A method for preparing high-purity metallic bismuth

Abstract

The present invention relates to a method for preparing high-purity metallic bismuth, and relates to the technical field of non-ferrous metal metallurgy. The preparation method comprises the following steps: (1) in an inert atmosphere, a bismuth-containing raw material, phosphorus pentoxide and sulfate accounting for 1 / 3 to 1 / 2 of the total amount of sulfate are melted to obtain a product, and then the product is skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N; (2) the metallic bismuth obtained by skimming in step (1) is ground and sieved, and then mixed with sulfate accounting for 1 / 2 to 2 / 3 of the total amount of sulfate and subjected to two-stage vacuum distillation; (3) while performing two-stage vacuum distillation in step (2), graded condensation is performed to obtain high-purity metallic bismuth with a purity of 5N. Compared with traditional vacuum distillation and zone smelting processes, the present invention has the advantages of good purification effect, high impurity removal efficiency, etc., and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal metallurgy, and in particular relates to a method for preparing high-purity metallic bismuth. Background Art

[0002] Bismuth-containing raw materials generally contain impurities such as lead, copper, silver, tin, and arsenic, and must be refined and refined to improve the purity of metallic bismuth. The methods for refining and purifying crude bismuth metal can be divided into two types: pyrometallurgical refining and electrolytic refining. Among them, electrolytic refining can remove impurities such as gold, silver, lead, iron, tin, and tellurium, but the electrolytic refining process requires large fixed investments in plant and equipment, and the refining cycle is long. Before electrolytic refining, preliminary pyrometallurgical refining must be used to remove impurities such as arsenic, antimony, and copper that have a greater impact on the electrolytic refining process, and pyrometallurgical final refining must be used to further remove impurities such as silver, iron, and calcium. The process flow is complicated and has gradually been replaced by pyrometallurgical refining. Pyrometallurgical refining of crude bismuth is usually carried out in a steel refining pot. Generally, after smelting and sulfur removal of copper, oxidation removal of arsenic and antimony, alkaline refining removal of tellurium and tin, zinc removal of silver, chlorination removal of lead and zinc, and final refining, a refined bismuth product with a purity of 99.99% can be produced.

[0003] As people's understanding of metallic bismuth deepens, non-toxic high-purity metallic bismuth is widely used in the fields of medicine, electronics, metallurgy, chemical industry, nuclear industry, etc., and the demand for high-purity bismuth is also increasing. However, the purity of refined bismuth still cannot meet the requirements of heavy metal impurity limits in industries such as medicine and cosmetics.

[0004] At present, the main methods for producing high-purity metallic bismuth are vacuum distillation and zone smelting. Vacuum distillation is to separate impurities from bismuth by distillation under vacuum conditions, but since the saturated vapor pressures of bismuth and lead are relatively close, the removal effect of lead is poor, and the zone smelting method has the disadvantages of long operation time and low production efficiency. It can be seen that the preparation method of high-purity metallic bismuth that is simple and easy to develop and has good purification effect has good application value. Summary of the invention

[0005] The purpose of the present invention is to address the shortcomings of the current method for preparing high-purity metallic bismuth, and the present invention provides an improved method for preparing high-purity metallic bismuth.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] The present invention provides a method for preparing high-purity metallic bismuth, comprising the following steps:

[0008] (1) Under an inert atmosphere, a bismuth-containing raw material, phosphorus pentoxide, and sulfate accounting for 1 / 3 to 1 / 2 of the total amount of sulfate are melted to obtain a product, and then the product is skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N;

[0009] () grinding and sieving the 4N purity metallic bismuth obtained by slagging in step (1), and then mixing it with sulfate accounting for 1 / 2 to 2 / 3 of the total amount of sulfate and performing two-stage vacuum distillation;

[0010] (3) In step (2), two-stage vacuum distillation is performed simultaneously with graded condensation to obtain high-purity metallic bismuth with a purity of 5N.

[0011] As a further optimization solution, in step (1), the bismuth-containing raw material is refined bismuth with a purity of 2N to 3N.

[0012] As a further optimization scheme, in step (1), the temperature condition of the melting treatment is 900° C. to 1200° C., and the time condition of the melting treatment is 0.5 h to 2 h.

[0013] As a further optimization scheme, in step (1), the amount of phosphorus pentoxide used is 5% to 15% of the amount of bismuth-containing raw material used.

