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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.

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In view of the characteristics and risks of ammonia, its removal is important for industrial production and environmental safety. In this study, viscose-based activated carbon fiber (ACF) was used as a substrate and chemically modified by nitric acid impregnation to enhance the adsorption capacity of the adsorbent for ammonia. A series of modified ACF-based adsorbents were prepared and characterized using BET, FTIR, XPS, and Boehm titration. Isotherm tests (293.15 K, 303.15 K, 313.15 K) and dynamic adsorption experiments were performed. The characterization results showed that impregnation with low concentrations of nitric acid not only increased the surface acidic functional group content but also increased the specific surface area, while impregnation with high concentrations of nitric acid could be able to decrease the specific surface area. ACF-N-6 significantly increased the surface functional group content without destroying the physical structure of the activated carbon fibers. The experimental results showed that the highest adsorption of ammonia by ACFs was 14.08 mmol-L-1 (ACF-N-6) at 293 K, and the adsorption capacity was increased by 165% compared with that of ACF-raw; by fitting the adsorption isotherm and calculating the equivalent heat of adsorption and thermodynamic parameters using the Langmuir-Freundlich model, the adsorption process could be found to exist simultaneously. Regarding physical adsorption and chemical adsorption, the results of the correlation analysis showed that the ammonia adsorption performance was strongly correlated with the carboxyl group content and positively correlated with the relative humidity (RH) of the inlet gas. This study contributes to the development of an efficient ammonia adsorption system with important applications in industrial production and environmental safety.

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The stoichiometry of the components of hexacyanoferrate materials affecting their final porosity properties and applications in CO2 capture is an issue that is rarely studied. In this work, the effect that stoichiometry of all element components and oxidation states of transition metals has on the structures of mesoporous K or Na-cobalt hexacyanoferrates (CoHCFs) and CO2 removal is reported. A series of CoHCFs model systems are synthesized using the co-precipitation method with varying amounts of Co ions. CoHCFs are characterized by N2 adsorption, TGA, FTIR-ATR, XRD, and XPS. N2 adsorption results reveal a more developed external surface area (72.69-172.18 m2/g) generated in samples containing mixtures of K+/Fe2+/Fe3+ ions (system III) compared to samples with Na+/Fe2+ ions (systems I, II). TGA results show that the porous structure of CoHCFs is affected by Fe and Co ions oxidation states, the number of water molecules, and alkali ions. The formation of two crystalline cells (FCC and triclinic) is confirmed by XRD results. Fe and Co oxidation states are authenticated by XPS and allow for the confirmation of charges involved in the stabilization of CoCHFs. CO2 removal capacities (3.04 mmol/g) are comparable with other materials reported. CO2 adsorption kinetics is fast (3-6 s), making CoHCFs attractive for continuous operations. Qst (24.3 kJ/mol) reveals a physical adsorption process. Regeneration effectiveness for adsorption/desorption cycles indicates ~1.6% loss and selectivity (~47) for gas mixtures (CO2:N2 = 15:85). The results of this study demonstrate that the CoHCFs have practical implications in the potential use of CO2 capture and flue gas separations.

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Adsorbed natural gas (ANG) is a promising solution for improving the safety and storage capacity of low-pressure gas storage systems. The structural-energetic and adsorption properties of active carbon ACPK, synthesized from cheap peat raw materials, are presented. Calculations of the methane-ethane mixture adsorption on ACPK were performed using the experimental adsorption isotherms of pure components. It is shown that the accumulation of ethane can significantly increase the energy capacity of the ANG storage. Numerical molecular modeling of the methane-ethane mixture adsorption in slit-like model micropores has been carried out. The molecular effects associated with the displacement of ethane by methane molecules and the formation of a molecule layered structure are shown. The integral molecular adsorption isotherm of the mixture according to the molecular modeling adequately corresponds to the ideal adsorbed solution theory (IAST). The cyclic processes of gas charging and discharging from the ANG storage based on the ACPK are simulated in three modes: adiabatic, isothermal, and thermocontrolled. The adiabatic mode leads to a loss of 27-33% of energy capacity at 3.5 MPa compared to the isothermal mode, which has a 9.4-19.5% lower energy capacity compared to the thermocontrolled mode, with more efficient desorption of both methane and ethane.

