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A Method for Leaching or Dissolving Gold from Ores or Precious Metal Scrap

Nicolas Geoffroy and François Cardarelli

Abstract. - The hydrometallurgical leaching of native gold from gold-bearing ores or the dissolution of gold metal during the recycling of electronic and precious metal scrap is performed every day using hazardous chemicals such as sodium cyanide or aqua regia. These chemicals represent health and safety risks for workers and a serious threat for the environment. However, even if several other reagents are known to dissolve gold at the laboratory scale, none of these are used industrially. Hot mixtures of hydrochloric acid with strong oxidizing compounds are known to generate in-situ nascent chlorine which is capable of dissolving gold efficiently. In this study, the authors investigated the capability of a hot mixture of hydrochloric acid and ground manganese (IV) oxide to dissolve gold metal either under atmospheric or pressurized conditions. The best result was obtained under a pressure of 639 kPa at 90°C with a dissolution rate of 0.250 g·cm–2h–1 and it was compared to that reported in the literature for other industrial reagents.

Journal of Materials
Volume 57, Number 8, August 2005, Pages 47-50 [Full text PDF file (280 KB)]

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