Wet chemically synthesized ZnO structures for photodegradation of pre-treated palm oil mill effluent and antibacterial activity

Abstract

Various ZnO structures including spherical-like, hexagonal rod-like, spindle-like and pompon-like structures engineering at different solution pHs were prepared using a facile and surfactant-free reflux fabrication technique. The samples were morphologically and structurally analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), Brunauer–Emmett–Teller (BET) surface area and photoluminescence (PL) spectroscopy. The growth mechanism of pompon-like ZnO was delineated by the self-assembly attachment technique. Photoactivities of ZnO samples with varying morphologies were employed for the UV degradation of pre-treated palm oil mill effluent (POME) and inactivation of Escherichia coli (E. coli). Especially, pompon-like ZnO synthesized at pH 12 showed excellent photoactivity as compared to those of other three samples. The PL spectra demonstrated that the pompon-like ZnO can efficiently separate the charge carrier. The cyclic and leakage of zinc ion tests showed that the pompon-like ZnO has stable recyclable ability up to five successive runs. Much effort was also emphasized on the ZnO photocatalytic inactivation of E. coli by assessing the antibacterial behaviour, biomolecule leakage and cell destruction assays. The trapping experiments implied that the hydroxyl radicals were the dominant reactive species for both photocatalytic and antibacterial activities. Overall, ZnO catalysts exceled in the distinct potential applications including photocatalysis and antibacterial activities with their tunable structures.