An investigation on the pre-concentration of Mouteh gold ore by Flotation

The aim of the present study is to decrease the amount of unwanted gangue minerals to enter the cyanidation process. The flotation process was introduced for the beneficiation of the feed to the cyanide leaching stage. Selection of a proper procedure for gold processing needs the accurate characterization of the gold bearing minerals comprising the ore. Diagnostic leaching tests were conducted to specify the gold mineral phases and associated gold in Mouteh ore. Fire assay analysis showed gold grade equal to 0.85 ppm and 0.86 ppm for the two representative samples of Mouteh plant feed. In pyrite flotation tests, the recovery and grade of gold in concentrate were found to be 38% and 8ppm, respectively. The cyanidation of concentrate can lead to an efficient beneficiation process for the gold recovery. The optimized conditions was found to be: pH: 9, solid percent: 25, potassium xanthate (KAX) as collector: 150 gr/t, MIBC as frother: 25ppm , and conditioning time: 10 minute. EPMA analysis demonstrated that gold in Mouteh ore was associated with pyrite which would need more grinding for liberation. The size of liberated gold particles in EPMA pictures was found to be 3-4 microns. According to the diagnostic leaching experiments and silicates flotation tests, no gold was detected with silicates mineral. Following the flotation of quartz particles and elimination of 20 percent of feed by weight, it would be possible to reduce the feed of cyanide leaching. Therefore, Quartz flotation can also be an effective pre-concentration method prior to cyanidation process.