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Investigation of the Photocatalytic Properties of TiO2-Based Composites for the Removal of Rhodamine B

Osanloo, Mohammad | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58647 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Khorashe, Farhad; Larimi, Afsaneh Sadat
  7. Abstract:
  8. One of the important issues that humans have faced in recent centuries is solving the problems caused by the entry of various pollutants into the environment. The entry of various pollutants such as dyes and pharmaceutical compounds is directly related to human survival. In this regard, one of the new methods of photodegradation of pollutants is through photocatalytic processes using semiconductors. Among semiconductors, TiO2 has attracted much attention from researchers due to its high photocatalytic properties, chemical and thermal stability, and availability. TiO2 has limitations such as low specific surface area, high band gap energy, and high electron-hole recombination, which has resulted in low efficiency of this compound in photocatalytic processes. As a result, researchers have proposed various methods such as surface modification, using support, doping of metal elements, and formation of a heterojunction structure to overcome these limitations. Therefore, two studies about TiO2-based composites were prepared by considering the methods of improving the photodegradation of compounds such as rhodamine B, naproxen, and metronidazole. In the first study, TiO2 nanodandelion, CuFe2O4 magnetic nanoparticles, and silver doping were synthesized by hydrothermal, sol-gel, and photodeposition processes. So that the composite containing 20% CuFe2O4 and 3% Ag (TC20-3Ag) by weight showed better performance in the photodegradation of naproxen (92.56%) and rhodamine B (91.16%) within 150 minutes. Also, based on the results, a type II mechanism was proposed for the photodegradation process by the TC20-3Ag composite. In the second study, a TiO2/CuBi2O4@GO nanobelt composite was prepared by a three-step hydrothermal method with different amounts of CuBi2O4 and GO, and the efficiency of this composite in the photodegradation of metronidazole was evaluated. Accordingly, the photodegradation of metronidazole showed superior performance (97.86%) of T-CB-5G (containing 15% CuBi2O4 and 5% GO wt.) in the photodegradation of metronidazole within 120 minutes. Also, the investigation of the reaction mechanism showed that the transfer of charge carriers is consistent with the Z-Scheme model. It should be noted that in both studies, the photocatalytic samples were characterized using XRD, FTIR, VSM, FESEM, EDX, TEM, BET-BJH, DRS and PL analyses. The XRD, FESEM and TEM results confirmed the successful synthesis of nanostructures. VSM analysis also showed an increase in the magnetic properties of the composite after loading CuFe2O4. DRS results showed that loading of the secondary photocatalyst, metal doping and using carbon support in the structure of the composites led to a decrease in the band gap energy (1.54-3.15 eV in the first study and 2.39-3.19 eV in the second study) and an increase in light absorption in the visible region compared to pure TiO2. According to PL analysis, the presence of CuFe2O4 and Ag in the first composite and CuBi2O4 and GO in the second composite reduced the electron-hole recombination rate and increased the charge carrier transport in the composite. In addition, the effects of operating parameters such as solution pH, photocatalyst dosage and initial pollutant concentration were also evaluated. It was also found that a pseudo-first-order model adequately describes the photodegradation kinetics
  9. Keywords:
  10. Titanium Oxide ; Heterojunction Structure ; Surface Modification ; Photodegradation ; Magnetic Photocatalyst ; Metal Doping ; Rhodamine B

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