Synthesis And Photocatalytic Property Of Zn-doped TiO₂/Graphene

With the development of medical industry, antibiotic wastewater pollution brings great harm to the entire natural environment and human. In recent years, people started to use photocatalytic oxidation technology to deal with tetracycline. Because of the chemical stability, photocatalytic ability, non-toxic, low-cost and other properties, titanium dioxide（Ti O₂） are widely used. However, low utilization of sunlight greatly influences the large-scale industrial applications of Ti O₂. Metal doping can improve the photocatalytic properties of Ti O₂. At the same time, graphene has excellent physical and chemical properties, so it can make up for some deficiencies of Ti O₂. Furthermore, it’s easy to form a composite, so Ti O₂/Graphene composites has now become a hotspot.I prepared Zn-doped Ti O₂ by sol-gel method. The photocatalytic activity of Zn-doped Ti O₂ nanoparticle was evaluated by photocatalytic degradation of tetracycline HCl. At the same time, the effects of Zn doping amount, calcination temperature and H2O₂ modification were disscussed. Structure characteristics analysis of as-prepared samples were studied by X-ray diffractometer, Transmission electron microscopy, Brunauer-Emmett-Teller, Diffuse reflectance UV-visible absorption spectra, X-ray photoelectron spectra. The results indicated that doping Zn into Ti O₂ nanoparticles could inhibit the transformation from anatase phase to rutile phase. Ti existed as Ti4+ and Ti3+ in the Zn-doped Ti O₂. Zn doping and H2O₂ modification narrowed the band gap and efficiently increased the optical absorption in visible region. Zn-doped Ti O₂ that synthesized by 5% Zn doping at 450 °C exhibited the best photocatalytic activity. After 330 min, the residual rate of tetracycline HCl was 14.73%. The optical H2O₂ modification condition was the volume ratio of H2O₂ and H2 O was 1:9. After 330 min, the residual rate of tetracycline HCl was only 11.86%. The results showed Zn doping and H2O₂ modification enhanced the photocatalytic activity. Furthermore, Zn-doped Ti O₂ modified by H2O₂ had relatively good reusability, exhibiting a potential practice application for tetracycline’s photocatalytic degradation.I prepared Zn-doped Ti O₂/Graphene by hydrothermal method. The photocatalytic degradation was tested on tetracycline HCl. The effects of the mass ratio of graphite oxide/Zn doped Ti O₂ and hydrothermal temperature were disscussed. Means of structure characteristics analysis showed that by hydrothermal method, graphite oxide has been reduced to graphene and the oxygen-containing functional goups were removed in the hydrothermal process. Zn doped Ti O₂ nanoparticles were dispersed on the surface layer of graphene sheet and they were combined closely by chemical bond. The spectral absorption range of the composite material was expanded from the ultraviolet region to the visible region. The band gap edge had a significant red shift. When the mass ratio of graphite oxide/Zn doped Ti O₂ was 5% and the hydrothermal temperature was 140°C, the Zn-doped Ti O₂/Graphene composites exhibited the best photocatalytic properties. After 120 min, the residual rate of tetracycline HCl was only 1.5%. The results showed Zn-doped Ti O₂/Graphene composites had great effect on tetracycline wastewater treatment and we can expect large-scale production and application of the material.