Slow, Mid-saturated Exchanges by Large Anions on Resins due to Increase in Independency of Exchange Sites with...

Ion exchanges by aromatic anions (AAs) of varying volumes on anion exchange resins of different cross linking (CL)-degrees were studied. The exchanges on the resins with low CL-degrees having the larger and the less independent exchange sites proceeded fast and completely at a high AA concentration; the selectivity coefficient increased with the progress of the exchange, due to the cooperative interaction between exchanged AAs. In contrast, in the exchanges on the resins with a CL-degree of 8% having the smaller (more specifically, having the average volume of 300 ų with a variance) and the more independent exchange sites, the large AA may not enter the exchange sites having sizes smaller than the volume of AA to cause mid-saturation of ion exchange and to increase the reaction time because of the need for detouring; the selectivity coefficients were substantially independent of the progress of the exchange, due to the isolation of each AA.