Gold Leaching Using Thiourea from Uranium Tailing Material, Gabal El-Missikat, Central Eastern Desert, Egypt
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RESEARCH ARTICLE
Gold Leaching Using Thiourea from Uranium Tailing Material, Gabal El‑Missikat, Central Eastern Desert, Egypt Mohammed R. Ahmed1 · Hesham S. Mohammed1 · Mohamed G. El‑Feky1 · Yasser K. Abdel‑Monem2 Received: 17 June 2020 / Accepted: 17 September 2020 © The Minerals, Metals & Materials Society 2020
Abstract The objective of this study was to investigate thiourea leaching of gold present in the uranium tailings. Sulfuric acid treatment for raw material is important in order to dissolve uranium as well as to remove easily leachable metals. The acidic thiourea solution was proposed as a non-toxic possible alternative process route to cyanide in gold dissolution. The acidic system of thiourea-sodium sulfite was studied in the gold dissolution process. The presence of sodium sulfite can significantly reduce thiourea decomposition, accelerate the gold dissolution process, decrease the leaching time, and decrease the activation energy of gold dissolution. The activation energy for gold dissolution was evaluated. The activation energy solution with sodium sulfite is 7.62 kJ mol−1 which is much lower than 9.32 kJ mol−1 in the absence of sodium sulfite. Low activation energy confirms the surface reaction dissolution mechanism. This method demonstrates the possibility of extracting gold directly from low-grade ores without any physical or chemical pre-concentration method with a more environmentally friendly process.
The contributing editor for this article was João António Labrincha Batista. * Hesham S. Mohammed [email protected] 1
Nuclear Materials Authority, Maadi Kattameya, P.O. Box 530, Cairo, Egypt
Department of Chemistry, Faculty of Science, Menoufia University, Shibin El Kom, Egypt
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Vol.:(0123456789)
Journal of Sustainable Metallurgy
Graphical Abstract
Keywords Acidic pretreatment · Waste as raw material · Cyanide-free · Formamidine disulfide · Sodium sulfite · FTIR
Introduction Gold extraction using cyanide solutions from different ores was the dominant process for over a century [1–3]. The acceptance of cyanide on other lixiviants is due to its higher chemical stability, better understanding of leaching chemistry, and lower cost. However, cyanidation has recently been banned in many countries around the world, due to its toxic nature. Also, there are many problems that often occur during gold leaching with cyanide solution from the ores containing copper, sulfur, arsenic, manganese, telluride, zinc, lead, and carbonaceous ores, resulting in low gold recovery and high cyanide consumption [1, 4, 5]. In cyanidation, there are basically two mechanisms that cause high cyanide consumption. The first results from a presence of some sulfide minerals that can react with the cyanide to produce thiocyanate and other products. The second mechanism is the presence of some base metals, such as zinc, copper, and lead, which can form very stable complexes with the cyanide. In addition, gold leaching
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process in cyanide system occurs through long time, it takes more than about 24 h
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