Effect of ammonium sulfate on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation

Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation. In this work, inductively coupled plasma optical emission spectrometer (ICP-OES) measurements, Visual MINTEQ calculation, X-ray photoelectron spectroscopy (XPS) analysis, time of flight secondary ion mass spectrometry (ToF-SIMS) analysis, and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate ((NH₄)₂SO₄) on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation. The results showed that (NH₄)₂SO₄ exhibited a positive influence on hemimorphite sulfidation flotation. It was ascribed to the number of zinc components in the form of Zn²⁺ and [Zn(NH₃)_i]²⁺ (i = 1–4) increased in the flotation system after hemimorphite treatment with (NH₄)₂SO₄, which was beneficial to its interaction with sulfur species in solution, resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface. [Zn(NH₃)_i]²⁺ participated in the sulfidation reaction of hemimorphite as a transition state. In addition, the sulfidation reaction of hemimorphite was accelerated by (NH₄)₂SO₄. Thus, (NH₄)₂SO₄ presents a vital role in promoting the sulfidation of hemimorphite.