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 AdsorptionJournal Prestige (SJR): 0.703 Citation Impact (citeScore): 2Number of Followers: 5      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1572-8757 - ISSN (Online) 0929-5607 Published by Springer-Verlag  [2658 journals]
• Special issue on the 13th Brazilian meeting on adsorption

PubDate: 2021-10-08

• Insights of adsorption isotherms with different gases at 77 K and their
use to assess the BET area of nanoporous silica materials

PubDate: 2021-09-20

• The binding interaction of protein on a charged surface using
Poisson–Boltzmann equation: lysozyme adsorption onto SBA-15

Abstract: A modified Poisson–Boltzmann model (PBEm) can be successfully used to determine the binding strength parameter, i.e., (Henry constant, K), for the protein adsorbent interaction in ion-exchanger columns. Lysozyme has been employed as a standard protein for the adsorption in a mesoporous silica adsorbent. The density of aminoacid groups and silanol groups were used as inputs to calculate the protein charge density as a function of pH, salt concentration, and type of salt. Using the electrostatic potential provided as solving the PBEm with the protein charge surface and silanol wall as boundaries conditions, we calculated the K through the potential of mean force to describe the whole set of experimental data. The unique estimated parameter in this work was the volumetric accessible surface area from isotherm data for different electrolyte conditions. The results show that the protocol applied includes a pH and ionic strength dependence in the Langmuir isotherm. A sensibility test with different anions ( $$\text {Cl}^{-}$$ , $$\text {Br}^{-}$$ , and $$\text {I}^{-}$$ ) showed an agreement with the Hofmeister series for the protein/adsorbent interaction. A modification in the electrolyte concentration and pH can change the behavior of the isotherm profile for a fixed value of saturation capacity, independently calculated for spheres packed in cylinders. The calculations provide here can be helpful for the optimization of the best condition for protein adsorption.
PubDate: 2021-09-17

• Mesoporous metal–organic framework MIL-100(Fe) as drug carrier

Abstract: The use of hybrid nanomaterials for the controlled delivery of drugs in the body has attracted great scientific attention. Indeed, much effort has been put in the experimental or theoretical screening of drug loading in different biocompatible frameworks, however, full molecular-level investigations of drug adsorption in porous structures are still scarce. Herein we aim to understand the molecular mechanisms behind the good performance of the mesoporous metal–organic framework MIL-100(Fe) with respect to the adsorption of a wide range of therapeutical drugs. To this purpose, a microscopic model was developed and further validated by comparing theoretical and experimental water isotherms and the maximum uptake of two model drugs (ibuprofen and caffeine). We have found that MIL-100(Fe) has an excellent mass uptake for the 5-fluorouracil (5-FU) anti-tumoral drug molecule despite presenting a relatively weak drug/MOF interaction. We also perform detailed studies in the adsorption mechanism and sitting of the doxorubicin (DOX) molecule and how the presence of water in the structure affects the DOX-framework interactions. The good performance of the MOF MIL-100(Fe) is closely related to the diversity of interaction sites, both hydrophobic and hydrophilic. This is a desirable feature to maximize the potential of any candidate for drug carrier.
PubDate: 2021-09-03

• Adsorption kinetics and equilibria of two methanol samples with different
water content on activated carbon

Abstract: To investigate the influence of fluid purity on the adsorption properties, adsorption kinetics and adsorption equilibria of two methanol samples with different water content on an activated carbon were studied. The purity of the methanol samples was 98.5% and 99.9%. Measurements were conducted at 298 K and 318 K using a magnetic suspension balance and cover a wide p/p0 range. To determine effective diffusion time constants and mass transfer coefficients, adsorption kinetics were evaluated using an isothermal and a nonisothermal Fickian diffusion model, and the linear driving force model. The pressure dependence of the kinetic parameters was studied and discussed. A small influence of sample purity on the adsorption equilibria was observed, as the purer methanol sample showed slightly higher equilibrium loadings than the less pure sample. However, significantly faster adsorption kinetics were observed for the purer sample at all temperature and pressure conditions. Compared to the less pure sample, the determined effective diffusion time constants and the mass transfer coefficients were up to 98% and 35% higher, respectively.
PubDate: 2021-09-03

