Recycling Of Metals Research Articles

Digital Shear Printing of Mechanically Robust Liquid Metal Circuits with Hierarchical Embedded Structure for Paper Electronics

The seamless integration of recyclable and deformable liquid metal (LM) conductors into paper is attractive to developing flexible, breathable, and green electronics. However, the weak adhesion between paper and LM complicates the patterning. In addition, the low damage endurance of LM, an open problem for on‐surface conductors, restricts the practical applications. Here, a simple yet efficient approach of shear printing is reported to directly pattern hierarchical embedded LM circuits with erasure resistance onto paper. This is achieved by digitally applying the shear force to the solid gallium film to induce its adhesive wear with the paper, allowing the gallium to be embedded into the paper's fiber networks. Meanwhile, the pressure‐induced formation of microgrooves on paper allows the LM circuits to be surface‐embedded onto paper. The hierarchical embedded structure endows the LM circuits with enhanced mechanical damage endurance that they can even withstand eraser rubbing and tape peeling. Applications of the hierarchical embedded, mechanically robust, and breathable LM‐enabled paper electronics in enhanced humidity sensing, electrophysiology monitoring, and digital droplet microfluidics are also shown. This work opens doors to developing sustainable yet robust paper electronics by rationally utilizing the solid properties of low‐melting‐point metals.

A highly efficient and recyclable zirconium-based metal organic framework for the effective removal of nanoplastics from multiple aqueous environments

A highly efficient and recyclable zirconium-based metal organic framework for the effective removal of nanoplastics from multiple aqueous environments

Selective adsorption and synchronous reduction of Au from water with difunctional cellulose aerogel: Performance and mechanism

Here, valonia tannin and sulfhydryl functional groups were added to the cellulose aerogel from waste textiles to form a thiol-modified tannin-immobilized cellulose-based aerogel (TVTCA) with selective adsorption and outstanding reducing properties. This aerogel was then utilized to recycle Au(III) in the water. The resulting 3D TVTCA contained abundant -SH groups and phenolic hydroxyl groups and exhibited stable crystal structure and good thermal properties. TVTCA showed excellent Au (Ⅲ) adsorption performance (598.3 mg/g of maximum adsorption capacity) and strong reductivity (78 %). The adsorption process was conducted using both the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. In addition, TVTCA displayed excellent anti-interference ability. Even though the coexisting ions concentration was as high as 100 mmol/L, TVTCA still owned a high Au adsorption capacity (178.91–224.14 mg/g) and selectivity factor (29.16–2629.34), which was much higher than valonia tannin-immobilized cellulose-based aerogel (VTCA). Furthermore, the recycling of Au with TVTCA mainly included adsorption and in-situ reduction processes. The mechanisms involved the electrostatic interaction and chelation effects, which were ascribed to the introduced sulfhydryl groups. Meanwhile, the in-situ Au reduction was mainly caused by the studies showing that the high adsorption capacity of TVTCA was owing to the phenolic hydroxyl groups on the introduced valonia tannin. All the findings would provide a new way to achieve the recycling of precious metals from wastewater by using valuable cotton waste.

A Gold Rush: Designing Hydrogels for Selective Recovery in Wastewater Containing Mixed Metal Ions.

The use of synthetic hydrogels in wastewater treatment represents a promising and scalable approach to achieving clean water. By modulation of their chemical structure, hydrogels can effectively remove a wide range of toxic compounds, including emerging organic pollutants and heavy metals. For the latter, recovery is essential for both environmental protection and metal recycling. The increasing demand for gold, a nonrenewable metal widely used in many technologies, calls for methods for its selective recovery from complex metal cation solutions. This study explores easy-to-make poly(acrylamide-co-acrylic acid) hydrogels as adsorbents for gold recovery from industrial wastewater containing other precious metals. Such material can reduce gold cations into elemental nanoparticles and microparticles in acid environments at room temperature. This process offers a potential route for metal recovery that is not based on weak interaction or complex formation. Batch tests demonstrate a good adsorption capacity (up to 124 mg/g) and efficient separation from other precious metal ions (Ru, Ir, Pd, Pt, and Rh) in a solution that closely mimics realistic industrial waste conditions. These hydrogels would enable gold recovery also from other complex metal solutions, including those derived from the dissolution of electronic wastes.

