This work regards the development of innovative copper-based and zinc-based Magnetic Metal-Organic Frameworks (MMOFs) for perfluorooctanoic acid (PFOA) remediation from groundwater, followed by chemical regeneration of the best working samples. PFOA is a persistent and widespread and carcinogenic pollutant belonging to the emerging contaminant class of poly- and perfluoroalkyl substances (PFASs). Metal-Organic Frameworks (MOFs) have been recently identified as an advanced material class for the efficient removal of PFASs, thanks to their high degree of porosity, high surface area and the presence of active sites which have affinity towards these compounds. In this study, it was chosen to grow copper-based and zinc-based MOFs onto magnetite particles, in this way the adsorbents were simply collected with the aid of a magnet, avoiding others potentially energy-demanding filtration steps. Both solvothermal and room-temperature methods were exploited as synthesis routes. Different solvents were tested, like dimethylformamide, ethanol, isopropanol and water. The characterization methods (powder XRD and IR spectroscopy) proved an effective crystalline growth onto magnetite of copper-based MOFs, on the contrary zinc-based MMOFs resulted highly amorphous. Adsorption tests gave not-optimal results. In fact, removal efficiencies lower than 60% ware obtained in the case of copper-based MMOFs and lower than 40% in the case of zinc-based MMOFs. For this reason, desorption tests were not performed onto zinc-based MMOFs. Regeneration solution was firstly tested on a zirconium-based MMOF with known adsorption capacity, giving optimal results (82%). Thus Copper-based MMOFs was subjected to regeneration, despite their performance in adsorption, just to show an example of lab scale adsorption-desorption cycle for water treatment. In this case regeneration was less efficient (> 60%) but still acceptable. Overall, due to their properties MMOFs are promising materials for PFOA water remediation. In this work adsorption efficiency was limited by production defects but synthesis method can be further improved. Besides, MMOFs can be regenerated for reuse, making the process cost-effective even if they don’t achieve 100% adsorption efficiency.
Questo lavoro riguarda lo sviluppo di innovativi framework metallorganici magnetici (MMOFs) a base di rame e zinco per la bonifica dell’acido perfluoroottanoico (PFOA) dalle acque, seguita dalla rigenerazione chimica dei campioni che hanno dato i migliori risultati. Il PFOA è un inquinante persistente e altamente diffuso, cancerogeno, che appartiene alla classe dei contaminanti emergenti nota come PFAS (sostanze per- e polifluoroalchiliche). I framework metallorganici (MOFs) sono stati recentemente identificati come una classe di promettenti materiali avanzati per una efficiente rimozione dei PFAS, grazie al loro elevato grado di porosità, elevata area superficiale specifica e alla presenza di siti attivi che hanno affinità verso questi composti. In questo studio, è stato scelto di far crescere MOFs a base di rame e zinco su particelle di magnetite, in modo che le polveri adsorbenti potessero essere facilmente raccolte tramite un magnete, evitando altri passaggi di filtrazione potenzialmente dispendiosi in termini di energia. Sono stati utilizzati sia metodi solvotermali che non-solvotermali per sintetizzare i MMOFs. Sono stati inoltre testati diversi solventi, come dimetilformammide, etanolo, isopropanolo e acqua. Analisi di spettroscopia a infrarossi e diffrazione di polveri a raggi X hanno evidenziato una crescita cristallina efficace dei MOFs a base di rame sulla magnetite, mentre i MMOFs a base di zinco sono risultati altamente amorfi. I test di adsorbimento hanno dato risultati non ottimali. Infatti, le efficienze di rimozione sono state inferiori al 60% nel caso dei MMOF a base di rame e inferiori al 40% nel caso dei MMOF a base di zinco; perciò, non sono stati effettuati test di desorbimento su questi ultimi. La soluzione chimica per la rigenerazione è stata inizialmente testata su un MMOF a base di zirconio con capacità di adsorbimento nota, ottenendo risultati ottimali (82%). I MMOF a base di rame sono stati sottoposti a rigenerazione, nonostante le loro performance in adsorbimento non ottimali, per mostrare un esempio di ciclo adsorbimento-desorbimento per il trattamento delle acque su piccola scala. In questo caso, la rigenerazione è stata meno efficiente (> 60%) ma comunque accettabile. Nel complesso, grazie alle loro proprietà, i MMOF si sono mostrati materiali promettenti per la bonifica delle acque da PFOA. In questo lavoro, l'efficienza di adsorbimento è stata limitata da difetti originatisi in fase di produzione, ma il metodo di sintesi può essere ulteriormente migliorato. Inoltre, i MMOF possono essere rigenerati per il riutilizzo, rendendo il processo conveniente dal punto di vista economico anche se non si raggiunge un'efficienza del 100% in adsorbimento.
Design and development of regenerable magnetic copper- and zinc-based Metal-Organic Frameworks for PFOA capture from water
Alessandria, Linda
2023/2024
Abstract
This work regards the development of innovative copper-based and zinc-based Magnetic Metal-Organic Frameworks (MMOFs) for perfluorooctanoic acid (PFOA) remediation from groundwater, followed by chemical regeneration of the best working samples. PFOA is a persistent and widespread and carcinogenic pollutant belonging to the emerging contaminant class of poly- and perfluoroalkyl substances (PFASs). Metal-Organic Frameworks (MOFs) have been recently identified as an advanced material class for the efficient removal of PFASs, thanks to their high degree of porosity, high surface area and the presence of active sites which have affinity towards these compounds. In this study, it was chosen to grow copper-based and zinc-based MOFs onto magnetite particles, in this way the adsorbents were simply collected with the aid of a magnet, avoiding others potentially energy-demanding filtration steps. Both solvothermal and room-temperature methods were exploited as synthesis routes. Different solvents were tested, like dimethylformamide, ethanol, isopropanol and water. The characterization methods (powder XRD and IR spectroscopy) proved an effective crystalline growth onto magnetite of copper-based MOFs, on the contrary zinc-based MMOFs resulted highly amorphous. Adsorption tests gave not-optimal results. In fact, removal efficiencies lower than 60% ware obtained in the case of copper-based MMOFs and lower than 40% in the case of zinc-based MMOFs. For this reason, desorption tests were not performed onto zinc-based MMOFs. Regeneration solution was firstly tested on a zirconium-based MMOF with known adsorption capacity, giving optimal results (82%). Thus Copper-based MMOFs was subjected to regeneration, despite their performance in adsorption, just to show an example of lab scale adsorption-desorption cycle for water treatment. In this case regeneration was less efficient (> 60%) but still acceptable. Overall, due to their properties MMOFs are promising materials for PFOA water remediation. In this work adsorption efficiency was limited by production defects but synthesis method can be further improved. Besides, MMOFs can be regenerated for reuse, making the process cost-effective even if they don’t achieve 100% adsorption efficiency.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/231023