Experimental study into the beneficiation of a ferruginous rare earth bearing lateritic ore by magnetising roasting and magnetic separation

The beneficiation of ferruginous rare earth bearing ores derived from lateritic deposits by conventional mineral dressing processes is usually difficult due to characteristics of these ores such as fine grain size, complex texture and similar physical characteristics between rare earth minerals and iron oxide gangue. The removal of iron oxides would offer significant advantages with respect to downstream rare earth mineral processing. The purpose of this study was to demonstrate at bench scale the feasibility of magnetically separating iron oxides from a ferruginous lateritic rare earth ore after the ore had been subjected to reduction roasting to convert feebly magnetic iron (III) oxides to magnetite. The effects of magnetic field strength and feed top size on the efficiency of low intensity magnetic separation (LIMS) was explored through rougher magnetic separation tests using a Davis tube tester and chemical and mineralogical analysis of the rougher magnetic concentrates and tails was performed. Magnetic separation was successful in removing iron (as magnetite) to the concentrate at a minimum field strength of 0.2 T; this was however non-selective, with significant amounts of rare earths reporting to the magnetic fraction. The rare earth enriched tails showed decreased grade and recovery and this was due to a number of factors including insufficient liberation, presence of iron oxide coatings on mineral surfaces and heteroflocculation. The findings of this study provided insight towards the potential optimisation and viability of the proposed process of magnetising roasting and low intensity magnetic separation as a means to beneficiate ferruginous lateritic rare earth ores