Arsen
As • Atomic Number 33
Arsenic
Arsenic is located in the nitrogen group of the periodic table. It is classified as a metalloid. Arsenic rarely occurs in its native elemental form and is most commonly found in sulfidic ores such as realgar and orpiment. In its most stable elemental form, arsenic is a steel-gray, brittle solid with low thermal and electrical conductivity.
Arsenic is often associated with its use as a poison. The compound arsenite is water-soluble, odorless, tasteless, and lethal—traits that led to its use as a murder weapon in ancient times.
In its elemental form, arsenic is carcinogenic. The maximum concentration considered safe in drinking water is 0.01 ppm. The higher average content in seawater (approximately 0.024 ppm) leads to bioaccumulation in shellfish and crustaceans.
Arsenic can enter the environment in various ways and contaminate groundwater and drinking water, posing a growing global concern due to its toxicity.
Arsenic also plays a significant role in semiconductor manufacturing and as an alloying element. Despite its toxicity, arsenic compounds are still used in medical treatments.
The leading arsenic-producing countries are Peru, China, and Morocco.
The largest arsenic mine in the world is Real de Ángeles in Mexico, where arsenic is obtained as a by-product of zinc mining. Another major producer is the Yongzhou Mine in China.
Key companies involved in arsenic production include Yunnan Luoping Zinc & Electricity (China), Codelco (Chile), and Managem (Morocco).
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History
Historically, arsenic-containing minerals such as realgar, orpiment, and arsenolite (arsenic trioxide) have been known since ancient times. Therapeutic preparations of realgar and orpiment have been used in Traditional Chinese Medicinefor at least 2,400 years, for instance, to treat parasites or neurodermatitis. Records from ancient Greece and Rome also describe the use of arsenic compounds to treat asthma and skin conditions.
The compound arsenite was already used in antiquity as a poison. One of the first documented arsenic poisonings is attributed to Nero. From the 17th century onwards, poisonings became increasingly common, only declining after James Marsh developed a reliable method for detecting arsenic in tissue in 1836.
The discovery of elemental arsenic is often credited to Albertus Magnus, a bishop from Regensburg, although it was apothecary Johann Schroeder who first isolated arsenic using charcoal in 1649.
In the late 18th century, Thomas Fowler developed a medicinal tincture known as Fowler’s solution, which was used as a general remedy for about 150 years. One of the most well-known arsenic-based drugs was arsphenamine, introduced by Hoechst in 1910 for the treatment of syphilis. For the parasitic disease sleeping sickness, Tryparsamide was used successfully from 1922, later replaced by melarsoprol, another arsenic-based compound. Despite its high toxicity and potentially lethal side effects, melarsoprol is still in use today due to a lack of alternatives.
Since 2003, an arsenite-based drug has been approved in the USA and several European countries for treating acute promyelocytic leukemia (APL), a rare form of leukemia that progresses rapidly and is fatal if untreated.
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Application
In 2024, an estimated 58,000 tons of arsenic trioxide were produced worldwide.
The most important commercial compounds include arsenic oxides, also referred to as “white arsenic.” Arsenic oxides are the starting materials for most other arsenic compounds.
The majority of arsenic is used as arsenic trioxide and diarsenic pentoxide, which are key components in numerous herbicides and pesticides. In the USA, large quantities of arsenic trioxide are used to produce arsenic acid, which is an important ingredient in the manufacture of wood preservatives for non-private use, such as for light poles, maritime applications, and retaining walls.
Due to environmental risks, the use of arsenic-containing herbicides, pesticides, and wood preservatives is declining worldwide. In the EU, for example, their use is heavily restricted due to numerous bans and therefore plays only a minor role.
The global consumption of metallic arsenic is relatively low, amounting to only a few hundred tons per year. The most important application of high-purity arsenic metal lies in the semiconductor industry, where it is used with silicon and germanium as well as in the form of gallium arsenide (GaAs) for diodes, lasers, and transistors.
An important manufacturer of high-purity arsenic is the company PPM High Purity Metals from Saxony-Anhalt, which is owned by the wafer manufacturer Freiberger Compound Materials (FCM). However, the arsenic consumption for these applications accounts for only 0.1 percent of the EU’s demand.
Seventy percent of the EU’s arsenic consumption goes into zinc production, 18 percent into the glass industry.
Arsenic is also a component of alloys. In lead alloys, arsenic improves flow properties, hardens the material, and increases corrosion resistance. This is very important for the production of lead-based batteries and accumulators, but also for lead ammunition.
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Occurence, Mining and Extraction
Although arsenic can rarely occur in its native form as smaltite or flystone, it is mostly found in sulfide ores such as realgar and orpiment.
The leading producing country is Peru, followed by China. Morocco ranks a distant third. 95 percent of the world’s production comes from these three countries.
Arsenic is mainly produced as a by-product during the processing of various ores but is especially associated with copper-gold ores (Chile, Canada). It is also generated as a by-product during the roasting of copper, lead, and certain other metal ores as well as during the roasting of arsenopyrite and arsenic sulfide ores.
Among the largest arsenic producers are Yunnan Copper and Hunan Gold Group in China, the Managem Group in Morocco, KazZinc in Kazakhstan, the Ural Mining and Metallurgical Company in Russia, and Umicore in Belgium.
The most important producer of arsenic trioxide in the EU is Belgium. The country covers 67 percent of the EU’s arsenic demand. In 2022, Belgium produced 1000 tons of arsenic oxide.
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Substitution
Many semiconductor manufacturers are switching from gallium arsenide (GaAs) and silicon-based laterally diffused metal-oxide-semiconductor field-effect transistors to those with gallium nitride.
Indium phosphide components can replace GaAs-based infrared laser diodes in certain wavelength applications. Helium-neon lasers compete with GaAs in visible laser diode applications.
Silicon is the main competitor to GaAs in solar cell applications.
In many defense industry applications, GaAs-based integrated circuits are used because of their unique properties, and there are no effective alternatives in these applications.
In heterojunction bipolar transistors, GaAs is replaced by silicon-germanium in some applications.
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