Method for preparing high-purity bismuth through electrolytic refining and electrolysis system

Abstract

The invention discloses a method for preparing high-purity bismuth through electrolytic refining and an electrolysis system. The method comprises the following steps that an electrolyte is added into an electrolytic bath, an impurity removal agent is added into an impurity removal tank, the electrolytic bath and the impurity removal tank are connected through a guide pipe, and liquid in the electrolytic bath and liquid in the impurity removal tank circularly flow through a circulating pump for impurity removal; and the negative plate and the refined bismuth positive plate are oppositely inserted into the electrolyte, direct current is introduced for electrolysis, in the electrolysis process, the impurity removal process is continuously carried out, and high-purity bismuth is obtained on the negative plate. The electrolysis system is composed of an impurity removal agent liquid storage tank, an impurity removal tank, a filtering system and an electrolytic bath. The synchronous impurity removal process is integrated in the electrolysis process, impurities generated by anode dissolution can be removed in time, the product purity of high-purity bismuth is guaranteed, damage of the impurities to the performance of the electrolyte is reduced, the service life of the electrolyte is effectively prolonged, the consumable replacement cost in the production process is reduced, and collaborative improvement of quality improvement and cost reduction is achieved.

Description

Technical Field

[0001] This invention belongs to the field of high-purity metal technology, and particularly relates to a method and electrolysis system for preparing high-purity bismuth by electrolytic refining. Background Technology

[0002] High-purity bismuth (usually referring to a purity of ≥99.999%, i.e., 5N grade) is a key strategic metal material with irreplaceable application value in cutting-edge technology, defense industry and other fields. It is mainly used to prepare high-performance products such as compound semiconductors, high-purity alloys, scintillation crystals, and electronic ceramics. Its preparation technology level directly affects the development of related high-end industries.

[0003] Currently, existing high-purity bismuth preparation technologies mainly include three types: zone melting, vacuum distillation, and electrolytic refining. Zone melting: This method utilizes the difference in solubility of impurity elements in solid and molten bismuth to allow these elements to migrate and redistribute between the solid and liquid phases, thereby achieving purification. However, to achieve 5N-level high-purity bismuth, repeated melting and condensation processes are required, resulting in high energy consumption and low direct metal recovery. This method is only suitable for small-batch laboratory-scale preparation and cannot meet the needs of large-scale industrial production. Vacuum distillation: Based on the difference in saturated vapor pressure and volatilization rate between bismuth and impurity elements, impurities are separated during volatilization or condensation. This method can effectively remove high-boiling-point impurities from bismuth, but its removal effect on low-boiling-point impurities is poor. Moreover, this process requires high temperature and high vacuum conditions, and the equipment structure is complex. It also suffers from high energy consumption and low direct metal recovery rate, which limits its industrial application. Electrolytic refining: This method purifies bismuth by utilizing the difference in the ease with which it dissolves at the anode or precipitates at the cathode compared to impurity elements. Compared to zone melting and vacuum distillation, electrolytic refining offers significant advantages such as high direct metal recovery, low energy consumption, and simple equipment structure, making it the preferred technological path for the industrial-scale production of high-purity bismuth.

