Key Takeaways & Executive Findings
- •• NaNO2-modified mesoporous MgO achieves a high CO2 adsorption capacity of 12.6 mmol/g at 325 °C under pure CO2. • The modification induces formation of NaNO3 and Na2CO3, which synergistically enhance oxygen vacancies and nucleation sites. • The adsorption mechanism involves MgCO3 formation and subsequent conversion to Na2Mg(CO3)2, with kinetics governed by surface reaction and diffusion. • The study provides mechanistic insights for rational design of advanced MgO-based CO2 adsorbents.
Abstract
The development of efficient CO2 adsorbents is critical for achieving net-zero targets. MgO represents a promising solid adsorbent for CO2 capture, yet its limited specific surface area and insufficient active sites restrict its adsorption capacity under moderate temperature conditions. A rod-like anhydrous MgCO3 precursor was hydrothermally synthesized and calcined at 500 °C for 3 h to obtain porous MgO (184.9 m2 g−1, 0.38 cm3/g), which was then modified with 20% NaNO2 (by mole) via impregnation. This adsorbent achieved an adsorption capacity of 12.6 mmol g−1 after 120 min under a pure CO2 atmosphere at 325 °C. Comprehensive characterization reveals that NaNO2 modification leads to the NaNO3 and Na2CO3 formation on the MgO surface during calcination. The introduced NaNO3 effectively promotes oxygen vacancy formation, while the generated Na2CO3 serves as heterogeneous nucleation sites, collectively reducing the reaction energy barrier and enhancing interfacial mass transfer. This synergistic effect facilitates the MgCO3 formation followed by its conversion to the thermodynamically more stable Na2Mg(CO3)2. Kinetic studies elucidate that adsorption is dominated by surface chemical reactions and diffusion mechanisms at different stages. These fundamental insights into the adsorption mechanisms of nitrite-modified MgO provide valuable guidance for the rational design of advanced MgO-based CO2 adsorbents with enhanced performance.
1. Introduction
Since the Industrial Revolution, atmospheric CO2 concentrations have shown a persistent upward trend. Recent monitoring data indicate that the global atmospheric CO2 mole fraction reached a historical peak of (420.0±0.1)×10−⁶ in May 2023, representing a 40% increase from the 1950s level (approximately 300×10−⁶), with a continuing growth rate of about 2×10−⁶ per year [1]. This sustained increase has significantly intensified the greenhouse effect, leading to more frequent extreme climate events worldwide [2,3]. In this context, developing efficient CO2 capture technologies is currently the most promising solution to avoid severe climate change.
Current mainstream CO2 capture technologies primarily include amine solution absorption, cryogenic distillation, solid adsorption, and membrane separation [4]. Among these, amine-based technologies using monoethanolamine (MEA) and diethanolamine (DEA), while relatively mature, face key challenges such as high regeneration energy consumption (approximately 4 MJ/kg CO2), solvent volatility losses, and equipment corrosion. In comparison, solid adsorption technology has attracted considerable attention due to its advantages of low energy consumption and minimal corrosiveness [5]. Common solid adsorbents include layered double hydroxides (LDHs), alkali metals, and their oxides [6]. However, LDH-based adsorbents still face significant challenges in large-scale industrial applications due to their limited adsorption capacity.
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Yulian Wang, Jiayi Liu, Jinze Song, Junze Gu, Binyan Wang, Rui Guan, Keqing Li, Wanzhong Yin, Haoran Sun, Huili Han (2026). NaNO2-loaded mesoporous MgO for high-efficiency CO2 capture: Synthesis, characterization and novel mechanistic insights. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2026.02.006
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Frequently Asked Questions
What is the maximum CO2 adsorption capacity of the NaNO2-modified MgO adsorbent?
The NaNO2-modified MgO adsorbent achieves a CO2 adsorption capacity of 12.6 mmol/g after 120 minutes under pure CO2 at 325 °C.
How does NaNO2 modification enhance CO2 capture performance?
NaNO2 modification leads to the formation of NaNO3 and Na2CO3 on the MgO surface during calcination. NaNO3 promotes oxygen vacancy formation, while Na2CO3 provides heterogeneous nucleation sites, collectively reducing the reaction energy barrier and enhancing interfacial mass transfer.
What is the role of Na2CO3 in the adsorption process?
Na2CO3 serves as heterogeneous nucleation sites, facilitating the formation of MgCO3 and its subsequent conversion to the more stable Na2Mg(CO3)2, thereby improving adsorption capacity.
What are the key kinetic mechanisms in the CO2 adsorption process?
Kinetic studies indicate that adsorption is dominated by surface chemical reactions at initial stages and diffusion mechanisms at later stages.
What is the significance of this study for CO2 capture technology?
The study provides novel mechanistic insights into nitrite-modified MgO adsorbents, offering valuable guidance for the rational design of advanced MgO-based CO2 adsorbents with enhanced performance, contributing to net-zero emission targets.
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