Preparation Of Graphene-based Composite Filter Membrane And Its Oil-water Separation Performance

The oily wastewater becomes a common pollutant in the living environment due to frequent oil leakage and oil spill accidents.It is imperative to develop low-cost and environmentally friendly oil-water separation materials and improve the separation efficiency.Graphene derivatives not only possess the structural characteristics and excellent properties of graphene,but also improve the dispersibility and poor wettability,making them ideal candidates for oil-water separation.In this paper,in order to solve the problems of low efficiency,high cost and complicated preparation of conventional oil-water separation materials,based on the surface wettability theory,three efficient and stable oil-water separation membranes are prepared by combining graphene-based materials with copper mesh and cotton substrate using physical and chemical methods.Their surface structure,wettability,oil-water separation capacity and stability under multiple cycles are analyzed.（1）Zinc oxide/polydopamine/graphene oxide（Zn O/PDA/GO）composite membranes are prepared on copper mesh substrates using magnetron sputtering,hydrothermal and vacuum extraction methods.Microstructural morphologies and wetting properties are characterized.These composite membranes have a laminar stacked structure and excellent hydrophilic/underwater superoleophobic properties with a water contact angle of 54.5°and a submerged oil contact angle of up to 153.0°.Based on gravity-driven oil-water separation experiments,it is found that the separation efficiency of the Zn O/PDA/GO composite membrane is above 99.2%for several oil-water mixtures,and the separation efficiency is greater than 97.8%after immersion in acid,alkali or neutral solutions,and the efficiency is still above 99.0%after 20 cycles of separation tests,indicating that the composite membrane has high efficiency of separation,excellent corrosion resistance and good cycling stability.（2）Micro-and nano-graded rough structured triiron tetraoxide/reduced graphene oxide/stearic acid（Fe₃O₄/RGO/SA）composite membranes are fabricated on cotton cloth by vacuum filtration and impregnation methods.The surface morphologies,crystal structures,infrared spectra and contact angle are tested to analyze the membrane structure and wettability properties.Compared with the original cotton,the composite membrane changed from superhydrophilic to superhydrophobic,with a contact angle as high as 156.1°,and have stable superhydrophobicity at different p H values.The oil-water separation experiments confirm that the separation efficiency of the membrane is higher than 98.4%for various oil-water mixtures,and the separation efficiency and flux test in 10 cycles show excellent stability,with the separation efficiency always above 98.0%.In addition,the membrane can absorb oil slick on the water surface by magnetic drive,which provides a new idea for contactless manipulation of oil removal.（3）Cerium oxide/graphene oxide/octadecylamine（Ce O₂/GO/ODA）composite membranes are synthesized on cotton cloth by hydrothermal and impregnation methods.The contact angle test show that the water contact angle of the composite membrane is increased from 0°to 151.3°compared with the original cotton cloth,which exhibits super hydrophobicity.Under the action of gravity,the Ce O₂/GO/ODA composite membrane can effectively separate a variety of oil-water mixtures with the separation efficiency higher than98.1%,among which the separation efficiency of petroleum ether/water mixture is up to98.7%.The separation efficiency can still be maintained more than 97.0%in 10 cycles without any significant decrease in flux,which indicates that it has stable recyclability.It provides a reference for the preparation of low-cost,efficient and durable graphene-based novel separation membranes.