Fabrication of fluoroalkylsilane/zeolitic imidazolate framework composites for highly efficient superhydrophobic coating

Abstract

Superhydrophobic bagasse paper was successfully engineered by facile spray coating with a zeolitic imidazolate framework composite modified by 3,3,3-trifluoropropyltrimethoxysilane (FAS) and used as a filter membrane with special wettability for oil/water separation. Surface characteristics such as surface morphology, surface moieties, roughness, and wettability were observed. The addition of FAS decreased the apparent surface energy between solid surfaces and liquids with a polar contribution of surface free energy as low as 0 mN m−1. The formation of the FAS layer was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy core-level spectra. Three-dimensional surface topography revealed an increase in the spray coating cycle that enhanced the hydrophobicity of the coated paper. The results confirmed that not only microstructures but also the presence of functional groups with low surface energy (such as FAS) can promote surface hydrophobicity. The spray-coated paper with FAS/ZIF in the presence of a small amount of nanocellulose provided a superhydrophobic surface after the first spray cycle. The separation efficiency was up to 85% and was slightly affected by oil viscosity. Moreover, this can be used as a filter membrane for water-in-oil emulsions. In the present work, simple spray-coated paper is a promising candidate material for gravity-driven oil/water separation and water repellent coating.

Keywords

• Superhydrophobic surface
• Spray-coating
• Zeolitic imidazolate framework
• Oil/water separation