[0014] As a further optimization scheme, in step (1), the amount of the sulfate used is 5% to 15% of the amount of the bismuth-containing raw material used.

[0015] As a further optimization scheme, the sulfate is sodium sulfate or sodium bisulfate.

[0016] As a further optimization solution, in step (2), the grinding and screening is specifically grinding through a 300-500 mesh sieve.

[0017] As a further optimization scheme, in step (2), the two-stage vacuum distillation is specifically as follows: first, metallic bismuth and sulfate are placed in a vacuum furnace, the vacuum furnace is evacuated once to a residual pressure of 5Pa to 10Pa, the vacuum furnace is heated to 800°C to 850°C, and distillation is performed at a constant temperature and pressure for 15min to 30min, then the temperature is raised to 850°C to 950°C, and the vacuum furnace is evacuated twice to a residual pressure of 10Pa to 15Pa, and distillation is continued at a constant temperature and pressure for 30min to 60min. After the distillation is completed, nitrogen is introduced into the vacuum furnace to normal pressure, and the temperature is lowered to room temperature.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention firstly melts 2N-3N pure bismuth, phosphorus pentoxide and sulfate at high temperature to form slag, so that the content of low-boiling impurities such as As, Ag and Pb in the 2N-3N pure bismuth is initially reduced, and metallic bismuth with a purity of 4N is obtained. Subsequently, the metallic bismuth with a purity of 4N and the sulfate are subjected to two-stage vacuum distillation and combined with graded condensation, and the temperature and residual pressure in the vacuum distillation process are controlled to remove high-boiling point impurity metals such as Cu and Fe contained in the 4N metallic bismuth, while the content of impurities such as As, Ag and Pb is further reduced, and finally a high-purity metallic bismuth with a purity of 5N is prepared;

[0020] (2) Compared with the traditional vacuum distillation and zone smelting processes, the present invention has the advantages of good purification effect and high impurity removal efficiency, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention provides a flowchart of the preparation process of high-purity metallic bismuth. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technicians in this field can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0023] Unless otherwise specified, the methods used in the present invention are conventional methods known to those skilled in the art. If no specific conditions are specified, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0024] The present invention provides a method for preparing high-purity metallic bismuth. The preparation process flow chart is as follows: Figure 1 As shown, the following steps are included:

[0025] (1) Under an inert atmosphere, a bismuth-containing raw material, phosphorus pentoxide, and sulfate accounting for 1 / 3 to 1 / 2 of the total amount of sulfate are melted to obtain a product, and then the product is skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N.

[0026] In some embodiments, the inert atmosphere can be selected as a nitrogen atmosphere or an argon atmosphere, the bismuth-containing raw material is a pure bismuth with a purity of 2N to 3N, that is, the bismuth grade is about 99% to 99.9%, and the impurity elements present in the bismuth-containing raw material include one or more of Cd, Sn, Al, Ni, Zn, Pb, As, Fe, Mg, Al, Cr, Au, Ag, and Cu.

[0027] In some embodiments, the temperature condition of the melt treatment is 900° C. to 1200° C., and the time condition of the melt treatment is 0.5 h to 2 h.

[0028] In some embodiments, the amount of phosphorus pentoxide is 5% to 15% of the amount of metallic bismuth with a purity of 2N to 3N, the amount of sulfate is 5% to 15% of the amount of metallic bismuth with a purity of 2N to 3N of the bismuth-containing raw material, and the sulfate is any one of sodium sulfate, sodium bisulfate or potassium sulfate.

[0029] (3) grinding and screening the metallic bismuth obtained by slagging in step (1), and then mixing it with sulfate accounting for 1 / 2 to 2 / 3 of the total amount of sulfate and performing two-stage vacuum distillation;

[0030] In some embodiments, grinding and screening specifically includes grinding and screening through a 300-500 mesh sieve.

[0031] (3) In step (2), high-purity metallic bismuth with a purity of 5N can be obtained by performing fractional condensation while performing two-stage vacuum distillation. In addition, in some embodiments, the distillation slag obtained by fractional condensation can be further recycled to the melting treatment in step (1) to ensure sufficient recovery of metallic bismuth.

