A comparative gold leaching study using cyanide, Jinchan and Jinfu

Abstract

The main objective of a gold mining company is to extract gold from its ores economically. Minerals present in ores can be linked to grindability, recovery, reagents consumption, and challenges in metallurgical accounting. Cyanide has been the lixiviant of choice for many years but due to its toxicity, others reagents have been recommended as possible replacements. This project focused on ore characterisation and a comparative study between the efficiency of cyanide, Jinchan and Jinfu on underground ore from Loulo Gold Mine at Gara. The methodology used included mineralogical studies, work and abrasion index determination to characterize the ore. Kinetic gold leaching and Carbon-In-Leach (CIL) was done to optimize gold recovery using cyanide and gold dressing agents (Jinfu and Jinchan). The ore investigated composed of mainly quartz, minor chlorite, sericite and feldspars. Ore minerals were mainly pyrite and carbonate. The work index of the ore was 14.5 kWh/t and abrasion ore parameter was 0.5 which meant the ore was medium hard rock due to the high quartz content as stated earlier. The gravity recoverable gold was 20.7%. Leaching at 1000 ppm reagent concentration was the best reagent concentration for all the reagents used and 75 µm was the best particle size for the three reagents studied in terms of gold recovery. At 500 ppm, the best particle size was also 75 µm for the three reagents. The 106 µm performed poorly compared to the 75 µm particles due to a possible higher gold liberation and surface area exposure. The maximum recoverable gold after 24 hours was 95% for cyanide, 60% for Jinfu, and 18% for Jinchan which was the lowest. This work suggests that Jinfu will be an excellent replacement for cyanide in gold leaching albeit more studies are required to understand its behaviour in a CIL systems