Activated carbon nanofibers incorporated metal oxides for CO2 adsorption: Effects of different type of metal oxides

Experimental, RSM modelling, and DFT simulation of CO2 adsorption on Modified activated carbon with LiOH

This research investigates the enhancement of CO2 adsorption capacity through the use of modified activated carbon (AC) with LiOH, focusing on operational conditions and adsorbent properties. Response Surface Methodology (RSM) is employed to optimize process parameters for maximizing CO2 adsorption capacity. The study considers temperature, pressure, LiOH concentration for modification, and adsorbent weight as independent variables across five levels. Analysis of Variance reveals that LiOH concentration, adsorbent quantity, pressure, and temperature significantly influence CO2 adsorption. Optimal values for temperature (30°C), pressure (9 bar), LiOH concentration (0.5 mol/L), and adsorbent weight (0.5 g) result in a maximal CO2 adsorption capacity of 154.90 mg/g. Equilibrium adsorption capacity is utilized for modeling, with the Freundlich model proving suitable for CO2 adsorption on LiOH-AC. Kinetic modeling indicates the second-order model's suitability for temperatures of 30 °C and 50 °C, while the Elovich model fits temperatures of 70 °C and 90 °C. Thermodynamic modeling at the optimized conditions (303 K and 6 bar) yields ∆H, ∆S, and ∆G values of adsorption as 12.258 kJ/mol, - 0.017 kJ/mol·K, and - 7.031 kJ/mol, respectively. Furthermore, structural considerations of AC are discussed alongside modeling and simulation, presenting the adsorption rate of CO2 and the binding energy index based on Density Functional Theory (DFT).

The Impact of N/O-Functional Groups on the Sorption Capabilities of Activated Carbons Derived from Furfuryl Alcohol

This work describes the effect of nitrogen and oxygen functional groups on the sorption properties of activated carbons produced from furfuryl alcohol. The poly(furfuryl) alcohol underwent carbonization in nitrogen, ammonia, and ammonia and air (in a 3:2 proportion) atmospheres at 600 °C for 4 h. The resulting materials were subsequently activated in a carbon dioxide atmosphere for 1 h at temperatures of 700 °C, 800 °C, 900 °C, and 1000 °C. The X-ray photoelectron spectroscopy (XPS) findings suggest that ammoxidation is superior to amination in terms of nitrogen doping. The maximum nitrogen concentration achieved after ammoxidation was 25 at.%, which decreased to 4 at.% after activation. Additionally, it was observed that oxygen functional groups have a greater impact on porous structure development compared to nitrogen functional groups. The materials activated through carbonization under an ammonia/air atmosphere attained the highest oxygen concentration of roughly 19 at.% as confirmed by XPS. The materials were evaluated for their sorption capacities for carbon dioxide and ethylene, which were 2.2 mmol/g and 2.9 mmol/g, respectively, at 30 °C.

Progress in advanced electrospun membranes for CO2 capture: Feedstock, design, and trend

The emission of large amounts of carbon dioxide has caused serious environmental problems and hindered the construction of a green and low-carbon society. Efficient carbon dioxide capture has become an important means to slow down global climate warming and achieve effective utilization of carbon dioxide. Membranes synthesized by electrospinning technology are becoming promising carbon capture materials due to their unique characteristics. This review describes the features of membranes prepared from available raw materials and presents their application performances in carbon capture. The preparation methods of various types of membrane materials with excellent capture performance are summarized, and the effects of electrospinning parameters on electrospun fibers are systematically analyzed. Furthermore, recommendations and expectations for further development of electrospun membranes for carbon capture applications are given. These works provide important references for an in-depth understanding of the development status of electrospun membranes in the field of carbon capture and for expanding future research.

Natural Products Derived Porous Carbons for CO2 Capture

As it is now established that global warming and climate change are a reality, international investments are pouring in and rightfully so for climate change mitigation. Carbon capture and separation (CCS) is therefore gaining paramount importance as it is considered one of the powerful solutions for global warming. Sorption on porous materials is a promising alternative to traditional carbon dioxide (CO2 ) capture technologies. Owing to their sustainable availability, economic viability, and important recyclability, natural products-derived porous carbons have emerged as favorable and competitive materials for CO2 sorption. Furthermore, the fabrication of high-quality value-added functional porous carbon-based materials using renewable precursors and waste materials is an environmentally friendly approach. This review provides crucial insights and analyses to enhance the understanding of the application of porous carbons in CO2 capture. Various methods for the synthesis of porous carbon, their structural characterization, and parameters that influence their sorption properties are discussed. The review also delves into the utilization of molecular dynamics (MD), Monte Carlo (MC), density functional theory (DFT), and machine learning techniques for simulating adsorption and validating experimental results. Lastly, the review provides future outlook and research directions for progressing the use of natural products-derived porous carbons for CO2 capture.

