The enhanced sulfidation mechanism of surface activation in hemimorphite through ammonium complexation: An experimental and density functional theory study

This study investigated the impact of ammonia (NH3) solution on the flotation behavior of hemimorphite sulfidation, employing a comprehensive analysis that encompasses micro-flotation experiments, X-ray photoelectron spectroscopy (XPS) analysis, contact angle testing, atomic force microscopy (AFM) imaging, and density functional theory (DFT) calculations. The introduction of ammonia water (NH3 center dot H2O) resulted in a significant 22.64 % increase in hemimorphite recovery rate, as demonstrated in flotation tests. In this study, both XPS and AFM analyses provided compelling evidence supporting the assertion that NH3 center dot H2O facilitated the sulfidation of the mineral surface, resulting in an increased formation of sulfide products. Contact angle testing indicated that surface modification with NH3 center dot H2O enhanced the hydrophobic properties of the hemimorphite. DFT calculations offered valuable insights into the effect of NH3 on the hydration layer, indicating that NH3 substituted H2O molecules and increased the distance between Zinc (Zn) and O5 (H2O) to 5.6 angstrom. Furthermore, the adsorption energy of HS- on the hemimorphite (110) surface significantly increased with NH3 enhancement (-18.05 eV) as opposed to without NH3 enhancement (-12.79 eV). These results indicated that the adsorption configuration of NH3 in conjunction with HS- was more stable than that of HS- alone on the hemimorphite (110) surface. Thus, the collective results provided valuable insights into the enhanced sulfidation mechanism activated by ammonium complexation on the hemimorphite surface.