Determination Of Specific Surface Area Research Articles

UoC‐2: A Fluorinated Derivative of the Robust Metal‐Organic Framework MFM‐300

By solvothermal reactions of fluoro substituted biphenyl‐3,3’,5,5’‐tetracarboxylic acids (H4BPTC) with the respective metal salts, four new MOFs with the MFM‐300 topology were synthesized, namely [MIII2(OH)2(L)] with MIII = Ga3+, In3+ and L = 4‐mF‐BPTC4‐ and 4,4’‐dF‐BPTC4‐. Three of them were refined from X‐ray single crystal diffraction data (I4122, Z = 4), [Ga2(OH)2(4,4’‐dF‐BPTC)] was confirmed by Le Bail fits based on synchrotron powder diffraction data. To the best of our knowledge, these four compounds represent the very first examples of MFM‐300 type MOFs with a substituted BPTC4‐ linker. With increasing fluorination of the linker, the thermal stability decreases, as the decarboxylation of the linker is facilitated. On the other hand, the gas uptake is enhanced significantly. E.g. the CO2 uptake (273 K, 1 bar) increases from 124 cm3/g for [Ga2(OH)2(4‐mF‐BPTC)] to 136 cm3/g for [Ga2(OH)2(4,4’‐dF‐BPTC)]. Surprisingly, the exact determination of specific surface areas (SBET) turned out to be difficult. It is supposed that due to transient open metal sites, complete removal of solvent molecules (DMF, acetone) is not always possible before degradation of the framework starts.

Exceptional Sorption of Heavy Metals from Natural Water by Halloysite Particles: A New Prospect of Highly Efficient Water Remediation.

Halloysite particles, with their unique multilayer nanostructure, are demonstrated here as highly efficient and readily available sorbent of heavy metals that can be easily scaled up and used in large-scale water remediation facilities. The various methods of raw material purification were applied, and their effects were verified using techniques such as BET isotherm (determination of specific surface area and size of pores), XRF analysis (composition), and SEM imaging (determination of morphology). A series of adsorption experiments for aqueous solutions of metal ions (i.e., lead, cadmium) were carried out to quantify the sorption capacity of halloysite particles for selected heavy metals. The ability of adequately activated halloysite to efficiently remove heavy metal ions from water solutions was confirmed. The value of the zeta potential of raw and purified halloysite particles in water was determined. This enables us to understand its importance for the sorption of positively charged ions (metal, organics) at various pH values. The adsorption process conducted in the pH range of 6.0-6.5 showed significant improvement compared to the acidic conditions (pH value 3.0-3.5) and resulted in a high sorption capacity of lead ions-above 24.3 mg/g for the sulphuric acid-treated sample. The atomic scale ab initio calculations revealed a significant difference in adsorption energy between the external siloxane surface and cross-sectional interlayer surface, resulting in pronounced adsorption anisotropy. A low energy barrier was calculated for the interlayer migration of heavy metals into the halloysite interior, facilitating access to the active sites in these regions, thus significantly increasing the sorption capacity and kinetics. DFT (density functional theory) calculations supporting this study allowed for predicting the sorption potential of pure halloysite structure towards heavy metals. To confront it with experimental results, it was crucial to determine proper purification conditions to obtain such a developed structure from the mineral ore. The results show a massive increase in the BET area and confirm a high sorption potential of modified halloysite towards heavy metals.

Polyaniline/aramid composite for carbon dioxide capture

AbstractA novel composite based on conducting polymer, polyaniline/aramid, was prepared with the aim of capturing carbon dioxide. Polyaniline was synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate and subsequently used for modification of the aramid surface. The prepared polyaniline/aramid composite was characterized using electrokinetic analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption/desorption isotherms for determination of specific surface area and porosity and using carbon dioxide adsorption/desorption isotherms for determination of carbon dioxide capture. The capture capacity markedly increased from 22 cm3 g−1 for pristine aramid to 60 cm3 g−1 for the polyaniline/aramid composite. The results show that the new composite material could be used as an effective adsorbent of carbon dioxide and for applications based on its adsorption. The vision of advanced adsorbents with properties controlled by electric potential applied to conducting polymers is worth being considered. © 2023 Society of Industrial Chemistry.

