Nitrogen Physical Adsorption Research Articles

Influence of alkali metal ions (K+ and Na+) on the preparation of magnesium hydroxide hexagonal flakes.

Magnesium hydroxide (Mg(OH)2), as a green halogen-free flame retardant, has attracted significant attention in the field of flame retardant composite materials. In addition to conventional indicators such as purity and whiteness, Mg(OH)2 is required to take the form of regular hexagonal sheets to ensure the dispersion of composite materials. We use irregular large particles of Mg(OH)2 prepared by the magnesium factory in western Qinghai as raw materials to study the influence of alkali metal ions K+ and Na+ mainly present in salt lakes on the physicochemical properties of Mg(OH)2. The products were characterized via X-ray diffraction, scanning electron microscopy, automatic nitrogen physical adsorption apparatus, and other modern characterization techniques. Results show that alkali metal ions K+ and Na+ considerably influence the crystal surface polarity, particle size, and morphology of the prepared Mg(OH)2. The mechanism analysis shows that the presence of K+ and Na+ alters the dissolution, recrystallization, and growth characteristics of Mg(OH)2. This study provides theoretical support for the realization of high-performance Mg(OH)2 using salt lake resources and demonstrates the value for promoting the large-scale industrial application of the salt lake industry.

Isobutanol gas sensor based on Fe2O3–SnO2 heterostructure nanostructure

The rough surface Fe2O3–SnO2 composite nanorod material was prepared by electrostatic spinning. The morphology and nanostructure of Fe2O3–SnO2 composite nanorods were characterized by scanning electron microscopy SEM, nitrogen physical adsorption and X-ray diffraction. Through the analysis of the test results, it can be shown that the Fe2O3–SnO2 nanorod samples prepared in this experiment have the advantages of high purity, good crystallinity and large specific surface area. The specific surface area of the sample obtained from the test is 19.27 m2/g. According to the gas sensitivity test results of Fe2O3–SnO2 nanorods, it can be seen that Fe2O3–SnO2 samples have high responsiveness and excellent gas sensitivity selectivity. Various gases were tested in this experiment, and it was found that the sensor has good gas selectivity to isobutanol. At 310 °C, the sensor's response to 100 ppm isobutanol reached 13. This experiment not only prepared Fe2O3–SnO2 nanorod sensor with good isobutanol gas sensitivity. And it realized the accurate measurement of continuous isobutanol concentration. In addition, the gas sensitivity mechanism of Fe2O3–SnO2 nanomaterials was discussed.

Super rapid preparation of biodiesel over highly dispersed K2CO3 supported by LDH

AbstractA new heterogeneous K2CO3 supported by a layered double hydroxide (LDH), Mg–Al hydrotalcite, was prepared and used as a catalyst for the biodiesel preparation by a tri‐component coupling transesterification of methanol, vegetable oil, and methyl acetate. K2CO3/Mg‐Al exhibits high catalytic activities, and biodiesel yield can reach 99.48% within 20 min under 60°C, with 6 wt.% of K2CO3/Mg‐Al, 1:1:12 molar ratio of rapeseed oil, methyl acetate, and methanol. Fourier‐transform infrared spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy, nitrogen physical adsorption, thermogravimetry analysis, and CO2‐chemical adsorption were used to assess the physical properties of the prepared K2CO3/Mg‐Al. Using the tri‐component coupling transesterification, 12.2% cost reduce can be get by reducing the cost from 8458 to 7424 ¥/t compared with di‐component transesterification containing oil and methanol as resource.

Evaluation of the Isomerization of α-Pinene Epoxide to Campholenic Aldehyde Using a Catalyst Obtained from Orange Peels (Citrus sinensis)

Orange peels (Citrus sinensis) are an abundant lignocellulosic residue that can be used as a carbon source to obtain solids with catalytic potential in the transformation of terpenes and their oxides into value-added products. This research seeks to evaluate the isomerization of α-pinene epoxide to campholenic aldehyde using a catalyst obtained from orange peels. The material OAC-Zn was obtained by activation of orange peel with ZnSO4.7H2O followed by thermal treatment at 500 °C; an additional solid was obtained from orange peel by pyrolysis at 500 °C (OC-500). XRD revealed the presence of ZnO and ZnS in OAC-Zn; TGA analysis indicated thermal stability in OAC-Zn and OC-500 materials; SEM images showed porous surfaces of different morphology, and the presence of microporosity in OC-500 and mesoporosity in the OAC-Zn that was confirmed by physical nitrogen adsorption. The elements C, O, Zn and S was identified in OAC-Zn by EDX analysis. The results of TPD-NH3 showed that the solids contained medium and weak acidity. Campholenic aldehyde was synthesized with a 96 % selectivity over a mesoporous carbonaceous material obtained from orange peels using ZnSO4.7H2O as activating agent

