CO2 Capture Capacity Research Articles

Self-Regenerative Ni-Doped CaTiO3/CaO for Integrated CO2 Capture and Dry Reforming of Methane.

In this work, a new type of multifunctional materials (MFMs) called self-regenerative Ni-doped CaTiO3/CaO is introduced for the integrated CO2 capture and dry reforming of methane (ICCDRM). These materials consist of a catalytically active Ni-doped CaTiO3 and a CO2 sorbent, CaO. The article proposes a concept where the Ni catalyst can be regenerated in situ, which is crucial for ICCDRM. Exsolved Ni nanoparticles are evenly distributed on the surface of CaTiO3 under H2 or CH4, and are re-dispersed back into the CaTiO3 lattice under CO2. The Ni-doped CaTiO3/CaO MFMs show stable CO2 capture capacity and syngas productivity for 30 cycles of ICCDRM. The presence of CaTiO3 between CaO grains prevents CaO/CaCO3 thermal sintering during carbonation and decarbonation. Moreover, the strong interaction of CaTiO3 with exsolved Ni mitigates severe accumulation of coke deposition. This concept can be useful for developing MFMs with improved properties that can advance integrated carbon capture and conversion.

Aiming at the valorization of CO2 through its capture by simply extruded high cell-density coal honeycombs

Integral coal honeycomb monoliths were easily prepared achieving the cell densities typical of commercial cordierites through extrusion plus physical activation. Different techniques such as volumetric adsorption, TGA, TPD and transient kinetic analysis were employed to study their interaction with CO2 at different temperatures (35–100 °C) and under both static and dynamic atmosphere. The CO2 capture capacity resulted to be 0.95 mmol/g at 35 °C, much higher than that of previously studied clay honeycomb adsorbents. The CO2 uptake exhibited fast second order kinetics, and a wide operative window for a highly efficient CO2 removal was found. Moreover, due to a weak interaction, most CO2 adsorbed could be released at 110 °C, what allows minimizing the costs related to controlled regeneration if ones wants to reuse the captured CO2 but at the same time prevents from desorption when this is undesirable. Treatment of the coal honeycomb monolith with a 1:1 CO2+CH4-containing stream revealed, through gas chromatography analysis, the conversion into syngas at relatively low temperatures (50% at 750 °C) in spite of the metal-free character of the monolith. Moreover, this activity reached 90% and remained quite stable for at least 12 h at 900 °C. These results demonstrate the potential of preparing honeycomb monoliths from coal as a strategy to diversify the uses of this abundant natural resource and as an alternative in the field of CO2 capture and valorization.

Solubility of carbon dioxide in Triton X-100 – Water – ethaline solvent mixtures at 298.15 K

Deep eutectic solvents (DESs) and liquid surfactants have been known as safe and low risk materials to prepare appropriate media for various physical and chemical processes. These compounds have demonstrated manifest properties while playing the solvent role. The solubility of carbon dioxide (CO2) were determined in aqueous solutions Triton X-100 at 298.15 K as a function of CO2 pressure. Also, ternary solvent mixtures including Triton X-100 as an additive in aqueous solutions of ethaline were evaluated for the capacity of CO2 capture. Triton X-100, DES, and water showed a three-component liquid–liquid equilibrium with a limited single-phase region. The determination of CO2 solubility in the single-phase region of ternary mixtures revealed that the Triton X-100 as an additive increases the solubility of CO2 in the aqueous solutions of ethaline. The effect of Triton X-100 on CO2 solubility in binary mixtures of ethaline and water appeared differently based on the concentration of Triton X-100.

