Recycling of Valuable Metals from Low-Grade Nickel Sulfide Ores by Preroasting Followed by Chlorination with FeCl3·6H2O: Thermodynamics, Kinetics, and Process Intensification

This study introduces an innovative approach that enables the simultaneous extraction of Ni, Cu, and Co from low-grade nickel sulfide ore through FeCl3·6H2O roasting following pretreatment. The feasibility of roasting and atmospheric conditions is determined by thermodynamic analysis. By optimization of the chlorination process, the key factors affecting the metal conversion are ore particle size and chlorination agent-to-ore mass ratio, while the secondary factors are roasting temperature and time. After preroasting at 300 °C for 2 h, 95.5% Ni, 94.4% Cu, and 92.1% Co can be extracted from the ore under the following optimal roasting conditions: roasting temperature of 200 °C, roasting time of 120 min, chlorination agent-to-ore mass ratio of 2:1, and ore particle size of 75–80 μm. The mineral phase transformation and its evolution under various control conditions are examined by using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The chlorination reaction, which is a typical gas–solid interaction, undergoes a kinetic process, where studies indicate that the internal diffusion primarily governs the conversion rates of Ni, Cu, and Co. This study establishes the necessary conditions, control parameters, and enhancement procedures for metal extraction from ore via chlorination roasting, thereby providing a significant theoretical foundation for advancing FeCl3·6H2O roasting technology.