Preparation And Properties Of PSF-based Composite Membranes Based On Synergistic Modification Of GO And Electric Field

Membrane separation has become an important technology to deal with the global water crisis.Polymer-based membrane technology is currently at the forefront of water purification and desalination.However,there are still some bottlenecks in the preparation of hybrid membranes by adding inorganic nanomaterials to organic polymer membranes.Layered graphene oxide（GO）membrane has a single atomic layer structure,hydrophilicity,rich modified oxygen-containing groups,mechanical and chemical stability,antifouling,easy to mass-produce and other advantages.It is used in water purification and desalination.The aspect showed excellent advantages.Therefore,GO-based membrane technology is considered to provide a huge opportunity for efficient and practical water treatment.This project is based on the modified polysulfone（PSF）-based composite membrane of GO and electric field synergistically.The synergistic effect of GO and external DC electric field is used to change the surface morphology,hydrophilicity,surface electronegativity and surface roughness of the membrane to obtain high-efficiency separation efficiency.And organic polymer composite film with excellent antifouling performance.In this paper,GO/TiO₂ is prepared by loading titanium dioxide（TiO₂）on the surface of graphene oxide（GO）by a one-step hydrothermal method,and then a PSF mixed matrix ultrafiltration membrane containing GO/TiO₂ is prepared by a phase inversion method.Compared with the original PSF ultrafiltration membrane,the permeability and separation efficiency of the mixed matrix membrane have been improved,but it cannot reach a satisfactory level.In addition,since most of the GO/TiO₂ is inside the mixed matrix film and is covered by the polymer solution,it is difficult to observe its distribution in the mixed matrix film and its effect on the performance of the film.Therefore,this subject design uses an external direct current electric field（DC）to disperse GO/TiO₂ on the surface of the membrane through electrostatic repulsion.The modified membrane surface has more hydrophilic sites and has better hydrophilicity.In addition,The internal structure of the membrane becomes loose and porous,the water flux is significantly improved and the retention rate of bovine serum albumin（BSA）is higher.The modified membrane also has good antifouling performance and dye separation performance,the water flux recovery rate is above 90.0%,and the retention rate of Congo red dye is above 95%.Based on the above experimental ideas and considering that the surface of the nanofiltration membrane has a thinner interfacial composite layer,the modification of the interfacial layer by the above method should obtain a more significant effect.At the same time,considering that the presence of TiO₂ interferes with the particles of the polyamide（PA）layer formed by interfacial polymerization,it is impossible to better observe the surface of the interfacial layer.Therefore,only GO is selected as an additive to be dispersed in the water phase.In this project,GO is used to modify the interfacial polymer composite layer under the synergistic effect of an external electric field to obtain a modified composite nanofiltration membrane.The modified nanofiltration membrane has a Turing-like structure on the surface,which greatly increases the hydrophilic sites on the membrane surface.The hydrophilicity of the membrane surface is improved,and the water flux is significantly improved,up to 28.5 L·m^-2·h^-1·bar^-1.At the same time,due to the synergistic effect of the electric field and GO,the membrane surface is more negatively charged,with higher salt rejection and protein pollution resistance.