Recycling

21 pages, 3828 KiB

Open AccessArticle

Investigating the Socio-Spatial Dynamics of WEEE Collection in São Paulo, Brazil: A Data Mining Approach

by Geraldo C. de Oliveira Neto, Marcos Alexandruk, Sidnei Alves de Araújo, Peterson Adriano Belan, Francisco C. Delmondes, Rafael Abreu Faioli, João Matias, Mario Rodrigues and Marlene Amorim

Recycling 2025, 10(2), 77; https://doi.org/10.3390/recycling10020077 - 16 Apr 2025

Abstract

The proliferation of electronic goods manufacturing and the subsequent rise in electronic waste (e-waste) generation necessitate the establishment of efficient Waste of Electrical and Electronic Equipment (WEEE) reverse logistics systems, fostering collaborative efforts among manufacturers, retailers, and government agencies. Given its importance, this [...] Read more.

The proliferation of electronic goods manufacturing and the subsequent rise in electronic waste (e-waste) generation necessitate the establishment of efficient Waste of Electrical and Electronic Equipment (WEEE) reverse logistics systems, fostering collaborative efforts among manufacturers, retailers, and government agencies. Given its importance, this theme has received considerable attention in recent literature. This study focused on investigating the relationships between socio-spatial characteristics and the distribution of WEEE collection points in the city of São Paulo, Brazil. To this end, data mining (DM) techniques were applied to generate rules representing knowledge that explains the relationship among the considered variables. The results achieved (accuracy 81.25% and Kappa statistic 74.71%), indicating consistent patterns, demonstrate the potential of the proposed approach to aid WEEE reverse chain management. From a practical point of view, the knowledge produced is an important support for decision-making on the installation of new collection points, considering the socio-spatial characteristics of the target locations. In addition, this research contributes to the responsible management of solid waste recommended by the Brazilian National Solid Waste Policy (NSWP), as well as to the advancement of the United Nations’ Sustainable Development Goals (UN SDGs), particularly SDG 11 (Sustainable Cities and Communities) and SDG 12 (Responsible Consumption and Production), by fostering sustainable practices in waste management and resource utilization within urban contexts. Full article

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18 pages, 4718 KiB

Open AccessArticle

Recovering Zinc and Iron from Waste Tire-Derived Pyrolysis Carbon Black to Prepare Layered Metal Hydroxide Composites for Efficient Adsorption of Dye Methyl Orange

by Pei Chen, Wenli Liu, Yanzhi Sun, Yongmei Chen and Junqing Pan

Recycling 2025, 10(2), 76; https://doi.org/10.3390/recycling10020076 - 15 Apr 2025

Abstract

The pyrolysis carbon black (CBp) from waste tires contains zinc, iron, and other metal elements, which have high recycling value. This study proposes a simple method of recovering zinc and iron from waste tire-derived CBp to synthesize hydrotalcite-type adsorbents for the treatment of [...] Read more.

The pyrolysis carbon black (CBp) from waste tires contains zinc, iron, and other metal elements, which have high recycling value. This study proposes a simple method of recovering zinc and iron from waste tire-derived CBp to synthesize hydrotalcite-type adsorbents for the treatment of anodic dye wastewater. Firstly, zinc-aluminum hydrotalcite (LDH) and zinc-iron aluminum hydrotalcite (FeLDH) were obtained by leaching the zinc and iron ions from CBp with an acid solution. As compared with LDH, FeLDH shows increased laminate metal ion arrangement density and layer spacing. By calcining the LDH and FeLDH at 500 °C, zinc aluminum oxides (LDO) and zinc iron aluminum oxides (FeLDO) were then prepared and applied for the adsorption of dye methyl orange (MO). The results demonstrate that the maximum adsorption capacity of LDO and FeLDO are 304.9 and 609.8 mg g⁻¹ at pH of 4.0, respectively. The adsorption processes of both LDO and FeLDO are consistent with the Langmuir adsorption isotherm and the proposed second-order kinetic model. The adsorption regeneration performance and adsorption mechanism of LDO and FeLDO were also investigated in detail. Regeneration experiments show that after three cycles, the removal rate of MO by LDO remains above 80%, while that of FeLDO only remains around 64% in the first cycle after regeneration. This work would provide a new pathway to realize the high-value metal recycling of waste tire-derived CBp and solve the contamination of dye wastewater. Full article

(This article belongs to the Special Issue Rubber Waste and Tyre Stewardship)

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21 pages, 3845 KiB

Open AccessArticle

Graphite Separation from Lithium-Ion Battery Black Mass Using Froth Flotation and Quality Evaluation for Reuse as a Secondary Raw Material Including Non-Battery Applications

by Johannes Rieger, Stephan Stuhr, Bettina Rutrecht, Stefan Morgenbesser, Thomas Nigl, Astrid Arnberger, Hartwig Kunanz and Stefanie Lesiak

Recycling 2025, 10(2), 75; https://doi.org/10.3390/recycling10020075 - 14 Apr 2025

Abstract

This study investigates graphite separation from Lithium-Ion Battery (LIB) black mass (which is a mixture of anode and cathode materials) via froth flotation coupled with an open-loop recycling approach for the graphite (froth) product. Black mass samples originating from different LIB types were [...] Read more.

