Structural Studies of Hydroxy-Ga Pillared Clays by Ga K-Edge X-Ray Absorption

Abstract
A natural montmorillonite clay was intercalated by hydroxy-Ga polycations (Ga₁₃), obtained by basis hydrolysis of metal salts. These species are structural analogues of Al₁₃. The clay interlayer cations were exchanged in Ga₁₃ solutions containing various amounts of organic polymer. The synthesized materials were aged and/or calcined to 150 and 500°C. In a first approach, Ga-K edge experiments were carried out to investigate the local environment of Ga atoms intercalated into the interlayer space. The study of the first nearest neighbours, oxygen atoms, revealed a decrease in the average bond distance after calcination, which traduced dehydroxylation of the Ga_l3 pillas. By studying the second nearest neighbours, gallium atoms, the Fourier transforms indicate the presence of the central tetrahedrally coordinated gallium of the Ga₁₃ polycations whose contribution disappears upon ageing or calcination.