Effect of ultrasonication of sodium silicate on selective adsorption of scheelite and fluorite surfaces

Effect of ultrasound on solution properties of sodium silicate (Na 2 SiO 3 ) was investigated in this study to separate scheelite from fluorite effectively. The effect of ultrasonicated sodium silicate solution on flotation separation of scheelite and fluorite and selective adsorption mechanism of scheelite and fluorite were also explored. Ultrasonicated Na 2 SiO 3 was found to significantly improve the scheelite grade, and the adsorption capacity and adsorption heat of Na 2 SiO 3 on fluorite surface were significantly improved, which can enhance the inhibitory effect. The ultrasonic cavitation effect promoted electrolysis of Na 2 SiO 3 in the solution, forms additional SiO 3 2− and SiO 4 4− ions, reduced surface tension of the solution, and thus reduced adhesion work between Na 2 SiO 3 and fluorite. Fourier transform infrared (FTIR) Spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses showed that sodium silicate was obviously adsorbed on the surface of fluorite, elemental Si content of the fluorite surface increased considerably and to a higher level than that of the scheelite surface, and Ca 2+ binding energy shifted less noticeably on the scheelite surface than that on the fluorite surface. These results indicated that the higher adsorption strength for Na 2 SiO 3 on the fluorite surface than that on the scheelite surface hindered the adsorption of benzohydroxamic acid (BHA) on the fluorite surface and ultrasound promoted selective separation of scheelite and fluorite.