Enhanced extraction of surface-modified iron oxide nanoparticles using supercritical carbon dioxide

The extraction of iron oxide nanoparticles (IONPs) was performed using hexane, cyclohexane, cyclopentane, and supercritical carbon dioxide (scCO2) in batch, semi-batch, and semi-batch bubbling systems for both unmodified and fatty acid-modified (C6 to C18) cases. The performance of these extraction processes was evaluated by observing the particle behavior in a transparent vessel and determining the extraction efficiency (EE). The EE increased with longer alkyl chain lengths, indicating that surface hydrophobicity is a key for high extraction performance. The utilization of scCO2 in semi-batch bubbling system gave the highest EE of 99.8 % at 100 min, superior to hexane and cyclohexane for hydrophobic IONPs. The particle extraction mechanism was estimated based on observed particle transfer behavior. This study highlights the potential of scCO2 for efficient nanoparticle extraction and provides insights into optimizing particle extraction processes for biomedical applications.