Multipoint BET Research Articles

Highly porous MnOx prepared from Mn(C2O4)·3H2O as an adsorbent for the removal of SO2 and NH3

In this work, the possibility of substituting metal impregnated activated carbon with nanoporous metal oxides for the adsorption of SO2 and NH3 was investigated. Nanoporous manganese oxide (MnOx) was prepared from manganese oxalate trihydrate by thermal decomposition in air. The physical properties of the oxalate precursor and the resulting MnOx samples were characterized with SEM, TGA-DSC, mass spectroscopy, FTIR and powder XRD. The specific surface areas and porosity of MnOx were studied by single-point and multi-point BET measurements. The amorphous needle-like MnOx had a specific surface area of over 500 m2/g when the precursor was heated at 225 °C for 6 h. Dynamic SO2 and NH3 flow tests indicated that the adsorption capacity of MnOx depends primarily on the surface area. Compared to Mn3O4-impregnated activated carbon, nanoporous MnOx could remove about twice as much SO2 and 15% more NH3 per gram of adsorbent. This could lead to respirators of lower weight and smaller size which will be attractive to users.

Preparation of a novel magnesium oxide nanofilm of honeycomb-like structure and investigation of its properties

A novel magnesium oxide nanofilm of honeycomb-like structure was prepared for the first time. The nanofilm was fabricated via sol-gel method and was characterized by Fourier infrared absorption spectra, scanning electron microscope, ellipsometer, X-ray diffraction, energy dispersive spectrometer, atomic absorption spectrum, surface area analyser and membrane density detector. The obtained nanofilm sample is single-phase, cubic in crystal structure, atomic ratio of O to Mg is approximate 3:1, the multipoint BET specific surface area is 5.2m2/g and the density is 3.16g/cm3. The thickness of the nanofilm is about 65nm. In view of the above, we derived the formation process and mechanism of the nanofilm, and proposed that the nanofilm would be made from cuboid units. The cuboid units should be connected one another by adsorption force. Moreover, the antimicrobial property and high temperature resistance of the nanofilm were investigated. The results showed that the nanofilm has well antibacterial effect on Staphylococcus aureus and could withstand high temperature at nearly 2000°C. This would provide a reference to improve the existing antibacterial and refractory materials.

Preparation and characterization of a nigerian mesoporous clay-based membrane for uranium removal from underground water

This study reports the removal of uranium in underground wastewater using a Nigerian clay-based membrane. The clay and sintered clay were characterized using XRD, XRF, TGA/DTA, FESEM and PSD. The raw clay was mixed with cassava starch (10, 15, 20 and 25wt%) and sintered at a temperature of 1300°C. A multi-point BET analysis of the produced clay-based membranes was conducted to determine the surface area, pore volume and average pore size. Sintering characteristics were determined by apparent porosity, bulk density and flexural strength. The radioactivity of the feed and the permeated water was counted using a gamma spectrometer with an HPGe detector. From the XRD, TGA and FESEM, 1300°C was found to be optimum for the mullite formation from the clay. The average pore sizes of the produced membranes from the BET results were observed to be in the range from 51 to 70Å and with a steady state flux range of the tested membranes in the range 1.92×10−5–2.09×10−4m3m−2s−1. The permeation flux produced is of high quality with a rejection in the range of 1.78–2.56Bq/l of the uranium activity by the tested membranes. This low-cost membrane will have an application for the treatment of uranium-containing wastewater from fracking, oil exploration and phosphate mining industries.

Hierarchically structured ZnO-graphene hollow microspheres towards effective reusable adsorbent for organic pollutant via photodegradation process

Present work reports on successful synthesis of hierarchical hollow microspheres (HHM) from ZnO-chemically converted graphene (CCG) nanocomposites by adopting low-temperature surfactant/template free solution method, varying graphene oxide (GO) to zinc acetate dihydrate weight ratio (R = 0.00, 0.01, 0.032, 0.063) in the precursors. It is found that the HHM consist of self-assembled ZnO nanoparticles, chemically interacted with CCG as evidenced from structural characterizations (X-ray diffraction, field emission scanning and transmission electron microscopes) with UV–Vis, FTIR, Raman and X-ray photoelectron spectroscopies. Multipoint BET nitrogen adsorption–desorption isotherms of ZG30, synthesized using an optimum GO content (R = 0.032) showed relatively high specific surface area. The sample showed significantly improved adsorption capacity of rhodamine B dye (as water pollutant) compare to pristine ZnO (R = 0.0) as well as commercially available P25 (TiO2). The ZG30 functioned as reusable adsorbent due to its highly efficient photocatalytic activity under UV (λ, 254 nm) irradiation. Methyl orange and phenol were also used to check the effectiveness of ZG30 for permanent cleaning of the pollutants. This facile process could create an avenue for synthesis of hollow microspheres from different metal oxide semiconductor–graphene nanocomposites for efficient and reusable adsorbent of water soluble organic pollutants.

