Recycling Strategies Research Articles

Peroxymonosulfate activation by microplastics coagulated sludge-derived iron-carbon composite for effective degradation of tetracycline hydrochloride: Performance and mechanism

A simple one-step pyrolysis method was adopted to prepare microplastics (MPs) coagulated sludge into an iron-carbon composite (Fe-PSMPC), which was used to activate peroxymonosulfate (PMS) for the degradation of tetracycline hydrochloride (TC). The iron species in coagulated sludge were thermally reduced by carbon at 800 °C to produce abundant Fe0, which was successfully loaded on the surface of carbon derived from MPs. Then, the effects such as Fe-PSMPC dosage, PMS dosage, initial pH, and pollutant concentration on TC degradation were further investigated. The results showed that the Fe-PSMPC/PMS system was able to degrade TC effectively over a wide pH range. Under the optimal process conditions, the removal rate of TC could reach 87.5 % within 16 min. In addition, quenching experiments, electron paramagnetic resonance, electrochemical measurements, and X-ray photoelectron spectroscopy analyses indicated that the non-free radical (1O2 and electron transfer) pathway was dominant in the TC degradation system, and the free radical (•OH and SO4• −) pathway also showed significant contribution. Fe0 on Fe-PSMPC was the main active site, and the keto group (C = O) also acted as an active site to facilitate the generation of 1O2. Furthermore, three possible degradation pathways of TC were elaborated based on the 17 intermediates detected by liquid chromatography-mass spectrometry. This work provides an economical and convenient recycling strategy for the MPs coagulated sludge, which can be converted into an effective catalyst to activate PMS for the degradation of organic pollutants, thus realizing “treating waste with waste”.

Direct Upcycling of Leached FePO4 from Spent Lithium‐Ion Batteries toward Gradient‐Doped LiMnxFe1−xPO4 Cathode Material

AbstractLithium‐ion batteries (LIBs) with LiFePO4 (LFP) cathode materials have occupied a significant market share in state‐of‐the‐art power storage systems and electric vehicles, yet the approaching “retiring wave” of these LIBs should be appropriately treated (i.e., recycling of spent LIBs). Current recycling strategies of degraded LFP materials largely direct on leaching of lithium elements, leaving the leached FePO4 residual as a waste. Inspiringly, LiMnxFe1−xPO4 material is considered one of the potential candidates for next‐generation cathode materials because of its high electrochemical performance, extraordinary stability, and low cost. Herein, the direct upcycling of leached FePO4 toward LiMn0.25Fe0.75PO4 (LMFP) cathode material is demonstrated via a green, simple, and scalable mechanochemical pathway. The product features a gradient‐doping of Mn, as well as a uniform carbon coating for LMFP particles. As a result, the LMFP cathode material delivers superior electrochemical performance; the capacity (161.3 mA h g−1 at 0.1 C), rate capability (90.1 mA h g−1 at 5 C), cycling stability (95.6% capacity retention after 800 cycles at 1 C), and energy density (≈15% increase as compared to LFP) are almost comparable with those of fresh materials. The as‐established upcycling protocol offers a favorable reuse method for leached FePO4 materials.

Electro-Responsive Breathing Transition of Conductive Hydrogel for Broadband Kinetic Energy Harvesting.

Reclaiming kinetic energy from vibrating machines holds great promise for sustainable energy harvesting technologies. Nevertheless, the impulsive current induced by vibrations is incompatible with conventional energy storage devices. The energy-management system necessitates novel designs of soft materials for lightweight, miniaturized, and integrated high-frequency electrochemical devices. Here, this work develops a conductive hydrogel with an electro-responsive polymeric network. The electro-responsive breathing transition of the crosslinking points facilitates the expeditious formation of a localized electrolyte layer. This layer features an exceedingly high local charge density, surpassing that of a saturated electrolyte solution by an order of magnitude, and thus enabling rapid charge transport under the influence of an applied voltage. The micro-capacitor based on the gel exhibits record-high capacitance of ≈2 mF cm-2 when the frequency of energy input reaches up to 104 Hz. This work also demonstrates a prototype battery charger that harvests energy from a running car engine. This study presents a feasible strategy for waste energy recycling using integrated electrochemical devices, opening a new avenue for ambient energy management.

