Method for preparing high-purity bismuth from bismuth-lead alloy

Abstract

The invention discloses a method for preparing high-purity bismuth from bismuth-lead alloy. The method comprises the following steps: carrying out alkaline oxidation refining on a bismuth-lead alloy with high tellurium content to obtain a bismuth-lead alloy with low tellurium content, and carrying out water quenching treatment on the bismuth-lead alloy with low tellurium content to form alloy particles; the preparation method comprises the following steps: preparing a bismuth mesylate solution, placing the alloy particles in a methanesulfonic acid (MSA) solution with a certain concentration, carrying out oxidation leaching to obtain a bismuth mesylate leaching solution, removing lead ions in the leaching solution through an H2SO4-BaCO3 two-stage precipitation method, and removing trace impurity elements which are easy to deposit in the electrolyte through a pre-electrodeposition mode. And the solution obtained after pre-electrodeposition serves as electrodeposition liquid, and bismuth ions in the solution are reduced into high-purity metal bismuth through direct-current electrodeposition.

Description

Technical Field

[0001] The present invention relates to a method for preparing high-purity bismuth from bismuth-lead alloy, belonging to the field of non-ferrous metal metallurgy. Background Art

[0002] Bismuth has the characteristics of low toxicity and low melting point. Its special electrical, thermal and optical properties can be used as materials for preparing semiconductor components. Bismuth oxides and chlorides can be applied in the fields of medical and health, cosmetics and beauty, etc., so bismuth is also called "green metal". Based on the above characteristics, bismuth can be used as a matrix substitute for toxic metal compounds. Bismuth mostly exists in the form of associated minerals in lead-zinc ore or copper ore in nature. Therefore, bismuth often exists in the flue gas of copper smelting and the by-products of lead electrolysis. In particular, a certain amount of anode slime will be produced during the lead electrolytic refining process. After recovering gold, silver, copper, tellurium or antimony by means of reduction blowing, bismuth-lead alloy is often obtained. Such alloys usually contain a relatively high content of bismuth and are a secondary resource with relatively high economic value. Considering the scarcity and strategic role of bismuth, it is of great significance to separate and purify the bismuth-containing alloys produced during the lead and copper smelting processes.

[0003] High-purity bismuth is widely used in the fields of electronic information, aerospace and military. Therefore, it is more strategically and economically advantageous to further convert crude bismuth compounds into high-purity bismuth. In the wet-process system for bismuth extraction, traditional electrolytic production of bismuth in chloride salt system and silicofluoric acid system faces problems such as too high lead content in cathode bismuth, difficulty in achieving a purity of 4N or even 5N for cathode bismuth, and non-negligible environmental problems. Methylsulfonic acid (MSA) is widely used in the recovery of precious metals such as lead, zinc, copper and tin due to its excellent natural degradability, low toxicity and mild acidity. Patents CN202210017395.0 and CN202111656922.4 report methods for electrodepositing metallic bismuth using methylsulfonic acid system, demonstrating the feasibility of electrodepositing bismuth in this system. Summary of the Invention

[0004] Aiming at the problems of low efficiency, heavy pollution, large amount of waste water and low added value of products in the existing separation and recovery of bismuth from bismuth-lead alloy, the purpose of the present invention is to provide a method for preparing high-purity bismuth from bismuth-lead alloy. The present invention obtains high-purity bismuth through preliminary tellurium removal by pretreatment - oxidative acid leaching in methanesulfonic acid for dissolution - cascade purification for deep impurity removal - electrodeposition of bismuth methanesulfonate solution. First, in the pretreatment stage, the tellurium element content in the raw material is reduced by oxidative refining, and then the alloy is subjected to water quenching treatment to form alloy particles. In the leaching stage, elements such as bismuth and lead are dissolved in the methanesulfonic acid solution. After that, impurities are removed from the bismuth methanesulfonate solution step by step through methods such as double salt precipitation, adsorption and electrochemical impurity removal. Finally, the purified solution is treated by direct current electrodeposition to recover bismuth in the form of high-purity metal. The present invention can not only separate and prepare high-purity bismuth from bismuth-lead alloy produced in the smelting process of non-ferrous metals such as lead and copper, but also be used to treat alloys of other bismuth-containing materials. The method provided by the present invention is green, environmentally friendly and efficient, and is of great significance for the high-value recycling and sustainable development of rare and precious metal resources.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A method for preparing high-purity bismuth from bismuth-lead alloy according to the present invention comprises the following steps:

