I/We have been assigned one of the most expensive metals, Platinum. It has widely application in dental implants, automotive catalytic converters (Rao & Reddi, 2000), biomedical implants such as catheters, stents, cardiac implants (Cowley & Woodward, 2011), manufacturing of optical glass, manufacturing of fuel cells (McDonald & Hunt, 1982) and jewelry.
Platinum ore deposits
Platinum ore contains palladium, iridium, rhodium, osmium and ruthenium, along with platinum. Platinum ore forms a) Placer deposits: Placer deposits are formed by water-based erosion of sedimentary rocks containing the ore (Example. Ural-Alaskan type). b) Layered igneous lode deposits: Such deposits are emplaced on stable cratons. Examples: South Africa as the Bushveld Complex, the Great Dyke and the Stillwater Complex (Economou-Eliopoulos, 2010).
Geological occurrence and tectonic settings
Platinum ore is prominently found in hard igneous rocks that are ultra basic or basic (rocks high in magnesium, iron and copper content and low in silica content) in nature (Rao & Reddi, 2000). Plate tectonic setting associated with Platinum ore is thought to be a subduction-influenced setting (Garuti, 2011). Platinum is a siderophile (iron-loving) element and hence sinks to the Earth’s core. It is brought up and deposited onto the surface via subduction, a process in which two plate tectonics collide and one of the plates slides beneath the other, causing a volcanic chain reaction (Arndt, Lesher & Czamanske, 2005).
Platinum ore mining techniques
Surface mining (open cut): Open pit mining is done to a certain extent. However, this type of mining is valid only at the initial phases of the ore extraction. Subsurface (underground) mining: Majority of the platinum ore extraction is done via underground mining by blasting the rocks and bringing the ore to the surface (Mudd, 2010).
Steps involved in platinum ore extraction and refining
Platinum ore is mined using open pit and/or underground mining. The blasted rocks are crushed and milled to expose the ore. The smaller rocks are froth-floated to extract crude platinum. Smelting removes iron and sulfur from crude platinum. Once smelted, the platinum ore undergoes electrolytic refining to remove copper, cobalt and nickel. Stubborn gold and palladium are removed using hydrochloric acid. Palladium, iridium, rhodium, osmium and ruthenium are dissolved in aqua regia, sodium bisulfate, sodium oxide. The resultant chloroplatinic acid is treated with ammonium chloride to form hexachloroplatinate which in turn is burned to obtain pure platinum (Ian, 2004).
Environmental issues associated with platinum
Platinum mine workers have high risk of silicosis, platinum induced respiratory problems (World Health Organization, 2000) and secreting platinum in bodily fluids, potentially causing health hazard (Schierl, Fries, Weyer & Fruhmann, 1998). Bioaccumulation of platinum is noted to occur due to emission from automotive catalytic convertors (Economou-Eliopoulos, 2010).
References
Arndt, N., Lesher, C. M., & Czamanske, G. K. (2005). Mantle-derived magmas and magmatic Ni-Cu-(PGE) deposits. Economic Geology, 100th Aniversary volume, 5-24.
Cowley, A & Woodward, B. (2011). Platinum Metals Rev. 55, (2), 98–107. A Healthy Future: Platinum in Medical Applications
Economou-Eliopoulos, M. Platinum-group elements (PGE) in various geotectonic settings: Opportunities and risks. Hellenic Journal of Geosciences,45, 65.
Garuti, G. (2011). Global tectonics and chromite – platinum mineralization monitoring genesis and evolution of ural–alaskan type complexes. Journal of the Spanish Society of Mineralogy, 15(September), 15-16.
McDonald, D., & Hunt, L. B. (1982). A history of platinum and its allied metals. Johnson Matthey.
Mudd, G. M. (2010). Platinum group metals: a unique case study in the sustainability of mineral resources. In The 4th International Platinum Conference, Platinum in Transition ‘Boom or Bust’, Sun City, South Africa, 11th–14th October.
Rao, C. R. M., & Reddi, G. S. (2000). Platinum group metals (PGM); occurrence, use and recent trends in their determination. TrAC Trends in Analytical Chemistry, 19(9), 565-586.
Schierl, R., Fries, H. G., van de Weyer, C., & Fruhmann, G. (1998). Urinary excretion of platinum from platinum industry workers. Occupational and environmental medicine, 55(2), 138-140.
WHO, (2000) Air quality guidelines for Europe. 2nd edition. Copenhagen, WHO Regional Office for Europe.
Wood, Ian. 2004. Platinum. Benchmark Books (New York). 11 -13.
