Brunauer Emmett Teller Surface Area Measurements Research Articles

Polymerizable sol–gel synthesis of dark-visible light antibacterial magnetically-recoverable AgBr-loaded iron oxide/alumina nanocomposite

The demand for a facile approach for synthesizing multifunctional nanocomposites is increasingly vital across diverse applications. In this study, a polymerizable sol–gel synthesis has been reported to obtain nanocomposites of magnetic iron oxide deposited over alumina nanopowder. The synthesis is mediated by the deposition of a calculated amount of iron(III) methacrylate, along with ethylene glycol dimethacrylate crosslinker, over alumina nanopowder, followed by thermally-inducing free radical polymerization at 125 °C for 30 min. The powder thus obtained has been subjected to calcination at 400 °C for 150 min and the resultant nanocomposites were characterized using wide-angle x-ray scattering, attenuated total reflectance—Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, field-emission scanning electron microscopy, ultraviolet-diffuse reflectance spectroscopy, vibrating sample magnetometer and Brunauer–Emmett–Teller surface area measurements. The nanocomposites containing 15 and 20 wt% of iron oxide have been found to exhibit a saturation magnetization (M s) value ranging from 12 to 14 emu g−1. To the nanocomposite containing 20 wt% of iron oxide, 5 wt% of AgBr was loaded through thoroughly mixing a surfactant-based precursor, silver-tetraoctyl ammonium bromide (Ag-TOAB), followed by thermolysis. All the nanocomposites have been studied for their antibacterial activity against a representative gram-negative bacterium, Escherichia coli, under dark and visible light conditions. While a 3 mg ml−1 loading of the AgBr-loaded nanocomposite has exhibited complete clearance of the bacterial growth by 90 min in the dark, a similar activity has been observed in 60 min under light. The study has revealed the multifunctionality and high potential of the AgBr-loaded iron oxide/alumina nanocomposite as a promising dual-mode antibacterial and magnetically recoverable photocatalyst material.

Photocatalytic and Cathode Active Abilities of Ni-Substituted α-FeOOH Nanoparticles.

The present study investigates the relationship between the local structure, photocatalytic ability, and cathode performances in sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) using Ni-substituted goethite nanoparticles (NixFe1-xOOH NPs) with a range of 'x' values from 0 to 0.5. The structural characterization was performed applying various techniques, including X-ray diffractometry (XRD); thermogravimetry differential thermal analysis (TG-DTA); Fourier transform infrared spectroscopy (FT-IR); X-ray absorption spectroscopy (XANES/EXAFS), both measured at room temperature (RT); 57Fe Mössbauer spectroscopy recorded at RT and low temperatures (LT) from 20 K to 300 K; Brunauer-Emmett-Teller surface area measurement (BET), and diffuse reflectance spectroscopy (DRS). In addition, the electrical properties of NixFe1-xOOH NPs were evaluated by solid-state impedance spectroscopy (SS-IS). XRD showed the presence of goethite as the only crystalline phase in prepared samples with x ≤ 0.20, and goethite and α-Ni(OH)2 in the samples with x > 0.20. The sample with x = 0.10 (Ni10) showed the highest photo-Fenton ability with a first-order rate constant value (k) of 15.8 × 10-3 min-1. The 57Fe Mössbauer spectrum of Ni0, measured at RT, displayed a sextet corresponding to goethite, with an isomer shift (δ) of 0.36 mm s-1 and a hyperfine magnetic distribution (Bhf) of 32.95 T. Moreover, the DC conductivity decreased from 5.52 × 10-10 to 5.30 × 10-12 (Ω cm)-1 with 'x' increasing from 0.10 to 0.50. Ni20 showed the highest initial discharge capacity of 223 mAh g-1, attributed to its largest specific surface area of 174.0 m2 g-1. In conclusion, NixFe1-xOOH NPs can be effectively utilized as visible-light-activated catalysts and active cathode materials in secondary batteries.

