Carbonation of MgO Single Crystals: Implications for Direct Air Capture of CO₂

Environmental Science & Technology, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 10, 2025

Direct air capture (DAC) may be feasible to remove carbon dioxide (CO2) from the atmosphere at gigaton scale, holding promise become a major contributor climate change mitigation. Mineral looping using magnesium oxide (MgO) is potentially an economical, efficient, and sustainable pathway gigaton-scale DAC. The hydroxylation carbonation of MgO determine efficiency process, but their rates mechanisms remain uncertain. In this work, single crystals were reacted in or CO2 varying humidities characterized by X-ray scattering, microscopy, vibrational spectroscopy. Results show that formed brucite (Mg(OH)2)-like layer immediately after crystal cleaving. Concurrently, hydrated carbonate phases, including barringtonite (MgCO3·2H2O) nesquehonite (MgCO3·2H2O), layer. Rapid initial growth also manifested short-range bending/warping nanocrystallites, resulting multiple orientations same phases on surface. slowed down over time, indicating surface passivation. formation with 1:1 CO3/Mg ratio indicates efficient when compared other lower ratio. Our results are essential for understanding passivation tackling issue mineral DAC technology.

Language: Английский

---

Passive direct air capture using calcium oxide powder: The importance of water vapor

Journal of Cleaner Production, Journal Year: 2024, Volume and Issue: 457, P. 142394 - 142394

Published: April 30, 2024

Calcium oxide (CaO; lime) looping is a proposed technology with the potential to capture gigatonnes of carbon dioxide (CO2) from atmosphere help mitigate climate change. The importance water in carbonation reactions widely understood as it needed for mineral and CO2 dissolution carbonate precipitation. However, effects vapor on CaO pathways rates have yet be elucidated systematic manner. Here, we examine impact relative humidity (RH) removal using powder at 20% 95% RH. Higher RH resulted faster hydration rates, forming Ca(OH)2 (portlandite); however, passivation limited all experiments, greatest occurring 80% (65% CaCO3; calcite). Thus, highly prone when drive carbonation. In swing was changed different times (hours or days) by amounts (e.g., 40–99%). Humidity swings can yield >85% CaCO3 complete low (<40%) occurs before high (∼99%). Importantly, separating these two processes yields nearly this case, achieved rate 1 t every 1.95 per day.

Language: Английский

---

pH-dependent reactivity of water at MgO(100) and MgO(111) surfaces

Physical Chemistry Chemical Physics, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

vSFG spectroscopy shows that water dipole reorientation occurs at the interface due to charge reversal MgO(100) and (111) surfaces pH above below PZC ∼ 12.

Language: Английский

---

Inhibition of Reaction Layer Formation on MgO(100) by Doping with Trace Amounts of Iron

The Journal of Physical Chemistry C, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 11, 2025

Despite extensive research on MgO's reactivity in the presence of CO2 under various conditions, little is known about whether impurities incorporated into solid, such as iron, enhance or impede hydroxylation and carbonation reactions. The purity MgO required for successful implementation looping a direct air capture technology affects deployment costs. With this motivation, we tested how iron impacts (100) passivation layer formation ambient conditions by using atomic force microscopy, electron synchrotron-based X-ray scattering. Based microprobe analysis, our samples were 0.5 wt % Mössbauer spectroscopy results indicated that 70% present Fe(II). We find even these low levels dopants impeded both at relative humidities (10%, 33%, 75%, >95%) (33%, surface. Crystalline reaction products formed. Reaction layers sample easily removed exposing to deionized water 2 min. Overall, findings demonstrate slows rate MgO, indicating without preferable mineral applications.

Language: Английский

---

Decreasing Hygroscopicity Slows Forsterite Carbonation under Low-Water Conditions

Environmental Science & Technology, Journal Year: 2025, Volume and Issue: unknown

Published: April 28, 2025

A fundamental understanding of processes that slow divalent metal silicate carbonation is important for developing effective strategies to durably store carbon dioxide and mitigate atmospheric CO2. This study presents a detailed investigation passivation effect unique low-water conditions during the forsterite (Mg2SiO4) highlights importance hygroscopicity in influencing carbonation. Integrated situ ex experimental results showed decrease rate observed after ∼10 h humid supercritical CO2 (50 °C, 90 bar) correlates with reduction water film thickness, particular, weakly hydrogen bonded adsorbed facilitates ion transport. We attribute thickness drop concentrations hygroscopic Mg2+, MgHCO3+, HCO3- ions within as predominate product evolves from amorphous magnesium carbonate (AMC) magnesite (MgCO3). When more soluble AMC present, are higher, drawing phase surface. Carbonation rates faster because thicker films can better mobilize growing carbonates. In contrast, when less predominates, lower, thinner, slower.

Language: Английский

---

Engineering oxide ceramic fillers for thermal interface materials: Enhanced thermal conductivity and thixotropy through hydrophobated MgO/PDMS composite materials

Advanced Composites and Hybrid Materials, Journal Year: 2025, Volume and Issue: 8(3)

Published: May 14, 2025

Language: Английский

---

Revealing the mechanism of MgO inhibiting the combustion of modified double-base propellants

Fuel, Journal Year: 2024, Volume and Issue: 381, P. 133632 - 133632

Published: Nov. 7, 2024

Language: Английский

---

Iron Impurity Impairs the CO₂ Capture Performance of MgO: Insights from Microscopy and Machine Learning Molecular Dynamics

ACS Applied Materials & Interfaces, Journal Year: 2024, Volume and Issue: 16(46), P. 64233 - 64243

Published: Nov. 11, 2024

Magnesium oxide (MgO) is a promising sorbent for direct air capture (DAC) of carbon dioxide. Iron (Fe) common impurity in naturally occurring MgO and minerals used to produce MgO, yet molecular-scale understanding Fe-doping effects on carbonation lacking. Here, we observed reduced performance Fe-doped experimentally. The energetics adsorbing (bi)carbonate ion pristine MgO(001) surfaces were further investigated using ab initio machine learning potential molecular dynamics coupled with metadynamics simulations. Both exhibited basic (OH–) hydration layer, where the adsorption thermodynamically favorable. However, dissolution surface Fe had smaller energy barriers was more favorable than Mg. Leached likely neutralized near-surface basicity, yielding reactivity MgO. Our observations offer critical insights material selection emphasize importance evaluating geologic origin earth materials DAC.

Language: Английский

---

Influence of Dissolved Iron in Solution on MgO Hydroxylation and Carbonation

The Journal of Physical Chemistry C, Journal Year: 2024, Volume and Issue: 129(1), P. 194 - 204

Published: Dec. 21, 2024

MgO (periclase) is a promising material for direct air capture of CO2 using mineral looping process, but it unknown how impurities in the environment will affect uptake and hence process economics. Here, we investigated effects dissolved iron on extents hydroxylation subsequent carbonation reactions to determine if this has beneficial or detrimental effect. On single-crystal MgO, prevented hydration Mg(OH)2 (brucite) instead formed shell lepidocrocite (γ-FeOOH). This did not passivate as dissolution below was observed. During powders presence iron, formation brucite containing Fe(II) In addition, nanoscale oxides Fe(III) observed magnetometry Mössbauer spectroscopy. Subsequent experiments showed increased hydroxylated iron. Our results indicate that solute during may be MgO.

Language: Английский

---