Pore Evolution in Refractory Gold Ore Formed by Oxidation Roasting and the Effect on the Cyanide Leaching Process

Refractory gold ore is usually affected by the associated carbonaceous matter through the preg-robbing effect, which is eliminated by oxidation roasting, followed by leaching, to achieve a satisfactory gold leaching efficiency. Roasting-leaching experiments, pore structure measurements, scanning electron microscopy (SEM), and X-ray diffraction are used to explore the structural evolution of pores on the surface and its effect on the leaching performance. Pores with optimal sizes were obtained by roasting at 650 °C for 2.0 h with a ventilation of 0.6 m³/h; approximately 92.55% gold could be recovered under these conditions. A porous structure observed by SEM became more compact as the temperature further increased to 850 °C. The formation of CaSiO₃ and CaSO₄ in pores led to pore shrinkage. The mechanism of oxidation roasting, followed by cyanide leaching, was schematically analyzed and revealed the effects of pore structural evolution and phase transformation on the leaching efficiency.