Hydrophobicity of montmorillonite synergistically controlled by silanization and aliphatic amine modification

Abstract

The hydrophobic modification of montmorillonite significantly extends its potential applications across various industrial sectors. In this study, montmorillonite with controlled hydrophobicity was prepared based on Cu2+-exchanged montmorillonite by synergistic modification with perfluorodecyltrimethoxysilane and aliphatic amines. Our findings indicate that copper ion-exchange process not only increases the interlayer spacing of montmorillonite but also promotes the formation of antlerite crystals on its surface. The presence of interlayer water impedes the silanization process with perfluorodecyltrimethoxysilane, confining the grafting to the external surface of the clay. Consequently, this method can only increase the water contact angle (WCA) from 0° to 54.4°. Conversely, treatment with aliphatic amines removes interlayer water and establishes a hydrophobic structure on the internal surface, raising the WCA to 47.0°. Remarkably, the synergistic modification of perfluorodecyltrimethoxysilane and aliphatic amine resulted in a WCA of 157.3°. Further investigations demonstrated that adjusting the type and concentration of the aliphatic amines allows for precise control of WCA, enabling adjustments within the range of 54.4° to 157.3°. This study offers a viable approach for the controllable hydrophobic modification of montmorillonite.