New Varieties of Zinc–Chromium–Sulfate Lamellar Double Hydroxides

Chromate uptake characteristics of the pristine layered double hydroxides of Mg with Al

“…A reorientation in the C 2v symmetry provides a more tightly packed interlayer. Such transitions in the anion orientation are quite common among the LDHs [28]. This difference in the coordination symmetry, as we show later, profoundly affects the chromate uptake capacity of the two LDHs.…”

Composition and structure of an iron-bearing, layered double hydroxide (LDH) – Green rust sodium sulphate

“…When SO 4 -bearing LDH compounds of Zn-Cr and Cu-Cr were washed with Na-SO 4 -containing solutions, no change in basal plane spacing was recorded. When the compounds were rinsed with Li-SO 4 or NH 4 -SO 4 solutions, the basal plane spacing decreased from 11.1 to 8.9 Å , suggesting removal of alkali ions from the interlayer (El Malki et al, 1989;Khaldi et al, 1997). If GR was washed with K-SO 4 -containing solutions, the basal plane distance increased from 11.1 to 11.3 Å .…”

“…The LDH family includes a range of phases where only one of the hydroxide layer cations is a transition metal, e.g. Until now, GR concentration was assumed to be maximum at x, but XRD shows 100% green rust at point a and development of some goethite at x. Mg-Cr(III), Mn(II)-Al, Fe(II)-Al and Ni(II)-Al (Bish, 1978;El Malki et al, 1989;Ennadi et al, 1994;Hansen et al, 1994b;Khaldi et al, 1997). Among these, the two sulphate compounds, nikischerite, NaFe(II) 6 Al 3 (SO 4 ) 2 (OH) 18 Á12H 2 O (Huminicki and Hawthorne, 2003) and shigaite NaAl 3 Mn(II) 6 (SO 4 ) 2 (OH) 18 Á12H 2 O (Cooper and Hawthorne, 1996) are particularly interesting, because of their similarities in composition with green rust.…”

Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

“…However, delamination of LDHs in aqueous medium is a rare phenomenon and there are only a few reports to date [22][23][24]. Other studies have employed organic solvents such as formamide, n-alkanols and toluene among others [27][28][29]. Given the increasing interest in aqueous delamination of LDHs, which is seen as a green process, in this paper, we examine the reversible hydration of acetate-intercalated Ni/Al LDH [Ni/Al-OAc] with the objective of obtaining a mechanistic view of the phenomenon.…”