Application of diagnostic roasting method in thermochemical treatment for Au recovery from gold-containing tailings in microwave field

Abstract In this study, the adaptability of gold-containing tailings to microwave chlorination roasting was investigated. The refractory characteristics of tailings were tested by diagnostic roasting method. Thermochemical treatment was conducted in different temperature regions to destroy the target mineral. At each roasting stage, the roasted tailings were analysed and characterised by atomic absorption spectroscopy (AAS) and X-ray diffraction (XRD) to retrieve the gold recovery rate, chlorine loss rate, oxidation characteristics, and grain size of the tailings before and after roasting to predict the gold content in different carriers. The contents of gold in combination of natural gold and bare inclusion, the vein gold state and locked gold state are 22.09%, 36.48% and 41.43%. The results of roasting diagnosis showed that the difference in recovery rate between microwave roasting and conventional roasting is mainly due to the difference in the amount of gold recovered from locked gold. After thermochemical treatment at 1173 K, recovery 26.73% of gold from locked gold state by microwave roasting, and recovery 1.43% of gold from locked gold state by conventional roasting. The microwave effectiveness of recycling gold from locked gold was 17.69 times higher than that of conventional methods. This study provides theoretical support for the industrialisation of the microwave heat treatment of gold-containing tailings on the basis of process mineralogy.