Adsorbents For CO2 Adsorption Research Articles

Carbon (IV) oxide adsorption efficiency of functionalized HKUST-1, IRMF-1, and UiO-66 metal organic frameworks

The ever-increasing consumption of fossil fuels to meet up with the global economic and industrial energy needs has led to climatic change due to uncontrollable emission of a major greenhouse gas (CO2). As a way of mitigating the amount of CO2 in the atmosphere, search for effective and efficient solid adsorbent has been at the front burner of current scientific research. A class of solid adsorbent known as metal organic frameworks (MOFs) have demonstrated immense potentials for CO2 adsorption due to its porous, high thermal and chemical stability, high versatility and ease of production. Upon functionalization, the adsorption efficiency of this class of materials was found to improve tremendously. In this review, the CO2 capture and sequestration potentials of three MOFs (UiO-66, HKUST-1, and MOF-5) and their composites were investigated in the search for economical, stable, and highly selective novel adsorbents for CO2 adsorption.

Capturing Acidic CO2 Using Surface-Active Difunctional Core-Shell Composite Polymer Particles via an Aqueous Medium.

Multifunctional surface-active polymeric composites are attractive materials for the adsorption of various small molecules. Herein, dual-functionalized micron-sized surface-active composite polymer particles were prepared by a three-step process for CO2 adsorption. First, polystyrene (PS) seed particles were prepared via the dispersion polymerization of styrene. PS/P(MMA-AAm-EGDMA) composite polymer particles were then synthesized by aqueous seeded copolymerization of methyl methacrylate (MMA) and acrylamide (AAm) in the presence of an ethylene glycol dimethacrylate (EGDMA) cross-linker. Finally, the amide moieties of PS/P(MMA-AAm-EGDMA) composite particles were converted into an amine-functionalized composite by using the Hofmann degradation reaction. The presence of primary amine groups on the surface of aminated composite particles was confirmed by some conventional chemical routes, such as diazotization and Schiff's base formation reactions. The formation and functionality of the PS seed, PS/P(MMA-AAm-EGDMA), and aminated PS/P(MMA-AAm-EGDMA) composite polymer particles were confirmed by Fourier transform infrared (FTIR) spectra analyses. Scanning electron microscopy (SEM) analysis revealed spherical shape, size, and surface morphologies of the PS seed, reference composite, and aminated composites. The elemental surface compositions, surface porosity, pore volume, pore diameter, and surface area of both composite particles were evaluated by energy-dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses. Dynamic light scattering (DLS) and ζ-potential measurements confirmed the pH-dependent surface properties of the functionalized particles. The amount of the adsorbed anionic emulsifier, sodium dodecyl sulfate (SDS), on the surface of aminated PS/P(MMA-AAm-EGDMA) is higher at pH 4 than that at pH 10. A vice versa result was found in the case of cationic surfactant, hexadecyltrimethylammonium bromide (HTABr), adsorption. Synthesized aminated composite particles were used as an adsorbent for CO2 adsorption via bubbling CO2 in an aqueous medium. The changes in dispersion pH were monitored continuously during the adsorption of CO2 under various conditions. The amount of CO2 adsorption by aminated composite particles was found to be 209 mg/g, which is almost double that of reference composite particles.

Highly porous carbon derived from hydrothermal-pyrolysis synergistic carbonization of biomass for enhanced CO2 capture

Highly porous carbon adsorbent is much desired to diminish greenhouse effect caused by CO2 emission and benefit for subsequent carbon cycle. Herein, a low-cost and environment-friendly carbonization strategy was reported for preparation of highly porous carbon derived from biomass. Such carbonization is a synergistic process with hydrothermal treatment coupled with a subsequent pyrolysis using sugarcane as biomass. The obtained hydrothermal-pyrolysis derived porous carbon (HPC) has a BET surface area of 938 m2/g, which is much higher than that of carbon produced through direct pyrolysis (PC, 528 m2/g). During the hydrothermal carbonization pretreatment, highly thermostable aromatic skeletons are formed and converted to carbon skeletons in the post-pyrolysis process, leading to formation of highly stable micropores and higher surface area. Further, HPC shows remarkable adsorption ability of CO2 (2.8 mmol/g, 25 °C, 1 bar), higher than that of PC (2.1 mmol/g). In addition, the HPC exhibits high CO2/N2 adsorption selectivity and recyclability, demonstrating its potential application in CO2 capture. This work not only gives new light for tailoring carbon materials with highly porous structure but also provides novel adsorbent for CO2 adsorption.

