Effect of Mixed Reduction Approach on the Oil Absorption Capacity of Graphene Oxide Aerogels

This study evaluates the impact of a comprehensive design integrating precursor type, reduction and freeze-casting on the development of aerogels with high sorption capacity for engine oil. In this respect, the graphene oxide was varied from commercial to expanded; the reduction approach relied either on purely hydrothermal or combined hydrothermal–chemical reduction approaches. Following the synthesis, freeze-casting was applied at −5 °C and −196 °C. To further improve the reduction degree, annealing in an inert atmosphere was employed upon drying. The effects of precursors, reduction approach, freeze-casting and annealing were systematically investigated. Characterization techniques, including FT-IR, Raman spectroscopy, SEM, and EDS, were used to correlate the degree of reduction and morphological features of the porous structure with the absorption properties. The use of expanded GO as a precursor yielded aerogels with more homogeneous three-dimensional networks, a reduced bulk density of 3 mg cm−3, and lower oxygen-containing functional group content, thereby achieving consistently superior oil absorption of 270 g g−1, with an oil occupancy of 94%. The process was found to fit well with the pseudo-first-order kinetic model. The results demonstrate that a comprehensive approach—considering combined reduction, freeze-casting, and thermal annealing—enables the tailored optimization of both the structure and absorption performance of GO aerogels for the remediation of oil spills.