Nitrogen Gas Adsorption Isotherms Research Articles

Compositional analysis of dark colored particulates homogeneously emitted with combustion gases (dark plumes) from brick making kilns situated in the area of Khyber Pakhtunkhwa, Pakistan

In Pakistan raw coal and a little quantity of waste plastics are burnt to sustain high temperature inside brick making kilns. The gaseous emissions of the kilns contain a considerable amount of darkish colored particulates. It is currently believed that the plastic burning produces these particulates. Advanced characterization instruments, such as a scanning electron microscope, energy dispersive spectroscopy, X-ray fluorescence, X-ray diffractometer, surface area analyzer using nitrogen gas adsorption isotherms, and thermogravimetric analyzer, were used to find out the chemistry and physics of the particulates. At a magnification of 30,000x, the SEM picture shows masses that are roughly roundish in shape and their size is in between 0.1 to 0.5 microns. The elements detected in these particles are carbon, oxygen, and sulfur (EDS analysis), or in other words, these elements are a typical composition of raw coal. This elemental analysis suggest that fine coal particles come out with usual combustion gases and these emitted particulates are not plastic combustion product. To strengthen this finding, the sample when calcined discarded a significant amount of sulphur oxides species, as determined in the XRF study by noticing a considerable decrease of sulphur content in the calcined particles, suggesting that the particles are actually a coal. The N2 isotherm graph reveals that the light weight flying coal particles has a very low surface area. Additionally, the XRD and TGA studies supports the conclusion that these dark colored particulate emissions are primarily fine coal particles (cenosphere).

Investigation of Textural And Surface Chemical Properties of Some Animal Bones

The aim of the study is to examine the textural structure and organic functional groups of horse-donkey, cow, dog, and sheep bones by nitrogen gas adsorption-desorption and Fourier Transform Infrared (FT-IR) spectroscopic methods, respectively. For this purpose, textural properties such as BET (Brunauer-Emmett-Teller) surface area, total pore volume, average pore diameter, and surface organic functional groups were determined by nitrogen gas adsorption/desorption at -196 oC and FT-IR spectral analysis methods, respectively. It was observed that the nitrogen gas adsorption isotherms obtained from the BET analysis results were similar to Type-V, which indicates that they have a mesoporous and/or macroporous textural structure, in the IUPAC nitrogen gas isotherm classification. In addition, it was determined from the FT-IR analysis results that they mainly contain organic functional groups such as amine, alcohol, carboxylic acid, ester, ether.

UV-activated efficient formaldehyde gas sensor based on cauliflower-like graphene-modified In-doped ZnO at room temperature

So far, for photoelectric metal oxide semiconductor gas sensors, it is a huge bottleneck to achieve high response performance and low detection limit of formaldehyde at room temperature. This work introduced the synthesis of cauliflower-like graphene-modified In-doped ZnO (GR/In-ZnO) composites via a facile one-pot method with a large comparative surface area for low-concentration formaldehyde sensing at room temperature. GR/In-ZnO-300 showed the highest response to 10 ppm formaldehyde, up to 1891%, which was 12 times that of In-ZnO-300. In addition, the theoretical detection limit of GR/In-ZnO-300 was as low as 13 ppb, and the response at this concentration was 137%. Through the characterization of Surface Photovoltage (SPV), Transient Photovoltage (TPV), Surface Photocurrent (SPC), X-ray Photoelectron Spectroscopy (XPS), and nitrogen gas adsorption isotherms, good formaldehyde sensing performance of GR/In-ZnO-300 was attributed to the excellent separation and transmission capacity of photogenerated carriers, the high specific surface area (109.2 m2/g), and abundant oxygen defects on the surface. This work provides a feasible strategy for the design of low-concentration formaldehyde sensing materials with a rapid response at room temperature.