Monomer Symmetry-Regulated Defect Engineering: In Situ Preparation of Functionalized Covalent Organic Frameworks for Highly Efficient Capture and Separation of Carbon Dioxide

Developing crystalline porous materials with highly efficient CO2 selective adsorption capacity is one of the key challenges to carbon capture and storage (CCS). In current studies, much more attention has been paid to the crystalline and porous properties of crystalline porous materials for CCS, while the defects, which are unavoidable and ubiquitous, are relatively neglected. Herein, for the first time, we propose a monomer-symmetry regulation strategy for directional defect release to achieve in situ functionalization of COFs while exposing uniformly distributed defect-aldehyde groups as functionalization sites for selective CO2 capture. The regulated defective COFs possess high crystallinity, good structural stability, and a large number of organized and functionalized aldehyde sites, which exhibit one of the highest selective separation values of all COF sorbing materials in CO2/N2 selective adsorption (128.9 cm3/g at 273 K and 1 bar, selectivity: 45.8 from IAST). This work not only provides a new strategy for defect regulation and in situ functionalization of COFs but also provides a valuable approach in the design and preparation of new adsorbents for CO2 adsorption and CO2/N2 selective separation.

Chitin-derived fibrous carbon microspheres as support of polyamine for remarkable CO2 capture

Supported polyamines are promising candidates for the chemical adsorption of CO2, the performance of which is highly dependent on the porous structure of supports. In this work, we synthesized a kind of fibrous carbon microspheres (FCMs) from environmentally friendly and low-cost chitin. The synthesized FCMs have microspheric morphology and fibrous sub-architecture, and the carbon fibers interweave to form pores with large diameters. The flexibility of the pores formed by the interweaving of carbon fibers also enable the supporting of high quantity of polyamines. Given these features, pentaethylenehexamine (PEHA) was physically dispersed in the pores of FCMs to prepare PEHA/FCMs adsorbents, which were systematically characterized and investigated for CO2 capture performance. It is found that PEHA/FCMs adsorbents show excellent ability for CO2 adsorption, with the highest CO2 capacity of 3.90 mmol g−1 at 75 °C when using 10 vol% of CO2 for determinations. The reversibility of PEHA/FCMs adsorbents for CO2 adsorption is also fairly good, and PEHA/FCMs adsorbents have strong ability for the selective adsorption of low-content CO2 from N2.

Polyethylene glycol/silica and carbon black/silica xerogel composites as an adsorbent for CO2 capture.

Mesoporous polyethylene glycol (PEG)/silica and carbon black (CB)/silica xerogel composites were prepared by the sol-gel method as an adsorbent for CO2 adsorption. The CO2 adsorption process was carried out under pure CO2 atmosphere at room temperature in addition to ambient air. The xerogel composites with high surface area and pore volume showed better CO2 adsorption capacity than the pure silica xerogel. After modifying samples with propylene diamine using the wet impregnation method, an increase in CO2 adsorption capacity was observed for the samples except CB/silica xerogel composite. The highest CO2 adsorption capacity was determined as approximately 0.80 mmol/g for amine modified PEG/silica xerogel composite under pure CO2 exposure. According to the adsorption-desorption cyclic stability test, it was clear that the stable samples were obtained, which is a desirable property for all CO2 adsorbents. The promising findings revealed that the xerogel composites can be efficiently used as a CO2 adsorbent instead of conventional materials in many CO2 adsorption applications. Additionally, it can be expected that the xerogel composites can provide an effective adsorption process without high-cost, complexity, corrosion, and toxicity problems.