THE EFFECT OF REPETITIVE METAL CASTING ON THE TENSILE STRENGTH OF DENTURES

Background: Dentures or prostheses function to replace chewing and dental arch structures. Denture plates used in dentistry are made with acrylic resin, metal, or a combination of acrylic and metal. Metals are shiny, opaque chemical substances and good conductors of heat and can be polished. Recycling or reusing used metal is an option in making prostheses because the price of new metal is increasing, and metal recycling is quite effective. Purpose: To determine the effect of repeated metal casting on the strength of the metal frame denture base. Method: The current research is a laboratory study with a tensile test in the form of dumbbells with iso 22674 with a length of 15 ± 1 mm and a diameter of 3 ± 1 mm. This research used 18 CoCr metal samples divided into three groups, namely 100% new metal group (control), 50% new + 50% repeated composition group, and 100% repeated group. Result: The mean strain of the new 100% CoCr metals group was 0.133%, strain mean of the new 50% CoCr + 50% repeated metals group was 0.1%, and the strain of the 100% repeated CoCr metals group was 0.066%. The average modulus of elasticity (MPa) for the new 100% CoCr metals group is 7866, or 711 MPa, the new 50% CoCr + 50% repeat metals group is 7538, or 833 MPa, the 100% CoCr metals group is 6659, or 336 MPa. Conclusion: The new 100% CoCr metal group has a higher average tensile strength value than the 50% new CoCr metal + 50% repeated group, and the lowest is the 100% repeated CoCr metal group.

Removal of Cr (VI) by crosslinked chitosan adsorbent prepared using simulated copper-containing wastewater

A chitosan (CS) hydrogel bead cross-linked by Cu2+ with a macroscopic spheral shape (designated as CS-Cu-B) was synthesized using simulated copper-containing wastewater without additional crosslinking agents. The optimal conditions for CS-Cu-B formation were identified as 1500 mg/L of Cu2+ concentration, pH 5.4 and 50 °C under which CS-Cu-B was further utilized as an adsorbent for Cr(VI). The adjacent chitosan chains were crosslinked by coordination between positive-charged Cu2+ ions and the amino and hydroxyl groups of chitosan. This enhanced the surface charge and increased the specific surface area of CS-Cu-B, thereby augmenting its Cr(VI) adsorption capacity. The effect of adsorbent dosage, pH of Cr(VI) solution, and presence of coexisting ions on Cr(VI) adsorption was investigated. Detailed analyses of the adsorption kinetics, isotherms and thermodynamics of Cr(VI) on CS-Cu-B were also conducted. CS-Cu-B demonstrated a maximum Cr(VI) adsorption capacity of 90.76 mg/g at pH 4.0 and exhibited excellent reusability, retaining 87.90 % of its adsorption capacity after five adsorption-desorption cycles. Both experimental characterizations and DFT calculation elucidated that the electrostatic attraction adsorption is the main driving force for the adsorption of CS-Cu-B on Cr(VI). A consecutive preparation-adsorption strategy using simulated copper-electroplating wastewater was proposed to facilitate the recycling of heavy metals.

Sustainable extraction and recycling of non-ferrous metals: a review from a European perspective.

