Abstract
The aim of this study was to optimize the chromite recovery from a South African chromite middle group seam plant tailings. A shaking table and magnetic separator were used as part of a multi-step process to achieve this. The sample was subjected to intensive characterization before the optimization process began. The chemical composition, mineral composition, mineral liberation, and particle size distribution of the sample were all determined using a variety of analytical techniques, including X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy-Dispersive Spectroscopy (SEM-EDS), and sieve size classification.
Response Surface Methodology (RSM) and Central Composite Design (CCD) were used in the optimization process. These combined methods made them easier to figure out how different factors that interact with each other affect chromite recovery. For the shaking table method, the tilt angle (in degrees), sample feed rate (in g/min), table vibration (in Hz), water flow rate (in L/h), and particle size range (in μm) were all investigated as independent variables. For magnetic separation, the independent variables included feed rate (in g/min), current (in amperes), gap width (in mm), and roll speed (in rpm). On the other hand, the response variables were described as recovery, Cr2O3 grade, and the Cr/Fe ratio.
The characterization results proved that the sample was a low-grade chromite ore with a Cr/Fe ratio of 1.07, assaying 19.86% Cr2O3, 18.12% Fe2O3, 10.45% MgO, 12.10 % Al2O3, and 33.7% SiO2. According to particle size distribution (PSD) measurements, 80% of the material was able to pass through 106 μm sieve. The RSM-CCD optimization results revealed that the optimum operating parameters for the shaking table process are 5˚ for the tilt angle, 152.3 g/min for the feed rate, 42.95 Hz for vibration frequency and 77.16 μm for the size fraction which led to an optimal recovery chromite of 67.01%, 37% of Cr2O3 grade and 1.52 ratio Cr/Fe. The operating parameters for the magnetic separation process are 124.24 g/min of feed rate, 1.63 amperes (A) of current, 19.09 mm of the gap, 154 rpm of roll speed for a maximum recovery of 79.02%, Cr2O3 grade of 46.15% and Cr/Fe ratio of 2.08.
Keywords: Chromite; Recovery; Shaking table; Magnetic separation; Characterization; Optimization; Response surface methodology (RSM); Central Composite Design (CCD)