Role of Oxygen in Dump Leaching

Hiskey, J. B.; Bhappu, Roshan B.

doi:10.1016/b978-0-08-035767-6.50016-7

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…The aqueous electrochemistry of pyrite in acid has been studied in various electrolytes, including H 2 SO 4 , [9][10][11] HClO 4 , 10,[12][13][14] HCl, 10,15,16 and HNO 3 . 10,17 Bailey and Peters, 9 who studied the anodic behavior of pyrite in 1.0 M HClO 4 at 110ЊC, proposed that the oxidation of pyrite proceeds via a combination of two pathways which produce both sulfur and sulfate ions, with the latter dominating as the product at higher potentials.…”

mentioning

confidence: 99%

The Effect of Chloride Ions on the Ambient Electrochemistry of Pyrite Oxidation in Acid Media

Lehmann¹,

Stichnoth²,

Walton³

et al. 2000

J. Electrochem. Soc.

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The current trend in the processing of refractory gold and base metal ores is to subject the concentrates to an oxidative pressure acid leach (PAL), 1-8 prior to metal ion collection. For gold collection, PAL might be followed by cyanidation. The purpose of the PAL step is most often to destroy and oxidize encapsulating or associated mineral sulfide matrices which would otherwise reduce metal ion recoveries in subsequent collection steps. A common sulfide mineral present in gold and base metal concentrates is pyrite (FeS 2 ). Often the water used to make the pulps that are treated by PAL comes from groundwater sources close to mine sites. This water frequently contains high levels of chloride salts. Consequently, the PAL process, and thus the oxidation of minerals such as pyrite, may be carried out in the presence of high concentrations of chloride ions. This study focuses on utilizing electrochemical techniques to evaluate the effect of chloride ions on the oxidation of pyrite under acidic conditions.The aqueous electrochemistry of pyrite in acid has been studied in various electrolytes, including H 2 SO 4 , [9][10][11]10,[12][13][14]10,15,16 and HNO 3 . 10,17 Bailey and Peters, 9 who studied the anodic behavior of pyrite in 1.0 M HClO 4 at 110ЊC, proposed that the oxidation of pyrite proceeds via a combination of two pathways which produce both sulfur and sulfate ions, with the latter dominating as the product at higher potentials. They also confirmed from leaching studies, using oxygen-18 as the oxidant, that the oxygen incorporated into the sulfate product is from water and not oxygen, thus proving that pyrite oxidation proceeds via an electrochemical pathway. Biegler and Swift, 10 who investigated the mechanism of pyrite oxidation mainly in sulfuric acid solutions at 25ЊC, concluded that the sulfur and sulfate ions form from two independent pathways described by Reactions 1 and 2. The sulfate route dominated over the potential range accessible at ambient temperature, and the sulfate yield increased linearly with potentialFlatt and Woods 17 investigated the temperature dependence of the yields of sulfur formed after anodic pyrite oxidation in mixed solutions of nitric and sulfuric acid. They also found that the sulfur yields decreased with increasing potential. However, they did not find any discernible change in the potential dependence of the relative yields of sulfur and sulfate in the range of 26 to 80ЊC.Yin et al. 16 have employed a platinum-pyrite ring-disk electrode to study the surface oxidation process of pyrite in hydrochloric solutions. They concluded that in the potential region of 0.4 to 0.6 V vs. saturated calomel electrode (SCE) approximately 50% of the pyrite was oxidized to ferric and sulfate ions, and the other 50% to sulfur and ferrous ions. The latter could be detected by holding the ring at a potential of 1.0 V. As the pyrite disk potential was increased to 1.2 V, more than 90% of the pyrite was oxidized to ferric and sulfate ions, and less than 10% formed ferrous ions. Yin et al. observe...

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confidence: 99%

The Effect of Chloride Ions on the Ambient Electrochemistry of Pyrite Oxidation in Acid Media

Lehmann¹,

Stichnoth²,

Walton³

et al. 2000

J. Electrochem. Soc.

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“…At 298 K the solubility of oxygen in pure water in equilibrium with air is only 2.6xlO-4 M (-8 ppm). As indicated by Hiskey and Bhappu [30], there is an associated decrease in oxygen solubility in the high ionic strength solution produced by the recycle of lixiviant. A 50% decrease in O2 solubility results from ionic strengths equal to 1.5.…”

Section: Sulfide Mineralsmentioning

confidence: 95%

In-situ leaching recovery of copper: what’s next?

Hiskey

1994

Hydrometallurgy ’94

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The recovery of mineral and metal values by solution mining has been practiced for centuries. What appears at first glance to be a simple, empirical technique, is in actuality a very complicated process involving a large number of critical parameters that encompass several scientific and engineering disciplines. Hydrometallurgy, hydrology, geology and geochemistry, rock mechanics, chemistry, and environmental engineering and management are a few of the specialties utilized by modern operators.Solution mining is conveniently divided into three main categories: heap leaching, dump leaching, and in situ leaching. In situ leaching (lSL) involves the application of a specific lixiviant to dissolve en masse minerals within the confines of a deposit or in very close proximity to its original geologic setting. Currently there is considerable interest in applying ISL technology to recover copper. Substantial research and engineering effort is being expended to recover copper from oxide ores. However, the greatest potential for copper ISL extraction remains with the deep seated deposits that would otherwise be left unmined by conventional methods. This paper highlights some historical aspects of copper in situ leaching, and also reviews some commercial and experimental projects involving both oxide and sulfide deposits. In addition, large whole-core leaching experiments using a copper oxide ore will be described. This work has provided better understanding of the physical and chemical factors associated with the in situ leaching response.

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