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The eight articles first appeared as volume 6 (no date) of Mineral processing and extractive metallurgy review. They review new methods of recovery for gold, and to some extent, silver, focus on the particular challenges of extraction from carbonaceous ores and from various sulfide-bearing ore, and the treatment of refractory gold ore, and discuss high-temperature and biological oxidation, high- temperature chlorination, and removing metals from leach liquor. Book club price, $40. Annotation copyrighted by Book News, Inc., Portland, OR
New discoveries of the properties of gold at a nanoscale, and its effective use in modern technologies, have been driving a virtual 'gold rush'. Depleting natural resources has meant that the recovery of gold continues to grow in importance and relevance.The Recovery of Gold from Secondary Sources analyses the most advanced technology in gold recovery and recycling from spent sources of mobile phones, unwanted electronic equipment and waste materials. State-of-the-art techniques of hydrometallurgical and bio-metallurgical processing, leaching, cementing, adsorbing and separation through bio-sorbents are all described in detail, providing a guide for students and researchers. Discussion of environmentally friendly methods of recovery are presented, in order to provide modern-day alternatives to previous techniques. For those interested in the study of gold recovery this book gives a comprehensive overview of current recovery, making it the ultimate source of information for students, researchers, chemists, metallurgists, environmental scientists and electronic waste recovery experts.
The nature of the gold species present in the ore during the bio-oxidation process at Fairview Gold Mine, Barberton, South Africa, was studied quantitatively using 197Au Mossbauer spectroscopy. In the feed ore, about 50 per cent of the gold is in a chemically-bound form, presumably substituting into the arsenopyrite lattice. The remainder of the gold, a metallic gold-silver alloy, if liberated, is leached by cyanidation. The chemically-bound gold is not leached. Significantly, the gold was found to become reduced to the metallic state during the bio-oxidation process, with most of the reduction occurring during the first stage of bio-oxidation. The degree of reduction impacted on the subsequent recovery of the gold by cyanidation. Only about 6 per cent of the gold remained in the chemically-bound form in the residue that reported to the carbon-in-pulp circuit for gold recovery. The iron compounds and minerals throughout the process were studied by 57Fe Mossbauer spectroscopy. The iron-containing sulphides in the feed ore were found to consist mainly of pyrite, with some arsenopyrite. Most of the arsenopyrite dissolved during the first stage of bio-oxidation, along with some of the pyrite. The bio-oxidation process produced jarosites and various hydrated iron oxides.
In recent years, urbanization and industrialization have produced large amounts of heavy metals, which are highly toxic to both humans and the environment. This book presents a comprehensive overview of heavy metals including their physiochemical properties, toxicity, transfer in the environment, legislation, environmental impacts, and mitigation measures. Written by experts in the field, chapters include scientific research as well as case studies.
The effects of some associated minerals on thiosulfate gold leaching were studied through thermodynamic analysis and leaching experiments on composite ore samples containing various minerals and a reference silicate gold ore. In the leaching test on the reference gold ore, about 93% of gold was extracted within 3.0 hours. The presence of various amount of pyrite, pyrrhotite, chalcopyrite, arsenopyrite, chalcocite, bornite, and some lead species, has significant detrimental effects. Under reduced oxygen conditions, the thiosulfate consumptions could be significantly reduced. High gold extractions (i.e.>= 90%) were observed in the leaching tests with reduced dissolved oxygen (i.e., 0.7% oxygen in the supplied gas) in the absence or in the presence of sulfide minerals such as pyrite, pyrrhotite, arsenopyrite and chalcopyrite. High copper concentration and a pre-aeration step was also found to largely increase the gold extractions under such conditions. Thiosulfate-copper-ethylenediamine system was found effective in the leaching of gold. The leaching kinetics was significantly slower than that of the conventional thiosulfate-copper-ammonia leaching. The consumption of thiosulfate, however, was largely reduced. This leaching system worked effectively on the reference gold ore within a wider pH range (e.g., 6-11), with or without ammonia. The presence of ammonia in a low concentration improved the leaching rate but also increase the consumption of thiosulfate. Comparable gold extractions were observed in the leaching of the composite ores containing various sulfide minerals, such as pyrite, pyrrhotite, chalcocite, galena and chalcopyrite. The leaching of gold in the presence of iron sulfides was also improved by applying chemical additives, such as, carbonate, calcium, galena, phosphate, and additional hydroxide anion. It is proposed that these additives either passivated the harmful surface of sulfide minerals or masked some detrimental aqueous species. Finally, some improved leaching methods concluded in this study were applied on a few industrial ore samples in order to demonstrate the effectiveness of these methods. It was found that by comprehensively applying these improved thiosulfate leaching strategies, satisfactory gold extractions and thiosulfate consumption results were archived on these ores.
The gold processing industry is experiencing change. As free-milling and oxide ores become depleted, more complex polymetallic and refractory ores are being processed, coupled with increasing pressure for stricter environmental compliance. Recent years have also seen a steady reduction in mineral processing and metallurgy graduates and a gradual loss of older operating experience. A contribution to documenting current and future best practice in gold ore processing seems timely. The focus of this volume is on advances in current gold plant operation, from conception to closure; chapters also cover innovations at the bench and pilot-scale level that would be expected to find commercial application at some stage. Sufficient coverage is also given to the chemistry and engineering aspects. The general principle behind the structure of the volume is that of flowsheeting based on unit operations and applied to a mineralogical classification of gold ore types. From concept to closure, this book covers all unit operations, mineralogies and processes that are relevant to dealing with today's complex orebodies. Practical experience is vital to the successful development, operation and closure of any operation. The 42 chapters have been contributed by a total of 66 authors and co-authors who are experts from countries spanning the globe, and representing exhaustive practical knowledge covering many disciplines relevant to gold processing. * Current best practice as elucidated by a select panel of experts in the field* Innovations at the bench and pilot-scale level that would be expected to find commercial application at some stage* Mineralogical-based approach to flowsheeting
Extensively revised and updated, this edition provides the broad base of knowledge required by all working in the gold extraction and gold processing industries. It bridges the gap between research and industry by emphasizing practical applications of chemical principles and techniques.