Recycling Process Research Articles

Mass balance of nickel manganese cobalt cathode battery recycle process

Batteries made from lithium, nickel, manganese, and cobalt are widely used, especially in the electrical industry, because they have high specific capacity, high safety, and low production costs. According to the International Energy Agency (IEA), the consumption of batteries used for electric vehicles will increase from 8 million in 2019 to 50 million in 2025 and to 140 million in 2030. As a result, the waste produced is also increasing. This type of lithium ion battery (LIB) which contains heavy metal elements such as nickel, manganese and cobalt can be recycled. This research aims to calculate the mass balance of the recycling process for nickel manganese cobalt (NMC) battery cathodes. The processing process begins with mixing, leaching, filtration, drying the results of the filtration process, molarity adjustment, Flame Assisted Spray Pyrolysis, and calcination. Based on the results of mass balance calculations for the NMC recycle battery cathode, the amount obtained was 43.427 kg/batch from 100 kg of cathode waste raw material. Apart from that, data was obtained on the metals that were successfully recycled, namely NiO, MnO, CoO, Fe2O3, MgO, Al2O3, Cr2O3, and Li2O. The research results provide information that NMC battery waste can be an opportunity for the NMC metal supply chain and can reduce environmental pollution.

A recyclable, toughening, extreme-condition resistant flame retardant for unsaturated polyester: Bridging performance and sustainability

Recycling thermosets presents significant economic benefits and social implications, and to date, a series of controllable recycling strategies have been proposed. However, prior research has primarily focused on neat polymers, neglecting the impact of the recycling process on composites whose additives may lose performance post-recycling. The paradigm shift towards sustainability necessitates the development of additives that not only exhibit high performance but also endure recycling conditions. Herein, taking flame-retardant unsaturated polyester (FRUP) as an example, we designed a new flame retardant (DPPONSi) with multiple flame-retardant elements and a low phosphorous oxidation state. FRUP with 16.7 wt% of DPPONSi achieves a V-0 rating in the UL-94 vertical burning test, and its limiting oxygen index (LOI) reaches 27.1%. Moreover, its peak heat release rate and total heat release are distinctively reduced by 65% and 42%, respectively. The high flame-retardant efficiency structure also protected DPPONSi from by-reactions. Without complex separation processes, FRUP degradation products were integrated with polyvinyl alcohol (PVA) to create flame-retardant aerogels with high flame retardancy. Additionally, we systematically studied the influence of flame retardants with varying oxidation states on FRUP, the corresponding flame-retardant mechanisms, and the degradation process of FRUP. This work realizes the organic combination of strategies to enhance the high efficiency of flame retardants with design methods for flame retardants that are resistant to existing unsaturated polyester degradation systems.

Redefining Packaging Solutions: The Advantages of Split-layer Packaging for Waste Reduction and Climate Action

The widespread use of multilayer packaging in industries such as food, beverages, pharmaceuticals, and cosmetics is driven by its ability to provide superior protection against environmental factors. However, the complex composition of multilayer packaging, involving bonded layers of different materials, presents substantial challenges for recycling, leading to low recycling rates and significant landfill accumulation. This study explores the potential of double packaging, which employs easily separable layers, as a solution to enhance recycling efficiency and mitigate environmental impacts. Primary recycling methods, including mechanical and chemical processes, are examined alongside advanced techniques like solvent-based and enzymatic recycling. Design considerations for double packaging are analyzed, emphasizing the use of minimal materials and adhesives, strategic sealing, and clear labeling to facilitate recyclability. Case studies from the food, beverage, and cosmetics sectors highlight the practical benefits of double packaging, demonstrating improvements in recycling rates, cost-effectiveness, and consumer compliance. The findings suggest that double packaging significantly simplifies the recycling process, reduces dependency on landfills, and lowers greenhouse gas emissions by decreasing the need for virgin materials. Effective implementation requires industry collaboration, regulatory support, economic incentives, investment in innovative recycling technologies, and robust consumer education programs. Double packaging emerges as a viable strategy for advancing sustainable packaging solutions and promoting a circular economy.

