Enhancing Co2 adsorption in sandstone formation using fly ash nanoparticles: A geo-sequestration approach

Synthesis, characterisation and CO2 adsorption potential of NaA and NaX zeolites and hydrotalcite obtained from the same coal fly ash

Enhancing CO2 adsorption capacity through Fe2O3/CaO ratio engineering in simulated fly ash-derived zeolite synthesis through gradient oxide modulation.

Increased energy consumption due to industrial growth has increased the levels of carbon dioxide (CO2) emission being released into the atmosphere. CO2 emission is a type of greenhouse gas which is a major cause of global warming. Since the issue of CO2 emissions has drawn much attention in recent years, the development of CO2 capture technology has become a necessity. Although CO2 adsorbents are still at the early development stage, it has been suggested that CO2 adsorbents are the most effective technology in controlling CO2 emissions. Solid adsorbents have great potential as an alternative method to conventional adsorbents in adsorbing CO2. In this paper, low cost adsorbents including activated carbon, zeolites, mesoporous silica and clays are discussed in terms of adsorbent preparation methods and CO2 adsorption capacity. The low cost adsorbents are mainly derived from waste materials such as fly ash, steel slag, red mud, bagasses wastes and wood wastes. Besides that, natural resources such as clays have also been applied as low cost CO2 adsorbents. Surface modifications have also been applied to the low cost adsorbents, including metal ion exchange and amine impregnation to enhance CO2 adsorption capacity. In the last section, the current status of CO2 adsorbents is summarized and future trends are discussed briefly to predict the potential materials which can be applied as CO2 adsorbents.

To enhance the CO2 adsorption of almond shell-derived activated carbon (AC) samples treated with cold oxygen plasma, the samples were impregnated with cholinium-amino acid ionic liquids ([Cho][AA] ILs) using the vacuum-assisted impregnation method. The physicochemical and textural properties of the resulting composites (ILs@AC) were characterized using various techniques, including Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX) spectroscopy, and Brunauer-Emmett-Teller (BET) surface area measurement. The CO2 adsorption performance of the samples was evaluated using a quartz crystal microbalance (QCM) over a temperature range of 288.15–308.15 K and gas pressures up to 1 bar. The IL@AC composite materials exhibited notably improved CO2 adsorption capacities compared to pristine AC. The CO2 adsorption isotherms onto the IL@AC composite samples closely conformed to the Langmuir isotherm model, indicating the dominant involvement of strong intermolecular interactions, particularly driven by amine functionalities. Meanwhile, the results revealed that [Cho][His]@AC showed lowered CO2 adsorption capacity compared to [Cho][Pro]@AC and [Cho][Gln]@AC. Among the studied ionic liquids, [Cho][Pro]@AC showed the highest absorption capacity (2.332 mmol·g−1 at 288 K and 1 bar). This was due to the obstruction of internal pores within the AC structure caused by excessive amine incorporation into its porous framework. In the meantime, for a deeper insight into the impregnation process of ILs onto the AC surfaces and their potential interactions with CO2 molecules, we conducted density-functional theory (DFT) calculations using the ωB97XD/6-31 + G(d,p) method. The calculated interaction energies, ranging from − 1.19 to − 1.44 eV, along with calculated quantum chemical descriptors, indicated a notable stabilization of IL species on the AC surfaces, with high affinity toward CO2 molecules.

Preparation and CO2 adsorption of N-doped biochar and effect of acetone on its adsorption performance.

The research examines the potential of employing nano technology to modify the physical characteristics of fly ash and improve the engineering performance of mortar. Utilizing Nano Fly Ash (NFA) as a substitute for cement at different ratios demonstrated that the meticulous approach impacted the sample size and surface area, but did not alter the chemical structure and constituents. The analysis of X-ray diffraction (XRD) indicated a reduction in particle size and a complex lattice phase strain in the Fly Ash nanoparticles. The analysis showed that the particles exhibited non-spherical shapes and dimensions measuring under 5 μm. The results of the compressive strength test indicated that the mortar with 15% Nano Fly Ash replacement exceeded the control mortar. Moreover, it was demonstrated that machine learning algorithms can accurately forecast experimental data and the connections between variables, as evidenced by metrics such as Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and the coefficient of determination (R2). The RSM model demonstrated a high level of accuracy in predicting the mechanical properties, achieving a degree of precision with R2 values equal to or greater than 0.9539. The ANN model showed its capability to capture the variability of the data, as shown by a robust R2 threshold (R2 > 0.9995) across training, testing, and validation phases. Utilizing high volumes of Fly Ash allows for the conservation of renewable resources, reduction of carbon emissions in cement production, and effective management of the disposal and contamination of inland Fly Ash.

