JOURNAL PAPER

Kinetic gold leach monitoring including cyanide speciation

P.W. Lotz^I; S. Janse van Rensburg^I; A. Swarts^II

^IMintek
^IITEAL Exploration and Mining

SYNOPSIS

Traditionally, bottle roll tests have been used to optimize the extraction process for best gold extraction and recovery. Such tests typically involve exposing the ore to defined reagent concentrations (lime, cyanide and sufficient oxygen) and balance the gold input with recoveries and losses. With mounting pressures to accommodate sustainability issues during development work, it became apparent that much more information would be required on the interactions and kinetic behaviour of solid and solution species during the entire leach process. This information is vital to enable proactive management of critical issues such as cyanide, arsenic, water and tailings management. Inadequate management of these aspects has led to temporary closures and, in cases of noncompliance, to the dynamically changing regulations.
MINTEK's advanced leach facility (ALF) is being developed with the aim of bridging the knowledge gap between the gold leach process and the predictable environmental impacts upon discharge. The facility aims to monitor all parameters of relevance such as pH, Eh, dissolved oxygen, metals, cyanide species, and viscosity during the entire process to enable more informed decisions on practical interventions.
The presented set of data reflects first experiences gained from processing a refractory gold ore concentrate. Attempts at optimizing the process were limited due to the developmental nature of the work. Data relating to leaches with differing preoxidation conditions and cyanide staging is presented.

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References

1. REES, K.L. and VAN DEVENTER, J.S.J. The role of metal-cyanide species in leaching gold from a copper concentrate. Minerals Engineering, 1999. vol. 12, no. 8, pp. 877-892.         [ Links ]

2. LI, J., DABROWSKI, B., MILLER, J.D., ACAR, S., DIETRICH, M., LEVIER, K.M., and WAN, R.Y. The influence of pyrite pre-oxidation on gold recovery by cyanidation. Minerals Engineering, 2006. vol. 19, pp. 883-895.         [ Links ]

3. MARSDEN, J.O. and HOUSE, C.I. The chemistry of gold extraction 2nd ed. Society for mining, metallurgy and exploration Inc (SME). Colorado USA, 2006. pp. 467-468.         [ Links ]

4. KUDRYK, V. and KELLOGG, H.H. Mechanism and rate controlling factors in the dissolution of gold in cyanide solutions. Journal of Metallurgy, 1954. vol. 6, pp. 541-548.         [ Links ]

5. NICOL, M.J., FLEMING, C.A., and PAUL, R.L. The chemistry of the extraction of gold. Stanley GG (ed.), The Extractive Metallurgy of Gold. vol 2. The Southern African Institute of Mining and Metallurgy, Johannesburg, 1987. pp. 831-905.         [ Links ]

6. YANNOPOULOS, J.C. The extractive metallurgy of gold. Van Nostrand-Reinhold. New York, 1991. pp. 242-245.         [ Links ]

7. LI, J., ZHONG, T.K., and WADSWORTH, M.E. Application of mixed potential theory in hydrometallurgy. Hydrometallurgy, 1992. vol. 29. pp. 47-60.         [ Links ]

8. XUE, T. and OSSEO-ASARE, K. Anodic behaviour of gold, silver and goldsilver alloys in aqueous cyanide solutions. Young, C.A., Twidwell, L.G and Anderson, C.G. (eds.) Cyanide: Social, Industrial and Economic Aspects. TMS, Warrendale Pennsylvania, 2001. pp. 563-575.         [ Links ]

9. ELLIS, S. and SENANAYAKE, G. The effects of dissolved oxygen and cyanide dosage on gold extraction for a pyrrhotite-rich ore. Hydrometallurgy, 2004. vol. 72. pp. 39-50.         [ Links ]

10. VORSTER, B.J. and FLATMAN, S.R. Cyanide control in the metallurgical process of gold extraction in AngloGold (S.A.). Journal of The South African Institute of Mining and Metallurgy, 2001. pp. 359-366.         [ Links ]

11. JOHNSON, C.A., GRIMES, D.J., LEINZ, R.W., and RYE, R.O. Cyanide speciation at four gold leach operations undergoing remediation. Environment Science Technology, 2008. vol. 42, no. 4. pp. 1038-1044.         [ Links ]

12. ASTM, Designation D 669601: Standard guide for understanding cyanide species. Annual book of ASTM standards. 2001. vol. 11, no. 2. ASTM international, West Conshohocken, PA.         [ Links ]