Excellent sensitivity of SnO2 nanoparticles to formaldehyde

The room temperature gas sensors have always been an important research direction of the gas sensor, and the room temperature gas sensors without the assistance of the light is more valuable. The SnO2 nanoparticles were synthesized by hydrothermal method, which showed good formaldehyde sensitivity, had the advantages of low test temperature, only [Formula: see text]C, good formaldehyde selectivity, and especially the good response to formaldehyde at room temperature. The nanostructure and gas-sensing properties were characterized by scanning electron microscopy, EDS mapping, nitrogen physical adsorption, and X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and WS-60B gas-sensing measurement system. Compared with the reported research results, we carefully discuss the physical mechanism of the SnO2 formaldehyde sensor with low operating temperature and good formaldehyde selectivity in this paper.

Aerosol Assisted Synthesis of Y/ZSM‐5 Composite Zeolite and Its Application in Cracking Reaction

AbstractY/ZSM‐5 composite zeolite was synthesized by an aerosol assisted hydrothermal method including a two‐step crystallization. The aerosol technique was used to prepare the precursor of Y/ZSM‐5 composite zeolite. This helped to fully utilize the amorphous silica‐alumina species left in the primary crystallization solution of NaY zeolite, and to bring the two zeolites close to each other during the second crystallization step. The optimal adding sequence and synthesis conditions were investigated to reduce the amount of template and accelerate the crystallization rate. The composite zeolites were analyzed using XRD, SEM, nitrogen physical adsorption, NH3‐TPD techniques. It was found that the acid properties can be adjusted by modulating the SiO2/Al2O3 molar ratio of the secondary crystallization feed. The BET specific surface area of the optimal Y/ZSM‐5(20) composite zeolite is 502 m2/g, the pyrolysis conversion rate of 1,3,5‐triisopropylbenzene reaches 95.1 %, and the selectivity to benzene reaches 53.4 %.

Investigation of the influences of the molecular weights and dosage ratios of polyvinyl alcohol on para‐aramid nanofibers/polyvinyl alcohol composite aerogels

AbstractPolymer‐based monolithic composite aerogels with a durable cross‐linked structure were fabricated using polyvinyl alcohol (PVA) and para‐aramid nanofibers (ANFs) as precursors, and supercritical fluid technology as a drying strategy. In order to give a clear insight into ANFs/PVA composite aerogels, we thoroughly investigated the influences of the molecular weights and dosage ratios of PVA on these composite aerogels, and clearly demonstrated the entire process of the evolution of “sol–gel‐aerogel.” The chemical composition, porous nanostructure, porosity, and mechanical performance of the ANFs/PVA composite aerogels were characterized by attenuated total reflectance‐Fourier transform‐infrared spectra (ATR‐FTIR), X‐ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE‐SEM), nitrogen physical adsorption, and uniaxial compression, respectively. The results revealed the mechanism of the stable composition of ANFs/PVA binary system, and that both the molecular weights and dosage ratios of PVA in the ANFs/PVA composite aerogels have a significant influence on their properties. This work is beneficial to design and fabricate polymer‐based aerogels with desirable chemical and physical characteristics, and the obtained ANFs/PVA composite aerogels with appropriate molecular weight and dosage ratio of PVA possess well‐balanced comprehensive properties, which offer the potential for a wide range of applications.