Bis(NHC)-Pd(II) and Pd(0) complexes supported on magnetic SBA-15 for the selective aerobic oxidation of benzyl alcohols to benzaldehydes and reduction of nitroarenes

The present study describes the synthesis, characterization, and use of two new supported magnetic Pd-NHC catalysts based on Pd(II) and Pd(0). A composite of magnetite-silica core shells and SBA-15 was successively treated with (3-aminopropyl) triethoxysilane (APTES), cyanuric chloride (CC), imidazole, 2-bromopyridine, and trans-[Pd(Cl)2(SMe2)2] complex. The obtained supported bis(NHC)-Pd(II) complex, Fe3O4@SiO2@SBA-AP-CC-bis(NHC)-Pd(II), was characterized by Fourier transform infrared spectroscopy (FT-IR), X‐ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), energy‐dispersive X‐ray analysis (EDX), and Brunauer-Emmett-Teller surface area measurement (BET). The catalytic potential of the supported bis(NHC)-Pd(II) complex was explored for the selective preparation of benzaldehydes from the corresponding benzyl alcohols. The Pd(0) catalyst, Fe3O4@ SiO2@SBA-AP-CC-bis(NHC)-Pd(0), was obtained via reduction of the Pd(II)-catalyst with NaBH4. The obtained Pd(0)-catalyst efficiently reduced nitroarenes to anilines in the presence of hydrazine hydrate. The Pd contents of the Pd(II)-catalyst (2.83%wt.; 0.266 mmol/g) and Pd(0)-catalyst (2.26%wt., 0.212 mmol/g) were measured by atomic absorption spectroscopy. Both reactions are conducted under optimal reaction conditions of the solvent, the base, and the catalyst dosage. The catalysts enjoy easy magnetic separation, recyclability over eight runs without significant loss activity, and noticeable stability. They showed negligible palladium leaching (0.83% in the oxidation of benzyl alcohol and 0.1% in the reduction of nitroarenes).

Comparing the ice nucleation properties of the kaolin minerals kaolinite and halloysite

Abstract. Heterogeneous ice nucleation on dust particles in the atmosphere is a key mechanism for ice formation in clouds. However, the conditions of a particle surface for efficient ice nucleation are poorly understood. In this study, we present results of immersion freezing experiments using differential scanning calorimetry on emulsified mineral dust suspensions, involving the two chemically identical, but morphologically different, kaolin minerals of kaolinite and halloysite. Kaolinite occurs in a platy morphology, while halloysites form predominantly tubular structures. We investigated six different halloysite and two different kaolinite samples. Our results show that, on average, the halloysite samples not only exhibit a higher ice nucleation (IN) activity than the kaolinite samples but also a higher diversity in terms of freezing onset temperatures and heterogeneously frozen fraction. Repeating the freezing experiments after shortly milling the samples led to a decrease in freezing onset temperatures and in the heterogeneously frozen fraction of the halloysite samples, bringing their IN activity closer to that of the kaolinites. To interpret these findings, the freezing experiments were complemented by dynamic vapor sorption (DVS), BET (Brunauer–Emmett–Teller) surface area measurements, pore ice melting experiments with slurries, and transmission electron microscopy (TEM) before and after milling. These measurements demonstrate an increase in surface area and the destruction of tubes by milling and provide evidence for the influence of the tubular structure of the halloysites on their IN activity. We identify the OH–Al–O–Si–OH functionalized edges as being the most likely site for ice nucleation, as the high geometric diversity of the edges best accounts for the high diversity in IN activity of halloysites. We hypothesize that the stacking of layers and the number of stacks in halloysite tubes and kaolinite platelets affect the freezing temperature, with thicker stacks having the potential to freeze water at higher temperatures. The notion that the edges constitute the IN-active part of kaolin minerals is further supported by comparing kaolin minerals with montmorillonites and feldspars, all of which exhibit enhanced IN activity in the presence of ammonia and ammonium-containing solutions. As OH–Al–O–Si–OH functionalized edge surfaces are the only surface type that kaolin particles have in common with montmorillonites and feldspars, the common feature of IN activity enhancement in ammoniated solutions can only be explained by ice nucleation occurring at the edges of kaolin minerals.

