Preparation Of Superhydrophilic And Underwater Superoleophobic PVDF/GO/A-MWCNTs Biomimetic Composite Membrane And Study On Their Performance Of Oil-water Emulsion Separation

Offshore oil spills and industrial oily wastewater are a serious threat to the aquatic environment and human health.Therefore,the treatment of oily sewage has become a difficult concern.The traditional oil-water separation methods mainly include gravity separation method,adsorption separation method,chemical precipitation separation method,air flotation separation method,chemical oxidation separation method,biodegradation separation method,membrane separation method and so on.For the separation problem of oil-water emulsion,membrane separation technology is widely used due to its excellent performance,such as,separation effect,no secondary pollution,simple operation,low energy demand and controllable pore size.In recent years,with the development of interface science and bionics,filters with special wettability surfaces provide a faster and more efficient method for the separation of oil-water emulsions.In summary,based on the membrane separation technology,using polyvinylidene fluoride?PVDF?as the base membrane material,superhydrophilic and underwater superoleophobic PVDF/GO/A-MWCNTs biomimetic composite membranes with excellent properties were prepared by blending modification and surface modification were applied to oil-water emulsion separation.The details and results are as follows:?1?Graphene oxide?GO?and Multi-walled carbon nanotubes?MWCNTs?modified by 3-aminopropyltriethoxysilane?APTES?were doped with PVDF as the matrix material,and PVDF/GO/A-MWCNTs biomimetic blend membrane was successfully prepared.The effects of the content of A-MWCNTs on the surface structure and surface roughness of the blended membrane were investigated,and the best experimental conditions were determined.The wettability of the surface of the blend membrane was characterized,which had a water contact angle of 71^o in air and an underwater oil contact angle of 136^o.Through emulsion separation experiments,the flux of toluene/water emulsion separated by PVDF/GO/A-MWCNTs blending membrane reached 1863 L·m^-2·h^-1·bar^-1,and the separation efficiency reached 87.23%.?2?Using PVDF/GO/A-MWCNTs biomimetic blend membrane as the base membrane,the hydrophilic polymer polyvinylpyrrolidone?PVP?was adhered to the surface of the blend membrane by surface biodegradability using dopamine bioadhesive.The PVDF/GO/A-MWCNTs@PVP biomimetic composite membrane was successfully prepared.The effect of PVP content on the emulsion flux and separation efficiency of PVDF/GO/A-MWCNTs@PVP biomimetic composite membrane was studied,and the best experimental conditions were selected.The PVDF/GO/A-MWCNTs@PVP biomimetic composite film showed excellent properties of superhydrophilic and underwater superoleophobic oil?underwater oil contact angle was 153^o?,and the adhesion of the membrane surface to oil was greatly reduced.Studies have shown that after one-step modification,the emulsion flux was as high as 8962 L·m^-2·h^-1·bar^-1,and the separation efficiency was also improved from87.23%to 99.27%.After 8 cycles of separation experiments,the flux recovery rate of the PVDF/GO/A-MWCNTs@PVP biomimetic composite membrane was finally stabilized at about 70%in the cycle test.Experiments show that PVDF/GO/A-MWCNTs@PVP biomimetic composite membrane has excellent oil-water emulsion separation efficiency and good cycle regeneration performance.?3?PVDF/GO/A-MWCNTs biomimetic blend membrane was used as the base membrane.After self-polymerization of dopamine on the surface of the blend membrane to obtain a secondary platform,the chitosan was modified on the surface of the membrane by sol-gel method.PVDF/GO/A-MWCNTs@chitosan biomimetic composite membrane was successfully prepared.The effect of chitosan content on the wettability of the composite membrane surface was studied to determine the optimal experimental conditions.The surface morphology of the biomimetic composite membrane was characterized.The chemical composition of the biomimetic composite membrane was characterized.The PVDF/GO/A-MWCNTs@chitosan biomimetic composite membrane was proved to have excellent superhydrophilic and underwater superoleophobicity through contact angle test,underwater oil contact angle was up to163^o,and have a certain salt tolerance.Through separation experiments,it was proved that the flux of the membrane separation toluene/water emulsion was as high as 8465L·m^-2·h^-1·bar^-1,and the separation efficiency was 99.59%.After 15 cycles of separation experiments,the flux recovery rate was stable at 87%,and still possesses the ability of underwater superoleophobic.PVDF/GO/A-MWCNTs@chitosan biomimetic composite membrane showed outstanding oil-water emulsion separation,efficiency,excellent stain resistance and superior cycle regeneration performance reflect the feasibility of application in actual oil-water separation.