Effects of element doping and H2O presence on CO2 adsorption using hexagonal boron nitride

The characteristics of CO2 adsorbing on hexagonal boron nitride (h-BN) under various conditions are key to its application in industries. In this study, h-BN is selected as the adsorbent for CO2 adsorption and carbon/nitrogen (C/N) is the doping element. By means of density functional theory (DFT) calculations, adsorption structures, adsorption energies, distribution of electron clouds, transition state (TS) processes (free state → adsorption state) and effects of H2O are used to explain adsorption mechanisms of CO2 on pure/doped h-BN. According to calculation results, with doping of C/N, the delocalized π bond of h-BN is transformed and then CO2 adsorption on the specific site is enhanced. In the meantime, this study also reveals that h-BN should be treated as the tertiary amine in a way because H2O presence could obviously facilitate CO2 adsorption on pure/doped h-BN, consistent with existing studies. What is more, the study uncovers that the TS energy barrier of CO2 adsorption is another factor that affects adsorption strength. It is found that doping of C/N and H2O presence could reduce adsorption energy barriers and facilitate CO2 adsorption. The research results could provide valuable information about exploiting h-BN for massive CO2 adsorption in industrial situations.

Radiation induced graft copolymerization of amine-containing monomer onto polyethylene coated propylene for CO2 adsorption

Modification of polyethylene coated polypropylene by radiation-induced graft copolymerization (RIGP) of N-vinylformamide film followed by hydrolysis was studied to produce polyvinylamine (PVAm) containing adsorbent for CO2 adsorption. A number of grafting parameters such as irradiation dose, monomer concentration, and reaction temperature were investigated to obtain desired degree of grafting (DOG) prior to hydrolysis. The DOG was found to be a function of reaction parameters and achieved a desired value of 131% at 40 wt% NVF concentration in toluene, 300 kGy dose, 70°C temperature and 1h reaction time. Subsequently the hydrolysis of formamide groups in the grafted films into amine functionalities was carried out in basic medium. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the NVF monomer was successfully grafted on PE/PP and consequently the hydrolysis of amide into amine functionalities has occurred in the grafted substrates. The CO2 adsorption capacity of PVAm modified adsorbent was brought to be a function of DOG, which is corresponding to the amine content after hydrolysis. The adsorbent showed the highest CO2 adsorption capacity of 1.32 mmol/g when tested with gas composition of 40% CO2 and 60% nitrogen at room temperature.

Carbon Nanoflakes and Nanotubes from Halloysite Nanoclays and their Superior Performance in CO2 Capture and Energy Storage.

Nanoporous carbon (HNC) with a flake and nanotubular morphology and a high specific surface area is prepared by using natural halloysite nanotubes (HNTs), a low-cost and naturally available clay material with a mixture of flaky and tubular morphology. A controlled pore-filling technique is used to selectively control the porosity, morphology, and the specific surface area of the HNC. Activated nanoporous carbon (AHNC) with a high specific surface area is also prepared by using HNT together with the activation process with zinc chloride (ZnCl2). HNC exhibits flakes and tubular morphologies, which offer a high specific surface area (837 m2/g). The specific surface area of AHNC is 1646 m2/g, 74 times greater than the specific surface area of pure HNT (22.5 m2/g). These data revealed that the single-step activation combined with the nanotemplating results in creating a huge impact on the specific surface area of the HNC. Both HNC and AHNC are employed as adsorbents for CO2 adsorption at different pressures and adsorption temperatures. The CO2 adsorption capacity of AHNC is 25.7 mmol/g at 0 °C, which is found to be significantly higher than that of activated carbon (AC), mesoporous carbon (CMK-3), mesoporous carbon nitride (MCN-1), and multiwalled carbon nanotube (MWCNT). AHNC is also tested as an electroactive material and demonstrates good supercapacitance, cyclic stability, and high capacitance retention. Specific capacitance of AHNC in the aqueous electrolyte is 197 F/g at 0.3 A/g, which is higher than that of AC, MWCNT, and CMK-3. The technique adopted for the preparation of both HNC and AHNC is quite unique and simple, has the potential to replace the existing highly expensive and sophisticated mesoporous silica-based nanotemplating strategy, and could also be applied for the fabrication of series of advanced nanostructures with unique functionalities.

