Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

Pair your accounts.

Export articles to Mendeley

Get article recommendations from ACS based on references in your Mendeley library.

You’ve supercharged your research process with ACS and Mendeley!

STEP 1:
Click to create an ACS ID

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

Please note: If you switch to a different device, you may be asked to login again with only your ACS ID.

MENDELEY PAIRING EXPIRED
Your Mendeley pairing has expired. Please reconnect
ACS Publications. Most Trusted. Most Cited. Most Read
My Activity
CONTENT TYPES

Figure 1Loading Img
RETURN TO ISSUEPREVEnergy and ClimateNEXT

Armoring of MgO by a Passivation Layer Impedes Direct Air Capture of CO2

Cite this: Environ. Sci. Technol. 2023, 57, 40, 14929–14937
Publication Date (Web):September 22, 2023
https://doi.org/10.1021/acs.est.3c04690

Copyright © 2023 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0.
  • Open Access

Article Views

1755

Altmetric

-

Citations

LEARN ABOUT THESE METRICS
PDF (11 MB)
Supporting Info (1)»

Abstract

It has been proposed to use magnesium oxide (MgO) to separate carbon dioxide directly from the atmosphere at the gigaton level. We show experimental results on MgO single crystals reacting with the atmosphere for longer (decades) and shorter (days to months) periods with the goal of gauging reaction rates. Here, we find a substantial slowdown of an initially fast reaction as a result of mineral armoring by reaction products (surface passivation). In short-term experiments, we observe fast hydroxylation, carbonation, and formation of amorphous hydrated magnesium carbonate at early stages, leading to the formation of crystalline hydrated Mg carbonates. The preferential location of Mg carbonates along the atomic steps on the crystal surface of MgO indicates the importance of the reactive site density for carbonation kinetics. The analysis of 27-year-old single-crystal MgO samples demonstrates that the thickness of the reacted layer is limited to ∼1.5 μm on average, which is thinner than expected and indicates surface passivation. Thus, if MgO is to be employed for direct air capture of CO2, surface passivation must be circumvented.

This publication is licensed under

CC-BY-NC-ND 4.0.
  • cc licence
  • by licence
  • nc licence
  • nd licence

Synopsis

Observation of passivation layer formation on MgO during direct air capture of CO2 identifies challenges of the MgO-based mineral looping process for direct air capture.

1. Introduction

ARTICLE SECTIONS
Jump To

Carbon dioxide removal from the atmosphere is a necessary step to limit climate change effects. To achieve these goals, magnesium oxide (MgO) looping has been proposed as a process for separation of atmospheric CO2. (1) In this proposed process, MgO reacts with ambient air to form MgCO3, which is calcined periodically, and liberated CO2 is sequestered. Regenerated MgO is then reused. (1)
Despite extensive previous research on using MgO as a CO2 sorbent in post-combustion processing (2) or cement, (3) reliable data on carbonation at low CO2 concentrations present in ambient air are lacking. Most studies have been conducted at higher temperatures (4) relevant to CO2 removal from flue gas or at lower temperatures (25–120 °C) but with higher CO2 pressures (>1 bar) than expected during direct air capture (e.g., 400 ppm). (5) Under ambient conditions, however, recent work (6) demonstrated that hydrated Mg carbonate phases form, which significantly change the efficiency and, hence, the economics of the proposed looping process. The formation of hydrous magnesium carbonates depends upon multiple variables, and it is not obvious which chemical pathway will be preferable under ambient environmental conditions. (7) Previous work on Mg(OH)2 (8) or forsterite (9−11) carbonation and evidence from weathering studies (12−14) show that mineral reactions in both laboratory and field environments can be slowed down by the formation of a passivation layer. While the formation of hydrated Mg carbonate phases was previously observed, (6) it was not assessed whether these passivate the reactive surface area. It therefore remains unclear if and how the formation of passivation layers influences the rate and economics of MgO looping for direct air capture of CO2.
To identify reaction products and test whether a passivation layer forms on MgO under ambient temperature and pressure conditions and low CO2 concentrations, we analyzed the reaction layers on MgO crystals synthesized at the Oak Ridge National Laboratory (ORNL) in 1995 and subsequently exposed to an indoor atmosphere for 27 years. We supplemented this “natural experiment” with short-term carbonation experiments of MgO in ambient air lasting days to months. Here, we present advanced microscopic characterization of the resultant mineralogy and structures combined with reaction–diffusion calculations to provide an estimate of reaction rates and assess refined economics of the looping process.

2. Materials and Methods

ARTICLE SECTIONS
Jump To

2.1. 27-Year-Old MgO Single Crystals

The MgO samples studied here were synthesized at ORNL in 1995. (15) While macrocrystalline MgO is not considered for direct air capture purposes, the single-crystal nature of these samples is useful to facilitate analysis of the reaction layer formation. Particularly significant is that, because the sample analyses were performed in 2022, the reaction time is 27 years, and these samples will be referred to as “27-year-old MgO” subsequently. Samples were stored in plastic buckets in an indoor storage room and exposed to ambient air. The buckets were covered with lids but not sealed. Moreover, large fractures were found on the side of the buckets (about 1 cm wide and about 10 cm long). At these conditions, we can assume the exchange of CO2 with the surroundings to be significant. Average humidity was likely between ∼40 and 60%.

2.2. Short-Term Experiments

For the short-term experiments, samples of the MgO single crystals were freshly cleaved using a razor blade to expose an unreacted surface with a perfect cleavage plane of the MgO (001) surface. Debris on the cleaved surface was removed using nitrogen gas. These were then left out to react with the atmosphere on a laboratory benchtop. To prevent dust from falling on the reaction surfaces, a cover was installed ∼10 cm above the crystals. Ambient humidity ranged between 40 and 60%.

2.3. Focused Ion Beam (FIB) Preparation

A Cressington sputter coater was used to coat the samples with a conductive carbon layer. Then, a Hitachi NB5000 FIB instrument was used to prepare lamellae for transmission electron microscopy (TEM) characterization following established protocols. (16) Lift-out locations are shown in Figures S1S5 of the Supporting Information.

2.4. Electron Microscopy

A FEI Titan aberration-corrected transmission electron microscope was used in scanning transmission electron microscopy (STEM) and TEM modes at 200 kV to identify the reaction layer thickness and phases formed. The scanning transmission electron microscopy electron energy loss spectroscopy (STEM–EELS) experiments were performed using a Gatan Quantum EEL spectrometer with a dispersion of 0.3 eV/channel. TEM data were obtained for four lamellae from long-term experiments. Two TEM lamella were analyzed from each of the two samples. For the sliding fast Fourier transform (FFT) analysis, d spacings for different magnifications were calibrated using MgO d spacings. The required corrections did not exceed 1.5%.

2.5. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) Characterization

Atomic force microscopy time-of-flight secondary ion mass spectrometry (AFM–ToF-SIMS) measurements were carried out using a TOF.SIMS.5-NSC instrument combining ToF-SIMS and AFM in the same vacuum chamber. A bismuth liquid metal ion gun [Bi+ with 30 keV energy and 30 nA current in direct current (DC) mode and 5 μm spot size] was used as a primary source for secondary ion extraction from the surface. Sputtered ions were analyzed by a time-of-flight mass analyzer running in positive ion detection mode. Mass resolution was in the range mm = 3000–10 000. Additionally, a cesium sputter source (2 keV energy, 150 nA current, and ∼20 μm spot size) was rastered over a 500 × 500 μm area of the sample for depth profiling in parallel with the primary ion gun. Integrated AFM was used to determine the sputter rate, which was 0.165 nm/s.