Asia’s battle against the perpetual plastic problem

Learning outcomes The learning outcomes are as follows: to analyse the issue(s) presented within specific case study context (C4); to formulate solutions to identified issue(s) within specific case study context (C5); and to synthesise a group plan to solve issue(s) within specific case study context (A4). Case overview/synopsis In 2017, China proclaimed that it would no longer accept plastic waste for recycling, this was in-line with China’s Operation “National Sword” to review the quality of these plastic imports to ensure their recyclability. This sent shock waves through a now globalised recycling network, with China previously having imported 95% of the EUs and 70% of US plastics that had been collected for recycling. This plastic backlog was then diverted to South-East Asian nations, particularly Malaysia, which this case focuses the discussion upon. While the potential for significant economic benefits drew the attention of illegitimate and unscrupulous businessmen alike, the environmental degradation from the often, low technological recycling processes and even burning of low-grade plastics brought profound negative impacts. This case focuses upon, then Minister, Yeo Bee Yin who led the Ministry of Energy, Science, Technology, Environment and Climate Change, in which she took an active and aggressive stance in attempt to stop Malaysia becoming the dumping ground for the global plastic crisis. Complexity academic level This case is appropriate for final year undergraduate and any postgraduate degrees in Business. Supplementary material Teaching notes are available for educators only. Subject code CSS 4: Environmental Management.

Application of High-pressure Carbon Dioxide in Japanese Anchovy Waste Recycling by Enzymatic Hydrolysis.

Anchovy waste, a protein resource with high nutritional value and potential for recycling with a relatively high economic effect, is essential for the Sustainable Development Goals of the United Nations. Preventing microbial contamination during the recycling process, through enzymatic hydrolysis, ensures the safety of recycled products. High-pressure carbon dioxide is a novel non-thermal decontamination technology, which inactivates cells by breaking their membranes. Here, we selected 40 °C_5.0 MPa and 50 °C_1.0 MPa treatment conditions for effectively decontaminating anchovy samples during the hydrolysis process. Next Generation Sequencing and real-time PCR experiments showed that a microbial growth promotion stage existed at the beginning of 40 °C_5.0 MPa, which may threaten hydrolysates, as some microbial genera were detected from the metabolites produced. Treatment at 50 °C_1.0 MPa ensured a high safety level for hydrolysates but this is limiting for various enzymatic hydrolysis processes. Orientaaze OP was selected as an additional enzyme with the highest hydrolysis efficiency under 40 and 50 °C among 10 different industrial proteases. Compared with control samples without high-pressure carbon dioxide treatment, 40 °C_5.0 MPa and 50 °C_1.0 MPa treated samples presented higher total amino acid concentrations by ultra-high-performance liquid chromatography. Hence, there was an increased enzyme activity by 40 °C_5.0 MPa and 50 °C_1.0 MPa treatments in endogenous or additional proteases hydrolytic processes. Despite the need for more future studies to be conducted, this research still provides essential information and instruction for industrial enzymatic hydrolysis applications on anchovy waste recycling.

Aqu‐Thermoplastics: Recycling Plastics with Water

AbstractRecycling of real waste plastics with diverse composition is extremely difficult. Herein, an eco‐friendly and easy‐to‐operate strategy is demonstrated to facilitate the recycling of plastic composites and mixtures by using only water. An aqu‐thermoplastic bioplastic (CPp‐TA) is constructed with switchable water solubility and excellent thermoplastic property from natural cellulose. CPp‐TA consisted of the cellulose main chain (C) and two functional groups, internal‐plasticizing group (Pp) and switchable group (TA). It not only has outstanding thermo‐plastic formability, water resistance, and mechanical property to satisfy the daily needs, but also can be easily recycled with water by switching to the water‐soluble state. CPp‐TA can processed into various high‐performance plastic parts, fibers, heat‐sealing packaging, transparent cups, paper‐plastic composites, and aluminum‐plastic composites by conventional thermoplastic processing methods. The obtained CPp‐TA/Al/paper composite exhibits better barrier performance than the famous Tetra Pak with a complex recycling process, and can be easily separated into CPp‐TA, Al foil, and paper by using basic aqueous solution to trigger the water solubility of CPp‐TA. Similarly, CPp‐TA can be effectively separated from plastic mixtures. The recovery yield achieves to 100%. The revolutionary aqu‐thermoplastic materials and water‐recycling strategy markedly reduce the recycling difficulty of intricate plastics and promote the sustainable development.

