E-waste recycled materials as efficient catalysts for renewable energy technologies and better environmental sustainability

A review on e-waste contamination, toxicity, and sustainable clean-up approaches for its management

Ecosystems and human health are being negatively impacted by the growing problem of electrical waste, especially in developing countries. E-waste poses a significant risk to ecological systems because it can release a variety of hazardous substances into the environment, containing polybrominated diphenyl ethers and heavy metals, brominated flame retardants, polychlorinated dibenzofurans and polycyclic aromatic hydrocarbons, and dioxins. This review article provides a critical assessment of the toxicological consequences of e-waste on ecosystems and human health and data analyses from scientific journals and grey literature on metals, BFRs, PBDEs, PCDFs, and PAHs in several environmental compartments of commercial significance in informal electronic trash recycling. The currently available techniques and tools employed for treating e-waste are sustainable techniques such as bioremediation, chemical leaching, biological leaching, and pyrometallurgy have been also discussed along with the necessity of implementing strong legislation to address the issue of unregulated exports of electronic trash in recycling practices. Despite the ongoing hurdles, implementing environmentally sustainable recycling methods have the potential to address the detrimental impacts of e-waste and foster positive economic development.

Circular economy, economic growth, and e-waste generation in EU27 countries: Further evidence from the novel circular economy index and threshold effect

The circular economy has been identified as a critical keyword for achieving the Sustainable Development Goals. Nevertheless, there is a lack of in-depth empirical literature on the impact mechanisms of the circular economy (CE) and economic growth (GDP) in mitigating e-waste generation (waste electrical and electronic equipment - WEEE). Given Europe's leading position in e-waste generation per capita, the study aims to scrutinize the interplay between CE, GDP, and WEEE for 2010-2020. The research applies advanced econometric methods, primarily centered around the system generalized method of moment and dynamic panel threshold. It was noteworthy that different CE indicators exhibited varying effects on WEEE through the econometric analysis. Therefore, the research uniquely utilized the entropy weight method to compute a holistic composite index for the circular economy (CEI) and gained some interesting findings. Firstly, CEI significantly reduced WEEE, while GDP drove its increase. However, an overly developed CEI of 0.7616 counteracted its beneficial effect. Secondly, the synergy of CEI*GDP engendered the circular economy rebound effect, diminishing environmental benefits. Thirdly, in the circular context, the environmental Kuznets curve was validated, showcasing an inverted U-shaped pattern. Finally, the study found CEI to have different threshold effects, with thresholds of 0.2161 to inhibit WEEE, 0.2114 to avert the circular economy rebound effect, and 0.2360 to leverage GDP in reducing WEEE. These outcomes give insights to policymakers in designing sound policies targeting circular economy development and decoupling e-waste generation from economic growth towards the United Nations' SDGs.

V-MXenes for Energy Storage/Conversion Applications

MXenes, a two-dimensional (2D) material, exhibit excellent optical, electrical, chemical, mechanical, and electrochemical properties. Titanium-based MXene (Ti-MXene) has been extensively studied and serves as the foundation for 2D MXenes. However, other transition metals possess the potential to offer excellent properties in various applications. This comprehensive review aims to provide an overview of the properties, challenges, key findings, and applications of less-explored vanadium-based MXenes (V-MXenes) and their composites. The current trends in V-MXene and their composites for energy storage and conversion applications have been thoroughly summarized. Overall, this review offers valuable insights, identifies potential opportunities, and provides key suggestions for future advancements in the MXenes and energy storage/conversion applications.

Recovery of copper/carbon matrix nanoheteroarchitectures from recyclable electronic waste and their efficacy as antibacterial agents

Innovative solutions are urgently needed with the growing environmental hazard of electronic waste (e-waste) and the rising global threat of bacterial infections. This study addresses both issues by using e-waste to produce copper nanoparticles within a carbon matrix (Cu/C NPs), mitigating environmental hazards while exploring their antibacterial properties. Printed circuit boards from discarded computers were collected and treated with 2 M ammonium citrate dissolved in 8% ammonia solution. The leached solution was used to synthesize copper particles using ascorbic acid. The synthesized Cu/C NPs were characterized using various techniques such as EDX, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The antibacterial activity of Cu/C NPs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated using colony-forming unit (CFU) reduction assay and calculating the minimum inhibitory concentrations (MICs). The Cu/C NPs were found to be effective against E. coli and S. aureus with 100% and 98% CFU reduction, respectively, with MICs ranging from 250 to 375 μg mL-1 for E. coli and 375 to 750 μg mL-1 for S. aureus, according to the bacterial load. The bactericidal kinetics showed complete bacterial elimination after 5 and 7 hours for E. coli and S. aureus, respectively. This study presents a sustainable approach for utilizing e-waste and demonstrates the potential of the recovered nanoparticles for antibacterial applications.

Physicochemical reactions in e-waste recycling

Electronic waste (e-waste) recycling is becoming a global concern owing to its immense quantity, hazardous character and the potential loss of valuable metals. The many processes involved in e-waste recycling stem from a mixture of physicochemical reactions, and understanding the principles of these reactions can lead to more efficient recycling methods. In this Review, we discuss the principles behind photochemistry, thermochemistry, mechanochemistry, electrochemistry and sonochemistry for metal recovery, polymer decomposition and pollutant elimination from e-waste. We also discuss how these processes induce or improve reaction rates, selectivity and controllability of e-waste recycling based on thermodynamics and kinetics, free radicals, chemical bond energy, electrical potential regulation and more. Lastly, key factors, limitations and suggestions for improvements of these physicochemical reactions for e-waste recycling are highlighted, wherein we also indicate possible research directions for the future.

