Platinum group#Applications

Naturally occurring platinum and platinum-rich alloys were known by pre-Columbian Americans for many years.{{cite book| title = Discovery of the Elements | url = https://archive.org/details/discoveryofeleme0000week | url-access = registration |pages = 385–407 |author = Weeks, M. E. |year= 1968 |edition = 7 |publisher = Journal of Chemical Education| isbn = 0-8486-8579-2| oclc = 23991202}} However, even though the metal was used by pre-Columbian peoples, the first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger (1484–1558) as a description of a mysterious metal found in Central American mines between Darién (Panama) and Mexico ("up until now impossible to melt by any of the Spanish arts").

The name platinum is derived from the Spanish word platina ("little silver"), the name given to the metal by Spanish settlers in Colombia. They regarded platinum as an unwanted impurity in the silver they were mining.{{cite book |title = The Elements: Platinum |author = Woods, Ian |publisher = Benchmark Books |url=https://books.google.com/books?id=hy2WcbKpXSkC |year = 2004 |isbn = 978-0-7614-1550-3}}

By 1815, rhodium and palladium had been discovered by William Hyde Wollaston, and iridium and osmium by his close friend and collaborator Smithson Tennant.Platinum Metals Rev., 2003, 47, (4), 175. Bicentenary of Four Platinum Group Metals PART I: RHODIUM AND PALLADIUM – EVENTS SURROUNDING THEIR DISCOVERIES (W. P. Griffith)

File:National prototype kilogram K20 replica.jpg national prototype kilogram standard, made in 90% platinum, 10% iridium alloy]]

The platinum metals have many useful catalytic properties. They are highly resistant to wear and tarnish, making platinum, in particular, well suited for fine jewellery. Other distinctive properties include resistance to chemical attack, excellent high-temperature characteristics, high mechanical strength, good ductility, and stable electrical properties.{{cite journal|last=Hunt|first=L. B.|author2=Lever, F. M.|year=1969|title=Platinum Metals: A Survey of Productive Resources to industrial Uses|url=http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf|journal=Platinum Metals Review|volume=13|issue=4|pages=126–138|doi=10.1595/003214069X134126138 |access-date=2009-10-02}} Apart from their application in jewellery, platinum metals are also used in anticancer drugs, industries, dentistry, electronics, and vehicle exhaust catalysts (VECs).{{Cite journal |title=Platinum group elements in the environment and their health risk |first1=Khaiwal |last1=Ravindra |first2=László |last2=Bencs |first3=René |last3=Van Grieken |year=2004 |journal=Science of the Total Environment |volume=318 |issue=1–3 |pages=1–43 |doi=10.1016/S0048-9697(03)00372-3 |pmid=14654273 |bibcode=2004ScTEn.318....1R |hdl=2299/2030 |hdl-access=free }} VECs contain solid platinum (Pt), palladium (Pd), and rhodium (Rh) and are installed in the exhaust system of vehicles to reduce harmful emissions, such as carbon monoxide (CO), by converting them into less harmful emissions.{{Cite journal |title=Palladium release from catalytic converter materials induced by road de-icer components chloride and ferrocyanide |first1=Deborah M. |last1=Aruguete |first2=Adam |last2=Wallace |first3=Terry |last3=Blakney |first4=Rose |last4=Kerr |first5=Galen |last5=Gerber |first6=Jacob |last6=Ferko |date=2020 |journal=Chemosphere |volume=245 |pages=125578 |doi=10.1016/j.chemosphere.2019.125578 |pmid=31864058 |bibcode=2020Chmsp.24525578A |s2cid=209440501 }}

