Construction Of The Transition Metal Doped TiO₂/Graphene Ternary Composite Photocatalytic System For Efficient Removal Of Wastewater

Among advanced catalytic oxidation technology,semiconductor photocatalytic is considered to be one of the"green"and effective strategies to solve global energy and environmental problems.Its mild reaction conditions,strong oxidation and broad spectrum have the advantages of providing economic technology for water treatment.Titanium dioxide composites have been widely studied because of the characteristics of green cleaning of catalytic process and low energy consumption,and have broad application prospects in environmental pollution control,energy conversion and synthesis of new substances.Based on the synthesis of new high-efficiency graphene composite catalytic materials and the development of technology,this work successfully obtained a low cost and superior performance M/TiO₂/graphene ternary composite catalytic material by ultrasonic assisted in-situ light reduction,hydrothermal and high temperature impregnation method.Transmission electron microscopy?TEM and HR-TEM?,X-ray diffraction?XRD?,UV-visible diffuse reflectance?DRS?,X-ray photoelectron spectroscopy?XPS?,Fourier Transform infrared spectroscopy?FTIR?,Electron paramagnetic resonance?EPR?,Specific surface area analyzer?BET?,ZETA potential and other characterization methods were using for photocatalytic composites analysis.The heavy metal Cr?VI?and tetracycline solutions were used as simulated target pollutants to systematically explore the effects of various factors on the degradation efficiency of pollutants,such as doping amount,pH,dosage,initial concentration,coexisting ions,etc.And,the mechanism of catalytic degradation of pollutants by transition metal doped graphene-based TiO₂ ternary composite catalytic materials was proposed by free radical trapping experiments,in order to provide some reference and basis for practical application of photocatalytic technology.?1?Ultra-trace silver doped TiO₂ catalyst was prepared by"green"ultrasonic impregnation assisted photoreduction strategy and complete photoreduction of Ag⁺without using any reducing agent.The results show that all the obtained Ag/TiO₂catalysts have remarkable photocatalytic activity in reducing Cr?VI?compared with commercial P25 nanoparticles.The construction of Schottky energy base in Ag/TiO₂shows significant e^-/h⁺separation efficiency,which directly leads to the enhancement of the obvious photocatalytic performance.?2?A single layer of graphene oxide?GO?was prepared by the improved Hummers oxidation method,and the Ag/TiO₂/rGO ternary composite nano-catalytic materials were obtained by in situ ultrasonic impregnation and light reduction technology.The effects of various factors on the removal rate of simulated wastewater were investigated by using Cr?VI?heavy metals and tetracycline as target pollutants.The results showed that the photocatalytic activity of graphene ternary composite catalyst was significantly improved,the photocatalytic activity of Ag/TiO₂/rGO was4.3 and 2.5 times times higher than that of commercially available P25,and the removal efficiency was mainly influenced by pH value,and five cycle experiments showed that the efficiency of the photocatalyst was maintained at more than 80%.It is proved that the constructed electronic coupling system can effectively enhance the light absorption and improve the separation efficiency of e^-/h⁺,and has excellent photocatalytic activity.?3?In order to avoid the high cost of precious metal nanoparticles and improve the wide applicability of the products,this experiment will further use the first transition system metal as doped element?Mn,Fe,Cu,Ni?,with butyl titanate as the precursor through a one-step hydrothermal method to successfully prepare the chemical in situ composite TiO₂/rGO.A series of ternary composite materials of graphite-based titanium dioxide doped with transition metal were prepared by high temperature impregnation method.The experimental results show that the pure titanium ore phase TiO₂ nanoparticles grow in situ on graphene surface,and the doping of metal ions does not change the crystalline phase of TiO₂/rGO.In addition,tetracycline was used as the target pollutant system to explore the effects of various influencing factors on catalytic degradation tetracycline.The results show that the ternary composite can effectively enhance its photocatalytic activity,and the order of catalytic activity is Cu?II?>Fe?III?>Mn?II?>Ni?II?.