Synthesis and characterization of amine-impregnated silica gel for potential carbon dioxide (CO2) absorption

The rising of CO2 concentration in atmosphere become global concern due to its effect to the global warming. One potentially economical for CO2 capture is through adsorption using solid sorbents. Silica gel has potential to adsorb carbon dioxide with modification of silica gel with amine groups which provide specific adsorption sides for carbon dioxide adsorption. Therefore, a study of impregnated silica gel with amine for carbon dioxide adsorption was done. A series of characterization was made between raw silica and impregnated silica with amine. Based on the results from Iodine Test Analysis and DSC characterization, it can be stated that the modification of Raw Desiccant Silica Gel (DSG) which had been modified with Aminopropyltrimethoxysilane (APMS), 95% had the highest possibilities of percentage to absorb CO2 from the environment with iodine value of 2736.85 mg/g that indicate the porosity and surface area of the adsorbent is higher. Amine 1A consist of 17.84 % of carbon, 5.41 % of hydrogen and 6.44 % of nitrogen. For FTIR result, Amine 1A has Si-O-Si stretching, C-C stretching, N-C stretching and C-N stretching due to the impregnation of amine to the raw silica gel. From DSC analysis, the higher the peak shows that water molecule bound to Amine 1A evaporated at a higher temperature of 92.4°C shows the highest porosity and have highest possibility as adsorbent for CO2 adsorption.

Hydroxide modified activated alumina as an adsorbent for CO2 adsorption: Experimental and modeling

Activated alumina (AA) was modified with sodium hydroxide and potassium hydroxide solutions to enhance carbon dioxide adsorption capacity. The process optimization was carried out using response surface methodology (RSM) based on central composite design (CCD) with two variables, the temperature and pressure in the range of (20–80 °C) and (2–10 bar), respectively. In addition, the effect of operating parameters including adsorbent amount, percentage of hydroxide solution, temperature and pressure on the CO2 adsorption process were investigated. The optimum CO2 adsorption capacities for modified activated alumina adsorbents with 30% NaOH and KOH at temperature of 20 °C and pressure of 6 bar were found to be 146.70 and 130.84 mg/g adsorbent, respectively. The Freundlich isotherm model was showed the best accordance with the experimental data and the kinetic modeling results indicated that the Elovich model is well-fitted for adsorption process by modified activated alumina. As well as thermodynamic parameters revealed that the adsorption process for the studied three adsorbents is exothermic and spontaneous.

A new method of processing CO2 and magnesite slag simultaneously

Calcining magnesite slag to capture CO2 is a new and simple method of processing CO2 and magnesite slag simultaneously. In this work, the CO2 capture capacity by calcined magnesite slag in wet flue gas simulated by adding water vapour was investigated. The magnesite slag exhibits excellent CO2 adsorption performance, with 3.01 mmol/g CO2 adsorption capacity, which is reduced to 2.18 mmol/g after 8 cycles and is obvious superior to magnesite. The structure and characterization of the magnesite slag are examined by XRF, FT-IR, TGDSC, XRD, CO2-TPD and BET. It can be confirmed by X-ray fluorescence analysis that the key component of magnesite slag is MgSiO3 and MgCO3. The results of this work indicate that the magnesite slag is an available adsorbent for CO2 adsorption after calcination.

Addition of Water in Calcium Based Adsorbent for CO2 Adsorption: Experimental and Isotherm Modelling Studies

In this work, a combined process of adsorption and gas hydrate formation is proposed as an alternative approach for the separation of carbon dioxide (CO2) content from gas stream. The objective of this research is to study adsorption isotherms of the CO2 gas onto the synthesized calcium oxide (CaO) via a static volumetric method at 2 °C at a different amount of water ratio (Rw). A large increment of CO2 adsorption was observed on the wetted sample due to formation of CO2 hydrates, particularly at high pressure. The highest adsorption capacity was obtained at Rw of 0.67. The experimental data of CO2 adsorption isotherms for Rw = 0 and Rw = 0.67 are further analyzed by five isotherm models which are Langmuir, Freundlich, Redlich-Peterson (R-P), Toth and Sips. The Freundlich model satisfactorily describes the CO2 adsorption onto the dried sample, whilst the R-P model is best fitted for the wetted sample.

A metal–organic framework MIL-101 doped with metal nanoparticles (Ni & Cu) and its effect on CO2adsorption properties

In this work, Cu- and Ni-doped MIL-101 were synthesizedviaa microwave irradiation technique and used as adsorbents for CO2adsorption. The loading of MNPs in MIL-101 showed a beneficial effect on the adsorption capacity and cyclability.

