Mechanism Of CO2 Adsorption Research Articles

Fabrication of tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel and its application as an adsorbent for copper ion removal.

An effective tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel with high-potential sorption capacity was developed for the removal of copper from aqueous solution. The composite hydrogel exhibited pH-dependent swelling, in which swelling and shrinking occurred reversibly with adjustment of the pH of the medium. At pH 4, the maximal adsorption capacity for copper at 30°C was 297.0mg g-1, and the adsorbent dose was 4g L-1. The adsorption kinetics were best fitted with a pseudo-second order kinetic model. The adsorption behavior was well predicted by the Freundlish isotherm. The thermodynamics parameters indicated a spontaneous and exothermic reaction with an increase in the entropy of the system. The chemical changes in the film structure before and after adsorption treatment were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). The FTIR, XPS and XAS results confirmed that Cu bound to the oxygens in the -OH, C = O and N-(C = O)- functional groups on the T-HD. XAS analysis revealed the chemical composition and molecular geometry of the adsorbed copper ions. The single-solute adsorption and coadsorption mechanisms, which provide insight into cobalt-copper, nickel-copper, or nickel-cobalt-copper complex solutions, were investigated. The composite hydrogel exhibited excellent regeneration ability in EDTA solution. Notably, the adsorbent retained an adsorption efficiency exceeding 87% even after five regeneration cycles. On the basis of both adsorbent characteristics and adsorption performance, it was determined that the composite hydrogel has the potential to be used as a platform for developing materials to treat wastewater containing high levels of metal contaminants such as those from the electroplating industry.

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.

Experimental and molecular simulation study of CO2 adsorption in ZIF-8: Atomic heat contributions and mechanism

We successfully synthesised ZIF-8 using the solvothermal method at room temperature to study CO2 adsorption storage at 273 and 298 K up to 35 bar. Characterisation methods such as BET, SEM-EDS, XRD, and TGA were used to measure the physical and composition properties of ZIF-8. Grand canonical Monte Carlo (GCMC) simulation was conducted to compare with experimental data and get inside of the CO2 adsorption mechanism by calculating the isosteric heat and its fluid–fluid and solid–fluid contributions. The second was also split into fluid–solid atom contributions to understand in detail the interaction between CO2 and ZIF-8. The analyses revealed that there are three main stages during the CO2 adsorption gas–solid atom contributions, developing, pore-filling and densification. During the developing and pore-filling stages the largest fluid–solid atom contribution to the isosteric heat is CO2-C2 interactions, indicating that the CO2 is adsorbed close to the hexagonal windows of the ZIF-8 structure, while during the densification stage the largest contribution is CO2-N interactions. Where C2 and N refers to C-atom and N-atom, respectively in NCH group of the solid framework. This is because CO2 changes its orientation to be able to accommodate more molecules in the pore cavity. This work provides a better understanding of the adsorption mechanism of CO2 on ZIF-8 and shows how molecular simulation can be used to improve the understanding gas adsorption storage on metal–organic frameworks.

Theoretical predictions of CO2, H2 and H2O adsorption mechanisms on M2C-MXene: Selectivity and potential application insights

M2C-MXenes, owing to their abundant adsorption sites, exhibit significant potential in CO2 capture, utilization, and storage (CCUS) and hydrogen energy applications, contributing to hydrogen utilization and global carbon reduction, and thus solving intractable energy and environmental problems. However, the extensive variety of M2C compounds poses challenges to the systematic evaluation of their applications in these fields. The exploration of the adsorption properties of M2Cs is a key fundamental aspect of these studies, and therefore, this study employs calculations across 456 adsorption systems to elucidate the adsorption mechanisms of 19 M2C compounds for small molecules (CO2, H2 and H2O). The results indicate that these M2C materials possess structural stability and metallic characteristics, with periodic variations in the d-band center aligning with trends in CO2 adsorption energy. Notably, molecular orientation impacts adsorption energy more significantly than adsorption sites, particularly for CO2, while M2C compounds primarily exhibit physical adsorption towards H2. Specifically, Sc2C preferentially adsorbs CO2 in atmospheric conditions, and shows chemical adsorption towards H2O, but exhibits negligible adsorption for H2; conversely, Cr2C demonstrates higher adsorption potential for H2. Both materials exhibit favorable thermodynamic stability, suggesting Sc2C is suitable for CCUS applications, while Cr2C holds promising prospects for hydrogen storage.

