Recycling Technology Research Articles

Enhancing the Thermoelectric Performance of n‐Type Mg3Sb2‐Based Materials via Ag Doping

AbstractThe n‐type Mg3(Sb, Bi)2 compounds show great potential for wasted heat energy harvesting due to their promising thermoelectric properties. This work discovers that doping transition element Ag into the n‐type Mg3(Sb, Bi)2 can effectively optimize the power factor and suppress the lattice thermal conductivity simultaneously. Interestingly, the Ag doping has different effects compared to the isoelectronic and same group element Cu addition studied previously. A high power factor of 19.6 µW cm−1 K−2 is obtained at 673 K owing to the increased electrical conductivity. At the same time, the lattice thermal conductivity is reduced to ≈0.5 W m−1 K−1 because of enhanced phonon scattering induced by Ag atoms. These improvements lead to a peak figure of merit (ZT) of 1.64 at 673 K as well as a high average ZT of 1.27 is obtained from 323 K to 673 K. Furthermore, a thermoelectric single leg with a competitive conversion efficiency of ≈11% under a hot‐side temperature of 673 K is fabricated successfully. In addition, a 2‐pair module composed of n‐type Mg3(Sb, Bi)2 alloy and p‐type MgAgSb‐based compound demonstrates the high conversion efficiency of ≈7.9% at a temperature difference of 277 K, which will significantly upgrade the sustainable energy recycling technology.

Advances in Global Oyster Reef Restoration: Innovations and Sustainable Ecological Approaches

Oysters have been recognized as ecological engineers for aquatic ecosystems, as oyster reefs provide critical habitats and foraging locations for other marine species. In the past few decades, anthropogenic activities have negatively impacted oyster reef ecosystems across the globe, resulting in a significant decline in their population. This review critically examines the causes and extent of oyster reef degradation, as well as the effectiveness of restoration initiatives employed to reverse this decline. Furthermore, this review evaluates the effectiveness of restoration strategies employed to rehabilitate oyster reefs. Different approaches, such as genetic improvement, suitable site selection, and oyster seeding to enhance oyster reef restorations, are critically reviewed in this paper. Furthermore, some advanced restoration approaches such as 3D printing, shell recycling, and acoustics technologies are also discussed in this paper, which opens the new doors for researchers in the field of restoration ecology. Challenges and barriers hindering successful restoration are also addressed, including financial constraints, regulatory complexities, and public engagement. The findings and insights presented herein contribute to the growing body of knowledge on oyster reef ecology and serve as a valuable resource for policymakers, scientists, and conservation practitioners seeking effective strategies for restoring these vital coastal ecosystems.

Pathways to Carbon Neutrality in Civil Engineering

Abstract. With the development of the global economy and trade exchanges worldwide, urban infrastructure and industrial development have become part of the competition among countries. However, the construction industry and the production of chemical materials emit a large amount of carbon dioxide, leading to the continuous deterioration of the environment, so it is necessary to effectively reduce emissions. As a synonym for global emission reduction, carbon neutrality plays an important role in different industries, especially in civil engineering. In this paper, we start with building materials and green construction to explore the realization of carbon neutrality at the source and center of carbon emission in civil engineering. Firstly, we introduce the low-carbon production technologies of cement and steel, including calcium recycling and membrane separation technology in the cement industry, high-temperature combustion technology and carbon capture technology in steel industry. Then, we take renewable concrete as an example to discuss the emission reduction path of green building materials. Finally, it outlines how to carry out green construction, introduces assembly carbon reduction technology and energy integration system, and demonstrates the possibility of this green construction program in the case of "T&A House".

