Abstract
ZnO nanoparticles (NPs) were synthesized using Rosmarinus officinalis leaf extract at 80 °C (ZnO-80) and 180 °C (ZnO-180). The powder was characterized and tested for the degradation of methylene blue (MB) and crystal violet (CV) under sunlight. FTIR analyzes revealed that Rosmarinus officinalis leaf extract contains phenolic compounds, and accordingly a mechanism for the formation of ZnO NPs was proposed. The characterizations by XRD, TEM and SEM and fluorescence spectroscopy showed that ZnO-80 NPs have smaller size than those of ZnO-180 which exhibited flakier agglomerated spherical structures. Photocatalytic tests showed that ZnO-80 degraded MB by 99.64% in 45 min while ZnO-180 degraded it by 98.82% in 60 min. The superior performance of ZnO-80 over ZnO-180 is due to the fact that ZnO-80 has smaller crystallites, higher specific surface area and higher pore volumes than ZnO-180. When reused, ZnO-80 only showed a slight decrease in the rate of degradation (2.95%). These results indicate that ZnO-80 can be considered as a promising photocatalyst for wastewater treatment. It was prepared by a simple and inexpensive procedure, and unlike many photocatalytic tests using an artificial light source, in the present work sunlight was used.