2.6. Raman Spectroscopy

A Renishaw InVia confocal Raman microscope with a 785 nm laser and 1200 lines/nm grating was used to characterize new phases on MgO surfaces. Collected spectra were compared to the RRUFF database. (17)

2.7. Numerical Modeling

To model the passivation layer growth on MgO, we used the diffusion equation for reactive species transport through the layer
ct=·(D*c)
(1)
where c is the reactive species concentration and D* is an effective diffusion coefficient for reactive species in the passivation layer (schematic in Figure 6a). The source of the reactant is set through a constant-concentration boundary condition at the inlet c(x = 0) = c0. The reactive flux, R, at the MgO boundary, Γ, is balanced by the diffusive flux as
n·(D*c)=R
(2)
where n is the normal to the surface. The velocity of reactive surface propagation, uΓ, is proportional to the reaction rate as
νm1uΓ=Rn
(3)
where vm is the molar volume of the growing phase. This simplified model does not consider multispecies transport, complex reaction pathways, or multiple phases. It provides a rough estimate of the rate of inert solid layer growth on MgO. We assume a diffusion-limited reaction, with concentration c = 0 at the interface, Γ. Numerical simulations of the interface propagation were conducted using a previously developed solver (18) for the reaction–diffusion system based on the OpenFOAM toolkit. Details are described in the Supporting Information. Speciation was calculated in Visual MINTEQ assuming an atmospheric CO2 concentration from 280 ppm (pre-industrial) to 418 ppm (current) in equilibrium with water. The dominant carbonate species were HCO3 and H2CO3(aq) at micromolar concentrations.

3. Results and Discussion

ARTICLE SECTIONS
Jump To

3.1. Reaction Layer Thickness

The reaction layer (Figure 1a) thickness on the bulk 27-year-old MgO single crystal was measured using AFM–ToF-SIMS (Figure 1b). A clear signal for the presence of Cs2CO22+ clusters, resulting from recombination of CO2 from the solid and Cs from the sputtering source, was observed using positive ion detection mode. This signal is correlated with the CO2 concentration in the sample bulk. An elevated Cs2CO2+ signal, which indicates the reacted layer, was observed to a depth of ∼1.5 μm in the 27-year-old samples. In contrast, a freshly cleaved sample showed only a few nanometers of an elevated Cs2CO2+ background signal. The thickness of 1.5 μm compares well to those measured using focused ion beam scanning electron microscopy (FIB–SEM) image analysis, ∼1.6 ± 0.09 μm (Figure 1a), and high angle annular dark field scanning transmission electron microscopy (HAADF–STEM) image analysis, ∼1.6 ± 0.05 μm (Figure 1c). HAADF–STEM imaging of a second lamella showed a reaction layer of thickness ∼1.3 ± 0.4 μm (Figure 2a and Figure S6 of the Supporting Information). Reaction layer thickness distribution from all methods is given in Figure 1d.

Figure 1

Figure 1. Reaction layer on the 27-year-old MgO single crystals. (a) SEM image of a TEM lamella prepared by FIB. (b) ToF-SIMS depth profiles of Cs2CO2+ (used as a proxy for CO2) and Mg+ showing a ∼1.5 μm thick layer containing CO2 in 27-year-old MgO in contrast to freshly cleaved MgO. (c) HAADF–STEM image of the area highlighted in panel a by the blue rectangle. The higher magnification characterization of the reaction layers demonstrates its complicated microstructure and potential porosity at the MgO interface. (d) Distribution of reaction layer thickness measurements from FIB, HAADF–STEM, and ToF-SIMS data.

Figure 2

Figure 2. Crystallographic analysis of the reaction layer in a second TEM sample prepared from the long-term experiment shown in Figure 1. (a) HAADF–STEM image of TEM lamella showing unreacted MgO, reaction layer, and protective W and C layers. The white rectangle indicates the area shown in the TEM–bright-field (BF) image in panel b). Visible lattice planes indicate crystallinity of the reaction layer. The electron diffraction image of panel b is shown in panel c, with rings indicating nanocrystallites. (d) Schematic of diffractogram analysis from radial profiles. Shaded boxes highlight the integration windows. The yellow shaded box highlights reflections observed at the edge of the reaction layer but not in its polycrystalline region.

In comparison to the economic assessments, (1) which assume 90% carbonation of a 20 μm particle within 1 year (on the basis of brucite dissolution alone), the observed layer thickness and, hence, the reaction rate are lower than expected. The reactive layer thickness of 1.5 μm on a 20 μm diameter particle means that 61% of the material remained unreacted. This discrepancy between the assumed and observed reaction layer thickness indicates that the reaction layer passivates the MgO surface. Previously, similar observations have been made in other systems, e.g., on the passivation of silicate surfaces during forsterite carbonation by a Mg-depleted layer. (19)

3.2. Reacted Product Texture and Phase Formation in 27-Year-Old MgO

As a first observation of the reacted layer texture, TEM images of 27-year-old MgO show the presence of macropores (1–2 μm diameter) and nanopores (∼10–20 nm diameter) in the reaction layer (Figures 1 and 2a). High-resolution transmission electron microscopy (HR-TEM) imaging showed that the reaction layer is crystalline with visible lattice planes (Figure 2b). The nanocrystallite size ranges from 10 nm to sub-nanometers. Phase identification was first attempted using d-spacing analysis of the electron diffraction pattern. Diffraction rings were visible in the diffraction patterns (Figure 2c) collected over the whole area visible in Figure 2b, indicating that the area is composed of nanocrystallites. Calculated d spacings were 2.447, 2.095, 1.489, 1.216, and 0.928 Å. Most of these d spacings are very close to those of MgO, (20) and therefore, it is difficult to identify newly formed Mg carbonate phases. Details can be found in section 4 of the Supporting Information, but it is clear that this area contains a mixture of MgO, brucite, hydromagnesite, magnesite, and artinite. HR-TEM analysis of a second location on the reaction layer showed similar findings (TEM images and detailed analysis given in Figure S7 of the Supporting Information).
Because d-spacing analysis of the diffraction patterns is inconclusive, the phase distribution within the reaction layer of 27-year-old MgO was further refined using a sliding FFT (21) to generate a two-dimensional (2D) array of partial image diffractograms. The resulting four-dimensional (4D) data set was then analyzed using a non-negative matrix factorization (NMF) approach. (22) Because the entire 2D diffractogram was analyzed, this approach is sensitive to both spatial frequencies (atomic scale periodicity) and the orientation of the crystalline material. For the polycrystalline part of the reaction layer (Figure 2b, with full NMF results given in Figure 3), NMF analysis suggests 12 independent spatially distinct components. Fewer components were tested (Figures S8 and S9 of the Supporting Information), but this provided the best fit. Some components (4, 7, and 11 in Figure 3) reflect image noise based on their mixing coefficient maps. Other components (3, 5, 6, and 8–10 in Figure 3) are low-index zone MgO with different orientations. Interestingly, some of the components (1, 2, and 12 in Figure 3) appear to be amorphous but show a well-defined spatial distribution and are clearly distinct from each other, which suggests that some of the phases in the reaction layer might be amorphous or lack long-range order.

Figure 3

Figure 3. 12-component NMF analysis of local image diffractograms for Figure 2c from the polycrystalline part of the reaction layer.

