Transformation and leaching kinetics of silicon from low-grade nickel laterite ore by pre-roasting and alkaline leaching process
(1. School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, China;
2. Key Laboratory of Resources Cleaner Conversion and Efficient Utilization at Qinhuangdao City, Qinhuangdao 066004, China;
3. School of Metallurgy, Northeastern University, Shenyang 110819, China)
Abstract: The mineralogical phase transformation of a low-grade nickel laterite ore during pre-roasting process and the extraction of silicon during alkaline leaching process were investigated. The results indicate that the reaction activity of nickel ores is effectively improved by pre-roasting at 650 °C for 2 h, because of the transformation of lizardite into magnesium olivine and protoenstatite. When finely ground ore samples (44-61 μm) pre-roasted firstly react with sodium hydroxide solution (60 g/L) with a solid/liquid ratio of 1:5 at 140 °C for 120 min, the extraction of silicon can reach 89.89%, and the other valuable elements of magnesium, iron and nickel are accumulated in the solid residues. The leaching kinetics of nickel laterite ore can be described successfully by the diffusion through the product layer control model. The activation energy is calculated to be 11.63 kJ/mol and the kinetics equation can be expressed as 1-3(1-x)2/3+2(1-x)=13.53×10-2exp[-11.63/(RT)]t.
Key words: low-grade nickel laterite ore; silicon extraction; mineralogical phase transformation; alkaline leaching kinetics