Transport of NaNO3 solutions across an activated composite membrane:: electrochemical and chemical surface characterizations

Electrochemical characterization of two different samples of an activated membrane, which consists of a polymeric support containing different amounts of Di-(2-ethylhexyl) phosphoric acid as a carrier was made by measuring the electrical resistance, salt diffusion and membrane potential for the activated membranes and the polymeric support in contact with NaNO3 solutions. Transport parameters such as the ion transport numbers and concentration of fixed charge in the membrane, salt and ionic permeabilities at different NaNO3 concentrations were obtained. A comparison of the different electrochemical parameters obtained with both activated membranes and the polymeric support shows how the carrier affects the transport of NaNO3 solutions across the activated membranes. On the other hand, chemical composition of the membrane surfaces as a function of the amount of carrier was determined by X-ray photoelectron spectroscopy technique, which also allows an envisagement of the chemical bonding between the carrier and the membrane top layer(polyamide). (C) 1999 Elsevier Science B.V. All rights reserved.