Dissolution behavior of gold in ammoniacal solutions with iodine as an oxidant
Organization: Society for Mining, Metallurgy & Exploration
Jan 1, 2002
The leaching behavior of gold in ammonical solutions with iodine as an oxidant was investigated using cyclic voltammogram and Tafel polarization. The majority of the experiments were carried out at 75°C, and the results were compared with consideraton given to the equilibrium of the iodine-ammonia system. The distribution of nine iodide-containing species at various pH values in the absence and presence of ammonia were considered at three different temperatures. It was found that, with the introduction of ammonia into the system, the concentration of iodide (I-), iodine (I2) and triiodide (I3-) is increased substantially, which in turn helps the rate of gold dissolution. The apparent activation energy was found to be about 46 kJ/mole, indicating a chemical-controlled mechanism.