Modified-ZnO-mediated dye detoxification by a heterogeneous Fenton process

The continuous and unchecked discharge of effluents by the dyeing industry into water bodies has led to the rising importance of water treatment. This study focuses on the successful abatement of the auramine O (AM) dye in an aqueous system through a heterogeneous Fenton process using ultrasonication. Zinc oxide (ZnO) nanoparticles (NPs) were obtained by using a straightforward precipitation method and then modified with glycine (M-ZnO). The NP size sharply decreased upon modification with glycine. X-ray diffraction was used to determine the basic crystal properties, such as crystallinity. It was observed that the size of NPs sharply decreased from 24.6 nm (pure zinc oxide) to 17.3 nm upon modification of zinc oxide with glycine. A bandgap of 3.4 eV was determined for M-ZnO using a UV–visible spectrophotometer. Thermal gravimetric analysis revealed the excellent thermal stability of M-ZnO compared with that of zinc oxide. The catalytic activity for AM abatement was determined using a Fenton process at pH 6. Detoxification assays showed that pure hydrogen peroxide (H₂O₂) and pure zinc oxide exhibited 38 and 37% AM dye degradation, respectively. Meanwhile, M-ZnO showed 97% AM dye degradation in 240 min. A plausible mechanism is proposed for AM abatement using zinc oxide.