Pillaring of synthetic hectorite by mixed [Al13-xFex] Pillars

Abstract

The pillaring of a Laponite by alumina pillars, iron pillars and mixed Al-Fe pillars was obtained by a simple in situ method starting from AlCl₃ and/or FeCl₃ solutions with different molar ratio Fe/(Fe + Al), and from NaOH solution added simultaneously to the clay suspension. The Al₁₃ pillars were evidenced by XRD and NMR spectra. The density and the charge of these pillars were calculated from the chemical analysis. The Fe pillars (in samples with Fe content >26%) are larger than Al₁₃ pillars and slowly reducible by hydrogen temperature programmed reduction (H₂TPR), but we do not have any information on their structure. There is also an excess of non-pillar Fe retained by the pillared clays probably as oxyhydroxides. The isomorphic substitution in the mixed (Al-Fe)₁₃ pillars (in samples with an Fe content >26%) was evidenced by H₂TPR results compared to the chemical analyses and by the interpretation of the ²⁷A1 peaks in the NMR spectra.