Polymer nanofiber ion exchangers (PNIE) are produced by electrospinning from solutions of dissolved polystyrene followed by sulfonation processes. A polystyrene nanofiber cation exchanger was developed for high ion exchange capacity, and rapid ion exchange velocity. In this paper, new experimental results investigating the performance of PNIE are presented in relation to the relevant parameters (ion exchange capacity (IEC), water uptake, and surface morphology). The ion exchange capacity (IEC) and water uptake of the PNIE depend upon the sulfonation time. The PNIE sample with 30 min sulfonation time showed the maximum IEC of 3.74 mmol/g and maximum water uptake of 0.77 g H2O/g-dry-PNIE at 40 min sulfonation time. (c) 2006 Elsevier B.V. All rights reserved.