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Minerals
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Hydrometallurgy in Gold Extraction
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Hydrometallurgy in Gold Extraction

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: closed (21 May 2022) | Viewed by 17811

Special Issue Editors

Prof. Dr. Sehliselo Ndlovu

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Guest Editor
School of Chemical and Metallurgical Engineering, University of the Witwatersrand, Johannesburg 2050, South Africa
Interests: hydrometallurgy; biohydrometallurgy; environmental hydrometalllurgy; mineral processing; precious metals extraction; secondary materials processing; tailings processing
Special Issues, Collections and Topics in MDPI journals
Dr. Abhilash

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Guest Editor
CSIR-National Metallurgical Laboratory, Jamshedpur 831007, India
Interests: hydro-biohydrometallurgy; waste recycling; rare-earth extraction; WEEE recycling; environmental
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

While the hydrometallurgical processing of gold has been successfully commercialised for more than a century, the extraction techniques for this precious metal remain one of the most well studied areas. This is mainly due to challenges associated with the variation in the deposits, the changes in mineralogy (from free milling to refractory ores) and the rising mining and operational costs which have driven companies to look for alternative cheaper but efficient processing methods and reagents. Furthermore, many rich ore deposits have become depleted, leading to lower grade and more complex ore feed, which require advanced technological interventions for their economic processing.

At the same time, mining and the recovery of metals have come under severe scrutiny from both regulators and the public, leading to the establishment of stringent environmental mining laws that have also had a significant impact on the approach to gold processing. Mining companies are thus becoming environmentally aware, moving away from linear extractive models that have been characterised by the last half-century of mining, to circular economic models focusing on cleaner production, greener reagents, reprocessing of tailings and process re-engineering. Additionally, secondary sources, such as WEEE’s, serve as a viable resource of this precious metal and has been extensively explored by researchers globally.

This Special Issue aims to bring together the research and development that has been generated as a result of some of these changes happening in the gold hydrometallurgical processing sector. We welcome papers on fundamental research, new and emerging technologies, integrated and multi-disciplinary techniques, environmental friendly reagents, reprocessing of tailings, extraction from WEEEs and any other topic as highlighted by the scope of this issue. The hope is that this Special Issue will contribute to giving a comprehensive view on the current and future directions of gold hydrometallurgical processing across the world.

Prof. Sehliselo Ndlovu
Dr. Abhilash
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • gold hydrometallurgy
  • gold mineralogy
  • refractory ores
  • tailings reprocessing
  • secondary gold sources
  • emerging technologies
  • green chemistry
  • alternative reagents

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Published Papers (3 papers)

