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Synthesis of Piezoelectric Nanomaterials and Kinetics Investigation of Their Performance for Degradation of Organic Pollutants Under Ultrasonic Vibrations

Mashhadizadeh, Samaneh | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55097 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Rahman Setayesh, Shahrbanoo
  7. Abstract:
  8. In this research, BiFeO3/Bi2WO6 nanocomposite was synthesized by hydrothermal method and utilized for piezocatalytic degradation of methyl orange dye. This nanocomposite was characterized by XRD, FE-SEM, FT-IR, DRS, PL and Raman spectroscopy. The results of XRD patterns confirmed the rhombohedral crystal structure of BiFeO3 nanoparticles and orthorhombic crystal structure of Bi2WO6 nanosheets. FT-IR and Raman spectroscopy approved the existence of chemical bonds and non-centrosymmetric structure of catalysts. The FE-SEM images displayed the formation of BiFeO3 nanodisks and the Bi2WO6 nanosheets and the decoration of BiFeO3 nanodisks on the Bi2WO6 nanosheets. By using the data of DRS analysis, the absorption edge wavelength and the bandgap energy of as-synthesized catalysts were obtained. The results of the PL analysis also expressed the effective electron-hole pairs separation in BiFeO3/Bi2WO6 nanocomposite and the enhancement of piezocatalytic activity. In the piezocatalytic degradation, ultrasonic vibrations were applied to the as-synthesized piezocatalysts as an external mechanical field and the influence of catalyst dosage and pollutant concentration was investigated for the determination of optimum conditions. At the optimum conditions (catalyst dosage: 1 g/L and initial concentration of pollutant :5 ppm) the methyl orange degradation efficiency reached 94% and COD removal reached 53.3% at 75 min. The investigation of nanocomposite performance in the degradation of other dye pollutants such as rhodamine B showed the degradation efficiency of 97%. The kinetics of piezocatalytic degradation of methyl orange was investigated and the results demonstrated that this process was followed by pseudo first order kinetics. To detect active radical species during piezocatalytic degradation, the specific scavengers were used and the results revealed that hydroxyl and superoxide radicals and holes were responsible for the degradation of methyl orange. Also, the evaluation of stability and reusability of nanocomposite showed that this catalyst possessed high stability and reusability.
  9. Keywords:
  10. Piezoelectric Materials ; Bismuth Ferrite ; Spontaneous Polarization ; Piezocatalytic Degradation ; Bismuth Tungstate Piezocatalytic ; Nanocomposite ; Nanoparticles ; Degradation Pollutants

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