Preparation of self-standing polyaniline-based membranes:: Doping effect on the selective ion separation and reverse osmosis properties

The selective ion transport of aqueous salt solutions including mono-, di-, trivalent cations across both doped and undoped polyaniline (PAni) membranes was described. PAni-based asymmetric membranes were prepared by the phase inversion method from the casting solution containing N-methyl pyrrolidone. It was found that the permeation rates (PR) decline in the sequence of P-R(NaCl) > P-R(MgCl2) > P-R(LaCl3). HCl-cloped PAni membrane exhibited higher permeation rates for the salts than undoped one due to its more hydrophilic nature. In reverse osmosis (RO) applications, it was observed no water permeation through undoped PAni due to less permeable and hydrophobic nature, under even at 40 bar pressure. Concerning HCl-doped PAni, this membrane showed very low water flux (J(w)) and it was found as 1.01 L m(-2) h(-1) under 40 bar pressure. On the other hand, the J increased linearly with the applied pressure. Furthermore, typical separation factor (a)values calculated from permeation rate ratios were found to be as 6.3 and 39 for Na+/Mg2+ and Na+/La3+ for HCl-doped PAni, respectively. Especially, HCl-doped PAni membrane can be used for removing rare-earth metal salts due to its high separation efficiency in high temperature applications. (C) 2007 Wiley Periodicals, Inc.