Characterizing the leaching of sperrylite (PtAs 2 ) in cyanide-based solutions

Mwase, James M.; Petersen, Jochen

doi:10.1016/j.hydromet.2017.06.019

Cited by 8 publications

(3 citation statements)

References 19 publications

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“…The three concentrations selected provide enough excess cyanide to prevent it from being a limiting factor. In industrial applications, cyanide concentration can vary in the range of 0.1-0.5 g/L in dilute systems [31] and, in higher concentrations, of 1-5 g/L [30,32,33]. In some instances, such as the leaching of high-grade Au ores or secondary materials (e.g., jewellery waste), cyanide concentrations can be as high as 12 g/L [34].…”

Section: Leach Testsmentioning

confidence: 99%

A Study on the Applicability of Agitated Cyanide Leaching and Thiosulphate Leaching for Gold Extraction in Artisanal and Small-Scale Gold Mining

2022

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Mercury amalgamation is the method of choice to recover gold in artisanal and small-scale gold mining (ASGM). However, despite the low cost and simplicity of this method, the use of mercury presents serious health and environmental risks, as well as low efficiency in gold extraction. This study investigates the application of cyanide and thiosulphate leaching as alternatives to mercury amalgamation. This investigation was undertaken by conducting leach experiments using cyanide at 1 g/L, 3 g/L, and 5 g/L, and ammonium thiosulphate at 0.1 M and 0.5 M, on three ore samples originating from an artisanal mining area in Zimbabwe. The operating conditions (T = 26 °C, solids loading: 30%, particle size: −300 + 150 µm) were selected to mimic as closely as possible the conditions of artisanal mining processes. It was found that cyanide leaching was the better performing technology compared to thiosulphate leaching, as it achieved gold extractions of 71.6%, 69.7%, and 67.8% for the three ore samples (Sample 1, Sample 2, and Sample 3, respectively), whereas thiosulphate leaching achieved gold extractions of 54.1%, 35.6%, and 38.0% for the three ores, respectively. Both methods outperformed mercury amalgamation, which typically achieves gold recoveries of 30%–50%. Studying the minerology of the ores, using XRF, XRD, QEMSCAN, SEM-EDS, and a diagnostic leach, revealed the presence of sulphide minerals hosting refractory gold which contributed to the low gold extractions observed. Besides achieving higher gold extraction, cyanide leaching proved to be a system that is easier to control compared to thiosulphate leaching, making it much more attractive to artisanal miners.

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Section: Leach Testsmentioning

confidence: 99%

A Study on the Applicability of Agitated Cyanide Leaching and Thiosulphate Leaching for Gold Extraction in Artisanal and Small-Scale Gold Mining

2022

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“…Cyanidation of low-grade PGM flotation concentrates was also considered as a potential route for recovery of PGMs from low-grade ores (Mwase, Petersen, and Eksteen, 2012), but such ores require preleaching of base metals (Cu and Ni) to avoid high lixiviant consumption. However, the limited base metal recoveries by the alkaline hydrometallurgical techniques investigated so far and the refractoriness of platinum minerals such as sperrylite (PtAs 2 ) have hampered the development of commercial cyanide processes for the recovery of PGMs from low-grade and oxidized ores (Mwase, Petersen, and Eksteen, 2012;Shaik and Petersen, 2017;Mwase and Petersen, 2017). The other alternative maybe be the preleaching of base metals with sulphuric acid to upgrade the low-grade concentrates.…”