Increasing thermostability of the key photorespiratory enzyme glycerate 3‐kinase by structure‐based recombination

SummaryAs global temperatures rise, improving crop yields will require enhancing the thermotolerance of crops. One approach for improving thermotolerance is using bioengineering to increase the thermostability of enzymes catalysing essential biological processes. Photorespiration is an essential recycling process in plants that is integral to photosynthesis and crop growth. The enzymes of photorespiration are targets for enhancing plant thermotolerance as this pathway limits carbon fixation at elevated temperatures. We explored the effects of temperature on the activity of the photorespiratory enzyme glycerate kinase (GLYK) from various organisms and the homologue from the thermophilic alga Cyanidioschyzon merolae was more thermotolerant than those from mesophilic plants, including Arabidopsis thaliana. To understand enzyme features underlying the thermotolerance of C. merolae GLYK (CmGLYK), we performed molecular dynamics simulations using AlphaFold‐predicted structures, which revealed greater movement of loop regions of mesophilic plant GLYKs at higher temperatures compared to CmGLYK. Based on these simulations, hybrid proteins were produced and analysed. These hybrid enzymes contained loop regions from CmGLYK replacing the most mobile corresponding loops of AtGLYK. Two of these hybrid enzymes had enhanced thermostability, with melting temperatures increased by 6 °C. One hybrid with three grafted loops maintained higher activity at elevated temperatures. Whilst this hybrid enzyme exhibited enhanced thermostability and a similar Km for ATP compared to AtGLYK, its Km for glycerate increased threefold. This study demonstrates that molecular dynamics simulation‐guided structure‐based recombination offers a promising strategy for enhancing the thermostability of other plant enzymes with possible application to increasing the thermotolerance of plants under warming climates.

Influence of Process Conditions During Aqueous and Direct Recycling of NMC811 Cathodes.

This study investigated the impact of various process conditions on the aqueous, direct recycling of LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Three model systems were used. The first system assumes that the current collector delamination is performed in a dry environment without the use of water as a process medium. Consequently, the NMC811 is only exposed to water during classification, where no aluminum foil is present. The second model system assumes that the current collector delamination occurs in water. Therefore, the NMC811 is exposed to water in the presence of aluminum foil. Due to the pH increase caused by the Li+/H+ exchange reaction, the pH value surpasses the stability window of the aluminum-oxide passivation layer (pH 4.5-8.5), resulting in the deposition of aluminum-containing species on the NMC811 surface. The third model system is identical to the second, with the exception that H3PO4 is added. This causes the pH to decrease and prevents corrosion of the aluminum foil. The findings reveal that process conditions significantly affect the surface chemistry on NMC811, influencing electrochemical performance. Notably, aluminum-containing species increase polarization. Heat treatment simulating regeneration led to cation mixing as surface species diffused into the NMC811 bulk structure, highlighting the need to control recycling process conditions.

Experimental and multiscale analysis of volume fraction effects in tensile properties of recycled PLA-PDA/kenaf fiber 3D printing filament composites

