The mechanism of gold lock-up in refractory wood chips

• Published in: Minerals engineering 1997-11, Vol.10 (11), p.1259-1267
• Main Authors: Petersen, F.W., Van Der Plas, P.J., Van Zyl, C.J.
• Format: Article
• Language: English
• Subjects: activated carbon; Applied sciences; cyanidation; Exact sciences and technology; Gold ores; Hydrometallurgy; Metals. Metallurgy; Production of metals; Production of non ferrous metals. Process materials
• ISSN: 0892-6875; 1872-9444
• DOI: 10.1016/S0892-6875(97)00112-X

Activated carbon has for long been the preferred adsorbent for the recovery of gold from leached slurries. Wood chips, produced by underground blasting, are moved with the gold-bearing material to the carbon-in-pulp plant. It was found that gold loaded onto wood chips via three mechanisms, viz : (a) Impregnation of gold ore into the wood matrix, (b) the adsorption as aurocyanide, and (c) absorption of aurocyanide into the wood matrix. Impregnation can take place during blasting underground, during the milling stage, and during the cyanidation and adsorption stages when the much harder gold (or its ore) is directly or indirectly impregnated into the wood swelled by the aqueous medium. Furthermore, aurocyanide can adsorb directly onto wood chips in an aqueous medium. This adsorption is enhanced by increase in pH, ionic strength and aurocyanide concentration. An increase in temperature reduces the sorption of aurocyanide. Temperature and particle size effected the kinetics and equilibrium of gold adsorption onto wood chips. Moreover, wood chips degraded in a strong alkaline environment, hence producing wood-constituents that effect the adsorption of gold onto activated carbon negatively. Elution studies showed that the recovery of gold cyanide is enhanced by low pH. The amount of electrolyte present in the elution solution as well as the amount of cations present on the wood matrix, has a significant effect on the percentage recovery of the loaded gold cyanide.