Development and Application of Green Catalysts: Challenges, Optimization, and Future Perspectives

This paper comprehensively reviews the development and application of green catalysts in modern chemical industries, with a focus on analyzing the significant advantages of various types of green catalysts, such as metal-organic frameworks (MOFs) and enzyme catalysts, in improving reaction efficiency, reducing energy consumption, and minimizing by-product generation. The paper delves into the design and synthesis of green catalysts, optimization of reaction conditions, and technologies for catalyst recycling and regeneration, highlighting their key roles in enhancing catalyst performance. Despite challenges such as high material costs, complex synthesis processes, and issues with stability and durability in practical applications, continuous technological innovation and process improvements offer promising solutions. As global attention to sustainable development grows, green catalysts are expected to have broad applications in emerging fields such as carbon capture and utilization, renewable energy conversion, and environmental remediation, thereby driving the green transformation and low-carbon development of the chemical industry and providing strong technical support for achieving global sustainability goals.

Graphite Regeneration and NCM Cathode Type Synthesis from Retired LIBs by Closed-Loop Cycle Recycling Technology of Lithium-Ion Batteries

A closed-loop regeneration process for spent LiCoO2 has been successfully designed with prior synthesis of LiNixCoyMnzO2, by the authors. This research applies the methodology to lithium-ion battery anodes, using spent graphite from a decommissioned battery in a leaching process with 1.5 mol∙L−1 malic acid and 3% H2O2 alongside LiCoO2. The filtered graphite was separated, annealed in an argon atmosphere, and the filtrate was used to synthesize NCM cathode material. Characterization involved X-ray diffraction, EDX, and SEM techniques. The regenerated graphite (RG) showed a specific discharge capacity of 340.4 mAh/g at a 0.1C rate in the first cycle, dropping to 338.4 mAh/g after 55 cycles, with a Coulombic efficiency of 99.9%. CV and EIS methods provided further material assessment. In a related study, the SNCM111 synthesized from the leaching solution showed a specific discharge capacity of 131.68 mAh/g initially, decreasing to 115.71 mAh/g after 22 cycles.

Optimisation and Composition of the Recycled Cold Mix with a High Content of Waste Materials

This research focuses on a mineral–cement mixture containing bitumen emulsion, designed for cold recycling procedures, the formulation of which includes 80% (m/m) of waste material. Deep cold recycling technology from the MCE mixture guarantees the implementation of a sustainable development policy in the field of road construction. The utilised waste materials include 50% (m/m) reclaimed asphalt pavement (RAP) from damaged asphalt layers and 30% (m/m) recycled aggregate (RA) sourced from the substructure. In order to assess the possibility of using a significant amount of waste materials in the composition of the mineral–cement–emulsion (MCE) mixture, it is necessary to optimise the MCE mix. Optimisation was carried out with respect to the quantity and type of binding agents, such as Portland cement (CEM), bitumen emulsion (EMU), and redispersible polymer powder (RPP). The examination of the impact of the binding agents on the physico-mechanical characteristics of the MCE blend was performed using a Box–Behnken trivalent fractional design. This method has not been used before to optimise MCE mixture composition. This is a novelty in predicting MCE mixture properties. Examinations of the physical properties, mechanical properties, resistance to the effects of climatic factors, and stiffness modulus were conducted on Marshall samples prepared in laboratory settings. Mathematical models determining the variability of the attributes under analysis in correlation with the quantity of the binding agents were determined for the properties under investigation. The MCE mixture composition was optimised through the acquired mathematical models describing the physico-mechanical characteristics, resistance to climatic factors, and rigidity modulus. The optimisation was carried out through the generalised utility function UIII. The optimisation resulted in indicating the proportional percentages of the binders, enabling the assurance of the required properties of the cold recycled mix while utilising the maximum quantity of waste materials.

Current recycling innovations to utilize e-waste in sustainable green metal manufacturing.

The ever-increasing market demand and the rapid uptake of the technologies of electronics create an unavoidable generation of high-volume electronic waste (e-waste). E-waste is embedded with valuable metals, alloys, precious metals and rare earth elements. A substantial portion of e-waste ends up in landfills and is incinerated due to its complex multi-material structure, creating loss of resources and often leading to environmental contamination from the release of landfill leachates and combustion gases. Conversely, due to the ongoing demand for valuable metals, global industrial and manufacturing supply chains are experiencing enormous pressure. To address this issue, researchers have put multifaceted efforts into developing viable technologies and emphasized right-scaling for e-waste reclamation. Several conventional and emerging recycling technologies have been recognized to be efficient in recovering metal alloys, precious and rare earth metals from e-waste. The recovery of valuable metals from e-waste will create an alternative source of value-added raw materials, which could become part of supply chains for manufacturing. This review discusses the urgency of metal recycling from e-waste for sustainability and economic benefit, up-to-date recycling technologies with an emphasis on their potential role in creating a circular economy in e-waste management.This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

