Surface fabrication of silica aerogels from inorganic precursor achieving elastic and superhydrophobic sponges for oil-water separation

Abstract

Some challenges exist in oil-water separation materials, including complex synthesis, high preparation costs, and weak recovery. Herein, the elastic and superhydrophobic silica aerogels/polyurethane sponges (SA/PUS) were prepared by fabricating silica aerogels (SA) on the skeleton of the cheap polyurethane sponges (PUS), through a simple dipping and sol-gel method under ambient pressure drying procedure. Importantly, boosted by the inorganic silicon precursors, the dense and rough coating by the functionalized SA on the surface was realized under environmentally friendly modification and adhesive-free, which contributed to the superhydrophobicity of the SA/PUS. The splendid thermal stability allowed the SA/PUS to maintain a hydrophobic property at high temperatures (over the flash point of the oil in this work). The excellent adsorption performance was confirmed on both oil/water mixture (11 times own weight) and oil-in-water emulsion (separation efficiency up to 98.78%). Moreover, the elastic SA/PUS could recover from large-scale deformations owing to the combination with the PUS with a three-dimensional skeleton, which improved the mechanical strength and overcome the limitation of the brittle SA. The recovery efficiency of the adsorbed oil from oil/water mixture was 92.70% and nearly no decline in reusing by simple mechanical squeezing. Such excellent performance was also demonstrated in oil-in-water emulsion. Advantages (superhydrophobic and lipophilic, elastic, and thermal stability, etc.) of the SA/PUS, which were prepared by simple synthesis, bring application potential for treating automobile maintenance sewages and expanded applications, including separation and recovery of oil from oily wastewater circularly and uptake of high-value-added hydrophobic molecules in biomass or other processes.