[0007] (1) Pretreatment

[0008] When the bismuth-lead alloy raw material is a bismuth-lead alloy with low tellurium content, the bismuth-lead alloy raw material is directly subjected to water quenching treatment to form alloy particles;

[0009] When the bismuth-lead alloy raw material is a bismuth-lead alloy with high tellurium content, the bismuth-lead alloy raw material is first subjected to alkaline oxidation and alkaline refining, and after cooling, a bismuth-lead alloy with low tellurium content is obtained, and then water quenching treatment is carried out to form alloy particles;

[0010] In the bismuth-lead alloy with low tellurium content, the mass fraction of tellurium < 1%;

[0011] (2) Oxidative acid leaching in methanesulfonic acid

[0012] The alloy particles obtained in step (1) are placed in a methanesulfonic acid solution for oxidative acid leaching to obtain a methanesulfonate solution containing bismuth ions and lead ions;

[0013] (3) Cascade purification

[0014] H2SO4 is added to the methanesulfonate solution obtained in step (2) for reaction, followed by solid-liquid separation. BaCO3 is added to the obtained filtrate A for reaction, and after solid-liquid separation, filtrate B is obtained. Filtrate B is subjected to pre-electrodeposition to obtain crude bismuth and electrodeposition solution;

[0015] (4) Electrodeposition for bismuth extraction

[0016] The electrowinning solution obtained in step (3) is subjected to electrodeposition to obtain metallic bismuth.

[0017] In the method of the present invention, when the raw material used is a bismuth-lead alloy with a tellurium mass fraction greater than 1%, it is first pretreated by alkaline oxidation refining to convert most of the tellurium element into sodium tellurate. After cooling and skimming off the slag, a bismuth-lead alloy with a low tellurium content is obtained, and then the bismuth-lead alloy is crushed by water quenching treatment to obtain alloy particles with a particle size of 0.5 - 2 cm. The alloy particles are placed in a methanesulfonic acid solution for oxidative acid leaching to fully dissolve the alloy particles, obtaining a bismuth methanesulfonate solution containing lead and a small amount of impurities such as tellurium, copper, and silver. In the cascade purification stage, first, H2SO4 is added to form a PbSO4 precipitate with lead ions, and the PbSO4 precipitate and the bismuth methanesulfonate solution (filtrate A) are obtained through solid-liquid separation. After adding BaCO3 to filtrate A, a lead-barium double salt is formed, and the lead-barium double salt can efficiently further remove the remaining lead ions in the solution; the filtrate B obtained after solid-liquid separation is subjected to electrodeposition pre-removal means to further deeply pre-remove some low-concentration lead, tellurium, silver and other ions remaining in the bismuth methanesulfonate solution, obtaining a highly pure bismuth methanesulfonate solution for electrodeposition to prepare high-purity bismuth.

[0018] In step (1), when the bismuth-lead alloy raw material and the base are subjected to alkaline oxidation refining in an oxidizing atmosphere, the base is selected from sodium hydroxide and / or sodium carbonate, and the oxidizing atmosphere is air or pure oxygen; the addition amount of the base is 2 - 6 times the theoretical amount required to convert tellurium into Na6TeO6. Controlling the addition amount of the base within this range can ensure the conversion of the bismuth-lead alloy with a high tellurium content into a bismuth-lead alloy with a low tellurium content.

[0019] In a preferred embodiment, in step (1), the base is sodium hydroxide, the oxidizing atmosphere is air, and the addition amount of sodium hydroxide is 4 - 6 times the theoretical amount required to convert tellurium into Na6TeO6.

[0020] In step (1), the temperature of the alkaline oxidation refining is 600 - 900 °C, and the time of the alkaline oxidation refining is 10 min - 1 h.

[0021] In a preferred embodiment, in step (1), the temperature of the alkaline oxidation refining is 600 - 700 °C, and the time of the alkaline oxidation refining is 0.5 h - 1 h.

[0022] In step (1), the temperature of the water quenching treatment is 300 - 400 °C, preferably 350 - 400 °C. During the water quenching treatment, the mass ratio of the bismuth-lead alloy to water is controlled to be 1:5 - 15, preferably 1:10 - 15. Through the water quenching treatment, alloy particles of 0.5 - 2 cm are obtained.

