Mechanism of boron uptake by hydrocalumite calcined at different temperatures

Qiu, Xinhong; Sasaki, Keiko; Takaki, Yu; Hirajima, Tsuyoshi; Ideta, Keiko; Miyawaki, Jin

doi:10.1016/j.jhazmat.2015.01.066

Cited by 36 publications

(12 citation statements)

References 47 publications

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“…Therefore, monovalent anions (i.e., Cl − and to a lesser extent, OH − ) in the interlayer position were not fully exchangeable with MoO 4 2− . This could result from partial accessibility of exchangeable sites, as reported previously for boron 61 , and/or because of high thermodynamic stability of the interstratified AFm containing Mo and monovalent anions, as reported by Mesbah et al . 62 for Kuzel’s salt.…”

Section: Resultssupporting

confidence: 61%

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Thermodynamic and crystallographic model for anion uptake by hydrated calcium aluminate (AFm): an example of molybdenum

Marty

Grangeon

Elkaı̈m

et al. 2018

Sci Rep

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Amongst all cement phases, hydrated calcium aluminate (AFm) plays a major role in the retention of anionic species. Molybdenum (Mo), whose 93Mo isotope is considered a major steel activation product, will be released mainly under the form of MoO42− in a radioactive waste repository. Understanding its fate is of primary importance in a safety analysis of such disposal. This necessitates models that can both predict quantitatively the sorption of Mo by AFm and determine the nature of the sorption process (i.e., reversible adsorption or incorporation). This study investigated the Cl−/MoO42− exchange processes occurring in an AFm initially containing interlayer Cl in alkaline conditions using flow-through experiments. The evolution of the solid phase was characterized using an electron probe microanalyzer and synchrotron high-energy X-ray scattering. All data, together with their quantitative modeling, coherently indicated that Mo replaced Cl in the AFm interlayer. The structure of the interlayer is described with unprecedented atomic-scale detail based on a combination of real- and reciprocal-space analyses of total X-ray scattering data. In addition, modeling of several independent chemical experiments elucidated that Cl−/OH− exchange processes occur together with Cl−/MoO42− exchange. This competitive effect must be considered when determining the Cl−/MoO42− selectivity constant.

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Section: Resultssupporting

confidence: 61%

“…Qiu et al . 61 reported a collapse of the AFm interlayer in the presence of interlayer OH − that inhibited the adsorption of B(OH) 4 − . In our experiments, the fitted AEC site 1 increased from experiment 1 to 3 to 2, consistent with the measured pH of the “initial reactor solution” decreasing from experiments 1 to 3 to 2 (Table 3 ).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic and crystallographic model for anion uptake by hydrated calcium aluminate (AFm): an example of molybdenum

Marty

Grangeon

Elkaı̈m

et al. 2018

Sci Rep

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“…using borate, see Table A1, deposited). Boron uptake by AFm has been studied by Qiu et al (2015). These authors indicate that the affinity of OHfor the AFm is stronger than that of B(OH) À 4 .…”

Section: Exchange Reactionsmentioning

confidence: 99%

Dissolution kinetics of hydrated calcium aluminates (AFm-Cl) as a function of pH and at room temperature

et al. 2017

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International audienceThe determination of reliable weathering/dissolution rates for cement phases is of fundamental importance for the modelling of the temporal evolution of both radioactive waste repositories and CO 2 geological storage sites (e.g. waste matrix, plug in boreholes). Here, the dissolution kinetics of AFm-Cl (hydrated calcium aluminates containing interlayer Cl) has been studied using flow-through experiments conducted at pH values ranging from 9.2 to 13. Mineralogical (XRD) and chemical (EPMA, TEM) analyses have been performed to determine the evolution of the phases during the dissolution experiments. For pH values between 10 and 13, the dissolution of AFm-Cl is congruent (i.e. Ca/Al ratios close to 2 both for solids and outlet concentrations). In contrast, the precipitation of amorphous Al-phases and possibly amorphous mixed Al/Ca phases is observed at pH 9.2, leading to Ca/Al ratios in the outlet solutions higher than those of the initial solid. Therefore, at pH 9.2, even if Cl – /OH – exchange occurs, estimation of dissolution rate from released Cl appears to be the best proxy. Dissolution rates were normalized to the final specific surface areas (ranging from 6.1 to 35.4 m 2 g −1). Dissolution rate appears to be pH-independent and therefore the far-from-equilibrium dissolution rate at room temperature is expressed as: logR(mol m –2 s –1) = –9.23 ± 0.1

