Immobilized Tio2/Fe3+- Doped Pani Bilayer System For Removal Of Methyl Orange Via Photocatalytic-Adsorptive Process

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Date
2015-05
Authors
Aminuddin, Noor Fathanah
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Abstract
An immobilized bilayer system comprising of P25-TiO2 photocatalyst as the top layer and Fe3+ doped polyaniline-polyvinyl alcohol-glutaraldehyde (PANI-PVA-GLA) adsorbent composite as the sublayer in the presence of silica was successfully fabricated. The optimum amount of Fe3+ dopant was determined as 1.24 x 10-4 moles. The prepared immobilized monolayer TiO2 and bilayer system were characterized by scanning electron microscopy, fourier transform infrared spectroscopy, UV-Vis DRS analysis, BET surface area and porosimetry analysis, photoluminescence analysis as well as atomic absorption spectroscopy. For the mineralization determination of methyl orange (MO) dye by the TiO2/FeSi-PANI-PVA-GLA bilayer system, total organic carbon (TOC) analysis had been carried out. The combination effect of the photocatalytic-adsorptive processes in the removal of MO by the bilayer system under a 45 W compact visible light fluorescent lamp was investigated. The highest adsorption of MO by the immobilized FeSi-PANI-PVA-GLA system was achieved at the loading of 0.65 mg cm-2 (6.68 ± 0.18 μm of thickness) under ambient pH (6.8) and room temperature (27oC). Fe3+ was found not involved in the adsorption process. Immobilized FeSi-PANI-PVA-GLA system obeyed Freundlich isotherm model. The qmax value was 67.3 mg g-1 suggesting that immobilized FeSi-PANI-PVA-GLA system was a suitable choice of adsorbent for removing the dye. In the case of the bilayer system, the optimum TiO2 loading was 1.31 mg cm-2 (15.1 ± 0.41 μm of thickness). It was also observed that photo-etching of the photocatalyst systems for 10 hours led to the generation of macro-pores within the TiO2 top layer, increased the light penetration and allowed better diffusion of the pollutant as well as oxidative radicals across the inner layer of the immobilized TiO2/FeSi-PANI-PVA-GLA bilayer system. The photocatalytic degradation rate of methyl orange dye by the TiO2/FeSi-PANI-PVA-GLA bilayer system was 0.083 ± 0.005 min-1 for 1 hour treatment where its total mineralization was 88.8 ± 0.04 % for an 8 hour treatment process. The MO removal efficiency of the bilayer system was 6.4 times better than the TiO2 mono layer system. Incorporation of Fe3+ into the PANI-PVA-GLA adsorbent sublayer was able to reduce the electron-hole recombination by acting as both electron and hole trap as proven by the photoluminescence spectra analysis. This phenomenon clearly contributed in enhancing the photocatalytic activity of the TiO2/FeSi-PANI-PVA-GLA bilayer system. Photocatalyst reusability has been tested for 10 times of reuse for the removal of MO. As observed in the 10th run application, the MO removal rate was 6 times higher compared to that of the TiO2 monolayer system.
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Keywords
Methyl Orange , Photocatalytic-Adsorptive Process
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