[0032] In some embodiments, the two-stage vacuum distillation is specifically as follows: first, metallic bismuth and sulfate are placed in a vacuum furnace, the vacuum furnace is evacuated once to a residual pressure of 5Pa to 10Pa, the vacuum furnace is heated to 800°C to 850°C, and distilled at a constant temperature and pressure for 15min to 30min, then the temperature is raised to 850°C to 950°C, and the vacuum furnace is evacuated a second time to a residual pressure of 10Pa to 15Pa, and distillation is continued at a constant temperature and pressure for 30min to 60min. After the distillation is completed, nitrogen is introduced into the vacuum furnace to normal pressure, and the temperature is lowered to room temperature.

[0033] In some embodiments, the graded condensation can use 10 levels of condensation reflux trays, and the condensation reflux trays are preferably made of graphite. The size of each level of graphite trays is 10 cm in diameter and 5 cm in height, and each level of graphite trays is connected by a frosted socket seal. The graphite tray is placed directly above the reaction raw materials, the upper graphite tray mainly realizes the condensation deposition of low-boiling impurities such as As / Pb, and the lower graphite tray realizes the condensation deposition of the main metal bismuth. The condensation reflux tray is also provided with a metal vapor rising channel from bottom to top, and the channel is also a vacuum channel.

[0034] Example 1

[0035] The method for preparing high-purity metallic bismuth provided in this embodiment uses a bismuth-containing raw material of 2N purity refined bismuth, and its composition table is shown in Table 1.

[0036] Table 1. Composition of 2N pure bismuth (%)

[0037]

[0038] The preparation method comprises the following steps:

[0039] (1) Under nitrogen atmosphere, 50 g of 2N pure bismuth, phosphorus pentoxide and sodium sulfate were melted at 900° C. for 2 h to obtain a product, and then the product was skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N. The amount of phosphorus pentoxide used was 5% of the amount of pure bismuth used, and the amount of sodium sulfate used was 5% of the amount of pure bismuth used.

[0040] After testing, the impurity contents of As, Ag, Pb, etc. in the metallic bismuth with a purity of 4N obtained in step (1) were reduced to 0.003%, 0.00035% and 0.00065%, respectively.

[0041] (2) The metallic bismuth obtained by slagging was ground through a 300-mesh sieve, and then mixed with 5% sodium sulfate used for refined bismuth and put into a vacuum furnace. The vacuum furnace was evacuated once to a residual pressure of 5 Pa, the vacuum furnace was heated to 850° C., and distilled at a constant temperature and pressure for 30 min. Subsequently, the temperature was raised to 950° C., and the vacuum furnace was evacuated twice to a residual pressure of 10 Pa. The distillation was continued at a constant temperature and pressure for 60 min. After the distillation was completed, nitrogen was introduced into the vacuum furnace to normal pressure, and the temperature was lowered to room temperature.

[0042] (3) performing graded condensation while performing vacuum distillation to recover high-purity metallic bismuth.

[0043] The composition of the high-purity metallic bismuth prepared in Example 1 is shown in Table 2.

[0044] Table 2. Composition of high purity metallic bismuth (%)

[0045]

[0046] By comparing Table 1 with Table 2, it can be seen that high-purity metallic bismuth is obtained through the above preparation steps, and the purity reaches 5N.

[0047] Example 2

[0048] The method for preparing high-purity metallic bismuth provided in this embodiment uses bismuth-containing raw material which is 3N pure bismuth, and its composition table is shown in Table 3.

[0049] Table 3. Composition of 3N pure bismuth (%)

[0050]

[0051] The preparation method comprises the following steps:

[0052] (1) Under a nitrogen inert atmosphere, 50 g of 3N pure bismuth, phosphorus pentoxide and sodium bisulfate were melt-treated at 1200° C. for 0.5 h to obtain a product, and then the product was skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N. The amount of phosphorus pentoxide used was 10% of the amount of pure bismuth used, and the amount of sodium bisulfate used was 5% of the amount of pure bismuth used.

[0053] After testing, the impurity contents of As, Ag, Pb, etc. in the 4N purity metallic bismuth obtained in step (1) were reduced to 0.001%, 0.00001%, and 0.0002%, respectively.

[0054] (2) The metallic bismuth obtained by slagging was ground through a 500-mesh sieve, and then mixed with 10% of the amount of sodium bisulfate used for refined bismuth and put into a vacuum furnace. The vacuum furnace was evacuated once to a residual pressure of 10 Pa, the vacuum furnace was heated to 800° C., and distilled at a constant temperature and pressure for 15 min. Subsequently, the temperature was raised to 900° C., and the vacuum furnace was evacuated twice to a residual pressure of 15 Pa. The distillation was continued at a constant temperature and pressure for 30 min. After the distillation was completed, nitrogen was introduced into the vacuum furnace to normal pressure, and the temperature was lowered to room temperature.

