Search Results (588)

Polyethylene terephthalate is a prominent polymer known for its mechanical properties, chemical resistance, and recyclability, and it is widely utilized across various industries. Enhancing the properties of polyethylene terephthalate (PET) through nanocomposite technology, particularly with the inclusion of nanoscale fillers, has garnered significant attention. This study investigates synthetic layered double hydroxides (LDHs), specifically MgAl LDH modified with calcium dodecylbenzene sulphonate in n-butyl alcohol (CDS) organic surfactant, as an alternative to natural clays for PET nanocomposites. Additionally, modified LDH serves a dual role as both a catalyst and a dispersive agent, promoting effective exfoliation within the PET matrix. A polymerization process was employed to ensure proportional and effective dispersion of the nanofillers, addressing the critical challenge of achieving uniform distribution. The resulting nanocomposites demonstrated superior mechanical strength, thermal stability, and barrier properties compared to traditional intercalated counterparts. Moreover, synthetic LDHs present a more sustainable solution, reducing the environmental footprint associated with natural clay mining, which includes land degradation, water pollution, energy consumption, and biodiversity loss. This research provides a promising pathway for developing high-performance, environmentally friendly PET nanocomposites, with significant implications for various industrial applications, from packaging to automotive and electronics. The findings highlight the potential of synthetic LDHs to advance material science while aligning sustainable development goals. Full article

The use of one-step products and their applications in sensory applications has gained much importance. Herein, Schiff’s base fluorescent turn-on sensor, namely FBTS, was synthesised via a condensation reaction between 6-fluorobenzo[d]thiazol-2-amine and 2-hydroxybenzaldehyde. The probe FBTS exhibits an intense “turn-on” blue fluorescence upon binding to Al³⁺ ions in a dimethyl sulfoxide–water (DMSO–H₂O (8:2, v/v)) medium. From photoluminescence (PL) titrations, the detection limit (LOD) for Al³⁺ is estimated to be 0.14 microM, and the Benesi–Hildebrand plot-based association constant (K_a) of 5.4 × 10⁴ M⁻¹ confirm a strong association between FBTS and Al³⁺. Negligible interference is observed in the presence of other metal ions. From the pH effect studies, the optimal pH range for Al³⁺ detection is 7–9. The recyclable reversibility of FBTS + Al³⁺ complex has been demonstrated via the sodium salt of ethylenediaminetetraacetic acid (Na₂-EDTA) chelation. A Job’s plot and interrogations, such as high-resolution mass spectrometry (HR-MS), ¹H-nuclear magnetic resonance (NMR) titration, and density functional theory (DFT), verified the 1:1 stoichiometry of binding between FBTS and Al³⁺. Based on multiple analyses, the binding mode and mechanism have been detailed. In addition, the practical application of FBTS for detecting Al³⁺ is demonstrated using the strip paper method, fish analysis, spiked real sample analysis, and cellular imaging. Full article

The homogeneous nature of L-proline organocatalysts restricts their application in aldol condensation due to poor recyclability and stability. Herein, L-proline was heterogenized by ionic intercalation into Mg–Al layered double hydroxides (LDHs), yielding a series of proline-intercalated catalysts with tunable layer structures. Co-precipitation and memory-effect reconstruction strategies were employed to regulate interlayer spacing and proline loading. The resulting catalysts exhibited efficient performance in the aldol condensation of furfural with ketones under mild conditions. The reconstructed catalyst re-Mg₄Al₁P achieved a furfural conversion of 88.67% and a total product yield of 85.54% at room temperature, with product selectivity exceeding 95%. Structural characterizations confirmed that proline was stabilized within the LDH interlayers via R–COO—Mg electrostatic interaction while preserving the secondary amine active site. Mechanistic analysis indicated that the reaction proceeded through enamine- or enol-mediated pathways depending on water content, while the layered LDH framework imposed geometric confinement that suppressed side reactions. Catalyst deactivation in aqueous systems was mainly attributed to proline leaching rather than structural collapse. Full article