Significant butanol gas sensor based on unique Bi2MoO6 porous microspheres and ZnO nanosheets composite nanomaterials

The heterostructure of metal oxide and other materials is one of the important ways for the development of electronic devices. The Bi 2 MoO 6 (BMO)/ZnO composites were synthesized by secondary hydrothermal method. The morphology and crystal structure of the compound were characterized by scanning electron microscopy, EDS mapping, X-ray photoelectron spectroscopy, transmission electron microscopy, nitrogen physical adsorption and X-ray diffraction. The synthesis technology and gas sensitivity of BMO and BMO/ZnO composites were discussed. The results showed that BMO and BMO/ZnO had better butanol gas sensitivity, faster response rate, lower working temperature, and good stability. Compared with methanol, benzene, methyl alcohol, ethanol, and acetone, BMO/ZnO sensor showed good selectivity to butanol at 270 ℃. The response time and recovery time for 100 ppm butanol were about 6 s and 33 s, respectively, the response value up to 128. The n-n type BMO/ZnO composites with unique microstructure has abundant diffusion channels, and the research work provides a valuable reference for the low-cost preparation of high-performance butanol sensors. The energy band, potential barrier and charge transfer of BMO/ZnO composites are discussed, and the optimization of their gas sensitivity is analyzed in detail. • The three-dimensional porous nanospheres Bi 2 MoO 6 were successfully synthesized. • The Bi 2 MoO 6 /ZnO composite were synthesized by hydrothermal method. • The Bi 2 MoO 6 /ZnO composite were employed as gas sensor for the detection of butanol gas.

Study on the hygroscopic performances of poplar wood fiber biomass brick

Poplar fiber biomass brick is an energy-saving and environmentally friendly biomass building material developed in recent years. It has good hygroscopic performance, can adjust indoor air humidity, helps reduce building energy consumption for dehumidification and humidification, and improves indoor air comfort. This paper studies the hygroscopic performance of poplar fiber brick from the microscopic pore structure experiment, nitrogen physical adsorption experiment, equilibrium moisture content experiment, moisture sorption and desorption cycle experiment, and water vapor transmission experiment. The model of the sorption-desorption curve of poplar fiber biomass brick at 23 °C is established. Moreover, the ideal moisture buffering value (MBV) of poplar fiber brick and the ideal and practical MBV values under the experimental procedures of this article are calculated. The results show that the Peleg model is most suitable for poplar fiber brick's moisture absorption and desorption curve at 23 °C. The MBV value is the “Excellent” level and has good moisture sorption and desorption performance. The obtained data and models provide potent data support for promoting and applying biomass bricks and theoretical model research.

Investigations on amidoxime grafted sepiolite based chitosan organic–inorganic nanohybrid composite beads towards wastewater detoxification

This work explores the fabrication of organic–inorganic nanohybrid based biopolymer composite systems for the cleaning of different contaminants from wastewater. This system involves the simultaneous radiation grafting techniques for sepiolite (SP) modification and the simple mixing of modified-SP with biopolymer matrix, chitosan (CS). The SP beads were chemically modified with amidoxime prior to its use in composite systems. The synthesized composite beads were characterized using scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), nitrogen physical adsorption (BET) investigations, Fourier transform infrared (FT-IR), atomic absorption and UV–visible spectroscopy. Hydrolytic stability of beads was also investigated in aqueous media, beads showed excellent stability in aqueous medium and in acidic environment. Here, the sorption profile of copper over amidoxime grafted SP-nanohybrid (MSP) incorporating CS-beads is reported. Furthermore, the key adsorptive variables, i.e. contact time, adsorbent dose, and concentration of adsorbate are discussed. Different isothermal (Langmuir and Freundlich) and kinetics model were also elaborated. Langmuir isotherm and pseudo-second-order models are proved to be the best fit models for Cu (II) removal in aqueous system. To explore the efficacy of the material towards organic pollutants, methylene blue (MB) was selected as model compound and adsorbed on nanohybrid beads. The results revealed that organic–inorganic nanohybrid incorporating CS beads are quite effective for contaminated water remediation, owing to their better adsorptive performance, high stability and easy application.

Detection of accumulated continuously ethanol concentration by ZnO–SnO2 composite nanorods sensor

ZnO–SnO2 composite nanorods with rough surfaces were synthesized via a coaxially nested needle electrospinning method. The morphology and nanostructure were characterized by scanning electron microscopy, atomic force microscope, EDS mapping, nitrogen physical adsorption, and X-ray diffraction. The synthesis mechanisms of ZnO–SnO2 nanorods were discussed, which combined the gas sensitivity advantages of different materials. ZnO–SnO2 nanorods sensor with good ethanol gas sensitivity achieved accurate measurement of continuous ethanol concentration. The sensor exhibited good selectivity to ethanol in the presence of formaldehyde, methanol, acetone, acetic acid, benzene, and xylene at 290[Formula: see text]C. The response and recovery time to 100 ppm ethanol were about 13 and 35 s, respectively. The energy band, barrier, charge transfer of ZnO–SnO2 composite material was discussed, and its optimization of gas sensitivity was analyzed in detail.

