Gold extraction

I. Marsden and I. House, The Chemistry of Gold Extraction, Ellis Horwood, Chichester, 1992, 597 pp. 

Zhao, J. Wu, Z. C. Chen, J. C. Gold extraction from thiosulfate solutions using mixed amines. Solvent Extr. Ion Exch. 1998, 16, 1407-1420. 

Several reports identified nonlethal effects in humans acutely exposed to arsine. These reports, however, lacked definitive exposure data but verified hematologic disorders leading to renal failure as critical effects of arsine exposure. Bulmer et al. (1940) (as cited in Elkins 1959) reconstructed an exposure incident at a gold extraction facility and estimated that subchronic (up to 8 mon) exposure to 0.12 ppm arsine resulted in jaundice and anemia (see Section 2.2.1). The lack of definitive exposure data for humans necessitates the use of animal data for quantitative estimation of AEGL values. Derivation of AEGL-2 values based upon limited human data (Flury and Zernik 1931) was considered but rejected because the data were poorly documented and inconsistent with other data showing lethality at lower cumulative exposures. 

Used industrially for gold extraction and wood treatment and to manufacture insecticides,... 

AuPLUS A hydrometallurgical process for extracting gold. Addition of calcium peroxide to the cyanide leaching liquor increases the rate and amount of gold extracted. 

Prior to gold extraction by cyanidation, refractory gold ores are either roasted or pressure oxidized to liberate the gold contained as submicroscopic particles or in solid solution in arsenopyrite and arsenic-rich pyrite. Gold extraction from such ores require roasting or pressure oxidation or bacterial oxidation prior to cyanidation to destroy the sulfide structure. 

No information could be found in the available literature on the levels of thiocyanate in ground, surface, or drinking water. Thiocyanate is found in concentrations ranging from 100 to 1,500 mg/L in coal plant waste waters (Ganczarczyk 1979 Jensen and Tuan 1993), and from 300 to 450 mg/L in mining (gold extraction) waste waters (Boucabeille et al. 1994b). 

Bromine (vapor) Bleaching, gold extraction, Very high... 

Of course, based on government policy for increasing employment in this part of the country and avoiding emigration from these parts to big cities, and as there are several veins like the studied one available in this area, country people can be guided to exploit veins like this and sell the ore to a central gold extraction refinery. 

Although mercury is known from early times and was used hy alchemists, its first modern scientific applications date hack to 1643 when Torricelli used it in the barometer to measure pressure and about eight decades later Fahrenheit used it in the thermometer to measure temperature. Before this, mercury s use was confined to decorative work, gold extraction and medicines. The element was named after the planet mercury and its symbol Hg is taken from the Latin word hydrargyrum, which means hquid silver. 

Castner turned his interest to gold extraction, which required high-quality sodium hydroxide. Castner developed a three-chambered electrolytic cell. The two end chambers contained brine and graphite electrodes. The middle chamber held water. The cells were separated excepted for a small opening on the bottom, which contained a pool of mercury that served as the cell s cathode. When current flowed through the cell and the cell was rocked, sodium reduced from the brine came into contact with water in the middle cell to produce a sodium hydroxide solution. As Castner built his mercury cell, Kellner was working on a similar design. Rather than compete with each other, Castner and Kellner joined forces to establish the Castner-Kellner Alkali Company to produce sodium hydroxide, which competed with soda ash and potash as an industrial base, and chlorine, which was used primarily to make bleach. 

It is used for the separation of minerals (for example, gold extraction), in making dyes, and as a local anesthetic, antispasmodic sedative medicine. It is also used to some extent as a disinfectant, absorbed in sticks of diatomite brick(Refs 7 9). Bromine was used during WWI,... 

High concentrations of mercury may occur in groundwater and surface water supplies in gold-mining areas where mercury has been used for gold extraction,... 

Extraction.4—There arc four main processes of gold extraction ... 

I. Marsden and I. House, in The Chemistry of Gold Extraction, Ellis Horwood, Chichester, 1992 S. Mann, Nature, 1992,357, 358 H. CoUey, Chem. Brit., 1992,720 J. Barrett, M.N. Hughes, G.I. Karavaiko and P.A. Spencer, in Metal Extraction by Bacterial Oxidation of Minerals, Ellis Horwood, Chichester, 1992. 

The importance of waste reduction through the use of a chemical catalyst can be exemplified by the use of yV-methylimidazole as a catalyst in the leaching step of gold extraction from ores in the mining industry. Cyanide, a toxic substance that poses a major health threat, has traditionally been used for these processes. A sample case is the 1999 leak in a Rumanian facility from a cyanide storage tank into the Rhine River that killed thousands of fish. 

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