The role of enhanced desliming and gravity separation as a precursor to flotation in the upgrading of cassiterite from tailings

Due to the depletion of high-grade mineral deposits, there is increasing demand for the reprocessing of minerals from tailings dams. However, tailings reprocessing can present several challenges due to the presence of slimes: reduced selectivity and kinetics resulting in low recovery, excessive entrainment, and high reagent consumption. This research focussed on a previously intractable problem, the processing of a low-grade cassiterite (SnO2) feed from a tailings dam. Conventional technologies have failed to achieve viable recoveries and saleable grades. Therefore, gravity separation and desliming were applied using the REFLUX (TM) Classifier and the REFLUX (TM) Graviton, targeting the tin down to similar to 10 mu m, followed by flotation. The REFLUX (TM) Classifier experiments were performed using an inclined channel spacing of 1.8 mm at similar to 5 t/m(2)/h and higher. Recoveries of up to 94 % above 20 mu m and 50 % below 20 mu m were achieved. Importantly, the deslimed product permitted highly effective recovery of the tin by flotation, with final decanted product grades higher than 30 +/- 2 wt% tin, and an overall recovery of up to 35 +/- 5 %. Desliming with the REFLUX (TM) Graviton achieved recovery up to 80 %. The scope for further improvement in the grade and recovery is discussed.