Enhanced laccase separation from fermentation medium using cryogel columns

The laccase enzyme family belongs to the oxidoreductase enzyme class and is one of the most commercially valuable enzymes that catalyzes the oxidation of one electron of a wide range of phenolic compounds. Separation and purification of laccases are crucial for industry since they play an important role in dye decolorization, biodegradation and food processing. Therefore, developing effective, high yielding and cost-effective methods for laccase production is vital. In this study, it was aimed to prepare cryogel columns for laccase purification following the bioproduction of laccase via Aspergillus niger. 2-hydroxyethyl methacrylate based cryogels were synthesized in the presence of 1-vinylimidazole as the affinity ligand and characterized by swelling tests, Brunauer–Emmett–Teller surface area measurement and scanning electron microscopy analysis. Surface area and water uptake ratio of cryogel columns were 35 m2/g and 93 %, respectively. The effect of pH, equilibrium laccase concentration, flow rate, interaction time and temperature on laccase adsorption were examined. The purification factor was calculated as 10.53 under optimum conditions and the enzyme recovery was found to be 86.7 % from fermentation medium. Current study revealed that laccase purification using cryogels following filtration of fermentation medium could be a promising candidate for industrial applications with eliminating the need for complex chromatographic steps.

Polydopamine/polypyrrole-modified graphite felt enhances biocompatibility for electroactive bacteria and power density of microbial fuel cell

The interactions between the microbes and the surface of an anode play an important role in capturing the respiratory electrons from bacteria in a microbial fuel cell (MFC). The chemical and electrochemical characteristics of the carbon material affect biofilm growth and direct electron transfer in MFCs. This study examined the electrodeposition of polydopamine (PDA) and polypyrrole (PPY) on graphite felt electrode (GF). The MFC with the modified PDA/PPY-GF reached 920 mW/m2, which was 1.5, 1.17, and 1.18 times higher than those of the GF, PDA-GF, and PPY-GF, respectively. PDA has superior hydrophilicity and adhesive force biofilm formation, while PPY provides electrochemically active sites for microbial electron transfer. Raman spectroscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area measurements, and contact angle analysis revealed the enhanced physicochemical properties of the carbon electrode. These results show that co-doped PDA/PPY provides a strategy for electroactive biofilm development and improves the bioelectrochemical performance in realistic MFC reactors.

Highly covalent FeIII–O bonding in photo-Fenton active Sn-doped goethite nanoparticles

The relationship between local structure and photo-Fenton catalytic ability of tin-doped goethite with the composition of α-SnxFe1-xOOH (x = 0, 0.05, 0.10, 0.15 and 0.20, abbreviated as Sn100x) was investigated by X-ray diffractometry (XRD), 57Fe-and 119Sn-Mössbauer spectroscopies, X-ray absorption near-edge spectroscopy (XANES), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area measurement (BET), diffuse reflectance spectroscopy (DRS), and ultraviolet–visible absorption spectroscopy (UV–vis). Room temperature 57Fe-Mössbauer spectra of Sn0 and Sn5 showed a sextet with isomer shift (δ) of 0.37 mm s−1, quadrupole splitting (Δ) of −0.27 mm s−1, and internal magnetic field (Hint) of 33.2 T due to goethite. In contrast, those of Sn10, Sn15 and Sn20 showed a doublet with increasing δ from 0.34 to 0.37 mm s−1 and Δ from 0.62 to 0.63 mm s−1 due to the superparamagnetic phase. On the other hand, increasing δ from −0.01 to 0.13 mm s−1 and decreasing Δ from 1.15 to 0.53 mm s−1 was observed from the 119Sn-Mössbauer spectra of Sn100x with ‘x’ from 0.05 to 0.20. These results indicate that the SnIV–O chemical bond becomes shorter, while that of FeIII–O longer by introducing tin into goethite, which causes a decrease in the bandgap energy (Eg). TEM image of Sn100x showed that needle-like particles with an average length of 181 and 61 nm were respectively observed in Sn0 and Sn5, whereas nanoparticles with the average size of 4.1, 6.4 and 10.2 nm were for Sn10, Sn15 and Sn20, respectively. From the BET measurement, the specific surface area (SSA) of Sn100x increased from 53 to 178 m2 g−1 with Sn concentration. Photo-Fenton catalytic ability of Sn100x using 20 μmol L−1 methylene blue aqueous solution and 0.4 mol L−1 H2O2 under visible-light irradiation revealed that Sn15 showed the largest apparent-first-order rate constant (k) of 35•10−3 min−1. We conclude that Sn15 is the best catalyst because of its large SSA of 187 m2 g−1 and the smallest bandgap energy of 1.77 eV.

