Modification Of Graphitic Carbon Nitride And Its Photocatalytic Degradation Of Organic Pollutants

Solar energy as a clean energy source has received more and more attention.But in most cases,solar energy cannot be directly used,and only can be converted into other forms of energy via media.Semiconductor is a type of material between insulator and conductor that absorbs sunlight to produce a redox-active substance and further converts it into other forms of energy.Graphite carbon nitride(g-C3N4)is such a semiconductor,which is applied in the field of visible light photocatalysis due to its suitable forbidden band width and special properties.However,the lower specific surface area of g-C3N4 and the higher photogenerated electron-hole recombination rate seriously restrict its photocatalytic activity.Therefore,g-C3N4 is suggested to be modified to improve its absorption efficiency for sunlight.It can expand its application field and have the economic and social value of practical application.In this paper,two types of g-C3N4 based photocatalysts,Na doped g-C3N4 and protonated g-O3N4 coating MIL-100(Fe)was designed and prepared.The photocatalytic activity of Na doped g-C3N4 in oxidative removal of pyridine and thiophene in fuel under visible light irradiation was investigated.The protonated g-C3N4 coated MIL-100(Fe)framework was used to treat rhodamine B(Rh B)and Methylene Blue(MB)in wastewater.Effects of Na doping and coating process on photocatalytic activity of the g-C3N4 based photocatalysts for dyes degradation and oxidative removal of pyridine in fuel were investigated.The g-C3N4 was first modified with Na doping.Na-doped g-C3N4 nanosheets were obtained by calcining the mixture using NaCl as the Na source and melamine as the precursor.The structure,photophysical and chemical properties of the nanosheets were characterized.Na-doped g-C3N4 exhibits enhanced catalytic activity in both photocatalytic oxidative denitrification and desulfurization.The optimum ratio of Na-doped g-C3N4 was optimized.When the mass ratio of NaCl to melamine was 0.3 and 0.5,respectively,the prepared catalyst obtained the maximum removal amount of pyridine and thiophene,and the removal of pyridine and thiophene.The amounts reached 333.6 and 373.7 ?g·g-1,respectively.The mechanism of denitrification and desulfurization of Na-doped g-C3N4 photocatalytic fuel was proposed.Hot concentrated nitric acid as a protonating reagent can achieve protonation of g-C3N4 for coating g-C3N4 on the surface of MIL-100(Fe).The structure,photochemical and physical properties of the novel hybrid photocatalysts were characterized.The optimum material maintains the complete skeletal structure,the surface and pores properties,and the inherent structural and physicochemical properties of MIL-100(Fe).Protonated g-C3N4 coated MIL-100(Fe)material exhibits enhanced degradation of Rh B or MB dyes and oxidative denitrification of pyridine by molecular oxygen under visible light compared to pure support materials Photocatalytic activity.The degradation rates of Rh B and MB dyes were 86.9%and 82.4%,respectively,and the removal of pyridine exceeded 400 ?g·g-1.In addition,Photocatalytic conversion of the three pollutants follows different mechanisms.Compared with pure g-C3N4 and MIL-100(Fe),the photocatalytic performance of Na-doped g-C3N4 and protonated g-C3N4 coated MIL-100(Fe)is significantly improved,which is beneficial to improve the photocatalyst pair.The utilization of sunlight also provides a simple and feasible solution for the preparation of highly catalytically active semiconductor materials.