Kinetics of the solvent-mediated transformation of hydromagnesite into magnesite at different temperatures

Lorenzo, Fulvio Di; Rodríguez-Galán, R. M.; Prieto, M.

doi:10.1180/minmag.2014.078.6.02

Cited by 24 publications

(22 citation statements)

References 25 publications

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“…For simplicity, we thus consider hydromagnesite as the most likely precursor to magnesite. The transformation of hydromagnesite into magnesite can occur either via (thermal) dehydration (Hollingberry and Hull, 2010;Zhang et al, 2000) or dissolution/re-precipitation (Di Lorenzo et al, 2014;Königsberger et al, 1999;Zhang et al, 2000), with the latter inducing an additional Mg-isotope fractionation step with Δ 26 Mghmgs-fluid ~ -1.0 ‰ (Shirokova et al, 2013) in the formation pathway of low temperature magnesite.…”

Section: Mg Isotope Fractionation During Precipitationmentioning

confidence: 99%

Mg isotope fractionation during continental weathering and low temperature carbonation of ultramafic rocks

Oskierski

Beinlich

Mavromatis

et al. 2019

Geochimica et Cosmochimica Acta

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The Mg-isotope systematics of peridotite weathering and low-temperature carbonation have not yet been thoroughly investigated, despite their potential to provide insights into reaction pathways and mechanisms of lithosphere-hydrosphere transfer of Mg and sequestration of CO2 in carbonate minerals. Here, we present new observations of the evolution of Mg isotope ratios during subtropical ultramafic rock weathering and associated magnesite formation, including the lowest δ 26 Mg of magnesite reported so far. At the investigated field sites in eastern Australia, the proximity of the ultramafic Mg source rocks and associated magnesite deposits provides boundary conditions that constrain Mg isotope fractionation during low-temperature alteration. Saprolite samples from Attunga, New South Wales, show that weathering of serpentinite is accompanied by Mg loss and formation of secondary Mg-bearing clay minerals. Furthermore, Mg isotope ratios increase systematically with weathering intensity, indicating that incorporation of 26 Mg into clay mineral structures controls Mg-isotope fractionation during ultramafic rock weathering. The Mg-bearing clay formed by decomposition of serpentine minerals has a δ 26 Mg value of ~ 0.35 ‰, which is up to ~ 0.6 ‰ heavier than the ultramafic precursor. In contrast, nodular magnesite hosted in ultramafic rock shows δ 26 Mg values between -3.26 ‰ and -2.55 ‰ that are significantly lower than those of magnesite and dolomite that formed by hydrothermal alteration of peridotite at higher temperature (δ 26 Mg = -0.69 ‰ and -0.62 ‰). The strong enrichment of 24 Mg in nodular magnesite does not reconcile with simple fractionation during direct precipitation from ultramafic host rock buffered meteoric fluids and instead suggests multiple formation steps involving dissolution and reprecipitation of pre-existing carbonate accompanied by fractionation between species of dissolved Mg. Our data highlight the potential of Mg isotope studies for distinguishing the formation pathways of low temperature magnesite and for tracing Mg in low temperature alteration processes based on the distinct signatures of secondary silicate and carbonate minerals.

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Section: Mg Isotope Fractionation During Precipitationmentioning

confidence: 99%

Mg isotope fractionation during continental weathering and low temperature carbonation of ultramafic rocks

Oskierski

Beinlich

Mavromatis

et al. 2019

Geochimica et Cosmochimica Acta

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“…The scenario is different if the process considered is the precipitation from aqueous constituents instead of a transformation reaction. The solid formed during the precipitation is enriched in Pb if compared with the initial stoichiometry of the solutions, which are characterized by a low abundance of Pb relative to Mg. MGS formation at room temperature is kinetically hindered [12,[48][49][50]. Instead, metastable hydrated Mg-bearing carbonates are formed [51][52][53][54].…”

Section: Discussionmentioning

confidence: 99%

“…Anhydrous magnesium carbonate, magnesite, has a rhombohedral structure, thus it should be less prone to suffer surface passivation by cerussite. However, magnesite (MGS) is renowned for the slow dissolution and growth kinetics at room temperature conditions in the framework of the so-called dolomite problem [11][12][13]. The reasons underlying this behaviour have been assigned to two peculiar characteristics of this mineral: (i) the lattice limitation in the spatial configuration of the carbonate unit in the crystalline structure [14,15]; (ii) the low polarizability of Mg 2+ that leads to a high hydration energy and an elevated residence time of water molecules in the first hydration shell [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics

