evaluation of advanced gravity and magnetic concentration of a pgm tailings waste for chromite recovery

This research was aimed at evaluating the efficiency of advanced gravity and magnetic separations on the recovery of chromite from the fine platinum group metals (pgm) tailings consisting of particles 80% passing 75 μm with about 45% being >45 μm resulting in high chromite losses. the pgm plant tailings were subjected to x-ray fluorescence, scanning electron microscopy and particle size distribution analyses. the feed was then optimally classified with 60 mm diameter hydro-cyclone into underflow and overflow streams. the coarser underflow was further beneficiated using the spiral concentrator. the results obtained showed that the removal of fines increased the cr2o3 grade for the spiral feed from 12.27% to 17.64% while spiral concentrate grade improved from 14.84% to 21.46% and recovery 69.85% to 95.53%. magnetic separation efficiency was found to increase with particle size such that at >75 μm a concentrate with up to 17.13% grade and 61.5% recovery was achieved. the advanced falcon concentration was also observed to be mainly particle size dependent and at <75>45 μm up to 17% grade and 60.3% recovery was achieved. the results obtained are based on particles >45 μm and the finer particles <45 μm are likely to give poorer results. the results obtained indicate that gravity and magnetic separation were reasonably efficient to pre-concentrate pgm tailings before flotation. however, the processes are mostly affected by particle size and should be preceded by size classification to improve separation efficiency.