Magnetic separation of monazite from mixed minerals

Magnetic separation is one of the key physical separation techniques utilised in the beneficiation of rare earth elements (REE) minerals. This technique generally aims at splitting highly magnetic (ferromagnetic) minerals from the less magnetic (paramagnetic) and non-magnetic (diamagnetic) minerals by applying differing magnetic field intensity. Monazite which is a phosphate mineral commonly containing REE (typically lanthanum, cerium and neodymium), occurs in association with hematite and quartz gangue minerals in some South Australian ores. Monazite is paramagnetic whilst hematite and quartz are ferromagnetic and diamagnetic, respectively. In this investigation we have investigated the feasibility of exploiting the differences in magnetic susceptibility of these minerals to concentrate monazite from hematite and quartz mineral mixtures. A wet high intensity magnetic separator (WHIMS) was used in stage-wise concentrate-tails separation tests at selected magnetic field intensities (0.11-1.08 T) for model mineral mixtures of varying monazite content (0.8, 10 and 33.3 wt.%). The tailings from each separation step were processed at increasing magnetic strengths (0.11, 0.29, 0.56, 0.82 and 1.08 T) to produce a monazite rich concentrate. It is reported that hematite was concentrated at <= 0.29 T, whilst monazite upgrade increased significantly with increasing field intensity in the range 0.29-1.08 T. A high grade quartz mineral concentrate was produced from the resulting tailings at the end of a five-stage separation test. The findings demonstrate that wet magnetic separation may be used to concentrate monazite mineral from low grade lateritic ores where complete liberation of the constituent minerals has been achieved.