Mortar film thickness on the autogenous shrinkage of concrete: Test and simulation

Coarse aggregate (CA) accounts for the largest volume in concrete, which has significant impact on the performance of this building material such as workability, strength and shrinkage. Based on the determination of specific surface area for CA through simple sieving curve, mortar film thickness (MFT) of fresh concrete is numerically calculated. Relationship between MFT and CA content is acquired as three-stage model with critical volume fractions of 17% and 67%. Autogenous shrinkage of concrete with various CA volume fractions were experimentally evaluated through integrated shrinkage test devices. Zero-time of autogenous shrinkage is determined based on the expansion-shrinkage behavior of concrete mixtures at very early age. The ultimate autogenous shrinkage of concrete decreases monotonously with increasing amount of CA or decrease in MFT. By comparing to existing theoretical and empirical models, new prediction model of autogenous shrinkage based on MFT is proposed with high correlation coefficient for concrete containing various CA content.

The assessment and treatment of waste from glass fibre production for use as a filler in composites

Waste glass from fibreglass production is waste that is generated at various stages of production. In nature, it is a combination of glass fibres, fine dust, but also larger glass grains, for example also from leakages during production. This material is or may be contaminated by impregnation, lubricants or some impurities that prevent its recovery during production. The main objective of this study is to assess the suitability of glass fibre waste and to optimise the pre-treatment of the raw material for use in the composite. This paper describes the determination of chemical composition, mineralogical composition by X-ray diffraction analysis, determination of bulk density, water absorption and specific surface area. The results obtained are compared with the primary raw material - glass fibre. The results showed that the waste from glass fibre production is primarily composed of silica, calcium, alumina and boron. Minor components include magnesium oxide, sodium oxide, fluorine, iron oxide, strontium oxide, potassium oxide, titanium dioxide, sulphur dioxide and chromium oxide. The specific surface area of treated glass fibre waste correlates with the specific surface area of cement, which is a prerequisite for the use of this waste as a partial substitute for cement in the production of building materials.

Adaptation of the Methylene Blue Adsorption Method for Specific Surface Area Determination of Betulin Particles

Application of the adapted methylene blue (MB) adsorption method in determining specific surface area was investigated on particles containing hydrogels obtained from purified (99 wt%) and unpurified (60 wt%) betulin samples. In order to study the adsorption isotherms of MB on betulin particles in aqueous dispersions, initial concentration of MB was varied. An analysis of the adsorption process with the Langmuir adsorption model was performed. The results indicate that the experimental data fits very well with the Langmuir adsorption model. Straight isotherms are obtained with very good determination coefficients (R2=0.99; R2=1.00), which means that the surface of purified and unpurified betulin particles is homogeneous energetically and a monomolecular coverage forms during adsorption. The MB adsorption method adapted for betulin particles is simple and requires less complex apparatus and time than other methods. The determined specific surface area can be used to characterize the surface properties of betulin particles.

The influence of relative humidity on the carrier particle surface characteristics used in dry powder inhalation formulation

Purpose: Investigation of the effect of carrier storage at elevated relative humidities on the carrier surface fines. The resulted effects of this storage conditions on the carrier surface characteristics when mixed with micronized salbutamol sulphate and the subsequent in vitro deposition were investigated. Methods: Lactose (InhaLac120) and mannitol (Pearlitol160) carrier particles (112 µm – 140 µm) were subjected to different relative humidities for 6 weeks period of time in order to get a smoother surface. In vitro deposition carried out for those modified carriers after mixing with salbutamol sulphate using a Next Generation Impactor (NGI). The modified carriers were characterized by scanning electron microscope, Brunauer Emmet and Teller specific surface area determination, differential scanning calorimetry, X-ray powder diffraction and water vapour sorption in comparison with the treated carrier without added fines. Results: The modified lactose and mannitol carriers stored at different relative humidities starting from 35% RH-75% RH show no change in fine particle fraction (FPFs). Subsequently, the carrier storage at 95% RH shows a significant decrease in the in vitro drug release. This probably by increasing drug-carrier adhesion and show a difficult detachment of the drug particles from the carrier surface smoothed at 95% RH. Conclusions: Storage of lactose and mannitol carriers at different relative humidities up to 75% result in un-significant change in drug fine particle fraction using the NGI. Additionally, storage of those carriers at high relative humidity up to 95% RH found to decrease significantly the dispersion of the drug and subsequently the FPF in the in vitro deposition test.