[0023] Since the melting point of the bismuth-lead alloy is relatively low and it can melt at 300 °C, in the present invention, the temperature of the water quenching treatment is controlled at 350 - 400 °C, so that the massive alloy melts and is broken into small particles during the water quenching process. During the actual operation, the height of the crucible is controlled at 40 - 50 cm above the tap water surface, and the massive alloy in the crucible is poured into the tap water to break the massive alloy to obtain alloy particles with a size of 0.5 - 2 cm.

[0024] In step (2), the concentration of the methanesulfonic acid solution is 3 - 4.5 mol / L, and the liquid-solid volume-mass ratio of the alloy particles to the methanesulfonic acid solution is 3 - 7 mL:1 g.

[0025] In a preferred embodiment, in step (2), the concentration of the methanesulfonic acid solution is 4 - 4.5 mol / L, and the liquid-solid volume-mass ratio of the alloy particles to the methanesulfonic acid solution is 5 - 6 mL:1 g.

[0026] In step (2), during the oxidative acid leaching, the oxidant introduced is selected from at least one of hydrogen peroxide, air, pure oxygen, or ozone, and the addition amount of the oxidant is 0.8 - 1.5 times the theoretical amount required to completely oxidize Bi and Pb in the bismuth-lead alloy particles to Bi2O3 and PbO.

[0027] In a preferred embodiment, in step (2), during the oxidative acid leaching, the oxidant introduced is hydrogen peroxide, and the addition amount of the hydrogen peroxide is 1 - 1.2 times the theoretical amount required to completely oxidize Bi and Pb in the bismuth-lead alloy particles to Bi2O3 and PbO.

[0028] In step (2), the temperature of the oxidative acid leaching is 30 - 70 °C, and the time of the oxidative acid leaching is 1.5 - 3.5 h.

[0029] In a preferred embodiment, in step (2), the temperature of the oxidative acid leaching is 40 - 60 °C, and the time of the oxidative acid leaching is 1.5 - 2 h.

[0030] In step (3), the addition amount of the H2SO4 is 1.2 - 2 times the theoretical amount required to completely form PbSO4 from the lead ions in the bismuth methanesulfonate solution.

[0031] In a preferred embodiment, in step (3), the addition amount of the H2SO4 is 1.2 - 1.4 times the theoretical amount required to completely form PbSO4 from the lead ions in the bismuth methanesulfonate solution.

[0032] In step (3), the addition amount of the BaCO3 is 0.5 - 1.5 times the excess molar amount of the added H2SO4.

[0033] Preferably, in step (3), the addition amount of BaCO3 is 0.5 to 1 times the excess molar amount of H2SO4 added. In the present invention, BaCO3 is added as a lead remover. When barium carbonate is added, the residual sulfate radicals in the system are removed, so the system is a methanesulfonic acid system, plus a very small amount of sulfuric acid, thus ensuring the subsequent electrodeposition process. If other soluble barium salts are added, the system will be changed. For example, if barium chloride is added, the system will become a hydrochloric acid-methanesulfonic acid system.

[0034] In step (3), during pre-electrodeposition, the current density is 20 to 80 A / m 2 , and the time is 4 to 10 h.

[0035] Preferably, in step (3), during pre-electrodeposition, the current density is 30 to 50 A / m 2 , and the time is 6 to 10 h. The pre-electrodeposition method preferentially deposits impurity elements that are more likely to deposit than bismuth ions in the filtrate B after lead removal on the cathode bismuth plate for enrichment and separation to obtain crude bismuth, and the obtained crude bismuth is produced as a product.

[0036] In step (4), during electrodeposition, the current density is 100 to 300 A / m 2 , the interpolar distance is 2 to 5 cm, and the temperature is 20 to 50 °C.

[0037] Preferably, in step (4), during electrodeposition, the current density is 150 to 200 A / m 2 , the interpolar distance is 2 to 3 cm, and the temperature is 30 to 40 °C.

