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Recycling, Volume 10, Issue 6 (December 2025) – 6 articles

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16 pages, 2038 KB

Open AccessArticle

Separation of Silver and Cellulosic Fibers for Recycling and Reuse of Printed Electronic Devices Components

by Ramzi Khiari, Nathalie Marlin, Denis Curtil, Marc Aurousseau, Lenka Svecová and Nadège Reverdy-Bruas

Recycling 2025, 10(6), 201; https://doi.org/10.3390/recycling10060201 - 29 Oct 2025

Abstract

The printed electronics sector is experiencing significant growth driven by societal expectations. The use of cellulosic substrates is an excellent strategy that offers interesting research prospects, but also sets challenges in terms of management and recycling of these new wastes to avoid their accumulation. This work investigates the recycling ability of paper-based printed electronics (a simple RFID antenna printed on paper), containing silver particles in the functional ink, using processes already applied in conventional paper and board recycling lines. These operations, commonly used in the papermaking industry, are pulping, screening, centrifugal cleaning, and flotation. The efficiency of each unit operation was evaluated. Mass balances between the inlet and the outlet of each studied operation have been established in order to evaluate the separation efficiency of Ag and cellulosic fibers, the objective being to reuse the fibers to manufacture a recycled paper, and to recover Ag in another fraction for further valorization. The results are encouraging, with more than 70% of silver and over 80% of cellulose fibers recovered, demonstrating a higher recovery efficiency compared to typical recycling methods reported in the literature. Thus, it has been shown that existing processes used in conventional recycling lines can be adapted to efficiently separate functional materials from cellulosic fibers, offering an improvement in both metal and fibers’ recovery. Full article

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16 pages, 5466 KB

Open AccessArticle

Effects of Contamination on the Recyclability of NdFeB Permanent Magnets via Short-Loop Processing: Review of Common Contaminants and Study on Ni Coating Residues

by Laura Grau, Fabian Burkhardt, Nicolas Moll, Stefan Rathfelder, Spomenka Kobe and Carlo Burkhardt

Recycling 2025, 10(6), 200; https://doi.org/10.3390/recycling10060200 - 29 Oct 2025

Abstract

Short-loop recycling of NdFeB trades a reduced ecological burden for a higher sensitivity towards contamination, as the powder is usually further processed as-is. In this investigation, the known effects of common contaminants (O, C, Ni, Cu, and Zn) introduced due to product design choices, namely from coating material and adhesive residue or a lack of corrosion protection, are reviewed. This study focuses on the impact of such contaminants on the magnetic properties and microstructure of recycled magnets via HPMS and re-sintering. Because of the lack of information regarding the practical effects of metallic coating residues, the impact of Ni contamination on the properties of re-sintered NdFeB magnets is assessed. HPMS processed scrap powder is blended with Ni powder and recycled by sintering. It is found that Ni partially substitutes Fe in the φ-phase, as expected from the literature review, leading to detrimental effects on the coercivity and remanence. The formation of an α-(Fe, Ni) phase is observed. The acceptable limit of Ni contamination without detrimental effects is found to be around 0.25 wt.%; however, due to the substitution in the φ-phase, the contamination is irreversible via short-loop recycling and would accumulate over multiple lifecycles. Full article

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15 pages, 5582 KB

Open AccessArticle

Design of an Energy-Efficient Pilot-Scale Pyrolysis Reactor Using Low-Cost Insulating Materials

by José Alfredo Torres Tovar, Hermelinda Servín-Campuzano, Mauricio González-Avilés, Hugo Sobral, Francisco Javier Sánchez-Ruiz and Saúl Leonardo Hernández Trujillo

Recycling 2025, 10(6), 199; https://doi.org/10.3390/recycling10060199 - 28 Oct 2025

Abstract

A pilot-scale reactor prototype was designed to produce hydrocarbons through the catalytic pyrolysis process of low-density polyethylene, thereby extending its life cycle and contributing to energy efficiency and sustainability. The reactor consists of a stainless-steel tank encased in a ceramic jacket with refractory cement and clay bricks. The tank, made of 304 stainless steel, ensures mechanical strength and efficient heat transfer to the reactor core. A spiral condenser was incorporated into a water tank to cool the vapors and recover the liquid oil. The insulating materials, ceramic, refractory cement and clay brick, demonstrated a high combined thermal resistance of 0.159 m²·K/W. Simulations and energy flow calculations demonstrated that heat is efficiently directed to the reactor core, reaching 350 °C with only 3000–3800 W, while the outside of the jacket remained close to 32 °C. These results confirm that the proposed design improves thermal efficiency and optimizes energy use for catalytic pyrolysis. The novelty of this design lies in its energy-efficient configuration, which can be replicated in rural regions worldwide due to the accessibility of its construction materials. This reactor was developed based on a smaller-scale model that previously yielded excellent results. Full article

