N2 Adsorption Porosimetry Research Articles

Lewis Acidic Aluminosilicates: Synthesis, 27Al MQ/MAS NMR, and DFT-Calculated 27Al NMR Parameters.

Porous aluminosilicates are functional materials of paramount importance as Lewis acid catalysts in the synthetic industry, yet the participating aluminum species remain poorly studied. Herein, a series of model aluminosilicate networks containing [L-AlO3] (L = THF, Et3N, pyridine, triethylphosphine oxide (TEPO)) and [AlO4]- centers were prepared through nonhydrolytic sol-gel condensation reactions of the spherosilicate building block (Me3Sn)8Si8O20 with L-AlX3 (X = Cl, Me, Et) and [Me4N] [AlCl4] compounds in THF or toluene. The substoichiometric dosage of the Al precursors ensured complete condensation and uniform incorporation, with the bulky spherosilicate forcing a separation between neighboring aluminum centers. The materials were characterized by 1H, 13C, 27Al, 29Si, and 31P MAS NMR and FTIR spectroscopies, ICP-OES, gravimetry, and N2 adsorption porosimetry. The resulting aluminum centers were resolved by 27Al TQ/MAS NMR techniques and assigned based on their spectroscopic parameters obtained by peak fitting (δiso, CQ, η) and their correspondence to the values calculated on model structures by DFT methods. A clear correlation between the decrease in the symmetry of the Al centers and the increase of the observed CQ was established with values spanning from 4.4 MHz for distorted [AlO4]- to 15.1 MHz for [THF-AlO3]. Products containing exclusively [TEPO-AlO3] or [AlO4]- centers could be obtained (single-site materials). For L = THF, Et3N, and pyridine, the [AlO4]- centers were formed together with the expected [L-AlO3] species, and a viable mechanism for the unexpected emergence of [AlO4]- was proposed.

A novel device for in situ study of gas adsorption under rotation.

The effect of rotation on adsorption kinetics of CO2 on activated carbon (AC) is studied using a novel rotation device. The device consists of a rotating cylindrical cell with inner dimensions of 4.5cm radius and 1mm height, while it operates at 5000 and 8000 rpm. Various cases of the CO2/AC system are examined under a rotation field: in particular, (a) solid at vacuum, (b) gas without solid, (c) gas/solid at a non-equilibrium state of the adsorption process, and (d) gas/solid near an equilibrium state of the adsorption process. Micro-fragmentation of solid particles is observed at 8000 rpm but not at 5000 rpm; the latter is then chosen as the preferable speed for the rest of the experiments. During rotation of the gas, a well is noticed at the pressure curve, the size of which is in accordance with theoretical predictions of the behavior of a spinning gas. Rotation at an early stage of the adsorption process can suppress the filling time of a rotating storage reservoir to half of its value. Rotation near the equilibrium point reveals an enhanced adsorption capacity of the solid. The physics behind these phenomena are discussed with the aid of N2-adsorption porosimetry and scanning electron microscopy measurements.

Green Synthesis of Copper Nanoparticles using Centaurea cyanus Plant Extract: A Cationic Dye Adsorption Application

In this study, copper nanoparticles (Cu-NPs) were synthesized through a green and economic technique. The Centaurea cyanus plant extract was used as an appropriate reducing and stabilizing agent in this process. The synthesized nanoparticles were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray Powder Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and N2 adsorption porosimetry analysis. The analysis showed that the average size of spherical nanoparticles was around 11.9 nm, with 74.2 m2/g and 0.36 cm3/g mane surface area and pore size, respectively. Then, Cu-NPs were studied as a low-cost adsorbent to remove methylene blue (MB) dye from aqueous solutions. For this purpose, Central Composite Design (CCD) under the Response Surface Methodology (RSM) was applied to design the experiments, model the data and optimize the operating conditions. The effect of various operating parameters such as pH, MB initial concentration, adsorbent amount and contact time on the MB removal was practiced. Analysis of variance (ANOVA) showed a good agreement between the experimental data and the predicted ones obtained from the quadratic model. The optimum conditions for MB removal (63.20 %) were found at pH of 6.6, MB initial concentration of 30 mg/L, adsorbent amount of 0.15 g and time of 101.5 min. The results showed that the Langmuir isotherm with maximum adoption capacity of 21.9 mg/g and pseudo-second order kinetic models with rate constant of 0.359 (g/mg) (1/min) can properly legitimize the experimental data.

