Hydrophobic Silica Nanorod Arrays Vertically Grown on Melamine Foams for Oil/Water Separation

Abstract

The development of economic oil absorbents with selective wettability, high absorption rate, and recyclability is of great importance owing to the environmental pollution caused by oil spills. Herein, we present a facile strategy to grow one-dimensional (1D) hydrophobic silica via one-step chemical vapor deposition (CVD) of methyltrimethoxysilane (MTMS), catalyzed by ammonia at 100 °C. The final morphology (nanosphere, nanorod, or nanowire) of 1D silica was affected by the amount of precursor nanodroplet. The formation of 1D silica was attributed to the vapor–liquid–solid mechanism. In addition, the hydrophobic silica nanorods (SNRs) growing on the foam skeletons exhibited a vertical growth direction, contributing to the formation of superhydrophobic surface by constructing the roughness and tuning the surface energy. Therefore, the SNR-modified foams demonstrated ultralow density, superhydrophobicity, excellent fire resistance, and robust mechanical stability. Furthermore, they exhibited an excellent heat-resistant wettability up to 550 °C because of their vertical SNR arrays and hydrophobic methyl groups. Compared with other reported materials, the SNR-modified foams displayed great competitiveness with respect to the oil/water separation performances, including the absorption capacities and recyclability. The facile CVD method used to fabricate 1D silica provides a reference strategy for synthesizing other 1D materials.