• Characterization of mesoporous region by the scanning of the hysteresis

Abstract: The scanning hysteresis loop provides information about the correlation of the pore network, its connectivity and pore size distribution; nonetheless, this correlation cannot be revealed from the complete isotherm. To analyze the connectivity of the porous network in ordered mesoporous materials modified with iron and cobalt oxides, Ar adsorption–desorption isotherms and their corresponding scanning of the hysteresis loops at three temperatures (65, 77, and 87 K) were measured. Two mathematical models based on the independent domains theory (i.e. Uncorrelated Model (UM) and Partial Correlated Model (PCM)) were applied to adjust the desorption branches in the hysteresis loops associating these results to the connectivity in the porous network and the presence of pore-blocking effects.
PubDate: 2021-09-01

• In-situ cost-effective synthesis of zeolite A in Al2O3–SiO2 glass fibers
for fixed bed adsorption of Cu2+, Cd2+ and Pb2+

Abstract: The in-situ coating of zeolite crystals on Al2O3–SiO2 glass fiber was investigated using two commercial fibers (FB1 and FB2). The fibers were submitted to hydrothermal treatment at different temperatures, resulting in the crystallization of zeolite on their surfaces. The materials obtained were characterized by X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Batch and fixed bed essays were carried out to evaluate the performance of the materials in the adsorption Cu2+, Cd2+ and Pb2+ from aqueous solutions, at 28 ± 2 °C. The syntheses in which the FB1 sample was employed resulted in zeolite A as the only crystalline phase. The exception was the FB1-100 material which sodalite was also formed. When FB2 samples were used, only the FB2-85 material indicated resulted in zeolite A without secondary phases, while the other materials presented a mixture of phases. The materials FB1-95 and FB2-95 presented better performance in batch adsorption experiments than the other samples, with Qe for FB1-95 being 0.049 mmol g−1 for the three metal ions, and Qe for FB2-95 being 0.043, 0.047, and 0.049 mmoL g−1 for Cu2+, Cd2+ and Pb2+, respectively. Therefore, these samples were selected for the study of fixed bed adsorption. The following adsorption order was verified: Pb2+  > Cd2+  > Cu2+. Linear Driving Force (LDF) model proved to be suitable for the adsorption experimental data, confirming the high potential of the FB1-95 and FB2-95 materials for the adsorption of Cu2+, Cd2+ and Pb2+ in aqueous solution.
PubDate: 2021-08-25

• Multiscale design of a pressure swing adsorption process for natural gas
purification

PubDate: 2021-08-25

• Saturation loadings on 5A zeolite above and below the critical conditions:
monatomic species data evaluation and modeling

Abstract: Isotherms for monatomic species (He, Ne, Ar, Kr and Xe) adsorption on 5A zeolite are extracted from the literature and analyzed for consistency and saturation. The saturation data below the critical adsorbate reduced temperature, TCAR, is modeled using the Rackett equation and the zeolite structure. Consideration is made regarding whether adsorbates can enter β cage in addition to the α cage. The data for argon and krypton suggest that both species may also enter the β cage, although there is not enough information to be conclusive. Xenon does not enter the β cage. The limited data establishes the need for further study on this point. The subTCAR data for both 5A and 13X are relatively consistent with the proposed subTCAR model. Although there is not sufficient data to determine this for helium or neon, their size and the literature suggest that both molecules enter the β cage. The data are divided into subTCAR and superTCAR regions, where TCAR is the critical reduced temperature for the adsorbed species, which often differs from 1. The subTCAR model predictions for argon and krypton are excellent, while that for xenon requires a steric factor of 0.76. For superTCAR data, helium has only one data point. The superTCAR data for argon, krypton and xenon are linear with excellent regression coefficients. Intersection of the linear superTCAR plots with the subTCAR model prediction curves gave TCAR’s of 0.996 for argon, 0.80 for krypton and 0.66 to 0.86 for xenon. Literature models Ruthven et al. (Chem Eng Sci 28:701–709, 1973), Ozawa et al. (J Colloid Interface Sci 56(1):83–91, 1976), and Dubinin (in: Caldenhead (ed) Prog. surface and membrane science, Academic Press, New York, 1975) expressed in terms of qmax are also fitted to the data with some success. A modified Ozawa et al. model fits the data reasonably well. Data for 4A, 5A and 13X are observed to be very similar.
PubDate: 2021-08-24

