Sustainable Materials and Technologies最新文献

The efficacy of Catharanthus roseus (Nayantara or Sadabahar) leaf extract as a green corrosion inhibitor for mild steel in chloride-contaminated environments has been investigated in the present work. This study has employed a straightforward, practical, and less expensive Maceration process to prepare leaf extract. The adaptability of the extract as a corrosion inhibitor has been evaluated through electrochemical polarization and impedance studies in chloride-contaminated environments with varying pH levels. In addition, long-term corrosion monitoring has been conducted to evaluate the sustainability of the inhibitor against chloride-induced corrosion at a neutral pH level. This novel study has revealed that the extract defends mild steel against chloride assaults better at pH 2 than it does in neutral or alkaline conditions. Moreover, electrochemical studies and subsequent characterizations have confirmed the film-forming nature of the inhibitor.

The intensive land use has led to soil degradation and contamination, resulting in concerns about food security and environmental health. Remediation of heavy metal-contaminated soils has become a critical global challenge. Hydrochar, derived from the hydrothermal carbonization of organic biomass, shows promise as a soil amendment due to its potential for carbon sequestration, greenhouse gas reduction, and soil improvement. Numerous studies have investigated hydrochar's application effects on improving the soil's physical properties and ability to immobilize heavy metals. This study aims to analyze data from the literature on how various factors, such as carbonization temperature, feedstock, soil texture, soil use type, and soil pH, affect heavy metal adsorption by hydrochars. By synthesizing existing research, this meta-analysis provides insights into the potential of hydrochar as a sustainable remediation solution for heavy metal-contaminated soils.

To fully utilize abundant marine resources and reduce the carbon footprint in the construction sector, this study developed a seawater sea-sand geopolymer mortar (SSGM) using seawater, sea-sand, and ternary solid waste. Three different alkaline content levels (4%, 5%, and 7%) were tailored for the SSGM, in addition to freshwater river sand mixed geopolymer mortars (FRGM), seawater sea-sand ordinary Portland cement mortar (SSCM), and SSGM without additional fibres (SSGM-0). The workability, setting time, mechanical performance, and drying shrinkage of all samples were studied. The microstructural characteristics of each mortar were meticulously scrutinized through techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and mercury intrusion porosimetry (MIP). The results showed that as alkaline content increased, SSGM formed more hybrid sodium, calcium aluminosilicate hydrate (N, C-A-S-H) gels, resulting in a denser matrix. Under the influence of magnesium ions and sulfate ions in seawater, the formation of magnesium aluminosilicate hydrates, magnesium silicate hydrates, and silica gels filled the pores, making SSGM has more mesopores and gel pores compared to FRGM, thus exhibiting superior mechanical properties. However, the Ca/Si ratio of the primary hydration products of SSGM was lower than that of SSCM and FRGM, indicating a more disordered microstructure of SSGM, leading to greater shrinkage. Despite moisture migration reaching a stable state, SSGM exhibited persistent shrinkage, revealing their inherent time-dependent (creep) response to drying conditions, indicative of typical viscoelastic/visco-plastic matrix behavior.

Red mud, a byproduct of alumina production, presents significant challenges due to its large-scale production and inefficient utilization, leading to substantial environmental and health hazards. Traditional disposal methods, such as land-based stockpiling, exacerbate environmental degradation, including soil and groundwater contamination, air pollution, and associated health risks. However, red mud, rich in valuable metals, particularly iron, offers a secondary resource for value-added utilization. This review evaluates various iron extraction methods, including physical, chemical, and pyrometallurgical techniques. Physical methods like magnetic separation and flotation, alongside chemical and hydrometallurgical methods like acid leaching, often encounter obstacles such as low iron recovery rates and acidic wastewater generation. Pyrometallurgical methods, despite their effectiveness, are hindered by high energy consumption and environmental concerns. Conversely, biomass pyrolytic reduction followed by magnetic separation within pyrometallurgical methods has emerged as a promising alternative. However, significant gaps remain in understanding the transformation mechanisms of iron minerals and impurities during biomass pyrolytic reduction, the kinetics of reduction specific to red mud, optimizing biomass quantities, and the nature of produced pyrolytic gases. Addressing these gaps is essential for realizing the full potential of biomass pyrolytic reduction as a sustainable solution for iron extraction from red mud, mitigating environmental impact and fostering sustainability.

Intermetallic catalysts, including quasicrystals, are considered a sustainable alternative to noble metal-based catalysts in hydrogenation reactions. This study discusses the manufacturing and catalytic potential of an Al-Ni-Co quasicrystalline alloy. Energy-effective and simple catalyst production was provided by a melt-spinning process. The obtained ribbons, characterized in terms of microstructure, phase and chemical composition using X-ray diffraction, scanning and transmission microscopy methods, were composed of a decagonal quasicrystalline phase with traces of crystalline phases. The form of the melt-spun ribbons ensured easy application in the phenylacetylene hydrogenation reaction. The catalyst provided a substrate conversion of approximately 80% and a styrene selectivity of 54% after 1 h of reaction carried out under mild conditions. The repeatability of the reaction course was verified, with a maximum deviation of 10%. Moreover, the catalyst recovered after the reaction was evaluated in terms of its phase composition and surface changes. X-ray diffractograms confirmed the phase stability, however, the surface degradation and oxidation occurred. The catalytic activity after three months of catalyst storage is also discussed.

