Search Results (110)

This article deals with the issue of electromagnetic radiation, specifically methods of eliminating radiation using protective coatings. Protective coatings were created from commercially available fabricated but also recycled metal powders and commonly available interior paint. The aim of the experiments was to produce protective coatings with different qualitative and quantitative compositions and subsequently test their shielding effects. For the preparation of the coatings, mixtures in the form of commercially produced powder with a particle size of <10 μm were used, namely aluminum oxide (Al₂O₃), manganese dioxide (MnO₂), and graphite (C). Recycled powders are powdered iron (Fe) and zinc oxide (ZnO) with a particle size of <50 μm. The powders were mixed in various ratios and compounds into a commercially available white interior paint. Measurements were performed in the frequency range of 0.9–9 GHz with a step of 0.1 GHz, evaluating the shielding effectiveness, absorption, and reflection. The best shielding values were achieved for samples containing 100 g of carbon powder, 100 g of iron powder, and 100 g of manganese dioxide, ranging from 0.38 to 6.2 dB in the full measured frequency range. Full article

Introducing and compacting lignocellulosic biomass in aluminum structures, though recommendable in terms of higher sustainability, the potential use of agro-waste and significant weight reduction, still represents a challenge. This is due to the variability of biomass performance and to its limited compatibility with the metal. Another question may concern possible moisture penetration in the structure, which may reduce environmental resistance and result in local degradation, such as wear or even corrosion. Despite these limitations, this hybridization enjoys increasing success. Two forms are possibly available for this: introduction into metal matrix composites (MMCs), normally in the form of char from biomass combustion, or laminate reinforcement as the core for fiber metal laminates (FMLs). These two cases are treated alongside each other in this review, first because they may represent two combined options for recycling the same biomass into high-profile structures, aimed primarily at the aerospace industry. Moreover, as discussed above, the effect on the aluminum alloy can be compared and the forces to which they are subjected might be of a similar type, most particularly in terms of their hardness and impact. Both cases considered, MMCs and FMLs involved over time many lignocellulosic residues, starting from the most classical bast species, i.e., flax, hemp, sisal, kenaf, etc., and extending also to less diffuse ones, especially in view of the introduction of biomass as secondary, or residual, raw materials. Full article

The conventional spent lithium-ion batteries (LIBs) recycling method suffers from complex processes and excessive chemical consumption. Hence, this study proposes an electrochemical strategy for achieving reductant-free leaching of high-valence transition metals and efficient separation of valuable components from spent cathode sheets (CSs). An innovatively designed sandwich-structured electrochemical reactor achieved efficient reductive dissolution of cathode materials (CMs) while maintaining the structural integrity of aluminum (Al) foils in a dilute sulfuric acid system. Optimized current enabled leaching efficiencies exceeding 93% for lithium (Li), cobalt (Co), manganese (Mn), and nickel (Ni), with 88% metallic Al foil recovery via cathodic protection. Multi-scale characterization systematically elucidated metal valence evolution and interfacial reaction mechanisms, validating the technology’s tripartite innovation: simultaneous high metal extraction efficiency, high value-added Al foil recovery, and organic removal through single-step electrochemical treatment. The process synergized the dissolution of CM particles and hydrogen bubble-induced physical liberation to achieve clean separation of polyvinylidene difluoride (PVDF) and carbon black (CB) layers from Al foil substrates. This method eliminates crushing pretreatment, high-temperature reduction, and any other reductant consumption, establishing an environmentally friendly and efficient method of comprehensive recycling of battery materials. Full article

