Synthesis of hydrophobic alumina aerogel with surface modification from oil shale ash

• We synthesize alumina aerogels using oil shale ash as alumina source.
• Alumina aerogels were modified by silylation and characterized.
• After silylation, the surface property of alumina aerogels changed to hydrophobic.

In this study, the hydrophobic alumina aerogels were successfully prepared using oil shale ash (OSA) as a new raw material. The process consisted of two stages, leaching of aluminum and hydrophobic modification. The effects of methyltrimethoxysilane (MTMS) and tetraethylorthosilicate (TEOS) used as surface modifying agents on the physicochemical properties of the alumina aerogels were investigated. The surface chemical group, thermal stability, structure properties and morphological features before and after modification were examined by Fourier transform infrared (FT-IR), Thermogravimetry–differential thermal analysis (TG–DTA), Brunauer–Emmett–Teller (BET) and Scanning electron microscope (SEM) techniques. The experimental results indicated that the obtained alumina aerogels without surface modification had ordered mesoporous structure and flaky morphology with average length of about 200–300 nm. After surface modified with MTMS, the surface property of alumina aerogels changed from hydrophilic to hydrophobic, meanwhile the morphology changed to catkin-like structure. The results obtained in this experiment prove that the OSA can be used to prepare hydrophobic alumina aerogels, which explores a new way for comprehensive utilization of OSA.

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