Search Results (183)

Quarry dust (QD) landfill causes environmental issues that cannot be ignored. In this study, we systematically explore its potential application as a supplementary cementitious material (SCM) in cemented paste backfill (CPB), revealing the activated mechanism of modified QD (MQD) and exploring the hydration process and workability of CPB containing QD/MQD. The experimental results show that quartz, clinochlore and amphibole components react with CaO to form reactive dicalcium silicate (C₂S) and amorphous glass phases, promoting pozzolanic reactivity in MQD. QD promotes early aluminocarbonate (M_c) formation through CaCO₃-derived CO₃²⁻ release but shifts to hemicarboaluminate (H_c) dominance at 28 d. MQD releases active Al³⁺/Si⁴⁺ due to calcination and deconstruction, significantly increasing the amount of ettringite (AFt) in the later stage. With the synergistic effect of coarse–fine particle gradation, MQD-type fresh backfill can achieve a 161 mm flow spread at 20% replacement. Even if this replacement rate reaches 50%, a strength of 19.87 MPa can still be maintained for 28 days. The good workability and low carbon footprint of MQD-type backfill provide theoretical support for—and technical paths toward—QD recycling and the development of low-carbon building materials. Full article

Plastic waste accumulation is one of the most pressing environmental challenges of the 21st century, owing to the widespread use of synthetic polymers and the limitations of conventional recycling methods. Among available strategies, chemical upcycling via depolymerization has emerged as a promising circular approach that converts plastic waste back into valuable monomers and chemical feedstocks. This article provides an in-depth narrative review of recent progress in the upcycling of major plastic types such as PET, PU, PS, and engineering plastics through thermal, chemical, catalytic, biological, and mechanochemical depolymerization methods. Each method is critically assessed in terms of efficiency, scalability, energy input, and environmental impact. Special attention is given to innovative catalyst systems, such as microsized MgO/SiO₂ and Co/CaO composites, and emerging enzymatic systems like engineered PETases and whole-cell biocatalysts that enable low-temperature, selective depolymerization. Furthermore, the conversion pathways of depolymerized products into high-purity monomers such as BHET, TPA, vanillin, and bisphenols are discussed with supporting case studies. The review also examines life cycle assessment (LCA) data, techno-economic analyses, and policy frameworks supporting the adoption of depolymerization-based recycling systems. Collectively, this work outlines the technical viability and sustainability benefits of depolymerization as a core pillar of plastic circularity and monomer recovery, offering a path forward for high-value material recirculation and waste minimization. Full article

As an important direction in industrial evolution, the synergistic agglomeration of manufacturing and productive service industries has become a key path to promote the green transformation of the economy. Based on China’s provincial panel data, this study utilizes a variety of econometric methods to explore in depth the mechanisms, spatial effects and regional differences in the impact of the synergistic agglomeration of manufacturing and productive service industries on the green, low-carbon and recycling development of the economy. The empirical results show that the synergistic agglomeration of manufacturing and productive services not only directly promotes the green, low-carbon and recycling development of the economy, but also generates an indirect impact through the intermediary channel and exhibits significant spillover characteristics in the spatial dimension. This conclusion holds firm after a series of robustness tests. In addition, environmental regulations and the level of regional industrialization play a moderating role on the impact of industrial synergistic agglomeration and green, low-carbon and recycling development of the economy, and the effect of the role varies across regions and levels of economic development. This paper provides a decision-making reference for further optimizing the regional layout of China’s industries and enhancing the green, low-carbon and recycling development of the economy in each province. Full article

The innovation of multi-material offers significant benefits to architectural systems. The fusion of multiple materials, transitioning from one to another in a graded manner, enables the creation of fused space without the need for mechanical connections. Given that plastic is a major contributor to ecological imbalance, this research on fused space aims to recycle plastic and use it as a multi-material for building applications, due to its capacity for being 3D printed and fused with other materials. Furthermore, to generate diverse properties for the fused space, several nature-inspired forming algorithms are employed, including Swarm Behavior, Voronoi, Game of Life, and Shortest Path, to shape the building enclosure. Subsequently, digital analyses, such as daylight analysis, structural analysis, porosity analysis, and openness analysis, are conducted on the enclosure, forming the color mapping digital diagram, which determines the distribution of varying thickness, density, transparency, and flexibility gradation parameters, resulting in spatial diversity. During the fabrication process, Dual Force V1 and Dual Force V2 were developed to successfully print multi-material gradations with fused plastic following an upgrade to the cooling system. Finally, three test sites in London were chosen to implement the fused space concept using multi-material. Full article

