Polyacrylonitrile-Based Zwitterionic Ultrafiltration Membrane With Improved Anti-Protein Fouling Capacity

Ultrafiltration technology is a new environmentally friendly separation method, applied in the field of biomedicine separation based on its unique advantages. Membrane fouling is an obstacle for its application, resulting in reduction of separation efficiency, shortening of service life, increasing of cost, therefore improving anti-protein fouling surface has become one of the most important research issues in the field of membrane separation. Membrane surface is an important factor to affect anti-protein fouling. Generally synthetic polymer materials easily lead to protein adsorption in the biological environment, which is unfavorable in biotechnology field, so improving anti-fouling property of membrane surface is effective method.In this study, a polyacrylonitrile-based zwitterionic ultrafiltration membrane was developed to improve its anti-protein fouling capacity.3-dimethylaminopropylamine was firstly grafted onto the hydrolyzed polyacrylonitrile(PAN) membrane by the activation of1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC). Subsequently, carboxylic zwitterion emerged on the membrane surface by the quaternization of3-bromopropionic acid, sodium2-bromoethanesulphonate and1,3-propanesulfonate. The zwitterionic membranes were rigorously characterized in terms of chemical compositions, morphology, and surface properties using FT-IR, XPS, SEM, Zeta potential and contact angle analyzer. It was noted that the zwitterion could successfully be assembled onto the PAN membrane whereas have insignificant effects on membrane morphologies. And hydrophilicity and charge of membrane surface had improved in some degree.The membrane filtration performance was characterized by protein static adsorption experiment and dynamic filtration experiment. Carboxylic zwitterionic graft-modified PAN-50membrane·by the quaternization of3-bromopropionic acid greatly improved the ability of inhibiting protein adsorption. Protein relative adsorption amounts of grafting2g/L,5g/L,10g/L3-dimethylaminopropylamine modified membrane were significantly lower than the blank membrane62.1%,67%,74.8%. It was noted that flux recovery rate was significantly improved by dynamic membrane filtration experiments. When the grafting concentration of3-dimethylaminopropylamine of10g/L, the flux recovery rate could reach96.1%, while the blank membrane flux recovery rate was only33%. Three cycles stability experiment showed that the modified membrane could maintain higher flux recovery. After three cycles experiment, pure water flux of the blank membrane decayed to22%of the original membrane, while water flux of the modified membrane only decayed to82%of the original membrane, the irreversible fouling index of the modified membrane was below10%. It was noted that the modified membranes could effectively reduce the irreversible contamination and have good flux recovery performance. Sulfonic salt zwitterionic graft-modified PAN-50membrane by the quaternization of sodium2-bromoethanesulphonate greatly improved the ability of inhibiting protein adsorption. The relative adsorption amounts of modified membrane were much lower than the blank membrane. By dynamic filtration experiments, The flux recovery rate was significantly improved and reached98.7%when the grafting concentration of10g/L3-dimethylaminopropylamine. After three cycles stability experiment, water flux of the PAN-M4modified membrane only decayed to82%of the original membrane. Irreversible fouling index of the modified membrane were less than8%.Sulfonic zwitterionic graft-modified PAN-50and PAN-350membrane by the quatemization of1,3-propanesulfonate greatly improved the ability of inhibiting protein adsorption. By protein static adsorption experiments, relative adsorption amount of modified membrane was significantly lower than that of the blank membrane. Relative adsorption amount of sulfonic zwitterionic graft-modified PAN-50and PAN-350membrane was significantly lower than that of the blank membrane. By dynamic filtration experiments, Flux recovery rate of PAN-50modified membrane reached98.3%when the grafting concentration of10g/L3-dimethylaminopropylamine. After three cycle stability experiments, water flux of PAN-50modified membrane only decayed to93%of the original membrane, the irreversible fouling index of the PAN-50modified membrane was below4%. But the flux loss was more serious. Switch membrane pores larger PAN-350. After three cycles stability test, pure water flux of the blank PAN-350decayed to the28.8%of the original membrane, water flux decay of the PAN-350modified membrane only decayed74.4%of the original membrane. The irreversible fouling index of the PAN-350modified membrane was below10%.