This study investigates graphite separation from Lithium-Ion Battery (LIB) black mass (which is a mixture of anode and cathode materials) via froth flotation coupled with an open-loop recycling approach for the graphite (froth) product. Black mass samples originating from different LIB types were used to produce a carbon-poor and a carbon-enriched fractions. The optimization of the flotation parameters was carried out depending on the black mass chemistry, i.e., the number of flotation stages and the dosing of flotation agents. The carbon-enriched product (with a carbon content of 92 wt.%, corresponding to a recovery of 89%) was subsequently used as a secondary carbon source for refractory material (magnesia carbon brick). Analyses of brick chemistry, as well as thermo-mechanic properties in terms of density, porosity, cold crushing strength (CCS), hot modulus of rupture (HMOR—the maximum bending stress that can be applied to a material before it breaks), and thermal conductivity showed no negative influence on brick quality. It could be demonstrated that flotation graphite can principally be used as a secondary source for non-battery applications. This is a highly valuable example that contributes to a more complete closure of a battery’s life cycle in terms of circular economy. Full article

(This article belongs to the Special Issue Lithium-Ion and Next-Generation Batteries Recycling)

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17 pages, 11496 KiB

Open AccessArticle

Secondary Treatment Facilitating the Mechanical Recycling of Film-Coated Waste Automobile Bumpers

by Tetsuo Takayama, Toshiyuki Niiyama, Tadao Tanabe and Jeongsoo Yu

Recycling 2025, 10(2), 74; https://doi.org/10.3390/recycling10020074 - 14 Apr 2025

Abstract

Concerns have been raised regarding the mechanical recycling rates of automotive parts, which appear to be low in comparison to those of other sectors. Addressing this issue demands the promotion of the mechanical recycling of waste automobile bumpers. This study investigates primer treatment [...] Read more.

Concerns have been raised regarding the mechanical recycling rates of automotive parts, which appear to be low in comparison to those of other sectors. Addressing this issue demands the promotion of the mechanical recycling of waste automobile bumpers. This study investigates primer treatment effects on the mechanical properties of injection-molded waste bumpers. The primer treatment effects vary depending on the bumper coating. The flexural strength of coated bumpers is greater: 27.6 MPa vs. 29.2 MPa. The flexural modulus is also greater: 1667 MPa vs. 1761 MPa. By contrast, the notched Charpy impact strength is less: 25.4 kJ/m² vs. 23.4 kJ/m². The flexural strength and flexural modulus of the bumpers lacking a coating are also lower, respectively, at 25.0 MPa vs. 22.9 MPa and 1523 MPa vs. 1314 MPa. However, the notched Charpy impact strength is greater: 40.0 kJ/m² vs. 73.6 kJ/m². These findings suggest that primer treatment can control the mechanical properties of injection-molded parts produced from waste automobile bumpers, which is an important achievement for promoting the mechanical recycling of waste automobile bumpers. Full article

(This article belongs to the Special Issue Challenges and Opportunities in Plastic Waste Management)

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22 pages, 3629 KiB

Open AccessReview

Replacing Sand in Concrete: Review on Potential for Utilization of Bottom Ash from Combustion of Wood in Circulating Fluidized Bed Boilers

by Anders Hedegaard Jensen, Carola K. Edvardsen and Lisbeth M. Ottosen

Recycling 2025, 10(2), 73; https://doi.org/10.3390/recycling10020073 - 14 Apr 2025

Abstract

Aggregates such as sand and gravel are the most mined resources on Earth and are the largest component in concrete. They are essential for construction but are becoming increasingly scarce. At the same time, large amounts of biomass ashes are produced in wood-fired [...] Read more.

