AlOH Research Articles

Sulfated attapulgite for catalyzing the conversion of furfuryl alcohol to ethyl levulinate: Impacts of sulfonation on structural transformation and evolution of acidic sites on the catalyst

Attapulgite (ATTP) is an abundant natural magnesium aluminosilicate mineral that can be used as support for manufacturing cost-effective solid acid catalysts. This study mainly focuses on structural change of ATTP and the formation of Brønsted and Lewis acid sites during sulfonation in H 2 SO 4 . The results indicate that the sulfonation leads to the drastic change of the crystal phases as sulfuric acid not only plays the roles of grafting the sulfur species but also reacts with the CaO, MgO, Al 2 O 3 and Fe 2 O 3 or their salts in ATTP to form the sulfates, resulting in the substantial change of the porous structure of ATTP. In such a process, the Brønsted acidic sites, which are the main active sites for the conversion of furfuryl alcohol (FA) to ethyl levulinate (EL), are introduced, while the abundance/strength of the Lewis acid sites are enhanced. The yield of EL up to 95.4% is achieved over the H 2 SO 4 /ATTP catalyst. The Fe 2 (SO 4 ) 3 and MgSO 4 in the catalyst leaches in ethanol but does not affect the catalytic stability. The formed polymer also does not affect much the catalytic activity after their removal via the calcination in air. • Sulfated attapulgite (ATTP) is prepared for conversion of furfuryl alcohol (FA) in ethanol. • Sulfonation transforms CaO, MgO, Al 2 O 3 and Fe 2 O 3 phase, changing structure in ATTP. • Sulfonation destroys Al–OH–Al, Si–O–Al and carbonate functionalities in ATTP. • Sulfonation enhanced abundance/strength of Brønsted and Lewis acid sites. • Leaching of sulfates does not affect the sulfur species that generate acidic sites.

Phosphorus removal by adsorbent based on poly-aluminum chloride sludge

Phosphorus adsorption tests were carried out using poly-aluminum chloride sludge (PACS), which was collected from a water treatment plant in Nanjing. The amount of phosphorus adsorbed by PACS increased quickly within the first hour and reached equilibrium after about 48 h. The adsorption behavior of PACS for phosphorus is consistent with the Langmuir adsorption isotherm equation (R2 > 0.99) and parallel first-order kinetic equation (R2 > 0.98). With the increase of the PACS concentration, the adsorption capacity of PACS for phosphorus decreased, and the removal rate increased. The results of batch tests showed that the adsorption capacities of PACS for phosphorus ranged from 1.64 to 1.13 mg/g when the pH value varied from 4 to 10. However, the adsorption capacity of PACS was not evidently influenced by temperature. In comparison with the ion exchange resin, the adsorption capacity of PACS was barely inhibited by competitive ions, such as SO42−, NO3−, and Cl−. The PACS surface after adsorption became smooth, and the vibration peaks of Al–O and Al–OH shifted. Both HCl and NaOH have a strong desorption effect on PACS after adsorption saturation, and with higher concentrations of HCl and NaOH, the desorption effect was stronger. Results of column adsorption experiments showed that with lower phosphorus and hydraulic loads, the adsorption column took longer to reach saturation. This indicated that PACS could be used as an efficient material for removal of phosphorus from water. This study provides a new treatment method with PACS.

Per-pixel analysis of ASTER data for porphyry copper hydrothermal alteration mapping: A case study of NE Isfahan, Iran

