Research On The Preparation And Performance Of Graphene-based Nanofiltration Membranes

Graphene is a perfect two-dimensional crystal,it has only a single layer of carbon atoms thickness.Due to its unique structural characteristics,it gives graphene excellent electrical conductivity,optical properties,mechanical properties,and thermal properties.Graphene has considerable value both theoretically and practically.In this paper,on the basis of graphene oxide,the following study was conducted:In this paper,graphene oxide was prepared by the modified Hummers method,and then graphene was prepared by using hydrazine hydrate as reducing agent.The structure properties of GO and graphene were characterized by TEM,SEM,UV-vis,FTIR,XRD and so on,it was found that graphene oxide has more oxygen-containing groups on the surface after oxidation.Graphene oxide can be better dispersed in water,and after the graphene is reduced,the dispersibility is worse than that of graphene oxide;after the graphene oxide is oxidized,the crystal structure also changes.After the reduction of graphene,the structure also changes.We added silver nanoparticles and silver nanowires to graphene oxide,in order to compare,we have prepared the different mass ratios of graphite oxide and silver nitrate.The silver nanoparticles can be homogeneously dispersed on the surface of the graphene sheet.The sample with the mass ratios 1:2of graphite oxide and silver nitrate has the best distribution of silver nanoparticles.As the mass of silver nitrate increases,the aggregation of silver nanoparticles tends to occur.Compared with silver nanoparticles,the distribution of silver nanowires on the graphene sheets is not uniform.Based on the previous chapter,the RGO–AgNP composite membranes were prepared by vacuum filtration.After SEM and FESEM tests,the average diameter of silver nanoparticles is around20-40 nm.The water flux of the RGO-AgNPs composite membrane is greater than the flux for the RGO membrane.For membranes prepared using the same concentration of AgNPs,increasing the thickness of the membrane reduces the water flux,water flux decreased from 280.7 to 14Lm^-2h^-1bar^-1.At the different concentration of AgNP and the same volume of the solution filtered,the greater higher concentrations of AgNPs used to prepare the membrane,result in greater water flux,water flux increased from 17.7 to 212.7Lm^-2h^-1bar^-1.Compared to the RGO membranes,the rejection is lower for the RGO-AgNP composite membranes,and decreases as the AgNP concentration increases,rejection rate reduced from 99.4 to 85%.At the same concentration of AgNP,the rejection rate decreases as the membrane thickness increases,rejection rate increased from 87.4 to 99.8%.In general,the rejection of rhodamine B by graphene-based membranes is in the range of 85-99.9%.