Developing Four Powder Recycling Strategy for Sustainable Additive Manufacturing 3D Printing Process

This paper presents a detailed analysis of four different powder recycling strategies for the metal additive manufacturing process focused on examining the efficacy of recycling Ti6Al4V alloy powder for the Laser-Based Powder Bed Fusion (LBPF) process. The study evaluates four distinct recycling strategies (A, B, C, D) and their impact on powder-saving mechanisms. The experimental methodology involves careful leftover powder sampling, implementation of recycling strategies and print cycle analysis from each recycling strategy. The results show that Strategies C and D exhibit the lowest powder waste, allowing 6 times the reuse of leftover powder and producing 384 parts with minimal powder waste at the end of the process. Strategy B also performs well, enabling 8 cycles and building 512 parts with only a small amount of powder wasted. Conversely, Strategy A yields the highest powder waste despite achieving the same number of cycles and prints. This proposed approach requires a total volume of 224,000 mm3 of powder for each build. This entails using 500g of gas-atomized Ti-6Al-4V powder, with an average particle size D90 of approximately 50 μm. This features a continuous mixing technique, wherein each build combines 50% virgin powder with 50% of the previously collected and sieved powder.

Recycling Strategy of Green Closed-Loop Supply Chain Under Urban and Rural Low-Carbon Planning

Abstract The low-carbon ecological city aims to harmonise sustainable urban development with low-emission planning approaches. Emissions from business production processes are central to low-carbon planning. This paper explores three closed-loop supply chain recycling models - manufacturer, retailer, and third-party -considering carbon trading and emission reduction technology investment. Respective Stackelberg game models are developed incorporating carbon emission reduction costs, recycling costs, carbon trading price, emission intensity, and recycling price. The influence of these variables on carbon emission reduction and profit is examined through numerical analysis. Results indicate the government’s free carbon quota does not impact per-unit carbon reduction or manufacturer profit, nor optimal recycling mode selection. Under specific remanufacturing emission intensity and production cost saving conditions, carbon quota trading can substantially incentivise manufacturers to invest in emission reduction and recycling. With carbon trading and emission reduction technology investment, manufacturer recycling optimises economic and environmental benefits when remanufactured products provide high production cost savings. This fosters sustainable development supporting low-carbon planning.

A Fast Multi-Frequency Iterative Acoustic Boundary Element Method Solver Based on a Preconditioned Accelerated Recycling Strategy

Common multi-frequency solution strategies for acoustic systems are either associated with high computational costs or resort to model reduction strategies, which potentially induce considerable approximation errors. In that context, this work proposes a fast multi-frequency solver for acoustic Boundary Element Method (BEM) analyses that combines conventional preconditioners with an accelerated recycling strategy, achieving in that way a fast and accurate iterative solution. Specifically, by approximating both the system and the related preconditioner by individual affine expressions, an upfront Galerkin projection on a global deflation basis is facilitated, therefore enabling the deployment of the accelerated recycling scheme. The latter acts by accelerating the construction of the related deflation projectors, therefore leading to a significantly faster recycling procedure. Finally, the efficiency of the global deflation basis is guaranteed through an Automatic Krylov subspaces Recycling for Deflation (AKR-D) [D. Panagiotopoulos, W. Desmet and E. Deckers, An accelerated subspaces recycling strategy for the deflation of parametric linear systems based on model order reduction, Comput. Methods Appl. Mech. Eng. 403 (2023) 115765] algorithm and thus, the cumulative number of iterations required by an iterative solver within a frequency sweep is drastically decreased. The proposed multi-frequency solver is tested on two industrially relevant examples of an interior and an exterior scattering problem, benchmarked against the traditional solution strategies.

