Aluminum Species Research Articles

Surfactant‐Free and Microporous AlOOH/Al2O3 Nanosheets on TiO2‐Based Nanofibers: A Sustained‐Release Dominated Topotactic Transformation

AbstractUp to now, the synthesis of non‐ligand‐capped 2D transition‐metal nanostructures remained big synthetic challenges. Herein, ultrathin and microporous AlOOH/Al2O3 nanosheets were topologically grown on the surface of TiO2‐based nanofibers by a water‐only hydrothermal strategy starting from electrospun Al2O3/TiO2 nanofibers. The TiO2 nanofibers lowered the surface energy for the sustained‐released aluminum species and thereby allowed them in situ hydrated to laminar AlOOH. The metastable AlOOH tended to dehydrate to Al2O3 simultaneously, leaving a well‐maintained 2D structure with sharp corners and steps, as well as enriched micropores. The nanosheets‐on‐nanofibers exhibited 2856–3370 mg/g of adsorption capacity toward RhB and an efficient removal efficiency over 70% at high throughput (30 mL/h). The promoted light‐harvesting by the perpendicularly attached nanosheets further endowed a significant photodegradation for RhB within 1 h. The presented green and facile approach toward the fabrication of 2D metal oxide nanostructures paves the way to a new variety of oxide nanomaterials.

Partitioning behavior and mechanisms of rare earth elements during precipitation in acid mine drainage

Rare earth elements (REEs) are frequently found concentrated in acid mine drainage (AMD). The recovery of REEs from AMD has been successfully achieved using selective chemical precipitation. However, a portion of the REEs is often lost to the precipitates of the dominant metal contaminant ions. To better understand the REE partitioning behavior and mechanisms during the precipitation process, a systematic study was performed on both natural and synthetic AMD solutions. Precipitation test results show that REE removal was noticeably elevated at pH 4.0 after adding H2O2 to convert ferrous to ferric ions, causing nearly complete precipitation of iron. Solution equilibrium calculations suggested that the REE removal increase was realized through adsorption onto the surfaces of the ferric precipitates. The presence of aluminum species in the solutions reduced the adsorption of REEs on the ferric precipitates. Based on electro-kinetic test results, it was concluded that aluminum species neutralize the negative surface charge of the ferric precipitates and compete with REEs for the adsorption active sites. The presence of ferrous ions in the solutions reduced REE adsorption on the aluminum precipitates at lower pH values (e.g., 5.0) due to competitive adsorption. However, at higher pH values (e.g., 6.0), REE removal to the precipitate product increased due to the precipitation of ferrous ions. In addition to the electro-kinetic tests and solution equilibrium calculations, mineralogy characterization, specific surface area measurement, particle size analysis, and morphology analysis were also conducted to investigate and identify the partitioning mechanisms.

Acidity and Aluminum Speciation in Biochar Amended Tropical Soils

ABSTRACT Soil acidification in the tropics has become a more pressing issue due to its associated aluminum (Al) phytotoxicity. The chemical reactive nature of biochar can alter Al speciation in soils. The study assessed the chemical properties and Al speciation in a Ultisol and an Oxisol amended with corn cob (CC) and rice husk (RH) biochars charred at 300, 450 and 650°C in an incubation study for 120 d. pH was determined periodically while organic carbon (OC), cation exchange capacity (CEC), exchangeable base cations, exchangeable acidity, and exchangeable Al3+ were measured at the end of the incubation period. Dissolved organic carbon (DOC) and pH were also determined in soil solution from each treatment. Throughout the incubation period CC and RH biochars significantly increased soil pH, with CC biochar showing a greater effect. Similar effects were also observed for OC, CEC, and exchangeable base cations (Ca2+, Mg2+ and K+). Soil exchangeable Al3+ and exchangeable acidity, soluble Al and Al3+ activity in soil solution decreased significantly upon biochar application; it was more significant at the 650°C. Biochars at 300–450°C exhibited a more notable increase in soil DOC. At pH ≤ 5.8, Al-DOC and free Al3+ dominated in soil solution while at pH > 5.8, Al species was mainly Al-OH ions (i.e. Al(OH)2+, Al(OH)2 +, Al(OH)3, and Al(OH)4 −). Biochars at 300–450°C promoted the large formation of Al-DOC while Al-OH ions dominated in 650°C-biochar treatments. Biochar can be used to ameliorate Al phytotoxicity in tropical acid soils, particularly at 300–450°C.

