Enhanced adsorption of citric acid at the calcite surface by adding copper ions: Flotation separation of scheelite from calcite

In this study, in light of the poor selectivity of single copper ions (Cu2+) and poor inhibition ability of citric acid (CA), the flotation separation effect of mixed depressant Cu2+/CA on scheelite and calcite was explored. The microflotation experiment showed that the mixed depressant had better separation effects on the two minerals than the single depressant, and the laboratory-scale experiment verified the efficient separation effect of the mixed depressant. The solution chemical analysis demonstrated the dominate components in the slurry environment. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis demonstrated the selective chemical co-adsorption of the mixed depressant in the form of copper species complexes on the calcite surface. The thermodynamic calculation of the complex formation and the conditional stability constant calculation prove that the copper species complex (CuL-) is more easily formed and more stable than the calcium species complex. The mixed depressant Cu2+/CA can efficiently separate scheelite and calcite, and scheelite can be efficiently enriched. [Display omitted] •Citric acid has weak depression on calcite.•The synergistic mechanism at solid-liquid interface was revealed.•Copper ions increase the depression of citric acid on calcite.•Copper ions and citric acid was selective co-adsorbed on the surface of calcite.•Flotation separation of scheelite from calcite was achieved using Cu2+/CA.