Magnetophoresis of superparamagnetic nanoparticles at low field gradient: hydrodynamic effect

Abstract

Convective current driven by momentum transfer between magnetic nanoparticles (MNPs) and their surrounding fluid during magnetophoresis process under a low gradient magnetic field (<100 T m(-1)) is presented. This magnetophoresis induced convective flow, which imposed direct hydrodynamic effects onto the separation kinetics of the MNPs under low gradient magnetic separation (LGMS), is analogous to the natural convection found in heat transportation. Herein, we show the significance of the induced convection in controlling the transport behavior of MNPs, even at a very low particle concentration of 5 mg L(-1), and this feature can be characterized by the newly defined magnetic Grashof number. By incorporating fluid flow equations into the existing magnetophoresis model, we reveal two unique features of this convective flow associated with low gradient magnetophoresis, namely, (1) the continuous homogenization of the MNPs solution and (2) accompanying sweeping flow that accelerates the collection of MNPs. According to both simulation and experimental data, the induced convection boosts the magnetophoretic capture of MNPs by approximately 30 times compared to the situation with no convection.

Investigation of Magnetic Nanoparticle Motion under a Gradient Magnetic Field by an Electromagnet

“…The main reasons for this phenomenon are related to the following two factors: (1) magnetic particles can be aggregated under the action of magnetic interactions between particles which has been widely mentioned in the studies relevant to magnetic manipulation of particles [14][15][16] and the formation of elongated aggregates will accelerate the process of particle focusing [17,18]. (2) Hydrodynamic interactions between particles could aid the focusing of magnetic particles [19][20][21]. Considering the MNP aggregation process has a little effect on the final MNP distribution, it is reasonable to validate the proposed numerical procedure according to the intermediate stages of MNP distribution by comparing the simulated results in Figure 3 and images of MNPs distribution in Figure 4.…”

Magnetophoresis of Superparamagnetic Nanoparticles Applied to the Extraction of Lanthanide Ions in the Presence of Magnetic Field

“…Its understanding is essential for the application of nanoparticles in magnetic separation processes, however, the theory involved is yet under development and has been the subject of many recent discussions [1][2][3][4][5]. In addition , the advances in the experimental procedures remain yet quite limited.…”

“…The response monitored in this way actually reflecs an average profile, because of the convective fluid motion induced by the different magnetophoretic velocities that the particles can have at the top and at the bottom of the system [1].…”

“…Superparamagnetic nanoparticles (MagNP) are being extensively explored in nanotechnology, and one of the recent applications deals with magnetic separations at the nanoscale (magnetophoresis) [1][2][3][4][5] and elemental processing in the mineral area [6,7] (magnetic nanohydrometallurgy) [8][9][10]. The understanding of such processes can lead to important technological advances in metal ion extraction, separation and recovery, as well as in electrowinning processes, including environmental remediation involving the capture and removal of heavy metal contaminants from industrial effluents [11,12].…”

Green Processing of Strategic Elements Based on Magnetic Nanohydrometallurgy

“…63 The subject is related to magnetophoresis, an emerging area of investigation, aiming the use of superparamagnetic nanoparticles in separation processes, by analogy to electrophoresis. However, magnetophoresis is not completely understood yet, and has been the subject of many recent studies, [64][65][66][67][68] particularly focusing on theoretical aspects.…”