Graphene Oxide-based Composite Membrane For Water Treatment

The shortage of water resources and water pollution are difficulties and challenges in the world.Using membrane separation technology to convert wastewater into available fresh water can effectively alleviate water crisis.Nanomembranes,especially graphene oxide-based nanomembranes,have attracted much attention due to their nano-scale size and channels,which can sieve macromolecular materials.Graphene oxide?GO?membranes are composed of nanosheets with unique atomic thickness and water molecules can pass through GO membrane without hindrance,which make GO membrane be ideal for water treatment.However,GO membranes can not be applied on a large scale because of its low water flux and poor anti-pressure ability.Although researchers have prepared a variety of GO-based composite membranes with different nano-channel sizes to improve water flux,the anti-pressure ability of GO-based composite membrane has still not been improved.In this paper,to solve the above problems,the GO-based composite membrane with high water flux,high rejection and excellent anti-pressure ability was obtained by intercalating two-dimensional rigid graphite phase carbon nitride?g-C₃N₄?nanosheets into GO nanosheets.In addition,the composite of nanomaterials with different dimensions was proposed.Two-dimensional GO nanosheets were inserted into one-dimensional nanocellulose whiskers?CNC?,so as to improve the rejection and anti-pollution performance of the composite membrane.The specific contents of this paper are as follows:?1?By preparing two-dimensional graphitic carbon nitride?g-C₃N₄?nanosheet-intercalated GO membranes?GOCNs?,the amount of permeable nanochannels?wrinkles or corrugation?in the membrane increased,besides,g-C₃N₄ nanosheets have numerous nanopores and thus do not hinder water transport.Hence,the water permeance was effectively improved?twice as high as that of GO membranes?.Moreover,as GO layers are supported by rigid g-C₃N₄ nanosheet,the rigidity and stability of the nanochannels are enhanced,the water flux and pressure maintain a linear relationship even at the pressure of 0.5MPa.The anti-pressure ability of the GOCN membranes was significantly enhanced.?2?CNC-GO composite membranes were prepared by combining two-dimensional GO nanosheets with one-dimensional nanocellulose whiskers?CNC?.Due to the large lateral size,the lamellar structure and atomic level thickness of GO nanosheets,the irregular and fluffy channels formed by rod-like CNC can be improved,thus the rejection rate of CNC membranes for Evans blue molecules can be increased by 15%.In addition,the insertion of GO nanosheets increased the number of oxygen-containing functional groups,enhanced hydrophilicity,and improved the anti-pollution performance and chemical stability of composite membrane.