What is Bismuth?
Element symbol Bi, grayish white with pink metal, belongs to group VA on the periodic table, atomic number 83, atomic weight 208
980, rhombic crystal, common valence is +3
People used bismuth in Greece and Rome, but they didn’t consider it an element.
The name of bismuth comes from the German Wismut (white metal).
In the sixteenth century, Agricola (G
Agricola) Latinized this name as beemutum, but for a long time since then, bismuth was still confused with lead, tin, silver, and antimony Wait
It was in 1753 when C
Geoffroy and T.
Bergman determined that bismuth was a new element
The bismuth industry took shape in the early 1860s; around 1930, due to the development of new uses of bismuth in fusible alloys and medicines, bismuth production developed rapidly
There is a small amount of elemental bismuth in nature.
Bismuth minerals include bismutite ( Bi 2 S 3 ), bismutite ( Bi 2 O 3 or bismuth Hua), bismutite ( n Bi 2 O 3 m CO 2 H 2 O), copper bismuth ore ( 3Cu 2 S 4Bi 2 S 3 ), galena (2PbS Bi 2 S 3 ), etc.
The main industrial resource is bismutite, which often coexists with lead, copper, tin, antimony, tungsten, molybdenum and other minerals.
The world’s main sources of bismuth ore are found in Peru and Mexico.
China’s main bismuth ore producing areas are in Jiangxi, Hunan, Guangdong, Yunnan and other provinces.
Among the raw materials for bismuth smelting in China, half are bismuth concentrates and half are by-products of lead, copper, tin and tungsten ore and smelting
Properties and uses: Bismuth is brittle and rich in luster
The volume of bismuth increases when it is suspected to be solidified and the expansion rate is 3.3%
Bismuth is the most diamagnetic metal, under the action of a magnetic field, the resistivity increases while the thermal conductivity decreases
Except for mercury, bismuth is the metal with the lowest thermal conductivity
Bismuth and its alloys have a thermoelectric effect
The selenium and tellurium compounds of bismuth have semiconducting properties.
Bismuth oxidizes slightly in moist air at room temperature and, when heated to the melting point, burns to produce bismuth trioxide (Bi 2 O 3 ).
Bismuth reacts slowly with hydrochloric acid, reacts with sulfuric acid to release SO2, and reacts with nitric acid to form nitrate.
Bismuth is mainly used in the preparation of castable alloys in metal form and is used in medicine in compound form.
The former has a melting point range of 47 to 262 °C, and the most commonly used are the binary, ternary, quaternary, and pentad alloys composed of bismuth and metals such as lead, tin, antimony, and indium.
By changing the percentage of these metals in the alloy, a number of alloys with different melting points and different physical properties can be obtained; These alloys are used in fire-extinguishing devices, such as temperature-sensitive components of automatic sprinklers and safety plugs for boilers and compressed air cylinders.
Welding, molten bath medium for heat treatment of metals, etc.
Bismuth alloy has the characteristic of not shrinking when condensed, and is used for casting impression-type and high-precision molds.
Bismuth and its alloys are often used as additives to cast iron, steel, and aluminum alloys to improve the cutting performance of the alloys.
A bismuth alloy containing 11% antimony is used to make infrared detectors
Bismuth tin and bismuth cadmium alloys are used as auxiliary electrodes of selenium rectifier
Using the characteristic of bismuth that the resistivity decreases sharply under the action of a magnetic field, a magnetometer is made.
Bismuth-manganese alloy can be used to make permanent magnet alloys
Bismuth has a small thermal neutron absorption cross section, a low melting point and a high boiling point, and can be used as a heat transfer medium for nuclear reactors.
Bismuth telluride (Bi 2 Te 3 ) is widely used in the manufacture of thermoelectric cooling elements and low-temperature thermoelectric power supplies.
BiSbTe 3 antimony telluride (BiSbTe 3 ) is used as a thermoelectric element for solar cells
Bismuth-silver-cesium alloy is used to make photoelectric amplifiers
Bismuth silver sulfide (BiAgS 2 ) is used in the manufacture of semiconductor instruments
Bismuth-cadmium temperature difference element is used in alarm device
The main physical properties of bismuth
Production and price In the late 1970s, the world’s annual production of bismuth ore (calculated as bismuth) was estimated to be 3
630 to 4
Peru is the country with the highest production of bismuth ore in the world, followed by Bolivia and Australia.
The country that consumes the most bismuth is the United States, it was 1093 tons in 1976 and 1
153 tons in 1979, depending mainly on imports
Among them, 25.5% is used for melting fusible alloys, 27% is used as metallurgical additives, 45.7% is used for pharmaceuticals, and about 1.8% is used for other purposes.
Bismuth prices with purity of 99.99% and 99.999% in 1976 were USD 16.52/kg and USD 17.62/kg respectively
In recent years, the annual production of bismuth in China is about 400 to 500 tons
Bismuth smelting is divided into two steps: roughing and refining.
Pyro-refining method of raw casting differs depending on the raw material
When bismuth sulfide concentrate, bismuth oxide and bismuth sulfide mixed ore, bismuth oxide slag and bismuth oxychloride are used as raw materials for bismuth smelting, the mixed smelting method is used and the appropriate amount of iron filings, pure iron, fluorite powder, powdered carbon, etc.
, in the reverberation furnace for mixing and smelting, raw bismuth is obtained and sent for refining
The refining method using calcium, magnesium, bismuth and slag produced in the pyrometallurgical lead refining process is as follows: the slag is first heated to sink the lead it contains
Continue heating the slag, and after smelting, add lead chloride or introduce chlorine gas to remove calcium and magnesium to obtain a bismuth-rich lead-bismuth alloy, which is then sent for refining.
Pyrorefining is generally divided into four steps: Elimination of arsenic, antimony, tellurium, etc.
by oxidation; Silver removal by adding zinc; Removal of lead and zinc by chlorination; High temperature dechlorination Refer to the figure on the next page for the fire refining process
Crude bismuth melts at 680-720°C and iron, arsenic, antimony, etc.
oxidize into dry slag
To reduce bismuth removal, sodium hydroxide is often used as a flux to melt dry slag and then remove it.
The explosion aims to further oxidize arsenic, antimony, tellurium, iron, tin and other impurities, so that arsenic and antimony form As 2 O 3 and Sb 2 O 3 , most of which they volatilize
Silver in crude bismuth can be removed by adding zinc
The remaining zinc, lead and copper in crude bismuth are removed by the introduction of chlorine gas at 350-500 °C
Finally, under the cover of sodium hydroxide and potassium nitrate molten salt, the cutting tree is dechlorinated, and the purity of the obtained bismuth ingot can reach 99.99%
If raw material contains high lead content, chlorinate and remove lead before removing silver
Bismuth wet extraction “Bismuth-containing raw materials are leached with hydrochloric acid (see leaching), and the leaching solution is diluted with a large amount of water to hydrolyze bismuth chloride into bismuth oxychloride precipitation.
If you need to improve the purity, you can repeat the operation several times
Bismuth oxychloride can be replaced and precipitated with iron powder or zinc powder in the presence of hydrochloric acid to prepare sponge bismuth; or it can be mixed with soda ash and carbon and then melted and reduced to directly prepare crude bismuth
China selects bismuth ore from tin ore and leaches it with hydrochloric acid
After the tin and arsenic are separated, the bismuth chloride solution is subjected to diaphragm electrolysis to produce sponge bismuth.
Sponge bismuth is an intermediate product and must be refined
Electrolytic refining is very effective in separating a large amount of silver, but when refining high purity bismuth, it still needs to be combined with fire refining