Enhancing the Demulsification of W/O Emulsions via Optimizing the Molecular Structure of Non-ionic Polyether Demulsifiers

Abstract

Polyether demulsifiers have attracted significant attention in oil–water emulsion separation for their efficiency, eco-friendliness, and cost-effectiveness. However, the structure–activity relationship between their molecular structure and demulsification performance requires further investigation. In this study, we examined the demulsification behavior of non-ionic polyether demulsifiers with diverse molecular structures using dissipative particle dynamics (DPD) simulations, aiming to enhance their oil–water separation efficiency through rational molecular structure design of non-ionic polyether demulsifiers. The results indicate that double comb-shaped demulsifiers has a dipole moment of 14.97 D and binding energy with water molecules of -645.87 kJ/mol, demonstrating superior demulsification performance compared to demulsifiers with other molecular structures. Notably, when the ethylene oxide (EO) to propylene oxide (PO) ratio is 1/1, the binding energy further decreases to -663.94 kJ/mol, shortening the water bridge formation time to 13.54 ns and demulsification time to 16 ns. Additionally, after the demulsifier replaced the oil molecules at the interface, it remained consistently located at the oil–water interface. This led to the destabilization of the emulsion system and a reduction in interfacial tension from 36.73 dyne/cm to 21.16 dyne/cm. This research offers valuable insights for developing efficient non-ionic polyether demulsifiers.