==Occurrence==

Generally, ultramafic and mafic igneous rocks have relatively high, and granites low, PGE trace content. Geochemically anomalous traces occur predominantly in chromian spinels and sulfides. Mafic and ultramafic igneous rocks host practically all primary PGM ore of the world. Mafic layered intrusions, including the Bushveld Complex, outweigh by far all other geological settings of platinum deposits.{{cite journal |last1=Buchanan |first1=D. L. |editor1-last=Cabri |editor1-first=L. J. |title=Geology of Platinum Group Elements |journal=CIM Special Volume 54: The Geology, Geochemistry, Mineralogy and Mineral Beneficiation of Platinum-group Elements |date=2002 |url=https://www.technology.matthey.com/article/47/2/59-60/ |publisher=Canadian Institute of Mining, Metallurgy and Petroleum |location=Montréal}}{{cite book |first=Walter L. |last=Pohl |title=Economic Geology : Principles and Practice |location=Oxford |publisher=Wiley-Blackwell |year=2011 |isbn=978-1-4443-3662-7 }}{{cite book |last1=Zereini |first1=Fathi |last2=Wiseman |first2=Clare L.S. |title=Platinum Metals in the Environment |date=2015 |publisher=Springer Professional |location=Berlin |url=https://www.springerprofessional.de/platinum-metals-in-the-environment/4376278}}{{cite journal |title=Ore Deposits of the Platinum-Group Elements |year=2008|doi=10.2113/GSELEMENTS.4.4.253|last1=Mungall|first1=J. E.|last2=Naldrett|first2=A. J.|journal=Elements|volume=4|issue=4|pages=253–258|bibcode=2008Eleme...4..253M }} Other economically significant PGE deposits include mafic intrusions related to flood basalts, and ultramafic complexes of the Alaska, Urals type.{{rp|230}}

Typical ores for PGMs contain ca. 10 g PGM/ton ore, thus the identity of the particular mineral is unknown.{{cite journal |last1=Bernardis |first1=F. L. |last2=Grant |first2=R. A. |last3=Sherrington |first3=D. C. |title=A review of methods of separation of the platinum-group metals through their chloro-complexes |journal=Reactive and Functional Polymers |year=2005 |volume=65 |issue= 3|pages=205–217 |doi=10.1016/j.reactfunctpolym.2005.05.011 |bibcode=2005RFPol..65..205B }}

Platinum can occur as a native metal, but it can also occur in various different minerals and alloys.{{Cite web|url=https://www.bgs.ac.uk/downloads/start.cfm?id=1401|title=Mineral Profile: Platinum|date=September 2009|website=British Geological Survey|access-date=6 February 2018}}{{Cite web|url=https://www.mindat.org/chemsearch.php?inc=Pt|title=Search Minerals By Chemistry - Platinum|website=www.mindat.org|access-date=2018-02-08}} That said, Sperrylite (platinum arsenide, PtAs₂) ore is by far the most significant source of this metal.{{Cite web|url=https://uwaterloo.ca/earth-sciences-museum/resources/detailed-rocks-and-minerals-articles/platinum|title=Platinum {{!}} Earth Sciences Museum {{!}} University of Waterloo|last=Feick|first=Kathy|website=University of Waterloo|date=28 February 2013 |access-date=6 February 2018}} A naturally occurring platinum-iridium alloy, platiniridium, is found in the mineral cooperite (platinum sulfide, PtS). Platinum in a native state, often accompanied by small amounts of other platinum metals, is found in alluvial and placer deposits in Colombia, Ontario, the Ural Mountains, and in certain western American states. Platinum is also produced commercially as a by-product of nickel ore processing. The huge quantities of nickel ore processed makes up for the fact that platinum makes up only two parts per million of the ore. South Africa, with vast platinum ore deposits in the Merensky Reef of the Bushveld complex, is the world's largest producer of platinum, followed by Russia.{{cite journal |doi = 10.1016/j.mineng.2004.04.001 |journal = Minerals Engineering |volume = 17 |year = 2004 |pages = 961–979 |title =Characterizing and recovering the platinum group minerals—a review |first = Z. |last = Xiao |author2=Laplante, A. R. |issue = 9–10|bibcode = 2004MiEng..17..961X }}{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/platinum/platimcs07.pdf |title=Platinum–Group Metals |publisher=U.S. Geological Survey, Mineral Commodity Summaries |date=January 2007 |access-date=2008-09-09}} Platinum and palladium are also mined commercially from the Stillwater igneous complex in Montana, USA. Leaders of primary platinum production are South Africa and Russia, followed by Canada, Zimbabwe and USA.{{cite journal |last1=Bardi |first1=Ugo |last2=Caporali |first2=Stefano |title=Precious Metals in Automotive Technology: An Unsolvable Depletion Problem? |journal=Minerals |date=2014 |volume=4 |issue=2 |pages=388–398 |doi=10.3390/min4020388 |bibcode=2014Mine....4..388B |doi-access=free |hdl=2158/1086074 |hdl-access=free }}

