Extractive Metallurgy Of Nickel Cobalt And Platinum Group Metals Free Download
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Abstract_Mineable platinum group metal (PGM) deposits are rare and found in relatively few areas of the world. At the same time, the use of PGM is predicted to expand in green technology and energy applications, and PGMs are consequently currently listed as European Union critical metals. Increased mineralogical complexity, lower grade ores, and recent PGM production expansions give rise to the evaluation of the value chain of the capital-intensive conventional matte smelting treatment and other processing possibilities of the ore. This article will review the processes and value chain developed to treat ores for PGM recovery, highlighting hydrometallurgical refining approaches. It groups processes according to their rationale and discusses the special features of each group.Keywords: platinum group metals; value chain; refining; leaching
The 1_____________________ (2____), also known as the 3__________, 4__________, 5__________, 6______________, 7_______________, 8_______________ or 9_______________________ (10____), are six noble, precious metallic elements clustered together in the periodic table. These elements are all transition metals in the d-block (groups 8, 9, and 10, periods 5 and 6).[1]
The six platinum-group metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum. They have similar physical and chemical properties, and tend to occur together in the same mineral deposits.[2] However, they can be further subdivided into the 11_____________________________________ (IPGEs: Os, Ir, Ru) and the 12_______________________________________ (PPGEs: Rh, Pt, Pd) based on their behaviour in geological systems.[3]
The three elements above the platinum group in the periodic table (iron, nickel and cobalt) are all ferromagnetic; these, together with the lanthanide element gadolinium (at temperatures below 20 C),[4] are the only known transition metals that display ferromagnetism near room temperature.
Platinum can occur as a native metal, but it can also occur in various different minerals and alloys.[16][17] That said, Sperrylite (platinum arsenide, PtAs2) ore is by far the most significant source of this metal.[18] 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.[19][20] 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.[21]
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.[20][22]
Metallic iridium is found with platinum and other platinum group metals in alluvial deposits. 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.[20]
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.[20]
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.[23]
Palladium is preferentially hosted in sulphide minerals, primarily in pyrrhotite.[12] 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.[23]
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.[24] Classical purification methods exploit differences in chemical reactivity and solubility of several compounds of the metals under extraction.[25] These approaches have yielded to new technologies that utilize solvent extraction.
It was previously thought that platinum group metals had very few negative attributes in comparison to their distinctive properties and their ability to successfully reduce harmful emission from automobile exhausts.[31] However, even with all the positives of platinum metal use, the negative effects of their use need to be considered in how it might impact the future. For example, metallic Pt are considered to not be chemically reactive and non-allergenic, so when Pt is emitted from VECs it is in metallic and oxide forms it is considered relatively safe.[32] However, Pt can solubilise in road dust, enter water sources, the ground, and increase dose rates in animals through bioaccumulation.[32] These impacts from platinum groups were previously not considered, however[33] over time the accumulation of platinum group metals in the environment may actually pose more of a risk then previously thought.[33] Future research is needed to fully grasp the threat of platinum metals, especially since as more internal combustion cars are driven, the more platinum metal emissions there are.
Platinum metals extracted during the mining and smelting process can also cause significant environmental impacts. In Zimbabwe, a study showed that platinum group mining caused significant environmental risks, such as pollution in water sources, acidic water drainage, and environmental degradation.[34]
While exposure of relatively low volumes of platinum group metal emissions may not have any long-term health effects, there is considerable concern for how the accumulation of Pt metal emissions will impact the environment as well as human health. This is a threat that will need more research to determine the safe levels of risk, as well as ways to mitigate potential hazards from platinum group metals.[35]
Platinum group metals (pgms) and other metals such as nickel are precious natural resources that we need to look after and use carefully. They are important in many applications like emissions control, fuel cells, industrial process chemistry, corrosion protection, medical implants and jewellery. So, developing methods to recover and purify these precious metals from a diverse range of sources means we can continue to use them.
The rapid growth of hydrogen use in the SDS underpins major growth in demand for nickel and zirconium for use in electrolysers, and for copper and platinum-group metals for use in fuel cell electric vehicles (FCEVs). Despite the rapid rise in FCEVs and the decline in catalytic converters in gasoline and diesel cars, demand for platinum-group metals in internal combustion engine cars remains higher than in FCEVs in the SDS in 2040.
While the automotive sector is set to become a dominant source of global demand for lithium, nickel and cobalt for EV batteries, it already leads demand for platinum and palladium for use in catalytic converters. For these so-called platinum group metals, a key issue is whether new demand from fuel cells will offset declining demand from internal combustion engine vehicles.
Catalytic converters represent around 40% of global platinum demand today, and are also the major source of demand for two other platinum group metals: rhodium and palladium. In the SDS, an increase in the coverage of emissions regulation to include all new cars by 2030, coupled with continued sales of internal combustion engine, especially hybrids, keeps demand for platinum group metals for use in catalytic converters above that for fuel cells by 2040.
This report considers a wide range of minerals and metals used in clean energy technologies, including chromium, copper, major battery metals (lithium, nickel, cobalt, manganese and graphite), molybdenum, platinum group metals, zinc, rare earth elements and others (see Annex A for the complete list). Steel and aluminium are not included in the scope for demand assessment, but aluminium use in electricity networks is exceptionally assessed given that the outlook for copper is closely linked with aluminium use in grid lines (see Introduction). 5376163bf9
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