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Niu B, E S, Song Q, Xu Z, Han B, Qin Y. Physicochemical reactions in e-waste recycling. Nat Rev Chem 2024:10.1038/s41570-024-00616-z. [PMID: 38862738 DOI: 10.1038/s41570-024-00616-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2024] [Indexed: 06/13/2024]
Abstract
Electronic waste (e-waste) recycling is becoming a global concern owing to its immense quantity, hazardous character and the potential loss of valuable metals. The many processes involved in e-waste recycling stem from a mixture of physicochemical reactions, and understanding the principles of these reactions can lead to more efficient recycling methods. In this Review, we discuss the principles behind photochemistry, thermochemistry, mechanochemistry, electrochemistry and sonochemistry for metal recovery, polymer decomposition and pollutant elimination from e-waste. We also discuss how these processes induce or improve reaction rates, selectivity and controllability of e-waste recycling based on thermodynamics and kinetics, free radicals, chemical bond energy, electrical potential regulation and more. Lastly, key factors, limitations and suggestions for improvements of these physicochemical reactions for e-waste recycling are highlighted, wherein we also indicate possible research directions for the future.
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Affiliation(s)
- Bo Niu
- Key Laboratory of Farmland Ecological Environment of Hebei Province, College of Resources and Environmental Science, Hebei Agricultural University, Baoding, China.
| | - Shanshan E
- College of Mechanical and Electrical Engineering, Hebei Agricultural University, Baoding, China
| | - Qingming Song
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zhenming Xu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Bing Han
- School of Agriculture, Food and Ecosystem Sciences, Faculty of Science, The University of Melbourne, Parkville, Victoria, Australia
- School of Engineering, Deakin University, Geelong, Victoria, Australia
| | - Yufei Qin
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, China
- Jiangxi Green Recycling Co., Ltd, Fengcheng, China
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Yu D, Zhan L, Xu Z. An environmentally-friendly permeable liquid salt pyrolysis method based on capillary heat transfer for recycling waste insulator materials. JOURNAL OF HAZARDOUS MATERIALS 2024; 469:133815. [PMID: 38428294 DOI: 10.1016/j.jhazmat.2024.133815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 02/14/2024] [Accepted: 02/15/2024] [Indexed: 03/03/2024]
Abstract
Molten salt pyrolysis technology stands out as a potent approach for achieving efficient degradation and energy recovery of composite organic materials. Nevertheless, challenges such as the high melting point of molten salt, product destruction, and the complexities of treating waste salt pose significant limitations to the widespread application and popularization of this technology. To tackle these issues, this study proposes a salt-assisted pyrolysis method based on capillary heat transfer called permeable liquid salt pyrolysis. Focusing on abandoned power industry insulators, the research delves into the thermal and mass transfer model of cluster-embedded materials under non-molten salt conditions. The investigation reveals that the capillary between glass fiber and resin proves beneficial in enhancing heat transfer conditions by creating a novel phase known as permeate liquid. Results demonstrate that salt-assisted pyrolysis can substantially lower the required temperature and enhance the pyrolysis reaction rate, achieving a maximum degradation efficiency of 98.99 %. Additionally, the pyrolysis products undergo in-situ modification, with a notable reduction in benzene series compounds ranging from 68 % to 85 %. Furthermore, an erosion diffusion capillary mode is established. This study presents an environmentally-friendly approach to recycle and modify products derived from waste resin-based composite materials generated in the electric power industry.
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Affiliation(s)
- Daheng Yu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lu Zhan
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
| | - Zhenming Xu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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Ma C, Kumagai S, Saito Y, Yoshioka T, Huang X, Shao Y, Ran J, Sun L. Recent Advancements in Pyrolysis of Halogen-Containing Plastics for Resource Recovery and Halogen Upcycling: A State-of-the-Art Review. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:1423-1440. [PMID: 38197317 DOI: 10.1021/acs.est.3c09451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Plastic waste has emerged as a serious issue due to its impact on environmental degradation and resource scarcity. Plastic recycling, especially of halogen-containing plastics, presents challenges due to potential secondary pollution and lower-value implementations. Chemical recycling via pyrolysis is the most versatile and robust approach for combating plastic waste. In this Review, we present recent advancements in halogen-plastic pyrolysis for resource utilization and the potential pathways from "reducing to recycling to upcycling" halogens. We emphasize the advanced management of halogen-plastics through copyrolysis with solid wastes (waste polymers, biomass, coal, etc.), which is an efficient method for dealing with mixed wastes to obtain high-value products while reducing undesirable substances. Innovations in catalyst design and reaction configurations for catalytic pyrolysis are comprehensively evaluated. In particular, a tandem catalysis system is a promising route for halogen removal and selective conversion of targeted products. Furthermore, we propose novel insights regarding the utilization and upcycling of halogens from halogen-plastics. This includes the preparation of halogen-based sorbents for elemental mercury removal, the halogenation-vaporization process for metal recovery, and the development of halogen-doped functional materials for new materials and energy applications. The reutilization of halogens facilitates the upcycling of halogen-plastics, but many efforts are needed for mutually beneficial outcomes. Overall, future investigations in the development of copyrolysis and catalyst-driven technologies for upcycling halogen-plastics are highlighted.
