title: Morphological, Chemical Surface, and Diffusive Transport Characterizations of a Nanoporous Alumina Membrane.
abstract: Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl transport across the membrane nanopores is determined from salt diffusion measurements performed with a wide range of NaCl concentrations, which allows the estimation of characteristic electrochemical membrane parameters such as the NaCl diffusion coefficient and the concentration of fixed charges in the membrane, by using an appropriated model and the membrane geometrical parameters (porosity and pore length). These results indicate a reduction of ~70% in the value of the NaCl diffusion coefficient through the membrane pores with respect to solution. The transport number of ions in the membrane pores (Na⁺ and Cl-, respectively) were determined from concentration potential measurements, and the effect of concentration-polarization at the membrane surfaces was also considered by comparing concentration potential values obtained with stirred solutions (550 rpm) and without stirring. From both kinds of results, a value higher than 0.05 M NaCl for the feed solution seems to be necessary to neglect the contribution of electrical interactions in the diffusive transport.
authors.affiliation: Department of Applied Physics I, Faculty of Sciences, University of Málaga, E-29071 Málaga, Spain. mvazquez@uma.es.
authors.forename: María I
authors.initials: MI
authors.lastname: Vázquez
authors.affiliation: Department of Applied Physics I, Faculty of Sciences, University of Málaga, E-29071 Málaga, Spain. virgirom@uma.es.
authors.forename: Virgina
authors.initials: V
authors.lastname: Romero
authors.affiliation: Department of Physics, Faculty of Sciences, University of Oviedo, E-33007 Oviedo, Spain. vegavictor@uniovi.es.
authors.forename: Victor
authors.initials: V
authors.lastname: Vega
authors.affiliation: Department of Physics, Faculty of Sciences, University of Oviedo, E-33007 Oviedo, Spain. jgarcia@physnet.uni-hamburg.de.|Institute of Applied Physics, University of Hamburg, 20355-Hamburg, Germany. jgarcia@physnet.uni-hamburg.de.
authors.forename: Javier
authors.initials: J
authors.lastname: García
authors.affiliation: Department of Physics, Faculty of Sciences, University of Oviedo, E-33007 Oviedo, Spain. vmpp@uniovi.es.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Prida
authors.affiliation: Department of Physics, Faculty of Sciences, University of Oviedo, E-33007 Oviedo, Spain. grande@uniovi.es.
authors.forename: Blanca
authors.initials: B
authors.lastname: Hernando
authors.affiliation: Department of Applied Physics I, Faculty of Sciences, University of Málaga, E-29071 Málaga, Spain. j_benavente@uma.es.
authors.forename: Juana
authors.initials: J
authors.lastname: Benavente
keywords: SEM analysis; diffusion coefficients; ion transport numbers; nanoporous alumina membrane