Every year, tens of millions of tons of waste glass are buried on-site, causing serious resource waste and challenging environmental problems. Therefore, dealing with the problem of waste glass is a technical challenge with important economic significance. We used waste glass as a precursor to obtain foam recycled glass and then used a simple impregnation method to obtain magnetic foamed recycled glass (MG) and MoS₂ nanosheets wrapped magnetic foamed recycled glass (NMG). Subsequently, we established an excellent NMG/H₂O₂ system for the efficient degradation of tetracycline (TC) under low-power light sources. The NMG/H₂O₂ system has a 92.2% removal rate of TC, accompanied by the apparent reaction kinetic constant is 0.01865 min⁻¹. Meanwhile, the degradation mechanism of ·OH and ¹O₂ as the main active species was determined. Finally, the theoretical reaction sites of TC in the NMG/H₂O₂ system were obtained through density functional theory (DFT) calculation. The theoretical reaction sites were consistent with the reaction sites in the possible degradation pathways we obtained through the degradation fragment. In our work, we approach environmental issues with a “treating waste with waste” mindset, which combines economic and environmental considerations and may become the mainstream mindset in future environmental treatment.

This study investigates the recycling of polyethylene terephthalate (PET) water bottles by material extrusion (MEX), an additive manufacturing (AM) technique, with a focus on characterising energy consumption and mechanical properties throughout the recycling process. The process encompasses shredding of the bottles, filament production, and the printing of tensile specimens. A full factorial design of experiment (DoE) was used to investigate the impact of various process parameters on product quality from an energy-saving perspective. The results provide important insights into energy efficiency and mechanical performance, identifying the optimal production conditions that balance environmental sustainability and material functionality. The results show that by optimizing printing parameters, energy consumption can be reduced by up to 30%, while the tensile strength of the printed samples can be increased by 20%. This research contributes to a broader understanding of the potential for AM in PET recycling, providing a pathway towards more localized and sustainable manufacturing practices.

Sodium-ion batteries are considered to be an advantageous alternative to lithium batteries because of the scarcity and expensive cost of lithium. To address the limitations of limited capacity and poor rate in sodium-ion batteries, it is necessary to explore advanced cathode materials to develop high-performance sodium batteries. Na₃V₂O₂(PO₄)₂F is a promising sodium cathode material, but its performance has been often restricted by poor conductivity. In this work, we report on the design and synthesis of a porous composite in which Na₃V₂O₂(PO₄)₂F nanoparticles are sandwiched between Ti₃C₂ MXene nanosheets. In this structure, the porous MXene nanosheets facilitate the infiltration of the electrolyte, allowing more paths for sodium ion conduction. At the same time, due to the good conductivity of MXene, the conductivity of Na₃V₂O₂(PO₄)₂F could be effectively improved. As a result, the composite exhibits outstanding performance when used as a sodium cathode, delivering a high capacity of 128 mAh g⁻¹ and excellent rate ability of 103 mAh g⁻¹ at 5C (1C = 130 mA g⁻¹), as well as robust stability up to 2500 cycles.

Bioplastics, or plastics made from renewable sources, are often touted as a solution to the problems of plastic pollution and resource depletion, but this is not always the case. Growing bioplastics production, regardless of biodegradability, necessitates efficient end-of-life procedures for bioplastic waste if a genuinely sustainable plastics economy is to be achieved. There is a strong correlation between the biodegradability of bioplastics and their molecular and atomic composition. However, their biodegradation is heavily influenced by the local ecosystem. This study summarizes the most up-to-date information regarding the biodegradation and recycling of bioplastics in a variety of environmental conditions, and degrees of biodegradation, as well as the microorganisms isolated from various microbial communities that are capable of bioplastic degradation.

The extensive growth of End-of-Life Tyres (ELTs) has raised significant environmental concerns, making ELTs recycling a crucial strategy in mitigating their impact on the environment. ELTs recycling process begins with complex mechanical processes aimed at size reduction of rubber material and the rubber production at various sizes. Mechanical recycling processes not only generate a variety of useful products for most applications but also serve as the foundation for subsequent chemical and thermal processes in ELTs recycling. This paper aims to review the status of research and development related to mechanical processes for recycling ELTs. It provides a comprehensive overview of mechanical processes and techniques used in ELTs recycling, examining essential input variables, performance indicators and their relationships. To produce powders smaller than 0.8 mm, a mechanical recycling system typically involves multiple grinding stages and various particle separation methods. In most shredding processes, the produced particle sizes range from 100 mm to 200 mm. To achieve better shredding performance, an optimal configuration includes multiple rotational shafts, fewer than three cutting edges, and operation at temperatures below −70 °C. Grinding processes can generate granulates smaller than 2 mm, with cryogenic and wet grinding techniques capable of producing particle sizes <0.1 mm. Cryogenic grinding achieves the smallest expected particle size of 0.075 mm with a distribution below 0.1 mm. A future work could focus on developing a thorough relationship between multiple input and output parameters for further design and optimization of the mechanical recycling of ELTs. By integrating advanced engineering knowledge with a good combination of latest technology, an optimum ELTs recycling plan is developed to efficiently extract the reusable materials of ELTs and convert the additional material into reusable forms like energy, hydrogen etc.