Copper concentrate from an active mine was received for direct gold leaching study. The main copper sulphide mineral was mainly chalcopyrite and small amount of chalcocite. The particle size of the concentrate was analysed to be P80 30 m by particle size analyser. Gold recovery from cyanidation was 18%, 32%, and 32% using 1000 ppm, 3000 ppm, and 5000 ppm NaCN, respectively in a 24 hour bottle roll leaching test while maintaining the initial cyanide concentration. The gold extractions using thiourea system in a specially synthesised solution show 82% and 92% in 60 g/L thiourea and 90 g/L thiourea, respectively. Direct gold extraction from the chalcopyrite concentrate can be implemented prior to smelting process resulting in increased revenues compared with the precious metal credit from the smelters. The other advantage is to make cleaner copper concentrate if it contains higher arsenic levels. The preliminary tests show that the arsenic dissolution is high enough during the gold leaching to decrease the arsenic content in the leached residue with majority of copper sulphides remaining in the solid form. The copper concentrates were also leached by POX (pressure oxidation) in different conditions. The resulting residues were leached by cyanidation and other alternative lixiviants including thiourea, thiosulfate and amino acids. Cyanidation gold recovery is performed using 100, 250, and 500 ppm NaCN. The gold recovery is gradually increased with increasing cyanide concentration. Cyanide consumptions ranged from 0.29 kg/t to 2.55 kg/t while lime consumption varies from 65.6 kg/t to 197.4 kg/t which are well expected from the POX residues. Three thiosulfate salts (Na+, (NH4) +, and Ca2+) were used to investigate gold leaching with sodium hydroxide, ammonium hydroxide and calcium hydroxide as pH control reagents.
CITATION:Wu, J, Ahn, J and Lee, J, 2019. Gold leaching from copper concentrate using alternative lixiviants, in Proceedings World Gold 2019, pp 259264 (The Australasian Institute of Mining and Metallurgy: Melbourne).