Adsorbents For CO2 Capture Research Articles

The influence of pore size and pore structure of silica-based material on the amine-modified adsorbent for CO2 capture

Silica impregnated with amines has attracted much attention as a promising alternative to amine scrubbing. This study selected SBA-15, MCM-41, and MCM-48 as support materials and set amine types (PEI and DETA), amine loadings (20–45 %), and temperatures (40–120 ℃) as parameters, systematically exploring the influence of pore size and pore structure on the adsorption performance. The pore size and pore structure had little impact on the type of chemical functional group and thermal stability, but played an important role in the CO2 adsorption capacity as well as the response of adsorption performance to temperature and amine. By comparison, the silica with large pore sizes was more suitable for PEI, while the silica with small pore sizes was more suitable for DETA. The hexagonal mesoporous structure was congenial to DETA and low PEI loading, while the cubic mesoporous structure was congenial to high PEI loading. The small pore size and the cubic mesoporous structure were proven to maintain the promotion effect of the adsorption temperature, while the hexagonal mesoporous structure could relieve the amine volatilization during the adsorption–desorption cycles. The cubic mesoporous structure could inhibit the generation of urea. By comparison, SBA-15 modified with 45 % had excellent performance, reaching a CO2 uptake of 160.55 mg/g and an amine efficiency of 0.360. This product could also control the total percentage of CO2 uptake lost after 30 cycles within 2.0 %, demonstrating the potential for practical application.

Nitrogen-doped porous carbon through K2CO3-activated bamboo shoot shell for an efficient CO2 adsorption

In this paper, a two-stage approach was employed to produce nitrogen-doped porous carbons from bamboo shoot shells. These shells were utilized as a cost-effective biomass resource for the production of activated carbon in gas adsorption. The initial step involved co-carbonization of the bamboo shoot shells with urea, followed by activation using potassium carbonate. A series of nitrogen-doped biochar was prepared by varying the activation temperature and activator ratio. This approach allowed for the investigation of their potential in capturing CO2. Surface analyses were conducted using BET, SEM, and TEM techniques to examine the structural evolution of nitrogen-doped biochar. The results revealed that the fibrous structure of the bamboo shoot shells was well-preserved after carbonization and nitrogen doping, while activation resulted in the formation of a distinct worm-like microporous structure. Among them, the sample BNC-800-2 possessed the largest specific surface area of 1985 m2/g. Notably, the nitrogen-doped biochar activated at 800 °C exhibited remarkable capacity for adsorbing carbon dioxide, with values of 7.52 mmol/g and 3.60 mmol/g at 1 bar and temperatures of 0 °C and 25 °C, respectively. The adsorbent also demonstrated excellent cyclic stability and selectivity for gas mixture (CO2 and N2), attributed to its large specific surface area and narrow pore size, which synergistically contributed to its performance. Furthermore, the adsorption equilibrium was analyzed using the Langmuir and Freundlich isotherm models, with the experimental data showing significant agreement with the Freundlich isotherm model. Additionally, thermodynamic calculations confirmed that the adsorption process of CO2 on nitrogen-doped biochar was spontaneous and exothermic, indicating physical adsorption. This further validates the efficacy of the adsorbent in capturing CO2. This study demonstrates the potential of bamboo shoot shells as a low-cost biomass resource for producing effective adsorbents for CO2 capture.

Nanosilica polyamidoamine dendrimers for enhanced direct air CO2 capture.

Exploring efficient systems to recover CO2 from the atmosphere could be a way to address the global carbon emissions issue. Herein, we report the synthesis of nanosilica (NS) functionalized with polyamidoamine (PAMAM) dendrimers (NS-PAMAM) as efficient adsorbents for CO2 capture under simulated direct air capture (DAC) (400 ppm CO2 in helium at 30 °C) and indoor air (≥400 ppm, 50 ± 3% RH at 30 °C) conditions. The results inferred that the 1st (NS-G1.0), 2nd (NS-G2.0), 3rd (NS-G3.0), and 4th (NS-G4.0) generations of the NS-PAMAM dendrimers exhibited excellent performance for CO2 capture. Compared to the other generations, NS-G3.0 demonstrated superior CO2 adsorption capacities of 0.50 mmol g-1 under simulated dry CO2 conditions (400 ppm in He), 1.02 mmol g-1 under indoor air (dry) CO2 conditions (≥400 ppm, 26 ± 3% RH), and 1.54 mmol g-1 under indoor air (humid) CO2 conditions (≥400 ppm, 50 ± 3% RH). The study included the evaluation of CO2 adsorption-desorption performance of the NS-PAMAM dendrimers under varying structural and chemical parameters, kinetics, regeneration at low temperature (80 °C), as well as CO2 adsorption under humid conditions. Additionally, NS-G3.0 displayed a substantially superior performance with stable CO2 capture displayed during ten short temperature swing adsorption (TSA) cycles, making it a promising candidate for CO2 capture from ambient air. Finally, we demonstrated the recovery and reutilization of the captured CO2 for both the synthesis of formate via carbonate hydrogenation and for the production of calcium carbonate pellets.

