This PhD thesis presents an interdisciplinary approach to address two major environmental challenges: the remediation of persistent organic pollutants, specifically per- and polyfluoroalkyl substances, and the detection of molecular iodine in aqueous systems. The research leveraged the unique properties of fluorinated and non-fluorinated ionic liquids to engineer advanced functional materials suitable for practical water treatment and sensing applications. The work originated from the recognition that current technologies for contaminant removal and monitoring often suffer from limitations in selectivity, scalability, stability, and cost-effectiveness, particularly when dealing with chemically inert and environmentally mobile species, such as perfluorocarboxylates and iodine. Conventional adsorbents such as granular activated carbon and ion exchange resins, while effective for some well-known fluorinated pollutants, have struggled with short-chain variants and emerging contaminants due to weak binding affinities and fouling issues. Similarly, standard analytical methods for iodine detection required complex instrumentation and pre-treatment, hindering rapid field-deployable monitoring. To overcome these barriers, the thesis proposed ionic liquids as versatile molecular platforms, specifically chosen to combine fluorinated side chains with positively charged imidazolium cores. As a result, fluorophilic and electrostatic interactions acted cooperatively in binding perfluorocarboxylic acids with different hydrophobicity and fluorophilicity. The key innovation lay in the rational design of imidazolium-based ionic liquids, varied in chain length and substitution, which were then incorporated into polymeric matrices via electrospinning, or deposited as thin films on solid supports. This modular strategy enabled precise control over active site density, surface exposure, and interaction mechanisms, including electrostatic attraction and fluorine-fluorine contacts. The research followed a logical progression. First, characterization of molecular interactions in solution using nuclear magnetic resonance and dynamic light scattering established the supramolecular basis for selective binding. Subsequent materials fabrication yielded electrospun poly(methyl methacrylate) fiber mats and quartz-supported sensing layers, which were fully characterized by scanning electron microscopy with energy-dispersive spectroscopy, attenuated total reflectance Fourier-transform infrared spectroscopy, thermogravimetric analysis, and Raman spectroscopy. Performance validation encompassed laboratory-scale batch filtration, continuous-flow pilot testing in collaboration with Pietro Fiorentini S.p.A. at their facilities, and optical sensing under controlled vapor exposure. Key outcomes included the demonstration of high adsorption capacities for perfluorooctanoic acid, exceeding 100 micrograms per milligram of fiber in optimally designed systems, coupled with insights into structure-performance relationships that highlighted the synergistic role of fluorinated chains and cationic centers, and the development of a covalent grafting strategy to mitigate leaching under thermal stress. Beyond technical achievements, the thesis emphasized scalability and translational potential, validated through 200-hour stability tests at elevated temperatures and reproducible fabrication protocols amenable to industrial upscaling. The same materials were exploited for the detection of molecular iodine (I2), exploiting their iodide counterion to form the triiodide (I₃⁻) species, and thereby quantify I₂ in aqueous solutions via solid-state UV-vis spectroscopy. By integrating supramolecular chemistry and polymer processing, this work delivered proof-of-concept evidence that fluorinated charged compounds exhibited strong and selective interactions with perfluorocarboxylic acids. It provided useful materials for dual-purpose contaminant management, and a generalizable framework for designing next-generation sorbents and sensors tailored for emerging pollutants, contributing meaningfully to sustainable water remediation strategies.
Questa tesi di dottorato presenta un approccio interdisciplinare per affrontare due grandi sfide ambientali: la bonifica di inquinanti organici persistenti, in particolare le sostanze per- e polifluoroalchiliche (PFAS), e il rilevamento dello iodio molecolare in sistemi acquosi. La ricerca ha sfruttato le proprietà uniche di liquidi ionici fluorurati e non fluorurati per progettare materiali funzionali avanzati adatti a trattamenti idrici pratici e applicazioni di sensori. Il lavoro è nato dalla consapevolezza che le tecnologie correnti per la rimozione e il monitoraggio dei contaminanti soffrono spesso di limitazioni in termini di selettività, scalabilità, stabilità ed economicità, specialmente con specie chimicamente inerti e mobili nell'ambiente, come i perfluorocarbossilati e lo iodio. Gli adsorbenti convenzionali, come il carbonio attivo granulare e le resine a scambio ionico, pur efficaci per alcuni inquinanti fluorurati ben noti, hanno mostrato difficoltà con le varianti a catena corta e i contaminanti emergenti a causa di affinità di legame deboli e problemi di intasamento. Allo stesso modo, i metodi analitici standard per il rilevamento dello iodio richiedono strumentazioni complesse e pretrattamenti, ostacolando il monitoraggio rapido in campo. Per superare questi ostacoli, la tesi ha proposto i liquidi ionici come piattaforme molecolari versatili, scelti specificamente per combinare catene laterali fluorurate con nuclei imidazolium cationici caricati positivamente. Di conseguenza, interazioni fluorofile ed elettrostatiche hanno agito in modo cooperativo nel legare acidi perfluorocarbossilici con diversa idrofobicità e fluorofilicità. L'innovazione chiave risiede nel design razionale di liquidi ionici a base imidazolium, variati in lunghezza della catena e sostituzione, che sono stati poi incorporati in matrici polimeriche tramite elettrofilatura o depositati come film sottili su supporti solidi. Questa strategia modulare ha permesso un controllo preciso sulla densità dei siti attivi, l'esposizione superficiale e i meccanismi di interazione, inclusa l'attrazione elettrostatica e i contatti fluoro-fluoro. La ricerca ha seguito una progressione logica: dapprima la caratterizzazione delle interazioni molecolari in soluzione mediante risonanza magnetica nucleare e scattering dinamico della luce ha stabilito le basi supramolecolari per il legame selettivo. Successivamente, la fabbricazione dei materiali