Preparation, Characterization And Application Of Novel Titanium Dioxide Visible Light Catalysts

As water pollution of environmental problems increasingly serious,environmental protection has become a global initiative.Photocatalytic degradation has also become the research hot technology in the world.TiO₂ is studied widely among all the semiconductors,due to its outstanding physical and chemical stability,inexpensiveness,non-toxicity and appropriate electronic band structure.However,TiO₂ can only be inspired by 4%?6%ultraviolet light??365 nm?in sunlight because of its larger band-gap??3.2eV?,thus to lower the rates of utilization of visible light.In addition,the efficiency of photoquantum is low due to the recombination of photo-induced electrons and holes.Beyond that powder catalyst are recycled difficultly.Based on the above factors,in order to reduce the width of band gap,silver doped TiO₂ visible light response photocatalyst was prepared using silver nitrate as silver source in the paper,thus to reduce optical electronic-hole recombination rate,so that to expand the application scope of TiO₂.The main detailed content of study as followed:?1?PPy-Ag coated TiO₂?denoted as PPy-Ag/TiO₂?was fabricated via PPy-Ag hybrid layer coating on the surface of TiO₂ by a chemical redox polymerization approach using silver nitrate as silver source,polypyrrole?PPy?as the middle template and degussa TiO₂ as matrix;Ag/TiO₂??40 nm?was further collected after removing PPy-assisted template by calcination.The microstructure,composition and photocatalytic activity of photocatalysts were investigated by inductively coupled plasma atomic emission spectrometer?ICP-AES?,field-emission scanning electron microscopy?FESEM?and transmission electron microscopy?TEM?,X-ray powder diffraction analyses?XRD?,Fourier transform infrared spectroscopy?FTIR?,X-ray photoelectron spectroscopy?XPS?,UV-visible absorption spectroscopy and thermogravimetric analysis?TG?.The results reveal that Ag/TiO₂ NPs have a lower energy band?2.95 eV?than core-shell PPy-Ag/TiO₂?3.06 eV?.The removal efficiency for MB can reach up to 90%and for RhB removal efficiency is 75%in 3 h visible light irradiation.In addition,the results reveal that Ag/TiO₂ could degraded oil/water emulsion under visible light irradiation,after 5 h irradiation,the size of oil drop became small and the color of oil/water emulsion changed from oyster white to colorless gradually in the presence of Ag/TiO₂ NPs.The removal efficiency was up to 80%,which could realize harmless treatment of oil/water emulsion.?2?Fiber photocatalyst was prepared by a co-dispersion solution dip-coating method and fabric was prepared with small sample loom,in order to solve the problem of powder catalyst recycled difficultly.A designated amount of Ag/TiO₂ was dispersed into DMSO and EtOH mixed solution?volume ratios 80/20?at a concentration of 0.05 g/L by ultra-sonication for 30 min.PAN filaments were un-winded from a bobbin and dipped in the Ag/TiO₂ dispersion bath.The filaments were then drawn into a coagulation bath?H2O?at a constant speed of 0.5 m/min.After removing residual solvent and polymer solidification,Ag/TiO₂ NPs were immobilized onto the surface of PAN fibers.The fiber photocatalyst was woven into the fabric by small sample loom.The micro structure,composition and photocatalytic activity of Ag/TiO₂-coated PAN fiber was investigated by field-emission scanning electron microscopy?FESEM?,fourier transform infrared spectroscopy?FTIR?and thermogravimetric analysis?TG?.The results reveal that Ag/TiO₂ particles have been successfully coated on the surface of PAN fiber and the amount of load is about 14.2%.The fabric of the cleaning effect is perfect.The photocatalytic performance of Ag/TiO₂-coated PAN fiber was investigated by removal efficiency of MB and RhB solution under visible light irradiation irradiation.The results reveal that 50%of removal efficiency of MB was removed after 3 h under visible light irradiation.Moreover,Ag/TiO₂-coated PAN fiber maintain the degradation efficiency to be 48%after 5 cycles,showing an excellent reusability.?3?After preliminary experiment,it found that Ag/TiO₂ particles were been coated on the surface of substrate?PAN fiber?directly,causing damage to the PAN fiber microstructure.Based on the reason,using ethyl silicate as silicon source,SiO₂@void@Ag/TiO₂ photocatalyst porous hollow nano composite microspheres were preparated by sol-gel method,in order to protect the substrate.The microstructure,composition and photocatalytic activity of SiO₂@void@Ag/TiO₂ was studied by XRD,FTIR,UV-Vis DRS,TG and visible-light catalytic degradation of RhB.