Metal-organic frameworks (MOFs) were studied as alternatives to zeolites and activated carbon for adsorptive removal of wasted inhalation anaesthetic agents (IAA). Monte Carlo simulation was used to predict equilibrium adsorption isotherms of IAA on selected MOFs. Rather than generic forcefields (FFs), the all-atom FF parameters published by Arcario were used for IAA modelling. Continuous fractional component Monte Carlo (CFCMC) proved crucial for speedy simulation of large molecules. We found that allocating 70% probability to the CFlambdaSwap move gave optimum fits between simulation and experiment. The simulations provided us with an insight into the adsorption mechanisms of IAA in these structures. Heats of adsorption, Brauner-Emmet-Teller (BET) surface area, and total pore volume were deduced to be the crucial parameters for low, medium, and high range of relative pressures in the isotherm. Therefore, the chromium atoms in MIL-101-Cr are better adsorbers of IAA than MIL-100-Al at lower pressures despite the similarities in terms of the type of linkers and topology. Our simulation results corroborated the earlier published studies on the self-association behaviour of sevoflurane molecules based on the experimental isotherms reported for MOF-177-Zn. Finally, the high polarity of IAA is thought to explain good low-pressure simulation/experiment data agreement for the MOFs possessing coordinatively unsaturated sites (CUS) despite using generic DREIDING FF for the framework atoms. Our in-house parsing code helped realize that the grand-canonical Monte-Carlo simulation speed is not the same for all pressure points but decreases for higher pressure points. This can be explained by increased density of the adsorbates making successful trial moves less probable.

MIL-101-Cr-X (X = OH-, F-) has been reported to be the most suitable material so far for adsorptive removal of inhalation anaesthetic agents (IAA) sevoflurane and desflurane at the working conditions in hospital operation rooms. To further enhance its affinity and uptake capacity towards IAA, several structural modifications were proposed, and their isotherms were predicted using our molecular simulation approach adopted in our previous publication for the case of the pristine MIL-101-Cr (X = F-, OH-) structure. The proposed modifications include (1) grafting the metal-cluster site with coordinated NH3 ligands to produce MIL-101-Cr@NH3 (X = F-, OH-), (2) anion exchange of the fluorine atom bonded to chromium with chlorine to synthesize MIL-101-Cr (X = Cl-), and (3) functionalization of the benzene rings of the ligand linkers in the MOFs with amino- and nitro- groups in order to form NH2-MIL-101-Cr (X = Cl-) and NO2-MIL-101-Cr (X = Cl), respectively. Simulated adsorption isotherms of IAA on these modifications were verified by the experimental results using the standard volumetric technique and they clearly demonstrated that MIL-101-Cr@NH3 (X = F-, OH-) possesses the highest equilibrium capacity for IAA. This observation can be attributed to the electron-transfer contribution of the coordinated ammonium molecules to the unsaturated coordinated sites of the MOF while doing away with steric hindrance inside the pore cages. The new compound can significantly enhance the economy of adsorptive removal of IAA from vented gas mixtures.

The mass transfer of hydrocarbon gases was studied in a commercial CMS and zeolite 5A (as a reference adsorbent). The zero length column (ZLC) technique was applied to determine the mass transfer resistances to gas sorbates. To confirm the ZLC results, a comprehensive study involving uptake and kinetic behavior of the constituent gas components was also carried out using the gravimetric technique. The comparison between ZLC and gravimetric results established the strong dominance of surface barrier for both adsorption and desorption of sorbates in CMS. As a result of surface barrier resistance in the CMS, the adsorption kinetics is extremely slow. The ZLC method required a considerably shorter measurement time compared to the gravimetric method, e.g., less than 14% of the time required for the gravimetric method, which proved the advantage of the ZLC as a fast screening technique to rank a large number of adsorbents particularly those with large surface barrier effects. To apply the ZLC technique for measuring the kinetics in CMS adsorbent, surface resistance model and modified form of ZLC model (combined surface and diffusion resistances model) were applied. Since the surface resistance is the main barrier to the sorbate molecules diffusing out from the CMS pores, the application of combined model resulted in a considerable inaccuracy in the kinetic parameter's estimations. This was primarily due to the existence of low experimental value of the L' criterion, representing the ratio of diffusion to surface resistance, e.g., < 0.33, thus contradicting the model criteria required by the ZLC method, i.e., L' > 0.33. Consequently, only surface barrier was considered using the ZLC model for the CMS kinetic parameter estimates. According to the experimental results, the combined model is suitable for ZLC analysis of adsorbents with minor to moderate surface resistance. In these adsorbents, the increase in e.g., higher than 0.33, indicates greater contribution of diffusion resistance compared to surface barrier. As a result, the zeolite 5A, which has a minor surface resistance effect (L'>> 0.33), was applied to verify the consistency of the combined model in predicting the kinetics of hydrocarbon gases.