Polylactic acid, a biodegradable thermoplastic derived from renewable sources, has notable environmental advantages and versatile properties. However, recycled PLA often experiences reduced mechanical strength and altered chemical composition due to the recycling process, limiting its suitability for 3D printing filament applications. Recognizing the inherent limitations of recycled PLA (rPLA), this research employs a unique method of coating rPLA with dopamine (DA) and reinforcing it with kenaf fibers (KF) at various weight fractions, introducing a novel multiscale modeling approach to address the challenges of interfacial bonding and tensile performance in recycled polymers. The methodology integrates experimental single filament tensile testing with multiscale finite element modeling to accurately predict the composite’s mechanical behavior across different scales. The findings reveal that a 5% kenaf fiber weight/volume fraction provides the optimal balance between tensile strength, stiffness, and toughness, achieving a significant 49.3% improvement over the unreinforced rPLA. However, increasing the kenaf fiber content beyond 5% leads to a decline in mechanical properties, attributed to higher fiber agglomeration and suboptimal fiber-matrix interactions. The novelty of this research lies in its combined use of PDA coating, natural kenaf fiber reinforcement, and advanced multiscale modeling to enhance and predict the performance of rPLA-PDA/kenaf composites, paving the way for sustainable, high-performance materials in 3D printing applications.

Recycling Li-Ion Batteries via the Re-Synthesis Route: Improving the Process Sustainability by Using Lithium Iron Phosphate (LFP) Scraps as Reducing Agents in the Leaching Operation

The development of hydrometallurgical recycling processes for lithium-ion batteries is challenged by the heterogeneity of the electrode powders recovered from end-of-life batteries via physical methods. These electrode materials, known as black mass, vary in composition, containing differing amounts of nickel, manganese, and cobalt (NMC), as well as other chemicals, such as lithium iron phosphate (LFP). This study presents the results of the hydrometallurgical treatment of mixed NMC and LFP black masses aimed at creating flexible recycling processes. This approach leverages the reducing power of LFP to optimize the leach liquor composition for re-synthesizing NMC precursors. In particular, the leaching conditions were optimized based on the LFP content in the solid feed to maximize the extraction of key metals (Ni, Mn, Co, and Li). The leaching solid residue, graphite, was treated and characterized as a secondary raw material for new anode preparation. Iron phosphate was recovered by increasing the pH of the leach liquor, and the NMC precursors were obtained via coprecipitation. This process achieved a recycling rate of 51%, based on the black mass input and the mass of recovered elements in the output products. Additionally, substituting LFP scraps as the reducing agent in place of H2O2 reduced the recycling process’s environmental impact by avoiding 1.7 tons of CO2-equivalent emissions per ton of NMC black mass.

Evaluation of Performance Improvement Rate of Plastic Production System Using ARENA: A Case Study of Phoenix Plastic Services

Production improvement has become essential to all industrial activity because of the fierce competition among today's production systems and organizations and the unquenchable customer demand. The shorter product life cycle has significantly increased the demand for prompt reactions to increase the productivity and efficiency of these industrial systems. This study examined the evaluation of performance improvement rate of plastic production system using ARENA. The report provided by the plastics industry was used in the study to analyze and assess the rate of performance improvement of the plastic manufacturing system. The location of the bottleneck was determined by the research following a thorough analysis of the plastic company's data, which included information on all manufacturing lines and procedures. The research employed Arena to assess and compute the rate of improvement in system performance while accounting for the material transporting process throughout the production line. The conveyor velocity maintains a lock at 75m/min, despite the company's report stating that the transports run at 30m/min. The optimized and unoptimized processes when obtained from a finished recycling process running for 1000 working hours, indicate that the conveyor process had 1045 and 1027 entity input and output, respectively, and the transporter process had 953 and 929 entities input and output respectively. The remaining number left when considering the number that enters the system with the number that leaves the system went to waste, resulting from the sorting and demagnetization process. The introduction of the conveyor brings 10.549% in the production rate and 50% decrease on expenses spent in labor. Through the conveyor system's speed control factor, which is an automated procedure, the system's percentage increment may be further raised. By raising the conveyor system's speed, more items will be produced. Conveyor system installation free up more space for additional production-related equipment, increasing products formed and the company's profit. The cost of purchasing and installing the conveyor will be covered by the excess profit.

Simulation study on heavy metals, phthalate esters, and organic halogens: Content and distribution characteristics during waste paper recycling.

