CO2 Adsorption Process Research Articles

Mechanistic Insights into CO2 Adsorption of Li4SiO4 at High Temperature.

The development of materials with high adsorption capacity for capturing CO2 from industrial exhaust gases has proceeded rapidly in recent years. Li4SiO4 has attracted attention due to its low cost, high capture capacity, and good cycling stability for direct high-temperature CO2 capture. Thus far, the CO2 adsorption mechanism of Li4SiO4 is poorly understood, and detailed phase transformations during the CO2 adsorption process are missing. Here, aided by in situ X-ray diffraction and in situ Raman spectroscopy, we find that Li4SiO4 reacts with CO2 to form Li2SiO3 and Li2CO3 in CO2 atmosphere at 973 K, with no detectable involvement of crystalline Li2O during the adsorption process. Moreover, we observe a formation of stepped structures in the Li4SiO4 surface after CO2 adsorption by scanning electron microscopy. To illustrate the formation of stepped structures, we propose a modified double-shell mechanism, suggesting a possible two-dimensional nucleation and growth of Li2CO3. This work provides a deeper understanding of the CO2 adsorption mechanism and paves a way for further optimization of Li4SiO4-based adsorbents.

CO2 adsorption on fluorinated covalent triazine frameworks (CTFs): Structure remodeling and performance enhancement

In consideration of the fact that covalent triazine frameworks (CTFs) have shown great potential and application prospects as CO2 adsorbent to alleviate the greenhouse effect and climate change by adsorption process for carbon emissions, a kind of promising activated fluorinated covalent triazine frameworks (referred to O-CTFs) was prepared as the adsorbent to enhance CO2 adsorption. The O-CTFs was prepared by structure remodeling of the fluorinated CTFs based on a series of ring-opening, substitution and polymerization reactions. The remodeling mechanism was revealed by theoretical calculations and those characterization methods of SEM, BET, EDS, FTIR, XPS, 13C-NMR and HRMS. Subsequently, the adsorption thermodynamics and kinetics of CO2 on the CTFs and O-CTFs were systematically investigated to reveal the influence of structure remodeling on CO2 adsorption behaviors. The results showed that the structure remodeling developed porous structure by forming more mesopores and micropores, then modified surface group distribution by forming new nitrogen- and oxygen-containing groups such as pyridine and pyrrole rings. The increase of pore volume, especially micropore volume, resulted in the dynamic capacity promotion by 217.5 % at 273 K. And the dual screening effects of surface group distribution and porous structure led to the CO2/N2 selectivity improvement by 202.4 %. Then the amount increase of the mesopores promoted the rate increase of CO2 adsorption by 59.9 % by means of accelerating the internal diffusion of CO2 in porous structure. In addition, the isosteric heat of adsorption decreased by 10.0 %, meaning that CO2 molecules were easily desorbed from the O-CTFs. These are beneficial for the preparation of promising CO2 adsorbent and extended application of CO2 adsorption processes.

Mechanistic insights into SO2-induced deactivation of Ni-based materials for integrated CO2 capture and methanation

Dual functional materials (DFMs) for cyclic CO2 capture and methanation exhibit significant potential in mitigating global climate change and achieving carbon neutrality. However, material deactivation caused by SO2 poisoning presents a major challenge for its industrial applications. Herein, we tailored a kind of Ni-based DFM, andthe sulfur poisoning effects on CO2 adsorption and in-situ conversion were systematically investigated. The experimental results reveal a striking inverse relationship between SO2 concentration, CO2 capture capacity, and methane yield. Increasing SO2 concentration promotes the form of stable sulfate species and undecomposable, lower CO2 capture capacity which further decreases methane yield with the rate of decrease in methane yield rising sharply from 7.14 % to 85.71 % as the SO2 concentration increases from 100 ppmv to 1000 ppmv, compared to the methane yield in the absence of SO2. Physicochemical characterizations demonstrate that SO2 accumulates on the surface of DFM, initially forming sulfite and oxidizing to sulfate during the CO2 adsorption process. Furthermore, sulfur poisoning accelerates the oxidation of metallic Ni to Ni2+ after cyclic reactions, which suppresses high-temperature basic sites and surface oxygen vacancies of DFM. In-situ DRIFT studies reveal that the deposited sulfate remains stable during H2 reduction at 340°C, contributing to the decomposition of formate intermediates and ultimately leading to a decrease in methane production.