To identify the phases in the reaction layer without regard to orientation, we have used the same sliding FFT approach but examined its radial profiles to identify regions from which peaks/rings originate with maximal reciprocal space resolution. Figure 2d shows two such radial profiles, from the polycrystalline part (Figure 2b) and the edge of the reaction layer (Figure S10 of the Supporting Information; analysis discussed below). The patterns are dominated by MgO peaks, which make the d-spacing range near them unusable for minor phase identification because of their intensity. However, the size range of d spacings is longer than the longest MgO d spacing (2.4312 Å) (20) and has several features that are not overwhelmed by the intensity of the MgO peaks and can be used for phase identification. Colored bands in Figure 2d represent d-spacing ranges of interest identified using radial profile intensity integration. One range that is only present at the edge of the reaction layer is shown in yellow (3.73–4.3 Å), and the rest are shown in blue. For a 256 × 256 FFT window, these ranges are 2–3 pixels wide, which is commensurate with the width of the observed peaks. Ranges 4–7 (1.19–1.25, 1.47–1.55, 2.00–2.15, and 2.33–2.54 Å) are centered on MgO peaks (1.2156, 1.14888, 2.1055, and 2.4312 Å, respectively), (20) while ranges 1–3 (2.67–2.94, 3.73–4.3, and 6.21–7.99 Å) correspond to other phases. When possible phases are compared to the d-spacing ranges, it appears that range 3 (2.67–2.94 Å) corresponds to magnesite [characteristic (104) peak at 2.7417 Å] (23) and/or hydromagnesite [characteristic (022) peak at 2.9031 Å], (24) while range 2 (3.72–4.3 Å) could be nesquehonite [characteristic (200) peak at 3.8504 Å]. (25) Range 1 (6.13–7.99 Å) is too broad to be clearly assigned to any phase. A visual representation of this comparison is provided in Figure S11 of the Supporting Information, (23,24,26−28) and full, integrated-intensity maps for each range (Figure S12 of the Supporting Information) show a significant overlap between magnesite/hydromagnesite and MgO distribution.
To understand phase distribution at the edge of the reaction layer, a red, green, and blue (RGB) composite of the ranges 2, 3, and 4 are overlaid on the original image in Figure 4 (for a radial profile, see Figure 2d; original image given in Figure S10 of the Supporting Information; and full integration output for all ranges is given in Figure S13 of the Supporting Information). Figure 4 shows that range 3 (magnesite/hydromagnesite) and range 4 (MgO) are located only in the polycrystalline region, which is the reacted layer, whereas range 2 (nesquehonite) is present in both the polycrystalline-reacted region and the part of the reacted layer without any real-space discernible crystallinity. This suggests that the signal for range 2 might originate from both nesquehonite in the polycrystalline part and an amorphous hydrated Mg carbonate phase at the edge of the reaction layer.

Figure 4

Figure 4. (a) RGB composite of integrated FFT intensity for ranges 2 (red, nesquehonite/amorphous Mg carbonate), 3 (green, magnesite/hydromagnesite), and 4 (blue, MgO) overlaid on the original image (given in Figure S10 of the Supporting Information). (b and c) Magnified image part for range 2 (red, nesquehonite/amorphous Mg carbonate) and the corresponding diffractogram. (d and e) Magnified image part for range 3 (green, magnesite/hydromagnesite) and the corresponding diffractogram. (f and g) Magnified image part for range 4 (blue, MgO) and the corresponding diffractogram.

Finally, it is important to ascertain that the amorphous material does not consist of a carbon coating of the sample prior to FIB preparation. The peak in range 2 can be fitted with a Gaussian with a center corresponding to an interatomic distance of 3.99 Å. This number is higher than reported values for amorphous carbon, which vary from ∼3.8 Å (29,30) to 3.34 Å. (31)
In addition to the hydrated Mg carbonate phases observed in the first sample, TEM analysis of the two FIB lamella prepared from another sample of 27-year-old MgO showed the presence of a layered mineral (Figure S14 of the Supporting Information). The morphology and lattice spacing indicate that it is most likely brucite [Mg(OH)2], consistent with a flaky mineral found during scanning electron microscopy (SEM) imaging from the lift-out location (Figures S4 and S5 of the Supporting Information).
In conclusion, our TEM results show that the passivation layer formed during the 27 year reaction of MgO with the atmosphere consists of a mixture of phases. The phases are nanocrystallites of brucite, magnesite/hydromagnesite, and nesquehonite. In addition, evidence for amorphous hydrated Mg carbonate phases were observed. The TEM results are consistent with Raman spectroscopical characterization (described in section 6 of the Supporting Information), which indicates a mixture of dypignite [Mg5(CO3)4(OH)2·5H2O] and nesquehonite. The formation of hydrated Mg carbonate phases was also observed during MgO powder experiments at atmospheric CO2 concentrations. (6) On the basis of their 5 month experiment, Rausis et al. estimates that, given the particles of 8.1 μm, 5–27 years of reaction with CO2 would be needed to reach 90% conversion, (6) but our experiments demonstrate that surface passivation is more severe than anticipated and further carbonation cannot be achieved even at longer reaction times.

3.3. Phase Formation in Short-Term Experiments

No Raman bands were observed immediately after cleaving the MgO crystal for the short-term experiments ranging from 83 to 217 days (Figure 5b). The crystal appeared to be optically transparent, and no secondary phase formation was evident in light microscopy. After reaction with the atmosphere (83 days), a uniformly distributed surface coating was visible in light microscopy in addition to a distinct new phase along steps (Figure 5a). The uniform surface coating did not show any clear Raman signal. TEM characterization including electron diffraction suggests (Figure 5c) that the surface coating consists of brucite, because measured d spacings (2.234, 1.568, and 1.274 Å) match reported values for brucite, (011) at 2.3680 Å, (110) at 1.5749 Å, and (202) at 1.1840 Å. (26) TEM–BF images (Figure 5g) show a reaction layer thickness from ∼48 to ∼83 nm, with an average of ∼69 nm. EEL spectrum imaging (panels h–j of Figure 5) of the reacted layer did not detect significant carbon, consistent with the identification of the secondary phase as brucite.

Figure 5

Figure 5. Characterization of the short-term experiments. (a) Light microscopy image of the measurement location of Raman spectra displayed in panel b for MgO reacted for 189 days with atmosphere. (c) TEM–BF image of MgO reacted for 167 days with atmosphere showing pristine MgO and small, newly formed crystallites. (d) Electron diffraction pattern of panel c. (e and f) FFT of areas highlighted in panel c, indicating single-crystal MgO and a new polycrystalline phase. Calculated d spacings indicate that this is most likely brucite. Diffraction spots stem from bulk MgO. (g) TEM–BF image of the reaction layer on MgO after 167 days of exposure to ambient air. (h) STEM–EELS imaging area shown for (i) carbon and (j) oxygen.

However, Raman spectra of the newly formed phases along steps showed lattice phonon modes of an unidentified phase at approximately 120, 161, 197, and 231 cm–1 (Figure 5b, with additional measurement spots for 217 days given in Figure S19 of the Supporting Information). These could be artinite (bands at 158m, 158m, 173m, 211vvw, 242w, and 277vvw cm–1) (32) or nesquehonite (bands at 119m, 167m, 187m, 199m, 228m, 273vvw, 311vw, and 344vw cm–1) (33) lattice modes (subscripts: m, medium; w, weak; and v, very). A peak was first observed around ∼1080 cm–1 after 83 days that likely represents the v1 symmetric stretching mode of carbonate. It is possible that this represents early formation of amorphous magnesium carbonate. (34−36) Its position was identical after 189 and 217 days. This band does not match any of the known Mg carbonates (magnesite v1 = 1094 cm–1, nesquehonite = 1100 cm–1, artinite = 1094 cm–1, and hydromagnesite = 1119 cm–1). (37) However, a Raman band red shift can occur as a result of lower crystallinity or impurities. Newly formed crystals did not exhibit well-defined crystal facets (Figure 5), and therefore, the observed shift is likely due to low crystallinity. On the basis of Raman and TEM results, we conclude that first formed brucite is preferentially replaced by hydrated Mg carbonate phases along features like atomistic steps on the MgO surface. The preferential formation along steps indicates that the reactive site density is important for the initial carbonation of MgO.
In conclusion, our short-term results show that the initial formation of brucite and subsequent hydrated Mg carbonate formation are fast and occur within 83 days. Rausis et al. show similar times with 60 days for first carbonate formation. (6) Our results are the first to show that hydrated Mg carbonate phases form preferentially along steps, highlighting the importance of the reactive site density in accelerating carbonate formation. Therefore, we propose increasing the reactive site density by intentionally creating defects in the MgO particles as a possible pathway to accelerate carbonation rates.