Robust Enhancement of Direct Air Capture of CO2 Efficiency Using Micro-Sized Anion Exchange Resin Particles

In the quest to mitigate carbon dioxide emissions, it becomes essential to address the existing atmospheric CO2. Effective and economical methodologies, particularly those without additional energy consumption, are crucial. Currently, a leading method is the direct capture of CO2 using ion exchange resins, which achieve the adsorption and desorption of carbon dioxide simply by using the humidity variations. This technology, though minimizing additional energy cost, still needs improvement in its efficiency in CO2 capture capacity and compared to other methods. In this work, we develop low-cost techniques to reduce the AmberLite™ IRA900 Cl (IRA-900) anion exchange resin to micro size, and observe significant performance enhancement on CO2 capture efficiency contingent on reducing the particle diameters. This performance disparity is attributed to the differential water adsorption capacities inherent in particles of diverse diameters. Our results reveal that smaller resin particles outperform their larger counterparts, exhibiting accelerated adsorption rates and expedited transitions from wet to dry states. Notably, these smaller particles display a quintupled enhancement in adsorption efficacy relative to non-treated particles and a marked increase in relative adsorption capacity. Upon treatment, IRA-900 demonstrates robust CO2 processing efficiency, achieving a peak adsorption rate of 1.28 g/mol·h and a maximum desorption rate of 1.18 g/mol·h. Also, the material is subjected to almost 100 cycles of testing, and even after 100 cycles, the resin particles maintain a capacity of 100%. Moreover, our material can be fully regenerated to 100% efficiency by simply immersing it in water. Simultaneously, storing it in water allows for the long-term maintenance of its performance without other treatment methods. A key observation is the resin’s sustained performance stability post extended exposure to humid conditions. These outcomes offer substantial practical implications, emphasizing the relevance of our study in practical environmental applications.

Why does CaX zeolite have such a high CO2 capture capacity and how is it affected by water?

CO2 capture is important in solving one of the major current environmental problems, namely global warming. Among the different approaches, adsorption is considered the most promising and CaX zeolite is one of the materials with the highest capacity. However, the knowledge on the mechanism of its interaction with CO2 is still not complete which hinders further optimization. In this work we report the results of a combined study of CO2 adsorption on a CaX zeolite by in-situ FTIR spectroscopy, adsorption measurements and DFT calculations. It was found that at ambient temperature CO2 initially forms linear Ca2+−OCO species which, with increasing equilibrium pressure, are first converted to Ca2+(CO2)2 and then to Ca2+(CO2)3 species. This is the reason for the very high CO2 adsorption capacity of the material. Because of the practical importance, the effect of H2O on the processes was also studied. Water suppress CO2 adsorption but the effect is softened by the formation of mixed ligand Ca2+(CO2)x(H2O)y complexes (x + y = 2 or 3). In agreement with the spectroscopic results it was found that the adsorption capacity of the material increases with the rise of activation temperature up to 673 K due to dehydration. Its value, 22.2 wt% at 273 K and 490 mbar, is among the highest values reported in the literature at similar conditions.

Development of Monoethanolamine Chloride-Ethylene Diamine Deep Eutectic Solvent for Ffficient Carbon Dioxide Capture

Deep eutectic solvents (DES) emerge as a compelling class of ionic liquids, with distinct advantages over traditional solvents, particularly in the realm of CO2 capture. In the present study, [MEACl][EDA] is synthesized across various molar ratios (1:3 to 1:10) and combined with the results of Differential Scanning Calorimetry (DSC) to identify DESs. The DESs are further characterized using Fourier Transform Infrared Spectroscopy (FTIR), and the properties and performance of the DESs with diverse water contents (30–60 wt%) are systematically studied for CO2 capture. The optimal aqueous solution is identified based on the CO2 uptake and viscosity, followed by the evaluation of the cyclic absorption experiments. Results demonstrate that 40 wt% of [MEACl][EDA] DES with (1:5) molar ratio exhibits higher CO2 uptake (22.09 wt%) and comparable viscosity (4.401 mPa·s before and 13.330 mPa·s after CO2 capture at 25 °C) compared to aqueous 40 wt% MEA (15.74 wt% CO2 capture capacity, viscosity of 3.318 mPa·s before and 8.413 mPa·s after CO2 capture), and its absorption rate is also more favorable than the aqueous MEA. Furthermore, recycling studies reveal ∼ 88 % regeneration of the aqueous DES solution at 100 °C.