Aggregates such as sand and gravel are the most mined resources on Earth and are the largest component in concrete. They are essential for construction but are becoming increasingly scarce. At the same time, large amounts of biomass ashes are produced in wood-fired power plants, offering potential as a partial substitute for decreasing sand resources. Due to the combustion technology of circulating fluidized bed boilers, their bottom ash offers high potential as a viable alternative to natural sand. This review examines previous research to assess the feasibility of replacing sand in concrete with bottom ash. Specific cementitious products are identified, where the substitution could realistically be performed in the concrete industry. Benefits and issues with partial substitution of bottom ash from wood combustion are discussed, and gaps in the research regarding sand replacements with bottom ash, notably the durability of the resulting concrete, are shown. Bottom ash has positive properties relevant for use in mortar and concrete, both regarding physical and chemical properties. Although limited research exists in the field, several researchers have demonstrated promising results when substituting sand for bottom ash in mortars. For lower substitution levels, little effect on the fresh and hardened properties is found. Full article

(This article belongs to the Topic Sustainable Building Materials)

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27 pages, 1358 KiB

Open AccessReview

Exploring the E-Waste Crisis: Strategies for Sustainable Recycling and Circular Economy Integration

by Shanti Quinto, Noah Law, Christopher Fletcher, Justin Le, Subin Antony Jose and Pradeep L. Menezes

Recycling 2025, 10(2), 72; https://doi.org/10.3390/recycling10020072 - 14 Apr 2025

Abstract

Electronic waste (e-waste) is the fastest-growing waste stream on the planet, yet it remains critically under-addressed in global waste management and recycling efforts. The rapid pace of technological advancement has led to increased consumption of electronic devices, many of which are challenging and [...] Read more.

Electronic waste (e-waste) is the fastest-growing waste stream on the planet, yet it remains critically under-addressed in global waste management and recycling efforts. The rapid pace of technological advancement has led to increased consumption of electronic devices, many of which are challenging and costly to recycle efficiently. Insufficient infrastructure for e-waste recycling has resulted in large quantities being exported to countries with minimal waste management capabilities. In these regions, waste is often processed manually, exposing workers to hazardous materials and toxic elements commonly found in electronic components, leading to serious health risks. E-waste consists primarily of fibrous composite materials and plastics mixed with valuable metals and reusable components. While metals are often recovered, the remaining materials are typically discarded, contributing to significant environmental harm. Addressing e-waste challenges requires more than just technological solutions. In the United States, limited policies promote large-scale reuse and recycling practices, particularly among corporations. To build a sustainable approach, a combination of next-generation, cost-effective chemical recycling technologies and forward-thinking policy reforms will be essential for the effective management and reduction of e-waste. This paper explores the global generation and composition of e-waste, highlighting its environmental and health impacts due to improper handling and disposal. It reviews current and emerging recycling technologies while examining the challenges and opportunities in e-waste management. Finally, it discusses sustainable solutions and future directions for improving e-waste recycling through innovative technologies and policy reforms, concluding with recommendations for a circular economy approach. Full article

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26 pages, 5528 KiB

Open AccessArticle

Quality Assurance Framework for Recovered Binders and Aggregates from Asphalt Mixtures Incorporating Recycled Materials

by Eslam Deef-Allah and Magdy Abdelrahman

Recycling 2025, 10(2), 71; https://doi.org/10.3390/recycling10020071 - 13 Apr 2025

Abstract

This study proposes that a proactive quality assurance (QA) framework for asphalt mixes with recycled materials, i.e., reclaimed asphalt pavement and recycled asphalt shingles, should be developed. Quality control (QC) is generally concerned with the contractor’s obligation to produce mixes which meet the [...] Read more.

This study proposes that a proactive quality assurance (QA) framework for asphalt mixes with recycled materials, i.e., reclaimed asphalt pavement and recycled asphalt shingles, should be developed. Quality control (QC) is generally concerned with the contractor’s obligation to produce mixes which meet the job mix formula (JMF) targets. However, QA considers the variability in fabrication processes and materials and offers monitoring by evaluating the contractor’s performance. Although both aggregate gradations and asphalt contents were within the JMF specifications, the recovered binders revealed significant differences from the contract binders in the JMF. Rheological tests indicated increased stiffness and elasticity but reduced capability to relax thermal stresses in binders recovered from plant–lab- and lab-fabricated mixtures, compared to field mixtures. Thermal-rheological analysis models corroborated these results by demonstrating reduced decomposition areas for more aged binders, enhancing performance prediction—especially for limited binder amounts. The creation of a QA decision matrix facilitated uniform, performance-oriented assessments. The matrix indicated only 23% of the mixtures satisfied JMF criteria and reported QC data—predominantly field mixtures—underscoring the impact of the fabrication mechanisms and the use of soft binders. This matrix integrates statistical analysis and binder performance assessments as a tool for verifying material compliance and tracking contractor efficiency. It reflects a transition from traditional QC toward a more proactive QA framework for sustainable pavements. Full article

(This article belongs to the Special Issue Recycled Materials in Sustainable Pavement Innovation)