3.4. Diffusion-Dependent Reaction Rate Calculations

To understand potential variation of the reaction rate with time, we modeled the passivation layer growth on MgO (Figure 6) and assessed the evolution of the layer thickness as a function of the effective diffusion rate. These results demonstrate that the reaction layer has an effective diffusion rate, D*, between 1.6 × 10–10 cm2 s–1 for h27 = 1.3 μm and 2.8 × 10–10 cm2 s–1 for h27 = 1.7 μm. This is faster than typical bulk solid diffusion at ambient conditions (e.g., 10–22 cm2 s–1) (38) but slower than ionic diffusion in aqueous solutions, which is on the order of 10–5 cm2 s–1. (39) Furthermore, the results are only about an order of magnitude slower than measured grain-boundary-dominated Mg replacement rates for tight limestones at 200 °C (∼1.2 × 10–9 cm2 s–1). (40) For MgO, bulk solid cation diffusion has been measured at higher temperatures (1100–2400 °C), with an extrapolated diffusion rate of 10–13 cm2 s–1 at 800 °C. (41) The calculated effective diffusion rate is much higher than in bulk solid, which is likely due to porosity, grain boundaries, and presence of amorphous phases in the reaction layer. Figure 6b shows that, for this purely diffusive model, the layer propagation rate drops by 87% over the first 2 years as a result of transport limitations. This implies that the majority of the carbonation occurs within the first few years and will not result in carbonation of an entire 20 μm grain on practical time scales.

Figure 6

Figure 6. Modeling of the inert layer growth on the MgO surface. (a) Schematic representation of a 1D model. The image on the top is part of the HAADF–STEM image in Figure 1c, which shows the reacted layer (darker gray with possible porosity) on top of MgO (lighter gray). (b) Results of 1D reaction–diffusion modeling. Dependence of the thickness of the inert phase layer upon the reaction time as a function of the diffusion coefficient. (c) Dependence of the reaction layer thickness at 27 years upon the diffusion rate in the inert solid phase (red dashed line is an analytical solution for the case of diffusion-limited reaction, and blue symbols are simulation results). The blue region indicates the minimum (1.3 μm) and maximum (1.7 μm) thickness of the layer measured in the experiment.

4. Environmental Implications

ARTICLE SECTIONS
Jump To

In summary, analyses of the long-term (27 years) experiments indicate a reaction layer between 1.3 and 1.7 μm thick, which consists of hydrated Mg carbonates, Mg hydroxide, and potentially amorphous Mg carbonates. Our short-term experiments (83 days) showed that new carbonate phases preferentially formed along steps in the MgO surface, indicating that the reactive site density is important for initial carbonation. Modeling results demonstrate most of the carbonation occurring within the first few years, and further carbonation cannot be achieved at a reasonable time scale. These findings imply that usage of sub-micrometer MgO particles, microstructure tuning, or surface morphology modification is needed to make it an economic sorbent for direct air capture of CO2, which can be scaled to make a significant environmental impact.
Although our work demonstrates significant passivation effects during MgO carbonation, the precise effects of the temperature, relative humidity, crystallinity, and surface area dependence have not been explored in depth for direct air capture applications. While we know that, e.g., water plays a critical role, the work of Rausis et al. (6) has focused on condensed phase water and not water vapor. With regard to increasing the reactive surface area by reducing the size of mineral particles, while MgO nanoparticles have thus far not yet been found to have toxic health effects, (42) the use of sub-micrometer particles poses potential concerns because there is a risk of the material been blown away by the wind in real-world settings. Additionally, production of sub-micrometer particles by grinding is energy-intensive, and recovery of the original size, microstructure, or surface roughness during the looping process is not guaranteed. This would make either size-targeted synthesis or the development of a particle size reduction necessary.

Supporting Information

ARTICLE SECTIONS
Jump To

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.3c04690.

  • Lift-out locations, details of numerical simulation, additional STEM images, additional d-spacing analysis of 27-year-old MgO, additional TEM characterization of 27-year-old MgO, Raman analysis of 27-year-old MgO, and additional Raman analysis of short-term experiments (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

ARTICLE SECTIONS
Jump To

  • Corresponding Authors
  • Authors
    • Ke Yuan - Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United StatesOrcidhttps://orcid.org/0000-0003-0565-0929
    • Lawrence M. Anovitz - Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United StatesOrcidhttps://orcid.org/0000-0002-2609-8750
    • Anton V. Ievlev - Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United StatesOrcidhttps://orcid.org/0000-0003-3645-0508
    • Raymond R. Unocic - Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United StatesOrcidhttps://orcid.org/0000-0002-1777-8228
    • Albina Y. Borisevich - Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United StatesOrcidhttps://orcid.org/0000-0002-3953-8460
    • Matthew G. Boebinger - Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
    • Andrew G. Stack - Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United StatesOrcidhttps://orcid.org/0000-0003-4355-3679
  • Author Contributions

    Juliane Weber led the research efforts, wrote the first draft of the manuscript, analyzed the data, and provided the majority of the funding (BES). Ke Yuan conducted speciation calculations. Lawrence M. Anovitz provided samples and aided with the scientific interpretation. Vitalii Starchenko conducted reaction–diffusion calculations. Anton V. Ievlev performed ToF-SIMS characterization. Raymond R. Unocic and Matthew G. Boebinger helped with TEM characterization and data interpretation. Albina Y. Borisevich performed TEM data analysis using sliding FFT and NMF. Andrew G. Stack provided part of the funding (LDRD) and helped in experiment conceptualization. All authors wrote and edited the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

ARTICLE SECTIONS
Jump To

This work was mainly supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division. A minor part of this research (ToF-SIMS characterization and preliminary TEM characterization) was funded by an ORNL Internal Laboratory Directed Research & Development (LDRD) project. AFM–ToF-SIMS and TEM characterization were conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility at ORNL and using instrumentation within ORNL’s Materials Characterization Core provided by UT-Battelle, LLC under Contract DE-AC05-00OR22725 with the U.S. Department of Energy. The authors thank James Kolopus for providing the MgO samples used in this study. Andrew Miskowiec is acknowledged for access to the Raman instrument. This manuscript has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript or allow others to do so for U.S. government purposes. The U.S. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Abbreviations

ARTICLE SECTIONS
Jump To

AFM–ToF-SIMS

atomic fight microscopy time-of-flight secondary ion mass spectrometry

FIB

focused ion beam

FIB–SEM

focused ion beam scanning electron microscopy

FFT

fast Fourier transform

HAADF–STEM

high angle annular dark field scanning transmission electron microscopy

NMF

non-negative matrix factorization

RGB

red, green, and blue

SEM

scanning electron microscopy

STEM

scanning transmission electron microscopy

STEM–EELS

scanning transmission electron microscopy electron energy loss spectroscopy

TEM

transmission electron microscopy

References

ARTICLE SECTIONS
Jump To

This article references 42 other publications.

