Batch experiments were performed to examine the BrO3- uptake from dilute aqueous solutions on amorphous aluminum hydroxide (Cl- type), which was synthesized by addition of a 3 mol/dm(3) NaOH solution to a 0.1 mol/dm(3) AlCl3 solution until the pH reached 5.8. The uptake from a 0.78 mu mol/dm(3) BrO3- solution (100 mu g of BrO3/dm(3)) was rapid: equilibrium was attained within 3 min. The BrO3- uptake was found to decrease slowly at pH 4-8 and rapidly at pH >8. The isotherm for BrO3-uptake was well fitted with the Freundlich isotherm model. From distribution coefficient (K-d) values determined from mixed solutions containing 0.10, 1.0, and 2.0 mmol/dm(3) NaCl, NaBrO3, NaNO3, Na2SO4, and Na2CO3, the selectivity order was reported as NO3- < BrO3- < SO42-at a pH range 4.8-7.9. These results suggest that the BrO3- uptake on the amorphous aluminum hydroxide occurs through an outer-sphere complex reaction.