Development of metal doped ZnO based nanophotocatalysts and their applications

Organic pollutants which are released from various industrial processes, poison the water sources and threaten the environment. There are many different methods applied to rid the water streams from such organic waste. These methods are not sufficient in means of applicability, economical aspects or bringing an extra amount of pollution to the applied environment and therefore there is a need for a superior, enviromentally friendly technique. When all these factors are taken into account, heterogenous photocatalytic degradation is quite a suitable method. With this method, which is based on interaction between a semi-conductor and UV-A light, organic pollutants can be mineralized into small and non-toxic molecules such as H2O and CO2. ZnO is the most extensively used semi-conductor photocatalyst, because it is a nontoxic, inexpensive, easily attainable and chemically stable compound. ZnO, one of the II-VI compound semiconductors, has a significant technological importance due to its abundance in nature and high transparency. Its structural, optical and electrical properties can be improved by using appropriate doping materials. It is an alternative material to other transparent materials since it has a high electrical conductivity, a feature that makes it preffered for many applications.Zinc oxide also has a wide band gap of 3:37 eV likely led to its short wavelength suitable for use in applications optoeletronik. In this study, nanoscale ZnO and different metals (Ag, Fe, Mn and Ni) doped ZnO photocatalysts were synthesized according to hydrothermal method. The as-synthesized photocatalysts were characterized by XRD, FESEM, FTIR and UV-Vis spectrophotometry. It is observed that doping metals did not significantly impact on the forbidden band gap. The photocatalytic degradation of tartrazine was investigated by employing the as-synthesized undoped and metal doped ZnO photocatalysts. The tartrazine degradation efficiency of ZnO, Ag/ZnO, Fe/ZnO, Mn/ZnO and Ni/ZnO photocatalysts was found to be Ni/ZnO, Ag/ZnO, ZnO, Fe/ZnO ve Mn/ZnO respectively. It is demonstrated that Ag and Ni doping enhanced the photocatalytic activity of ZnO, while Fe and Mn doping impaired the photocatalytic activity of ZnO. Keywords: Zinc oxide, metal doping, photocatalyst, photocatalysis, tartrazine