Adsorption study of sesbania gum onto calcite surface: Implications for smithsonite-calcite flotation separation

In the present study, sesbania gum (SG) was introduced as a depressant to achieve the selective flotation separation of smithsonite from calcite , and the deep adsorption mechanism was systematically examined using a variety of methods, including density functional theory (DFT) calculation and a series of advanced analytical manners. Micro-flotation experiments indicated that SG strongly depressed the flotation of calcite at pH 9.5, while having little impact on the flotation of smithsonite, leading to the successful separation of the two minerals. DFT calculation predicted that SG could be adsorbed onto the calcite surface, but not onto the hydroxylated smithsonite surface in an aqueous solution system. This was supported by zeta potential tests, Fourier-transform infrared spectroscopy (FTIR) tests, and time-of-flight secondary ion mass spectrometry (TOF-SIMS) detection. As a result, the adsorption of sodium oleate (NaOL) onto the calcite surface was hindered by the pre-adsorption of SG, while the adsorption of NaOL onto the smithsonite surface was not affected. X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM) tests confirmed that SG was mainly adsorbed onto the calcite surface via physical adsorption . This finding provided a new perspective for the interaction between mineral and hydroxyl containing depressant.