الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The degradation of different dyes such as MO, MB, P3R, EBT and CR in aqueous solutions by Fenton and photo-Fenton reactions has been studied at different experimental conditions; these include the concentration of H2O2, the concentration of FeSO4 in homogeneous system or the weight of Fe2O3 catalyst in heterogeneous system, the initial dye concentrations and the pH of the solution.
The main conclusions derived from this study can be summarized as follows:
• The UV–VIS spectra of the dyes were recorded from the wavelength 200 to 800 nm using a UV–VIS spectrophotometer. from the spectra, the maximum absorbance wavelengths (λmax) obtained for MO, MB, P3R, EBT and CR dye are 464, 662, 504, 551 and 498 nm, respectively.
• The calibration curve for each dye was constructed by plotting the different concentrations of the dye against its absorbance at maximum wavelength of each dye and it was found that the values of the regression coefficients (R2) are 0.99981, 0.99953 , 0.99985 , 0.99991 and 0.9998 and the slopes are 0.26202 , 0.63798 ,0.16739 , 0.0802 and 0.24877 for MO, MB, P3R, EBT, CR dyes, respectively.
• A suitable operating condition of MO dye was selected as: initial MO dye concentration of 5.4×10-5 M, FeSO4 concentration of 1.9×10-4 M, H2O2 concentration of 2.93×10-3 M and pH value of 2.7 at room temperature. Under the given conditions, more than 98.09% of degradation efficiency was achieved within 30 min. of the reaction.
• The optimal condition obtained from the results of the degradation of MB dye by Fenton reaction was selected as : initial MB dye concentration of 5.5×10-5 M, H2O2 concentration of 2.93×10-3M, FeSO4 concentration of 1.9×10-4 M and pH value of 2.08. It was found that the degradation efficiency achieved by Fenton reaction was 98.98 % at 30 min. of the reaction.
• The degradation efficiency of P3R dye obtained by Fenton reaction was achieved to 98.32 % at 20 min. of the reaction at optimal condition which was selected as : H2O2 concentration of 2.93×10-3 M, FeSO4 concentration of 1.0×10-4 M , P3R dye initial concentration of 3.77×10-5 M and pH value of 3.0
• A suitable operating condition of EBT dye was selected as: H2O2 concentration of 1.14×10-2M, FeSO4 concentration of 1.85×10-4 M, EBT dye initial concentration of 9.34×10-5 M and pH value of 3.2 at room temperature. Under the given conditions, more than 98.37 % of degradation efficiency was achieved within 60 min. of the reaction.
• The optimal condition obtained from the results of the degradation of CR dye by Fenton reaction was selected as : H2O2 concentration of 1.14×10-2 M, FeSO4 concentration of 6.64×10-5 M, CR dye initial concentration of 1.99×10-5 M and pH value of 3.7. It was found that the degradation efficiency achieved by Fenton reaction was 96.64% at 60 min. of the reaction.
• By comparing the results obtained from the degradation of the dyes by Fenton and photo-Fenton reactions when the different parameters were kept constants at optimal condition for each dye. It was found that the degradation efficiency of MO dye was increased at the first 2 min. of the reaction from 94.12 % by Fenton reaction to 96.75 % by photo-Fenton reaction and increased from 97.6% by Fenton reaction to 98.6% by photo-Fenton reaction at 10 min. of the reaction. The degradation efficiency of MB dye was increased at the first 2 min. from 97.92% by Fenton reaction to 99.13 % by photo-Fenton reaction and was increased from 98.98% by Fenton reaction to 99.57% by photo-Fenton reaction at 30 min. of the reaction. The degradation efficiency of P3R was increased at the first 2 min. from 90.35% by Fenton reaction to 96.42 % by photo-Fenton reaction and increased from 98.32% by Fenton reaction to 98.72% by photo-Fenton reaction at 20 min. of the reaction. The degradation efficiency of EBT was increased at the first 2 min. of the reaction from 81.40 % by Fenton reaction to 91.61% by photo-Fenton reaction and increased from 94.0 % by Fenton reaction to 99.83% by photo-Fenton reaction at 15 min. of the reaction. The degradation efficiency of CR dye was increased at the first 2 min. from 80.88 % by Fenton reaction to 83.88 % by photo-Fenton reaction and increased from 91.6% by Fenton reaction to 100% by photo-Fenton reaction after 20 min. of the reaction.
In the heterogeneous system ferric oxide prepared by precipitation method was utilized as a catalyst in the heterogeneous system on the degradation of MB dye by photo-Fenton reaction. This catalyst is much cheaper and can markedly accelerate the degradation of MB under irradiation by ultra violet (UV) light.
Ferric oxide was characterized by X-ray diffraction (XRD) analysis, infrared spectroscopy (IR), transmission electron microscopy (TEM), surface area measurements (BET), differential thermal analysis (DTA) and thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) techniques.
• XRD patterns showed that iron oxide prepared by precipitation method was nanocrystalline with the fine particles nature of iron oxide. According to the Scherrer’s equation, the average crystallite size of the product was 5.58 nm.
• FTIR spectra confirmed the structure of iron oxide and illustrated several absorption peaks at 444.4 and 531.2 cm-1 due to Fe–O stretching vibration bands, which indicates the formation of metal-oxygen bond (Fe-O); also, two bands at 998.9 and 974.3 cm-1 are due to Fe–O–H bending vibration bands.
• Analysis of TEM image for iron oxide which prepared by precipitation method have rod like morphologies with an average particle diameter of 17.0 nm (range 13.7–20.0 nm).
• The TGA/DTA thermograms of Fe3O4 nanoparticles showed four derivative peaks in the DTA thermograms at 63.36, 258.13, 575.1 and 749.1 °C which are related to a loss of water of crystallization, decomposition of the precursor iron sulfate occurs suddenly in a single step to Fe2O3, phase transition from Fe2O3 to Fe3O4 and the phase transition from Fe3O4 to FeO, respectively.
• The N2 adsorption-desorption isotherms were closed to be type H4 of the IUPAC classification.
• The magnetization of the iron oxide nanoparticles was measured with reference to the external field at room temperature. Its saturation magnetization was predicted as 20.47 emu/g and it exhibits super paramagnetic behavior.
• The three kinetic models (zero-order, first-order and second-order equations) were studied for the degradation effect of each dye. from regression coefficients (R2), the fit is better with the second-order equation than that with zero-order and first-order equations. So that the kinetic study indicated that the degradation kinetics of all the studied dyes followed the second-order kinetics.