Additive manufacturing of sodalite monolith for continuous heavy metal removal from water sources

Herein, we present a simple strategy for preparing monolithic sodalite adsorbents via sequential additive manufacturing and post-treatments. In detail, the method includes (i) 3D printing of cylindrical monoliths using clay as the base material; (ii) thermal activation of the 3D-printed clay monoliths by calcination (to produce reactive alumina and silica species and enable mechanical stabilization); (iii) conversion of the activated clay monoliths to hierarchical porous sodalite monoliths via hydrothermal alkaline treatment. Parametric studies on the effect of calcination temperature, alkaline concentration and hydrothermal treatment time on the property of the resulting materials (such as phase composition and morphology) at different stages of preparation was conducted. Under the optimal conditions ( i.e. , calcination temperature of 850 °C, NaOH concentration of 3.3 mol⋅L −1 , reaction temperature of 150 °C, and reaction time of 6 h), a high-quality pure sodalite monolith was obtained, which possesses a relatively high BET surface area (58 m 2 ⋅g −1 ) and hierarchically micro-meso-macroporous structure. In the proposed application of continuous removal of heavy metals (chromium ion as the model) from wastewater, the developed 3D-printed sodalite monolith showed excellent Cr 3+ removal performance and fast kinetics (∼98% removal efficiency within 25 cycles), which outperformed the packed bed using sodalite pellets (made by extrusion).

Enhanced Catalytic Performance through In Situ Encapsulation of Ultrafine Ru Clusters within a High-Aluminum Zeolite

Zeolite-encapsulated metal clusters have been shown to be an effective bifunctional catalyst for tandem catalysis. Nevertheless, the efficient encapsulation of nanometric metal species into a high-aluminum ZSM-5 zeolite still poses a significant challenge. In this contribution, we have prepared well-dispersed and ultra-small Ru clusters encapsulated within a high-aluminum ZSM-5 zeolite (with a Si/Al ratio of ∼30–40) via an in situ two-stage hydrothermal synthesis method. Small Ru clusters with an average size of ∼1 nm have been identified by scanning transmission electron microscopy and hydrogen chemisorption. Shape-selective hydrogenation experiments with different probe molecules reveal a predominant encapsulation (∼90%) of metal clusters within the MFI zeolite cavities, which significantly enhances thermal stability of metal clusters against sintering. 27Al magic angle spinning nuclear magnetic resonance and Brønsted acid site (BAS) titration experiments show the successful incorporation of aluminum species (>99%) into the zeolite framework and build-up of intimacy between the Ru clusters and BASs at a sub-nanometric level. The resulting Ru@H-ZSM-5 shows an enhanced activity and stability for the crucial hydrodeoxygenation (HDO) of phenol to cyclohexane, in biomass valorization. This synthesis strategy could be of great help for the rational design and development of zeolitic bifunctional catalysts and could be extended to other crystalline porous materials.

New insights on the effect of the hydrolysing agents in the synthesis of pristine fibrous silica zeolite X for enhancement of side chain methylation of toluene: Theoretical and experimental studies

This article aims to clarify the role of hydrolysing agent in the synthesis of a pristine fibrous silica zeolite X (FZX) catalyst using DFT simulation, thermodynamics, and experimental data. FZX was fabricated using various hydrolysing agents such as urea (FZXU), formamide (FZXF) and N, N methylenediacrylamide (FZXN), to perform the side chain methylation of toluene process. It was found that disparity of hydrolysing agents resulted in different degree of silica hydrolysation which eventually altered the each FZX catalyst properties. Based on the chemical reactivity and visualized charge distributions as revealed by the DFT simulations, it was discovered that most electronegative regions located around negatively charged oxygen in hydrolysing agents structure exhibited a higher degree of silica hydrolysation resulted in excellent catalyst behaviour. Higher density of dendrimeric silica fiber in FZXN reduced the coke formation and induced the formation of extra-framework alumina (EFAl) species. The hydrolysing agents also affect the basicity of the decorated FZX catalyst and followed the sequence FZXN > FZXU > FZXF. The FZXN exhibited higher side chain methylation of toluene catalytic activity of 57 % toluene conversion and 49.6 % of styrene and ethylbenzene yield. Furthermore, a thermodynamic analysis was carried out, and it was discovered that the Boudouard reaction was the primary source of carbon deposition during the side chain methylation of toluene.