Osmiridium is a naturally occurring alloy of iridium and osmium found in platinum-bearing river sands in the Ural Mountains and in North and South America. Trace amounts of osmium also exist in nickel-bearing ores found in the Sudbury, Ontario, region along with other platinum group metals. Even though the quantity of platinum metals found in these ores is small, the large volume of nickel ores processed makes commercial recovery possible.{{cite book |title = Nature's Building Blocks: An A-Z Guide to the Elements |last = Emsley |first=J. |publisher = Oxford University Press |year = 2003 |location = Oxford, England, UK |isbn = 0-19-850340-7 |chapter = Iridium |pages=201–204 |chapter-url=https://books.google.com/books?id=j-Xu07p3cKwC&pg=PA202}}

Metallic iridium is found with platinum and other platinum group metals in alluvial deposits.{{cite web |url=https://www.samaterials.com/5-common-uses-of-iridium.html |title=5 Common Uses of Iridium |last=Trento |first=Chin |date=May 9, 2024 |website=Stanford Advanced Materials |access-date=Oct 1, 2024}} Naturally occurring iridium alloys include osmiridium and iridosmine, both of which are mixtures of iridium and osmium. It is recovered commercially as a by-product from nickel mining and processing.

Ruthenium is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario, and in pyroxenite deposits in South Africa.

The industrial extraction of rhodium is complex, because it occurs in ores mixed with other metals such as palladium, silver, platinum, and gold. It is found in platinum ores and obtained free as a white inert metal which is very difficult to fuse. Principal sources of this element are located in South Africa, Zimbabwe, in the river sands of the Ural Mountains, North and South America, and also in the copper-nickel sulfide mining area of the Sudbury Basin region. Although the quantity at Sudbury is very small, the large amount of nickel ore processed makes rhodium recovery cost effective. However, the annual world production in 2003 of this element is only 7 or 8 tons and there are very few rhodium minerals.{{cite web |publisher = Natural Resources Canada |title = Platinum Group Metals |first = Patrick |last = Chevalier |url = http://www.nrcan.gc.ca/mms-smm/busi-indu/cmy-amc/content/2004/71.pdf |access-date = 2008-10-17 |url-status = dead |archive-url = https://web.archive.org/web/20110811170221/http://www.nrcan.gc.ca/mms-smm/busi-indu/cmy-amc/content/2004/71.pdf |archive-date = 2011-08-11 }}

Palladium is preferentially hosted in sulfide minerals, primarily in pyrrhotite. Palladium is found as a free metal and alloyed with platinum and gold with platinum group metals in placer deposits of the Ural Mountains of Eurasia, Australia, Ethiopia, South and North America. However it is commercially produced from nickel-copper deposits found in South Africa and Ontario, Canada. The huge volume of nickel-copper ore processed makes this extraction profitable in spite of its low concentration in these ores.

File:PtMetalExtraction II.jpg

The production of individual platinum group metals normally starts from residues of the production of other metals with a mixture of several of those metals. Purification typically starts with the anode residues of gold, copper, or nickel production. This results in a very energy intensive extraction process, which leads to environmental consequences. Carbon dioxide emissions are expected to rise as a result of increased demand for platinum metals and there is likely to be expanded mining activity in the Bushveld Igneous Complex because of this. Further research is needed to determine the environmental impacts.{{cite web|url=https://www.researchgate.net/publication/257673542|title=Anthropogenic Platinum Enrichment in the Vicinity of Mines in the Bushveld Igneous Complex, South Africa|last=Sebastien|first=Rauch|date=November 2012|access-date=14 February 2020}} Classical purification methods exploit differences in chemical reactivity and solubility of several compounds of the metals under extraction.{{cite journal|last=Hunt|first=L. B.|author2=Lever, F. M.|year=1969|title=Platinum Metals: A Survey of Productive Resources to industrial Uses|url=http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf|journal=Platinum Metals Review|volume=13|issue=4|pages=126–138|doi=10.1595/003214069X134126138 |access-date=2009-10-02}} These approaches have yielded to new technologies that utilize solvent extraction.

