Nitrogen Isotherms Research Articles

Numerical Analysis of the Influence of Air Flow Rate on the Development of the Porous Structure of Activated Carbons Prepared from Macadamia Nut Shells.

This paper presents the numerical analysis of the influence of air flow rate on the porous structure development of activated carbons prepared from macadamia nut shells. The analyses based on nitrogen and carbon dioxide isotherms were carried out by the new numerical clustering-based adsorption analysis method. Therefore, it was possible to evaluate the porous structure with high precision and reliability. In particular, the results obtained showed that activated carbon prepared at an air flow rate of 700 cm3/min has the highest adsorption capacity with respect to this adsorbate, but with surface heterogeneity. On the other hand, numerical analysis based on carbon dioxide adsorption isotherms showed that the activated carbon with the highest adsorption capacity towards carbon dioxide is the sample obtained at an air flow rate of 500 cm3/min. The analyses conducted have shown that too high an air flow rate causes a violent oxidation reaction, leading to uncontrolled burning of the carbonaceous substance and destruction of the structure of the smallest micropores.

Surface areas and adsorption energies of biochars estimated from nitrogen and water vapour adsorption isotherms

Nitrogen adsorption isotherms, along with the BET model for interpretation, are recommended for estimating biochar surface area. The frequently measured small surface areas of biochars contrast with their high sorption and cation exchange capacities. We hypothesised that water adsorption provides a better tool for estimating the surface area of biochars. Although adsorption energy also appears to be a valuable surface characteristic, there is a lack of studies on this subject. We studied the surface areas and adsorption energies of three waste deposits – peat, willow dust and biochar prepared from these materials at different temperatures – using nitrogen and water vapour adsorption isotherms. The BET model accurately described all water vapour adsorption isotherms but failed for some nitrogen isotherms. Alternative methods for estimating surface areas and adsorption energies were proposed in cases where the BET model did not apply. Nitrogen adsorption was typically much lower than water vapour adsorption, and the estimated surface areas reflected this. However, nitrogen adsorption energies were significantly higher. Nitrogen surface areas increased with pyrolysis temperature, while water vapour surface areas decreased. The surface area estimated from nitrogen adsorption was generally much lower than needed to accommodate the surface-charged groups responsible for the cation exchange capacity of biochars.

Boosting CO2 selectivity by mono- and dicarboxylate-based ionic liquids impregnation into ZIF-8 for post-combustion separation

Post-combustion carbon dioxide (CO2) capture/separation is considered one of the main ways to minimize the impact of global warming caused by this greenhouse gas. This work used eight mono- and dicarboxylate-based ionic liquids (ILs) to impregnate metal-organic framework (MOF) ZIF-8. This anionic effect was studied for these mostly unreported IL@MOF composites to determine its impact on gas sorption and selectivity performance. Characterization results confirmed IL impregnation into the structure of ZIF-8, along with the conservation of microporosity and crystallinity in composites. Sorption-desorption equilibrium measurements were performed, and CO2 and nitrogen (N2) isotherms were obtained at 303 K for ZIF-8 and IL@ZIF-8 composites. At 0.15 bar, the dicarboxylate-based composite [C2MIM]2[Glu]@ZIF-8 showed the highest CO2 gas sorption, showing 50 % more sorption capacity than the best monocarboxylate-base composites at this pressure. Dicarboxylate-based composites also showed remarkable N2 sorption in the low-pressure range. The ideal CO2/N2 selectivity for a typical post-combustion composition was calculated, and a trend regarding the anionic carbon chain size was observed. The composite [C2MIM][Cap]@ZIF-8 showed nearly five times more selectivity than the pristine ZIF-8 at 1 bar of total pressure. Dicarboxylate-based composites, given their low-pressure high N2 sorption capacity, were not as selective as their respective monocarboxylate-based IL@ZIF-8 materials with the same carbon chain size.