Revealing the effect of synthetic method on integrated CO2 capture and conversion performance of Ni-Na2ZrO3 bifunctional materials

Integrated CO2 capture and utilization by reverse water gas shift (ICCU-RWGS) reaction for syngas production for C1 chemical industry has gained increasing attention. Designing highly active bifunctional materials that enables CO2 adsorption and in-situ conversion is essential. In this work, Ni-Na2ZrO3 bifunctional materials are prepared by different synthetic methods for ICCU-RWGS. N2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO2 temperature-programmed desorption (CO2-TPD) and H2 temperature-programmed reduction (H2-TPR) analysis reveals that Ni-Na2ZrO3-CP prepared by the co-precipitation (CP) method shows small Ni crystalline size, moderate surface basicity, and excellent reducibility. ICCU-RWGS performance is investigated under isothermal conditions of 650 °C, 10 %CO2 and 35 %H2. The results indicate that Ni-Na2ZrO3-CP demonstrates excellent performance in ICCU-RWGS, with a notable CO2 capture capacity of 3.76 mmol CO2/g and a CO production rate of 3.10 mmol CO/g. Additionally, it exhibits relatively good operational stability. Detailed reaction paths of the ICCU-RWGS procedure for the Ni-Na2ZrO3 bifunctional materials are proposed. The findings will shed new perspectives on the design of synthetic bifunctional catalysts for ICCU-RWGS.

Popping and Locking: Balanced Rigidity and Porosity of Zeolitic Imidazolate Frameworks for High-Productivity Methane Purification.

Zeolitic imidazolate frameworks (ZIFs) hold great promise in carbon capture, owing to their structural designability and functional porosity. However, intrinsic linker dynamics limit their pressure-swing adsorption application to biogas upgrading and methane purification. Recently, a functionality-locking strategy has shown feasibility in suppressing such dynamics. Still, a trade-off between structural rigidity and uptake capacity remains a key challenge for optimizing their high-pressure CO2/CH4 separation performance. Here, we report a sequential structural locking (SSL) strategy for enhancing the CO2 capture capacity and CH4 purification productivity in dynamic ZIFs (dynaZIFs). Specifically, we isolated multiple functionality-locked phases, ZIF-78-lt, -ht1, and -ht2, by activation at 50, 160, and 210 °C, respectively. We observed multiple-level locking through gas adsorption and powder X-ray diffraction. We uncovered an SSL mechanism dominated by linker-linker π-π interactions that transit to C-H···O hydrogen bonds with binding energies increasing from -0.64 to -2.77 and -5.72 kcal mol-1, respectively, as evidenced by single-crystal X-ray diffraction and density functional theory calculations. Among them, ZIF-78-ht1 exhibits the highest CO2 capture capacity (up to 18.6 mmol g-1) and CH4 purification productivity (up to 7.6 mmol g-1) at 298 K and 30 bar. These findings provide molecular and energetic insights into leveraging framework flexibility through the SSL mechanism to optimize porous materials' separation performance.

The co-promoting mechanism of EMEA/DEEA/PZ ternary water-lean solvent on CO2 capture- a study based on 13C-qNMR and DFT calculations

Amine based CO2 absorption is currently the most promising means of capturing CO2 in industry, and the water-lean amine solvent has received widespread attentions. The reaction mechanism of the EMEA/DEEA/PZ ternary water-lean amine solvent (WLS) during the process of CO2 capture was investigated theoretically to understand the synergistic effect between the different amine components. The concentrations of intermediate products were analyzed by 13C-qNMR (quantitative Nuclear Magnetic Resonance) spectroscopy, while the reaction mechanisms were calculated using gaussian 16. The NMR results showed that carbamate (EMEACOO-), HCO3–/CO32– were the main products in the carbon capture process of EMEA WLS. The protonated amine concentration varies according to the change of carbon dioxide concentration. The balance between deprotonation (forming carbamates) and CO2 removal (regenerating EMEA) depends largely on how ampholytes interact with nearby water molecules. The DFT result showed that EMEA is the key component of CO2 capture, while DEEA and PZ primarily assist in transferring protons, catalyzing the conversion of H2CO3 into HCO3– to accelerate the process of CO2 capture. Furthermore, they assist in the redaction of EMEAH+ to EMEA, allowing it continue to participate in capture reactions. DEEA, PZ and water could promote activating the protonated EMEA and enhanced its capacity of CO2 capture. Furthermore, the desorption process confirmed the proton transfer from DEEAH+, ultimately leading to the regeneration of EMEA, thereby demonstrating the effective performance of regeneration.