Experimental Investigation of Coal Dust Wettability Based on Surface Contact Angle

Wettability is one of the key chemical properties of coal dust, which is very important to dedusting. In this paper, the theory of liquid wetting solid was presented firstly; then, taking the gas coal of Xinglongzhuang coal mine in China as an example, by determination of critical surface tension of coal piece, it can be concluded that only when the surface tension of surfactant solution is less than 45 mN/m can the coal sample be fully wetted. Due to the effect of particle dispersity, compared with the contact angle of milled coal particle, not all the contact angles of screened coal powder with different sizes have a tendency to increase. Furthermore, by the experiments of coal samples’ specific surface areas and porosities, it can be achieved that the volume of single-point total pore decreases with the gradual decreasing of coal’s porosity, while the ultramicropores’ dispersities and multipoint BET specific surface areas increase. Besides, by a series of contact angle experiments with different surfactants, it can be found that with the increasing of porosity and the decreasing of volume percentage of ultramicropore, the contact angle tends to reduce gradually and the coal dust is much easier to get wetted.

Low-temperature surfactant-free synthesis of tin oxide-reduced graphene oxide nanocomposites and their textural property-dependent lithium storage characteristics

Tin oxide-graphene composite has emerged as a promising material for numerous applications such as energy storage. In the present work, we report one-pot low-temperature (95 °C) surfactant-free synthesis of tin oxide-reduced graphene oxide (rGO) nanocomposites by varying graphene oxide (GO) to tin (II) 2-ethylhexanoate weight ratio (R = 0.00, 0.02, 0.06, 0.12). X-ray diffraction and electron microscopy measurements confirm the existence of nanocrystalline tetragonal SnO2 (size, ~3.0 nm), decorated on rGO sheets. Also, FTIR spectral study of the samples is performed to understand the chemical bond vibrations in the nanocomposites. Relative structural defects in rGO of nanocomposites are analyzed by Raman spectroscopy. The chemical reactions possibly proceed via oxidation of Sn2+ used as tin precursor, forming SnO2 with the simultaneous reduction of GO to rGO. Multipoint BET nitrogen adsorption–desorption isotherm analysis shows that the specific surface area increases with R value but external surface area related to mesoporosity (pore diameter, ~3 nm) initially increases, reaches a maximum at R = 0.06 and then decreases for further increase in the R in the samples. On increasing R value, the trend of change of 1st cycle Coulombic efficiency is found to be identical with the change of external surface area of the samples. At R = 0.06, the sample demonstrates a reversible lithium storage capacity of 626 mAhg−1 (80 % of theoretical capacity) with good cyclability, signifying the positive effect on the structural defects and also in the textural property of the materials. This study can be adopted for other metal oxide semiconductor–rGO nanocomposites for energy storage application. SnO2–rGO nanocomposites for improved lithium storage characteristics

Hybrid Organic-Inorganic Nanocomposites Based on Poly(ϵ-Caprolactone)/Polyhedral Oligomeric Silsesquioxane: Synthesis and In Vitro Evaluations

Hybrid poly(ϵ-caprolactone) (PCL) containing nanocomposites and non-hybrid linear PCL diols were synthesized by anionic ring opening polymerization of ϵ-caprolactone on a POSS or ethylene glycol central blocks, respectively. Monolith scaffolds were then fabricated from the hybrid nanocomposites and non-hybrid linear PCL diols via non-solvent induced phase separation technique. The effects of inclusion of POSS nanocage in the polymer chain structure on specific surface area and pore size of the scaffolds was investigated by multipoint BET method. This perfect scrutiny will introduce an excellent nanoparticle pendent to the PCL chains to promote the in vitro properties of the implants potentially applicable in tissue engineering.

