Hydrogen decrepitation of post-consumer NdFeB magnets: a sustainable pre-processing route for rare earth recycling
Agnes Mitzi Kich; Rafael Menezes Nunes; Camila Lemos Teixeira; Milena Mattje; Carlos Alberto Mendes Moraes; Feliciane Andrade Brehm
Abstract
The growing generation of waste electrical and electronic equipment (WEEE) has driven the search for sustainable strategies to recover critical and strategic minerals, such as NdFeB magnets, widely used in hard disk drives (HDDs). These magnets contain elements with increasing demand and limited supply, making the development of efficient recycling processes essential. In this context, hydrogen decrepitation stands out by enabling selective fragmentation of the magnets and recovery of their constituents. This study addressed the disassembly of post-consumer HDDs to extract NdFeB magnets and their processing through the decrepitation hydrogen method. The samples were characterized using XRF, ICP-OES, and XRD techniques, revealing variations in major elements such as Fe and Nd, along with traces of Si, Al, Zr, and Co, influenced by the type of magnet. SEM analysis confirmed the presence of intergranular cracks typical of the hydrogen decrepitation mechanism. It was observed that the untreated sample had a milling efficiency of 25.33%, while the hydrogen-treated sample reached 73.33%, indicating a significant improvement in particle embrittlement. The results demonstrate that hydrogen decrepitation is a beneficiation alternative aimed at the direct recycling of NdFeB magnets, promoting circularity and reducing the need for extraction of virgin raw materials.
Keywords
Referências
1 Baldé CP, Kuehr R, Yamamoto T, Mcdonald R, D’angelo E, Althaf S, et al. Global E-waste Monitor. Genebra: International Telecommunication Union (ITU) and United Nations Institute for Training and Research (UNITAR); 2024.
2 Stalter CF. Análise comparativa da utilização de ácido orgânico versus ácido inorgânico na recuperação de neodímio presente em hard disk drives (HDs): uma abordagem técnica, ambiental e econômica [tese]. São Leopoldo: PPGEC, Universidade do Vale do Rio dos Sinos; 2022.
3 Brasil. Câmara dos Deputados. Projeto de Lei nº 2780, de 2024. Estabelece a Política Nacional de Minerais Críticos e Estratégicos. Diário Oficial da União. 2024.
4 International Organization for Standardization. ISO 59000: Circular economy — Overview and principles. Geneva: ISO; 2020.
5 International Organization for Standardization. ISO 59014: Circular economy — Guidelines for the characterization, classification and traceability of secondary materials. Geneva: ISO; 2020.
6 Instituto Brasileiro de Mineração, organizador. Minerais críticos e estratégicos no brasil: um passaporte para o futuro. Brasília: IBRAM, 2025. 268 p. E-book.
7 Xavier LH, Lins A. Mineração Urbana de Resíduos Eletroeletrônicos: uma nova fronteira a explorar no Brasil. Brasil Mineral. 2018;(379):22-26.
8 Adibi N, Lafhaj Z, Payet J. New resource assessment characterization factors for rare earth elements: applied in NdFeB permanent magnet case study. The International Journal of Life Cycle Assessment. 2019;24(4):712-724. https://doi.org/10.1007/s11367-018-1489-x.
9 Smith BJ, Riddle ME, Earlam MR, Iloeje C, Diamond D. Rare earth permanent magnets: supply chain deep dive assessment. Washington: U.S. Department of Energy; 2022. https://doi.org/10.2172/1871577.
10 Fila D, Hubicki Z, Kołodyńska D. Applicability of new sustainable and efficient alginate-based composites for critical raw materials recovery: general composites fabrication optimization and adsorption performance evaluation. Chemical Engineering Journal. 2022;446(Pt 4):137245.
11 Kaya M. An overview of NdFeB magnets recycling technologies. Current Opinion in Green and Sustainable Chemistry. 2024;46:100884.
12 Cong L, Yu L, Zhou Q, Lu Q, Yue M. Short-process recycling of Nd-Fe-B sintered magnet sludge wastes: challenges and approaches. Journal of Rare Earths. 2023;41(10):1467-1477.