Lignin-based porous carbon adsorbents for CO2 capture.

A major driver of global climate change is the rising concentration of atmospheric CO2, the mitigation of which requires the development of efficient and sustainable carbon capture technologies. Solid porous adsorbents have emerged as promising alternatives to liquid amine counterparts due to their potential to reduce regeneration costs. Among them, porous carbons stand out for their high surface area, tailorable pore structure, and exceptional thermal and mechanical properties, making them highly robust and efficient in cycling operations. Moreover, porous carbons can be synthesized from readily available organic (waste) streams, reducing costs and promoting circularity. Lignin, a renewable and abundant by-product of the forest products industry and emerging biorefineries, is a complex organic polymer with a high carbon content, making it a suitable precursor for carbon-based adsorbents. This review explores lignin's sources, structure, and thermal properties, as well as traditional and emerging methods for producing lignin-based porous adsorbents. We examine the physicochemical properties, CO2 adsorption mechanisms, and performance of lignin-derived materials. Additionally, the review highlights recent advances in lignin valorization and provides critical insights into optimizing the design of lignin-based adsorbents to enhance CO2 capture efficiency. Finally, it addresses the prospects and challenges in the field, emphasizing the significant role that lignin-derived materials could play in advancing sustainable carbon capture technologies and mitigating climate change.

Amino-modified biochar-silica hybrid aerogels with ordered pore structure templated by cellulose nanocrystals for highly efficient and selective CO2 capture

Carbon dioxide (CO2) emissions from the combustion of fossil fuels are contributing to global climate change and ocean acidification, and the development of low-cost, highly efficient CO2 capture adsorbents for the reduction of CO2 concentrations is now a matter of urgency. Herein, we developed amine-modified biochar-silica hybrid aerogels template cellulose nanocrystals (CNCs) for CO2 capture. CNCs can self-assemble into an ordered lamellar structure and maintain their original structure after calcination in N2 atmosphere. At the same time, we chemically modified the hybrid aerogels with amines. The ordered pore structure and chemical modification effectively enhanced the CO2 adsorption capacity and rate of hybrid aerogels. The test showed that our material exhibited high adsorption properties of 2.81 mmol g−1 (0 °C, 1 bar). This work offers research ideas and methods for fabricating amine-modified biochar-silica hybrid aerogels for CO2 capture.

Triethanolamine-modified layered double oxide for efficient CO2 capture with low regeneration energy

Various adsorbents for CO2 capture have been developed to mitigate the greenhouse effect. In this work, a novel CO2 adsorbent was fabricated by depositing triethanolamine (TEOA) onto the surface of nickel-cobalt-aluminum layered double oxide (NiCoAl-LDO) via the impregnation method. The CO2 capacity of the TEOA-LDO composite reached 1.27 mmol/g at 0 °C and 100 kPa, which was twice that of unmodified NiCoAl-LDO. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the hydroxyl groups (–OH) on the surface of NiCoAl-LDO played a significant role in facilitating CO2 adsorption, similar to CO2 adsorption in the presence of H2O, where CO2 is not converted to carbamates but to bicarbonates through base-catalyzed hydration. This bicarbonate pathway doubles the theoretical amine efficiency, increases the CO2 capacity, and reduces the energy consumption during CO2 desorption. The work provides valuable insights into the development of CO2 adsorbents with high capacity, excellent cycling stability, and low regeneration energy.

Activated Carbon as an Adsorbent for CO2 Capture: Adsorption, Kinetics, and RSM Modeling.