Castor Leaves-Based Biochar for Adsorption of Safranin from Textile Wastewater

The prospect of synthesizing biochar from agricultural wastes or by-products to utilize them as a promising adsorbent material is increasingly gaining attention. This research work focuses on synthesizing biochar from castor biomass (CBM) and evaluating its potential as an adsorbent material. Castor biomass-based biochar (CBCs) prepared by the slow pyrolysis process at different temperatures (CBC400 °C, CBC500 °C, and CBC600 °C for 1 h) was investigated for the adsorption of textile dye effluents (safranin). The pyrolysis temperature played a key role in enhancing the morphology, and the crystallinity of the biochar which are beneficial for the uptake of safranin. The CBC600 adsorbent showed a higher safranin dye removal (99.60%) and adsorption capacity (4.98 mg/g) than CBC500 (90.50% and 4.52 mg/g), CBC400 (83.90% and 4.20 mg/g), and castor biomass (CBM) (64.40% and 3.22 mg/g). Adsorption data fitted better to the Langmuir isotherm model than to the Freundlich isotherm model. The kinetics of the adsorption process was described well using the pseudo-second-order kinetic model. The study on the effect of the contact time for the adsorption process indicated that for CBC600, 80% dye removal occurred in the first 15 min of the contact time. After three regeneration cycles, CBC600 exhibited the highest dye removal efficiency (64.10%), highlighting the enhanced reusability of CBCs. The crystalline patterns, functional binding sites, and surface areas of the prepared CBCs (CBC400, CBC500, CBC600) were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller surface area measurements, respectively.

Facile Synthesis of Micro CuO Crystals for Li Ion Full Battery

Micro CuO crystals are synthesized by hydrothermal method in one step. The CuO-Li ion full battery is assembled using the porous lithium foil-graphite as a anode and the prepared CuO crystals as a cathode. The micro CuO crystals are characterized by scanning electron micro porousscopy, X-ray powder diffractometer, Fourier Transform infrared spectrometer, thermogravimeter, Brunauer–Emmett–Teller surface area measurements, and differential scanning calorimeter. The full battery is tested by the galvanostatic current charge-discharge technology at higher current densities of 0.25–0.5 mA/cm2. The porous lithium foil-graphite anode can effectively inhibit the powder of anode lithium, and improve the reversibility of the battery.

Adsorption of Malachite Green Dye onto Mesoporous Natural Inorganic Clays: Their Equilibrium Isotherm and Kinetics Studies

Contamination of water with organic dyes is a major environmental concern as it causes serious life-threatening environmental problems. The present research was designed to evaluate the potential of three different natural inorganic clays (NICs) i.e., Pakistani bentonite clay (PB), bentonite purchased from Alfa Aesar (BT), and Turkish red mud (RM) for malachite green (MG) dye removal from an aqueous solution. Various analytical techniques, namely X-ray fluorescence spectrometry (XRF), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller surface area measurement (BET), and thermogravimetric analysis (TGA), were used to investigate the physicochemical properties of the NICs samples. The effect of adsorption operational parameters such as contact time, aqueous phase pH, dye concentration, and amount of NICs on the adsorption behavior of MG onto NICs samples were investigated under the batch adsorption system. The equilibrium and kinetic inspection reflected the best description of MG adsorption behavior by the Langmuir isotherm model and pseudo-first-order kinetic model, respectively. The results indicated that the adsorption was favorable at higher pH. The maximum adsorption capacities calculated by Langmuir isotherm for PB, BT, and RM were found to be 243.90 mg/g, 188.68 mg/g, and 172.41 mg/g, respectively. It can be concluded that natural inorganic clays with a higher surface area can be used as an effective adsorbent material to remove the MG dye from an aqueous solution.

