The Study On Urban Sewage Purification Technology And Mechanism Of Graphene

According to the modified Hummers method,modified graphene dispersion was prepared firstly.Then the modified graphene film was prepared by the uniform coating,and the optimized process was determined.Methylene blue was used as a target to evaluate the photocatalytic activity of the modified graphene film under visible light irradiation,and the effect of different heat treatment processes on the photocatalytic performance of the modified graphene film was studied.Meanwhile its visible light photocatalytic principle was preliminarily revealed.Finally the modified graphene and its film photocatalytic purification applications of different urban sewage were also studied.The results are as follows:The modified graphene was prepared by the modified Hummers method,and its microscopic features were characterized by different instruments.The SEM showes a typical fold structure of graphene.The EDS spectra showes that the modified graphene has only C and O elements,and the atomic ratio of C/O is 2.12:1,indicating that there are a large number of oxygen functional groups in the modified graphene.The Raman spectrum showes that the I_D/I_G of the modified graphene is 0.973,indicating that the modified graphene is highly oxidized and exhibits very high activity.The modified graphene film was prepared by the uniform coating,and the effect of rotating speed,dropping time,acceleration,pH value on the film quality was studied.The optimized process of uniform coating is as follows:The pH value of the modified graphene dispersion is adjusted to 8.First,0.5mL modified graphene dispersion is used to wet the glass sheet for 30s which has been treated with hydrophilicity.Then,it sets the spin coater machine acceleration to 100r/?min·s?.After the gel has been started,by rotating the modified graphene dispersion whose dropping time is 20s at the low speed of800r/min for 60s,and then keeping the acceleration at 100r/?min·s?until it reaches the medium speed of 1500r/min,and holding at this speed for 30s.At last the modified graphene film is obtained after continuing rotating at the high speed of 4000r/min for 60s.Methylene blue as a target,the photocatalytic performance of the modified film was studied by the peristaltic pump cycle of the methylene blue solution on the film.It showes35.3%photocatalytic degradation under visible light irradiation.The catalytic principle of the modified graphene film is that the film generates a strong oxidant·OH in the visible light,which can gradually degrade methylene blue and other pollutants into carbon dioxide and water,and the purpose of degradation is ultimately achieved.Methylene blue as a target,the effect of vacuum reduction and air reduction on the photocatalytic performance of the modified graphene film was studied under visible light irradiation.With the increase of the heat treatment temperature,the deoxidized reduction reaction occurres on the surface of the modified graphene film,and the oxygen functional groups have been gradually removed.The atomic ratio of C/O in the EDS spectrum increases gradually,and the I_D/I_G in the Raman spectrum showes the same trend.Meanwhile the reaction rate constant of the modified graphene film decreases slowly,and its photocatalytic degradation ability of methylene blue also decreases accordingly.However,the photocatalytic degradation capacity of the vacuum heat treatment film is higher than that of the air heat treatment film at the same temperature.Modified graphene and its films show good purification effect for both urban aquaculture wastewater and reclaimed water,which has a bright photocatalytic application prospect in future.