Pyrometallurgical recycling of lithium-ion batteries presents distinct advantages including streamlined processing, simplified pretreatment requirements, and high throughput capacity. However, its industrial implementation faces challenges associated with high energy demands and lithium loss into slag phases. This investigation develops an integrated reduction smelting–chloridizing volatilization process for the comprehensive recovery of strategic metals (Li, Mn, Cu, Co, Ni) from spent ternary lithium-ion batteries; calcium chloride was selected as the chlorinating agent for this purpose. Thermodynamic analysis was performed to understand the phase evolution during reduction smelting and to design an appropriate slag composition. Preliminary experiments compared carbon and aluminum powder as reducing agents to identify optimal operational parameters: a smelting temperature of 1450 °C, 2.5 times theoretical CaCl₂ dosage, and duration of 120 min. The process achieved effective element partitioning with lithium and manganese volatilizing as chloride species, while transition metals (Cu, Ni, Co) were concentrated into an alloy phase. Process validation in an induction furnace with N₂-O₂ top blowing demonstrated enhanced recovery efficiency through optimized oxygen supplementation (four times the theoretical oxygen requirement). The recovery rates of Li, Mn, Cu, Co, and Ni reached 94.1%, 93.5%, 97.6%, 94.4%, and 96.4%, respectively. This synergistic approach establishes an energy-efficient pathway for simultaneous multi-metal recovery, demonstrating industrial viability for large-scale lithium-ion battery recycling through minimized processing steps and maximized resource utilization. Full article

This study signifies the development and characterization of a composite material with a metallic matrix of aluminum reinforced with a steel mesh, utilizing centrifugal casting technology. An evaluation was conducted to ascertain the influence of the formulation process and the presence of the insert on the mechanical behavior with regard to tensile strength. The aluminum matrix was obtained from commercial and scrap alloys, elaborated by advanced methods of degassing and chemical modification. Meanwhile, the steel mesh reinforcement was cleaned, copper plated, and preheated to optimize wetting and, consequently, adhesion. The structural characterization was performed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analyses (EDX), which highlighted a well-defined interface and uniform copper distribution. The composite was produced by means of horizontal-axis centrifugal casting in a fiberglass mold, followed by cold rolling to obtain flat specimens. A total of eight tensile specimens were examined, with measured ultimate tensile strengths ranging from 78.5 to 119.8 (MPa). A thorough examination of the fractured specimens revealed a brittle fracture mechanism, devoid of substantial plastic deformation. The onset of failures was frequently observed at the interface between the aluminum matrix and the steel mesh. The use of SEM and EDX investigations led to the confirmation of the uniformity of the copper coating and the absence of significant porosity or interfacial defects. A bimodal distribution of tensile strength values was observed, a phenomenon that is likely attributable to variations in mesh positioning and local differences in solidification. A correlation was established between the experimental results and an analytical polynomial model, thereby confirming a reasonable fit. In sum, the present study provides a substantial foundation for the development of metal matrix composites with enhanced performance, specifically designed for challenging structural applications. This method also demonstrates potential for recycling aluminum scrap into high-performance composites with controlled microstructure and mechanical integrity. Full article

Energy conversion and infrastructure facilities consist of large amounts of metal and have lifetimes of several decades. When recycling metals, the methods of allocation play a decisive role in evaluating how primary and secondary materials, as well as the products that are produced with them, are to be evaluated ecologically. So-called credits for recycling are the subject of a particularly controversial discussion. This article shows that the current practice of giving credits for long-lasting products leads to a significant distortion of the actual emissions. Using the examples of steel, aluminum, and copper, prospective LCA data is used to show how the carbon footprint actually behaves. When credits are applied, the time dependency of emissions must be taken into account; otherwise, burden shifting into the future occurs, which can hardly be considered sustainable. The increase compared to the conventional time-independent practice lies, depending on the metal, at 70 to 300%. It is recommended that the cutoff approach be used conservatively when allocating recycling cascades in order to optimize environmental impact and avoid greenwashing. Full article

