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The Wohlwill process is an industrial-scale chemical procedure used to refine gold to the highest degree of purity (99.999%). [1] The process was invented in 1874 by Emil Wohlwill . This electrochemical process involves using a cast gold ingot , often called a doré bar , of 95%+ gold to serve as an anode .
The borax method of gold extraction has been used by artisanal gold miners in the Benguet area north of Manila in the Philippines for more than 30 years. Some believe it was in practice as early as the 1900s. [who?] The method is increasingly being seen as a safe alternative to the widespread use of toxic mercury in artisanal gold mining today ...
Craddock, P. T. 2000a Historical Survey of Gold Refining: 1 Surface Treatments and Refining Worldwide, and in Europe Prior to AD 1500. In A. Ramage and P. T Craddock (eds) King Croesus' Gold; Excavations at Sardis and the History of Gold Refining. London: British Museum Press, 27–53. ISBN 978-0-674-50370-0, 0-674-50370-8
Bioleaching is the extraction or liberation of metals from their ores through the use of living organisms.Bioleaching is one of several applications within biohydrometallurgy and several methods are used to treat ores or concentrates containing copper, zinc, lead, arsenic, antimony, nickel, molybdenum, gold, silver, and cobalt.
Gold extraction is the extraction of gold from dilute ores using a combination of chemical processes. Gold mining produces about 3600 tons annually, [1] and another 300 tons is produced from recycling. [2] Since the 20th century, gold has been principally extracted in a cyanide process by leaching the ore with cyanide solution.
The chemical reaction for the dissolution of gold, the "Elsner equation", follows: 4 Au + 8 NaCN + O 2 + 2 H 2 O → 4 Na[Au(CN) 2] + 4 NaOH. Potassium cyanide and calcium cyanide are sometimes used in place of sodium cyanide. Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen.
In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining the final material is chemically identical to the raw material. Refining thus increases the purity of the raw material ...
Metal refineries refining metals such as alumina, copper, gold, lead, nickel, silver, uranium, zinc, magnesium and cobalt Iron refining, a stage of refining pig iron (typically grey cast iron to white cast iron), before fining , which converts pig iron into bar iron or steel [ 1 ]