Influence of counterion concentration on the ion-exchange equilibria of crosslinked weak-acid polyelectrolyte gels

✍ Scribed by Jacob A. Marinksy; Tohru Miyajima; Erik Högfeldt; Mamoun Muhammed

• Publisher: Elsevier Science
• Year: 1989
• Weight: 685 KB
• Volume: 11
• Category: Article
• ISSN: 0923-1137
• DOI: 10.1016/0923-1137(89)90113-9

✦ Synopsis

The sensitive response of weak-acid ion exchangers to counterion concentrations in the aqueous phase has been attributed to a Donnan potential term. By correcting for this term a constant pK a has, in a number of cases, been resolved for the repeating unit at each point of their titration with base. It has been suggested that this approach leads to the resolution of the intrinsic pKa of the weak-acid functionality repeated in these ion exchangers. In other cases, however, this approach has not led to a constant pKg. An error in the Donnan term introduced by macroporosity of these exchangers has been suggested as the source of this incongruity. A method based on the premise that the Donnan term is uniquely responsible for the variability of the uncorrected pK~ has been outlined and shown to give a satisfactory result.