Interfacial assembly of micro/nanoscale nanotube/silica achieves superhydrophobic melamine sponge for water/oil separation

The regulation of surficial micro/nanoscale architecture assisted by interfacial assembly with nanomaterials is effective for the attainment of superhydrophobic surface, thus promising for fractionation of surfactant-containing oil/water mixtures. However, the pricey materials and elaborate preparation procedures make it infeasibility for mass production. In this work, a superhydrophobic/superoleophilic melamine sponge (MS-PAF-HNTs/SiO2) is prepared by combining an interfacial polymerization (IP) technique for halloysite nanotubes (HNTs) loading with superhydrophobic silicification derived from in situ tetraethoxysilane (TEOS) and octadecyl trimethoxysilane (ODTMS)-hydrolyzed condensation. The integration of naturally occurring micro-scale HNTs and nanoscale SiO2 endows the modified sponge with ridge-and-valley configuration and low-surface-energy, thus contriving a robust superhydrophobic/superoleophilic sponge evincing an extremely wetting selectivity for water and oil phases with a high water contact angle (WCA) of 158° and low water adhesion with a sliding angle of 5°. In this context, the MS-PAF-HNTs/SiO2 sponge displays superior separation performance with 99.99% and 99.58% separation efficiency toward immiscible oil/water mixtures and oil-in-water emulsions, respectively. The superhydrophobic sponge also features remarkable absorption capacity (169.7 times of its own mass) and exceptional compressibility which could withstand 1000 cycles compression without backbone collapsing. Furthermore, the as-prepared superhydrophobic sponge inherits the fire resistance property of pristine melamine sponge, which decreases the risk of flame and explosion when being employed for practical oil/water separation activities. This study provides a facile strategy containing moderate formation conditions and low-priced materials for design of superhydrophobic surface with an enhanced oil/water separation efficiency.