الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Photocatalytic activity of prepared zinc oxide nanoparticles (ZnO) has been investigated and improved its photocatalytic efficiency by loading silver (Ag/ZnO). Ag-doping onto ZnO, various mole % (1, 3, 5, 7 and 9) of silver has been investigated for the photoactivity of the doped material in reactive blue 21 (RB21) degradation. The enhancement of photocatalytic activity is due to the fact that the modification of ZnO with an appropriate amount of Ag can increase the separation efficiency of photogenerated electrons and holes in ZnO. The calculated average crystallite size increases from 12.24 nm of ZnO to 13.25 nm of Ag/ZnO (3%). The optical band gap of the samples was found to be 3.21 eV for ZnO and 3.14 eV for Ag/ZnO (3%), which proves the change in the acceptor level induced by the Ag atoms. Optimal experimental conditions on catalysts amount, pH value, illumination time, and dye concentration have been determined. UV light was used as the energy source for the photocatalytic experiments. These catalysts were characterized for surface area, particle size and crystallinity. The photodegradation rate was determined for each experiment and the highest values were observed for Ag/ZnO suggesting that it absorbs large fraction of the UV spectrum and absorption of more light quanta than ZnO. The mineralization of RB21 has been confirmed by Chemical Oxygen Demand measurements. Furthermore, the kinetics and scavengers of the reactive species during the degradation were also investigated. It was found that the degradation of RB21 fitted the first-order kinetics and OH• radicals were the main species. Formation of OH• free radicals during irradiation is ascertained by photoluminescence studies using terephthalic acid as probe molecule.