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12 pages, 1274 KiB

Open AccessArticle

Environmental Pollution Mitigation: The Chemical Transformation of Residual Frying Oil into Biodiesel

by Yolanda C. Pérez-Luna, Paola T. Vázquez-Villegas, Roberto Berrones-Hernández, Yazmin Sánchez-Roque, Sergio Saldaña-Trinidad, Miguel A. Canseco-Pérez, Elvia G. Gómez-Vázquez, Anayancy Lam-Gutiérrez and Ludwi Rodríguez-Hernández

Recycling 2025, 10(2), 70; https://doi.org/10.3390/recycling10020070 - 11 Apr 2025

Abstract

Currently, residual frying oil has three purposes: it is used again in the preparation of fried foods, mixed with new vegetable oil, which can cause cardiovascular disease in the consumer; it is collected by government institutions, without having an exclusive use; or it [...] Read more.

Currently, residual frying oil has three purposes: it is used again in the preparation of fried foods, mixed with new vegetable oil, which can cause cardiovascular disease in the consumer; it is collected by government institutions, without having an exclusive use; or it is thrown into the drain, causing serious pollution problems to water resources. An alternative is to transform it into biodiesel, through transesterification with methanol, to be used in internal combustion engines, biodiesel-diesel mixtures of 10:90, 15:85 and 20:80 (v/v), according to international regulations in such a way that, in the combustion process, less CO₂ and greenhouse gas emissions are generated. Residual frying oil served as raw material, which was collected, mixed and homogenized to evaluate physicochemical properties before transformation. The biodiesel generated had a density of 0.886 g L⁻¹, an acidity of 0.516%, a viscosity of 7.535 mm² s⁻¹, a flash point of 166.8 °C and an oxidative stability of 49 days at 25 °C. Additionally, the content of functional groups characteristic of biodiesel formation was evaluated by Infrared Spectroscopy. The Biodiesel obtained is of good quality for use in internal combustion engines and agricultural machinery, thus validating its continuous production and complying with the standard values of international regulations. Full article

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16 pages, 5430 KiB

Open AccessArticle

Macro Stickies Content Evaluation of Different Cellulose-Based Materials Through Image Analysis

by António de O. Mendes, Joana C. Vieira, Vera L. D. Costa, Paula Pinto, Belinda Soares, Paulo Barata, Joana M. R. Curto, Maria E. Amaral, Ana P. Costa and Paulo T. Fiadeiro

Recycling 2025, 10(2), 69; https://doi.org/10.3390/recycling10020069 - 11 Apr 2025

Abstract

In this work an evaluation of Macro Stickies was performed on thirteen different cellulose-based materials through image analysis. In particular, the materials that were evaluated consisted of different types/categories of papers/products produced by the industry, namely, molded cellulose products, unbleached kraft papers, barrier [...] Read more.

In this work an evaluation of Macro Stickies was performed on thirteen different cellulose-based materials through image analysis. In particular, the materials that were evaluated consisted of different types/categories of papers/products produced by the industry, namely, molded cellulose products, unbleached kraft papers, barrier papers, one recycled paper, and a laminated paper package. The Macro Stickies Evaluation was carried out using an image analysis tool developed by our research group to perform this kind of work from now on. The results indicated that eight of the processed samples revealed low/residual contents of Macro Stickies, whereas the remaining five revealed higher amounts of Macro Stickies in their surfaces. Of the eight samples showing a low/residual Macro Stickies content, five of them belonged to the unbleached kraft papers category, with an area per mass of Macro Stickies ranging from 8.60 to 29.04 mm²/kg. However, the lowest case did not belong to this category, but to the molded cellulose products category with a value of 6.10 mm²/kg. Of the five samples showing higher amounts of Macro Stickies, the worst three cases were associated to one of the barrier papers, the recycled paper and the laminated paper, with an area per mass of Macro Stickies of 28,973.42, 6998.56, and 14,058.76 mm²/kg, respectively. Macro Stickies can assume different sizes, numbers and distributions depending on the characteristics and nature of each sample, and can be a great concern in the recycling of cellulose-based materials. In this sense, the proper assessment of Macro Stickies provides valuable information for the recycling sector to classify them in the products, and to anticipate which materials might give rise to potential stickies related problems in the recycling process. Full article

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40 pages, 2834 KiB

Open AccessReview

Sustainable Recycling of End-of-Life Electric Vehicle Batteries: EV Battery Recycling Frameworks in China and the USA

by Amjad Ali, Mujtaba Al Bahrani, Shoaib Ahmed, Md Tasbirul Islam, Sikandar Abdul Qadir and Muhammad Shahid

Recycling 2025, 10(2), 68; https://doi.org/10.3390/recycling10020068 - 10 Apr 2025

Abstract

The increasing adoption of electric vehicles (EVs) has led to a surge in end-of-life (EOL) lithium-ion batteries (LIBs), necessitating efficient recycling strategies to mitigate environmental risks and recover critical materials. This study compares the EV battery recycling frameworks in China and the United [...] Read more.

