Preparation and properties of oriented and hydrophobic aerogels from corn stover

The whole-component aerogel (CA) of corn stover was obtained by using the whole-component corn stover without component separation as raw material and under the optimal preparation conditions (1:200, 150 °C, 40 min, 70 wt% LiBr) obtained from the previous work. An oriented frozen aerogel (d-CA) was successfully prepared by using the oriented freezing method to modify CA in this paper. The directional freezing modification can improve the pore structure of the aerogel, which is beneficial to improve the performance of aerogel. Both CA and d-CA are amphiphilic, but the existence of hydrophilicity is not conducive to the adsorption of the prepared aerogel in oil-water mixed solution, which will narrow the use range of the prepared CA and d-CA. Therefore, the hydrophobic modification of d-CA was carried out in this paper. Hydrophobically oriented corn stalk aerogel (d-HCA) was prepared by chemical vapor deposition (CVD) with methyl trichlorosilane (MTS). A series of detailed characterisations of aerogels obtained before and after modification are presented in this paper. Both d-CA and d-HCA radially have a distinct pore structure, which increases their mechanical properties. It could be observed that the composition and elements of the aerogels before and after the directional freezing modification are similar. The adsorption capacity of d-CA was significantly improved, and the adsorption amounts of methylene blue and soybean oil were increased from 130.62 mg/g and 116.94 g/g to 156.18 mg/g and 131.28 g/g respectively. At the same time, the adsorption capacity of d-CA for waste engine oil, toluene, cyclohexane, hexane and ethyl acetate was also improved. The water contact angle of d-HCA could be stabilised at 100° and had good hydrophobic and lipophilic properties. It could be acted as an adsorbent that could quickly adsorb oil components from water-oil mixtures. Due to the poor adsorption capacity of d-HCA, the oil adsorbed for dyeing was discolored, which could also be equivalent to the discoloration indicators for liquid separation of water oil mixed solutions.