Abstract

AMWELE, M.N.  and  GROOT, D.R.. Test work to examine the potential for improving gold leaching performance at Navachab Gold Mine, Namibia. J. S. Afr. Inst. Min. Metall. [online]. 2018, vol.118, n.5, pp.457-460. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2018/v118n5a2.

The Navachab Gold Mine is an open-pit gold operation located in Namibia. The metallurgical flow sheet consists of crushing, milling, leaching by CIP (carbon in pulp), and electrowinning. Extraction in the leach section is approximately 67%, increases to approximately 86% by the end of carbon adsorption, indicating that extraction in the leach section is far from complete. The purpose of this study was to examine the potential for improving the performance of the leach section. Bottle roll leach tests were conducted using different parameters to observe their impact on gold extraction and cyanide consumption. The factors varied included the cyanide concentration and pH. The effect of introducing lead nitrate on the leach performance was also investigated. Furthermore, it is suspected that constituents in the ore that adsorb gold from solution (known as preg-borrowing constituents) suppress the overall extraction of gold, and thus the benefit of CIL (carbon in leach) was investigated. Finally, bottle roll tests as well as plant tests were conducted to determine the influence of residence time, as it was thought that this may be a limiting factor. An increase in extraction was observed when the cyanide levels were increased and when lead nitrate was introduced. The CIL test also showed an improvement in extraction compared to the normal leach tests. An increment in the pH did not show the same benefit, however. Plant tests showed a decline in the solid residue grade with an increase in residence time. The results indicate possible areas for further research in order to improve leach performance.

Keywords : gold leaching; CIP; CIL; cyanidation; lead nitrate; optimization.

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