The main objective of this research is to investigate the adsorption isotherms and the optimization of the carbon dioxide (CO2) adsorption process on activated carbon (AC). The AC has been characterized by X-ray diffraction, scanning electron microscopy, and nitrogen (N2) adsorption-desorption. The CO2 isotherms measured under three adsorption temperatures (318, 308, and 298 K) were investigated by the Langmuir and linear driving force model. It is found that the Langmuir model could well predict the adsorption behavior of AC with a correlation factor of about 0.99. The kinetic model shows that the amount of CO2 increases at higher pressures. The response surface methodology (RSM) was applied to investigate the effects of process variables and their interaction on the response to reach the optimal conditions. Based on the analysis of variance, pressure and temperature are the main factors influencing the CO2 adsorption capacity. The effective parameters obtained through this model are found to have a value of p < 0.05. In addition, a semiempirical correlation was developed under the optimal operating conditions which are 25 °C and 9 bar. The results indicated that RSM models provide an effective method for evaluating CO2 adsorption. These results point that AC is a potential adsorbent for CO2 capture.

Synergy tetraethylenepentamine and diethanolamine impregnated within silica nanotubes derived from natural halloysite for efficient CO2 capture

Amine-impregnated porous solid adsorbents are promising commercial CO2 capture adsorbents for CO2 mitigation due to relatively large CO2 capacity and high CO2 selectivity. However, the intrinsic viscosity and aggregation of the polyamine leads to low amine efficiency and greatly limits its further development. In this work, a facile and efficient approach was carried out to manipulate the porosity of natural halloysite (HNTs) support with hollow tubular structure and impregnate mixed-polyamines, i.e., both tetraethylenepentamine (TEPA) and diethanolamine (DEA) to synergistically enhance CO2 adsorption capacity, fast adsorption kinetics and thermal/chemical stability compared to the individual supported TEPA and DEA. The effects of the blend amount for TEPA and DEA, adsorption temperature and CO2 partial pressure on CO2 adsorption capacity and adsorption kinetics were specifically discussed. Due to the auxiliary effect of DEA, the chemical reaction between non-hydroxylated TEPA and CO2 was altered thus improving amine efficiency and the agglomeration layer between protonated TEPA molecules and carbamate, which existed due to electrostatic interaction when TEPA was loaded alone, was loosened thus improving amine efficiency and adsorption kinetics. Therefore, the maximum CO2 adsorption capacity of MHNTs loaded with 20 wt% TEPA and 20 wt% DEA was 3.25 mmol/g at 75 °C in the flow of 40 vol% N2/60 vol% CO2. Compared with loading individual TEPA with multiple amino groups on MHNTs, individual DEA with hydroxyl groups could increase the utilization efficiency of the amino groups of TEPA and ultimately obtain excellent CO2 capture capacity and adsorption kinetics. The experimental results show that the adsorbents obtained in this study using mixed amine impregnated silica nanotubes derived from natural minerals have a promising application in practical CO2 capture and separation processes.

Self-Assembled Core-Shell Structure MgO@TiO2 as a K2CO3 Support with Superior Performance for Direct Air Capture CO2.

Traditional carbon capture and storage technologies for large point sources can at best slow the rate of increase in atmospheric CO2 concentrations. In contrast, direct capture of CO2 from ambient air, or "direct air capture" (DAC), offers the potential to become a truly carbon-negative technology. Composite solid adsorbents fabricated by impregnating a porous matrix with K2CO3 are promising adsorbents for the adsorption capture of CO2 from ambient air. Nevertheless, the adsorbent can be rapidly deactivated during continuous adsorption/desorption cycles. In this study, MgO-supported, TiO2-stabilized MgO@TiO2 core-shell structures were prepared as supports using a novel self-assembled (SA) method and then impregnated with 50 wt % K2CO3 (K2CO3/MgO@TiO2, denoted as SA-KM@T). The adsorbent exhibits a high CO2 capture capacity of ∼126.6 mg CO2/g sorbent in direct air adsorption and maintained a performance of 20 adsorption/desorption cycles at 300 °C mid-temperature, which was much better than that of K2CO3/MgO. Analysis proved that the core-shell structure of the support effectively inhibited the reaction between the active component (K2CO3) and the main support (MgO) by the addition of TiO2, resulting in higher reactivity, thermal stability, and antiagglomeration properties. This work provides an alternative strategy for DAC applications using adsorbents.