• CO2 capture by ethanolamines functionalized resins: amination and kinetics
of adsorption in a fixed bed

PubDate: 2021-08-21

in the low partial pressure range

Abstract: Mesoporous silicas are known to be high-performing water adsorbents in high humidity levels due to their large pore volumes. However, for low humidity conditions, these materials typically present a less expressive performance, which is a drawback for many applications. In the present report, mesoporous silica SBA-15 was functionalized with Al, Ti, Zr and Li in order to improve their performance in this condition. The influence of functionalization in porosity, morphology and acidic sites was investigated. Samples with an increased number of acidic sites and with higher microporosity when compared to pure silica were produced. This was responsible for their enhanced performance for water adsorption in low moisture conditions. Sample functionalized with zirconium in SBA-15 synthesis improved the water adsorption capacity of pure silica by three times, reaching up to 127 g kg−1 at a relative pressure of 0.2 and 570 g kg−1 close to saturation pressure. This sample was found to be a promising material to be applied in processes which require high adsorption capacities in both low and high water partial pressure ranges. Moreover, the understanding of the mechanisms behind the heteroatom functionalization can be applied to any silica material in order to enhance its attractiveness towards any polar molecule.
PubDate: 2021-08-17

mineral coal

PubDate: 2021-08-17

• Water adsorption in fresh and thermally aged zeolites: equilibrium and
kinetics

Abstract: Zeolites are widely employed in the industrial drying of gases by Temperature Swing Adsorption (TSA). In a typical TSA process, the adsorbent is packed in a fixed bed, which is sequentially subjected to a “cold” feed (adsorption) and a hot flush (desorption). Due to the hydrothermal stress, adsorbents may suffer from reduced drying capacity in long-term service. The aim of this work is to assess the impact of thermal aging of two zeolite materials (LTA and CHA) having similar pore openings but different Si/Al ratios. We examined how simulated thermal aging affected porous texture, coke deposition and water vapor adsorption equilibrium and kinetics. Both zeolites showed reduced uptake of probe molecules (N2 at 77 K and CO2 at 273 K) and water vapor (303 K) when subjected to simulated thermal aging. In Fourier-Transform Infrared Spectroscopy (FTIR) analyses, only the aged LTA zeolite showed bands related to the presence of aromatic compounds. Water vapor adsorption uptake decreased 28.6% and 18.4% for LTA and CHA at 30 mbar, respectively. Kinetic studies indicate a reduction in water diffusion coefficient after the aging cycles. Although LTA has a significantly higher affinity for water as compared to CHA, the latter is much more resistant to hydrothermal aging with comparatively faster water diffusion.
PubDate: 2021-08-11

• Performance of adsorption isotherms kernels of CO2 models for
γ-alumina characterization

Abstract: γ-alumina is the most studied metastable phase of the alumina. It is recognized as a strategic material in many industrial processes, acting as adsorbent, catalyst or support due to its high surface area, thermal and chemical stability. Its heterogeneous surface imposes a challenge for characterization by adsorption. The use of experimental adsorption data, combined with the theoretical approach of molecular simulation is becoming the standard adsorption-based technique to characterization. Therefore, this study aims to launch a first insight in the performance of the atom–atom (AA) and united-atom (UA) molecular models of the CO2, a probe gas less prone to diffusion limitations, given the lack of an appropriate kernel for the γ-alumina characterization. A detailed experimental isotherm of CO2 in γ-alumina was performed and a collection of isotherms was calculated applying Monte Carlo method in the grand canonical ensemble. To build the kernel, isotherm in 10 different slit-pore sizes were calculated. The different pore filing regimes result in a kernel with good reliability window. With these CO2 kernels (AA and AU models), reasonable pore size distributions were predicted, capturing the low range of microporosity. Additional assessment with others probes gas is recommended to confirm the feasibility of CO2 as a characterizing molecule.
PubDate: 2021-08-11

