An innovative study for pretreatment of high-phosphorus oolitic hematite via high-temperature heating: phase, microstructure, and phosphorus distribution analyses

Abstract

To investigate the effects of heating pretreatment on the distribution of phosphorus elements, phase transformation, and microstructure evolution mechanisms of high-phosphorus oolitic hematite (HPOH), particularly from the Tindouf regions of Algeria, several analyses, including HSC Chemistry software, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Image-Pro Plus software, specific surface area, pore size distribution (BJH), and N2 adsorption–desorption isotherms. The results show that the conventional heating pretreatment has a significant effect on the phase and microstructure of HPOH. Cracks appeared within mineral phases and around the interphase boundaries owing to the co-promotion of different thermal expansions of minerals and dehydration and chemical reactions via the heating treatment of ore samples. As the pretreatment temperature increased within the studied range, increases in crack perimeter (from 8.062 to 87.236 μm), percentage of crack area (from 0.135 to 7.988 %), and BJH desorption average pore diameter (from 6.1788 to 23.4384 nm) were observed. The specific surface area and pore volume decreased from 23.2054 to 1.0661 m2/g and 0.0237 to 0.0017 cm3/g, respectively. In addition, the distribution of phosphorus did not change or repartition during the heating pretreatment period in the mineral phases.