[0055] (3) performing graded condensation while performing vacuum distillation to recover high-purity metallic bismuth.

[0056] The composition of the high-purity metallic bismuth prepared in Example 2 is shown in Table 4.

[0057] Table 4. Composition of high purity metallic bismuth (%)

[0058]

[0059] By comparing Table 3 with Table 4, it can be seen that high-purity metallic bismuth is obtained through the above preparation steps, and the purity reaches 5N.

[0060] Comparative Example 1

[0061] The preparation method for preparing high-purity metallic bismuth provided in this comparative example uses the same bismuth-containing raw material as in Example 1, and the composition table is the same as shown in Table 1.

[0062] The preparation method comprises the following steps:

[0063] (1) Under a nitrogen inert atmosphere, 50 g of 2N pure bismuth, phosphorus pentoxide and sodium sulfate were melted at 800° C. for 2 h to obtain a product, and then the product was skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N. The amount of phosphorus pentoxide used was 5% of the amount of refined bismuth used, and the amount of sodium sulfate used was 10% of the amount of refined bismuth used.

[0064] (2) The bismuth metal obtained by slagging was ground through a 300-mesh sieve and then placed in a vacuum furnace. The vacuum furnace was evacuated once to a residual pressure of 5 Pa. The vacuum furnace was heated to 850° C. and distilled at a constant temperature and pressure for 30 min. Subsequently, the temperature was raised to 950° C. and the vacuum furnace was evacuated twice to a residual pressure of 10 Pa. The distillation was continued at a constant temperature and pressure for 60 min. After the distillation was completed, nitrogen was introduced into the vacuum furnace to normal pressure and the temperature was lowered to room temperature.

[0065] (3) performing graded condensation while performing vacuum distillation to recover high-purity metallic bismuth.

[0066] The composition of the high-purity metallic bismuth prepared in Comparative Example 1 is shown in Table 5.

[0067] Table 5. Composition of high purity metallic bismuth (%)

[0068]

[0069] Comparative Example 2

[0070] The preparation method for preparing high-purity metallic bismuth provided in this comparative example uses the same bismuth-containing raw material as in Example 1, and the composition table is the same as shown in Table 1.

[0071] The preparation method comprises the following steps:

[0072] (1) Under a nitrogen inert atmosphere, 50 g of 2N pure bismuth, phosphorus pentoxide and sodium sulfate were melted at 800° C. for 2 h to obtain a product, and then the product was skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N. The amount of phosphorus pentoxide used was 5% of the amount of refined bismuth used, and the amount of sodium sulfate used was 5% of the amount of refined bismuth used.

[0073] (2) The metallic bismuth obtained by slagging was ground through a 300-mesh sieve, and then mixed with 5% sodium sulfate used for refined bismuth and put into a vacuum furnace. The vacuum furnace was evacuated to a residual pressure of 5 Pa, and the vacuum furnace was heated to 850° C. and distilled at a constant temperature and pressure for 90 minutes. After the distillation was completed, nitrogen was introduced into the vacuum furnace to normal pressure, and the temperature was lowered to room temperature.

[0074] (3) performing graded condensation while performing vacuum distillation to recover high-purity metallic bismuth.

[0075] The composition of the high-purity metallic bismuth prepared in Comparative Example 2 is shown in Table 6.

[0076] Table 6. Composition of high purity metallic bismuth (%)

[0077]

[0078] Comparative Example 3

[0079] The preparation method for preparing high-purity metallic bismuth provided in this comparative example uses the same bismuth-containing raw material as in Example 1, and the composition table is the same as shown in Table 1.

[0080] (1) Under a nitrogen inert atmosphere, 50 g of 2N pure bismuth, phosphorus pentoxide and sodium sulfate were melted at 800° C. for 2 h to obtain a product, and then the product was skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N. The amount of phosphorus pentoxide used was 5% of the amount of refined bismuth used, and the amount of sodium sulfate used was 5% of the amount of refined bismuth used.