Nitrogen fixation‐driven carbon sequestration: Brief communication

AbstractPrior to the commercial nitrogen fertilizer production in 1919, all the world's terrestrial and aquatic carbon was supported by nitrogen fixation. Annual N deposition to semi‐arid lands and temperate forests is less than 5 kg/ha‐year and 10 kg/ha, respectively. Plant and soil C/N ratios range from 9.9 to 29.8 and 9 to 14, respectively. In an equilibrium, sustainable ecosystem where N is not removed from soil pools and is only dependent on annual N inputs, maximum C sequestration rates are approximately 3.25 kg to 46 kg/ha for arid ecosystems and 23 to 101 kg/ha for forest ecosystems. Commercial N applications range from approximately 70 to 160 kg/ha‐year. Managed nitrogen fixation rates range from approximately 50 to 130 kg N/ha‐year. For each additional kg N‐entering forests, the additional C is approximately 13 kg. N‐fixing plants range from alder and lupines in the arctic, to Prosopis and Acacias in semi‐arid lands and the large trees Inga and Pentaclethra in tropical rainforests. If N‐fixing plants achieving 50 kg N/ha‐year were planted on the equivalent of a 447 km square, on six continents, the IEA target of 1.7Gt CO2 (0.72 Gt of carbon) capture capacity by 2030 https://www.ief.org/news/whats‐the‐target‐for‐carbon‐sequestration‐and‐how‐do‐we‐get‐there could be achieved.

Experimental testing and mechanism investigation of amine-functionalized layered vermiculite for CO2 capture

Solid amine adsorbents have attracted significant attention due to their low energy consumption, high selectivity, and environmental friendliness, positioning them as the most promising technology for CO2 capture. However, current adsorbent carrier materials commonly encounter challenges such as expensive costs and inadequate stability. In this study, acid-activated expanded vermiculite carrier (AEV) with a large pore volume and hierarchical pore structure was prepared. Subsequently, a series of functionalized polyethyleneimine (PEI) adsorbents were synthesized and employed in CO2 capture experiments to investigate the impact of PEI loading and temperature on adsorption characteristics. The results showed that the acid-modified expanded vermiculite with a large pore volume structure significantly increased amine loading, while the layered structure network promoted amine dispersion. Under the conditions of 50 wt% PEI loading, the CO2 capture capacity of AEV reached 3.29 mmol/L at 75 ℃. Furthermore, density functional theory was utilized to calculate the adsorption energy and Gibbs free energy change of CO2 and polyethyleneimine molecules. The HOMO and LUMO distributions of CO2 molecules with different polyethyleneimine chains were determined using frontier orbital theory, combined with infrared spectroscopy results confirming the conversion of CO2 into carbamate. Additionally, AEV-PEI50 adsorbent exhibited good stability during 8 cycles of the adsorption process. The obtained results demonstrate that the utilization of layered mesoporous scaffolds offers notable benefits in terms of efficient CO2 capture.

Process Operability Analysis of Membrane-Based Direct Air Capture for Low-Purity CO2 Production.

Addressing climate change constitutes one of the major scientific challenges of this century, and it is widely acknowledged that anthropogenic CO2 emissions largely contribute to this issue. To achieve the "net-zero" target and keep the rise in global average temperature below 1.5 °C, negative emission technologies must be developed and deployed at a large scale. This study investigates the feasibility of using membranes as direct air capture (DAC) technology to extract CO2 from atmospheric air to produce low-purity CO2. In this work, a two-stage hollow fiber membrane module process is designed and modeled using the AVEVA Process Simulation platform to produce a low-purity (≈5%) CO2 permeate stream. Such low-purity CO2 streams could have several possible applications such as algae growth, catalytic oxidation, and enhanced oil recovery. An operability analysis is performed by mapping a feasible range of input parameters, which include membrane surface area and membrane performance metrics, to an output set, which consists of CO2 purity, recovery, and net energy consumption. The base case for this simulation study is generated considering a facilitated transport membrane with high CO2/N2 separation performance (CO2 permeance = 2100 GPU and CO2/N2 selectivity = 1100), when tested under DAC conditions. With a constant membrane area, both membranes' intrinsic performances are found to have a considerable impact on the purity, recovery, and energy consumption. The area of the first module plays a dominant role in determining the recovery, purity, and energy demands, and in fact, increasing the area of the second membrane has a negative impact on the overall energy consumption, without improving the overall purities. The CO2 capture capacity of DAC units is important for implementation and scale-up. In this context, the performed analysis showed that the m-DAC process could be appropriate as a small-capacity system (0.1-1 Mt/year of air), with reasonable recoveries and overall purity. Finally, a preliminary CO2 emissions analysis is carried out for the membrane-based DAC process, which leads to the conclusion that the overall energy grid must be powered by renewable sources for the technology to qualify within the negative emissions category.

