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تحوير فجوة طاقة ثاني اوكسيد التيتانيوم بواسطة تفاعلات الحالة الصلبة مع صوديوم بوروهيدريد والمنيوم ليثيوم هيدريد وتحديد فعالية التحفيز الضوئي == Modifying The Band Gap of Nano Titanium Dioxide By Solid State Reactions With Aluminum Lithium Hydride and Sodium Borohydride and Determining Their Photocatalytic Activity
Author name:
سراج علي رحيم
Supervisor name:
محسن عريبي الدخيلي | ابراهيم عبود فليفل
General topic:
Chemistry
Specific topic:
Chemistry
Degree:
Master
University:
University of Thi-Qar - College Of Science - Chemistry Department
Language:
English
University location:
Dhi Qar
Abstract:
This study includes preparation of nanoparticles of titanium dioxide using sol-gel method and then, the band gap was modified by solid state reaction with (AlLiH4،NaBH4) reductive compounds. Modification reduced the band gap separating | energy levels between valance band (VB) and conduction band (CB), therefor; facilitating the transfer of excited electrons from (VB) to (CB). Absorption of the energy from incident photons having the same or larger energy than the energy of the | band gap promote the formation of the couple (electron - hole) . The resulting (e--h+) couple acts to produce (OH.) radicals. OH. radicals hav a high capability to destroy organic pollutants that adsorbed on surface of the photocatalytic TiO2. | The optical properties measured using UV-visible spectrophotometer (Absorbance (A), energy band gap (Eg) and absorption coefficient ( α ) . TiO2 and TiO2- solid state reaction showed clear blue shift of the absorption band gap which were (2.8ev, 2.7ev, 2.25ev, 2.0ev) to )TiO2- NaBH4(550 ) ,TiO2-NaBH4 (750 ) , TiO2-AlLiH4 (500 ) and TiO2 -AlLiH4 (750 )) respectively. The structure of prepared TiO2 nanopowders were identified using XRD, particle size distribution varied appreciably in comparison with crystallite size (D) calculated from Sheerer formula which was in a good accordant compared with ASTM results , the particle size and their distribution were characterized using (AFM) . To the surface forms and compositions diameters of nanoparticles)SEM) was implemented . The energy dispersive X-ray (EDX) microanalysis was utilized to investigate the chemical composition of the whole samples. | Photocatalytic reaction was studied by using UV-Vis spectrophotometry. | In photocatalytic reaction the effect of the catalyst on photocatalytic rate of decomposition of methylene blue dye through the use of catalyst TiO2 and TiO2- solid state reaction (TiO2 - NaBH4 (550 ,750 )) and (TiO2 - AlLiH4 (500 ,750 )) . Using constant weight of the catalyst and dye. The most effective weight was found (1*10-4 M). At best weight the influence of many factors on rate of decomposition of dye were studied the impact of change pH varies (4.5, 7.1 and 9.4) found that the highest percentage in the decomposition of the MB was in the acidic media than in neutral and then alkaline. The effect of temperature variation from (20, 30, 40ºC) and found that increased rate of decomposition with increasing the temperature of the MB. Activation energy (Ea) for each reaction was calculated by using the equation of Arrhenius equation between (5.73-11.31) kJ mol-1 . | A series of dark reactions with absorbance measurement by UV-Vis spectrophotometry, within different periods of time with the change of pH and temperature. The results indicate that no degradation of the methylene blue dye although all the factors affecting in photocatalytic present except UV-light .
