MATHEMATICAL-MODELING OF 1,10-PHENANTHROLINE EXTRACTION INTO NAFION(R)-117 MEMBRANES

The diffusion of the nitrogen heterocyclic base, 1,10-phenanthroline, into the perfluorosulfonated ion-exchange polymer membrane, Nafion(R) 117, has been studied in aqueous solutions via specially designed diff usion cells. Solutions of identical composition were mechanically stir red and the concentration of the neutral species was monitored spectro photometrically with time. A mathematical model describing the system was developed. It takes into account the coupled character of the diff usion and the protolytic equilibria within the Nafion(R) membrane. The model was numerically solved using an implicit alternating-direction finite difference method and the corresponding software was written in ANSI C. Simulated extraction curves were fitted to the experimental d ata, in which the diffusion coefficient of 1,10-phenanthroline in the Nafion(R) membranes was determined and the relevant mechanisms of extr action discussed. (C) 1998 Elsevier Science B.V.