[0038] Beneficial effects

[0039] Different from the traditional electrowinning methods for preparing metallic bismuth such as electrowinning in a silicofluoric acid system, diaphragm electrowinning in a hydrochloric acid system or a methanesulfonic acid system, etc., the present invention aims at the problem of deep separation of bismuth from elements such as lead and tellurium in a methanesulfonic acid system. The present invention innovatively proposes a method for separating and preparing high-purity bismuth from a bismuth-lead alloy by a route of pretreatment-methanesulfonic acid oxidative acid leaching-gradient purification-electrodeposition. This method has small wastewater volume, low actual consumption, high product added value, and does not generate toxic gases such as chlorine or hydrogen fluoride. Especially in the gradient purification step, the lead-barium double salt can not only efficiently remove lead ions in the solution, but also the lead-barium double salt acts as an adsorbent to adsorb and remove trace impurity ions such as tellurium, silver, and iron in the solution. At the same time, combined with the pre-removal means of electrowinning, some residual low-concentration lead, tellurium, silver and other ions in the bismuth methanesulfonate solution are further deeply pre-removed to obtain a highly pure bismuth methanesulfonate solution for electrowinning to prepare high-purity bismuth. The present invention is not only applicable to treating bismuth-lead alloys produced in the non-ferrous smelting process, but also can be used to treat alloys of other bismuth-containing materials. Specific embodiments

[0040] The following uses examples to illustrate the essence of the present invention, but the protection scope of the present invention is not limited thereto.

[0041] Example 1 (Bismuth-Lead-High-Tellurium Alloy)

[0042] The main components in the bismuth-lead alloy are Bi 65.1 ωt.%, Pb 31.7 ωt.%, Te 1.8 ωt.%, Fe 1.4 ωt.%, and Ag 0.015 ωt.%. Sodium hydroxide is added in the pretreatment stage (the addition amount of sodium hydroxide is 5 times the theoretical amount for converting tellurium into Na6TeO6), and it is refined in an oxygen atmosphere at 600 °C for 30 min. Subsequently, the alloy is subjected to water quenching treatment (the mass ratio of the alloy to water is 1:10) to form metal particles with a particle size in the range of 0.5 - 2 cm. In the leaching stage, with a 4 mol / L MSA solution, at a liquid-solid ratio of 5 (mL):1 (g), a leaching temperature of 50 °C, and the addition amount of hydrogen peroxide being 1.2 times the theoretical amount required to completely oxidize Bi and Pb in the alloy particles to Bi2O3 and PbO, leaching for 2 h gives the leaching solution. In the purification stage, in the first step, H2SO4 is added in an amount 1.2 times the theoretical amount according to the lead element content in the leaching solution (completely reacting with the lead element to form lead sulfate precipitate). After reacting for 1 h, it is left to stand for 30 min and then filtered; barium carbonate is added to the filtrate, and the addition amount of barium carbonate is added at 0.5 times the excess molar amount of sulfuric acid. After reacting for 1 h, it is left to stand for 30 min and then filtered to obtain the leaching solution after lead removal; in the second step, under the condition of a current density of 30 A / m 2 electrowinning is carried out for 6 h by pre-electrodeposition to reduce trace impurity elements in the leaching solution to obtain the electrowinning solution. Finally, metallic bismuth in the solution is recovered by direct current electrodeposition. Under the conditions of a current density of 150 A / m 2 and a pole pitch of 2 cm and a temperature of 30 °C, electrodeposition is carried out for 12 h to obtain metallic bismuth.

[0043] After chemical detection and calculation, in the pretreatment stage, the direct recovery rate of bismuth is 95%, and the tellurium removal rate is 97%; in the leaching stage, the leaching rates of bismuth and lead are 98% and 97% respectively, where the bismuth ion concentration is 124 g / L and the lead ion concentration is 62.7 g / L. The tellurium and silver contents in the leaching residue are 60% and 81% respectively. In the purification stage, after removing lead by H2SO4 - BaCO3 and removing impurities by pre-electrodeposition, the lead ion concentration can be reduced to below 50 ppm, and the other impurity concentrations are below 5 ppm respectively. After direct current electrodeposition, the cathode current efficiency and purity are 96% and 99.996% respectively.

