Physico-magnetic properties and dynamics of magnetite (Fe3O4) nanoparticles (MNPs) under the effect of permanent magnetic fields in contaminated water treatment applications

• Published in: Separation and purification technology Vol. 296; p. 121342
• Main Authors: Falciglia, Pietro P., Gagliano, Erica, Scandura, Pietro, Bianco, Carlo, Tosco, Tiziana, Sethi, Rajandrea, Varvaro, Gaspare, Agostinelli, Elisabetta, Bongiorno, Corrado, Russo, Antonio, Romano, Stefano, Malandrino, Graziella, Roccaro, Paolo, Vagliasindi, Federico G.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2022
• Subjects: Advanced water treatment; Electric field maps; Magnetic separation; Magnetite nanoparticles; Modelling; Particle trajectories; Particles separation; Permanent magnet; Particles separation; Magnetite nanoparticles; Electric field maps; Magnetic separation; Modelling; Particle trajectories; Permanent magnet; Advanced water treatment
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2022.121342

[Display omitted] •Study on magnetite nano-particles agglomeration and magnetic map generation.•Understand the dynamics of magnetite nano-particles under an external magnetic field.•Trajectories of the larger particles converge more rapidly towards the magnet.•A global particles’ removal of ∼ 90% was observed for aggregate diameters > 1.2 µm.•Obtained data are useful for scaling-up and pilot-scale future practical application. In this work, a modelling and experimental study was performed to understand the dynamic behaviour of magnetite nano-particles (MNPs) released in a water flow when subjected to an external magnetic field. MNPs physical and magnetic properties and their tendency to form aggregates were also investigated. A mathematical model was developed and applied using MNPs characterization and 3-D field maps generated by OPERA software, considering different magnet bar dimensions and particle aggregate sizes. Model was run to assess the MNPs trajectories, and the capture efficiency of a 10-cm height permanent magnet bar placed on the upper wall of a bench-scale rectangular duct in which MNPs are injected. Shorter MNPs trajectories were observed in the flow regions farther from the duct walls (lateral or bottom walls) where the frictional forces are lower. It is relevant to notice that the MNPs attraction is possible also in regions where the magnetic field is weak due to the high magnetic susceptibility of the system. MNP aggregate size significantly influences the particle dynamics with the trajectories of the larger particles converging more rapidly towards the magnet leading to their capture. However, this does not affect the global removal (∼90%) for aggregate diameters higher than 1.2 µm, demonstrating the general effectiveness of the investigated magnetic capture system, which is only partially influenced by the aggregate size variation. The comparison of modelled and experimental results shows the goodness of the developed model. Along with magnetic and aggregation studies and generated 3-D magnetic field maps, it represents a valid tool for future studies towards the development of practical applications for the magnetic removal of MNPs loaded by water contaminants.