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

Abstract

Effect of ultrasound on solution properties of sodium silicate (Na2SiO3) 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 Na2SiO3 was found to significantly improve the scheelite grade, and the adsorption capacity and adsorption heat of Na2SiO3 on fluorite surface were significantly improved, which can enhance the inhibitory effect. The ultrasonic cavitation effect promoted electrolysis of Na2SiO3 in the solution, forms additional SiO32− and SiO44− ions, reduced surface tension of the solution, and thus reduced adhesion work between Na2SiO3 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 Ca2+ binding energy shifted less noticeably on the scheelite surface than that on the fluorite surface. These results indicated that the higher adsorption strength for Na2SiO3 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.