A CO2-responsive PAN/PAN-co-PDEAEMA membrane capable of cleaning protein foulant without the aid of chemical agents

Chemical cleaning is essential to remove the protein foulants and restore the membrane flux, but it suffers from the excessive emission of effluent consisting of chemical agents and potential deterioration to the membrane integrity. In this study, we synthesized a novel CO2-responsive copolymer polyacrylonitrile-co-poly(2-diethylaminoethyl methacrylate) (PAN-co-PDEAEMA) through the free-radical copolymerization, and then fabricated the PAN/PAN-co-PDEAEMA blend membrane with a switchable flux and permeability. We proposed, for the first time, a novel and green method to clean the protein fouling, by alternative aeration of N2/CO2. The cleaning efficiency of the prepared CO2-responsive membrane by this green method was compared with the traditional methods including acid cleaning and alkaline cleaning in terms of flux recovery. The results indicate that the protein foulant on the prepared membrane can be efficiently removed by alternative aeration of N2/CO2, without the aid of chemical agents. The flux recovery of PAN/PAN-co-PDEAEMA membrane by this green method is fairly satisfactory (90%), which is comparable with the results of acid cleaning (90%) and alkali cleaning (98%). The nature transition from hydrophobic to hydrophilic on the membrane surface, due to the deprotonation and protonation of the tertiary amine groups in PDEAEMA, is responsible for the membrane cleaning.