Efficient reductive leaching of valuable elements from oxygen pressure leaching residue of high-grade nickel matte within sulfur dioxide

There are about 5 % nickel, 50 % iron and other valuable metal in the oxygen pressure leaching residue of high nickel matte (NPLR),1 the existing treatment methods can not realize the comprehensive utilization of valuable components. In order to realize the efficient utilization of nickel, iron and germanium, this article systematically studied the leaching behaviors, thermodynamics and kinetics of nickel, iron and germanium in the NPLR in the H2SO4-SO2 system by using an efficient reductive leaching method. Thermodynamic research proved the feasibility of leaching, and the effects of initial sulfuric acid concentration, sulfur dioxide flow rate, temperature, liquid–solid ratio and leaching time on the leaching ratios of each element were explored, under the optimal condition: the initial sulfuric acid concentration 95 g/L, sulfur dioxide flow rate 350 mL/min, temperature 85 ℃, liquid–solid ratio 7:1 and leaching time 180 min, the extractions of nickel, iron and germanium were 92.50 %, 88.89 % and 92.53 % respectively, it was confirmed that the leaching of nickel and germanium were determined by iron through fitting at the same time. The kinetic of iron leaching followed the shrinking core model and was controlled by chemical reaction, and the activation energy was 66.07 kJ/mol. The reaction orders of initial sulfuric acid concentration and flow rate of sulfur dioxide were obtained. In addition, the strengthening mechanism of SO2 was expounded from thermodynamics and kinetics respectively. The morphology changes before and after leaching were studied by SEM/EDS, and the leaching behaviors of Ni, Fe and Ge were confirmed.