Effect of Bi(III) on flotation of copper sulfide from leaching residue of copper smelting dust

Flotation is a potential method for extracting residual copper sulfide (CuS) from the acid-leaching residue of copper smelting dust; however, the inhibitory impact of Bi(III) in the flotation pulp significantly hampers its practical application. In this study, we systematically investigated the inhibition mechanism of Bi(III) on CuS flotation and propose a method to prevent inhibition. Microflotation test results show that a pulp environment with pH 3 and a Bi(III) concentration greater than 1 × 10–2 mol/L significantly depresses the floatability of CuS. Scanning electron microscopy and energy-dispersive spectroscopy results confirmed that Bi(III) hydrolyzes on the surface of CuS to form a precipitate cover layer, which adsorbs onto the surface of CuS. This precipitate was confirmed by X-ray photoelectron spectroscopy analysis and thermodynamic calculations to be BiOCl. Fourier transform infrared analysis revealed that BiOCl reduces the recovery of CuS by hindering the adsorption of xanthate. Finally, the pre-treatment of the leaching residue with H2SO4 + NaCl solution can dissolve BiOCl precipitates on the surface of CuS, eliminate the influence of Bi(III), and result in efficient flotation recovery of CuS from leaching residue.