Aluminum is the most used non-ferrous metal, with a well-established recycling procedure, but this process also produces new residues. We recently proposed an integrated laboratory practice based on the recovery of aluminum from the slag generated during its recycling. Now, we expand upon this research by proposing the preparation of a layered material, namely hydrocalumite, from recovered Al³⁺. The synthesis of this solid, its characterization, and the use of the mixed oxides produced after its calcination for the photocatalytic removal of ibuprofen from aqueous solutions are structured as a laboratory practice for students in the last years of Chemistry, Chemical Engineering, Environmental Engineering, Materials Engineering, and related university or masters degrees. In this way, the work integrates material synthesis and characterization procedures with a practical introduction to catalysis photodegradation, incorporating key concepts of the Circular Economy and Sustainable Development Goals, and educating students with respect to the environment. Full article

Stricter drinking water regulations intensify the need to replace leaded brasses in fittings. This work reports preliminary results on internally coated fittings using the wrought zinc alloy ZnAl15Cu1Mg (ZEP1510). A straight-tube Model Geometry 1 was lined internally with HDPE by gas-assisted injection molding, achieving a continuous barrier of 1.55–1.70 mm without altering the external envelope. A press-type T-fitting (32–32–32) was defined as Model Geometry 2 to benchmark forgeability; process layout (FEM) and warm-forging trials are summarized. Recycling relevance was addressed via a partial-melt (drip-off) route, which removed a substantial polymer fraction but left measurable residues. A production-cycle PCF from material production to finished tee indicates 3.156 kg CO₂e for ZEP1510 vs. 5.385 kg CO₂e (CuZn40Pb2) and 6.301 kg CO₂e (CuZn21Si3), i.e., 41.85% and 50.06% savings. These findings establish manufacturability, indicate recycling feasibility, and quantify a CO₂ advantage, outlining the next steps toward lining complex geometries and drinking water compliance. Full article

The recycling of carbon fiber-reinforced polymers (CFRPs), particularly carbon fiber-reinforced epoxy polymers (CFREPs), is a challenging problem because of their broad application spectrum, the amount of laminates produced per year, and the cost per kg of the carbon fiber fabric. Recently, several papers were published on the recycling of CFREPs through solvothermal methods that allow the recovery of the carbon fiber fabrics with a relatively low environmental impact. In the present paper, for the first time, the effect of the presence of flame retardants is discussed. A carbon fiber-reinforced epoxy polymer (CFREP) charged with P-, Zn-, B- and Al-based flame retardants, supplied by the aerospace industry, was subjected to a double-step solvothermal treatment. The epoxy matrix was successfully dissolved in monoethanolammine after a preswelling step in acetic acid. The experimental results show that the proposed process allows the full recovery of the carbon fabric with its original sizing layer without injury to the fiber. As confirmation, CFREP laminates produced with the recycled carbon fiber fabrics exhibited mechanical properties close to that of laminates obtained from the virgin epoxy/carbon prepreg. Contrary to what is reported in the literature, the present paper also shows that, in the studied case, whilst acetic acid treatment promotes swelling, it also causes the formation of a degraded surface layer that would impede complete removal of the polymeric matrix and full recovery of the carbon fabric if only acetic acid was used. On the basis of the known mechanism of flame retardancy of phosphates and borates, the degraded layer formation is attributed to the acidic character of the acetic acid. It is worth pointing out that the paper suggests, therefore, that the presence of flame retardants may strongly affect the solvothermal processes. Full article

High-ash coal slime water, characterized by its stable colloidal suspension of fine kaolinite particles, poses a significant challenge in the coal preparation industry because it is hard to achieve efficient solid–liquid separation. While traditional coagulants and flocculants often suffer from limited bridging capabilities and distinct pH sensitivity, novel molecular architectures offer potential solutions. In this study, a star-shaped inorganic–organic hybrid flocculant (Al-PAM) was synthesized via in situ polymerization. Its flocculation performance and interfacial adsorption mechanism on the specifically targeted aluminol basal plane of kaolinite were systematically investigated and compared with Polyaluminum Chloride (PAC), Non-ionic Polyacrylamide (NPAM), and their combination (PAC + NPAM). Settling tests revealed that Al-PAM exhibited superior performance at a significantly lower dosage (10 mg∙L⁻¹) compared to the PAC + NPAM binary reagent system. It achieved a rapid initial settling velocity and reduced the supernatant turbidity to 48.45 NTU, while maintaining a near-neutral pH favorable for water recycling. Furthermore, Quartz Crystal Microbalance with Dissipation (QCM-D) monitoring confirmed that Al-PAM forms a thick, viscoelastic, and irreversible adsorption layer on the Al₂O₃ substrate. The dissipation shifts (ΔD) revealed that the star-shaped architecture promotes distinct bridging and electrostatic adsorption, overcoming the limitation of linear polymers. This work elucidates the specific contribution of the alumina-surface interaction with flocculants and proposes an efficient strategy for treating refractory coal slime water. Full article

