Flotation separation of scheelite from fluorite by using DTPA as a depressant

Abstract

The selective separation of scheelite from fluorite is difficult because of their similar surface properties. In this study, diethylenetriaminepentaacetic acid (DTPA) was used as a novel depressant for the efficient removal of fluorite from scheelite, and its depression effect and mechanism were systematically investigated by conducting micro-flotation experiments and a series of surface analyses. The micro-flotation experiments showed that the floatability of fluorite was significantly reduced by DTPA, whereas that of scheelite was minimally affected. Zeta potential measurements revealed that DTPA selectively adsorbed on fluorite surface and decreased the zeta potentials, whereas the zeta potentials of scheelite were negligibly influenced by DTPA. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy further proved that the interaction between DTPA and the fluorite surface was chemisorption, and in the adsorption configuration, the carboxyl groups of DTPA chelated with Ca sites on the fluorite surface. Additionally, an electrical analysis showed that electrostatic attraction facilitated the adsorption of DTPA on the fluorite surface. The adsorption of DTPA on fluorite surface could strongly inhibit the further adsorption of NaOL on fluorite surface, and therefore significantly depressed the floatability of fluorite. In contrast, the interaction between DTPA and scheelite was very weak and was impeded by steric hindrance caused by WO42- and electrostatic repulsion. Therefore, DTPA has the potential to act as a depressant for the effective separation of scheelite from fluorite.