CO2-responsive membranes enable self-cleaning of BSA foulant by alternating N2/CO2 stimulation

In this research, a new type of CO2-responsive polyacrylonitrile/polyacrylonitrile-co-poly (N, N-Diethyl-2-Acrylamide) (PAN/PAN-co-PDEAAm) membrane was fabricated, which can self-clean protein fouling on membrane surfaces by alternating aeration of CO2/N2. The structural characterization of the functional PAN-co-PDEAAm copolymer was performed by Fourier Transform Infrared Spectrometer (FT-IR) and Nuclear Magnetic Resonance (NMR), and membrane morphologies were characterized by Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM). The water flux of the newly prepared membrane is 222.5 L·m−2·h−1 under CO2 pressure, which is much higher than that under N2 pressure (209.1 L·m−2·h−1), suggesting a CO2-sensitive performance. It is closely related to the conformational transition from the collapsed to the extended state for the PDEAAm segment within the membrane pores. The membrane cleaning efficiency by alternating aeration was compared to traditional methods. The flux recovery ratio of protein-contaminated membranes by alternating aeration achieves 90.4%, which is roughly equivalent to acid washing (92.2%) and alkali washing (94.8%), but far better than water cleaning (81.0%). Alternating aeration is an environmentally friendly membrane cleaning method that does not require any chemical reagents, thereby posing no secondary environmental pollution.