Extraction of gold from typical Carlin gold concentrate by pressure oxidation pretreatment - Sodium jarosite decomposition and polysulfide leaching

Abstract

Most of the gold is encapsulated in sulfides and arsenopyrite in Carlin type gold concentrate; the gold leaching efficiency is less than 8% without pretreatment. Cyanide process is a traditional gold leaching method with the disadvantages of several environmental pollution incidents occurred due the breach of tailings disposal. In view of the difficulties in gold extraction and serious pollution incidents of typical Carlin type gold concentrate, this paper proposes pressurized oxidation - sodium jarosite decomposition - polysulfide leaching method to recover gold from typical Carlin type gold concentrate. Standard characterization/analytical methods of XRD, ICP, MLA, XPS, and SEM-EDS were employed in the experiment. In the pressurized oxidation pretreatment process with high temperature and ferric sulfate concentration, jarosite minerals with stable properties were easily formed due to the appropriate amounts of K+ introduced in the flotation of the ore and a small amount of mica minerals containing Na+. The results show that pressurized oxidation pretreatment can efficiently liberate gold from the mineral, but causes secondary inclusion of sodium jarosite. The one-step sodium jarosite decomposition treatment of the residue produced by oxygen pressure leach, can effectively liberate gold from the sodium jarosite pHase. Thus, the influence of factors on extracting gold from sodium jarosite decomposition residue using polysulfide were systematically studied. Under the most suitable conditions, the leaching efficiency of gold increased up to 90.2%, which was 8.4% higher than that of the direct cyanidation of oxygen pressure leach residue. This study provides an efficient, clean, and environmentally friendly way for the resource utilization of refractory gold concentrate, with a potential industrial application.