Functionalized nanofibers in gas sorption process: a critical review on the challenges and prospective research

Air pollution has become the most important environmental and human health threat as it is accounting for about 7 million deaths across the globe every year. Particulate matter (PM) derived from the combustion of fossil fuels, biomass, and other agricultural residues pollutes the atmospheric air which affects the quality of the environment and poses a great threat to human health. Ecological imbalance, climatic variation, and cardiovascular and respiratory problems among humans are significant extortions due to PM pollution. Scientific approaches were initiated to limit the levels of PM in the atmospheric air and the use of nanofiber mats has received wide attention as these possess versatile properties including nanoscale-sized pore structure, homogeneity in their size distribution with high specific surface area, and low basis weight. To exploit their filtration potential towards wide classes of pollutants and also to enhance the capturing efficacy, functionalized nanofibers are currently in practice with tailor-made modifications on the surface. The present review provides a comprehensive report on the different fabrication processes of functionalized nanofibers along with the controlling factors affecting the efficacy of the gas separation process. Also, it provides technical insights on the mass transfer aspects of PM filtration by elucidation their mechanism which can provide vital information on the rate-controlling diffusive flux(es). Conclusively, the practical challenges encountered in the large-scale air filtration systems such as filter cleaning, flow-rate regulation, pressure drop, and extent of reusability are discussed, and the review has identified potential gaps in the current research and can be considered for the prospective research in the area of PM separation process.

Novel Core/Shell Nylon 6,6/La-TMA MOF Electrospun Nanocomposite Membrane and CO2 Capture Assessments of the Membrane and Pure La-TMA MOF

Membrane technology plays a vital, applicable, and essential role in human life and industry. The high adsorption capacity of membranes can be employed for capturing air pollutants and greenhouse gases. In this work, we tried to develop a shaped industrial form of a metal-organic framework as an adsorbent material with the ability to capture CO₂ in the laboratory phase. To do so, a core/shell Nylon 6,6/La-TMA MOF nanofiber composite membrane was synthesized. This organic/inorganic nanomembrane is a kind of nonwoven electrospun fiber that was prepared using the coaxial electrospinning approach. FE-SEM, surface area calculations, nitrogen adsorption/desorption, XRD grazing incidence on thin films, and histogram diagrams were applied to assess the quality of the membrane. This composite membrane as well as pure La-TMA MOF were assessed as CO₂ adsorbent materials. The CO₂ adsorption abilities of the core/shell Nylon 6,6/La-TMA MOF membrane and pure La-TMA MOF were as high as 0.219 and 0.277 mmol/g, respectively. As a result of preparing the nanocomposite membrane from microtubes of La-TMA MOF, the %A of the micro La-TMA MOF (% 43.060) increased to % 48.524 for Nylon 6,6/La-TMA MOF.

Innovative metal oxides (CaO, SrO, MgO) impregnated waste-derived activated carbon for biohydrogen purification

In this work, a series of innovative metal oxide impregnated waste-derived activated carbons (MO/AC) was synthesized and used to purify the simulated biohydrogen based on the concept of CO₂ removal from the gas stream. Effects of metal oxide types (CaO, SrO and MgO) and contents of the best metal oxides on the morphology and the CO₂ adsorption capacity from the biohydrogen were investigated. It was found that both metal oxide types and contents played an important role on the adsorbent textural property and surface chemistry as well as the CO₂ adsorption capacity. Among all synthesized adsorbent, the MgO-impregnated AC with 12 wt.% MgO (12MgO/AC) exhibited the highest CO₂ adsorption capacity of around 94.02 mg/g. With this successive adsorbent, the biohydrogen with the H₂ purity higher than 90 mol% can be achieved from the gas stream with 50 mol% CO₂ for the first 2 min of adsorption period in a fixed bed reactor. The mechanism of CO₂ adsorption occurred via a combined process of the physisorption and chemisorption. Besides, the 12MgO/AC exhibited a high recyclability after several repetitive adsorption/desorption cycles.

