CN116005008A

CN116005008A - Bismuth purifying method

Info

Publication number: CN116005008A
Application number: CN202310023629.7A
Authority: CN
Inventors: 赵科湘; 谢宗华
Original assignee: Zhuzhou Keneng New Material Co ltd
Current assignee: Zhuzhou Keneng New Material Co ltd
Priority date: 2023-01-09
Filing date: 2023-01-09
Publication date: 2023-04-25

Abstract

The invention discloses a method for purifying bismuth, which comprises the steps of burning crude bismuth and oxygen to obtain beta-bismuth oxide, reacting the beta-bismuth oxide with acetic acid to obtain bismuth acetate I, heating and dissolving the bismuth acetate I by nitric acid, cooling and crystallizing to obtain bismuth nitrate crystals, reacting the bismuth nitrate crystals with acetic acid to obtain bismuth acetate II, and calcining the bismuth acetate II to obtain the metal bismuth with more than 6N level. The method has the advantages of simple process, simple and convenient operation, low energy consumption, high efficiency, environmental friendliness, suitability for large-scale production, capability of purifying 3N-4N crude bismuth to more than 6N grade high-purity bismuth without passing through high pressure and other additives, and capability of meeting different application requirements.

Description

Bismuth purifying method

Technical Field

The invention relates to a metal purification method, in particular to a method for purifying metal bismuth, and belongs to the technical field of metal purification.

Background

Bismuth is stable in chemical property, exists in the form of free metal and mineral in nature, and has higher and higher purity requirements along with wider and wider application of the metal bismuth. The high-purity bismuth refers to bismuth with purity of more than or equal to 99.999 percent, and is mainly applied to medical supplies, cosmetics, industrial pigments, catalysts, flame retardants, electronic ceramics, metallurgical additives, semiconductors, nuclear reactions and the like. The bismuth industry in China is late in development and start, and is mainly used for producing 99.9-99.99% of refined bismuth, and a high-purity bismuth production technology with stable process is lacked.

There are many methods for purifying high purity bismuth, of which vacuum distillation and zone melting are the most industrially valuable. Zone melting is based on the segregation phenomenon in metallurgy: impurities in the molten bismuth are firstly condensed and separated out at the edge of the container compared with bismuth during cooling and crystallization, so that the impurities in the center of a bismuth ingot are less than the impurities at the edge, and the purification purpose is achieved through repeated operation for many times; the vacuum distillation is to introduce chlorine outside the vacuum furnace to remove lead, then to let the melted bismuth pass through a quartz tube to remove antimony, and then to carry out vacuum distillation in the vacuum furnace. The literature ("research on new technology for preparing pentahedronate high purity bismuth by adding a lead removing agent through vacuum distillation", xiong Lizhi, university of Kunming, 2003) adopts a method combining vacuum distillation and zone smelting, but the production process of the method is very complicated, the efficiency is poor, the cost is high, and the pollution is easy to influence the purity of bismuth.

Disclosure of Invention

Aiming at the defects existing in the prior art, the invention aims to provide a method for purifying bismuth, which has the advantages of simple process, mild operation condition, low energy consumption and high efficiency, and can purify 3N-4N crude bismuth into high-purity bismuth with more than 6N level.

In order to achieve the technical object, the present invention provides a method for purifying bismuth, comprising the steps of:

1) The crude bismuth and oxygen are combusted to obtain beta-bismuth oxide;

2) Reacting beta-bismuth oxide with acetic acid to obtain bismuth acetate I;

3) Heating and dissolving bismuth acetate I by nitric acid, and cooling and crystallizing to obtain bismuth nitrate crystals;

4) Reacting bismuth nitrate crystals with acetic acid to obtain bismuth acetate II;

5) Calcining bismuth acetate II to obtain the metal bismuth with the purity of more than 6N.

According to the technical scheme, 3N (99.9%) to 4N (99.99%) crude bismuth is taken as a raw material, impurities in the crude bismuth can be deeply removed through high-temperature combustion, precipitation, crystallization, reprecipitation, calcination and other combined processes, and finally the high-purity bismuth with more than 6N grade is obtained. According to the technical scheme, the high-temperature combustion method is adopted to selectively oxidize the metal bismuth to generate beta-bismuth oxide which is easy to react with acetic acid, so that impurities with lower boiling points such As As, zn and the like in the metal bismuth are volatilized and removed in a high-temperature combustion process. The reaction of acetic acid and beta-bismuth oxide can make Fe, ag, pb, ni and other impurities easy to react with acetic acid dissolve in acetic acid in the reaction process, so that the impurity content in bismuth acetate is reduced to below 0.5ppm, most of impurities in crude bismuth can be removed in the process, the purity of the obtained bismuth acetate can reach 5N (99.999%), and the process does not need high pressure and other additives. The 5N-grade bismuth acetate is dissolved and crystallized by nitric acid, a small amount of impurities are removed, and then the bismuth acetate is converted into bismuth acetate, and the purity of the bismuth acetate is improved to 6N (99.9999%). The 6N grade bismuth acetate is directly calcined at low temperature and pyrolyzed into 6N (99.9999%) grade high purity bismuth.

