We reported fabrication of electrospun nano-fibrous ion-exchange membrane (IEM) composed of sulfonated poly(ether ether ketone) (SPEEK). Prepared membrane was employed for electro-dialytic separation of Na+ from Mg 2+ or Ca2+, which is an urgent problem for the production potable water from brackish water and chlor-alkali industries. Nano-fibrous membrane was successfully fabricated onto spun-bonded non-woven polypropylene fabric. Electrospun SPEEK (ESPEEK) and SPEEK thin film membrane's suitability, for the electro-dialytic separation of cations, was assessed by their conductivity measurements under different electrolytic environment using electrochemical impedance spectroscopy. Counter-ion transport number and membrane permselectivity were strongly depended on the nature of counter-ions. ESPEEK membrane showed very low selectivity (about negligible) for Mg 2+ and Ca2+, because formation of nano-fibrous pore or channels, which restricted the migration of bi-valent cations. Additionally, very low flux and electro-transport efficiency for bi-valent cations in compare with Na+ across ESPEEK membrane, suggested its possible application for electro-driven separation of mono-valent and bi-valent electrolytes. Electrospun nano-fibrous IEMs may be the promising candidate for electro-dialytic selective separation of ions depending on their charge and hydrated ionic size. © 2010 Elsevier B.V. All rights reserved.