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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.
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.
Gold and Silver occur natively here and there but much more commonly they occur with Sulfides and Tellurides. In order to separate the Gold and Silver from say a sulfide ore one of the methods used is known as Roasting. The process involves heating up the ores with certain salts in order to burn off the sulfides allowing you to recover the precious metals. There are many different charges and salts you may need to use depending on whether the ore is a Gold Telluride, A Gold-Silver Telluride, or a Copper-Silver Sulfide etc. This book discusses the different temperatures and mixtures that you need based on the type of ore you roasting. These methods are still used today in a lot of process plants. Once the ore is roasted the Gold and Silver can be recovered more easily by leaching and precipitation or by gravity methods which are all discussed in this book. Long out of print this book is now available again from Miningbooks.com.