PREPARATION OF HOMOIONIC EXCHANGED SMECTITES IN BENTONITES: INFLUENCE OF VALENCE OF CATIONS AND INFLUENCE OF IMPURITIES ON THE EXCHANGE PROCEDURE

摘要

The interlayers of natural smectites store a mixture of sodium and/or calcium and magnesium, respectively, and rarely potassium. Many chemical, mechanical and thermal properties of smectites and smectite-rich materials depend on the interlayer cations. Therefore, homoionic exchanged materials are prepared to investigate reaction mechanism as function of the interlayer cation or as function of the layer structure with uniform interlayer occupation. 54 publications from different journals from 1950 to 2009 were reviewed with respect to the applied homoionic exchange procedure. Only 6 papers reported on the result of homoionic exchange. Up to now there exists no general instruction to prepare homoionic exchanged smectites in dependency of layer charge, cation exchange capacity (CEC) and the obtained level of homoionic interlayers. The aim of the present study was to create a general instruction to prepare homoionic exchanged smectites and smectite-rich materials in dependency of the required cation and impurities of the used materials.