Aluminum Source Research Articles

Synthesis of Cu-Al layered double hydroxides from aluminum saline slags

The use of saline slag, a hazardous waste generated during the recycling of aluminum, as aluminum source for the synthesis CuAl layered double hydroxides (LDH) is for the first time reported in this study. Due to the Jahn-Teller effect, divalent copper–aluminum LDH come usually with impurities and a pure CuAl LDH is not easy to obtain. The effect of synthesis pH has been examined by comparing LDH synthesized at various pH, ranging from 6 to 12 via a co-precipitation method using aluminum obtained from an alkaline extraction of the slag. For comparison purposes, a sample was synthesized at pH = 9 using commercial aluminum Al(NO3)3·9H2O instead of extracted aluminum. The effects of the aging time and calcination temperature are also discussed. The LDH and their calcined metal mixed oxide (layered double oxide, LDO) have been analyzed with several characterization techniques: powder X-ray diffraction (PXRD), N2 adsorption at −196 °C, thermogravimetric analysis (TGA), temperature programmed reduction (TPR), scanning electron microscopy (SEM), transmission electron microscopy and energy-dispersive X-ray spectroscopy (TEM and EDS). Synthesis pH has been proved not only to have a significant effect on the nature of secondary phases but also on the structure and morphology of the samples.

Simultaneous adsorption of Cu(II), Zn(II), Cd(II) and Pb(II) from synthetic wastewater using NaP and LTA zeolites prepared from biomass fly ash

Herein, NaP and LTA zeolites were successfully synthesised from woody biomass ash with alkali fusion-assisted hydrothermal method by altering the NaOH/ash ratio, crystallisation time and crystallisation temperature. In order to reduce the synthesis costs, NaP zeolite was synthesised with no additional source of aluminium and silicon. The synthesised zeolites were utilized for the monocomponent and simultaneous adsorption of Cu(II), Cd(II), Pb(II) and Zn(II) ions. The maximum adsorbed amount of metals had the trend Pb(II) > Cu(II) > Cd(II) > Zn(II) for both NaP and LTA zeolite. The kinetic data fit well to the pseudo-second order model indicating that chemisorption is the rate-limiting step. The isotherm data were well described with Sips and Redlich-Peterson models indicating a non-ideal heterogeneous adsorption process. Maximum adsorption capacity of NaP zeolite was 42.9 mg/g for Cu(II) and 117.3 mg/g for Cd(II), while LTA had 140.1 mg/g and 223.5 mg/g for Cu(II) and Cd(II) ions, respectively.

Effect of low-calcium fly ash inclusion on long-term mechanical properties and durability of ground granulated blast furnace slag-based cement-free mortars

The present study focused on fabricating cement-free mortar based on ground granulated blast furnace slag incorporating low-calcium fly ash as precursors in an alkaline solution of sodium hydroxide and sodium silicate. The main purposes of the study were not only to find the optimum mixture proportions to confirm the fly ash role in contributing to the long-term mechanical properties and durability but also to expand the use of fly ash in cement-free binders based on ground granulated blast furnace slag. The ground granulated blast furnace slag was replaced with fly ash in the cement-free mortar at various levels of 30, 40, 50, 60, and 70% by mass. The cement-based sample as a control sample was prepared for comparison purposes. Results showed that the cement-free mortar samples with fly ash had the more superior long-term mechanical properties (i.e. flexural and compressive strengths and volumetric compaction via ultrasonic pulse velocity test) and durability (i.e. total charge passed via rapid chloride penetration test and sulfate resistance via length change of samples exposed to sulfate solution), lower water absorption and porosity, and denser microstructure than the control sample up to 120 days. The 40% replacement of ground granulated blast furnace slag by fly ash as an auxiliary source of alumina and silica was the optimum ratio in enhancing the long-term mechanical properties and durability of the cement-free mortar samples, which is in agreement with reducing the porosity and water absorption. The results of the environmental analysis indicate that using cement-free mortar samples has much lower environmental impacts. The cement-free mortar sample using 60% ground granulated blast furnace slag and 40% fly ash is found as an optimal mixture in terms of technical and environmental features.