Effect of Pore Structure on CO2 Adsorption Performance for ZnCl2/FeCl3/H2O(g) Co-Activated Walnut Shell-Based Biochar

Walnut shell is a very potential biochar precursor because of its wide source, low cost, and easy structure modification. In this paper, the co-activation method of FeCl3, ZnCl2 and H2O(g) was adopted to prepare walnut shell-based biochar with high microporosity and the effect of pore structure on CO2 adsorption performance at different temperatures was investigated. The prepared biochar had a larger specific surface area (2647.8 m2 g−1), satisfactory micropore area (2008.7 m2 g−1) and high total pore volume (2.58 cm3 g−1). At 273 K and 298 K, its CO2 adsorption capacity was 4.79 mmol g−1 and 3.20 mmol g−1, respectively. Particularly, CO2 adsorbed uptake on biochar was strongly sensitive to their narrow micropore volume, instead of the total specific surface area, total pore volume, and micropore specific surface area. The optimal pore size beneficial for CO2 adsorption was 0.33–0.82 nm at 273 K, but the optimal pore size was 0.33–0.39 nm at 298 K. It provides theoretical guidance for future material preparation and selection, and FeCl3, ZnCl2 and H2O(g) may be effective biochar activators.

Valorization of spent disposable wooden chopstick as the CO2 adsorbent for a CO2/H2 mixed gas purification

A series of activated carbons (ACs) derived from spent disposable wooden chopsticks was prepared via steam activation and used to separate carbon dioxide (CO₂) from a CO₂/hydrogen (H₂) mixed gas at atmospheric pressure. A factorial design was employed to investigate the effects of the activation temperature and time as well as their interactions on the production yield of ACs and their CO₂ adsorption capacity. The activation temperature exhibited a much higher impact on both the production yield and the CO₂ adsorption capacity of ACs than the activation time. The interaction of both parameters did not significantly affect the yield of ACs, but did affect the CO₂ adsorption capacity. The optimal preparation condition provided ACs with a desirable yield of around 23.18% and a CO₂ adsorption capacity of 85.19 mg/g at 25 °C and 1 atm and consumed the total energy of 225.28 MJ/kg AC or 116.4 MJ/g-mol CO₂. A H₂ purity of greater than 96.8 mol% was achieved from a mixed gas with low CO₂ concentration (< 20 mol%) during the first 3 min of adsorption and likewise around 90 mol% from a mixed gas with a high CO₂ concentration (> 30 mol%) during the first 2 min. The CO₂ adsorption on the as-prepared ACs proceeded dominantly via multilayer physical adsorption and was affected by both the surface area and micropore volume of the ACs. The adsorption capacity was diminished by around 18% after six adsorption/desorption cycles. The regeneration of the as-prepared chopstick-derived ACs can be easily performed via heating at a low temperature and ambient pressure, suggesting their potential application in the temperature swing adsorption process.

Metal Oxides as Catalyst/Supporter for CO2 Capture and Conversion, Review

Various carbon dioxide (CO2) capture materials and processes have been developed in recent years. The absorption-based capturing process is the most significant among other processes, which is widely recognized because of its effectiveness. CO2 can be used as a feedstock for the production of valuable chemicals, which will assist in alleviating the issues caused by excessive CO2 levels in the atmosphere. However, the interaction of carbon dioxide with other substances is laborious because carbon dioxide is dynamically relatively stable. Therefore, there is a need to develop types of catalysts that can break the bond in CO2 and thus be used as feedstock to produce materials of economic value. Metal oxide-based processes that convert carbon dioxide into other compounds have recently attracted attention. Metal oxides play a pivotal role in CO2 hydrogenation, as they provide additional advantages, such as selectivity and energy efficiency. This review provides an overview of the types of metal oxides and their use for carbon dioxide adsorption and conversion applications, allowing researchers to take advantage of this information in order to develop new catalysts or methods for preparing catalysts to obtain materials of economic value.

