To test the reusability, the HBCAs contain diesel were
treated as three steps, which have been amply described in the
Experimental Section, to thoroughly remove the diesel. Then,
the HBCAs were used to absorb oil again. The cleaning−
absorption cycle was performed 10 times, and the Cm value
maintained at nearly 120 g/g after each cycle (Figure 10b).
Moreover, the macro-morphology of the HBCAs remained
unchanged. This means that the HBCAs have the potential to
be recycled. The compressive stress−strain curves (Figure S4,
Supporting Information), and the relative mechanical properties
of oil-filled HBCAs have been discussed in the Supporting
Information.
■ CONCLUSIONS
Surface-only modification of the 3D web-like skeleton of BCAs
was accomplished via a feasible liquid-phase reaction followed
by freeze-drying to obtain HBCAs without shape and
microstructure change. In this process, the hydroxyl groups in
the surface molecule chains of the cellulose nanofibers took part
in the trimethylsilylation with TMCS. Then, the surface energy
of the cellulose nanofibers was decreased effectively.
Furthermore, the 3D web-like microstructure, which was
comprised of ultrathin (20−80 nm) cellulose nanofibers, was
maintained because of the very low DS (≤0.132) of the
HBCAs. Hence, the high roughness and low surface energy
endowed the HBCAs with hydrophobic and oleophilic
properties, and highly selective absorption of oils and nonpolar
liquids. Moreover, the surface-only modification of BCAs made
sure that the low density (≤6.77 mg/cm3
), high surface area
(≥169.1 m2
/g), and high porosity (≈ 99.6%) were well
preserved in the HBCAs. Accordingly, the HBCAs exhibited
high mass absorption capacities for a wide variety of oils and
organic solvents (up to 185 g/g). This means that the HBCAs
are wonderful candidates for oil adsorption. In conclusion, the
surface only trimethylsilylation of BCA for oil absorbents was
achieved, which provided another way to multifunctionalize
cellulose aerogels in addition to CVD method