Imported waste paper and recycled pulp may contain pollutants, posing potential environmental risks to the ecosystem of China. This study examined the presence and distribution patterns of heavy metals, phthalate esters (PAEs), and adsorbable organic halogens (AOX) in recycled pulp and production wastewater after various recycling processes of three typical restricted types of imported waste paper. The results indicated that the concentration ranges of heavy metals, PAEs, and AOX in the three types of imported recycled waste paper were 21.61-40.38mg/kg, 15.35-27.88mg/kg, and 19.21-57.72mg/kg, respectively. The comparative analysis with the initial waste paper demonstrated a reduction in heavy metal content in the recycled pulp by 17.80-49.75%, PAEs by 65.42-90.55%, and AOX by 32.80-42.34%. The average concentrations of these pollutants in wastewater were 0.85-1.66mg/L, 27.28-59.86mg/L, and 1.15-3.34mg/L, respectively. Chromium and lead were identified as the primary heavy metals present in the waste paper. Following pulping, No. 1 and No. 2 met the arsenic and lead levels specified in the "Reuse Fiber Pulp" standard (GB/T24320-2021), whereas No. 3 met these criteria after de-inking only. The main PAEs detected in the waste paper were dibutyl phthalate and di(2-ethylhexyl) phthalate, most of which were removed during the pulping stage. Significantly higher levels of AOX were observed in No. 2 and No. 3 than in No. 1, with a minimal impact on AOX removal from the pulp during the recycling process.

Circular Economy and Chemical Conversion for Polyester Wastes.

Polyester waste in the environment threatens public health and environmental ecosystems. Chemical recycling of polyester waste offers a dual solution to ensure resource sustainability and ecological restoration. This minireview highlights the traditional recycling methods and novel recycling strategies of polyester plastics. The conventional strategy includes pyrolysis, carbonation, and solvolysis of polyesters for degradation and recycling. Furthermore, the review delves into exploring emerging technologies including hydrogenolysis, electrocatalysis, photothermal, photoreforming, and enzymatic for upcycling polyesters. It emphasizes the selectivity of products during the polyester conversion process and elucidates conversion pathways. More importantly, the separation and purification of the products, the life cycle assessment, and the economic analysis of the overall recycling process are essential for evaluating the environmental and economic viability of chemical recycling of waste polyester plastics. Finally, the review offers perspective into the future challenges and developments of chemical recycling in the polyester economy.

Formation of aluminum nitride in dross by contact-diffusion reaction during aluminum recycling

Secondary aluminum dross is a solid waste after aluminum extraction from the slag produced during aluminum recycling. It is classified as a hazardous waste due to the high content of active aluminum nitride (AlN). This work studied the thermodynamics and kinetics of AlN formation in aluminum dross. Aluminum tends to react with N2 to form AlN, when the partial pressure of nitrogen (N2) is much greater than that of oxygen (O2) (PN2≫PO2) in thermodynamics. Additionally, the reaction between aluminum and N2 is accelerated with the increasing temperature. Approximately 36.37 wt% of aluminum was transformed into AlN at 700°C according to kinetic analysis. Aluminum recycling involves smelting, refining, and dross processing. The dross produced from these different processes has various compositions and hazardous properties. The formation mechanism of AlN from the three processes was revealed based on the thermodynamic and kinetic analyses. The reaction mechanisms in these processes were identified as surface contact reaction, internal and surface contact reaction, and rotational surface contact reaction between the aluminum melt and N2, respectively. X-ray diffraction (XRD) and electron probe microanalysis (EPMA) analyses were used to determine the phase and composition of the aluminum dross. The nitrogen content in the aluminum dross from smelting, refining, and dross processing was found to be 3.3 wt%, 5.2 wt%, and 9.6 wt%, respectively. The monthly dross production were 276.3 tons, 22.7 tons, and 318.2 tons, respectively, according to statistics. It was calculated that the nitrogen generated in the three process was 9.12 tons, 1.18 tons, and 20.25 tons, respectively. Therefore, dross processing is the primary source of AlN. A rapid dross processing method with small-scale vertical stirring was proposed to shorten the reaction between the aluminum melt and N2, thereby reducing AlN formation. This work could provide guidance for reducing hazardous AlN in aluminum dross and optimizing the aluminum recycling process.

