Characterizations on phase reconstruction, microstructure evolution and separation of magnetic ferrite ceramics from low-grade manganese ores by novel uphill reaction diffusion and magnetic separation

Abstract

Traditional utilization of ferruginous manganese ore has mainly concentrated on the separation of Mn and Fe. However, an alternative process of novel uphill reaction diffusion followed by magnetic separation was developed for the synchronous recovery of manganese and iron as the form of ferrite ceramics from the ferruginous manganese ore in this work. The phase reconstruction, interfacial uphill reaction diffusion, ferrite size quantification and separation behavior were characterized via various means of XRD, XPS, TEM, VSM, SEM-EDS, optical microscopy, microhardness and thermodynamic analyses. In the phase reconstruction course, manganese and iron oxides reacted to form ferrites, whereas the impurities were enriched in liquid silicate phases due to the uphill reaction diffusion. Meanwhile, the ferrite particles grew and the liquid silicates aggregated owing to the intensified reaction diffusion by CaO addition. During the water quenching process, microcracks at the cleavage plane between the silicate and ferrites are preferentially generated due to fast cooling shrinkage of liquid silicates. Huge differences in hardness, magnetism, fusibility and cooling shrinkage of ferrites and silicates provided excellent mineralogical conditions for the successful grinding and magnetic separation of ferrites. Eventually, a soft magnetic manganese ferrite precursor with recoveries of 89.2 wt% iron and 85.6 wt% manganese was obtained. The interfacial reaction mechanisms for the formation of ferrites and silicates were also discussed in this work.