In this work, the Aspergillus niger strain CICC 2475 was inoculated on pristine wheat bran to obtain fermented wheat bran. The influence of Aspergillus niger on the removal efficiency of wheat bran toward Co(II) was evaluated via sorption kinetics and sorption isotherms. In addition, the sorption behaviors of Co(II) on fermented wheat bran were investigated as a function of particle size, pH, ionic strength, solid content, and thermodynamic parameters. The results indicated that the Aspergillus niger fermentation significantly improved the removal efficiency of wheat bran toward Co(II). The sorption kinetic data were well fitted by the pseudo-second-order rate equation. The sorption isotherms could be well described by the Freundlich model. The sorbent particle size played a key role in Co(II) removal from solutions, and the sorption of Co(II) on fermented wheat bran was strongly dependent on pH and ionic strength. The thermodynamic parameters (Delta H degrees, Delta S degrees, and Delta G degrees) calculated from the temperature-dependent sorption isotherms indicated that the sorption process of Co(II) on fermented wheat bran was spontaneous and endothermic. The results of the present study suggest that the fermented wheat bran is a suitable material for the cost-effective preconcentration and solidification of radiocobalt from large volumes of aqueous solutions.