Nanoconfined Metal Hydrides As Alternatives to Lithium Ion Battery Energy Storage

Energy densities of metal hydrides are competitive with lithium ion batteries (Fig. 1), highlighting their potential as contenders for emerging energy storage technologies. Metal hydrides have long been of interest for hydrogen storage for both transportation and stationary applications. However, most of these materials are too stable, i.e. their enthalpy of H2 desorption is too high to use the residual heat of a proton exchange membrane (PEM) fuel cell to drive the H2 release. Alternatively, metastable metal hydrides (MMH), for which H2 release is exothermic or only slightly endothermic, have received much less attention. Compounds such as LiAlH4 and AlH3 are so thermodynamically unstable that direct rehydrogenation following H2 release is thought to be impossible. This is unfortunate because these hydrides have high gravimetric and volumetric energy densities with potential for fast, low-temperature hydrogen release to power a fuel cell.The goal of this work was to synthesize nanoscale metal hydrides from earth-abundant elements and demonstrate that they can achieve energy densities higher than state-of-the-art lithium ion batteries, achieving full recharge using the residual heat from a PEM fuel cell. We employed a nanoconfinement strategy to improve the thermodynamics and kinetics of hydrogen release and uptake, which has been shown to be effective for many thermally stable metal hydrides.2 We will describe the synthesis and properties of nanoconfined alane (AlH3) using a bipyridine-functionalized covalent triazine framework (CTF) and the Metal-Organic Framework (MOF) UiO-67bpy (Zr6O4(OH)4(bpydc)6; bpydc2− =2,2′-bipyridine-5,5′dicarboxylate), which can coordinate AlH3 through the aromatic linker nitrogens.We find that the MOF and CTF both maintain the porous structure after infiltration. Brunauer-Emmett-Teller (BET) surface areas derived from nitrogen isotherms indicate significant decreases in the surface area and pore volume. Using a focused ion beam (FIB) to cut a channel in a MOF crystal surface, we obtained cross-sectional transmission electron microscopy (TEM)/energy-dispersive X-ray spectroscopy (EDS) images indicating that AlH3 is uniformly infiltrated throughout the MOF. Electron energy loss (EELS) spectra reveal that signals from MOF linker carbon atoms and aluminum atoms alternate along the FIBed channel, providing convincing evidence that AlH3 is located within the pores. Solid state 27Al-NMR, DFT calculations, and single crystal X-ray diffraction provide additional evidence that AlH3 is located in the vicinity of the bipyridine groups.We also demonstrate that AlH3 is thermodynamically stabilized by nanoconfinement within the CTF. AlH3@CTF-bipyridine rapidly desorbs hydrogen between 95 – 150 °C. Even more surprising, AlH3@CTF-bipyridine dehydrogenation is reversible at only 60 °C and 700 bar hydrogen, a pressure 36 times lower than the experimentally measured H2 plateau pressure of bulk aluminum. Together, these results suggest that metastable hydrides could be practical materials for H2 storage, and in selected cases with theoretical energy densities exceeding those of Li-ion batteries. L. Snider, M. Witman, M. E. Bowden, K. Brooks, B. L. Tran, T. Autrey Nat. Chem., DOI: 10.1038/s41557-022-01056-2Girishkumar, B. McCloskey, A. C. Luntz, S. Swanson, W. Wilcke J. Phys. Chem. Lett. 2010, 1, 2193–2203. Figure 1. Comparison of volumetric energy density vs. gravimetric energy density for various energy carriers and batteries. Adapted from Ref. 1. Figure 1

Fabricating a Robust Ultramicroporous Metal-Organic Framework for Purifying Natural Gas and Coal Mine Methane.

Purifying methane (CH4) from natural gas and coal mine methane (CMM) is of great significance but challenging in the chemical industry. Herein, a robust ultramicroporous metal-organic framework (MOF) is reported, which can be synthesized on a gram scale by stirring under room temperature. Single-component adsorption isotherms of gases (CH4, ethane (C2H6), propane (C3H8), nitrogen (N2)) and breakthrough experiments indicate that the MOF can separate CH4 efficiently from CH4/C2H6/C3H8 ternary mixture, with super high purity-CH4 production of 154.7 cm3g-1. Additionally, the MOF shows higher CH4 capacity than N2, resulting in excellent separation performance for the CH4/N2 mixture. Notably, the binding sites of gases can be precisely determined by single-crystal X-ray data, further confirmed by molecular simulation. It is found that there are multiple hydrogen bonds and C─H···π interactions between the gases and the framework. This work offers an excellent candidate material for CH4 purification with both high capacity and separation efficiency.

