Reduced Graphene Oxide ?rGo? Decorated TiO₂ Microspheres For Visible-light Photocatalytic Reduction Of Cr???

In recent decades,the use of semiconductor photocatalyst to degradation of pollutants increasingly aroused people's concern.And in more photocatalytic system,using visible light to degrade pollutants,especially the reduction of heavy metal ions in water is still a big challenge.For industrial waste water treatment,removing heavy metal pollutants has become a huge challenge.Chromium is a common heavy metal pollutant in waste water,in fact,the presence of chromium elements mainly has two forms,namely the Cr???and Cr???.However,Cr???has minimal damage to human cells,Cr???has a strong toxicity to humans and animals or plants.According to reports,Cr???has a strong carcinogenic and very high mobility in the environment,so for the removing of Cr???whatever is needed.Deal with a lot of methods of heavy metal pollution,such as ion exchange,physical adsorption,electrochemicalreduction,chemicalprecipitation,etc.However,these technologies will need elaborate apparatus and a large number of chemicals,and in the process can produce secondary pollution to the environment.Recently,the use of semiconductor heterojunction photocatalyst has become for dealing with water pollution,more economic and simple method,especially in the low concentration of heavy metal pollutants in particularly.Titanium dioxide,possessing an outstanding performance of photocatalytic response,is a kind of the most widespread research and an in-depth semiconductor material in the field of photocatalysis.At the same time,The researching of new crystal structure,finding new morphology,the using of different composite or doping methods of titanium dioxide to improve the photocatalytic performance is the mainstream of the present research direction in the future.But its forbidden band is very wide,normally only absorbs relatively short wavelengths,unable to effectively utilize the sunlight.In addition,the photoexcitation electron-hole of TiO₂ has a high recombination risk,further reducing the photocatalytic properties of TiO₂,it is also amain reason for the none extensive use TiO₂ in actual application of the semiconductor material.So,the researchers have adopted various methods to improve the photocatalytic performance of TiO₂ has been reported as C,N and S elements doping titanium dioxide,deposition of heavy metal ions in the surface of titanium dioxide,compound with some narrow band gap semiconductor and so on,these are all effective measures to improve the performance of TiO₂ photocatalyst.In addition,TiO₂ compound with graphite carbon composite material,especially with graphene synthesis of composite material showed high photocatalytic activity.Because the graphene can promote carrier separation and the migration of electronic,broaden the range of light absorption and graphene has large specific surface area.Aiming at this problem,this article using titanium sulfate as the raw material,using solvent hot method to obtain the titanium dioxide nano-ball.And then using the hydrothermal preparation to obtain the TiO₂/reduction of graphene oxide composite materials.And under the condition of visible light,discussed the reduction oxidation graphene proportion in the composite material how to influence the light catalytic reduction of Cr???.The main contents are as follows:With the graphite powder as raw material,adopting the improved Hummers to oxidize graphite powder into a single layer or layers structure of graphite oxide.Using solvent hot method,with the aid of the surfactant CTAB prepared a strawberry structure of TiO₂ nano-ball.Results show that the obtained TiO₂ nanometer ball belongs to the typical anatase type,particle size in 300-400 nm,and each spherical TiO₂ polymerized by smaller particles from 20 nm to 30 nm.On the basis of the above experiment,adding a certain amount of titanium dioxide and graphene oxide to water and ethanol mixed solution,prepared by hydrothermal method to obtain TiO2/reduced graphene oxide composite material.By adjusting the addition amount of graphene oxide,preparation the TiO₂/reduced graphene oxidecomposite material of different Content of graphene.Test results show that the morphology of TiO₂ is still before,the graphene successed uniform load on TiO₂ nanometer ball surface.At the same time,the addition of graphene makes the forbidden band of titanium dioxide drops to 2.69eV,specific surface area from 62.42 m²/g increases to 85.023 m²/g,and effectively restrains the recombination of electrons and holes.Photocatalytic reduction of Cr???experiments show that the effect of composite material is better than commercial P25,the photocatalytic reduction efficiency of Cr???was 98%within 180 min,illustrate that the composition of graphene composite can effectively improve the photocatalytic performance of TiO₂.