Improving the gold leaching process of refractory ores using the Jetleach reactor

Gold ores have been a subject of numerous investigations aimed at enhancing gold recovery and improving leaching kinetics. This is because the cyanidation process cycle, although well established and well researched, remains a process of long duration. To reach the acceptable gold recoveries i.e., +80%, some ores are leached for 24 h, or more, depending on the type of ore. Faster kinetics would help in lowering the processing cost. This work examines the development and application of the Jetleach reactor, as a device for improving the leaching kinetics of gold ores. The Jetleach reactor is designed to propagate micro-cavitation by impacting two pulp streams against one another at a relatively high velocity, through a pair of coaxially aligned nozzles in a chamber filled with oxygen under pressure. When applied to free milling ores, the Jetleach reactor has been shown to improve the gold recovery by almost 10% after only 2 h. The Jetleach has the potential to considerably reduce the leaching time required in cyanidation processes. In experiments the Jetleach was applied to refractory gold ores including Diorites (DIO) and Meta-volcanic Ore (MVO) ores from West Africa. The reactor has shown improvements in gold recoveries when compared to the conventional stirred tank and bottle roll leaching methods. On the DIO sample, the Jetleach reactor was able to improve the gold recovery by almost 8% and 10% respectively compared to the conventional and bottle roll method; while the improvement was about 10% and 15% on the MVO samples. Pilot plant test-work, on Witwatersrand gold plant tailings has suggested improvement in recoveries of some 10% with concomitant reduction in reagent consumption. This suggests that the employment of such reactor in a cyanidation process for the treatment of refractory ores could provide economic benefits.