Modification And Property Of Forward Osmosis Membrane With GO

Forward osmosis(FO)is an emerging membrane process with potential applications in the seawater desalination and wastewater treatment since its process requires a very low hydraulic pressure,less energy input,and lower fouling tendency.This thesis using cellulose triacetate(CTA)prepared FO membrane,and then the membrane was modified by graphene oxide(GO).The membrane structure and properties were investigated.Also,the potential application in desalination and concentrating sewage were tested.The effects of CTA content,relatively humidity,coagulation bath temperature and the mesh of support layer for the best membrane preparation conditions were investigated.And the optimum conditions were-8wt%,200 mesh of support layer,70%relatively humidity and 30? coagulation bath.The optimized membrane showed 15.0L/m2.h water flux and 96%salt rejection using FS of 0.1M NaCI solution and a DS of 2M glucose solution.Surface and cross-section images of FO membrane were observed by SEM.The optimized membrane has typical asymmetric structure,dense top surface.Meanwhile,cross-section image reveals finger-like voids near the top.The prepared GO was confirmed by FTIR,TEM and XRD,which presence of carboxyl and carbonyl groups,a thin and laminar structure were observed in GO.This study developes GO as modification agent added into casting solution.Due to the hydrophilicity of GO,it could increase the thermodynamic incompatibility between polymer and the solvent or the agglomeration of GO in casting solution.So in this study a new method was developed to uniformly disperse GO into the CTA membrane casting solution with addition of dimethylacetamide(DMAC)to the conventional CTA solvent.This method improved the miscibility of casting solution and solved the usual aggregation problem due to direct blending GO in the CTA membrane casting solution.When the content of DMAC was 40wt%,the compatibility of GO blending casting solution was best.GO was blended into casting solution.Also the effect of GO content on the membrane structure,contact angle and permeability were investigated.It is found that even with very small amount(-0.15wt%)of GO addition,modified membrane exhibited superior property in term of hydrophilicity,membrane structure,permeability,and meachanical properties,which low contact angle,more and large finger-like voids,high water flux and salt rejection were achieved.And the maximum water flux of the modified membrane reached to 25.2L/m2.h and 96%salt rejection using FS of 0.1M NaCl solution and a DS of 2M glucose solution.In order to test the fouling resistance of membranes,the BSA adsorption and separation experiments were conducted.Due to the hydrophilicity of GO,CTA/GO membrane exhibits lowest BSA absorption.And it presented higher flux recovery ratio and lower flux decline rate than pure membrane.At last,the FO membrane was used for desalination and concentrating sewage,which 0.5M NaCl solution was used as FS and different content of glucose solution,sucrose solution and fructose solution were as DS in desaliantion.The sewage was used for concentrating sewage from the river near the school.It was found that sucrose solution was more fit used as nutrition draw solution in desalination,which the stable flux was 24.4L/m2.h and 96%salt rejection.The water flux,rejection and pollution characteristic of contaminants on membrane surface were analyzed in concentrating sewage,which CTA/GO membrane showed lighter polluting than unmodified membrane and the rejection of TOC,NH3-N and TP were 88.9%,80.9%and 65.8%.Also membrane fouling is mainly losseded cake layer formed in the membrane surface.