Development of an amine-impregnated polymer aerogel for CO2 capture

The synthesis and characterization of amine-impregnated polymer aerogels for CO2 capture represents a groundbreaking advancement in combating the urgent challenges of carbon dioxide (CO2) emissions and climate change mitigation. The traditional way of synthesizing aerogels for CO2 capture is to use a one-step gelation process without functionalizing the aerogel, which, to some extent, has low CO2 capture capacity and kinetics. This study finds a method of synthesizing the functionalized aerogel, which has high CO2 adsorption capacity, faster kinetic, and is more stable. The polymer aerogel was developed using an oil-water emulsion polymerization method, followed by freeze-drying. It was impregnated with a mono-ethanolamine (MEA) solution to enhance CO2 adsorption. The performance of the amine-impregnated poly (AAm-co-AAc) aerogels was tested in a continuous adsorption column filled with aerogel. The adsorption results showed the amine-impregnated aerogels having an amine equilibrium uptake value of 40% had significantly improved CO2 capture capacity up to 2.34 mmole g−1 at 1 bar pressure, 25 °C reaction temperature, and 10 ml/min flow rate. The polymeric aerogel has a very fast adsorption rate, as it can capture 90% of its maximum capacity within just 10 minutes. Then the kinetic data of the CO2 adsorption was modelled and found to best fit on both pseudo-1st and 2nd-order kinetic models, proposing that the adsorption mechanism on aerogel was controlled by surface diffusion and chemisorption. Furthermore, the isotherm data were evaluated and observed to be best represented by the Langmuir isotherm model, suggesting monolayer formation on the aerogel. After five adsorption-desorption cycles, the amine impregnated poly (AAm-co-AAc) aerogel was able to preserve the initial capacity without a significant decrease. These findings underscore the immense ability of amine-impregnated poly (AAm-co-AAc) aerogels as highly efficient adsorbents for CO2 capture, thus offering a speedy adsorption process and showing stable regeneration capacity, thereby exhibiting greater industrial application potential.

Co-grafting of polyethyleneimine on facilely synthesized mesoporous P(DVB-D) for highly effective CO2 adsorption and enhanced oxidation resistance

Solid amine adsorbents are showing promise as effective adsorbents for the capture of CO2 from various gas mixtures, including biogas and flue exhaust gas. In this study, we introduced a co-grafting strategy using 1,4-butanediol diglycidyl ether (BDDE) on the surface of P(DVB-D). This approach aimed to exploit the reaction involving the opening of epoxy groups with amine groups, forming covalent bonds between polyethyleneimine (PEI) and mesoporous organic polymers, along with the introduction of hydroxy groups to enhance adsorbent long-term stability and antioxidation ability. After an extensive assessment, P(DVB-D)@B-41.2 %PEI exhibited a maximum CO2 capture capacity of 4.53 mmol/g at 50 °C and 50 % RH. Notably, its remarkable CO2 adsorption performance persisted across a diverse temperature spectrum (30–90 °C) and an extensive concentration span (5–30 % vol.). In contrast to conventional adsorbents prepared solely through impregnation methods, P(DVB-D)@B-41.2 %PEI exhibited impressive long-term stability throughout 50 successive cycles and excellent resistance to oxidative degradation. These findings underscore the considerable potential of P(DVB-D)@B-41.2 %PEI in the realm of carbon capture and sequestration (CCS) technology.

