Facile preparation of a SiO₂-Al₂O₃ aerogel using coal gangue as a raw material via an ambient pressure drying method and its application in organic solvent adsorption

Because of its outstanding properties such as a large specific area and Brønsted acidity, the SiO₂-Al₂O₃ aerogel has been used for various applications such as adsorption, catalysis, and in synthetic chemistry. Regarding preparation of the SiO₂-Al₂O₃ aerogel, however, expensive raw materials are always used. In addition, the traditional preparation method is supercritical drying, which is complex and has safety issues. Here, we successfully prepare a SiO₂-Al₂O₃ aerogel utilizing coal gangue as a raw material, which is a zero-cost mining waste. More importantly, ambient pressure drying used in this work overcomes the drawbacks of supercritical drying. Characterizations show that the specific surface area of the SiO₂-Al₂O₃ aerogel prepared from coal gangue can be comparable to that prepared from relative costly raw materials such as Al(NO₃)₃·9H₂O or Al isopropoxide and tetraethoxysilane with supercritical drying conditions. In addition, adsorption tests show that the SiO₂-Al₂O₃ aerogel demonstrates good adsorbability of an organic solvent. Our work provides an effective route to synthesize a SiO₂-Al₂O₃ aerogel in mass quantities and opens a new direction for the comprehensive utilization of coal gangue.