Synthesis and reversible hydration behavior of the thiosulfate intercalated layered double hydroxide of Zn and Al

Abstract

The thiosulfate-intercalated layered double hydroxide of Zn and Al undergoes reversible hydration with a variation in the relative humidity of the ambient. The hydrated and dehydrated phases, which represent the end members of the hydration cycle, both adopt the structure of the 3R 1 polytype. In the intermediate range of relative humidity values (40-60%), the hydrated and dehydrated phases coexist. The end members of the hydration cycle adopt the structure of the same polytype, and vary only in their basal spacings. This points to the possibility that all the intermediate phases have a kinetic origin.

Relative Humidity-Induced Reversible Hydration Of Sulfate-Intercalated Layered Double Hydroxides

“…The larger a parameter of this phase (a = 5.34 Å = H36a o ), compared to that of the more prevalent phases (a o = 3.11 Å ), corresponded to a cation-ordered cell and the corresponding supercell reflections 100 and 101 were observed at 19.2 and 20.8º2y, respectively. The structure of this phase was refined using the cation-ordered structure model (space group P3 ) proposed for the ] LDH (Radha and Kamath, 2013). Details of the structure (Supporting Information SI.…”

“…Three non bonded in-plane O1ÀO1 (O1: Hydroxyl O atom) distances exist, whereas for a perfectly hexagonal array, as in the 3R 1 polytype (Radha and Kamath, 2013), only one distance exists at 3.12 Å (Figure 6). A comparison of the hydroxyl ion array in the two LDHs shows that the distortion from The differences in the hydration-dehydration behavior of these two sulfate-intercalated LDH systems may be interpreted in terms of two competing interactions involving water molecules in the interlayer: (1) hydrogen bonding with the array of hydroxyl ions defining the surface of the metal hydroxide layers; and (2) hydrogen bonding interactions with other intercalated water molecules.…”

“…The reversible hydration behavior of the [Zn-Al-S 2 O 3 ] LDH (Radha et al, 2013) offers an interesting comparison with two significant differences: (1) the end members of the hydration-dehydration cycle both adopt the structure of the 3R 1 polytype and no detectable interpolytype transitions are noted; and (2) both end members coexist over a significant range of RH values (40À60%). Irrational basal reflections are not observed under any conditions, ruling out the possibility of the existence of interstratified phases.…”

“…Irrational basal reflections are not observed under any conditions, ruling out the possibility of the existence of interstratified phases. The coexistence of the end members was, therefore, attributed to kinetic factors (Radha et al, 2013).…”

“…Evidence in favor of cation ordering is provided by an array of techniques such as extended X-ray absorption fine structure (Vucelic et al, 1997;Bigey et al, 1997;Roussel et al, 2000Roussel et al, , 2001, magic angle spinningnuclear magnetic resonance (Sideris et al, 2008(Sideris et al, , 2012Cadars et al, 2011), and X-ray diffraction (XRD) (Krivovichev et al, 2010;Radha and Kamath, 2013). Cation ordering generates a large unit cell with a = Hn6a o (n = 3 for x = 0.33) (Hofmeister and Platen, 1992).…”