In this thesis research project it has been conducted a study on the degradation process of PFAS and other organic contaminants, most of which characterized by surfactant properties. For this purpose, radial discharge atmospheric plasma reactors were used (RAdial Plasma, RAP, reactors), in which the plasma is produced by applying electrical discharges to the surface of the solution, using an electrode configuration consisting of a pointed electrode, to which an high voltage is applied, and a ring counter electrode partially immersed in the solution. These reactors are particularly effective in the treatment of compounds having surfactant properties because the filamentary discharge channels are distributed on the surface of the solution, where the surfactant compounds tend to concentrate. Atmospheric plasma is advantageous in the degradation of these compounds, as it contains multiple reactive species (free electrons, ions, radicals, excited species), capable of reacting with the organic contaminants present in aqueous solution, leading to their degradation. The treated solution samples were analyzed by HPLC-UV/Vis or HPLC-ESI/MS, in order to obtain the degradation curves for the specific contaminants and the trend of the degradation products as a function of the treatment time. A perfluoroalkyl substance (perfluorooctanoic acid, PFOA), a pesticide (Metolachlor) and a non-fluorinated surfactant compound (Triton X-100) were treated under the same operating conditions. The conformation of the RAP reactor is optimal for the degradation of the previous mentioned compounds, which follows a pseudo-first order kinetics. On the contrary, perfluorobutanoic acid (PFBA), having no surfactant properties, proved to be particularly refractory to degradation. In the case of PFBA, the application of plasma was therefore combined with the addition of additives in solution, which allowed to accelerate its degradation.
In questo lavoro di tesi è stato studiato il processo di degradazione di PFAS e di altri contaminanti organici, la maggior parte dei quali caratterizzati da proprietà surfattanti. A tale scopo sono stati utilizzati reattori al plasma atmosferico a scarica radiale (RAdial Plasma, RAP, reactors), in cui il plasma è prodotto tramite l’applicazione di scariche elettriche sulla superficie della soluzione, usando una configurazione elettrodica costituita da un elettrodo a punta, cui viene applicato un alto voltaggio, e un controelettrodo ad anello parzialmente immerso nella soluzione. Questi reattori sono particolarmente efficaci nel trattamento di composti aventi proprietà surfattanti perché i canali filamentari di scarica si distribuiscono sulla superficie della soluzione, dove i composti surfattanti tendono a concentrarsi. Il plasma atmosferico risulta vantaggioso nella degradazione di tali composti, in quanto contiene molteplici specie reattive (elettroni liberi, ioni, radicali, specie in stato eccitato), in grado di reagire con i contaminanti organici presenti in soluzione acquosa, portando alla loro degradazione. I campioni di soluzione trattata sono stati analizzati tramite HPLC-UV/Vis o HPLC-ESI/MS, in modo da ottenere le curve di degradazione per gli specifici contaminanti e l'andamento dei prodotti di degradazione in funzione del tempo di trattamento. Sono stati trattati, nelle stesse condizioni operative, una sostanza perfluoroalchilica (l’acido perfluoroottanoico, PFOA), un pesticida (Metolachlor) e un composto surfattante non fluorurato (Triton X-100). La conformazione del reattore RAP risulta ottimale per la degradazione dei composti sopracitati, la quale segue una cinetica di pseudo-primo ordine. Al contrario, l’acido perfluorobutanoico (PFBA), non avendo proprietà surfattanti, si è dimostrato particolarmente refrattario alla degradazione. Nel caso del PFBA, l’applicazione del plasma è stata dunque combinata con l’aggiunta di additivi in soluzione, che hanno permesso di accelerarne la degradazione.
Studio della degradazione di contaminanti organici indotta da plasma atmosferico in reattori a scarica radiale
PINTON, ANNA
2021/2022
Abstract
In this thesis research project it has been conducted a study on the degradation process of PFAS and other organic contaminants, most of which characterized by surfactant properties. For this purpose, radial discharge atmospheric plasma reactors were used (RAdial Plasma, RAP, reactors), in which the plasma is produced by applying electrical discharges to the surface of the solution, using an electrode configuration consisting of a pointed electrode, to which an high voltage is applied, and a ring counter electrode partially immersed in the solution. These reactors are particularly effective in the treatment of compounds having surfactant properties because the filamentary discharge channels are distributed on the surface of the solution, where the surfactant compounds tend to concentrate. Atmospheric plasma is advantageous in the degradation of these compounds, as it contains multiple reactive species (free electrons, ions, radicals, excited species), capable of reacting with the organic contaminants present in aqueous solution, leading to their degradation. The treated solution samples were analyzed by HPLC-UV/Vis or HPLC-ESI/MS, in order to obtain the degradation curves for the specific contaminants and the trend of the degradation products as a function of the treatment time. A perfluoroalkyl substance (perfluorooctanoic acid, PFOA), a pesticide (Metolachlor) and a non-fluorinated surfactant compound (Triton X-100) were treated under the same operating conditions. The conformation of the RAP reactor is optimal for the degradation of the previous mentioned compounds, which follows a pseudo-first order kinetics. On the contrary, perfluorobutanoic acid (PFBA), having no surfactant properties, proved to be particularly refractory to degradation. In the case of PFBA, the application of plasma was therefore combined with the addition of additives in solution, which allowed to accelerate its degradation.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/41678