Recycling for solar photocatalytic activity of Dianix blue dye and real industrial wastewater treatment process by zinc oxide quantum dots synthesized by solvothermal method

Solar photocatalytic activity of zinc oxide quantum dots (ZOQDs) was investigated and two samples of ZOQDs were synthesized by solvothermal method and characterized using different spectroscopic techniques. Crystal and morphological properties were obtained from XRD and HRTEM showed the purity, high crystallinity single phase and the elongated shape of prepared quantum dots. The measured crystallite size of the S1 and S2 samples is 8.4 and 9.6 nm respectively. The results of BET analysis and the optical properties of the samples shown that the first sample have larger values for both the specific surface area and band gap energy. Estimation of the photocatalytic performance indicated that the first sample give the best degradation rate of the synthetic Dianix Blue dye (DB) dye (2.47 × 10−2 s−1). Likewise, in the photo-oxidation of coumarin, the sample with the smallest particle size achieves the highest by 20% fluorescence rate than the largest particle size sample. In addition, the work included a study of the mineralization and recycling efficiency of industrial wastewater as a study case in the presence of different doses of ZOQDs by sun light for a one year and this evaluation done according to Egyptian allowed COD limit according to local environmental ministry law.