This review article provides a comprehensive examination of sustainable extraction and recycling methods for non-ferrous metals, which are critical to a wide range of industries including electronics, construction and renewable energy. Focusing on metals such as aluminium, copper and silicon, the study highlights the importance of recycling in conserving resources and minimizing environmental impact. It discusses the challenges posed by material diversity in recycling processes and the advances in recycling technologies that have emerged in response. Special emphasis is placed on the importance of a circular economy in maintaining a sustainable balance between consumption and conservation of metal resources. Through detailed analysis, it advocates innovative recycling practices and improved design for recyclability and highlights the role of policy, industry and consumer behaviour in achieving sustainability goals. The findings contribute to the discourse on strategic self-sufficiency in Europe through recycling, providing insights into how to improve efficiency and manage the complexity of the global material cycle. This work calls for a collaborative effort towards sustainable metallurgy and underlines the critical need for advances in recycling infrastructure and technology to ensure the long-term availability and environmental stewardship of non-ferrous metals.This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

Effects of 3D Printing Parameters on the Flexural Properties of Semi-Crystalline PEKK

Fused filament fabrication (FFF), a leading additive manufacturing (AM) methodology has revolutionised the production of 3D objects. FFF enables the manufacture of complex geometries not achievable with traditional manufacturing methods. This study investigates the use of the high-performance polymer, polyetherketoneketone (PEKK) for advanced AM applications in the growing field of in-space manufacturing (ISM), where lightweight recyclable metal alternatives can greatly reduce launch payloads. Utilising a response surface methodology, this research examines the effects of print speed, layer thickness, nozzle temperature, and build platform temperature on PEKK's mechanical, physical, and thermal properties.Optimum print conditions for maximising the flexural modulus were identified as 30mm/s print speed, 0.1mm layer thickness, 380°C nozzle temperature, and 140°C build platform temperature. These parameters improve the material's crystallinity by extending its residence time in the printer's heated chamber. This prolonged exposure facilitates better molecular alignment and reduces thermal gradients, leading to a 30% enhancement in crystallinity compared to conditions with higher print speeds and greater layer thicknesses. Scanning Electron Microscopy (SEM) and micro-computed tomography(µCT) analyses revealed that layer thickness significantly influences void formation, with thinner layers yielding superior interlayer bonding and reduced void volume. Differential Scanning Calorimetry (DSC) confirmed that increased crystallisation had a direct impact on flexural modulus, increasing it to 3682MPa, approaching 80% of PEKKs injection moulding performance. This study highlights the complex relationships between the FFF parameters and PEKK's mechanical properties, highlighting its potential for industrial and ISM applications.

Surface display and application of cadmium-binding protein CADR on the cell wall of Chlamydomonas reinhardtii

Algae has been proven to have the potential to be efficient biosorbents in the detection and remediation of heavy metal pollution such as cadmium in the environment. This study aims to enhance the cadmium adsorption capacity of Chlamydomonas reinhardtii by expressing the cadmium-binding protein CADR on the cell wall by the surface display technology. Firstly, the golden gate technique was employed to construct the transformation vector PET-X-CADR, which anchored CADR to the cell wall with the cell wall protein GP1. The high-throughput screening with the fluorescence signal of the fusion tag YFP resulted in three engineered algal strains with high expression of CADR on the cell wall. Physiological experiments demonstrated that the CADR displayed on the cell wall did not affect the growth of the engineered algal strains exposed to cadmium with the concentration below 200 μmol/L. In the presence of 200 μmol/L cadmium, the growth rates of CADR-engineered algal strains were three times as that of the wild-type, indicating stronger tolerance of the CADR-engineered algae to cadmium. The protein lyase GLE released during the mating of Chlamydomonas was used to isolate the cell walls of wild-type and engineered strains, the cadmium content of which was compared. The results showed that the cell wall of the engineered strain exhibited an increase of 33% in cadmium adsorption capacity. This study gives insights into the application of algae in the management of cadmium pollution in the environment, especially in the recycling of heavy metals from the environment.

