Recovering cobalt from cobalt oxide ore using suspension roasting and magnetic separation technique

Abstract

Cobalt ore is a scarce resource in China, often associated with iron ore, and it is well known that its separation and effective recovery are extremely difficult. In this paper, cobalt oxide ore is used as raw material and reduced by suspension roasting method at the atmosphere of H2. Magnetic separation is carried out to obtain cobalt (Co) and Fe concentrate. The experimental results show that the optimal magnetic separation performance of cobalt oxide ore is achieved at 650 °C and 30 % H2 concentration. The Co and Fe concentration are obtained synchronously with the grade of 7.32 % and 62.13 % respectively. X-ray diffraction (XRD) and scanning electron microscope (SEM) reveals that the phase of cobalt oxide ore in H2 roasting process is transformed into CoO→Co and Fe2O3→Fe3O4. The surface of the sample appears cracks after roasting. The vibrating sample magnetometer (VSM) test reflects the magnetic changes of minerals that the optimum roasting condition leads to an increased magnetism. The specific surface and fracture structure are analyzed to illustrate the specific surface area and pore volume of the particles decrease and the average pore size increases as the roasting temperature increases. In general, reduction roasting of cobalt ore makes it possible to recover Co and Fe simultaneously, following by magnetic separation. The beneficiation efficiency is improved along with the reduced cost.