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Cyanide Process
Gold cyanidation (also known as the cyanide process or the MacArthur-Forrest process) is a hydrometallurgical technique for extracting gold from low-grade ore by converting the gold to a water-soluble coordination complex. It is the most commonly used leaching process for gold extraction. Cyanidation is also widely used in the extraction of silver, usually after froth flotation. Production of reagents for mineral processing to recover gold represents more than 70% of cyanide consumption globally. Other metals are recovered from the process include copper, zinc, and silver, but gold is the main driver of this technology. Due to the highly poisonous nature of cyanide, the process is controversial and its use is even banned in some parts of the world. Cyanide can be safely used in the gold mining industry. A key feature for safe use of cyanide is to ensure adequate pH control at an alkaline pH level above 10.5. At industrial scale, pH control is mainly achieved using lime, as an i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrometallurgy
Hydrometallurgy is a technique within the field of extractive metallurgy, the obtaining of metals from their ores. Hydrometallurgy involve the use of aqueous solutions for the recovery of metals from ores, concentrates, and recycled or residual materials.Brent Hiskey "Metallurgy, Survey" in Kirk-Othmer Encyclopedia of Chemical Technology, 2000, Wiley-VCH, Weinheim. Processing techniques that complement hydrometallurgy are pyrometallurgy, vapour metallurgy, and molten salt electrometallurgy. Hydrometallurgy is typically divided into three general areas: *Leaching *Solution concentration and purification *Metal or metal compound recovery Leaching Leaching involves the use of aqueous solutions to extract metal from metal bearing materials which is brought into contact with a material containing a valuable metal. The first examples come from 11-12th centuries China where it was applied to extraction of copper and accounted for a significant share of total copper production. In the 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Stewart MacArthur
John Stewart MacArthur was a chemist from Glasgow. Born on 9 December 1856, he is credited with the development of the MacArthur-Forrest cyanidation process in 1887, used to extract gold in South Africa. His patent for the process was voided. With the long-lasting legal issues about the cyanidation patents, MacArthur turned to other businesses. First, he investigated vanadium extraction from ore containing significant amounts of radium. From this enterprise he turned to the production of radium. He founded the Radium Works in Halton in 1911. In 1915 he moved it to Balloch, West Dunbartonshire and renamed it as Loch Lomond Radium Works. MacArthur died on 16 March 1920, aged 63. See also *Gold cyanidation Gold cyanidation (also known as the cyanide process or the MacArthur-Forrest process) is a hydrometallurgical technique for extracting gold from low-grade ore by converting the gold to a water-soluble coordination complex. It is the most commonly ... References Further r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comminution
Comminution is the reduction of solid materials from one average particle size to a smaller average particle size, by crushing, grinding, cutting, vibrating, or other processes. In geology, it occurs naturally during faulting in the upper part of the Earth's crust. In industry, it is an important unit operation in mineral processing, ceramics, electronics, and other fields, accomplished with many types of mill. In dentistry, it is the result of mastication of food. In general medicine, it is one of the most traumatic forms of bone fracture. Within industrial uses, the purpose of comminution is to reduce the size and to increase the surface area of solids. It is also used to free useful materials from matrix materials in which they are embedded, and to concentrate minerals. Energy requirements The comminution of solid materials consumes energy, which is being used to break up the solid into smaller pieces. The comminution energy can be estimated by: * Rittinger's law, which assu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dicyanoaurate
Potassium dicyanoaurate is an inorganic compound with formula K u(CN)2 It is a colorless to white solid that is soluble in water and slightly soluble in alcohol. The salt itself is often not isolated, but solutions of the dicyanoaurate ion ( u(CN)2sup>−) are generated on a large scale in the extraction of gold from its ores. Production In mining of gold from dilute sources, gold is selectively extracted by dissolution in aqueous solutions of cyanide, provided by dissolving sodium cyanide, potassium cyanide and/or calcium cyanide. The reaction for the dissolution of gold, the "Elsner Equation", is: :4 Au + 8 KCN + O2 + 2 H2O → 4 K u(CN)2+ 4 KOH In this process, oxygen is the oxidant. It can also be produced by reaction of gold(I) salts with excess potassium cyanide. :AuCl + 2 KCN → K u(CN)2 + KCl Structure : Potassium dicyanoaurate is a salt. The dicyanoaurate anion is linear according to X-ray crystallography. On the basis of infrared spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium Cyanide
Calcium cyanide is the inorganic compound with the chemical formula, formula Ca(CN)2. It is the calcium Salt (chemistry), salt derived from hydrocyanic acid. It is a white solid, although the pure material is rarely encountered. It hydrolyses readily (even in Moisture, moist air) to release hydrogen cyanide and is very toxic. Preparation Solutions of calcium cyanide can be prepared by treating calcium hydroxide with hydrogen cyanide. Solid calcium cyanide is produced commercially by heating calcium cyanamide with sodium chloride. The reaction is incomplete. The product is only of 50% purity, other components being sodium cyanide, calcium cyanamide, and carbon. Because of the carbon impurity, the solid is black, hence material is often called black cyanide. Reactivity At temperatures around 600 °C, calcium cyanide converts to calcium cyanamide:"Production of Hydrocyanic Acid" ''United States Patent Office.'' 1933.(accessed April 22, 2012). :Ca(CN)2 → CaCN2 + C It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Cyanide
