Selective Flotation Behavior of Dolomite from Fluorapatite Using Hydroxy Ethylene Diphosphonic Acid as High-Efficiency Depressant

In the reverse flotation of fluorapatite and dolomite, high-efficiency depressors of fluorapatite have received considerable attention. In this paper, the depression mechanism of hydroxy ethylene diphosphonic acid (HEDP) was studied for the first time as a novel fluorapatite depressant on the surface of fluorapatite. The effect of HEDP on the flotation behavior of the two minerals was studied by single and mixed minerals in flotation tests. HEDP exhibited an excellent depression effect on fluorapatite flotation, whereas its adsorption on dolomite surface was minimal. Fluorapatite and dolomite were effectively separated by applying sodium oleate as a collector and HEDP as a depressant at pH 6.0. The depression mechanism of HEDP on fluorapatite was further analyzed via contact angle measurement, zeta potential and X-ray photoelectron spectroscopic (XPS) analysis. We found that HEDP seriously hindered the adsorption of sodium oleate (NaOL) on the fluorapatite surface and had a minimal effect on the dolomite surface. XPS analysis results indicate that the strong adsorption of HEDP on the fluorapatite surface can be attributed to the strong chelation between the electron-rich groups of HEDP and Ca ions on the fluorapatite surface. Therefore, HEDP is used as a selective depressant of fluorapatite in the fluorapatite–dolomite flotation–separation process.