Research on the microscopic mechanism and model applicability differences of CH4 and CO2 adsorption based on molecular dynamics

To verify the accuracy and rationality of the molecular simulation model, the microscopic mechanism of gas adsorption was analyzed and clarified from a microscopic perspective. The effect of molecular models created by direct construction and supercell expansion on the adsorption capacities of CH4 and CO2 has been analyzed. Eight coal-based molecular configurations were created to simulate the isothermal adsorption process of CH4 and CO2 using various coal-based molecular configurations. Using physical experiments, the validity of different construction methods for coal-based molecular structures was verified. The direct construction method was chosen to simulate the effect of various coal-based molecular numbers on the adsorption capacity of CH4 and CO2. The results show that the adsorption capacity of CO2 on coal is greater than that of CH4. The isothermal adsorption curves of CH4 and CO2 in coal-based molecular systems constructed using different methods reveal that the adsorption of methane on coal molecules adheres to the Langmuir monolayer adsorption theory. The adsorption sites for methane increase with the rise in free volume. The structure directly constructed and the supercell expansion directly determines the amount of methane adsorbed by each coal based molecule. The adsorption constants of CH4 and CO2 on the supercell extended structure are more volatile than those on the directly constructed structure, and the structure constructed directly for different coal based molecules is better than the supercell extended structure. The simulation using the direct construction method shows that as the number of coal-based molecules in the molecular configuration increases, The isothermal adsorption quantities of CH4 and CO2 increase linearly. The molecular configuration is not affected by the number of anthracite molecules. Molecular configuration is not affected by the number of anthracite molecules. The rationality of model construction has no obvious relationship with the number of coal based molecules.

Crystal plane engineering-tailored Co-Ni bimetallic sites in CoNiO2 to achieve efficient photocatalytic CO2 reduction

Aligning the atomic structure of catalyst by the crystal-plane engineering is an effective strategy to enhance the photocatalytic activity. In this paper, the CoNiO2 nanosheets (NSs) with (200) and nanorods (NRs) with (111) crystal planes were successfully prepared through a simple hydrothermal method for CO2 photoreduction. The experimental results indicated that the CNO NRs had excellent CO2 photoreduction performance. The CO and CH4 yields over CNO NRs were about 48.66 and 5.84 μmol·g−1·h−1, which were about 2.62 and 2.61 times stronger than that of CNO NSs. Moreover, it was also about 10.70 and 6.25 times as good as the TiO2 commercial powder, respectively. Experimental and theoretical calculations demonstrated that the Co-Ni bimetallic sites on the (111) crystal plane of CNO NRs can effectively enhance the CO2 adsorption and activation ability compared with the single Ni site on the (200) crystal plane of CNO NSs. Besides, the energy barrier required for the development of the critical intermediate *COOH from *CO2 was greatly reduced on the Co-Ni bimetallic sites, thereby improving the CO2 photoreduction activity. The reaction paths were inferred by in-situ FTIR and 13C isotope tracer techniques, and finally a potential enhancement mechanism of the crystal plane engineering induces bimetallic sites to promote CO2 adsorption and activation process has been proposed.

Utilization of cocoa pod husk waste biomass for post-combustion CO2 adsorption

Biomass-derived activated carbon for carbon dioxide (CO2) post-combustion has been drawing attention because they are cost-effective and environment-friendly. In this study, activated carbon was prepared from cocoa pod husk waste (COP) biomass for CO2 adsorption. The COP was pyrolyzed and activated using potassium hydroxide (KOH). The activated carbon prepared was characterized using scanning electron microscopy (SEM), Scanning Electron Microscopy- Energy Dispersive Spectroscopy and Fourier transform infrared spectroscopy (FTIR) analysis. The performance of the activated carbons prepared for CO2 was evaluated using a CO2 gas analyzer. Optimization of the adsorption process of CO2 was carried out by varying some important variables affecting the adsorption process. Results showed activated carbon prepared has a good pore structure with high carbon content that supported CO2 adsorption. The Freundlich model provided the best fit with the experimental data while data fitted well to pseudo-second-order kinetics with an adsorption capacity of 6.5 mg/g. The optimal condition for CO2 adsorption, was an adsorption time of 1 min, a Carbonization temperature of 700 °C, and Bed height of 5 cm, and % CO2 removal of 99.5%. The study revealed (COP) biomass as a suitable activated carbon precursor for CO2 capture.