Tailoring structural and photocatalytic features of nitrogen-doped Bi2MoO6 structures under different nitrogen sources

The present research aimed to obtain Bi2MoO6 and nitrogen-doped Bi2MoO6 compounds capable of extending their light absorption capability toward the visible regime through nitrogen doping of those structures. It were obtained employing a high pressure-hydrothermal method assisted by microwave heating by using different nitrogen precursors including urea, thiourea, hydrazine, and ethylenediamine. The effect of nitrogen precursors on the physicochemical and structural properties was investigated in detail through scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and specific surface area determination using the BET method. The energy bandgap was calculated by UV–Vis spectroscopy, which exhibits high absorption from the UV region up to the visible regime. Nitrogen-doped Bi2MoO6 compounds show high specific surface area values as well as a reduction in their bandgap energy values compared to pristine Bi2MoO6. Regarding the influence of the different nitrogen sources, it was observed that thiourea provided the highest percentage of nitrogen content in the Bi2MoO6 structure (15.76 at. %), while hydrazine showed the highest specific surface area (11.01 m2/g). The compounds showed a positive effect, reaching a degradation of 66% under UV and 68%, under Vis irradiation of the lignin molecule. Also, the results indicate that the N-doped Bi2MoO6 compounds are more active than the pristine Bi2MoO6. The methodology presented here provides an easy and low-cost way for the synthesis of Bi2MoO6 structures with potential use in the field of photocatalysis.

Application of Methylene Blue Adsorption Technique in the Determination of Specific Surface Area of Termite Feathers

Methylene Blue (MB) adsorption technique was employed in the measurement of the Specific Surface Area (SSA) of Termite Feathers (TF). The adsorption study was carried out at 25°C and 270 rpm after which the residual concentration of MB was determined spectrophotometrically at a wavelength of 660 nm. The adsorption data was found to conform to the Langmuir model within the concentration range studied and Langmuir constants were determined for TF. The specific surface area was then calculated from the Langmuir isotherm constant ‘b’. Effect of pre-treatment temperature on SSA was also considered at 30, 40, 50 and 60OC. The specific surface area was found to be 58.85 m2/g for the raw TF with values of 60.34, 78.52, 99.64 and 118.26 m2/g for the samples pre-treated at 30, 40, 50 and 60OC respectively. Finally, the specific surface area value obtained by MB adsorption technique was then compared with those obtained by Orth phenanthroline (OP) and p-nitrophenol (PNP) adsorption

Preparation of Co-Doped Graphitic Carbon Nitride and Degradation of MB by Heterogeneous Photo-Fenton-like Reaction System

In this study, Co-porous-g-C3N4(porous Co-Doped graphitic carbon nitride) was synthesized by a one-step calcination method successfully. Co-porous-g-C3N4 was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance, and specific surface area determination. The Photo- Fenton-like system was successfully constructed under the condition of coexistence of Co-porous-g-C3N4 and H2O2. The synergistic effect of Fenton-like system and photo-catalysis was realized. Through the optimization of experimental conditions, the best photocatalytic performance of this heterogeneous reaction system was achieved. The degradation rate of MB (methylene blue, 40 mg/L) could reach 98.3% at 90 min. Co-porous-g-C3N4 had photocatalytic degradation activity for different organic pollutants and had wonderful recyclability and stability. The main degradation effect was attributed to �O2- which could be generated through two channels in the Photo- Fenton-like system. Moreover, the rate of photogenerated electron-hole complexation could be decreased due to the reaction of low-valent cobalt and photoelectrons in this heterogeneous reaction system.

