Insights into the amorphous calcium carbonate (ACC) → ikaite → calcite transformations

Lázár, Anett; Molnár, Zsombor; Demény, Attila; Kótai, László; Trif, László; Béres, Kende Attila; Bódis, Eszter; Bortel, Gábor; Aradi, László Előd; Karlik, Máté; Szabó, Máté; Pekker, Áron; Németh, Gergely; Garvie, L. A. J.; Németh, Péter

doi:10.1039/d2ce01444k

Cited by 8 publications

(5 citation statements)

References 67 publications

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“…Several ikaite break down models have been presented in [20,29,47] and demonstrated that Amorphous Calcium Carbonate (ACC) played an important role during the ikaite to calcite transition, and it is suggested that carbonate and calcium ions change orientation during loss of structural water [48]. Both these mechanisms are consistent with the observation illustrated in Figure 2a,(e3) of a possible structural element rarely observed in the glendonite (Figure 2f) forming along inner structures preserved in the pseudomorph.…”

Section: Petrographic Comparison Of Ikaite and Fur Formation Glendonitesupporting

confidence: 73%

Links between Ikaite Morphology, Recrystallised Ikaite Petrography and Glendonite Pseudomorphs Determined from Polar and Deep-Sea Ikaite

et al. 2023

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Petrography of recrystallised ikaite from Ocean Drilling Program material has been presented previously from Nankai Trough and Congo (ex-Zaire) deep-sea fan. This paper expands on the Nankai Trough ikaite observations, drawing on evidence from Laptev Sea, South Georgia, Okhotsk Sea, and coastal lagoon Point Barrow. However, even though many ikaite and glendonite sites occur at high latitudes, it cannot be that ikaite forms exclusively in polar environments, as demonstrated by the occurrences in the low latitude low temperature deep sea sediments offshore Gulf of Guinea (Angola Congo) and mid-latitude deep-sea trenches offshore Japan. Recrystallised ikaite occurs as mm large, zoned calcite crystals in all samples, along with secondary phases of calcite. Our data set is unique in that the origin, storage, and recrystallisation process of natural formed ikaite is recorded in detail and confirms that glendonite petrographic characteristics are a consequence of the structure and chemistry of recrystallising ikaite and not the physical or geochemical environment. The transformation of man-made ikaite to calcite as recorded in laboratory studies, is a process very similar to the one we have observed for natural ikaite. Most significant is that there is variation in the order of the calcite types within a single sample, leading to the conclusion that the variation is a consequence of impurities and geochemical variability in the ikaite, not the external environment. Morphological observations reveal similarities in ikaite and glendonite, this and the similarity in internal textures in glendonite and recrystallised ikaite confirms that glendonite may be used as an indicator of past presence of ikaite.

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Section: Petrographic Comparison Of Ikaite and Fur Formation Glendonitesupporting

confidence: 73%

Links between Ikaite Morphology, Recrystallised Ikaite Petrography and Glendonite Pseudomorphs Determined from Polar and Deep-Sea Ikaite

et al. 2023

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“…peroxides dissolved/incorporated in the amorphous Li 2 CO 3 shell, is more likely. We also note that Raman did not detect Li 2 CO 3 peaks from this sample, this is probably due to its low loading (5 wt.%) and the peak broadening effect of amorphous carbonate as the temperature increases 41 . This peak broadening effect was confirmed via an in-situ Raman experiment on LaPrO 3+x @5Li 2 CO 3 under 5%CO 2 (balance Ar) with temperature ramping up from 120 to 700 °C.…”

Section: Resultsmentioning

confidence: 74%

Lithium carbonate-promoted mixed rare earth oxides as a generalized strategy for oxidative coupling of methane with exceptional yields

Zhao,

Gao,

Wang

et al. 2023

Nat Commun

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The oxidative coupling of methane to higher hydrocarbons offers a promising autothermal approach for direct methane conversion, but its progress has been hindered by yield limitations, high temperature requirements, and performance penalties at practical methane partial pressures (~1 atm). In this study, we report a class of Li2CO3-coated mixed rare earth oxides as highly effective redox catalysts for oxidative coupling of methane under a chemical looping scheme. This catalyst achieves a single-pass C2+ yield up to 30.6%, demonstrating stable performance at 700 °C and methane partial pressures up to 1.4 atm. In-situ characterizations and quantum chemistry calculations provide insights into the distinct roles of the mixed oxide core and Li2CO3 shell, as well as the interplay between the Pr oxidation state and active peroxide formation upon Li2CO3 coating. Furthermore, we establish a generalized correlation between Pr4+ content in the mixed lanthanide oxide and hydrocarbons yield, offering a valuable optimization strategy for this class of oxidative coupling of methane redox catalysts.

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“…The peak at 1430 cm −1 corresponds to the C-O antisymmetric tensile vibration in CaCO 3 . Apart from the characteristic absorption peaks of calcite, 3460 cm −1 corresponds to the hydroxyl (-OH) groups that can be attributed to the physically adsorbed water molecules [46]. CaCO 3 -10 SDBS-12 has new absorption peaks at 1087 cm −1 and 746 cm −1 corresponding to symmetrical stretching vibration and shear bending vibration respectively in vaterite form, indicating the presence of the vaterite phase [47].…”

Section: Mechanism Explorationmentioning

confidence: 99%

Controllable Synthesis of Nano-Micro Calcium Carbonate Mediated by Additive Engineering

Shen,

Hao,

Suonan

et al. 2023

Crystals

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Nano-micro calcium carbonate has a small particle size, uniform distribution, and good dispersion performance, offering great research value and development prospects. It has been widely used as a filler material for rubber, paper, ink, pigments, and coatings. Developing an efficient and controllable approach to preparing nano-micro calcium carbonate with adjustable morphology and controllable size has significant economic and environmental benefits. This study reports the controllable synthesis of nano-micro calcium carbonate meditated by additive engineering. The effects of various additives including inorganic acids, organic acids, alcohol, and surfactants on the particle size and morphology of the prepared materials were investigated. SEM, FT-IR and other characterization methods were used to analyze the prepared nano-micro calcium carbonate particle size, dispersion, and uniformity. The results showed that the particle size of calcium carbonate was 4~7 μm with a cubic structure. The particle size of calcium carbonate prepared by adding surfactant additives is in the range of 1~4 μm, and the crystal shape of calcium carbonate changes from calcite to vaterite after adding sodium dodecyl benzene sulfonate. With the aid of additives, the calcium carbonate particles dispersed more evenly. The mechanism of the controllable synthesis of nano-micro calcium carbonate mediated by additive engineering is elucidated and discussed. SDBS was found to be the best additive for preparing nano-micro calcium carbonate, and the synthesis conditions were explored and optimized.

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Insights into the amorphous calcium carbonate (ACC) → ikaite → calcite transformations

Abstract: Amorphous calcium carbonate (ACC) is a precursor material that plays a key role in polymorph selection and crystallization of carbonates. It is involved in the formation of the cryogenic carbonate...

Cited by 8 publications

References 67 publications

Links between Ikaite Morphology, Recrystallised Ikaite Petrography and Glendonite Pseudomorphs Determined from Polar and Deep-Sea Ikaite

Links between Ikaite Morphology, Recrystallised Ikaite Petrography and Glendonite Pseudomorphs Determined from Polar and Deep-Sea Ikaite

Lithium carbonate-promoted mixed rare earth oxides as a generalized strategy for oxidative coupling of methane with exceptional yields

Controllable Synthesis of Nano-Micro Calcium Carbonate Mediated by Additive Engineering

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