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Antimony is cla metalloid element having common oxidation states of 5+ and 3+. It is a lustrous silvery-white solid, which is quite brittle and exhibits a flaky texture. Antimony is classified as a critical/strategic metal. Stibnite, jamesonite, and antimony-gold ores are the most common sources of antimonyssified as a critical/strategic metal. Its primary production is predominated by China via pyrometallurgical routes such as volatilization roasting—reduction smelting or direct reduction smelting.
- antimony
- critical metals
- extractive metallurgy
1. Introduction
Antimony is one of the medieval metals, and antimony-containing castings were found from 4000 BC in China. Metallic antimony was mistaken for stibnite until the early 17th century (1604) when Basilius Valentinus published a book titled “The Triumphal Chariot of Antimony” explaining antimony properties, applications, and winning methods. This is renowned as the beginning of human knowledge about antimony. Later in 1707, the French chemist Lémery published his “Traité de l’Antimoine”, which led to considerable acclaim for antimony.
The English word “antimony” is derived from the Greek words: anti [opposed] and monos [solitude], which means a metal that rarely occurs alone [1]. Native antimony has a strong affinity for sulfur and other metals such as copper, lead, and gold [2][3][2,3]. As a result, the development of extraction methods was very slow until the Japanese war in 1905. Its ability as an alloying element for lead, which could be used in the production of ammunitions that can penetrate armor plates, resulted in its wide usage during World Wars I and II, at which time China was the major producer by 30,000 to 40,000 tons of antimony per year [1]. Antimony use in military applications led to its classification as an important member of the “Strategic Metals” [4].
Antimony is a metalloid element having common oxidation states of 5+ and 3+. It is a lustrous silvery-white solid, which is quite brittle and exhibits a flaky texture. Natural antimony consists of a mixture of two stable isotopes that have atomic weights of 121 (57.25 wt%) and 123 (42.75 wt%); more than thirty radioactive isotopes of antimony are also known [3]. Table 1 summarizes the important physicochemical and mechanical properties of antimony.
Table 1.
Physicochemical and mechanical properties of antimony.
| Properties/Characteristics | Value | Unit | |
|---|---|---|---|
| Sb | 2 | ||
| PbO (wt%) | |||
| <0.25 | |||
| >0.25 and <0.3 | ≥0.3 and <2.5 | ||
| As2O3 (wt%) | <0.1 | <0.1 | <0.1 |
| O | 4 | ||
| Other impurities (wt%) | |||
| <1.75 | |||
| ≤2.6 | |||
| ≤0.4 | |||
| Atomic number | 51 | N/A | |
| Name(s) |
|
|
|
| Atomic weight | 121.76 | u | |
| Melting point | 630.5 | °C | |
| Boiling point (at 101.3 kPa) | 1325 | °C | |
| Density (at 20 °C) | 6.688 | g/cm3 | |
| Tensile strength | 10.8 | N/mm2 | |
| Mohs hardness | 3.0-3.5 | N/A |
ATO is mainly used in flame-retardants, in conjunction with halogens for sealants, plastics, paints, rubber, fiberglass, aircraft, and automotive seat covers, children’s clothing, textile goods, and electronic equipment [6]. Antimony trioxide is also used as a catalyst for polyethylene terephthalate (PET) production, polyester resins, phosphorescent agent in fluorescent light bulbs, and as an opacifier for porcelain [10].
Antimony pentoxide (Sb2O5) and sodium antimonate (NaSb(OH)6) are also used in flame retardants. Another application for sodium antimonate is in decolorizing and refining agents for optical and cathode ray tube glasses. Antimony trisulfide (Sb2S3) is used in the liners of automobile brakes and safety match compositions. Antimony pentasulfide (Sb2S5) is used as a vulcanizing agent in the production of red rubber [11][12][11,12]. The intermetallic compounds AsSb, GaSb, and InSb have found some applications in electronics as semiconductors [5][13][14][5,13,14].
3. Mineralogy of Antimony Ores
Antimony is not an abundant element, averaging ~0.2 g/tonne in the earth’s crust, but it can be found in more than 100 different minerals [15]. Anderson [4] and Habashi [16] have provided detailed information on the occurrence, geology, and mineralogy of the antimony ores. In the current Tpaper, therefore, only antimony-containing minerals that are of higher industrial significance are listed in Table 3. These minerals have been categorized into three major groups, sulfides, oxides, and mixed minerals.
Table 3.
Minerals of antimony with industrial significance.
| Mineral | Chemical Formula | Sb (wt%) | |
|---|---|---|---|
| Sulfides | Stibnite | Sb2S3 | 71.7 |
| |||
].
According to U.S. Geological Survey 2022, almost 90% of the antimony mine production currently comes from three countries of China, Russia, and Tajikistan. The remaining 10% comes from other countries [21], shown in Table 5.
Secondary production accounts for ~20% of the total antimony production, and mainly originates from the recycling of lead-acid batteries and antimony-containing residues from lead-, copper- and gold-smelting processes [4].
