Table of Contents
Magnetic and Electrical Separation
Volume 11 (2002), Issue 1-2, Pages 51-61

The Effect of Magnetic Susceptibility on The Motion of Particles in A Ferrohydrostatic Separator

Deb Tech, De Beers Consolidated Mines Ltd., P.O. Box 82851, Southdale, Johannesburg 2135, South Africa

Received 2 June 2001; Accepted 18 June 2001

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Separation in magnetic fluids is a sink-and-float technique based on the generalised Archimedes law whereby, in addition to the conventional force of gravity, a magnetically induced force acts on the fluid. Since this density-based process takes place in a nonuniform magnetic field, magnetic properties of the material to be separated also play a role. The objective of this study is to derive an equation of motion of a non-magnetic particle in a magnetised magnetic fluid and to solve this equation analytically so that particle trajectories could be derived. Furthermore, the magnetic susceptibility of magnetisable particles is taken into account by means of the effective density of the particle. This effective density is the sum of the physical (true) density of the particle and the density associated with the interaction of the particle with the external non-homogeneous magnetic field. A criterion for the accuracy of separation in the form of threshold mass magnetic susceptibility is obtained. This criterion is then verified experimentally.