[0081] (2) The metallic bismuth obtained by slagging was ground through a 300-mesh sieve, and then mixed with 5% sodium sulfate used for refined bismuth and put into a vacuum furnace. The vacuum furnace was evacuated once to make the residual pressure reach 10 Pa, and the vacuum furnace was heated to 850° C. and distilled at constant temperature and pressure for 30 min. Subsequently, the temperature was raised to 950° C. and distilled at constant temperature and pressure for 60 min. After the distillation was completed, nitrogen was introduced into the vacuum furnace to normal pressure, and the temperature was lowered to room temperature.

[0082] (3) performing graded condensation while performing vacuum distillation to recover high-purity metallic bismuth.

[0083] The composition table of the high-purity metallic bismuth prepared in Comparative Example 3 is shown in Table 7.

[0084] Table 7. Composition of high purity metallic bismuth (%)

[0085]

[0086] Comparative Example 4

[0087] The method for preparing high-purity metallic bismuth provided in this comparative example uses refined bismuth with a purity of 3N as a raw material, and its composition table is shown in Table 1.

[0088] The preparation method comprises the following steps:

[0089] (1) Under a nitrogen inert atmosphere, 50 g of 2N pure bismuth, phosphorus pentoxide and sodium sulfate were melted at 800° C. for 2 h to obtain a product, and then the product was skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N. The amount of phosphorus pentoxide used was 5% of the amount of refined bismuth used, and the amount of sodium sulfate used was 5% of the amount of refined bismuth used.

[0090] (2) The metallic bismuth obtained by slagging was ground through a 300-mesh sieve, and then mixed with 5% sodium sulfate used for refined bismuth and put into a vacuum furnace. The vacuum furnace was evacuated once to make the residual pressure reach 5 Pa, the vacuum furnace was heated to 950° C., and distilled at constant temperature and pressure for 30 minutes. The vacuum furnace was evacuated twice to make the residual pressure reach 10 Pa. The vacuum furnace temperature was maintained at 950° C., and distillation was continued at constant temperature and pressure for 60 minutes. After the distillation was completed, nitrogen was introduced into the vacuum furnace to normal pressure, and the temperature was lowered to room temperature.

[0091] (3) performing graded condensation while performing vacuum distillation to recover high-purity metallic bismuth.

[0092] The composition table of high-purity metallic bismuth prepared in Comparative Example 4 is shown in Table 8.

[0093] Table 8. Composition of high purity metallic bismuth (%)

[0094]

[0095] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing high-purity metallic bismuth, characterized in that: The following steps are involved: (1) Under an inert atmosphere, a bismuth-containing raw material, phosphorus pentoxide, and sulfate accounting for 1 / 3 to 1 / 2 of the total amount of sulfate are melted to obtain a product, and then the product is skimmed to remove the generated phosphate scum to obtain metallic bismuth with a purity of 4N; (2) grinding and sieving the 4N purity metallic bismuth obtained by slagging in step (1), and then mixing it with sulfate accounting for 1 / 2 to 2 / 3 of the total amount of sulfate and performing two-stage vacuum distillation; (3) In step (2), two-stage vacuum distillation is performed simultaneously with graded condensation to obtain high-purity metallic bismuth with a purity of 5N.

2. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: In step (1), the bismuth-containing raw material is refined bismuth with a purity of 2N to 3N.

3. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: In step (1), the temperature condition of the melt treatment is 900° C. to 1200° C., and the time condition of the melt treatment is 0.5 h to 2 h.

4. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: In step (1), the amount of phosphorus pentoxide used is 5% to 15% of the amount of the bismuth-containing raw material used.

5. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: In step (1), the amount of the sulfate is 5% to 15% of the amount of the bismuth-containing raw material.

6. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: The sulfate is sodium sulfate or sodium bisulfate.

7. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: In step (2), the grinding and screening specifically includes grinding through a 300-500 mesh sieve.

8. The method for preparing high-purity metallic bismuth according to claim 1, characterized in that: In step (2), the two-stage vacuum distillation is specifically as follows: first, placing metallic bismuth and sulfate in a vacuum furnace, evacuating the vacuum furnace once so that the residual pressure reaches 5Pa~10Pa, heating the vacuum furnace to 800°C~850°C, and distilling at constant temperature and pressure for 15min~30min, then heating to 850°C~950°C, and evacuating the vacuum furnace for a second time so that the residual pressure reaches 10Pa~15Pa, and continuing to distill at constant temperature and pressure for 30min~60min. After the distillation is completed, nitrogen is introduced into the vacuum furnace to normal pressure, and the temperature is lowered to room temperature.

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