Preparation And Application Research Of GO-Based Selective Separation Membrane

Graphene,a two-dimensional material（2D）,is known as the"material of the future"due to its excellent conductivity and mechanical strength.Graphene oxide（GO）,an important derivative of graphene,has good hydrophilicity due to the abundant oxygen-containing functional groups on its surface and edges.By controlling the interlayer spacing of the GO membrane material and modifying the surface charge of the membrane,selective separation of a certain component（molecule or ion）can be achieved.However,nanofiltration（NF）membranes commonly face the problem of permeability-selectivity,making it challenging to achieve high selectivity while maintaining high water flux.This paper aims to prepare membrane materials using graphene oxide as raw material to achieve selective separation of a certain component.It also attempts to address the trade-off between high water flux and high selectivity.The research focuses on the following three aspects:（1）The large-area monolayer graphene oxide nanosheets were prepared using an modified Hummers method,and the graphene oxide water dispersion was obtained by ultrasonic dispersion.Membranes with different thicknesses were prepared by vacuum filtration.The GO membrane was successfully used for the rejection of dye molecules（MB、CV and OG）.The rejection rates of dye molecules by graphene oxide membrane reached 100%at the optimal membrane thickness.However,the water flux of unmodified graphene oxide membrane is relatively low,and the p H has a certain effect on the water flux of the membrane.The swelling effect of graphene oxide membrane material can cause the membrane to disperse and rupture,resulting in a weaker resistance to strong acids and bases.（2）In order to further optimize the performance of GO membranes,this work prepared graphene oxide-ethylene diamine（GO-EDA）composite cross-linked membrane.EDA was used as a reducing agent and cross-linking agent,and GO was partially reduced to reduced graphene oxide（r GO）by chemical reduction,resulting in the presence of both GO and r GO in the formed GO-EDA cross-linked membrane.The originally wrinkled surface of the GO membrane became flat,reducing water resistance.EDA successfully cross-linked the layers inside the membrane through amide reaction,not only increasing the d-spacing and enhancing the stability of the membrane material,but also increasing the water flux of the membrane by more than 3 times compared to GO membrane.The composited membrane successfully achieved the selective separation of orange G through the synergistic effect of adsorption,charge,and size exclusion.This work is not limited to the removal of dyes,but has great potential for application in the dyes treatment and recovery in the printing and dyeing industry.（3）Based on the exploration of the preparation process of the（2）composited membrane,this work employed an extended reaction time to prepare an improved GO-EDA crosslinked membrane material.The d-spacing of the membrane material was further reduced.To address the issue of the reduced water flux caused by the decrease in interlayer spacing,this work reduced the thickness of the membrane material.Under the effects of size exclusion and charge exclusion,this membrane exhibited a significant trend in Li⁺/Mg²⁺separation,with a separation factor of 3.03.In addition,this work also explored the selective separation of Li⁺/Na⁺and Li⁺/K⁺.The separation factors of Li⁺/Na⁺and Li⁺/K⁺were 1.32 and 1.65,respectively.This composite membrane material has great potential for application in ion selective separation.