The strong adhesion between cathode materials and aluminium (Al) foil substrates presents a significant challenge in the recycling of spent lithium-ion batteries (LiBs). Conventionally, high temperatures and high concentrations of costly organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAC), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) are used to enhance ultrasonication-based delamination. In this study, a novel, eco-efficient approach was demonstrated for delaminating cathode materials from Al foil using a low-concentration organic citric-acid-assisted low-power ultrasonic treatment coupled with a gentle, low-power-per-volume mechanical mixing system at room temperature. The separation mechanism was attributed to the structure disruption, possibly swelling, of the polyvinylidene fluoride (PVDF) binder using low-concentration citric acid and the cavitation effects induced by ultrasound. Key parameters influencing the delamination efficiency included the solvent type, temperature, ultrasonic power, and treatment duration. Under optimised conditions, citric acid was used as the sonication reagent, with a process temperature of 20 °C, 60 W ultrasonic power, and 80 min of ultrasonication; a delamination efficiency of approximately 92% was achieved. The recovered cathode materials exhibited low agglomeration, favouring subsequent leaching processes. This work proposes an environmentally friendly and effective method for cathode and Al foil recovery from spent LiBs, integrating manual dismantling, ultrasonic treatment, and material separation. Full article

Spent carbon cathode (SCC), a hazardous solid waste discharged from aluminum electrolysis, exhibits significant fluoride and cyanide leaching toxicities. Existing high-temperature disposal strategies are constrained by high investment costs for specialized equipment, low product added value, and unclear application scenarios, hindering their large-scale implementation. Consequently, substantial quantities of SCC remain underutilized, resulting in the waste of valuable carbon and fluoride components. This study focuses on the targeted conversion of valuable components in SCC through the innovative integration of simple processes, including atmospheric high-temperature roasting, deep purification, Al-based inducer addition, and pH regulation. Volatilization kinetics and solution equilibrium chemistry were used to investigate impurity removal mechanisms and to guide cryolite synthesis, respectively. The results demonstrate the successful recovery of high-purity regenerated graphite with a high carbon content, low sulfur content, and a high degree of graphitization. Simultaneously, cryolite with a high NaF/AlF₃ molecular ratio was synthesized from the roasting flue gas absorption liquor by controlling ionic composition and pH. Guided by the principles of cleaner production and resource recycling, the entire recovery process generates negligible waste gas, wastewater, or solid residue emissions. In conclusion, the proposed disposal strategy achieved the targeted conversion of SCC into high-value products while mitigating environmental pollution risks, offering both environmental and economic benefits. This innovative design provides a feasible pathway for the large-scale disposal and utilization of SCC. Full article

To address the challenge of controlling Fe impurity content during the recycling of aluminum alloys, this study utilized commercial 5083 aluminum alloy as a matrix to prepare alloy samples with four different Fe contents via smelting. The effects of Fe content on the microstructure, mechanical properties, and corrosion resistance of the as-cast 5083 aluminum alloy were systematically investigated. The results indicate that increasing the Fe content induces a significant morphological evolution of the Fe-rich phases, transitioning from compact Chinese-script α-Al(Fe,Mn)Si phases at low Fe levels to coarse needle-like β-AlFeSi phases. Concurrently, both the quantity and size of the second phases increase significantly. Mechanical testing reveals that the hardness of the alloy gradually rises from 67 HV to 72 HV due to second-phase strengthening. The tensile strength shows a trend of initially increasing and then decreasing, peaking at 0.45 wt.% Fe; however, excessive Fe leads to the formation of needle-like phases that cause stress concentration, resulting in a decline in tensile strength. The elongation decreases gradually with increasing Fe content, with a maximum reduction of 19.7%. Electrochemical tests show that higher Fe content increases the self-corrosion current density and decreases the capacitive loop radius, indicating a significant degradation in the alloy’s corrosion resistance. This work provides an experimental basis for the tolerance control of Fe impurities and the performance optimization of recycled 5083 aluminum alloys. Full article