Molecular encapsulation of 5, 10, 15, 20-tetrakis (4-methylphenyl) porphyrinato iron (III) chloride (FeTPP) into MIL-101(Cr) for superior CO2/N2 separation performance

The greenhouse effect associated with excessive CO2 emission has led to a series of environmental issues, thus developing excellent adsorbents for CO2 capture from flue gas offers a sustainable approach. To combine the merit of multiple functional components, novel FeTPP@MIL-101(Cr) was prepared by incorporation of 5,10,15,20-tetrakis(4-methylphenyl)porphyrinato iron (III) chloride (FeTPP) into MIL-101(Cr) cages via in-situ packaging strategy. The cage-confined FeTPP can both regulate the pore structures of MIL-101(Cr) and provide additional binding sites for CO2 adsorption. Profiting from extra interactions for CO2 component and the “sieving effect” for N2 component induced by incorporation of FeTPP, the discrepancy of isosteric heat for CO2 and N2 was largely amplified. Notably, the CO2/N2 selectivity (15/85, v/v) calculated by ideal adsorbed solution theory (IAST) increased from 17.1 (MIL-101 (Cr)) to 41.8 (FeTPP@MIL-101 (Cr) with FeTPP loading of 4.98 wt%) at 273 K, 100 kPa, which is 2.44 times larger than that of pristine MIL-101 (Cr) and also exceeds most reported adsorbents.

Impact of H2O on CO2 adsorption and co-adsorption: Mechanism and high-performance adsorbents for efficient H2O-CO2 capture

Physical adsorbents used for CO2 capture from air directly and wet CO2 flue gas have limited effectiveness due to competitive adsorption of H2O and CO2. Therefore, it is crucial to understand the impact of H2O on CO2 adsorption and investigate the co-adsorption mechanism in order to enhance the screening, design, and optimization of carbon capture systems. Herein, heat treatments are performed on commercial NaX zeolites to modify the composition of the O-T-O (T = Al, Si) framework. Our systematic investigation based on thermogravimetric analysis/differential scanning calorimetry (TG-DSC), infrared spectroscopy (IR), solid-state nuclear magnetic resonance (SSNMR), and density-functional theory (DFT) calculation, the connection between the structure of NaX zeolite and H2O and CO2 adsorption/desorption is established. The heat-induced changes in the O-T-O (T = Al, Si) framework produce movements of the loaded Na+ ions. Hydrogen bonds formed by agglomerated adsorbed H2O constitute the primary source of desorption heat, which adversely affects CO2 mass transfer and adsorption. Our findings illustrate that modifying the distribution of Na+ ions in the O-T-O (T = Al, Si) framework can reduce the CO2 adsorption energy and prevent the formation of water agglomerates. Our findings provide insights into the design of efficient and high-capacity adsorbents for CO2 capture that can be operated in the presence of H2O.

Sulfur-Doped porous carbon Adsorbent: A promising solution for effective and selective CO2 capture

The effective and selective capture of CO2 through the rational design of microstructures and the synthesis of carbon materials with enriched surface functionality is of utmost importance in mitigating CO2 emissions. In this study, we successfully prepared a novel type of S-doped porous carbon material with a high surface area and a significant volume of micropores in a straightforward manner. This was achieved by pyrolyzing carbonized coconut shells (CS) with potassium thiosulfate K2S2O3 (PT) as an activating and sulfur supply agent. By adjusting the pyrolysis temperature within the range of 650–750 °C, we obtained carbon materials with varying surface areas (887–1924 m2/g), pore volumes (0.35–0.95 cm3 g−1), and a homogeneous distribution of sulfur content (up to 12.26 wt%) within the carbon framework. The optimal S-doped porous carbon demonstrated the adsorption capacities of 3.59 mmol g−1 at 25 °C and 5.31 mmol g−1 at 0 °C under 1 bar. Additionally, the prepared sorbent exhibited favorable CO2/N2 selectivity, high isosteric heat, and stable cycling performance. These excellent CO2 capture properties can be attributed to the materials' high microporosity and well-dispersed sulfur functionality in the carbon framework. Collectively, these findings highlight the potential of these novel carbon materials with heteroatom doping as efficient adsorbents for the selective capture of CO2, presenting a viable solution in the quest for effective CO2 mitigation.