The increasing adoption of electric vehicles (EVs) has led to a surge in end-of-life (EOL) lithium-ion batteries (LIBs), necessitating efficient recycling strategies to mitigate environmental risks and recover critical materials. This study compares the EV battery recycling frameworks in China and the United States, focusing on policy effectiveness, technological advancements, and material recovery efficiencies. China’s extended producer responsibility (EPR) policies and 14th Five-Year Plan mandate strict recycling targets, achieving a 40% battery recycling rate with 90% material recovery efficiency. Hydrometallurgical methods dominate, reducing energy consumption by 50% compared to virgin material extraction. The US, leveraging incentive-based mechanisms and private sector innovations, has a 35% recycling rate but a higher 95% resource recovery efficiency, mainly due to direct recycling and AI-based sorting technologies. Despite these advancements, challenges remain, including high recycling costs, inconsistent global regulations, and supply chain inefficiencies. To enhance sustainability, this study recommends harmonized international policies, investment in next-generation recycling technologies, and second-life battery applications. Emerging innovations, such as AI-driven sorting and direct cathode regeneration, could increase recovery efficiency by 20–30%, further reducing lifecycle costs. By integrating synergistic policies and advanced recycling infrastructures, China and the US can set a global precedent for sustainable EV battery management, driving the transition toward a circular economy. Future research should explore life cycle cost analysis and battery reuse strategies to optimize long-term sustainability. Full article

(This article belongs to the Special Issue Lithium-Ion and Next-Generation Batteries Recycling)

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15 pages, 2752 KiB

Open AccessArticle

Feasibility of a Sustainable On-Site Paper Recycling Process

by Karl Jakob Levin, David dos Santos Costa, Lii Urb, Anna-Liisa Peikolainen, Tanel Venderström and Tarmo Tamm

Recycling 2025, 10(2), 67; https://doi.org/10.3390/recycling10020067 - 10 Apr 2025

Abstract

Several EU initiatives and directives emphasize waste reduction and immediate reuse at the source. This study introduces a novel on-site recycling method for transforming printing house paper waste into high-quality, eco-friendly cardboard without mixing it with lower-quality or heterogeneous waste streams. Instead of [...] Read more.

Several EU initiatives and directives emphasize waste reduction and immediate reuse at the source. This study introduces a novel on-site recycling method for transforming printing house paper waste into high-quality, eco-friendly cardboard without mixing it with lower-quality or heterogeneous waste streams. Instead of traditional water- and energy-intensive recycling processes, the proposed dry defibration method involves mechanical grinding, spray-on binder application, and heat pressing, significantly reducing the ecological footprint. The process was optimized using environmentally safe binders, such as poly(vinyl alcohol), sodium alginate, sorbitol, cellulose nanofibrils, and water, applied at low concentrations. A binder-to-dry-pulp ratio of 160 wt.% offered the best balance, yielding cardboard properties comparable or superior to those obtained by traditional methods. Focusing on book covers, the method demonstrated a 50% reduction in GHG emissions compared to conventional paper recycling and purchased cardboard use. The findings highlight the potential of localized, resource-efficient recycling processes to support sustainable production practices within the printing industry. Full article

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16 pages, 11180 KiB

Open AccessArticle

Packed-Bed Pyrolysis of Alkali Lignin for Value-Added Products

by Carmen Branca and Colomba Di Blasi

Recycling 2025, 10(2), 66; https://doi.org/10.3390/recycling10020066 - 9 Apr 2025

Abstract

Lignin is the largest renewable source of aromatic biopolymers on Earth, and it is commercially available as by-product of biorefineries and pulp/paper industries. It is mainly burned for heat and power, but pyrolysis can provide high-value-added products. In this study, the pyrolysis characteristics [...] Read more.

Lignin is the largest renewable source of aromatic biopolymers on Earth, and it is commercially available as by-product of biorefineries and pulp/paper industries. It is mainly burned for heat and power, but pyrolysis can provide high-value-added products. In this study, the pyrolysis characteristics of alkali lignin pellets are investigated using a packed-bed reactor at a laboratory scale for heating temperatures of 800–900 K. Conversion dynamics are analyzed by means of the thermal field and the rates of gaseous species release, which is a very innovative aspect of the study. The yields of the lumped product classes do not vary significantly in the range of heating temperatures examined (biochar yields around 58–63 wt%, together with gas and liquid yields around 9–12 and 28–30 wt%, respectively). Carbon dioxide is the most abundant gaseous product, followed by methane and carbon monoxide (smaller amounts of C₂ hydrocarbons and hydrogen), while bio-oil is rich in phenolic compounds, especially guaiacols, cresols, and phenol. A comparison with the conversion dynamics of fir, beech, and straw reveals that, mainly as a consequence of softening and melting, the lignin heat- and mass-transfer rates as well as actual reaction temperatures are profoundly different. In fact, the characteristic process size becomes the diameter of the reactor rather than that of the pellets. Full article