ZnO/Cu/Al2O3 catalysts are used in industrial applications to produce methanol from CO2 gas. Because of the high barriers and also of the poor interaction between CO2 and the catalysts, current methods require extreme conditions, thereby significantly increasing production costs. In the search for more efficient catalysts based on the ZnO/Cu/Al2O3 system, this work investigates CO2 adsorption, activation, and hydrogenation on N-doped ZnO clusters supported on Cu(111). Our results show that N-doping significantly enhances CO2 adsorption compared to pure ZnO/Cu. Even in a hydrogen-rich environment, N-doped ZnO/Cu systems show a dramatically higher CO2 adsorption energy than the undoped ZnO/Cu configuration, sufficient to counterbalance the gas-phase entropic penalty in a wide range of conditions. In addition to enhancing CO2 adsorption, the overall reaction barrier to CO2 reduction is significantly reduced, enabling methanol production through a reverse water–gas shift (RWGS) pathway. These findings demonstrate that N-doping of ZnO/Cu catalysts can enhance CO2 adsorption and activation, thereby facilitating methanol synthesis under less demanding reaction conditions.

Enhancement of CO2 adsorption on natural zeolite, modified clinoptilolite with cations, amines and ionic liquids

Enhancement of CO2 adsorption on phenolic resin-based mesoporous carbons by KOH activation

Global warming is primarily driven by the rapid accumulation of carbon dioxide (CO₂) in the atmosphere. Metal–organic frameworks (MOFs) have emerged as promising materials for mitigating CO₂ emissions due to their tunable porosity, large surface area, and structural flexibility. Among them, MIL-53(Al) has attracted widespread interest owing to its excellent thermal and chemical stability. Recent studies show that modifying MOFs with secondary metals can significantly enhance their CO₂ adsorption performance. In this work, a one-pot synthesis method was employed to incorporate calcium (Ca), functioning as a Lewis basic metal, into the MIL-53(Al) framework to produce a series of bimetallic materials: MIL-53(Al, Ca)-1, -2, and − 3. These materials were further treated with NaOH to yield MIL-53(Al, Ca, Na)-1, -2, and − 3. Introducing Ca into the framework increased the affinity toward CO₂—a Lewis acidic gas—thereby enhancing adsorption. All materials were characterised and compared with pristine MIL-53(Al). CO₂ adsorption was evaluated at 273 K under both low pressure (up to 100 kPa) and high pressure (up to 980 kPa), while N₂ adsorption was measured at 273 K and 100 kPa. N₂ uptake decreased significantly with increasing Ca content, from 0.7177 mmol·g⁻¹ for MIL-53(Al) to 0.173 mmol·g⁻¹ for MIL-53(Al, Ca)-3 and MIL-53(Al, Ca, Na)-3. Moderate Ca incorporation improved CO₂ adsorption: at 100 kPa, MIL-53(Al, Ca)-1 and MIL-53(Al, Ca, Na)-1 achieved 4.09 and 3.56 mmol·g⁻¹, respectively, compared with 2.19 mmol·g⁻¹ for MIL-53(Al). However, excessive Ca loading (samples − 3) reduced CO₂ uptake due to structural distortion and reduced surface area. Despite this, the highly Ca-modified samples (-3) exhibited superior CO₂/N₂ selectivity. These findings demonstrate that controlled Ca incorporation can tune the adsorption behaviour and separation efficiency of MIL-53-type MOFs, offering a promising pathway for designing high-performance adsorbents for CO₂ capture and CO₂/N₂ separation. Graphical Abstract

