Eco-friendly and economical extraction of gold from a refractory gold ore in iodide solution using persulfate as the oxidant

Iodine–iodide leaching is an effective and environmentally friendly gold extraction method that is expected to replace cyanidation. However, as the price of iodine is relatively high, for the industrial application of iodine–iodide leaching, decreasing the required amount of iodine is important to reduce production costs. In this study, persulfate was used to replace iodine as the oxidant for the extraction of gold from refractory gold ore. Using single-factor tests, the optimal leaching conditions were determined as a solid–liquid ratio of 1:3, a stirring speed of 350 rpm, 0.02 mol/L ammonium persulfate, and 0.1 mol/L potassium iodide. At pH 5, the gold extraction rate reached 83.69% after stirring for 1.5 h at room temperature. Even under neutral conditions, a gold extraction rate of more than 80% could be achieved. Using the activated carbon adsorption method to recover the gold from the leaching solution, a high gold recovery rate was obtained without solid–liquid separation. Compared with cyanidation, the S2O82− – I− – H2O system has the advantages of nontoxicity, eco-friendly, a fast leaching speed, and a high gold extraction rate. Thus, this system was a promising alternative method for gold extraction from refractory ore.