Surface modification of azurite with lead ions and its effects on the adsorption of sulfide ions and xanthate species

Highlights: • Pb ions can adsorb onto azurite surface and form Pb-O species. • Pb-S species formed on azurite surface in the azurite-Pb(NO₃)₂–Na₂S system. • S species distribution increased on azurite surface after treatment with Pb ions. • Addition of Pb ions before sulfidization positively affected the azurite floatability. Enhancing the sulfidization of copper oxide minerals has been widely studied to improve flotation recovery. In this study, we investigated azurite surface modification with lead ions and its effects on the adsorption of sulfide ions and xanthate species on the surface with X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), zeta potential measurements, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet (UV) adsorption analysis, and micro-flotation tests. In the azurite–Pb(NO₃)₂ system (pH 8.5–9.5), XPS and ToF-SIMS analyses showed lead ions can adsorb on to the azurite surface, forming Pb-O species. In the azurite–Pb(NO₃)₂–Na₂S system, XPS results showed that some Pb-O species formed on the Pb(II)-treated azurite surface. The analysis also detected Pb-S species after further treatment with Na₂S and demonstrated that most Cu(II) species were reduced to Cu(I) species, which assisted xanthate adsorption on to the surface and improved surface hydrophobicity. The zeta potential results indicated that lead ions can chemisorb on the azurite surface and promote its interaction with sulfide ions. The FT-IR and UV results demonstrated that the adsorption of xanthate on the azurite surface was greatly increased after the addition of lead ions and before sulfidization of the surface with Na₂S. Micro-flotation results showed that the azurite flotation recovery improved after the surface was modified with lead ions before sulfidization. Therefore, lead ions had a positive influence on the sulfidization flotation of azurite.