The extraction of Na(+), Ni(2+), and Cr(3+) using six different membranes made of polyaniline composited with high-impact polystyrene, which differ in the doping agent and/or the preparation method, has been investigated. The swelling and ion-exchange capacities of the six polyaniline composited with high-impact polysterene (HIPS/PAni) membranes have been determined and compared with that of the commercial Selemion membrane. Electrodialysis tests using a five-compartment cell evidenced that the extraction of ions depends on the electronic structure of the SO(3)(-) groups, which is modulated by the doping agent, and on both microstructure and electrical resistance of the membrane, which are regulated by the preparation method. The transport of ions through HIPS/PAni and Selemion membranes was found to be comparable. Quantum mechanical calculations on model complexes have been performed to characterize the electronic structure of the dopants. Results indicate that the strength of the interaction between the different doping agents and the polyaniline is inversely proportional to the concentration of negative charge in the SO(3)(-) group of the former. Moreover, both the binding energy and the distribution of charges calculated for dopant center dot center dot center dot PAni complexes have been compared with those predicted for dopant center dot center dot center dot metallic ion complexes.