The impact of k-value-based aluminium speciation and basicity of coagulants on flocs resistance to breakage

The impact of k-value-based aluminium speciation and basicity of coagulants on flocs resistance to breakage

Comparative Study of Aluminum (Al) Speciation on Apoptosis-Promoting Process in Pc12 Cells: Correlations between Morphological Characteristics and Mitochondrial Kinetic Disorder

Comparative Study of Aluminum (Al) Speciation on Apoptosis-Promoting Process in Pc12 Cells: Correlations between Morphological Characteristics and Mitochondrial Kinetic Disorder

Coloured hybrid materials: exploiting an emergent surface property of fluorinated Al2O3 containing anthocyanins and betacyanins

Not just simple colours: inorganic matrixes were evaluated to characterize aluminium and fluorine species ([AlO45−], [AlO57−], [AlO69−], [AlF4−], [AlF52−] and [AlF63−]) by PXRD, XPS, 27Al MAS-NMR and IR-ATR.

Comparative Study of Aluminum Speciation on Brain-Type Creatine Kinase: Enzyme Kinetic, Molecular Docking, Cellular Experiment, and Mouse Model Study

Comparative Study of Aluminum Speciation on Brain-Type Creatine Kinase: Enzyme Kinetic, Molecular Docking, Cellular Experiment, and Mouse Model Study

Characteristics and Mechanisms of As(Iii) Removal by Potassium Ferrate Coupled with Al-Based Coagulants: Analysis of Aluminum Speciation Distribution and Transformation

Characteristics and Mechanisms of As(Iii) Removal by Potassium Ferrate Coupled with Al-Based Coagulants: Analysis of Aluminum Speciation Distribution and Transformation

Global optimization of extraframework ensembles in zeolites: structural analysis of extraframework aluminum species in MOR and MFI zeolites.

Metal-modified zeolites are versatile catalytic materials with a wide range of industrial applications. Their catalytic behaviour is determined by the nature of externally introduced cationic species, i.e., its geometry, chemical composition, and location within the zeolite pores. Superior catalyst designs can be unlocked by understanding the confinement effect and spatial limitations of the zeolite framework and its influence on the geometry and location of such cationic active sites. In this study, we employ the genetic algorithm (GA) global optimization method to investigate extraframework aluminum species and their structural variations in different zeolite matrices. We focus on extraframework aluminum (EFAl) as a model system because it greatly influences the product selectivity and catalytic stability in several zeolite catalyzed processes. Specifically, the GA was used to investigate the configurational possibilities of EFAl within the mordenite (MOR) and ZSM-5 frameworks. The xTB semi-empirical method within the GA was employed for an automated sampling of the EFAl-zeolite space. Furthermore, geometry refinement at the density functional theory (DFT) level of theory allowed us to improve the most stable configurations obtained from the GA and elaborate on the limitations of the xTB method. A subsequent ab initio thermodynamics analysis (aiTA) was chosen to predict the most favourable EFAl structure(s) under the catalytically relevant operando conditions.

Extending chain growth beyond C1 → C4 in CO homologation: aluminyl promoted formation of the [C5O5]5- ligand.

(NONDipp)Al-K(TMEDA)2 (NONDipp = [O(SiMe2NDipp)2]2-, Dipp = 2,6-iPr2C6H3), containing an Al-K bond, activates and reductively couples cabon monoxide gas to form the [C4O4]4- ligand. This oxocarbon anion is thermally isomerised in the presence of CO and TMEDA. In contrast, the dimeric potassium aluminyl [K{Al(NONDipp)}]2 yields an aluminium complex containing the hitherto unknown [C5O5]5- ligand.

Synthesis of hollow HZSM-5 zeolite-based catalysts and catalytic performance in MTA reaction