Cholesterol removal from various samples by cholesterol-imprinted monosize microsphere-embedded cryogels

Cholesterol-imprinted monosize poly(glycidyl methacrylate-N-methacryloyl-(L)-tyrosine methylester) microspheres were embedded into the poly(hydroxyethyl methacrylate) (PHEMA) cryogels and the resulting composite cryogel was used for the selective removal of cholesterol. Composite cryogels were characterized by swelling tests, multipoint BET apparatus, SEM, FTIR and elemental analysis studies. Specific surface area of the PHEMA cryogel was increased from 13 to 72.7 m2/g by embedding of microspheres. Composite cryogels removed 80% of cholesterol from homogenized milk. The maximum adsorption capacity was found as 42.7 mg/g for intestinal mimicking solution. After 20 adsorption–desorption cycles, there was no remarkable decrease in the adsorption capacity.

Basic properties of sintering dust from iron and steel plant and potassium recovery

With the production of crude steel, China produces several million tons of sintering dusts which contain a great deal of valuable metals such as, K, Na, Zn, Pb. If discharged directly without adequate treatment, these elements can lead to adverse effects on the environment. Therefore, it is very necessary to determine how to separate these elements from the dust before discharge. Several physical and chemical detection methods were used to study the basic properties of sintering dust. At the same time, preliminary experiments on the recovery of the potassium resources from the sintering dust were carried out. The mean particle size of the electrostatic precipitator (ESP) dust determined by a laser granulometer was 41.468 μm. Multi-point BET and single-point BET analysis showed that the surface area of the ESP dust was 2.697 m2/g. XRD measurements detected the following phases in the ESP dust: Fe2O3, Fe3O4, KCl and NaCl, and Fe2O3, Fe3O4 and SiO2 in the water-washed dust. SEM-EDS results proved that in the ESP dust, K mostly existed in the form of KCl particles without being coated. Leaching experiments showed that the KCl in the ESP dust could be separated and recovered by water leaching and fractional crystallization. Through the recovery experiments, the yield of K-Na vaporized crystalline salt was 18.56%, in which the mass fractions of KCl, NaCl, CaSO4 and K2SO4 were about 61.03%, 13.58%, 14.03% and 9.97%, respectively. This process is technically viable and considerable in economic benefit. There was almost no secondary pollution produced in the whole recovery process.

Structural characterization, optical and magnetic properties of Ni-doped CdO dilute magnetic semiconductor nanoparticles

Abstract

Synthesis of monolithic HPLC stationary phase with self‐assembled molecular recognition sites for 4‐aminophenol

AbstractA molecularly imprinted polymer (MIP) monolith for selective recognition of 4‐aminophenol (4‐AMP) was prepared by in situ polymerization technique as high‐performance liquid chromatography (HPLC) stationary phase. For this purpose, several 4‐AMP imprinted monoliths were synthesized by using only methacrylic acid (MAA), acrylamide (AAM), or isobornyl methacrylate (IBMA) in the presence of high amount of crosslinker, ethylene glycol dimethacrylate (EDMA), and these polymeric monolith columns were connected to HPLC to evaluate their separation capabilities. By selection of appropriate functional monomer and optimization of polymerization conditions, MAA‐based monolithic MIP showed good flow through properties, high selectivity to the templated molecule, and high resolution in the separation of paracetamol and its main impurity, 4‐AMP. Besides, effective binding site density and dissociation constant of this monolith were estimated by using frontal chromatography and found as 7.95 μmol/g and 1.06 mM, respectively. Surface area of the same monolith was found as 23.48 m2/g from multipoint BET analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

High-temperature X-ray diffraction and specific heat studies on GdAlO 3, Gd 3Al 5O 12 and Gd 4Al 2O 9

Gadolinium aluminates, GdAlO 3, Gd 3Al 5O 12 and Gd 4Al 2O 9 were synthesized by the solution combustion method. Very fine particles in the nanoparticle range of ∼10–20 nm could be prepared by this method as evidenced by surface area measurement by multipoint BET method. Thermal studies on these compounds were carried out using high-temperature X-ray diffraction (HT-XRD) and differential scanning calorimetry (DSC) methods. The thermal expansion coefficients of GdAlO 3, Gd 3Al 5O 12 and Gd 4Al 2O 9 were calculated from the lattice parameter data and specific heats were calculated from DSC data. The lattice parameters of GdAlO 3 and Gd 3Al 5O 12 were found to increase linearly with temperature whereas Gd 4Al 2O 9 did not show a linear trend. The specific heats of these compounds show an increasing trend with increase in aluminum atom fraction. Based on the thermodynamic data available in the literature and the specific heat data obtained in this study, oxygen potential diagram was constructed at 1000 K.

