Role of iron in the enhanced reactivity of pulverized Red mud: Analysis by Mössbauer spectroscopy and FTIR spectroscopy

The present study is carried out to investigate the contribution of iron in the hematite phase in enhancing the reactivity of red mud. Compressive strength test was performed on the binder synthesized from both unpulverized and pulverized red mud. The results indicated an increase in strength of the pulverized red mud based binder. Test results of Mössbauer Spectroscopy showed transition of metastable ferrihydrite phase to hematite phase when the red mud was processed. An increase in line-width of the Moessbauer sextet and an increase in the area of doublet of pulverized red mud based binder hinted at the increase in Fe3+ ions which could have replaced Al3+ ions in the geopolymer network. Results of Fourier-Transform Infrared Spectroscopy (FTIR) test validated the Mössbauer Spectroscopy results. The participation of Fe3+ ions in geopolymerisation was confirmed from the reduction of hematite peak (wavenumber at 462 cm−1). Keywords: Red mud, Pulverization, FTIR, Mössbauer spectroscopy, Compressive strength