Photocatalytic Degradation Of Phenol In A Fluidized Bed Reactor Using Tio2 Prepared By A Hydrothermal Method Immobilized On Granular Activated Carbon
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Date
2010-05
Authors
Sin, Jin Chung
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Publisher
Universiti Sains Malaysia
Abstract
TiO2 immobilized on granular activated carbon (TiO2/GAC) was successfully prepared using a hydrothermal method. The prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and N2 physisorption. Their photocatalytic activities were evaluated through phenol degradation in a fluidized bed reactor. The characterization results revealed that the prepared photocatalysts had a single crystal phase, which was anatase. The crystallinity and crystal size of TiO2/GAC increased as the hydrothermal temperature increased from 120oC to 200oC. The surface morphology of prepared photocatalysts was agglomerated. EDX analysis confirmed the presence of TiO2 on the surface of the GAC supports. The surface area and total pore volume of prepared photocatalysts were significantly affected by hydrothermal temperature. However, no much change was found on the average pore diameter. The photocatalytic efficiency of TiO2/GAC was strongly influenced by hydrothermal temperature and the optimum hydrothermal temperature was 180oC. For the comparison, the same photocatalysis experiment was performed using commercial Degussa P25. TiO2/GAC had shown better phenol degradation and total organic carbon removal (TOC), which was 96.9 % and 85 %, respectively higher than that of commercial Degussa P-25. The GAC support with high surface area and adsorption capacity had worked well for the phenol adsorption, and the adsorbed phenol migrated continuously onto the surface of TiO2, where it is photocatalytically degraded. Moreover, the photocatalytic ability of TiO2/GAC was decreased slightly after four cycles for phenol degradation. The results for the studied operating parameters were: optimum TiO2 loading was 322.2 mg/L; the inorganic anions had a negative effect on the phenol degradation in the order of HCO3- > CO32- > SO42- > Cl; the optimum pH was found to be 5.2; the air flow rate gave an optimum value of 2 L/min; high phenol degradation can be achieved at H2O2 concentration of 400 mg/L; the increase of initial phenol concentration gave a lower phenol degradation. An experimental design based on response surface methodology (RSM) was employed to optimize the phenol degradation. A maximum phenol degradation of 98.8 % was obtained at 30 mg/L of initial phenol concentration, 2 layers of TiO2 loading (322.2 mg/L) and 200 mg/L of H2O2 concentration. Finally, the kinetics of phenol degradation was fitted well with the Langmuir-Hinshelwood model. The reaction rate constant and the adsorption constant were calculated to be k = 8.18 mg/L.min and K = 0.00086 L/mg, respectively.
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Keywords
Photocatalytic degradation of phenol , in a fluidized bed reactor using tio2