Chemiluminescence "Add-and-Measure" Sensing Paper Based on the Prussian Blue/Metal-Organic Framework MIL-101 Nanozyme for Rapid Hydrogen Peroxide Detection.

In this work, a chemiluminescent sensing paper has been developed using a peroxidase biomimetic metal-organic framework as a versatile host platform. For the first time, we have explored the use of in situ growth of Prussian Blue nanoparticles (PB-NPs) onto the MIL-101(Fe) structure for the assembly of a ready-to-use sensing paper. In situ growth of PB-NPs has been performed on the surface of the MIL-101(n) family. This novel composite, named PB-NPs@MIL-101(Fe), has been successfully used to develop a sensing paper for one-step detection of H2O2 in real samples (commercial disinfectant solutions and tap water samples). The as-prepared material was fully characterized, including X-ray analysis, Fourier transform infrared, scanning and transmission electron microscopies, nitrogen isotherms, and elemental analysis. After the characterization, the analytical performance of the PB-NPs@MIL-101(Fe) sensing paper was evaluated. The low-cost sensor (0.15 euro per unit) was able to detect down to 8.2 μM (corresponding to 8.2 × 10-11 mol) H2O2 using only 10 μL of sample with satisfactory reproducibility (relative standard deviation 17%).

Activated carbons from Brazilian lignocellulosic residues from baru and jurubeba as adsorbents for removal of diethyl phthalate in aqueous phase

New insights were achieved for the removal of plasticizer in the aqueous phase, through adsorption by H3PO4 and H2SO4 activated carbons. The preparation was made from Brazilian lignocellulosic residues from of the baru shell (Dipteryx alata) and the jurubeba fruit (Solanum paniculatum). Such residues were characterized by biochemical, elemental, thermogravimetric, Fourier Transform Infrared analyses. Subsequently, the influence of the biomass/acidity ratio (1/2; 1/3) was analyzed by applying adsorption kinetics for a diethyl phthalate concentration of 0.2 g L‐1, isotherms, and modeling. Chemical activation was carried out at 80 ºC 30 min‐1, drying at 110 ºC 15 h‐1 and carbonization under N2 flow at 800 ºC 60 min‐1 at a heating rate of 20 ºC min‐1. Precursors and ACs were characterized by nitrogen isotherm at 77 K, TGA-DTG, FT-IR, pHPZC. The reaction mechanisms, applicability of ACs were analyzed. ACs' yields varied: 31.7–50.4% (baru); 30–41.7% (jurubeba). The ACs exhibited a range of textural properties from: specific surface area (SBET): 2–269 m² g‐1, micropore volume (W0): 0.10–0.56 cm3 g‐1, micropore width (L0): 9.3–17.6 Å. Results revealed high thermal resistance, amorphous structure, mesoporous surfaces for baru ACs, microporous surfaces for jurubeba ACs, both predominantly acidic: pHPZC 1.8–3.9. This acidity facilitated non-electrostatic interactions during the adsorption.

Evaluation of oil transesterification in a packed‐bed reactor containing lipase immobilized in starch–alginate jet cutting beads

