The isotopic exchangeability of phosphate in Mg-Al layered double hydroxides

Everaert, Maarten; Slenders, Kris; Dox, Kris; Smolders, Simon; Vos, Dirk De; Smolders, Erik

doi:10.1016/j.jcis.2018.03.010

Cited by 22 publications

(15 citation statements)

References 43 publications

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“…After 168 h incubation in 3 mM CO3, 54 % of PO4 is desorbed from LDH12(2) treated in 20 mM PO4, while only 33 % of PO4 is desorbed from PO4 exchanged LDH10 (2). This could be a result of a more pronounced PO4 intercalation in LDH10(2) compared to LDH12(2), as the counter diffusion of PO4 and CO3 is known to be a limiting factor for PO4 desorption [31].…”

Section: Ldh Exchange With Co3mentioning

confidence: 99%

Solid-state speciation of interlayer anions in layered double hydroxides

Everaert

Dox

Steele

et al. 2019

Journal of Colloid and Interface Science

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Layered double hydroxides (LDH) have been proposed for phosphate (PO4) recovery and recycling from waste streams due to their high anion exchange capacity, good stability and high affinity towards PO4. The high affinity towards PO4 strongly relates to the electrostatic interaction with PO4, and thus the charge of PO4. However, the anion speciation of intercalated PO4, i.e. either H2PO4-, HPO4 2or PO4 3is often overlooked. This study was set up to measure solid phase PO4 speciation through ion exchange stoichiometry, x-ray diffraction (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and modelling. Six phase pure Mg/Al LDH materials were synthesized using co-precipitation of metal nitrate (NO3-) solutions with varying M 2+ /M 3+ ratio at pH 12 and pH 10. The LDHs synthetized at pH 12 contained larger equivalent fractions of intercalated OH-, smaller fractions of NO3and smaller interlayer distance than those prepared at pH 10, likely because of the higher OHconcentration in the more alkaline synthesis solutions. Two high charge LDHs prepared at pH 12 or 10 were selected, exchanged with PO4 (0-20 mM initial PO4, 24h) at one starting pH (7.20); desorption was subsequently performed with carbonate (3 mM, initial pH 8.4) during 480 h. The resulting solution concentrations of NO3, PO4 and CO3 and the pH allowed the identification of the anion exchange stoichiometry. The LDH synthesized at pH 12, which had a large fraction of exchangeable OH-, adsorbed PO4 as HPO4 2-/PO4 3-, in exchange for both NO3and OHanions. The material synthesized at pH 10 containing a lower fraction of exchangeable OH-, therefore, adsorbed mainly HPO4 2in exchange for NO3anions. The carbonate exchange was consistent with adsorption of divalent CO3 2-. The pH dependent speciation modelling showed that the exchanged PO4 ions have higher charge compared to those in the contacting solution. This study suggests that the highest P content of LDH is obtained in high charge materials holding divalent PO4 anions, i.e. materials synthesized at lower pH and/or exchanged in solutions with low alkalinity.

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Section: Ldh Exchange With Co3mentioning

confidence: 99%

Solid-state speciation of interlayer anions in layered double hydroxides

Everaert

Dox

Steele

et al. 2019

Journal of Colloid and Interface Science

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“…equilibrium salt adsorption as a function of cell voltage for the MgAl-LDHs/AC electrode. The electrosorption capacity of phosphate ions on the electrode increased from 42.43 mg•g -1 to 67.92 mg•g -1 as the anode potential increased from 0 V to 1.2 V. This finding could be due to the strengthened interaction between the electrode material and phosphate ions as a result of phosphate ion intercalation[43], phosphate group complexation (monocomplexation and dicomplexation) to metal ions[43], and formation of an electric double layer[44]. A previous study reported similar results[45], indicating that the anode potential is a critical operational parameter in electrosorption systems.Electrode materials play an important role in electrosorption performance.…”

mentioning

confidence: 87%

Enhanced phosphate removal under an electric field via multiple mechanisms on MgAl-LDHs/AC composite electrode

