| Ultrafiltration(UF)is the membrane technology for water purification by size sieving effects under external pressure.Ultrafiltration technology has the advantages of no phase transition,low operating cost and high separation efficiency.However,the strong hydrophobic characteristic of membrane substrate can easily accelerate membrane fouling.Cell membrane is an ideal separation membrane in nature.Inspired by the composition,structure and formation process of cell membrane,two kinds of functional membrane surface were prepared by biomimetic design of lipid hydrophilic and hydrophobic block structure,protein mosaic synergistic modification,and the the influence of different structures on anti-fouling performance was preliminarily investigated by natural organic pollutants.In addition,organisms generates mineralized protective shells in situ to protect cells from external invasion.Inspired by this,the organic-inorganic composite functional coating was prepared by in-situ hydrolysis and crosslinking with additional precursors.The influence of mineralized coating on the performance of chemical stability and anti-fouling ability were investigated.Finally,the application performance in the treatment of Songhua river water and the anti-fouling mechanism which was analyzed by using XDLVO theory were investigated.The hydrophilic and antifouling properties of the membr ane were improved by surface grafting surfactant with hydrophilic-hydrophobic block structure which was similar to that of lipid.Reactive surfactant 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene(10)ether ammonium sulfate(AHPS) was selected as the monomer with hydrophilic-hydrophobic block structure,and the biomimetic functional coating was prepared by one-step copolymerization-codeposition of dopamine and AHPS,taking advantage of the fact that dopamine can generate semiquinone radical under alkaline conditions to initiate the copolymerization of between unsaturated monomer and dopamine,and then adhere to various materials surfaces by self-assembly.AHPS not only inhibited the formation of insoluble precipitate of polydopamine,but also significantly improved the hydrophilicity and anti-fouling performance of membrane surface.The contact angles of the membrane surface decreased from 77.2° to 55.4°.The static absorption of bovine serum albumin(BSA)decreased from 77.18?g/cm2 to 34.31?g/cm2.The relative fluorescence intensity of static adsorbed Fluorescein conjugated protein(BSA-FITC)was 65.7%.After three cycles of dynamic fouling-cleaning process,bovine serum albumin,humic acid and sodium alginate solution with high concentration were used as the simulated pollutants,the water flux recovery rates of biomimetic membrane were all about 99.0%,and had better recycle availability.However,the modified membrane had poor alkali resistance and poor oxidation resistance.The influence of membrane protein mosaiced in lipid hydrophilic and hydrophobic block structure on anti-fouling performance was also investigated.The bionic functional coating was prepared by one-step copolymerization and codeposition of bovine serum protein(BSA)and AHPS with dopamine based on the Schiff base reaction of dopamine with BSA.Research showed that BSA could increase the interfacial free energy of the membrane surface,which was beneficial to improve the coverage of modifier.The synergistic modification effectively improved the hydrophilicity and anti-fouling performance of modified membranes.The contact angle decreased from 77.2° to 33.1°.The static absorption of BSA decreased from 77.18?g/cm2 to 15.06?g/cm2.The relative fluorescence intensity of static adsorbed Fluorescein conjugated protein(BSA-FITC)was decreased to57.8%.After three cycles of dynamic fouling-cleaning process,bovine serum albumin,humic acid and sodium alginate solution with high concentration were used as the simulated pollutants,the water flux recovery rates of biomimetic membrane were 93.0%,63.1% and 94.3% respectively.The fouling resistance of polyethersulfone ultrafiltration(PES)membrane mainly came from the deposition and concentration polarization of pollutant,accounting for about 61%of the total membrane resistance.However,that of the modified membrane only accounted for35.2%.The modified membrane still had poor alkali resistance and poor oxidation resistance.The inorganic mineralized coating,which was prepared by Schiff base reactionandself-hydrolysiscrosslinkingreactionbetween aminopropyltrimethoxysilane(APTMS)and dopamine,improved the chemical stability and anti-fouling performance.The hydrophilicity of the modified membrane was enhanced,and the contact angle decreased from 77.2° to 46.5°.The pure water flux increased from 162 LMH to 245 LMH.The modified membrane had better anti-fouling performance.The static adsorption amount of BSA decreased from 77.18?g/cm2 to 7.53?g/cm2,and the relative fluorescence intensity of static adsorbed BSA-FITC was decreased to 32.8%.After three cycles of dynamic fouling-cleaning process,which selected BSA,humic acid and sodium alginate solution as the simulated pollutants,t he water flux recovery rates of biomimetic membrane were 99.1%,86.0%and 94.6%,respectively.According to the resistance analysis during BSA fouling process,the membrane-self resistance accounted for about 80%of the total membrane resistance.Biomineralization synergistic modification improved the acid,alkali and oxidation resistance.The anti-fouling performance of modified membrane in the treatment of Songhua river water was investigated.The dynamic fouling process was analyzed by using membrane fouling model and the anti-fouling mechanism was analyzed by XDLVO theory.Compared to that of PES membrane,the modified membrane had the higher removal of DOC and UV254,and the higher water flux after three cycles of fouling-cleaning process.The fouling process of PES membrane and modified membranes accorded with the standard blocking mode and cake filtration mode.The modified membranes had the longer adhesion time to pollutants than that of PES membrane.The adhesion free energy of modified membranes was high than that of PES membrane.Such as the adhesion free energy of PES to humic acid,sodium alginate and BSA were-20.60 m J/m2,-27.55 m J/m2 and-27.08m J/m2,respectively.That of inorganic mineralized membrane were 5.42 m J/m2,-7.73 m J/m2and-0.12 m J/m2,respectively.Over all,the hydrophilic group of dopamine,the silica hydroxyl group,the hydrophilic segment of AHPS and BSA were all favor to enhance the antifouling performance. |
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