Dissolution behavior of gold in ammoniacal solutions with iodine as an oxidant

leaching behavior of gold in ammonical solutions with iodine as an oxidant was investigated using cyclic voltammogram and Tafel polarization. The majo rity of the experiments were carried out at 75 degreesC, and the results we re compared with consideration given to the equilibrium of the iodine-ammon ia system. The distribution of nine iodide-containing species at various pH values in the absence and presence of ammonia were considered at three dif ferent temperatures. It was found that, with the introduction of ammonia in to the system, the concentration of iodide (I-), iodine (I-2) and triiodide (I-3(-)) is increased substantially, which in turn helps the rate of gold dissolution. The apparent activation energy was found to be about 46 kJ/mol e, indicating a chemical-controlled mechanism.