Influence of Oxidation Roasting on Pore Structure Evolution and Gold Extraction in Refractory Gold Concentrate

The reserves of non-refractory gold ores are continuously declining, while refractory gold ore deposits remain abundant. Therefore, developing more efficient technologies to utilize these ores is crucial for gold-related industries. Oxidation roasting is commonly used to eliminate the adverse effects of sulfur- and arsenic-bearing minerals, but its underlying mechanisms are still not fully understood. To address this gap, the present study investigated the effect of oxidation roasting on gold leaching rate. A combination of roasting–leaching experiments, X-ray diffraction (XRD), pore structure analysis, and scanning electron microscopy (SEM) was employed to examine the evolution of surface pore structures and their impact on leaching performance. The gold leaching rate of the raw material was only 10.13%, due to the encapsulation of gold particles within pyrite. Under optimal roasting conditions—600 °C for 2 h—the gold leaching rate reached a peak value of 88.06%. At this temperature, the dense surface of pyrite decomposed, forming a highly porous structure that allowed the JinChan lixiviant to fully contact the gold particles. However, increasing the roasting temperature or extending the roasting time promoted the formation of CaSO4 and Mg2SiO4. These newly formed phases may have contributed to pore blockage on the hematite surface, which could explain the more compact structure and the subsequent decline in gold extraction. Based on these observations, a possible mechanism is proposed linking pore structure evolution and phase transformation during roasting to the leaching performance.