Oxidative pyrolysis for enhanced-CO2 adsorption capacity in biosolid-derived biochar

The study conducts the adsorption kinetic analysis of biosolid-derived biochar produced from pyrolysis and oxidative pyrolysis. The adsorption kinetic analysis is performed at three different temperatures. The characteristics of the adsorption and diffusion mechanisms are evaluated by applying adsorption kinetic models and diffusion mechanism models. The pseudo-first-order model (PFO) and the pseudo-second-order model (PSO) reveal that the CO2 adsorption process of the biosolid can be categorised as physisorption with activation energy below 40 kJ/mol. The CO2 adsorption capacities of the biochar produced at 700 °C, 800 °C, and 900 °C are 6.3, 7.9, and 6.4 mg/g at 45 °C, respectively. In contrast, the biochar produced from oxidative pyrolysis shows a CO2 adsorption capacity of 7.5 mg/g at 45 °C. Film and intraparticle diffusions are primary rate-limiting factors of the adsorption process. The biochar samples maintain 84–85 % of their adsorption capacities after five cyclic tests. The present study demonstrates the CO2 adsorption capacity of biosolid-derived biochar produced from different conditions of pyrolysis, providing an energy-efficient and sustainable solution to CO2 adsorption with solid adsorbents.

Ultra-strong adsorption of ammonia nitrogen from low-temperature and complex systems by Prussian blue analogue

The aquatic ecosystem is threatened globally by eutrophication due to ammonia nitrogen inputs from wastewater. Developing high-performance adsorbents with high removal efficiency and selectivity for ammonia nitrogen is pivotal to ecological equilibrium. Here, the removal of ammonia nitrogen by a combined process of Co-based Prussian blue (NaCo-PBA) and coagulants was studied for the first time. The maximum adsorptive capacity of ammonia nitrogen by NaCo-PBA was 52.72 mg/g, and the removal reached 99 %. Compared with traditional adsorbents, NaCo-PBA showed high adsorption amounts (9–42 times). Most importantly, NaCo-PBA exhibited selectivity in complex systems and its adsorption quantity reached 42.6 mg/g in real domestic wastewater, compared to 4.7 mg/g for commercial adsorbent. NaCo-PBA was used in the coagulation and co-adsorption process to facilitate the separation of multiple contaminants in water. It is reasonable to believe that the collaboration between NaCo-PBA with special structure and coagulation will bring a new perspective to nitrogen removal in complex systems.

Investigating the microscopic enhancement mechanisms of adsorption-based CO2 capture with Cu-loaded γ−Al2O3 using density functional theory

Transition-metal-loaded γ−alumina (Al2O3) is considered to be an effective adsorbent for CO2 capture, but its microscopic process and mechanisms of CO2 adsorption are not fully understood. To investigate the microscopic enhancement role of Cu atoms in CO2 adsorption, this work compares various adsorption configurations and parameters of CO2 on γ−Al2O3 (110) facets with or without Cu atoms and small Cu cluster loading (Cun (n=1,2,3)/γ−Al2O3) using the first-principles approach. According to the adsorption energy, charge transfer, difference charge density, and other parameters of different configurations, the γ−Al2O3 (110) slab loaded with the Cu atom is found to exhibit enhanced adsorption of CO2 molecules compared to that without Cu loading. Moreover, the surface stability increases with the number of loaded Cu atoms. However, the hydroxyl groups in the active sites partially undermine the adsorption effect during the CO2 adsorption process. The density of states indicates that the doping of Cu atoms in the system creates an orbital peak closer to the Fermi energy level. This facilitates the transfer of charge within the slab, making the activation of CO2 easier and promoting stable adsorption. Finally, the amount of crystal orbital overlap population and crystal orbital Hamilton population shows that the stability of adsorption is due to the formation of C-Cu and C-Al bonds. It is demonstrated that the Cun-loaded γ−Al2O3 (110) slab improves the adsorption performance and contributes to a better understanding of the effect of transition-state metal loaded γ−Al2O3 on CO2 adsorption.

