Hydration, expansion, structure, and dynamics of layered double hydroxides

Hou, Xiaoqiang; Bish, David L.; Wang, Shan‐Li; Johnston, Cliff T.; Kirkpatrick, R. James

doi:10.2138/am-2003-0120

Cited by 101 publications

(116 citation statements)

References 57 publications

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“…The d basal of the H 2 PO À 4 type phase agrees with the reported ZnAl-H 2 PO 4 LDH (11.1 Å) [34] and LiAl-PO 4 LDH (10.62 Å) [35]. The shoulders may be attributed to SO 2À 4 , since the d basal ranged from 8.37 to 10.64 Å and were observed for LiAl 2 -SO 4 LDH and the latter has a bilayer-hydrated layer structure [36]. The ZnAl-Cl LDH pattern shows (Fig.…”

Section: Selectivity Toward Phosphatesupporting

confidence: 86%

High adsorption selectivity of ZnAl layered double hydroxides and the calcined materials toward phosphate

Kang

et al. 2010

Journal of Colloid and Interface Science

131

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Section: Selectivity Toward Phosphatesupporting

confidence: 86%

High adsorption selectivity of ZnAl layered double hydroxides and the calcined materials toward phosphate

Kang

et al. 2010

Journal of Colloid and Interface Science

131

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“…The hydration-dehydration behavior of many simple inorganic anions in the [Mg-Al] system with different compositions of the metal hydroxide layer were investigated thoroughly by Iye et al (2007) 2À -LDH showed a one-step change in the basal spacing. Similar studies of [Mg-Al] and [Li-Al] LDHs intercalated with different anions were reported by Kirkpatrick (2000, 2002) and Hou et al (2003). Based on those observations with different anions, the hydration behavior among LDHs were classified into three types: significantly expandable, slightly expandable, and non-expandable.…”

Section: Introductionsupporting

confidence: 77%

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

Radha

Jayanthi

Breu

et al. 2014

Clays and clay miner.

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Abstract-Layered double hydroxides (LDH) are extremely important materials for industrial processes and in the environment, and their physical-chemical behavior depends in large part on their hydration state, but the characterization of these hydration effects on their properties are incomplete. The present study was designed to explore the interpolytype transitions induced by variation in the ambient humidity among LDHs. The cooperative behavior of intercalated water molecules resulted in a sudden, single-step, reversible dehydration of the [Zn-Cr-SO 4 ] LDH. The [Zn-Al-SO 4 ] LDH provided an interesting contrast with (1) the coexistence of the end members of the hydration cycle over the 40À20% relative humidity range during the dehydration cycle, and (2) a random interstratified intermediate in the hydration cycle. These observations showed that the [Zn-Al-SO 4 ] LDH offered sites having a range of hydration enthalpies, whereby, at critical levels of hydration (20À40%), the non-uniform swelling of the structure resulted in an interstratified phase. The variation in domain size during reversible hydration was also responsible for the differences observed in the hydration vs. the dehydration pathways. This behavior was attributed to the distortion in the array of hydroxyl ions which departs from hexagonal symmetry on account of cation ordering as shown by structure refinement by the Rietveld method. This distortion was much less in the [Zn-Cr-SO 4 ] LDH, whereby the nearly hexagonal array of hydroxyl ions offered sites of uniform hydration enthalpy for the intercalated water molecules. In this case, all the water molecules experienced the same force of attraction and dehydrated reversibly in a single step. The changes in basal spacing were also accompanied by interpolytype transitions, involving the rigid translations of the metal hydroxide layers relative to one another.

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“…5 A as compared to 7.7 A of Ni-Al-C03 LDH. Also note that the layer spacing of sulfate LDHs can be further expanded by hydration after the materials are exposed to water [30]. Then, according to Figure 6, sulfate LDHs should have higher Kd values than their carbonate counterparts for Tc04-sorption.…”

Section: Effect Of Ph and Ionic Strengthmentioning

confidence: 98%

Compositional and structural control on anion sorption capability of layered double hydroxides (LDHs)

Wang¹,

Gao²

2006

Journal of Colloid and Interface Science

180

102

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Layered double hydroxides (LDHs) have shown great promise as anion getters. In this paper, we demonstrate that the sorption capability of a LDH for a specific oxyanion LDHs is dominated by the edge sites of LDH layers and strongly correlated with the basal spacing doo3 of the materials, which increases with the decreasing radii of both divalent and trivalent cations. The sorption reaches its maximum when the layer spacing ' is just large enough for a pertechnetate anion to fit into a cage space between two neighboring octahedra of metal hydroxides at the edge. Furthermore, the sorption is found to increase with the crystallinity of the materials. For a given combination of metal cations and an interlayer anion, a best crystalline LDH material is obtained generally with a M(II)/M(III) ratio of 3 : 1. Replacement of interlayer carbonate with readily exchangeable nitrate greatly increases the sorption capability of a LDH material for pertechnetate, due to the enhanced adsorption on edge sites and the possible contribution from interlayer anion exchanges. The work reported here will help to establish a general structure-property relationship for the related layered materials.

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Hydration, expansion, structure, and dynamics of layered double hydroxides

Cited by 101 publications

References 57 publications

High adsorption selectivity of ZnAl layered double hydroxides and the calcined materials toward phosphate

High adsorption selectivity of ZnAl layered double hydroxides and the calcined materials toward phosphate

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

Compositional and structural control on anion sorption capability of layered double hydroxides (LDHs)

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