Coarse Froth Flotation to Optimise Scheelite Recovery

The flotation of coarse-sized particles is an important step in the pathway to sustainable recovery as it can reduce reagents usage, energy consumption, and environmental impact, as well as minimise overgrinding. This study assessed the floatability of coarse-sized scheelite, a mineral containing the critical element tungsten (W), using plant-derived samples from the Kara mine magnetite–scheelite skarn deposit in Tasmania, Australia. The recovery of three sizes of coarse-size scheelite (+150, +300, and +425 µm) was tested under optimised conditions determined through laboratory experiments (i.e., 900 rpm, pH 9, collector sodium oleate 5 g/t, and depressant mixture of 4 g/t of sodium silicate and 4 g/t of quebracho). Results show that WO3 recoveries of 91.76% and 84.14% and grades of 61.03% and 58.73%, respectively, were achieved for samples containing the +425 µm and +300 µm size scheelite. These samples had lower mass recoveries (70.95% and 84.15%), reflecting the selective flotation of coarse scheelite. Lower WO3 recovery (79.44%) and grade (45.76%) but higher mass recovery (88.81%) were obtained for the samples with +150 um scheelite. This paper provides details of the test work and provides a framework for adapting coarse scheelite particle flotation strategies to other scheelite skarn deposits and high-density mineral systems to help enable improved recovery and enhanced economic efficiency in mineral processing plants.