Preparation And Properties Of PVDF-g-PEGMA/PVDF/CNTs Membranes

Because of the excellent physical and chemical properties of polyvinylidene fluoride film?PVDF?film,such as good mechanical properties,good toughness,good chemical stability,and not easy to be corroded by acids and alkalis,it has been widely used at home and abroad.However,PVDF membrane is relatively hydrophobic and its flux is not high,which greatly limits its application in water treatment process.At present,the main problems in water treatment applications are:first,the water flux in the water treatment process is low,and increasing the external membrane pressure can only increase the water flux of the membrane to a certain extent,which not only increases the operating cost And the effect is not very ideal;secondly,during the water treatment process,organic pollutants such as proteins will be adsorbed on the surface of the membrane or in the membrane pores,which is more likely to cause pollution,shorten the membrane life cycle,and increase the cleaning cost;finally,the low mechanical strength of PVDF membranes results in a low membrane life.Therefore,physical or chemical modification of PVDF membranes is necessary to improve membrane hydrophilicity,antifouling properties and mechanical strength.First,the effects of organic and inorganic coagulation baths on the structure and properties of self-made hydrophilic PVDF-g-PEGMA/PVDF membranes were investigated.Inorganic coagulation baths represented by sodium chloride and organic coagulation baths represented by ethanol were selected as non-solvent coagulation baths.The effects of organic and inorganic coagulation baths on the chemical composition?membrane pore size?membrane flux and antifouling performance of membrane surfaces were studied.The influence of hydrophilic functional groups on the structure and properties of self-made hydrophilic PVDF-g-PEGMA/PVDF/CNTs membranes was studied.Carbon nanotubes containing four different functional groups-COOH?-OH?-NH₂and-O⁺were selected as additives to prepare PVDF-g-PEGMA/PVDF/CNTs membranes.The effects of carbon nanotubes with different functional groups on membrane structure and membrane pore size were studied.,Flux,etc.Finally,taking PVDF-g-PEGMA/PVDF/CNTs-COOH membrane as an example,the adsorption performance of bovine serum protein was studied.The main conclusions of this study are obtained through the above experiments:?1?In this study,sodium chloride and ethanol coagulation baths were selected as non-solvent coagulation baths.The effects of inorganic and organic coagulation baths on the structure and properties of PVDF-g-PEGMA/PVDF membranes were investigated.The results show that the sodium chloride coagulation bath makes the membrane more inclined to form molecules of the?crystal form,while the ethanol coagulation bath makes the membrane more inclined to form molecules of the?crystal form;the sodium chloride coagulation bath makes the film surface hydrophilic.The angle was reduced to 64.5°,while the ethanol coagulation bath made the membrane surface hydrophilic,and the contact angle increased to 80.0°;the sodium chloride coagulation bath increased the membrane water flux.Increased to 1500.02L/?m²·h?and the ethanol coagulation bath increased the water flux more significantly,and its pure water flux could reach 2371.96L/?m²·h?;sodium chloride the coagulation bath improved the anti-fouling performance of the membrane,the flux recovery rate increased to 92.78%and the rejection rate to BSA was 84.2%.The retention rate is only 55.32%.Therefore,combining the above experimental conclusions,it can be concluded that the performance of the modified membrane in the sodium chloride coagulation bath is better.?2?In this study,carbon nanotubes containing four different functional groups-COOH?-OH?-NH₂and-O⁺were selected as additional blending additives and their effects on the structure and properties of PVDF-g-PEGMA/PVDF membranes were explored.Influences,taking PVDF-g-PEGMA/PVDF/CNTs-COOH as an example,the adsorption performance of the modified membrane was explored.The results show that carbon nanotubes containing carboxyl functional groups are more inclined to form molecules of the?crystal form,and can make the pore size distribution of the membrane more uniform,and the number of membrane pores can increase.At the same time,it can also reduce the contact angle of the membrane and make the surface of the membrane more compatible.The water-reinforced,CNT-containing carbon nanotube film has a contact angle of 56.4°.Under the pressure difference of 10 psi across the membrane,the pure water flux can reach2089.07L/m2·h,which significantly enhances the pure water flux of the modified membrane.The modified film containing hydroxy-functional carbon nanotubes can also appropriately reduce the contact angle on the surface of the modified film and improve the hydrophilic property of the film surface.The contact angle of the modified film is 60.5°.Synthesizing all the properties of the membrane,it is believed that the carbon nanotubes containing-COOH functional groups are added to the modified membrane,which has the best effect on improving the various properties of the modified membrane.At this time,PVDF-g-PEGMA/PVDF/CNTs-COOH ultrafiltration membrane,the pure water flux reached 2089.07L/m²·h.The isothermal adsorption model of PVDF-g-PEGMA/PVDF/CNTs-COOH for BSA is more consistent with the Langmuir model,and the kinetic model is more consistent with the pseudo-first order kinetic model.