Separation begins with dissolution of the sample. If aqua regia is used, the chloride complexes are produced. Depending on the details of the process, which are often trade secrets, the individual PGMs are obtained as the following compounds: the poorly soluble (NH₄)₂IrCl₆ and (NH₄)₂PtCl₆, PdCl₂(NH₃)₂, the volatile OsO₄ and RuO₄, and [RhCl(NH₃)₅]Cl₂.Bernardis, F. L.; Grant, R. A.; Sherrington, D. C. "A review of methods of separation of the platinum-group metals through their chloro-complexes" Reactive and Functional Polymers 2005, Vol. 65,, p. 205-217. {{doi|10.1016/j.reactfunctpolym.2005.05.011}}

{{main|Synthesis of precious metals}}

Significant quantities of the three light platinum group metals—ruthenium, rhodium and palladium—are formed as fission products in nuclear reactors.{{cite journal |url = http://www.technology.matthey.com/pdf/pmr-v14-i3-088-092.pdf |title=Platinum Metals from Nuclear Fission – an evaluation of their possible use by the industry |author=R. J. Newman, F. J. Smith |journal=Platinum Metals Review |volume=14 |issue=3 |year=1970 |pages=88|doi=10.1595/003214070X1438892 }} With escalating prices and increasing global demand, reactor-produced noble metals are emerging as an alternative source. Various reports are available on the possibility of recovering fission noble metals from spent nuclear fuel.{{cite journal |url=http://www.technology.matthey.com/pdf/pmr-v47-i2-074-087.pdf |title=Recovery of Value Fission Platinoids from Spent Nuclear Fuel; PART I: general considerations and basic chemistry |author=Zdenek Kolarik, Edouard V. Renard |journal=Platinum Metals Review |volume=47 |issue=2 |year=2003 |page=74|doi=10.1595/003214003X4727487 }}{{cite journal |url=http://www.technology.matthey.com/pdf/79-90-pmr-apr05.pdf |doi=10.1595/147106705X35263 |title=Potential Applications of Fission Platinoids in Industry |year=2005 |last1=Kolarik |first1=Zdenek |last2=Renard |first2=Edouard V. |journal=Platinum Metals Review |volume=49 |pages=79 |issue=2|doi-access=free }}{{cite journal |url=http://www.technology.matthey.com/pdf/pmr-v47-i3-123-131.pdf |title=Recovery of Value Fission Platinoids from Spent Nuclear Fuel; PART II: Separation process |author=Zdenek Kolarik, Edouard V. Renard |journal=Platinum Metals Review |volume=47 |issue=3 |year=2003 |page=123|doi=10.1595/003214003X473123131 }}

