The objective of the present research is to evaluate the performance of three advanced oxidation processes. In particular, this work focuses on the comparison, in terms of energy efficiency, quantum yield and operating costs, of two processes in the homogeneous phase, namely hydrogen peroxide in combination with UV radiation (H2O2/UV) and peracetic acid in combination with UV radiation (PAA/UV), and an heterogeneous one, the photocatalysis on titanium dioxide (TiO2/UV). The photodegradation of methylene blue (MB) dye, selected as a reference organic compound, was investigated using an annular photoreactor at the laboratory scale. The experimental decolorization data were successfully modelled by a pseudo first order reaction model. The residual concentrations of H2O2 and PAA were measured, after the development of the related measurement methods, as well as the production of hydroxyl radicals OH° in heterogeneous photocatalysis and the UV fluence were monitored, respectively by means of a selective probe (i.e., terephthalic acid) and radiometric measures. Using computational fluid-dynamics optical models were implemented to simulate radiation transfer. Finally, a chemical model for H2O2/UV process was proposed for the description of MB decolorization and H2O2 consumption, and two different approaches were compared: the pseudo-steady state approach and the AdOx model. A modification of the two models was proposed to improve the effectiveness in the prediction of MB decolorization.
Il presente elaborato ha come obiettivo la valutazione delle prestazioni di tre processi di ossidazione avanzata. In particolare il lavoro si focalizza sul confronto tra due processi in fase omogenea, definiti dalla combinazione della radiazione UV con perossido d’idrogeno (H2O2/UV) e acido peracetico (PAA/UV), con il processo di fotocatalisi eterogenea con biossido di titanio in sospensione TiO2/UV in termini di efficienze di processo, rese energetiche e costi. La ricerca è stata svolta a scala di laboratorio utilizzando blu di metilene (MB) come composto organico di riferimento e la medesima configurazione reattoristica con lampada immersa e geometria cilindrica. I dati sperimentali di decolorazione di MB sono stati ben descritti da cinetiche del primo ordine. Sono state eseguite misure delle concentrazioni residue di H2O2 e PAA, dopo aver messo a punto i rispettivi metodi di misura, di produzione di radicali ossidrile OH° per fotocatalisi eterogenea mediante composto sonda TA (acido tereftalico) e di intensità radiante tramite misure radiometriche. Tramite tecniche di fluidodinamica computazionale sono stati implementati modelli ottici per ricostruire i fenomeni di irraggiamento. Infine, in riferimento al processo H2O2/UV sono stati confrontati due diversi approcci per la modellazione chimica del processo, l’approccio pseudostazionario e la modellazione AdOx, proponendo modifiche al fine di migliorare la capacità interpretativa in termini di decolorazione di MB.
Processi di ossidazione avanzata (AOPs) promossi da radiazione UV : confronto di prestazioni
BERNI, ANNALISA
2014/2015
Abstract
The objective of the present research is to evaluate the performance of three advanced oxidation processes. In particular, this work focuses on the comparison, in terms of energy efficiency, quantum yield and operating costs, of two processes in the homogeneous phase, namely hydrogen peroxide in combination with UV radiation (H2O2/UV) and peracetic acid in combination with UV radiation (PAA/UV), and an heterogeneous one, the photocatalysis on titanium dioxide (TiO2/UV). The photodegradation of methylene blue (MB) dye, selected as a reference organic compound, was investigated using an annular photoreactor at the laboratory scale. The experimental decolorization data were successfully modelled by a pseudo first order reaction model. The residual concentrations of H2O2 and PAA were measured, after the development of the related measurement methods, as well as the production of hydroxyl radicals OH° in heterogeneous photocatalysis and the UV fluence were monitored, respectively by means of a selective probe (i.e., terephthalic acid) and radiometric measures. Using computational fluid-dynamics optical models were implemented to simulate radiation transfer. Finally, a chemical model for H2O2/UV process was proposed for the description of MB decolorization and H2O2 consumption, and two different approaches were compared: the pseudo-steady state approach and the AdOx model. A modification of the two models was proposed to improve the effectiveness in the prediction of MB decolorization.| File | Dimensione | Formato | |
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2016_04_Berni.pdf
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https://hdl.handle.net/10589/120343