Oil spills pose a persistent environmental threat to both freshwater and marine ecosystems, motivating the development of more efficient and sustainable remediation materials. Graphene aerogels have emerged as promising candidates for oil spill cleanup due to their extremely low densities, high surface areas, and selective affinity for hydrophobic compounds. In this study, graphene aerogels were synthesized from graphene oxide using L-ascorbic acid as a reducing agent and fabricated using two different drying techniques: rapid supercritical extraction (RSCE) and freeze-drying. The resulting aerogels were characterized and evaluated for their oil adsorption performance under simulated environmental conditions.
Significant structural differences were observed between the two fabrication methods. RSCE-derived graphene aerogels experienced substantial shrinkage during processing (~75% decrease in volume) and exhibited an average density of 23 ± 8 mg/mL. In contrast, freeze-dried graphene aerogels retained a more organized pore structure and had a significantly lower average density of 7 ± 2 mg/mL. These structural differences strongly influenced adsorption behavior. RSCE aerogels demonstrated adsorption capacities of approximately 10-17.8 g of oil per g of aerogel across deionized water, freshwater, and saltwater conditions, whereas freeze-dried aerogels showed substantially higher adsorption capacities ranging from 70-88 g/g under similar conditions.
Environmental conditions also influenced performance. Additional experiments under refrigerated conditions and turbulent mixing revealed that the materials maintained adsorption capability, although freeze-dried aerogels occasionally exhibited minor water uptake due to their lower hydrophobicity. Despite this limitation, freeze-dried graphene aerogels consistently demonstrated superior overall adsorption performance.
Overall, the results demonstrate that graphene aerogels, particularly those produced via freeze-drying, are promising materials for oil spill remediation across diverse aquatic environments. Continued optimization of synthesis conditions and processing parameters may further improve their adsorption efficiency and mechanical stability, supporting the development of scalable and environmentally sustainable oil spill cleanup technologies.