Abstract
Polyaniline (PANI)-wrapped TiO2 nanorods (PANI/TiO2), obtained through the oxidative polymerization of aniline at the surface of hydrothermally presynthesized TiO2 nanorods, were evaluated as photocatalysts for the degradation of Bisphenol A (BPA). Fourier-transform infrared spectroscopy analysis revealed the successful incorporation of PANI into TiO2 by the appearance of peaks at 1577 and 1502 cm-1 that are due to the C=C and C-N stretch of the benzenoid or quinoid ring in PANI. Brunauer-Emmett-Teller analysis revealed that PANI/TiO2 had almost double the surface area of TiO2 (44.8999 m2/g vs 28.2179 m2/g). Transmission electron microscopy (TEM) analysis showed that TiO2 nanorods with different diameters were synthesized. The TEM analysis showed that a thin layer of PANI wrapped the TiO2 nanorods. X-ray photon spectroscopy survey scan of the PANI/TiO2 nanocomposite revealed the presence of C, O, Ti, and N. Photocatalytic activity evaluation under UV radiation through the effect of key parameters, including pH, contact time, dosage, and initial concentration of BPA, was carried out in batch studies. Within 80 min, 99.7% of 5 ppm BPA was attained using the 0.2 g/L PANI/TiO2 photocatalyst at pH 10. The quantum yield (QY) of these photocatalysts was evaluated to be 9.86 × 10-5 molecules/photon and 2.82 × 10-5 molecules/photon for PANI/TiO2 and TiO2, respectively. PANI/TiO2 showed better performance than as-synthesized TiO2 with a rate constant of 4.46 × 10-2 min-1 compared to 2.18 × 10-2 min-1. The rate of degradation of PANI/TiO2 was also superior to that of TiO2 (150 mmol/g/h vs 74.89 mmol/g/h). Nitrate ions increased the rate of degradation of BPA, while humic acid consistently inhibited the degradation of BPA. LC-MS analysis identified degradation products with m/z 213.1, 135.1, and 93.1. The PANI/TiO2 nanocomposite was reused up to five cycles with a removal of at least 80% in the fifth cycle. LC-MS results revealed three possible BPA degradation intermediates. LC-MS analysis identified degradation products which included protonated BPA, [C14H13O2 +], and [C9H11O+]. The PANI/TiO2 nanocomposite demonstrated superior photocatalytic activity with respect to improved QY and figure of merit and lower energy consumption.