Molecular simulation study of adsorption-diffusion of CH4, CO2 and H2O in gas-fat coal

In order to clarify the microscopic dynamics mechanism of CH4, CO2 and H2O adsorption and diffusion in coal, and to reveal the mechanism of the influence of different temperatures and pressures on the adsorption and diffusion characteristics of coal adsorbed CH4, CO2 and H2O molecules. In this paper, the macromolecular structure model of Jixi gas-fat coal was constructed, based on the Giant Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The adsorption-diffusion characteristics of CH4,CO2 and H2O single-component gases in the gas-fat coal macromolecule model at temperatures ranging from 273.15 K to 313.15 K and pressures ranging from 0.01 MPa to 15 MPa were investigated by using Material Studio software. The research results indicated that: The adsorption of three gases, CH4, CO2 and H2O, increased with the increase of equilibrium pressure, and the adsorption isotherms conformed to Langmuir type I isotherms. The amount of saturated adsorption of CH4 ranged from 11.18 to 14.37 ml/g, the saturated adsorption of CO2 ranged from 20.40 to 24.70 ml/g, and the saturated adsorption of H2O ranged from 66.61 to 84.21 ml/g. With the increase of temperature, the saturated adsorption of CH4 and CO2 both decreased, and the saturated adsorption of H2O firstly increased and then decreased, and the adsorption of H2O by low temperature and high temperature had both an inhibitory effect on the adsorption of H2O. The potential energy distributions of CH4, CO2 and H2O molecules are poisson distributed. The absolute values of the most available interaction energies are, from highest to lowest: H2O > CO2 > CH4; the activation energies for diffusion of CH4, CO2 and H2O are 12.20 kJ/mol, 3.36 kJ/mol, and 8.47 kJ/mol, respectively, and the diffusion of CO2 is the more likely to occur. The adsorption of CH4 and CO2 in coal is physical adsorption, while the adsorption process of H2O molecules is beyond the scope of physical adsorption. The absolute value of the interaction energy is H2O > CO2 > CH4 in descending order.

In-situ nitrogen-doped porous carbon derived from penicillin mycelial residue for CO2 adsorption and adsorption mechanism investigation

The in-situ nitrogen-doped porous carbon materials was synthesized using penicillin mycelial residue (PMR) as the sole endogenous nitrogen-rich precursor through a two-step process applied for CO2 adsorption. Precise control over the structural properties and CO2 adsorption performance of the porous carbon was achieved by varying the KOH dosage and activation temperature. The porous carbon prepared under mild activation conditions (600 ℃, KOH/BC = 1) exhibited high nitrogen content and abundant ultramicroporous structures (pore size ≤ 0.7 nm), and demonstrated outstanding adsorption performance. The CO2 adsorption capacities reached 6.55 mmol/g at 0 ℃ and 3.48 mmol/g at 25 ℃, showing promising CO2/N2 selectivity and robust cyclic adsorption stability. Quantitative structure–activity relationship analysis displayed a strong correlation between adsorption density, CO2/N2 selectivity, and nitrogen content. Density functional theory calculations further confirmed that nitrogen-doping, especially pyrrolic-N, serves as favorable structural sites for CO2 adsorption. Additionally, Grand Canonical Monte Carlo simulations verified that the ultramicroporous structures significantly enhances CO2 adsorption due to their strong affinity for CO2. This study provides an economic strategy for the preparation of in-situ nitrogen-doped porous carbon with enriched micropore using PMR, highlighting their promising performances in CO2 adsorption, synchronously extending the harmless treatment and resource utilization of PMR to demonstrate a sustainable approach for environmental remediation.

Adsorption mechanism of CO, CO2, NO, NO2, and SO2 gases onto AlNNT(m,n)_k, (m = 5, 7; n = 0, 5, 7; k = 3–9)

This study provides valuable insights into two key areas. First, we conduct a detailed examination of aluminum nitride nanotubes (AlNNT (m,n)_k), where m = 5,7; n = 0,5,7; and k = 3−9, focusing on their electronic properties across different lengths and diameters. We then investigate how these nanotubes interact with various gases, including CO, CO2, NO, NO2, and SO2. To determine the most energetically favorable configurations, we use the bee colony algorithm for global optimization. Our computational approach employs several Density Functional Theory (DFT) methods, such as PBE0, B3LYP(GD3BJ), CAM-B3LYP, HSE06, M06–2X, TPSSh, and ωB97XD functionals, in combination with the Def2svpp basis set. We prioritize the optimization of structural configurations and analyze the changes in energy band gaps within the nanotubes using conceptual DFT analysis. Additionally, we examine charge transfer mechanisms during gas/nanotube interactions through Natural Bond Orbital (NBO) analysis and assess the nature of these interactions with the Quantum Theory of Atoms in Molecules (QTAIM) framework. Our findings reveal that the interaction with SO2 tends to be slightly stronger compared to the other gases, as evidenced by various analytical techniques. This comprehensive analysis enhances our understanding of gas interactions with aluminum nitride nanotubes and provides insights into their practical applications.

