Magnetic separation of nanoparticles

Magnetic particles in the nanometer size range can be captured by sufficiently large magnetic forces in competition with thermal diffusion. This paper reports on the results of applying two types of magnetic separation, matrix and continuous, to particles in the nanometer size range. Rather than capture particles on a matrix, it is advantageous for some applications to employ a continuous method of separation. We used a dilute ferrofluid in both matrix and continuous flow through an axial HGMS separator in a transverse magnetic field of 0.01 T. The initial particle size distribution was designed to be 5-20 nm. but had some larger clusters. The measured size distribution of the feed material had two peaks, at 12-14 nm. and at 81-84 nm. Particle size distributions of separated fractions were obtained by dynamic laser scattering and show peaks at 12 and 47 nm. for 0.01 T and 5 and 63 nm. for 0.02 T for matrix separations and at 74, 78, and 115 nm. respectively for the continuous. The size distribution of the largest particles was extremely narrow.