Antibacterial Activity and Mechanism of ZnO/Cu2+-Chitosan/Montmorillonite.

A new composite antibacterial material ZnO/Cu2+-Chitosan/Montmorillonite (ZCCM) was prepared with montmorillonite as carrier, Zn(Ac)2•2H2O, Cu(NO3)2•3H2O and chitosan as raw materials. ZCCM was characterized by X-ray diffraction, nitrogen physical adsorption, scanning electron microscopy and energy dispersion spectrometry. The antibacterial activity of ZCCM against Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus was evaluated by minimal inhibitory concentration, minimum bactericidal concentration and the influence of growth curves. ZCCM displays excellent antibacterial activity which is higher than ZnO-Montmorillonite, Cu2+-Montmorillonite and ZnO/Cu2+-Montmorillonite. In addition, the antibacterial mechanism of ZCCM was investigated by analyzing bacterial morphology, integrity of cell membrane, lipid peroxidation and the effect of histidine on antibacterial activity of materials. It is found that cell morphologies of bacteria are damaged and bacterial cells are shrunken. With the increase of cell membrane permeability, the intracellular dissolved matters leak continuously. What’s more, the reactive oxygen species are generated and biomacromolecules are oxidized.

Valorization of carnauba straw and cashew leaf as bioadsorbents to remove copper (II) ions from aqueous solution

This work proposes the use of cashew leaf (CL) and carnauba straw (CS) powders as natural bioadsorbents to remove cooper (II) ions from aqueous solution. The bioadsorbents were evaluated from physical nitrogen adsorption (BET), thermogravimetry (TGA), scanning electron microscopy (SEM), infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The parameters studied were: pH effects, bioadsorbent dose and particle size. The adsorption experiments for both powders showed a low equilibrium time of about 120 min. The adsorption kinetics followed for both bioadsorbents the pseudo-second order model. The experimental CS data were best adjusted by the Langmuir monolayer model while the CL data were adjusted for the Freundlich model. For the same experimental conditions, the maximum adsorption capacity of copper (II) was 9.51 mg/g and 1.73 mg/g for CS and CL powders, respectively. Therefore, the results described in this study value the use of native plant residues to remove copper (II) ions in order to provide a more suitable destination.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Bisindole [3]arenes—Indolyl Macrocyclic Arenes Having Significant Iodine Capture Capacity

Bisindole [3]arenes—Indolyl Macrocyclic Arenes Having Significant Iodine Capture Capacity

Preparation and characterization of triangular hollow porous polyacrylonitrile fiber made by coaxial wet spinning

AbstractHollow porous fiber with both hollow and mesoporous structural characteristics can play an important role in storage, adsorption, and other fields. Triangular hollow porous fiber was prepared by coaxial wet spinning in this paper. Polyacrylonitrile (PAN) and N‐N dimethylformamide (DMF) were blended to get cortical solution. Polyvinylpyrrolidone (PVP) and DMF were blended to get core solution. Subsequently, coaxial triangular spinneret was adopted to inject solution into coagulation bath for double diffusion and obtain primary fiber. Then PAN‐based triangular fiber with high porosity was prepared after washing and drying. Scanning electron microscopy, nitrogen physical adsorption instrument, thermogravimetric analyzer, and other instruments were used to test and characterize. The results show that the cross‐section of the fiber is triangular and has a sense of luster. The hollow degree of the fiber is as high as 84.17%, and the sheath has three‐level structure with multi‐scale pore diameters, including micropores (200 μm), submicron pores (200 nm), and nanopores (20 nm). Through the range analysis of orthogonal experiment, it is found that the concentration of cortical solution is the main factor affecting the fiber tensile strength. When the concentration of cortical solution is 17%, the concentration of core solution is 10%, the flow rate ratio of cortical solution to core solution is 10:1, and the concentration of coagulation bath is 10%, the fiber tensile strength reaches 1.43 N/mm2. The thermal insulation performance of fiber is better than that of silk, cotton and polyester. The results in this paper will provide an experimental foundation for the design and application of hollow porous profiled fibers.

