Recycling Strategies Research Articles

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.

Effective Ti-6Al-4V Powder Recycling in LPBF Additive Manufacturing Considering Powder History

Laser powder bed fusion (LPBF) is an outstanding additive manufacturing (AM) technology that can enable both complicated geometries and desired mechanical properties in high-value components. However, the process reliability and cost have been the obstacles to the extensive industrial adoptions of LPBF. This work aims to develop a powder recycling procedure to reduce production cost and minimize process uncertainties due to powder degradation. We used a recycle index (R) to reuse Ti-6Al-4V powder through 10 production cycles. Using this recycle index is more reasonable than simply replying on recycle numbers as it incorporates the powder usage history. A recycling procedure with simple virgin powder top-up can effectively mitigate powder degradation and maintain stable powder properties, chemical compositions, and tensile properties. The experimental finding points to a sustainable recycling strategy of Ti alloy powders with minimal material waste and without noticeable detriment to observed mechanical performance through LPBF production cycles.

Proposed holistic strategy for mechanical recycling of wind turbine blades for 3D printing and compression molding

There are many solutions being proposed for recycling discarded wind turbine blades, but most solutions are not very ecological, involving either burning or harsh chemicals. In this research, a solution is proposed that has a very low environmental impact and has potential of being scaled to a very large industrial process. The entire wind turbine blade should be recycled and transformed into other products that are recycled and that have economic benefits in the long term. Two of the output products from the current recycling strategy are recycled 3D printing filament and recycled reinforced pellets for compression molding. The research outlines the process, the numerical simulations that help optimize the output and the outline for planning to bring the recycling solution from a small industrial scale to a large scale. This represents ongoing research in this important field of composite recycling.

The efficacious electrochemical reduction strategy for ammonia leaching recycling of spent battery

The normalization of the recycling process is considered a crucial guarantee for the sustainable development of lithium-ion batteries. Ammonia leaching is known for its capability of selective extraction, which is of vital importance to alleviate the burden of impurity separation. However, the sluggish reaction rate limits its practical application. Herein, an electrochemical reduction strategy is well-designed for ammonia leaching by introducing Fe/Fe2+ which functions as negative electrodes to form galvanic cells with cathode material (LiNi0.33Co0.33Mn0.33O2, NCM). Due to its superior mechanism, reaction time can be shortened with a satisfied result of valuable metals extraction. Around 100% Li and Ni, 91.74% Co can be extracted within 105 min by introducing Fe powder; 91.75% Li, 85.24% Ni and 75.25% Co can be extracted within an even shorter time of 15 min by introducing FeSO4. This strategy provides inspiration and a new perspective on large-scale battery recycling, especially for the practical application of ammonia leaching.

Polyphenylene sulfide for high-rate composite manufacturing: Impacts of processing parameters on chain architecture, rheology, and crystallinity

High performance semi-crystalline thermoplastics necessitate high temperature processing to form useful structures, but the effects of repeated exposure to these extreme environments on key polymer properties are not well understood. This work investigates the influence of degradation-driven structural changes resulting from exposure to standard melt processing conditions in oxygen rich environments on the rheological properties, crystallization behavior, and crystal structure of polyphenylene sulfide (PPS). Melt processing temperatures (300°C, 320°C, and 340°C) and hold times (up to 60 min) are varied to probe the effects of thermal exposure on polymer properties. Extended melt-state exposure causes an increase in PPS melt viscosity due to the formation of complex branched/crosslinked structures where increasing temperature causes this process to occur more rapidly. Dynamic isothermal rheology of PPS displays a 70x increase in the complex viscosity at 10 rad/s after 60 minutes at 340°C. Frequency sweep rheological experiments reveal a notable deviation from linearity (terminal slope = 2) with slopes as low as 0.14 after thermal exposure. Stress recovery experiments indicate thermally processed PPS requires more time to relax stress under an applied strain. Imperfections along the polymer backbone in the form of branches/crosslinks decrease overall crystallinity and reduce lamellar thickness, with no changes to the unit cell structure. For semi-crystalline high performance thermoplastic matrix composites relying on high degrees of crystallinity to provide solvent resistance and strength, these results have serious implications for the need to tightly control melt processing steps and understand the final material state. Furthermore, viscoelastic properties of post-processed PPS polymers should be considered for recycling and reuse strategies.