This paper evaluates the efficiency and capability of per-pixel methods comprising spectral feature fitting (SFF), multi range spectral feature fitting (MRSFF), and spectral information divergence (SID) algorithms in mapping alteration minerals using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. The study area is located in the Saveh-Yazd belt, northeastern Isfahan, Iran, which is the central part of the Urumieh–Dokhtar Magmatic Arc (UDMA). Porphyry copper mineralization formed in association with Oligo-Miocene intrusive bodies, are located in this belt. The hydrothermal alteration zones in the study area are manifested by phyllic, argillic, propylitic, and silicic. Mineralogically, these zones are marked by sericite-illite, kaolinite, montmorillonite, chlorite, epidote, and overprint of iron oxide/hydroxides. The pixel purity index (PPI) was used for extraction of image spectra, which were subsequently used as spectral reference. The SFF algorithm could map the Al–OH bearing mineral assemblages as a mixed alteration zone (phyllic-argillic zone), whereas the MRSFF provided an improved discrimination of sericite-illite and kaolinite minerals. The SID algorithm had the best performance for identifying and mapping these alteration minerals, comparing to the SFF and MRSFF. On the other hand, the results showed that SID and MRSFF algorithms were more efficient than SFF in discriminating the propylitic alteration zone. The field surveys, X-ray diffraction, spectral measurements, and microscopic studies confirmed the occurrence of hydrothermally altered minerals containing sericite-illite, kaolinite-dickite, and chlorite– epidote, which corresponded well to the ground criteria. Considering the potential of SID algorithm in discriminating the target minerals, it could be proposed for mineral mapping as part of exploration projects.

Catalytic Performance and Mechanistic Insights into the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene over ZSM-5 Zeolite

Acidic zeolites are considered a kind of efficient catalysts in the synthesis of polyoxymethylene dimethyl ethers (PODEn) with the fomula of CH3O–(CH2O)n–CH3, a promising green diesel fuel or additive from methanol derivatives; however, the crucial parameters that determine PODEn yield and reaction mechanism over zeolite catalyst remains rather ambiguous. In this work, the relationship between the catalytic performance of HZSM-5 zeolite and Si/Al ratio and reaction temperature was revealed through PODEn synthesis from dimethoxymethane (DMM) and trioxymethylene (TOM). The results indicate that the Si/Al ratio and reaction temperature are interdependent in determining the PODEn yield; High Al HZSM-5 zeolites( Si/Al ≤ 50) show the highest PODE2-8 selectivity and yield only at 70–90 °C, whereas low Al zeolites (Si/Al ≥ 109) possess the better activity to PODE2–8 at 70–150 °C. The reaction mechanism was then investigated through in-situ IR characterization and DFT calculation. The important intermediates ZO-CH2OCH2OCH2OH, ZOCH2OCH3 and ZO(CH2O)nCH3 (ZOH: HZSM-5 zeolite) were detected by In situ IR spectra during the exposure of HZSM-5 to TOM, DMM and co-feed. DFT calculations further verified above reaction intermediates and elucidated the reaction elementary steps. Reaction mechanism was proposed as follows: the Bronsted acidic sites provided by Al–OH of HZSM-5 zeolite promote the dissociation of TOM to monomer CH2O and transform DMM to ZOCH2OCH3 and CH3OH; Next, the CH2O species react with short chain ZO(CH2O)nCH3, forming long chain ZO(CH2O)nCH3; After that, the PODEn products are formed by sealing ZO(CH2)nOCH3 with CH3OH. Ultimately, the difference of catalytic performance resulting from the effect of Si/Al ratio and reaction temperature, based on the proposed mechanisms, was given a logical explanation. The detailed reaction mechanism in the synthesis of polyoxymethylene dimethyl ethers from dimethoxymethane and trioxymethylene over HZSM-5 zeolite were investigated through a series of in-situ IR characterization and DFT calculation. Subsequently, the difference of catalytic performance resulting from the effect of Si/Al ratio and reaction temperature, was given a possible explanation.

