content of other common metal impurities such as copper, lead, and bismuth, and can stably produce high-quality cathode antimony products with the characteristics of "low copper, lead, and bismuth content and extremely low arsenic content". Attached Figure Description

[0018] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0019] Figure 1 This is a schematic diagram of a low-arsenic cathode antimony obtained by electrodeposition during pre-electrolysis; Figure 2 This is a schematic diagram of the antimony cathode obtained by electrodeposition without pre-electrolysis; Figure 3 This is a schematic diagram of a low-arsenic cathode antimony obtained by electrodeposition using an AE4 anion exchange membrane; Figure 4This is a schematic diagram of a low-arsenic antimony cathode obtained by electrodeposition without using an anion exchange membrane. Detailed Implementation

[0020] The embodiments of this application will now be described in more detail with reference to the examples. While embodiments of this application are shown in the examples, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0021] Example 1 This embodiment describes a method for preparing low-arsenic antimony via electrolysis in an alkaline system, comprising the following steps: (1) Analytical grade antimony trioxide, sodium hydroxide and sodium sulfide were placed in pure water, heated and stirred continuously. After the reaction was complete, sodium thioantimonyate solution was obtained. The solution was purified by filtration using a 0.45 micrometer filter membrane to obtain sodium thioantimonyate solution with an antimony ion concentration of 80 g / L; a sodium hydroxide solution with a concentration of 60 g / L was prepared. (2) Pre-treat the cathode and anode by first polishing with sandpaper, then removing oxides and oil stains from the electrode surface with 10% sulfuric acid solution, and then rinsing with pure water; place the AE2 type anion exchange membrane in an electrolytic cell containing electrolyte and soak for 1 hour before use.

[0022] (3) Place the stainless steel mesh anode into the anode chamber containing 60 g / L sodium hydroxide solution, and place the stainless steel plate cathode into the cathode chamber containing 80 g / L sodium thioantimonyate solution containing antimony ions, and separate the anode and cathode chambers with an AE2 type anion exchange membrane. (4) Connect the anode to the positive terminal of the DC regulated power supply and the cathode to the negative terminal of the DC regulated power supply. Apply DC current for pre-electrolysis with a current density of 200 A / m. 2 The electrolyte was circulated at a temperature of 60℃ and a flow rate of 200mL / min for 12 hours. (5) After pre-electrolysis, let the electrolyte in the electrolytic cell stand for 20 h, then place a new stainless steel plate as the cathode for electrolysis. The average current density of the electrolysis is 150 A / m. 2 The electrolyte was circulated at a flow rate of 200 mL / min at a temperature of 60℃ for 8 hours to obtain a low-arsenic antimony cathode. The main components of the electrolyte and the low-arsenic antimony cathode are shown in Table 1.

[0023] Table 1. Main components of the electrolyte and antimony in the low-arsenic cathode Example 2 This embodiment describes a method for preparing low-arsenic antimony via electrolysis in an alkaline system, comprising the following steps: (1) Analytical grade antimony trioxide, sodium hydroxide and sodium sulfide were placed in pure water, heated and stirred continuously. After the reaction was complete, sodium thioantimonyate solution was obtained. The solution was purified by filtration using a 0.45 micrometer filter membrane to obtain sodium thioantimonyate solution with an antimony ion concentration of 100 g / L; a sodium hydroxide solution with a concentration of 80 g / L was prepared. (2) Pre-treat the cathode and anode by first polishing with sandpaper, then removing oxides and oil stains from the electrode surface with 10% sulfuric acid solution, and then rinsing with pure water; place the AE4 type anion exchange membrane in an electrolytic cell containing electrolyte and soak for 1 hour before use.

[0024] (3) Place the stainless steel mesh anode into the anode chamber containing 80 g / L sodium hydroxide solution, and place the stainless steel plate cathode into the cathode chamber containing 100 g / L sodium thioantimonyate solution containing antimony ions, and separate the anode and cathode chambers with an AE4 type anion exchange membrane. (4) Connect the anode to the positive terminal of the DC regulated power supply and the cathode to the negative terminal of the DC regulated power supply. Apply DC current for pre-electrolysis with a current density of 200 A / m. 2 The electrolyte was circulated at a temperature of 70℃ and a flow rate of 150 mL / min for 12 hours. (5) After pre-electrolysis, let the electrolyte in the electrolytic cell stand for 24 hours, then place a new stainless steel plate as the cathode for electrolysis. The average current density of the electrolysis is 250 A / m. 2 The electrolyte was circulated at a flow rate of 150 mL / min at a temperature of 70℃ for 5 hours to obtain a low-arsenic antimony cathode. The main components of the electrolyte and the low-arsenic antimony cathode are shown in Table 2.