Deep learning approaches for classification of copper-containing metal scrap in recycling processes

Separating copper from iron scrap is a critical operation in metal recycling and achieving this with low cost sensoric equipment like RGB cameras instead of XRF/XRT is becoming increasingly attractive. In this article, the groundwork for creating an image classification model to separate copper from iron scrap has been performed. Twenty of the most common and most easily available CNN architectures were trained on 2200 metal scrap specimens and evaluated inline on a sensor-based sorting rig for their prediction accuracy and their inference latency to mimic real circumstances in an industrial setting. Out of these evaluated architectures, DenseNet-201 with 98% accuracy in inline tests is recommended if potent hardware is available. Otherwise AlexNet with 92% accuracy or MobileNet-V2 with 90% accuracy are recommended for further investigation and model creation if hardware restrictions apply. Based on the presented results in this article, the initial cumbersome surveyance of the most suitable network architecture can be substantially reduced and the creation of a sorting model can be streamlined. This article thus provides the basis for creating an inline applicable sorting method for scrap metal that uses low cost sensorics equipment and can provide reasonably high accuracy in its prediction.

Biotechnological Approaches for Metal Recovery from Electronic Wastes.

The disposal of electronic waste (EW) in open landfills has caused several toxic environmental effects. The harmful metallic components released in the environment due to deposition of EW act as hazards for living systems. EW management has been widely studied in recent days across the world. Though, several processes are implemented in extraction, recycling and recovery of heavy metals from the EW, most of them are not effective in recovering the precious metals. Various chemical processes are executed for efficient extraction of precious metals from e-wastes. Though the techniques are easy to process and rapid, however, the chemical leaching also has detrimental environmental consequences. Biological approaches, on the other hand, solves the purpose for efficient and environmentally friendly recovery of precious metals. Thus, both resource recovery as well as remediation can be targeted simultaneously. Biotechnological methods offer sustainable and efficient solutions for metal recovery from electronic wastes, presenting a viable alternative to traditional methods. Continued advancements in this field hold significant promise for addressing the growing e-waste challenge.

Performance evaluation on recycling metals from lithium cobaltate by supercritical water combining with leaching-precipitation methods

The recycling of metals from spent lithium-ion batteries is currently a hotspot of research. This paper introduces a novel recovery method that integrates supercritical water and leaching-precipitation techniques to efficiently extract metals from lithium cobaltate electrodes. This study investigates the dissolution behavior of lithium cobaltate in supercritical water, and the interaction between lithium cobaltate and organic impurity (Polyvinylidene Fluoride and N-methylpyrrolidone) during the supercritical water treatment process. Lithium cobaltate reacts with supercritical water to form cobaltous hydroxide and reacts with polyvinylidene fluoride to form cobalt oxide. During the reaction of supercritical water with polyvinylidene fluoride and N-methylpyrrolidone in supercritical water, lithium cobaltate is reduced to cobalt oxide. The addition of N-methylpyrrolidone promotes the reduction of cobalt ion and the decomposition of polyvinylidene fluoride. Subsequently, the cathode materials treated with supercritical water are leached by using hydrochloric acid and sulfuric acid respectively. Cobalt and lithium ions in the leaching solution are precipitated by adding sodium hydroxide and sodium carbonate. The maximum recovery efficiencies of lithium and cobalt are 73 % and 79.60 %, respectively.

Prediction of metal recovery potential of end-of-life NEV batteries in China based on GRA-BiLSTM

