Study On Photocatalytic Degradation Of Organic Wastewater By Nano-NG/TiO₂

Due to the rapid development of industry and agriculture in today’s society,many chemicals cause serious pollution to the water environment due to the abuse of chemicals and drugs and the inadequate disposal of waste water,some of which are difficult to degrade organic pollutants with complex chemical composition and the degradation effect of traditional methods is the same.Therefore,how to realize the effective degradation of refractory organic pollutants and reduce their pollution and harm has become a research hotspot in the field of environment.Among many semiconductor photocatalysts,TiO₂ has the characteristics of low cost,stable properties,environmental friendliness and so on,showing the most excellent performance.However,the development of TiO₂ is limited by its low quantum efficiency,poor adsorption capacity and poor utilization of sunlight.Graphene has a high conductivity and a large specific surface area,and because the atomic radius of N atom is similar to that of C atom,it can be doped as an electron donor,so nitrogen doped graphene（NG）can provide a carrier for TiO₂photogenerated electrons,reduce the recombination of photoexcited carriers,make the absorption range red shift,and improve photocatalytic activity,which is an excellent carrier for TiO2.In this paper,NG/TiO₂ composite photocatalyst was prepared by hydrothermal method,and characterized by XRD,SEM,TEM,XPS,Raman,BET,UV-Vis DRS and PL eight characterization methods.Taking methyl orange（MO）and acetochlor as the target pollutants,the photocatalytic properties of NG/TiO₂ were studied,and the factors influencing the degradation efficiency were analyzed.The main research contents are as follows:（1）Nano NG/TiO₂ composite photocatalyst was prepared by hydrothermal method with HF as the surface etchant and urea as the nitrogen source of NG.The characterization results show that:NG/TiO₂ composite is a pure anatase phase;the nano particle size is 43 nm;TiO₂ is hollow ball type,and some of the NG thin layers stack to form a multilayer structure;TiO₂ and NG are closely linked by chemical bonds;the specific surface area is large and the pore diameter is mainly 3.95 nm mesoporous structure;it has good response ability in the visible light region;photogenerated electron hole pair can be effectively separated.（2）The degradation efficiency of nano-sized NG/TiO₂ on MO and its influencing factors were studied by laboratory experiments.When the composite ratio is 7 wt%,the adsorption capacity of MO is the highest;when 0.1 g photocatalyst is added,the degradation efficiency of MO is the highest;the reaction conditions have great influence on the degradation efficiency,and the order of the efficiency is UV/H₂O₂>UV>Sunlight/H₂O₂>Sunlight according to the high to low order;the degradation efficiency of MO by different composite ratio of photocatalyst is different,the order of the high to low order is 5 wt%>7 wt%>9 wt%>3 wt%>1 wt%>pure TiO₂.（3）Under the condition of sunlight,the degradation efficiency of acetochlor by nano NG/TiO₂ and the influencing factors were studied in the laboratory.In a certain range of pH,the best degradation condition is pH=9,the amount of photocatalyst is 0.2g and the amount of H₂O₂ is 2 mL,the degradation efficiency of acetochlor solution is the highest,and the degradation rate of acetochlor can reach 92.33%after 240 min reaction in sunlight.