The Recovery of Gold from a Copper-Rich Zimbabwean Gold Ore by Cold Stripping

The global gold ore grade has been decreasing, and the mineralogy is now more diverse and complex. This has necessitated the utilization of low-grade ores previously not used. During the cyanidation process of such ores, copper cyanide complexes form that are competitively adsorbed with gold onto activated carbon. Therefore, to decrease the amount of copper in the pregnant electrowinning electrolyte, a series of copper adsorption experiments were done to limit the amount of copper that adsorbs onto activated carbon. Tests on selective copper cold stripping were also conducted to selectively elute copper from loaded head carbon before the elution process. The results showed that increasing the solution pH from 9 to 11 decreased the copper adsorption from about 15.1% to 8.2%, but on the other hand the gold adsorption decreased from 98.7% to 95.1%. The optimal determined cold stripping parameters were 2% cyanide strength, 1% sodium hydroxide, 27 g/L carbon concentration and 4 h residence time. This experimental procedure effectively reduced the amount of copper in the gold leaching process and has potential to be used in large-scale applications.