China dominates mining of the raw materials and production of major antimony-bearing products (trioxide and metal). Antimony production in China is mainly concentrated in Hunan, Guangxi, Guizhou, Yunnan, and Gansu provinces [19]. China strictly controls the export rates and can put pressure on the market, which has led to an uncertain situation regarding the antimony price and availability for the demand of the western countries. Binz and Friedrich [9] highlighted that this has been the main reason why the European Commission considered high supply risk and economic importance for antimony and listed it as one of the critical raw materials for the period 2015–2020. To manage the risk of dependence on foreign sources of antimony, the USA Government has stockpiled antimony for national defence purposes for several decades [3].
In addition to Europe and USA, Canada, Japan, and Australia also called antimony a critical metal due to its importance for transition to green energies (e.g., solar panels, windmills, and batteries), and the advance of the semiconductor industry and electronics [22][23][24][22,23,24].
Table 5.
Main producers of antimony in the world.
| Country | Mine Product. (t) [21] |
Reserves (×1000 t) [21] | Main Producers [4] | Product [4] | Total Production Capacity (×1000 t/y Sb) [4] | |||
|---|---|---|---|---|---|---|---|---|
| USA | NA | 60 | Amspec Chemical Corporation Laurel Industries Inc. Great Lakes Chemical (Anzon) United States Antimony Corporation Sunshine Mining and Refining |
|
Trioxide Trioxide Trioxide Metal, Trioxide, Na-antimonate Metal, Na-antimonate
|
15 12.5 6 1.5 1.5 |
|
|
| Tetrahedrite | ||||||||
| Cu | 6Sb | Melting point | 2S6 | 630 °C | 29.8 | |||
| 546–548 °C | ||||||||
| Australia | 3400 | 656 °C | 100 | 120–170 °C (decomposes to Sb2S | 3 and S) | 380 °C (decomposes) | 930 °C (decomposes to ATO and oxygen) |
|
| Jamesonite | Pb4FeSb6 | Boiling point | S14 | 35.4 | ||||
| 1635 °C | 1000–1150 °C | 1425 °C (sublimes) | N/A | N/A | N/A |
4. Antimony Production
In the ’70s and ’80s, Canada, Malaysia, Thailand, Japan, Italy, Spain, former Yugoslavia, and Czechoslovakia were among the main producers of antimony, but their production was ceased completely or reduced significantly. Canada, for example, was used to produce ~3000 tonnes/year of antimony in the late ’70s, mainly using ores extracted from Consolidated Durham Mines and Resources Ltd., in New Brunswick, Canada. However, the mine operation was stopped in 1981. Teck’s lead-smelter in Trail, British Columbia, was also used to produce antimony as a by-product, in small quantities [2], but the antimony metal is no longer among product lists of the operation [20
| Bolivia | |||||
| 2700 | 310 | Enal | Trioxide | 9.3 | |
| Zinckenite | PbSb2 | ||||
| Burma | S4 | 200042.1 | |||
| 140 | Oxides | Senarmontite (cubic) | |||
| Canada | Sb | 2O3 | 83.5 | ||
| Valentinite (rhombohedral) | Sb2O3 | Modulus of elasticity | 566 | N/mm2 | |
| Surface tension of solid (at 432 °C) | 317.2 | mN/m | |||
| Surface tension of liquid (at 1200 °C) | 255 | mN/m | |||
| Crystal structure | Rhombohedral | N/A | |||
| Lattice constant | a = 0.437, c = 1.1273 | nm | |||
| Latent heat of fusion | 10.49 | kJ/mol | |||
| Latent heat of evaporation | 195.10 | kJ/mol | |||
| Coefficient of linear expansion (at 20 °C) | 8-11 | µm/m-°C | |||
| Electrical resistivity (at 0 °C) | 37 | µΩ.cm | |||
| Molar heat capacity of solid (at 630.5 °C) | 30.446 | J/mol-K | |||
| Molar heat capacity of liquid (at 630.5 °C) | 31.401 | J/mol-K | |||
| Thermal conductivity (at 0 °C) | 25.9 | W/m-K |
2. Applications
Metallic antimony is brittle and has limited workability, but when alloyed in small amounts with other metals, it typically increases the hardness, resistance to wear, and improves castability. Historical applications of antimony included medicine and cosmetics (in powder form), battery grids, anti-friction bearing metals based on lead and tin, sheets and pipes [2], and type metals (60% Pb, ~25% Sb, and ~15% Sn), which is no longer the case because of off-set printing processes [5].
In World War II, antimony trichloride (SbCl3) was widely used in tents and vehicle covers. In a fire, antimony and chlorine recombine to form unstable compounds that consume oxygen in the environment, leading to the flame suffocation. Later, antimony was significantly used in lead-acid batteries in automobiles to harden the lead from which the electrodes (grids) are made of. The hard lead contains 15–25% antimony [4]. Lead-antimony alloys are used in starting-lighting-ignition batteries, ammunition, corrosion-resistant pumps and pipes, tank linings, and antifriction bearings [6]. High-purity antimony is used in semi-conductors, infrared detectors, and diodes. Antimony is also used in nuclear reactors together with beryllium [7] and pharmaceutical industry. Organic antimony compounds, such as antiprotozoal drugs, are used for certain parasitic diseases [6].
