Interaction mechanism of a novel reagent scheme in the selective separation of scheelite from calcite

Abstract

Up to now, the selective separation of scheelite and calcite is still tricky. Etidronic acid (abbreviated as EA or H4L) is an environmental scale inhibitor capable of chelating metal ions. This research adopted the EA as a selective depressant to separate scheelite from calcite. Flotation results of the single mineral, binary mixed minerals, and real ore showed that EA had better selectivity for calcite at pH 10.0 with sodium oleate (NaOL) as a collector. Zeta potential results found that EA adsorption amount on the positively charged calcite surfaces was more significant than that on the negatively charged scheelite surfaces. X-ray photoelectron spectroscopy, solution chemistry, and density functional theory (DFT) calculation further proved that on calcite, the active O atoms in the dominant species (HL3-) of EA had a strong chemical interaction with Ca sites to form a hydrophilic Ca–EA complex by O 2 s and Ca 3p orbitals hybrid. In contrast, the interaction with these on scheelite was significantly weaker. Afterward, NaOL tended to occupy the scheelite surfaces due to its higher activity of Ca rather than the calcite surfaces. Therefore, the difference in HL3- and OL- adsorption on both minerals achieved the selective separation of scheelite and calcite.