Removal of Cr(VI) from wastewater by artificial zeolite spheres loaded with nano Fe–Al bimetallic oxide in constructed wetland

In order to solve the problems of poor adsorption capacity and low stability in treating heavy metal wastewater with traditional constructed wetland (CW) fillers, a new type of filler, artificial zeolite spheres loaded with nano Fe–Al bimetallic oxide (hereinafter referred to as composite zeolite spheres), was prepared for Cr(VI) removal from wastewater. The results indicated that nano Fe–Al bimetallic oxide was an effective material for Cr(VI) removal with the maximal removal efficiency of 84.9% at initial Cr(VI) concentration of 20 mg/L (pH = 3). The micro-reactor experiment further verified that composite zeolite spheres had better removal performance on Cr(VI) than traditional filler. Fourier-transform infrared (FT-IR), X-ray diffractometry (XRD) and X-Ray photoemission spectroscopy (XPS) results demonstrated that –OH groups reduced Cr(VI) to Cr(III), and then the Cr(III) was removed by forming CrxFe1-x(OH)3 precipitation with Fe(III) or formed Cr(OH)3 precipitation with Al–OH through the ion exchange. This study provided an effective approach for treating Cr(VI) wastewater by using a new composite zeolite in constructed wetlands (CWs).

Identifying high potential zones of gold mineralization in a sub-tropical region using Landsat-8 and ASTER remote sensing data: A case study of the Ngoura-Colomines goldfield, eastern Cameroon

Climatic conditions and vegetation constrain the use of optical satellite imagery as an exploration tool for hydrothermal ore mineralization in tropical and subtropical regions. In this investigation, Landsat-8 and ASTER satellite imagery were used to detect hydrothermal alteration zones associated with gold mineralization in the Ngoura-Colomines region, Eastern Cameroon. The study area contains several gold-bearing quartz veins associated with zones of pyritization, muscovite/sericite, iron oxides, and silicification. Principal Component Analysis (PCA), Independent Component Analysis (ICA), and specialized spectral band ratios were used to extract spectral information related to vegetation, iron oxide/hydroxide minerals, Al–OH, Fe-Mg–OH, carbonate group minerals, and silicification using Landsat-8 data at regional scale. Linear Spectral Unmixing (LSU) algorithm was implemented to ASTER VNIR + SWIR bands for detailed discrimination of hematite, jarosite, kaolinite, muscovite, chlorite and epidote at district scale. The Automated Spectral Hourglass (ASH) technique was employed to extract reference spectra directly from the ASTER bands for producing fraction images of end-members using the LSU. A comprehensive field survey was used to verify the remote sensing results. Petrographic study, X-ray diffraction analysis and reflectance spectroscopy indicated the presence of quartz, goethite and sericite, as well as the absorption features of Fe3+/Fe2+, Al–OH, OH/H2O and SiO2 in the alteration zones. Several hydrothermal alteration zones of iron oxide/hydroxide, clay, carbonate minerals and silicification zones were identified, which are spatially associated with known mining areas and gold occurrences in the study area. High potential prospects were also delineated, including the Ngoura-Colomines prospects and the newly discovered Yangamo-Ndatanga and Taparé-Tapondo prospects in the southwestern and southeastern parts of the study area. Consequently, satellite-based mineral prospectivity maps at regional and district scales were generated for the study area by implementing the fuzzy logic model to the most informative thematic layers derived from image processing results. The satellite-based prospectivity maps are reliable for exploration of new gold prospective zones in the Ngoura-Colomines goldfield.

Short wavelength infrared (SWIR) spectroscopy of phyllosilicate minerals from the Tonglushan Cu-Au-Fe deposit, Eastern China: New exploration indicators for concealed skarn orebodies