[0004] The key to preparing high-purity bismuth by electrolytic refining lies in the selection of the electrolyte system. Currently, the industry mainly uses three types of electrolyte systems, each with obvious technical limitations: Chloride salt system: In the 1970s, Yunnan Tin Company used a chloride salt system as the electrolyte and refined bismuth as the anode to produce 5N grade high-purity bismuth (see "Electrolytic Production of High-Purity Bismuth", Yunnan Metallurgy, 1973). However, this system suffers from large fluctuations in product purity and easily generates a large amount of acid mist during electrolysis, resulting in a harsh working environment and serious environmental pollution, making it difficult to meet the requirements of modern industrial production for environmental protection and product stability. Fluorosilicic acid system: The published literature "Experimental Study on Electrolytic Production of 5N High-Purity Bismuth from Refined Bismuth" reports the application of this system in the electrolysis of refined bismuth. However, the experimental results show that the copper and lead impurities in the high-purity bismuth prepared by this system both exceed 1 ppm, which does not meet the requirements of the 5N high-purity bismuth industry standard YS / T 818-2012. Although a patent (application number: 202510008548.9) has improved the deep impurity removal process of the electrolyte to prepare 5N high-purity bismuth that meets the standard, the fluorosilicic acid system is volatile and decomposes to produce toxic HF and SiF4 gases, which will also form a large amount of acid mist, resulting in a harsh working environment and great harm to the health of operators and the ecological environment. Methanesulfonic acid system: Compared with chloride and fluorosilicic acid systems, the methanesulfonic acid system has advantages such as low toxicity, low volatility, high conductivity, and good solubility for metallic bismuth. Furthermore, methanesulfonic acid is biodegradable into sulfates and carbon dioxide, posing less environmental harm. Theoretically, it is the most suitable electrolyte system for the electrolytic refining of high-purity bismuth. Existing patent (CN110578153B) has disclosed the use of a methanesulfonic acid system for the electrolytic purification of crude bismuth to refined bismuth (purity typically <99.99%). However, to date, there are no reports on technologies using the methanesulfonic acid system for the electrolytic refining of 5N grade and above high-purity bismuth. In other words, there is still a technological gap in the existing technology regarding the "methanesulfonic acid system's suitability for the electrolytic refining of high-purity bismuth (5N grade)," which cannot meet the industrial production needs of high-end fields for 5N grade high-purity bismuth. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method and electrolysis system for preparing high-purity bismuth by electrolytic refining.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing high-purity bismuth through electrolytic refining, the method comprising the following steps: S1. An electrolyte is added to an electrolytic cell, and a purification agent is added to a purification tank. The electrolytic cell and the purification tank are connected by a conduit. A circulation pump is used to circulate the liquid in the electrolytic cell and the liquid in the purification tank for purification. The electrolyte includes water, free methanesulfonic acid, and bismuth methanesulfonate. The purification agent is one or more of iodized salts, phosphates, and water-soluble inorganic sulfides. S2. Insert the cathode plate and the refined bismuth anode plate into the electrolyte opposite to each other, and pass direct current to perform electrolysis. During the electrolysis process, the impurity removal process continues, and high-purity bismuth is obtained on the cathode plate.

[0007] In the above method, further, in S1, the iodized salt is one or more of sodium iodide, potassium iodide, calcium iodide, barium iodide, and ammonium iodide; the phosphate is one or more of sodium phosphate, potassium phosphate, lithium phosphate, and ammonium phosphate; and the water-soluble inorganic sulfide is one or more of ammonium sulfide, barium sulfide, sodium sulfide, sodium hydrosulfide, potassium sulfide, and potassium hydrosulfide.

[0008] The above method, further, in the electrolyte, Bi 3+ The concentration is 30 g / L to 150 g / L, and the free methanesulfonic acid concentration is 50 g / L to 250 g / L. Further, the Bi... 3+ The concentration is 40 g / L to 120 g / L; the concentration of the free methanesulfonic acid is 60 g / L to 00 g / L. Further, the Bi... 3+ The concentration is 50 g / L to 100 g / L; the concentration of the free methanesulfonic acid is 75 g / L to 150 g / L.

[0009] Further, in the above method, the electrolyte circulation rate is 3 L / min to 30 L / min. During circulation, a purifying agent of 1 mg / L to 100 mg / L electrolyte is injected into the purifying tank at a constant flow rate, and the precipitate in the purifying tank is discharged through a filtration system. Further, the electrolyte circulation rate is 5 L / min to 20 L / min; the purifying agent dosage is 2 mg / L to 50 mg / L electrolyte.

