Morphological effect of ZnO nanoparticles for photocatalytic degradation of azo dyes in water

Discharge of organic dyes from different industries into receiving rivers and natural streams poses serious problems for the environment because of their toxicity. These dyes are not readily biodegradable and therefore, their removal from effluents is urgent. Various methods used for removal of dyes from wastewater, such as coagulation, flocculation, filtration or reverse osmosis are quite expensive and have a low removal efficiency. On the contrary, Advanced oxidation processes (AOPs) using metal oxide semiconductors like ZnO, are capable to operate effectively and efficiently to degrade many dye pollutants.

In this work, ZnO nanoparticles were successfully synthesized via a simple solvothermal method with different solvents. Scanning electron microscopy (SEM) imaging showed that nanoflower, nanorod, and nanosphere ZnO particles were produced when water, 1-hexanol, and ethylene glycol were used as the solvent, respectively. Nanoflower ZnO particles exhibited higher photocatalytic reduction efficiencies under UV light irradiation than nanosphere and nanorod particles. Results suggested a close relationship between the photocatalytic activity and the particle morphology and size which was due to using different solvents in preparation processes. Also, the recovery of ZnO nanoparticles was investigated and samples showed stable photodegradation efficiencies after being reused for three times.