Flotation separation of chalcopyrite from molybdenite with sodium thioglycolate: Mechanistic insights from experiments and MD simulations

The pivotal roles of Cu and Mo in industrial applications accentuate the importance of effectively separating and recovering chalcopyrite and molybdenite. They commonly exist together in natural environments, necessitating their segregation prior to engaging in smelting processes. The separation is mainly accomplished through flotation. The inadequate comprehension of the mechanisms of thiol depressants, commonly used in the separation of chalcopyrite and molybdenite, poses challenges to both resource recovery and the development of depressants. Based on the bulk flotation practice of copper-molybdenum sulfide minerals, this study investigated the separation effect and mechanism of sodium thioglycolate (STG) on xanthate-treated chalcopyrite and molybdenite. Flotation and contact angle tests validate that STG enhances the hydrophilicity of chalcopyrite surfaces, leading to an 83.79% flotation separation efficiency for molybdenite. Various methodologies were employed to explore the mechanism of the depressant, encompassing open-circuit potential measurements, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, infrared and ultraviolet spectroscopy, time-of-flight secondary ion mass spectrometry, classical molecular dynamics and ab initio molecular dynamics simulations. The stable adsorption layer of STG is established by the interaction of thiol groups from STG with Cu and Fe sites on the chalcopyrite surface, resulting in the formation of Cu(I)-S and Fe(III)-S structures. The adsorption density of STG layer on the chalcopyrite surface is four times greater than that on molybdenite. Additionally, following the adsorption of STG, the previously adsorbed xanthate chalcopyrite surface is desorbed with an efficiency of 65.88%. These findings contribute to the elucidation of the mechanistic understanding of thiol-containing depressants in the flotation separation process of copper-molybdenum sulfide minerals and establish a basis for the prospective advancement of mineral processing reagents.