Influence of Co over magnetically benign Zn ferrite system and study of its structural, dielectric, superparamagnetic and antibacterial efficacy

A series of nano-sized Co-Zn ferrite, CoxZn1-xFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) was synthesized by precursor combustion method. The phase purity, composition, surface area, and oxidation states of corresponding metal ions were confirmed by using the techniques such as X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, inductive coupled plasma-atomic emission spectroscopy, Brunauer–Emmett–Teller surface area measurement, and X-ray photoelectron spectroscopy. The transmission electron microscopy analysis revealed cuboidal shaped ferrite particles with 20−30 nm size. The dielectric studies with change in frequency and temperature, and magnetization studies with a change in temperature and applied field, exhibited marked enhancement with cobalt content in the ferrites. The transition from paramagnetic to superparamagnetic nature with rising cobalt content was observed in our investigation based on magnetization and supported by Mössbauer studies. The synthesized ferrites also revealed good antimicrobial activity against gram-negative E. coli ATCC 8439.

Green Synthesis of Highly Dispersed Zinc Oxide Nanoparticles Supported on Silica Gel Matrix by Daphne oleoides Extract and their Antibacterial Activity.

Background: ZnO nanoparticles (ZnO-NPs) are one of the most popular metal oxide nanoparticles, which exhibit significant antibacterial properties against various pathogens. Among nanoparticle synthesis methods, the green synthesis using plant extract is considered as an eco-friendly and cost-effective method for ZnO-NPs production, compared to the chemical procedures.Background: This study aimed to evaluate the green synthesis of ZnO-NPs loaded on silica gel matrix (ZnO/SG nanocomposite) by using methanol leaf extract of Daphne oleoides as a new extract and a cost-effective method. Furthermore, the antibacterial activity of the synthesized structure is evaluated against some pathogenic bacteria and the results are compared with unsupported ZnO-NPs.Materials and Methods: For ZnO/SG nanocomposite synthesis, a solution of Zn (NO3)2 was stirred with silica gel. Then the Daphne oleoides extract was added and stirred continuously until white precipitate was formed. The precipitate was heated at 200 ˚C for calcination, and ZnO/SG nanocomposite was obtained. The phytochemical constituents of leaf extract were then analyzed by gas chromatography–mass spectrometry (GC-MS). Afterwards, the structure of ZnO-NPs on SiO2 matrix (ZnO/SG nanocomposite) was characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FTIR). Surface area measurement was also determined by Brunauer-Emmett-Teller (BET) techniques. Furthermore, the antibacterial activity of ZnO/SG nanocomposites against pathogenic bacteria was evaluated using agar-based disk diffusion method standardized by clinical and laboratory guidelines. Results: The leaf extract of Daphne oleoides encompassed five major polyphenolic components. The results of the nanocomposite structure showed that ZnO-NPs with an average particle size of 38 nm were obtained and stabilized on the silica gel matrix. The BET surface area measurement of ZnO/SG nanocomposite was compared with unsupported ZnO-NPs, and the results indicated that the surface area of ZnO/SG nanocomposite was increased. Furthermore, the structure showed more powerful antibacterial activity against pathogens than unsupported ZnO-NPs. Conclusions: Green synthesis of ZnO-NPs supported on the silica gel matrix with the leaf extract of Daphne oleoides is a benign and effective procedure for ZnO/SG nanocomposite synthesis. Embedding ZnO-NPs in silica gel matrix prevents the agglomeration of nanoparticles and prepare homodispersed nanoparticles. This structure revealed great antibacterial activity against many pathogens.

