Evaluation of 1-hydroxyethylidene-1,1-diphosphonic acid as an efficient and low-toxic sphalerite depressant in the selective flotation of galena from sphalerite

In this work, an environment-friendly sphalerite depressant 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) was exploited in the flotation separation of sphalerite and galena . The flotation performances of sphalerite and galena treated by HEDP were investigated by mineral flotation tests. The depression mechanisms of HEDP on sphalerite were investigated by various characterization techniques such as zeta potential tests, Fourier Transform Infrared Spectrometer (FTIR), X-ray Photoelectron Spectroscopy (XPS) analysis, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and density functional theory (DFT) calculation. Flotation tests showed that HEDP selectively depressed sphalerite but almost did not influence the flotation of galena in sodium isobutyl xanthate (SIBX) system, which achieved effective flotation separation results. zeta potential tests and FTIR results proved the preferential adsorption of HEDP on sphalerite surface, but the pre-adsorbed of HEDP on galena could be replaced by SIBX easily. XPS, ToF-SIMS analysis and DFT calculation demonstrated that HEDP was coordinated with Zn atom through two different phosphonic acid group, forming a six membered chelating ring.