Uptake of As(V) from aqueous solution by anionic clays type FeLDHs

Cârjă, Gabriela; Ratoi, Simona; Ciobanu, Gabriela; Balasanian, Ion

doi:10.1016/j.desal.2007.01.222

Cited by 20 publications

(24 citation statements)

References 11 publications

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“…For example, Mandal and Mayadevi reported that the fluoride uptake was increased by 21.2% after calcination of the Zn-Al LDHs at 450-500 • C [26]. Carja et al found that calcination (450 • C) markedly increased the removal efficiency of As(V) oxyanions up to >90% for all the Fe-containing LDHs tested [27].…”

Section: Calcinationmentioning

confidence: 99%

Phosphate adsorption from sewage sludge filtrate using zinc–aluminum layered double hydroxides

Cheng

Huang

Wang

et al. 2009

Journal of Hazardous Materials

208

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a b s t r a c tA series of layered double hydroxides (LDHs) with different metal cations were synthesized to remove phosphate in waste sludge filtrate from a municipal wastewater treatment plant for phosphorus recovery and to help control eutrophication. The highest phosphate adsorption capacity was obtained by using Zn-Al-2-300, that is LDHs with Zn/Al molar ratio of 2 and calcined at 300 • C for 4 h. Circumneutral and mildly alkaline waters appeared suitable for the possible application of Zn-Al LDHs due to the amphoteric nature of aluminum hydroxide. Phosphate adsorption from the sludge filtrate by the LDHs followed pseudo-second-order kinetics, and the adsorption capacity at equilibrium was determined to be ∼50 mg P/g. Adsorption isotherms showed that phosphate uptake in this study was an endothermic process and had a good fit with a Langmuir-type model. The absorbed phosphate can be effectively desorbed (more than 80%) from LDHs particles by a 5 wt% NaOH solution. The regeneration rate of used LDHs was ∼60% after six cycles of adsorption-desorption-regeneration.

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Section: Calcinationmentioning

confidence: 99%

Phosphate adsorption from sewage sludge filtrate using zinc–aluminum layered double hydroxides

Cheng

Huang

Wang

et al. 2009

Journal of Hazardous Materials

208

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“…The Mg/Fe LDH has been prepared by addition of a mixed metal (Mg 2+ + Fe 3+ ) salt solution to a solution of NaOH, [17] Na 2 CO 3 , [19] or NaHCO 3 [20] at a high constant pH. The solubility product of "Fe(OH) 3 " at 10 -33 is far below that of Mg(OH) 2 at 10 -10 . [21] Thereby, coprecipitation reactions do not yield single-phase products, but generate copious amount of X-ray amorphous unitary products of Fe 3+ .…”

Section: Introductionmentioning

confidence: 99%

“…The layered double hydroxide (LDH) of Mg and Fe has potential applications in catalysis, [1] water purification, [2,3] safe storage of vitamins, [4] anion exchange, [5] as well as cation sorption.…”

Section: Introductionmentioning

confidence: 99%

Structure and Composition of the Layered Double Hydroxides of Mg and Fe: Implications for Anion‐Exchange Reactions