Coadsorption mechanisms of copper and sulfamethoxazole by functionalized cellulose: A kinetic and DFT study

In order to address the issue of compound pollution from heavy metals and antibiotics in aquatic environments, multibranched functionalized cellulose materials (DACS) with abundant adsorption affinity groups (such as amino, carboxyl and imine groups) were prepared by oxidation, etherification and grafting. The maximum adsorption capacities of DACS for copper (Cu) and sulfamethoxazole (SMZ) were 42.27 and 117.92 mg/g, respectively. In addition, its excellent pH buffering capacity, resistance to coexisting interfering substances and great regeneration performance of up to 91 % after 5 cycles. In the coadsorption experiment, the multibranched structure strengthened the bridge effect during the coadsorption process, and weakened the inhibition of SMZ adsorption caused by competition. Kinetic models and error functions analysis showed that PNO model and F&S model were the most consistent with the adsorption process, and the limiting step of adsorption was the external diffusion of Cu and SMZ around the surface of DACS. Moreover, the density functional theory (DFT) was used to quantitatively calculate the adsorption binding energy of multiple sites on DACS, and clarified the adsorption tendency of DACS as electron donors for Cu and as acceptor for SMZ. In addition, the binding energy of sequential adsorption was greater than that of single and binary adsorption, and the binding stability of SMZ was significantly increased in sequential adsorption for the increasing of binding energy. The electron exchange process in the adsorption showed that SMZ played a bridging role in the binary adsorption, while Cu was the main reaction part of the complex adsorption.

Study on the adsorption performance of zeolite imidazole frameworks materials for Co(II) and Mn(II) in solution

Abstract The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67.

Revealing the mechanism of hydration on the CO2 kinetic adsorption of CaO surface via ReaxFF MD simulations with experiments

Hydration has been regarded as an effective method to improve the cyclic activity of CaO during the Calcium looping CO2 capture process, but its mechanism remains unclear. In this work, the hydration reaction of CaO surface and its underlying mechanism was studied by ReaxFF molecular dynamics simulation combing with TGA experiments. The effect of hydration on the initial CO2 adsorption rate showed a trend of promoting at low H2O degree and inhibiting at high H2O concentration. The CaO surface was easily passivated, and it can maintain its crystal structure and begin to distort at about 1.0 H2O monolayer contents. Hydration failed to promote the CO2 adsorption rate, inversely the CO2 adsorption process accelerated the diffusion of H ions inward the CaO lattice·H2O dissociation produced two hydroxyl groups: direct OwH and indirect OsH. Atomic density profiles showed that the direct hydroxyl pairs were always, and indirect OsH groups can consume surface oxygen active sites, reducing the initial rapid CO2 adsorption activity. On the pre-hydrated CaO surface, CO2 molecules were more likely to bind to solid oxygen active sites than OH groups. The H free radical diffused inside the lattice in the form of transition HO2 state, promoting the slow CO2 adsorption amount.

Cobalt(II) removal with dolomite: Use of radiotracer technique in aqueous solution

Industrial processes have the potential to release cobalt into the environment, and exposure to cobalt in quantities higher than specific amounts can have harmful impacts on living organisms. This study aimed to determine whether natural dolomite from the Thrace region of Türkiye could effectively remove Co(II) from aqueous solutions. Batch studies were conducted to examine the impact of various experimental factors, including adsorbent dosage, initial Co(II) concentration, contact time, solution pH, and temperature. The cobalt concentrations in aqueous solutions were determined by employing 60Co radionuclide as a radiotracer. Experimental results revealed that optimum adsorption conditions were obtained at a solid-liquid ratio of 20 g·L−1, initial Co(II) concentration of 128 mg·L−1, contact time of 120 min, and pH 6 with a maximum adsorption capacity of 2.32 mg⋅g−1. The pseudo-second-order kinetic and Redlich-Peterson isotherm models described the experimental data well. The adsorption process of Co(II) ions on the dolomite was spontaneous and exothermic. The results showed the potential use of dolomite to remove such a toxic metal ion from industrial wastewater.

