New insights into the activation mechanism of ammonium ions on the malachite sulfidization flotation.

[Display omitted] • Found that NH 4 + eliminated the inhibitory effect of Cu2+ on sulfidization. • Found that NH 4 + worked with Cu2+ to further promote sulfidization. • Reveal the mechanism of action between NH 4 + and Cu2+. • Reveal the effects of Cu2+ and Cu(NH 3) 4 2+ on surface sulfidization. Ammonium sulfate [(NH 4) 2 SO 4 ] is an effective activator of malachite sulfidization flotation. In this work, we explored the effects of ammonium ion (NH 4 +) and copper ion (Cu2+) on malachite sulfidization flotation and investigated the underlying mechanism. Flotation experiments demonstrated that NH 4 + can not only eliminate the negative effects of Cu2+, but also work together with Cu2+ to further promote malachite sulfidization flotation in a certain concentration range. Zeta potential, SEM-EDS, and X-ray photoelectron spectroscopy analysis results indicated that the single Cu2+ weakened the oxidation of S (II) species on the malachite surface and reduced the formation of sulfides. In the presence of NH 4 +, Cu2+ did not inhibit the formation of sulfides on malachite surface but worked with NH 4 + to promote it. Aqueous speciation calculation and adsorption test revealed that NH 4 + and Cu2+ interacted to form Cu (II)–NH 3 complexes, which reacts with S (II) species to form a copper sulfide substance that is more easily adsorbed on the malachite surface than the copper sulfide colloid formed by the reaction between Cu2+ and S (II) species. This leads to the improvement of surface sulfidization. [ABSTRACT FROM AUTHOR]