On-site gold refining of cyanide liquors by solvent extraction

摘要

Gold producers are currently being forced to cut costs, to increase plant throughput or to selectively mine out higher-grade areas. Another approach is to produce a value-added product, such as 99.99 percent gold, currently being produced at some minesites via a chloride re-leach route. There may be an opportunity for the refining of gold directly from cyanide liquors such as eluates and intensive leachates of gravity concentrates. While previous work with solvent extractants ha focused on the recovery of gold from leach liquors as a replacement for carbon-in-pulp processing, the present work presents an alternative idea, the notion of on-site refining of gold with no re-leaching step. The current work indicates that it is possible to produce gold of 99.99 percent purity or higher by direct SX from a cyanide eluate type solution containing high copper tenors (about 200 mg/1 Cu and 2 mg/1 Ag). Excellent selectivity can be achieved in the extraction stage for gold over copper and silver. The small amount of co-extracted silver and copper can easily be scrubbed from the gold-loaded organic phase, which is subsequently easily stripped. The gold may then be recovered by electrowinning or reduction. Gold-loaded organic phase, which is subsequently easily stripped. The gold may then be recovered by electrowinning or reduction. Other work on a mixed-metal intensive cyanide leachate type solution (700 ppm Au, 400 ppm Ag, 200 ppm Cu, 150 ppm Ni, Fe, and Zn) has shown that the process is very selective against base metals such as Ni, Co, Fe and Zn, and that loadings as high as 5000 mg/1 gold can be obtained on the organic. This process may well be suited to gold plants at remote sites, or where high copper or silver levels are present. There are several possible advantages over both electrowinning/smelting or chloride re-leach/SX routes, including costs, occupational health and safety (OH&S) and recovery of by-products.