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Affiliation(s)
- Chuan Ma
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China
| | - Shogo Kumagai
- Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki-aza, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Yuko Saito
- Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki-aza, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Toshiaki Yoshioka
- Graduate School of Environmental Studies, Tohoku University, 6-6-07 Aoba, Aramaki-aza, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Xin Huang
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China
| | - Yunlin Shao
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China
| | - Jingyu Ran
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China
| | - Lushi Sun
- State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China
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Li XG, Gao Q, Jiang SQ, Nie CC, Zhu XN, Jiao TT. Review on the gentle hydrometallurgical treatment of WPCBs: Sustainable and selective gradient process for multiple valuable metals recovery. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 348:119288. [PMID: 37864943 DOI: 10.1016/j.jenvman.2023.119288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 09/20/2023] [Accepted: 10/06/2023] [Indexed: 10/23/2023]
Abstract
The metal resource crisis and the inherent need for a low-carbon circular economy have driven the rapid development of e-waste recycling technology. High-value waste printed circuit boards (WPCBs) are an essential component of e-waste. However, WPCBs are considered hazardous to the ecosystem due to the presence of heavy metals and brominated organic polymers. Therefore, achieving the recycling of metals in WPCBs is not only a strategic requirement for building a green ecological civilization but also an essential guarantee for achieving a safe supply of mineral resources. This review systematically analyzes the hydrometallurgical technology of metals in WPCBs in recent years. Firstly, the different unit operations of pretreatment in the hydrometallurgical process, which contain disassembly, crushing, and pre-enrichment, were analyzed. Secondly, environmentally friendly hydrometallurgical leaching systems and high-value product regeneration technologies used in recent years to recover metals from WPCBs were evaluated. The leaching techniques, including cyanidation, halide, thiourea, and thiosulfate for precious metals, and inorganic acid, organic acid, and other leaching methods for base metals such as copper and nickel in WPCBs, were outlined, and the leaching performance and greenness of each leaching system were summarized and analyzed. Eventually, based on the advantages of each leaching system and the differences in chemical properties of metals in WPCBs, an integrated and multi-gradient green process for the recovery of WPCBs was proposed, which provides a sustainable pathway for the recovery of metals in WPCBs. This paper provides a reference for realizing the gradient hydrometallurgical recovery of metals from WPCBs to promote the recycling metal resources.
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Affiliation(s)
- Xi-Guang Li
- College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
| | - Qiang Gao
- College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
| | - Si-Qi Jiang
- College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
| | - Chun-Chen Nie
- College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China
| | - Xiang-Nan Zhu
- College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China.
| | - Tian-Tian Jiao
- College of Chemical and Biological Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China.
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Chen Z, Zhan L, Xu Z. Enhancing Debromination Efficiency through Introducing Water Vapor Atmosphere to Overcome Limitations of Conventional Pyrolysis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:20941-20950. [PMID: 38032848 DOI: 10.1021/acs.est.3c06640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Bromine removal is significant in the recycling of waste printed circuit boards (WPCBs). This study found that the critical factors limiting the debromination efficiency of conventional pyrolysis are the formation of coke impeding mass transfer and conversion of bromine into less volatile species, such as coking-Br and copper bromide. According to frontier molecular orbital analysis and thermodynamic equilibrium analysis, C-O bonds of resin are sites prone to electrophilic reactions and copper bromide in residue may undergo hydrolysis; therefore, introducing H2O during pyrolysis was a feasible method for thorough debromination. Through pyrolysis in a water vapor atmosphere, the diffusion limitation of debromination was overcome, and resin was converted into light components; thereby, rapid and deep removal of bromine was achieved. The result indicated that 99.7% of bromine was removed, and the residue could be used as a clean secondary resource. According to life-cycle assessment, pyrolysis of WPCBs in water vapor could be expected to reduce 77 Kt of CO2 emission and increase financial benefits by 60 million dollars, annually.
