Wet magnetic concentration for weakly magnetic mineral fines and ultrafines

Abstract: The first objective of the thesis was to reveal the characteristic magnetic behaviour of natural weakly magnetic minerals (such as hematite and chromite), and the size limits of the particles recoverable by the existing modem high intensity and high gradient magnetic separators. The second objective was to enhance the particle aggregation andlor the magnetic response for wet magnetic concentration of the ultrafines which escaped from the separators. It was observed that weakly magnetic natural minerals (hematite and chromite) exhibited variations in the magnetic behaviour with respect to magnetizing field, temperature and even particle size, It was indicated that high gradient magnetic separation with industrial matrices was efficient for weakly magnetic minerals as small as 10 um, but below this size, poor separation efficiency was obtained. In this thesis, modifications to the existing magnetic technology or alternative methods were investigated for the efficient recovery of particles below 10 gm. The technology or methods included "carrier" or "piggy-back" method, aggregation with magnetic bonding (with permanent or fieldinduced magnetic moment), and hydrophobic magnetite seeding. The thesis discusses the theoretical aspects of the problem and the experimental work. It was clearly demonstrated that wet magnetic concentration was more efficient for the ultrafine fractions whereas other methods could be used to increase the effective particle size dimensions andlor the magnetic susceptibilities.