Selective separation of galena and sphalerite by flotation using metformin as a collector: Adsorption mechanism and DFT calculation

The similar flotability of galena and sphalerite makes their selective separation challenging. In this study, metformin (MF) was used as a flotation collector for the separation of galena from sphalerite. Micro-flotation tests demonstrated that at pH 7 with 3.5 × 10 −4 mol/L MF, galena recovery reached 80.5%, while sphalerite recovery was only 9.5%. Contact angle, zeta potential, and Fourier transform infrared spectroscopy confirmed that MF selectively adsorbed onto galena and enhanced its surface hydrophobicity. X-ray photoelectron spectroscopy revealed that MF chemisorbed onto galena through Pb–N coordination bonds formed between its C N and –NH 2 groups and surface Pb sites. Density functional theory calculations further demonstrated that MF exhibited a much stronger adsorption affinity for galena (-161.17 kJ/mol) than for sphalerite (-67.05 kJ/mol). Molecular electrostatic potential analysis indicated that the electron-rich nitrogen atoms of the C N and –NH 2 groups serve as the active sites for Pb 2+ coordination. The use of MF as a flotation collector offers a promising approach for developing high-performance collectors for lead minerals. Download: Download high-res image (170KB) Download: Download full-size image Schematic diagram of flotation separation of galena and sphalerite