Preparation of Nb2O5-decorated hierarchical porous ZnO microspheres with enhanced photocatalytic degradation of palm oil mill effluent

Abstract

In the present work, Nb2O5-decorated hierarchical porous ZnO microspheres (ZnO/Nb2O5) were successfully prepared through a facile surfactant-free method. The as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy and Brunauer–Emmett–Teller surface area analyses. Under UV light irradiation, the ZnO/Nb2O5 composites degraded palm oil mill effluent (POME) efficiently and demonstrated much higher photocatalytic activity compared to those of pure ZnO and Nb2O5. The enhanced photocatalytic degradation performance of ZnO/Nb2O5 composites was attributed to the high charge separation efficiency and hydroxyl radical generation ability as verified by the photoluminescence spectra. Phytotoxicity test upon the POME degradation over ZnO/Nb2O5 photocatalysis considerably decreased through the measurement of radicle lengths of Vigna radiata. Moreover, the ZnO/Nb2O5 composites were reused several times without appreciable loss of activity. This work revealed that the as-prepared ZnO/Nb2O5 composites have great potential for practical applications in the field of wastewater treatment.