Mechanical characteristics of waste-printed circuit board-reinforced concrete with silica fume and prediction modelling using ANN

The use of electronic waste in cement concrete as a fibre additive has proven to be very promising for improving mechanical characteristics and developing sustainable construction materials to reduce the waste dumped in landfills. The following study investigated the effect of electronic waste (printed circuit boards (PCBs)) on the mechanical properties of concrete and predicted the same properties with an appropriate machine learning technique. PCB fibres 45 mm in length and 1.5 mm in width were manufactured and added as fibre additions to two sets of concrete mixes with and without silica fume. A 10% volume replacement of cement was substituted with silica fume (SF) to enhance the characteristics of PCB fibre-reinforced concrete and minimize cement consumption. The study included an evaluation of the fresh properties and mechanical characteristics after a 28-day curing period; thereafter, the results were compared and studied using the Levenberg-Marquardt backpropagation algorithm for predictions. The results show that the mechanical properties improved up to a 5% addition of PCB fibres, resulting in strengths of 63.55 MPa and 69.92 MPa for mixtures of PCB5% and SFPCB5%, respectively. A similar trend was achieved for other properties, such as the tensile and flexural strengths. The results of the ANN model predicted values with R2 values ranging from 0.94 to 0.99, indicating the efficacy of the model.

Intercalated PtCo Electrocatalyst of Vanadium Metal Oxide Increases Charge Density to Facilitate Hydrogen Evolution

Efforts to develop high-performance electrocatalysts for the hydrogen evolution reaction (HER) are of utmost importance in ensuring sustainable hydrogen production. The controllable fabrication of inexpensive, durable, and high-efficient HER catalysts still remains a great challenge. Herein, we introduce a universal strategy aiming to achieve rapid synthesis of highly active hydrogen evolution catalysts using a controllable hydrogen insertion method and solvothermal process. Hydrogen vanadium bronze HxV2O5 was obtained through controlling the ethanol reaction rate in the oxidization process of hydrogen peroxide. Subsequently, the intermetallic PtCoVO supported on two-dimensional graphitic carbon nitride (g-C3N4) nanosheets was prepared by a solvothermal method at the oil/water interface. In terms of HER performance, PtCoVO/g-C3N4 demonstrates superior characteristics compared to PtCo/g-C3N4 and PtCoV/g-C3N4. This superiority can be attributed to the notable influence of oxygen vacancies in HxV2O5 on the electrical properties of the catalyst. By adjusting the relative proportions of metal atoms in the PtCoVO/g-C3N4 nanomaterials, the PtCoVO/g-C3N4 nanocomposites show significant HER overpotential of η10 = 92 mV, a Tafel slope of 65.21 mV dec-1, and outstanding stability (a continuous test lasting 48 h). The nanoarchitecture of a g-C3N4-supported PtCoVO nanoalloy catalyst exhibits exceptional resistance to nanoparticle migration and corrosion, owing to the strong interaction between the metal nanoparticles and the g-C3N4 support. Pt, Co, and V simultaneous doping has been shown by Density Functional Theory (DFT) calculations to enhance the density of states (DOS) at the Fermi level. This augmentation leads to a higher charge density and a reduction in the adsorption energy of intermediates.

A study on waste PCB fibres reinforced concrete with and without silica fume made from electronic waste

This research goal is to appraise the effect of electronic waste on concrete properties by examining the mechanical properties of concrete reinforced with waste printed circuit boards (PCBs). PCB fibres, each 50 mm long, were mixed in varying proportions (1-5% by weight of cement). Silica fume (SF) was used as a 12% weight replacement for cement to conserve the properties of PCB fibre-reinforced concrete while tumbling cement consumption. Following a 28-day curing period, the fresh and hardened characteristics of PCB fibre-reinforced concrete were juxtaposed with those of conventional concrete. The experimental results led to the conclusion that 5% by weight of cement is the most effective proportion of PCB fibres to include in both PCB fibre-reinforced concrete and silica fume-modified PCB fibre-reinforced concrete. The addition of PCB fibres and silica fume significantly increased the mechanical strength of the concrete, making it suitable for high-strength concrete applications. Based on a similar investigational research design, an artificial neural network model was created, and it played a critical role in predicting the mechanical properties of the concrete. The model produced accurate results, with an R-squared (R2) value greater than 0.99.

Recycling of Electrical Cables-Current Challenges and Future Prospects

Civilization and technical progress are not possible without energy. Dynamic economic growth translates into a systematic increase in demand for electricity. Ensuring the continuity and reliability of electricity supplies is one of the most important aspects of energy security in highly developed countries. Growing energy consumption results not only in the need to build new power plants but also in the need to expand and increase transmission capacity. Therefore, large quantities of electric cables are produced all over the world, and after some time, they largely become waste. Recycling of electric cables focuses on the recovery of metals, mainly copper and aluminum, while polymer insulation is often considered waste and ends up in landfills. Currently, more and more stringent regulations are being introduced, mainly environmental ones, which require maximizing the reduction in waste. This article provides a literature review on cable recycling, presenting the advantages and disadvantages of various recycling methods, including mechanical and material recycling. It has been found that currently, there are very large possibilities for recycling cables, and intensive scientific work is being carried out on their development, which is consistent with global climate policy.