This study achieved the preparation of budget-friendly stratified Ca-Al adsorbents using a simplified precipitation synthesis route with subsequent pyroprocessing, showing superior defluoridation capabilities in aqueous environments. The structural properties and defluoridation performance of the adsorbents were systematically investigated by optimizing critical synthesis parameters, including calcium-to-aluminum molar ratios, the solution pH during co-precipitation, and calcination temperature. Characterization results revealed that the optimal sample (prepared at a Ca/Al ratio of 2:3, initial pH of 10, and calcination temperature of 600 °C) exhibited a high specific surface area, ordered mesoporous structure, and abundant surface hydroxyl groups, facilitating efficient fluoride adsorption. Batch adsorption experiments demonstrated significant effects of adsorbent mass, solution pH, and initial fluoride concentration on removal efficiency. The isothermal adsorption characteristics conformed to the Langmuir model, complemented by pseudo-second-order kinetic compliance, which jointly confirmed chemisorption-dominated monolayer coverage. Notably, the maximum adsorption capacity reached 263.33 mg g⁻¹, surpassing most comparable adsorbents reported in the literature. The material maintained a superior fluoride removal performance across a wide pH range (4~12) and exhibited superior recyclability. Rapid adsorption kinetics were observed, with equilibrium achieved within 60 min. The material showed a good removal effect in actual fluoride-containing smelting wastewater, which further proved its application potential. In addition, the analysis of the adsorption mechanism showed that the removal of fluoride was mainly achieved through the coordination between fluoride and metal ions and the ion-exchange reaction with surface hydroxyl groups. These findings suggest that the adsorbent has significant prospects for practical water quality fluoride removal applications. Full article

In recent years, thermoplastic polymers and composites have seen increasing application across various industrial sectors to develop lightweight structures. These materials have gained popularity in the market due to advancements in additive manufacturing. Thermal direct joining serves as an effective solution for integrating such thermoplastic materials into existing or de-novo metal structures. This method enables the creation of lightweight and virtually reversible joints, which foster end-of-life recyclability, thus aligning with the principles of a circular economy. However, these joints are still affected by a low strength, which is mostly related to the poor polymer–metal interaction. The use of surface treatments that promote mechanical interlocking of the polymer within surface asperities in the mating metallic adherend can be an effective strategy to enhance the strength, as well as to improve the toughness and damage tolerance of the joints. In this work, a laser treatment was used to modify the surface texture of an aluminum sheet prior to thermal bonding with 3D-printed polylactic acid (PLA). Different surface textures were analyzed by modifying the main process parameters. Roughness and wettability measurements were performed to identify the most effective processing condition. Finally, mechanical tests were performed to verify the improvement in joint resistance obtained by interface modification. Full article

The pyrolysis carbon black (CBp) from waste tires contains zinc, iron, and other metal elements, which have high recycling value. This study proposes a simple method of recovering zinc and iron from waste tire-derived CBp to synthesize hydrotalcite-type adsorbents for the treatment of anodic dye wastewater. Firstly, zinc-aluminum hydrotalcite (LDH) and zinc-iron aluminum hydrotalcite (FeLDH) were obtained by leaching the zinc and iron ions from CBp with an acid solution. As compared with LDH, FeLDH shows increased laminate metal ion arrangement density and layer spacing. By calcining the LDH and FeLDH at 500 °C, zinc aluminum oxides (LDO) and zinc iron aluminum oxides (FeLDO) were then prepared and applied for the adsorption of dye methyl orange (MO). The results demonstrate that the maximum adsorption capacity of LDO and FeLDO are 304.9 and 609.8 mg g⁻¹ at pH of 4.0, respectively. The adsorption processes of both LDO and FeLDO are consistent with the Langmuir adsorption isotherm and the proposed second-order kinetic model. The adsorption regeneration performance and adsorption mechanism of LDO and FeLDO were also investigated in detail. Regeneration experiments show that after three cycles, the removal rate of MO by LDO remains above 80%, while that of FeLDO only remains around 64% in the first cycle after regeneration. This work would provide a new pathway to realize the high-value metal recycling of waste tire-derived CBp and solve the contamination of dye wastewater. Full article