The Effect of Silica Coating on the Drug Release Profile and Biocompatibility of Nano-MOF-5

The purpose of this study was the surface modification of nano MOF-5 (NMOF-5) or IRMOF-1 (Zn4O(C8H4O4)3) in order to prevent its rapid degradation in the phosphate-buffered saline (PBS), along with the simultaneous increase in its biocompatibility. The NMOF-5 sample was synthesized under the ultrasound irradiation and then it was loaded with acetaminophen and ibuprofen. Each assembly (NMOF-5@drug) was then coated with a silica layer. The obtained nanoparticles were identified by FT-IR spectroscopy, N2 adsorption porosimetry (BET), X-ray powder diffraction (XRD), the thermogravimetric analysis (TGA), and the field emission scanning electron microscopy (FE-SEM). UV/Vis spectroscopy was used to determine the release profile of the drugs from the bare and silica coated assemblies. Silica coating resulted in an enhanced stability in PBS, and the sustained release of each drug was achieved within 3 days. MTT (Methylthiazolyldiphenyl-tetrazolium bromide) assay on NIH3T3 mouse embryonic fibroblast cells as a model of the cell line showed that silica coating NMOF-5 with silica leads in the more biocompatibility and less cytotoxicity. The cell viability was increased up to 100% for the silica coated NMOF-5 compared to the bare NMOF-5. NMOF-5 and NMOF-5@silica were utilized in the injectable drug delivery for the first time. In this study, the toxicological studies about silica coated NMOF-5 in the drug delivery systems were developed.

Experimental methods in chemical engineering: specific surface area and pore size distribution measurements—BET, BJH, and DFT

AbstractGas physisorption is an experimental technique based on equilibrium Van der Waals interactions between gas molecules and solid particles, that quantifies the specific surface area (SSA), pore size distribution (PSD), and pore volume of solids and powders. The performance of catalysts, absorbents, chromatography column materials, and polymer resins depends on these morphological properties. Here we introduce the basic principles and procedures of physical adsorption, especially nitrogen physisorption, as a guide to students and researchers unfamiliar with the field. The Brunauer‐Emmett‐Teller theory (BET) is a common approach to estimate SSA that extends the Langmuir monolayer molecular adsorption model to multilayer layers. It relies on an equilibrium adsorption isotherm, measured at the normal boiling point of the adsorbate, eg, 77 K or 87 K for N2 and Ar, respectively. Web of Science indexed 45 400 articles in 2016 and 2017 that mentioned N2 adsorption porosimetry—BET and BJH (Barrett‐Joyner‐Halenda) keywords. The VOSViewer bibliometric tool grouped these articles into four research clusters: adsorption, activated carbon in aqueous solutions for removal of heavy metal ions; synthesis of nanoparticles and composites; catalysts performance in oxidation and reduction processes; and photocatalytic degradation with TiO2. According to the literature, the accuracy of the density function theory (DFT) method is higher than with the BJH theory and it is more reliable.

Improving physicochemical properties of upgraded Indonesian lignite through microwave irradiation with char adsorbent

To upgrade Indonesian lignite by significantly reducing volatile matter content, char adsorbent was employed to accelerate lignite pyrolysis through microwave irradiation. Physicochemical properties of pyrolyzed lignite were determined with the assistance of char adsorbent on Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray spectroscopy, N2 adsorption porosimetry, and contact angle analysis. Under the same microwave power of 800 W and irradiation time of 12.5 min, the lignite temperature remarkably increased from 150 °C to 656 °C with the aid of 10 g char adsorbent. Its apparent aromaticity increased from 0.50 to 0.97. The relative content of superficial carbon functional groups attributed to π–π∗ transitions increased from 1.18% to 6.71%. The volatile matter content (dried basis) markedly decreased from 48.94% to 6.47% due to the release of volatile compounds in the lignite.