Hong

Zhu

et al. 2019

Journal of Electroanalytical Chemistry

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Phosphorus removal is essential to avoid eutrophication in water bodies. Layered double hydroxides (LDHs) are widely used to scavenge phosphate through intercalated ion exchange or surface complexation. Moreover, LDHs have attracted increasing attention as electrode modifiers for supercapacitors. Researchers have begun to re-delve the electrosorption technology according to the fundamental principle of electrical double layers. Herein, we propose a new phosphate removal method inspired by the adsorption characteristic and electrical double-layer capacitive properties of LDHs through electrosorption via capacitive deionization. We present a series of experiments to study the enhanced phosphate removal under an electric field via multiple mechanisms on the MgAl-LDHs/AC electrode. The uptake of phosphate by MgAl-LDHs/AC was investigated as a function of phosphate concentration, applied voltage, electrode materials, and temperature. The MgAl-LDHs/AC electrode possessed a salt removal capacity of 67.92 mg PO4 3-•g-1 (1.2 V, 250 mg•L-1 KH2PO4, 30 °C). The electrosorption kinetics of phosphate ions onto the capacitive deionization electrode followed the pseudo-second-order kinetics model rather than the pseudo-first-order kinetics model. Furthermore, the adsorption isotherms of phosphate on the MgAl-LDHs/AC electrode fitted the Freundlich model better than the Langmuir model. The proposed method could be used for phosphate removal.

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“…Their structure is generally expressed by the formula [M 2+ 1‐ x M 3+ x (OH) 2 ] x + [A m ‐ x / m ·nH 2 O] x ‐ , where M 2+ and M 3+ are di‐ and trivalent metallic cations [ x = M 3+ /(M 2+ +M 3+ )], respectively, and A m ‐ is the intercalated anion. During synthesis, the greater the proportion of aluminum included, the greater the anion exchange capacity of the material (Everaert et al, 2018). Recently used in a variety of applications, such as controlled‐release pharmaceuticals, they have received attention both as a material capable of preferentially recovering P from wastewater and as a slow‐release source of P fertility in agriculture (Koilraj et al, 2013; Kong et al, 2019; Nalawade et al, 2009).…”

Section: Slow Releasersmentioning

confidence: 99%

“…In 2016, Everaert and colleagues found the optimal Mg/Al ratio to be 2:1 to increase both P loading and desorption (Everaert et al, 2016, 2018). Maximum sorption capacity by mass is currently similar to the graphene oxides and seems to be around 4% (Benício et al, 2016; Bernardo et al, 2018; Everaert et al, 2017).…”

Section: Slow Releasersmentioning

confidence: 99%

“…Mechanistic work on these products reveals that P becomes trapped on the interior of the interlayer gallery as the nutrient exchanges with solution anions closer to scaffold edges. Everaert et al (2018) witnessed that isotopic exchangeability (proxy measure of lability) of P after LDH products were subjected to desorption experiments was indirectly correlated to the amount of P desorbed, and the amount of P desorbed was dependent on the concentration of sodium bicarbonate used as a competing anion. The higher the NaHCO 3 concentration in the solution to which the product was subjected, the more total P was desorbed, and the less the remaining P was isotopically exchangeable.…”

Section: Slow Releasersmentioning

confidence: 99%

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A Review of the Latest in Phosphorus Fertilizer Technology: Possibilities and Pragmatism

2019

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The development of highly concentrated phosphorus (P) fertilizers, such as triple superphosphate, by the Tennessee Valley Authority helped mark the beginning of a revolution in the way we manage food crop nutrition. Since then, scientists, with the help of farmers, have made great advancements in the understanding of P fate and transport across many environments but largely have failed to produce a new generation of products and/or application techniques that are widely accepted and that vastly improve plant acquisition efficiency. Under certain conditions, important advancements have been made. For example, applying liquid formulations of phosphates in lieu of dry granules in some highly calcareous soils has dramatically reduced precipitation as sparingly soluble calcium phosphate minerals, but other attempts, such as the co‐application of humic substances, sorption to layered double hydroxides, or use of nanoparticles, have not generated the kind of results necessary to continue economically increasing crop yields without further environmental cost. New sources of fertility will need to be affordable to produce, transport, and furnish P to soil solution in a manner well synchronized with crop demand. This paper provides a review of recent literature on cutting‐edge phosphorus fertilizer technology. The goal is that this synthesis will be used as a starting point from which a larger discussion on responsible nutrient management and increased P use efficiency research can be built. Core Ideas Reaction with some soil constituents limits P availability and crop yield. A variety of approaches to improve fertilizer use efficiency are being explored. Ideally, P availability should be well synchronized to crop demand. More innovation along with mechanistic and field‐scale trials is required.

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The isotopic exchangeability of phosphate in Mg-Al layered double hydroxides

Cited by 22 publications

References 43 publications

Solid-state speciation of interlayer anions in layered double hydroxides

Solid-state speciation of interlayer anions in layered double hydroxides

Enhanced phosphate removal under an electric field via multiple mechanisms on MgAl-LDHs/AC composite electrode

A Review of the Latest in Phosphorus Fertilizer Technology: Possibilities and Pragmatism

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