Asymmetric Microenvironment Tailoring Strategies of Atomically Dispersed Dual-Site Catalysts for Oxygen Reduction and CO2 Reduction Reactions.

Dual-atom catalysts (DACs) with atomically dispersed dual-sites, as an extension of single-atom catalysts (SACs), have recently become a new hot topic in heterogeneous catalysis due to their maximized atom efficiency and dual-site diverse synergy, because the synergistic diversity of dual-sites achieved by asymmetric microenvironment tailoring can efficiently boost the catalytic activity by optimizing the electronic structure of DACs. Here, this work first summarizes the frequently-used experimental synthesis and characterization methods of DACs. Then, four synergistic catalytic mechanisms (cascade mechanism, assistance mechanism, co-adsorption mechanism and bifunction mechanism) and four key modulating methods (active site asymmetric strategy, transverse/axial-modification engineering, distance engineering and strain engineering) are elaborated comprehensively. The emphasis is placed on the effects of asymmetric microenvironment of DACs on oxygen/carbon dioxide reduction reaction. Finally, some perspectives and outlooks are also addressed. In short, the review summarizes a useful asymmetric microenvironment tailoring strategy to speed up synthesis of high-performance electrocatalysts for different reactions.

Transition metal-loaded C2N catalysts for selective CO2 reduction to CH4: Insights from first-principles calculations

The escalating atmospheric CO2 levels due to fossil fuel consumption pose significant environmental challenges, including the greenhouse effect and ocean acidification. Converting CO2 into valuable fuels and chemicals through electrochemical CO2RR is a promising strategy to mitigate these issues. However, the high thermodynamic stability of CO2 and the competing HER present challenges in achieving high selectivity and efficiency. This study employs first-principles calculations to investigate the performance of transition metal trimer catalysts (3TM-C2N, TM = Mn, Mo, Ru, Ti) supported on porous graphitic C2N for CO2RR to CH4. The catalysts were constructed and their stability, electronic structure, and CO2 adsorption mechanisms were systematically analyzed using DFT. The results indicate that 3TM-C2N catalysts are structurally stable, efficiently adsorb and activate CO2, and effectively suppress HER. Notably, 3Mn-C2N demonstrated optimal selectivity for CH3OH and CH4 with a limiting potential of −0.44 V, while 3Ru-C2N showed superior selectivity for the same products at limiting potentials of −0.86 V and −0.73 V, respectively. These findings provide theoretical insights for the experimental optimization of C2N-based catalysts and guide the development of efficient CO2RR electrocatalysts.

Co-adsorption performance and mechanism of ammonium and phosphate by iron-modified biochar in water

To recover nitrogen and phosphorus from water bodies and reduce their potential risk of causing eutrophication, high-temperature pyrolysis-produced biochar (HBC) modified by ferric chloride (Fe-HBC) was adopted to investigate its surface modification on the co-adsorption performance of nitrogen and phosphate. In comparison to HBC, Fe-HBC exhibited superior specific surface area, well-developed pore structure, and enriched surface functional groups while successfully loading Fe2+ and Fe3+. It has been determined that the co-adsorption mechanism of ammonium and phosphate by Fe-HBC involves a combination of pore filling, ion exchange, functional group coordination, electrostatic attraction, and coprecipitation. The results from the batch adsorption experiments indicate that the ammonium adsorption capacities for Fe-HBC1, Fe-HBC2, and Fe-HBC3 were 10.59 mg/g, 10.38 mg/g, and 7.59 mg/g, respectively, while the phosphate adsorption capacities were 13.46 mg/g, 10.46 mg/g, and 15.22 mg/g, respectively. The results of the column adsorption experiments showed that too high or too low biochar percentage and flow rate were not conducive to improving the adsorption capacity of the adsorption column, and the maximum adsorption capacity of the adsorption column was achieved at a biochar percentage of 1 % and a flow rate of 1 mL/min. This study demonstrates the potential of this iron-modified biochar derived from agricultural wastes for practical application in the removal of ammonium and phosphate from wastewater.