Soilless cultivation technology is a key means of overcoming traditional agricultural resource limits, providing an important path to efficient and sustainable modern agriculture by precisely regulating crop rhizospheric environments. This paper systematically reviews the technical system of soilless cultivation, nutrient solution management strategies, the interaction mechanism of rhizosphere microorganisms, and future development directions, aiming to reveal its technical advantages and innovation potential. This review shows that solid and non-solid substrate cultivation improves resource utilization efficiency and yield, but substrate sustainability and technical cost need urgent attention. The dynamic regulation of nutrient solution and intelligent management can significantly enhance nutrient absorption efficiency. Rhizosphere microorganisms directly regulate crop health through nitrogen fixation, phosphorus solubilization, and pathogen antagonism. However, the community structure and functional stability of rhizosphere microorganisms in organic systems are prone to imbalance, requiring targeted optimization via synthetic biology methods. Future research should focus on the development of environmentally friendly substrates, the construction of intelligent environmental control systems, and microbiome engineering to promote the expansion of soilless cultivation towards low-carbon, precise, and spatial directions. This paper systematically references the theoretical improvements and practical innovations in soilless cultivation technology, facilitating its large-scale application in food security, ecological protection, and resource recycling. Full article

Agricultural production waste (APW) is characterized by pollution, increasing volume, spatial dispersion, and temporal and spatial variability in its generation. The improper handling of APW poses a growing risk to the environment and public health. This paper focuses on the planning of APW recycling networks, primarily analyzing the selection of temporary storage sites and treatment facilities, as well as vehicle scheduling and route optimization. First, to minimize the required number of temporary storage sites, a set coverage model was established, and an immune algorithm was used to derive preliminary site selection results. Subsequently, the analytic hierarchy process and fuzzy comprehensive evaluation method were employed to refine and determine the optimal site selection results for recycling treatment facilities. Second, based on the characteristics of APW, with the minimization of recycling transportation costs as the optimization objective, an ant colony algorithm was used to establish a corresponding vehicle scheduling route optimization model, yielding the optimal solution for recycling vehicle scheduling and transportation route optimization. This study not only improved the recycling efficiency of APW but also effectively reduced the recycling costs of APW. Full article

The sludge produced by the Fenton process contains mixed-valence iron particulates (hereafter called Fenton wastes). Using a solvothermal method, we fabricated a new heterogeneous photo-Fenton catalyst using Fenton wastes and metal–organic frameworks (MOFs). Nanoporous metal carboxylate (MIL-88) MOF impregnated with Fenton waste was functionalized using 2,5-dihydroxyterephthalic acid (x-HO-MIL-88-C, x, concentration of the 2,5-dihydroxyterephthalic acid). The efficiency of x-HO-MIL-88-C was examined under visible light radiation using methylene blue (MB) as an index pollutant. We observed the best catalytic performance for MB degradation by 4-HO-MIL-88-C. In the photo-Fenton process, the simultaneous presence of singlet oxygen, superoxide, and hydroxyl radicals is confirmed by free radical quenching and electron spin resonance spectral data. These free radicals associate with holes in the non-selective degradation of MB. The 4-HO-MIL-88-C catalyst shows good stability and reusability, maintaining over 80% efficiency at the end of five consecutive cycles. This work opens up a new path for recycling Fenton wastes into usable products. Full article

Concerning building acoustics, the impact of sound propagation in the building structure can be considered one of the most relevant problems. Floating floors are an efficient solution, composed of a rigid walking surface above a resilient material. Functioning as a spring, the resilient layer must have adequate damping properties and compressive strength against permanent and imposed loads to guarantee its performance over time. In this context, this study aims to completely evaluate the impact sound reduction of composite lightweight floating floors formed by ceramic tiles and recycled rubber mats when subjected to prolonged loads, from material characterization to their application in a hypothetical scenario. This study was based on the dynamic stiffness (ISO 9052-1) and compressive creep (ISO 16534) of the resilient layer and the physical characterization of the ceramic tiles, predicting the present and future (15 years) impact sound reductions and their application in a hypothetical room, considering direct and indirect transmissions paths (ISO 12354-2). The results showed that the lightweight floating floor compositions lost their damping capability to a degree that can reduce their weighted reduction in the impact sound pressure level by up to 2 dB over prolonged periods (15 years). Howsoever, the compositions had considerable initial impact sound insulation capability and adequate performance maintenance over time. Full article

Waste valorization involves reusing and recycling waste materials to create useful products such as materials, chemicals, fuels, or energy. The primary goal is the transition to a circular economy model while minimizing the impacts of hazardous waste. Adopting such policies appears to be a one-way path due to the continuous increase in the consumption of raw materials. According to recent projections, by 2050, 180 billion tonnes of materials will be consumed annually. Since natural resources cannot meet these requirements, new sources must be explored. Waste can serve as an alternative source and cover at least part of the needs that arise. In this work, good practices regarding waste valorization are presented. The case studies examined include the waste/by-products of ultrabasic rocks resulting in chromite and magnesite mining, as well as the tannery sludge produced after the corresponding wastewater treatment. Full article