Ultrasound-assisted Synthesis and Characterization of Silicon Centered Porous Aromatic Frameworks

Silicon centered porous aromatic frameworks( Si-PAF) was synthesized by ultrasound-assisted Yamamoto coupling reaction. The ultrasound amplitude and reaction time were adjusted to optimize the reaction parameters. The obtained Si-PAF exhibits high chemical stability. It is insoluble in common organic solvents such as CHCl3,tetrahydrofuran( THF),ethanol,acetone and dimethylformamide( DMF). The polymer was characterized by Fourier transform infrared spectroscopy( FTIR),scanning electron microscopy( SEM),highresolution transmission electron microscopy( TEM),powder X-ray diffraction( PXRD),and N2 gas absorption.From the disappearance of the C—Br bands( at 529 cm-1) in the FTIR spectra,the formation of the product can be confirmed. SEM image shows that Si-PAF affords a spherical morphology. Simultaneously,TEM reveals that it possesses a worm-like texture. PXRD result indicates the amorphous texture which might be due to distortion and interpenetration of the phenyl rings. The N2 sorption isotherms were measured at 77 K to characterize the porosity of the Si-PAF networks. All networks give rise to typeⅠ nitrogen gas adsorption isotherms with a distinct hysteresis for the whole range of relative pressure. Si-PAF exhibits high surface areas( up to 601 m2/g) and good adsorption ability of N2.

Small and wide angle X-ray studies of impregnated activated carbons

Small angle X-ray scattering (SAXS) and powder X-ray diffraction (XRD) measurements were made on CuO-impregnated activated carbons, prepared with and without an HNO3 co-impregnant, in order to determine the effect of impregnant loading and HNO3 content on impregnant distribution. A comprehensive matrix of 30 CuO-impregnated samples with five HNO3 concentrations and six impregnant loadings was prepared and studied. As a highlight, in Cu-based samples prepared with no HNO3, relatively small particle size CuO impregnant (approximately 3nm) was observed at low impregnant loading and additional CuO appeared in large particles (>10nm diameter) in meso and macropores as the impregnant loading increased. By contrast, when 4M HNO3 was present during the impregnation, the largest impregnant particles found were less than 4nm. Results from SAXS data were shown to be in good agreement with XRD and data obtained from nitrogen gas adsorption isotherms. The combination of SAXS and XRD is shown to be a powerful combination in elucidating the nanostructure of impregnated activated carbons.

A Size‐Exclusion Nanocellulose Filter Paper for Virus Removal

This is the first time a 100% natural, unmodified nanofibrous polymer-based membrane is demonstrated capable of removing viruses solely based on the size-exclusion principle, with a log10 reduction value (LRV) ≥ 6.3 as limited by the assay lower detection limit and the feed virus titre, thereby matching the performance of industrial synthetic polymer virus removal filters.

Surface microtopography of surfactant modified montmorillonite

Low-pressure gas adsorption experiments and Atomic Force Microscopy (AFM) were used to investigate the microtopography of surfactant modified montmorillonites. These two methods not only permit measurement of the specific surface area, mapping the images of surfactant modified montmorillonites on the nano-scale, but also provide the possibility to determine surface roughness and irregularities. The fractal Frenkel–Halsey–Hill model ( D F ) and Neimark–Kiselev model ( D N ) were applied to quantitatively evaluate the heterogeneities of organo-montmorillonite surface by analyzing low-pressure nitrogen gas adsorption isotherms at 77 K. When the dosage of surfactant, expressed as a function of the cation exchange capacity (CEC), increased from 0.2 to 4 CEC, the fractal dimensions changed from D F = 2.88 to 2.59 and D N = 2.58 to 2.12, reflecting that the surface roughness of montmorillonite was influenced by surfactant loading. Higher surfactant loading caused smoother surfaces, which was consistent with the AFM observation.

Oxygen Reduction Kinetics in Nafion-Impregnated Gas Diffusion Electrode under Mixed Control Using EIS and PCT

The oxygen reduction kinetics in a Nafion-impregnated gas diffusion electrode was investigated as a function of the Nafion content under the mixed migration and charge transfer control, using electrochemical impedance spectroscopy (EIS) and a potentiostatic current transient (PCT) technique. For this purpose, the gas diffusion electrodes were prepared with different Nafion contents in order to control the Nafion length distribution across the active catalyst layer (ACL). From the comparison of the nitrogen gas adsorption isotherms of Nafion-impregnated powder specimens with the isotherm of pure powder specimen, it was found that as the Nafion content within the ACL increased, the average Nafion length increased, and the Nafion length distribution became narrower. From the analysis of the impedance spectra considering the Nafion length distribution, it was confirmed that as the Nafion content increased, the charge transfer resistance was reduced slowly, but the component diffusivity of proton was enhanced rapidly. From the analysis of the cathodic PCTs in consideration of the Nafion length distribution, it was concluded that when the Nafion content increased, oxygen reduction was dominantly controlled by charge transfer rather than by proton migration under the mixed migration and charge transfer-controlled constraint.

