| Description |
In Carlin type ores, submicron gold particles are disseminated throughout sulfide host minerals, i.e., pyrite. In order to recover and further process the refractory gold, the host mineral should be separated from gangue minerals. Due to the natural hydrophobicity of sulfide minerals, flotation separation is the best practical method to separate them from gangue minerals. Newmont USA Ltd. introduced a new process for the recovery of auriferous pyrite and other sulfide minerals in Carlin type ores using flotation with nitrogen as the flotation gas and lead as the activator. So-called N2TEC process was optimized at pH 4.5-5.5 for the highest recovery of sulfide minerals. Increasing amount of carbonates in gangue minerals, however, has significantly affected the process recovery as the pH of the pulp increases in presence of carbonate minerals, i.e., calcite, dolomite, etc. It was found that using CO2 in the conditioning and flotation process decreases the slurry pH significantly and consequently increases the recovery and rate of pyrite flotation. The effect of CO2 on the hydrophobic state of pyrite in the absence of collector has been investigated with various methods in this thesis research. In addition, flotation recovery of pyrite in the presence of collector in saturated solutions with CO2 and N2 gases was also investigated. It was found that both fresh and oxidized pyrite particles in CO2 saturated solution exhibited more apparent hydrophobicity. In saturated CO2 and N2 solutions, flotation rate and recovery and the water contact angle on the pyrite surface increased, while bubble attachment time and surface oxidation decreased. |