[0010] Further, in the above method, the impurity removal time in S1 is 6 h to 48 h; the electrolysis time in S2 is 18 h to 120 h. Further, the impurity removal time in S1 is 13 h to 36 h; the electrolysis time in S2 is 24 h to 72 h. Further, the impurity removal time in S1 is 18 h to 24 h; the electrolysis time in S2 is 24 h to 72 h.

[0011] Further, in step S2 of the above method, a refined bismuth anode covered with a polypropylene anode bag and a 316L stainless steel cathode plate are placed in the electrolytic cell. The distance between the anode and cathode is controlled to be 3 cm to 10 cm, the electrolyte temperature to be 25°C to 50°C, and the current density to be 30 A / m. 2 ~300 A / m 2 The electrolysis cycle is energized for 36 to 72 hours. Further, in step S2, a refined bismuth anode fitted with a polypropylene anode bag and a 316L stainless steel cathode plate are placed in the electrolytic cell. The distance between the anode and cathode is controlled to be 4 cm to 8 cm, the electrolyte temperature to be 25°C to 35°C, and the current density to be 40 A / m. 2~180 A / m 2 The energizer is applied for 36 to 72 hours. Further, in step S2, a refined bismuth anode fitted with a polypropylene anode bag and a 316L stainless steel cathode plate are placed in the electrolytic cell. The distance between the anode and cathode is controlled to be 5 cm to 8 cm, the electrolyte temperature to be 25°C to 30°C, and the current density to be 100 A / m. 2 ~150 A / m 2 Power on for 36 to 72 hours.

[0012] Based on a general technical concept, the present invention also provides an electrolysis system used in the method, which consists of four parts: a decontaminant storage tank, a decontaminant tank, a filtration system, and an electrolytic cell; the decontaminant storage tank is connected to the decontaminant tank via a peristaltic pump for transferring the decontaminant to the decontaminant tank; the decontaminant tank is connected to the filtration system via a circulation pump, the filtration system is connected to the electrolytic cell via a pipeline, and the electrolytic cell is connected to the decontaminant tank via a pipeline, forming an electrolyte circulation loop.

[0013] Compared with the prior art, the advantages of the present invention are as follows: (1) This invention provides a method for preparing high-purity bismuth by electrolytic refining. The methanesulfonic acid electrolyte system used in this invention has the environmentally friendly characteristics of being low in toxicity and environmentally friendly, non-oxidizing, highly stable, having a high boiling point and being non-volatile. It also has the core technical advantages of high conductivity and high bismuth solubility. The electrolysis method with this electrolyte can achieve the dual effects of high current efficiency and low energy consumption. From core materials to process, the invention fully guarantees energy saving and environmental protection, solving the technical pain point of traditional electrolytes that "performance and environmental protection are difficult to balance".

[0014] (2) This invention provides a method for preparing high-purity bismuth through electrolytic refining. The electrolyte purification method has a high purification depth, ensuring stable product quality. The electrolyte purification method of this invention can perform deep purification treatment on the electrolyte, effectively removing impurities that affect the purity of bismuth products, ensuring the consistency and stability of high-purity bismuth product quality from the source, and providing reliable process support for the large-scale production of high-purity bismuth.

[0015] (3) This invention provides a method for preparing high-purity bismuth through electrolytic refining, with simultaneous impurity removal processes working synergistically to balance product quality and electrolyte lifespan. This invention integrates a simultaneous impurity removal process during electrolysis, which can promptly remove impurities generated by anodic dissolution. On the one hand, this directly ensures the purity of the high-purity bismuth product and avoids the impact of impurity accumulation on product quality; on the other hand, it reduces the damage of impurities to electrolyte performance, effectively extends the electrolyte's lifespan, and reduces the cost of replacing consumables during production, achieving a synergistic improvement in both quality and cost.