Adsorption of carbon dioxide by solution-plasma-synthesized heteroatom-doped carbon nanospheres

Porous carbon nanospheres (CNSs) synthesized by a plasma-in-liquid technique were applied as an adsorbent for CO2 adsorption. Two different types of aromatic solvents, benzene and pyridine, were used as precursors to generate CNSs. The prepared CNSs were carbonized and then activated with CO2 to obtain carbon materials with a suitable porous structure for CO2 adsorption. To improve CO2 adsorption capacity, activated CNSs were then chemically modified using different approaches of surface treatment, namely, HNO3 oxidation, amination without HNO3 preoxidation, and amination with HNO3 preoxidation. The CO2 adsorption capacities of the samples were investigated at 1 atm and 40 °C using a simultaneous thermal analyzer. It was found that the CO2 adsorption of CNSs was enhanced through the development of textural properties. All of the surface treatment approaches led to the increase in CO2 adsorption capacity of the activated CNSs owing to the presence of nitrogen or oxygen functional groups introduced onto the carbon surface during the treatment.

Synthesis of Mixed-Ligand Zeolitic Imidazolate Framework (ZIF-8-90) for CO2 Adsorption

Microporous metal–organic frameworks (MOFs) exhibit advantages on gas adsorption and catalysis of small molecules owing to high surface area and suitable pore size. One of the members in MOF, zeolitic imidazolate framework (ZIF), has attracted much attention in recent days, and different kinds of ZIFs had been synthesized with single organic linker. However, only few reports discussed the effect of mixed linkers. In this research, we synthesized mixed linker ZIF structure, ZIF-8-90. Different mole percentage of 2-methylimidazole and 2-imidazolecarboxaldehyde were mixed together to form ZIF-8-90 X %. We found that DMF had good effect on controlling the particle size but reducing the productivity ratio. The ZIF-8-90 X % NPs had different physical properties, such as surface area, pore size distribution and gas adsorption. The results showed that ZIF-8-90 30 and 50 % were the better adsorbents for CO2 adsorption (2.37 and 2.82 mol/g, respectively) at room temperature, as compared with other microporous framework, MIL-series, HKUST-1, ZIF-100.

Adsorption of carbon dioxide by sodium hydroxide-modified granular coconut shell activated carbon in a fixed bed

In the present work, commercial coconut shell activated carbon was impregnated with alkaline NaOH to investigate the efficiency of modified activated carbon for CO2 adsorption in a fixed-bed column adsorption system. The modification parameters, such as the NaOH concentration (24–48%) and dwelling time (1–4 h), were also investigated. The results showed that a 32% NaOH concentration with a 3 h dwelling time provided the best CO2 adsorption capacity. Later, the modified activated carbon was characterized by nitrogen adsorption–desorption, scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of the CO2 % in the feed, the adsorption temperature, the feed flow rate and the amount of adsorbent in the column were investigated in the adsorption experiments. The maximum CO2 adsorption capacity in this study was 27.10 mg/g at 35 °C. This study also suggests that NaOH-modified activated carbon is a state-of-the-art adsorbent for CO2 adsorption.

Pith based spherical activated carbon for CO2 removal from flue gases

Serials of pitch based spherical activated carbons (PSACs) were prepared and used as adsorbent for CO2 adsorption from flue gases. The results indicate that the ultrafine micropores (<1 nm) are effective pores for CO2 adsorption, and the equilibrium adsorption capacity of CO2 has a linear relationship with the specific surface area of ultrafine micropores (S<1 nm). The adsorption capacity of CO2 can obtain 1.12 mmol/g at 15 kPa and 30 °C on one of PSAC sample due to its high S<1 nm (845 m2/g). Because the molecular CO2 can be polarized into polar molecules and has four kinds of adsorption configuration, the adsorption selectivities of CO2 vs. N2 and O2 are 86.99% and 69.91%, respectively. When the combined Electric Swing Adsorption and Vacuum Swing Adsorption were applied for CO2 desorption, about 100% desorption efficiency can be obtained, the desorption rate is twice of that with Temperature Swing Adsorption (TSA) and the energy consumption is only 69% of that with TSA.