(This article belongs to the Special Issue Biomass Revival: Rethinking Waste Recycling for a Greener Future)

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20 pages, 4333 KiB

Open AccessArticle

A Plastic Classification Model Based on Simulated Data

by Alexander Pletl, Roman-David Kulko, Andreas Hanus and Benedikt Elser

Recycling 2025, 10(2), 65; https://doi.org/10.3390/recycling10020065 - 8 Apr 2025

Abstract

Plastic recycling holds significant potential to reduce global carbon emissions. Despite advances in recycling technologies, challenges such as limited data availability, contamination in sorted materials, and the complexity of real-world material flows continue to hinder progress. This study addresses these issues by introducing [...] Read more.

Plastic recycling holds significant potential to reduce global carbon emissions. Despite advances in recycling technologies, challenges such as limited data availability, contamination in sorted materials, and the complexity of real-world material flows continue to hinder progress. This study addresses these issues by introducing a novel approach to plastic classification, leveraging simulated spectral data to reduce reliance on large datasets and improve classification accuracy. Using near-infrared spectroscopy and deep learning models, the framework integrates data augmentation techniques and spectral simulation to augment datasets with synthetic spectra based on a data sample of 25 plastic granules. The proposed classification framework achieves excellent recall and robust balanced accuracy for both binary and multi-target polymer classification with minimal data input (only 50 spectra per class). Thus, the measurement effort is drastically reduced while maintaining an equally high model accuracy. The model significantly outperforms conventional unsupervised approaches. By overcoming the limitations of supervised learning models, the proposed framework provides a scalable and efficient solution for plastics recycling. Full article

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16 pages, 2027 KiB

Open AccessArticle

Effective Recovery of Gold from Chloride Multi-Metal Solutions Through Anion Exchange

by Isabel F. F. Neto, Márcia A. D. Silva and Helena M. V. M. Soares

Recycling 2025, 10(2), 64; https://doi.org/10.3390/recycling10020064 - 7 Apr 2025

Abstract

Leachates from electronic waste, slag dusts generated during the processing of electronic waste, sweeping jewelry, and municipal solid-waste incineration residues contain a myriad of base metals, such as aluminum (Al: 10–2000 mg/L), copper (Cu: 10–1000 mg/L), iron (Fe: 10–500 mg/L), nickel (Ni: 0.1–500 [...] Read more.

Leachates from electronic waste, slag dusts generated during the processing of electronic waste, sweeping jewelry, and municipal solid-waste incineration residues contain a myriad of base metals, such as aluminum (Al: 10–2000 mg/L), copper (Cu: 10–1000 mg/L), iron (Fe: 10–500 mg/L), nickel (Ni: 0.1–500 mg/L), lead (Pb: 1–500 mg/L), tin (Sn: 1–100 mg/L), and zinc (Zn: 5–500 mg/L), which are present at much higher quantities than Au (0.01–10 mg/L), which raises several drawbacks to the efficient recycling of Au with high purity using hydrometallurgical strategies. The aim of this work was to study the efficiency and selectivity of two strong basic anion exchange (DOW^TM XZ-91419.00 and Purogold^TM A194) resins to recover Au from a chloride multi-metal solution containing these metals. For both resins, the adsorption kinetic and equilibrium parameters for Au(III), determined at 1.12 mol/L HCl, Eh = 1.1 V, and 25 °C, proceeded according to a pseudo-second order and a Langmuir isotherm (qmax was 0.94 and 1.70 mmol/g for DOW^TM XZ-91419.00 and Purogold^TM A194 resins, respectively), respectively. Continuous adsorption experiments of Au (48 µmol/L; 2.0%) from a chloride multi-metal solution evidenced high Au retention capacity and selectivity to Au over Al, Cu, Fe, Ni, and Zn but low selectivity to Au over Ag and Sn for both resins. Concentrated (>3.3 mmol/L) and pure (>94%) Au eluates were obtained for both resins. Full article

(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)

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21 pages, 3858 KiB

Open AccessArticle

Upgrading and Characterization of Glass Recovered from MSWI Bottom Ashes from Fluidized Bed Combustion

by Julia Mühl, Simon Mika, Alexia Tischberger-Aldrian and Jakob Lederer

Recycling 2025, 10(2), 63; https://doi.org/10.3390/recycling10020063 - 7 Apr 2025

Abstract

Glass in mixed municipal solid waste (MSW) is often lost for recycling. Glass recovery from incineration bottom ash (IBA) after MSW incineration (MSWI) is technically feasible by sensor-based sorting, but rarely applied. Especially IBAs from fluidized bed combustion contain high recoverable glass amounts, [...] Read more.