Amine-Functionalized Mesoporous Silica Nanoparticles: A New Nanoantibiotic for Bone Infection Treatment

Abstract This manuscript reports an effective new alternative for the management of bone infection by the development of an antibiotic nanocarrier able to penetrate bacterial biofilm, thus enhancing antimicrobial effectiveness. This nanosystem, also denoted as “nanoantibiotic”, consists in mesoporous silica nanoparticles (MSNs) loaded with an antimicrobial agent (levofloxacin, LEVO) and externally functionalized with N-(2-aminoethyl)-3- aminopropyltrimethoxysilane (DAMO) as targeting agent. This amine functionalization provides MSNs of positive charges, which improves the affinity towards the negatively charged bacteria wall and biofilm. Physical and chemical properties of the nanoantibiotic were studied using different characterization techniques, including Xray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption porosimetry, elemental chemical analysis, dynamic light scattering (DLS), zeta (ζ)-potential and solid-state nuclear magnetic resonance (NMR). “In vial” LEVO release profiles and the in vitro antimicrobial effectiveness of the different released doses were investigated. The efficacy of the nanoantibiotic against a S. aureus biofilm was also determined, showing the practically total destruction of the biofilm due to the high penetration ability of the developed nanosystem. These findings open up promising expectations in the field of bone infection treatment.

Mechanochemical solvent-free in situ synthesis of drug-loaded {Cu2(1,4-bdc)2(dabco)}n MOFs for controlled drug delivery

In the present study, ibuprofen-loaded nano metal–organic frameworks (NMOFs) {Cu2(1,4-bdc)2(dabco)}n and {Cu2(1,4-bdc-NH2)2(dabco)}n (bdc=benzenedicarboxylic acid, and dabco=diazabicyclooctane) were synthesized by ball-milling at room temperature in 2h. The produced drug-loaded Cu-NMOFs were studied as ibuprofen drug delivery system and exhibited well-defined drug release behavior, exceptionally high drug loading capacities and the ability to entrap the model drug. The loading efficiency for ibuprofen was determined about 50.54% and 50.27%, respectively. The drug release of NMOFs was also monitored, and all of the loaded drug was released in 1 day. The NMOFs were characterized by FT-IR spectroscopy, X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA), SEM (scanning electron microscopy), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP), UV–vis spectroscopy and N2 adsorption porosimetry (BET&BJH).

Molecularly Imprinted Polymer of Colocynthin, An Effective Tool for Quality Control of Citrullus colocynthis Extracts

Different parts of Colocynth, Citrullus colocynthis (L.) Schrad., are used in traditional phytotherapy and homeopathy. In our new approach, a molecularly imprinted polymer was synthesized to absorb colocynthin, the major plant marker, and its capability was evaluated using HPLC-UV. A new method was considered to achieve optimal conditions. FT-infrared, N2 adsorption porosimetry, fluorescent and scanning electron microscopy and thermo gravimetric profile of the polymers were studied. The imprinted polymer was applied as molecularly imprinted solid phase extraction sorbent to enrich colocynthin from colocynth oil extract, a traditional medicine dosage form. The imprinted polymer showed high capacity and affinity toward colocynthin. Physical assessments demonstrated no major differences between imprinted and nonimprinted polymers. The imprinted polymer was able to absorb colocynthin more efficiently than non-imprinted and control simple solvent extraction from the real sample. In conclusion, this polymer is capable of being applied as a promising adsorbent for analysis of colocynth traditional medicine products.

