Extraction of gold from typical Carlin gold ores by pressure oxidation pretreatment - sodium jarosite decomposing - polysulfide leaching and its mechanism

In connection with the depletion of mineral resources base of gold, the engagement of refractory ores reserves in the processing becomes a necessary condition to stabilize gold market. Standard methods of processing of refractory sulphide carbon-bearing gold ores and float concentrates extracted from them include pressure oxidation and bacterial oxidation enabling the liberation of dispersive gold and oxidation of carbon having parasitical sorption with further cyanation. The alternative solution of the aforementioned problem is pre-oxidation of refractory ores with water-and-gas emulsions. Theoretical basis for active water-and-gas emulsions formation with the use of electrolytes solutions electrolysis in combination with ultraviolet exposure is stated in the article. Given method of water-and-gas emulsions preparation ensures the formation of active oxidants complex. Gold recovery into pregnant solutions up to 55.7 - 73.5% by chloride scheme was reached in laboratory experiments on samples of sulphide carbon-bearing ore, herewith 18% was recovered using cyanic solution. Based upon experimental findings, process scheme for combined oxidative preparation of sulphide carbon-bearing ore with dispersive deportment of gold was developed.

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Biooxidation of High-Sulfur Refractory Gold Concentrate by Ferroplasma acidiphilum

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.997.642 ◽

2014 ◽

Vol 997 ◽

pp. 642-645 ◽

Cited By ~ 1

Author(s):

He Shang ◽

Jian Kang Wen ◽

Biao Wu

Keyword(s):

Pulp Density ◽

Cyanide Leaching ◽

Gold Extraction ◽

Pressure Oxidation ◽

Gold Ores ◽

Refractory Gold Ores ◽

Refractory Gold ◽

Initial Ph ◽

Pre Treatment ◽

Number Of Bacteria

Gold ores can be categorized into two types-free milling and refractory. Free milling ores are easy to treat. Gold in such ores is recovered by gravity separating techniques or direct cyanidation. Refractory gold ores, on the contrary, are difficult to treat and require pre-treatment prior to cyanidation, such as roasting, pressure oxidation, fine grinding and biooxidation. A number of bacteria are used in biomining but the prominent ones that are known to be involved in the oxidation of sulfide ores include Thiobacillusferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans. In this study, the gold concentrate was biooxidized in a reactor at 45°C over a period of 10 days at a pulp density of 15% solids using a culture of already grown Ferroplasma acidiphilum. The initial pH was adjusted to 1.5 with sulfuric acid, resulted in 85.39 % oxidation of sulfur from initial grade of 33.83 %, and the slag rate was 68.52 %. The products of sulfide biooxidation were leached at a pulp density of 20 %(v/w) for 24 h at pH 11. The pH was adjusted using CaO and cyanide strength was 10 kg/t, we got a gold extraction of 90.71 %, which ncreaseed 80.09 % compared with the direct cyanide leaching.

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A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065110 ◽

1971 ◽

Vol 29 ◽

pp. 212-213

Author(s):

R. H. Geiss ◽

R. L. Ladd ◽

K. R. Lawless

Keyword(s):

High Vacuum ◽

Microscopy Study ◽

Electron Microscopy Study ◽

Ultra High Vacuum ◽

Pure Oxygen ◽

Pressure Oxidation ◽

High Voltage Electron Microscopy ◽

Oxidation Study ◽

Voltage Electron ◽

Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

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Formation of defects in implanted hipox-structures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100131668 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1406-1407

Author(s):

Peter Pegler ◽

N. David Theodore ◽

Ming Pan

Keyword(s):

High Pressure ◽

Cross Section ◽

Semiconductor Devices ◽

Silicon Substrates ◽

Processing Conditions ◽

Pressure Oxidation ◽

Deep Trench ◽

Local Oxidation ◽

Trench Isolation ◽

And Behavior

High-pressure oxidation of silicon (HIPOX) is one of various techniques used for electrical-isolation of semiconductor-devices on silicon substrates. Other techniques have included local-oxidation of silicon (LOCOS), poly-buffered LOCOS, deep-trench isolation and separation of silicon by implanted oxygen (SIMOX). Reliable use of HIPOX for device-isolation requires an understanding of the behavior of the materials and structures being used and their interactions under different processing conditions. The effect of HIPOX-related stresses in the structures is of interest because structuraldefects, if formed, could electrically degrade devices.This investigation was performed to study the origin and behavior of defects in recessed HIPOX (RHIPOX) structures. The structures were exposed to a boron implant. Samples consisted of (i) RHlPOX'ed strip exposed to a boron implant, (ii) recessed strip prior to HIPOX, but exposed to a boron implant, (iii) test-pad prior to HIPOX, (iv) HIPOX'ed region away from R-HIPOX edge. Cross-section TEM specimens were prepared in the <110> substrate-geometry.

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