Sol–gel production of zirconia nanoparticles with a new organic precursor

This article describes exploratory experiments into the feasibility of using sucrose, C 6H 12O 6, as an organic precursor for production of zirconia, ZrO 2, nanoparticles by the sol–gel method. The experiments show that this is, indeed, feasible and that the resulting particles appear to be at least as small as they are when using conventional organic precursors. Analyses of the produced particles are presented, including TEM microscopy and X-ray diffraction to determine chemical composition, crystal structure and mean particle size using the Scherrer formula, single and multipoint BET analysis to determine the specific surface area and thermal analysis (TA) to determine the chemical and physical properties of the samples. The advantages of producing nanoparticles with this method include ease and flexibility in terms of the particle chemical composition. In addition to producing high-quality particles, the new organic precursors have the advantage of being ubiquitous, cost-effective and non-toxic.

Gas and Mercury Adsorption Properties of Woodceramics Made from Chicken Waste

Gas-adsorption properties of woodceramics prepared from chicken waste, which was found to be amorphous carbon reinforced by glassy carbon generated from phenolic resin, was studied. The specific surface area as determined by the multipoint BET method was 33.41 m2 g-1 (N2, 77 K) and 63.40 m2 g-1 (CO2, 195 K), and the adsorption isotherm was of Type IIb (IUPAC classification). These results suggested the presence of narrow micropores and the formation of aggregates with nonrigid slit-shaped pores. Furthermore, from gas-adsorption studies and by preliminary field testing for mercury adsorption using flue gas from a coal-firing power plant, chicken-waste woodceramics was found to function as active carbon. The chicken-waste woodceramics was found to have higher mercury adsorption properties as compared with other woodceramics or a commercially available active carbon. It was presumed that calcium, potassium, sulfur, and other chemical species which were contained as impurities increased the sorption capacity ...

Incorporation of Single-Wall Carbon Nanotubes into an Organic Polymer Monolithic Stationary Phase for μ-HPLC and Capillary Electrochromatography

Single-wall carbon nanotubes (SWNT) were incorporated into an organic polymer monolith containing vinylbenzyl chloride (VBC) and ethylene dimethacrylate (EDMA) to form a novel monolithic stationary phase for high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The retention behavior of neutral compounds on this poly(VBC-EDMA-SWNT) monolith was examined by separating a mixture of small organic molecules using micro-HPLC. The result indicated that incorporation of SWNT enhanced chromatographic retention of small neutral molecules in reversed-phase HPLC presumably because of their strongly hydrophobic characteristics. The stationary phase was formed inside a fused-silica capillary whose lumen was coated with covalently bound polyethyleneimine (PEI). The annular electroosmotic flow (EOF) generated by the PEI coating allowed peptide separation by CEC in the counterdirectional mode. Comparison of peptide separations on poly(VBC-EDMA-SWNT) and on poly(VBC-EDMA) with annular EOF generation revealed that the incorporation of SWNT into the monolithic stationary phase improved peak efficiency and influenced chromatographic retention. The structures of pretreated SWNT and poly(VBC-EDMA-SWNT) monolith were examined by high-resolution transmission electron microscopy, Raman spectroscopy, scanning electron microscopy, and multipoint BET nitrogen adsorption/desorption.

Preparation and characterization of alkylated polymethacrylate monolithic columns for micro‐HPLC of proteins

Protein separations were carried out by micro-high performance liquid chromatography (micro-HPLC) with surface alkylated monolithic columns, which were prepared by in situ copolymerization of glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) in the presence of dodecanol and toluene as porogens. First, glycidyl groups at the surface of the porous monolith were hydrolyzed with sulfuric acid. The hydroxyl groups thus formed were then reacted with n-alkyl chloride to form alkylated stationary phase. Separation performance for proteins on columns with C18 and C8 stationary phases was compared. The results showed that a poly(GMA-EGDMA) support derivatized with octadecyl moieties could achieve much better resolution than one with octyl groups. A protein mixture was separated with the octadecylated poly-(GMA-EGDMA) monolithic column, and the effluent peaks were collected and analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The physical properties of the monolithic columns such as column morphology, surface area, mesopore size distribution, and column permeability were further characterized by scanning electron microscopy (SEM), multipoint BET nitrogen adsorption/desorption, and Darcy's law, respectively.