The increasing accumulation of plastic waste—especially from packaging and post-consumer sources—calls for the development of sustainable recycling strategies. Due to the challenges associated with sorting mixed waste, directly processing waste streams offers a practical approach. Polyethylene terephthalate (PET) and high-density polyethylene (HDPE) are common consumer plastics, but they are difficult to recycle together due to immiscibility and degradation. In mixed waste, recycled HDPE (r-HDPE) often contaminates the recycled PET (r-PET) stream. Additive manufacturing (AM) offers a promising solution to upcycle these mixed polymers into functional products with minimal waste. This study investigates the processing and characterization of r-PET/r-HDPE blends for AM, focusing on the role of compatibilizers in enhancing their properties. Blends were melt-compounded using a twin-screw extruder to improve dispersion, followed by direct pellet-based 3D printing. A compatibilizer (0–7 php) was incorporated to improve miscibility. Rheological testing showed that the 5 php compatibilizer optimized viscosity and elasticity, ensuring smoother extrusion. Thermal analysis revealed a 30 °C increase in crystallization temperature and a shift in decomposition temperature from 370 °C to 400 °C, indicating improved thermal stability. Mechanical testing showed a tensile strength of 35 MPa and 17% elongation at break at optimal loading. Scanning electron microscopy (SEM) confirmed reduced phase separation and improved morphology. This work demonstrates that properly compatibilized r-PET/r-HDPE blends enable sustainable 3D printing without requiring polymer separation. The results highlight a viable path for the conversion of plastic waste into high-value, customizable components, contributing to landfill reduction and advancing circular economy practices in polymer manufacturing. Full article

The anthropogenic deployment of plastic waste, especially petroleum-based plastics with toxic hydrocarbons, presents a significant environmental and health threat in sub-Saharan Africa (SSA). Herein, the high demand and rapid plastic production, coupled with improper disposal and inadequate waste management, have led to widespread contamination of air, water, and soil. Conventionally, plastic waste management, such as incineration and recycling, provides limited long-term solutions to this growing crisis. This necessitates urgent, sustainable, and eco-friendly remediation techniques to mitigate its far-reaching environmental implications. This comprehensive review focused on sustainable and eco-friendly techniques by exploring strengths, weaknesses, opportunities, and threats (SWOT) analysis of plastic waste management. Bioremediation techniques were found as potential solutions for addressing plastic waste in SSA. This paper examines advancements in physiochemical methods, the challenges in managing various plastic types, and the role of enzymatic and microbial consortia in enhancing biodegradation. It also explores the potential of genomic technologies and engineered microbial systems to convert plastic waste into valuable products, including bioenergy via bio-upcycling. These bioremediation strategies align with the United Nations Sustainable Development Goals (UN SDGs), offering a promising path to reduce the environmental and health impacts of plastic pollution in the region. This paper also considers future directions of integrating AI-powered recycling systems to facilitate the development of a circular economy in SSA. Additionally, this paper provides progress and future perspectives on bioremediation as a sustainable solution for plastic waste management in SSA. Full article

With the large-scale application of lithium-ion batteries in the field of new energy, many retired lithium batteries not only cause environmental pollution problems but also lead to serious waste of resources. Repairing failed lithium batteries and regenerating new materials has become a crucial path to break through this dilemma. Based on the research on the failure mechanism of ternary cathode materials, this paper systematically combs through the multiple factors leading to their failure, extensively summarizes the influence of heat treatment process parameters on the performance of recycled materials, and explores the synergistic effect between heat treatment technology and other processes. Studies have shown that the failure of ternary cathode materials is mainly attributed to factors such as cation mixing disorder, the generation of microcracks, phase structure transformation, and the accumulation of by-products. Among them, cation mixing disorder damages the crystal structure of the material, microcracks accelerate the pulverization of the active substance, phase structure transformation leads to lattice distortion, and the generation of by-products will hinder ion transport. The revelation of these failure mechanisms lays a theoretical foundation for the efficient recycling of waste materials. In terms of recycling technology, this paper focuses on the application of heat treatment technology. On the one hand, through synergy with element doping and surface coating technologies, heat treatment can effectively improve the crystal structure and surface properties of the material. On the other hand, when combined with processes such as the molten salt method, coprecipitation method, and hydrothermal method, heat treatment can further optimize the microstructure and electrochemical properties of the material. Specifically, heat treatment plays multiple key roles in the recycling process of ternary cathode materials: repairing crystal structure defects, enhancing the electrochemical performance of the material, removing impurities, and promoting the uniform distribution of elements. It is a core link to achieving the efficient reuse of waste ternary cathode materials. Full article