Synthesis of Nanostructured Alumina from Byproduct Aluminum Filings: Production and Characterization

Aluminum oxide production from aluminum filings, which are a byproduct of several industrial machining processes and cannot be recycled to attain bulk aluminum (Al), is vital due to its wide use in scientific research and industry. The goal of this paper is to produce ultrafine and down-to-the-nanoscale alumina powder (Al2O3), starting from a waste Al filings. The microstructure and composition of the starting Al used were investigated using scanning electron microscopy (SEM), which was equipped with an attached energy dispersive spectrometer (EDS) unit. The results of this investigation confirmed that the starting Al was mainly Al–Mg alloy. Al2O3 was produced using two routes: The first involved the burning of aluminum hydroxide Al(OH)3 that was precipitated from aluminum chloride solution (AlCl3) resulting from dissolving the Al filings in 2M HCl. The second route involved direct precipitation as a reaction product of aluminum chloride with sodium carbonate solution. The Al2O3 produced using both routes, as well as the intermediate product Al(OH)3, were studied by SEM. The results demonstrate that the nanoscale range size was reached after milling of the produced Al2O3. Following thorough washing with distilled water, the EDS and the XRD techniques confirmed the formation of Al2O3, with no residual salt detected. The EDS results showed that the ratios of Al and O in the produced Al2O3 were about 96% of the ideal compound ratios. The XRD analysis also revealed the amorphous structure of the standard and the produced Al(OH)3, whereas the phases of the produced Al2O3 were either crystalline or amorphous. In our study, the Al2O3 percentage yield was about 77%, and this value obviously depends on the percentage of Al dross in the original Al filings. Overall, this research provides a novel contribution to the production of alumina powder in the nano-range starting from an aluminum filings byproduct, thereby reducing the dependence on known sources of aluminum.

STUDYING THE FORMATION AND STABILIZATION OF CUR-AL+3 COMPLEXES BY USING CITRIC ACID AS CATALYST

Cooking ware that is made of aluminum is used in different nations, particularly developing nations, and are a free source of aluminum. Due to its possible harmful effects on human health, aluminum is acknowledged as a public health problem. The goal of the current investigation is to evaluate curcumin's (CUR) capacity to decrease aluminium’s toxicity by forming stable complexes. Rhizomes that are sold in the local marketplaces have an 8.5% crude pigment content of CUR. At various pH levels, CUR's maximum absorbance was identified. Citric acid was used as a catalyst to create the CUR-Al+3 combination at various pH levels, which correspond to the rates at which Al+3 was eliminated from the solution. At pH 2.5, 3.0, 3.5, and 4.0, the highly complexation was seen. At such pH levels, the Al+3 elimination was 79.22, 78.28, 79.26, and 79.41%, respectively. The CUR-Al+3 complexes’ stability represent, respectively, 96.94, 96.29, 95.55, and 95.52% of the initial concentration at 25o, 50o, 75o, and 100o C for 60 min at pH value of 2.50. Using Fourier-transform infrared spectroscopy (FT-IR), it has been possible to identify CUR and its complex with Al+3. At varied pH levels, 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5 at boiling point, the leached aluminium from 3 regions of the aluminium cooking ware (Syrian, Iranian and local) was specified. Comparatively to Syrian and local cooking wares, Iranian cooking ware generally leached more aluminum. In comparison to other pH values, the percentages of the elimination of the aluminum that is leached by utilizing the most leaching cookware (Iranian) have been 79.23 and 79.26% at pH values of 2.50 and 3.50, respectively.

Hydrothermal synthesis of kaolin-based ZSM-5 zeolite: Effect of synthesis parameters and its application for bioethanol conversion