Glass in mixed municipal solid waste (MSW) is often lost for recycling. Glass recovery from incineration bottom ash (IBA) after MSW incineration (MSWI) is technically feasible by sensor-based sorting, but rarely applied. Especially IBAs from fluidized bed combustion contain high recoverable glass amounts, but upgrading this glass is required for recycling in the packaging glass industry. This study examines different upgrading setups based on sensor-based sorting to improve the glass quality from two Austrian fluidized bed IBAs. Sensor-based sorting removed extraneous material like ceramic, stones, porcelain, metals, and lead glass. The fractions produced were characterized by manual sorting and X-ray fluorescence analysis. The glass fractions before upgrading contained 85–89% glass, of which 67% and 83% could be recovered after four sorting steps. Previous sieving caused high glass losses and is therefore not recommended. By sensor-based sorting, the extraneous material contents were lowered from 13% and 9% in the two IBAs to below 2.2%. Four-step upgrading could even ensure extraneous material contents <0.11% and Pb contents <200 mg/kg. Although limit values for packaging glass recycling were still exceeded, this study shows that upgrading of glass recovered from fluidized bed IBAs suggests a novel opportunity to enhance closed-loop glass recycling, thereby reducing the amount of landfilled glass. Full article

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13 pages, 4589 KiB

Open AccessArticle

Development and Implementation of a Machine to Increase the Production and the Quality of a Compost

by Camila Mori de Oliveira, Andrea Sammito, Mauro Boano, Matteo Fischetti, Lorenzo Toso, Roberta Pizio, Rossana Bellopede and Paola Marini

Recycling 2025, 10(2), 62; https://doi.org/10.3390/recycling10020062 - 5 Apr 2025

Abstract

The composting sector plays a crucial role in the urban waste management system and is essential for advancing towards a circular economy. All organic matter can be entirely recovered from waste collection, except for the extraneous fractions present as impurities. In the studied [...] Read more.

The composting sector plays a crucial role in the urban waste management system and is essential for advancing towards a circular economy. All organic matter can be entirely recovered from waste collection, except for the extraneous fractions present as impurities. In the studied waste composting plant, three fractions are produced: >50 mm (waste not idoneous for compost), <12 mm (suitable for compost market) and 50–12 mm (overflow). The latter is used as inoculum and therefore recirculates many times, reducing the sizes of its constituents, which are mainly plastic films falling into the lower class <12 mm, where they are concentrated. The goal of this study is to reduce the quantity of undesirable materials present in the 50–12 mm class in order to increase the quality of the compost produced. For this reason, a compost characterization was carried out and a plant solution was proposed: the inclusion of a mesh conveyor belt, with beater rollers and an aspiration system at the end. The fine organic material passes through the mesh sieve, and it is moved apart from the overflow material, in which the light plastics are aspirated. More than 10% of the overflow weight is recovered as clean compost, with very low percentages of undesired remaining. A reduction in plastic impurity of 75% is reached. Full article

(This article belongs to the Topic Sustainable Recycling and Reuse of Industrial By-Products or Waste from Geo-Resource Exploitation)

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25 pages, 5651 KiB

Open AccessArticle

Kinetic and Thermodynamic Analysis of Fried Tilapia Fish Waste Pyrolysis for Biofuel Production

by Mohamed Koraiem M. Handawy, Ik-Tae Im, Gyo Woo Lee and Hamada Mohamed Abdelmotalib

Recycling 2025, 10(2), 61; https://doi.org/10.3390/recycling10020061 - 1 Apr 2025

Abstract

Converting food waste into biofuel resources is considered a promising approach to address the rapid increase in energy demand, reduce dependence on fossil fuels, and decrease environmental hazards. In Egypt, large quantities of fried tilapia fish waste are produced in restaurants and households, [...] Read more.

