Surface chemical and electrokinetic characterizations of membranes containing different carriers by x-ray photoelectron spectroscopy and streaming potential measurements: study of the effect of pH

摘要

Two activated membranes containing 200 mm of di-(2-ethylhexyl) phosphoric acid (DEHPA-2) and di-(2-ethylhexyl)dithiophosphoric acid (DTPA-2) as carriers have been studied. The electrokinetic characterization of the membrane/solution interface was carried out by means of tangential streaming potential measurements, with the membranes in contact with an NaCl solution (5 x 10(-4) m) at different pH (3.5 less than or equal to pH less than or equal to 8.5). These measurements allow the determination of the zeta potential, the electrokinetic surface charge density and the isoelectric point of the membranes. Other membrane characteristic parameters such as the acidic dissociation constant or the number of acidic sites per membrane area (density of acidic sites) can be determined if a site dissociation model is used. On the other hand, chemical changes in the membrane surfaces due to contact with solutions at different pH were determined by comparing XPS spectra of the used samples with the original ones. In order to see the influence of each type of carrier on electrokinetic parameters, a comparison with the polymeric base membrane (B0) has also been made. Copyright (C) 2002 John Wiley Sons, Ltd. [References: 19]