Amine-modified SiO2 aerogel for efficient adsorption of low-pressure CO2: Response surface methodology optimization and adsorption mechanism

Amine-modified SiO2 aerogel (AMSA) has shown tremendous potential in CO2 capture due to its unique three-dimensional network structure and excellent stability. However, it still faces many challenges in the preparation optimization, adsorption enhancement at low CO2 partial pressure, and mechanism elucidation. Hence, in this paper, the response surface methodology is employed for the first time and the optimal preparation conditions for AMSA are determined. A regression model is successfully established to accurately predict the CO2 adsorption capacity of AMSA under different synthesis conditions (with a relative error of only 0.98 %). Additionally, the AMSA prepared at optimal conditions exhibits high CO2 adsorption capacity of 2.11 mmol/g and excellent stability (only decreased by 1.44 % after 8 cycles) at 10 % CO2 partial pressure, indicating enormous application potential. Notably, the CO2 adsorption mechanism by AMSA at different temperatures and partial pressures are revealed in detail through fitting with the Freundlich isotherm and the double-exponential model, as well as thermodynamic parameter calculations. Firstly, the CO2 adsorption behavior belongs to the multi-layer adsorption behavior with uneven energy of active sites. Secondly, the CO2 adsorption capacity and rate are jointly controlled by molecular motion and chemical reaction equilibrium, diffusion and chemical reaction steps, respectively. Finally, the adsorption process is exothermic and spontaneous, and the level of disorder decreases at the gas-solid interface. This study not only achieves efficient adsorption of low-pressure CO2, but also deepens the understanding of gas-solid interface adsorption mechanisms, providing scientific basis and technological support for the development of novel efficient AMSA adsorbent materials.

A theoretical simulation of carbon dioxide adsorption capture on amine-functionalized graphene oxides

Amine-functionalized graphene oxides (AFGOs) are potential candidates for CO2 capture applications, as the amine functional groups could act as effective sites, promoting CO2 adsorption strength and selectivity. However, the CO2 adsorption mechanism on AFGO appears to be ambiguous, particularly with no explicit identification of the chemically bonded species. In this work, density functional theory and microkinetic simulations were carried out to investigate the physical and chemical adsorption mechanisms and behavior between AFGO and CO2. Our findings indicate that the van der Waals and hydrogen bonding (HB) interactions constitute physical binding modes between the aminated GO and CO2. The chemical adsorption pathways on AFGO materials have been revealed by the transition state search method, in which the relevant CO2 adsorption species, including carbamic acid and carbamate, and their formation conditions were theoretically identified on AFGOs. The chemisorption mechanisms have been recognized to be the nucleophilic interaction between GO-supported amines and CO2, simultaneously assisted by the cooperative effect of multiple HB interactions. More specifically, the surface hydroxyl groups and water molecules can serve as proton transfer media and offer HB interactions, thus regulating the reaction activity and chemical adsorption species. This theoretical work presents a new insight into CO2-AFGO interaction mechanisms, which is valuable for designing aminated GO adsorbents.

Harmonizing Between Chemical Functionality and Surface Area of Porous Organic Polymeric Nanotraps for Tuning Carbon Dioxide Capture.

The energy sector has demonstrated significant enthusiasm for investigating post-combustion CO2 capture, storage, and separation. However, the practical application of current porous adsorbents is impeded by challenges related to cost competitiveness, stability, and scalability. Intregation of heteroatoms in the porous organic polymers (POPs) dispense it more susceptible for CO2 adsorption to attenuate green house gases. In this regard, two hydroxy rich hypercrosslinked POPs, namely Ph/Tt-POP have been developed by one-pot condensation polymerization using a facile synthetic strategy. The high surface areas of both the Ph/Tt-POP (1057 and 893 m2g-1, respectively), and the heteroatom functionality in the POP framework instigated us to explore our material for CO2 adsorption study. The CO2 uptake capacities in Ph/Tt-POP are found to be 2.45 and 2.2 mmol g-1, at 273 K respectively. Further, in-situ static 13C NMR experiment shows that CO2 molecules in Tt-POP appear to be less mobile than those in Ph-POP which probably due to the presence of triazine functional groups along with high abundant -OH groups in the Tt-POP framework. An in-depth study of the CO2 adsorption mechanism by density functional theory (DFT) calculations also shows that CO2 adsorption at the cages formed by two benzyl rings represents the most stable interaction and CO2 molecule is more favorably adsorbed on the Ph-POP with the more negative interaction energies values compared to that of Tt-POP. Further, Non-covalent interaction (NCI) plot reveals that CO2 molecules adsorb more on the Ph-POP than Tt-POP, which can be explain by hydrogen bond formation in case of Tt-POP repeating units turning aside CO2 molecule to interact with the Ph component. Overall, our present study reflects the comprising effects of surface area of the solid adsorbents as well as their functionality can be beneficial for developing efficient hypercrosslinked porous polymers as solid CO2 adsorbent.

