Abstract: Methods for separating particles in a ferrofluid, along with apparatus for performing the same, are provided. The method may include introducing the ferrofluid through a separation tube; applying a magnetic field to the separation tube such that a fluid constriction is created within the tube that leads to a density gradient in the fluid with a maximum value (dmax) at some region along the tube; and introducing a plurality of particles into the ferrofluid within the separation tube such that particles having densities greater than dmax flow through the ferrofluid.

Abstract: Methods for separating particles in a ferrofluid, along with apparatus for performing the same, are provided. The method may include introducing the ferrofluid through a separation tube; applying a magnetic field to the separation tube such that a fluid constriction is created within the tube that leads to a density gradient in the fluid with a maximum value (dmax) at some region along the tube; and introducing a plurality of particles into the ferrofluid within the separation tube such that particles having densities greater than dmax flow through the ferrofluid.

Abstract: A particulate feed comprising a first particle type and a second particle type is separated by providing a separation apparatus having a separation vessel having a top and a bottom, and wherein the separation vessel includes inwardly sloping side walls. A magnet structure has a first pole positioned exterior of and adjacent to each of the side walls of the separation vessel, and a second pole positioned above the separation vessel. A mixture of the particulate feed and a ferrofluid is introduced into the separation vessel, and the particulate feed is separated into a first particle fraction comprising a majority of the first particle type, which sinks in the separation vessel, and a second particle fraction comprising a majority of the second particle type which floats in the separation vessel.