Vegetation Greening Promoted the Precipitation Recycling Process in Xinjiang

Under the combined influences of climate and vegetation change, land–atmosphere interactions have enhanced, and precipitation recycling is an important part of this. Previous studies of the precipitation recycling process have focused on calculating the precipitation recycling rate (PRR) and analyzing the influencing factors. However, the climate-driven and vegetation-induced precipitation recycling process variations were not quantified. This study has systematically examined the precipitation recycling process in a typical arid region using the Eltahir and Bras model, random forest algorithm, and partial least-squares structural equation modeling. During 1982–2018, the leaf area index (LAI) and evapotranspiration (ET) rate both increased significantly, with growth rates of 0.06 m2m−2/decade and 13.99 mm/decade, respectively. At the same time, the average PRR in Xinjiang was 13.92% and experienced significant growth at a rate of 1.28%/decade. The climate-driven and vegetation-induced PRR variations were quantified, which contributed 79.12% and 20.88%, respectively. In addition, the positive effects of both of these on PRR variations through ET did not increase with the increase in ET, but rather decreased sharply and then stabilized. This study can provide favorable theoretical support for mitigating the contradiction in water use and balancing economic development and ecological security by quantifying the regulation of precipitation by vegetation.

Production of calcium and magnesium titanates using concentrated solar energy

Solar energy is an adequate technology for different processes in metallurgy, materials processing, recycling, or ceramic-refractory materials, because of the high temperatures attained which are reached when the solar radiation is concentrated. This growing interest has also emerged from the obtaining of such temperatures without releasing pollutants such as carbon dioxide, SOx, NOx, or dioxins. Other benefits associated with concentrated solar energy are that this energy source is virtually free and the possibility of operating in places isolated from the electrical grid. Therefore, this research proposes the integration of concentrated solar energy in the production of calcium and magnesium titanates, which are materials with increasing demand in the field of electric components. Experimental work was carried out in the Odeillo solar furnace located in Font-Romeu-Odeillo-Via (France) using a 1.5-meter parabolic concentrator and mixtures of CaO and TiO2 and MgO and TiO2 in 1:1 molar ratio. Mixtures were subjected to values of incident radiation exceeding 900 W/m2 without using any special atmosphere and in very short times, which did not surpass 10 min. X-ray diffraction technique was employed to confirm the formation of the CaTiO3 and MgTiO3 perovskites. Therefore, concentrated solar energy might be a novel, fast, and environmentally sustainable manner of producing calcium and magnesium titanates.

Fire parameters of recycled plastic pellets

AbstractDuring the recycling process, waste plastic undergoes various processes that change its geometry. The thermal properties and fire behaviour of plastic in different geometries has not been widely studied. This paper aims to determine critical thermal properties of plastic pellets made of recycled plastic. For this paper, cone calorimeter tests of various volumes of recycled plastic pellets of low‐ and high‐density polyethylene and polypropylene were conducted. During these tests, the heat release rate (HRR), mass loss rate and time‐to‐ignition were measured, thereafter the heat of combustion (HOC) was calculated. A calibration of suitable time‐to‐ignition equations is carried out. The average HRR is between 353 and 581 kW/m2 with an external heat flux of 50 kW/m2. The measured time‐to‐ignition values ranged between 27 s at 50 kW/m2 and just more than 90 s at 25 kW/m2. Values obtained analytically from the thermally thin time‐to‐ignition equations for these materials describe ignition well, which appears to be due to the particulate nature of the samples. The HOC (40–41 MJ/kg) shows good agreement with the HOC for virgin plastic found in literature. These properties can be used as a basis for material characterisation, and further testing will be done before using this as simulation inputs to determine how bulk stored plastic pellets will behave in the event of a fire.