  1. 1
    McQueen, N.; Kelemen, P.; Dipple, G.; Renforth, P.; Wilcox, J. Ambient Weathering of Magnesium Oxide for CO2 Removal from Air. Nat. Commun. 2020, 11 (1), 110,  DOI: 10.1038/s41467-020-16510-3
  2. 2
    Akeeb, O.; Wang, L.; Xie, W.; Davis, R.; Alkasrawi, M.; Toan, S. Post-Combustion CO2 Capture via a Variety of Temperature Ranges and Material Adsorption Process: A Review. J. Environ. Manage. 2022, 313, 115026,  DOI: 10.1016/j.jenvman.2022.115026
  3. 3
    Walling, S. A.; Provis, J. L. Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?. Chem. Rev. 2016, 116 (7), 41704204,  DOI: 10.1021/acs.chemrev.5b00463
  4. 4
    Hu, Y.; Guo, Y.; Sun, J.; Li, H.; Liu, W. Progress in MgO Sorbents for Cyclic CO2 Capture: A Comprehensive Review. J. Mater. Chem. A 2019, 7 (35), 2010320120,  DOI: 10.1039/C9TA06930E
  5. 5
    Hänchen, M.; Prigiobbe, V.; Baciocchi, R.; Mazzotti, M. Precipitation in the Mg-Carbonate System-Effects of Temperature and CO2 Pressure. Chem. Eng. Sci. 2008, 63 (4), 10121028,  DOI: 10.1016/j.ces.2007.09.052
  6. 6
    Rausis, K.; Stubbs, A. R.; Power, I. M.; Paulo, C. Rates of Atmospheric CO2 Capture Using Magnesium Oxide Powder. Int. J. Greenhouse Gas Control 2022, 119 (April), 103701,  DOI: 10.1016/j.ijggc.2022.103701
  7. 7
    Santos, H. S.; Nguyen, H.; Venâncio, F.; Ramteke, D.; Zevenhoven, R.; Kinnunen, P. Mechanisms of Mg Carbonates Precipitation and Implications for CO2 Capture and Utilization/Storage. Inorg. Chem. Front. 2023, 10 (9), 25072546,  DOI: 10.1039/D2QI02482A
  8. 8
    Harrison, A. L.; Dipple, G. M.; Power, I. M.; Mayer, K. U. Influence of Surface Passivation and Water Content on Mineral Reactions in Unsaturated Porous Media: Implications for Brucite Carbonation and CO2 Sequestration. Geochim. Cosmochim. Acta 2015, 148, 477495,  DOI: 10.1016/j.gca.2014.10.020
  9. 9
    Béarat, H.; McKelvy, M. J.; Chizmeshya, A. V. G.; Gormley, D.; Nunez, R.; Carpenter, R. W.; Squires, K.; Wolf, G. H. Carbon Sequestration via Aqueous Olivine Mineral Carbonation: Role of Passivating Layer Formation. Environ. Sci. Technol. 2006, 40 (15), 48024808,  DOI: 10.1021/es0523340
  10. 10
    Daval, D.; Sissmann, O.; Menguy, N.; Saldi, G. D.; Guyot, F.; Martinez, I.; Corvisier, J.; Garcia, B.; Machouk, I.; Knauss, K. G.; Hellmann, R. Influence of Amorphous Silica Layer Formation on the Dissolution Rate of Olivine at 90 °C and Elevated pCO2. Chem. Geol. 2011, 284 (1–2), 193209,  DOI: 10.1016/j.chemgeo.2011.02.021
  11. 11
    Grayevsky, R.; Reiss, A. G.; Emmanuel, S. Carbon Storage through Rapid Conversion of Forsterite into Solid Oxalate Phases. Energy Fuels 2023, 37 (1), 509517,  DOI: 10.1021/acs.energyfuels.2c03245
  12. 12
    Nugent, M. A.; Brantley, S. L.; Pantano, C. G.; Maurice, P. A. The Influence of Natural Mineral Coatings on Feldspar Weathering. Nature 1998, 395 (6702), 588591,  DOI: 10.1038/26951
  13. 13
    Zhu, C.; Veblen, D. R.; Blum, A. E.; Chipera, S. J. Naturally Weathered Feldspar Surfaces in the Navajo Sandstone Aquifer, Black Mesa, Arizona: Electron Microscopic Characterization. Geochim. Cosmochim. Acta 2006, 70 (18), 46004616,  DOI: 10.1016/j.gca.2006.07.013
  14. 14
    Ruiz-Agudo, E.; Putnis, C. V.; Rodriguez-Navarro, C.; Putnis, A. Mechanism of Leached Layer Formation during Chemical Weathering of Silicate Minerals. Geology 2012, 40 (10), 947950,  DOI: 10.1130/G33339.1
  15. 15
    Abraham, M. M.; Butler, C. T.; Chen, Y. Growth of High-Purity and Doped Alkaline Earth Oxides: I. MgO and CaO. J. Chem. Phys. 1971, 55 (8), 37523756,  DOI: 10.1063/1.1676658
  16. 16
    Schaffer, M.; Schaffer, B.; Ramasse, Q. Sample Preparation for Atomic-Resolution STEM at Low Voltages by FIB. Ultramicroscopy 2012, 114, 6271,  DOI: 10.1016/j.ultramic.2012.01.005
  17. 17
    Laetsch, T.; Downs, R. Software for Identification and Refinement of Cell Parameters from Powder Diffraction Data of Minerals Using the RRUFF Project and American Mineralogist Crystal Structure Databases. Proceedings of the 19th General Meeting of the International Mineralogical Association ; Kobe, Japan, July 23–28, 2006.
  18. 18
    Starchenko, V.; Marra, C. J.; Ladd, A. J. C. Three-Dimensional Simulations of Fracture Dissolution. J. Geophys. Res.: Solid Earth 2016, 121 (9), 64216444,  DOI: 10.1002/2016JB013321
  19. 19
    Mergelsberg, S. T.; Rajan, B. P.; Legg, B. A.; Kovarik, L.; Burton, S. D.; Bowers, G. M.; Bowden, M. E.; Qafoku, O.; Thompson, C. J.; Kerisit, S. N.; Ilton, E. S.; Loring, J. S. Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg2SiO4) When Water Is Limited. Environ. Sci. Technol. Lett. 2023, 10 (1), 98104,  DOI: 10.1021/acs.estlett.2c00866
  20. 20
    Hazen, R. M. Effects of Temperature and Pressure on the Cell Dimension and X-ray Temperature Factors of Periclase. Am. Mineral. 1976, 61 (3–4), 266271
  21. 21
    Vasudevan, R. K.; Ziatdinov, M.; Jesse, S.; Kalinin, S. V. Phases and Interfaces from Real Space Atomically Resolved Data: Physics-Based Deep Data Image Analysis. Nano Lett. 2016, 16 (9), 55745581,  DOI: 10.1021/acs.nanolett.6b02130
  22. 22
    Kannan, R.; Ievlev, A. V.; Laanait, N.; Ziatdinov, M. A.; Vasudevan, R. K.; Jesse, S.; Kalinin, S. V. Deep Data Analysis via Physically Constrained Linear Unmixing: Universal Framework, Domain Examples, and a Community-Wide Platform. Adv. Struct. Chem. Imaging 2018, 4 (1), 6,  DOI: 10.1186/s40679-018-0055-8
  23. 23
    Ross, N. L. The Equation of State and High-Pressure Behavior of Magnesite. Am. Mineral. 1997, 82 (7–8), 682688,  DOI: 10.2138/am-1997-7-805
  24. 24
    Akao, M.; Iwai, S. The Hydrogen Bonding of Hydromagnesite. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1977, 33 (4), 12731275,  DOI: 10.1107/S0567740877005834
  25. 25
    Giester, G.; Lengauer, C. L.; Rieck, B. The Crystal Structure of Nesquehonite, MgCO3·3H2O from Lavrion, Greece. Mineral. Petrol. 2000, 70, 153163,  DOI: 10.1007/s007100070001
  26. 26
    Zigan, F.; Rothbauer, R. Neutron Diffraction Measurement on Brucite. Neues Jahrb. Mineral., Monatsh. 1967, 4, 137143
  27. 27
    Akao, M.; Iwai, S. The Hydrogen Bonding of Artinite. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1977, 33 (12), 39513953,  DOI: 10.1107/S0567740877012576
  28. 28
    Liu, B.; Zhou, X.; Cui, X. Synthesis of Lansfordite MgCO3·5H2O and Its Crystal Structure Investigation. Sci. China 1990, 33, 13501356,  DOI: 10.1360/YB1990-33-11-1350
  29. 29
    Short, M. A.; Walker, P. L., Jr Measurement of Interlayer Spacings and Crystal Sizes in Turbostratic Carbons. Carbon N. Y. 1963, 1 (1), 39,  DOI: 10.1016/0008-6223(63)90003-4
  30. 30
    Li, F.; Lannin, J. S. Radial Distribution Function of Amorphous Carbon. Phys. Rev. Lett. 1990, 65 (15), 1905,  DOI: 10.1103/PhysRevLett.65.1905
  31. 31
    Manoj, B.; Kunjomana, A. G. Study of Stacking Structure of Amorphous Carbon by X-ray Diffraction Technique. Int. J. Electrochem. Sci. 2012, 7 (4), 31273134,  DOI: 10.1016/S1452-3981(23)13940-X
  32. 32
    Frost, R. L.; Bahfenne, S.; Graham, J. Raman Spectroscopic Study of the Magnesium-carbonate Minerals─Artinite and Dypingite. J. Raman Spectrosc. 2009, 40 (8), 855860,  DOI: 10.1002/jrs.2152
  33. 33
    Coleyshaw, E. E.; Crump, G.; Griffith, W. P. Vibrational Spectra of the Hydrated Carbonate Minerals Ikaite, Monohydrocalcite, Lansfordite and Nesquehonite. Spectrochim. Acta, Part A 2003, 59 (10), 22312239,  DOI: 10.1016/S1386-1425(03)00067-2
  34. 34
    Zhang, X.; Lea, A. S.; Chaka, A. M.; Loring, J. S.; Mergelsberg, S. T.; Nakouzi, E.; Qafoku, O.; De Yoreo, J. J.; Schaef, H. T.; Rosso, K. M. In Situ Imaging of Amorphous Intermediates during Brucite Carbonation in Supercritical CO2. Nat. Mater. 2022, 21 (3), 345351,  DOI: 10.1038/s41563-021-01154-5
  35. 35
    Loring, J. S.; Thompson, C. J.; Zhang, C.; Wang, Z.; Schaef, H. T.; Rosso, K. M. In Situ Infrared Spectroscopic Study of Brucite Carbonation in Dry to Water-Saturated Supercritical Carbon Dioxide. J. Phys. Chem. A 2012, 116 (19), 47684777,  DOI: 10.1021/jp210020t
  36. 36
    Montes-Hernandez, G.; Renard, F. Time-Resolved in Situ Raman Spectroscopy of the Nucleation and Growth of Siderite, Magnesite, and Calcite and Their Precursors. Cryst. Growth Des. 2016, 16 (12), 72187230,  DOI: 10.1021/acs.cgd.6b01406
  37. 37
    Edwards, H. G. M.; Villar, S. E. J.; Jehlicka, J.; Munshi, T. FT-Raman Spectroscopic Study of Calcium-Rich and Magnesium-Rich Carbonate Minerals. Spectrochim. Acta, Part A 2005, 61 (10), 22732280,  DOI: 10.1016/j.saa.2005.02.026
  38. 38
    Cherniak, D. J. Diffusion in Carbonates, Fluorite, Sulfide Minerals, and Diamond. Rev. Mineral. Geochem. 2010, 72 (1), 871897,  DOI: 10.2138/rmg.2010.72.19
  39. 39
    Richens, D. T. The Chemistry of Aqua Ions: Synthesis, Structure and Reactivity: ATour Through the Periodic Table of the Elements; John Wiley & Sons, Inc.: Hoboken, NJ, 1997.
  40. 40
    Weber, J.; Cheshire, M. C.; Bleuel, M.; Mildner, D.; Chang, Y.-J.; Ievlev, A.; Littrell, K. C.; Ilavsky, J.; Stack, A. G.; Anovitz, L. M. Influence of Microstructure on Replacement and Porosity Generation during Experimental Dolomitization of Limestones. Geochim. Cosmochim. Acta 2021, 303, 137158,  DOI: 10.1016/j.gca.2021.03.029
  41. 41
    Wuensch, B. J.; Steele, W. C.; Vasilos, T. Cation Self-diffusion in Single-Crystal MgO. J. Chem. Phys. 1973, 58 (12), 52585266,  DOI: 10.1063/1.1679138
  42. 42
    Mittag, A.; Schneider, T.; Westermann, M.; Glei, M. Toxicological Assessment of Magnesium Oxide Nanoparticles in HT29 Intestinal Cells. Arch. Toxicol. 2019, 93, 14911500,  DOI: 10.1007/s00204-019-02451-4