The Middle–Lower Yangtze River Metallogenic Belt (MLYRB) is one of the most important Cu–Au–Fe–Mo skarn–porphyry metallogenic belts in Eastern China. After several decades of mining, the shallow-level mineral resources have been gradually exhausted, which call for new exploration tools for concealed orebodies. The Tonglushan Cu–Au–Fe skarn deposit (86.3 Mt @ 1.66% Cu, 0.94 g/t Au and 39.4% Fe) is located in the western MLYRB. Skarn alteration/mineralization are mainly hosted in the contact zone between Cretaceous (~141 Ma) quartz monzodiorite (and its porphyry) and the Lower Triassic carbonate rocks. Based on the mineral assemblages and their macro/microscopic textural relationships, the Tonglushan Cu–Au–Fe mineralization/alteration can be divided into five stages: pre-ore (S1: skarn–potassic alteration), Fe ore (S2: retrograde alteration and Fe-oxides), Cu–Au ore (S3: quartz–sulfides), carbonate alteration (S4) and supergene alteration (S5). Apart from the major skarn and retrograde alteration and carbonate minerals, abundant fine-grained phyllosilicate minerals, including chlorite, white mica (illite, muscovite and phengite), smectite (montmorillonite and saponite) and kandite (kaolinite, dickite and halloysite) group minerals have been identified at Tonglushan by SWIR spectrometry. Integrating petrographic observations and SWIR spectral analysis, four alteration zones (with distinct phyllosilicate assemblages) have been distinguished from the intrusion outward: (I) ore-barren quartz monzodiorite and its porphyry (montmorillonite–illite–chlorite), (II) endoskarn close to the skarn–hydrothermal mineralization center (montmorillonite–illite–chlorite–kaolinite–dickite), (III) skarn–hydrothermal mineralization center (saponite–chlorite), and (IV) the external contact zone in (dolomitic) marble (montmorillonite–chlorite ± kaolinite ± dickite).For the Tonglushan altered rock samples, SWIR spectrometry has identified wavelength shifts in the Fe–OH, Al–OH and sub-Al–OH absorption features of chlorite, white mica–montmorillonite and kandite, respectively. Chlorite Fe–OH absorption occurs at longer wavelengths (>2,250 nm), white mica–montmorillonite Al–OH absorption occurs at unusually long (>2,212 nm) and short (<2,202 nm) wavelengths, and kandite sub-Al–OH absorption occurs at longer wavelengths (>2,170 nm) in strongly-altered skarn proximal samples. Moreover, the presence of kaolinite, dickite, saponite, actinolite, phlogopite and/or chlorite–quartz–sulfides veins in these samples can be used as new vectors to explore deep-level mineralization centers at Tonglushan. The distribution of various kinds of phyllosilicate alteration minerals at Tonglushan, especially the white mica and kandites (with higher crystallinity) in the deep contact zones, indicates that the neutral to acidic hydrothermal fluids may have been generated with the precipitation of Fe-oxides and sulfides. This study also highlights the potential of SWIR spectroscopy of phyllosilicate minerals for exploring concealed skarn orebodies in the MLYRB.

Removal of Ciprofloxacin with Aluminum-Pillared Kaolin Sodium Alginate Beads (CA-Al-KABs): Kinetics, Isotherms, and BBD Model

In recent years, the problem of water pollution caused by antibiotics has attracted wide attention. The common use of antibiotics represents a threat to both human health and environmental safety. The modification of kaolin clay is promising due to its high efficiency, easy operation, and low cost. In this study, a novel material, aluminum-pillared kaolin sodium alginate beads (CA-Al-KABs), was synthesized by gelling and solidification processes. The structure and chemical properties were characterized by various analytical methods. The influencing factors (such as adsorbent dosage, contacting time, pH, ion strength, temperature, and initial concentration) and adsorption mechanism of ciprofloxacin (CIP) were studied. Furthermore, adsorption kinetics, adsorption isotherms, and a Box–Behnken design (BBD) model were conducted. Moreover, CA-Al-KABs’ adsorption efficiency towards other antibiotics were also evaluated. The adsorption experiments showed that the acidic environment (pH = 4) was more favorable for the adsorption of ciprofloxacin. The adsorption kinetics of ciprofloxacin by CA-Al-KABs microspheres were confirmed to be more suitable with the pseudo-first-order kinetics model. The Langmuir isotherm model showed that the maximum adsorption capacity of CA-Al-KABs microspheres to ciprofloxacin was 68.36 mg/g at 308.15 K. The adsorption driving force of CIP near CA-Al-KABs may be the electrostatic attraction. Further, CIP could also form complexes with Ca2+ and Al—Al—OH on CA-Al-KABs, and thus CIP was attracted to the adsorbent. Adsorption thermodynamics showed that the adsorption process was exothermic, feasible, and spontaneous. In addition, the adsorption performance on other antibiotics indicated CA-Al-KABs’ broad application in the treatment of antibiotic wastewater.