Experimental Study on High-Efficiency Cyclic CO2 Capture from Marine Exhaust by Transition-Metal-Modified CaO/Y2O3 Adsorbent

CaO-based adsorbent cycling carbon capture technology is an effective way to reduce CO2 emissions from marine exhaust gases. Metal-modified CaO-based adsorbents represent one of the important ways to improve the cyclic CO2 capture capacity. In order to obtain economical and efficient CaO-based adsorbents, transition metal (Cu, Fe, Co, Cr, Ni)-modified CaO/Y2O3 adsorbents were prepared using the sol–gel method. CO2 cyclic adsorption capacity tests were carried out in a fixed bed. The microstructure of the adsorbents was analyzed using XRD, SEM, and BET. The adsorption performance and cycle stability of the modified CaO/Y2O3 adsorbents were investigated in depth. The results show that the Fe-CaY adsorbent had the best adsorption performance. The initial adsorption capacity of Fe-CaY was 0.62 g/g at 650 °C, and the adsorption capacity was 0.59 g/g at the 25th cycle. Fe-CaY-doped samples with the largest pore size and specific surface area showed the best adsorption performance due to the contribution of macropores in the prevention of sintering. Fe doping can greatly improve the CO2 adsorption capacity and cycle stability of an adsorbent and also reduce the CaO-based adsorbent cycle temperature. In addition, the Fe-Ni-CaY adsorbent had the best adsorption performance among the bimetallic (Cu-Ni, Fe-Ni, Co-Ni, Cr-Ni)-modified CaO/Y2O3 adsorbents. However, compared with Fe-CaY, the adsorption capacity decreased. The reason for this might have been that the addition of Ni destroyed the rich pore structure between Fe-Ca-Y and the stability of the adsorbent particle structure, which led to the aggregation of CaO crystals and reduced the CO2 adsorption capacity. Therefore, the Fe-CaY developed in this study has excellent adsorption capacity and cyclic stability, which makes it a promising adsorbent for CO2 capture in marine exhaust gases.

Cellulose-based materials for carbon capture and conversion

With the worldwide attention on decreasing carbon dioxide (CO2) emissions, carbon capture and storage (CCS) is utilized to stop CO2 from escaping into the atmosphere. Selecting appropriate materials is crucial for the establishment of a dependable and secure carbon capture and storage technology infrastructure. The natural cellulose materials possess inherent characteristics such as eco-friendliness, high utility, remarkable physical and mechanical properties, which make them particularly available for CCS. In the field of carbon capture, utilization and sequestration technologies, cellulose-based materials can be used as adsorbents for CO2 capture and as catalyst carriers for CO2 conversion. Firstly, the application of cellulose-based materials in carbon capture and conversion is introduced. Secondly, the research progress of cellulose-based films, aerogels and solid adsorbents in the field of carbon capture are summarized. Subsequently, the research mechanisms of cellulose-based materials for the conversion of CO2 to methanol format, carbonate and CO are also described in detail. Finally, the challenges and the key problems of cellulose-based materials in carbon capture and utilization are described.

Improved structure of Zr-BTC metal organic framework using NH2 to enhance CO2 adsorption performance

Modified mesoporous NH2-Zr-BTC mixed ligand MOF nanocomposites were synthesized via the hydrothermal method as a novel adsorbent for CO2 capture. The newly modified MOF-808 with NH2 demonstrated a similar mesoporous morphology as MOF-808, whereas the specific surface area, pore volume, and average particle size, respectively, increased by 15%, 6%, and 46% compared to those of MOF-808. The characterization analyses exhibited the formation of more active groups on the adsorbent surface after modification. In addition, a laboratory adsorption setup was used to evaluate the effect of temperature, pressure, and NH2 content on the CO2 adsorption capacity in the range of 25–65 °C, 1–9 bar, and 0–20 wt%, respectively. An increase in pressure and a decrease in temperature enhanced the adsorption capacity. The highest equilibrium adsorption capacity of 369.11 mg/g was achieved at 25 °C, 9 bar, and 20 wt% NH2. By adding 20 wt% NH2, the maximum adsorption capacity calculated by the Langmuir model increased by about 4% compared to that of pure MOF-808. Moreover, Ritchie second-order and Sips models were the best-fitted models to predict the kinetics and isotherm data of CO2 adsorption capacity with the high correlation coefficient (R2 > 0.99) and AARE% of less than 0.1. The ΔH°, ΔS°, and ΔG° values were − 17.360 kJ/mol, − 0.028 kJ/mol K, and − 8.975 kJ/mol, respectively, demonstrating a spontaneous, exothermic, and physical adsorption process. Furthermore, the capacity of MH-20% sample decreased from 279.05 to 257.56 mg/g after 15 cycles, verifying excellent stability of the prepared mix-ligand MOF sorbent.