Facile fabrication of sodium carboxymethyl cellulose/reduced graphene oxide composite hydrogel and its application for Pb(II) removal

The sodium carboxymethyl cellulose/reduced graphene oxide (rGO-CMC) composite hydrogel was fabricated via environmental friendly one-step hydrothermal reduction method. The morphology, pore structure and surface properties of the as-prepared sample were characterized by scanning electron microscopy, Brunauer–Emmett–Teller surface area measurement and zeta potential analyser, respectively. To investigate the adsorption behaviour of rGO-CMC for Pb(II), effects of contact time, temperature, initial concentration and pH were studied in detail. The rGO-CMC composite before and after adsorption of Pb(II) was analysed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy to further explore adsorption mechanism. Compared with rGO, the adsorption capacities of rGO-CMC-3 composite for heavy metals including Pb(II), Cu(II), Ni(II), Mn(II), Co(II) were increased to 156.85, 35.70, 21.40, 20.85 and 15.80 mg g−1, respectively. In addition, the rGO-CMC composite formed a complete aerogel after freeze-drying, which confirms its great potential as an easily separable adsorbent to remove heavy metals in aqueous solutions.

Intrinsically Porous Polydiacetylene from a Functionalized Bowl-Shaped Hexaphenoxycyclotriphosphazene Derivative

Intrinsic porosity in polymeric materials arises from the formation of a continuous network of interconnected voids and is a direct consequence of the shape and rigidity of the molecular building blocks. To obtain well-defined pores with narrow size distributions, the polymerization of rigid and sterically hindered monomers must not interfere with the pore formation and should avoid the use of additives that may occupy voids. Polydiacetylenes can be generated by the topochemical polymerization of diacetylene-bearing molecules favorably arranged in crystals, gels, thin films, or vesicles. Polydiacetylene formation in amorphous materials has been sparsely studied because higher-order self-assembled structures are assumed to be required for the topochemical polymerization of 1,3-butadiyne to occur. In this study, a bulky hexachlorocyclotriphosphazene core (N3P3Cl6) was functionalized with six diacetylene-containing alkyl chains and successfully converted to an intrinsically porous multifunctional polydiacetylene. The successful formation of the polydiacetylene was confirmed by Raman spectroscopy, and the porous structure of the resulting materials was verified by X-ray diffraction and Brunauer–Emmett–Teller surface area measurements. This investigation revealed a significant change in the porous structure after polymerization, leading to a 5-fold increase in specific surface area. Overall, the topochemical polymerization of diacetylenes is a promising strategy for the preparation of functional materials, which is shown to be compatible with rather amorphous phases of bulky molecules. The results obtained from this investigation give access to a range of porous polydiacetylene materials for potential applications in organic electronics, gas adsorption, and other related fields.

Preparation of a Hybrid Membrane from Whey Protein Fibrils and Activated Carbon to Remove Mercury and Chromium from Water

Water contamination by mercury and chromium has a direct effect in human health. A promising technology to remove heavy metals by membrane filtration is the use of hybrid membranes produced with whey protein fibrils (WPF) and activated carbon (AC). In this study, the best conditions to produce WPF by heat treatment were determined to maximize the removal of mercury and chromium from water using a central composed design. The results indicated that the best conditions to prepare WPF were 74 °C, 7 h and 3.8% of whey protein with adsorption capacities of 25 and 18 mg/g and removal efficiencies of 81 and 57% for mercury and chromium, respectively. WPF and AC were used to prepare a hybrid membrane that was characterized using transmission electron microscopy, atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller surface area measurements. Batch filtration experiments were performed with the hybrid membrane for chromium and mercury removal at 25, 50 and 100 mg/L to determine its adsorption capacities. A high performance of the hybrid membrane was demonstrated removing efficiently mercury and chromium from water, thus supporting more than ten filtration cycles.