Enhancing slurryabilities of five lignites from Inner Mongolia of China by microwave irradiation

ABSTRACTFive typical lignites from Inner Mongolia were upgraded by microwave irradiation to improve their slurryabilities. This procedure was performed to utilize abundant cheap lignites recently exploited in China to produce quality coal water slurry (CWS) fuel for gasification and combustion. The physicochemical properties of upgraded lignites were investigated through Fourier transform infrared spectroscopy, zeta potential analysis, contact angle analysis, and N2 adsorption porosimetry. The oxygen functional groups and oxygen/carbon ratios decreased in five upgraded lignites after microwave irradiation, but their zeta potentials and contact angles increased. The specific surface areas of five upgraded lignites decreased because of collapse and shrinkage of pores. These changes in five upgraded lignites resulted in increased coal rank and decreased hydrophilicity, which were beneficial to prepare CWS with high solid concentrations. The maximum solid concentrations of CWS prepared from five upgraded lignites increased by 4.0–9.8%.

Study of the physicochemical interactions between Thermomyces lanuginosus lipase and silica-based supports and their correlation with the biochemical activity of the biocatalysts

The interactions between Thermomyces lanuginosus lipase (TLL) and phenyl silica-based supports affect the immobilization mechanisms and their catalytic behavior. The modulation of phenyl groups density on the silica surface and porous characteristics were determined by TGA, FTIR, 29Si NMR and N2 adsorption porosimetry. The correlation of the affinity constant and maximum adsorption capacity with the lixiviation results allowed determine differences in the enzyme adsorption mechanism in function of the immobilization pH and phenyl groups density. In the support with low phenyl groups density, the adsorption of a higher amount of enzyme is promoted. However, the pore confinement and the microenvironment generate decrease expressed activity. This can be due to the stiffness and structural changes of the adsorbed enzymes, which were studied by following the thermal stability at 65°C, protein distribution, kinetic parameters and diffusion restrictions. The biocatalyst prepared on support with low density of phenyl groups at pH6.0, exhibits the best balance between expressed activity, thermal stability and immobilization efficiency. This due to homogeneous distribution of the enzyme in the support with phenyl groups, which increases the affinity of the enzyme by the substrate, even the diffusion restrictions decrease the Vmax. These results contribute to rationalize the effects of the immobilization conditions and supports type on its catalytic behavior.

Super-microporous solid base MgO-ZrO2 composite and their application in biodiesel production

The super-microporous microcrystalline MgO-ZrO2 nanomaterials (pore size 1–2nm) was prepared successfully via a facile one-pot evaporation-induced self-assembly (EISA) method and employed in the transesterification of soybean oil and methanol. X-ray diffraction, transmission electron microscope, temperature programmed desorption of CO2, and N2 adsorption porosimetry were employed to characterize the nanocomposites. Nitrogen sorption isotherms revealed that these materials had large surface areas of more than 200m2/g. Moreover, the sample with a Mg/Zr molar ratio of 0.5 and calcined at 400°C showed high biodiesel yield (around 99% at 150°C).

Two-Solvent Method Synthesis of NiO/ZnO Nanoparticles Embedded in Mesoporous SBA-15: Photocatalytic Properties Study.

Different loadings of NiO/ZnO nanoparticles embedded in mesoporous silica (SBA-15) were prepared via a two-solvent method with the ordered hexagonal mesoporous structure of SBA-15 kept. X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, diffusive reflective UV-vis spectroscopy, and N2 adsorption porosimetry were employed to characterize the nanocomposites. The results indicate that the ordered hexagonal mesoporous structure of SBA-15 is kept and the absorption band edges of the nanocomposites shift into the ultraviolet light regime. The photocatalytic activity of our samples for degradation of methylene orange was investigated under UV light irradiation, and the results show that the nanocomposites have higher photodegradation ability toward methylene orange than commercial pure P-25. The photocatalytic activity of the nanocomposites was found to be dependent on both the adsorption ability of the SBA-15 and the photocatalytic activity of NiO-ZnO nanoparticles encapsulated in SBA-15. In addition, there is an optimal loading of NiO-ZnO nanoparticles. Too high or low loading will lower the photodegradation ability of the nanocomposites.

