Effect of primary alkylamine adsorption on muscovite hydrophobicity

Abstract

The adsorption of surfactants on mineral surface has a great influence on the solid hydrophobicity and flotation behavior. The relationship between the hydrocarbon tail length of the primary alkylamines and muscovite hydrophobicity was investigated by contact angle measurement, atomic force microscopy (AFM), density functional theory (DFT), and molecular dynamics (MD) simulation. By comparing the oxygen density and the hydrogen bonds number profile, we observed that the formed hydrogen bonds for each water molecule on the interface between hydrocarbon tails and the water phase were fewer than that in the bulk. Additionally, the muscovite that absorbed alkylamines transformed from a hydrophilic surface to hydrophobic one. We also found that the octadecylamine (ODA)-absorbed muscovite surface was more hydrophobic than the dodecylamine (DDA)-absorbed surface while they were both in a monolayer state. Furthermore, because octadecylamine has a much lower hemi-micelle concentration (HMC) than dodecylamine, it forms multilayer more easily, meaning that the primary alkylamine with longer hydrocarbon tail is a better choice for the hydrophobicity enhancement of muscovite surface. The experimental results are in good agreement with theoretical calculations. © Editorial office of Acta Physico-Chimica Sinica.