Isomerization of α-pinene with a hierarchical mordenite molecular sieve prepared by the microwave assisted alkaline treatment

Abstract To develop effective catalysts for α-pinene isomerization reaction is important to get high valuable products. A hierarchical mordenite molecular sieve is prepared using alkaline treatment assisted by the microwave radiation. After the alkaline treatment, the relative crystalline decreases by ~20% and mesopores are introduced in the mordenite molecular sieve. Compared to conventional heating method, microwave assisted alkaline treatment exhibits a selective etching of zeolitic silicon atoms. Aluminum atoms adjacent to silicon atoms are extracted to form Al–OH hydroxyl groups. These extracted aluminum atoms are reconnected to zeolitic silicon atoms. Mordenite after microwave assisted alkaline treatment has a good dispersion of mesopores, higher retention of BrOnsted acid sites in 12-membered rings, and lower concentration of Lewis acid sites. The isomerization reaction of α-pinene suggests that alkaline treatment increases the accessibility of acid sites for α-pinene molecules. The hierarchical porosity increases the conversion of α-pinene from 46.1 to 94.7%. The yields for camphene and limonene increase by 17.0 and 5.4%, respectively. Disproportionation of limonene is inhibited when using microwave assisted alkaline treated mordenite due to a low concentration of Lewis acid sites. These results are important to propose a facile post modification method to realize a selective extraction of zeolitic framework atoms.

Different Insights into Silicate Rectorite Modification and Its Role in Removal of Heavy Metal Ions from Wastewater

In the field of water management, the separation of metal contaminants from wastewater is very important and challenging. This study systematically investigated the effect and underlying mechanism of silicate rectorite (REC) on the removal of heavy metal ions (Cr(VI) and Pb(II)) from wastewater. The adsorption and removal capacity of REC was further improved by its novel modification with ferric chloride hexahydrate. Compared to natural REC, the modified rectorite (Fe-REC) showed comparatively superior adsorption efficiency for both Cr(VI) and Pb(II) due to the chemisorption of Fe3+ on the REC surface as its oxidation state (Fe–O, Fe–OH, Fe–OOH). Adsorption on Cr(VI) attributed to the reaction between iron hydroxy complexes (FeOH2+, Fe(OH)2+ and Fe(OH)3(aq)) and Cr(VI) species (HCrO4− and CrO42−) in the aqueous solution. This reaction was perfectly consistent with the binding energy shifts in O 1s and Fe 2p species, as reflected by XPS analysis. While, the existence of –Al–OH and –Si–OH in silicate REC slurry reacted with PbOH+ colloids produced from lead ions hydrolysis to promote Pb(II) adsorption. Zeta potential after modification and removal occurred to shift positively or negatively to testify the adsorption of Fe3+ and heavy metal ions. Freundlich and Langmuir isotherms conformed adsorption process for Cr(VI) and Pb(II), respectively.

Understanding phosphate sorption characteristics of mineral amendments in relation to stabilising high legacy P calcareous soil

In China, excessive phosphorus (P) application in protected vegetable fields has led to high legacy P stores. Soil amendment with alum or dolomite is one of many best management practices (BMPs) used to reduce P losses in calcareous soils. However, both the kinetics and mechanisms of P sorption and soil available P in amended soils are understudied. Herein, both aspects were looked at under controlled conditions. Firstly, a sorption study which coupled P concentrations with poorly-crystalline Al hydroxides and dolomite was conducted. Results from this batch experiment showed that P sorption on poorly-crystalline Al hydroxides was homogenous and occurred mainly via displacement of inner-sphere hydroxyl (Al–OH) instead of the formation of AlPO4. However, the amount of sorbed P reached maximum sorption of 73.1 mg g−1 and did not change with further increase in P concentration. It was observed that P adsorbed onto the dolomite surface at low P concentrations, whereas hydroxyl replacement and uneven cluster precipitation of Ca3(PO4)2 occurred at high P concentrations. A second 90 day incubation experiment investigated changes to soil available P and sorption-desorption across variable rates of amendments (0–50 g kg−1). Results showed that alum amendment at a rate of 50 g kg−1 decreased soil CaCl2–P and Olsen-P concentrations by 91.9% and 57.8%, respectively. However, Olsen-P increased when the dolomite rates were <20 g kg−1. Phosphorus sorption-desorption of the amended soil showed alum had higher P sorption efficiency than dolomite at low addition rates (<10 g kg−1). However, soil amended with high dolomite rates (>10 g kg−1) could sorb more P in comparison with alum when P concentrations were increased. The P status of the amended soil was closely connected to the P sorption mechanisms on mineral amendments, soil P concentrations and soil properties.

