Separation of Fe₃O₄ Nanoparticles from Water by Sedimentation in a Gradient Magnetic Field

I. Medvedeva^1,2*, Iu. Bakhteeva¹, S. Zhakov¹, A. Revvo², M. Uimin¹, A. Yermakov¹, I. Byzov¹, A. Mysik¹, N. Shchegoleva¹

¹Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia.
²Ural State Mining University, Ekaterinburg, Russia.

DOI: 10.4236/jwarp.2015.72009                

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.

Keywords

Magnetite, Nanoparticles, Water, Sedimentation, Gradient Magnetic Field

Conflicts of Interest

The authors declare no conflicts of interest.

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