Taking the importance and significance of wastewater treatment into consideration, mono-dispersed Mn2O3 powders with sphere-like morphology and mesopore features has been firstly synthesized from the thermal decomposition of MnCO3 which is prepared via a modified carbonization method using CO2 gas as the sole carbonate source. The measured isoelectric point, the pH value at which the zeta-potential is zero, of uniformly dispersed Mn2O3 particles is 9.13. Benefiting from the surface electrostatic interaction, as-prepared Mn2O3 microparticles has high adsorption capacity up to 135.5 mg/g toward Congo red dye in aqueous solution. Accordingly, the adsorption process of Congo red by Mn2O3 microspheres could be explained by Langmuir isotherm model and the pseudo-second-order kinetic model. Especially, it is necessary to point out that the removal efficiency of Mn2O3 toward Congo red dye still be well maintained at about 90.78% even after five cycles. Therefore, as-prepared Mn2O3 powders has potential application in large-scale wastewater treatment. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.