Interfacial mechanics of β-casein and albumin mixed protein assemblies at liquid-liquid interfaces

Protein emulsifiers play an important role in formulation science, from food product development to emerging applications in biotechnologies. The impact of mixed protein assemblies on surface composition and interfacial shear mechanics remains broadly unexplored, in comparison to the impact that formulation has on dilatational mechanics and surface tension or pressure. In this report, we use interfacial shear rheology to quantify the evolution of interfacial shear moduli as a function of composition in bovine serum albumin (BSA)/β-casein mixed assemblies. We present the pronounced difference in mechanics of these two protein, at oil interfaces, and observe the dominance of β-casein in regulating interfacial shear mechanics. This observation correlates well with the strong asymmetry of adsorption of these two proteins, characterised by fluorescence microscopy. Using neutron reflectometry and fluorescence recovery after photobleaching, we examine the architecture of corresponding protein assemblies and their surface diffusion, providing evidence for distinct morphologies, but surprisingly comparable diffusion profiles. Finally, we explore the impact of crosslinking and sequential protein adsorption on the interfacial shear mechanics of corresponding assemblies. Overall, this work indicates that, despite comparable surface densities, BSA and β-casein assemblies at liquid–liquid interfaces display almost 2 orders of magnitude difference in interfacial shear storage modulus and markedly different viscoelastic profiles. In addition, co-adsorption and sequential adsorption processes are found to further modulate interfacial shear mechanics. Beyond formulation science, the understanding of complex mixed protein assemblies and mechanics may have implications for the stability of emulsions and may underpin changes in the mechanical strength of corresponding interfaces, for example in tissue culture or in physiological conditions.

Carbon foams for CO2 adsorption: Synthesis, characterization and application

Carbon foams from phenolic resins of the resol and novolac type were synthesized and characterized, based on different experimental parameters and characterization techniques; with the objective of studying the synthesis process of carbon foams, their physicochemical characteristics, their CO2 adsorption capacities, and the influence that the different parameters applied in the synthesis process may have on the characteristics and adsorption capacity of each foam. The parameters applied in the synthesis of the carbon foams included the use of three different catalysts (sodium hydroxide, ammonia and oxalic acid), two foaming agents (n – pentane and dichloromethane) and two carbonization temperatures (600 and 800 °C).); and the characterization techniques used were CO2 adsorption isotherms, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy with X-ray scattering spectroscopy (SEM). – EDS). It is obtained that the highest adsorption capacities were obtained using sodium hydroxide as catalyst, and a carbonization temperature of 600 °C, this is reflected in the theoretical model of adsorption isotherms being the one that best describes the process of CO2 adsorption from carbon foams the Tóth model; with a maximum adsorption capacity (Qmax) higher than 50 cm3/g, up to 103 cm3/g.

Synthesis and Cation Exchange of LTA Zeolites Synthesized from Different Silicon Sources Applied in CO2 Adsorption

Zeolites have a well-ordered crystalline network with pores controlled in the synthesis process. Their composition comprises silicon and aluminum, so industrial residues with this composition can be used for the synthesis of zeolites. The use of zeolites for CO2 adsorption is feasible due to the characteristics that these materials have; in particular, zeolites with a low Si/Al ratio have greater gas adsorption capacities. In this work, the synthesis of LTA (Linde Type A) zeolites from silica fumes obtained from the industrial LIASA process and light coal ash is presented. We explore three different synthesis routes, where the synthesized materials undergo cation exchange and are applied in CO2 adsorption processes. Studying the synthesis processes, it is observed that all materials present characteristic diffractions for the LTA zeolite, as well as presenting specific areas between 6 and 19 m2/g and average pore distributions of 0.50 nm; however, the silica fume yielded better synthesis results, due to its lower impurity content compared to the light coal ash (which contains impurities such as quartz present in the zeolite). When applied for CO2 adsorption, the standard materials after cation exchange showed greater adsorption capacities, followed by the zeolites synthesized from silica fume and, finally, the zeolites synthesized from coal ash. By analyzing the selectivity of the materials for CO2/N2, it is observed that the materials in sodium form present greater selectivity when compared to the calcium-based materials.

Understanding the adsorption properties of CO2 and N2 by a typical MOF structure: Molecular dynamics and weak interaction visualization

An extensible molecular dynamics (MD) force field for a typical metal–organic framework (MOF) has been developed and verified in comparison with experimental data. The visualization of the important weak interactions based on density functional theory (DFT) calculations is performed. The dynamic process of CO2 and N2 adsorption by MOF was then studied by MD methods. The gas adsorption and desorption during temperature and pressure swing were also investigated. It is found that the structural features of MOF have an important effect on the regional range and strength of the weak interactions, and the region of the van der Waals potential surface of the MOF can determine the gas density distribution. The adsorption is dominated by van der Waals interactions on the whole and the variation of the total weak interaction energy can reflect that of the adsorbed amount. The sorption/desorption responds more slowly to temperature swing than to pressure swing.

