Photocatalytic degradation of P-Cresol using TiO 2 /ZnO hybrid surface capped with polyaniline

• Published in: Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering Vol. 53; no. 2; pp. 99 - 107
• Main Authors: Brooms, Thabo J, Otieno, Benton, Onyango, Maurice S, Ochieng, Aoyi
• Format: Journal Article
• Language: English
• Published: England 28.01.2018
• Subjects: Annular reactor; titanium dioxide; polyaniline; UV light; p-cresol; zinc oxide
• ISSN: 1093-4529; 1532-4117
• DOI: 10.1080/10934529.2017.1377583

This study evaluated the photocatalytic activity of polyaniline (PANI)-capped titanium dioxide and zinc oxide (TiO /ZnO) hybrid, for the degradation of P-Cresol. The hybrid was synthesized by precipitating ZnO on the surface of commercial TiO . An "in situ" chemical oxidative polymerization method was used to prepare the PANI capped hybrid (TiO /ZnO/PANI). The photocatalysts were characterized by powder X-ray diffraction (XRD), a Brunauer Emmett Teller (BET) analyzer, Fourier-transform infrared (FTIR) and photoluminescence spectroscopies, high resolution-transmission electron microscopy (HR-TEM) and thermogravimetric analysis (TGA). During photodegradation under ultraviolet (UV) irradiation, ZnO, TiO , TiO /ZnO hybrid and TiO /ZnO/PANI composite had P-Cresol removal of 43%, 50%, 61% and 99%, respectively. The higher activity of the TiO /ZnO hybrid as compared to TiO and ZnO was attributed to a reduced electron-hole pair recombination. The recombination was further significantly reduced upon introduction of PANI; hence, the highest activity observed with TiO /ZnO/PANI. The initial reaction rate constant for TiO /ZnO/PANI (0.9679 min ) was more than twice compared to that for TiO /ZnO hybrid (0.1259 min ). A synergistic effect between PANI and TiO /ZnO resulted in a highly efficient charge separation caused by the transfer of photogenerated holes from the hybrid to highest occupied molecular orbitals (HOMO) of PANI. The best TiO /ZnO/PANI (PANI to TiO /ZnO) ratio observed was 0.5:2 for the photodegradation of P-Cresol. Total organic carbon (TOC) analysis indicated a 97.4% mineralization of P-Cresol with PANI/TiO /ZnO.