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Calcium oxide incorporated porous carbon materials were synthesized by the impregnation method to study CO2 adsorption and separation of CO2/CH4. The X-ray diffraction, Raman analysis, N2 isotherms at 77 K, and SEM with EDX analysis were used to characterize synthesized materials. XRD and N2 isotherm results have confirmed that synthesized carbon has porosity, and EDX analysis has reported that the presence of CaO on porous carbon. 10CaO/porous carbon has shown 31 cm3 g-1 of CO2 adsorption which was higher than bare porous carbon CO2 adsorption 17.5 cm3 g-1 at 298 K, 1 bar. It was attributed to electrostatic interaction between CaO and CO2. However, CH4 adsorption was decreased by a decrease in surface area. The selectivity of CO2/CH4 was higher for 10CaO/porous carbon and the heat of CO2 adsorption was 36 KJ/mol at high adsorption of CO2. Moreover, CO2 adsorption was the same in each adsorption cycle.

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Objective:To investigate the moisture adsorption and thermodynamic characteristics of raw products， wine-processed products and fried charcoal products of Rhei Radix et Rhizoma， in order to guide their drying and storage. Method:Static isotherm weighing method was used to determine the adsorption isotherm curves of three Rhei Radix et Rhizoma decoction pieces at 25， 35， 45 ℃， and the test data were fitted with 7 commonly used water adsorption models to determine the best model for studying the adsorption thermodynamic parameters of these decoction pieces. Result:The best adsorption models of these three decoction pieces were all GAB model. At 25， 35， 45 ℃， the absolute safe moisture content of fried charcoal products was 7.43%， 6.79% and 6.20%， of wine-processed products was 8.68%， 8.17% and 7.03%， of raw products was 9.88%， 9.36% and 7.77%， respectively. At 25， 35， 45 ℃， the relative safe moisture content of fried charcoal products was 9.46%， 8.63% and 8.21%， of wine-processed products was 11.49%， 11.03% and 9.74%， of raw products was 13.49%， 12.66% and 11.14%， respectively. The net equivalent heat of adsorption （Qst） and differential entropy （Sd） of these three kinds of decoction pieces all decreased with the increase of equilibrium moisture content， Qst and Sd were in accordance with the entropy-enthalpy complementary theory. The constant velocity temperatures of raw products， wine-processed products and fried charcoal products of Rhei Radix et Rhizoma were 386.66， 391.15， 394.34 K （unit conversion of 1 K=-272.15 ℃）， their Gibbs free energies were 0.372 2， 0.406 0， 0.372 2 kJ·mol-1， respectively. Their adsorption processes were an unspontaneous process driven by enthalpy. Conclusion:The orders of equilibrium moisture content， monomolecular layer moisture content， Qst and Sd of three Rhei Radix et Rhizoma decoction pieces are all raw products>wine-processed products>fried charcoal products. The moisture absorption capacity of the decoction pieces is ranked as raw products>wine-processed products>fried charcoal products. The frying and roasting process significantly affects the hygroscopicity and thermodynamic properties of the three decoction pieces， the reason for this difference may be that the high temperature of the stir-frying results in the decrease of the hygroscopic groups and the increase of the hydrophobic materials in raw products， and the change in the texture of the decoction pieces. The research on the water adsorption characteristics of three Rhei Radix et Rhizoma decoction pieces can provide reference for selecting their storage conditions and drying process.