Enhanced surface hydroxyl groups by using hydrogen peroxide on hollow tubular alumina for removing fluoride

Abstract A novel modified method of hollow tubular alumina was investigated for improving the ability to remove fluoride. In this paper, we designed two parts to improve the adsorption capacity of fluoride: (1) increased the exposed surface area by compounding hollow tubular structure; (2) hydroxylated with different concentrations of H2O2 from 0 to 10 wt%. The modified alumina had uniform hollow tubular and crystal form of γ-Al2O3. Modified hollow tubular alumina exhibited a good performance of 74.25% with 1% H2O2. The kinetic and thermodynamic were thoroughly explained to fit different models. It demonstrated that the pseudo-second-order model and Freundlich model, indicating that chemical and heterogeneous adsorption. The adsorptive velocities of 1% H2O2/Al2O3 were 8.07 × 10−8 and 1.39 × 10−6 m/s when the initial concentrations were 10 ppm and 100 ppm, respectively. The adsorption mechanism was discussed and the adsorbent was stable after adsorbing fluoride. The addition of hydrogen peroxide promoted the more hydroxyl groups, and the exchange hydroxyl groups with fluoride were the main mechanism of adsorption. The ratio of hydroxyl groups with the form of Al–O–OH and Al–OH descended from 80%, 29.3%–30.4%, 20.1%, respectively. These results show hollow structure and modified with H2O2 are the economic and environmental methods for enhancing to remove fluoride.

Water defluorination using granular composite synthesized via hydrothermal treatment of polyaluminum chloride (PAC) sludge

In this work, we newly synthesized granular composite (GASA) via hydrothermal treatment of polyaluminum chloride (PAC) and subsequently granulation pelleting with starch gel as an organic binder. The resulting composite was characterized with analytic instruments, and the feasibility of utilizing GASA as adsorbent for the removal of fluoride (F−) was tested in the batch and column experiments. The characterization results revealed that GASA possessed a spherical/porous framework consisting of aluminosilicate (i.e., ordered albite, NaAlSiO3O8). The results of final pH effect experiments and XRD/XPS analyses showed the dominant adsorption mechanisms of F− on GASA were electrostatic attraction by protonated surface Al–OH, ligand exchange between surface hydroxyl groups and F ions, and surface precipitation (i.e., cryolite formation). Based on the results of adsorption kinetics and adsorption isotherm, granulation resulted in the relatively slow kinetics of F adsorption compared to the powder type, but was preferred to retain good adsorption capacity. The regeneration possibility of GASA was also proven with the adsorption/desorption cyclic test. In the column study, 15-cm length of the GASA layer and the flow rate less than 0.85 mL min−1 were proposed to keep the satisfactory level of F in water. The experimental results offer a potential of PAC sludge-derived composite as adsorbent for the removal of F from water.

