title: Modification of polysulfone membranes with polyethylene glycol and lignosulfate: electrical characterization by impedance spectroscopy measurements.
abstract: Two sets of composite membranes having an asymmetric sulfonated polysulfone membrane as support layer have been obtained and electrically characterized (membranes SPS-PEG and PA-LIGS). The skin layer of the membrane SPS-PEG contains different percentages of polyethylene glycol in the casting solution (5, 25, 40, and 60 wt%), while lignosulfonate was used for manufacturing PA-LIGS membranes (5, 10, 20, and 40 wt%). Membrane electrical characterization was done by means of impedance spectroscopy (IS) measurements, which were carried out with the membranes in contact with NaCl solutions at different concentrations (10(-3) < or = c(M) < or = 5x10(-2)). Electrical resistance and equivalent capacitance of the different membrane samples were determined from IS plots by using equivalent circuits as models. Results show a clear decrease in the membrane electrical resistance as a result of both polysulfone sulfonation and the increase of the concentration of modifying substances, although a kind of limit concentration was obtained for both polyethylene glycol and lignosulfonate (40 and 20%, respectively). Results also show a decrease of around 90% in electrical resistance due to polysulfone sulfonation, while the value of the dielectric constant (hydrated state) clearly increases.
authors.affiliation: Grupo de Caracterización Electrocinética de Membranas e Interfases, Departamento de Física Aplicada I, Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga, Spain. j_benavente@uma.es
authors.forename: J
authors.initials: J
authors.lastname: Benavente
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: R
authors.initials: R
authors.lastname: Garcia Valls
mesh_terms: D017097:Electric Impedance; D004563:Electrochemistry / Q000379:methods; D004573:Electrolytes; D008031:Lignin / Q000031:analogs & derivatives* / Q000737:chemistry; D008567:Membranes, Artificial; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D012996:Solutions; D013450:Sulfones / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D004573:Electrolytes; D008567:Membranes, Artificial; D011108:Polymers; D012996:Solutions; D013450:Sulfones; C017662:polysulfone P 1700; D011092:Polyethylene Glycols; C001545:lignosulfuric acid; D008031:Lignin