Design of Amine-Containing Nanoporous Materials for Postcombustion CO2 Capture from Engineering Perspectives.

ConspectusCarbon dioxide (CO2) capture and storage (CCS) is a means to enable the continued use of fossil fuels in the short term. In particular, postcombustion CO2 capture has attracted considerable attention because it can be retrofitted into existing power plants and industrial plants. Among various CO2 capture technologies, the absorption of CO2 using aqueous amines has been industrially employed for decades. However, such amine scrubbing technologies have inherent limitations of environmental and health concerns due to volatile amine loss, corrosion, and high energy demands for regeneration. To overcome these limitations, CO2 adsorption using solid adsorbents has emerged as a promising alternative due to its noncorrosiveness and low energy demand. Various amine-containing adsorbents have been synthesized and investigated for postcombustion CO2 capture. These materials are prepared by physically impregnating low-vapor-pressure amine polymers or by chemically grafting amines onto nanoporous materials. A wide variety of amine guests and nanoporous hosts (e.g., SiO2, Al2O3, zeolites, MOFs, and polymers) have been combined to develop advanced CO2 adsorbents.The design of CO2 adsorbents is a multifaceted puzzle that must ultimately consider integration with large-scale CO2 capture processes. Various engineering aspects need to be carefully considered. Unfortunately, a significant proportion of previous studies has primarily focused on the use of novel materials for improving the CO2 adsorption capacity. In this Account, we describe key challenges and solutions to develop energy-efficient and stable amine-containing adsorbents for postcombustion CO2 capture via temperature swing adsorption (TSA). We found that a high CO2 working capacity, often overemphasized in the literature, does not necessarily guarantee a low energy demand for CO2 capture. Suppressing coadsorption of H2O during the CO2 adsorption in humid flue gas is also a significant factor. Amine-containing adsorbents can be degraded through various pathways, including hydrothermal degradation of nanoporous hosts and chemical degradation of amine guests via urea formation and oxidation. To inhibit such degradation pathways, it is extremely important to properly design the nanoporous structures of the hosts and the molecular structures of the amine guests. By combining macroporous silica hosts, poly(ethylenimine) (PEI) functionalized with various alkyl epoxides, and phosphate-based oxidative stabilizers, we could synthesize adsorbents exhibiting low energy demands for CO2 capture and unprecedentedly high thermochemical stability under TSA conditions. The macroporous silica host synthesized by assembling fumed silica particles via spray-drying exhibited high hydrothermal stability and enabled uniform distribution of bulky amine polymers within its pores. The functionalization of PEI with alkyl epoxides converted its primary amines into hindered secondary amines, leading to a significant reduction in energy demand for TSA cycles and a remarkable improvement in long-term stabilities. The oxidative stability of amines could be drastically improved by adding phosphate metal-binding reagents, which can poison ppm-level metal impurities that catalyze amine oxidation. The present discussions will provide important insights into designing practical adsorbents for CO2 capture from engineering perspectives.

Ultrasonication Assisted Urea Treated Biochar: An Eco‐Friendly Adsorbent for CO2 Capture

AbstractCheap, efficient and eco‐friendly adsorbents have received great attention for CO2 capture. Nowadays, biochars are promising CO2 adsorbents with the advantages of their low‐cost, tunable porous structural characteristics, facile surface treatment and easy regeneration. In this work, biochar synthesized from wheat straw, an agricultural waste, by pyrolysis was used as a CO2 adsorbent. CO2 capture studies were conducted by thermogravimetric analyses (TGA) at 25 °C under 100 mL min−1 CO2 for 2 h. The CO2 adsorption capacity of the biochar was determined as 23.33 mg g−1. To enhance CO2 adsorption capacity, ultrasonication and urea treatment were applied to the biochar. With the combination of these treatment methods, CO2 adsorption capacity of the biochar increased to 73.56 mg g−1 due to an increase in its micro‐pore volume and presence of functional amine groups. Possible CO2 capture mechanisms were stated as pore filling with CO2 molecules, van der Waals forces, weak hydrogen bond, and Lewis acid‐base interactions in addition to reactions of amine groups with CO2 molecules. After five CO2 adsorption‐desorption cycles, ultrasonication assisted urea treated biochar was still used with over 90 % performance. The results show that the low‐cost and eco‐friendly physicochemical treated biochar is a favorable adsorbent for CO2 capture.