Although HZSM-5 zeolite is more and more widely used in petrochemical industry and other fields, its single narrow micropore system often leads to mass transfer issues during some types of catalytic reactions. In addition, dealumination in the presence of steam and coking due to the presence of strong acids sites are issues of aluminosilicate catalysts in general. In this work, a simple post-treatment method based on the traditional prepared HZSM-5 catalyst was proposed and an outlayer SiO2 encapsulated Gd/HZSM-5 catalyst with hollow and hierarchical porous systems ([email protected]/Z5-T) was obtained. This catalyst can overcome those defects for the traditional HZSM-5 mentioned above, such as, the outermost SiO2 layer can protect the aluminum species in the framework of Gd/HZSM-5 and cover part of strong acid sites, and the hollow and hierarchical porous systems can minimize the mass transfer resistance, etc. The [email protected]/Z5-T catalyst exhibited high selectivity of BTX (65.7%), especially xylene (39.7%), in the methanol to aromatics reaction (MTA) owing to the suitable acidity and optimized porous system. In addition, the [email protected]/Z5-T catalyst possessed much better hydrothermal stability and the excellent anticoking ability in the MTA reaction as expected. Thus, this should be a general method for the modification of silica alumina molecular sieve catalysts to obtain the novel catalyst with hollow and hierarchical porous systems, adjustable acidity and high hydrothermal stability.

A volumetric and intra-diffusion study of solutions of AlCl3 in two ionic liquids - [C2TMEDA][Tf2N] and [C4mpyr][Tf2N

Intra-diffusion coefficients (DSi) have been measured for the ionic liquid constituent ions and aluminium-containing species in aluminium chloride (AlCl3) solutions in the ionic liquids 1-(2-dimethyl-aminoethyl)-dimethylethylammonium bis(trifluoromethylsulfonyl)amide ([C2TMEDA][Tf2N]) and N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C4mpyr][Tf2N]), to investigate whether spectroscopically detected interactions between the ions and AlCl3 affect these properties. Such electrolyte solutions are of interest for the electrowinning of aluminium. The temperature, composition and molar volume dependences are investigated. Apparent (Vϕ,1) and partial molar (V1) volumes for AlCl3 have been calculated from solution densities. For [C2TMEDA][Tf2N] solutions, Vϕ,1 increases with increasing solute concentration; for [C4mpyr][Tf2N] solutions, it decreases. In pure [C2TMEDA][Tf2N], the cation diffuses more quickly than the anion, but this changes as the AlCl3 concentration increases. In the [C4mpyr][Tf2N] solutions, the intra-diffusion coefficient ratio remains equal to that for the pure ionic liquid and the aluminium species diffuses at approximately the same rate as the anion at each composition. The intra-diffusion coefficients can be fitted to the Ertl-Dullien free volume power law by superposing the iso-concentration curves with concentration dependent, but temperature independent, molar volume offsets. This suggests that they are primarily dependent on the molar volume and secondarily on a colligative thermodynamic factor due to dilution by AlCl3. AlCl3 complexation by [Tf2N]- and [C2TMEDA]+, confirmed by 27Al, 15N and 19F NMR spectroscopy, seems to play a minor role. Our results indicate that the application of free volume theories might be fruitful in the study of the transport properties of ionic liquid solutions and mixtures.

Mesoporous sodium four-coordinate aluminosilicate nanoparticles modulate dendritic cell pyroptosis and activate innate and adaptive immunity.

Pyroptosis is a programmed cell death widely studied in cancer cells for tumour inhibition, but rarely in dendritic cell (DC) activation for vaccine development. Here, we report the synthesis of sodium stabilized mesoporous aluminosilicate nanoparticles as DC pyroptosis modulators and antigen carriers. By surface modification of sodium-stabilized four-coordinate aluminium species on dendritic mesoporous silica nanoparticles, the resultant Na-IVAl-DMSN significantly activated DC through caspase-1 dependent pyroptosis via pH responsive intracellular ion exchange. The released proinflammatory cellular contents further mediated DC hyperactivation with prolonged cytokine release. In vivo studies showed that Na-IVAl-DMSN induced enhanced cellular immunity mediated by natural killer (NK) cells, cytotoxic T cells, and memory T cells as well as humoral immune response. Our results provide a new principle for the design of next-generation nanoadjuvants for vaccine applications.

The role of curing temperature and reactive aluminum species on characteristics of phosphate geopolymer.

