Hydrophilic Modification Of Polyacrylonitrile (PAN) Ultrafiltration Membranes And Study On Antifouling Property

As a green and energy-efficient separation technology, ultrafiltration exhibits a vast prospect of application in bioseparation, while membrane fouling still constitutes a bottleneck of its development. Membrane materials show great impact on membrane fouling. In order to reduce membrane fouling during biosepration, modified ultrafiltration membranes were investigated.A weak polyelectrolyte ultrafiltration membranes based on poly(acrylonitrile and 2-Dimethylamino ethyl methacrylate) (PAN-DMAEMA) copolymer was prepared by phase inversion in a wet process. The result of X-ray photoelectron spectroscopy (XPS) analysis provided that enrichment of PDMAEMA on the surface of membranes. Water flux of PAN-DMAEMA ultrafiltration membrane is turnable due to the switch of the stretched and collapsed states of the polymer chains for PDMAEMA at different pH and NaCl concentration in the feed solution. The amount of bovine serum albumin (BSA) absorption on PAN-DMAEMA membrane is dramatically decreased at 1.0 mol/L NaCl and pH 9.5. A general viewpoint based on the minimizing electrostatic interactions between PDMAEMA groups after environment stimuli leading to the conformation switch of PDMAEMA chains from stretched to shrunk states, which results in higher surface enrichment of ester groups enhancing hydrophilic property of the PAN-DMAEMA membrane, was put forward to explain the resistance of protein adsorption on the membrane.A series of polyacrylonitrile–poly(ethylene glycol) (PAN–PEG400,1000,2000,4000,6000) block copolymer were synthesized by water-phase precipitation copolymerization, using ceric ammonium nitrate–PEG pair as an initiator. PAN-PEG ultrafiltration membranes were prepared by phase inversion using DMF as solvent and water as non-solvent. FTIR revealed that C-O-C adsorption peak at 1105.3 cm-1 attributed to PEG exits membrane. The water contact angle measurement of PAN-PEG revealed that the introduction of PEG could effectively enhance the hydrophilicity. Ultrafiltration experiments were carried out to investigate the antifouling property. PAN/PAN-PEG2000 blend membranes were prepared by phase inversion. Ultrafiltration experiments revealed that membrane fouling, especially irreversible fouling, was remarkably reduced.The 2-methacryloyloxyethyl- phosphorylcholine (MPC), an electrically neutral zwitterionic head group, which represents the dominant property of the phospholipids existing on the external surfaces of cell membranes, can effectively reduce protein adsorption. The synthesized phosphorylcholine copolymer composed of MPC and n-butyl methacrylate (BMA), blended with polyethersulfone (PES), was used to fabricate antifouling ultrafiltration membranes. Water contact angle measurements confirmed that the hydrophilicity of the MPC modified PES membrane was enhanced to certain extent. X-ray photoelectron spectroscopy (XPS) analysis verified the substantial enrichment of MPC at the surface of the MPC modified PES membranes. The adsorption experiments indicated that the adsorption amounts of bovine serum albumin (BSA) on the MPC modified PES membranes were dramatically decreased in comparison with the control PES membrane. Ultrafiltration experiments were carried out to investigate the effect of MPC modification on the antifouling and permeation properties of the PES membranes. The MPC modified PES membranes could run several cycles without substantial flux loss. Ultrafiltration operation under different pH values indicated that modified PES membranes possessed antifouling property in pH=4.5～9.0.