[0044] Example 2

[0045] The main components of the bismuth-lead alloy are Bi 65.1 ωt.%, Pb 31.7 ωt.%, Te 1.8 ωt.%, Fe 2.2 ωt.%, and Ag 0.015 ωt.%. Sodium hydroxide is added in the pretreatment stage (the addition amount of sodium hydroxide is 5 times the theoretical amount for converting tellurium into Na6TeO6), and it is refined in an oxygen atmosphere at 600 °C for 30 min. Subsequently, the alloy is quenched with water to form metal particles. In the leaching stage, with a 4 mol / L MSA solution, at a liquid-solid ratio of 5 (mL):1 (g), a leaching temperature of 60 °C, and the addition amount of hydrogen peroxide being 1 times the theoretical amount required to completely oxidize Bi and Pb in the alloy particles to Bi2O3 and PbO, the leaching solution is obtained after leaching for 1 h. Then, according to the lead element content in the leaching solution, H2SO4 with an excess coefficient of 1.5 times (completely reacting with lead elements to form lead sulfate precipitate) is added. After reacting for 1 h, it is left standing for 30 min and then filtered; barium carbonate is added to the filtrate, and the addition amount of barium carbonate is 0.5 times the molar amount of sulfuric acid. After reacting for 1 h, it is left standing for 30 min and then filtered to obtain the leaching solution after lead removal; in the second step, under the condition of a current density of 60 A / m 2 the trace impurity elements in the leaching solution are electrowon for 5 h by pre-electrodeposition to obtain the electrowinning solution. Finally, metallic bismuth in the solution is recovered by direct current electrodeposition. Under the conditions of a current density of 150 A / m 2 and a pole pitch of 3 cm and a temperature of 30 °C, high-purity cathode bismuth is obtained after electrodeposition for 12 h.

[0046] Through chemical detection and calculation, the direct recovery rate of bismuth in the pretreatment stage is 95%, and the tellurium removal rate is 97%; in the leaching stage, the leaching rates of bismuth and lead are 95% and 97.6% respectively, where the bismuth ion concentration is 121 g / L and the lead ion concentration is 61 g / L. The tellurium and silver contents in the leaching residue are 62% and 83% respectively. After removing lead by the H2SO4-BaCO3 method and removing impurities by pre-electrodeposition, the lead ion concentration can be reduced to below 50 ppm, and the other impurity concentrations are below 5 ppm. After direct current electrodeposition, the cathode current efficiency and purity are 96% and 99.997% respectively.

[0047] Example 3 (bismuth-lead low-tellurium alloy)

[0048] The main components of the bismuth-lead alloy are Bi 66.2 ωt.%, Pb 32.9 ωt.%, Te 0.2 ωt.%, Fe 1.1 ωt.%, and Ag 0.019 ωt.%. In the pretreatment stage, the alloy is quenched in water to form metal particles. In the leaching stage, with a 4 mol / L MSA solution, at a liquid-solid ratio of 5 (mL):1 (g), a leaching temperature of 50 °C, and the addition amount of hydrogen peroxide being 1.2 times the theoretical amount required to completely oxidize Bi and Pb in the alloy particles to Bi2O3 and PbO, the leaching solution is obtained after 2 h of leaching. Then, according to the lead element content in the leaching solution, H2SO4 with an excess coefficient of 1.2 times (fully reacting with lead elements to form lead sulfate precipitate) is added. After reacting for 1 h, it is left standing for 30 min and then filtered; barium carbonate is added to the filtrate, and the addition amount of barium carbonate is added at 0.5 times the excess molar amount of sulfuric acid. After reacting for 1 h, it is left standing for 30 min and then filtered to obtain the leaching solution after lead removal; in the second step, under the condition of a current density of 30 A / m 2 The trace impurity elements in the leaching solution are reduced by electro-deposition for 8 h through pre-electrodeposition under the conditions. The electro-deposited solution is obtained. Finally, metallic bismuth in the solution is recovered by direct current electro-deposition. Under the conditions of a current density of 150 A / m 2 and a pole pitch of 4 cm and a temperature of 30 °C, metallic bismuth is obtained after 12 h of electro-deposition.

[0049] Through chemical detection and calculation, in the leaching stage, the leaching rates of bismuth and lead are 95.3% and 98.2% respectively, where the bismuth ion concentration is 120 g / L and the lead ion concentration is 62 g / L. The tellurium and silver contents in the leaching residue are 66% and 91% respectively. After removing lead by H2SO4 - BaCO3 and removing impurities by pre-electrodeposition, the lead ion concentration can be reduced to below 50 ppm, and the other impurity concentrations are below 5 ppm respectively. After direct current electro-deposition, the cathode current efficiency and purity are 97% and 99.998% respectively.

[0050] Comparative Example 1 (hydrogen peroxide was not used in the acid leaching stage)

[0051] The other conditions of Comparative Example 1 are the same as those of Example 1. The only difference is that hydrogen peroxide was not added during the leaching process with methanesulfonic acid, and the bismuth-lead alloy was leached conventionally in the methanesulfonic acid solution. The results show that the indicators in the pretreatment stage are close to those of Example 1, but in the acid leaching stage, the leaching rate of bismuth is only 0.6% and the leaching rate of lead is 18%. The bismuth ion content in the leaching solution is too low, which is not conducive to the subsequent electro-deposition process.