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Affiliation(s)
- Zhenyu Chen
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Lu Zhan
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
| | - Zhenming Xu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
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Diaz F, Latacz D, Friedrich B. Enabling the recycling of metals from the shredder light fraction derived from waste of electrical and electronic equipment via continuous pyrolysis process. WASTE MANAGEMENT (NEW YORK, N.Y.) 2023; 172:335-346. [PMID: 37948829 DOI: 10.1016/j.wasman.2023.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 10/28/2023] [Accepted: 11/02/2023] [Indexed: 11/12/2023]
Abstract
The surge in Waste Electrical and Electronic Equipment (WEEE) generation, reaching 53.6 million metric tons (Mt) in 2019, demands efficient recycling solutions. This study focuses on the Shredder Light Fraction (SLF), a material stream derived from the mechanical pre-processing of WEEE, which is considered "municipal waste". SLF constitutes 4.2% of the output material and is rich in metals like copper, tin, lead, zinc, silver, and gold. Pyrolysis treatment was applied to SLF, enabling recyclability. Both batch and continuous setups were employed for materials flow analysis and technical evaluation of the resource potential. The research evaluates the impact of pyrolysis technology on solid fraction metal content and pyrolysis gas/oil energy potential. Scaling up the process addressed material heterogeneity and increased the reliability of the obtained results. An innovative pyrometallurgical extraction approach was suggested, to recover valuable metals in SLF which otherwise could be lost via energy recovery methods. The resulting solid product after pyrolysis showed enriched concentrations of copper, zinc, lead, and precious metals with concentrations acceptable for industrial use. Additionally, it displayed reduced mass and diminished hazardous constituents. The non-condensable gas, rich in hydrogen, carbon monoxide, and methane, exhibited potential as an alternative energy source or reducing agent in the metallurgical sector. This research advances metal recycling from SLF, offering valuable insights for environmental impact mitigation as waste was transformed into a valuable by-product for potential use in the copper industry.
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Affiliation(s)
- Fabian Diaz
- Institute of Process Metallurgy and Metal Recycling IME, RWTH Aachen University, Intzestraße 3, 52056 Aachen, Germany.
| | - Damien Latacz
- Institute of Process Metallurgy and Metal Recycling IME, RWTH Aachen University, Intzestraße 3, 52056 Aachen, Germany.
| | - Bernd Friedrich
- Institute of Process Metallurgy and Metal Recycling IME, RWTH Aachen University, Intzestraße 3, 52056 Aachen, Germany.
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Hu D, Zeng X, Lin Y, Chen Y, Chen W, Jia Z, Lin J. High Value-Added Reutilization of Waste-Printed Circuit Boards Non-Metallic Components in Sustainable Polymer Composites. Molecules 2023; 28:6199. [PMID: 37687027 PMCID: PMC10489137 DOI: 10.3390/molecules28176199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 08/16/2023] [Accepted: 08/21/2023] [Indexed: 09/10/2023] Open
Abstract
The reutilization non-metallic components from a waste-printed circuit board (WPCB) has become one of the most significant bottlenecks in the comprehensive reuse of electronic wastes due to its low value and complex compositions, and it has received great attention from scientific and industrial researchers. To effectively address the environmental pollution caused by inappropriate recycling methods, such as incineration and landfill, extensive efforts have been dedicated to achieving the high value-added reutilization of WPCB non-metals in sustainable polymer composites. In this review, recent progress in developing sustainable polymer composites based on WPCB non-metallic components was systematically summarized. It has been demonstrated that the WPCB non-metals can serve as a promising reinforcing and functional fillers to significantly ameliorate some of the physical and chemical properties of polymer composites, such as excellent mechanical properties, enhanced thermal stability, and flame retardancy. The recovery strategies and composition of WPCB non-metals were also briefly discussed. Finally, the future potentials and remaining challenges regarding the reutilization of WPCB non-metallic components are outlined. This work provides readers with a comprehensive understanding of the preparation, structure, and properties of the polymer composites based on WPCB non-metals, providing significant insights regarding the high value-added reutilization of WPCB non-metals of electronic wastes.
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Affiliation(s)
- Dechao Hu
- School of Materials Science and Hydrogen Energy, Foshan University, Foshan 528000, China; (D.H.)
| | - Xianghong Zeng
- School of Materials Science and Hydrogen Energy, Foshan University, Foshan 528000, China; (D.H.)
| | - Yinlei Lin
- School of Materials Science and Hydrogen Energy, Foshan University, Foshan 528000, China; (D.H.)
| | - Yongjun Chen
- Key Lab of Guangdong High Property and Functional Macromolecular Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
| | - Wanjuan Chen
- School of Materials Science and Hydrogen Energy, Foshan University, Foshan 528000, China; (D.H.)
| | - Zhixin Jia
- Key Lab of Guangdong High Property and Functional Macromolecular Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
| | - Jing Lin
- Research Center of Flexible Sensing Materials and Devices, School of Applied Physics and Materials, Wuyi University, Jiangmen 529020, China
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