Photocatalytic decomposition of perfluorooctanoic acid by noble metallic nanoparticles modified TiO2

Abstract

Photocatalytic decomposition of a typical emerging pollutant perfluorooctanoic acid (PFOA) in aqueous solution by using noble metallic nanoparticles modified TiO2 (M–TiO2, M=Pt, Pd, Ag) were investigated. The M–TiO2 photocatalysts were obtained by chemical reduction method and were characterized by field emission scanning electron microscope with energy dispersive spectrometer, transmission electron microscopy, X-ray diffractometer system and UV–vis diffuse reflectance spectroscopy. Compared with pure TiO2, M–TiO2 exhibited higher activities for PFOA decomposition. The rate constants of pseudo-first-order kinetics for Pt, Pd, Ag modified TiO2 were 0.7267, 0.4369 and 0.1257h−1, which were 12.5, 7.5 and 2.2 times higher than that for TiO2 respectively. Shorter chain perfluorinated carboxylic acids were identified as main products. The great photo-activities of M–TiO2 were attributed to the noble metal nanoparticles, acting as electron sinks to store the excess electrons in conduction band when the holes in valence band were utilized in PFOA decomposition. Noble metal with larger work function such as Pt and Pd were more effective to capture the electrons, thereby Pt–TiO2 and Pd–TiO2 showed higher photo-activities.