Surface Functionalization of Doxorubicin loaded MCM-41 Mesoporous Silica Nanoparticles by 3-Aminopropyltriethoxysilane for Selective Anticancer 9 Effect on A549 and A549/DOX Cells

In this study, MCM-41 mesoporous silica nanoparticles were successfully synthesized by the condensation of a tetraorthosilicate precursor on a template self-assembled by cetyltrimethylammonium bromide in alkaline. The small-angle x-ray diffraction patterns of MCM-41 indicate that silica nanoparticles possess hexagonal structures with a high degree of structural ordering. Transmission electron microscopy images show that the size of the MCM-41 particles is around 100-120 nm, and the pore sizes range from 2 nm to 4 nm. In addition, the specific surface area of MCM-41 obtained by Brunauer–Emmett–Teller analysis is as high as 987 m2.g−1 and the pore size extracted from nitrogen physical adsorption isotherms is in accordance with the TEM result. Thermogravimetric analysis, Fourier-transform infrared spectroscopy, Zeta potential measurements and photoluminescence measurements show that 3-aminopropyltriethoxysilane (APTES) and doxorubicin were grafted and loaded successfully onto MCM-41 nanoparticles. An assay on fibroblasts, A549 and doxorubicin-resistant A549/DOX cells indicates that the prepared MCM41 grafting APTES nanoparticles are safe to normal cells and toxic to cancer cells in vitro.

CeO2/Co3O4 porous nanosheet prepared using rose petal as biotemplate for photo-catalytic degradation of organic contaminants

CeO2/Co3O4 porous nanosheets were prepared by biotemplate for photo-catalytic degradation of methylene blue (MB) and tetracycline (TC).The samples were systematically characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), nitrogen physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). The results showed that the CeO2/Co3O4 porous nanosheets prepared by the petal biotemplate successfully replicated the morphology of the template. The band gap energies of Eg1: 1.70 eV, Eg2: 2.42 eV, and Eg3: 3.56 eV were calculated by UV–Vis diffuse reflectance spectroscopy. The results showed that the removal rate of MB within 70 min was 96.42% and the removal rate of TC within 30 min was 85.35%. The degradation process was consistent with the first-order reaction kinetics. The results in this work show that the proposed algorithm has high degradation efficiency, stability and reusability.

High-loading washcoat of γ-alumina on FeCrAlloy mesh with acid-free slurry

Acid slurry for washcoating tends to cause acid pollution on substrate and active components and even reduces the loading capacity. To solve the problems, washcoat of γ-Al2O3 on FeCrAl mesh was prepared with acid-free slurry in this study. Effects of additives on loading and adhesive property were investigated. The macromorphology, microstructure, phase constituents, pore characteristics and adhesive strength of the washcoat were analyzed with scanning electron microscopy, X-ray diffraction, nitrogen physical adsorption and ultrasonic oscillation tests. Experimental results indicated that adding 0.7 wt% hydroxyethyl methyl cellulose (HEMC) to the slurry could improve the loading capacity and adhesive property of washcoats. With the same additive added, washcoats prepared by neutral slurry demonstrated the highest adhesive strength, with its bonding strength sharply reduced under strong acidic or alkaline conditions. More importantly, the washcoat prepared with acid-free slurry could disperse homogeneously on the structured substrate, which could enhance the mechanical properties of the washcoat. There was no blockage of the coated meshes. The maximum washcoat loading was 24.52% and the average mass loss after ultrasonic oscillation was 1.66%, showing a high loading capacity and excellent adhesive strength.

Effect of microstructure of supports on catalytic activities of carbonylation catalysts

Nickel (Ni)-based catalysts supported by different active carbons (C) were prepared and used for vapor-phase carbonylation of ethanol. The microstructural properties of carbon supports were well investigated by using physical adsorption of nitrogen (N2), X-ray photoelectron spectroscopy, infrared spectrometry, Boehm titration and scanning electron microscopy. The catalytic activities of nickel/carbon catalysts were also studied. The results showed that wood charcoal had a large quantity of mesopores, a larger specific surface area and more oxygen (O)-containing groups such as carbonyl groups. The nickel catalyst supported by wood charcoal showed the highest catalytic activity, with 72.43% of ethanol conversion and 67.46% of product combined selectivity.