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Here, we report two novel water-stable amine-functionalized MOFs, namely IISERP-MOF26 ([NH2 (CH3 )2 ][Cu2 O(Ad)(BDC)]⋅(H2 O)2 (DMA), 1) and IISERP-MOF27 ([NH2 (CH3 )2 ]1/2 [Zn4 O(Ad)3 (BDC)2 ]⋅(H2 O)2 (DMF)1/2 , 2), which show selective CO2 capture capabilities. They are made by combining inexpensive and readily available terephthalic acid and N-rich adenine with Cu and Zn, respectively. They possess 1D channels decorated by the free amine group from the adenine and the polarizing oxygen atoms from the terephthalate units. Even more, there are dimethyl ammonium (DMA+ ) cations in the pore rendering an electrostatic environment within the channels. The activated Cu- and Zn-MOFs physisorb about 2.7 and 2.2 mmol g-1 of CO2 , respectively, with high CO2 /N2 and moderate CO2 /CH4 selectivity. The calculated heat of adsorption (HOA=21-23 kJ mol-1 ) for the CO2 in both MOFs suggest optimal physical interactions which corroborate well with their facile on-off cycling of CO2 . Notably, both MOFs retain their crystallinity and porosity even after soaking in water for 24 hours as well as upon exposure to steam over 24 hours. The exceptional thermal and chemical stability, favorable CO2 uptakes and selectivity and low HOA make these MOFs promising sorbents for selective CO2 capture applications. However, the MOF's low heat of adsorption despite having a highly CO2 -loving groups lined walls is quite intriguing.

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Isosteric heat of adsorption is exquisitely sensitive to structural changes in carbon surfaces based on the energetic behavior of the interactions between adsorbates and carbon materials. We discuss the relationships between porous structures, oxygen functional groups, and heat of adsorption based on the behavior of the heat of adsorption of polar and non-polar fluids on porous carbon materials with oxygen functional groups. The porosity and functional groups of porous carbon materials were estimated from N2 adsorption isotherms at 77 K and temperature-programmed desorption. High-resolution adsorption isotherms of water, acetonitrile (polar fluid), and n-hexane (non-polar fluid) were measured on porous carbon materials with different pore size distributions and amounts of oxygen functional groups at various temperatures. The heats of adsorption were determined by applying the Clausius-Clapeyron equation to the adsorption isotherms. The heat of adsorption curves directly reflect the effects of interactions of fluid-oxygen functional groups, fluid-basal planes of pore walls, and fluid-fluid interfaces. In particular, the heat of adsorption curve of water is very sensitive to surface oxygen functional groups. This finding indicates the possibility of estimating the relative amounts of oxygen functional groups on porous carbon materials based on the amounts of water adsorbed at specific relative pressures.

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An extended two-site exchange model is presented, which is used to evaluate pulsed field gradient (PFG) nuclear magnetic resonance (NMR) measurements of water in the nanoporous metal-organic framework MIL-100(Al). Here the water molecules exchange between the inter- and the intracrystalline space during the observation time, but are also restricted in their movement by the crystal surface. The evaluation of temperature and loading dependent PFG NMR data yields information about the intracrystalline diffusion process, the radius of the restricting geometry and the time constants of the exchange process. The intracrystalline mean residence time is found to decrease with increasing temperature, which allows an estimate of the heat of adsorption under the equilibrium conditions of the NMR measurements.

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In this article, an assessment of the impact of alkali-metal-ion impregnation on metal-organic frameworks (MOF) is presented employing CH4 and CO2 adsorption isotherm data. At first, the parent MOF, MIL-101(Cr), is prepared by a fluorine-free hydrothermal reaction procedure and impregnated with Li, Na, and K alkali cations. These synthesised MOFs are characterized by N2 adsorption/desorption isotherm analysis, X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM). The amount of CH4 and CO2 adsorption uptakes onto parent and alkali ions impregnated MIL-101(Cr) are conducted for wide ranges of pressures and temperatures. For understanding the effects of MOF synthesis process and alkali cations impregnation, CH4 /CO2 uptakes on perfect crystalline MIL-101(Cr) MOF are also calculated by Grand Canonical Monte Carlo (GCMC) simulation and the results are compared with experimental isotherm data of synthesised parent and alkali ions impregnated MIL-101(Cr) MOFs. It is found that the limiting uptakes and the isosteric heats are mainly influenced by the modified adsorbent structures due to alkali ions impregnation and the polarity of adsorbate molecules. Employing Dubinin-Astakhov (DA) equation, the energy distribution of synthesised parent and alkali doped MIL-101 (Cr) MOFs are also presented to identify the alkali cation effects and the surface heterogeneity.