The cyclic process of the circular supply chain (CSC) involves many stakeholders, and how to synergistically promote the active participation of different entities in CSC practices in the complex context of interacting factors is an important condition for moving towards low-carbon sustainable development and realizing the economic benefits as well as the competitive advantages of enterprises. Therefore, based on the technology cycle perspective (recycling, remanufacturing, refurbishing, repairing, and reusing), this study combines text mining and bibliometrics to identify CSC drivers, establish a factor prioritization assessment model, and construct a comprehensive framework for a set of CSC implementation pathways covering multiple subjects and multidimensional factor interaction mechanisms. The results emphasize that the most critical drivers are policies and regulations, resource use efficiency, and consumer awareness and attitudes, with contribution rates of 5.1%, 4.5%, and 4.5%, respectively. On this basis, this paper explores the efficiency-enhancing path strategy for the synergistic implementation of CSC by multiple subjects from the perspectives of the four key subjects of CSC. It puts forward policy recommendations to promote the successful implementation of CSC at the level of mechanism construction and specific operation, to provide theoretical guidance for the cooperation of upstream and downstream subjects. Full article

The global plastic crisis, with over 400 million metric tons produced annually and minimal recycling, demands urgent solutions. Photocatalytic plastic photoreforming offers a dual benefit: converting non-recyclable plastics into hydrogen fuel and valuable chemicals using solar energy under mild conditions. This critical review highlights recent advances in photocatalyst design, including semiconductors, MOF-derived materials, and co-catalyst systems, and explores key insights into plastic degradation mechanisms and reactor configurations. Operational factors such as pH, light intensity, and flow dynamics are discussed for their impact on hydrogen yield and product selectivity. Life cycle and techno-economic assessments reveal current challenges in efficiency, scalability, and cost to illuminate the feasibility of implementing the technology at industrial scale. This study suggests that innovations in catalyst engineering, light management, and system integration provide viable paths forward. With its potential to upcycle plastic waste and contribute to low-carbon hydrogen economies, photoreforming represents a promising approach in advancing circular economy goals, especially when coupled with policy support and smart separation strategies. Full article

As the global ecological environment faces serious challenges and extreme climate change threatens the survival of humankind, the promotion of green development has become the focus for all countries in the world. As one of the world’s major greenhouse gas emitters, China has put forward the “twin goals” of achieving carbon peaking and carbon neutrality and is committed to promoting the green and low-carbon transformation of its cities. As the core of economic and social development, cities are the main source of carbon emissions. In response to the dual challenges of carbon emission control and traffic growth, it is particularly important to promote the development of green transportation. With the acceleration of urbanization, urban traffic pollution is becoming more and more serious. As a zero-emission transportation mode, electric vehicles have become a key way to achieve the carbon peak and carbon neutrality targets. In order to deeply analyze the research status of electric vehicles in the field of the green and low-carbon transformation of urban transportation in China and to explore the research hot spots, evolution trends, and their roles and strategies in the construction of green transportation networks, this paper uses the CiteSpace, VOSviewer, and Tableau analysis tools to review and analyze the 2460 articles and reviews in the Web of Science Core Collection (WOS) and 2650 articles and reviews in the China National Knowledge Infrastructure (CNKI), including the “publication volume and publication trend”, “subject citation path”, “countries cooperation and geographical distribution”, “author cooperation and institution cooperation”, “keyword co-occurrence and keywords clusters”, and the “evolution trend of research hot spots in timeline”. The results show that: (1) Since 2010, the research focus on electric vehicles has gradually increased, and especially in the past three years, the number of such publications has increased significantly. (2) China holds the lead in research output regarding electric vehicles and related fields, but its international cooperation needs to be strengthened. (3) In recent years, the research has focused on “energy transformation”, “energy-saving technology”, “carbon emissions”, “battery recycling”, and other relevant topics. The promotion and development of electric vehicles will continue to usher in new opportunities concerning technological innovation, policy support, and market expansion. Finally, based on the research hot spots and evolution trends of electric vehicles in the field of urban green transportation and low-carbon transportation in China, this paper discusses the key paths and strategies for electric vehicles to promote the transformation of urban transportation in China to green and low-carbon types and looks forward to future research directions. The research in this paper can provide theoretical support and practical guidance for China to promote electric vehicles, build low-carbon cities, and realize green transportation. It is expected to act as a useful reference for relevant policy formulation and academic research. Full article