Analytical Sciences

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

Takuya YONESAKA, Souta YAGI, Takashi YASUI, and Akio YUCHI

Graduate School of Engineering, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan

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.

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