The metal adsorbability of the chitosan electrospun nanofiber (similar to 235 nm in diameter) mats was examined in an aqueous solution. The chitosan nanofiber mats (which were neutralized with potassium carbonate) showed good erosion stability in water and high adsorption affinity for metal ions in an aqueous solution. The adsorption data of Cu(II) and Pb(II) (which were determined by a spectrophotometric method) were fitted well with Langmuir isotherm indicating that mono-layer adsorption occurred on the nanofiber mats. The equilibrium adsorption capacities (from Langmuir isotherm data) for Cu(II) and Pb(II) were 485.44 mg g(-1) (2.85 mmol g(-1)) and 263.15 mg g(-1) (0.79 mmol g(-1)), respectively. The Cu(II) adsorption data were similar to 6 and similar to 11 times higher than the reported highest values of chitosan microsphere (80.71 mg g(-1)) [W.S. Wan Ngah, C.S. Endud, R. Mayanar, Removal of copper(H) ions from aqueous solution onto chitosan and cross-linked chitosan beads, React. Funct. Polym. 50 (2002) 181-190] and the plain chitosan (45.20 mg g(-1)) [C. Huang, Y.C. Chung, M.R. Liou. Adsorption of Cu(II) and Ni(II) by pelletized biopolymer, J. Hazard. Mater. 45 (1996) 265-277], respectively. This high adsorption capacity suggests that the chitosan electrospun nanofiber mats can be applied to filter out (or neutralize) toxic metal ions and microbes without losing their original chitosan properties such as biocompatibility, hydrophilicity, bioactivity, non-antigenicity, and non-toxicity. (c) 2008 Elsevier B.V. All rights reserved.