[0052] Comparative Example 2 (no water quenching treatment)

[0053] Other conditions of Comparative Example 2 were the same as those of Example 1. The only difference was that after alkaline oxidation refining, water quenching treatment was not carried out, and the alloy still presented a large block shape. The results showed that the indexes in the pretreatment stage were close to those of Example 1. To achieve a leaching rate of bismuth and lead elements in the leaching stage close to that of Example 1, it took about 5 times longer, which was not conducive to industrial production. The indexes in the subsequent purification and electrodeposition processes were close to those of Example 1, and the cathode current efficiency and purity were 97% and 99.992% respectively.

Claims

1. A method for preparing high-purity bismuth using bismuth-lead alloy, characterized in that: It includes the following steps: (1) Pretreatment When the bismuth-lead alloy raw material is a bismuth-lead alloy with a low tellurium content, directly subject the bismuth-lead alloy raw material to water quenching treatment to form alloy particles; When the bismuth-lead alloy raw material is a bismuth-lead alloy with a high tellurium content, first subject the bismuth-lead alloy raw material to alkaline oxidation and alkaline refining, and after cooling, obtain a bismuth-lead alloy with a low tellurium content, and then perform water quenching treatment to form alloy particles; In the bismuth-lead alloy with a low tellurium content, the mass fraction of tellurium < 1%; (2) Methylsulfonic acid oxidation and acid leaching Place the alloy particles obtained in step (1) in a methylsulfonic acid solution for oxidation and acid leaching to obtain a methylsulfonate solution containing bismuth ions and lead ions; (3) Stepwise purification Add H2SO4 to the methylsulfonate solution obtained in step (2) for reaction, perform solid-liquid separation, add BaCO3 to the obtained filtrate A for reaction, perform solid-liquid separation to obtain filtrate B, and subject filtrate B to pre-electrodeposition to obtain crude bismuth and electrowinning solution; (4) Electrodeposition for bismuth extraction Perform electrodeposition on the electrowinning solution obtained in step (3) to obtain metallic bismuth.

2. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (1), when performing alkaline oxidation and alkaline refining of the bismuth-lead alloy raw material with an alkali in an oxidizing atmosphere, the alkali is selected from sodium hydroxide and / or sodium carbonate, and the oxidizing atmosphere is air or pure oxygen; the addition amount of the alkali is 2 to 6 times the theoretical amount required to convert tellurium into Na6TeO6; In step (1), the temperature of the alkaline oxidation refining is 600 to 900 °C, and the time of the alkaline oxidation refining is 10 min to 1 h.

3. A method for preparing high-purity bismuth using bismuth-lead alloy according to claim 1, characterized in that: In step (1), the temperature of the water quenching treatment is 300 to 400 °C. During the water quenching treatment, control the mass ratio of the bismuth-lead alloy with a low tellurium content to water to be 1:5 to 1:

15. Through the water quenching treatment, alloy particles with a particle size of 0.5 - 2 cm are obtained.

4. A method for preparing high-purity bismuth using bismuth-lead alloy according to claim 1, characterized in that: In step (2), the concentration of the methylsulfonic acid solution is 3 to 4.5 mol / L, and the liquid-solid volume-mass ratio of the alloy particles to the methylsulfonic acid solution is 3 to 7 mL:1 g.

5. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (2), during the oxidation and acid leaching, the oxidant introduced is selected from at least one of hydrogen peroxide, air, pure oxygen, or ozone, and the addition amount of the oxidant is 0.8 to 1.5 times the theoretical amount required to completely oxidize Bi and Pb in the alloy particles to Bi2O3 and PbO.

6. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (2), the temperature of the oxidation and acid leaching is 30 to 70 °C, and the time of the oxidation and acid leaching is 1.5 to 3.5 h.

7. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (3), the addition amount of the H2SO4 is 1.2 to 2 times the theoretical amount required to completely form PbSO4 from the lead ions in the bismuth methylsulfonate solution.

8. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (3), the addition amount of BaCO3 is 0.5 to 1.5 times the excess molar amount of H2SO4 added.

9. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (3), during pre-electrodeposition, the current density is 20~80 A / m 2 , and the time is 4~10 h.

10. A method for preparing high-purity bismuth using a bismuth-lead alloy according to claim 1, characterized in that: In step (4), during the electro-deposition, the current density is 100~300 A / m 2 , the distance between the electrodes is 2~5 cm, and the temperature is 20~50 °C.