The aims of this work were to prepare porous activated carbon from peanut shell by chemical activation using ZnCl2 and study its volatile organic compounds adsorption capacities. The adsorption properties of ethyl on the prepared activated carbon were experimentally determined at different temperatures. The surface textural characteristic of the activated carbon was evaluated by N2 adsorption isotherm measurements. The average BET surface area, pore size, and micro‐pore volume of the prepared activated carbon were 1025 m2/g, 0.70 nm, and 0.37 cm3/g, respectively, with narrow pore size distribution. Higher adsorption capacity of toluene on the activated carbon was observed compared to ethyl benzene and p‐xylene, in particular at low vapour concentration ranges. The experimental isotherm data were also analyzed using the Langmuir, Langmuir‐Freundlich, and multisite Langmuir isotherm model. The Langmuir‐Freundlich and multisite Langmuir model provide the best fit for volatile organic compound adsorption isotherms. In addition, the surface and thermal properties of the activated carbon were also investigated using FT‐IR, Zeta‐potential, and TGA. Overall, the peanut shell activated carbon prepared in this study exhibited comparable surface properties and adsorption performance with the available commercial activated carbons and activated carbons prepared from other various sources reported in other literature.

The microwave-assisted dry reforming of methane over Ni and Ni–MgO catalysts supported on activated carbon (AC) was studied with respect to reducing reaction energy consumption. In order to optimize the reforming reaction using the microwave setup, an inclusive study was performed on the effect of operating parameters, including the type of catalysts’ active metal and their concentration in the AC support, feed flow rate, and reaction temperature on the reaction conversion and H2/CO selectivity. The methane dry reforming was also carried out using conventional heating and the results were compared to those of microwave heating. The catalysts’ activity was increased under microwave heating and as a result, the feed conversion and hydrogen selectivity were enhanced in comparison to the conventional heating method. In addition, to improve the reactants’ conversion and products’ selectivity, the thermal analysis also clarified the crucial importance of microwave heating in enhancing the energy efficiency of the reaction compared to the conventional heating.

In order to better understand the adsorption of volatile halogenated anesthetics on metal organic frameworks (MOFs), sevoflurane vapor adsorption experiments were performed on commercial MOF-177 at different temperatures. Due to the surface homogeneity of such an adsorbent, arising from its almost unimodal pore size distribution and the absence of specific, coordinatively unsaturated adsorption active sites, sevoflurane adsorption isotherms exhibited a peculiar deviation from the Langmuirian behavior. Consequently, they show a "kink" at a specific pressure that increases with increasing equilibrium temperature. Successful modeling of such data by means of the Talu-Meunier equation confirmed clustering of adsorbate molecules inside adsorbent micropores, similarly to water vapor adsorption on activated carbon, which may play an important role when designing a system using MOFs as the potential adsorbents for capturing anesthetics.

