Al-Pillared saponites. Part 2.—NMR studies

Abstract

A saponite from Ballarat was intercalated with Al polycations by four different procedures involving different sources of polycations, and stabilised by calcination (pillared). ²⁹Si and ²⁷Al solid-state MNR of both the intercalated and the pillared samples have been measured and are discussed. ²⁹Si NMR leads us to propose a pillaring mechanism, involving H⁺ attack of the clay tetrahedral sheet followed by AlO₄ tetrahedra inversion, similar to that previously proposed for beidellites. ²⁷Al NMR reveals that the pillars are not fundamentally modified upon calcination at 500 °C although they undergo reversible dehydration reactions; at 750 °C and above, a strong pillar reorganisation occurs prior to collapse of the global structure.