This PhD thesis explores novel approaches for the extraction, separation, and functional reuse of rare earth elements, focusing particularly on neodymium (Nd) and dysprosium (Dy) from end-of-life permanent magnets. These elements, crucial for various technological applications, present significant recovery challenges due to their chemical similarity. The work is divided into two principal sections, each addressing a different phase of recovery and functionalization. In the first part, the research examines the design, synthesis, and characterization of specialized organic ligands capable of selectively complexing Nd and Dy. By utilizing a range of ligands with varied coordination environments, a selective precipitation method was developed, enhancing both the economic and environmental sustainability of the separation process. Ligands were synthesized through the condensation of tren or 1,3-diaminopropanol with functionalized salicylaldehyde derivatives, yielding heptadentate and pentadentate Schiff-base ligands. Subsequent reduction of these Schiff bases produced a more stable ligand structure suitable for harsher processing conditions. This part of the thesis provides a foundation for effective rare-earth separation by optimizing the solubility and stability of the metal-ligand complexes. The second part develops lanthanide-based materials aimed at biomedical applications. Using recovered Nd and Dy ions, dimeric, trimeric, and tetrameric 12-metallacrown-4 (12-MC-4) complexes were synthesized for potential use in bio-imaging and/or targeted therapy. The assembly of these complexes involved linking monomeric 12-MC-4 units with dicarboxylic ligands with different angle bond to form structures suited for fluorescence and stability studies. Functionalization with NBD-based chromophores enabled luminescence at visible wavelengths, making these materials suitable as fluorescent probes. Additionally, metallacrowns were modified with biotin to allow selective interaction with streptavidin, useful for targeted tumor imaging. This thesis underscores the viability of a coordinated approach to rare-earth recovery and functionalization, advancing the field of sustainable recycling while expanding the scope of biomedical applications for recovered materials.
Questa tesi di dottorato esplora nuovi approcci per l’estrazione, la separazione e il riutilizzo funzionale degli elementi delle terre rare, con un focus particolare su neodimio (Nd) e disprosio (Dy) provenienti da magneti permanenti a fine vita. Questi elementi, cruciali per varie applicazioni tecnologiche, presentano sfide significative per il recupero a causa della loro somiglianza chimica. Il lavoro è suddiviso in due sezioni principali, ognuna delle quali affronta una fase diversa del recupero e della funzionalizzazione. Nella prima parte, la ricerca esamina la progettazione, sintesi e caratterizzazione di ligandi organici specializzati, capaci di complessare selettivamente Nd e Dy. Utilizzando una gamma di ligandi con ambienti di coordinazione variabili, è stato sviluppato un metodo di precipitazione selettiva, migliorando la sostenibilità economica e ambientale del processo di separazione. I ligandi sono stati sintetizzati attraverso la condensazione di tren o 1,3-diaminopropanolo con derivati salicilaldeidici funzionalizzati, ottenendo ligandi Schiff-base epta- e penta-dentati. La successiva riduzione di queste basi di Schiff ha prodotto una struttura di ligando più stabile, adatta a condizioni di lavorazione più severe. Questa parte della tesi fornisce una base per una separazione efficace delle terre rare, ottimizzando la solubilità e la stabilità dei complessi metallo-ligando. La seconda parte sviluppa materiali a base di lantanidi con potenziali applicazioni biomediche. Utilizzando ioni di Nd e Dy recuperati, sono stati sintetizzati complessi 12-metallocorona-4 (12-MC-4) dimerici, trimerici e tetramerici per un potenziale utilizzo in bio-imaging e/o terapia mirata. L’assemblaggio di questi complessi ha coinvolto il collegamento di unità monomeriche 12-MC-4 con ligandi dicarbossilici con diversi angoli di legame per formare strutture adatte a studi di fluorescenza e stabilità. La funzionalizzazione con cromofori a base di NBD ha permesso di ottenere luminescenza a lunghezze d’onda visibili, rendendo questi materiali adatti come sonde fluorescenti. Inoltre, le metallocorone sono state modificate con biotina per consentire l’interazione selettiva con la streptavidina, utile per l’imaging tumorale mirato. Questa tesi sottolinea la fattibilità di un approccio coordinato al recupero e alla funzionalizzazione delle terre rare, avanzando nel campo del riciclo sostenibile e ampliando l’ambito delle applicazioni biomediche per i materiali recuperati
Recovery and recycling of lanthanides from permanent magnets: techniques for reuse in innovative applications
Alex, Falco
2025
Abstract
This PhD thesis explores novel approaches for the extraction, separation, and functional reuse of rare earth elements, focusing particularly on neodymium (Nd) and dysprosium (Dy) from end-of-life permanent magnets. These elements, crucial for various technological applications, present significant recovery challenges due to their chemical similarity. The work is divided into two principal sections, each addressing a different phase of recovery and functionalization. In the first part, the research examines the design, synthesis, and characterization of specialized organic ligands capable of selectively complexing Nd and Dy. By utilizing a range of ligands with varied coordination environments, a selective precipitation method was developed, enhancing both the economic and environmental sustainability of the separation process. Ligands were synthesized through the condensation of tren or 1,3-diaminopropanol with functionalized salicylaldehyde derivatives, yielding heptadentate and pentadentate Schiff-base ligands. Subsequent reduction of these Schiff bases produced a more stable ligand structure suitable for harsher processing conditions. This part of the thesis provides a foundation for effective rare-earth separation by optimizing the solubility and stability of the metal-ligand complexes. The second part develops lanthanide-based materials aimed at biomedical applications. Using recovered Nd and Dy ions, dimeric, trimeric, and tetrameric 12-metallacrown-4 (12-MC-4) complexes were synthesized for potential use in bio-imaging and/or targeted therapy. The assembly of these complexes involved linking monomeric 12-MC-4 units with dicarboxylic ligands with different angle bond to form structures suited for fluorescence and stability studies. Functionalization with NBD-based chromophores enabled luminescence at visible wavelengths, making these materials suitable as fluorescent probes. Additionally, metallacrowns were modified with biotin to allow selective interaction with streptavidin, useful for targeted tumor imaging. This thesis underscores the viability of a coordinated approach to rare-earth recovery and functionalization, advancing the field of sustainable recycling while expanding the scope of biomedical applications for recovered materials.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/213312
URN:NBN:IT:UNIPR-213312