Binary carbon dioxide and nitrogen adsorption on pomelo peel-derived porous sorbent

The rising concern regarding CO2 emission from fossil fueled-power plants, along with the heightened interest in repurposing biowaste has necessitated the utilization of biowaste as an adsorbent for CO2 capture. In this study, the pomelo peel-derived activated carbon (POM-AC) was investigated as a potential adsorbent for post-combustion CO2 capture application, which involves capturing CO2 from the CO2 and N2 gas mixture. The POM-AC was characterized, revealing a microporous-mesoporous structure that contains various surface functional groups including hydroxyl, carbonyl, carboxyl, and alkene groups. The strong affinity of POM-AC towards CO2 over N2 was demonstrated from the increment in the CO2 and N2 gas mixture uptake with the increase in CO2 gas compositions. The total adsorption capacity of POM-AC at ambient conditions for 100% CO2, 15% CO2, 10% CO2, and 5% CO2 is 127.8 mg/g, 55.7 mg/g, 49.1 mg/g, and 38.3 mg/g, respectively. Notably, POM-AC outperformed the commercial activated carbon (Chemiz-AC) at simulated post-combustion conditions due to POM-AC having smaller pores than Chemiz-AC. The Ideal Adsorbed Solution Theory (IAST) prediction of binary CO2 and N2 adsorption equilibria showed higher CO2 adsorption capacity than N2 at post-combustion gas compositions (5–15% CO2), which further suggests its stronger preferential of CO2 over N2. Furthermore, a relatively high CO2/N2 selectivity of 23.9 was predicted for 15% CO2 gas composition. The adsorption isotherm and kinetic analysis revealed that the surface of POM-AC is heterogenous, and the rate-controlling step of CO2 and N2 adsorption is physisorption. Coupled with the utilization of a zero-cost biowaste as an activated carbon precursor, these findings showed that POM-AC could be a promising adsorbent for post-combustion CO2 capture application.

High-performance CO2 adsorption of jellyfish-based activated carbon with many micropores and various heteroatoms

In this study, microporous activated carbon was produced from jellyfish-based biomass to capture carbon dioxide (CO2), toward addressing one of the biggest modern problems. The surface functional groups and porosity of activated carbon derived from jellyfish were investigated according to the activation conditions. It was confirmed that the jellyfish-based porous carbon prepared by NaOH activation comprised many micropores that facilitated CO2 adsorption under the influence of Na and P present in the microstructure of the jellyfish. In addition, the JFBC-based activated carbon had surface functional groups such as nitrogen, calcium, and magnesium, which facilitated CO2. The jellyfish-based activated carbon shows very excellent CO2 adsorption capacity (9.52 mmol/g and 5.18 mmol/g at 273 K and 298 K, respectively) compared to activated carbon prepared from porous carbon-based adsorbents for CO2 capture. This performance is attributed to the microstructure and various heteroatoms of the jellyfish biochar. Therefore, this study may provide insight into new biomass with competitive adsorption power and without requiring complicated manufacturing steps.

Biomass waste as an alternative source of carbon and silicon-based absorbents for CO2 capturing application

The production of low-cost solid adsorbents for carbon dioxide (CO2) capture has gained massive consideration. Biomass wastes are preferred as precursors for synthesis of CO2 solid adsorbents, due to their high CO2 adsorption efficiency, and ease of scalable low-cost production. This review particularly focuses on waste biomass-derived adsorbents with their CO2 adsorption performances. Specifically, studies related to carbon (biochar and activated carbon) and silicon (silicates and geopolymers)-based adsorbents were summarized. The impact of experimental parameters including nature of biomass, synthesis route, carbonization temperature and type of activation methods on the CO2 adsorption capacities of biomass-derived pure carbon and silicon-based adsorbents were evaluated. The development of various enhancement strategies on biomass-derived adsorbents for CO2 capture and their responsible factors that impact adsorbent's CO2 capture proficiency were also reviewed. The possible CO2 adsorption mechanisms on the adsorbent's surface were highlighted. The challenges and research gaps identified in this research area have also been emphasized, which will help as further research prospects.