Complex Formation of Hydroxoaluminum polycations with Synthetic Expandable Li-fluorine Micas Having Different Layer Cha r ges

Abstract

Complex formation of hydroxoaluminum polycations and Li-fluorine micas having different layer charges, which are obtained from Na-fluorine micas, by cation exchange method, has been carried out in order to clarify the effect of interlayer cation, layer charge, and OH/A1 ratios of hydroxoaluminum solutions on the properties of complexes. While Na-micas having high layer charge cannot form complexes for the lack of swellability, those corresponding Li-exchanged micas can form complexes because of the increase of induced swellabulity: i. e., Li-micas have enough swellability to intercalate bulky hydroxoaluminum polycations regardless of the magnitude of their layer charges. However, selectivity of each Al-species in hydroxoaluminum solutions changes with increasing layer charge for the exchange reaction of intercalation with Li-micas: The ratio of intercalated Al-monomer vs. P 3 species, which corresponds to so-called [A113(OH)24(H20)12]7+species, increases with increasing layer charge at hydroxoaluminum solution having OH/A1ratio 2.09, while that of intercalated P 3 vs. P 2 species, which has nearly 6-times larger molecular weight than P 3, increases with increasing layer charge at hydroxoaluminum solution having OH/A1 ratio 2.48. Micropore volume of complexes formed decreases with increasing layer charge in despite of OFI/A1 ratios of solutions. This indicates that complexes obtained from high layer-charged micas have densely stuffed structure of pillar compounds in the interlayer region, resulting in the decrease of micropore size and volume. This can also explain the decrease of specific surface area of complexes with increasing layer charge.