Polyaniline (PANI) nanofibers were assembled on the micro- or millimeter-scale calcium alginate (CA) beads by "competitive adsorption-restricted polymerization" approach. The CA beads made the dimensional expansion of PANI nanofibers evident, which overcame the serious aggregation of PANI nanofibers and benefited the practical operation of PANI nanofibers. Batch adsorption results showed that the millimeter-scale CA beads decorated by PANI nanofibers had high affinity to Cu2+ and Pb2+ in aqueous solutions. The removal percentages of Cu2+ and Pb2+ in aqueous solutions by this PANI/CA composite with milli/nano hierarchical structure surpassed 90% in a wide pH range from 3 to 7. Sorption of the two kinds of ions to PANI/CA composite sorbent agreed well with the Freundlich adsorption model. The adsorption kinetic results of Cu2+ and Pb2+ showed that the adsorption reached equilibrium within 120 min and 40 min, respectively. And their adsorption rates could be described by pseudo-second-order kinetics. The desorption percentages of Pb2+ and Cu2+ from this PANI/CA composite are 62% and 75%, respectively. The Pb2+ and Cu2+ removal capacity of the sorbent could be further reinforced when the diameter of CA beads turned from millimeter to micrometer. (C) 2012 Elsevier B.V. All rights reserved.