13 Zakotnik M, Harris IR, Williams AJ. Multiple recycling of NdFeB-type sintered magnets. Journal of Alloys and Compounds. 2009;469(1-2):314-321. https://doi.org/10.1016/j.jallcom.2008.01.114.
14 Burkhardt C, Lehmann A, Fleissner P, Grau L, Trautz M, Mungenast M, et al. Comparative Evaluation of Anti-Corrosion Coatings for NdFeB-Type Magnets with Respect to Performance and Recyclability via Hydrogen- Assisted Recycling (HPMS). Materials Proceedings. 2021;5(1):87.
15 Walton A, Yi H, Rowson NA, Speight JD, Mann V, Sheridan RS, et al. The use of hydrogen to separate and recycle neodymium–iron–boron-type magnets from electronic waste. Journal of Cleaner Production. 2015;104:236-241. https://doi.org/10.1016/j.jclepro.2015.05.033.
16 Takehara L. Avaliação do potencial de Terras Raras no Brasil. Brasília: CPRM; 2015.
17 Venkatesan P, Sun Z, Sietsma J, Yang Y. Simultaneous electrochemical recovery of rare earth elements and iron from magnet scrap: a theoretical analysis. In: Borges de Lima I, Leal W Fo, editors. Rare earths industry: technological, economic, and environmental implications. USA: Elsevier. 2016. p. 335-346.
18 Liu A, Hu G, Wu Y, Guo F. Life cycle environmental impacts of pyrometallurgical and hydrometallurgical recovery processes for spent lithium-ion batteries: present and future perspectives. Clean Technologies and Environmental Policy. 2024;26(2):381-400. https://doi.org/10.1007/s10098-023-02640-x.
19 Michalski B, Szymanski M, Gola K, Zygmuntowicz J, Leonowicz M. Experimental evidence for the suitability of the hydrogen decomposition process for the recycling of Nd-Fe-B sintered magnets. Journal of Magnetism and Magnetic Materials. 2022;548:168979.
20 Wei WW. Avaliação de métodos de moagem de ímãs provenientes de HDs de computadores e notebooks em fim de vida útil [dissertação]. São Leopoldo: Programa de Pós-graduação em Engenharia Civil, Universidade do Vale do Rio dos Sinos; 2022.
21 Li Z, Diaz LA, Yang Z, Jin H, Lister TE, Vahidi E, et al. Comparative life cycle analysis for value recovery of precious metals and rare earth elements from electronic waste. Resources, Conservation and Recycling. 2019;149:20-30. https://doi.org/10.1016/j.resconrec.2019.05.025.
22 München DD, Veit HM. Neodymium as the main feature of permanent magnets from hard disk drives (HDDs). Waste Management. 2017;61:372-376. https://doi.org/10.1016/j.wasman.2017.01.032. PMid:28161335.
23 Zakotnik M, Tudor CO. Commercial-scale recycling of NdFeB-type magnets with grain boundary modification yields products with ‘designer properties’ that exceed those of starting materials. Waste Management. 2015;44:48-54. https://doi.org/10.1016/j.wasman.2015.07.041. PMid:26239935.
24 München DD. Recuperação de Neodímio a partir de Ímãs de Neodímio-Ferro-Boro por Meio de Processos Mecânicos e Hidrometalúrgicos [dissertação]. Programa de Pós-graduação em Engenharia de Minas, Metalurgia e de Materiais. Porto Alegre: Universidade Federal do Rio Grande do Sul; 2016.
25 Matsanga, N, Nheta, W, Chimwani N. A review of the grinding media in ball mills for mineral processing. Minerals. 2023;13(11):1373.
26 Binnemans K, Jones PT, Blanpain B, Van Gerven T, Yang Y, Walton A, et al. Recycling of rare earths: a critical review. Journal of Cleaner Production. 2013;51:1-22. https://doi.org/10.1016/j.jclepro.2012.12.037.
Submetido em:
24/10/2025
Aceito em:
01/06/2026
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