Investigating the behavior of six limestones in presence of steam in dual interconnected fluidized beds, under operating conditions relevant for sorption-enhanced gasification

This paper presents results on the behavior, in terms of CO2 capture capacity and attrition/fragmentation tendency, for six limestones processed in a dual interconnected fluidized beds system under operating conditions simulating those of sorption-enhanced gasification in presence of water vapor. Ten calcination/carbonation cycles have been carried out for each sorbent; in particular, carbonation has been carried out at two temperature levels (650 °C and 700 °C), with a CO2 and H2O inlet concentration of 10% for both gases. Degree of CaO carbonation (with related modelling) along the cycles, and particle size distribution at the end of the cycles, have been analyzed and discussed, together with results coming from ex situ impact fragmentation tests carried out in a specifically devoted apparatus. The discussion has been extended to particular cases in which the system was operated in the absence of steam, to analyze the role of this species on the sorbent behavior.

Characteristics of cold-adapted carbonic anhydrase and efficient carbon dioxide capture based on cell surface display technology

Carbonic anhydrase (CA) is currently under investigation because of its potential to capture CO2. A novel N-domain of ice nucleoproteins (INPN)-mediated surface display technique was developed to produce CA with low-temperature capture CO2 based on the mining and characterization of Colwellia sp. CA (CsCA) with cold-adapted enzyme structural features and catalytic properties. CsCA and INPN were effectively integrated into the outer membrane of the cell as fusion proteins. Throughout the display process, the integrity of the membrane of engineered bacteria BL21/INPN-CsCA was maintained. Notably, the study affirmed positive applicability, wherein 94 % activity persisted after 5 d at 15 °C, and 73 % of the activity was regained after 5 cycles of CO2 capture. BL21/INPN-CsCA displayed a high CO2 capture capacity of 52 mg of CaCO3/mg of whole-cell biocatalysts during CO2 mineralization at 25 °C. Therefore, the CsCA functional cell surface display technology could contribute significantly to environmentally friendly CO2 capture.

Nanoarchitectured composite of polysulfone and carbon-based fillers bearing magnetically stimulable function for efficient CO2 capture

Mitigating the global warming caused by CO2 emissions from anthropogenic sources is a hot research topic in the current era. The high cost and difficulty in handling liquid solvent absorbents for CO2 capture are the main barriers to their industrial application. Earth-abundant solid sorbents are favorable candidates for CO2 separation, offering a low energy penalty for CO2 desorption. Here, Polysulfone (PSF) nanocomposites were prepared by simple solution blending. The carbon-based fillers, namely carbon nanotubes (CNT), and activated carbon (CA) in the range of 5–20 wt%, containing iron nanoparticles, were used as fillers. Their morphological, thermal, CO2 capture capacity and magnetic properties were comprehensively studied. Transmission electron microscopy (TEM) evidenced uniform filler distribution in the polymer matrix with sizes of 47–54 nm. Thermal analysis revealed an approximately 4 °C improvement in both the initial (Tonset) and maximum (Tmax) degradation temperatures by adding 5 wt% of nanoparticles compared to the pristine polymer. The glass transition temperature (Tg) of the pristine PSF and produced nanocomposites showed identical values as estimated by differential scanning calorimetry (DSC). The increase in filler amount gradually decreased the water contact angle values, indicating a hydrophilic classification of the PSF nanocomposites. The obtained PSF nanocomposites exhibited an efficient CO2 capture capacity of about 40–61 mgCO2/g at 45 °C, higher than pristine PSF. This remarkable achievement sets a new benchmark compared to previously developed systems. The introduction of the filler transforms the diamagnetic polymer matrix into a ferromagnet, presenting a coercivity of about 480 Oe, enhancing the material's potential for applications in microelectronics.

