Flotation separation of apatite and calcite using gum arabic as a depressant

Abstract

Flotation separation of apatite and calcite has always been difficult because of their similar physiochemical properties. To realize the flotation separation of the two minerals, many inorganic depressants are usually used, which contaminate the environment. In this study, the behavior of the polymer molecule gum arabic (GA) as a depressant of calcite in the apatite flotation was investigated by the pure mineral flotation experiments, and the mechanism was discussed by the contact angle measurement, adsorption tests, Fourier transform infrared (FTIR) spectroscopy and X–ray photoelectron spectroscopy (XPS). The flotation results showed that GA had a significant depressive effect on calcite but not on apatite. The separation of apatite from calcite was realized by adding 50 mg/L of the depressant GA followed by 0.5 × 10−4 mol/L of the collector sodium oleate (NaOl) at pH 7–11. The contact angle measurements showed that GA considerably enhanced the hydrophilicity of the calcite surface but had no significant effect on that of the apatite surface. The adsorption tests showed that the amount of GA adsorbed on the calcite surface was obviously greater than that on the apatite surface, indicating that calcite had a stronger affinity for GA. The FTIR and XPS analysis indicated that GA was adsorbed weakly on the apatite surface, but strongly adsorbed on the calcite surface. After GA was strongly adsorbed on the calcite surface, the abundant free –OH and –COOH groups in the GA molecule made the calcite surface more hydrophilic. Subsequently, it was hard for NaOl to be adsorbed on the calcite surface due to the reduction of active site calcium as well as the steric hindrance and electrostatic repulsion effect of GA on the NaOl molecule, which resulted in the selective depression of calcite in the apatite flotation.