As a preferred embodiment, the crude bismuth is in the order of 3N (99.9%) to 4N (99.99%).

As a preferred embodiment, the oxygen is 3N (99.9%) or more. The metallic bismuth of 3N-4N limits the utilization range of bismuth in industry, and the high-purity oxygen content is more favorable for generating the high-purity beta-bismuth oxide.

In the step 1), the crude bismuth is heated to 1150-1250 ℃ and then oxygen is introduced to contact the bismuth for combustion. At lower temperatures, bismuth cannot undergo rapid oxidation, and increasing the temperature above 1250 ℃ requires more electricity to be consumed and the reaction rate is not significantly increased.

In a preferred scheme, in the step 2), the mass percentage concentration of the acetic acid is 50-100%, and the mass ratio of the acetic acid to the beta-bismuth oxide is 1.5-2:1. The acetic acid is easy to waste due to the too high acetic acid proportion, and the incomplete reaction phenomenon can occur due to the too low acetic acid proportion, so that the impurity removal effect is poor.

As a preferable scheme, in the step 3), the mass percentage concentration of the nitric acid is 68-75%, and the mass ratio of the nitric acid to the bismuth acetate I is 1:5-7.

As a preferable embodiment, in the step 3), the temperature of the heated dissolution is 50 to 100 ℃.

As a preferable mode, in the step 3), the temperature of the cooling crystallization is-10 ℃ to 0 ℃. The crystallization temperature can ensure that the bismuth nitrate has high crystallization rate and impurities are left in the solution at the same time, and if the temperature is too high, the crystallization efficiency is poor; if the temperature is too low, the impurity removing effect is lowered.

In a preferred scheme, in the step 4), the mass percentage concentration of the acetic acid is 80-100%, and the mass ratio of the acetic acid to bismuth nitrate crystals is 1:0.6-1.0.

As a preferable scheme, in the step 5), the calcining temperature is 400-600 ℃ and the heat preservation time is 1-3 hours. Too low a calcination temperature may result in incomplete decomposition of bismuth II acetate, while too high a calcination temperature may result in reoxidation of the resultant metallic bismuth.

The invention provides a method for purifying bismuth, which comprises the following specific steps:

1) Placing the crude metal bismuth into a silicon carbide crucible, heating to 1150-1250 ℃ by high-frequency electromagnetic heating, introducing oxygen into the crucible to burn and oxidize the metal bismuth, and collecting a product beta-bismuth oxide;

2) Stirring beta-bismuth oxide and acetic acid with the mass concentration of 50-100% for reaction according to the mass ratio of 1:1.5-2, washing a solid product with ultrapure water, and filtering to obtain bismuth acetate I;

3) Bismuth acetate I and nitric acid with the mass concentration of 68-75% are mixed according to the mass ratio of 5-7: 1 heating to 50-100 ℃ to dissolve completely, cooling to-10-0 ℃ to crystallize, filtering and recovering the crystal to obtain bismuth nitrate crystal;

4) Reacting bismuth nitrate crystals with acetic acid with the mass percentage concentration of 80-100% according to the mass ratio of 0.6-1.0:1 to obtain bismuth acetate II;

5) Washing bismuth acetate II with ultrapure water, filtering, and calcining at 400-600 ℃ for 1-3 hours to obtain bismuth with more than 6N grade.

Compared with the prior art, the technical scheme of the invention has the beneficial technical effects that:

1. the method for purifying bismuth provided by the invention has the advantages of simple process, simple and convenient operation, low energy consumption, higher efficiency, environmental friendliness and suitability for large-scale production.

2. The method for purifying bismuth provided by the invention can directly purify 3N-4N crude bismuth to high-purity bismuth above 6N without high pressure and other additives, thereby meeting different application requirements.

Detailed Description

The following examples are intended to further illustrate the present invention and are not intended to limit the scope of the claims.

The calcination crucible used in the following examples is made of isostatic high-purity graphite, the beaker used is made of high-purity polytetrafluoroethylene, and the purification steps are carried out in a hundred thousand-level clean workshop, and bismuth purity detection equipment is an inductively coupled plasma mass spectrometer (ICP-MS) and an inductively coupled plasma emission spectrometer (ICP-OES).

In the following examples, nitric acid and acetic acid were purified and used again.

Example 1

Adding crude bismuth with the bismuth content of 3N (99.9%) into a silicon carbide ink crucible, heating to 1230 ℃, introducing 3N pure oxygen to burn the bismuth, and collecting a combustion product, namely beta-bismuth oxide, wherein the weight ratio of the beta-bismuth oxide to acetic acid is 1:1.6, starting stirring until the mass concentration of the acetic acid is 100%, converting all the orange bismuth oxide into white bismuth acetate, washing and filtering the bismuth acetate with pure water, heating the bismuth acetate to 60 ℃ for dissolution after the bismuth acetate is washed with pure water (the nitric acid concentration is 70% and the mass ratio of the bismuth acetate to the nitric acid is 5:1), heating the solution until bismuth nitrate crystal solids appear on the surface of the solution after the solution is clarified, stopping heating, cooling to normal temperature, putting the solution into a freezer, adjusting the temperature to-5 ℃ for crystallization, directly filtering the solution after all the solution is crystallized, and washing the solution with a small amount of ultrapure water. Bismuth nitrate crystals and acetic acid with the mass concentration of 100% are mixed and stirred according to the mass ratio of 0.7:1 to carry out precipitation reaction for 0.5 hour, so that the bismuth nitrate crystals are converted into white high-purity bismuth acetate. The white high-purity bismuth acetate is washed by pure water, filtered and dried, and the dried bismuth acetate is contained in a graphite crucible for 2 hours at 500 ℃ to obtain 6N (99.9999%) bismuth.