Study of the effect of sample preparation on the chemical composition and hydrophobicity of the coal surface

Sample preparation for determination of the chemical and technological properties of coals is carried out using standard methods when coal samples come into contact with air. However, the outer surface of the resulting small particles is inevitably oxidized during grinding by the molecular oxygen present in air. Therefore, the physicochemical properties of the laboratory sample do not match the properties of the original native coal or coal of larger fractions. We present the results of studying the laboratory samples of low- metamorphized coal. Preparation of the native coal sample was carried out in a pure inert atmosphere (nitrogen) of a glove box. Methods of IR- and EPR- spectroscopy, chemical functional analysis of oxygen groups, determination of specific surface area, as well as methods for determining the wettability (determination of the wetting edge angle by a drop of liquid and the rate of absorption of a drop into a coal briquette) were used to characterize changes in the surface of coal particles. It is shown that the method of coal sample preparation significantly affects the functional composition and hydrophilicity of the outer surface of coal particles. The results obtained can be used in determination of the properties of native stratal coals, improvement of the technology of coal sample preparation, as well as in enrichment and processing of coals.

Specific Surface Area Characterization of Spinel Ferrite Nanostructure Based Compounds for Photocatalysis and Other Applications Using Extreme Learning Machine Method

Nanocrystalline spinel ferrite based compounds are technological driven materials with interesting potentials in photocatalysis for renewable energy generation, gas sensing for pollution control, magnetic drug delivery, rod antennas, storage media (high density) and supercapacitive materials, among others. Specific surface area of spinel ferrite based compounds contributes immensely to the application of this semiconductor in industrial domains. Experimental determination of specific surface area is laborious and costly and consumes appreciable time. Compositional substitutions in crystal structure effectively improve physical properties and enhance specific surface area through alteration of moment distribution between tetrahedral oxygen sites and octahedral coordination. With the aid of distorted lattice parameters due to compositional substitution and the spinel ferrite nanocrystallite size as model descriptors, this present work models the specific surface area of spinel ferrite nanomaterial through extreme learning machine (ELM) based intelligent modeling method. The developed sigmoid activation function-based ELM (S-ELM) model shows superior performance over genetic algorithm based support vector regression (GBSVR) and stepwise regression (STWR) models existing in the literature with performance improvement of 61.31% and 70.01%, respectively, using root mean square error performance metric. The significances of cobalt and lanthanum compositional substitution on the specific surface area of spinel ferrite nanomaterials were investigated using S-ELM model. Ease of implementation of S-ELM model as compared with the existing GBSVR model, coupled with the demonstrated improved performance and persistent closeness of its predictions with the experimental values, would be highly meritorious for quick and precise characterization of specific surface area of spinel ferrite nanomaterials for various desired applications.

Determination of density and specific surface area of nanostructured zinc oxide films by X-ray fluorescence and scanning electron microscopy

Films of zinc oxide (ZnO), with thickness ranging from 100-400 nm and perforated by pores, are fabricated using variable angle magnetron sputtering and characterized using X-ray fluorescence (XRF) and scanning electron microscopy (SEM). The nanopores of such films make them suitable for gas-sensors and other applications, but the effective surface area for films this thin cannot be measured easily using conventional techniques. We propose and apply a method that uses XRF to measure the bulk film density and SEM to determine the size and distribution of pores on the sample exterior. Combining these results, we determine the specific surface area of the crystalline ZnO films that is up to 11.8 m2/g. This is a viable approach for characterizing the ZnO nanocolumnar ultrathin films.

Determination of Graphene Oxide Adsorption Space by Lysozyme Uptake─Mechanistic Studies.