On the role of system integration in plastic waste management

The management of plastic waste is a growing concern that can harm wildlife and ecosystems, and its end-of-life policies are key to mitigating plastic environmental impact. This work presents a decision-making methodology for the thermal and material valorization of plastic waste, coupling a supply chain model with multi-objective optimization and data analytics. It highlights the challenges and vulnerabilities of plastic waste management, the importance of system integration and holistic analysis, as well as the potential for carbon capture to reduce emissions. Our results suggest that efficient incineration, coupled with simplified waste logistics, can compete with existing mechanical recycling strategies in terms of emissions and costs. This study provides insights into municipal, regional, and European waste management, with the potential for a common EU platform and savings of 210 Mton of CO2 by harvesting benefits from plastic recycling and incineration with carbon capture.

Medium entropy metal oxide induced *OH species targeted transfer strategy for efficient polyethylene terephthalate plastic recycling

Increasing plastic waste is environmentally and biologically detrimental, and converting plastic waste into value-added chemicals and fuels by electrocatalytic methods is recognized as an up-cycling process that facilitates resource utilization. Here, we report a generalized medium entropy metal oxide Ni0.5Ce0.5Co2O4 induced *OH species targeted transfer strategy to selectively electrocatalytic upgrade various polyester plastics into value-added chemicals under alkaline conditions. Polyethylene terephthalate (PET) was upgraded to potassium diformate with high Faraday efficiency (95 %) and selectivity (>91 %) at a high current density of 343 mA cm−2, generating both terephthalic acid and hydrogen. The synergistic interplay between Ni and Ce in Ni0.5Ce0.5Co2O4 facilitates the adsorption of ethylene glycol molecules and hydroxide ions, prompting the directionally oriented hydroxyl (*OH) to partake in the oxidation of ethylene glycol, thereby fostering the oxidation of hydrolyzed PET products. This work not only develops an excellent electrocatalyst for the upcycling of various polyester plastics but also guides the design of medium entropy metal oxides as electrocatalysts.

Enhancing Sustainability through Automated Waste Classification: A Machine Intelligence Framework

This study presents a novel framework integrating a deep learning image classifier into waste classification systems for enhancing sustainability. Leveraging diverse waste image datasets, our approach employs a convolutional neural network (CNN) architecture tailored for precise waste material identification and sorting from images. Through transfer learning and dataset augmentation techniques, the CNN model demonstrates robust performance in real-time waste categorization, surpassing conventional methods. Experimental validation using comprehensive waste image datasets showcases notable advancements in classification accuracy and operational efficiency. The results underscore the potential of deep learning image classifiers in optimizing waste sorting processes, contributing to more effective recycling strategies, and promoting environmental sustainability. This research emphasizes the practical implications of integrating deep learning techniques into waste management systems, offering actionable insights for stakeholders and waste management professionals seeking innovative solutions for sustainable waste handling.

Amino acid based ionic liquids for revitalization of sulfated lead anodes

Lead acid batteries (LABs) are currently recycled using hazardous, polluting, and energy intensive procedures. Here we report a novel LAB recycling strategy with hydrophilic amino acid-based ionic liquids (ILs) to dissolve the water-insoluble PbSO4 crystals formed during deleterious hard sulfation at the anodes and then electrodeposit metallic Pb on a new surface. We identified two ILs, [Ch][Ser] and [Ch][Thr] ILs that show dramatic solubility towards PbSO4 at room temperature. [Ch][Ser] IL was successfully used in refurbishing hard sulfated anodes that had lost 99 % of their original capacity into a fresh Pb surface. More than 75 % of the capacity was renewed after a complete treatment on a half-cell. Electrodeposition of Pb from the Pb-[Ch][Ser] complex produced a uniform Pb microstructure. A remarkable 99 % of the IL-dissolved Pb2+ ions was electrodeposited. Furthermore, we solved the first crystal structure of the compound formed between Pb2+ and the amino acid-based IL. Based on 1H Nuclear Magnetic Resonance (NMR) spectrum of PbSO4 dissolved in the [Ch][Ser] IL and single crystal X-ray diffraction (XRD) studies, we discovered that the Pb2+ was coordinated with two [Ser] molecules and displayed a hemidirected five-coordinate geometry. ILs that can selectively dissolve PbSO4 thus hold promise for an environment-friendly alternative recycling paradigm for the LAB industry.

