The optical and photo-electrochemical characterization of nano-ZnO particles and its application to degradation of Reactive Blue 19 under solar light

• Published in: Optik (Stuttgart) Vol. 238; p. 166751
• Main Authors: Cherif, S., Yazid, H., Rekhila, G., Sadaoui, Z., Trari, M.
• Format: Journal Article
• Language: English
• Published: Elsevier GmbH 01-07-2021
• Subjects: Chemical synthesis; Optical band gap; Photodegradation; Reactive Blue 19; Semiconductor; Solar light; ZnO nanopowder; ZnO nanopowder; Photodegradation; Semiconductor; Solar light; Reactive Blue 19; Optical band gap; Chemical synthesis
• ISSN: 0030-4026; 1618-1336
• DOI: 10.1016/j.ijleo.2021.166751

To assess its photocatalytic activity under sunlight, ZnO nano powder with crystallites sizes in the range (18–29 nm) was synthesized by decomposition from nitrate (ZnO-Nit) and acetate (ZnO-Ac) precursors by one-step calcinations. The powders were characterized by X-ray diffraction, transmission electron microscopy and Fourier-transform infrared spectroscopy. The optical band gap of ZnO-Ac, determined from the diffuse reflectance, was found to be 3.23 eV and the transition is directly allowed, due to the charge transfer O2−: 2p → Zn2+: 4s. The capacitance-potential (C−2 – E) characteristic plotted at pH ∼7 shows n type behaviour with a conductionband (−0.42 VSCE), made up of Zn2+: 4s orbital and positive of the O2/O2 level and a valence band (2.81 VSCE) deriving mostly from O2−: 2p orbital whose potential is less anodic than the OH/H2O level. So, ZnO was successfully used for the degradation of the Reactive Blue 19 (RB 19) a hazardous dye, by both radicals O2−and OH under solar light. Indeed, RB 19 is a vinylsulphone dye, difficult to eliminate by chemical oxidation because its anthraquinone structure is highly stabilized by resonance. The best photoactivity occurs over ZnO-Ac owing to its large active surface area (59 m2 g−1). The oxidation obeys a zero order kinetic with a rate constant of 7.3 × 10−3 mol L−1 min−1. The elaborated material showed an outstanding recyclability.