Cobalt-containing aqueous wastes have been treated by electrosorption on a carbon electrode composed of activated carbon fibers(ACFs) in a continuous flow-through cell. Effective cobalt(II) removal is accomplished when a negative potential in the range of -0.35 to -0.7V (vs. Ag/AgCl) is applied to the carbon electrode. The absorbed cobalt is released from the carbon fiber by applying a positive potential on the electrode, showing the reversibility of the sorption process.