Preparation And Properties Of Oil-Water Separation Composite Membrane Based On Metal Oxides Coated Stainless Steel Mesh

Traditional separation processes,such as distillation and flash distillation,are gradually replaced by more energy efficient separation processes due to excessive energy consumption in heating and cooling processes.For example,membrane separation progress with room temperature,gravity-driven,simple operation and low energy consumption has been paid more and more attention.Superhydrophilic and superhydrophobic oil-water separation membranes have become a hot research direction in the oil-water separation field due to their advantages of good versatility,high separation efficiency and strong oil-pollution resistance,which can be achieved by establishing micro-nano hierarchical structures on the surface of different substrate to regulate the surface roughness and low surface energy.In this paper,"water removing"low-surface-energy polymer composite membrane and in-situ metal oxide coated mesh membrane were prepared and studied based on stainless steel mesh with excellent mechanical properties.The main research contents and results are as follows:（1）A low-surface-energy polymer composite membrane was constructed.With cationic polymer（PDADMAC）as binder,doping different ratios of aerosol silica（SiO₂）and graphene oxide（GO）mixed nanomaterials,and then positively charged PDADMAC alternately assembled with perfluorooctanoic acid anion（PFO）by the strong electrostatic interaction.The PDADMAC-PFO/GO&SiO₂ composites were prepared and modified on stainless steel mesh by dip coating,and their surface morphology,chemical composition,wettability and oil/water separation performance were characterized.Results show that film coated with PDADMAC-PFO/GO has the fastest water-response hydrophilicity,and the contact angle of vegetable oil reaches up to 126°,shows low oil adhesion.And film coated with PDADMAC-PFO/GO shows the highest flux of 1875 L·m^-2h^-1,separation efficiency of 94.9%,has good oil-water separation ability.Although the GO of the flake structure did not significantly improve the surface roughness,its hydrophilicity also improved the oil-water separation performance.（2）A low-surface-energy polymer composite membrane was constructed.For more hierarchical structure,rambutan-like poly（styrene-acrylic acid）-α-Fe₂O₃（PAF）mixed with SiO₂ in different ratio to prepare of PDADMAC-PFO/PAF&SiO₂ composites,then modified on stainless steel mesh by dip-coating method.The surface morphology,chemical composition,wettability and oil/water separation properties were characterized.Results show that PDADMAC-PFO/PAF&SiO₂（1:1）modified 600 mesh has good water-response hydrophilic and oleophobic properties for several kinds of oil.Contact angle of vegetable oil is 130.3°in the air.When ratio of PAF and SiO₂ were 1:1,the highest water flux of coated mesh is 2585 L·m^-2h^-1,and the separation efficiency is 96.5%.The hydrophilic and oleophobic properties of FeCl₃ etched 600 mesh membranes are slightly improved.It also has a higher water flux of 2724 L·m^-2h^-1,and the oil-water separation efficiency is 96.5%.Combined with the SEM results,the holes of mesh increase after etched,improving the surface roughness,and the doping of PAF improves the hydrophilicity and oil-water separation performance.（3）An in-situ metal oxide micro-nano composite membrane was constructed.Tussock-like micro/nano hierarchical structure of ZnCo₂O₄ was grown on stainless steel mesh by hydrothermal method and calcination.The surface morphology,chemical composition,wettability,oil/water separation property,mechanical stability and stability were studied.Results show that the concentration of Co（NO₃）₂·6H₂O and Zn（NO₃）₂·6H₂O are 0.05 mol/L and 0.025 mol/L,autoclave heated and maintained at 120℃for 6 h,annealing performed at 400℃for 3 h as the best technique.Flux of water of ZnCo₂O₄coated mesh can reach 12485 L·m^-2h^-1,separation efficiency is 98%.Flux and separation efficiency remain above 8819 L·m^-2h^-11 and 96.6%after 5 cycles.ZnCo₂O₄-coated mesh shows superhydropilicity and under water superoleophobicity for several kinds of oil.The ZnCo₂O₄-coated mesh has excellent alkali and salt corrosion resistance,mechanical stability and low under water oil-adhension.Comparing the three strategies,a general conclusion has been made that the flux of water and separation efficiency of ZnCo₂O₄-coated membrane are higher than those of the membrane modified by immersion coating.Although ZnCo₂O₄-coated membrane can not show oleophobic in air,it also has excellent underwater superoileophobic and anti-oilfouling properties,which shows better performance.