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“…As seen in Figure , Mg–CLDH exhibited little adsorptive effect on them. Because its electrostatic potential was larger than that of OH – [ESP of benzoic acid, −94.75 kcal/mol; phenol, −102.44 kcal/mol; 2-hydroxynaphthalene, −88.53 kcal/mol; 1-naphthoic acid, −82.52 kcal/mol; and 4-phenylbutyric acid, −158.04 kcal/mol and p K a of benzoic acid, 4.19; phenol, 9.98; 2-hydroxynaphthalene, 9.34; 1-naphthoic acid, 4.17; and 4-phenylbutyric acid, 4.76 (25 °C)], it was easier to fix OH – to the interlayer during regeneration . Their interlayer spacing after the reaction was smaller than that in deionized water (Table ), suggesting that a small number of organic models entered the interlayer or acted at the edge to reduce the interlayer spacing.…”

Section: Resultsmentioning

confidence: 99%

“…LDHs can lose their layered structure at a certain calcination temperature and restore their original structure in aqueous solution and even humid atmosphere, which is called the structural memory effect. This process would produce new minerals depending upon the types of regenerated LDHs and interlayer anion species. − Therefore, these phenomena should inevitably affect the interaction between LDHs and the natural environment.…”

Section: Introductionmentioning

confidence: 99%

Effect of Natural Organic Matter Model Compounds on the Structure Memory Effect of Different Layered Double Hydroxides

Zhao

et al. 2019

ACS Earth Space Chem.

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The structural transformation of layered double hydroxides (LDHs) plays an important role in a variety of natural environmental behaviors. As one of the important ways of structure transformation in LDHs, the structure memory effect closely interacted with humic acid (HA). However, the role of functional groups in HA is unclear because its structure is relatively complex. Therefore, seven representative small molecules of single or double aromatic compounds were selected to explore their influence on the regeneration of different LDHs, thereby revealing key function groups in HA. As a result, ortho-benzene compounds could more effectively affect the regeneration of LDHs than other model compounds. For these compounds, the aliphatic chain length and aromatic ring size have little effect on regeneration of LDHs. However, increasing the number of carboxyl or hydroxyl groups affected the results, although all of them accelerated the regeneration rate of LDHs. Additionally, LDHs during the regeneration have a positive adsorption effect on both o-carboxyl and o-hydroxyl aromatic compounds; however, they have shown different effects on the regeneration of LDHs. Phthalic acid revealed no effect on the structure and crystallinity of regenerated LDH, while catechol inhibited the regeneration process and decreased the crystallinity of regenerated LDHs. The effects of o-hydroxyl aromatic compounds, such as catechol, are also dependent upon the type of LDHs. They have an inhibitory effect on the crystallinity of the regenerated Mg−LDH within a short time or with a high concentration but have no effect on its morphology. Although o-hydroxyl aromatic compounds have no effect on the crystallinity of regenerated Ca−LDH, the crystal growth was suppressed. This is due to the difference in the regeneration processes between two LDHs. These results provide a more detailed theoretical basis for understanding the influence of HA on the structural transformation of LDHs or even other minerals, such as hydroxides, in the environment.

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Mechanism of boron uptake by hydrocalumite calcined at different temperatures

Cited by 36 publications

References 47 publications

Thermodynamic and crystallographic model for anion uptake by hydrated calcium aluminate (AFm): an example of molybdenum

Thermodynamic and crystallographic model for anion uptake by hydrated calcium aluminate (AFm): an example of molybdenum

Dissolution kinetics of hydrated calcium aluminates (AFm-Cl) as a function of pH and at room temperature

Effect of Natural Organic Matter Model Compounds on the Structure Memory Effect of Different Layered Double Hydroxides

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