[0016] (4) This invention provides an electrolysis system that constructs a complete electrolyte circulation loop through precise connection of a purification agent storage tank, a purification tank, a filtration system, and an electrolytic cell, allowing the electrolyte to continuously circulate between the electrolytic cell and the purification / filtration unit. This closed-loop design avoids electrolyte leakage or waste, while ensuring that all electrolyte undergoes purification-filtration treatment, thus guaranteeing the comprehensiveness of the purification effect from a spatial structure perspective. Attached Figure Description

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of an electrolysis system. Detailed Implementation

[0019] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0020] The materials, reagents, and instruments used in the following examples are all commercially available. Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art.

[0021] Example 1 The present invention discloses a method for preparing high-purity bismuth by electrolytic refining, which employs an electrolytic system for processing.

[0022] See Figure 1 The electrolysis system mainly consists of four parts: a purification agent storage tank, a purification tank, a filtration system, and an electrolytic cell. The purification agent storage tank transfers liquid to the purification tank via a peristaltic pump. After the liquid in the purification tank is pumped out, it is filtered by the filtration system and then fed into the electrolytic cell. The electrolyte overflowing from the electrolytic cell flows into the purification tank through a pipeline.

[0023] The specific operation process is as follows: When the electrolyte purification operation or electrolysis operation is carried out, the electrolyte in the electrolytic cell flows into the impurity removal tank through the pipeline. In the impurity removal tank, the electrolyte mixes with the impurity removal agent pumped in from the impurity removal agent storage tank and reacts to generate precipitate. The electrolyte containing precipitate in the impurity removal tank is pumped into the filtration system by the circulation pump. In the filtration system, the precipitate is intercepted and purified electrolyte is obtained. The purified electrolyte flows back into the electrolytic cell through the pipeline and starts a new cycle.

[0024] The method for preparing high-purity bismuth includes the following steps: (1) Electrolyte and impurity removal agent for preparing high-purity bismuth.

[0025] The electrolyte for high-purity bismuth contains water, free methanesulfonic acid, and bismuth methanesulfonate, wherein Bi 3+The concentration is 60 g / L, and the free methanesulfonic acid is 100 g / L.

[0026] The impurity removal agent includes: 10 mg sodium sulfide solution per liter of electrolyte.

[0027] (2) Before electrolysis, the electrolyte needs to be purified. The specific method is as follows: turn on the circulation pump of the electrolysis system and the electrolyte circulation rate is 10 L / min. Then, inject the sodium sulfide solution into the purification tank at a constant flow rate using a peristaltic pump or injection pump. The purification operation is completed after 24 hours. (3) After the electrolyte is cleaned, keep the circulating pump of the electrolysis system running continuously with a circulation rate of 10 L / min. Add a certain amount of sodium sulfide solution to the cleaning agent storage tank. The amount of sodium sulfide is 50 g / ton of refined bismuth. Inject it into the cleaning tank at a constant rate within 48 hours after the electrolysis cell is powered on.

[0028] A bismuth anode (encased in a polypropylene anode bag) and a 316L stainless steel cathode plate were placed in an electrolytic cell. The anode-cathode distance was 5 cm, the electrolyte temperature was 25℃, and the current density was 100 A / m. 2 Under certain conditions, energizing for 48 hours yielded a high-purity bismuth product.

[0029] Example 2 A method for preparing high-purity bismuth by electrolytic refining according to the present invention, see [link to relevant documentation]. Figure 1 This includes the following steps: (1) Electrolyte and impurity removal agent for preparing high-purity bismuth.

[0030] The electrolyte for high-purity bismuth contains water, free methanesulfonic acid, and bismuth methanesulfonate, wherein Bi 3+ The concentration is 50 g / L, and the free methanesulfonic acid is 90 g / L.

[0031] The impurity removal agent includes: 50 mg sodium phosphate solution per liter of electrolyte.

[0032] (2) Before electrolysis, the electrolyte needs to be purified. The specific method is as follows: turn on the circulation pump of the electrolysis system and the electrolyte circulation rate is 15 L / min. Then, inject the sodium sulfide solution into the purification tank at a constant flow rate using a peristaltic pump or injection pump. The purification operation is completed after 24 hours. (3) After the electrolyte is cleaned, keep the circulating pump of the electrolysis system running continuously with a circulation rate of 15 L / min. Add a certain amount of sodium phosphate solution to the cleaning agent storage tank. The amount of sodium sulfide is 150 g / ton of refined bismuth. Inject it into the cleaning tank at a constant rate within 36 h after the electrolysis cell is powered on.