The reaction of an acid phosphate with ferro/aluminosilicate materials is a slow-setting process at room temperature that requires several days to harden. Thus, various setting accelerators are generally used to achieve quick setting and demolding in a short period. This work aims to evaluate the benefits of phosphoric acid-containing soluble aluminum and heat curing on accelerating the reaction kinetic and strength development of phosphate geopolymers. The diluted phosphoric acid (PA, 50 wt%) and acid aluminum phosphate (PA, 50 wt%, Al/P = 1/3) solutions were prepared to activate volcanic ash, and the samples were cured at 20, 40, and 60 °C to produce the phosphate geopolymer binder. The phosphate geopolymer's reaction kinetics, mechanical properties, mineralogy, and microstructure were evaluated. The results revealed that when volcanic ash was activated with diluted phosphoric acid, the reaction mechanism that prevailed was the dissolution-enhancement-precipitation-condensation, and was also fostered when the heat curing was applied. While for the acid aluminum phosphate-activated volcanic ash, the mechanism is dissolution-inhibition-precipitation-condensation. That difference in reaction mechanism led to a higher compressive strength improvement at an early age (1 d, 3 d) for room temperature cured acid aluminum phosphate activated volcanic ash. In contrast, phosphoric acid-activated volcanic ash phosphate geopolymer developed a higher compressive strength at a late age (28 d). Moreover, heat curing is the most crucial parameter having a beneficial effect on compressive strength development as compared to acid aluminum phosphate activating solution.

Effect of rare earths on acidity of high-silica ultrastable REY zeolites and catalytic performance of NiMo/REY+Al2O3 catalysts in vacuum gas oil hydrocracking

A series of low-sodium ultrastable Y zeolites (SiO 2 /Al 2 O 3 ≈ 25) partially exchanged with different amounts of rare earth ions (RE 2 O 3 = 0.55–3.32 wt%) was prepared and characterized by XRD, IR spectroscopy, elemental analysis, N 2 adsorption, as well as 29 Si and 27 Al NMR. The effect of RE content on the number and relative strength of acid sites of REY zeolites was studied by IR spectroscopy of absorbed CO and pyridine. The increase in the RE content in the zeolites leads to a decrease in the concentration of strong Brønsted acid sites (BAS) in faujasite cages (bridged Si–O(H)–Al groups), especially the concentration of stronger BAS associated with Si–O(H)–Al groups polarized by extra-framework aluminum species. At the same time, the concentration of less acidic OH groups connected with extra-framework ions increases possibly due to the formation of additional RE–O(H)–Al groups. The total number of BAS in all the samples remains close. An increase in the RE 2 O 3 content from 0.55 to 3.32 wt% decreases almost by half the ratio of strong BAS in faujasite cages to less acidic extra-framework BAS. The catalytic performance of NiMo/(30 wt% REY + 70 wt% Al 2 O 3 ) catalysts was evaluated in hydrocracking of vacuum gas oil. The enhanced hydrocracking activity and selectivity to middle distillates are mainly achieved due to the optimal acidity of the zeolites. • Synthesis of USY zeolites (Si/Al≈12.5) exchanged with different amount of RE ions. • Strong BAS/less acidic extraframework BAS ratio decreases with RE content increase. • Stronger BAS (Si–O(H)–Al groups polarized by EFAL species) are exchanged first. • Additional BAS are associated with the formation of RE–O(H)–Al groups in supercages. • NiMo/REY + Al 2 O 3 with optimal acidity exhibits improved hydrocracking performance.

Dehydration of methanol and ethanol over ferrierite originated layered zeolites - the role of acidity and porous structure.

Ferrierites and their delaminated (ITQ-6) and silica intercalated (ITQ-36) forms, with the intended molar Si/Al ratios of zeolite layers of 30 and 50, were synthesized and tested as catalysts of methanol to dimethyl ether (DME) as well as ethanol to diethyl ether (DEE) and ethylene dehydration. It was shown that increased content of acid sites, especially of Brønsted type, resulted in more active catalysts of alcohol dehydration. Brønsted acid sites dominate in ferrierites and their delaminated forms (ITQ-6). Contribution of the Lewis type of acid sites increased in silica pillared ferrierites (ITQ-36) possibly by deposition of aluminium species on the surface of amorphous silica. Conversion of methanol to DME was not limited by internal diffusion of reactants in narrow pores of ferrierite. Such limitation was observed for synthesis of larger DEE molecules over ferrierites. The ITQ-6 catalysts with the opened interlayer structure presented better efficiency in ethanol to DEE conversion due to overcoming these diffusional restrictions. Moreover, selectivity to DEE over ITQ-6 was higher than in the presence of three-dimensional ferrierite.

Identifying Key Residual Aluminum Species Responsible for Aggravation of Nanofiltration Membrane Fouling

Identifying Key Residual Aluminum Species Responsible for Aggravation of Nanofiltration Membrane Fouling