Abstract
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•Zinc oxide quantum dots (ZnO QDs) were successfully prepared via a modified sol–gel method.•XRD and TEM proved the formation of high purity single phase of ZnO QDs prepared samples.•Quantum size has an interesting effect on photocatalytic activity processes by the fluorescent probe method.•The mineralization efficiency of real industrial wastewater carried out by sunlight for six months as a study case.•Recycle process for reusable of 8 times for ZnOQDs and nano ZnO prepared samples investigated and evaluated.
Three samples of ZnO quantum dots (ZQDs) were synthesized by a modified sol–gel method at different temperatures for 3 h. The first sample (S1) was prepared at room temperature 27 °C, while second and third samples (S2) and (S3) were prepared by the calcination process at 500 and 900 °C, respectively. A study of XRD and TEM determines the purity, high crystallinity and the presence of elongated shape of the prepared catalysts. On using TEM, DRS and EBT analysis, the crystallite size values, bandgap energy, and active surface area were (7.1 nm, 3.49 eV, and 150.1 m2/g), (9.8 nm, 3.45 eV and 112.2 m2/g) and (13.5 nm, 3.39 eV and 78.94 m2/g) for S1, S2, and S3, respectively. The Photoluminescence properties showed that the fluorescence rate for S1 was doubled the observed one in the S2 sample. The photodegradation results of both methyl orange as an industrial raw material and real industrial wastewater of S1 sample showed the finest activity when compared with the rest samples. It was cleared from the collecting data that the photocatalytic performance decreases with the crystallite size increases The mineralization efficiency of the real industrial wastewater that exposed to sunlight for six months were evaluated according to the allowed COD limit for Egyptian Environmental Law, In addition the recycling process for reusable for ZnO prepared samples for 8 times investigated and evaluated.