[0025] Table 2. Main components of electrolyte and antimony in low-arsenic cathode. Example 3 This embodiment describes a method for preparing low-arsenic antimony via electrolysis in an alkaline system, comprising the following steps: (1) Analytical grade antimony trioxide, sodium hydroxide and sodium sulfide were placed in pure water, heated and stirred continuously. After the reaction was complete, sodium thioantimonyate solution was obtained. The solution was purified by filtration using a 0.45 micrometer filter membrane to obtain sodium thioantimonyate solution with an antimony ion concentration of 60 g / L; a sodium hydroxide solution with a concentration of 40 g / L was prepared. (2) Pre-treat the cathode and anode by first polishing with sandpaper, then removing oxides and oil stains from the electrode surface with 10% sulfuric acid solution, and then rinsing with pure water; place the AE2 type anion exchange membrane in an electrolytic cell containing electrolyte and soak for 1 hour before use.

[0026] (3) Place the stainless steel mesh anode into the anode chamber containing 40 g / L sodium hydroxide solution, and place the stainless steel plate cathode into the cathode chamber containing 60 g / L sodium thioantimonyate solution containing antimony ions, and separate the anode and cathode chambers with an AE2 type anion exchange membrane. (4) Connect the anode to the positive terminal of the DC regulated power supply and the cathode to the negative terminal of the DC regulated power supply. Apply DC current for pre-electrolysis with a current density of 100 A / m. 2 The electrolyte was circulated at a temperature of 60℃ and a flow rate of 150 mL / min for 24 hours. (5) After pre-electrolysis, let the electrolyte in the electrolytic cell stand for 20 h, then place a new stainless steel plate as the cathode for electrolysis. The average current density of the electrolysis is 250 A / m. 2 The electrolyte was circulated at a flow rate of 150 mL / min at a temperature of 70℃ for 5 hours to obtain a low-arsenic antimony cathode. The main components of the electrolyte and the low-arsenic antimony cathode are shown in Table 3.

[0027] Table 3 Main components of electrolyte and low-arsenic cathode antimony Example 4 This embodiment describes a method for preparing low-arsenic antimony via electrolysis in an alkaline system, comprising the following steps: (1) Analytical grade antimony trioxide, sodium hydroxide and sodium sulfide were placed in pure water, heated and stirred continuously. After the reaction was complete, sodium thioantimonyate solution was obtained. The solution was purified by filtration using a 0.45 micrometer filter membrane to obtain sodium thioantimonyate solution with an antimony ion concentration of 69 g / L; a sodium hydroxide solution with a concentration of 40 g / L was prepared. (2) Pre-treat the cathode and anode by first polishing with sandpaper, then removing oxides and oil stains from the electrode surface with 10% sulfuric acid solution, and then rinsing with pure water; place the AE4 type anion exchange membrane in an electrolytic cell containing electrolyte and soak for 1 hour before use.

[0028] (3) Place the stainless steel mesh anode into the anode chamber containing 40 g / L sodium hydroxide solution, and place the stainless steel plate cathode into the cathode chamber containing 69 g / L sodium thioantimonyate solution containing antimony ions, and separate the anode and cathode chambers with an AE4 type anion exchange membrane. (4) Connect the anode to the positive terminal of the DC regulated power supply and the cathode to the negative terminal of the DC regulated power supply. Apply DC current for pre-electrolysis with a current density of 250 A / m. 2 The electrolyte was circulated at a temperature of 70℃ and a flow rate of 200mL / min for 6 hours. (5) After pre-electrolysis, let the electrolyte in the electrolytic cell stand for 20 h, then place a new stainless steel plate as the cathode for electrolysis. The average current density of the electrolysis is 250 A / m. 2 The electrolyte was circulated at a flow rate of 200 mL / min at a temperature of 70℃ for 6 hours to obtain a low-arsenic antimony cathode. The main components of the electrolyte and the low-arsenic antimony cathode are shown in Table 4.

[0029] Table 4. Main components of electrolyte and antimony in low-arsenic cathode Example 5 This embodiment describes a method for preparing low-arsenic antimony via electrolysis in an alkaline system, comprising the following steps: (1) Analytical grade antimony trioxide, sodium hydroxide and sodium sulfide were placed in pure water, heated and stirred continuously. After the reaction was complete, sodium thioantimonyate solution was obtained. The solution was purified by filtration using a 0.45 micrometer filter membrane to obtain sodium thioantimonyate solution with an antimony ion concentration of 115 g / L; a sodium hydroxide solution with a concentration of 50 g / L was prepared. (2) Pre-treat the cathode and anode by first polishing with sandpaper, then removing oxides and oil stains from the electrode surface with 10% sulfuric acid solution, and then rinsing with pure water; place the AE2 type anion exchange membrane in an electrolytic cell containing electrolyte and soak for 1 hour before use.

[0030] (3) Place the stainless steel mesh anode into the anode chamber containing 50 g / L sodium hydroxide solution, and place the stainless steel plate cathode into the cathode chamber containing 115 g / L sodium thiostite solution, and separate the anode and cathode chambers with an AE2 type anion exchange membrane. (4) Connect the anode to the positive terminal of the DC regulated power supply and the cathode to the negative terminal of the DC regulated power supply. Apply DC current for pre-electrolysis with a current density of 200 A / m. 2 The electrolyte was circulated at a temperature of 70℃ and a flow rate of 250 mL / min for 22 hours. (5) After pre-electrolysis, let the electrolyte in the electrolytic cell stand for 20 h, then place a new stainless steel plate as the cathode for electrolysis. The average current density of the electrolysis is 250 A / m. 2 The electrolyte was circulated at a flow rate of 250 mL / min at a temperature of 80℃ for 6 hours to obtain a low-arsenic antimony cathode. The main components of the electrolyte and the low-arsenic antimony cathode are shown in Table 5.