Super Tough PA6/PP/ABS/SEBS Blends Compatibilized by a Combination of Multi-Phase Compatibilizers

Development of multi-component blends to prepare high-performance polymer materials is still challenging, and is a key technology for mechanical recycling of waste plastics. However, a multi-phase compatibilizer is prerequisite to create high-performance multi-component blends. In this study, POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) compatibilizers are prepared via melt-grafting of maleic anhydride (MAH) and styrene (St) dual monomers to polyolefin elastomer (POE) and poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), respectively. Subsequently, these compatibilizers are utilized to compatibilize the PA6/PP/ABS/SEBS quaternary blends through melt-blending. When POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) are added, respectively, both can promote the distribution of the dispersed phases, significantly reducing the dispersed phase size. When adding 10 wt% POE-g-(MAH-co-St) and 10 wt% SEBS-g-(MAH-co-St) together, compared to the non-compatibilized blend, the fracture strength, fracture elongation, and impact strength surprisingly increased by 106%, 593%, and 823%, respectively. It can be attributed to the hierarchical interfacial interactions which facilitate gradual energy dissipation from weak to strong interfaces, resulting in the improvement of mechanical properties. The synergistic effect of the enhanced phase interfacial interactions and toughening effect of elastomer compatibilizer achieved simultaneous growth in strength and toughness.

Mitigation of phosphorus contamination from livestock farms with La-containing hydrochar adsorbent

Phosphorus releases from livestock and poultry farms cause environmental contamination that must be mitigated through robust and effective recycle technologies. Lanthanum-modified hydrochars (La-HCN) prepared via mechanochemical modification had 96.8 mg g−1 phosphorus adsorption capacities and unprecedented fast uptake rates (half-maximum absorption capacity in 1.5 min). Presence of nitrogen in the hydrochars enhanced ion electrostatic interactions between lanthanum and carbon and accelerated phosphorus adsorption, which was confirmed theoretically with density functional theory calculations. Life cycle assessment (LCA) on a one-animal one-year basis revealed that production of La-containing hydrochar required fewer resources, had lower greenhouse gas emissions (171 kg CO2) and lower environmental impact than comparable adsorbent materials. Phosphorus removal levels achieved using the La-HCN adsorbent on actual wastewater from livestock and poultry breeding farms reached an adsorption rate of 93.6 %, exceeded sewage effluent standards of China, US EPA and EU, thus, demonstrate the practicality and scope of the developed technology.

Silver cementation mechanism for leaching silicon solar cells in nitric acid

Silicon solar panels are often overlooked in e-waste recycling technology, even though they contain precious silver (Ag). In order to help meet future global Ag demands and prevent contamination of the environment, all the Ag from end-of-life modules must be recovered instead of landfilled. The most mature Ag recycling recipes use high concentration nitric acid (HNO3) solutions often in combination with heating and agitation. After the Ag is leached, chemical precipitation or electrochemistry is used to recover metallic Ag. However, the process of Ag leaching in the HNO3 system with competing elements from silicon solar cells is not well understood. In this paper, we investigate the thermodynamics governing Ag leaching in low-concentration HNO3 without agitation or heating to expand fundamental knowledge in support of Ag recovery efforts from end-of-life solar panels. ICP-OES is used to quantify the amount of Ag leached in the HNO3 solution over time. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) are used to study the changes on the silicon solar cell surface. Our results suggest when trace tin (Sn) is used in solar cell fingers, it causes Ag to cement in dendritic form.