New synthesis routes and catalytic applications of ferrierite crystals. Part 2: The effect of OSDA type on zeolite properties and catalysis

Tailoring of physicochemical properties of synthetic zeolites is of paramount importance when these materials are applied as heterogenous catalysts. In this work, the effect of the synthesis system and in particular of the organic structure directing agent (OSDA) on acidity, crystal morphology, and catalytic behaviour of FER-type materials is studied. FER-type zeolites with similar Si/Al ratio and crystal size range 0.3–15 μm are synthesised by changing OSDA type or by adding surfactant. A crystallization kinetic analysis shows that the stability of the zeolitic phase strongly depends on the OSDA type. In particular, the crystallization time strongly affects the purity of the FER phase when tetrahydrofuran is used as a template. Furthermore, it is found that long amines as 1,8-diaminooctane can play a role of OSDA obtaining highly crystalline FER-type crystals and with a high Lewis acid sites concentration. FT-IR and 27Al-NMR analyses show that all of the synthesised samples possess different Lewis acid sites concentration associated with extra-framework Al–OH species that are not detected by NMR analysis. Catalytic tests in methanol-to-dimethyl ether reaction reveal that synthesised samples exhibit different catalytic behaviour. In particular, large (10–15 μm) FER-type catalyst synthesised with tetrahydrofuran suffer deactivation caused by a higher carbon deposit level. On the contrary, nano-sized FER-type crystals, prepared by using pyrrolidine as OSDA and a surfactant, exhibits high selectivity and considerable resistance to coke deposition.

Production of polyacrylonitrile/boehmite nanofibrous composite tubular structures by opposite‐charge electrospinning with enhanced properties from a low‐concentration polymer solution

AbstractPolyacrylonitrile (PAN)/boehmite nanofibrous composite tubular structures were fabricated from dilute polymer solutions using an opposite‐charge electrospinning method. The samples were characterized by X‐ray diffraction, Differential scanning calorimetry, scanning electron microscopy, Fourier‐transform infrared spectroscopy, fast Fourier transform, and tensile tests. The presence of boehmite nanoparticles in the electrospun PAN nanofibers prevented bead formation, resulting in uniform fibers with smaller diameters, and improved alignment from low‐concentration PAN polymer solutions. 1 wt% boehmite‐loaded nanofibrous composite tubular structure was selected as the optimal formulation to proceed with the crystallinity and tensile tests, which showed enhanced crystalline properties as well as an abrupt shift in tensile performance. The tensile properties of the nanofiber strongly depended on their crystalline properties. The strong intermolecular forces (hydrogen bonds) between the AlOH groups formed at the surface of boehmite nanoparticles and the polar CN groups along the polymer chains. In addition, the high electrical force between the two tips of the needles in the opposite charge set‐up can contribute to the control of electrical jet deposition instability when using a low‐concentration electrospinning solution, leading to enhanced properties.

Interfacial and electrical properties of nanolaminated HfO2/Al2O3 dielectrics on GaN with an AlN interlayer

In this work, we investigated the interfacial properties of AlN/GaN heterostructure with HfO2/Al2O3 (single bilayer) and HfO2/Al2O3/HfO2/Al2O3 (double bilayer) dielectrics prepared by atomic layer deposition (ALD). From capacitance–voltage measurements, significant frequency dispersion was observed for the single bilayer. The interface traps for the double bilayer showed the exponential dependence of trap time constant to the applied voltage, indicating the high quality and uniform interface, whereas the single bilayer deviated from this dependence, revealing the non-uniformity of oxide charges. According to current–voltage measurements, the double bilayer showed much lower leakage current than the single bilayer. X-ray photoelectron spectroscopy measurements showed that Hf–Al–O bonding formed wider region for the double bilayer. For the single bilayer, the outdiffusion of Ga atoms into the AlN layer and the formation of Al–OH were observed more significantly. This work indicates that the double bilayer is a promising dielectric on the AlN/GaN heterostructure.