[0031] Table 5. Main components of electrolyte and antimony in low-arsenic cathode Comparative Example 1 The preparation method of the low-arsenic cathode antimony in this comparative example, compared with Example 1, does not perform pre-electrolysis, that is, the pre-electrolysis described in step (4) is not performed before the cyclic electrolysis. The other conditions are the same as in Example 1. Without pre-electrolysis, the content of impurity elements will increase and the morphology will deteriorate. The morphology of the product in Example 1 is shown in the figure. Figure 1 As shown, the morphological diagram of the product in Comparative Example 1 is as follows. Figure 2 As shown in Table 6, the composition of the antimony produced at the cathode is as follows.

[0032] Table 6 Main components of antimony in electrolyte and cathode Comparative Example 2 This comparative example provides a method for preparing low-arsenic cathode antimony. Compared with Example 1, the membrane used is an anion exchange membrane, including but not limited to the following models (AE2 / AE4). That is, anion exchange membranes, including but not limited to the following models (AE2 / AE4), are used in steps (1) and (2). The other conditions are the same as in Example 1. Comparative Example 2, using an anion exchange membrane different from that in Example 1, has minimal impact on the content and morphology of impurity elements in the product, indicating that different types of anion exchange membranes can produce low-arsenic cathode antimony. The surface morphology of the cathode antimony obtained in Comparative Example 2 is as follows. Figure 3 As shown, the components are shown in Table 7.

[0033] Table 7 Main components of antimony in electrolyte and cathode Comparative Example 3 This comparative example provides a method for preparing a low-arsenic cathode antimony. Compared with Example 1, a diaphragm is not used, that is, a diaphragm is not used in steps (3), (4), and (5). The remaining conditions are the same as in Example 1. In Comparative Example 3, without the use of an anion exchange membrane, the content of impurity elements in the product increases, and the morphology deteriorates or even cracks. The surface morphology of the cathode antimony obtained in Comparative Example 3 is as follows. Figure 4 As shown in Table 8, the composition of the antimony produced at the cathode is as shown in Table 8.

[0034] Table 8 Main components of antimony in electrolyte and cathode The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for the electrolytic preparation of low-arsenic antimony in an alkaline system, characterized in that, Includes the following steps: (1) An anion exchange membrane is used as a diaphragm to separate the anode and cathode chambers. A sodium thioantimonate solution with an antimony ion concentration of 60-120 g / L is injected into the cathode chamber, and a sodium hydroxide solution with a concentration of 40-100 g / L is injected into the anode chamber. (2) Use stainless steel plate or stainless steel mesh as anode and stainless steel plate as cathode. Before electrolysis, pre-treat the anode and cathode plates, connect the anode to the positive terminal of the power supply, and connect the cathode to the negative terminal of the power supply. (3) Using the electrolysis system of steps (1) and (2), select appropriate electrolysis process parameters for pre-electrolysis to remove target impurities such as arsenic that have similar electrode potentials to antimony, and obtain highly purified post-electrolysis liquid; (4) After the pre-electrolysis described in step (2) is completed, the electrolyzed liquid is left to stand for a certain period of time, and then a new stainless steel cathode plate is replaced. Appropriate electrolysis process parameters are selected to carry out formal electrolysis and obtain a low-arsenic cathode antimony product.

2. The method for electrolytic preparation of low-arsenic antimony in an alkaline system according to claim 1, characterized in that, The anion exchange membrane used in step (1) is either AE2 or AE4.

3. The method for electrolytic preparation of low-arsenic antimony in an alkaline system according to claim 1, characterized in that, In step (2), the cathode and anode are pretreated before electrolysis. The pretreatment steps include: sanding the cathode and anode with sandpaper, removing surface oxides and oil stains with sulfuric acid solution, rinsing with pure water, and finally drying for later use.

4. The method for electrolytic preparation of low-arsenic antimony in an alkaline system according to claim 1, characterized in that, The process parameters for pre-electrolysis in step (3) are a current density of 50-300 A / m. 2 The electrolysis temperature is 40-80℃, the electrolysis cycle is 6-24h, and the electrolyte circulation rate is 100-300mL / min.

5. The method for electrolytic preparation of low-arsenic antimony in an alkaline system according to claim 1, characterized in that, The settling time of the pre-electrolyzed liquid in step (4) is 20-30 h.

6. The method for electrolytic preparation of low-arsenic antimony in an alkaline system according to claim 1, characterized in that, The process conditions for formal electrolysis in step (4) are: current density 100-250 A / m 2 The electrolysis temperature is 40-80℃, the electrolysis cycle is 6-24h, and the electrolyte circulation rate is 100-300mL / min.

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