Structural collapse of Al_13- intercalated montmorillonite by Na- salicylate solutions

Abstract

The chemical, textural and structural transformations of Al13-intercalated montmorillonite, resulting from the depolymerization of the interlamellar Al13 polycations by Na salicylate solutions, were studied. Nitrogen gas adsorption shows a dramatic decrease in specific surface area from 493 to 39 m2g–1, due to the loss of microporosity. Modelling of small-angle X-ray scattering (SAXS) curves shows that the final product contains two phases: a Na-exchanged swelling phase accounting for 40% of the clay, and a fixed interlayer distance (20.8 Å ) phase accounting for 60% of the clay. The Al remaining in the clay galleries (45% of the initial Al) is composed of 13% Al13– and 87% hexacoordinated Al, probably Al(OH)03 and oligomeric Al-salicylate complexes, as shown by 27Al NMR. The instability of Al13-intercalated montmorillonite towards organic ligands is related to the hydration shell of the tridecamer, revealed by SAXS. These results focus on the necessity to take into account the presence of organic ligands in natural media when using materials such as Al13-intercalated clays.

Spectroscopic Studies of Poly(ε-Caprolactone)/Sodium Montmorillonite Nanocomposites

“…For pure montmorillonite we observed two asymmetric lines of the 27 Al nuclei. The line at about 0 ppm is related to the octahedral coordination of the aluminium ions, whereas the line at ∼ 50 ppm indicates that some of the 27 Al ions are present in the tetrahedral environment [11,12]. These coordinations appear as a consequence of isomorphic ions substitution within the layers.…”

Use of modified hydroxy-aluminum bentonites for chromium(III) removal from solutions

“…A high ligand addition promotes adding reaction products. Depending on the anion charge, the Al-OH anion complexes will further have a positive charge density lower than that of the intercalated Al compound (Cambier and Sposito, 1991;Violante and Huang, 1992;Molis et al, 2001). Therefore, induced changes in surface properties such as charge, specific surface, and pore volume may prove to be useful in industrial catalysis and specific molecule sorption.…”

Catalytic acetalization of carbonyl compounds over cation (Ce3+, Fe3+ and Al3+) exchanged montmorillonites and Ce3+-exchanged Y zeolites

“…0 ppm is related to the octahedral coordination of the aluminium ions, whereas the line at ca. 60 ppm indicates that some of the 27 Al ions are present in a tetrahedral environment (Engelhardt and Michel, 1987;Molis et al, 2001;Salerno and Mendioroz, 2002). These coordination states appear as a consequence of isomorphic ion substitution within the layers of the clay structure.…”