AbstractThere has been a growing interest in ecofriendly enzymatic processes. However, enzyme solubility limits the application of many biocatalysts in continuous systems, requiring the development of cost‐effective strategies for enzyme immobilization. Based on this premise, this study investigated the application of lipase immobilized in starch–alginate beads for oil transesterification in a tubular reactor. An economical derivative was produced by immobilizing Eversa Transform 2.0 in 50:50 (w/w) starch–alginate beads using the jet‐cutting technique. The biocatalyst had a particle size of about 500 μm and activity of 138.67 ± 18.53 U g−1. X‐ray photoelectron spectroscopy showed nitrogen content ranging from 6.38% to 7.29%, with uniform distribution of lipase throughout the beads. Nitrogen isotherms were characteristic of mesoporous materials, with an average pore diameter of 48.09 Å and low surface area (0.69 m2 g−1). A face‐centered central composite design was used to study soybean oil transesterification. In the best four runs, the process achieved a mean triglyceride conversion of 45%. High ester productivity levels (2.05 × 10−2% ester g−1 biocatalyst min−1 or 1.5 × 10−4% ester U−1 min−1) were obtained. Biocatalyst reuse led to a twofold increase in ester concentration (14.57% vs 7.7%). These findings confirm the successful development of a low‐cost biocatalyst suitable for use in continuous reactions.

Temperature-regulated gas adsorption on LTA zeolites: Observation of sorption isotherms for methane, hydrogen, nitrogen and carbon dioxide

Temperature-regulated gas adsorption of various zeolite LTAs with different cations of Cs2+, K+, Na+, and Ca2+ (namely, Cs-A, 3A, 4A, and 5A) was analysed in the presence of different gas molecules of H2, CO2, N2, and CH4 for pressures up to 800 kPa and temperatures ranging from 77.15 to 363.15 K. Over the range of test conditions, zeolite 5A (containing Ca2+ cations) exhibited the highest uptake at 800 kPa for CO2, H2, CH4, and N2, with capacity values of 5.69 mmol.g−1, 1.14 mmol.g−1, 6.60 mmol.g−1, and 6.10 mmol.g−1, at 298.15 K and 201.15 K respectively. Zeolite 4A (containing Na+ cations) exhibited 0.74 mmol.g−1 for H2 adsorption at 201.15 K, and 800 kPa. In contrast, pores were inaccessible to H2 on ion-exchange Cs-A zeolite at a temperature range of 77.15–343.15 K, due to larger cation Cs2+ (CsA) comparison with Na+ (4A). Interestingly, zeolite 3A (containing K+ cations) showed a negligible capacity for the larger gas molecules, CH4 and N2, ascribed to the pore space blocked by the larger K+ cations (relative to the smaller Na+ and Ca2+ cations). Zeolite 3A exhibited a temperature-dependent behaviour (i.e., presumably a “trapdoor” effect) with H2 wherein adsorption was negligible at 77.15 K, but was significant above approximately 200 K. For N2, zeolite 4A exhibits similar temperature-regulated adsorption characteristics (i.e., presumably a “trapdoor” mechanism as well). These zeolite materials used in various temperature swing processes could be particularly beneficial in natural hydrogen production (with H2/N2 separation with 3A), the production of synthetic fuels from CO2/H2 mixtures (with both 3A and 4A), CO2 capture from waste streams, and applications for H2/N2 separation.

Optical n(p, T90) Measurement Suite 3: Results at λ=1542nm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda = 1542\\,\ ext{nm}$$\\end{document}

Single-isotherm n(p, T90) results are reported for the gases Ar, N2, H2O, and D2O at vacuum wavelength λ=1542.383(1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda = 1542.383(1)$$\\end{document} nm. The argon and nitrogen isotherms were measured near 303 K; the water isotherms were measured near 373 K. Combined with the two previous articles of this series, the present results beget several insights via dispersion analyses. The argon result is highly consistent with static measurement plus ab initio calculation of dispersion polarizability. The nitrogen result is nominally consistent with one recent experiment and the dipole oscillator strength distributions, but the present work offers a refined estimate of the molar refractivity at optical wavelengths. For ordinary and heavy water, the dispersion trend is nominally consistent with existing liquid measurements. However, water’s absorption features in the near-infrared preclude a reliable comparison of the present result with literature.

Magnetically nanorized seaweed residue for the adsorption of methylene blue in aqueous solutions.