Evaluation of the effect of nanoporous nanorods Zn2(bdc)2(dabco) dimension on ibuprofen loading and release

This work presents an experimental investigation of drug loading in metal-organic frameworks (MOFs). Porous metal organic framework [Zn2(bdc)2(dabco)] was synthesized under solvothermal conditions. Characterization of samples was studied by IR spectroscopy, X-ray powder diffraction, thermogravimetric analysis, ultraviolet–visible spectroscopy, N2 adsorption porosimetry and scanning electron microscopy. In vitro cytotoxicity assessment and IC50 values for the human hepatoma cell (HuH7) was determined by MTT assay. Two different sizes of Zn2(bdc)2(dabco) were prepared by solvothermal method under the presence and absence of modulator. The prepared samples were used for ibuprofen loading. Ibuprofen loadings of 22 and 30 % (w/w) were obtained for samples with average diagonal sizes of 250 and 100 nm, respectively. The release of ibuprofen from these materials was prolonged for 2 and 3 weeks for 250 and 100 nm samples, respectively. The results obtained in this study revealed that two significant factors, surface area and pore size, affect ibuprofen drug loading and release.

Activated carbon and graphite facilitate the upgrading of Indonesian lignite with microwave irradiation for slurryability improvement

To upgrade Indonesian lignite by significantly reducing moisture and volatile matter content for the preparation of quality coal water slurry (CWS) gasification fuel, carbonaceous materials with high dielectric permittivity were employed to accelerate heating rate via microwave irradiation. The physicochemical properties of lignite upgraded through microwave irradiation with the addition of activated carbon and graphite were investigated through Fourier transform-infrared spectroscopy, X-ray photoelectron spectra and N2 adsorption porosimetry. The oxygen functional groups of the upgraded lignite decreased remarkably, whereas coal rank increased. Furthermore, the atomic ratio of oxygen to carbon and the molar ratio of carbonyl to the aromatic groups of the lignite upgraded with the aid of activated carbon were both lower than those of lignite upgraded with the inclusion of graphite. On the contrary, the aromaticity and aromatic-to-aliphatic ratio of the first type of upgraded lignite were both higher than those of the second type. The hydrophilic functional groups on the surfaces of lignite upgraded with the aid of activated carbon were lower in number than those on the surfaces of lignite upgraded with the inclusion of graphite; the opposite was true given hydrophobic functional groups. The maximum solid concentration of CWS prepared from upgraded lignite with activated carbon-assisted microwave irradiation increased markedly from 41.3wt% to 66.6wt%.

Upgrading Chinese Shengli lignite by microwave irradiation for slurribility improvement

Shengli lignite with high moisture content from the Inner Mongolia region of China was upgraded by microwave irradiation to prepare high-quality coal water slurry (CWS) fuel for combustion and gasification. The physicochemical properties of the upgraded lignite on the as-received basis were investigated with Fourier transform-infrared spectroscopy, X-ray diffraction spectroscopy, N2 adsorption porosimetry, scanning electron microscopy, contact angle analysis and rotary viscometry. Oxygen functional groups with high hydrophilicity decreased in the upgraded lignite. The decreased molar ratio of aliphatic hydrogen to aromatic hydrogen implied an increase in coalification degree. The particle size and contact angle of the upgraded lignite increased. When the upgraded lignite with a decreased hydrophilicity index was used to prepare CWS, the maximum solid concentration increased from 45.6wt.% to 51.7wt.%. Microwave irradiation was more efficient for removing external free moisture than internal bonded moisture in Shengli lignite. The unit energy consumption for external moisture removal and CWS concentration promotion was lower than that for internal moisture removal.