Converting food waste into biofuel resources is considered a promising approach to address the rapid increase in energy demand, reduce dependence on fossil fuels, and decrease environmental hazards. In Egypt, large quantities of fried tilapia fish waste are produced in restaurants and households, posing challenges for proper waste management due to its decaying nature. The current study investigates the kinetic triplet and thermodynamic parameters of fried tilapia fish waste (FTFW) pyrolysis. Kinetic analysis was carried out using four iso-conversional models, Friedman, Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink, at heating rates of 10, 15, and 20 °C/min. The study findings indicate that FTFW decomposes within the temperature range of 382–407 °C. The estimated activation energy using the Friedman, FWO, KAS, and Starink methods ranged from 43.2 to 208.2, 31.3 to 148.3, 22.3 to 179.3, and 24.1 to 181.3 kJ/mol, respectively, with average values of 118.4, 96.7, 109.7, and 100.5 kJ/mol, respectively. The average enthalpy change determined using the Friedman, FWO, KAS, and Starink methods was 113.45, 91.78, 95.58, and 104.73 kJ/mol, respectively. The average values of Gibbs free energy change for the Friedman, KAS, FWO, and Starink, methods were 192.71, 171.04, 174.83, and 183.99 kJ/mol, respectively. Full article

(This article belongs to the Topic Circular Economy in Interdisciplinary Perspective: Valorization of Raw Materials, Sustainable Products, and Pro-Ecological Industrial Developments)

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32 pages, 328 KiB

Open AccessReview

Rutting and Aging Properties of Recycled Polymer-Modified Pavement Materials

by Nuha S. Mashaan and Chathurika Dassanayake

Recycling 2025, 10(2), 60; https://doi.org/10.3390/recycling10020060 - 1 Apr 2025

Abstract

Recycled polymer-modified binders have emerged as a sustainable solution for improving the performance and durability of pavement materials. This review examines the rutting and aging properties of pavements modified with recycled polymers, highlighting their potential for sustainable infrastructure development. The incorporation of recycled [...] Read more.

Recycled polymer-modified binders have emerged as a sustainable solution for improving the performance and durability of pavement materials. This review examines the rutting and aging properties of pavements modified with recycled polymers, highlighting their potential for sustainable infrastructure development. The incorporation of recycled polymers into bitumen enhances resistance to rutting and aging by improving the binder’s mechanical stability and oxidative durability. Key laboratory techniques, including the rolling thin-film oven test (RTFOT) and the pressure aging vessel (PAV), are evaluated for their effectiveness in assessing the thermal and oxidative aging behavior of modified binders. The review demonstrates that recycled polymers improve binder elasticity, delay oxidative degradation, and mitigate deformation under repeated loading, thus extending pavement lifespan and reducing maintenance costs. However, challenges such as optimizing polymer dosage, ensuring homogeneity, and predicting long-term performance require further investigation. This paper underscores the environmental and economic benefits of utilizing recycled polymers in pavement construction and advocates for improved testing protocols and advanced characterization techniques to enhance the reliability and sustainability of polymer-modified pavements. Full article

(This article belongs to the Special Issue Recycled Materials in Sustainable Pavement Innovation)

19 pages, 7778 KiB

Open AccessArticle

Mechanical and Thermal Properties of Recycled Fishing Net-Derived Polyamide 6/Switchgrass Fiber Composites for Automotive Applications

by Zakariae Belmokhtar, Patrice Cousin, Saïd Elkoun and Mathieu Robert

Recycling 2025, 10(2), 59; https://doi.org/10.3390/recycling10020059 - 1 Apr 2025

Abstract

The increasing demand for sustainable materials in automotive applications, coupled with the critical need to address marine plastic pollution, presents an opportunity for innovative material development. This study explores composites made from recycled polyamide 6 (PA6) fishing nets reinforced with switchgrass fibers (0–30 [...] Read more.

The increasing demand for sustainable materials in automotive applications, coupled with the critical need to address marine plastic pollution, presents an opportunity for innovative material development. This study explores composites made from recycled polyamide 6 (PA6) fishing nets reinforced with switchgrass fibers (0–30 wt%). The composite with 30 wt% switchgrass fibers increased tensile strength by 23% and Young’s modulus by 126% compared to unreinforced recycled PA6, achieving 93% of the tensile strength of commercial automotive-grade neat PA6 and surpassing another grade by 22%. However, higher fiber loading hindered processability, as evidenced by incomplete mold filling and reflected by a decrease in melt flow rate from 19.35 to 8.63 g/10 min. Thermal analysis revealed reduced crystallinity and crystallization temperatures with fiber addition, attributed to restricted polymer chain mobility. While dynamic mechanical analysis demonstrated improved stiffness below the glass transition temperature, scanning electron microscopy indicated optimal fiber-matrix adhesion at up to 20 wt% fiber loading, with aggregation at higher concentrations. These findings establish recycled fishing net-derived PA6/switchgrass fiber composites as a viable alternative to virgin materials in automotive applications, with mechanical properties comparable to commercial grades. Although the composites demonstrate enhanced mechanical strength and modulus, the significant reduction in ductility restricts their use to rigid, semi-structural components where flexibility is not critical. Future research should address processing challenges to enhance fiber dispersion and interfacial adhesion at higher loadings. Full article

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