Anionic clays interlamellar space

LDHs, which belong to the clay family, present several and various applications in different fields, such as catalysis or medicine. The general formula for these compounds is [Mi xnMxni(OH)2]+.Ax, nH20 (labelled [M11-Mm-A]) where the Ms are divalent and trivalent cations and A is an anion. LDH is composed of infinite sheets of positively charged brucite-type Mg(OH)2, where trivalent cations have replaced a fraction x of divalent cations in octahedral coordination. The interlamellar space is occupied by anions, keeping the electroneutrality of the structure, and completed by water molecules. 

The influence of neutral polymer polyethylene glycol and two surfactants with different charge, anionic sodium dodecylsulfate and cationic cetyltrimethylammonium bromide, on the intercalation of pre-formed Au nanoparticles into a clay matrix under ultrasonic treatment has been investigated. The polymer (surfactant) addition has been used to modify the active surface area of NaLmontmorillonite and to change the interlamellar space between the clay layers. Then, intercalated polymer (surfactant) in clay composites has been successfully replaced by Au nanoparticles under sonication. 

We have studied by the Rietveld method [Zn-Cr-X] and [Zn-Cr-X] anionic clays with X = Cl, Br, CO3 (de Roy 1990 and unpublished results). We refined the structure of these compounds with the same space group, and we obtained results very similar to those of single crystal measurements on minerals. This confirms the structural analogy of these structures. As an example, for [Zn-Al-Cl], the best results were obtained with interlamellar species in 18(g) X, 0,1/2 with X 0.255 (Figure 7-9) although no significant difference with site 18(h) was evidenced. 

In fact, the interlamellar space of anionic clays is generally cluttered by the pillars and the overall interactions of the pillars with the sheets and the interlamellar water molecules reduces the... 

Table -4 Interlamellar spacings (A) and stacking sequences of anionic clays intercalated with some oxo-anions or halides.

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