We synthesized crystalline akaganeite (beta-FeOOH; Cl- type) by hydrolysis of FeCl3 solution at 100 degrees C. and examined the ion-exchange properties with BrO3-. The uptake rate of BrO3- was so fast that equilibrium was attained in 60 min. The uptake was significantly dependent on pH, showing a maximum uptake at pH 4. From distribution coefficients (K-d) determined with a mixed solution (BrO3-, Cl-, CO32-, and 5O(4)(2-); each concentration = 0.1 mmol/dm(3)), crystalline akaganeite showed the highest selectivity toward BrO3-. The BrO3- uptake was fitted well with the Langmuir model.