Catalytic effect of lithium titanate oxide doped with praseodymium on thermal decomposition of ammonium nitrate

In this work, lithium titanate oxide (Li4Ti5O12) (LTO) and praseodymium ion doped in lithium titanate oxide (Pr-LTO) were synthesized in a sol–gel simple method, and their catalytic effects on thermal decomposition of ammonium nitrate were reported using thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) techniques. The X-ray powder diffraction, Brunauer–Emmett–Teller surface area measurements, particle size analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy techniques were used to identify the structural properties and morphology of LTO and Pr-doped LTO. By doping the praseodymium ion within the LTO spinel structure, the surface area increases (from 204.2 m2 g−1 for LTO semiconductor to 318.9 m2 g−1 for Pr-doped LTO), and the catalytic activity improved. The catalytic effects of LTO and Pr-LTO on the thermal behavior of AN were studied via TG-DSC techniques. The thermal decomposition of pure AN (196–400 °C) shifted to lower temperatures, 154–280 °C, and 131–241 °C, in the presence of LTO and Pr-LTO, respectively. The results showed that the catalytic effects of LTO were improved by praseodymium doping. The Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink, and Tang methods were used to determine activation energies of all AN samples at different conversion values (α). The activation energies of pure AN values were 166 ± 3, 166 ± 2, 166 ± 2, and 162 ± 2 kJ mol−1, while AN/LTO activation energies were 145 ± 2, 144 ± 1, 144 ± 1, and 144 ± 2 kJ mol−1 and finally, those of AN/Pr-LTO were 112 ± 1, 109 ± 2, 110 ± 1, and 110 ± 1 kJ mol−1 using FWO, KAS, Starink, and Tang methods, respectively.

Improved Analysis of Nuclear-Magnetic-Resonance Measurements in Organic-Rich Mudrocks Through Experimental Quantification of the Hydrocarbon/Kerogen Intermolecular-Interfacial-Relaxation Mechanism

Summary Nuclear-magnetic-resonance (NMR) measurements have become a popular choice for estimating hydrocarbon saturations in organic-rich mudrock reservoirs. Previous publications have shown that the dominant mechanism for surface relaxation during NMR measurements in organic pores is intramolecular dipolar coupling among hydrocarbon protons. However, the influence of kerogen/hydrocarbon intermolecular interactions and kerogen thermal maturity on the surface relaxivity has not been reliably quantified. The objectives of this paper are to experimentally quantify the influence of intermolecular coupling on kerogen surface relaxivities; compare the experimentally determined surface relaxivities with those obtained from our previously published analytical model; and quantify the effect of intermolecular coupling on estimates of the adsorbed-hydrocarbon phase volume in simple geometries. First, we selected two organic-rich mudrock formations with different kerogen thermal maturities and extracted pure kerogen from them. The extracted-kerogen samples were synthetically matured by increasing the temperature at 4°C/min from 25 to 450°C under a controlled environment. The petrophysical properties of kerogen samples at different thermal maturities were quantified using pyrolysis and Brunauer-Emmett-Teller (BET) measurements. The untreated and thermally mature kerogen samples were then saturated with protonated and partially deuterated chloroform mixtures. Consequently, we performed longitudinal (T1) and transverse (T2) measurements on the kerogen/chloroform mixtures. Then, we compared the surface relaxivities estimated from T1/T2 and BET surface-area measurements with those predicted by a previously published theoretical model derived from generalized adsorption theory. Finally, we performed a sensitivity study demonstrating the effect of intermolecular dipolar coupling on estimates of adsorbed-hydrocarbon volume by modeling kerogen pores as synthetic spherical objects. Results indicate that synthetic maturation of kerogen samples relatively increased their specific surface areas by up to 97.1%. When chloroform deuteration is kept constant and kerogen samples were heat treated from temperatures of 25 to 450°C, the T1 and T2 surface relaxivities relatively decreased by up to 70.1 and 80.3%, respectively. Our recently introduced analytical model was able to reliably quantify the kerogen surface relaxivities estimated from experimental measurements with a relative error of 30.5%. The results of the sensitivity analysis showed that improved assessment of kerogen surface relaxivity by including intermolecular coupling enhanced the NMR-based adsorbed-hydrocarbon-volume estimates relatively by up to 41.9% when kerogen pores were modeled as synthetic spherical objects. The results of the experimental measurements support the observations of the analytically developed surface-relaxivity model derived from the generalized adsorption theory. Accurately quantifying the mechanism contributing to surface relaxation helps in providing accurate temperature and frequency corrections for T2 and T1/T2 cutoff values. Such cutoff values can then be extended to in-situ conditions improving downhole estimates of NMR-based hydrocarbon saturations in organic-rich mudrocks.