The interaction between graphene oxide (GO) and lysozyme (LYZ) in aqueous solution was investigated for GO specific surface area determination and for the thermodynamic description of the process. It was experimentally proved that LYZ is a much better adsorbate than the most common methylene blue, allowing the determination of genuine GO surface area. Our fluorescence spectroscopy results indicate that LYZ molecules interact with GO at high- and low-affinity sites depending on the surface coverage, reflecting the protein mono- and multilayer formation, respectively. The lack of the secondary structure changes confirms LYZ usability as a model adsorbate. The calculated values of thermodynamic parameters (Δ(ΔH0) = −195.0 kJ/mol and Δ(ΔS0) = −621.3 J/molK) indicate that the interactions are exothermic, enthalpy-driven. All the reported results reveal the physical nature of the LYZ–GO interaction at the studied concentration ratios.

Reliable surface area determination of powders and meso/macroporous materials: Small-angle X-ray scattering and gas physisorption

The specific surface area is key for various application fields of porous materials. Its reliable and fast determination is therefore crucial for materials development and product quality management. Surface area assessment is usually based on physical adsorption using the Brunauer-Emmett and Teller (BET) theory. However, the BET method/gas adsorption exhibits a number of limitations and challenges including (i) time consuming sample preparation and measurement time, and (ii) reliable surface areas only possible for non-porous and meso-/macroporous materials to obtain reliable surface areas. In addition, the accuracy of surface area data obtained from adsorption depends on the proper choice of adsorptive/probe. Within this context, this work evaluates in a rigorous way in-depth Small Angle X-ray Scattering (SAXS) as an alternative and complimentary approach for reliable and fast surface area assessment. To our knowledge, this work can be considered the first systematic study where the surface areas from SAXS are compared and validated with true benchmark surface area data. We utilize silica-based nanoparticles as well as a well-defined mesoporous controlled pore glass for systematic SAXS and adsorption studies (argon and nitrogen at 87 K and 77 K, respectively). Owing to the lack of micro- and narrow mesopores of these model materials, the BET method based on argon 87 K adsorption can be applied to determine benchmark surface areas. Indeed, excellent agreement was found between surface areas derived from argon 87 K adsorption and SAXS. In fact, we demonstrate that the determination of specific surface area can be brought with SAXS to a new level, where parameters such as size of the probing adsorptive, its orientation and thus its effective cross-sectional area (when adsorbed on the surface) are no longer affecting the value of the specific surface area determined. Furthermore, SAXS was shown to be significantly faster than gas adsorption. For the silica materials used, the study shows that SAXS does not require degassing and – along with analysis times of only few minutes per sample – provides an accurate and extremely fast, high-throughput approach. This fundamental study can be considered a major step in enabling SAXS for reliable surface area assessment for applications both in nanoporous materials development and quality control, thus boosting SAXS for surface area determination in general, but in particular also for materials, where the usage of gas adsorption is restricted or not possible at all.

Specific Surface Area by Colorimetry and Image Analysis

Abstract Specific surface area is more informative than grain size for fine-grained sediments where Ss > 1 m2/g. In fact, specific surface area plays a central role in engineering properties and processes in fine-grained soils, including pore size and bioactivity; fabric, plasticity, and rheology; hydraulic and electrical conductivity; compressibility and residual friction angle; and all forms of coupled processes. This research advanced a dye adsorption method using digital image colorimetry implemented with smartphone technology. In particular, this research adopted a water-based approach to reach internal surfaces in platy phyllosilicates, selected short dye molecules to reduce the range of potential molecular contact area, and developed a physics-based adsorption model to analyze the complete data set to minimize the uncertainty in specific surface area determinations. The study involved fine-grained soils with distinct mineralogy and specific surface area (from 1 to 600 m2/g) and various cationic dyes and a protein to explore the effect of molecular size, shape, and pH. Crystal violet emerged as a reliable dye for soil characterization. Time-dependent measurements confirmed second-order kinetics and highlight the importance of adsorption time.