Synthesis of hydrophobic CuCl/LaA modified by butyltrichlorosilane towards enhanced CO adsorption under humid environment

Clay minerals are laminated structures with numerous chemically active sites and high surface area to volume ratio which favors CO2 adsorption and storage. However, CO2 adsorption contributes to mechanical degradation of clay minerals. Eventually, clay minerals become vulnerable regions for mechanical failure in clay-rich rocks, affecting both their storage and sealing efficiency. To ensure the long-term sealing performance of clay-rich rocks in CO2 geological storage, it is essential to quantify the level of rock mechanical due to CO2-clay interaction. Clay-rich rocks comprise various clay minerals, each exhibiting different degrees of mechanical degradation under CO2 adsorption. The CO2 adsorption capacity, swelling, and structural changes of clay minerals upon CO2 adsorption have been previously investigated. However, quantifying the impacts of clay type and fluid saturations on the mechanical properties of clay structures during CO2 adsorption remain inadequately understood. Therefore, this paper aims to quantify the impacts of (i) clay type, (ii) CO2 injection pressure, and (iii) water saturation on the mechanical properties of clay minerals upon CO2 adsorption. To achieve the outlined objectives, we construct layered clay structures of different types including illite, kaolinite, and sodium-montmorillonite. We solvate the structures with water at different hydration levels. Subsequently, we perform molecular dynamics (MD) simulations under the isothermal-isochoric (NVT) and the isothermal-isobaric (NPT) ensembles to equilibrate the clay structures. Afterwards, we perform Monte Carlo simulations under the Grand-Canonical ensemble to quantify the CO2 adsorption capacity of the hydrated structures. Moreover, we create synthetic cases with various water-CO2 volumetric saturations in contact with clay structures under reservoir conditions. Then, we equilibrate the fluid-saturated clay structures to swell as a result of fluid-clay interactions. We adopt the strain- controlled loading approach to plot the stress-strain profiles of the structures and quantify their mechanical properties. Throughout this process, we calculate the initial and the subsequent mechanical properties of the clay structures before and after fluid-interaction from the stress-strain curves. Results demonstrate that the mechanical properties of all three clay minerals decrease with increasing hydration level. The exposure of hydrated clay minerals to gaseous CO2 further degrades their mechanical properties. The increase in injection pressure induced a phase change to supercritical CO2 and a decrease in the rate of mechanical degradation of all clay structures. Water has a more pronounced impact on the elastic properties and strength of clay minerals than CO2. Consequently, higher water- to-CO2 volumetric saturation results in lower strength and Young's moduli and higher Poisson's ratios for all clay structures compared to cases with lower water-to- CO2 volumetric saturation. The outcomes of this work highlight the distinct mechanical behavior of each clay mineral under CO2 storage conditions. The molecular- scale investigation of CO2-adsorption-induced deformation on the elasticity of clay-rich rocks enables accurate prediction of the rock mechanical failure during CO2 sequestration. This, in turn, provides reliable quantification of the long-term sealing efficiency and optimal CO2 uptake capacity, helping to prevent mechanical failure.

Foam has been employed as an improved or enhanced oil recovery method to overcome gravity override and the channeling and fingering of the injected gas, which arises because of the low density and viscosity of the injected fluid combined with the rock heterogeneity. A major challenge, however, is the stability of the generated foam when it contacts the oil. In this study we investigate the feasibility of using inexpensive nanoparticles made of coal fly ash, an abundantly available waste product of coal power plants, as a foam booster. We investigate the viability of reducing the size of fly ash particles to 100–200 nm using high-frequency ultrasonic grinding. We also study the foaminess (foamability), strength, and stability of the foams made with minor concentrations of fly ash nanoparticles and surfactant, both in bulk and porous media. The effect of monovalent and divalent ion concentration on the foaminess of the nanoash suspension combined with very low concentrations of a commercial alpha olefin sul...

Pebax mixed matrix membrane with bimetallic CeZr-MOFs to enhance CO2 separation

A thermogravimetric study of the adsorption of CO 2 on zeolites synthesized from fly ash