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20 pages, 13496 KB

Open AccessArticle

Effect of Pretreatment on the Structure and Enzymatic Hydrolysis of Pineapple Waste Biomass in Hydrothermal Deconstruction

by Carlos Méndez-Durazno, Nilo M. Robles Carrillo, Valeria Ramírez, Oscar M. Rodriguez-Narváez, Pablo A. Cisneros-Pérez, Diego Chulde, Alexis Debut and Patricio J. Espinoza-Montero

Recycling 2025, 10(6), 198; https://doi.org/10.3390/recycling10060198 - 28 Oct 2025

Abstract

Pineapple biomass represents an abundant renewable source of carbon and a promising feedstock with considerable potential for the production of sustainable fuels. In the present study, the influence of liquid hot water (LHW) pretreatment on the pineapple mother plant was investigated at different controlled severities, then characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results show that LHW pretreatment causes structural changes, leading to lignin and hemicellulose depolymerization up to a severity factor of 2.36–3.55, whereas at severity factors in the range of 4.13–5.90, cellulose, hemicellulose, and lignin appear to repolymerize. This pretreatment resulted in a higher hydrolysis efficiency (94.92 ± 0.04%) at 50 °C for 72 h. Compared with the untreated sample, the hydrolysis rate under these conditions increased by a factor of 2.16. SEM imaging revealed significant disruption of the PMP microstructure following LHW treatment, while XRD data confirmed an increase in the crystallinity index. FTIR analysis further indicated modifications in functional group profiles, supporting the structural and compositional changes induced by pretreatment. Overall, this study demonstrates the effectiveness of LHW pretreatment in enhancing the enzymatic digestibility and modifying the physicochemical properties of PMP biomass, providing a foundation for its valorization into high value bioproducts. Full article

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13 pages, 643 KB

Open AccessArticle

Recycling of Post-Consumer HDPE Bottle Caps into New Caps for Food Contact

by Frank Welle

Recycling 2025, 10(6), 197; https://doi.org/10.3390/recycling10060197 - 22 Oct 2025

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Abstract

HDPE caps are collected together with PET bottles, which have been recycled into new bottles for decades. Due to Deposit Return Schemes, the bottle caps are sorted by type and are suitable to be recycled again for sensitive applications e.g., food contact. While there are evaluation criteria for mechanical PET recycling processes, no such evaluation crite-ria have been published for recycled HDPE caps in food contact. As part of the study, possible evaluation criteria are derived from other polymers or applications and critically discussed. Recycling of post-consumer caps from beverage bottles into new HDPE caps in direct contact with food is realistic even if worst-case considerations on the evaluation criteria are applied. The required cleaning efficiencies are within a range that is technically feasible for today’s mechanical HDPE recycling processes. The evaluation criteria can be used for a preliminary assessment of post-consumer HDPE recyclate in food contact. Based on the evaluation, the recycling of HDPE caps is to be submitted as a novel technology according to Regulation 2022/1616. Full article

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25 pages, 10369 KB

Open AccessArticle

Properties of Green Foam-Type Composites Made from Recycled Paper and Cardboard

by Mohammad Hassan Mazaherifar, Antonela Lungu, Maria Cristina Timar, Sergiu Valeriu Georgescu, Mihai Ispas and Camelia Cosereanu

Recycling 2025, 10(6), 196; https://doi.org/10.3390/recycling10060196 - 22 Oct 2025

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Abstract

This study developed sustainable foam-type composites from recycled paper (P), corrugated cardboard (C), and their 1:1 mixture (PC) for use in thermal and acoustic insulation. The materials were produced by water-assisted defibration, gas foaming with sodium bicarbonate and yeast, and oven curing, resulting in lightweight porous panels without synthetic binders. The composites exhibited distinct density and porosity profiles that influenced moisture behavior and stability. Cardboard-based panels absorbed the most water and swelled the most, while paper-based panels were more resistant. Despite these differences, all materials showed uniformly low thermal conductivity, confirming their strong insulation capability. Acoustic performance was enhanced by perforation and multilayer assembly. Cardboard panels with a triple-layer perforated design achieved the highest sound absorption, while mixed paper–cardboard composites provided balanced broadband performance. Microscopy revealed that fiber morphology—coarse in cardboard, fine in paper, and interlaced in mixtures—shaped the porous structure and bonding. Mechanical tests indicated comparable stiffness and strength across all types, with cardboard showing the strongest internal bonding. Overall, the results demonstrate that fiber structure and porosity govern material performance. These foam composites combine effective thermal insulation, competitive sound absorption, and sufficient mechanical strength, positioning them as biodegradable, low-cost alternatives for sustainable construction and acoustic applications. Full article

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