X-Ray Powder Diffraction and Mössbauer Study of Red Mud Residue from Alumina Production

We have performed phase analysis on industrial waste red mud by X-ray powder diffraction and Mossbauer spectroscopy. In the as-received specimen after standard heat-treatment at 120 degrees C at least eight phases were evaluated quantitatively in order to reproduce satisfactorily the whole diffraction pattern. From the analysis it turned out that the major component of the mixture was hematite. Ball milling of red mud powders effected the gradual disappearance of secondary phases, which became presumably incorporated in the hematite lattice or transformed to an amorphous multi-atomic oxide component. The relevant Mossbauer spectra showed initially a preponderant presence of iron atoms in a magnetic environment. Going on with the mechanical treatment caused the non-magnetic component to increase at the expenses of the magnetic sextet.