Reaction characteristics and kinetics of gallium in chlorination roasting of copper tailings using calcium chloride

The mineral composition of copper tailings was examined, and the phase analysis of gallium was conducted for recovery of the rare scattered metal gallium from copper tailings. The reaction characteristics and kinetics of gallium in the chlorination roasting of copper tailings were investigated in a tube furnace apparatus under different conditions, including roasting temperature, quantity of chlorination agent, roasting time, and airflow. Calcium chloride was chosen for the chlorination reaction because it is highly effective for volatilization of metals. The results show that gallium mainly exists in limonites in the form of oxides, and increases in roasting temperature, quantity of chlorination agent, and roasting time are conducive to increasing the chloridizing volatilization rate of gallium. The tailings gradually melt when the roasting temperature exceeds 900 °C, resulting in a decrease in the chloridizing volatilization rate of gallium. The chloridizing volatilization rate of gallium reaches 78.86 % at roasting temperature of 900 °C for 40 min, airflow of 0.1 m3·h−1, and calcium content of 33.33 wt%. Study of the reaction kinetics of gallium in chlorination roasting shows that the values of activation energy both for chemically controlled and diffusion-controlled reactions are 44.64 and 11.93 kJ·mol−1, respectively. This indicates that the chemical reaction serves an important function in the chlorination volatilization of gallium. Taken together, the results reveal the usefulness of tailings as a source of rare metals and provide a basis for gallium recovery and environmentally friendly disposal of copper tailings.