Research progress of hydrophobic modification of silica aerogel for oil spill pollution treatment

Oil spill pollution seriously endangers human and ecosystem health. Therefore, it is urgent to develop oil-absorbing materials to effectively remove oil spill pollution. Among the traditional oil-absorbing materials, natural organic adsorption material has low oil absorption capacity and hydrophilicity; inorganic adsorption materials are difficult to recover and have low oil absorption efficiency and high price; and although the synthetic organic adsorbent has outstanding oil absorption capacity, its biodegradation is poor. Silica aerogel (SA) has the characteristics of high porosity, low density, and high specific surface area, which make it an excellent oil-absorbing material. However, the hydrophilic surface and pearl necklace structure of SA limit its wide applications in the oil absorption field. Hydrophobically modified hydrophobic silica aerogel (HSA) has not only excellent SA characteristics but also good hydrophobic/lipophilic properties. In this paper, focusing on HSA preparation by surface posttreatment modification and coprecursor modification, the research progress on these two methods combined with supercritical drying and ambient pressure drying is systematically introduced, and the advantages and disadvantages of the two methods are analyzed and summarized. The coprecursor modification is mainly combined with a supercritical drying process to prepare HSA, while the surface posttreatment modification is often combined with an ambient pressure drying process. Both methods normally use silylating agents as hydrophobic modifiers. The surface posttreatment modification does not change the formed pore structure, and the pore size and particle size of HSA are relatively uniform. However, the modification process of surface posttreatment is long, the solvent consumption is large, and the cost is high. In addition, incomplete internal modification may be a problem. In the coprecursor modification method, wet gel is formed and modified simultaneously, shortening the modification time and saving costs. The prepared HSA of coprecursor modification has a larger specific surface area and better hydrophobicity, but its pore size is uneven, and the introduced hydrophobic groups are limited. Excessive silylating agents affect the sol–gel process of HSA. In addition, the current methods for strengthening HSA mechanical properties and the research progress on HSA oil absorption properties are reviewed. Finally, based on the current development of HSA as oil-absorbing materials, the development direction of these materials is discussed, for example, developing low-cost and eco-friendly raw materials, shortening the hydrophobic modification process, preparing bulk HSA, strengthening the mechanical properties, and improving the oil-absorbing properties of HSA.