Construction And Performance Study Of A New Anti-biofouling Membrane Based On Polyethyleneimine And Chitosa

Biofouling is highly harmful and difficult to eliminate in membrane fouling.The development of anti-biofouling membrane is the fundamental way to solve it.The synergy of anti-fouling mechanisms,modification of membrane materials and regulation of membrane microstructure are the key to construct high-performance membranes.In this paper,the aim is to improve the anti-biofouling performance of the membrane,taking the active removal mechanism and the active and passive anti-fouling mechanism as the starting point.Combined with strategies such as interfacial polymerization(IP)and surface cross-linking,the antibacterial agents are introduced into the membrane surface to prepare the new type of anti-biofouling composite membrane with polyethyleneimine(PEI)and chitosan(CS).The multi-layer structure and the surface properties of the membrane were investigated.The separation and anti-biofouling performance were systematically studied,and the mechanism of membrane anti-biofouling was discussed.The main research contents and conclusions are as follows:(1)The construction of polyethyleneimine modified anti-biofouling reverse osmosis(RO)membrane and the study of performance.The anti-biofouling RO was fabricated by sequential interfacial polymerization method with PEI introduced into polyamide RO based on active removal mechanism.2,6-diaminopyridine(DAP)was used as a control.The relationship between the structure and properties was studied by various means.The results showed that PEI and DAP were successfully cross-linked to the membrane surface.The modification improved the hydrophilicity and zeta potential of the membrane,and achieved simultaneous improvement of membrane separation performance and anti-biofouling performance.The antibacterial rates of PEI-modified membranes against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)reached 96.7%and 97.8%,respectively,which was related to the active removal mechanism on the cationic membrane surface.(2)The construction of anti-biofouling RO membrane with PEI participates in interfacial polymerization and the study of performance.Polysulfone(PSf)ultrafiltration membrane was used as support substrate,and the anti-biofouling RO membrane was prepared by using PEI and MPD comonomer and PEI as water phase monomer to participate in the IP reaction by one-step.The branched PEI successfully participated in the IP reaction through the characterization of the structure and chemical composition.The separation performance and anti-biofouling performance of the membrane were investigated.The results showed that the hydrophilicity and zeta potential of the membrane prepared by PEI improved,the water flux increased,and the antibacterial performance was better than that of the polyamide membrane.(3)The construction of chitosan-grafted zwitterion modified anti-biofouling RO membrane and the study of performance.The synthesis of CS-g-PSBMA copolymer was preparation with free radical initiated graft method.Anti-biofouling RO was fabricated through cross-linked CS-g-PSBMA on the polyamide membrane surface by glutaraldehyde with active and passive anti-biofouling mechanisms synergistically.The successful synthesis of CS-g-PSBMA was verified by ~1H NMR,ATR-FTIR and XPS.The relationship between the structure and properties was systematically studied.The results showed that the introduction of CS-g-PSBMA increased the hydrophilicity and zeta potential,the water flux was significantly improved,and the salt rejection was slightly reduced.The anti-biofouling behavior was related to the hydrophilic effect,hydration layer effect and steric repulsive effect.The synergistic mechanism of active removal and passive resistance improved the anti-biofouling ability.The antibacterial rates of E.coli and S.aureus were both over 99%.(4)The construction of chitosan-grafted zwitterion modified anti-biofouling loose nanofiltration(NF)membrane and the study of performance.CS-g-PSBMA was cross-linked on the PSf membrane surface with glutaraldehyde to prepare loose NF membrane.The relationship between the structure and properties of NF membrane was systematically studied.The results showed that the introduction of CS-g-PSBMA improved the hydrophilicity of the membrane surface,endowed low positive potential.The monovalent salt(sodium chloride)can be completely permeated,the rejection of the divalent salt(magnesium chloride)was less than 5%,and the effective separation of the salt mixed with Congo red and Methyl green dyes was realized.The separation mechanisms of dyes was related to electrostatic sieving and size sieving.The prepared NF membrane exhibited superior antibacterial adhesion and antibacterial properties,which realized the synergistic strengthening of dual anti-biofouling mechanisms.