Effect of Exposed Facets and Oxidation State of CeO2 Nanoparticles on CO2 Adsorption and Desorption.

CeO2 nanoparticles exhibit potential as solid adsorbents for carbon dioxide (CO2) capture and storage (CCS), offering precise control over various facets and enhancing their efficiency. This study investigated the adsorption and desorption behaviors of two types of CeO2 nanoparticles: cubic CeO2 with primarily {001} facets and polyhedral CeO2 with mainly {111} facets. The results showed that despite polyhedral CeO2's lower quantity, it demonstrated successful adsorption-desorption cycles in both oxidized and reduced states. However, reduced CeO2-x exhibited a higher adsorption capacity but displayed irreversible adsorption-desorption cycles. Reversible adsorption occurred through weak bond formation with CO2, while cubic CeO2 with a high oxygen vacancy concentration exhibited irreversible adsorption due to strong bond formation. These insights contribute significantly to understanding CeO2 nanoparticle characteristics and their impact on the CO2 adsorption and desorption processes, aiding in the development of advanced CCS techniques.

Preparation of amine functionalized micro-mesoporous silicon adsorbent from fly ash and its kinetic characteristics of CO2 adsorption/desorption process

Micro-mesoporous silicon materials were prepared using silicate filtrate produced from fly ash as a silicon source. Then, the micro-mesoporous silica material was used as the carrier and amine compounds as modifiers to prepare a micro-mesoporous CO2 adsorbent. Afterwards, the structural properties, surface groups, thermal stability of micro-mesoporous silicon materials and micro-mesoporous CO2 adsorbent were studied. The results reveal that the micro-mesoporous CO2 adsorbent maintains the same micro-mesoporous structure as the micro-mesoporous silica material. And the thermal stability temperatures of adsorbent is below 383 K. Later, the CO2 adsorption performance and kinetic characteristics of adsorption process were studied through thermogravimetric analysis (TGA) and adsorption column experiments. The results indicated that the optimal CO2 adsorption capacity of 2.31 mmol/g-adsorbent was achieved at 343 K, and the adsorption capacity remained basically unchanged after 10 adsorption/desorption cycles. Dynamics studies have shown that the Avrami fraction model fits the CO2 isothermal adsorption curve very well, and the fitting results reveal that the intra-particle diffusion dominates the speed of the adsorption process. Additionally, the Yasyerli deactivation model can perfectly fit the CO2 adsorption breakthrough curve, and the fitting results indicate that the CO2 adsorption process is the deactivation process of the adsorbent. Finally, the adsorption/desorption kinetic simulation parameters can be used for the design and optimization of CO2 adsorption and desorption processes in industry.

Competitive adsorption of CO2/CH4 on coal: Insights from thermodynamics

The main reason for CO2 enhanced coalbed methane recovery is the competitive adsorption of CO2 and CH4 on coal. Therefore, it is necessary to study the equilibrium adsorption of CO2, CH4 and their mixed gases on coal over a wide range of pressures. This work investigates the mechanism adsorption of CO2/CH4 on coal by thermodynamics. The findings indicate that CO2 demonstrates a greater increase in Gibbs free energy and a larger decrease in entropy loss related to CH4, indicating that the adsorption process of CO2 is more to occur spontaneously. In CO2/CH4 mixed gas adsorption system, the amount of gas adsorbed for different gas ratios (yCO2:yCH4 = 1:3; yCO2:yCH4 = 2:2; yCO2:yCH4 = 3:1) falls between the amounts adsorbed for pure CO2 and CH4 components. As CO2 concentration rises, the amount of mixed gases adsorbed similarly increases. Additionally, the amount of CH4 adsorbed in any combination is lower than that of CO2, suggesting that CO2 has a predominant influence regarding the adsorption process. Furthermore, isosteric heat of adsorption for CO2 in the mixed gases exceeds that of CH4, suggesting a stronger connection between CO2 and the surface of the coal matrix during the competitive adsorption stage.