Multicomponent adsorption mechanism of CO2, SO2, NO, and C7H8 from flue gases on nitrogen-doped biochar: Experimental and computational insights

The comprehensive control of CO2 and gaseous pollutants in coal-fired flue gas is urgent and difficult. As a green low-cost adsorbent, nitrogen-doped biochar has potential application in the control technology of flue gas pollutants. Still, its multi-component adsorption characteristics for flue gas are unclear. In this study, the multi-component adsorption characteristics of CO2, SO2, NO, and C7H8 on nitrogen-doped biochar were explored at different temperatures (25–120 °C), and the competitive mechanism of multi-component adsorption was revealed through continuous adsorption experiments and numerical calculation. The adsorption capacities of CO2, SO2, NO, and C7H8 by nitrogen-doped biochar can reach 38.1, 78.9, 3.1, and 245.2 mg/g, among which CO2, SO2, and C7H8 show strong competitive effects. Their adsorption capacities are decreased by 42 % (CO2), 28 % (SO2), and 27 % (C7H8) respectively compared with the single-component adsorption. This is because there are not only more C7H8 adsorption sites on nitrogen-doped carbon, but also C7H8 can partially occupy the adsorption sites of SO2 and CO2 during multi-component adsorption. Combined with the calculation results of density functional theory, the competitive ability of the three gases can be ranked as follows: C7H8 > SO2 > CO2.

TiO2-loaded phosphogypsum-modified biochar for the removal of ofloxacin and Cu2+: Performance, mechanisms, and toxicity assessment

The combined contamination of antibiotics and heavy metals usually occurs in aquaculture wastewater and has high ecological toxicity. Currently, most research only focuses on the removal of a single heavy metal or antibiotics, and there is little research on the simultaneous removal of both. Therefore, to effectively treat them, this study prepared TiO2-loaded phosphogypsum-modified biochar (TYBC450) for adsorption and photocatalytic removal of ofloxacin (OFL) and copper (Cu2+). The removal performance and mechanisms of OFL and Cu2+ were explored, and their ecological toxicity was assessed through zebrafish acute toxicity experiments. The results suggested a synergistic effect between OFL and Cu2+. The adsorption efficiencies of TYBC450 for OFL and Cu2+ were 88.16% and 90.87% (the adsorption capacities were 1.75 and 3.65 mg/g, respectively). Bridging, precipitation, and complexation effects were the main co-adsorption mechanisms. The photocatalytic efficiencies of OFL and Cu2+ were 91.23% and 72.09% (the rate constants were 0.0101 and 0.0045 min-1, respectively). OFL acted as a hole-trapping agent, while Cu2+ acted as an electron acceptor, hindering the combination of e- and h+. There were 12 intermediates in the OFL degradation process, which had lower toxicity than the mother organism. Both the cyclic regeneration and actual aquaculture wastewater application tests indicated that TYBC450 had potential application prospects.

Adsorption of CO2/CH4 on the aromatic rings and oxygen groups of coal based on in-situ diffuse reflectance FTIR

The adsorption mechanisms of CH4 and CO2 on the coal surface is the theoretical basis for CO2 sequestration with enhanced coalbed methane recovery (CO2-ECBM). Molecular simulation is the main method to study the adsorption mechanism at present, but the model used in the process of molecular simulation could not accurately characterize the coal macromolecular structure. Therefore, we used in-situ diffuse reflectance Fourier-transform infrared spectroscopy (FTIR) to study the adsorption of CO2/CH4 on the aromatic rings and oxygen groups of coal. The results showed that CO2 and CH4 were physisorbed on the aromatic rings, and the aromatic rings represented the primary competitive adsorption sites for CO2 and CH4, CO2 was preferentially adsorbed at the top of the aromatic ring compared to CH4. Both carboxyl and carbonyl groups were beneficial for CO2 adsorption but not for CH4 adsorption. Compared to aromatic rings, the adsorption affinity of carboxyl groups for CO2 were stronger. The results of this study revealed the adsorption mechanisms of CO2 and CH4 on the aromatic rings and oxygen groups, as well as the impact of oxygen groups on the gas adsorption capacity, providing a theoretical basis for applying CO2-ECBM in the medium-volatile bituminous coal reservoirs.