Thiourea-linked covalent triazine frameworks enable efficient and selective gold recovery from e-waste leachate

The surging electronic waste (e-waste) has been stimulating the unremitting exploration about the advanced gold recycling technology, which is of great significance to alleviate the shortage of metal resources and minimize the negative environmental impact. Herein, the thiourea-linked covalent triazine frameworks (denoted as PbTu-CTFs) have been designed and constructed by the nucleophilic substitution between cyanuric chloride (CC) and 1,4-phenylene bis(thiourea) (named PbTu) for gold recovery from the actual e-waste leachate. Benefiting from the unique structural characteristics, including large surface areas, abundant porosity, excellent chemical stability, and high-density S, N coordinative sites, the fabricated PbTu-CTFs afford ultrahigh gold adsorption capacity up to 2255 mg/g and fast kinetics, as reflected by 99 % of Au recovery efficiency within 5 min. Meanwhile, satisfactory recyclability and regeneration are maintained after six rounds of consecutive adsorption/desorption tests. Furthermore, the resulting adsorbent is well competent for highly efficient and selective gold recovery from the acidic leaching solution of wasted central processing unit (CPU), exemplify its promising actual application potential.

Analysis of Citric Acid Recovery Technology for Recycling of Citric Acid from Waste Solution

Analysis of Citric Acid Recovery Technology for Recycling of Citric Acid from Waste Solution

Investigation of a Hydrophobic Sputtered Cu Electrode to Electrocatalyze CO2 Towards a C2+ Product: The Effect of Substrate and Catalyst Thickness

The overuse of fossil fuels has resulted in massive CO2 emissions, causing global environmental problems. Renewable energy-driven electrocatalysis, which can convert CO2 into fuels and chemicals, is considered an emerging technology for carbon resource recycling. Cu-based catalysts sputtered on hydrophobic carbon paper and a polytetrafluoroethylene (PTFE) membrane were comparatively investigated, while the effect of the thickness of the Cu sputtering layer on the electrocatalytic CO2 reduction performance was investigated. Additionally, the effect of substrate properties on the distribution and morphology of sputtered Cu metal was investigated by SEM and XRD. With carbon paper as the substrate, the highest FEC2+ achieved was 70% at 200 mA/cm2, while the maximum value of FEC2+ on the Cu/PTFE electrode was realized with a Cu thickness of 400 nm (72%). Additionally, the PTFE substrate demonstrated a better inhibiting effect on HER, with a lower FEH2 and high FEC2+ over different applied current densities.

E-Waste and Hazardous Elements: A Comprehensive Study of Chemical Components and Environmental Threats

Electronic waste, or "e-waste," has grown significantly as a result of the exponential rise of electronic gadgets and is currently one of the waste streams with the fastest rate of growth in the world. Many dangerous substances, such as organic pollutants like brominated flame retardants and heavy metals like lead, mercury, and cadmium, can be found in e-waste. The chemical components of e-waste are thoroughly analyzed in this work, with an emphasis on the identification, measurement, and health and environmental effects of these hazardous materials. According to study, e-waste improper disposal and unofficial recycling can release dangerous substances into the environment, posing a major risk to human health including endocrine disruption and neurological damage. This can result in soil, water, and air contamination. The results highlight the necessity of more advanced recycling technology, stringent laws, and environmentally friendly design principles in order to reduce these hazards. This study adds to the expanding body of information on e-waste and urges immediate action to mitigate the risks that electronic trash poses to the environment and public health.

Hydroconversion of waste polyethylene plastics under mild conditions using mechanically mixed bifunctional catalysts: Impact of metal-acid balance and proximity

The disposal of non-biodegradable waste polyolefin plastics poses a serious environmental threat, highlighting the need for cleaner and more efficient thermochemical recycling technologies. This study introduces a scalable mechanical method to synthesize a metal-acid bifunctional catalyst. The mechanical ball milling process not only exposes more acidic sites but also enhances metal-acid proximity without blocking the pores. By varying the metal-acid balance (MAB) through different mixing ratios, we achieved higher yields and selectivity for soluble products at the optimal MAB level. Under mild conditions (250°C) for 8 h, polyethylene (PE) is efficiently converted into liquid phase iso-paraffins with an isomer selectivity of up to 56 % in the diesel and aviation kerosene fractions (C11-C18). This research underscores the importance of the accessibility of acidic sites to long-chain macromolecules, metal-acid site distance, and their balance in the hydrocracking of PE. It provides valuable theoretical insights and catalytic strategies for converting waste PE plastics into high-value fuel fractions.