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Research

18 pages, 2248 KiB  
Article
Mineralogical Characterization and Acid Pretreatment of a Gold Calcine Leach Residue
by Godfrey Tinashe Bare, Jean Jacques Kalombo Mbayo, Sehliselo Ndlovu, Alan Shemi and Liberty Chipise
Minerals 2022, 12(1), 10; https://doi.org/10.3390/min12010010 - 23 Dec 2021
Cited by 6 | Viewed by 4191
Abstract
Miners around Zimbabwe used to supply gold concentrates from sulphide flotation to the Kwekwe Roasting Plant (Zimbabwe) for toll treatment. The concentrates were roasted in Edward’s roasters and the calcine product was leached by cyanidation. Due to inefficient roasting, overall gold recoveries of [...] Read more.
Miners around Zimbabwe used to supply gold concentrates from sulphide flotation to the Kwekwe Roasting Plant (Zimbabwe) for toll treatment. The concentrates were roasted in Edward’s roasters and the calcine product was leached by cyanidation. Due to inefficient roasting, overall gold recoveries of 75–80% left behind a rich calcine leach residue at the Kwekwe Roasting Plant. The characterization performed to establish a potential process route involved several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), fire assaying and inductively coupled plasma (ICP). Assays conducted on samples from the 350,000 tons tailings dam residue, created over the operational years, gave an average Au grade of 8.58 g/t and 12.54 g/t for Ag. The base metals assayed—0.11% Cu, 0.10% Pb, 0.17% Zn and 26.05% Fe. SiO2 (36.1%), Fe2O3 (36.9%), Mg3Si4O10 (OH)2 (8.9%), NaAlSi3O8 (6.9%), and Fe3O4 (6.4%)—were the major mineral phases in the cyanide leach residue. SEM gold scans on 24 polished sections showed only 2 discrete gold particles of less than 5 µm, with one partially liberated and associated with quartz, while the other was fully liberated. Therefore, the particulate gold in the calcine leach residue was negligible. It was deduced from the analysis after ultrafine milling (P80 < 5 µm) followed by cyanidation that 68.53% of the gold was sub-microscopic. Direct cyanidation using bottle roll resulted in only 2.33% of the total gold being leachable, indicating that the calcine leach residue was highly refractory. Diagnostic leaching by sequential use of acids in order of their strength resulted in HCl leachable phases (CaCO3, CaMg(CO3)2, PbS, Fe1-XS, and Fe2O3) freeing 4.2% of the total Au during subsequent cyanidation leach. H2SO4 leachable phases (Cu–Zn sulphides, labile FeS2) released an additional 26.57% during cyanidation, whereas HNO3 leachable phases (FeS2, FeAsS) released a further 20.98% of Au. After acid treatment and subsequent cyanidation, hot caustic leach of the residue followed by carbon in pulp resulted 4.43% of the total gold being eluted. Therefore, 4.43% of the total gold was surface bound. From the analysis after diagnostic acid leaching, it was deduced that a total of 54.08% of the gold was in the acid-leachable phase. Due to cost and environmental considerations, H2SO4 was selected for the evaluation of acid digestion as a pretreatment stage followed by cyanidation. Increasing the H2SO4 strength for the pretreatment of the calcine leach residue increased gold recoveries during cyanidation. Full article
(This article belongs to the Special Issue Hydrometallurgy in Gold Extraction)
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15 pages, 5215 KiB  
Article
Oxidation Roasting of Fine-Grained Carbonaceous Gold Ore: The Effect of Aeration Rate
by Hui Li, Wei Xiao, Jianping Jin and Yuexin Han
Minerals 2021, 11(6), 558; https://doi.org/10.3390/min11060558 - 24 May 2021
Cited by 9 | Viewed by 5643
Abstract
The oxidation roasting of carbon-bearing micro-fine gold can eliminate or weaken the robbing effect of carbonaceous materials and clay, and destroy the encapsulation of micro-fine gold. The micropores produced by gas escaping during the roasting process are conducive to the diffusion of leaching [...] Read more.
The oxidation roasting of carbon-bearing micro-fine gold can eliminate or weaken the robbing effect of carbonaceous materials and clay, and destroy the encapsulation of micro-fine gold. The micropores produced by gas escaping during the roasting process are conducive to the diffusion of leaching agents, thus enhancing the cyanide leaching of gold. In this paper, the influence of the aeration rate during roasting on the leaching rate of fine-grained carbonaceous gold ore and its mechanism were studied using thermodynamic calculations, crystal structure analysis, surface chemical groups and bonds analysis, microporous structure analysis, and surface morphology detection. Under suitable roasting conditions, the carbonaceous and pyrite in the ore are oxidized, while carbonate minerals such as dolomite and calcite as well as clay minerals are decomposed, and the gold-robbing materials lose their activity. The experimental results have theoretical and practical significance for the popularization and application of oxidation roasting technology of fine carbon-bearing gold ore. Full article
(This article belongs to the Special Issue Hydrometallurgy in Gold Extraction)
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17 pages, 4163 KiB  
Article
Simulation-Based Analysis of Hydrometallurgical Processes. Case Study: Small-Scale Gold Mining in Ecuador
by Santiago D. Salas, Yris González, Pamela Cango, Jean Carlos Gómez, Ronald Koepke and Elizabeth Peña-Carpio
Minerals 2021, 11(5), 534; https://doi.org/10.3390/min11050534 - 19 May 2021
Cited by 5 | Viewed by 5344
Abstract
In this work, two hydrometallurgical processes for gold recovery are explored for a small-scale gold mining case study located at Ponce Enriquez, Azuay, Ecuador. The hydrometallurgical systems consider the use of sodium cyanide and sodium thiosulfate as leaching agents, with and without the [...] Read more.
In this work, two hydrometallurgical processes for gold recovery are explored for a small-scale gold mining case study located at Ponce Enriquez, Azuay, Ecuador. The hydrometallurgical systems consider the use of sodium cyanide and sodium thiosulfate as leaching agents, with and without the incorporation of a subsystem for residual mercury removal. The proposed processes are modelled using the commercial simulator PRO/II interconnected with a Python scientific computing environment for performing stochastic simulations. Monte Carlo simulations, in which the conversion of the main units and the prices of gold vary following a random uniform distribution, permit observing the effects of these uncertainties on key recovery and economic indicators. The results facilitate the correlation between the inputs and outputs of interest as well as the visualization of the outputs variability for an adequate assessment of the systems under study by following a technical and social responsibility approach. Full article
(This article belongs to the Special Issue Hydrometallurgy in Gold Extraction)
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