Section: Introductionmentioning

confidence: 99%

PGM extraction from oxidized ores using flotation and leaching

Sefako¹,

Sibanda²,

Sekgarametso³

2019

J. S. Afr. Inst. Min. Metall.

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Flotation and leaching were investigated as possible processing routes for improving PGM recovery from a Southern African oxidized PGM ore. Different flotation reagent schemes and lixiviants were evaluated and their PGMs extraction response measured. Characterization of the PGM ore used in this study indicated that it was enriched in oxide minerals as a result of weathering and therefore oxidic. The maximum PGM flotation recovery achieved using sulphide co-collector schemes was 55.1% 3E (Pt, Pd, and Au). Application of the hydroxamate oxide collector improved the flotation recovery to 74.7% 3E. The superior PGM recoveries achieved with hydroxamates probably lies in their ability to form complexes with base metals such as iron. Direct leaching of oxidic PGM ore using different acids yielded relatively low PGM extractions. Leaching in hydrochloric acid achieved extractions of 36.6% Pt and 8.8% Pd, nitric acid achieved extractions of 34.5% Pt and 7.1% Pd. The best leaching results were obtained using aqua regia, with extractions of 48% Pt and 24.5% Pd. In view of the low PGM extractions obtained by leaching ROM ore, it was considered more promising to leach the concentrate as a way of further upgrading it. The flotation concentrate with the highest PGM recovery was leached using sulphuric acid in order to remove the base metals and further enrich it in PGMs. Extractions of 73.3% Cu, 82.9% Ni, and 8.1% Fe were achieved.

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“…X-ray photoelectron spectroscopy (XPS) has a depth sensitivity on the order of 10 nm and provides information on the oxidation states and the chemical environment of different elements on a surface. There have been several investigations relying on XPS to obtain information regarding surface transformation of individual, pure minerals [5][6][7][8]. Even though this strategy provides important information regarding surface processes, many processes occur only when one mineral is in the presence of another.…”

Section: Introductionmentioning

confidence: 99%

Identification of Surface Processes in Individual Minerals of a Complex Ore through the Analysis of Polished Sections Using Polarization Microscopy and X-ray Photoelectron Spectroscopy (XPS)

Silva-Quinones

Jacome-Collazos

et al. 2018

Minerals

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Understanding the changes of a mineral during ore processing is of capital importance for the development of strategies aimed at increasing the efficiency of metal extraction. This task is often difficult due to the variability of the ore in terms of composition, mineralogy and texture. In particular, surface processes such as metal re-adsorption (preg-robbing) on specific minerals are difficult to evaluate, even though they may be of importance as the re-adsorbed material can be blocking the valuable mineral and negatively affect the extraction process. Here, we show a simple yet powerful approach, through which surface processes in individual minerals are identified by combining polarization microscopy (MP) and X-ray photoelectron spectroscopy (XPS). Taking as an example a silver-containing polymetallic sulfide ore from the Peruvian central Andes (pyrite-based with small amounts of galena), we track the changes in the sample during the course of cyanidation. While polarization microscopy is instrumental for identifying mineralogical species, XPS provides evidence of the re-adsorption of lead on a pyrite surface, possibly as lead oxide/hydroxide. The surface of pyrite does not show significant changes after the leaching process according to the microscopic results, although forms of oxidized iron are detected together with the re-adsorption of lead by XPS. Galena, embedded in pyrite, dissolves during cyanide leaching, as evidenced by PM and by the decrease of XPS signals at the positions associated with sulfide and sulfate. At the same time, the rise of a lead peak at a different position confirms that the re-adsorbed lead species cannot be sulfides or sulfates. Interestingly, lead is not detected on covellite surfaces during leaching, which shows that lead re-adsorption is a process that depends on the nature of the mineral. The methodology shown here is a tool of significant importance for understanding complex surface processes affecting various minerals during metal extraction.

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Characterizing the leaching of sperrylite (PtAs 2 ) in cyanide-based solutions

Cited by 8 publications

References 19 publications

A Study on the Applicability of Agitated Cyanide Leaching and Thiosulphate Leaching for Gold Extraction in Artisanal and Small-Scale Gold Mining

A Study on the Applicability of Agitated Cyanide Leaching and Thiosulphate Leaching for Gold Extraction in Artisanal and Small-Scale Gold Mining

PGM extraction from oxidized ores using flotation and leaching

Identification of Surface Processes in Individual Minerals of a Complex Ore through the Analysis of Polished Sections Using Polarization Microscopy and X-ray Photoelectron Spectroscopy (XPS)

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