The leaching kinetics of an oxide gold ore with iodide/iodine solutions

Two types of gold ores were subjected to iodide/iodine leaching at room temperature. The effects of three factors, including ore type (a carbonaceous and an oxide gold ores), iodide/iodine concentration, and the presence of oxygen in solution on gold leaching performance were investigated. The carbonaceous ore showed only 20% gold extraction, since gold–iodide complexes readily adsorb on organic matter. In contrast, gold extraction from the oxide ore in a solution containing 20 g/L iodide and 4 g/L iodine reached 77% in 6 h and 89% in 24 h. With iodate as the oxidant, no gold could be leached in 48 h. When the iodate was partially converted to iodine by adding HCl to the solution, gold leaching was then started. Iodine reactions with the sulfide and ferrous minerals of the oxide ore slowly consumed iodine within 48 h. Based on the obtained experimental data, a power law rate equation was applied to model the gold extraction kinetics in iodide/iodine solutions. The reaction was found to be first order with respect to tri-iodide concentration.