Example 2

Adding crude bismuth with the bismuth content of 4N (99.99%) into a silicon carbide ink crucible, heating to 1190 ℃, introducing 3N pure oxygen to burn the bismuth, burning until the metallic bismuth is completely reacted, collecting the combustion product beta-bismuth oxide, wherein the weight ratio of the beta-bismuth oxide to acetic acid is 1:1.8, the mass concentration of acetic acid is 90%, starting stirring until all orange bismuth oxide is converted into white bismuth acetate, washing and filtering the bismuth acetate with pure water, heating to 80 ℃ to dissolve the bismuth acetate with nitric acid (the concentration of nitric acid is 70%, the mass ratio of the bismuth acetate to the nitric acid is 7:1), heating until bismuth nitrate crystal solids appear on the surface of the solution after the solution is clarified, stopping heating after the solution is cooled to normal temperature, placing the solution into a freezing cabinet, adjusting the temperature to be crystallized at-3 ℃, directly filtering after the solution is completely crystallized, and washing the solution with a small amount of ultrapure water. Bismuth nitrate crystals and acetic acid with the mass concentration of 90% are mixed and stirred according to the mass ratio of 0.8:1 to carry out precipitation reaction, and the bismuth nitrate crystals are precipitated for 0.5 hour, so that the bismuth nitrate crystals are converted into white high-purity bismuth acetate. The white high-purity bismuth acetate is washed by pure water, filtered and dried, and the dried bismuth acetate is contained in a graphite crucible for 2 hours at 520 ℃ to obtain 6N (99.9999%) bismuth.

Comparative example 1

Adding crude bismuth into a quartz crucible, heating and melting the crude bismuth, introducing chlorine to enable the lead to react with the chlorine to generate lead chloride, timely fishing out the lead chloride generated on the surface of molten metal, stopping introducing the chlorine to continuously heat to 500 ℃, adding metal zinc powder, continuously stirring for 2 hours, fishing out zinc-silver alloy scum on the surface, loading the crude bismuth after removing the lead and the silver into a quartz tube of a single tube furnace, heating to 900 ℃ for 1 hour, distilling to remove antimony and residual zinc, adding the obtained crude bismuth into a vacuum furnace, adjusting the vacuum degree to 1Pa, keeping the temperature to 950 ℃ for 4 hours, collecting distilled metal vapor, obtaining 5N metal bismuth, loading the purified metal bismuth into the high-purity graphite crucible, placing the high-purity graphite crucible into a zone furnace, adjusting the vacuum degree to 2Pa, and carrying out zone melting at 600 ℃, and finally obtaining 6N metal bismuth.

Table 1 comparison of impurity contents of purified bismuth by different methods

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Claims

1. A method for purifying bismuth, characterized in that: the method comprises the following steps:

1) The crude bismuth and oxygen are combusted to obtain beta-bismuth oxide;

2) Reacting beta-bismuth oxide with acetic acid to obtain bismuth acetate I;

2. A method of purifying bismuth as claimed in claim 1 wherein:

the coarse bismuth is 3N-4N grade;

the oxygen is above 3N grade.

3. A method of purifying bismuth as claimed in claim 1 wherein: in the step 1), in the combustion process, the crude bismuth is heated to 1150-1250 ℃ and then oxygen is introduced to contact the bismuth for combustion.

4. A method of purifying bismuth as claimed in claim 1 wherein: in the step 2), the mass percentage concentration of the acetic acid is 50-100%, and the mass ratio of the acetic acid to the beta-bismuth oxide is (1.5-2): 1.

5. A method of purifying bismuth as claimed in claim 1 wherein: in the step 3), the mass percentage concentration of the nitric acid is 68-75%, and the mass ratio of the nitric acid to the bismuth acetate I is 1 (5-7).

6. A method for purifying bismuth as claimed in claim 1 or 5 wherein: in the step 3), the temperature of the heating dissolution is 50-100 ℃.

7. A method of purifying bismuth as claimed in claim 1 wherein: in the step 3), the temperature of the cooling crystallization is-10 ℃ to 0 ℃.

8. A method of purifying bismuth as claimed in claim 1 wherein: in the step 4), the mass percentage concentration of the acetic acid is 80-100%, and the mass ratio of the acetic acid to bismuth nitrate crystals is 1:

(0.6～1.0)。

9. a method of purifying bismuth as claimed in claim 1 wherein: in the step 5), the calcining temperature is 400-600 ℃ and the heat preservation time is 1-3 hours.