Corncobs addition enhances the nitrogen removal in a constructed wetland for the disposal of secondary effluent from wastewater treatment plants

Secondary effluent from wastewater treatment plants poses a persistent threat to the aquatic ecosystems owing to substantial nitrogen residues. For efficient nitrogen removal, this study explores the utilization of agricultural waste (corncob) to promote nitrogen removal in an up-flow constructed wetland (CW). Meanwhile, the corncob dosage and nitrogen transformations in CW are investigated. A proper dosage (70 g·m−2) of corncobs was determined, resulting in efficient and stable nitrogen removal, with average total nitrogen (TN), ammonia (NH4+-N) and nitrate (NO3−-N) removals of 99.22%, 99.25% and 99.54%, respectively. During an addition cycle, equivalent of 2648.17 mg chemical oxygen demand (COD) of organics was released from corncobs, and most organics were effectively utilized. After adding corncobs in the CW, the main dominant genera were norank_Chloroplast, unclassified_Comamonadaceae, and norank_SBR1031. Functional genes predictions highlighted that organic degradation predominantly occurred in the lower region of CW, with the enhancement of nitrification and denitrification simultaneously in the CW. Findings in this research provide the theoretical reference for proper dosage and adding strategy of biomass recycling in CWs.

Design and Optimization of an Economically Viable and Highly Efficient Strategy for Li Recycling from Spent LiFePO4 Batteries

Design and Optimization of an Economically Viable and Highly Efficient Strategy for Li Recycling from Spent LiFePO₄ Batteries

Escherichia coli utilizes multiple peptidoglycan recycling permeases with distinct strategies of recycling.

Bacteria produce a structural layer of peptidoglycan (PG) that enforces cell shape, resists turgor pressure, and protects the cell. As bacteria grow and divide, the existing layer of PG is remodeled and PG fragments are released. Enterics such as Escherichia coli go to great lengths to internalize and reutilize PG fragments. E. coli is estimated to break down one-third of its cell wall, yet only loses ~0 to 5% of meso-diaminopimelic acid, a PG-specific amino acid, per generation. Two transporters were identified early on to possibly be the primary permease that facilitates PG fragment recycling, i) AmpG and ii) the Opp ATP binding cassette transporter in conjunction with a PG-specific periplasmic binding protein, MppA. The contribution of each transporter to PG recycling has been debated. Here, we have found that AmpG and MppA/Opp are differentially regulated by carbon source and growth phase. In addition, MppA/Opp is uniquely capable of high-affinity scavenging of muropeptides from growth media, demonstrating that AmpG and MppA/Opp allow for different strategies of recycling PG fragments. Altogether, this work clarifies environmental contexts under which E. coli utilizes distinct permeases for PG recycling and explores how scavenging by MppA/Opp could be beneficial in mixed communities.

Long-term surface composts application enhances saline-alkali soil carbon sequestration and increases bacterial community stability and complexity

Organic composts could remediate saline-alkali soils on agricultural land by amending soil micro-environment which is one of the main strategies for resourceful treatment and recycling of livestock manure. However, it was still unknown how long-term surface application of organic composts affects the microhabitat and bacterial community characteristics and assembly processes on the profile. We examined the features of the soil properties, bacterial community, and assembly models after 7-years composts application. Physicochemical indicators, enzyme activities, and bacterial diversity of the saline-alkali farmland were all enhanced by the surface composts application, particularly in the 0–20 cm. The network analysis showed that the surface application of composts significantly enhanced the robustness and topological characteristics of the bacterial community and that bacteria from Acidobacteriota were the keystone of the saline-alkali soils improvement. Composts also greatly increased the ecological niche of the bacterial community, while stochastic processes (mainly dispersal limitation) significantly shaped the bacterial community compared to the control. Structural equation modeling indicated that composts application promoted bacterial community succession, which in turn promoted elevated total organic carbon and improved saline-alkali soils properties. Overall, the study linked the ecological characteristics of soil microhabitats and bacterial communities during the restoration of saline-alkali soils by long-term surface application of composts, providing the management and remediation of saline-alkali agricultural soil with a theoretical foundation and technological support.

Tracing the multiregional evolution of the global dysprosium demand-supply chain

Dysprosium (Dy) is a critical rare earth element, indispensable for realizing low-carbon technologies. A holistic understanding of global Dy supply-demand chains is essential for ensuring its future sustainable supply and use. This study conducts the first multiregional analysis of Dy flows and stocks to comprehensively trace the global Dy cycle from 1988 to 2021. Results show a rising demand for Dy-comprising intermediate and final products with complex trade fluctuations since 2000. In total, 22,009 tons of intermediate products, primarily as neodymium-based permanent magnets (NdFeB), accumulatively entered the global manufacturing phase, of which China accounted for approximately 55%. Dy use was notable in the United States and Japan for internal combustion engine (ICE) vehicles manufacturing and for industrial machinery production in the European Union. Less than 3% of globally mined Dy was recycled. Considering the growing global demand for Dy, alternate supply sources, and regional efforts to promote recycling and circular economy strategies are required.