The cost-effective and green separation of dye pollutants from wastewater is of great importance in environmental remediation. Industrial seaweed residue (SR), as a low-cost cellulose source, was used to produce carboxylated nanorized-SR (NSR) via oxalic acid (OA)-water pretreatments followed by ultrasonic disintegration. Fourier transform infrared spectroscopy, X-ray polycrystalline diffraction, nitrogen isotherms, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray photoelectron spectrometry, particle charge detection, zeta potential and retro titration experiments were utilized to explore the physiochemical properties of samples. The NSRs with carboxyl content of 4.58-6.73 mmol g-1 were prepared using 10-60% OA-water pretreatment. In the case of 20% OA-water pretreatment, the highest NSR yield (73.9%) and nanocellulose content (80.2%) were obtained. Through self-assembly induced by the electrostatic interaction, magnetic NSR composite adsorbents (MNSRs) were prepared with the combination of NSR and Fe3O4 nanoparticles (NPs). The carboxylated NSR with negative charge demonstrated good affinity for Fe3O4 NPs. The Fe3O4 NPs were perfectly microencapsulated with the NSR when the NSR/Fe3O4 mass ratio was higher than 1/1. The adsorption properties of the MNSR for methylene blue (MB) removal from aqueous solution were investigated. The adsorbent with NSR/Fe3O4 mass ratio of 1/1 (MNSR1/1) exhibited optimum performance in terms of the magnetic properties and adsorption capacity. The MNSR1/1 showed high adsorption ability in a pH ≥7 environment. According to the Langmuir fitting, the maximum adsorption capacity of MNSR1/1 for MB reached 184.25 mg g-1. The adsorption of MB complies with the pseudo-second-order kinetic model. MNSR1/1 still maintained good adsorption properties after the fifth cycle of adsorption-desorption. MNSR1/1 could selectively adsorb cationic dye (i.e., MB and methyl violet) from wastewater, with hydrogen bonding and electrostatic interaction as the main force.

Optimization of zeolite ETS-10 synthesis for enhanced Pb(II) adsorption from aqueous solutions

The synthesis of zeolite ETS-10 is strongly influenced by factors such as pH, the amount of the structure-directing agent, hydrothermal temperature and duration, which collectively affect the material’s morphology and structure. This study thoroughly investigates the effects of these parameters on the synthesis of ETS-10 zeolite using TiCl3 and a waterglass solution. Characterization of the materials was performed through X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and nitrogen isotherm adsorption-desorption at 77 K (BET-BJH) techniques. The findings indicate that pH and the structure-directing agent significantly influenced the phase composition, while hydrothermal temperature predominantly determined the crystallization rate of ETS-10. Optimal synthesis conditions were established at an initial pH of 11, employing 0.3 g of the structure-directing agent and conducting hydrothermal crystallization at 230 °C for 24 h. Under these conditions, the ETS-10 zeolite produced exhibited a high surface area of 300.1 m2/g, making it effective in removing Pb2+ ions from solution. In particular, when tested under optimal conditions (pH 5) for 600 min, Pb (II) adsorption by ETS-10 reached a maximum uptake capacity of 956.19 mg/g, as determined by the Langmuir isotherm model. This capacity surpasses that of as-synthesized ETS-10 prepared from alternative Ti sources and other materials used in previous studies on Pb(II) adsorption.

Fabrication of new in‐situ ternary nano/microcomposite LDH/Ag2O/Bayerite in trimetallic NiAg/Al layered double hydroxides for CO2 capture material

