Magnetic separation studies of a lateritic nickel ore.

Abstract

Hydrogen reduction and thermal treatment experiments were carried out in the laboratory using a transition zone lateritic nickel ore. The products of the pyrometallurgical operations were subjected to magnetic separation. The ore and samples produced after the thermal processing (reduction and thermal treatment) were characterized by X-ray diffractometry (XRD), thermogravimetric analysis (TG), scanning electronic microscopy (SEM), and energy dispersive spectrometry (EDS). The qualitative identification of the main mineral transformations was performed and the influence of these thermal transformations in the magnetic properties of the sample was studied. When the reduction experiments were performed at 800 ° C, with a magnetic flux of 97.5 ± 10.6 mT, the nickel content increased by up to 33 % (recovery of ≈ 75 %) in the magnetic fraction. During the formation of magnetite in the reduction experiments, carried out at 400°C, the sample became very magnetic and, consequently, the unit operation of magnetic separation was not selective. It was possible to remove magnesium from all samples, regardless of the thermal treatment or reduction temperature used. The contents of this element were adjusted to the characteristic values of a limonitic ore.