Effect of Phosphate and Fluoride on the Flotation of Aluminum-Silicates with Cationic Collector

Abstract

Phosphates and fluorides are adopted as regulators for the removal of silicates from diasporic-bauxite by flotation. Micro-flotation tests show that sodium hexametaphosphate has a stronger depressing power on diaspore than sodium fluorosilicate at pH 6.5 while using dodecylamine chloride as a collector. Zeta potentials of diaspore and silicate minerals become more negative in the presence of both sodium hexametaphosphate and sodium fluorosilicate. Adsorption studies indicate that the adsorption density of sodium hexametaphosphate on diaspore is much larger than that on silicate minerals at a concentration of 75 mg/L. Fourier transform infrared spectroscopy studies show that sodium hexametaphosphate interacts with the Al sites on the diaspore and silicate minerals to form P-O-Al bonds through PO2 groups. In the case of sodium fluorosilicate, the specific interaction on the surface involves [SiF6]2− or F− anions as suggested by Auger Electron Spectroscopy.