Photo-catalytic Removal of Methyl Orange Dye by Polyaniline Modified ZnO using Visible Radiation

Abstract

Polyaniline modified zinc oxide (PANI/ZnO) nanocomposite was synthesized by in-situ polymerization process. The as-synthesized nano-ZnO, PANI and PANI/ZnO nanocomposite were characterized by X-ray diffraction (XRD), FT-IR, and UV-Vis spectroscopy. The UV–visible spectroscopy studies showed that the absorption peak for PANI/ZnO nanocomposite has a red shift toward visible wavelengths compared with the ZnO nanoparticles and PANI. Photocatalytic efficiency of PANI/ZnO nanocomposite was investigated for the degradation of methyl orange (MeO) dye as a model organic compound under Visible light irradiation. The photocatalytic activities of ZnO, PANI and PANI/ZnO nanocomposite were studied. The results showed that ZnO/PANI nanocomposite had greater photocatalytic activity than ZnO nanoparticles and PANI under visible light irradiation. According to these results, application of PANI as a shell on the surface of ZnO nanoparticles causes the enhanced photocatalytic activity of the PANI/ZnO nanocomposite. Influence of some operational parameters such as: amount of photocatalyst, pH of solution, and MeO dye initial concentration on the photodegradation reaction rate was investigated. The optimum values of pH and catalyst dose found to be 6 and 1.50 gmL^-1 respectively. It was demonstrated that the photocatalytic degradation of MeO follows pseudo first-order kinetics. The PANI/ZnO nanocomposite photocatalysts have good photocatalytic stability and can be reused three times with only gradual loss of activity. Thus, the PANI/ZnO nanocomposites are efficient photocatalytic materials for degrading contaminated colored wastewater for reuse in textile industries under mild conditions.

Keywords: PANI/ZnO Nanocomposite; Methyl orange; Visible light; photo-catalysis; Degradation rate constant