The formation and transformation mechanism of calcium carbonate in water

Ogino, Takeshi; Suzuki, Toshio; Sawada, Kiyoshi

doi:10.1016/0016-7037(87)90155-4

Cited by 568 publications

(510 citation statements)

References 16 publications

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“…The first process involves the period before the formation of aragonite (step 1), while the second involves the period after the formation of aragonite (step 2). Ogino et al (1987) studied the transformation mechanisms of metastable polymorphic calcium carbonate (aragonite and vaterite) to a stable -phase calcium carbonate (calcite). They suggested that the polymorphic transformation occurred through the dissolution of the metastable phase and the formation of the more stable phase.…”

Section: Resultsmentioning

confidence: 99%

Transformation kinetics of monohydrocalcite to aragonite in aqueous solutions

Munemoto

Fukushi

2008

Journal of Mineralogical and Petrological Sciences

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Monohydrocalcite (CaCO 3 ·H 2 O; MHC) is a rare mineral in geological settings. It is metastable with respect to calcite and aragonite. This metastability of MHC is considered to make it a rare mineral in geological settings. Alteration experiments of MHC in aqueous solutions in a closed system were conducted at temperatures between 10 and 50 °C in order to measure its metastability quantitatively. In the present study, monohydrocalcite transformed to aragonite with time. There are two rate -limiting steps in the transformation of monohydrocalcite to aragonite: the nucleation and crystal growth of aragonite. On the other hand, the dissolution of monohydrocalcite is a faster process than the nucleation and crystal growth of aragonite. The amounts of aragonite were calculated from the X -ray diffraction (XRD) intensity to evaluate the rate of both the processes at different temperatures. The induction times for the nucleation of aragonite were estimated to be 2.7 ± 0.9×10 , and 1.6 ± 0.3×10 -6 mmol·s -1 at 10, 25, 40, and 50 °C, respectively. From Arrhenius plots, the apparent activation energies were estimated to be 108.1 kJ·mol -1 and 80.7 kJ·mol -1 for the nucleation and crystal growth steps, respectively.

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Section: Resultsmentioning

confidence: 99%

Transformation kinetics of monohydrocalcite to aragonite in aqueous solutions

Munemoto

Fukushi

2008

Journal of Mineralogical and Petrological Sciences

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“…4. The quality of the fit was evaluated by the normalized square-sums of residuals (R factor), S(mobserved -mfit) 2 /mobserved 2 over the whole region of the spectrum. The R factors of the fits were 1.8% for the binary system and 2.2% for a mixture of three polymorphs; the results of the fits were satisfactory.…”

Section: Resultsmentioning

confidence: 99%

“…The precipitation of calcium carbonate from supersaturated solutions of Ca 2+ and CO3 2-has been studied extensively, and the transformation of the initial amorphous calcium carbonate (ACC) to a mixture of polymorphs has been discussed in terms of the ion activity product (IAP), the reaction temperature and the addition of foreign cations. [1][2][3] Recently, the selective formation of a special polymorph under ambient conditions has been reported. 4,5 Experiments were carried out by using an organic template and soluble additives, and the conditions employed were biotic.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Calcium Carbonate Polymorphs with Ca K Edge X-ray Absorption Fine Structure Spectroscopy

et al. 2008

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Ca K edge X-ray absorption fine structure (XAFS) spectroscopy was utilized for the characterization and quantification of calcium carbonate polymorphs and their mixtures. The advantage of the XAFS is the small sample quantity required for measurements, and a flexible sample environment. The near-edge XAFS spectra of calcite, aragonite and vaterite were measured with the conversion electron yield (CEY) method, and the obtained spectra showed characteristic features that can be utilized as fingerprints. The quantification of mixed polymorphs was examined by using a linear combination fitting of reference XAFS spectra. Though the quality of the fits was satisfactory, discrepancies in the evaluated values were observed between those with X-ray diffraction (XRD) and XAFS. The nonuniformity of samples may be enhanced by the surface sensitivity of the CEY method.

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“…Aragonite was synthesized 466 according to a method after Ogino et al (1987), by mixing equal amounts of 0.5 mol/L Na 2 CO 3 and 0.5 467 mol/L CaCl 2 ·•2H 2 O solution at 90°C. After two to three minutes the precipitated powder is separated from 468 the solution by filtration, dried at 105°C over--night, and analyzed by powder XRD, N 2 --BET and SEM.…”

Section: Aragonite Recrystallization Experiments 455mentioning

confidence: 99%