A DFT-based method to determine the ammonium-induced activation and sulfidation pathway of tenorite

Abstract

BackgroundThe ammonia modification of minerals surfaces has been successfully applied to obtain a successful flotation performance and plays an important role in the sulfidation flotation of copper oxides. First principle calculations based on density functional theory (DFT) are able to provide information on the electronic structures, properties, adsorption energies, and electron transfer of the mineral surface and floatation reagents, thus helping to understand the interaction mechanisms of reagents with copper oxides. MethodsThe DFT was explored to discuss the mechanisms underlying the HS– species and NH3 direct and activated sulfidation of tenorite (1 1 1) surfaces. The relationship between Cu–S–NH3 species distribution and pH value in the solution was simulated by visual MINTEQ. Significant findingsThe Cu 3d orbital peak was observed to be stronger at the Fermi level than that of the O 2p orbit on the tenorite (1 1 1) surface, and the negative adsorption energy and adsorption effect of HS– get better results through calculations, while the Cu 3d and 4 s peaks overlapped the corresponding S 3 s and 3p peaks at the HS– adsorption on tenorite (1 1 1) surface. The maximum adsorption energy of NH3 and HS– on the tenorite (1 1 1) surface was determined as –19.63 eV, which is more negative than that with just the adsorption of HS– on the tenorite (1 1 1) surface. Herein, we combined Visual MINTEQ and DMOL3 models to indicate that the addition of NH3 ions catalyzes the formation of CuS(s), ie., NH3 mainly catalyzes the interaction between HS– species and Me(OH)2 on the hydroxylated oxidized ore surface or solution, that is, Me(OH)2 first dehydroxylates to metal ions, and then forms sulfide species with HS–. The flotation experiment was consistent with the DFT calculation results.