Bismuth
Bismuth metal has been known from ancient times, although until the 18th century it was often confused with lead and tin, which share some physical properties. The etymology is uncertain, but possibly comes from Arabic bi ismid, meaning having the properties of antimony or German words weisse masse or wismuth ("white mass"), translated in the mid sixteenth century to New Latin bisemutum.
Bismuth has long been considered as the highest-atomic-mass element that is stable. However, it was recently discovered to be slightly radioactive: its only primordial isotope bismuth-209 alpha decays with a half life more than a billion times the estimated age of the universe.
Bismuth compounds account for about half the production of bismuth. They are used in cosmetics, pigments, and a few pharmaceuticals, notably Pepto-Bismol. Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead has become more apparent in recent years, there is an increasing use of bismuth alloys (presently about a third of bismuth production) as a replacement for lead.
Occurrence and production
In the Earth's crust, bismuth is about twice as abundant as gold. The most important ores of bismuth are bismuthinite and bismite. Native bismuth is known from Australia, Bolivia, and China.
According to the United States Geological Survey, the world mining production of bismuth in 2010 was 8,900 tonnes, with the major contributions from China (6,500 tonnes), Peru (1,100 tonnes) and Mexico (850 tonnes). The refinery production was 16,000 tonnes, of which China produced 13,000, Mexico 850 and Belgium 800 tonnes.
The difference between world bismuth mine and refinery production reflects bismuth's status as a byproduct of extraction of other metals such as lead, copper, tin, molybdenum and tungsten. Bismuth travels in crude lead bullion (which can contain up to 10% bismuth) through several stages of refining, until it is removed by the Kroll-Betterton process which separates the impurities as slag, or the electrolytic Betts process. Bismuth will behave similarly with another of its major metals, copper.
The raw bismuth metal from both processes contains still considerable amounts of other metals, foremost lead. By reacting the molten mixture with chlorine gas the metals are converted to their chlorides while bismuth remains unchanged. Impurities can also be removed by various other methods for example with fluxes and treatments yielding high-purity bismuth metal (over 99% Bi). World bismuth production from refineries is a more complete and reliable statistic.
Price
The price for pure bismuth metal has been relatively stable through most of the 20th century, except for a spike in the 1970s. Bismuth has always been produced mainly as a byproduct of lead refining, and thus the price, usually reflected the cost of recovery and the balance between production and demand.
Demand for bismuth was small prior to World War II and was pharmaceutical – bismuth compounds were used to treat such conditions as digestive disorders, sexually transmitted diseases and burns. Minor amounts of bismuth metal were consumed in fusible alloys for fire sprinkler systems and fuse wire. During World War II bismuth was considered a strategic material, used for solders, fusible alloys, medications and atomic research. To stabilize the market, the producers set the price at $1.25 per pound (2.75 $/kg) during the war and at $2.25 per pound (4.96 $/kg) from 1950 until 1964.
In the early 1970s, the price grew rapidly due to increasing demand for bismuth as a metallurgical additive to aluminium, iron and steel. This was followed by a decline owing to increased world production, stabilized consumption, and the recessions of 1980 and 1981–82. In 1984, the price began to climb as consumption increased worldwide, especially in the United States and Japan. In the early 1990s, research began on the evaluation of bismuth as a nontoxic replacement for lead in ceramic glazes, fishing sinkers, food-processing equipment, free-machining brasses for plumbing applications, lubricating greases, and shot for waterfowl hunting. Growth in these areas remained slow during the middle 1990s, in spite of the backing of lead replacement by the US Government, but intensified around 2005. This resulted in a rapid and continuing increase in price.
Recycling
Whereas bismuth is most available today as a byproduct, its sustainability is more dependent on recycling. Bismuth is mostly a byproduct of lead smelting, along with silver, zinc, antimony, and other metals, and also of tungsten production, along with molybdenum and tin, and also of copper production. Recycling bismuth is difficult in many of its end uses, primarily because of scattering.
Probably the easiest to recycle would be bismuth-containing fusible alloys in the form of larger objects, then larger soldered objects. Half of the world's solder consumption is in electronics (i.e., circuit boards). As the soldered objects get smaller or contain little solder or little bismuth, the recovery gets progressively more difficult and less economic, although solder with a higher silver content will be more worthwhile recovering. Next in recycling feasibility would be sizeable catalysts with a fair bismuth content, perhaps as bismuth phosphomolybdate, and then bismuth used in galvanizing and as a free-machining metallurgical additive.
Bismuth in uses where it is dispersed most widely include stomach medicines (bismuth subsalicylate), paints (bismuth vanadate) on a dry surface, pearlescent cosmetics (bismuth oxychloride), and bismuth-containing bullets that have been fired. The bismuth scattered in these uses is unrecoverable with present technology.
The most important sustainability fact about bismuth is its byproduct status, which can either improve sustainability (i.e., vanadium or manganese nodules) or, for bismuth from lead ore, constrain it; bismuth is constrained. The extent that the constraint on bismuth can be ameliorated or not is going to be tested by the future of the lead storage battery, since 90% of the world market for lead is in storage batteries for gasoline or diesel-powered motor vehicles.
The life-cycle assessment of bismuth will focus on solders, one of the major uses of bismuth, and the one with the most complete information. The average primary energy use for solders is around 200 MJ per kg, with the high-bismuth solder (58% Bi) only 20% of that value, and three low-bismuth solders (2% to 5% Bi) running very close to the average. The global warming potential averaged 10 to 14 kg carbon dioxide, with the high-bismuth solder about two-thirds of that and the low-bismuth solders about average. The acidification potential for the solders is around 0.9 to 1.1 kg sulfur dioxide equivalent, with the high-bismuth solder and one low-bismuth solder only one-tenth of the average and the other low-bismuth solders about average. There is very little life-cycle information on other bismuth alloys or compounds.
| Symbol | Bi | |
| Atomic Number | 83 | |
| Atomic Weight | 208.98037 | |
| Oxidation States | +3,+5 | |
| Electronegativity, Pauling | 2 | |
| State at RT | solid | |
| Melting Point, K | 544.5 | |
| Boiling Point, K | 1883 |
Harmful effects:
Bismuth is not known to be toxic.
Characteristics:
- Bismuth is a crystalline, brittle, metal. Lying on the right side of the periodic table, bismuth is the most naturally diamagnetic metal; this means it resists being magnetized and is repelled by a magnetic field.
- Bismuth also has unusually high electrical resistance for a metal. Its thermal conductivity is lower than any metal, except mercury.
- Bismuth has the unusual property that (like water) it expands as it freezes. Four other elements expand when they freeze: silicon, gallium, antimony and germanium.
Uses of Bismuth
- Bismuth is used in medicine (bismuth subnitrate and subcarbonate), cosmetics (bismuth oxychloride), low-melting alloys, fire detection/extinguishing systems, replacement for lead in shot and bullets (bismuth-tin alloy).
