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

Abstract

• A CO 2 -responsive PVDF/PVDF-g-PDEAEMA blend membrane was fabricated. • The blend membrane exhibits a switchable water flux by alternate aeration of N 2 /CO 2. • The protein fouling can be efficiently removed by alternate aeration of N 2 /CO 2. • Flux recovery of membrane by this method is fairly satisfactory. • Switchable hydrophobic/hydrophilic transition is responsible for membrane cleaning. In this work, a novel CO 2 -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 (N 2 /CO 2 ). The water flux of the blend membrane under the pressure of CO 2 is significantly lower than that under N 2 pressure, indicating the CO 2 -responsive property of the membrane, which is due to the protonation or deprotonation reaction of tertiary amine groups in PDEAEMA. After CO 2 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 CO 2 -stimulus responsiveness, the alternate aeration (N 2 /CO 2 ) 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 CO 2 /N 2 , is mainly responsible for membrane cleaning.