CO adsorption mechanisms on transition metal surfaces and factors influencing the adsorption

CO adsorption on transition metal (TM) surfaces has been extensively studied. Compared to the "vertical adsorption" (CO⊥M) in which the C–O bond is normal to the surface with the C bonded to the surface, few studies are devoted to the "parallel mode" (CO||M) where the C–O bond is (near) parallel to the surface with both C and O atoms interacting with the surface. Here we report density functional calculations of CO adsorption on the stable surfaces of 27 TMs. The results show that CO adsorbs only in CO⊥M mode on IB, IIB, VIIB and VIII TMs while both CO⊥M and CO||M modes exist on IIIB to VIB TMs, with CO||M being more stable. Overlap population analysis reveals that the interactions between metal d AOs and O 2p AOs dominate the CO||M mode where the CO π bond is greatly weakened, resulting in significantly activated CO. The adsorption mode and adsorption energy can be tuned by ensemble effect, lattice strain and crystal structure, while the ligand effect is weak and is not able to change the adsorption mode of CO. The present work demonstrates that ensemble effect, lattice strain and crystal structure can be utilized to modify surface chemistry and promote catalytic performance effectively.

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.

Engineering CALF-20/graphene oxide nanocomposites for enhancing CO2/N2 capture performance

Ever-increasing atmospheric CO2 concentrations has necessitated the development of novel and cost-effective nanostructured composites with favorable physicochemical properties. Recently, the potential of metal-organic framework (MOF)-based nanocomposites towards boosting CO2 capture capability has become apparent indicating the importance of the relationship between their structure and properties. Herein, a novel nanocomposite of zinc-based CALF-20 MOF hybridized with graphene oxide is successfully fabricated using the solvothermal method. The construction of the well-structured nanocomposite is confirmed by performing PXRD, BET, FTIR, FESEM/EDX, TEM, and TGA characterization analyses. CO2 and N2 adsorption capacities and CO2/N2 separation performance of these nanocomposites are evaluated by experiment and mathematical modeling for the first time. The CALF-20/GO interfacial interaction and CO2 adsorption mechanisms are also discussed. As the best-performing adsorbent, the CALF-20 containing 20 wt% GO indicates a 42.6 % increment in CO2 uptake at 1.6 bar and a 32.7 % enhancement in CO2/N2 selectivity at 1 bar and 298 K and 1.28 times more CO2 retention time in a fixed bed column compared to that of the pristine MOF. The results show that the MOF and GO form chemical bonds at the interface resulting in generating new pore structures and increasing the porosity which are mostly responsible for boosting CO2 capture capacity. Interestingly, no meaningful effect is observed by the variation of the zinc atomic concentration at the surface. The simple synthesis procedure and understanding the interfacial structure of the novel CALF-20/GO composite as a promising adsorbent for CO2 capture applications can provide new insights for future work.

Investigation of Ultramicroporous Structure of One-Dimensional Lepidocrocite Titanates Using Carbon Dioxide and Nitrogen Gases.

The novel material, one-dimensional lepidocrocite (1DL) titanate, is attracting industrial and scientific interest because of its applicability to a wide range of practical applications and its ease of synthesis and scale up of production. In this study, we investigated the CO2 adsorption capability and pore structures of 1DL freeze-dried and lithium chloride washed air-dried powders. The synthesized 1DL was characterized by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Using the constant-volume method, CO2 gas adsorption revealed that the 1DL exhibits type IV adsorption-desorption isotherms. The heats of adsorption obtained from the adsorption branches are lower than those obtained from the desorption branches. Brunauer-Emmett-Teller (BET) analysis, using N2 gas adsorption isotherms at 77 K showed that 1DL possesses 80.2 m2/g of BET specific surface area. Nonlocal density functional theory analysis indicated that two types of pores, meso-pores and ultramicro pores, exist in the 1DL freeze-dried powders. This work provides deep insights into the pore structures and CO2 adsorption mechanisms of 1DL powders.