TITLE:
Separation of Fe3O4 Nanoparticles from Water by Sedimentation in a Gradient Magnetic Field
AUTHORS:
I. Medvedeva, Iu. Bakhteeva, S. Zhakov, A. Revvo, M. Uimin, A. Yermakov, I. Byzov, A. Mysik, N. Shchegoleva
KEYWORDS:
Magnetite, Nanoparticles, Water, Sedimentation, Gradient Magnetic Field
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.7 No.2,
January
30,
2015
ABSTRACT: Sedimentation
dynamics of magnetite (γ-Fe3O4)
nanopowders (10 - 20 nm) in water in the presence of a gradient magnetic field
was studied by optical and Nuclear Magnetic Resonance (NMR) relaxometry
methods. The magnetic field B ≤ 0.3 T, dB/dz ≤ 0.13 T/cm was produced by the
system of permanent strip magnets. The initial sedimentation rate of the
nanoparticles in water and under magnetic fields is higher for less
concentrated suspensions (c0 = 0.1 g/l) than for more concentrated
ones (c0 = 1 g/l). This might be connected with the formation of gel
structures due to strong magnetic attraction between ferromagnetic
nanoparticles. In the gravitation field, the suspensions of the particles (10 -
20 nm) remain stable for over 20 hours. The sedimentation process can be
greatly accelerated by the action of a vertical gradient magnetic field,
reducing the sedimentation time down to several minutes. In a gradient magnetic
field enhanced by a steel grid, sedimentation of the nanopowder (c0 =
0.1 g/l) for 180 minutes resulted in reduction of the iron concentration in
water down to 0.4 mg/l. In flowing water regime, the residual iron
concentration in water 0.3 mg/l is reached after 80 minutes.