Characterisation of geometric and structural properties of pore surfaces of reactivated microporous carbons based upon image analysis and gas adsorption

The geometric and structural properties of pore surfaces of microporous carbon specimens were investigated using high resolution transmission electron microscopy (HRTEM) and nitrogen gas adsorption method based upon the fractal theory. The carbon powder specimens with various pore structures were prepared by reactivation of commercially as-activated carbon powder at 1273 K in an atmosphere of a CO 2/CO gas mixture for different activation times. The surface fractal dimensions d F,surf of the carbon specimens were evaluated from the image analysis of the HRTEM images using perimeter–area method. In addition, the pore fractal dimensions d F,pore of the carbon specimens were determined from the analyses of nitrogen gas adsorption isotherms using non-linear fitting method based upon Dubinin–Astakhov adsorption theory in consideration of fractal pore size distribution. From the results of the image analyses of the HRTEM images, it was found that the surface fractal dimension d F,surf of the carbon specimens decreased in value with increasing degree of burn-off, which is ascribed to the more agglomeration of micropores by collapsing the pore walls between the pores. Moreover, from the quantitative coincidence of the nitrogen gas adsorption isotherms experimentally obtained with those theoretically calculated, it is suggested that the pore fractal dimension d F,pore of the carbon specimens is closely related to their porosity, i.e. as the pore fractal dimension d F,pore decreases, the relative volume fraction of the pores with larger size increases as well.

Electrochemical catalytic modification of activated carbon fabrics by ruthenium chloride for supercapacitors

A novel method, electrochemical catalytic oxidation via a ruthenium redox couple in an aqueous RuCl 3 · xH 2O solution rather than the anodic deposition of Ru oxides, was developed to modify the microstructure and electrochemical properties of activated carbon fabrics (ACFs). The variation in microstructures (i.e., specific surface area and mean pore size) for the modified ACFs was examined by means of nitrogen gas adsorption isotherms. The distribution of oxygen-containing functional groups within the modified ACFs was identified by temperature programmed desorption (TPD) and X-ray photoelectron (XPS) spectra. Effects of the electrochemical catalytic modification on the electrochemical characteristics and reversibility of ACFs were investigated systematically by means of cyclic voltammetry (CV) and chronopotentiometry (CP) in 0.5 M H 2SO 4. The total specific capacitance of ACFs reached a maximum (ca. 180 F/g measured at 10 mA/cm 2) when they were catalytically modified at 1.15 V with a passed charge density of 5 C/cm 2. These modified ACFs were demonstrated to be an excellent candidate for the supercapacitor application.

Effect of Pore Size on the Gaseous Adsorption of Ethenzamide on Porous Crystalline Cellulose and the Physicochemical Stability of Ethenzamide after Storage.

The effect of pore size on the gaseous adsorption of ethenzamide (EZ) on porous crystalline cellulose (PCC) in a mixture of PCC-EZ, and the physicochemical stability of EZ in a mixture of PCC-EZ after storage at various relative humidities (RHs) were investigated by powder X-ray diffractometry, differential scanning calorimetry, specific surface area and pore size distribution measurements. After heating a mixture of PCC-EZ, which contained less than 7% EZ, at 70°C at reduced pressure, the EZ became amorphous. The specific surface areas and pore size distribution curves of PCC and the heated mixtures of PCC-EZ were calculated from the nitrogen gas adsorption isotherms. The specific surface area of PCC was 82.3m2/g, while the specific surface areas of the heated mixtures of PCC-3% EZ, PCC-5% EZ and PCC-7% EZ were 74.1, 72.7 and 63.8m2/g, respectively. The specific surface area of the heated mixture of PCC-EZ decreased with an increase in the mixing ratio of EZ. In the pore size distribution curves of the heated mixtures of PCC-EZ, the pore volumes in the range of pore diameters from 2 to 40nm decreased compared with the pore volume of PCC. The volumes of pores with diameters ranging from 3 to 10nm decreased markedly with an increase in the mixing ratio of EZ. These results indicate that the adsorption of EZ on the pore surfaces of PCC occurred principally in the range of diameters from 3 to 10nm. After storage of the heated mixtures of PCC-7% EZ at various RHs for 7d at 30°C, recrystallization of EZ was observed in the X-ray diffraction spectrum when the mixtures were stored above RH 72.8% due to condensation of water vapor in pores.