ha prodotto tappeti di fibre di polimetilmetacrilato elettrofilate e strati sensibili su quarzo, completamente caratterizzati tramite microscopia elettronica a scansione con spettroscopia energy-dispersive (SEM-EDS), spettroscopia infrarossa FTIR in riflessione totale attenuata, analisi termogravimetrica (TGA) e spettroscopia Raman. La validazione delle prestazioni ha incluso filtrazione batch su scala da laboratorio, test pilota in flusso continuo in collaborazione con Pietro Fiorentini S.p.A. presso i loro impianti, e sensistica ottica sotto esposizione controllata a vapori. I risultati principali includono la dimostrazione di elevate capacità di adsorbimento per l'acido perfluorottanoico (PFOA), superiori a 100 microgrammi per milligrammo di fibra nei sistemi ottimizzati, unite a insight sulle relazioni struttura-prestazioni che hanno evidenziato il ruolo sinergico delle catene fluorurate e dei centri cationici, e lo sviluppo di una strategia di innesto covalente per mitigare la lisciviazione sotto stress termico. Oltre ai successi tecnici, la tesi ha enfatizzato scalabilità e potenziale traslazionale, validati tramite test di stabilità a 200 ore a temperature elevate e protocolli di fabbricazione riproducibili adatti all'upselling industriale. Gli stessi materiali sono stati sfruttati per il rilevamento dello iodio molecolare (I₂), sfruttando il controione ioduro per formare la specie triioduro (I₃⁻) e quantificarlo in soluzioni acquose tramite spettroscopia UV-vis in stato solido. Integrando chimica supramolecolare e processamento polimerico, questo lavoro ha fornito prove di concetto che composti caricati fluorurati mostrano interazioni forti e selettive con acidi perfluorocarbossilici. Ha offerto materiali utili per la gestione duale dei contaminanti e un framework generalizzabile per progettare sorbenti e sensori di prossima generazione su misura per inquinanti emergenti, contribuendo in modo significativo a strategie di bonifica idrica sostenibile.
Design and development of ionic liquid-based materials for the detection and removal of halogenated water contaminants
Secundo, Lorenzo
2025/2026
Abstract
This PhD thesis presents an interdisciplinary approach to address two major environmental challenges: the remediation of persistent organic pollutants, specifically per- and polyfluoroalkyl substances, and the detection of molecular iodine in aqueous systems. The research leveraged the unique properties of fluorinated and non-fluorinated ionic liquids to engineer advanced functional materials suitable for practical water treatment and sensing applications. The work originated from the recognition that current technologies for contaminant removal and monitoring often suffer from limitations in selectivity, scalability, stability, and cost-effectiveness, particularly when dealing with chemically inert and environmentally mobile species, such as perfluorocarboxylates and iodine. Conventional adsorbents such as granular activated carbon and ion exchange resins, while effective for some well-known fluorinated pollutants, have struggled with short-chain variants and emerging contaminants due to weak binding affinities and fouling issues. Similarly, standard analytical methods for iodine detection required complex instrumentation and pre-treatment, hindering rapid field-deployable monitoring. To overcome these barriers, the thesis proposed ionic liquids as versatile molecular platforms, specifically chosen to combine fluorinated side chains with positively charged imidazolium cores. As a result, fluorophilic and electrostatic interactions acted cooperatively in binding perfluorocarboxylic acids with different hydrophobicity and fluorophilicity. The key innovation lay in the rational design of imidazolium-based ionic liquids, varied in chain length and substitution, which were then incorporated into polymeric matrices via electrospinning, or deposited as thin films on solid supports. This modular strategy enabled precise control over active site density, surface exposure, and interaction mechanisms, including electrostatic attraction and fluorine-fluorine contacts. The research followed a logical progression. First, characterization of molecular interactions in solution using nuclear magnetic resonance and dynamic light scattering established the supramolecular basis for selective binding. Subsequent materials fabrication yielded electrospun poly(methyl methacrylate) fiber mats and quartz-supported sensing layers, which were fully characterized by scanning electron microscopy with energy-dispersive spectroscopy, attenuated total reflectance Fourier-transform infrared spectroscopy, thermogravimetric analysis, and Raman spectroscopy. Performance validation encompassed laboratory-scale batch filtration, continuous-flow pilot testing in collaboration with Pietro Fiorentini S.p.A. at their facilities, and optical sensing under controlled vapor exposure. Key outcomes included the demonstration of high adsorption capacities for perfluorooctanoic acid, exceeding 100 micrograms per milligram of fiber in optimally designed systems, coupled with insights into structure-performance relationships that highlighted the synergistic role of fluorinated chains and cationic centers, and the development of a covalent grafting strategy to mitigate leaching under thermal stress. Beyond technical achievements, the thesis emphasized scalability and translational potential, validated through 200-hour stability tests at elevated temperatures and reproducible fabrication protocols amenable to industrial upscaling. The same materials were exploited for the detection of molecular iodine (I2), exploiting their iodide counterion to form the triiodide (I₃⁻) species, and thereby quantify I₂ in aqueous solutions via solid-state UV-vis spectroscopy. By integrating supramolecular chemistry and polymer processing, this work delivered proof-of-concept evidence that fluorinated charged compounds exhibited strong and selective interactions with perfluorocarboxylic acids. It provided useful materials for dual-purpose contaminant management, and a generalizable framework for designing next-generation sorbents and sensors tailored for emerging pollutants, contributing meaningfully to sustainable water remediation strategies.| File | Dimensione | Formato | |
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Lorenzo Secundo PhD thesis_rev.pdf
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Descrizione: Lorenzo Secundo PhD thesis
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https://hdl.handle.net/10589/253857