A solid surface morphology is of great importance for the fundamental research in the field of hydrophobic materials. Commercial sand core funnels (SCs) are embedded with multilevel pore size and surface roughness, which are excellent models to study the mechanism of surface wettability. This article described a simple, green, and facile method to fabricate hydrophobic surfaces on SCs via reacting with perfluorooctyltriethoxysilane (PFTS) vapor. Systematic analyses on the reaction, properties, and applications of the PFTS-modified SCs were conducted, which involved the reaction time and temperature, water resistance, mechanical durability, self-cleaning test, surface adhesion, and underoil superhydrophobicity. The water contact angle of the modified SCs increased with a decrease of the pore size and an increase of the surface roughness of the sand core particles. The wettability of the modified SCs agrees well with the intermediate states between Wenzel and Cassie-Baxter. The PFTS-modified SCs retained excellent chemical stability in rigid conditions and good mechanical properties. The hydrophobic SCs showed oil/water separation performance with excellent efficiency, reusability, and high flux. Especially for the PFTS-modified SCs with small pore sizes, water-in-oil emulsion separation was successfully realized. The easily accessible, relatively cheap raw materials and facile process in this work are very desirable to obtain a specific wetting surface, which will offer promising applications in various fields.
Keywords: hydrophobicity; oil/water separation; perfluorooctyltriethoxysilane; sand core funnels; water contact angle.