Cited By

ARTICLE SECTIONS
Jump To

This article is cited by 2 publications.

  1. Cristina Ruiz-Agudo, Helmut Cölfen. Exploring the Potential of Nonclassical Crystallization Pathways to Advance Cementitious Materials. Chemical Reviews 2024, Article ASAP.
  2. Jacquelyn N. Bracco, Gabriela Camacho Meneses, Omar Colón, Ke Yuan, Joanne E. Stubbs, Peter J. Eng, Anna K. Wanhala, Jeffrey D. Einkauf, Matthew G. Boebinger, Andrew G. Stack, Juliane Weber. Reaction Layer Formation on MgO in the Presence of Humidity. ACS Applied Materials & Interfaces 2024, 16 (1) , 712-722. https://doi.org/10.1021/acsami.3c14823
  • Abstract

    Figure 1

    Figure 1. Reaction layer on the 27-year-old MgO single crystals. (a) SEM image of a TEM lamella prepared by FIB. (b) ToF-SIMS depth profiles of Cs2CO2+ (used as a proxy for CO2) and Mg+ showing a ∼1.5 μm thick layer containing CO2 in 27-year-old MgO in contrast to freshly cleaved MgO. (c) HAADF–STEM image of the area highlighted in panel a by the blue rectangle. The higher magnification characterization of the reaction layers demonstrates its complicated microstructure and potential porosity at the MgO interface. (d) Distribution of reaction layer thickness measurements from FIB, HAADF–STEM, and ToF-SIMS data.

    Figure 2

    Figure 2. Crystallographic analysis of the reaction layer in a second TEM sample prepared from the long-term experiment shown in Figure 1. (a) HAADF–STEM image of TEM lamella showing unreacted MgO, reaction layer, and protective W and C layers. The white rectangle indicates the area shown in the TEM–bright-field (BF) image in panel b). Visible lattice planes indicate crystallinity of the reaction layer. The electron diffraction image of panel b is shown in panel c, with rings indicating nanocrystallites. (d) Schematic of diffractogram analysis from radial profiles. Shaded boxes highlight the integration windows. The yellow shaded box highlights reflections observed at the edge of the reaction layer but not in its polycrystalline region.

    Figure 3

    Figure 3. 12-component NMF analysis of local image diffractograms for Figure 2c from the polycrystalline part of the reaction layer.