[0033] A bismuth anode (encased in a polypropylene anode bag) and a 316L stainless steel cathode plate were placed in an electrolytic cell. The anode-cathode distance was 5 cm, the electrolyte temperature was 25℃, and the current density was 150 A / m. 2 Under certain conditions, high-purity bismuth was obtained by energizing for 36 hours.

[0034] Example 3 A method for preparing high-purity bismuth by electrolytic refining according to the present invention, see [link to relevant documentation]. Figure 1 This includes the following steps: (1) Electrolyte and impurity removal agent for preparing high-purity bismuth.

[0035] The electrolyte for high-purity bismuth contains water, free methanesulfonic acid, and bismuth methanesulfonate, wherein Bi 3+ The concentration is 70 g / L, and the free methanesulfonic acid is 120 g / L.

[0036] The impurity removal agent includes: 25 mg potassium iodide solution per liter of electrolyte.

[0037] (2) Before electrolysis, the electrolyte needs to be purified. The specific method is as follows: turn on the circulation pump of the electrolysis system and the electrolyte circulation rate is 10 L / min. Then, inject the sodium sulfide solution into the purification tank at a constant flow rate using a peristaltic pump or injection pump. The purification operation is completed after 24 hours. (3) After the electrolyte is cleaned, keep the circulating pump of the electrolysis system running continuously with a circulation rate of 10 L / min. Add a certain amount of potassium iodide solution to the impurity removal agent storage tank. The amount of sodium sulfide is 100 g / ton of refined bismuth. Inject it into the impurity removal tank at a constant rate within 36 h after the electrolysis cell is powered on.

[0038] A bismuth anode (encased in a polypropylene anode bag) and a 316L stainless steel cathode plate were placed in an electrolytic cell. The anode-cathode distance was 8 cm, the electrolyte temperature was 25℃, and the current density was 100 A / m. 2 Under certain conditions, energizing for 48 hours yielded a high-purity bismuth product.

[0039] Example 4 A method for preparing high-purity bismuth by electrolytic refining according to the present invention, see [link to relevant documentation]. Figure 1 This includes the following steps: (1) Electrolyte and impurity removal agent for preparing high-purity bismuth.

[0040] The electrolyte for high-purity bismuth contains water, free methanesulfonic acid, and bismuth methanesulfonate, wherein Bi 3+ The concentration is 100 g / L, and the free methanesulfonic acid is 100 g / L.

[0041] The impurity removal agent includes: a mixture of sodium sulfide and potassium iodide in a mass ratio of 1:1, and 15 mg of the sodium sulfide and potassium iodide mixture per liter of electrolyte.

[0042] (2) Before electrolysis, the electrolyte needs to be purified. The specific method is as follows: turn on the circulation pump of the electrolysis system and the electrolyte circulation rate is 20 L / min. Then, inject the mixture of sodium sulfide and potassium iodide into the purification tank at a constant flow rate using a peristaltic pump or injection pump. The purification operation is completed after 24 hours. (3) After the electrolyte is cleaned, keep the circulating pump of the electrolysis system running continuously with a circulation rate of 20 L / min. Add a certain amount of sodium sulfide and potassium iodide mixture solution to the cleaning agent storage tank. The dosage is 70 g / ton of refined bismuth. Inject it into the cleaning tank at a constant rate within 72 h after the electrolysis cell is powered on.

[0043] A bismuth anode (encased in a polypropylene anode bag) and a 316L stainless steel cathode plate were placed in an electrolytic cell. The anode-cathode distance was 5 cm, the electrolyte temperature was 30℃, and the current density was 150 A / m. 2 Under certain conditions, high-purity bismuth was obtained by energizing for 72 hours.

