The transformation of mixed sodium manganese ferrite into manganese ferrite induced by carbon dioxide was investigated. The reaction was performed in controlled conditions at different temperatures (600 degrees C and 800 degrees C). Transformation kinetics were followed in terms of powder composition evolution and weight gain by in-situ high temperature X-ray diffraction and thermogravimetric analysis respectively. Differently than expected by the reaction stoichiometry, the comparative analysis of the obtained experimental results reveals that sodium carbonate and manganese ferrite compounds formation is asynchronous. A mechanism describing mixed sodium manganese oxide transformation into manganese ferrite following sodium extraction by carbon dioxide is proposed and discussed. (C) 2011 Elsevier B.V. All rights reserved.