A Business Management Model in the Circular Economy: Technological Solutions for Plastic Recycling

Objectives: this article develops a model for managing business processes in a circular economy using technologies for plastic recycling. Theoretical Framework: The theoretical idea and basis of the article consists in the development of project management methodology, process approach in the closed-loop economy, development of methods and economic tools aimed at effective resource management taking into account waste reduction and increased reuse of plastic fractions in Municipal Solid Waste (MSW). The application of digital technologies and solutions in the context of business process management in the field of plastics recycling will be substantiated, which will allow to identify new opportunities and reserves for optimising business processes in this field, increasing the efficiency of resource use, improving the environment and reducing costs. Method: the work uses a project approach, a process approach, digital modeling methods, and the “polluter pays” method. To implement the process approach, it is proposed to use the concept of Business Process Management (BPM). Competent business process management allows the company to react quickly to changing market conditions and customer orientation. Digital modelling in this paper means the representation of actions in the form of business processes in the organisation of solid waste management, the 'polluter pays' method means the economic assessment and accounting of environmental damage in waste management in the costs of business processes. Results and Discussion: The results of the study can be used to introduce the process approach to plastics recycling in individual regions and countries for the development of a green economy. According to the estimates of the authors, the optimisation and cost reduction of business processes, taking into account the environmental factor and the increase of the revenue part of the project from the reuse and inclusion in the economic turnover of plastic waste recycling products on the scale of the considered city (population of 1800 thousand people, area of 2856 ha, 18.14 tonnes of plastic waste accumulated per day) will reduce the costs of business process management by more than 200 thousand euros. Research Implications: the results of the study can be used to justify projects for the processing and recycling of solid municipal waste, including plastic waste, to introduce environmentally friendly production, to reduce the negative impact on the environment, to develop a process approach to the organisation of all activities for the collection of plastic waste in the city, district. In addition, the application of the proposed approach allows to obtain economic benefits for companies through the sale of secondary resources for the processing of plastic waste, as well as to reduce the negative impact on the environment. Originality/ Value: The originality of the research and its value lies in a new scientific formulation of the problem of reducing environmental pollution from plastic waste through the use of business processes in the field of plastic recycling and digital solutions, as well as the possibility of practical application of the results obtained in the field of green economy.

The Potential of Wood Construction Waste Circularity

Wood construction waste circularity presents enormous potential to significantly de-crease total greenhouse gas (GHG) emissions in the European Union (EU). Latvia could become a frontrunner due to its historic relationship with forestry, wood construction practises and unused potential of the innovative application of wood. This research examines what the potential of “circular wood” in Latvia is, how ready the Latvian wood house construction sector is to engage in a circular economy and wood waste circularity and whether the legal framework is ready to support wood waste management in the country. This study presents a combined approach for systematic wood construction product circularity assessment that includes a review of existing EU and Latvian frameworks for construction and demolition waste (CDW) management and wood construction, a general analysis of wood waste recycling systems and technologies, a quantitative data analysis of construction waste management in Latvia and qualitative data analysis of the Latvian wood house construction sector, and interviews with a focus group of Latvian wood industry representatives. The Latvian scope has allowed us to clarify the pattern methodology and impact points to be replicated, tested and measured further on a broader scale, in other countries, or throughout the whole EU. The main findings reveal a potential life cycle assessment (LCA) verifying the circularity of wood and limitations of wood construction waste circularity in Latvia in terms of wood house construction industry readiness and a legal framework as well as overall social prejudices for circular construction. Findings indicate an overall awareness and level of willingness to participate and engage in the circular construction models among Latvians; however, proactiveness and support (legal and financial) is expected from the government and municipalities. The recommendations point towards improvements in wood waste data management, the wood construction sector and the overall impact on sustainable development goals.

