Dissolution kinetics and carbon adsorption for the cyanidation of gold ores in oxygen-enriched slurry

CIM Bulletin, Vol. 88, No. 986, 1995

G.Q. Liu, Department of Materials and Metallurgical Engineering, and W.T. Yen, Department of Mining Engineering, Queen's University, Kingston, Ontario

The application of oxygen-enriched cyanidation to three Canadian gold ore samples has been investigated. The results showed that the use of oxygen can improve gold dissolution kinetics, reduce grinding time, and lower cyanide and lime consumptions. To obtain the same gold extraction, the required cyanide leaching time was reduced from 48 hours in slurry containing 8 ppm O2 to 12 ~ 24 hours in 20 ppm O2 slurry. Reagent consumptions were reduced by 23 ~ 37% for cyanide and by 35 ~ 54% for lime. There was little advantage to further increasing the dissolved oxygen to 32 ppm from 20 ppm. Gold extraction from the + 200 mesh fraction improved 4 ~ 14% in oxygen-enriched slurry. A general kinetic model derived from the cyanidation of three ore samples can be described by the following equation: E = El (1-ve-i") where E is the gold extraction (%) at time t (hours), El is the ultimate gold extraction (%) , and if and k are constants depending on cyanide concentration, level of dissolved oxygen, and the characteristics of the ore samples. Comparative studies of conventional carbon adsorption and carbon adsorption in oxygen-enriched slurry have also demonstrated that oxygen enrichment resulted in more favourable conditions for gold adsorption.

Keywords: Oxygen-enriched cyanidation, Cyanidation, Kinetics, Particle size, Carbon adsorption.