Rates of atmospheric CO2 capture using magnesium oxide powder

Rausis, Kwon; Stubbs, A. R.; Power, Ian M.; Paulo, Carlos

doi:10.1016/j.ijggc.2022.103701

Cited by 11 publications

(25 citation statements)

References 59 publications

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“…The formation of hydrated Mg carbonate phases was also observed during MgO powder experiments at atmospheric CO 2 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 CO 2 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.…”

Section: Resultsmentioning

confidence: 59%

“…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 submicrometer particles poses potential concerns because there is a risk of the material been blown away by the wind in realworld settings.…”

Section: Environmental Implicationsmentioning

confidence: 99%

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

Weber,

Starchenko,

Yuan

et al. 2023

Environ. Sci. Technol.

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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.

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Section: Resultsmentioning

confidence: 59%

Section: Environmental Implicationsmentioning

confidence: 99%

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

Weber,

Starchenko,

Yuan

et al. 2023

Environ. Sci. Technol.

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“…Recent studies observed a strong correlation between mineral reactivity and relative humidity (RH) during silicate mineral carbonation. ,,− The low availability of water can lead to an accumulation of reaction products on silicate mineral surfaces that slows dissolution and/or carbonation by orders of magnitude, commonly termed a passivation effect. − Extensive results from bulk water experiments suggest passivation mechanisms include formation of leached layers, , coupled interfacial dissolution–reprecipitation, ,,,, or a combination of both. ,,, For example, cation-depleted coatings on the order of 20 to >100 nm form on the model divalent cation silicate mineral forsterite (Mg 2 SiO 4 ) in scCO 2 under a wide range of conditions. ,,− In bulk water systems, these depleted layers can passivate forsterite dissolution under specific conditions ( T , pH, and SA/ V ) that do not favor carbonate mineral formation. − ,,, When such a system does produce carbonate minerals, the silicate mineral reacts completely to form amorphous silica and the metal carbonate, even if leached layers form. This is in contrast to our recent observations under thin water film conditions, where the rate of carbonation of forsterite in scCO 2 at 50 °C, 90 bar, and 79% RH decreased significantly after only 20% of the mineral had reacted and carbonates were still precipitating .…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg₂SiO₄) When Water Is Limited

Mergelsberg

Rajan

Legg

et al. 2022

Environ. Sci. Technol. Lett.

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Passivation of silicate surfaces by accumulated reaction products is an obstacle to efficient CO2 mineralization. In this study, we investigate a unique passivation effect during the carbonation of the basalt mineral forsterite (Mg2SiO4) in humid supercritical CO2 (50 °C, 90 bar). Using in situ high-pressure infrared spectroscopy, we demonstrate that dissolution of forsterite into a thin water film slows significantly after reaction for ≈24 h, even under far-from-equilibrium conditions. 29Si magic angle spinning nuclear magnetic resonance spectroscopy detects a highly polymerized amorphous silica at this stage. On the basis of transmission electron microscopy and energy dispersive X-ray spectroscopy, we show that the silica is present as a Mg-depleted layer that is just 2–3 nm thick on the reacted forsterite particles. The decrease in the level of forsterite dissolution in the presence of an extraordinarily thin Mg-depleted layer can be strongly linked to properties of the thin fluid film at the surface, highlighting the importance of water during mineral carbonation. This study furthers our understanding of silicate mineral carbonation under select low-water, humidified fluid conditions relevant to basaltic geologic reservoirs, recovery of critical elements by carbonation of mafic ores, and sequestration of atmospheric CO2 by enhanced rock weathering.

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“…After the carbonation process, the generated carbonates are collected and calcined again. Experimental results indicate that only 3-18% of the spread metal oxides would react in one year (Rausis et al 2022). The cost of this NETP could range between 47 and 161 $ t −1 CO 2 captured (McQueen et al 2020).…”

Section: Terrestrial Enhanced Weatheringmentioning

confidence: 99%

Sustainable scale-up of negative emissions technologies and practices: where to focus

Cobo

Negri

Valente

et al. 2023

Environ. Res. Lett.

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Most climate change mitigation scenarios restricting global warming to 1.5 oC rely heavily on Negative Emissions Technologies and Practices (NETPs). Here we updated previous literature reviews and conducted an analysis to identify the most appealing NETPs. We evaluated 36 NETPs configurations considering their technical maturity, economic feasibility, greenhouse gas removal potential, resource use, and environmental impacts. We found multiple trade-offs among these indicators, which suggests that a regionalised portfolio of NETPs exploiting their complementary strengths is the way forward. Although no single NETP is superior to the others in terms of all the indicators simultaneously, we identified 16 Pareto-efficient NETPs. Among them, six are deemed particularly promising: forestation, Soil Carbon Sequestration (SCS), enhanced weathering with olivine and three modalities of Direct Air Carbon Capture and Storage (DACCS). While the co-benefits, lower costs and higher maturity levels of forestation and SCS can propel their rapid deployment, these NETPs require continuous monitoring to reduce unintended side-effects – most notably the release of the stored carbon. Enhanced weathering also shows an overall good performance and substantial co-benefits, but its risks – especially those concerning human health – should be further investigated prior to deployment. DACCS presents significantly fewer side-effects, mainly its substantial energy demand; early investments in this NETP could reduce costs and accelerate its scale-up. Our insights can help guide future research and plan for the sustainable scale-up of NETPs, which we must set into motion within this decade.

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Rates of atmospheric CO2 capture using magnesium oxide powder

Cited by 11 publications

References 59 publications

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

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

Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg₂SiO₄) When Water Is Limited

Sustainable scale-up of negative emissions technologies and practices: where to focus

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Rates of atmospheric CO2 capture using magnesium oxide powder

Cited by 11 publications

References 59 publications

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

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

Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg2SiO4) When Water Is Limited

Sustainable scale-up of negative emissions technologies and practices: where to focus

Contact Info

Product

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About

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

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

Nanoscale Mg-Depleted Layers Slow Carbonation of Forsterite (Mg₂SiO₄) When Water Is Limited