AbstractWe reported new in‐situ ternary nano/microcomposite layered double hydroxides/Ag2O/bayerite in trimetallic NiAg/Al layered double hydroxides (LDH) via hydrothermal technique; and characterization by powder X‐ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT‐IR), field emission scanning electron microscopy (FE‐SEM), energy dispersive spectroscopy (EDS), and N2 adsorption‐desorption. The formation of bayerite and silver oxide species on the LDH nanosheet depended on the excess of Al3+ and Ag+ in the solution under alkaline and hydrothermal conditions. The nitrogen isotherm adsorption profile for all ternary composites exhibited uniformity with mesoporous and lamellar characteristics. The surface area of all the composites ranged from 81.17 to 150.23 m2. g−1, the Barret‐Joyner‐Halenda (BJH) pore volume from 0.22 to 0.27 cm3. g−1, and the average pore diameter ranged from 3.47 to 5.78 nm. All composites show a laminar plate‐like structure covered with elongated pieces. The particle size of the composites ranged from 54.86 to 115.96 nm, indicating the size changed from nano to microcomposite because of the different molar ratios of Ag and Ni in the solid. The ternary composite reveals CO2 capture activity with adsorption capacity ranging from 13.93 to 19.61 mmol g−1. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Adsorption simulation of 2,4-D pesticide on novel zinc-based 2-amino-4-(1H-1,2,4-triazole-4-yl)benzoic acid coordination complexes using machine learning approach.

The capacity of zinc-based 2-amino-4-(1H-1,2,4-triazole-4-yl)benzoic acid coordination complex (Zn(NH2-TBA)2) and modified Zn(NH-TBA)2COMe complex for removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions was investigated through adsorption modeling and artificial intelligence tools. Analyzing the adsorption characteristics of pesticides helps in studying the groundwater pollution by pesticides in agriculture area.In this study, Zn(NH2-TBA)2 was synthesized using Schiff base and its surface was modified using acetic anhydride group and their physical characteristics were identified using proton NMR, FTIR, and XRD. NMR results showed maximum modification yield obtained was 65% after 5days. The porous structure and surface area monitored using nitrogen isotherm and BET surface area analysis presented relatively less surface area and porosity after modification. Adsorption modelling indicated that Toth model with a maximum adsorption capacity of 150.8mg/g and 100.7mg/g represents the homogenous adsorption systems which satisfy both low- and high-end boundary of adsorbate concentration in all settings according to the optimum point, while the kinetics and rate of 2,4-D adsorption follow the pseudo-first-order kinetic model in all situations. Artificial neural network (ANN), support vector regression, and particle swarm optimized least squares-support vector regression (PSO-LSSVR) were used for the optimization and modelling of adsorbent mass, adsorbate concentration, contact time, and temperature to develop predictive equations for the simulation of the adsorption efficiency of 2,4-D pesticide. The obtained results exhibited the better performance of ANN and PSO-LSSVR for prediction of adsorption results. The mean square error values of ANN (0.001, 0.012) and PSO-LSSVR (0.121, 0.105) were obtained for Zn(NH2-TBA)2 and Zn(NH-TBA)2COMe, respectively, while their respective coefficient of determination (R2) obtained were 0.999 and 0.988 for ANN and 0.980 and 0.825 for PSO-LSSVR. The study specified that machine learning predictive behavior performed better for Zn(NH2-TBA)2 compared to Zn(NH-TBA)2COMe that is also supported by theoretical kinetics and isotherm models. The research concludes that artificial intelligence models are the most efficient tools for studying the predictive behavior of adsorption data.

Synthesis of Composite Sorbents with Chitosan and Varied Silica Phases for the Adsorption of Anionic Dyes.

In this work, various types of silica materials were used for the synthesis of chitosan-silica composites. The composites were obtained using the chitosan (Ch) immobilization process from an aqueous solution on various silica phases, i.e., amorphous diatomite (ChAD), crystalline diatomite (ChCD), mesoporous silica MCM-41 (ChMCM), and mesoporous silica SBA-15 (ChSBA). Textural, structural, morphological, and surface properties of the materials were determined by using various measurement techniques, i.e., low-temperature adsorption/desorption isotherms of nitrogen, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), potentiometric titration, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The adsorption properties towards various anionic dyes, i.e., acid red 88 (AR88), acid orange 8 (AO8), and orange G (OG), were evaluated based on kinetic and equilibrium measurements. The ChSBA, ChAD, and ChMCM composites were characterized by relatively high adsorption capacities (am) for AR88, with values equal to 0.78, 0.71, and 0.69 mmol/g, respectively. These composites were also distinguished by the rapid AR88 adsorption rate, with the values of half-time parameter t0.5 equal to 0.35, 2.84, and 1.53 min, respectively. The adsorption equilibrium and kinetic data were analyzed by applying the generalized Langmuir isotherm and the multi-exponential equation (m-exp), respectively. An interaction mechanism between the dyes and the obtained materials was proposed.