Dewatering and Transport in Sustainable Sediment Management: A Review

This paper deals with the dewatering and handling of dredged sediments in the context of sustainability and renewability of natural resources. Dewatering is a critical part of sediment management, as the high water content of dredged sediments becomes a challenge for transportation, final storage and/or recycling. This is why it is necessary to reduce their water content before transportation. Conventional methods suggest using land-based drained basins, which is a sustainable solution. However, this solution has certain drawbacks: dewatering the sediment is time-consuming and involves the use of large land areas. The main problem with this method of dewatering can be solved by proposing mechanical dewatering in the vicinity of the dredging operation. Once the sediment has been sufficiently dewatered, it should be shoveled and transported again. The proposed paper covers the study of the dewatering and shoveling ability of sediments. After introducing why dewatering is a critical phase in the recycling process of sediment, some techniques for dewatering large volumes of high-water sediments are briefly reported. Typical dewatering laboratory tests are detailed, demonstrating their usefulness for understanding the mechanisms of natural dewatering. A laboratory dewatering press machine is reported and the procedure used for a sediment sludge. The last section concerns a recent innovative test implemented for the study of the shoveling ability and adhesion of sediments. This study improves our understanding of the phenomenon of sediment dewatering, for both natural and mechanical dewatering. It also provides the protocols for typical laboratory tests on sediment dewatering and shoveling ability.

Geochemical evidence for terrigenous sediment recycling in the Late Permian subcontinental lithospheric mantle of the northern North China Craton

Understanding the recycling process of subducted slab in subduction zones is vital to deciphering the heterogeneity of cratonic mantle and the variable compositions of continental arc igneous rocks. This study presents a comprehensive analysis of zircon U-Pb ages, Hf-O isotopes, hornblende major elements, whole-rock major and trace elements, as well as Sr-Nd-Hf isotopes of mafic igneous rocks from the northern North China Craton. These data constrain metasomatic processes in the cratonic mantle. The Late Permian mafic igneous rocks (ca. 254−252 Ma) studied are characterized by arc-like trace element signatures and enriched whole-rock Sr-Nd-Hf isotopes, with (87Sr/86Sr)i ratios of 0.7063−0.7076, εNd(t) values of −18.0 to −9.3, and εHf(t) values of −29.7 to +0.5. In addition, they also have elevated zircon δ18O values of 5.9‰−7.0‰, and variable zircon εHf(t) values of −19.4 to +6.0. These features suggest the rocks were derived from an enriched mantle with the involvement of terrigenous sediments. We propose that the subcontinental lithospheric mantle of the northern North China Craton was mainly metasomatized by terrigenous sediment-derived hydrous melt during the southward subduction of the Paleo-Asian Ocean. Moreover, partial melting of the metasomatic mantle may be triggered by the slab rollback related to the closure of the Paleo-Asian Ocean in the Late Permian, which resulted in the formation of the mafic igneous rocks studied. Thus, the Late Permian igneous rocks studied provide petrological and geochemical evidence of the crust-mantle interaction during the subduction of the Paleo-Asian Ocean.

Oxygen diffusion effects in thermo-oxidative degradation of typical tire rubber

Thermo-oxidative degradation of tire rubber has been demonstrated as a green method for upcycling waste tire rubber. However, the complicated tire compositions present challenges to achieving the homogeneity and efficiency of the reclaimed products, which restricts their widespread industrial adoption. To address this challenge, natural rubber(NR)and natural rubber/butadiene rubber(NR/BR)were innovatively designed to simulate complex tire compositions and investigate the influence of oxygen diffusion on thermo-oxidative degradation at 150–240 °C. The evolution of chemical structural changes and mechanical properties during degradation was traced by FTIR, UV–vis, and nanoindentation test. A basic reactive-diffusion model based on Fickian oxygen diffusion was used to simulate the diffusion profiles. It was found that recrosslinking decreases the oxygen permeability coefficient during NR/BR degradation as the temperature increases, making it difficult for oxygen to diffuse into the inner layer, and therefore tire rubber degrades unevenly. Lower temperatures and prolonged treatment times were recommended to enhance degradation. These findings provide substantial guidance for optimizing the recycling process of tire rubber and its sustainable utilization.