Systematic effects of Fe doping on the activity of V2O5/TiO2-carbon nanotube catalyst for NH3-SCR of NOx

The present investigation concentrates on the reduction of NOx emissions, the indirect greenhouse gases, which generate ozone by reacting with the atmosphere. A series of composite catalytic support (TiO2-CNTs) with a constant TiO2-CNT ratio prepared by precipitation method was utilized to synthesize Fe-modified V2O5/TiO2-CNT catalyst for selective catalytic reduction (SCR) of NOx with ammonia (NH3). The structural and surface characteristics of the prepared catalyst were investigated by using Brunauer–Emmett–Teller surface area measurement, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, and temperature-programmed desorption (TPD) techniques. In terms of catalytic activity, VFe3TiC10 catalyst showed better SCR performance having a NOx conversion efficiency of 95% and 98% at 250 °C and 300 °C, respectively. The improved performance could be attributed to high surface chemisorbed oxygen on the surface of the catalyst by the added Fe species which promotes the SCR activity. The catalytic activity results depicted that the addition of CNTs to TiO2 support enhanced the SCR activity of the catalyst at low reaction temperatures and it also provides better resistance to SO2. In addition, the effects of Fe modification on the NH3 removal efficiency of the catalyst were also investigated.

Design and Fabrication of Green Magnetic/Graphene Oxide/Chitosan/Allium sativum/Quercus/Nanocomposite: Characterization and Application

A novel nanocomposite based on green magnetic–graphene oxide—chitosan—Allium sativum—Quercus in presence of Alhagi maurorum as very effective green chemical agent was successfully synthesized and fabricated. The physicochemical properties of the fabricated nanocomposite including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential analyzer, Brunauer-Emmett-Teller surface area measurement (BET), scanning electron microscope (SEM), and UV-visible spectroscopy (UV) were investigated. The magnetic property of nanocomposite was also evaluated by vibrating sample magnetometer (VSM). Compared with graphene oxide and chitosan, the fabricated nanocomposite demonstrated excellent properties, which may be attributed to the fact that the structural properties of nanocomposite due to the natural components used chemically has been fundamentally promoted. According to the results, the developed nanocomposite provided the excellent feature, confirming that a more effective component for use at various industrial especially medical utilizations could be essentially considered.

Highly sensitive detection of ammonia gas by 3D flower-like ɤ-MnO2 nanostructure chemiresistor

In this work, a ɤ-MnO2 flower-like nanostructure was synthesized. The structural and morphological characterization of ɤ-MnO2 flower-like nanostructure was performed by X-ray powder diffraction (XRD), N2–sorption studies (Brunauer–Emmett–Teller surface area measurements) (BET), particle size distribution (PSA), energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). The ammonia gas sensor was fabricated based on the high surface area of ɤ-MnO2 flower-like nanostructure. According to the results, tetragonal tunnels were advantageous for trapping and adsorption-desorption of NH3 gas molecules. The results indicated that the gas sensor based on ɤ-MnO2 flower-like nanostructure had high sensitivity (40% response to 100 mg L−1 NH3 gas), selectivity, detectability up to 2 mg L−1 NH3 gas, long-term stability, and repeatability for two months at room temperature. Of the study also examined the effect of compounds such as ethanol, acetone, hydrazine, n-heptane, monomethylamine (MMA), triethylamine (TEA) and trimethylamine (TMA) on the detection of ammonia gas.