Magnetic flocculation of paramagnetic particles

摘要

An experimental apparatus has been assembled for the flocculation study of paramagnetic particles under the influence of a strong magnetic field. A magnetic field of strength up to 6 T is generated by a cryogenic magnet operating near liquid helium temperatures. Experimental information is obtained from fluctuation and intensity measurements of light passing through a particle suspension located in a uniform magnetic field. Particle flocculation is described by a Brownian flocculation model in which hydrodynamic, van der Waals, double-layer, and magnetic forces are incorporated for the estimation of the particle flocculation rate. A population-balance model is employed in conjunction with the flocculation model to predict the evolution of the particle size and composition or magnetic susceptibility with time. The effects of magnetic-field strength, magnetic susceptibility of the particles, particle size, and zeta potential are investigated. Results show that particle size and magnetic susceptibility each play an important role in the selective flocculation of particles of different properties.