Precipitation in the Mg-carbonate system—effects of temperature and CO2 pressure

Hänchen, Markus; Prigiobbe, Valentina; Baciocchi, Renato; Mazzotti, Marco

doi:10.1016/j.ces.2007.09.052

Cited by 415 publications

(401 citation statements)

References 21 publications

(29 reference statements)

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“…4a). The gain itself is related to the formation of magnesite MgCO 3 as shown by Bearat et al (2002) and/or a series of crystalwater-bearing Mg carbonates (Hänchen et al 2008). The main weight loss is due to a combination of dehydroxylation of remaining brucite and decarbonisation of magnesite (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

2013

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a much higher apparent E a characterised by an initial stage of around 290 kJ/mol. Afterwards, the apparent E a comes down to around 250 kJ/mol at α ~ 65 % before rising up to around 400 kJ/mol. The delivered kinetic data have been investigated by the z(α) master plot and generalised time master plot methods in order to discriminate the reaction mechanism. Resulting data verify the multi-step reaction scenarios (reactions governed by more than one rate-determining step) already visible in E a versus α plots.Keywords Serpentine dehydroxylation · Generalised master plot · Chrysotile · Brucite · Thermogravimetry · In situ high-temperature X-ray powder diffraction

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Section: Resultsmentioning

confidence: 99%

“…a weight gain below the onset of the brucite dehydroxylation under inert N 2 atmosphere. A reaction involving hydrated carbonate species is also possible and would complicate the reaction sequence (Hänchen et al 2008). For the chosen heating rates, it is impossible to achieve a completion of the carbonation reaction (Bearat et al 2002).…”

Section: Resultsmentioning

confidence: 99%

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

2013

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“…Thus, it becomes logical to surmise that the dolomite problem and the magnesite problem probably share the same root, that is, the difficulty to incorporate unhydrated magnesium ions into carbonate from aqueous solutions without appealing to temperature and/or pressure changes. Given the 50% abundance of dolomites in the world's carbonate reservoirs (6, 17) and the potential of magnesium carbonate for carbon sequestration (18,19), as well as the critical role of Mg in carbonate biomineralization (20)(21)(22), it is safe to assume that scientific interests in the Ca-Mg-CO 3 system will remain for years to come.Aqueous 24). Nesquehonite is the most commonly formed phase under low temperature and pressure [e.g., 25°C and a pCO 2 of ∼10 −2 atm (25-27)], whereas hydromagnesite and other basic forms become dominant in an intermediate temperature range [e.g., 40-60°C (28-30)].…”

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confidence: 99%

“…Aqueous 24). Nesquehonite is the most commonly formed phase under low temperature and pressure [e.g., 25°C and a pCO 2 of ∼10 −2 atm (25-27)], whereas hydromagnesite and other basic forms become dominant in an intermediate temperature range [e.g., 40-60°C (28-30)].…”

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Testing the cation-hydration effect on the crystallization of Ca–Mg–CO ₃ systems

Yan

Zhang

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

134

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Dolomite and magnesite are simple anhydrous calcium and/or magnesium carbonate minerals occurring mostly at Earth surfaces. However, laboratory synthesis of neither species at ambient temperature and pressure conditions has been proven practically possible, and the lack of success was assumed to be related to the strong solvation shells of magnesium ions in aqueous media. Here, we report the synthesis of MgCO 3 and Mg x Ca (1−x) CO 3 (0 < x < 1) solid phases at ambient conditions in the absence of water. Experiments were carried out in dry organic solvent, and the results showed that, although anhydrous phases were readily precipitated in the water-free environment, the precipitates' crystallinity was highly dependent on the Mg molar percentage content in the solution. In specific, magnesian calcite dominated in low [Mg 2+ (1−x) CO 3 were formed. These findings exposed a previously unrecognized intrinsic barrier for Mg 2+ and CO 3 2− to develop long-range orders at ambient conditions and suggested that the long-held belief of cation-hydration inhibition on dolomite and magnesite mineralization needed to be reevaluated. Our study provides significant insight into the long-standing "dolomite problem" in geochemistry and mineralogy and may promote a better understanding of the fundamental chemistry in biomineralization and mineral-carbonation processes.sedimentary geology | carbon sequestration | nonaqueous solvent R arely is there a geological challenge that has endured as long a search for answers as the "dolomite problem" has. Identified more than 220 y ago by the French mineralogist Déodat de Dolomieu, the calcium magnesium carbonate mineral known as dolomite [CaMg(CO 3 ) 2 ] has since been synthesized repeatedly but exclusively at high-temperature and, in some instances, highpressure conditions (1-4). However, in many cases other than igneous-originated carbonatite and deep-burial dolomitization, the formation of dolomitic phases (e.g., microbial and cave deposits) are certainly not associated with such high-temperature and/or -pressure environments (5-8). This obvious discrepancy, compounded by the sharp contrast of massive ancient dolomite formations to the scarcity of modern observations, prompted an arduous search for answers for the past two centuries and, because of a lack of success, has been referred to as the dolomite problem (6, 9-16). Our inability to form dolomite at ambient conditions is hardly the only challenge in mineralogy; a similar situation exists in the case of pure magnesium carbonate [magnesite (MgCO 3 )], which has posed the same level of difficulty to nucleate and grow at room temperature and atmospheric pressure in laboratories but frequently occurs in natural sedimentary settings at earth (sub)surfaces. Interestingly, both dolomite and magnesite belong to the mineral class of anhydrous carbonates. Thus, it becomes logical to surmise that the dolomite problem and the magnesite problem probably share the same root, that is, the difficulty to incorporate unhydrated magnesium ions i...

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“…In fact, magnesite precipitation is so slow that it would likely also control the rate of magnesite formation at the expense of serpentine. An additional complicating factor is that the rate of magnesite nucleation at similar temperatures is also slow (Giammar et al, 2005;Hanchen et al, 2008). In fact, magnesium carbonate precipitation often does not occur until the saturation state has reached levels at which hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ×H 2 O) or other mixed carbonate-hydrate phases form.…”

Section: Serpentinite Carbonation At Linnajavrimentioning

confidence: 99%

Sculpting of Rocks by Reactive Fluids

Jamtveit¹,

Hammer²

2012

Geochem Persp

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Precipitation in the Mg-carbonate system—effects of temperature and CO2 pressure

Cited by 415 publications

References 21 publications

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

Testing the cation-hydration effect on the crystallization of Ca–Mg–CO ₃ systems

Sculpting of Rocks by Reactive Fluids

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Precipitation in the Mg-carbonate system—effects of temperature and CO2 pressure

Cited by 415 publications

References 21 publications

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

Kinetics of the chrysotile and brucite dehydroxylation reaction: a combined non-isothermal/isothermal thermogravimetric analysis and high-temperature X-ray powder diffraction study

Testing the cation-hydration effect on the crystallization of Ca–Mg–CO 3 systems

Sculpting of Rocks by Reactive Fluids

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Testing the cation-hydration effect on the crystallization of Ca–Mg–CO ₃ systems