Photocatalytic Degradation Of Phenol By Silica Gel-Supported Titania Nanotubes
Loading...
Date
2012
Authors
Wong, Chung Leng
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
TiO2 nanotubes and immobilized TiO2 nanotubes were successfully
synthesized by a hydrothermal method and binding method. The produced
photocatalysts were characterized by the Brunauer-Emmett-Teller (BET) method,
scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX),
transmission electron microscope (TEM) and X-ray diffraction (XRD). The
photocatalytic activities of the photocatalysts were evaluated through the
photocatalytic degradation of aqueous phenol solution in a batch reactor. TiO2
nanotubes produced at 130 °C for 3 h showed the highest degradation rate of phenol
compared with the other samples prepared at 130 °C for 1 h, 5 h and 7 h, complete
degradation being achieved in 130 min. Special focus was given in order to
determine the optimum composition of each component (catalyst, support and binder)
in the immobilization of TiO2 nanotubes. The highest efficiency of phenol
degradation was achieved when the ratios of TiO2 nanotubes: silica gel: colloidal
silica was 1:2:20. For the comparison, TiO2 nanotubes and immobilized TiO2
nanotubes showed higher photocatalytic activity as compared with pure TiO2. The
photocatalytic performance of TiO2 nanotubes and immobilized TiO2 nanotubes
achieved 100 % and 98.0 % respectively, of phenol degradation, whereas pure TiO2
attained only 77.0 % degradation. The photocatalytic activity of the immobilized
TiO2 nanotubes was slightly decreased after four cycles for phenol degradation. The loss in percentage of photocatalytic degradation was less than 2 % even after four
cycles. The results for the studied operating parameters were: the presence of the
anions were found to inhibit the photocatalytic degradation of phenol in the order of
SO4
2- > Cl- > HCO3
-; the optimal medium pH was found to be pH 5.5 (natural pH);
the air flow rate gave an optimum value of 0.3 L/min; the phenol degradation
efficiency decreased as initial phenol concentration increased. Response surface
methodology (RSM) based on the central composite design (CCD) was used to
optimize and predict the interactions between process variables by reducing the
numbers and the times for the experimental runs. Finally, the reaction kinetics of
phenol degradation by the immobilized TiO2 nanotubes obeyed well with the
Langmuir-Hinshelwood model. The values of the reaction rate constant, k and the
adsorption constant, K obtained were found to be 0.9324 mg/L.min and 0.0121 L/mg,
respectively.
Description
Keywords
Waste products