An acidic leachate obtained from a contaminated soil was generated using hydrochloric acid (HQ as a soil-washing agent and treated by nanofiitration (NF) membranes. This solution was studied in terms of different parameters, such as transmembrane pressures and flow rate, to evaluate membrane permeabilities and ion separation. The experimental results showed that the application of NF membranes is a promising alternative for the removal of metal ions from washing-solutions. For example, both membranes demonstrated a retention capacity higher for multivalent ions such as Al3+, Ca2+, Mg2+ and Mn2+ (between 84 and 100%) compared to monovalent ions such as K+ and Na+ (less than 68 %). Additionally, variation in dynamic permeability using the acidic leachate solution due to concentration polarization is presented. Furthermore, the permeation of NaCl-H2O solutions at different feed pH values (5.8, 3.7 and 2.2) was investigated. This study will not only outline a process for treating contaminated soils and waste waters directly but will also offer a new approach to treating industrial residues produced during mining or leather processes. (c) 2006 Elsevier B.V. All rights reserved.