Investigation of Magnetic Nanoparticle Recovery using a Quadrupole Magnetic Field via Numerical Simulation and SAXS.

Magnetic nanoparticles (MNPs) have recently attracted considerable attention for various chemical and biomedical applications due to their unique properties. However, their separation from liquid solutions through magnetophoresis is challenging, as Brownian forces play a significant role when the particle size decreases below 50 nm. In this study, we investigate the separation of 27.5 nm superparamagnetic iron oxide nanoparticles (SPIONs) using a quadrupole magnetic sorter (QMS) with high magnetic field gradients. Small-angle X-ray scattering (SAXS) was employed to track SPION manipulation, revealing migration in specific directions and absence of aggregation outside the field, demonstrating the particle's superparamagnetic behavior. Although the QMS exerted radial magnetophoretic forces, SPIONs also exhibited axial movement upon their removal from the magnetic field. COMSOL simulation results agreed with our experimental findings, providing insights into the axial magnetic forces that the particles were subjected to during the process. This combined SAXS and simulation approach offers valuable insights for designing novel separation systems able to isolate small nanomaterials from liquid suspensions.