Lixiviant

A lixiviant is a chemical used in hydrometallurgy to extract elements from its ore. ^{[1] [2]} The term lixiviant can be somewhat obscure, as it is not mentioned in reviews of metallurgy. ^{[3] [4]}

Extraction of gold

One of the most famous lixiviants is cyanide, which is used in extracting 90% of mined gold. The combination of cyanide and the oxygen in air converts gold particles into a soluble salt. Once separated from the bulk gangue, the solution is processed in a series of steps to give the metal. ^[5] A wide variety of less toxic alternatives to cyanide have been evaluated including thioureas, thiocyanate]], and thiosulfate. Several of these lixiviants are applicable to metals other than gold. ^[6]

Dissolution of other metals

Typically lixiviants are applied to the extraction of ions of valuable metals from some processed form of an ore. Lixiviants are also used for the recovery of metals from wastes and scrap. Circuit boards and spent catalysts often contain platinum and other valuable metals. Some of the lixiviants that have been evaluated in such situations include: aqua regia, cyanide (as in gold extraction), hydrogen peroxide, and iodide/iodine. ^[7]

Lixiviants have also been applied to the recycling of lithium ion batteries. ^[8]

"Lixiviant systems" also refer to the dissolution of purified metals. The purpose of such a process is to produce metal complexes for synthesis or for analysis. As for gold, the lixiviant must include an oxidant, which can include halogens, and a Lewis base, which can be a thiourea. ^[9]

Etymology

The origin is the word lixiviate , meaning to leach or to dissolve out, deriving from the Latin lixivium. ^[10] A lixiviant assists in rapid and complete leaching, for example during in situ leaching. The metal can be recovered from it in a concentrated form after leaching.

See also

• Cementation refers to processes that reverse the action of a lixiviant.

References

1. American Institute of Mining Engineers (1917). Transactions of the American Institute of Mining Engineers, Volume 49. Princeton University: The Institute. p. 617.
2. Mular, Andrew; Halbe, Doug; Barratt, Derek, eds. (2002), Mineral Processing Plant Design, Practice, and Control Proceedings, Vancouver, Canada: Society of Mining Engineers, p. 1631, ISBN   0-87335-223-8
3. Voeste, Theodor; Weber, Klaus; Hiskey, Brent; Brunner, Gerd (2006). "Liquid–Solid Extraction". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.b03_07.pub2. ISBN   978-3-527-30385-4.
4. Krüger, Joachim; Reisener, Jan; Reuter, Markus; Richter, Klaus (2000). "Metallurgy". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a16_375. ISBN   978-3-527-30385-4.
5. Renner, Hermann; Schlamp, Günther; Hollmann, Dieter; Lüschow, Hans Martin; Tews, Peter; Rothaut, Josef; Dermann, Klaus; Knödler, Alfons; Hecht, Christian; Schlott, Martin; Drieselmann, Ralf; Peter, Catrin; Schiele, Rainer (2000). "Gold, Gold Alloys, and Gold Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a12_499. ISBN   3527306730.
6. Akcil, Ata; Erust, Ceren; Gahan, Chandra Sekhar; Ozgun, Mehmet; Sahin, Merve; Tuncuk, Aysenur (2015). "Precious metal recovery from waste printed circuit boards using cyanide and non-cyanide lixiviants – A review". Waste Management. 45: 258–271. Bibcode:2015WaMan..45..258A. doi:10.1016/j.wasman.2015.01.017. PMID   25704926.
7. Jha, Manis Kumar; Lee, Jae-Chun; Kim, Min-Seuk; Jeong, Jinki; Kim, Byung-Su; Kumar, Vinay (2013). "Hydrometallurgical recovery/Recycling of platinum by the leaching of spent catalysts: A review". Hydrometallurgy. 133: 23–32. Bibcode:2013HydMe.133...23J. doi:10.1016/j.hydromet.2012.11.012.
8. Choubey, Pankaj K.; Chung, Kang-Sup; Kim, Min-Seuk; Lee, Jae-Chun; Srivastava, Rajiv R. (2017). "Advance review on the exploitation of the prominent energy-storage element Lithium. Part II: From sea water and spent lithium ion batteries (LIBs)". Minerals Engineering. 110: 104–121. Bibcode:2017MiEng.110..104C. doi:10.1016/j.mineng.2017.04.008.
9. Li, Xiaohua; Binnemans, Koen (2021). "Oxidative Dissolution of Metals in Organic Solvents". Chemical Reviews. 121 (8): 4506–4530. doi:10.1021/acs.chemrev.0c00917. PMC   8154329 . PMID   33724831.
10. The New English Dictionary