Decoding the beneficiation of ultra-fine scheelite values from gold mine tailings: mineralogical investigation and flowsheet development

Abstract

The article assimilates mineralogical and morphological investigations to carve out a route to beneficiate scheelite values from the Hutti gold mine tailings. Conventional and advanced characterization techniques, such as X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Mineral Liberation Analyzer (MLA) have been exploited to ascertain the feed mineralogical behavior, subsequently deriving an effective beneficiation strategy. The gold mine tailing exhibited an ultrafine particle size distribution (d50: 17 mu m) and was predominantly composed of ferromagnesian silicates of amphibole and pyroxene groups along with quartz, arsenopyrite, mica and calcite. The tungsten particles were found to be mineralized in the form of a scheelite mineral (CaWO4), with an average WO3 content of 0.02%. The MLA analysis helped visualize the shapes of different mineral particles and their association with scheelite. It indicated that scheelite particles have an ultrafine particle size distribution (d50 = 10.7 mu m) with a high degree of liberation (about 90% free surface). The ultrafine particle size distribution and a high degree of liberation paved the way for adopting the concentration route via the Falcon concentrator followed by froth flotation. Falcon ended up with gravity concentrate a WO3 recovery of 81.9%; the corresponding grade was as low as 0.19%, primarily due to the presence of coarse and heavy minerals like amphibole, pyroxene, arsenopyrite and pyrite. The froth flotation of the Falcon gravity concentrate using oleic acid as a collector and sodium hexametaphosphate as a depressant could enrich the WO3 content to about 2.8% (about 15 times enrichment). Consequentially, a process flowsheet was proposed based on the pre-concentration studies, which could achieve 2.56% WO3 with an overall recovery of 66%.