Highly selective separations of multivalent and monovalent cations in electrodialysis through Nafion membranes coated with polyelectrolyte multilayers

Nafion membranes coated with 5.5-bilayer poly(4-styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) films show Li+/Co2+ and K+/La3+ selectivities >1000 in electrodialysis (ED). The corresponding selectivities of bare Nafion are <2. Even with adsorption of only 3 polyelectrolyte layers, Nafion membranes exhibit a Li+/Co2+ selectivity >23. However, the resistance to monovalent-ion passage does not decrease significantly with fewer...