Preparation And Separation Performance Of Graphene-based Composite Nanofiltration Membranes

With the rapid development of social economy and industrial technology,a large number of pollutants have been generated and discharged into the natural environment,which has a significant impact on human life.Severe pollution caused by reactive dyes has become a problem of widespread concern.The thesis uses graphene,a membrane separation material with great application potential,as the starting point,and uses membrane separation technology and photocatalysis to separate wastewater.The work content of this paper is divided into three parts.First,the hydrophilicity tunable homogeneous structure material,hydroxylated graphene（GOH）as a nanosheet spacer intercalated into the GO layer to prepare GO/GOH composite film.The change of the water flux of the composite membrane and its influence on the typical dyes Rhodamine B（Rh B）and methyl orange（MO）rejection rate are discussed.Then,graphene oxide nanosheets of different sizes were prepared by an improved Hummers method,and silicon dioxide（Si O2）of different particle sizes was embedded between graphene oxide layers to prepare GO/Si O2 composite nanofiltration membranes and characterize them.Finally,on the basis of the above experiment and GOH nanosheets,the photocatalyst material,titanium dioxide（Ti O2）and hydroxylated graphene were used to prepare Ti O2/RGOH composite materials and dispersed and intercalated in GO nanosheets,successfully prepared A GO/TRH composite membrane with catalysis and separation was developed.This paper uses a variety of methods to characterize membrane materials and membrane performance,and discusses in detail the degradation performance of composite photocatalysts on dyes and the effect of composite membranes on dye separation performance.This article uses a variety of methods to characterize membrane materials and membrane properties.The specific conclusions of the experiment are as follows:（1）In the experiment,the GO/GOH composite membrane was successfully prepared by the method of vacuum filtration.After adding GOH,the retention effect on methyl orange（MO）,rhodamine（Rh B）and bovine serum albumin（BSA）was not significantly affected（>99.4）.At the same time,the pure water flux of the composite membrane was 3.6-4.5 times higher than that of the pure GO membrane,reaching22.7-26.5 L·m^-2·h^-1.（2）The smaller the size of the pure GO nanosheets added to the composite membrane,the higher the flux of the prepared membrane;when the composite membrane was prepared by mixing Si O2 with different particle sizes and GO,the smaller the particle size,the higher the water flux of the composite membrane.The pure water flux of the GO/Si O2 composite nanofiltration membrane prepared in this work can reach 72.8 L·m^-2·h^-1,and the rejection rate of methyl orange（MO）and rhodamine（Rh B）dyes was greater than 99.5%,Even after 8 cycles of recycling,the repellency rate of the membrane to the dye can still reach over 97.5%.（3）The T/RGOH composite photocatalyst material was successfully prepared,and its photocatalytic MB degradation efficiency was about 48.5%higher than that of pure Ti O2,and about 19.7%higher than that of Ti O2/reduced graphene oxide（T/RGO）nanocomposite photocatalyst.Secondly,the GO/TRH composite membrane was prepared by mixing the composite photocatalytic material with GO.The pure water flux of GO/TRH composite membrane can reach 47.8 L m^-2 h^-1.Under light,the rejection rate of the MB dye solution by the composite membrane running for 200min is still greater than 99%,which was due to the synergistic effect of photocatalysis and membrane separation.