TRANSACTION PAPER

Influence of surface effects on the electrostatic separation of zircon and rutile

J.A. Venter; M.K.G. Vermaak; J.G. Bruwer

Department of Materials Science and Metallurgical Engineering, University of Pretoria

SYNOPSIS

Electrostatic separation is employed in the concentration of zircon and rutile. The zircon concentrate undergoes an acid treatment to remove impurities from the surface of both the zircon and rutile. The purpose of the acid treatment is to increase the difference in the resistivities of the two minerals, thus ensuring the best possible electrostatic separation efficiencies. Previous test work suggested that these impurities are not removed, but only modified; the surface modification seemed more prevalent in the case of the rutile. The resistivity of the rutile changes with pH and thus the electrostatic separation of the rutile is influenced. X-ray photoelectron spectroscopy (XPS) indicates that there is an increase in the OH and adsorbed H₂O concentrations on the rutile surface. XPS also showed significant differential charging on the rutile surface, which indicates that the species on the rutile surface have different resistivities. The zircon particles from the conducting and nonconducting streams have similar resistivities and no major differences in their surface species. Zircon losses during the final electrostatic separation appear not to be due to surface effects, but due to shielding of particles during the separation.

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