Leachates from electronic waste, slag dusts generated during the processing of electronic waste, sweeping jewelry, and municipal solid-waste incineration residues contain a myriad of base metals, such as aluminum (Al: 10–2000 mg/L), copper (Cu: 10–1000 mg/L), iron (Fe: 10–500 mg/L), nickel (Ni: 0.1–500 mg/L), lead (Pb: 1–500 mg/L), tin (Sn: 1–100 mg/L), and zinc (Zn: 5–500 mg/L), which are present at much higher quantities than Au (0.01–10 mg/L), which raises several drawbacks to the efficient recycling of Au with high purity using hydrometallurgical strategies. The aim of this work was to study the efficiency and selectivity of two strong basic anion exchange (DOW^TM XZ-91419.00 and Purogold^TM A194) resins to recover Au from a chloride multi-metal solution containing these metals. For both resins, the adsorption kinetic and equilibrium parameters for Au(III), determined at 1.12 mol/L HCl, Eh = 1.1 V, and 25 °C, proceeded according to a pseudo-second order and a Langmuir isotherm (qmax was 0.94 and 1.70 mmol/g for DOW^TM XZ-91419.00 and Purogold^TM A194 resins, respectively), respectively. Continuous adsorption experiments of Au (48 µmol/L; 2.0%) from a chloride multi-metal solution evidenced high Au retention capacity and selectivity to Au over Al, Cu, Fe, Ni, and Zn but low selectivity to Au over Ag and Sn for both resins. Concentrated (>3.3 mmol/L) and pure (>94%) Au eluates were obtained for both resins. Full article

Recycling of spent lithium-ion batteries is important due to the increasing demand for electric vehicles and efforts to realize a circular economy. There is a need to develop environmentally friendly processes for the refining of nickel, cobalt, and other metals contained in the batteries. Electrodialysis is an appealing method for recycling of battery metals with selective separation and low chemical input. In this study, sodium sulfate was used in an electrodialysis metathesis procedure to sequentially separate EDTA-chelated nickel and cobalt. Replacing hitherto used sulfuric acid with sodium sulfate mitigates membrane fouling caused by precipitation of EDTA. It was possible to separate up to 97.9% of nickel and 96.6% of cobalt at 0.10 M, a 30-times higher concentration than previously reported for electrodialysis of similar solutions. Through the thermally activated persulfate method, new to this application, 99.7% of nickel and 87.0% of cobalt could be precipitated from their EDTA chelates. Impurity behavior during electrodialysis of battery leachates has not previously been described in the literature. It is paramount to remove copper, iron, and phosphorous prior to electrodialysis since they contaminate the nickel product. Aluminum was difficult to remove in the solution purification step and ended up in all electrodialysis products. Full article

The rapid expansion of the cosmetic products market, growing consumer eco-consciousness, and stricter packaging regulations, such as the PPWR, present significant challenges for the cosmetic industry. To assess the sustainability of cosmetic packaging, a benchmarking study was conducted across various product categories available in the DACH region (Germany, Austria, and Switzerland) using a set of selected indicators. The findings highlight an urgent need for action to ensure compliance with future PPWR requirements. While glass and aluminum packaging demonstrated high recyclability, plastic tubes often failed to meet the 70% recyclability target due to incompatible material combinations. Key barriers to recyclability included material incompatibility, metallization, and excessive colorization. Additionally, the use of recycled content in plastic and paper-based packaging was generally low, with only a few samples containing secondary materials. Other critical issues included packaging efficiency, the widespread use of secondary packaging, and use of uncertified renewable materials. Addressing these challenges will require industry-wide efforts to enhance material compatibility, increase recycled content, and optimize packaging design for greater sustainability. Full article