Background: Agriculture degrades soils, affects the delivery of ecosystem services, and contributes to climate change. Methods: This research examined nitrogen and sulfur recycling in soils under cropland expansion in Ghana at (a) reconnaissance scale in northern Guinea savannah (NGS), southern Guinea savannah (SGS), forest–savannah transition (FST), and semi-deciduous forest (SDF) agro-ecological zones (AEZs), and (b) farm level in rain Forest and the FST AEZs based on “duration of cultivation”. Fresh soils (20 cm depth) were incubated for 28 days at 28 °C, followed by the determination of mineralized nitrogen and sulfur at 14 and 28 days using standard methods. Results: Low nitrogen and sulfur contents led to predominant nitrogen and minor sulfur immobilizations, particularly in FST and savannah AEZs. Microbial biomass and pedogenic Fe controlled much of the nitrogen immobilization. At the farm level, dithionite Al and soil pH controlled nitrogen immobilization, particularly in relatively older farms, being pronounced in forest-related AEZs. Conclusions: Although the study is laboratory-based, it highlights the severe nature of soil degradation (SD) under cropland expansion in regions prone to poor nutrient budgets. Therefore, it calls for drastic measures to halt SD by adopting ecozone- and climate-driven sustainable soil management and agricultural systems. Full article

With global plastic production creating immense environmental pressure and conventional recycling methods facing limitations, advanced chemical recycling techniques are crucial. This paper presents details of the design, construction, and operation of two fluidized reactors: a laboratory-scale (LS) reactor and a large-scale laboratory reactor (LSLR) for the catalytic pyrolysis of mixed plastic waste. A waste stream simulating municipal collection, consisting of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS), was processed using a custom Ni/γ-Al₂O₃ catalyst and an industrial G-0110 catalyst in a two-stage system. The large-scale reactor demonstrated high efficiency, achieving a 90% yield of valuable pyrolysis oil and waxes, a 2% yield of syngas, and an 8% yield of solid residue containing mainly carbon at operating temperatures between 400 and 453 °C. The resulting liquid and wax fractions contained a rich mixture of aliphatic and aromatic hydrocarbons (such as styrene, indene, benzoic acid, toluene, and cumene), confirming their potential as a feedstock for the chemical industry. These results establish that two-stage catalytic pyrolysis in a fluidized bed reactor is a highly effective and promising technology for upcycling mixed plastic waste into valuable resources. Full article

The incorporation of recycled metallurgical slags into refractory materials constitutes a promising approach to enhancing sustainability in the refractory industry. This study investigates the effect of vanadium-bearing slag aggregates as partial replacements for tabular alumina in castables and compares their behaviour with high-alumina and bauxite-based castables. Two vanadium-bearing slags with different mineralogical compositions were introduced in the 1–3 mm aggregate fraction with substitution up to 25 wt.%. Their effects on microstructure, thermo-mechanical performance, and corrosion resistance were evaluated. The introduction of vanadium-bearing slag significantly alters the microstructure of the castables, affecting their performance. Both slags displayed grains with higher porosity, microcracking, and heterogeneity compared with tabular alumina, but showed similarities to bauxite grains. Slag 1, enriched in calcium aluminate phases, provides limited mechanical strength but improved corrosion resistance due to improved bonding with the matrix. Slag 2, containing a higher spinel content, enhances mechanical strength, showing behaviour comparable with bauxite-based castables, particularly at 10 wt.% replacement. Vanadium is mainly present in metallic form and as Mg(Al,V)₂O₄ spinels in both slags. Upon firing, vanadium migrates toward the grain boundaries and reacts with the surrounding calcium aluminate phases to be incorporated in Ca(Al,V)₂O₄ and Ca(Al,V)₄O₇, while the spinel phase remains stable. Full article