الفهرس 
Aim of WorkOnly 14 pages are availabe for public view
 |  | from | 190 |  |  |
| | | from | 190 | | |
Abstract
Dye pollution represents a fundamental problem in the environment because dyes are dangerous to human beings. So, the dye-polluted water must be treated before discharging it into the environment. There are several methods that can be used to treat wastewater like adsorption, chlorination and photocatalytic degradation.
This thesis focused on fabrication of novel photocatalysts which are effective under uv and visible light irradiations. These catalysts must be able to remove or degrade the organic pollutants in wastewater.
ZnO is considered a promising n-type semiconductor material due to its low cost, non–toxicity and stability. However, ZnO has a wide band gap (3.37 eV) which limits the photocatalytic activity of ZnO to uv light only that represents 3-5% of solar light. In addition, the high recombination rate of the produced charge carriers when subjected to illumination limits the optimization of the nanoparticles in photocatalytic process. Moreover, the low surface area of ZnO reduces the number of radicals generated from its surface.
The study includes exploring the optimum experimental conditions for the synthesis of modified zinc oxide nanoparticles for exploring a better photocatalytic degradation performance. The relationships between structures, physicochemical properties of photocatalysts and dye removal performances have also been studied in the thesis.
The first part of this thesis focusses on the water crisis, methods of wastewater treatment, photocatalysis and the conditions of preparing a good catalyst.
The second chapter focusses on preparation of ZnO, Ag2S, AgVO3 and BiVO4 pristine materials. In addition, several modified nanocomposites are prepared by modifying the primitive ZnO using (Ag2S, AgVO3 and BiVO4) semiconductors. The weight ratios between ZnO and the modifier (Ag2S, AgVO3 and BiVO4) were adjusted to get the optimum synthetic condition.
The Third chapter of this thesis is about the characterization and evaluation of the prepared catalysts. The prepared samples were evaluated using various techniques including X–ray diffraction [XRD], Field emission scanning electron microscope [FE-SEM], Energy dispersive x-ray spectroscopy [EDS], high-resolution transmission electron microscope [HR-TEM], x-ray Photoelectron Spectroscopy [XPS], N2-adsorption-desorption isotherm [BET], diffuse reflectance spectroscopy [DRS].
For Ag2S/ZnO, AgVO3/ZnO and BiVO4/ZnO nanostructures, the physicochemical characterization indicated that the heterojunctions were established and there was a well-distribution of dopant among ZnO samples.
The photocatalytic activities were investigated by photochemical degradation of rhodamine B dye under uv and sunlight illumination. All photocatalytic measurements and calculations indicated that there was a measurable enhancement in the photocatalytic performances of the modified heterojunctions. In addition, different parameters including changes in pH and catalyst amount were studied. The most probable mechanisms for enhancing the photocatalytic performance were predicted.
Sum up, the thesis presents the key findings in this work and raises the perspective for the future research direction.