High Mechanical Cellulose-Based Aerogel Induced by Fe³⁺ at Ambient Temperature and Pressure

Nanocellulose aerogels are usually produced by methods such as freeze-drying or critical point drying, which have the disadvantages of high equipment requirements and high energy consumption. In this study, the Fe³⁺-containing ethanol bath was employed to dissolve and replace ice crystals in the prefrozen precursors of cellulose-based aerogels. The method achieved both solvent substitution and metal ion complexation and successfully prepared nanocellulose aerogels with a total solid concentration of 2.0 wt % under drying conditions at ambient temperature and pressure. In comparison to the untreated nanocellulose aerogels, the Fe³⁺-complexed cellulose-based aerogel exhibited better mechanical properties. At the same time, with the increase of Fe³⁺ concentration in the ethanol bath, the specific strength demonstrated a notable enhancement, rising from 1.39 to 2.63 kN·m/kg, and the specific modulus increased from 0.57 to 0.67 kPa/(kg·m^-3) while the shrinkage of the aerogels decreased from 38.21 to 25.51%. Furthermore, the Fe³⁺-complexed aerogels exhibited distinctive reversible compressibility. The rate of work consumption per turn during fixed strain (50%) cycling versus gradient strain (10, 20, 30, 40, 50%) cycling of the Fe³⁺-complexed aerogels demonstrated a tendency to reach a stable value, which demonstrated that the aerogel has some structural robustness.