Application of layered double hydroxides for removal of oxyanions: A review

Goh, Kok Hui; Lim, Teik−Thye; Dong, Zhili

doi:10.1016/j.watres.2007.10.043

Cited by 1,532 publications

(867 citation statements)

References 192 publications

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“…After 10 cycles, the cell capacity plateaued at approximately 90 mAh/g, tenuously confirming long-term reversibility of PF 6 − intercalation. Eventually, the material preferentially cycles between 0.58 < x < 1.92.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 68%

“…The first peak matches the open-circuit potential of the pristine electrode at 2.75 V. The reductive sweep shows one very broad peak and a second sharper peak at 2.63 V juxtaposed to the initial oxidative peak. Although the Coulombic efficiency of this cycle was greater than 99%, the peak asymmetry suggests that the deinsertion process is different from the insertion process which is possibly a result of changes in ion packing as the concentration of PF 6 − increases or that the asymmetry of the reductive process is convoluted by simultaneous cation insertion and anion deinsertion.…”

Section: Resultsmentioning

confidence: 88%

“…Addition of an acetonitrile solution of this oxidant results in an immediate color change of the solid from white to dark green, together with the evolution of bubbles from the solution. As shown in Figure 3a, the UV−vis−NIR spectrum of the resulting material, Mg 2 (dobpdc)(PF 6 ) 0.48 , displays a new peak at 1.49 eV with a narrower bandwidth than that observed for the Fe II/III intervalence charge-transfer band of Fe 2 (dobpdc)-(PF 6 ). This matches nicely with other reported oligophenyl quinone radical anions and is diagnostic of the formation of the semiquinoid radical.…”

Section: Resultsmentioning

confidence: 95%

“…49 The larger TFSI − (212 Å 3 ) and tetrakis(perfluorophenyl)borate (BArF − , 580 Å 3 ) ions exhibit significantly reduced capacities, x = 1.36 and 0.60 equiv, respectively. Interestingly, at 1.18 equiv, PF 6 − (89 Å 3 ) affords a lower charge capacity than TFSI − , despite its much smaller size. This may be the result of coinsertion of neutral LiPF 6 or some otherwise convoluted ion pairing of the cation.…”

Section: Resultsmentioning

confidence: 99%

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A Dual−Ion Battery Cathode via Oxidative Insertion of Anions in a Metal–Organic Framework

2015

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A redox−active metal−organic framework, Fe 2 (dobpdc) (dobpdc 4− = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), is shown to undergo a topotactic oxidative insertion reaction with a variety of weakly coordinating anions, including BF 4 − and PF 6 − . The reaction results in just a minor lattice contraction, and a broad intervalence charge-transfer band emerges, indicative of charge mobility. Although both metaland ligand-based oxidations can be accessed, only the former were found to be fully reversible and, importantly, proceed stoichiometrically under both chemical and electrochemical conditions. Electrochemical measurements probing the effects of nanoconfinement on the insertion reaction revealed strong anion size and solvent dependences. Significantly, the anion insertion behavior of Fe 2 (dobpdc) enabled its use in the construction of a dual-ion battery prototype incorporating a sodium anode. As a cathode, the material displays a particularly high initial reduction potential and is further stable for at least 50 charge/discharge cycles, exhibiting a maximum specific energy of 316 Wh/ kg.

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Section: Journal Of the American Chemical Societymentioning

confidence: 68%

Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

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A Dual−Ion Battery Cathode via Oxidative Insertion of Anions in a Metal–Organic Framework

2015

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“…arsenate (AsO 4 3-) [5][6][7][8], selenite (SeO 4 2-) [8][9][10][11], molybdate (MoO 4 2-) [6][7][8][9][12][13][14] and chromate (CrO 4 2-) [8,9,12,13]. LDHs which are also known as anionic clays or hydrotalcite like materials are a group of clay minerals with a similar structure to the mineral brucite (Mg(OH) 2 ), which consists of divalent magnesium ions occupying octahedral positions surrounded by OH groups in a complex layered structure.…”

Section: Introductionmentioning

confidence: 99%

Removal of boron species by layered double hydroxides: A review

Theiss

Ayoko

Frost

2013

Journal of Colloid and Interface Science

117

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Boron, which is an essential element for plants, is toxic to humans and animals at high concentrations. Layered double hydroxides (LDHs) and thermally activated LDHs have shown good uptake of a range of boron species in laboratory scale experiments when compared to current available methods, which are for the most part ineffective or prohibitively expensive. LDHs were able to remove anions from water by anion exchange, the reformation (or memory) effect and direct precipitation. The main mechanism of boron uptake appeared to be anion exchange, which was confirmed by powder X-ray diffraction (XRD) measurements. Solution pH appeared to have little effect on boron sorption while thermal activation did not always significantly improve boron uptake. In addition, perpetration of numerous LDHs with varying boron anions in the interlayer region by direct co-precipitation and anion exchange have been reported by a number of groups. The composition and orientation of the interlayer boron ions could be identified with reasonable certainty by applying a number of characterisation techniques including: powder XRD, nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy. There is still considerable scope for future research on the application of LDHs for the removal of boron contaminants.

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