Influence of microbial hydroxamate siderophores on Pb(II) desorption from α-FeOOH

Siderophores are low-molecular weight organic molecules secreted by plants and micro-organisms in response to Fe stress. With stability constants commonly exceeding 10 30, siderophores are considered to have higher affinities for Fe(III) than for any other major or trace element dissolved in soil solution. However, several siderophores have affinities for trace metals that approach those for Fe(III), and certain actinides form siderophore complexes of surprisingly high stability. The purpose of this study was to examine the role of hydroxamate siderophores in controlling Pb sorption to an Fe(III) oxide adsorbent. Goethite [α-FeOOH], prepared by standard methods and identified by X-ray diffraction, gave a specific surface of 36 m 2 g −1 as determined by N 2 multipoint BET analysis. Adsorption experiments were performed aseptically using a batch method with a goethite concentration of 1.0 g l −1 and an ionic strength of 0.01 M NaClO 4. Soluble Pb and Fe were measured between pH 3 and 8 by first adding Pb (10 μM) and then siderophore (10, 20, or 40 μM) to the goethite suspension. Three hydroxamate siderophores were employed: desferrioxamine B (DFB), ferrichrome (FC), and rhodotorulic acid (RA). Following 20 h reaction, Pb and Fe in solution were measured by ICP–MS and ICP–AES, respectively. The efficacy of siderophore-mediated Pb desorption varied with siderophore type and generally increased with pH and siderophore/Pb molar ratio. Desferrioxamine B, at pH 6.5 and a DFB/Pb molar ratio of 4, solubilised nearly 25% of the total sorbed Pb. In the presence of 10 μM FC, Pb adsorption largely mimicked that for the siderophore-free system, whereas significant amounts of Pb were desorbed with 20 μM FC at pH >5.5. The dihydroxamate siderophore, RA, was the least effective Pb chelator, requiring 20 μM to desorb detectable amounts of Pb.

Isopropylation of benzene over sulfated ZrO2–TiO2 mixed-oxide catalyst

Zirconia–titania mixed oxide containing 60mol% of zirconium was synthesized by co-precipitation method with and without sodium dodecyl sulfate (SDS) as surfactant. The 110°C dried mixed oxides were loaded with 10wt.% sulfate by wetness impregnation method. Each of the sulfated samples was calcined for 3h at 500, 600 and 800°C, and characterized by surface area and pore size distributions using multipoint BET method. Further, the 600°C calcined sulfated mixed-oxide samples were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, and ammonia temperature programmed desorption (TPD). The results revealed that amorphous, high surface area materials were obtained possessing both Lewis and Bronsted acid sites. However, the sample prepared with surfactant showed higher total pore volume and average pore diameter and was more acidic than that prepared without surfactant. The catalytic activity of these samples was tested for isopropylation of benzene with isopropanol varying different reaction parameters. The results are correlated to the acidity and textural properties, which show that catalyst prepared in presence of SDS, with improved texture and high acidity, is excellent for this reaction with cumene selectivity more than 97mol%. The deactivation was found to be faster at lower reaction temperature.

Preparation and Characterization of Metal Sulfide Electro-catalysts for PEM Fuel Cells

ABSTRACTRuthenium sulfide samples were prepared by flowing pure hydrogen sulfide into an aqueous solution of ruthenium chloride followed by further sulfidation in hydrogen sulfide. The final products were characterized by X-ray diffraction and crystallite-sizes were estimated from line broadening. The specific surface areas of catalysts were measured using the multipoint BET method and compositions were determined by thermogravimetric analysis. Ruthenium sulfide loaded gas diffusion electrodes were fabricated by a spraying technique and their electrochemical behavior studied. The electrochemical oxidation of hydrogen was investigated in a three -electrode cell using a ruthenium sulfide loaded gas diffusion electrode as the working electrode with humidified hydrogen containing small amounts of carbon monoxide. Results on the activity and the effects of carbon monoxide with reference to a standard platinum electrode measured at the same conditions show that ruthenium sulfide has a lower activity for hydrogen oxidation but is not susceptible to CO poisoning.

Mechanochemical synthesis of nanocrystalline hydroxyapatite from CaO and CaHPO 4

Ceramic hydroxyapatite phase was triggered to occur by high-energy mechanical activation of a dry powder mixture of calcium oxide (CaO) and anhydrous calcium hydrogen phosphate (CaHPO 4). A singe-phase hydroxyapatite of high crystallinity was realised by >20 h of mechanical activation without further thermal treatment at high temperatures. The resulting hydroxyapatite powder exhibits an average particle size of ∼25 nm and a specific surface area of 76.06 m 2/g, as measured by multi-point BET technique. It was sintered to a density of 98.20% theoretical density at 1200°C for 2 h.