Enhancing the optical properties of immobilized TiO2/polyaniline bilayer photocatalyst for methyl orange decolorization

Abstract

Several strategies had been employed to enhance the photocatalytic efficiency of titanium (IV) oxide/polyaniline (TiO2/PANI). In this particular study, ferric (Fe3+) ion was incorporated on the PANI sub-layer backbone instead of TiO2 purposely to improve the removal of methyl orange (MO) dye during the photocatalysis by means of optical properties. The framework of present work involves three stages of preparation which was synthesis of PANI crosslinked with polyvinyl alcohol-glutaraldehyde, doping with Fe3+ ion before coating with TiO2 to form a bilayer photocatalyst. The adhesive and Fe3+ ion solution were added via in-situ and ex-situ of PANI polymerization, respectively. The Fe3+-PANI-polyvinyl alcohol-glutaraldehyde (Fe-PPG) composite solution was then immobilized on the glass support using a facile brushing technique. The presence of Fe3+ ion enhanced the electron-hole separation as well as visible light response of the PPG when coupled with TiO2 in the form of layer by layer assemblage. The properties of light harvesting of the bilayer assemblage were then improved by simple photo-etching under light irradiation which produced more porous TiO2 layer on the sub-layer adsorbent. The thickness increased proportionally with loading in which the best loading of TiO2 on top of Fe-PPG was found to be 1.3 mg cm−2 whereas the photocatalytic-adsorption removal was the highest when MO solution was adjusted to pH 6. The mineralization of MO was also faster when TiO2-Fe-PPG was used to treat the dye as compared to single TiO2 layer. With robust mechanical strength and excellent photocatalytic activity, TiO2/Fe-PPG can possibly find its potential application in the real wastewater treatment plant.