Potassium cyanide is a compound with the formula KCN. This colorless crystalline salt, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewellery for chemical gilding and buffing.Andreas Rubo, Raf Kellens, Jay Reddy, Joshua Wooten, Wolfgang Hasenpusch "Alkali Metal Cyanides" in Ullmann's Encyclopedia of Industrial Chemistry 2006 Wiley-VCH, Weinheim, Germany. Potassium cyanide is highly toxic. The moist solid emits small amounts of hydrogen cyanide due to hydrolysis, which may smell like bitter almonds. Not everyone, however, can smell cyanide; the ability to do so is a genetic trait. The taste of potassium cyanide has been described as acrid and bitter, with a burning sensation similar to lye. Production KCN is produced by treating hydrogen cyanide with an aqueous solution of potassium hydroxide, followed by evaporation of the solution in a vacuum: About 50,000 to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gold Heap Leaching
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile metal in a pure form. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions. Gold often occurs in free elemental ( native state), as nuggets or grains, in rocks, veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid), forming a soluble tetrachloroaurate anion. Gold i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dicyanoaurate(I)-3D-balls
Potassium dicyanoaurate is an inorganic compound with formula K u(CN)2 It is a colorless to white solid that is soluble in water and slightly soluble in alcohol. The salt itself is often not isolated, but solutions of the dicyanoaurate ion ( u(CN)2sup>−) are generated on a large scale in the extraction of gold from its ores. Production In mining of gold from dilute sources, gold is selectively extracted by dissolution in aqueous solutions of cyanide, provided by dissolving sodium cyanide, potassium cyanide and/or calcium cyanide. The reaction for the dissolution of gold, the "Elsner Equation", is: :4 Au + 8 KCN + O2 + 2 H2O → 4 K u(CN)2+ 4 KOH In this process, oxygen is the oxidant. It can also be produced by reaction of gold(I) salts with excess potassium cyanide. :AuCl + 2 KCN → K u(CN)2 + KCl Structure : Potassium dicyanoaurate is a salt. The dicyanoaurate anion is linear according to X-ray crystallography. On the basis of infrared s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Merrill–Crowe Process
The Merrill–Crowe Process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores. It is an improvement of the MacArthur-Forrest process, where an additional vacuum is managed to remove air in the solution (invention of Crowe), and zinc dust is used instead of zinc shavings (improvement of Merrill). The solution is separated from the ore by methods such as filtration (e.g. vertical leaf type clarifier filters) and counter current decantation (CCD). Afterwards a very clear solution is achieved by using pre-coated filters applying diatomaceous earth. Oxygen is then removed by passing the solution through a vacuum de-aeration column. Zinc dust is added to the clarified, de-aerated solution which precipitates the gold; zinc having a higher affinity for the cyanide ion than gold. Other precious metals, silver, and base metals, like copper, will also precipitate, if present. Automated membrane filtration offers a cost savings alter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Washington Merrill
Charles Washington Merrill (December 21, 1869 – February 5, 1958) was an American mining metallurgist. Biography He was born in Concord, New Hampshire to Sylvester and Clara L. (née French) Merrill. He attended elementary and high school in Alameda, California and then attended the College of Mining of the University of California, where he received a Bachelor of Science in 1891. After his graduation he was first connected with the noted old Standard Consolidated mine in Bodie, California, and from there went to the Harqua Hala mine in Arizona, thence to the Montana Mining Company in Marysville, California. In 1899, he became affiliated with the widely known Homestake Mining Company of South Dakota as a metallurgist, and in this capacity he manifested the brilliant talents which became the foundation of his future career. He became extensively known by his work, and acquired material prosperity, and his creation of new methods, particularly in the process of extracting gold ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%–6% by weight) in water for consumer use, and in higher concentrations for industrial use. Concentrated hydrogen peroxide, or " high-test peroxide", decomposes explosively when heated and has been used as a propellant in rocketry. Hydrogen peroxide is a reactive oxygen species and the simplest peroxide, a compound having an oxygen–oxygen single bond. It decomposes slowly when exposed to light, and rapidly in the presence of organic or reactive compounds. It is typically stored with a stabilizer in a weakly acidic solution in a dark bottle to block light. Hydrogen peroxide is found in biological systems including the human body. Enzymes that use or decompose hydrogen peroxide are classified as peroxidases. Properties The boiling poi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercur, Utah
Mercur is a historical hard rock mining ghost town in Tooele County, Utah, United States. In 1891, it became the site of the first successful use of the cyanide process of gold extraction in the United States, the dominant metallurgy today. Its elevation above sea level is approximately 2,042 m. The nearby Mercur Gold Mine was re-opened by Barrick Gold in 1985, with mining operations again coming to an end in 1997. The reclamation and restoration project was set to continue up to 2010. History The town first came into being in 1870 as ''Lewiston'' (not to be confused with the present-day city of Lewiston in Cache County), when gold was discovered at the head of the Lewiston Canyon, six miles west of present-day Cedar Fort. A small gold rush began, peaking about 1873; the population reached as high as 2000. During the mid-1870s, silver boomed, and silver mines were opened and quartz mills to process the ore were built. A million dollars worth of silver bullion was shipped ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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