Preparation Of Composite Membrane Based On Graphene Oxide For Water Treatment

Graphene oxide（GO）,as a new type of two-dimensional nanomaterial,has an ultra-thin lamellar structure,good hydrophilic properties and excellent mechanical properties.It has great potential for the appliaction of membrane separation.It has great potential for the membrane separation,especially in the field of the water treatment.In this thesis,the ordered porous materials were inserted into the space between the GO layers to overcome the wide distribution and expension of GO layer spacing.Two composite membranes based on GO were prepared.A series of structure and morphology characterizations were carried out on these membrane materials,such as XRD,SEM,TEM,AFM,FTIR,TGA analysis,etc.On this basis,the Forward Osmosis（FO）and nanofiltration（NF）performance of these membrane materials were studied.The main research contents are described as follows:（1）Forward osmosis is an emerging membrane process driven by the osmotic pressure gradient for freshwater production.Low water flux,reverse solute diffusion,and membrane biofouling are three major issues affecting the FO performances,and the membrane material is one of the keys to solving them.The graphene oxide membrane exhibits high water flux,indicating its promising potential for application in the field of water purification.However,precisely control of the pore size of the GO membranes are necessary for efficient ion sieving.In this work,hydrophilic metal-organic framework（Ui O-66）nanoparticles,as the microporous fillers,are intercalated into the GO layers to form ultrathin"sandwich"membranes for improving the FO performances.The incorporated Ui O-66 introduces uniform and suitable nanochannels that can effectively allow water to permeate through,while hinder the solutes of Na⁺ions.Furthermore,the GO layers form the matrix of nanometer-thick membranes possess the antimicrobial activity（bacteriostasis of 90%）,which would prevent the biofouling.In the FO model,the Ui O-66/GO membrane exhibits a water flux of 29.16LMH,which was 270%higher than the pristine GO membrane,while the reverse solute diffusion was reduced by 83.5%（12.86 g MH）.（2）Nanofiltration technology has been widely used in industry,especially in water treatment,because of its economic,high efficiency and environmental protection.The nanofiltration membrane is driven by pressure,and the working pressure range is generally 0.5～2 MPa,which is significantly lower than the reverse osmosis membrane,thereby achieving an energy-saving and efficient operation process and greatly reducing the investment cost of the equipment.The characteristics of easy formation of film and functionalization of graphene oxide have made it a good promising candidate for the NF application.However,NF only by the interlayer spacing of GO results in a low retention capacity.Therefore,a COF-Tp Pa/GO nanofiltration membrane with improved performance was prepared by adding COF material with suitable pore diameter to graphene oxide.The experiment carried out a nanofiltration test on COF-Tp Pa/GO,and the results showed that:the COF-Tp Pa/GO membrane has excellent nanofiltration performance for organic dyes,the retention rate for crystal violet is as high as 98.90%,and the water flux is 78.89 Lm^-2h^-1bar^-1,the rejection rate for methylene blue is 97.05%,and the water flux is 57.76 Lm^-2h^-1bar^-1.The retention rate of composite membrane has been improved significantly compared with pure GO membrane.