Silica extracts from fly ash modified via sol-gel methods and functionalized with CMPO for potential scavenging of rare earth elements La³⁺ and Ce³⁺

A mesoporous material was synthesized using silica extracts from fly ash and its properties were studied. Subsequently, it was functionalized with carbamoylmethylphosphine oxide (CMPO) to capture La3+ and Ce3+. The developed mesoporous material was obtained by the sol-gel method and was called Si-MMS (siliceous mesoporous materials), subsequently functionalized with APTMS (1-(2-aminoethyl)-3-aminopropyl trimethoxysilane) in a reflux system, which led to the synthesis of Si-MMS-APTMS. This derivative was modified with carbonyldiimidazole (CDI) and diethylphosphonoacetic acid, which finally resulted in the synthesis of Si-MMS-CMPO as the final product. The materials were characterized by DRIFT, XRD, SEM-EDS, TEM, XPS, elemental analysis and nitrogen isotherms at −196 °C, confirming that the synthesis and subsequent modification of the mesoporous structure was successful. Adsorption studies in batch systems indicated that the optimal pH for La3+ was 6, the Langmuir isotherm model and the non-linear Sips models were perfectly fitted and the best fitting kinetics is the Elovich model. For Ce3+ the optimal pH was 7.5, the non-linear Sips isotherm fit the best and the non-linear Pseudo-second order kinetics was the mechanism that best represents the adsorption. The maximum experimental adsorption capacity qe of La3+ was 17.00 mg g−1 and for Ce3+ was 30.09 mg g−1. In both cases, the rapid adsorption suggests an open porous matrix that facilitates the formation of chelates between the adsorbates and the phosphoryl group -PO32-.

Temperature Evolution of Sorbonorit-4 Methane-Induced Deformation through the Eyes of Classical Density Functional Theory.

Activated carbons are widely used industrial adsorbents due to their attractive sorption properties. Although extensive research on activated carbon has been carried out for several centuries, some aspects of the adsorption-induced deformation of activated carbon remain unclear. The puzzling temperature dependence of the methane-induced deformation of activated carbon is investigated in the present work. Several experimental studies have shown that an increase in temperature leads to a reversal of the sign of adsorption strain at low pressures, i.e., the contraction turns into an expansion. Here we suggest a possible explanation for this effect by applying classical density functional theory to the adsorption isotherms of nitrogen, carbon dioxide, and methane as well as to methane-induced deformation isotherms. Our calculations show that the adsorption stress generated in the smallest pores predominates at higher temperatures and leads to material swelling. Lowering the temperature, on the other hand, leads to a predominance of larger pores and compression of the activated carbon material. We also investigated the possibility of determining the pore size distribution from methane-induced deformation and adsorption data and the predictive capabilities of our theoretical approach.

Tailoring the pore structure of iron oxide core@stellate mesoporous silica shell nanocomposites: effects on MRI and magnetic hyperthermia properties and applicability to anti-cancer therapies.

Core-shell nanocomposites made of iron oxide core (IO NPs) coated with mesoporous silica (MS) shells are promising theranostic agents. While the core is being used as an efficient heating nanoagent under alternating magnetic field (AMF) and near infra-red (NIR) light and as a suitable contrast agent for magnetic resonance imaging (MRI), the MS shell is particularly relevant to ensure colloidal stability in a biological buffer and to transport a variety of therapeutics. However, a major challenge with such inorganic nanostructures is the design of adjustable silica structures, especially with tunable large pores which would be useful, for instance, for the delivery of large therapeutic biomolecule loading and further sustained release. Furthermore, the effect of tailoring a porous silica structure on the magneto- or photothermal dissipation still remains poorly investigated. In this work, we undertake an in-depth investigation of the growth of stellate mesoporous silica (STMS) shells around IO NPs cores and of their micro/mesoporous features respectively through time-lapse and in situ liquid phase transmission electron microscopy (LPTEM) and detailed nitrogen isotherm adsorption studies. We found here that the STMS shell features (thickness, pore size, surface area) can be finely tuned by simply controlling the sol-gel reaction time, affording a novel range of IO@STMS core@shell NPs. Finally, regarding the responses under alternating magnetic fields and NIR light which are evaluated as a function of the silica structure, IO@STMS NPs having a tunable silica shell structure are shown to be efficient as T2-weighted MRI agents and as heating agents for magneto- and photoinduced hyperthermia. Furthermore, such IO@STMS are found to display anti-cancer effects in pancreatic cancer cells under magnetic fields (both alternating and rotating).