This work focused on the preparation and characterization of cysteine‐formaldehyde cross‐linked complex derived from cysteine hydrochloride and formaldehyde. The cross‐linked complex was prepared based on the nucleophilic substitution reaction of cysteine with formaldehyde accompanied by π bond breakage of carbonyl from formaldehyde. Meanwhile, its surface morphology, element composition, group distribution, and thermodynamics were experimentally investigated by means of SEM, XRD, EA, EDS, 1 H‐NMR, FTIR, BET, and TGA as well as an analysis of the characteristics of CO 2 adsorption. The results indicated that the as‐prepared cross‐linked complex exhibited a rod‐shaped hollow crystal structure with a lateral distribution of sulphur and nitrogen atoms toward the crystal surface. As a mesoporous crystal material, the cross‐linked complex presented a four‐step (amide forming, fast pyrolysis, slow pyrolysis, and dehydrogenation) pyrolysis above 430 K, yet possessed a relatively acceptable thermodynamic stability below 430 K. In addition, the interaction mechanism between the cysteine hydrochloride and formaldehyde was revealed by characteristics and simulation.

This work focused on the preparation and characterization of a promising biochar as a novel solid adsorbent towards CO2. The biochar was prepared by catalytic pyrolysis of waste roasted peanut shell in molten salt; it was characterized by means of SEM-EDS, BET, FTIR, and TGA, followed by determining the adsorption characteristics, such as adsorption capacity, isosteric heat of adsorption, uptake rate, and selectivity via adsorption temperature and gas pressure. The results indicated that the as-prepared biochar had a rich microporous structure with a peak pore size in the range of 0.69-1.3nm, and exhibited a good performance of CO2 adsorption with a capacity of 3.8mmol/g at 273K and 100kPa. Moreover, the adsorption selectivity of CO2 over N-2, O-2, CO, and CH4 was found to be above 12, 11, 8, and 7, respectively. In addition, an interesting phenomenon of an initial increase and then a decrease in the selectivity of CO2/N-2 adsorption with increasing gas pressure was experimentally revealed.

In this study, a novel headspace technique, based on liquid calibration, was developed and compared to the standard headspace or vapor calibration technique. The technique was applied for the measurements of single component liquid adsorption isotherms of xylene isomers, ethylbenzene and toluene on a commercial NaX (13X) zeolite. In comparison to the vapor calibration technique, the liquid calibration technique provided more effective means by faster generating liquid isotherms with more accuracy and less computational complexity. The isotherms were measured at 30, 60 and 90 degrees C using both headspace techniques, and the results were found reasonably consistent. Among the alkylaromatic compounds studied, the NaX zeolite was more selective to toluene and showed the lowest selectivity to m-xylene. In contrast to larger adsorption capacity of toluene compared to ethylbenzene and p-xylene, the isosteric heats of adsorption indicated that ethylbenzene and p-xylene created stronger bonds to the NaX sites. The effects of solute concentration in the liquid phase were investigated with regard to the adsorption capacity and selectivity. The results indicates that the adsorbent selectivity is generally dependent on the concentration of the solute in the solution. (C) 2017 Elsevier B.V. All rights reserved.

In this work, bionanocomposites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared via a solution intercalation process using two types of organomodified clay minerals (0 to 40w%). The effect of Cloisite®30B (C30B) and an intercalated clay mineral, which was synthesized via ring opening polymerization of polyhydroxybutyrate in the presence of Cloisite®30B (PHB-C30B), on the wettability of the assemblies has been investigated in detail. Moreover, phase morphology of the nanocomposite films was investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The moisture adsorption of PHBV and its nanocomposite films was determined using Belsorp-Max. The nanocomposite films derived from PHB-C30B exhibited higher wettability than those derived from C30B. An explanation, based on the surface topographies, has been proposed. Phase morphology, filler dispersion and root mean square roughness (RMS) were also analyzed. The results revealed the impact of aggregates on water vapor transmission rate (WVTR) and contact angle of the composites.

