Cross-Linked Smectites. I. Synthesis and Properties of Hydroxy-Aluminum-Montmorillonite

Abstract

Abstraet--A stable porous system consisting of montmorillonite cross-linked by Al-hydroxide oligomers was synthesized by reacting at room temperature an aqueous solution of such oligomers with a unit-layer dispersion of montmorillonite. The resulting cross-linked montmorillonite (AI-CLM) is a nonswelling material, showing basal spacings of 14.4 to 18.8/~, after air drying and between 14.2 to 18.0/~ after treatment at 119~ The basal spacing is found to depend on the age and OH/AI ratio of the Al-hydroxide solution, as well as on the relative amounts of the two reactants. A specific surface area of 160 m~/g and a diffraction pattern with a dominant basal spacing of 17.5 ]~ is obtained by using Al-hydroxide with OH/ AI = 1.85, aged for at least 5 days, and by applying an Al/montmorillonite ratio greater than 1.5 in the cross-linking process. The basal spacing of AI-CLM remains essentially unchanged after heating at 220~ while the specific surface area is not affected by heat treatment up to 480~Two possible configurations of Al-hydroxide oligomers, homogeneously distributed between parallel montmorillonite unit-layers, were considered in order to account for the basal spacing of 17.5-18.8/~, viz. (a) stacking of two oligomeric ring units in parallel orientation relative to the clay lamellae and (b) perpendicular orientation of individual oligomeric units.

Dioxon Sorption by Hydroxy-Aluminum-Treated Clays

“…Furthermore, the OCDD partitioning results also indicate that the height of the pillar was not the critical variable in determining the extent ofdioxin sorption. The XRD resuits presented are in agreement with those reported by Pinnavaia et al (1984), Lahav et al (1978), and Oades (1984).…”

Synthesis and Fabrication of Inorganic Porous Materials: From Nanometer to Millimeter Sizes

“…A method has been proposed to obtain bridges using metal oxide pillars by intercalating these large metal hydroxide ions between the layers of clay minerals using ion exchange, then firing the compounds between clay layers at high temperature. Brindley et al [28] and Lahav et al [29] used this method to prepare a montmorillonite bridge using alumina as pillars. The distance between layers is about 0.75 nm.…”

Redox Treatment of an Fe/Al Pillared Montmorillonite. A Mössbauer Study

“…The steric and electronic constraints prevailing in this super-zeolitic structure (Vaughan, 1988) render to these novel materials a high selectivity. The list of metal oxides used in pillaring various smectites has rapidly expanded and already comprises quite a few metals, e.g., A1 (Lahav et al, 1978), Zr (Bartley, 1988), Si (Endo et al, 1980), Cr (Tzou and Pinnavaia, 1988), Fe (Yamanaka et aL, 1984), Ti (Sterte, 1986), Nb and Ta (Christiano et aL, 1985), Mo (Christiano and Pinnavaia, 1986), Sn (Petridis et aL, 1989). Furthermore, the synthetic route to PILCs shows a new way to engineer out of swelling clays a multitude of nanophases.…”