CO2 Sequestration through Mineral Carbonation: Effect of Different Parameters on Carbonation of Fe-Rich Mine Waste Materials

Mineral carbonation is an increasingly popular method for carbon capture and storage that resembles the natural weathering process of alkaline-earth oxides for carbon dioxide removal into stable carbonates. This study aims to evaluate the potential of reusing Fe-rich mine waste for carbon sequestration by assessing the influence of pH condition, particle size fraction and reaction temperature on the carbonation reaction. A carbonation experiment was performed in a stainless steel reactor at ambient pressure and at a low temperature. The results indicated that the alkaline pH of waste samples was suitable for undergoing the carbonation process. Mineralogical analysis confirmed the presence of essential minerals for carbonation, i.e., magnetite, wollastonite, anorthite and diopside. The chemical composition exhibited the presence of iron and calcium oxides (39.58–62.95%) in wastes, indicating high possibilities for carbon sequestration. Analysis of the carbon uptake capacity revealed that at alkaline pH (8–12), 81.7–87.6 g CO2/kg of waste were sequestered. Furthermore, a particle size of <38 µm resulted in 83.8 g CO2/kg being sequestered from Fe-rich waste, suggesting that smaller particle sizes highly favor the carbonation process. Moreover, 56.1 g CO2/kg of uptake capacity was achieved under a low reaction temperature of 80 °C. These findings have demonstrated that Fe-rich mine waste has a high potential to be utilized as feedstock for mineral carbonation. Therefore, Fe-rich mine waste can be regarded as a valuable resource for carbon sinking while producing a value-added carbonate product. This is in line with the sustainable development goals regarding combating global climate change through a sustainable low-carbon industry and economy that can accelerate the reduction of carbon dioxide emissions.

Porous Carbon Nanofibers with Heteroatoms Doped by Electrospinning Exhibit Excellent Acetone and Carbon Dioxide Adsorption Performance: The Contributions of Pore Structure and Functional Groups

Rich chemical properties and a well-developed pore structure are the key factors of porous materials for gas storage. Herein, rich heteroatom-doped porous carbon nanofibers (U₁K₂-X) with a large surface area were prepared by electrospinning followed by potassium hydroxide (KOH) activation. Low-cost urea was chosen as the nitrogen source and structural guiding agent. U₁K₂-X have a high specific surface area (628-2688 m² g^-1), excellent pore volume (0.468-1.571 cm³ g^-1), and abundant nitrogen (2.5-12.8 atom %) and oxygen (4.5-12.5 atom %) contents. Acetone and carbon dioxide were used as target adsorbents to evaluate the adsorption properties of U₁K₂-X by experiments. These U₁K₂-X exhibit excellent adsorption performance (260.03-955.74 mg g^-1, 25 °C, 18 kPa) and multilayer adsorption (the adsorption layer number n > 2) for acetone, which is mainly attributed to the large specific surface area and pore volume. Besides this, the carbon dioxide uptake reached 2.73-3.34 mmol g^-1 at 25 °C. This was attributed to the combination of high nitrogen-oxygen contents and microporous structure. Furthermore, U₁K₂-X show the desirable repeatability. This study provides a new direction for the preparation of heteroatom-doped porous carbon nanofibers, which will be a promising material for gas adsorption.

Synthesis, characterization, CO2 mineralization in air, and thermal decomposition of nano- C8H10MgO10·4H2O powder

Effective solutions for efficient carbon dioxide (CO₂) capture in air at room temperature are in high demand due to the major impacts CO₂ has on global climatic changes. Solid adsorbents materials for CO₂ capture received great attention over the past years, among them, magnesium-based sorbents have been identified as a promising solution for CO₂ capture at intermediate temperatures. This study reports for the first time (1) the synthesis of monoclinic magnesium malate tetrahydrate by combining electrospinning and aging processes, and (2) its room temperature CO₂ adsorption and mineralization in air. Commercial magnesium hydroxide (Mg(OH)₂) powder was used as raw material in the synthesis of magnesium carbonate hydrates (MCH), by three processes; (1) direct calcination, (2) electrospinning and calcination, and (3) electrospinning, calcination, and aging (at room temperature and in air to incubate CO₂ mineralization). The synthesized powder samples were characterized thoroughly using XRD, SEM, EDS, and TGA analyses. Effects of calcination temperature/aging time on CO₂ adsorption (at room temperature), crystallization, and mineralization of MCH were studied. Interestingly, the results showed that the 6-month aged samples (via the third synthesis process above), recorded a CO₂ adsorption capacity of 15.5 wt% within 90 min at 30 °C. Subsequently, three novel mechanisms of thermal decomposition CO₂ adsorption/mineralization were proposed, and a theoretical upper limit of carbon saving potentials was estimated, i.e., 8 mol CO₂ per 1 mol MgO. This work provides a novel CO₂ mineralization approach that results in (1) effective and practical solutions of carbon dioxide (CO₂) emission management and which holds (2) great potential for novel carbon-based fuels development.