An Overview of Management Status and Recycling Strategies for Plastic Packaging Waste in China

Given their exceptional performance, plastic packaging products are widely used in daily life, and the dramatic expansion in plastic packaging waste (PPW) has exacerbated environmental problems. Many countries have enacted laws and developed recycling technologies to manage plastic packaging waste in consideration of the nature of PPW as both garbage and a resource. As the world’s largest producer and consumer of plastics, China has also taken measures to address this issue. This paper presents the latest management regulations and recycling strategies for PPW in China. Based on an analysis of the current management status of PPW and recycling technologies and their carbon emission impacts, some management suggestions and a comprehensive full-chain recycling process were put forward. We supposed that management challenges that need to be overcome in the future can be solved through the improvement of green designs for plastic packaging, manufacturing technology updates, consumption concept changes, and the high-value utilization of PPW. This paper aims to provide valuable references for government decisions on PPW management and, furthermore, to set up an economically sensible and industrially feasible PPW solution and boost the development of PPW recycling.

High-efficiency recycling of Mo and Ni from spent HDS catalysts: Enhanced oxidation with O2-rich roasting and selective separation with organic acid leaching- complexation extraction

Spent petroleum refining catalyst is regarded as the important secondary resource for valuable metals. However, common recycling strategies, including soda roasting, acid and alkaline solutions leaching and chemically precipitation, produced large quantities of high salinity wastewater. This study proposed an efficient method to recovery of Mo and Ni from the spent hydrodesulfurization (HDS) catalyst via O2-rich roasting and organic acid leaching with the advantage of less salinity wastewater production. The transformation of Mo(IV) into soluble Mo(VI) was enhanced by O2-rich atmosphere roasting, and 98.64% of Mo(IV) was oxidized at 650 ℃ for 2 h in atmosphere containing 30% of O2. The oxidation process of Mo(IV) was agreed with the shrinkage pore model, and regulated by surface reaction and internal diffusion. 97.97% of Mo(VI) was leached from roasted product by oxalic acid, separated with complexation extraction agent of Ala-TBP and recovered as (NH4)8Mo10O34 and (NH4)2Mo3O10 by evaporative crystallization. Ni was leached out from spent catalyst with 1 mol/L acetic acid, and precipitated as NiC2O4 with oxalic acid. 95.92% of Mo and 96.77% of Ni were recovered from spent HDS catalyst with this recycling route. This study provided a high-efficient and eco-friendly method to recovery of valuable metals from spent catalyst.

Recycling of fiber reinforced composites: Online mass spectrometric tracing, offline physicochemical speciation and toxicological evaluation of a pilot plant pyrolytic conversion

The increasing demand for lightweight materials with exceptional stability and durability has resulted in a significant rise in fiber-reinforced plastic (FRP) production. These materials find applications in various fields. However, the exceptional properties and diverse compositional range of FRPs pose challenges to conventional recycling strategies. Pyrolysis has emerged as a highly promising approach for separating the fibers from the polymer matrix. In this study, we employed thermal analysis coupled with high-resolution mass spectrometry to investigate the pyrolysis process. Representative FRP showed a starting decomposition temperature of 300 °C and bisphenol A, styrene, alkenes, and phenols could be identified. The identified parameters were used to operate a pilot plant with a capacity of up to 50 kg/h FRP, and reactor products were directly analyzed with soft photoionization mass spectrometry. The findings demonstrated good agreement between the pilot plant results and laboratory experiments, particularly for smaller compounds (m/z<200). The non-condensable fraction showed a range of 17 to 22 MJ/m3 as lower heating value. Analysis of the recovered fibers (diameter between 6.20 and 8.05 μm) revealed residual coke, but no toxic fibers were detected, according to the World Health Organization's definition. Yet, the organic coating of the fibers contained small amounts of potentially harmful PAHs. A toxicological assessment using a multicellular in vitro model confirmed the low hazardous potential of the recovered fibers. The findings contribute to developing sustainable and environmentally friendly recycling strategies for FRP while addressing important aspects related to the safety and toxicological implications of the resulting chemicals and fibers.