The Environmental and Economic Impacts of Tire Recycling Technologies

Aims: Study of physical and chemical characteristics of technical carbon obtained by pyrolysis of worn automobile tires. Development of carbon-containing filler of composite elastomer materials for obtaining products based on them with a given structure, physical, mechanical and dynamic properties. Study Design: The physicochemical characteristics of carbon black obtained by pyrolysis of worn-out automobile tires were studied, and its composition was determined using modern physicochemical methods. Place and Duration of Study: Sample: Navoi State Mining and Technological University, Faculty of Chemical Technology Navai in the period from June 2023 to July 2024. Methodology: The density, ash content, pH and granulometric composition of the obtained technical carbon were studied using standardized methods and its qualitative and quantitative composition was determined using X-ray phase and IR spectroscopic methods. Results: The physicochemical characteristics of carbon black obtained by pyrolysis of worn-out automobile tires were studied. The bulk density, ash content, pH, mass fraction of moisture and granulometric composition of crushed carbon black were determined. It was found that a decrease in the particle size of carbon black leads to an increase in bulk density, acidity, humidity and has virtually no effect on ash content. X-ray phase analysis showed that carbon black mainly consists of amorphous carbon (88.4%), calcite (7.59%), ankerite (1.21%), zinc oxide (1.14%) and other components. Based on the results of thermal analysis, the temperature range of decomposition of carbon black residues was determined to be in the range of 150-9000C. Conclusion: The physicochemical characteristics of technical carbon obtained by pyrolysis of worn-out automobile tires were studied. The bulk density, ash content, pH, mass fraction of moisture and granulometric composition of crushed technical carbon were determined. It was established that a decrease in the particle size of technical carbon leads to an increase in bulk density, acidity, humidity and has virtually no effect on ash content.

Closed Circuit of 3-Dimensional Polymer Powders

This article describes the most important stages of testing the levels of innovative readiness of a new machine and material construction solutions for closed loops of polymer powders in 3D additive manufacturing. The aim of this study was to indicate the state and directions of development of the technology of geometric recycling of polymer powders in 3D additive manufacturing, the need to control the geometric quality of the powders, and the quality of the design of machines for their processing in a closed circuit. The method was aimed at creating a strategy and verifying the stages of development of a new idea for stabilizing the geometric and dynamic design features of polymer powders for additive manufacturing (3D printing). Connections and relationships of the variable design features of powders, machines and devices with variable postulated states of products and processes allowed for the analysis, knowledge, description and development of variables for stabilizing geometric features of polymer powders in recycling. The results show the possibilities of supporting innovative creativity according to the adopted method, allow for determining the level of compliance of the quality of the products of the technical system, the effectiveness of preparatory processes for recycling and the non-toxicity of the products and processes of the new technology and their closed loop. The goal of developing useful design values, according to an integrated method of analysis, assessment and environmental development, was achieved, including the proposal of design features of razor blade shredders, supported by genetic algorithms, and devices for stabilizing polymer powders in additive manufacturing with recycling.

Magnetic Supraparticles as Identifiers in Single-Layer Lithium-Ion Battery Pouch Cells.

The development of effective recycling technologies is essential for the recovery and reuse of the raw materials required for lithium-ion batteries (LIBs). Future recycling processes depend on accessible information, necessitating the implementation of a digital battery passport. The European battery regulation mandates the use of a machine-readable identifier physically attached to the batteries for accessing digital information. Since externally applied optical labels are vulnerable to mechanical damage, technologies for identification without these restrictions could be beneficial. This study demonstrates that magnetic supraparticles (SPs) can be used for contactless identification of lithium nickel manganese cobalt oxide (NMC) battery pouch cells via magnetic particle spectroscopy (MPS) and that multiple pouch cells can be discriminated based on their specific magnetic code. A comparison of three independent model scenarios revealed that the detection of SPs and the impact on cell performance are dependent on the integration location. The results validate the concept of magnetic identification in metallic environments with MPS as an alternative to optical labeling methods. This study provides a foundation for the development of a new selective labeling and identification technology for batteries, with the potential to facilitate recycling and contribute to a more sustainable future.