Efficient Extraction of Ni, Cu and Co from Mixed Oxide–Sulfide Nickel Concentrate by Sodium Chloride Roasting: Behavior, Mechanism and Kinetics

Facing the situation of nickel resource shortage and increasing nickel demand, it is an important task for the development of nickel industry to realize efficient utilization of low-grade nickel sulfide ore. In this work, the process of NaCl roasting-water leaching was proposed to simultaneously extract valuable metals from low-grade nickel concentrate. Based on the thermodynamic analysis of roasting process, the effect of several key factors on metal extraction was investigated. The results show that the extraction of Ni, Cu and Co can reach approximately 94.08, 92.81 and 91.85 pct, respectively, under the following optimum conditions: temperature 400 °C, time 90 minutes, NaCl dosage 100 pct and concentrate particle size 70–88 µm. The evolution behavior and mechanism of metallic minerals are determined through thermodynamic analysis, differential thermogravimetric analysis, and phase composition analysis of roasted product. The kinetics of the roasting process based on the differential thermal and thermogravimetric experiment was analyzed by Kissinger method and Doyle-Ozawa method. The average apparent activation energy of metallic minerals being chlorinated is determined as 400.12 kJ/mol and the kinetic equation was expressed as dα/dt = 2.41 ×10^12e^ - 400.12/RT(1 - α)^1.27 .