In petrochemical applications, improving the catalytic activity and stability of Zeolite as a cutting-edge material has gained research interest. Herein, a local South African clay as a source of high silica and alumina with an organic template of tetrapropylammonium bromide (TPABr) was synthesized hydrothermally. The study then examined the effect of crystallization temperature (120–180 °C), crystallization time (24–96 h) and ageing time (0–48 h) on the crystallinity, surface morphology and functional group of the Kaolin-based ZSM-5 Zeolite formed. Characterization results by X-ray diffraction, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the hydrothermal synthesis of the crystalline powder was successful. The XRD revealed the highest intensity at ∑5 with the most intense peaks at 2Ѳ° and a relative crystallinity from 74.6% to 76.66% at the temperature of 180°C and 48 h of ageing and crystallization time of sampled powder. The crystals' growth and pore structure (openings of 5–5.5 Å) was affirmed by the SEM results. Likewise, the BET revealed the surface area (146.15 m2/g), pore volume (0.056 cm3/g) and pore size (59.12 Å). The FTIR spectra vibration within the wavenumber from 545 to 1224 cm−1 also confirmed the sharpness of the beta and pentasil index peaks. Moreso, the bioethanol conversion at the temperature of 180°C over the synthesized ZSM-5 catalyst yielded 2.03% H2, 1.03% CH4, 37.07% C2H4, and 62.4% liquids. This study has demonstrated the synthesized Kaolin-based ZSM-5 Zeolite has the potential for industrial decomposition of ethanol with good catalyst stability.

CaAlFe–mixed metal oxides prepared from an aluminum salt–cake and their evaluation as CO2 sorbents at moderate temperature

Potentially–CO2 adsorbing solids at moderate temperature have been prepared by calcination at 400 °C and 750 °C of CaAlFe hydrocalumites (a sort of Ca2+–layered double hydroxide), which had been prepared using a salt cake as aluminum source. The characterization of the obtained solids was carried out by powder X–ray diffraction, FT–infrared spectroscopy, thermal analysis, N2 adsorption–desorption isotherms at –196 °C and electron microscopy. After calcination, different crystalline phases were identified as a function of the amount of Fe3+ incorporated. Static sorption equilibrium experiments were performed at 300 °C and pCO2 = 0.3 bar. The CO2 sorption capacity was affected by the presence of different phases in the CaAlFe–mixed oxides (MMOs), being maximum when the amount of Fe3+ was 40 mol % of the trivalent positions. No differences in CO2 sorption capacities were observed between CaAlFe–MMOs–400 and CaAlFe–MMOs–750 (materials calcined respectively at 400 and 750 °C), suggesting that CO2 sorption capacity was not related to SBET. Experiments under dynamic conditions at 400 °C and pCO2 = 0.15 bar showed good behaviors for CaAl–400, CaAl0.60Fe0.40–400 and CaFe–400. In addition, CaAl0.60Fe0.40–400 was evaluated in several CO2 sorption–desorption cycles in the presence of water vapor, finding that the steam presence enhanced the CO2 capture.

Effect of alkali doping on the preparation of calcium aluminate by aluminum dross calcification process

The emission of hazardous aluminum dross is increasing with the rapid development of China’s aluminum industry. It is not only a waste of valuable aluminum resources, but also a serious ecological problem. Aluminum dross, calcium based additives, and trace alkaline additives are used for roasting reactions to achieve high-temperature synergistic detoxification. A new method for extracting valuable aluminum elements from aluminum dross has been proposed. The research results indicate that a small amount of sodium carbonate added to the aluminum dross calcination system can enable Na2O to solidly dissolve in 12CaO⋅7Al2O3 (C12A7). The crystal plane spacing and cell volume of C12A7 are increased, the structural activity of the crystal is improved, and the leaching performance of C12A7 is strengthened. High quality aluminum sources can be extracted and separated from other impurities that are insoluble in alkaline solution. Under the optimal roasting conditions, the aluminum leaching rate is 95.84%, and the removal rates of nitrogen, chlorine, and soluble fluorine elements all exceed 99%. The toxic components in aluminum dross are efficiently removed during the roasting process. The leaching reaction of calcium aluminate conforms to the unreacted core model controlled by internal diffusion. The crystal structure activity of calcium aluminate was enhanced by alkali doping, and the activation energy of the leaching reaction was 15.50 kJ mol−1.

