Theoretical Study of the Intercalation Behavior of Ethylene Glycol on Kaolinite

Abstract

Different kinds of models of ethylene glycol (EG) intercalated on kaolinite are investigated by means of density functional theory (DFT). It is found that the most possible mode of EG intercalated on kaolinite is a mixing of physical intercalation and covalent grafting of EG. If the existence of water was considered, the possibility for EG intercalating on kaolinite is as follows: mixing of physical intercalation and covalent grafting > physical intercalation > covalent grafting. The distance between the carbon atom of the bonded EG and the Al atom of the kaolinite lamella are calculated to be about 3 Å, which is in good agreement with the experimental value. The methylene and hydroxyl groups of EG or grafting EG can form hydrogen bonds with both adjacent layers of kaolinite with d(001) of 9.40 Å. With the expanding of the d(001) value from 9.40 to 10.85 Å, the van der Waals forces become more important in the stabilization of EG molecule in the interlayer space.