It was previously thought that platinum group metals had very few negative attributes in comparison to their distinctive properties and their ability to reduce harmful emission from automobile exhausts.{{Cite journal|url=https://www.researchgate.net/publication/224039043|doi=10.1002/etc.1833|title=Accumulation and distribution characteristics of platinum group elements in roadside dusts in Beijing, China|year=2012|last1=Gao|first1=Bo|last2=Yu|first2=Yanke|last3=Zhou|first3=Huaidong|last4=Lu|first4=Jin|journal=Environmental Toxicology and Chemistry|volume=31|issue=6|pages=1231–1238|pmid=22505271|s2cid=39813004 }} However, even with all the positives of platinum metal use, its possible future harm should be considered. Metallic Pt is considered not chemically reactive and non-allergenic, so that Pt emitted from VECs in metallic and oxide forms is considered relatively safe.{{Cite journal|title=Platinum group elements in the environment and their health risk|last=Khaiwal Ravindra,László Bencs,René Van Grieken|date=5 January 2004|journal=Science of the Total Environment|volume=318|issue=1–3|pages=1–43|doi=10.1016/S0048-9697(03)00372-3|pmid=14654273|bibcode=2004ScTEn.318....1R|hdl=2299/2030|hdl-access=free}} However, Pt can solubilise in road dust, enter water sources, the ground, and increase dose rates in animals through bioaccumulation. These impacts from platinum groups were previously not considered, however{{Cite journal|title=Airborne particulate matter, platinum group elements and human health: A review of recent evidence|last=Clare L.S. Wiseman, Fathi Zereini|date=2012|journal=Science of the Total Environment|volume=407|issue=8|pages=2493–2500|doi=10.1016/j.scitotenv.2008.12.057|pmid=19181366}} over time the accumulation of platinum group metals in the environment may actually pose more of a risk than previously thought. As more internal combustion cars are driven, platinum metal emissions increase.

The bioaccumulation of PGMs in animals can pose a health risk to both humans and biodiversity. Species whose food source is contaminated by these hazardous PGMs emitted from VECs may accumulate them, as may the species that consume them, including humans.

File:Cisplatin-2D.png is a platinum-based drug used in therapy of human neoplasms. The medical success of cisplatin is compromised by its severe side effects.]]

Platinum metals extracted during the mining and smelting process can also cause environmental damage. In Zimbabwe, platinum-group mining caused pollution in water sources, acidic water drainage, and environmental degradation.{{Cite journal|url=https://www.researchgate.net/publication/223631080|doi=10.1016/j.pce.2006.08.029|title=Zimbabwean mine dumps and their impacts on river water quality – a reconnaissance study|year=2006|last1=Meck|first1=Maideyi|last2=Love|first2=David|last3=Mapani|first3=Benjamin|journal=Physics and Chemistry of the Earth, Parts A/B/C|volume=31|issue=15–16|pages=797–803|bibcode=2006PCE....31..797M}}

Another hazard of Pt is being exposed to halogenated Pt salts, which can cause allergic reactions leading to high rates of asthma and dermatitis. This response is sometimes seen in workers employed in production of industrial catalysts. Workers removed immediately from further contact with Pt salts showed no evidence of long-term effects, however continued exposure could lead to health effects.

Platinum use in drugs also may need to be reevaluated, as some of the side effects to these drugs include nausea, hearing loss, and nephrotoxicity. Handling of these drugs by medical personal also led to side effects including chromosome aberrations and hair loss. The long-term medical effects of platinum drug use and exposure await evaluation.

While exposure to relatively low volumes of platinum group metal emissions may not have long-term health effects, it is unknown how the accumulation of Pt metal emissions will affect the environment as well as human health, what levels of risk are safe, and how potential hazards from platinum-group metals can be mitigated.{{cite journal|last=Hunt|first=L. B.|author2=Lever, F. M.|year=1969|title=Platinum Metals: A Survey of Productive Resources to industrial Uses|url=http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf|journal=Platinum Metals Review|volume=13|issue=4|pages=126–138|doi=10.1595/003214069X134126138 |access-date=2009-10-02}}

• Platinum group metals in Africa
• Merensky Reef
• Johnson Matthey Technology Review (formerly published as Platinum Metals Review)

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{{Reflist|2}}

• [https://matthey.com/products-and-markets/pgms-and-circularity/pgm-management Platinum group prices] (provided by Johnson Matthey) - spot prices on the global commodities market
• [https://ered.library.upenn.edu/cgi-bin/res/fullview.cgi?resID=15348 Platinum Group Metals (PGM) Database], created by Johnson Matthey
• [https://www.usgs.gov/centers/national-minerals-information-center/platinum-group-metals-statistics-and-information/ Platinum-Group Metals Statistics and Information] from the U.S. Geological Survey's National Minerals Information Center

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