Evaluating regeneration performance of amine functionalized solid sorbents for direct air CO2 capture using microwave

The urgent challenge of climate change, primarily driven by global warming and carbon dioxide (CO2) emission, necessitates innovative solutions for carbon capture. CO2 capture by liquid amine has many drawbacks. These processes require significant energy to regenerate the solvents, releasing the captured CO2 for storage or utilization, which leads to increased operational costs and can diminish the overall efficiency of carbon capture systems. Recent research explores new promising techniques by CO2 capture using highly efficient solid sorbents. This study then focuses on enhancing a porous alumina material with potassium carbonate (K2CO3) and monoethanolamine (MEA) to optimize CO2 capture capacity and regeneration performance. The developed sorbent was conducted in a fluidized bed reactor, showcasing its effectiveness in capturing CO2 from air. This adsorbent can be reused by applying with microwave radiation for sorbent regeneration, a cutting-edge approach that allows precise temperature control and reduces regeneration time. The electrical microwave power, regeneration time and %closing regeneration time were study variables in sorbent regeneration process. By harnessing microwave, this method not only improves efficiency but also enhances the sorbent's reusability. This innovative technique presents a significant step forward in advancing cost-effective and energy-efficient CO2 capture technologies, crucial for mitigating the impact of climate change.

Experimental study on eco-friendly one-part alkali-activated slag-fly ash-lime composites under CO2 environment: Reaction mechanism and carbon capture capacity

This work studied the reaction mechanism and carbon capture capacity of novel type eco-friendly one-part alkali-activated slag-fly ash-lime composites (SFL) based on the change in SFL under CO2 environment from the macroscale to the microscale. Experimental results showed that SFL had a higher carbonation rate and led to the formation of carbonates (calcite, vaterite, aragonite), gypsum, amorphous calcium carbonate, and alumino-silicate gel. The carbonation reaction of SFL can be generally divided into three periods. In period 3, Al from the decomposed aluminum-bearing hydrates was gradually incorporated into the amorphous silica phase in the form of tetrahedral Al(-SiO)4 sites, which finally resulted in the formation of an alumino-silicate gel. The mass ratio of carbon capture in the complete carbonation zone of SFL is approximately 13%. Due to a large amount of CO2 binding in hydrates in a wider carbonation zone, the actual total capacity of carbon capture in SFL under CO2 environment was slightly lower than that in Portland cement. Thus, SFL had a better and adjustable capacity for CO2 capture compared to other low carbon binder materials.

Experimental kinetics and thermodynamics investigation: Chemically activated carbon-enriched monolithic reduced graphene oxide for efficient CO2 capture

In this research, we have developed solid MGOs by self-assembled reduction process of GO at 90 °C with different weight ratios of oxalic acid (1:1, 1:0.500, and 1:0.250). The as-synthesized monoliths were carbonized (at 600 °C) and chemically activated with varying proportions of NaOH (1:1, 1:2, and 1:3). This materials offer the CO2 adsorption effect under dynamic conditions, fast mass transfer, easy handling, and outstanding stability throughout the adsorption-desorption cycle. FE-SEM, and HR-TEM analyses confirmed the porous nature and shape of the adsorbents, while XPS examination revealed the presence of distinct functional groups on the surface of the monolith. By increasing the mass ratios (MGO:NaOH) from 1:1 to 1:2, the surface areas increased by approximately 2.6 times, ranging from 520.8 to 753.9 m2 g⁻1 (surface area of the untreated MGO was 289.2 m2 g⁻1). Consequently, this resulted in a notable enhancement of 2.10 mmol g⁻1 in dynamic CO2 capture capacity. The assessment encompassed the evaluation of production yield, selectivity, regenerability, kinetics, equilibrium isotherm, and isosteric temperatures of adsorption (Qst). The decrease in CO2 capture effectiveness with rising adsorption temperature indicated an exothermic and physisorption process. The regenerability of 99.1 % at 100 °C and excellent cyclic stability with efficient CO2 adsorption make this monolithic adsorbent appropriate for post-combustion CO2 capture. The significant Qst lend support to the heterogeneity of the adsorbent's surface, and the pseudo-second-order kinetic model along with the Freundlich isotherm model emerged as the most fitting. Therefore, the current investigation shows that the carbon-enriched adsorbents enhance the CO2 adsorption capacity. It may be used as a low-cost pretreatment method on an industrial scale before carbon capture.