Combination of natural silica and alumina sources for synthesis of MCM-22 zeolite

Zeolite has become a promising material that can potentially play a pivotal role in resolving environmental crises. Among zeolite families, MCM-22 zeolite shows outstanding intrinsic properties associated with the topology and porous structure, offering ion-exchange advantages for catalytic activity processes. The synthesis of MCM-22 zeolite becomes challenging when concerning the cost and catalytic performance. To overcome this bottleneck, we demonstrate a sustainable route of a hydrothermal process using natural resources as starting materials. Rice husk from agricultural waste was used as a silica source while natural clays (kaolin and bentonite) were applied as alumina sources. The products from natural sources were compared with the use of commercial starting materials, e.g., NaAlO2 (for alumina) and Na2SiO3 and TEOS (for silica), in points of crystal, compositional, and morphological views. We showed that the high purity of MCM-22 zeolite can be obtained from rice husk silica (RHS) and aluminosilicate gel (ASG) extracted from kaolin, while the use of ASG extracted from bentonite tended to be unsuitable to generate the zeolite formation. We also studied the effects of reaction time and the ratio of RHS/ASG on the crystallinity and surface area of MCM-22. The architecture and acidity of an optimal product were explored by Nuclear magnetic resonance spectroscopy and Temperature-programmed desorption of ammonia, demonstrating the success of achieving well acidity.

Pressure leaching of aluminum from kaolin by HCl: Experimental and DFT study

Kaolin is an important industrial mineral which has many industrial applications. It is also considered as an important source of aluminum; however, great technical challenges are required to be overcome to extract Al from kaolin. In this work, the extraction of aluminum from kaolin using HCl, as a leaching agent, was studied. Kaolin samples were collected from Wadi Al-Hafira, south of Jordan; these were crushed and ground to a particle size of 100% <75 μm. The ground samples were characterized in terms of chemical and mineral composition using X-ray fluorescence (XRF) and X-ray diffraction analysis (XRD) techniques. Kaolin was found to contain kaolinite, muscovite, and quartz as main mineral phases, in addition to anatase and hematite as trace mineral phases, while the chemical analysis revealed that kaolin contains about 36.1% Al2O3, 54% SiO2, 2.5% CaO, 1.96% Fe2O3 and 1.2% TiO2 as major oxides. The minor oxides were K2O, Na2O, and SO3. A microwave digestion vessel was used to provide a suitable environment for high pressure and temperature leaching. The effect of several leaching parameters was studied in this work including, leaching time (30 to 120 min), leaching temperature (80 to 200 °C), and molarity of leaching reagent (1, 2, 3 and 4 M). Additionally, two sources of HCl were used, including analytical grade HCl and HCl collected from the potassium sulphate industry. The extraction of four main elements were monitored during the leaching process employing ICP-OES multi element analysis technique, namely, aluminum, iron, titanium and silicon. The findings of this work suggest that the recovery of these elements increases with the increase of temperature and leaching time. The recovery of silicon decreased with the increase of acid molarity. Complete extraction of Al from kaolinite was obtained at temperatures above 180 °C and leaching time of 120 min, while Al present in muscovite was not amenable to leaching. However, traces of H2SO4 and chloride salts in waste HCl, from potassium sulphate industry, provided complete destruction of muscovite as evident from the XRD analysis of leach residues. Lower energy requirements (computed by DFT simulation) for chlorination of Al sites in reference to Si sites explains a higher recovery percentage of the former.

Pharmaceutical blister waste recycling using biogenic sulfuric acid: Effect of sulfur source and blister material on bioleaching efficiency

Several thousand tons of plastic are produced globally for pharmaceutical blister packages every year, leading to an expected consumption of over 2.8 million tons by 2026. Comprising a complex multilayer structure, blisters cannot be recycled in conventional recycling processes, leading to a loss of aluminium and valuable polymers during incineration and landfilling. As a promising secondary source of aluminium, new recycling strategies need to be developed to selectively separate the different layers. In this study, three types of blister packaging materials consisting of 13–68% (w/w) aluminium were investigated regarding aluminium and polymer recovery by using biogenic sulfuric acid for bioleaching. Waste elemental sulfur from biogas desulfurisation was assessed for biogenic sulfuric acid production by the two sulfur-oxidizing bacteria Acidithiobacillus thiooxidans and Acidithiobacillus caldus and compared to commercial elemental sulfur. For biogenic sulfur, higher sulfate production yield (320 mM), lower pH-value (pH = 0.56) and complete sulfur oxidation within 14 days was observed when compared to commercial sulfur. Application of a more concentrated biogenic acid (pH = 0.22) led to more effective and complete (∼100%) aluminium bioleaching up to 7.5% (w/v) blister waste within 7–9 days of incubation compared to 83% and 63% chemical leaching efficiency of transparent and white blisters using commercial sulfuric acid at the same pH, respectively. In addition, the plastic fraction after bioleaching was characterized and tested regarding re-processability. Results showed that sulfur from a biological origin can be oxidized faster by bacteria and biogenic acid is more effective in aluminium bioleaching compared to commercial sulfuric acid. Furthermore, results indicated that the plastic material is suitable for re-processing making this process an economically and environmentally friendly treatment option.

