Details
| Original language | English |
|---|---|
| Qualification | Doctor rerum naturalium |
| Awarding Institution | |
| Supervised by |
|
| Date of Award | 17 Oct 2019 |
| Place of Publication | Hannover |
| Publication status | Published - 2019 |
Abstract
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Hannover, 2019. 161 p.
Research output: Thesis › Doctoral thesis
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TY - BOOK
T1 - Development of new reactors for the photocatalytic treatment of polluted aquifers
AU - Megatif, Lena
PY - 2019
Y1 - 2019
N2 - An enhancement of the activity of photocatalytic systems requires an efficient reactor design and a suitable standard method to compare the performance of various systems. In almost all recommended measuring methods, the reaction rate is affected by the optical properties of photocatalysts through reflection and scattering. Moreover, the quantitative assessment of the performance of photocatalytic systems requires the determination of the amount of absorbed photons inside the photoreactor. In the present work, a standard method for the comparison of different photocatalysts is proposed employing a black body reactor. In a black body reactor almost the entire incident light will be absorbed by the photocatalyst particles. Therefore, the volume-averaged reaction rate is almost independent from the scattering properties of the photocatalyst and the photocatalytic activity can be compared through reaction rate measurements. In this study, dichloroacetic acid (DCA) was chosen as the probe compound. Titanium dioxide and some other semiconducting oxides were applied as the photocatalysts. Variation of effecting parameters including the initial concentration of the probe molecule (C0), the photocatalyst loading (γ), and the reaction volume (V) were studied in order to provide a comparison method which is independent from the mentioned parameters. The degradation rate of DCA defined as the converted amount of molecules per unit time was found to be constant at all reaction volumes and independent when C0 and γ were larger than 5 mM and 1 g L-1, respectively. The presented method was found to be generally applicable for different titanium and non-titanium based photocatalysts. Moreover, to determine the reaction rate, a kinetic study was performed for both, reactants decay and product generation. Photon flux and photon flux density are known to strongly affect the charge carriers’ recombination and, consequently, the reaction rate and the quantum yield. The black body reactor was employed to investigate the impact of the geometry of the light inlet on the reaction rate and on the quantum yield of a photocatalytic reaction. Accordingly, employing a hollow sphere light inlet providing uniform light distribution and low photon flux density, the quantum yield was constant and independent from the photon flux. However, in systems with high photon flux density, a square root correlation between the quantum yield and the photon flux was observed.
AB - An enhancement of the activity of photocatalytic systems requires an efficient reactor design and a suitable standard method to compare the performance of various systems. In almost all recommended measuring methods, the reaction rate is affected by the optical properties of photocatalysts through reflection and scattering. Moreover, the quantitative assessment of the performance of photocatalytic systems requires the determination of the amount of absorbed photons inside the photoreactor. In the present work, a standard method for the comparison of different photocatalysts is proposed employing a black body reactor. In a black body reactor almost the entire incident light will be absorbed by the photocatalyst particles. Therefore, the volume-averaged reaction rate is almost independent from the scattering properties of the photocatalyst and the photocatalytic activity can be compared through reaction rate measurements. In this study, dichloroacetic acid (DCA) was chosen as the probe compound. Titanium dioxide and some other semiconducting oxides were applied as the photocatalysts. Variation of effecting parameters including the initial concentration of the probe molecule (C0), the photocatalyst loading (γ), and the reaction volume (V) were studied in order to provide a comparison method which is independent from the mentioned parameters. The degradation rate of DCA defined as the converted amount of molecules per unit time was found to be constant at all reaction volumes and independent when C0 and γ were larger than 5 mM and 1 g L-1, respectively. The presented method was found to be generally applicable for different titanium and non-titanium based photocatalysts. Moreover, to determine the reaction rate, a kinetic study was performed for both, reactants decay and product generation. Photon flux and photon flux density are known to strongly affect the charge carriers’ recombination and, consequently, the reaction rate and the quantum yield. The black body reactor was employed to investigate the impact of the geometry of the light inlet on the reaction rate and on the quantum yield of a photocatalytic reaction. Accordingly, employing a hollow sphere light inlet providing uniform light distribution and low photon flux density, the quantum yield was constant and independent from the photon flux. However, in systems with high photon flux density, a square root correlation between the quantum yield and the photon flux was observed.
U2 - 10.15488/5585
DO - 10.15488/5585
M3 - Doctoral thesis
CY - Hannover
ER -