Mechanism of sodium lauryl sulfate reducing froth stability of dodecylamine in hematite flotation: Experiments and molecular dynamics simulation

Abstract

In this study, the influence of sodium lauryl sulfate (SLS) on the stability of dodecylamine (DDA) froth during the reverse flotation of hematite was investigated due to the frequent issue of excessively viscous foam leading to suboptimal reverse flotation outcomes. The research involved conducting flotation tests and two/three-phase froth stability assessments to explore how a specific molar ratio combination of DDA and SLS could enhance the flotation performance while simultaneously mitigating froth stability. The investigation into the mechanism by which SLS reduces the stability of DDA froth was aided by molecular dynamics simulations. The findings revealed that in the collector system comprising DDA and SLS, several key changes occurred at the molecular level. These included a decrease in the thickness of the electric double layer at the interface, a reduction in the thickness of the gas–liquid interface layer, weakening of the interaction strength between the head group and water molecules, a decrease in the coordination numbers of water molecules in the first hydration layer, and an enhanced migration ability of water molecules. Furthermore, there was an increased inclination angle between the head groups or molecular chains of the collector and the Z-axis, resulting in a diminished interaction depth between the head group and water and a closer positioning of the molecular tail chain to the gas–liquid interface with a more pronounced curvature. Consequently, these molecular adjustments led to a sparser arrangement of DDA molecules at the gas–liquid interface, lower coverage of the interface adsorption layer, and increased gas permeation, ultimately reducing DDA froth stability. The aforementioned conclusions provide a comprehensive molecular-level analysis of the principal mechanisms that can effectively reduce foam stability, including the attenuation of molecular head group-water interactions, reduction in gas–liquid interface layer thickness, decrease in gas–liquid interface orderliness, and enhancement of water molecule migration capability. The implications of this research extend to providing theoretical insights for addressing foam control challenges in DDA flotation processes.