Recent Advances for Phase Transformation and Reconstruction of Gold-bearing Inclusions during the Pre-oxidation of Refractory Gold Ores

This is an article in the field of mining engineering. Under the background of "double carbon" and "ballast stone" of refractory gold ore resources, pre-oxidation is an effective pretreatment method for efficient gold extraction from refractory gold ores. Destroying the finely impregnated gold inclusions, and eliminating or avoiding the passivation, robbing or secondary wrapping of gold by harmful substances, are the key and bottleneck problems to determine the gold recovery rate in refractory gold ores. Understanding the phase transformation and reconstruction evolution of gold-bearing minerals during pre-oxidation process is critical for inclusions destruction directly and gold leaching. In this article, the typical characteristics of refractory gold ores and existing pre-oxidation techniques were outlined, and the research advances in phase transformation and reconstruction of gold-bearing inclusions in roasting oxidation, hot-press oxidation, biological oxidation, chemical oxidation and other pre-oxidation processes were summarized. The result shows that the gold-bearing sulfides are mainly transformed into Fe oxides (or As oxides) and sulfate (or arsenate) by pre-oxidation. However, due to the coupling effect of multiple factors such as oxidation temperature, atmosphere or oxygen concentration, pH value, redox potential, Bacterial characteristics, etc., sulfides may also be converted into elemental sulfur, sulfur oxide, thiosulfate, jarosite and scorodite. In addition, jarosite, iron oxide and calcium sulfate are the main solid matters leading to the secondary package of gold. Pre-oxidation process and microscopic mechanisms, such as neutral thermobaric oxidation with low temperature and pressure, bacteria domestication with thermophilic, alkalophilic and arsenic-resistant properties, process enhancement of bacterial oxidation under multi-factor coupling, green and efficient oxidant screening, and chemical oxidation based on multi-field coupling, etc., still need to be deeply researched. The coupling relationship and regulation among ore characteristics, process reaction of pre-oxidation, phase transformation and reconstruction of gold-bearing materials and gold recovery rate are the research hotspots and difficulties in the green and efficient pre-oxidation field for refractory gold ores in the future.