Engineering of 0D/1D architectures in 3D networks over CDs/PPy-CPP biomass foam with high efficiency on seawater evaporation

Converting waste biomass into solar evaporator foam has been recognized as an effective strategy for waste recycling and solving the problem of water shortage, but problems of salt deposition and mechanical stability seriously hinder their practical application. Herein, this work proposes a sustainable and high mechanical strength biomass foam (CDs/PPy-CPP) evaporator with zero-dimensional/one-dimensional (0D/1D) hierarchical structure by hydrophilic carbon dots (CDs) and tubular polypyrrole (PPy) are seamlessly integrated into the outer surface of the three-dimensional (3D) carbonized pomelo peel (CPP) biomass foam. The evaporator achieved a high-efficient evaporation rate of up to 2.46 kg m−2 h−1 in 3.5 wt% NaCl solution at 1 sun irradiation, and similarly exhibited outstanding salient evaporation efficiency and resistance to salt deposition in 25 wt% NaCl solution, as well as prominent swage purification ability. Excellent photothermal conversion efficiency is demonstrated attributed to the 0D/1D structure in 3D networks of the CDs/PPy-CPP evaporator, as well as superior mechanical and water transport properties based on the multilayer mesh structure and microscopic water transport pores. The research intends to offer a low-cost, energy-efficient, and environmentally friendly approach to obtain multifunctional photothermal biomass foams and demonstrate the potential applications in seawater desalinization and swage purification.

Setting behavior and mechanical properties of geopolymers from fly ash and real construction waste

AbstractSustainability is becoming an increasingly important factor in the development of new building materials. In terms of the sustainability of concrete components, the biggest challenge is the high energy consumption and associated greenhouse gas emissions in the production of Portland cement. A common strategy used by the construction industry to improve sustainability is to use residuals to develop lower‐emission geopolymer concretes that eliminate high‐emission cement‐based concretes. Because construction and demolition waste, at 3 trillion tons per year worldwide, also represents an environmental risk, this work will investigate the suitability of geopolymers based on real construction waste. In the course of the investigations, the manufactured geopolymer samples are examined for the material parameters relevant to building materials, namely compressive strength, flexural strength, raw density, total porosity, and thermal conductivity. The setting behavior and the forming structures are investigated by infrared spectroscopy, X‐ray diffraction analysis and scanning electron microscopy. The present study is intended to contribute to the development of a suitable recycling strategy for the material recycling of construction waste in novel geopolymer material.

Complementary roles for mechanical and solvent-based recycling in low-carbon, circular polypropylene.

Plastic recycling presents a vexing challenge. Mechanical recycling offers substantial greenhouse gas emissions savings relative to virgin plastic production but suffers from degraded aesthetic and mechanical properties. Polypropylene, one of the most widely used and lowest-cost plastics, features methyl pendants along the polymer backbone, rendering it particularly susceptible to declining properties, performance, and aesthetics across a succession of mechanical recycles. Advanced processes, such as solvent-assisted recycling, promise near-virgin quality outputs at a greater energy and emissions footprint. Mechanical and advanced recycling are often presented as competing options, but real-world plastic waste streams are likely to require preprocessing regardless of whether they are routed to an advanced process. This study quantifies the life-cycle greenhouse gas implications of multiple recycling strategies and proposes a system in which mechanical and solvent-assisted recycling can be leveraged together to boost recycling rates and satisfy demand for a wider range of product applications. Polypropylene can be recovered from mixed-plastic bales produced at material recovery facilities and processed through mechanical recycling, with a varying fraction sent for further upgrading via solvent-assisted recycling to produce material approved for food packaging and other higher-quality applications. The resulting mechanically recycled rigid polypropylene reduces life-cycle greenhouse gas emissions by 80% relative to the same quantity of virgin material, while the upgraded higher-quality material achieves GHG savings of 30%.

