Mixed phase lamellar titania-titanate anchored with Ag2O and polypyrrole for enhanced adsorption and photocatalytic activity

Abstract

Ag2O/TiO2/polypyrrole composite was synthesized by stepwise modification of the rutile TiO2 though hydrothermal alkaline treatment to obtain mixed phase sodium titanate/titania (Na-TiO2) followed ion-exchange replacement of Na+ by Ag+ to get Ag2O/TiO2 (through precipitation) and H2O2 oxidative polymerization of pyrrole onto Ag2O/TiO2 to get final composite Ag2O/TiO2/polypyrrole (Ag2O/TiO2/PPY). Composite materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), Diffuse reflectance ultraviolet–visible spectroscopy (UV–vis DRS) and Raman analysis. The synthesized materials showed increase in the optical property, adsorption and photocatalytic scavenging of the methylene blue (MB). The adsorption capacity of MB onto the prepared materials was observed in the following order: TiO2<Ag2O/TiO2<Na-TiO2<Ag2O/TiO2/PPY. While the photocatalytic decontamination of MB was as follows: TiO2<Na-TiO2<Ag2O/TiO2<Ag2O/TiO2/PPY. The maximum adsorption and photocatalytic decontamination was observed at pH 9. The kinetics studies revealed that the adsorption of MB followed the pseudo-first-order kinetic model. While kinetics for MB degradation were well defined by the Langmuir–Hinshelwood model at low and high concentrations. The obtained results demonstrate that the synergistic effect of adsorption and visible light photocatalysis is enough capable for 100% removal of MB from aquatic solution.