    Figure 4

    Figure 4. (a) RGB composite of integrated FFT intensity for ranges 2 (red, nesquehonite/amorphous Mg carbonate), 3 (green, magnesite/hydromagnesite), and 4 (blue, MgO) overlaid on the original image (given in Figure S10 of the Supporting Information). (b and c) Magnified image part for range 2 (red, nesquehonite/amorphous Mg carbonate) and the corresponding diffractogram. (d and e) Magnified image part for range 3 (green, magnesite/hydromagnesite) and the corresponding diffractogram. (f and g) Magnified image part for range 4 (blue, MgO) and the corresponding diffractogram.

    Figure 5

    Figure 5. Characterization of the short-term experiments. (a) Light microscopy image of the measurement location of Raman spectra displayed in panel b for MgO reacted for 189 days with atmosphere. (c) TEM–BF image of MgO reacted for 167 days with atmosphere showing pristine MgO and small, newly formed crystallites. (d) Electron diffraction pattern of panel c. (e and f) FFT of areas highlighted in panel c, indicating single-crystal MgO and a new polycrystalline phase. Calculated d spacings indicate that this is most likely brucite. Diffraction spots stem from bulk MgO. (g) TEM–BF image of the reaction layer on MgO after 167 days of exposure to ambient air. (h) STEM–EELS imaging area shown for (i) carbon and (j) oxygen.

    Figure 6

    Figure 6. Modeling of the inert layer growth on the MgO surface. (a) Schematic representation of a 1D model. The image on the top is part of the HAADF–STEM image in Figure 1c, which shows the reacted layer (darker gray with possible porosity) on top of MgO (lighter gray). (b) Results of 1D reaction–diffusion modeling. Dependence of the thickness of the inert phase layer upon the reaction time as a function of the diffusion coefficient. (c) Dependence of the reaction layer thickness at 27 years upon the diffusion rate in the inert solid phase (red dashed line is an analytical solution for the case of diffusion-limited reaction, and blue symbols are simulation results). The blue region indicates the minimum (1.3 μm) and maximum (1.7 μm) thickness of the layer measured in the experiment.

  • References

    ARTICLE SECTIONS
    Jump To

    This article references 42 other publications.