carboxymethyl-β-cyclodextrin sodium salt (CMCSS) was synthesized as an adsorbent for CO2 capture. The adsorption characteristics, such as adsorption capacity and selectivity via temperature and gas pressure were analyzed. The results from SEM, EDX and 1H NMR demonstrated that the β-cyclodextrin derivative possessed porous surface structure with grafted functional groups such as CH2COONa. The etherification of β-cyclodextrin enhanced its performance toward CO2 sorption, increasing the adsorption capacity of CO2 to 0.46mmol/g at 298K. More interestingly, the CO2 adsorption was not sensitive to temperature at CO2 pressure below 1.2bar, and even increased as temperature increasing at CO2 pressure above 1.2bar, which is very unique behavior. The high selectivity of CO2 to N2 adsorption up to 272 was achieved at 298K.

In this study, adsorption isotherms of o-xylene, ethylbenzene and toluene liquid solutions on a commercial 13X zeolite adsorbent were measured using the gas chromatographic headspace technique. According to this technique, the vapor, in equilibrium with the liquid phase and solid adsorbent, is analyzed using a GC column. In the first part of the study, a novel technique was introduced based on liquid calibration curve procedure. In addition, the earlier introduced vapor calibration technique was further extended to measure single component isotherms of non-ideal liquid solutions. In this part of the study, both vapor and liquid calibration techniques were extended to measure liquid adsorption isotherms of the multi-component solutions involving both, ideal solutions e.g., aromatic sorbates, and non ideal solutions, e.g., aromatic sorbates and n-decane as a solvent. Consequently, Raoult's law and extended Raoult's vapor-liquid equilibrium (VLE) law for calculations of ideal and non-ideal solutions were applied, respectively. Extended Wilson and NRTL models were used to determine the sorbates' activity coefficients in the non-ideal liquid solutions. The multicomponent isotherms involving both ideal and non-ideal liquid solutions were experimentally determined at 30, 60 and 90 degrees C and also predicted by the extended Sips adsorption model. Based on these results, the selectivity of the NaX zeolite towards different sorbates from the selected mixtures were determined at different temperatures and concentrations. (C) 2016 Elsevier Inc. All rights reserved.

Separation and purification of gas mixtures using selective adsorbents is widely used in different industries such as gas drying, air separation, and H-2 purification. Equilibrium analysis involving adsorption of binary gas mixtures provides important information related to the adsorbent performance in the separation of gases. In this study, a novel technique termed "differential column technique" was developed for binary isotherm measurement employing streams containing carbon dioxide, carbon monoxide, and ethylene at different compositions. This technique is based on measuring the gas desorption by changing equilibrium pressure conditions. The isotherm curve was generated by summing desorption amounts desorbed at each pressure step. Through the application of this technique, the single-component isotherms of CO2, CO, and ethylene on zeolite NaY were measured, and the isotherms were compared to the results obtained by a standard gravimetric technique. (The average relative deviation is less than 6%.) The main advantage of the technique is the significant time savings, e.g., one experimental run is required to generate an isotherm compared to multirun experiments using a standard breakthrough technique, in addition to using a simpler experimental setup and generally smaller amount of sample (agglomerated or in a powder form). Another important feature of this technique is the relatively simple extension that allows measurements of gas mixture equilibria. As such, the proposed technique has the potential to be used as a fast screening technique for adsorbent selection based on single-component or mixture analysis. To investigate the consistency of the proposed technique, the binary isotherms of competitive, CO2-C2H4, and noncompetitive, CO2 CO, mixtures were investigated at different gas compositions. In addition, the effects of sorbate concentrations in the gas phase and interactions with the NaY zeolite active surface were investigated in relation to the adsorption selectivity and capacity, i.e, strong interaction of both CO2 and ethylene with NaY site resulted in close adsorption selectivity 0.8 <= S-CO2/C2H4 <= 1.7, while CO2 adsorbed more selectively compared to CO, 14 <= S-CO2/CO <= 30, as a result of weak CO interaction with the adsorbent sites. Finally, the binary adsorption isotherms and selectivity were predicted by the multisite Langmuir model using the single component's isotherm parameters. Modest agreements (error <= 28%) were obtained between the predicted and experimental results.

