Recovery of ultrafine scheelite particles by magnetic seeding flocculation and its mechanism

Abstract Froth flotation has been proven to be the most efficient mineral processing technology for fine particles. However, it cannot be applied to processing ultrafine particles, especially ultrafine scheelite with sizes of −10 µm, thereby wasting a lot of tungsten resources. In this study, positively-charged and hydrophobic magnetic seeds were fabricated and employed instead of bubbles to capture ultrafine scheelite particles, significantly improving the recovery of the ultrafine particles via magnetic separation. Here, a novel surfactant, lead complexes with benzohydroxamic acid (Pb–BHA), were developed to modify the magnetite. The zeta potential, Fourier-transform infrared (FT–IR) spectroscopy and surface hydrophobicity measurements indicated that Pb–BHA was adsorbed on the magnetite surface, inducing a positively-charged hydrophobic surface. Ultrafine scheelite (−10 µm) was treated with sodium oleate (NaOL) to impart it with negative charges and surface hydrophobicity. The flocculation of magnetite and scheelite is directly observable via scanning electron microscopy (SEM). The extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) theory was applied to analyse the mutual attraction of two kinds of particles, and the calculation results demonstrated that they aggregated mainly through electrostatic and hydrophobic interactions. This technology affords an alternative solution for processing ultrafine valuable particles.