Synthesis, characterization, cytotoxicity and antimicrobial activity of a nanostructured mineral clay

Clay minerals nanostructured appear as an alternative to increase textural property and mechanical strength, such as montmorillonite (MMT-NPs). Nanocomposites are nanomaterials made up of a matrix and reinforcement, to obtain a higher quality nanomaterial. In parallel, (agro)industrial waste constitutes a major socio-environmental problem, such as rice husk (RH - a source of silica) and residual sludge (RS – a source of silica and aluminum). In this context, the present work aims to synthesize and characterize montmorillonite nanoparticles (MMT-NPs) for use as nanocomposite support to evaluate the safety profile in 293T embryonic kidney human and antimicrobial activity against E. coli, S. aureus and P. aeruginosa strains. X-ray diffraction (XRD) showed the presence of characteristic peaks of montmorillonite in the crystalline phases of the neighborite, muscovite, kaolinite and quartz low. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectra indicated the stretching of Si-O-Si (at 991.29 cm−1) and Si-O-Al at 470.54 cm−1. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) micrographs indicated a heterogeneous morphology with a semicube shape and composition containing sodium, aluminum, potassium, and magnesium. MMT-NPs showed type V isotherms with H3 hysteresis (mesoporous characteristics) and SBET = 18 ± 0.2 m2 g−1, Dp = 33.5 ± 0.5 nm with zeta potential (ZP) of the −18.2 ± 0.4 mV and a contact angle around 26.1°. Biological results showed a minimal antibacterial inhibition concentration against S. aureus, E. coli and P. aeruginosa of the 15.6, 500 and 500 mg L−1, respectively. Furthermore, the safety profile of MMT-NPs using 293T cells indicated the 100% concentration as safe (>60% cells) and showed the release of reactive oxygen species and nitrates and nitrites similar to the negative control. Therefore, it was possible to synthesize montmorillonite nanoparticles from rice husk and residual sludge for use as a nanocomposite matrix, correlating sustainability and environmental nanotechnology.

Lead, zinc, nickel and chromium ions removal from polluted waters using zeolite formed from bauxite, obsidian and their combination with red mud: Behaviour and mechanisms

Synthetic zeolites obtained combining natural sources (bauxite and obsidian), pure alumina/silica reagents, and waste material (red mud) were tested for heavy metals (i.e., Pb2+, Zn2+, Ni2+, Cr3+) removal. The adsorption capabilities of the formed sodalite, zeolite A and zeolite X (LTA and FAU topology, respectively), were compared through thermodynamic and kinetic experiments. Although all the newly-formed zeolites were able to remove the pollutant elements within 24 h, Zeolite X and sodalite synthesized combining obsidian (natural material as silica source) and red mud (waste material as alumina source) proved to be a better sorbent phase (qmax 20–25 mg g−1) compared to Zeolite A formed from treated bauxite (qmax 4–18 mg g−1). Their removal efficiency was also evaluated in polluted waters (wastewater treatment plant [WWTP] effluent, heavy metals mixture, native pH). Depending on synthesized zeolite type, the adsorption mechanism was accredited to ion exchange and precipitation mechanisms. The location of metal-ions inside the zeolite channels was defined by X-ray Powder Diffraction (XRPD) Rietveld analysis. Host–guest interactions among the framework oxygen atoms, co-adsorbed water molecules, and metal-ions were highlighted by the refined bond distances. Finally, magnetic characterization allowed the recognize of different magnetic properties as a function of raw materials used for zeolite synthesis.

Preparation of a High-Silicon ZSM-5 Molecular Sieve Using Only Coal Gangue as the Silicon and Aluminum Sources.

