Extraction of Metals from Nickel Concentrate by Low-Temperature NH 4 HSO 4 Roasting-Water Leaching and Efficient Separation of Iron and Copper

Aiming at the problems of high energy consumption and low metal recovery in traditional smelting of nickel concentrate, a novel process, namely NH 4 HSO 4 roasting followed by water leaching to simultaneously extract metals and then separate them step by step, was proposed. The effect of some key factors on the extraction of metals was investigated by orthogonal experiments, and the optimal sulfated roasting conditions were determined as: concentrate particle size 75–80 µ m, roasting time 180 min, roasting temperature 400°C and N/C 8:1. The metal extractions were 94.2% for nickel, 97.0% for copper and 96.4% for cobalt; also 81.9% iron and 67.7% Mg were sulfated. The clinker was selectively roasted at 600°C for 2 h to convert soluble iron salts into water-insoluble iron oxides, followed by conducting oxidation neutralization of the leaching solution; 97.1% of iron could be removed. Solvent extraction of copper from iron-removed solution was carried out with LIX984, and the extraction of Cu could reach 99.0%, while the losses of Ni, Co and Mg were < 2.0%. When the organic phase was back-extracted with 3–5 mol/L sulfuric acid for 2–6 min, the back-extraction of copper could reach 99.5%.