Photocatalytic Degradation Of Phenol In Fluidized Bed Reactor Using TiO2-P25/Activated Carbon Prepared By Modified Sol-Gel Method
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Date
2010-05
Authors
Lam, Sze Mun
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
TiO2-P25 immobilized on activated carbon (TPA) was successfully prepared by modified sol-gel method. The study included optimization of calcination temperature and P25 loading in the photocatalyst preparation. Experiments on the photocatalytic degradation of phenol in a fluidized bed reactor showed that the photocatalytic activity of the prepared photocatalyst can be significantly improved by increasing the calcination temperature from 400 to 600oC, which was due to an increase in both the anatase and rutile crystalline material and increase slightly in BET surface area, total pore volume and average pore size. It was found that the optimum calcination temperature in the photocatalyst preparation was 600oC. The results revealed that increasing P25 loading within a certain range (up to 3 g/L) could significantly improve the photocatalytic activity because of a decreased in crystal size, increased in BET surface area, total pore volume and average pore size and increased in viscosity in the sol and film weight of prepared photocatalyst. EDX analysis also showed that the presence of K, Na and Si on the surface of the photocatalyst films. The optimum P25 loading in the photocatalyst preparation was found to be 3 g/L. The prepared photocatalyst was stable for repeated usage after five cycles of phenol degradation and had TOC removal better than the suspended TiO2. Some phenol remained adsorbed on the photocatalyst when no traces of phenol were detected in the solution. This adsorbed phenol could be degraded by illuminated TiO2-P25 while maintaining UV irradiation. The effect of process variables such as UV light intensity, solution pH, air flow rate, photocatalyst loading and initial
substrate concentration were examined. The optimum conditions were as follows:
UV light intensity of 921 W/cm2, solution pH 5.2, air flow rate of 2 L/min,
photocatalyst loading of 2 layers and initial phenol concentration of 25 mg/L. The
kinetic of the phenol degradation was also analyzed. The results indicated that the
kinetics of this reaction fitted the Langmuir-Hinshelwood model well and the value
of the reaction rate constant (kL-H) and the adsorption equilibrium constant (K) were
found as 1.644 mg/L.min and 1.686 x 10-2 L/mg, respectively. In addition, response
surface methodology (RSM) based on central composite design (CCD) was applied
to access the effect of critical variables on the degradation of phenol. The model
predicted maximum degradation rate of phenol of at least 99.3% was achieved with
an optimum condition set at photocatalyst loading of 2 layers, solution pH 7 and
initial phenol concentration of 25 mg/L.
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Keywords
Photocatalytic degradation of phenol in fluidized bed reactor , using TiO2-P25/activated carbon