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Owing to their high stability against corrosive gases, carbon-based adsorbents are preferentially used for the adsorptive removal of SO2. In the present study, SO2 adsorption on different carbon nanomaterials namely carbon nanohorns (CNHs), multiwalled carbon nanotubes (MWNTs), single-walled carbon nanotubes (SWNTs) and vertically aligned carbon nanotubes (VACNTs) are investigated and compared against the adsorption characteristics of activated carbon and graphene oxide (GO). A comprehensive overview of the adsorption behavior of this family of carbon adsorbents is given for the first time. The relative influence of surface area and functional groups on the SO2 adsorption characteristics is discussed. The isosteric heat of adsorption values are calculated to quantify the nature of the interaction between the SO2 molecule and the adsorbent. Most importantly, while chemisorption is found to dominate the adsorption behavior in activated carbon, SO2 adsorption on carbon nanomaterials occurs by a physisorption mechanism.

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Accurate estimation of the isosteric heat of adsorption is mandatory for a good modeling of adsorption processes. In this paper a thermodynamic formalism on adsorbed phase volume which is a function of adsorption pressure and temperature has been proposed for the precise estimation of the isosteric heat of adsorption. The estimated isosteric heat of adsorption using the new correlation has been compared with measured values of prudently selected several adsorbent-refrigerant pairs from open literature. Results showed that the proposed isosteric heat of adsorption correlation fits the experimentally measured values better than the Clausius-Clapeyron equation.

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A qualitative interpretation is proposed to interpret isosteric heats of adsorption by considering contributions from three general classes of interaction energy: fluid-fluid heat, fluid-solid heat, and fluid-high-energy site (HES) heat. Multiple temperature adsorption isotherms are defined for nitrogen, T=(75, 77, 79) K, argon at T=(85, 87, 89) K, and for water and methanol at T=(278, 288, 298) K on a well-characterized polymer-based, activated carbon. Nitrogen and argon are subjected to isosteric heat analyses; their zero filling isosteric heats of adsorption are consistent with slit-pore, adsorption energy enhancement modelling. Water adsorbs entirely via specific interactions, offering decreasing isosteric heat at low pore filling followed by a constant heat slightly in excess of water condensation enthalpy, demonstrating the effects of micropores. Methanol offers both specific adsorption via the alcohol group and non-specific interactions via its methyl group; the isosteric heat increases at low pore filling, indicating the predominance of non-specific interactions.

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Nanostructured carbon adsorbents containing high nitrogen content were developed by templating melamine-formaldehyde resin in the pores of mesoporous silica by nanocasting technique. A series of adsorbents were prepared by altering the carbonization temperature from 400 to 700 °C and characterized in terms of their textural and morphological properties. CO2 adsorption performance was investigated at various temperatures from 30 to 100 °C by using a thermogravimetric analyzer under varying CO2 concentrations. Multiple adsorption-desorption experiments were also carried out to investigate the adsorbent regenerability. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the development of nanostructured materials. Fourier transform infrared spectroscopy (FTIR) and elemental analysis indicated the development of carbon adsorbents having high nitrogen content. The surface area and pore volume of the adsorbent carbonized at 700 °C were found to be 266 m(2) g(-1) and 0.25 cm(3) g(-1) respectively. CO2 uptake profile for the developed adsorbents showed that the maximum CO2 adsorption occurred within ca. 100 s. CO2 uptake of 0.792 mmol g(-1) at 30 °C was exhibited by carbon obtained at 700 °C with complete regenerability in three adsorption-desorption cycles. Furthermore, kinetics of CO2 adsorption on the developed adsorbents was studied by fitting the experimental data of CO2 uptake to three kinetic models with best fit being obtained by fractional order kinetic model with error% within range of 5%. Adsorbent surface was found to be energetically heterogeneous as suggested by Temkin isotherm model. Also the isosteric heat of adsorption for CO2 was observed to increase from ca. 30-44 kJ mol(-1) with increase in surface coverage.