Miniaturized components for enhanced integrated functionality or thin sheets for lightweight applications often consist of face-centered cubic metals. They exhibit good strength, corrosion resistance, formability and recyclability. Microfabrication technologies, however, may introduce cold work or detrimental heat-induced lattice defects into the material, with consequences for the mechanical properties. Austenitic stainless steels (1.4310, 1.4301) and aluminum alloys (EN AW-5005-H24, EN AW-6082-T6) were selected for this study. The influence of pulsed fiber laser cutting, microwaterjet cutting, and annealing on the strain–stress behavior was investigated. The micro-tensile test setup comprised a flex-structure force sensor, a laser extensometer, and a dedicated sample holder. Fiber laser cut 1.4310 samples exhibited early failure at low fracture strain in narrow shear band zones. The shear band zones were detectable on the sample surface, in the laser extensometer images, in the horizontal sections of the stress–strain curves, and in the microstructure. Inside the shear band zones, grains were strongly elongated and exhibited numerous parallel planar defects. Heat-induced chromium carbides, in combination with low stacking fault energy (SFE) and elevated carbon content, favored shear band zone formation in 1.4310. In contrast, microwaterjet cut high SFE materials EN AW-5005-H24 and EN AW-6082-T6, as well as low-carbon austenitic stainless steel 1.4301, exhibited uniform plastic deformation. Full article

With the advancement of industrial production and urban modernization, pollution from heavy metal ions and the accumulation of solid waste have become critical global environmental challenges. Establishing an effective recycling system for solid waste and removing heavy metals from wastewater is essential. Coal gangue was used in this study as the primary material for the synthesis of a fully coal gangue-based phosphorus-silicon-aluminum (SAPO-5) molecular sieve through a hydrothermal process. The SAPO-5 molecular sieve was characterized through several methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface analysis, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), to examine its mineral phases, microstructure, pore characteristics, and material structure. Adsorption performance towards wastewater with Cd²⁺ and Pb²⁺ ions was investigated. It was found that the adsorption processes of these ions are well described by both the pseudo-second-order model and the Langmuir isotherm. According to the Langmuir model, the coal gangue-based SAPO-5 molecular sieve exhibited maximum adsorption capacities of 93.63 mg·g⁻¹ for Cd²⁺ and 157.73 mg·g⁻¹ for Pb²⁺. After five cycles, the SAPO-5 molecular sieve retained strong stability in adsorbing Cd²⁺ and Pb²⁺, with residual adsorption capacities of 77.03 mg·g⁻¹ for Cd²⁺ and 138.21 mg·g⁻¹ for Pb²⁺. The excellent adsorption performance of the fully solid waste coal gangue-based SAPO-5 molecular sieve is mainly attributed to its mesoporous channel effects, the complexation of -OH functional groups, and electrostatic attraction. Full article

The manufacturing sector is a major contributor to global energy consumption and greenhouse gas emissions, positioning sustainability as a critical priority. Aluminum, valued for its lightweight and recyclable properties, plays a vital role in advancing energy-efficient solutions across transportation and aerospace industries. The processing of aluminum alloys through laser-based powder bed fusion of metals (PBF-LB/M), a cutting-edge additive manufacturing technology, enhances sustainability by optimizing material usage and enabling innovative lightweight designs. Based on the published literature, the present study analyzed the ecological impacts of aluminum PBF-LB/M manufacturing through life cycle assessment, circular economy principles, and eco-design strategies, identifying opportunities to reduce environmental footprints. The study also stated the critical challenges, such as the high energy demands of the aluminum PBF-LB/M process and its scalability limitations. Potential sustainable solutions were discussed starting from powder production techniques, as well as optimized processes and post-processing strategies. By adopting an interdisciplinary approach, this research highlighted the pivotal role of PBFed aluminum alloys in achieving sustainable manufacturing goals. It provided actionable insights to drive innovation and resilience in industrial applications, offering a roadmap for balancing environmental stewardship with the demands of high-performance standards. Full article