[0044] Comparative Example 1 In this comparative example, the methanesulfonic acid solution system for electrolytic refining of bismuth consisted of water, bismuth methanesulfonate, and free methanesulfonic acid, with a Bi3+ concentration of 60 g / L and a free methanesulfonic acid concentration of 100 g / L. No impurity removal treatment was performed on the electrolyte, and no impurity removal agent was added during electrolysis; electrolysis was carried out directly. The circulating pump was kept running continuously at a circulation rate of 10 L / min. A bismuth anode (covered with a polypropylene anode bag) and a 316L stainless steel cathode plate were placed in the electrolytic cell. The anode-cathode distance was 5 cm, the electrolyte temperature was 25℃, and the current density was 100 A / m. 2 Under certain conditions, bismuth was obtained by energizing for 48 hours.

[0045] Comparative Example 2 In this comparative example, the methanesulfonic acid solution system for electrolytic refining of bismuth consists of water, bismuth methanesulfonate, and free methanesulfonic acid, wherein Bi 3+ The concentration is 60 g / L, and the free methanesulfonic acid concentration is 100 g / L. The electrolysis system's circulating pump is kept running continuously at a circulation rate of 10 L / min. A certain amount of sodium sulfide solution is added to the impurity removal agent storage tank at a dosage of 50 g / ton of refined bismuth. This solution is injected into the impurity removal tank at a constant rate within 48 hours after the electrolytic cell is energized. A refined bismuth anode (covered with a polypropylene anode bag) and a 316L stainless steel cathode plate are placed in the electrolytic cell. The anode-cathode distance is 5 cm, the electrolyte temperature is 25℃, and the current density is 100 A / m. 2 Under certain conditions, high-purity bismuth products were obtained by energizing for 48 hours.

[0046] Comparative Example 3 In this comparative example, the methanesulfonic acid solution system for electrolytic refining of bismuth consists of water, bismuth methanesulfonate, and free methanesulfonic acid, wherein Bi 3+ The concentration is 60 g / L, and the free methanesulfonic acid concentration is 100 g / L. Before electrolysis, the electrolyte needs to be purified. The specific method is as follows: Figure 1 As shown, the circulation pump of the electrolysis system is turned on, and the electrolyte circulation rate is 10 L / min. A certain amount of sodium sulfide solution is added to the impurity removal agent storage tank, with a sodium sulfide addition rate of 10 mg / L electrolyte. Subsequently, the sodium sulfide solution is injected into the impurity removal tank at a constant flow rate using a peristaltic pump or syringe pump. The impurity removal operation is completed after 24 hours. After the electrolyte impurity removal is completed, the circulation pump is kept running continuously at a circulation rate of 10 L / min. A bismuth anode (covered with a polypropylene anode bag) and a 316L stainless steel cathode plate are placed in the electrolytic cell. The anode-cathode distance is 5 cm, the electrolyte temperature is 25℃, and the current density is 100 A / m. 2 Under certain conditions, bismuth was obtained by energizing for 48 hours.

[0047] Experiment 1: Testing the quality of high-purity bismuth in Examples 1 to 4 and Comparative Examples 1 to 3.

[0048] The high-purity bismuth of Examples 1 to 4 and the high-purity bismuth of Comparative Examples 1 to 3 were tested for impurity content according to the 5N bismuth industry standard YS / T 818-2012. The test results are listed in Table 1.

[0049] Table 1: Detection results of impurity content in high-purity bismuth of Examples 1 to 4 and Comparative Examples 1 to 3

[0050] As shown in Table 1, the silver impurity content in Comparative Example 1 is as high as 25.1 ppm, which does not meet the industry standard requirements for 5N high-purity bismuth. The silver impurity content in Comparative Example 2 is as high as 12.8 ppm, which also does not meet the industry standard requirements for 5N high-purity bismuth. Although the total impurity content of Comparative Example 3 is less than 10 ppm, the silver impurity content in the product is as high as 6.5 ppm, which also does not meet the industry standard requirements for 5N high-purity bismuth.