2011

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Partial cation exchange of Mg 2+ ions with Fe 3+ ions employing solid Mg(OH) 2 as precursor yielded an ordered layered double hydroxide of Mg and Fe in the presence of carbonate anions. Structure refinement revealed that the compound adopts the polytype structure 3R 1 (space group R3m, a = 3.108 Å, c = 23.08 Å) and does not show any signs of cation order. It crystallizes with a unique cation ratio of [Mg]/ [Fe] = 4. At this ratio, the compound shows a single sharp absorption in its electronic spectrum at 280 nm. Attempts to prepare the LDH with a higher Fe content resulted in the IntroductionThe layered double hydroxide (LDH) of Mg and Fe has potential applications in catalysis, [1] water purification, [2,3] safe storage of vitamins, [4] anion exchange, [5] as well as cation sorption.[6] The oxide residue obtained by the thermal decomposition of the Mg/Fe LDH is a bifunctional catalyst with both acidic and basic surface sites.[7] The Fe 0 /Fe 2+ / Fe 3+ composition of the catalyst can be finely tuned by controlled reduction, whereby catalysts with high olefin selectivity can be generated for use in the Fischer-Tropsch reaction. Given the magnetic properties of the oxides of Fe III , the Mg/Fe LDH is also used as a precursor for the synthesis of single-phase magnetic ferrites [8] and magnetic nanocomposites.[9] Furthermore, the Mg/Fe LDH is less toxic than many combinations of di-and trivalent cations and is proposed as a model medium for drug delivery. [10] The Mg/Fe LDH is obtained by the isomorphous substitution of a fraction x of Mg 2+ ions by Fe 3+ ions in Mg-(OH) 2 to yield positively charged layers with the composi-x+ . [11] Anions are incorporated into the interlayer. Many pairs of di-and trivalent cations can be combined with a variety of anions [12][13][14] to obtain a large and diverse family of layered double hydroxides. The Mg/ Fe LDH in many ways stands apart from other LDHs.(1) There is limited literature on the anion-exchange and -uptake properties of the pristine and calcined Mg/Fe LDH. Evidence for the anion-exchange of Mg/Fe LDHs is phase separation of excess Fe into X-ray amorphous binary compounds, the existence of which can be discerned only by the appearance of absorptions at λ Ͼ 350 nm, a characteristic of oxide-hydroxides of Fe 3+ . The nitrate-containing compound also forms with a similarly low Fe content. At this composition, the compound does not exhibit any anion-exchange properties as the nitrate ions intercalated in layered hydroxides of low layer charge are not labile. This explains the paucity of information on anion-exchange reactions of layered double hydroxides of Mg and Fe.at best equivocal and there are some definitive reports, [4] including this work, of the absence of anion-exchange reactions in Fe-containing LDHs.(2) In general, the a parameter of LDHs decreases with increasing trivalent metal content.[ (3) If the composition is fixed at x = 0.25, as suggested by some authors, [17] or at x = 0.2, as suggested by others, [5,18] does the Mg/Fe LDH crystallize in a cation-ord...

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“…Anions contribute to the thermodynamic stability of the LDH by affecting both enthalpy and entropy [10]. For a given pair of metal ions, the affinity of the LDH for different anions varies in the order CO ions by a mineral acid (HCl or HNO 3 ) at pH 4.5 [14] and (b) calcination of the pristine LDH to yield a defect oxide phase and subsequent reconstruction of the LDH by soaking the oxide residue in As(V) solution [15]. The uptake by the former method is essentially through anion exchange at a pH close to the dissolution pH of the LDH, while the latter is based on the memory-effect of LDHs.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of arsenate-intercalated layered double hydroxides (LDHs): Prospects for arsenic mineralization

Prasanna

Kamath

2009

Journal of Colloid and Interface Science

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The arsenate-intercalated layered double hydroxide (LDH) of Mg and Al is synthesized by coprecipitation. The higher thermodynamic stability and the consequent lower solubility of the unitary arsenates preclude the formation of arsenate-intercalated LDHs of other metals directly from solution. However other M/AlAsO 4 (M = Co, Ni, Zn) LDHs could be prepared by anion exchange, showing that arsenate intercalation proceeds topotactically. The intercalation of various species of As(V) into the interlayer of LDHs and the subsequent arsenate carrying capacity are dependent upon the pH of the solution. Upon thermal decomposition, the intercalated arsenate ion undergoes reductive deintercalation to give a mixture of As(III) and As(V) oxides. The product oxides revert back to the LDH upon soaking in water on account of the compositional and morphological metastability of the former. This is in contrast with the phosphateintercalated LDHs, in which the reversibility is suppressed, consequent to the formation of stable metal phosphates.

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Uptake of As(V) from aqueous solution by anionic clays type FeLDHs

Cited by 20 publications

References 11 publications

Phosphate adsorption from sewage sludge filtrate using zinc–aluminum layered double hydroxides

Phosphate adsorption from sewage sludge filtrate using zinc–aluminum layered double hydroxides

Structure and Composition of the Layered Double Hydroxides of Mg and Fe: Implications for Anion‐Exchange Reactions

Synthesis and characterization of arsenate-intercalated layered double hydroxides (LDHs): Prospects for arsenic mineralization

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