2021

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The thermodynamic properties of carbonate minerals suggest a possibility for the use of the abundant materials (e.g., magnesite) for removing harmful divalent heavy metals (e.g., Pb2+). Despite the favourable thermodynamic condition for such transformation, batch experiments performed in this work indicate that the kinetic of the magnesite dissolution at room temperature is very slow. Another set of co-precipitation experiments from homogenous solution in the Mg-PbII-CO2-H2O system reveal that the solids formed can be grouped into two categories depending on the Pb/Mg ratio. The atomic ratio Pb/Mg is about 1 and 10 in the Mg-rich and Pb-rich phases, respectively. Both phases show a significant enrichment in Pb if compared with the initial stoichiometry of the aqueous solutions (Pb/Mg initial = 1·10−2–1·10−4). Finally, the growth of {10.4} magnesite surfaces in the absence and in the presence of Pb2+ was studied by in situ atomic force microscopy (AFM) measurements. In the presence of the foreign ion, a ten-fold increase in the spreading rate of the obtuse steps was observed. Further, the effect of solution ageing was also tested. We observed the nucleation of a secondary phase that quickly grows on the {10.4} surfaces of magnesite. The preferential incorporation of Pb2+ into the solid phase observed during precipitation and the catalytic effect of Pb2+ on magnesite growth are promising results for the development of environmental remediation processes. These processes, different from the transformation of magnesite into cerussite, are not limited by the slow dissolution rate of magnesite. Precipitation and growth require an external carbon source, thus they could be combined with carbon sequestration techniques.

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“…For example, Montes-Hernandez, Renard, Chiriac, Findling and Toche [39] previously showed that the duration of this phase transformation at moderate pressure and temperatures below 150 °C is in the order of days. Di Lorenzo, Rodriguez-Galan and Prieto [40] has also reported phase transformation at considerably lower pressure although temperature was demonstrated to be a key variable with times of transformation also extending to many days at temperature of 120 °C [40].…”

Section: Discussionmentioning

confidence: 99%

Experimental study on the precipitation of magnesite from thermally activated serpentine for CO2 sequestration

Farhang

Oliver

Rayson

et al. 2016

Chemical Engineering Journal

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Mineral carbonation has the potential to store billions of tonnes of CO 2 safely and permanently. Enhancement of the kinetics of the formation of magnesium carbonate from magnesium-bearing silicate minerals has been the subject of numerous research studies. However, significant progress is yet to be achieved. This is, in part, due to a lack of understanding of the mechanism of the formation of magnesite in the presence of additives and under mineral carbonation conditions. In this work, an indepth study was performed to investigate the precipitation of magnesium carbonate during single step high pressure, high temperature carbonation of thermally activated serpentine in an aqueous bicarbonate solution. Slurry samples were obtained throughout the duration of the carbonation experiments, enabling analysis of both the aqueous and solid compositions over time, providing insight into the reaction mechanism. Additionally, the effect of operating temperature on the formation of various magnesium carbonate species was examined. TGA-MS, in combination with XRD and SEM, confirmed the formation of hydromagnesite in the absence of carbon dioxide (CO 2) during the reactor heat up period, owing to a reaction with the sodium bicarbonate (NaHCO 3) carrier solution. Hydromagnesite was transformed to magnesite over time, with the rate of this phase transformation highly dependent on the reaction temperature. At 185 °C all hydromagnesite converted to magnesite in a few minutes whereas at 120 °C even after 90 minutes hydromagnesite remained in the reactor. 2 PHREEQC thermodynamic software was used to assess the observed formation of carbonate species. The model prediction was consistent with the experimental results obtained in this work.

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Kinetics of the solvent-mediated transformation of hydromagnesite into magnesite at different temperatures

Cited by 24 publications

References 25 publications

Mg isotope fractionation during continental weathering and low temperature carbonation of ultramafic rocks

Mg isotope fractionation during continental weathering and low temperature carbonation of ultramafic rocks

Pb2+ Uptake by Magnesite: The Competition between Thermodynamic Driving Force and Reaction Kinetics

Experimental study on the precipitation of magnesite from thermally activated serpentine for CO2 sequestration

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