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Polymer inclusion membranes (PIMs) have been prepared using cellulose triacetate (CTA) as polymer and derivatives of the commercial ionic liquid (IL) Aliquat 336, trioctyl methylammonium chloride (AlqCl), as extractants. The different ILs were prepared by exchanging chloride anion from AlqCl for other more lipophilic anions, obtaining IL derivatives AlqNO 3 and AlqSCN. PIMs containing these extractants at two different concentrations (30% and 60%) were prepared and characterized using X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), contact angle and impedance spectroscopy to obtain information on the material properties of both the surface and bulk membranes. The IL counter-anion affects the membrane's electrical parameters (dielectric constant and conductivity) as well as its hydrophobic character, which also depends on the IL concentration in the PIM formulation. Passive transport across the different PIMs using HCl and NaCl aqueous solutions was also considered, and the results obtained seem to be directly related to the hydrophilic/hydrophobic character of the studied membranes The financial support of the Spanish government through research project CTM2013-48967-C2-2-P is acknowledged. R. Vera acknowledges a grant from the Spanish Ministerio de Economía y Competitividad (ref. BES-2014-068314)

Surface and bulk chemical changes in a Nafion membrane as a result of room temperature ionic liquids (RTILs) incorporation were determined by X-ray photoelectron spectroscopy (XPS) and elemental analysis, respectively. RTILs with different physicochemical properties were selected. Two imidazolium based RTIL-cations (1-octyl-3-methylimidazolium and 1-butyl-3-methylimidazolium) were used to detect the effect of cation size on membrane modification, while the effect of the RTIL hydrophilic/hydrophobic character was also considered by choosing different anions. Angle resolved XPS measurements (ARXPS) were carried out varying the angle of analysis between 15° and 75° to get elemental information on the Nafion/RTIL-modified membranes interactions for a deepness of around 10 nm. Moreover, changes in the RTIL-modified membranes associated to thermal effect were also considered by analyzing the samples after their heating at 120 °C for 24 h. Agreement between both chemical techniques, bulk and destructive elemental analysis and surface and non-destructive XPS, were obtained.

Physical–chemical characterization of supported liquid membranes (SLMs), that is, a porous structure containing room temperature ionic liquids (RTILs) was carried out by analyzing XPS and FTIR spectra, while determination of cation transport number from concentration potentials measured with the membranes in contact with NaCl solutions gives transport/electrical information. SLMs filled with two different RTILs (C8MIMPF6 and C10MIMBF4) were studied, and the comparison of results obtained with fresh and aged membranes seems to indicate ion transport modification for aged samples at relatively high NaCl concentrations, which could be associated to changes in the polymer matrix–RTILs interactions.