The Application of Hollow Carbon Nanofibers Prepared by Electrospinning to Carbon Dioxide Capture

Coaxial electrospinning has been considered a straightforward and convenient method for producing hollow nanofibers. Therefore, the objective of this study was to develop hollow activated carbon nanofibers (HACNFs) for CO₂ capture in order to reduce emissions of CO₂ to the atmosphere and mitigate global warming. Results showed that the sacrificing core could be decomposed at carbonization temperatures above 900 °C, allowing the formation of hollow nanofibers. The average outer diameters of HACNFs ranged from 550 to 750 nm, with a shell thickness of 75 nm. During the carbonization stage, the denitrogenation reactions were significant, while in the CO₂ activation process, the release of carbon oxides became prominent. Therefore, the CO₂ activation could increase the percentages of N=C and quaternary N groups. The major nitrogen functionalities on most samples were O=C-NH and quaternary N. However, =C and quaternary N groups were found to be crucial in determining the CO₂ adsorption performance. CO₂ adsorption on HACNFs occurred due to physical adsorption and was an exothermic reaction. The optimal CO₂ adsorption performance was observed for HACNFs carbonized at 900 °C, where 3.03 mmol/g (1 atm) and 0.99 mmol/g (0.15 atm) were measured at 25 °C. The degradation of CO₂ uptakes after 10 adsorption-desorption cyclic runs could be maintained within 8.9%.

Sewage Sludge Derived Materials for CO2 Adsorption

The study tried to contribute to solving two serious environmental issues: CO2 reducing and sewage sludge disposal. Thus, sewage-sludge-derived materials were obtained in order to be evaluated for CO2 adsorption capacity. Therefore, the char resulted after the sewage sludge pyrolysis was subjected to oxidation and chemical activation processes by using different quantities of alkaline hydroxide. One of the obtained materials, activated with a lower quantity of alkaline hydroxide, was also treated with acid chloride. Further, the materials were structural and texturally characterized, and material treated with acid chloride was used for CO2 adsorption tests, due to high surface area and pore volume. The handmade system coupled to a gas chromatograph allowed the adsorption efficiency evaluation using different feed gases (rich and poor in CO2) by completed purge of pipe line and on-line check. Additionally, the adsorption capacity, separation efficiency, and CO2 recovery were calculated. Taking into account the values for adsorption capacity (separation efficiency and CO2 recovery), it can be concluded that the sewage sludge derived material could be a promising solution for CO2 reduction and waste disposal.

A review on application of activated carbons for carbon dioxide capture: present performance, preparation, and surface modification for further improvement

The atmosphere security and regulation of climate change are being continuously highlighted as a pressing issue. The crisis of climate change owing to the anthropogenic carbon dioxide emission has led many governments at federal and provincial levels to promulgate policies to address this concern. Among them is regulating the carbon dioxide emission from major industrial sources such as power plants, petrochemical industries, cement plants, and other industries that depend on the combustion of fossil fuels for energy to operate. In view of this, various CO2 capture and sequestration technologies have been investigated and presented. From this review, adsorption of CO2 on porous solid materials has been gaining increasing attention due to its cost-effectiveness, ease of application, and comparably low energy demand. Despite the myriad of advanced materials such as zeolites, carbons-based, metal-organic frameworks, mesoporous silicas, and polymers being researched, research on activated carbons (ACs) continue to be in the mainstream. Therefore, this review is endeavored to elucidate the adsorption properties of CO2 on activated carbons derived from different sources. Selective adsorption based on pore size/shape and surface chemistry is investigated. Accordingly, the effect of surface modifications of the ACs with NH3, amines, and metal oxides on adsorption performance toward CO2 is evaluated. The adsorption performance of the activated carbons under humid conditions is also reviewed. Finally, activated carbon-based composite has been surveyed and recommended as a feasible strategy to improve AC adsorption properties toward CO2. The activated carbon surface in the graphical abstract is nitrogen rich modified using ammonia through thermal treatment. The values of CO2 emissions by sources are taken from (Yoro and Daramola 2020).