• Influence of functionalization method on isomorphic substitution and
formation of extra-framework oxides in silica for water vapor adsorption

Abstract: Water vapor adsorption is a process of great importance for several industries. Because of that, new materials formed by mesoporous silica with metallic heteroatom functionalization have been studied for water adsorption. This functionalization process is still little studied in the literature, with many topics remaining to be evaluated. One of them is how each functionalization method (grafting and co-condensation) influences the generation of isomorphic substitution or extra-framework oxides. Another is which of these configurations is most interesting for water adsorption. This work aims to address both questions. For this, two groups of samples were synthesized using grafting and co-condensation for the insertion of Al, Ti, Zr and Li into mesoporous silica SBA-15. These samples were analyzed using nitrogen adsorption, high resolution scanning microscopy, energy dispersive X-ray spectroscopy, magic angle spinning nuclear magnetic resonance, Fourier transform infrared spectroscopy, pyridine adsorption and water adsorption. These techniques revealed that the co-condensation approach used in this work was most interesting for water adsorption at low partial pressures. This occurred because it generated a higher degree of isomorphic substitution, which was found to be the most active configuration of heteroatoms for this application.
PubDate: 2021-08-09

• Letter to the editor

PubDate: 2021-08-07

• Martin Bülow: response

PubDate: 2021-08-01

• Correction to: The effect of atomic point charges on adsorption isotherms
of CO2 and water in metal organic frameworks

Abstract: Recently, we presented a detailed and systematic molecular simulation study of the effect of point charges on adsorption of carbon dioxide and water in a series of typical MOF materials [1]. Unfortunately, we have since detected a mistake in one of the input files pertaining to water adsorption isotherm simulations—concretely, the structure of the water molecule was modelled as linear instead of obeying the correct H-O-H angle of 109.47º for the SPC/E model [2]. As we later found out, this led to a significant underestimation of the amount adsorbed in all water isotherms reported in our original paper, although the relative differences between isotherms obtained using different charge sets are qualitatively the same. We have repeated all the water adsorption simulations, and report the new results here in graphical format. With the exception of a few minor statements, which we also correct below, the conclusions of the original work remain unchanged.
PubDate: 2021-08-01

• Letter to the editor

PubDate: 2021-08-01

• Prediction of affinity coefficient for estimation of VOC adsorption on
activated carbon using V-matrix regression method

Abstract: Volatile organic compounds (VOCs) pose an ever-growing threat on human health and environment. Predicting VOC affinity coefficient and consequently estimating activated carbon adsorption requires fundamental understanding of adsorbate-adsorbent interaction, shape and hydrophilicity effects. Hence, a model which expressed these three factors with molecular descriptors was investigated with Ridge and V-matrix regression methods in two cases, k-fold cross-validation and random sampling technique. The results showed, the sole interaction term and the complete model decreased the root mean square error (RMSE) of polarizability ratio by approximately 19% and 26% respectively. The V-matrix regression, reduced the average Ridge RMSE by 9 and 19% for the first and second case. Lower than 10% errors were displayed by 104 out of 155 data and only 4 data which were small molecules with very high polarity had more than 30% error. For both cases the proposed model with V-matrix regression had better or similar results compared to previous research. However, the effect of reference compounds on highly polar VOCs requires further investigation. From the VOC adsorption estimation, it was evident that affinity and adsorption errors were in the same magnitude. Hence, with accurate prediction of affinity coefficient, adsorption isotherms of any VOC can be calculated.
PubDate: 2021-08-01

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