[0051] The product prepared using the method of this invention, as detected by GD-MS, has a content of 13 impurity elements, including Mg, Al, Cr, Fe, Ni, Cu, Zn, As, Ag, Cd, Sn, Au, and Pb, all far below 1 ppm, meeting the requirements of the 5N bismuth industry standard. The total impurity content is between 0.322 ppm and 0.509 ppm, which is also far below the industry standard requirement of 10 ppm.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-purity bismuth through electrolytic refining, characterized in that, The method includes the following steps: S1. An electrolyte is added to an electrolytic cell, and a purification agent is added to a purification tank. The electrolytic cell and the purification tank are connected by a conduit. A circulation pump is used to circulate the liquid in the electrolytic cell and the liquid in the purification tank for purification. The electrolyte includes water, free methanesulfonic acid, and bismuth methanesulfonate. The purification agent is one or more of iodized salts, phosphates, and water-soluble inorganic sulfides. S2. Insert the cathode plate and the refined bismuth anode plate into the electrolyte opposite to each other, and pass direct current to perform electrolysis. During the electrolysis process, the impurity removal process continues, and high-purity bismuth is obtained on the cathode plate.

2. The method according to claim 1, characterized in that, In S1, the iodized salt is one or more of sodium iodide, potassium iodide, calcium iodide, barium iodide, and ammonium iodide; the phosphate is one or more of sodium phosphate, potassium phosphate, lithium phosphate, and ammonium phosphate; and the water-soluble inorganic sulfide is one or more of ammonium sulfide, barium sulfide, sodium sulfide, sodium hydrosulfide, potassium sulfide, and potassium hydrosulfide.

3. The method according to claim 1, characterized in that, In the electrolyte, Bi 3+ The concentration is 30 g / L to 150 g / L, and the concentration of free methanesulfonic acid is 50 g / L to 250 g / L.

4. The method according to claim 3, characterized in that, The Bi 3+ The concentration of the free methanesulfonic acid is 50 g / L to 100 g / L; the concentration of the free methanesulfonic acid is 75 g / L to 150 g / L.

5. The method according to claim 1, characterized in that, The electrolyte circulation rate is 3 L / min to 30 L / min. During the circulation process, 1 mg / L to 100 mg / L of electrolyte impurity removal agent is injected into the impurity removal tank at a constant flow rate. The precipitate in the impurity removal tank is discharged through the filtration system.

6. The method according to claim 5, characterized in that, The electrolyte circulation rate is 5 L / min to 20 L / min; the amount of impurity remover is 2 mg / L electrolyte to 50 mg / L electrolyte.

7. The method according to claim 1, characterized in that, The purification time in S1 is 6 h to 48 h; the electrolysis time in S2 is 18 h to 120 h.

8. The method according to claim 7, characterized in that, The purification time in S1 is 18 h to 24 h; the electrolysis time in S2 is 24 h to 72 h.

9. The method according to claim 1, characterized in that, In step S2, a refined bismuth anode fitted with a polypropylene anode bag and a 316L stainless steel cathode plate are placed in the electrolytic cell. The distance between the anode and cathode is controlled to be 5 cm to 8 cm, the electrolyte temperature to be 25°C to 30°C, and the current density to be 100 A / m. 2 ~150 A / m 2 The power-on time is 36 h to 72 h.

10. An electrolysis system used in the method according to any one of claims 1 to 9, characterized in that, It consists of four parts: a purification agent storage tank, a purification tank, a filtration system, and an electrolytic cell. The purification agent storage tank is connected to the purification tank via a peristaltic pump to transfer the purification agent to the purification tank. The purification tank is connected to the filtration system via a circulation pump. The filtration system is connected to the electrolytic cell via a pipeline. The electrolytic cell is connected to the purification tank via a pipeline, forming an electrolyte circulation loop.

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