Graphene Oxide And Its Composite Membrane Preparation Process And Dye Separation Application

Graphene,a carbon-based material,has a two-dimensional layered structure with a single atomic layer thickness.Graphene oxide(GO)is one of the main derivatives of graphene,which has a skeleton structure similar to graphene and contains a large number of oxygen-containing functional groups on the edge.It not only endows GO excellent hydrophilicity,but also the electronegativity due to deprotonation effect of-COOH.Moreover,GO membrane has abundant chemical reaction sites for its modification.Although GO membrane has many advantages in water treatment,the permeability of GO membranes is uncertain.It's described inconsistently from different literatures,due to the methods and conditions they employed were different.Therefore,we must discuss factors which affect the permeability of GO membrane in detail.Moreover,GO membrane is unstable in water and has poor separation performance,which limits its practical application.Hence,seeking for a suitable modification method is prerequisite for putting GO membrane into practical application.In this study,we selected vacuum filtration to prepare GO membrane on mixed cellulose support membrane.The effect of different conditions include ultrasonic time,GO oxidation degree,concentration and pH of GO dispersion and feed solution on the nanofiltration performance were discussed in detail.As a consequence we obtained the optimal conditions of preparing GO membrane.In order to further improve the stability and retention for dyes of GO membrane,we chose methylene blue(MB)as a modifier and prepared GO/MB composite membrane by blending method.MB combined GO through ?-? conjugation and electrostatic adsorption,which not only adjusted inter-layer structure of membrane,but also enhanced the stability of GO/MB membrane.Moreover,the retention for different dyes was improved obviously.Studies showed that rejection of 1 g·L-1 sodium sulfate solution by GO membrane was up to 92%with the secondary osmosis device.The rejection of methyl orange,disperse black 9 and rhodamine B dyes rejected by GO/MB membrane was 93.32%,99.85%and 82.56%,respectively,indicating GO/MB membrane had good application prospects in water treatment.In addition,we also discussed the influences of charge,molecular weight,molecular structure of dyes and the interaction between dyes and composite membrane on the retention performance in detail,which laid the foundation for the research of dyes separation.