A CO2-stimulus responsive PVDF/PVDF-g-PDEAEMA blend membrane capable of cleaning protein foulants by alternate aeration of N2/CO2

In this work, a novel CO2-stimulus responsive copolymer polyvinylidene fluoride-graft- (2-diethylaminoethyl methacrylate) (PVDF-g-PDEAEMA) was synthesized by a free-radical copolymerization method, and then PVDF/PVDF-g-PDEAEMA blend membrane was fabricated, with a switchable pure water flux by alternate aeration (N2/CO2). The water flux of the blend membrane under the pressure of CO2 is significantly lower than that under N2 pressure, indicating the CO2-responsive property of the membrane, which is due to the protonation or deprotonation reaction of tertiary amine groups in PDEAEMA. After CO2 aeration, the PDEAEMA segments within pores of the membrane are extended due to the protonation reaction, which results in the shrinkage of membrane pores, thereby decreasing the water flux of the membrane. Taking advantage of the CO2-stimulus responsiveness, the alternate aeration (N2/CO2) method is adopted to clean protein on the blend membrane surface without the introduction of chemical reagents. The flux recovery rate of the blend membrane cleaned by this green method is fairly satisfactory (89.9%), which is comparable to the results of acid cleaning (90.6%) and alkaline cleaning (95.2%). The switchable hydrophilic/hydrophobic transition on membrane surfaces upon alternating exposure of CO2/N2, is mainly responsible for membrane cleaning.