Alkaline leaching pretreatment and cyanidation of arsenical gold ore from the Carlin-type Zarshuran deposit

ABSTRACT

Carlin-type refractory gold deposits are complex bodies which only occur in certain regions such as the western United States, southwest China, and northwest Iran. It is important to investigate the most suitable treatment option for each deposit from the point of the mineralogical composition. The present study investigates the effect of atmospheric NaOH alkaline pretreatment on the cyanidation gold recovery of the arsenical Carlin-type gold ore from the Zarshuran deposit, Iran (4.2 g t⁻¹ Au feed grade). The results are explained based on the mineralogical considerations and with the aid of thermodynamic and kinetic investigations of the leaching behaviour of the main gold-bearing phases including orpiment, pyrite, and sphalerite. It was found that the high arsenic content of Zarshuran (3.7%) has some implications on the pretreatment and cyanidation processes. Solution potential and pH decreased significantly by the oxidation of arsenic sulphides which resulted in the decreasing oxidation extent of the other sulphides, specifically sphalerite. It was also found that pretreatment only in highly alkaline media (pH > 13) can be effective in gold recovery. Gold and silver extractions during subsequent cyanidation were improved from 69.4 to 80.7% for gold and 44.4 to 88.9% for silver, where the extraction yields of arsenic, iron, and zinc were 93.7, 75.9, and 26.9%, respectively.

RÉSUMÉ

Les dépôts d’or réfractaire de type Carlin sont des corps complexes que l’on trouve seulement dans certaines régions comme dans l’ouest des Etats-Unis, le sud-ouest de la Chine et dans le nord-ouest de l’Iran. Il est important d’examiner l’option de traitement la plus appropriée pour chaque dépôt, du point de vue de la composition minéralogique. La présente étude examine l’effet du prétraitement alcalin atmosphérique de NaOH sur la récupération de l’or par cyanuration du minerai d’or arsenical de type Carlin du dépôt de Zarshuran, en Iran (avec qualité de charge d’Au de 4.2 g t⁻¹). On explique les résultats en se basant sur les considérations minéralogiques et à l’aide d’investigations thermodynamiques et cinétiques du comportement de lixiviation des principales phases porteuses d’or, incluant l’orpiment, la pyrite et la fausse galène. On a trouvé que la haute teneur en arsenic de Zarshuran (3.7%) avait certaines implications sur le prétraitement et la cyanuration. Le potentiel de la solution et son pH diminuaient significativement par l’oxydation des sulfures d’arsenic, ce qui avait pour résultat la diminution du degré d’oxydation des autres sulfures, spécifiquement de la fausse galène. On a également trouvé que le prétraitement pouvait être efficace pour la récupération d’or seulement en milieu hautement alcalin (pH > 13). L’extraction de l’or et de l’argent lors da la cyanuration ultérieure s’améliorait de 69.4% à 80.7% pour l’or et de 44.4% à 88.9% pour l’argent, alors que le rendement de l’arsenic, du fer et du zinc était de 93.7%, de 75.9% et de 26.9%, respectivement.

KEYWORDS:

• Refractory gold
• alkaline leaching
• orpiment
• pyrite
• sphalerite
• cyanidation

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on Contributors

Ehsan Bidari is received my Bachelor of Science degree in Mining engineering in 2009 and Master of Science in Minerals processing in 2012 working on the solvent extraction separation of cadmium and copper at Amirkabir University of Technology, Tehran. In 2013 I started my Ph.D. work at the Sahand University of Technology, Tabriz, Iran. My thesis is focused on the kinetic investigation of the alkaline leaching of gold bearing pyrite and arsenopyries.

Valeh Aghazadeh is currently Associate professor in Hydrometallurgy and I have seven years of teaching and research experience in the field of Hydrometallurgy at Sahand University of Technology. I completed a PhD in Hydrometallurgy of copper sulphide mineral, Chalcopyrite, at Tarbiat Modares University in 2011, MSc in Hydrometallurgy of copper oxide minerals at Tehran University in 2003 and B.Sc. in Mining Engineering at Sahand University of Technology in 1999. I have a deep understanding of the disciplines covered within Hydrometallurgy, which I have developed through my research and through the courses that I have taught. My research has been focused in the area of kinetics and thermodynamic of hydrometallurgy of base and precious metals like copper, zinc, aluminum and gold.

ORCID

Ehsan Bidari http://orcid.org/0000-0002-0001-3800

Additional information

Funding

The authors acknowledge the support of IMIDRO, Iranian Mines & Mining Industries Development & Renovation, for providing the financial support to carry out this research.