Carbon Emission Reduction Evaluation of End-of-Life Buildings Based on Multiple Recycling Strategies

With the promotion of sustainability in the buildings and construction sector, the carbon saving strategies for the end-of-life (EoL) phase have been receiving increasing attention. In this research, life cycle assessment (LCA) theory was employed to study and compare the carbon savings benefits of three different management strategies (i.e., recycling, remanufacturing, and reuse) on the EoL phase of various buildings (including residential, office, commercial, and school buildings). Moreover, the carbon savings potential (CSP) was calculated and analyzed, which is defined as the percentage of the actual carbon savings to the sum of the total embodied carbon of the building. Results show that compared with traditional demolition and landfill treatment, the implementation of integrated management strategies for residential, office, commercial, and school buildings can reduce carbon emissions by 193.5–526.4 kgCO2-e/m2. Among the building materials, steel bar, structural steel, and concrete account for the major proportion of the total carbon savings of buildings (81.5–93.2%). The sequence of the CSPs for the four types of buildings, in descending order, is school, residential, commercial, and office buildings. A building with a life span of 50 years has the greatest CSP. The results of the study can be used to reduce environmental impacts, and have broad positive implications in terms of sustainable construction.

Research on the recycling methods for lithium-ion batteries in the electric vehicle industry

The accelerating threat of climate change has spotlighted the imperative for greener transportation solutions, resulting in the swift transition to electric vehicles (EVs). An essential aspect of this transformation is the integration of lithium-ion batteries as energy storage. However, the subsequent challenge of managing end-of-life batteries has underscored the urgency for efficient recycling strategies to mitigate environmental risks and economic losses. By researching current valuable articles, this article gives an overview of the current challenges in recycling lithium-ion batteries, including issues with electrode materials, ageing, and safety concerns, as well as various recycling techniques explored in response to these challenges, such as pyrometallurgical and hydrometallurgical processes, direct recycling, and emerging biological recycling methods.

Transforming electronic plastics into bioadaptive 3D porous construct for advanced cell culture applications

Electronic plastics (e-plastics) are indispensable in modern society, but their low recycling rate and environmental persistence have raised significant concerns. Prevailing plastic recycling strategies are inadequate to fully capture the economic benefits inherent to e-plastics, providing limited incentives for recycling. Therefore, there is an urgent need to develop innovative approaches aimed at maximizing the capture of value from e-plastics. Herein, acrylonitrile butadiene styrene (ABS) from discarded keyboards was unconventionally “re-tooled” to produce highly porous bioadaptive 3D sponge-like constructs for advanced in vitro applications. The ABSponge was surface functionalized via layer-by-layer (LBL) electrostatic deposition method to generate 3D human breast, colorectal and bone cancer spheroids as a drug screening tool or adapted for co-culturing of cancer spheroids and cancer-associated-fibroblasts to emulate the complex tumor niche. Collectively, our findings reveal the promising potential of using discarded keyboards as a "waste-to-resource" feedstock for advanced in-vitro biotechnological applications, achieving waste reduction and maximizing value-capture.

Fluorescent carbon dots synthesized by waste wind turbine blade for photocatalytic degradation.

Developing novel waste recycling strategies has become a feasible solution to overcome environmental pollution. In this work, a method of using waste wind turbine blade (WTB) as a carbon source to synthesize blue fluorescent carbon dots (B-CDs) by hydrothermal treatment is proposed. B-CDs are spherical and have an average particle size of 5.2nm. The surface is rich in C-O, C=O, -CH3 , and N-H bond functional groups, containing five elements: C, O, N, Si, and Ca. The optimal emission wavelength of B-CDs is 463 nm, corresponding to an excitation wavelength of 380 nm. Notably, a relatively high quantum yield of 29.9% and a utilization rate of 40% were obtained. In addition, B-CDs can serve as a photocatalyst to degrade methylene blue dye, with a degradation efficiency of 64% under 40-min irradiation conditions. The presence of holes has a significant influence on the degradation process.