As Chinese new energy vehicle (NEV) sales continue to grow, end-of-life batteries have great potential for recycling in the future. In this study, a combined model based on Gray Relation Analysis and Bi-directional Long Short-Term Memory (GRA-BiLSTM) is proposed for predicting NEV sales, and the NEV battery life is modeled using the Weibull distribution. Then, the amount of end-of-life batteries, secondary utilization and metal recycling are calculated. The impact of end-of-life battery recycling on the supply and demand of key metals is studied. The results show that in 2040, the secondary utilization of end-of-life batteries in the Standard Growth Rate-Lithium Iron Phosphate Battery Dominated-High Secondary Utilization rate scenario (SGR-LFPH) is 391.76 GWh. The recycling volumes of lithium, nickel and cobalt are 45,900 tons, 92,900 tons and 22,100 tons, respectively. In the Standard Growth Rate-lithium nickel cobalt manganese oxide Battery Dominated-Low Secondary Utilization rate scenario (SGR-NCML), the recycling of lithium, nickel and cobalt is even greater, at 62,600 tons, 372,200 tons and 71,700 tons, respectively. End-of-life batteries recycling can reduce the demand for metals. However, as NEV sales continue to grow, the gap between metal supply and demand remains significant. The findings urge the Chinese government develop appropriate battery management strategies to increase the recycling rate of end-of-life batteries; and to encourage enterprises to research new types of batteries to resolve the conflict between supply and demand for metals.

Processing and Characterization of Spent Nickel-Metal Hydride Type AA Batteries to Recover Valuable Materials (Cobalt, Nickel and Rare Earth Elements).

The experimental research was focused on the investigation of valuable material from spent Ni-MH type AA batteries, namely the metal grid anodes and the black mass material (anode and cathode powder). The materials of interest were analyzed by X-ray fluorescence spectroscopy (XRF), ICP-OES (inductively coupled plasma optical emission spectrometry), optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The analyzed grids have a high Fe content, but some of them correspond to the Invar alloy with approx. 40% Ni. In the black mass material, round particles and large aggregations were observed by SEM analysis, showing a high degree of degradation. The XRD analysis reveals the presence of only three compounds or phases that crystallize in the hexagonal system: La0.52Ce0.33Pr0.04Nd0.11Co0.6Ni4.4, Ni(OH)2, and La5Ni19. The obtained results provide useful and interesting information that can be used for further research in the recycling and economic assessment of metals from spent Ni-MH batteries.

Research on Magnetic Field of Permanent Magnet Rolls Arranged Periodically in Circumferential—Axial Direction

The separation of non-magnetic non-ferrous metals such as copper and aluminum from scrapped automobiles is a critical area of research due to the increasing number of end-of-life vehicles. Traditional eddy current separation methods have limitations, particularly in handling large-sized broken copper and aluminum parts. This paper proposes a novel magnetic roller model featuring a circumferential–axial periodic arrangement of permanent magnets. This study explores the external magnetic field distribution of this new roller design by constructing an equivalent current model, solving magnetic scalar potential equations, and employing simulation tools. The findings indicate that the new magnet array enhances both the magnetic field strength and the range of the external magnetic field, leading to improved separation efficiency of large-sized metal fragments. The results provide a theoretical basis for advancing the separation technology of large-sized broken copper and aluminum parts in scrapped automobiles, offering potential improvements in the recycling of non-ferrous metals from end-of-life vehicles.

Enhancing the recyclability of ELV plastic bumpers: Characterization of molecular, morphological, rheological, mechanical properties and ageing degradation

While the automotive industry has traditionally prioritized metal recycling, the increasing use of plastics in vehicles underlines the need for sustainable management of these materials. Recycling rates of plastics from end-of-life vehicles (ELVs) in Europe are low, but recent EU legislation requires 25 % of the plastics in new vehicles to be recycled, forcing innovative designs and strategies to enhance the recovery and quality of recycled resins. This study focuses on post-consumer bumpers, a significant recoverable component of ELVs, by assessing their molecular, morphological, rheological, and mechanical properties to investigate their homogeneity and quality from various sources to assess their suitability for recycling. Since the aging of these materials, caused by thermo-oxidative and thermo-mechanical degradation processes, can compromise the quality of recycled bumpers, we propose a blend of recycled PP from different bumper cars with virgin resin, representing a realistic scenario where the post-consumer ELV bumpers are collected. Interestingly, this blend, which can replace up to 50 % of the virgin resin without additional compatibilizers or additives, mitigates the degradation effects. Furthermore, the study evaluates the degradation resistance of these blends through multiple extrusion cycles and accelerated weathering tests in a temperature-controlled UV chamber to ascertain the number of cycles the material can tolerate without significant quality degradation, and to determine its suitability for long-term applications. Our results not only support the feasibility of using recycled PP for automotive components but also contribute to meeting the EU's recycling targets. This research highlights the potential for significant advances in the circularity of automotive plastics, providing a sustainable pathway for integrating recycled materials into new vehicle production.

