Studies on characterisation of phosphorous in haematite iron ore

Abstract

Due to the rapid depletion of high-grade iron ores in the world, the iron production from comparatively lower grade iron ores containing higher amount of gangue or higher impurities like phosphorous is now the main focus for the iron and steel industries. The current study has been carried out to understand the distribution and association of phosphorus in a high-phosphorous iron ores from the eastern part of India containing ∼55.4% Fe and 0.56% phosphorous (P). Mineralogical and thermal characterisation studies were carried out by using advanced characterisation techniques like optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, thermogravimetric analysis, differential scanning calorimetry, etc. SEM and electron probe micro-analyser study suggests that iron and alumina-rich gangue minerals are mostly associated with the phosphorous content of iron ore. This high-phosphorous iron ore consists of major phosphorus-bearing phase called berlinite (AlPO₄). The gangue minerals (alumina) were found to be principally associated with the phosphorous. The size-wise chemical analysis suggests that the presence of phosphorous increases at finer size fractions, phosphorous mineral liberation is possible at finer size factions for better beneficiation. XRD analysis suggests that phosphorus in iron ores is most likely found as a crystalline phase (berlinite AlPO₄) rather than as an amorphous phase and the berlinite phase increases with an increase in the phosphorous level of iron ores.