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Ordered mesoporous carbon (OMC) with high specific surface area and large pore volume was synthesized and tested for use as an adsorbent for volatile organic compound (VOC) disposal. Benzene, cyclohexane and hexane were selected as typical adsorbates due to their different molecular sizes and extensive utilization in industrial processes. In spite of their structural differences, high adsorption amounts were achieved for all three adsorbates, as the pore size of OMC is large enough for the access of these VOCs. In addition, the unusual bimodal-like pore size distribution gives the adsorbates a higher diffusion rate compared with conventional adsorbents such as activated carbon and carbon molecular sieve. Kinetic analysis suggests that the adsorption barriers mainly originated from the difficulty of VOC vapor molecules entering the pore channels of adsorbents. Therefore, its superior adsorption ability toward VOCs, together with a high diffusion rate, makes the ordered mesoporous carbon a promising potential adsorbent for VOC disposal.

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Isosteric heat of adsorption is indispensable in probing the energetic behavior of interaction between adsorbate and solid, and it can shed insight into how molecules interact with a solid by studying the dependence of isosteric heat on loading. In this study, we illustrated how this can be used to explain the difference between adsorption of non-polar (and weakly polar) fluids and strong polar fluids on a highly graphitized carbon black, Carbopack F. This carbon black has a very small quantity of functional group, and interestingly we showed that no matter how small it is the analysis of the isosteric heat versus loading can identify its presence and how it affects the way polar molecules adsorb. We used argon and nitrogen as representatives of non-polar fluid and weakly polar fluid, and methanol and water for strong polar fluid. The pattern of the isosteric heat versus loading can be regarded as a fingerprint to determine the mechanism of adsorption for strong polar fluids, which is very distinct from that for non-polar fluids. This also allows us to estimate the interplay between the various interactions: fluid-fluid, fluid-basal plane and fluid-functional group.

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Doped porous carbons exhibiting highly developed porosity and rich surface chemistry have been prepared and subsequently applied to clarify the influence of both factors on carbon dioxide capture. Nanocasting was selected as synthetic route, in which a polyaramide precursor (3-aminobenzoic acid) was thermally polymerized inside the porosity of an SBA-15 template in the presence of different H3PO4 concentrations. The surface chemistry and the porous texture of the carbons could be easily modulated by varying the H3PO4 concentration and carbonization temperature. Porous texture was found to be the determinant factor on carbon dioxide adsorption at 0 °C, while surface chemistry played an important role at higher adsorption temperatures. We proved that nitrogen functionalities acted as basic sites and oxygen and phosphorus groups as acidic ones toward adsorption of CO2 molecules. Among the nitrogen functional groups, pyrrolic groups exhibited the highest influence, while the positive effect of pyridinic and quaternary functionalities was smaller. Finally, some of these N-doped carbons exhibit CO2 heats of adsorption higher than 42 kJ/mol, which make them excellent candidates for CO2 capture.

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A series of hydrosilated stationary phases were compared with respect to their hydrophilic-hydrophobic properties. The stationary phases were also compared to the bare silica gel used for this synthesis. The investigations were done using microcalorimetric measurements of methanol and acetonitrile heats of immersion. Because these stationary phases are used in both the reversed-phase and aqueous normal phase modes of liquid chromatography, the excess isotherm of water from acetonitrile solution was measured. From the materials tested the highest polarity was exhibited by the silica hydride and the bare silica. The Diamond Hydride is less polar. The highest hydrophobicity is exhibited by the hydrosilated stationary phase which contains bonded octadecyl ligands.

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This study is dedicated to the investigation of the potential of volatile organic compounds (VOC) adsorption over low cost natural minerals (bentonite and diatomite). The performances of these solids, in terms of adsorption/desorption properties, were compared to commercial adsorbents, such as silica, alumina and titanium dioxide. The solids were first characterized by different physico-chemical methods and di-methyl benzene (dMB) was selected as model VOC pollutant for the investigation of adsorptive characteristics. The experiments were carried out with a fixed bed reactor under dynamic conditions using Fourier Transform InfraRed spectrometer to measure the evolution of dMB concentrations in the gaseous stream at the outlet of the reactor. The measured breakthrough curves yields to adsorbed amounts at saturation that has been used to obtain adsorption isotherms. The latters were used for determination of the heat involved in the adsorption process and estimation of its values using the isosteric method. Furthermore, the performances of the studied materials were compared considering the adsorption efficiency/cost ratio.

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