On the multifunctional character of strong basic anion-exchange resin

Abstract

The method of potentiometric titration for the strong basic anion-exchange resin AB-17-8, synthesized on a styrene-divinylbenzene matrix, revealed the presence of three kinds of functional groups. Their presence is confirmed by non-aqueous titration of anion-exchange resin samples with a solution of perchloric acid in acetone in the «isopropyl alcohol-ethylene glycol» medium in a 1:1 ratio by volume. The ionization
constants of ionogenic groups that can characterize strongly dissociated benzyltrimethylammonium groups (pKb1=1.72÷1.78) are determined; tertiary, secondary and primary amino groups located in the aliphatic chain of the matrix have pKb2 = 4.32÷4.38; tertiary, primary and secondary amino groups attached directly to the aromatic ring have pKb3=7.72÷7.82. It turned out that only the first two groups with low pKb values
participate in the ion exchange with silicic acid. The content of weakly dissociating ionogenic groups with pKb3=7.72÷7.82 in different batches of anion-exchange resin can be as much as 12÷34% according to our data. This fact (polyfunctionality of the anion-exchange resin) must be taken into account when discussing the various regularities of ion-exchange processes, as well as in predicting the sorption of anions of weak
organic and mineral acids.