The traditional preparation of ZSM-5 molecular sieves relies on chemical reagents to provide silicon and aluminum sources, which are limited as raw materials and cannot be commonly used in production practice. Using coal gangue as the raw material and using medium-temperature chlorination roasting and the pressure acid leaching process to control the silicon-aluminum ratio [n(Si/Al)] of coal gangue, a ZSM-5 molecular sieve was prepared using the alkali melting hydrothermal method. The pressure acid leaching process solved the limitation that kaolinite and mica cannot simultaneously be activated. Under optimal conditions, the n(Si/Al) of the coal gangue increased from 6.23 to 26.14 and complied with the requirements for the synthesis n(Si/Al) of a ZSM-5 molecular sieve. The effect of n(Si/Al) on the preparation of the ZSM-5 molecular sieve was studied. Finally, spherical granular ZSM-5 molecular sieve material with a microporous specific surface area of 169.6329 m2/g, an average pore diameter of 0.6285 nm, and a pore volume of 0.0988 cm3/g was prepared. Providing ideas for the high-value utilization of coal gangue, it is significant for solving the problem of coal gangue solid waste, as well as the problem of ZSM-5 molecular sieve feed stock.

Engineering the Interface and Interaction Structure on Highly Coke-Resistant Ni/CeO2-Al2O3 Catalyst for Dry Reforming of Methane

Designing and tailoring metal-support interaction in Ni-based catalysts with plentiful interfacial sites is of significant interest for achieving a targeted catalytic performance in dry reforming of methane (DRM), but remains as a challenging task. In this work, Ni/Al2O3 and Ni/CeO2-Al2O3 catalysts with the same strong metal-support interaction (SMSI) but distinct interface structure are developed by an improved evaporation-induced self-assembly method using pseudobohemite gel as aluminum source. Ni/CeO2-Al2O3 exhibits superior catalytic activity and stability in DRM in comparison with Ni/Al2O3. The highest CH4 and CO2 conversion reaches at 71.4% and 82.1% for Ni/CeO2-Al2O3, which are higher than that of 64.3% and 75.6% for Ni/Al2O3 at 700 °C. The SMSI effect in Ni/CeO2-Al2O3 provides more active interfacial sites with less coke deposition, and promotes the generation of active formate species which are the key intermediates for DRM. The findings of the present work could possibly pave the way for fabricating catalysts with SMSI strategy for efficient heterogeneous catalysis.

Ultrafast Synthesis and Regulating Al Status of Mesoporous ZSM-48 Zeolite via a Pretreated-Seed-Solution-Assisted Strategy

Ultrafast synthesis of nanocrystal assembled mesoporous ZSM-48 zeolite spheres of highly crystalline was achieved within 1.5 h by using pretreated-seed-solution-assisted strategy. Interestingly, by altering the introducing sequence of aluminum source (in the pretreated seed solution or in the synthesis gel), the obtained ZSM-48 with similar particle size and total acid sites exhibited quite different crystallization behavior and acid property in terms of Al distribution and acid strength, because of the distinct local microenvironment (Al-rich or Al-free) in the pretreated seed solution. The HZ48-Al-pre (introduce an Al source to the pretreated seed solution) had more framework Al(IV) content and stronger acid strength than that of the HZ48-Al-post (synthesized by the Al-free pretreated seed solution). The corresponding Pt supported catalysts showed a great difference in the n-C12 hydroisomerization reation. The Pt/HZ48-Al-pre catalyst had a very low selectivity (41.1%), and the maximum iso-yield was only 35.5%. However, the ultrafast synthesizedPt/HZ48-Al-post-1.5h catalyst exhibited a superior selectivity (90.1%) with a total i-C12 yield of 82.3% at 330 °C, which was a high level in the exist literature reports.

