الفهرس 
Chapter (I): IntroductionOnly 14 pages are availabe for public view
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Abstract
Thesis aims to degrade some environmental pollutants by using TiO2 nanoparticles whichmodified by different percentages of graphene oxide like 3 wt%, 7 wt%, 10 wt%, 12 wt% and 15 wt%. These samples were calcined in muffle furnace for 2 h at 300 oC, 350 oC, 400 oC, 450 oC, 500 oC and 550 oC. These composites enhance the photocatalytic degradation of organic dyes. Another dopants like Ag2S is incorporated into TiO2 nanoparticles calcined at 400 oC and 550 oC with different percentage like 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 5 wt% and 7 wt%. These photocatalysts were used in degradation of rhodamine B and methylene blue under UV/visible light. Structural characterization of the prepared samples was determined using TEM, SEM, X‐ray, FTIR, UV/vis spectroscopy and XPS analysis. For X‐ray diffraction patterns, it showed a crystalline peak for graphite powder at 2θ = 26.4° with d‐spacing size 0.34 nm, after oxidation to a crystalline peak was appeared at 2θ = 10.56° and the d‐spacing increased to 0.82 nm. After modification the characteristic peak of GO sheets disappeared due to the amount of GO is very small to be shown in the charts. At calcination temperatures 300 oC and 400 oC, we found that the anatase (Tetragonal) and brookite (Orthorhombic) polymorphous but by increasing the calcination temperature the percentage of brookite structure decreased. At 550oC, the XRD pattern shows pure anatase structure which shows the crystal faces of tetragonal shape. The prepared Ag2S is existed in monoclinic acanthite (β-form) phase. The characteristic peaks of Ag2S are eliminated in case of loading on TiO2 due to the concentration of Ag2S is highly small. FTIR spectra of graphite flakes and graphene oxide. Graphene oxide spectrum shows band characteristic to OH stretching vibration function group present during oxidation of graphite flakes. Also, at C=O stretching vibration, C=C stretching vibration, unoxidized graphite domains, at C-OH stretching vibration, and at 1051 cm-1 C-O stretching vibration. The FTIR spectra for the loaded graphene oxide on TiO2photocatalyst show the same function groups. In the case of Ag2S, the band of OH stretching vibration, C=O stretching vibration and C-O stretching vibration. The characteristic bands are due to the adsorption of H2O, CO2 and may be also from ethanol (CH3CH2OH) during preparation or washing the samples. SEM images revealed that the GO sheets consisted of thin, randomly aggregated and crumpled sheets closely to each other forming a disordered solid. The same results obtained in the case of TEM. TEM images show that TiO2 nanoparticles are highly agglomerated. The crystal size increased by increasing the calcination temperature. TEM images of loaded GO on TiO2 present good distribution of TiO2 nanoparticles on the surface of GO at low temperature, it also can be considered a self-assembling of TiO2 nanoparticles on the surface of GO during the preparation process. In case of Ag2S/TiO2, TEM images also show good distribution. XPS spectrum of GO sheets includes signals at C(1s) and O(1s). Symmetrical broad peaks of C(1s) suggests the existence of distinguishable models. we found that, 10 wt% GO/TiO2 and 1 wt% Ag2S/TiO2 are the best percentage prepared in case of two dopants. By increasing the dopant concentration, the photocatalytic degradation efficiency decreased. Thus, may be due to the dopant block the active sites present at the surface TiO2 nanoparticles. By increasing the concentration of dye, the amount of light absorption by the photocatalyst decreased.The photocatalytic degradation decreased due to the dye with high concentration which prevent the light to reach to the catalyst. By increasing the dose of photocatalyst, the percentage of degradation of pollutants increased. The optimum pH for degradation of rhodamine B, methylene blue and acid green are 4, 10 and 2 respectively.