Re-manufacturing of Pre-deformed Automotive Sheet Metal Stamping Scrap Without Melting

Abstract The recycling of aluminium sheet metal typically involves shredding and re-melting, processes which are both energy-intensive and challenged by the presence of metallic contaminants. To mitigate these issues, this study explores an alternative approach: the re-manufacturing of deep-drawn parts directly from scrap aluminium sheets, thus bypassing the melting step. We used 2 mm thick Al-Mg sheet metal in H111 temper to produce simulated stamping scrap (miniaturized bonnets). Blanks were cut from these bonnets and secondary parts in a cross-cup geometry were deep-drawn using two different forming processes: warm-forming at 200 °C and O-temper forming at room temperature. The resulting maximum draw depths were 20-22 mm for warm-forming and 25-30 mm for O-temper forming. While warm-forming resulted in lower draw depths, O-temper forming led to coarse recrystallized grain formation in some regions. Our approach could significantly reduce the energy consumption associated with aluminium recycling.

Direct construction of imidazoles via oxidative C(sp3)–H amination and annulation of aryethylamines by a Single-Atom cobalt catalyst

The development of reusable catalytic systems for achieving site-selective functionalization of C(sp3)-H bond remains a significant challenge. Herein, we designed a modified metal–organic framework (MOF)-derived N, P co-doped carbon supported single-atom cobalt catalyst, which was successfully applied in oxidative C(sp3)–H amination and cyclization of aryethylamines for construction of polysubstituted imidazoles. The advantages of the present method include: broad substrate scope, recyclable base metal catalyst, and naturally abundant O2 as green oxidant. The structural − activity relationship of the catalyst indicated that the atomically dispersed CoN3P1 is the active species responsible for the catalytic process. Furthermore, the synthesized imidazoles exhibited exceptional insecticidal activity against wheat pests, and may become lead molecules in the development of novel agricultural pesticide candidates, with significant application potential.

Utilisation of acid-tolerant bacteria for base metal recovery under strongly acidic conditions.

Hydrometallurgical bioprocesses for base metal recovery in environmentally friendly electronic device waste (e-waste) recycling are typically studied under neutral pH conditions to avoid competition between metals and hydrogen ions. However, metal leachate is generally strongly acidic, thus necessitating a neutralisation process in the application of these bioprocesses to e-waste recycling. To solve this pH disparity, we focused on acid-tolerant bacteria for metal recovery under strongly acidic conditions. Four acid-tolerant bacterial strains were isolated from neutral pH environments to recover base metals from simulated waste metal leachate (pH 1.5, containing 100 or 1000 mg L-1 of Co, Cu, Li, Mn, and Ni) without neutralisation. The laboratory setting for sequential metal recovery was established using these strains and a reported metal-adsorbing bacterium, Micrococcus luteus JCM1464. The metal species were successfully recovered from 100 mg L-1 metal mixtures at the following rates: Co (8.95%), Cu (21.23%), Li (5.49%), Mn (13.18%), and Ni (9.91%). From 1000 mg L-1 metal mixtures, Co (7.23%), Cu (6.82%), Li (5.85%), Mn (7.64%), and Ni (7.52%) were recovered. These results indicated the amenability of acid-tolerant bacteria to environmentally friendly base metal recycling, contributing to the development of novel industrial application of the beneficial but unutilised bioresource comprising acid-tolerant bacteria.

Engineered Biochar for Metal Recycling and Repurposed Applications

Engineered Biochar for Metal Recycling and Repurposed Applications