Formation of Ni nanoparticles in Al2O3–SiO2 glass by reacting with hydrogen gas

Metal nanoparticles (NPs) are precipitated on the surface or within the glass; such glass has attracted considerable interest because of its potential practical applications in optics, electromagnetics, and biosensing devices. Although such glass has been prepared via the deposition of separately synthesized NPs or via secondary heating of glass doped with metal ions, developing a well-designed NP-doped glass still remains a formidable challenge. Here, we succeeded in precipitating Ni NPs on the surface and within the glass by heating the Ni2+-doped Al2O3–SiO2 glass under hydrogen gas. The Al2O3–SiO2 glass prepared via melt quenching comprised two phases in which the Ni2+ ions were preferentially bound in the Al3+-rich phase. When hydrogen gas was loaded, it diffused in the glass; then, Ni2+ ions were reduced to Ni atoms, concurrently forming Al–OH bonds. The reduction of Ni2+ ions was discussed in relation to the hydrogen diffusion and reaction with the Ni2+ ions. The optical absorption band at ~ 350 nm wavelength could be assigned to the surface plasmon resonance of Ni nanoparticles. The precipitated Ni NPs moved toward the glass surface, which were removed using an acid solution. Thus, Ni-free glass exhibited fast H2 and He gas diffusion rates compared to silica glass.

Physical and electrical properties of ALD-Al2O3/GaN MOS capacitor annealed with high pressure water vapor

High pressure water vapor annealing (HPWVA) was performed on GaN metal/oxide semiconductor capacitor with Al2O3 film prepared using atomic-layer deposition. The fixed charge density and interface trap density are significantly improved by applying HPWVA (0.5 MPa at 400 °C for 30 min). These results are mainly related to a reaction of the Al2O3/GaN structure with the diffused active H2O monomer derived from HPWVA. It was found that the oxidation and Al–OH formation occurred in the Al2O3 film and thin gallium oxide was formed at the Al2O3/GaN interface.

Enhanced Catalytic Performance of the FCC Catalyst with an Alumina Matrix Modified by the Zeolite Y Structure-Directing Agent

The surface acid property of γ-Al2O3 has been modified by a zeolite Y structure-directing agent (SDA). Thus, modified γ-Al2O3 as a matrix material was used in fluid catalytic cracking (FCC) catalysts, and its performance of cracking vacuum gas oil (VGO) was evaluated. In comparsion with unmodified γ-Al2O3, the modified matrix material exhibited superior catalytic performance with heavy oil conversion increased by 5.64%, enhancing the gasoline yield by 2.19% and the LPG yield by 3.00%. Characterization results indicated that the zeolite Y SDA modification effectively introduced Si species into the framework of γ-Al2O3. The interaction between hydroxyl groups on silanol and Al–OH led to the formation of bridged hydroxyl groups (Si–OH–Al), which are the origin of medium-strength Bronsted acid sites on the modified alumina matrix accounting for the enhanced catalytic performance of FCC catalysts.

Energy-efficient and simultaneous extraction of lithium, rubidium and cesium from lepidolite concentrate via sulfuric acid baking and water leaching

Lepidolite is a valuable mineral resources of lithium, rubidium and cesium. However, most researches only focused on the lithium extraction without recovery of rubidium and cesium, and most of these processes involved energy-intensive high-temperature roasting and/or mechanical activation. In this study, simultaneous extractions of lithium, rubidium and cesium from a lepidolite concentrate were conducted through a low-temperature sulfuric acid baking and water leaching route. The influence of the extraction process parameters were systematically investigated. An optimized baking and leaching condition was determined as follows: H2SO4 concentration 85 wt%, baking temperature 200 °C, acid-to-concentrate mass ratio 1.7:1, baking time 4 h, 88% concentrate particles <74 μm, and water leaching temperature 85 °C. Under the optimal condition, the maximum extractions of Li, Rb and Cs reached 97.1%, 96.0% and 95.1%, respectively. Besides, the chemical formula of the lepidolite mineral in the concentrate was determined as KLi1.6Al2.2Si3.2O10FOH via AMICS characterization. During the baking process, the lepidolite reacted with hot sulfuric acid to generate water-soluble but acid-insoluble sulfates, KAl(SO4)2, Al(SO4)OH·5H2O and Li2SO4, while the rubidium and cesium might be converted to RbAl(SO4)2 and CsAl(SO4)2 existing in the form of isomorphism in KAl(SO4)2.