Research On The Prepartion And Photocatalytic Activity Of TiO₂-C Composite

TiO₂ is widely known to be the best photocatalyst due to its high photocatalytic activity,chemical inertness,eco-friendly nature,resistance to photocorrosion, photostability,low cost.It can make pesticide residue,dye,industrial sewage,medical sewage,waste water of paper mill and so on to be decolourization,degradation,detoxifcation,mineralization,then changed to be small inorganic molecules.However,because of its large band gap of 3.20 eV only the small UV fraction of solar light(about 2-5%),can be utilized.And the recycling of photocatalyst is very difficult.Therefore,many attempts have been made to sentilize titanium dioxide for much larger visible fraction.For example,there were many reports about doping or composite preparation.It's very important to realize the industralization of the organic wastewater's treatment by photocatalytic degradation.For achieving the objective,we have fabricated the TiO₂-C composite.The composites were characterized by X-ray diffraction(XRD),differential scanning calorimetry and thermal gravimetric analysis(DSC-TG),UV-Vis diffuse reflection spectrum(DRS),transmission electron microscope(TEM),scan electronic microscopy (SEM and EDS),XPS analysis and so on.The XRD results indicated that the composites consist of carbon and anatase phases.UV-Vis DRS showed that composites not only have a good performance in the ultraviolet region,but also have a very good performance in the visible light region.And then,we have made the experiment of photocatalysis degradation of methyl orange and reactive brilliant red X-3B to survey and evaluate the photocatalytic activity of TiO₂-C composite sample.Photocatalysis degradations of methyl orange with purity nano-TiO₂ and TiO₂-C composite were tested.After methyl orange and reactive brilliant red X-3B liquid was illuminated for 1 hour,the decolorization ratio can be up to 98.9%at the most. The TiO₂-C composites have much better photocatalytic activity then nano-TiO₂ powders under any circumstances(UV or solar light,quartz beaker or glass breaker). Under the ultraviolet ray(UV) irradiation,the catalytic effect of TiO₂-C composite' are more excellent than the nano-TiO₂ powder and activated carbon.Methyl orange ultraviolet photochemical catalysis experimental result indicated that TiO₂-C composite's decolorization have achieved 98.9%at the most after 1 hour later,but the nanometer TiO₂ powder and the activated carbon respectively only were 25%and 10%(glass beaker).Under the condition of visible light(indoor) shines,the TiO₂-C compound materials have more outstanding catalyzed effect compared to the nanometer TiO₂ powder,too.In the quartz beaker,joined the TiO₂-C composite and the visible light shined one hour later reactive brilliant red X-3B and the methyl orange solution,the decolorization of TiO₂-C composite materials respectively have achieved 96.3%and 98.7%;Under the same condition,after joining the nano-TiO₂ powder's decolorization respectively were 34.7%and 66.9%only.Another discovery is that the efficiency was raised with the increase of photocatalyst(TiO₂-C composite or nano-TiO₂ powders)——at least in the range of 1.0g/l—2.5g/l.The suppression of the phase transformation from anatase to rutile by carbon gives certain advantages to the composite,conducting to increase the photocatalytic activity of TiO₂-C.The carbonaceous materials can absorb visible light so that the TiO₂-C composite materials have higher photocatalytic activity.It was reported that the doping vario-property of carbon atom generated OH-radical by visible light's excitation.TiO₂ and the activated carbon's intergranulars which are coexistent have produced the close laying surface,have accelerated the degeneration and the migration of organic matter to TiO₂ surface,and cause the product to be rapidly separated from the TiO₂ grains' surface possibly.It's said that TiO₂ and the activated carbon's synergy can reduce the middle by-product density,adsorb goal pollutant, and raise the mineralization rate and the photocatalysis rate.Through the carbon film coated on the TiO₂ catalyst,there were produced a valence band close to the surface state,and formed free hydroxyl by the visible light excitation,all these can improve the TiO₂-C composite materials' catalytic activity under the visible light.