    1. 1
      McQueen, N.; Kelemen, P.; Dipple, G.; Renforth, P.; Wilcox, J. Ambient Weathering of Magnesium Oxide for CO2 Removal from Air. Nat. Commun. 2020, 11 (1), 110,  DOI: 10.1038/s41467-020-16510-3
    2. 2
      Akeeb, O.; Wang, L.; Xie, W.; Davis, R.; Alkasrawi, M.; Toan, S. Post-Combustion CO2 Capture via a Variety of Temperature Ranges and Material Adsorption Process: A Review. J. Environ. Manage. 2022, 313, 115026,  DOI: 10.1016/j.jenvman.2022.115026
    3. 3
      Walling, S. A.; Provis, J. L. Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?. Chem. Rev. 2016, 116 (7), 41704204,  DOI: 10.1021/acs.chemrev.5b00463
    4. 4
      Hu, Y.; Guo, Y.; Sun, J.; Li, H.; Liu, W. Progress in MgO Sorbents for Cyclic CO2 Capture: A Comprehensive Review. J. Mater. Chem. A 2019, 7 (35), 2010320120,  DOI: 10.1039/C9TA06930E
    5. 5
      Hänchen, M.; Prigiobbe, V.; Baciocchi, R.; Mazzotti, M. Precipitation in the Mg-Carbonate System-Effects of Temperature and CO2 Pressure. Chem. Eng. Sci. 2008, 63 (4), 10121028,  DOI: 10.1016/j.ces.2007.09.052
    6. 6
      Rausis, K.; Stubbs, A. R.; Power, I. M.; Paulo, C. Rates of Atmospheric CO2 Capture Using Magnesium Oxide Powder. Int. J. Greenhouse Gas Control 2022, 119 (April), 103701,  DOI: 10.1016/j.ijggc.2022.103701
    7. 7
      Santos, H. S.; Nguyen, H.; Venâncio, F.; Ramteke, D.; Zevenhoven, R.; Kinnunen, P. Mechanisms of Mg Carbonates Precipitation and Implications for CO2 Capture and Utilization/Storage. Inorg. Chem. Front. 2023, 10 (9), 25072546,  DOI: 10.1039/D2QI02482A
    8. 8
      Harrison, A. L.; Dipple, G. M.; Power, I. M.; Mayer, K. U. Influence of Surface Passivation and Water Content on Mineral Reactions in Unsaturated Porous Media: Implications for Brucite Carbonation and CO2 Sequestration. Geochim. Cosmochim. Acta 2015, 148, 477495,  DOI: 10.1016/j.gca.2014.10.020
    9. 9
      Béarat, H.; McKelvy, M. J.; Chizmeshya, A. V. G.; Gormley, D.; Nunez, R.; Carpenter, R. W.; Squires, K.; Wolf, G. H. Carbon Sequestration via Aqueous Olivine Mineral Carbonation: Role of Passivating Layer Formation. Environ. Sci. Technol. 2006, 40 (15), 48024808,  DOI: 10.1021/es0523340
    10. 10
      Daval, D.; Sissmann, O.; Menguy, N.; Saldi, G. D.; Guyot, F.; Martinez, I.; Corvisier, J.; Garcia, B.; Machouk, I.; Knauss, K. G.; Hellmann, R. Influence of Amorphous Silica Layer Formation on the Dissolution Rate of Olivine at 90 °C and Elevated pCO2. Chem. Geol. 2011, 284 (1–2), 193209,  DOI: 10.1016/j.chemgeo.2011.02.021
    11. 11
      Grayevsky, R.; Reiss, A. G.; Emmanuel, S. Carbon Storage through Rapid Conversion of Forsterite into Solid Oxalate Phases. Energy Fuels 2023, 37 (1), 509517,  DOI: 10.1021/acs.energyfuels.2c03245
    12. 12
      Nugent, M. A.; Brantley, S. L.; Pantano, C. G.; Maurice, P. A. The Influence of Natural Mineral Coatings on Feldspar Weathering. Nature 1998, 395 (6702), 588591,  DOI: 10.1038/26951
    13. 13
      Zhu, C.; Veblen, D. R.; Blum, A. E.; Chipera, S. J. Naturally Weathered Feldspar Surfaces in the Navajo Sandstone Aquifer, Black Mesa, Arizona: Electron Microscopic Characterization. Geochim. Cosmochim. Acta 2006, 70 (18), 46004616,  DOI: 10.1016/j.gca.2006.07.013
    14. 14
      Ruiz-Agudo, E.; Putnis, C. V.; Rodriguez-Navarro, C.; Putnis, A. Mechanism of Leached Layer Formation during Chemical Weathering of Silicate Minerals. Geology 2012, 40 (10), 947950,  DOI: 10.1130/G33339.1
    15. 15
      Abraham, M. M.; Butler, C. T.; Chen, Y. Growth of High-Purity and Doped Alkaline Earth Oxides: I. MgO and CaO. J. Chem. Phys. 1971, 55 (8), 37523756,  DOI: 10.1063/1.1676658
    16. 16
      Schaffer, M.; Schaffer, B.; Ramasse, Q. Sample Preparation for Atomic-Resolution STEM at Low Voltages by FIB. Ultramicroscopy 2012, 114, 6271,  DOI: 10.1016/j.ultramic.2012.01.005
    17. 17
      Laetsch, T.; Downs, R. Software for Identification and Refinement of Cell Parameters from Powder Diffraction Data of Minerals Using the RRUFF Project and American Mineralogist Crystal Structure Databases. Proceedings of the 19th General Meeting of the International Mineralogical Association ; Kobe, Japan, July 23–28, 2006.
    18. 18
      Starchenko, V.; Marra, C. J.; Ladd, A. J. C. Three-Dimensional Simulations of Fracture Dissolution. J. Geophys. Res.: Solid Earth 2016, 121 (9), 64216444,  DOI: 10.1002/2016JB013321
    19. 19
      Mergelsberg, S. T.; Rajan, B. P.; Legg, B. A.; Kovarik, L.; Burton, S. D.; Bowers, G. M.; Bowden, M. E.; Qafoku, O.; Thompson, C. J.; Kerisit, S. N.; Ilton, E. S.; Loring, J. S. Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg2SiO4) When Water Is Limited. Environ. Sci. Technol. Lett. 2023, 10 (1), 98104,  DOI: 10.1021/acs.estlett.2c00866
    20. 20
      Hazen, R. M. Effects of Temperature and Pressure on the Cell Dimension and X-ray Temperature Factors of Periclase. Am. Mineral. 1976, 61 (3–4), 266271
    21. 21
      Vasudevan, R. K.; Ziatdinov, M.; Jesse, S.; Kalinin, S. V. Phases and Interfaces from Real Space Atomically Resolved Data: Physics-Based Deep Data Image Analysis. Nano Lett. 2016, 16 (9), 55745581,  DOI: 10.1021/acs.nanolett.6b02130
    22. 22
      Kannan, R.; Ievlev, A. V.; Laanait, N.; Ziatdinov, M. A.; Vasudevan, R. K.; Jesse, S.; Kalinin, S. V. Deep Data Analysis via Physically Constrained Linear Unmixing: Universal Framework, Domain Examples, and a Community-Wide Platform. Adv. Struct. Chem. Imaging 2018, 4 (1), 6,  DOI: 10.1186/s40679-018-0055-8
    23. 23
      Ross, N. L. The Equation of State and High-Pressure Behavior of Magnesite. Am. Mineral. 1997, 82 (7–8), 682688,  DOI: 10.2138/am-1997-7-805
    24. 24
      Akao, M.; Iwai, S. The Hydrogen Bonding of Hydromagnesite. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1977, 33 (4), 12731275,  DOI: 10.1107/S0567740877005834
    25. 25
      Giester, G.; Lengauer, C. L.; Rieck, B. The Crystal Structure of Nesquehonite, MgCO3·3H2O from Lavrion, Greece. Mineral. Petrol. 2000, 70, 153163,  DOI: 10.1007/s007100070001
    26. 26
      Zigan, F.; Rothbauer, R. Neutron Diffraction Measurement on Brucite. Neues Jahrb. Mineral., Monatsh. 1967, 4, 137143
    27. 27
      Akao, M.; Iwai, S. The Hydrogen Bonding of Artinite. Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 1977, 33 (12), 39513953,  DOI: 10.1107/S0567740877012576
    28. 28
      Liu, B.; Zhou, X.; Cui, X. Synthesis of Lansfordite MgCO3·5H2O and Its Crystal Structure Investigation. Sci. China 1990, 33, 13501356,  DOI: 10.1360/YB1990-33-11-1350
    29. 29
      Short, M. A.; Walker, P. L., Jr Measurement of Interlayer Spacings and Crystal Sizes in Turbostratic Carbons. Carbon N. Y. 1963, 1 (1), 39,  DOI: 10.1016/0008-6223(63)90003-4
    30. 30
      Li, F.; Lannin, J. S. Radial Distribution Function of Amorphous Carbon. Phys. Rev. Lett. 1990, 65 (15), 1905,  DOI: 10.1103/PhysRevLett.65.1905
    31. 31
      Manoj, B.; Kunjomana, A. G. Study of Stacking Structure of Amorphous Carbon by X-ray Diffraction Technique. Int. J. Electrochem. Sci. 2012, 7 (4), 31273134,  DOI: 10.1016/S1452-3981(23)13940-X
    32. 32
      Frost, R. L.; Bahfenne, S.; Graham, J. Raman Spectroscopic Study of the Magnesium-carbonate Minerals─Artinite and Dypingite. J. Raman Spectrosc. 2009, 40 (8), 855860,  DOI: 10.1002/jrs.2152
    33. 33
      Coleyshaw, E. E.; Crump, G.; Griffith, W. P. Vibrational Spectra of the Hydrated Carbonate Minerals Ikaite, Monohydrocalcite, Lansfordite and Nesquehonite. Spectrochim. Acta, Part A 2003, 59 (10), 22312239,  DOI: 10.1016/S1386-1425(03)00067-2
    34. 34
      Zhang, X.; Lea, A. S.; Chaka, A. M.; Loring, J. S.; Mergelsberg, S. T.; Nakouzi, E.; Qafoku, O.; De Yoreo, J. J.; Schaef, H. T.; Rosso, K. M. In Situ Imaging of Amorphous Intermediates during Brucite Carbonation in Supercritical CO2. Nat. Mater. 2022, 21 (3), 345351,  DOI: 10.1038/s41563-021-01154-5
    35. 35
      Loring, J. S.; Thompson, C. J.; Zhang, C.; Wang, Z.; Schaef, H. T.; Rosso, K. M. In Situ Infrared Spectroscopic Study of Brucite Carbonation in Dry to Water-Saturated Supercritical Carbon Dioxide. J. Phys. Chem. A 2012, 116 (19), 47684777,  DOI: 10.1021/jp210020t
    36. 36
      Montes-Hernandez, G.; Renard, F. Time-Resolved in Situ Raman Spectroscopy of the Nucleation and Growth of Siderite, Magnesite, and Calcite and Their Precursors. Cryst. Growth Des. 2016, 16 (12), 72187230,  DOI: 10.1021/acs.cgd.6b01406
    37. 37
      Edwards, H. G. M.; Villar, S. E. J.; Jehlicka, J.; Munshi, T. FT-Raman Spectroscopic Study of Calcium-Rich and Magnesium-Rich Carbonate Minerals. Spectrochim. Acta, Part A 2005, 61 (10), 22732280,  DOI: 10.1016/j.saa.2005.02.026
    38. 38
      Cherniak, D. J. Diffusion in Carbonates, Fluorite, Sulfide Minerals, and Diamond. Rev. Mineral. Geochem. 2010, 72 (1), 871897,  DOI: 10.2138/rmg.2010.72.19
    39. 39
      Richens, D. T. The Chemistry of Aqua Ions: Synthesis, Structure and Reactivity: ATour Through the Periodic Table of the Elements; John Wiley & Sons, Inc.: Hoboken, NJ, 1997.
    40. 40
      Weber, J.; Cheshire, M. C.; Bleuel, M.; Mildner, D.; Chang, Y.-J.; Ievlev, A.; Littrell, K. C.; Ilavsky, J.; Stack, A. G.; Anovitz, L. M. Influence of Microstructure on Replacement and Porosity Generation during Experimental Dolomitization of Limestones. Geochim. Cosmochim. Acta 2021, 303, 137158,  DOI: 10.1016/j.gca.2021.03.029
    41. 41
      Wuensch, B. J.; Steele, W. C.; Vasilos, T. Cation Self-diffusion in Single-Crystal MgO. J. Chem. Phys. 1973, 58 (12), 52585266,  DOI: 10.1063/1.1679138
    42. 42
      Mittag, A.; Schneider, T.; Westermann, M.; Glei, M. Toxicological Assessment of Magnesium Oxide Nanoparticles in HT29 Intestinal Cells. Arch. Toxicol. 2019, 93, 14911500,  DOI: 10.1007/s00204-019-02451-4
  • Supporting Information

    Supporting Information

    ARTICLE SECTIONS
    Jump To

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.3c04690.

    • Lift-out locations, details of numerical simulation, additional STEM images, additional d-spacing analysis of 27-year-old MgO, additional TEM characterization of 27-year-old MgO, Raman analysis of 27-year-old MgO, and additional Raman analysis of short-term experiments (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.