Fly ash supported photocatalytic nanocomposite poly(3,4‐ethylenedioxythiophene)/TiO 2 for azo dye removal under simulated solar irradiation

The main objective of this study was to develop a supported photocatalyst for wastewater treatment with extended efficiency under solar light. For that purpose titanium dioxide (TiO 2 ) was immobilized by sol–gel synthesis on the surface of the waste fly ash (FA). On such prepared composite material, conductive polymer poly(3,4‐ethylenedioxythiophene) was grafted by in situ chemical oxidative polymerization with different oxidants, ammonium persulfate (APS), and iron(III) chloride, FeCl 3 . Characterization was performed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis, and gas sorption analysis. Photocatalytic activity of composite photocatalyst was evaluated by testing removal efficiency of C.I. Reactive Red 45 (RR45) azo dye in three consecutive photocatalytic cycles under different pH. Discoloration of RR45 was measured using UV/Vis spectroscopy. It was determined that oxidant type plays major role in structure of composite as sample synthesized with APS had higher fraction of polymer and largest pore volume. The same composite had much better photocatalytic efficiency than sample synthesized with FeCl 3 oxidant. It was also determined that there is a very strong adsorption of dye molecules on the surface of photocatalyst that quickly causes saturation of photocatalyst and efficiency drop after first cycle. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 46316.