Multiple-cycle breakthrough tests of a binary gas mixture of the halogenated anesthetic sevoflurane (SF) and water vapor were performed on both the synthesized chromium-based metal organic framework (Cr-MOF) and a conventionally used reference adsorbent. At 1 vol% SF and 50% relative humidity mixture composition, the Cr-MOF (MIL-101) showed a significantly higher SF adsorption capacity, lower water vapor adsorption capacity, and no roll-up effect compared to the reference sample. After each adsorption measurement, the saturated column was regenerated. MIL-101 showed higher stability with minor SF capacity loss after 14 cycles, while the reference sample lost about a half of the SF capacity after 17 cycles.

The comprehensive study involving uptake and kinetics behaviour of methane and ethane was carried out on a commercial carbon molecular sieve. The gravimetric technique was applied to measure the adsorption isotherms at different temperatures. The kinetic behaviours of methane and ethane were investigated by extracting the uptake data from isotherms at different pressure steps. Considering CMS as a homogenous microporous adsorbent, only two main resistances: surface barrier (at the pore mouth) and diffusion resistance (inside the pores) were considered in analysing the kinetic data. The kinetic analysis showed dominance of surface barrier resistance at all temperatures and pressures investigated in this study. Modified Darken equation was used to calculate the sorbates' activation energies for adsorption in CMS pores. Compared to Darken equation, the modified Darken model predicted the concentration dependency of the surface rate constants more accurately, especially at higher sorbates' concentrations. The activation energy of methane and ethane was greater than the heat of adsorption demonstrating a large impedance and barrier at the pore surface to the methane and ethane molecules. The kinetic selectivity of methane over ethane was calculated from the combined surface barrier/diffusion model parametric analysis. The results generally showed a greater selectivity to methane over ethane, i.e., the higher mass transfer rates.

The theory of mass transport in porous media is of fundamental importance for different applications such as food, paper packaging, textiles, and wood for building materials. In this study, a theoretical water vapor transport model has been developed for cellulose-based materials, such as paper and regenerated cellulose film. Pore diffusivities were determined from the dynamic moisture breakthrough experiments comprising a stack of paper sheets and regenerated cellulose films in a configuration similar to a packed adsorption column. Other mass transfer parameters were determined from transient moisture uptake rate measurements. The model incorporates pore and surface diffusion as a lump parameter into a variable effective diffusion coefficient. The mass transport, involving both pore and surface diffusions, is evaluated independently. The theoretical water vapor transmission rates (WVTRs) obtained from the model were compared with experimentally determined WVTRs measured under steady-state conditions. The theoretical model, based on intrinsic diffusion, stipulates higher WVTR values compared to the experimental results. However, the theoretical water vapor transfer rates agree well with the experimental results when external mass transfer resistance is incorporated in the model.

A carbon molecular sieve (CMS) is a carbonaceous material with a narrow pore size distribution, which can separate molecules based on their size, shape, and adsorption kinetic rate. In this study, a commercial CMS was used to measure the adsorption kinetics of carbon dioxide and carbon monoxide. The rate of adsorption was investigated by considering two main resistances, surface barrier and diffusion. The results showed that molecular parameters, such as difference in shape, size, and interactions of molecules, lead to different adsorption kinetics mechanisms. In the system investigated in this study, the adsorption kinetics of both CO2 and CO sorbates were controlled by combined diffusion and surface barrier mechanisms, in which the surface barrier was found to be the main resistance to gas molecule uptake. Even though this study confirmed surface resistance as a dominant transfer mechanism, the systematic use of the combined model in the analysis provided further insights in the mass transfer due to adsorption of CO2 and CO molecules in the CMS adsorbent. The rate constants were found to follow the Darken equation for both sorbates. The kinetic selectivity of CO2 over CO was calculated from the combined surface barrier/diffusion model parametric analysis. The results generally showed a greater selectivity to carbon dioxide over carbon monoxide, i.e. higher mass transfer rates.