The importance of gold recovery from low grade ores and flotation tailings is continuously increasing\ndue to raising gold demand and thereby high gold prices. However, due to raising social awareness\nof the ecological impacts of cyanidic gold extraction and environ-mental specifications, the development\nand the implementation of alternative hydrometallurgical extraction processes have\nbeen a focus for many research institutions in last decades. Present work gives a comparison between\ncompatible extraction reagents, with focus on less harmful processes. The target of this review\nis to point out the best cyanide-free processes of following methods and reagents: Bioleaching,\nChlorination, Aqua Regia, Bromine, Thiocyanate, Thiosulfate and Thiourea leaching. For this propose,\nthe gold leaching reagents are described and discussed in terms of their environmental and\neconomical points of view. As result of this comparison, thiourea stands out as the most promising\nalternative gold leaching reagent to cyanide.
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