Antimony trioxide (ATO or antimony white) is now the most important antimony compound. Commercial grade is typically a fine and white powder, containing between 99.2% and 99.5% Sb2O3 and varying levels of other impurities (such as arsenic, lead, and iron) depending on the targeted application [4]. International Antimony Association provides the specifications required for the antimony trioxide products [8], provided in Table 2.
| Physical Form | Powder | ||
| Particle size (µm) | 0.2–44 | ||
| Constituents | Low PbO | Medium PbO | High PbO |
| Sb2O3 (wt%) | >98 | >97.1 and ≤99.6 | >97 and ≤99.6 |
| 83.5 | |||
| Cervantite (orthorhombic) | |||
| Sb | 2O4/Sb2O3⋅Sb2O5 | 79.2 | |
| Stibiconite (antimony hydroxides) | Sb2O4⋅H2O | 74.8 | |
| Mixed | Kermesite | 2Sb2S3⋅Sb2O3 | 83.5 |
Stibnite, jamesonite, and antimony-gold ores are the most common sources of antimony. The two formers are typically found with lead ores in nature [17]. Antimony-gold ores mostly consist of gold and antimony sulfide intergrowth and aurostibite (AuSb2) [18]. Russia, Bolivia, Australia, and China have gold-antimony ore deposits [19]. Copper-rich sulfidic ores (e.g., tetrahedrite) have also received significant attention in recent years due to the depletion of richer ore bodies.
The most significant antimony-containing components that are present in different ore bodies, and intermediate or final products of the antimony production are listed in Table 4.
Table 4.
Major antimony-containing compounds.
| Element/ Compound |
Sb | Sb2S3 | Sb2O3 | Sb2S5 | Sb2O5 |
|---|---|---|---|---|---|
| 2 | |||||
| 78 | |||||
| China | 60,000 | 480 | Hsikwangshan Mining Administration Dachang Mining Administration Guzhou Dushan Dongfeng Hubei Chongyang Hunan Chenzhou Mining Co, Ltd., Guangxi China Tin Group Limited Yunnan Muli antimony industry Co., Ltd. Xikuangshan Flash-Antimony Industry Limited |
Metal, Oxides, Na-antimonate Metal Metal, Trioxide Metal, Trioxide N/A N/A N/A Metal [25] |
30 N/A 10 4 4 N/A N/A N/A 40 |
| Guatemala | 80 | NA | |||
| Iran | 400 | NA | |||
| Kazakhstan | 100 | NA | |||
| Kyrgyzstan | NA | 260 | Kadamjaisk Antimony Combine | Metal, Trioxide | 20 |
| Mexico | 700 | 18 | |||
| Pakistan | 20 | 26 | |||
| Russia (Recoverable) | 25,000 | 350 | |||
| Tajikistan | 13,000 | 50 | |||
| Turkey | 1300 | 100 | |||
| Vietnam | 400 | NA | |||
| France | NA | Société Industrielle et Chimique de L’Aisne Mines de la Lucette AMG antimony [26] |
Metal, Trioxide Metal Trioxide |
12 9.5 10 |
|
| Belgium | NA | Campine Union Minière/Umicore [5] |
Trioxide Na-antimonate |
10 6 |
|
| Oman | Strategic and Precious Metals Processing (SPMP) | Metal, Trioxide | 20 [27] | ||
| World Total (Rounded) | 110,000 | >2000 |
It has been projected that extractable global resources of antimony will be exhausted by 2050, assuming an increase in the extraction rate by 3% per year [10][28][10,28]. Therefore, significant research effort has been devoted to developing methods for recovery of antimony from secondary raw materials [13][29][13,29], but these contentsurrent review article only focuses on primary pyrometallurgical production routes.
Generally, the production of antimony can be via pyro- or hydro-metallurgical processes. More recently, bio-hydrometallurgical processes have also been proposed, but still at lab-scale [30][31][30,31]. Similar to lead, copper, and tin production, antimony is mainly extracted by pyrometallurgical methods. Hydrometallurgical routes, which are typically used for low-grade ores (<5% Sb) [32][33][32,33] and to minimize losses of precious metals (PMs), can be classified into two groups of alkaline leaching and acid leaching, followed by the electrodeposition of metallic antimony at the cathode or hydrolysis with NaOH or NaH4OH to produce Sb2O3 [32][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][32,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48]. An example is a process used at Sunshine Mining Co (between Kellogg and Wallace, ID, USA) [49]. Furthermore, the production of antimony based on electrolysis of Sb2S3 [50] have been recently developed in a lab scale to mitigate SO2 pollution and CO2 emissions. More specifically, molten salt electrolysis of antimony smelting is a new development in the direction of antimony clean production [51][52][51,52].
