The interaction mechanism and collecting performance of three sulfydryl collectors with Au(1 0 0) surface: A study combining DFT and molecular dynamics

Amyl xanthate (AMX), ammonium dibutyl dithiophosphate (ADD) and diisobutyl dithiophosphinate (DTPI) have proved to be common and effective sulfydryl collectors for gold flotation. In this study, density functional theory (DFT) and molecular dynamics (MD) methods are used to investigate the interaction mechanism and collecting performance of three sulfydryl collectors with Au(1 0 0) surface. The adsorption energy of DTPI is −283.30 kJ/mol, which is the largest among the three, suggesting its chemisorption on gold surface is the most stable. This is agreed with the prediction of polarizability and frontier orbital energy difference. The gold-collector interaction on the surface is realized by the bonding of surface Au atom and collector S atom. Density of states (DOS) results suggest that after collector adsorption the delocalization of S 3p orbital is increased, resulting in the enhancement of nephelauxetic effect, and this proves that the covalency of Au − S bond has been facilitated. DOS analysis further confirms that the S atom of DTPI is most likely to form a covalent bond with Au atom because of its strongest reactivity. Besides, molecular dynamics simulation suggests that the wetting process of water droplets on the gold surface would be hindered by the adsorption of three collectors, thus the wettability of the gold surface would change significantly. In summary, it can be considered that the gold collecting performance of three collectors follows the order of DTPI > ADD > AMX. This comparative study is helpful to understand the interaction mechanism between sulfydryl collectors and gold surface.