Physicochemical characteristics of porous crystalline cellulose and formation of an amorphous state of ethenzamide by mixing

The physicochemical characteristics of porous crystalline cellulose (PCC) have been investigated. The specific surface area and pore size distribution curve of PCC were determined from nitrogen gas adsorption isotherms. The specific surface area and pore volume of PCC were decreased on grinding with a mortar and pestle or after storage at high relative humidities, which was attributed to the destruction of the porous structure of PCC. When a physical mixture of ethenzamide (EZ) and PCC was stored for 1 month under dry conditions, amorphization of EZ was observed. After heating the mixture of PCC and EZ at 100°C for 2 h, crystalline EZ changed to an amorphous state. In the stored or heated mixtures of PCC-EZ, EZ molecules would be adsorbed physically onto the pore surface of PCC. The heated mixture of PCC-EZ showed a high rate of dissolution of EZ in polar and nonpolar solvents. Nonporous microcrystalline cellulose was unable to transform crystalline EZ to the amorphous state.

Posttreatment effects on pore size distribution of loeb‐sourirajan‐type modified cellulose acetate ultrathin membranes

AbstractThe nitrogen gas adsorption isotherms at −195°C on modified cellulose acetate ultrathin membranes were measured, and the surface area of the pores was determined by the method employed by Cranston and Inkley. A relationship between reverse osmosis characteristics and the mean pore radius was correlated, and it was observed that any method (such as longer evaporation period, heat treatment, or reduction of swelling agent) reducing the mean pore radius to below 20–22 Å improves membrane characteristics of reverse osmosis separation significantly.

Crystallinity and physical characteristics of microcrystalline cellulose. II. Fine structure of ground microcrystalline cellulose.

Nitrogen gas adsorption isotherms are obtained on intact, 8 and 32 hours ground microcrystalline cellulose. Before the determination of adsorption isotherms, each specimen is dispersed into water, then the water is changed to ethanol, ethanol to n-pentane, and the n-pentane is evaporated in vacuo. Specific surface area is determined from the nitrogen gas adsorption method as 79, 153 and 250 m2/g for each sample, using B.E.T. equation. This result shows that the effective surface available to water molecules is equivalent to that available to nitrogen molecules. Pore size distribution was determined from both nitrogen gas desorption isotherms and X-ray small angle scattering. Significant change in pore size distribution by grinding is not observed. The effective surface area of microcrystalline cellulose is composed of pores which range in diameter is up to 300 Å, and relatively small pores, up to 100 Å, play an important role. Recrystallization of amorphous cellulose is observed to be caused by the solvent displacement, to the same crystal form as cellulose II. The possible relation of these observations to the fine structure of ground microcrystalline cellulose is discussed.

A study on pore size distribution of modified ultrathin membrances

An equation to estimate the thickness of ultrathin membranes obtained by Levich, assuming constant physical properties, was compared with the measured thickness in the range of 0.3–40 μ. The proportionality constant was found to be 0.4, and the equation is expressed as follows: The nitrogen gas adsorption isotherms at −195°C on the modified ultrathin membranes were measured and the surface area of the pores was determined by the B.E.T. equation. Distribution of pore volume was calculated by the method of Cranston and Inkley. On the assumption of straight cylindrical pores in the membrane, the crosssectional area of pores and the mean pore radius were calculated. Symmetric structure of the modified ultrathin membranes was confirmed by reverse osmosis tests with both the air and glass sides of the membrane facing the pressure solution.