Low-temperature synthesis of mullite by molten molybdenum trioxide assisted mesoporous aluminum source dissolution

Porous ceramics with more than 99% mullite (3Al2O3·2SiO2) content were fabricated at the low sintering temperature of 800 °C using silicon debris and mesoporous aluminum oxide (Al2O3) obtained from calcining aluminium hydroxide (Al(OH)3) as silicon source and aluminium source, respectively. The study found that adding ammonium molybdate tetrahydrate (AMT) as sintering additive allowed the complete mullitization reaction temperature of the raw materials to be reduced to approach the melting point of molybdenum trioxide (MoO3). Specifically, the silicon debris is continuously oxidized to silicon dioxide (SiO2) in the sintering process, prompting the formation of a silicon-rich liquid phase in the molten MoO3. Meanwhile, a large number of mesopores in the Al2O3 contributed to the dissolution of aluminum source in the silicon-rich liquid phase. Resultantly, synthesizing mullite can be performed at a temperature as low as 800 °C. Additionally, the research showed that the porous mullite ceramics sintered at this temperature had a flexural strength of 22.07 MPa, an open porosity of 52.58%, a linear shrinkage rate of 0.9%, and a bulk density of 1.49 g/cm3. This study not only presents a novel low-cost method for preparing porous mullite ceramics at low temperatures but also provides a simple method for the complete recycling of waste silicon debris.

Upcycling can seals into high-value boehmite-like for the synthesis of MnAl2O4: A circular economy approach

Boehmite is a mineral of aluminum oxyhydroxide widely used as a catalyst support, adsorbent for dyes, and a key component in producing advanced optical and electronic devices. This study focuses on the synthesis of boehmite using recycled metallic aluminum through acid digestion (HCl) and subsequent precipitation by pH correction (NaOH). The aluminum source used was can seals, which were characterized using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). XRD analysis confirmed a boehmite-like phase of the recycled aluminum oxyhydroxide powder. SEM analysis revealed that the synthesized boehmite-like powder consisted of agglomerate plates, which influences its thermal and optical behavior, resulting in a lower dihydroxylation temperature and smaller band gap (∼3.7 eV) compared to the literature value (∼5.5 eV) for boehmite. The boehmite-like powder derived from recycling was used as a precursor for the synthesis of manganese aluminate (MnAl2O4). XRD analysis confirmed the formation of the MnAl2O4 galaxite phase, with XPS and absorbance spectroscopy in the visible region indicating the presence of mainly Mn2+ ions. The resulting brown manganese aluminate powder exhibited stability in harsh chemical environments, with a color change imperceptible to the human eye. Moreover, a near-infrared (NIR) reflectance of approximately 50% was achieved, superior to other brown pigments reported in the literature. These findings suggest that recycled aluminum can seals in aluminate have potential applications as pigments for coatings.

High aluminum content in bone of marine mammals and its relation with source levels and origin

Although aluminum is widely distributed in the earth's crust, its environmental availability and wildlife assimilation rates are only partially known. Here we analyze aluminum concentrations in bone from 10 species of marine mammals inhabiting 3 geographic areas subject to different aluminum inputs: the Río de la Plata estuary (Uruguay), the coastal waters of Mauritania and the Galapagos archipelago (Ecuador). Overall, concentrations were unusually high as compared to those of terrestrial animals, with lowest concentrations in the Galapagos archipelago, then the Río de la Plata estuary and finally Mauritania. The aluminum source varied between regions, prevailing anthropogenic sources in the Río de la Plata Estuary and natural sources (wind-blown dust) in Mauritanian waters. The type of source determined contamination levels: anthropogenic sources were most significant for coastal species and showed a decline with distance of habitat from shoreline, while natural sources had a higher influence on open waters because of the dearth of biogenic silica that eliminates aluminum from the water column. Since aluminum remains in bone for several decades, marine mammal bone reflects historical levels of aluminum and therefore is a good bioindicator of the aluminum concentration of the marine environment.

Improved RFET Performance Using Dual-Aluminum-Contact (DAC)

This work presents for the first time the use of dual aluminum contacts (DAC) to improve the performance of reconfigurable field effect transistors (RFET), integrating two aluminum contact in BESOI MOSFET (with and without annealing process). Using TCAD simulations, the charge density in the channel region below the aluminum source contact depends on the channel thickness and bias in the programming gate. This thickness making possible to create a hole’s channel below the Schottky aluminum contact for silicon thickness below the aluminum contacts higher than 30nm, enabling conduction in the dual aluminum contact transistor. The DAC BESOI MOSFET had a current level increase of 3 times for BESOI pMOSFET and 9 times in BESOI nMOSFET compared to using NiSi contacts