Intensification of alkaline delignification of sugarcane bagasse using ultrasound assisted approach

Ultrasound-assisted approach has been investigated for delignification so as to develop green and sustainable technology. Combination of NaOH with ultrasound has been applied with detailed study into effect of various parameters such as time (operating range of 15–90 min), alkali concentration (0.25 M−2.5 M), solvent loading (1:15–1:30 w/v), temperature (50–90 ˚C), power (40–140 W) and duty cycle (40–70 %) at fixed frequency of 20 kHz. The optimized operating conditions established for the ultrasonic horn were 1 M as the NaOH concentration, 1 h as treatment time, 70˚C as the operating temperature, 1:20 as the biomass loading ratio, 100 W as the ultrasonic power and 70% duty cycle yielding 67.30% as the delignification extent. Comparative study performed using conventional and ultrasonic bath assisted alkaline treatment revealed lower delignification as 48.09% and 61.55% respectively. The biomass samples were characterized by SEM, XRD, FTIR and BET techniques to establish the role of ultrasound during the treatment. The morphological changes based on the ultrasound treatment demonstrated by SEM were favorable for enhanced delignification and also the crystallinity index was more in the case of ultrasound treated material than that obtained by conventional method. Specific surface area and pore size determinations based on BET analysis also confirmed beneficial role of ultrasound. The overall results clearly demonstrated the intensification obtained due to the use of ultrasonic reactors.

Modification of CaCO3 and CaCO3 pin-coated cellulose paper under supercritical carbon dioxide-ethanol mixture for enhanced NO2 capture.

In this work, we examine two modifications of fine-ground calcium carbonate material (GCC) in order to enhanced sorption of NO2 and subsequent reaction properties toward NO2-/NO3- formation by firstly exposing the GCC to supercritical (sc) CO2 in order to increase particle surface area, a choice specifically made to avoid altering the surface chemistry, and secondly considering the potential advantage of using a surface coupling agent toward NO2. The modification by the coupling agent amino silane (AMEO silane) was applied in a supercritical CO2-ethanol mixture. The samples were characterised before and after modification by field emission scanning electron microscopy (FESEM), specific surface area determination (BET nitrogen adsorption), ATR-FTIR spectroscopy and ion chromatography to reveal the effects of the surface modification(s) on the morphology, surface textural properties and sorption versus reaction properties with NO2. The performance of the treated sorbents for NO2 capture was evaluated at room temperature. Results show that reactivity of NO2 with GCC was observed to increase as a function of increased surface area resulting from scCO2 exposure, but that the presence of AMEO silane on the surface, while enhancing initial adsorption of NO2 was seen subsequently to act to block reactivity. Thus, judicious use of coupling agent can provide desired rapid initial adsorption of the gas, but the goal of long-term CaCO3-consuming reactivity, so as to prolong the uptake of NO2 beyond surface saturation alone, is achieved by increasing surface area while retaining chemical-free exposed CaCO3 surface.

The Use of Starch Drying Kinetics Curves for Experimental Determination of Its Specific Surface Area.

The most popular method for the calculation of specific surface area is its determination from water vapour sorption isotherms. The study presented here has been designed for the purpose of optimisation and selection of the conditions of drying so as to allow the determination of specific surface area from plotted curves of the drying process. The results indicate that drying curves can be used as the basis for the determination of specific surface area, the values of which do not differ statistically significantly (α = 0.05) from those determined from isotherms of water vapour sorption (adsorption/desorption).

Methodological Aspects of Evaluating the Particle Size Distribution of Powder Elastomeric Materials

The properties of crumb rubber (CR) of unsorted end-of-life tires and of gas masks face part crushed at ambient temperature, as well as powder elastomeric materials (PEM) obtained by high-temperature shear grinding (HTSG) of CR and high-temperature shear co-grinding of CR with thermoplastic elastomer have been investigated. The methods of dry screening with vibrating sieve, wet laser diffraction, scanning electron microscopy, determination of the specific surface area by the BET method by sorption nitrogen and powder agglomeration were used. The effect of an anti-agglomerating additive on the results of determining the particle size distribution by the methods of dry vibrating sieving and wet laser diffraction has been investigated. Methodological recommendations for determining the particle size distribution of powder elastomeric materials (PEM) obtained by the HTSG have been developed.