Beneficiation of Low-Grade Laterite Nickel by Calcination-Magnetic Separation Method

In this research, Effect of thermal treatment on beneficiation of low-grade laterite nickel by calcination-magnetic separation method was studied. In order to determine the components and elements of the sample, to recognize the main and minor minerals and their bond, and phase transformation caused by thermal treatment, Chemical analysis (XRF and ICP), microscopic studies and XRD analysis were done, respectively. SEM analysis was done to study the content of nickel and other minerals. In order to determine the phase transformation of the sample because of calcination treatment, thermal analysis of DTA/TG and XRD analysis, before and after of calcination were done. Wet magnetic separation tests with two methods of calcination-magnetic separation and only magnetic separation were done on the sample and the results in grade and recovery of nickel concentrate were compared. According to results, nickel content in the sample was0.94%. Main minerals of laterite sample were Hematite, Goethite, Quartz, and dolomite and minor minerals were Magnetite and minerals of serpentine group. Furthermore, there is no independent nickel mineral in the sample. SEM studies declared that nickel was substituted in iron-containing minerals (Hematite and Goethite). XRD and thermal analysis (DTA/TG) showed that at 350 °C, Goethite transformed to Hematite and at 750 °C, Hematite transformed widely to Magnetite. Calcination of feed at 750°C followed by wet magnetic separation with the magnetic field of 6000 Gauss in comparison with alone magnetic separation caused an increase in recovery and grade of magnetic concentrate to 12.7% and 0.41%, respectively. Results showed that an increase in temperature of more than 750 °C, caused a decrease in recovery and grade of nickel in magnetic concentrate.