Novel Nanostructured Zn-substituted Monetite Based Biomaterial for Bone Regeneration

A bone regeneration biomaterial must be biocompatible, osteoconductive and osteoinductive, and be gradually replaced by newly formed bone in the shorter time possible. Nanostructured materials, emulating bone composition and morphology, have shown great potential in bone repair because of their higher reactivity, faster reabsorption and improved biological behavior over microstructured materials. This work was aimed at developing a new biomaterial that meets the requirements for effective bone regeneration. Combination of elements with different solubility such as monetite, hydroxyapatite, amorphous calcium phosphate and silica gel, provided with the means to modulate the rate of material reabsorption of this novel biomaterial were Zn was found to be present as a partial substitution of Ca in the monetite lattice. The biomaterial was obtained by a hydraulic cementing reaction and was characterized by XRD, FTIR, NMR, chemical analysis, N2 adsorption porosimetry, Hg porosimetry, picnometry, SEM, TEM and evaluated in vitro and in vivo. Biomaterial showed a nanometric structure with a very high specific surface area (≈80 m2/g), high surface roughness and high intragranular porosity (50%) ranging from macro to nanopores. All of these are key features for a bone regeneration material. Solubility studies demonstrate the different solubility of its components and the release of Ca, P, Si and Zn. In vivo evaluation showed the effectiveness of the material to regenerate and to maintain 89 ± 9% of the volume of a critical size bone defect in sheep at 16 weeks. In the restored volume residual biomaterial was found to occupy 9 ± 5% of the space while newly formed trabeculae occupied 32 ± 6% of the space. The newly formed bone showed abundant vascularization and osteogenic activity. Biomaterial was estimated to have resorbed by 86 ± 7% with a reduction of 67 ± 8% in diameter and clear signs of cell-mediated resorption.

Characterization and photocatalytic activity of (ZnO–CuO)/SBA-15 nanocomposites synthesized by two-solvent method

Two-solvent method was employed to prepare ZnO–CuO nanoparticles embedded in mesoporous silica SBA-15 ((ZnO–CuO)/SBA-15). The as-obtained (ZnO–CuO)/SBA-15 nanocomposites were characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, N2 adsorption porosimetry, and diffusive reflective UV–vis spectroscopy. The photocatalytic activity of (ZnO–CuO)/SBA-15 nanocomposites toward methylene orange was investigated under simulated solar light irradiation, and the measurement results indicated that (ZnO–CuO)/SBA-15 nanocomposites exhibit higher photodegradation activity toward methylene orange than commercial TiO2 P-25. The photocatalytic activity of (ZnO–CuO)/SBA-15 nanocomposites were found to be dependent on both the adsorption ability of the nanocomposites and the loading dosage of ZnO–CuO nanoparticles in SBA-15. The optimal loading dosage of ZnO–CuO nanoparticles was determined. Too high or too low loading will lower the photodegradation ability of (ZnO–CuO)/SBA-15 nanocomposites.

Two-solvent method synthesis of SnO2 nanoparticles embedded in SBA-15: Gas-sensing and photocatalytic properties study

Different loadings of SnO2 nanoparticles embedded in mesoporous silica (SBA-15) were prepared via a two-solvent method with the ordered hexagonal mesoporous structure of SBA-15 kept. X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy and N2 adsorption porosimetry were employed to characterize the nanocomposites. Compared with pure SnO2 nanoparticles, the SnO2/SBA-15 nanocomposites show higher response to H2 at lower operating temperature. The photocatalytic activity of as-prepared SnO2/SBA-15 for degradation of methylene blue was investigated under UV light irradiation and the results show that the SnO2/SBA-15 nanocomposites have higher photodegradation ability toward methylene blue than pure SnO2 nanoparticles.

Alkali silicates and structured mesoporous silicas from biomass power station wastes: the emergence of bio-MCMs

The waste ashes from a commercial biomass combustion facility are successfully converted into mesoporous structured silica utilising a biorefinery approach, with potential high value applications in catalysis, adsorption and separation processes. Potassium silicate solutions are formed via a simple hydrothermal extraction of miscanthus bottom ashes, rich in amorphous silica, with a reproducible extraction of 60–70%. The extension and validation of a rapid and facile infrared method for the quantification of the silicate solutions is demonstrated with important industrial applications for continuous online screening and tuning of the silicate solution ratio and concentration. The alkali solutions from the waste ashes are used for the formation of a structured high surface area mesoporous silica, MCM-41 (1043 m2 g−1, 1.12 cm3 g−1). The resulting mesoporous silica was analysed by XRD, N2 adsorption porosimetry and TEM.