Liquid-phase adsorption of nitrogen compounds from model diesel fuel on activated carbons

One of the great challenges in deep hydrodesulfurization (HDS) to produce ultra-low-sulfur diesel (ULSD) is the coexisting heterocyclic nitrogen-containing compounds in middle distillates, which significantly inhibit the HDS reactions. This study investigates various activated carbon (AC) samples for selectively removing nitrogen compounds from a model diesel fuel through adsorption. The physical and chemical properties of the AC samples were characterized using low-temperature N2 adsorption–desorption, SEM–EDS, and FT-IR to explore their impact on the adsorption performance. The results indicate that the adsorption performance is influenced not only by the surface area and by the number of oxygen-containing functional groups on the surface but also by the pore diameter distribution. Among all AC samples tested, AC-W exhibited the highest adsorption capacity, achieving a nitrogen removal rate of 97.8% with the addition of 10 wt.% of AC-W. The adsorption capacity was approximately 24.0 mg-N/g-A at a nitrogen equilibrium concentration of 200 ppmw. The adsorption isotherms for total nitrogen and individual nitrogen compounds in the fuel over AC can be described well by the Freundlich isotherm model. An approach for improving the ADN performance of AC is discussed based on the findings in this study.

The Structure-Function Relationship of Branched Polyethylenimine Impregnated over Mesoporous Carbon Aerogels: An In-Depth Thermogravimetric Insight.

We present a comprehensive thermogravimetric analysis (TGA) of polyethylenimine (PEI)-impregnated resorcinol-formaldehyde (RF) aerogels. While numerous studies focus on PEI-impregnated SBA, RF materials have been less examined, despite their interest and specificities. As most articles on PEI-impregnated porous materials follow typical experimental methods defined for SBA, particularities of RF-PEI materials could remain unheeded. The design of nonisothermal TGA protocols, completed with nitrogen isotherms, based on the systematic filling of the matrix delivers a fundamental understanding of the relationship between the structure and function. This study demonstrates (i) the competition between the matrix and PEI for CO2-physisorption (φ) and CO2-chemisorption (χ), (ii) the hysteresis ([Formula: see text]) of CO2 capture at low temperature attributed to the kinetic (K) hindrance of CO2 diffusion (D) through PEI film/plugs limiting the chemisorption, and (iii) the thermodynamic (θ) equilibrium limiting the capture at high temperature. At variance with SBA-PEI materials, the first layers of PEI in RF are readily available for CO2 capture given that this matrix does not covalently bind PEI as SBA. A facile method allows the discrimination between physi- and chemisorption, exhibiting how the former decreases with PEI coverage. The CO2 capture hysteresis, while seldom introduced or discussed, underlines that the commonly accepted operating temperature of the "maximum capture" is based on an incomplete experiment. Through isotherm adsorption analysis, we correlate the evolution of this maximum to the morphological distribution of PEI. This contribution highlights the specificities of RF-PEI and the advantages of our TGA protocol in understanding the structure/function relationship of this kind of material by avoiding the typical direct applications of SBA-specific protocols. The method is straightforward, does not need large-scale facilities, and is applicable to other materials. Its easiness and rapidness are suited to high-volume studies, befitting for the comprehensive evaluation of interacting factors such as the matrix's nature, pore size, and PEI weight.